Geosphere · Kuehn and Negrini 398 Geosphere, August 2010 1996; Sarna-Wojcicki et al., 2001) and...
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Geosphere doi: 10.1130/GES00515.1 2010;6;397-429 Geosphere Stephen C. Kuehn and Robert M. Negrini lacustrine sediments near Summer Lake, Oregon, USA A 250 k.y. record of Cascade arc pyroclastic volcanism from late Pleistocene Email alerting services articles cite this article to receive free e-mail alerts when new www.gsapubs.org/cgi/alerts click Subscribe to subscribe to Geosphere www.gsapubs.org/subscriptions/ click Permission request to contact GSA http://www.geosociety.org/pubs/copyrt.htm#gsa click official positions of the Society. citizenship, gender, religion, or political viewpoint. Opinions presented in this publication do not reflect presentation of diverse opinions and positions by scientists worldwide, regardless of their race, includes a reference to the article's full citation. GSA provides this and other forums for the the abstracts only of their articles on their own or their organization's Web site providing the posting to further education and science. This file may not be posted to any Web site, but authors may post works and to make unlimited copies of items in GSA's journals for noncommercial use in classrooms requests to GSA, to use a single figure, a single table, and/or a brief paragraph of text in subsequent their employment. Individual scientists are hereby granted permission, without fees or further Copyright not claimed on content prepared wholly by U.S. government employees within scope of Notes © 2010 Geological Society of America on April 8, 2012 geosphere.gsapubs.org Downloaded from
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Geosphere
doi: 10.1130/GES00515.1 2010;6;397-429Geosphere
Stephen C. Kuehn and Robert M. Negrini lacustrine sediments near Summer Lake, Oregon, USAA 250 k.y. record of Cascade arc pyroclastic volcanism from late Pleistocene
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A 250 k.y. record of Cascade arc pyroclastic volcanism from late Pleistocene lacustrine sediments near Summer Lake, Oregon, USA
Stephen C. Kuehn*Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, Alberta T6G 2E3, Canada
Robert M. NegriniDepartment of Physics and Geology, California State University, Bakersfi eld, California 93311, USA
397
Geosphere; August 2010; v. 6; no. 4; p. 397–429; doi: 10.1130/GES00515.1; 10 fi gures; 4 tables; 38 supplemental fi gures; 4 supplemental tables.
*Corresponding author. Present address: Department of Physical Sciences, Concord University, Athens, West Virginia 24712, USA; [email protected].
ABSTRACT
Distal tephra beds provide impor-tant records of pyroclastic volcanism that enhance our overall understanding of erup-tive frequencies, magnitudes, compositions, and hazards. Some beds also serve as wide-spread chronostratigraphic markers. Lacus-trine sediments near Summer Lake, Oregon (United States), record numerous eruptions of Cascade arc sources over a period exceeding 2.5 m.y. Late Pleistocene sediments exposed in outcrop have yielded 88 visible tephra beds, including many beds not previously docu-mented. Of these beds, 44 are characterized by rhyolitic glass, 40 contain predominantly basaltic or intermediate glass, and 4 are strongly heterogeneous in composition. Only 23 have been correlated to deposits outside of the Summer Lake basin. The remaining 65 beds provide a record of Cascade arc volca-nism that is as yet unique to Summer Lake. Age-depth relations are well constrained for the upper 6 m of section, but are less certain in the lower 12.4 m. Tephra correlations and an overall age model suggest the following: bed B1 originates from an eruption of Mount Mazama (Crater Lake) ca. 20 ka. Beds I and W likely originate from eruptions of Mount St. Helens ca. 80 and 190 ka. A 7-cm-thick tephra bed correlated to Shevlin Park Tuff probably dates to ca. 198 ka. Tephra corre-lated to the Antelope Well tuff from Medicine Lake volcano dates to ca. 215 ka. Bed NN, at the base of the section, has an estimated age of at least 240–250 ka and probably origi-nated from Newberry Volcano. Overall, this record signifi cantly refi nes the Pleistocene
tephrostratigraphic framework for western North America.
INTRODUCTION
Much of what we know about the Cascade volcanic arc (western North America) has been determined through studies of lava fl ows and proximal tephra deposits (e.g., Bacon and Lanphere, 2006; Hildreth, 2007). Because unconsolidated pyroclastic materials on vol-canic slopes are readily eroded, and because of the signifi cant potential for burial by subse-quent eruptions, proximal pyroclastic records are often incomplete (e.g., the set C tephras of Mount St. Helens; Mullineaux, 1996). Distal tephra deposits, especially those from favorable depositional settings like lakes, offer the poten-tial to fi ll in many of the gaps in the proximal record, thereby enhancing our understanding of eruptive frequencies, magnitudes, compositions, and related hazards. Distal tephra beds also pro-vide information on particle size and thickness distributions that enhances our understanding of ash-dispersal processes.
Tephra beds are also widely used as chro-nostratigraphic markers, providing independent age control for a large array of interdisciplinary studies ranging from archaeology to paleoseis-mology to surfi cial processes (e.g., Mehringer and Foit, 1990; Langridge, 1998; Hermanns et al., 2000). Tephra correlation also offers the potential to link together glacial, lacustrine, marine, and terrestrial records over long dis-tances (e.g., Sarna-Wojcicki et al., 1991; Zdano-wicz et al., 1999; Negrini, 2002). Furthermore, because tephra is dispersed rapidly across large areas, it can be used to test the synchroneity of
environmental and climate changes with a pre-cision often unmatched by radiometric dating techniques.
Summer Lake, which occupies a portion of the northwestern subbasin of pluvial Lake Chewaucan in south-central Oregon (Figs. 1 and 2), is a key reference locality with numer-ous tephra beds found together in a single strati-graphic context. Much work has also been done studying the paleoclimate, paleomagnetic, and paleoseismic records preserved in ~18.4 m of outcrop and multiple cores (e.g., Negrini et al., 1988, 1994, 2000; Langridge, 1998; Cohen et al., 2000; Sarna-Wojcicki et al., 2001; Zic et al., 2002). The earliest work on the tephrostratigra-phy is that of Allison (1945), who described the top few meters of section from two locations along the Ana River (Fig. 2). Starting from the bottom of this interval, Allison divided the stra-tigraphy into 19 distinct units, 6 of which (2, 4, 6, 8, 12, 18) are tephra layers. Conrad (1953) revis-ited the same localities and described many more beds, 42 in total. From sites C, E, and F (Fig. 2), Davis (1985) documented 54 beds, including the 6 numbered beds of Allison (1945) and 48 beds that he designated A–NN. Davis (1985) also obtained major element glass compositions by electron probe microanalysis (EPMA) for 33 of the 54 total beds and used these data to cor-relate several of the beds to locations outside of the basin and to identify some of the source vol-canoes. Additional tephra beds from two cores, the Wetland Levee (WL) and Bed and Breakfast (B&B) cores (Fig. 2), and an age-depth model for the combined core and outcrop sequence were added later (Negrini et al., 2000). Four additional cores also exist, including two taken adjacent to outcrop site C (31 and 64 m) (Erbes,
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1996; Sarna-Wojcicki et al., 2001) and two from the Summer Lake Playa site G (SPG) site (33 and 37 m) (Negrini, 2001) (Fig. 2). The total thickness of basin-fi ll sediment is thought to be ~1.5 km (Travis, 1977), so the potential exists to also obtain much older records.
In a composite measured section on the Ana River, Lake County, Oregon, reproduced in Erbes (1996) and Negrini et al. (2001), J.O. Davis sug-gested the existence of additional tephra beds in the C, E, and F outcrop sections. Erbes (1996) and Langridge (1998) also suggested the pres-ence of additional tephra beds based on study of
site C outcrop and core, the WL and B&B cores, and additional outcrop locations.
Our study, which focuses primarily on the outcrop tephrostratigraphy in the Ana River canyon, was initiated on the basis of: (1) the presence of many tephra beds of undetermined glass composition, (2) the suggested presence of additional tephra beds, (3) the apparent lack of suitable correlatives to large pyroclastic depos-its such as the Shevlin Park Tuff, and (4) uncer-tainties in the stratigraphic relations between outcrop locations. To this end, the C, E, and F outcrop sites were reexcavated (Figs. 3–5) and
Oregon
California
Nevada
0 100 km50
Figure Area
39o
Nevada
WA-5
Carp Lake
Pringle Falls
Tulelakecore
Benton CrossingPaoha Island
Walker Lake
Mt. St. Helens
Crater Lake
Three Sisters
Mt. Jefferson
Mt. Hood
Mt. Adams
Mt. Rainier
Newberryvolcanic
field
WashingtonIdaho
Medicine Lakevolcanic
field
Mt. Lassen
Mt. Shasta
KP-1
Pluviallakes
QuaternaryCascade arc
volcanism
Pac
ific
Oce
an
Approximateoutline of theGreat Basin
Summer Lake
118o 116o
42o
40o
36o
119o
42o
114o
Figure 1. Regional location map. Includes location of Summer Lake, selected volcanic centers, and selected tephra localities. Extent of Quaternary volcanism of the Cascade arc (dark-est shading) is largely after Hildreth (2007). Maximal extents of two selected rear-arc volcanic fi elds, Medicine Lake and Newberry, are after Donnelly-Nolan et al. (2008) and Sher-rod et al. (1997), respectively. Calderas of Medicine Lake and Newberry volcanoes are outlined by dashed lines within their respective areas. Pleistocene lakes (lightest shading) and mar-gin (thick dashed line) of the Great Basin are after Smith and Street-Perrott (1983).
sampled in detail for tephra (Table 1 and Sup-plemental Tables S1–S31).
ANALYTICAL METHODS
More than 200 tephra samples from the 3 out-crop locations have been analyzed for their glass compositions by EPMA (Table 2; Supplemental Table S4, see footnote 1). We chose to focus on glass compositions because these provide one of the most consistent and distinguishing char-acteristics for the identifi cation and correlation of tephra beds (Sarna-Wojcicki et al., 1991). Whereas bulk tephra compositions typically vary with distance due to differential settling of glass and crystals, glass compositions are often uniform over long distances (Sarna-Wojcicki et al., 1991). In situations where major element glass compositions of two or more tephra beds overlap, additional information from miner-alogy, age, stratigraphic relations, and/or the trace element composition of the glass are often used to distinguish and identify them (Sarna-Wojcicki, 2000). Note also that glass composi-tions may differ substantially from bulk compo-sitions when crystallinity is high, the glass often containing a greater proportion of silica than the bulk tephra. For example, the latest Pleistocene tephras from Glacier Peak volcano have dacitic bulk compositions (Gardner et al., 1998), but contain homogeneous, high-silica rhyolite glass (Kuehn et al., 2009). Thus, glass and bulk com-positions often are not directly comparable.
Most analyzed samples were mounted in epoxy as bulk tephra, polished, and then car-bon coated. Wavelength-dispersive analyses of the site C and core samples were conducted primarily at the GeoAnalytical Laboratory of Washington State University (WSU) using a Cameca Camebax microprobe (15 keV accel-erating voltage; 8–10 μm beam diameter, and 12 nA current). Similar analyses of the site E and F samples were conducted primarily at the University of Alberta (UA) using a JEOL 8900 microprobe (15 keV accelerating voltage; 10 μm beam diameter, and 6 nA current). For the four most abundant elements, Na, K, Al, and Si, both instruments were calibrated using the same natural obsidian standard, UA5831 (also known as CCNM 211 at WSU), which originates from Lipari Island, Italy. The remaining elements were calibrated on differing glass and mineral standards. As both of these long-established
1Supplemental Table File. Excel fi le of four sup-plemental tables. If you are viewing the PDF of this paper or reading it offl ine, please visit http://dx.doi.org/10.1130/GES00515.S1 or the full-text article on www.gsapubs.org to view the supplemental table fi le.
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Geosphere, August 2010 399
analytical procedures were designed primarily for rhyolitic glasses, P
2O
5, which is typically
near detection limits in rhyolitic glasses, is not included in the data set.
At the University of Alberta, UA5831 obsid-ian and Old Crow tephra (UT1434) were peri-odically reanalyzed as secondary standards (typically 5–10 points each at the beginning and end of each day and again between about every 4 unknowns) to monitor calibration quality and detect any instrument drift. To maximize con-sistency between analyses obtained on different days, minor corrections were applied based on the secondary standard values obtained for UA5831. At WSU, the obsidian standard was analyzed as an unknown at the beginning and end of each day to assess calibration quality and detect drift, and the instrument was recalibrated as needed.
All results in Tables 2 and S4 (see footnote 1) are reported as oxide values normalized to 100%, volatile free (Froggatt, 1992). Most indi-vidual analyses with especially low totals (below ~90%–92%) and obvious crystalline contami-nants have been removed from the data set. Some of the mafi c samples analyzed are very microcryst rich, and scatter in analytical data for these samples suggests some residual crystalline contamination (Table S4 [see footnote 1]). For the glass standard and the most homogeneous tephra samples (i.e., those with the smallest standard deviations), the observed variability (Tables 2 and S4 [see footnote 1]) largely refl ects the precision of the analytical method.
Ana RiverSections
C,E,F
Ana RiverSections
C,E,F
0 5 km
SPG coresSPG cores
Approximateshoreline ofPleistocenehighstand(1378 m)
Approximateshoreline ofPleistocenehighstand(1378 m)W
inter Ridge
Winter R
idge
WL coreWL core
B&B coreB&B core
Summer Lake(1264 m shoreline)
Summer Lake(1264 m shoreline)
AnaRiverAnaRiver
Chewaucan RiverChewaucan RiverHighway 31Highway 31
N
Figure 2. Summer Lake area map with outcrop and core localities indicated. B&B—Bed and Breakfast; WL—Wetland Levee; SPG—Summer Lake Playa site G.
1212 1212
1818
88
Major UnconformityMajor Unconformity
Ana RiverAna River
88 22
LLLL
AA1AA1
Site C
Trench 3Trench 3
Trench 2Trench 2Trench 1Trench 1
Trench 4Trench 4
1 m1 m
Minor Unconformity?Minor Unconformity?
Figure 3. Overview of site C (42°59.55 N, 120°44.64 W) with excavated areas and selected stratigraphic features labeled.
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NN
1212
1818
1818
Major UnconformityMajor Unconformity
Minor Unconformity ?Minor Unconformity ?
Ana RiverAna River
22
Site E
Trench 3Trench 3
Trench 2Trench 2Trench 1Trench 1
Trench 5Trench 5
RoadRoad
Trench 4Trench 4
1 m1 m
N (N1)N (N1)
W (OO)W (OO)
S, T, T1S, T, T1
LLLL
KKKK
AA1AA1
LL
1212
FF88
Major UnconformityMajor Unconformity
Minor UnconformityMinor Unconformity
Ana RiverAna River
22
Site F
1 m1 m
Figure 5. Overview of site F (42°59.12′N, 120°43.81′W) with the excavated area and selected stratigraphic features labeled.
Figure 4. Overview of site E (42°59.10′N, 120°44.09′W) with exca-vated areas and selected stratigraphic features labeled. Trenches 1, 3, and 5 are hidden in this view, but their approximate locations are indicated by arrows (1 and 5) and a dashed out-line (3). The lowermost part of trench 4 was excavated after this photograph was taken and is also indicated by a dashed outline.
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TABLE 1. SUMMARY DESCRIPTIONS OF TEPHRA BEDS FOUND IN OUTCROPS ALONG THE ANA RIVER CANYON
Tephra bed Sites where identifi ed
Typical glass SiO2 (wt%, normalized)
Thickness (cm) Color in outcrop Particle size Notes
B E
A E 0.6–1 gray silt to very fine sand Contains a secondary population that is indistinguishable from tephra B
major mode: ~58.5
73.1–76.4 0.2–0.3 white to gray silt to medium sandB1 E ~75.5 0.1 gray to white silt to medium sand DiscontinuousB2 E 70.2–73.8 0.1 gray to white silt to medium sand DiscontinuousC E ~58 0.3 dark gray to black fi ne sand to medium
sandAbundant microcrysts
C1 E ~57.1 0.1 gray to white silt to medium sand Discontinuous; glass is microcryst rich; contains a second population that is indistinguishable from tephra 18; second population may represent redeposited material.
C2 E ~65.8 0.1 gray to white silt to medium sand Discontinuous; glass contains few microcrysts; contains a second population that is indistinguishable from tephra 18; second population may represent redeposited material.
D E ~76.5 1 white silt to fi ne sand, fi nes upward
Langridge (1998) reported the presence of hornblende and cummingtonite.
18 C, E ~75.5 5 white silt to fi ne sand, fi nes upward
Typically overlain by several centimeters of reworked tephra with ripple cross-bedding. Langridge (1998) reported the presence of orthopyroxene and hornblende.
E E ~75.5 0.1 white silt to very fi ne sandE1 C, E ~77 0.2–0.3 white coarse siltF C, E, F ~73–76.6 up to 6 white silt to coarse sand Typically overlies a tufa bed from which it
is usually separated by a thin layer of silt; at site C, discontinuous sand and tufa beds overlie the tephra, and some erosion of the tephra bed is apparent. Langridge (1998) reported the presence of orthopyroxene and minor hornblende.
F1 E, F ~73.5–76.5 up to 0.3 white silt to very fi ne sand DiscontinuousG C, E, F ~77.8 0.3–1.5 white silt to fi ne sand DiscontinuousG1 F 55.7–62.1 0.3 dark gray to black silt to fi ne sand Microcryst rich
12 C, E, F ~77 10 gray to white silt to medium sand, fi nes upward
One of the most prominent and recognizable marker beds in the fi eld; color is gradational with darker base; biotite is concentrated toward the base. Langridge (1998) also reported the presence of cummingtonite and orthopyroxene.
H C, E, F ~66.5 0.5 gray to white silt to fi ne sand, fi nes upward
H0.2 C, E ~70 0.1–0.2 white silt to fi ne sand8 C, E, F ~70 10 gray silt to coarse sand Typically forms a hard, resistant layer;
together with beds 6 and 4 below, forms an easily recognizable set consisting of one thick, coarse bed overlying two closely spaced thinner beds.
6 C, E, F ~73 0.5–1 pink to white silt to coarse sand, fi nes upward
4 C, E, F ~72.5 0.5–1 white silt to very fi ne sandH0.4 E, F ~59 0.1–0.3 dark gray to black silt to very fi ne sand Microcryst rich2 C, E, F ~74 3–4 pink to white silt to medium sand,
fi nes upwardConsists of multiple layers.
H1 C, E ~56–~57 0.1 black silt to fi ne sand Somewhat discontinuous; contains brown, microcryst-rich glass.
H2 C, E ~55 0.05–0.1 dark gray silt to medium sand Contains brown glass with few microcrysts.
H3 C ~57.7 0.1 dark gray to black silt to fi ne sand Contains brown, microcryst-bearing glass.
I C, E, F ~77 0.2 silt to fi ne sandI1 E ~53.3 0.1 dark gray to black Often diffuseJ C, E, F ~72–77.5 1 white silt to medium sand,
fi nes upwardJ1 C, E, F bimodal: ~57 and
~640.5–1 gray silt to medium sand Diffuse; contains two main populations of
mafi c to intermediate composition; also contains numerous silicic shards of varying compositions; silicic shards may represent redeposited material.
(continued)
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402 Geosphere, August 2010
(continued)
TABLE 1. SUMMARY DESCRIPTIONS OF TEPHRA BEDS FOUND IN OUTCROPS ALONG THE ANA RIVER CANYON (continued)
Tephra bed Sites where identifi ed
Typical glass SiO2 (wt%, normalized)
Thickness (cm) Color in outcrop Particle size Notes
J3 C, E, F ~53–58 0.2–2 dark gray to black silt to fi ne sand 2 mm thick at sites C and E; occurs at site F as a dark band up to 2 cm thick with sharp base and gradational top.
K C, E, F 68.5–73.6 0.3 white silt to medium sandL C, E ,F bimodal: ~58.8 and
~62.10.3–0.4 dark gray to black silt to medium sand Contains microcryst-rich brown glass; lower
silica population only observed in sample from site C.
L1 C bimodal: ~59.3 and ~61.5
0.1–0.2 dark gray to black silt to fi ne sand Discontinuous; contains microcryst-rich brown glass.
M E, F ~71.4 up to 0.6 white silt to fi ne sand DiscontinuousN (N1) E, F ~71.4 5–6 white to gray silt to medium sand,
fi nes upward
N2 C ~58.1 up to 0.2 gray silt to fi ne sand DiscontinuousO C, E, F ~71 0.3–0.5 white to pale pink silt to very fi ne sandP C, E, F ~72.5–73 0.5–1 white silt to fi ne sandQ C, F ~72.5–73 0.2–0.3 white to pale pink silt to fi ne sandR C, E, F ~74 1 white silt to very fi ne sand Underlying sediment often contains
numerous tephra-fi lled tubes 0.5–1 mm in diameter; these may represent ostracode burrows.
R1 C, E, F 68.0–74.7 0.5–1 white to pale yellow
fi ne to coarse sand Typically present as two or sometimes threeclosely spaced beds; Color and texture resemble ostracode sand.
R2 C, E, F bimodal: ~58 and ~62
0.1–0.2 dark gray to black silt to fi ne sand Discontinuous; upper boundary often diffuse or gradational; contains two main glass populations; a heterogeneous mixture of other glasses is also present and likely represents redeposited material.
R3 C ~63 1 gray silt to fi ne sand Diffuse and discontinuous; contains both brown, microcryst-bearing mafi c tephra and silicic tephra; silicic component is indistinguishable from beds S and T and may represent redeposited material.
S C, E, F ~75–75.5 1 white silt to medium sand, fi nes upward
T C, E, F ~75–75.5 2–3 gray to white silt to coarse sand, fi nes upward
Bottom 1.5–2 cm mainly coarse sand sized, top 1 cm silt to fi ne sand sized.
T0.5 F ~75.5 (mafi c component not
analyzed)
0.2–0.4 brown silt to fi ne sand Very discontinuous; contains colorless silicic glass and less abundant, brown, microcryst-bearing mafi c glass; silicic glass could be redeposited T1.
T1 C, E, F ~75.5 1 white silt to medium sand, fi nes upward
Slightly higher SiO2 and slightly lower CaO and FeO compared to beds S and T
U C, E bimodal: ~54–55 and ~56.7
0.6–1 gray sandy Consists primarily of mafi c tephra and ostracode valves; silicic tephra also present; silicic component may be redeposited; only the lower silica population observed in sample from site C.
V C, E ~73.7 0.5–0.8 white silt to fi ne sandW (OO) C, E, F ~77 0.3–0.5 white silt to medium sand Contains biotiteX C ~56.7 0.1 black silt to fi ne sand Highly discontinuousY C, E bimodal: ~58–59
and ~64.80.2– 0.3 black silt to medium sand Discontinuous
Z C, E, F bimodal: ~57–58 and ~66.3
0.4–0.5 black silt to fi ne sand Mostly continuous
AA C, E ~56.5 0.1–0.2 dark gray to black silt to fi ne sandAA1 C, E, F ~56–~69 7–8 tan to gray silt to very coarse sand
with some pumice as large as 5 mm, fi nes
upward
Except for the bottom 6–8 mm, the color is very similar to that of the surrounding sediments; also present in the SPG-A core; overlain by tephra-rich laminated sediments at site C.
AA2 F major mode ~71.7 gray to white sandy Contains brown mafi c glass, clear silicic glass, and ostracode valves; possibly redeposited; found in a zone of disturbed sediments.
J2 C, E, F bimodal: ~57 and ~64
0.5–1 gray silt to fi ne sand Same as J1
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TABLE 1. SUMMARY DESCRIPTIONS OF TEPHRA BEDS FOUND IN OUTCROPS ALONG THE ANA RIVER CANYON (continued)
Tephra bed Sites where identifi ed
Typical glass SiO2 (wt%, normalized)
Thickness (cm) Color in outcrop Particle size Notes
BB1 C, E ~55–~59 0.1–0.2 gray silt to fi ne sand Contain brown glass with few microcrysts.
CC C ~57.7–~59 0.1 black silt to fi ne sand Contain microcryst-rich brown glass.DD C,E,F ~70–71 0.7–0.8 pale gray to white silt to fi ne sand
DD1 C ~57.5 0.1 dark gray to black silt to fi ne sand Contain microcryst-bearing brown glass.EE C,E,F ~71 ~0.4 white silt to medium sand,
fi nes upwardEE1 C ~55.5 0.1–0.2 dark gray to black silt to fi ne sand Relatively few microcrysts compared to
other mafi c tephras in this sequence.EE2 C ~73.9 0.1–0.2 white silt to medium sandEE3 E
E
predominantly ~70.8, minor mode
~73.8
0.1 white silt to medium sand
FF C, E ~70 0.2–0.3 gray silt to medium sand, fi nes upward
Somewhat discontinuous
FF1 bimodal: ~70 and ~72
0.1 gray to white predominantly silt to fi ne sand, some
medium sand
Discontinuous
GG C, E ~71 5 white to dark gray silt to very coarse sand Layers of varying color are conspicuous: 1 cm white base is overlain by alternating lighter and darker gray layers; upper part is coarser than the base.
GG1 C ~57 0.1 black silt to fi ne sand Microcrysts abundantHH C, E ~73.5 0.1–0.2 gray to white silt to very fi ne sandII C, E ~73 0.8–1 gray to white predominantly silt
to fi ne sand, some medium sand, fi nes upward
II1 C, F ~74.5 0.1 white DiscontinuousJJ C, E, F 58–75.5 1–1.5 black, white,
and dark gray to orange
silt to very coarse sand Bimodal in color and texture; layers with different colors are conspicuous.
JJ0.2 C, E ~74.5 0.2 at site C, 0.5–1 and diffuse at E
gray to white silt to fi ne sand Discontinuous
JJ0.4 C, E Same as KK 1 dark gray silt to very fi ne sand Diffuse boundariesJJ0.6 E Same as KK 1 dark gray silt to fi ne sand Diffuse boundariesJJ1 C bimodal: ~74 and
~75.50.1–0.3 gray to white silt to medium sand Sparse and discontinuous; occurs as spots
of tephra about 1–3 mm in diameter?KK C, E, F primarily 62–69 with
few data points as high as ~74
7–8 gray primarily silt to very coarse sand, graded bed, a few pumice
fragments exceed 4 mm
KK and KK1 together with fi ne, laminated sediments above KK form a distinctive and easily recognized set.
KK1 C, E, F 55–61 1 dark gray to black silt to medium sand Often consists of multiple ripple cross-bedded layers, each ~1 mm thick; glass is typically brown with a variable abundance of microcrysts.
LL C, F 66.2–71 3–3.5 gray to white silt to very fi ne sand, fi nes upward
LL1 C, F 60.7–64 0.5–1 gray to white silt to medium sand, fi nes upward
LL2 C ~76.5 0.1–0.2 gray to white silt to fi ne sandLL3? C 0.2 dark gray to black Dark, tephra-bearing silt suggests a third
bed above MM and MM1.MM C ~57 0.2–0.3 dark gray to black silt to very fi ne sand Contain microcryst-bearing brown glass;
Davis (1985) represented bed MM as a thick single bed. Our reexamination revealed a closely spaced dark gray to black pair of beds, which we designate as MM and MM1.
MM1 C ~53.3 0.1–0.2 dark gray to black silt- to fi ne sand Contain microcryst-bearing brown glass.NN C ~70 13 variable: yellowish
brown to orange to gray with a darker
base
primarily silt to very coarse sand, a few pumice fragments
exceed 4 mm
Present several centimeters below the surface of the Ana River. One of the thickest and coarsest beds in the sequence.
Note: Bed A is the uppermost bed found in lacustrine sediments, and bed NN is the lowermost bed observed in outcrop. See Tables S1, S2, and S3 (see text footnote 1) for more detailed stratigraphic information for sites C, E, and F, respectively.
BB C, E ~57–~60 0.1–0.4 black silt to fi ne sand Contain microcryst-rich, dark brown glass.
on April 8, 2012geosphere.gsapubs.orgDownloaded from
Kuehn and Negrini
404 Geosphere, August 2010
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
A -
pop
. 1E
VT-
A58
.99
1.73
14.6
08.
573.
816.
434.
091.
670.
101
1.24
WS
U
E1
58.7
8 (0
.69)
1.73
(0.
07)
15.2
4 (0
.29)
7.42
(0.
39)
3.03
(0.
16)
5.59
(0.
49)
0.16
(0.
05)
4.73
(0.
43)
3.18
(0.
46)
0.15
(0.
04)
101.
89 (
0.77
)U
A
Bed
A -
pop
. 2E
VT-
A75
.37
(0.9
7)0.
29 (
0.06
)13
.90
(0.3
6)1.
76 (
0.20
)0.
28 (
0.06
)1.
27 (
0.18
)3.
80 (
0.34
)3.
21 (
0.17
)0.
13 (
0.02
)10
4.63
(0.
84)
WS
U
E1
75.2
0 (0
.55)
0.29
(0.
06)
13.8
3 (0
.23)
1.97
(0.
24)
0.29
(0.
03)
1.25
(0.
15)
0.05
(0.
03)
3.78
(0.
15)
3.22
(0.
09)
0.12
(0.
03)
54.
05 (
0.53
)U
A
Bed
BE
VT-
B74
.85
(0.8
7)0.
31 (
0.05
)14
.07
(0.3
9)1.
80 (
0.16
)0.
31 (
0.06
)1.
37 (
0.18
)3.
99 (
0.26
)3.
16 (
0.14
)0.
13 (
0.02
)22
4.43
(1.
17)
WS
U
E2
74.6
3 (0
.72)
0.29
(0.
05)
14.1
8 (0
.29)
1.82
(0.
18)
0.29
(0.
06)
1.36
(0.
16)
0.06
(0.
03)
4.08
(0.
26)
3.17
(0.
11)
0.13
(0.
02)
183.
20 (
1.38
)U
A
DR
-574
.30.
3114
.21.
740.
231.
180.
044.
83.
10.
135.
9(1
)
Bed
B1
EV
T-B
175
.80
(0.5
7)0.
24 (
0.05
)13
.66
(0.2
3)1.
72 (
0.25
)0.
28 (
0.07
)1.
22 (
0.16
)3.
71 (
0.14
)3.
24 (
0.11
)0.
13 (
0.02
)7
5.22
(0.
49)
WS
U
E3
75.4
4 (0
.34)
0.25
(0.
05)
13.6
7 (0
.19)
1.67
(0.
11)
0.24
(0.
04)
1.19
(0.
12)
0.07
(0.
03)
4.01
(0.
29)
3.33
(0.
13)
0.13
(0.
04)
134.
17 (
1.10
)U
A
Maz
ama
Llao
Roc
k pu
mic
e75
.05
0.25
13.7
41.
590.
241.
144.
553.
290.
1532
(10)
Bed
B2
E4
71.8
4 (0
.87)
0.57
(0.
07)
15.0
6 (0
.43)
2.84
(0.
21)
0.49
(0.
13)
2.04
(0.
31)
0.06
(0.
03)
4.19
(0.
26)
2.80
(0.
20)
0.13
(0.
03)
191.
83 (
1.85
)U
A
Bed
CE
558
.07
(0.3
5)2.
05 (
0.09
)14
.38
(0.2
2)10
.83
(0.3
9)2.
89 (
0.17
)5.
98 (
0.16
)0.
19 (
0.03
)4.
11 (
0.25
)1.
46 (
0.07
)0.
05 (
0.02
)14
0.37
(0.
85)
UA
Bed
C1
- po
p. 1
E6
57.1
1 (0
.22)
1.63
(0.
10)
16.2
5 (0
.16)
9.01
(0.
17)
3.31
(0.
08)
6.78
(0.
15)
0.14
(0.
04)
4.56
(0.
15)
1.14
(0.
07)
0.07
(0.
02)
101.
19 (
0.46
)U
A
Bed
C1
- po
p. 2
E6
75.5
1 (0
.28)
0.22
(0.
04)
13.3
1 (0
.20)
1.62
(0.
07)
0.22
(0.
04)
1.16
(0.
06)
0.03
(0.
03)
4.58
(0.
16)
3.24
(0.
21)
0.13
(0.
02)
86.
22 (
1.39
)U
A
Bed
C2
- po
p. 1
E7
65.8
4 (0
.46)
1.29
(0.
06)
14.6
6 (0
.20)
5.97
(0.
21)
1.13
(0.
07)
3.34
(0.
16)
0.12
(0.
03)
5.00
(0.
19)
2.55
(0.
06)
0.10
(0.
03)
132.
02 (
1.14
)U
A
Bed
C2
- po
p. 2
E7
75.1
5 (0
.23)
0.22
(0.
04)
13.5
4 (0
.13)
1.61
(0.
12)
0.22
(0.
05)
1.08
(0.
06)
0.05
(0.
04)
4.62
(0.
19)
3.38
(0.
06)
0.12
(0.
02)
77.
12 (
0.94
)U
A
Bed
DE
876
.53
(0.2
9)0.
16 (
0.04
)13
.38
(0.1
8)1.
10 (
0.06
)0.
30 (
0.03
)1.
52 (
0.05
)0.
04 (
0.02
)4.
34 (
0.15
)2.
50 (
0.07
)0.
12 (
0.02
)24
7.41
(1.
46)
UA
DR
-676
.50.
2113
.91.
110.
261.
390.
034.
22.
30.
105.
7(1
)
Bed
18
C1B
76.1
2 (0
.24)
0.23
(0.
02)
13.3
7 (0
.08)
1.48
(0.
06)
0.23
(0.
03)
1.05
(0.
05)
4.09
(0.
15)
3.29
(0.
07)
0.13
(0.
03)
125.
15 (
0.84
)W
SU
E9
75.1
8 (1
.08)
0.24
(0.
06)
13.5
0 (0
.45)
1.60
(0.
27)
0.23
(0.
10)
1.16
(0.
30)
0.05
(0.
03)
4.61
(0.
19)
3.31
(0.
21)
0.12
(0.
03)
385.
53 (
1.38
)U
A
DR
-2, D
R-2
3, D
R-
58, D
R-9
975
.40.
2513
.71.
490.
201.
000.
044.
63.
20.
123.
4(1
)
Tule
lake
(7.
16–
7.23
m)
75.6
(0.
2)0.
23 (
0.01
)13
.6 (
0.1)
1.42
(0.
04)
0.21
(0.
01)
1.02
(0.
03)
0.05
(0.
01)
4.5
(0.
1)3.
32 (
0.06
)4.
8 (
1.0)
(4)
Bed
EE
1075
.48
(0.3
8)0.
22 (
0.04
)13
.50
(0.1
8)1.
51 (
0.11
)0.
21 (
0.04
)1.
09 (
0.10
)0.
03 (
0.02
)4.
47 (
0.12
)3.
37 (
0.11
)0.
11 (
0.02
)35
6.13
(0.
96)
UA
DR
-3, D
R-8
375
.30.
2513
.71.
470.
180.
980.
044.
63.
30.
125.
0(1
)
Bed
E1
C2
77.3
3 (0
.20)
0.17
(0.
02)
12.8
7 (0
.12)
1.14
(0.
02)
0.14
(0.
02)
0.80
(0.
02)
3.76
(0.
14)
3.67
(0.
11)
0.11
(0.
04)
105.
89 (
0.57
)W
SU
E11
76.7
6 (0
.23)
0.16
(0.
03)
13.1
8 (0
.13)
1.21
(0.
06)
0.15
(0.
03)
0.83
(0.
02)
0.05
(0.
03)
3.90
(0.
17)
3.66
(0.
07)
0.12
(0.
02)
257.
22 (
1.00
)U
A
DR
-82
76.6
0.18
13.1
1.17
0.14
0.75
0.05
4.2
3.6
0.12
3.6
(1)
Tule
lake
T24
38
(9.3
4 m
)76
.90.
2013
.01.
200.
170.
800.
044.
23.
525.
41(4
)
Bed
FC
475
.07
(0.2
0)0.
29 (
0.02
)13
.77
(0.1
2)1.
87 (
0.04
)0.
28 (
0.03
)1.
30 (
0.04
)4.
14 (
0.11
)3.
16 (
0.07
)0.
12 (
0.02
)12
4.15
(0.
97)
WS
U
E14
, E15
74.6
0 (0
.80)
0.26
(0.
06)
13.7
2 (0
.32)
1.87
(0.
27)
0.28
(0.
05)
1.33
(0.
15)
0.06
(0.
03)
4.57
(0.
19)
3.20
(0.
12)
0.11
(0.
02)
624.
75 (
1.28
)U
A
(con
tinue
d)
on April 8, 2012geosphere.gsapubs.orgDownloaded from
250,000-year tephra record from Summer Lake
Geosphere, August 2010 405
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE (
cont
inue
d)
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
F (
cont
.)F
274
.61
(1.0
1)0.
28 (
0.07
)13
.74
(0.3
5)2.
03 (
0.33
)0.
31 (
0.07
)1.
45 (
0.22
)0.
06 (
0.03
)4.
22 (
0.34
)3.
19 (
0.15
)0.
11 (
0.02
)32
4.36
(1.
78)
UA
Teph
ra 9
879C
at
New
berr
y V
olca
no74
.71
(0.6
8)0.
30 (
0.05
)13
.97
(0.3
4)1.
89 (
0.24
)0.
31 (
0.07
)1.
36 (
0.18
)4.
26 (
0.19
)3.
09 (
0.13
)0.
11 (
0.02
)10
2(8
)
Bed
F1
E17
74.4
2 (0
.37)
0.26
(0.
03)
14.0
9 (0
.21)
1.89
(0.
07)
0.31
(0.
04)
1.46
(0.
06)
0.06
(0.
02)
4.22
(0.
25)
3.19
(0.
08)
0.10
(0.
02)
337.
26 (
1.70
)U
A
F2.
574
.86
(0.7
9)0.
30 (
0.08
)13
.69
(0.2
4)2.
02 (
0.32
)0.
30 (
0.08
)1.
40 (
0.17
)0.
07 (
0.03
)4.
07 (
0.35
)3.
18 (
0.13
)0.
12 (
0.02
)26
4.25
(1.
41)
UA
Bed
GC
578
.05
(0.1
3)0.
09 (
0.01
)12
.85
(0.0
9)0.
94 (
0.04
)0.
11 (
0.01
)0.
79 (
0.02
)3.
71 (
0.07
)3.
36 (
0.05
)0.
10 (
0.01
)10
5.88
(0.
32)
WS
U
E18
, E19
, E20
77.3
7 (0
.27)
0.09
(0.
04)
13.1
8 (0
.14)
0.94
(0.
06)
0.11
(0.
03)
0.84
(0.
04)
0.04
(0.
03)
3.85
(0.
14)
3.48
(0.
12)
0.10
(0.
02)
787.
11 (
0.90
)U
A
F3
78.0
8 (0
.30)
0.09
(0.
04)
12.8
7 (0
.11)
0.88
(0.
09)
0.10
(0.
03)
0.81
(0.
05)
0.05
(0.
03)
3.65
(0.
18)
3.39
(0.
08)
0.10
(0.
02)
225.
11 (
0.75
)U
A
DR
-4, D
R-8
177
.10.
1013
.30.
930.
100.
750.
044.
23.
40.
095.
3(1
)
Teph
ra 9
715K
at
New
berr
y V
olca
no77
.90
(0.1
5)0.
09 (
0.02
)12
.89
(0.1
0)0.
93 (
0.07
)0.
13 (
0.02
)0.
78 (
0.03
)3.
83 (
0.13
)3.
38 (
0.10
)0.
08 (
0.02
)43
(8)
Bed
G1
F6
58.8
2 (2
.28)
1.82
(0.
27)
14.1
1 (0
.27)
9.85
(1.
27)
3.07
(0.
57)
5.93
(0.
66)
0.17
(0.
04)
4.37
(0.
47)
1.77
(0.
36)
0.09
(0.
02)
141.
93 (
0.78
)U
A
Bed
12
E21
, E22
, E23
77.1
2 (0
.32)
0.10
(0.
04)
13.6
5 (0
.22)
0.94
(0.
08)
0.22
(0.
03)
1.59
(0.
11)
0.03
(0.
03)
3.74
(0.
19)
2.56
(0.
15)
0.06
(0.
02)
575.
30 (
1.04
)U
A
GS
-54S
, DR
-94,
D
R-9
876
.60.
1014
.00.
890.
241.
500.
044.
12.
40.
104.
4(1
)
GS
-54M
77.5
0.13
14.3
1.10
0.34
1.67
0.03
2.6
2.2
0.06
5.0
(1)
Bed
HC
866
.69
(0.2
6)0.
98 (
0.03
)15
.41
(0.0
8)4.
98 (
0.12
)1.
53 (
0.05
)4.
07 (
0.15
)4.
15 (
0.10
)2.
07 (
0.04
)0.
11 (
0.04
)13
2.49
(1.
69)
WS
U
E24
66.1
5 (0
.67)
0.93
(0.
07)
15.5
5 (0
.19)
5.13
(0.
24)
1.38
(0.
14)
4.08
(0.
29)
0.07
(0.
03)
4.52
(0.
18)
2.08
(0.
10)
0.10
(0.
02)
230.
84 (
1.16
)U
A
F7
66.5
0 (0
.51)
0.95
(0.
06)
15.2
7 (0
.27)
5.14
(0.
25)
1.42
(0.
09)
4.10
(0.
24)
0.08
(0.
04)
4.31
(0.
15)
2.10
(0.
11)
0.11
(0.
03)
282.
03 (
1.31
)U
A
GS
-55
66.5
1.01
15.6
4.97
1.46
3.88
0.07
4.5
1.9
0.11
-1.2
(1)
Bed
H0.
2C
9, C
1070
.12
(0.5
0)0.
80 (
0.04
)14
.96
(0.2
9)3.
46 (
0.08
)0.
89 (
0.11
)2.
53 (
0.25
)4.
31 (
0.17
)2.
77 (
0.17
)0.
15 (
0.04
)14
2.13
(0.
65)
WS
U
E24
.569
.76
(0.4
6)0.
70 (
0.06
)15
.11
(0.2
2)3.
43 (
0.27
)0.
84 (
0.09
)2.
62 (
0.15
)0.
07 (
0.04
)4.
58 (
0.11
)2.
74 (
0.10
)0.
16 (
0.03
)21
1.74
(1.
28)
UA
Bed
8E
2670
.17
(0.5
9)0.
64 (
0.07
)15
.16
(0.3
0)3.
04 (
0.14
)0.
75 (
0.08
)2.
59 (
0.20
)0.
05 (
0.03
)4.
60 (
0.25
)2.
83 (
0.14
)0.
17 (
0.06
)19
5.98
(6.
50)
UA
GS
-56
70.5
0.62
15.1
2.82
0.73
2.43
0.04
4.9
2.7
0.15
0.4
(1)
DR
-97
69.9
0.69
15.5
3.14
0.33
2.64
0.06
4.9
2.6
0.17
1.9
(1)
Bed
6E
2772
.98
(0.4
1)0.
46 (
0.04
)14
.40
(0.2
7)2.
25 (
0.10
)0.
46 (
0.07
)1.
82 (
0.13
)0.
05 (
0.03
)4.
32 (
0.12
)3.
13 (
0.13
)0.
14 (
0.03
)18
3.64
(1.
13)
UA
F9
73.1
1 (0
.62)
0.47
(0.
05)
14.3
4 (0
.30)
2.26
(0.
15)
0.46
(0.
07)
1.84
(0.
17)
0.05
(0.
03)
4.15
(0.
19)
3.17
(0.
16)
0.15
(0.
03)
254.
09 (
1.90
)U
A
GS
-57
72.4
0.49
14.7
2.23
0.49
1.77
0.03
4.7
3.0
0.14
1.8
(1)
Bed
4E
2872
.50
(0.4
6)0.
47 (
0.04
)14
.50
(0.2
3)2.
38 (
0.09
)0.
50 (
0.04
)1.
96 (
0.12
)0.
05 (
0.03
)4.
39 (
0.22
)3.
12 (
0.09
)0.
14 (
0.03
)20
4.11
(1.
40)
UA
GS
-58
72.6
0.46
14.6
2.18
0.46
1.73
0.02
4.7
3.0
0.14
2.14
(1)
Tule
lake
T23
82
(16.
99 m
)72
.40.
4714
.52.
370.
491.
730.
054.
63.
323.
6(4
)
Bed
H0.
4E
2959
.38
(0.7
7)1.
73 (
0.25
)14
.49
(0.6
1)8.
59 (
0.97
)3.
17 (
0.52
)6.
18 (
1.00
)0.
14 (
0.03
)4.
50 (
0.77
)1.
71 (
0.45
)0.
10 (
0.03
)12
1.20
(1.
17)
UA
F10
58.9
6 (1
.16)
1.68
(0.
16)
14.7
9 (0
.72)
8.44
(0.
32)
3.27
(0.
73)
6.45
(0.
52)
0.14
(0.
02)
4.42
(0.
56)
1.75
(0.
21)
0.10
(0.
05)
71.
62 (
2.14
)U
A
Bed
2E
30, E
31, E
3273
.95
(0.2
4)0.
32 (
0.05
)14
.27
(0.1
4)2.
24 (
0.09
)0.
27 (
0.04
)1.
13 (
0.06
)0.
07 (
0.03
)4.
14 (
0.24
)3.
52 (
0.12
)0.
10 (
0.03
)68
4.82
(1.
40)
UA
GS
-59
73.0
0.33
14.6
2.20
0.26
1.07
0.04
5.0
3.4
0.08
2.14
(1)
(con
tinue
d)
on April 8, 2012geosphere.gsapubs.orgDownloaded from
Kuehn and Negrini
406 Geosphere, August 2010
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE (
cont
inue
d)
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
2 (
cont
.)N
ewbe
rry
- Ic
e Q
uarr
y73
.93
(0.2
9)0.
30 (
0.04
)14
.32
(0.1
4)2.
09 (
0.12
)0.
29 (
0.03
)1.
10 (
0.06
)4.
25 (
0.24
)3.
59 (
0.09
)0.
12 (
0.03
)15
45.
86 (
2.10
)(8
)
Bed
H1
C11
57.0
0 (0
.84)
1.79
(0.
11)
14.9
6 (0
.69)
10.0
7 (0
.39)
4.11
(0.
57)
7.12
(0.
39)
3.79
(0.
20)
1.08
(0.
19)
0.08
(0.
02)
92.
49 (
1.70
)W
SU
E35
56.0
8 (0
.77)
1.56
(0.
12)
15.1
5 (0
.38)
10.2
5 (0
.51)
4.30
(0.
48)
7.14
(0.
64)
0.18
(0.
05)
4.21
(0.
52)
1.07
(0.
23)
0.06
(0.
03)
252.
24 (
1.96
)U
A
Bed
H2
C12
55.0
2 (1
.09)
2.27
(0.
32)
14.7
8 (0
.80)
10.3
4 (0
.55)
4.46
(0.
55)
8.10
(0.
59)
3.93
(0.
24)
1.05
(0.
11)
0.06
(0.
02)
92.
50 (
0.50
)W
SU
E36
54.8
1 (0
.45)
2.29
(0.
12)
14.2
9 (0
.31)
11.0
1 (0
.46)
3.98
(0.
27)
7.99
(0.
21)
0.20
(0.
04)
4.14
(0.
52)
1.27
(0.
31)
0.03
(0.
02)
172.
56 (
1.26
)U
A
Bed
H3
C13
57.7
1 (0
.71)
1.63
(0.
15)
15.3
8 (0
.80)
8.93
(0.
50)
3.99
(0.
51)
7.03
(0.
36)
4.08
(0.
16)
1.17
(0.
11)
0.08
(0.
02)
102.
54 (
1.78
)W
SU
Bed
IC
1477
.18
(0.3
9)0.
09 (
0.02
)13
.76
(0.2
0)0.
87 (
0.03
)0.
25 (
0.04
)1.
53 (
0.06
)3.
79 (
0.27
)2.
44 (
0.10
)0.
08 (
0.01
)10
6.02
(0.
75)
WS
U
E37
77.3
1 (0
.19)
0.10
(0.
03)
13.6
3 (0
.09)
0.95
(0.
08)
0.22
(0.
02)
1.53
(0.
09)
0.05
(0.
02)
3.62
(0.
24)
2.52
(0.
10)
0.07
(0.
02)
157.
93 (
0.99
)U
A
F11
77.6
4 (0
.44)
0.11
(0.
05)
13.4
9 (0
.31)
0.94
(0.
08)
0.22
(0.
04)
1.46
(0.
12)
0.03
(0.
03)
3.62
(0.
14)
2.43
(0.
13)
0.05
(0.
02)
214.
92 (
0.52
)U
A
Car
p A
sh-8
(T
281-
3)76
.57
(0.6
8)0.
10 (
0.03
)14
.18
(0.1
6)0.
90 (
0.08
)0.
23 (
0.02
)1.
52 (
0.05
)0.
04 (
0.02
)3.
96 (
0.08
)2.
49 (
0.05
)13
8.22
(0.
86)
(7)
Car
p A
sh-9
(T
281-
5)77
.13
(0.8
1)0.
11 (
0.04
)13
.74
(0.5
8)0.
84 (
0.10
)0.
18 (
0.05
)1.
58 (
0.21
)0.
03 (
0.03
)3.
85 (
0.21
)2.
53 (
0.20
)13
6.72
(0.
72)
(7)
EM
SH
(K
P-1
D)
77.0
70.
1213
.71
0.95
0.28
1.70
3.69
2.42
0.06
15(3
)
EM
SH
(W
A-5
D)
77.8
10.
1113
.93
1.06
0.30
1.77
2.57
2.36
0.10
31(3
)
Car
p A
sh-1
0 (T
279-
5)75
.53
(0.7
0)0.
12 (
0.01
)14
.40
(0.0
7)1.
08 (
0.06
)0.
38 (
0.05
)1.
81 (
0.04
)0.
04 (
0.03
)4.
40 (
0.15
)2.
24 (
0.09
)6
6.92
(0.
83)
(7)
Car
p A
sh-1
0
(T25
5-3
CL-
90A
2)75
.48
(0.6
8)0.
13 (
0.05
)14
.53
(0.1
7)1.
16 (
0.07
)0.
35 (
0.04
)1.
84 (
0.04
)0.
06 (
0.03
)4.
20 (
0.16
)2.
25 (
0.05
)16
7.28
(7)
Car
p A
sh-1
0
(T25
5-3
CL-
90A
1)75
.70
(0.6
8)0.
11 (
0.04
)14
.54
(0.1
7)1.
09 (
0.07
)0.
24 (
0.03
)1.
82 (
0.04
)0.
05 (
0.02
)4.
15 (
0.12
)2.
30 (
0.05
)10
7.47
(7)
Pal
ouse
WA
5-1
9 (T
127-
3)76
.29
0.12
13.6
51.
130.
361.
910.
064.
272.
215
6.46
(7)
WA
-5C
77.8
00.
1514
.00
1.21
0.34
1.74
2.80
1.87
160.
14(3
)
Bed
I1E
3853
.31
(0.3
2)2.
64 (
0.27
)14
.28
(0.8
2)12
.70
(0.9
0)3.
66 (
0.33
)7.
63 (
0.30
)0.
22 (
0.05
)4.
39 (
0.21
)1.
09 (
0.15
)0.
06 (
0.02
)17
1.77
(0.
74)
UA
Bed
JC
15B
72.8
7 (1
.45)
0.43
(0.
08)
14.4
4 (0
.54)
2.27
(0.
32)
0.64
(0.
14)
2.37
(0.
36)
4.40
(0.
18)
2.39
(0.
08)
0.19
(0.
02)
113.
57 (
1.60
)U
A
E39
74.8
2 (1
.83)
0.35
(0.
10)
13.7
7 (0
.76)
1.98
(0.
41)
0.46
(0.
16)
2.06
(0.
46)
0.05
(0.
03)
3.85
(0.
26)
2.49
(0.
18)
0.17
(0.
03)
195.
04 (
1.40
)U
A
F12
74.4
9 (1
.65)
0.36
(0.
08)
13.9
2 (0
.70)
2.03
(0.
31)
0.44
(0.
13)
2.14
(0.
40)
0.05
(0.
03)
3.93
(0.
22)
2.44
(0.
11)
0.18
(0.
02)
125.
02 (
1.02
)U
A
Bed
J1
- po
p. 1
F13
57.2
5 (0
.86)
1.50
(0.
17)
14.5
9 (0
.47)
9.71
(0.
55)
3.50
(0.
40)
7.64
(0.
17)
0.18
(0.
04)
4.44
(0.
44)
1.09
(0.
06)
0.10
(0.
02)
60.
36 (
1.49
)U
A
Bed
J1
- po
p. 2
F13
63.9
6 (1
.18)
1.18
(0.
13)
15.3
6 (0
.48)
6.26
(0.
44)
1.82
(0.
31)
4.71
(0.
48)
0.09
(0.
04)
4.60
(0.
24)
1.92
(0.
30)
0.10
(0.
03)
71.
25 (
1.52
)U
A
Bed
J2
- po
p. 1
F14
57.0
2 (1
.05)
1.60
(0.
06)
14.8
6 (0
.67)
10.0
8 (0
.26)
3.57
(0.
53)
7.15
(0.
50)
0.18
(0.
03)
4.23
(0.
45)
1.20
(0.
12)
0.12
(0.
02)
81.
36 (
0.98
)U
A
Bed
J2
- po
p. 2
F14
63.7
51.
2814
.66.
761.
594.
460.
085.
162.
270.
042
1.4
UA
Bed
J3
C16
54.0
7 (0
.57)
2.16
(0.
13)
14.8
7 (0
.41)
10.0
5 (0
.45)
4.72
(0.
27)
8.23
(0.
35)
4.09
(0.
25)
1.72
(0.
12)
0.08
(0.
01)
113.
34 (
0.72
)W
SU
E40
54.7
9 (1
.78)
2.14
(0.
15)
14.5
6 (0
.38)
10.1
1 (0
.41)
4.02
(0.
71)
7.72
(0.
89)
0.16
(0.
04)
4.48
(0.
47)
1.92
(0.
50)
0.09
(0.
02)
71.
95 (
0.94
)U
A
F15
55.1
6 (1
.24)
2.09
(0.
11)
14.4
5 (0
.34)
10.3
7 (0
.68)
3.88
(0.
44)
7.41
(0.
81)
0.18
(0.
04)
4.31
(0.
45)
2.07
(0.
51)
0.09
(0.
02)
222.
44 (
1.22
)U
A
Bed
KC
1769
.79
(0.7
8)0.
79 (
0.04
)15
.11
(0.4
9)3.
48 (
0.14
)0.
95 (
0.12
)2.
75 (
0.32
)4.
34 (
0.18
)2.
65 (
0.16
)0.
13 (
0.01
)12
2.25
(1.
51)
WS
U
E42
N, E
42S
70.5
7 (1
.01)
0.75
(0.
07)
14.8
1 (0
.52)
3.47
(0.
25)
0.77
(0.
17)
2.69
(0.
33)
0.06
(0.
03)
4.03
(0.
32)
2.73
(0.
17)
0.12
(0.
03)
232.
72 (
1.33
)U
A
(con
tinue
d)
on April 8, 2012geosphere.gsapubs.orgDownloaded from
250,000-year tephra record from Summer Lake
Geosphere, August 2010 407
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE (
cont
inue
d)
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
K (
cont
.)F
1770
.57
(1.4
1)0.
76 (
0.09
)14
.49
(0.6
1)3.
62 (
0.30
)0.
81 (
0.21
)2.
63 (
0.46
)0.
07 (
0.03
)4.
11 (
0.31
)2.
82 (
0.23
)0.
12 (
0.02
)15
3.02
(1.
79)
UA
GS
-70
70.7
0.81
15.0
3.71
0.83
2.40
0.05
3.5
2.8
0.14
3.3
(1)
Bed
L -
pop
. 1C
18, C
1958
.78
(0.8
6)1.
58 (
0.08
)14
.81
(0.4
9)8.
56 (
0.28
)3.
97 (
0.63
)6.
25 (
0.71
)4.
14 (
0.32
)1.
81 (
0.40
)0.
10 (
0.03
)14
2.53
(0.
92)
WS
U
Bed
L -
pop
. 2C
18, C
1962
.15
(0.5
5)1.
47 (
0.06
)14
.90
(0.5
1)7.
00 (
0.14
)2.
64 (
0.39
)4.
73 (
0.19
)4.
50 (
0.09
)2.
50 (
0.13
)0.
12 (
0.02
)5
2.41
(0.
76)
WS
U
E41
62.2
3 (0
.34)
1.49
(0.
10)
14.4
5 (0
.56)
7.27
(0.
72)
2.30
(0.
61)
4.64
(0.
32)
0.13
(0.
05)
5.23
(1.
25)
2.14
(0.
68)
0.12
(0.
03)
61.
99 (
0.94
)U
A
F18
62.1
2 (0
.79)
1.44
(0.
05)
14.6
4 (0
.41)
7.33
(0.
29)
2.06
(0.
23)
4.87
(0.
29)
0.10
(0.
03)
4.69
(0.
35)
2.63
(0.
46)
0.12
(0.
03)
124.
52 (
1.87
)U
A
Bed
L1
- po
p. 1
C20
59.3
0 (0
.27)
1.60
(0.
11)
14.6
4 (0
.22)
8.64
(0.
20)
3.42
(0.
13)
6.90
(0.
20)
0.19
(0.
04)
3.50
(0.
13)
1.74
(0.
26)
0.06
(0.
02)
40.
77 (
0.49
)U
A
Bed
L1
- po
p. 2
C20
61.4
6 (0
.64)
1.45
(0.
11)
14.8
0 (0
.62)
7.56
(0.
39)
2.56
(0.
24)
6.03
(0.
40)
0.17
(0.
05)
4.11
(0.
27)
1.82
(0.
10)
0.05
(0.
01)
62.
59 (
1.84
)U
A
Bed
ME
4371
.29
(0.3
3)0.
48 (
0.05
)14
.84
(0.1
1)3.
26 (
0.11
)0.
51 (
0.05
)1.
77 (
0.09
)0.
09 (
0.03
)4.
55 (
0.26
)3.
11 (
0.11
)0.
10 (
0.02
)22
4.94
(1.
26)
UA
SK
37-2
(W
L co
re)
71.2
4 (0
.13)
0.50
(0.
03)
15.0
5 (0
.11)
3.13
(0.
05)
0.53
(0.
03)
1.76
(0.
02)
0.00
(0.
00)
4.63
(0.
18)
3.07
(0.
04)
0.10
(0.
02)
75.
11 (
0.93
)W
SU
GS
-78
70.1
0.49
15.1
3.22
0.50
1.68
0.07
5.4
3.3
0.11
3.0
(1)
Bed
NE
4471
.47
(0.2
9)0.
48 (
0.03
)14
.91
(0.1
2)3.
27 (
0.10
)0.
51 (
0.03
)1.
83 (
0.06
)0.
11 (
0.03
)4.
26 (
0.26
)3.
06 (
0.09
)0.
10 (
0.04
)24
5.02
(2.
78)
UA
SK
37-3
, SK
37-6
(W
L co
re)
71.0
9 (0
.19)
0.50
(0.
02)
15.0
9 (0
.13)
3.14
(0.
06)
0.52
(0.
03)
1.73
(0.
03)
0.00
(0.
00)
4.76
(0.
17)
3.06
(0.
03)
0.11
(0.
01)
154.
20 (
1.63
)W
SU
DR
-16,
GS
-79
70.3
0.50
14.9
3.28
0.50
1.64
0.09
5.5
3.1
0.11
3.2
(1)
Bed
N1
F21
A, F
21B
71.3
6 (0
.39)
0.48
(0.
04)
14.8
1 (0
.13)
3.33
(0.
10)
0.51
(0.
04)
1.80
(0.
07)
0.10
(0.
03)
4.38
(0.
28)
3.12
(0.
12)
0.11
(0.
03)
425.
58 (
1.55
)U
A
RC
-25
70.6
0.49
15.2
3.26
0.52
1.67
0.09
5.1
3.0
0.12
1.8
(1)
New
berr
y -
9912
D70
.72
(0.3
3)0.
52 (
0.03
)15
.13
(0.1
9)3.
22 (
0.22
)0.
55 (
0.04
)1.
74 (
0.07
)4.
93 (
0.27
)3.
08 (
0.08
)0.
11 (
0.02
)57
2.78
(2.
33)
WS
U
Bed
N2
C21
58.1
3 (0
.63)
2.08
(0.
10)
14.0
7 (0
.46)
10.5
8 (0
.43)
3.52
(0.
76)
6.14
(0.
40)
3.83
(0.
30)
1.60
(0.
11)
0.05
(0.
01)
102.
97 (
1.12
)W
SU
Bed
OC
2271
.00
(0.8
4)0.
58 (
0.12
)14
.96
(0.1
2)2.
87 (
0.14
)0.
76 (
0.22
)2.
50 (
0.60
)4.
29 (
0.13
)2.
88 (
0.26
)0.
15 (
0.03
)12
3.97
(1.
87)
WS
U
E45
71.0
8 (0
.58)
0.60
(0.
05)
14.8
0 (0
.19)
2.98
(0.
19)
0.74
(0.
11)
2.75
(0.
15)
0.05
(0.
03)
3.99
(0.
26)
2.84
(0.
10)
0.16
(0.
05)
244.
97 (
4.50
)U
A
F22
71.0
4 (0
.65)
0.60
(0.
09)
14.5
5 (0
.26)
3.12
(0.
20)
0.73
(0.
14)
2.72
(0.
40)
0.05
(0.
02)
4.15
(0.
20)
2.89
(0.
18)
0.15
(0.
03)
194.
11 (
1.90
)U
A
DR
-18
70.7
0.60
14.9
3.00
0.81
2.67
0.04
4.4
2.8
0.14
2.7
(1)
Bed
PC
2372
.57
(0.1
4)0.
32 (
0.02
)14
.65
(0.0
8)2.
71 (
0.04
)0.
35 (
0.03
)1.
22 (
0.05
)4.
65 (
0.16
)3.
41 (
0.03
)0.
11 (
0.01
)11
4.17
(1.
02)
WS
U
E46
72.9
9 (0
.33)
0.32
(0.
05)
14.4
4 (0
.10)
2.70
(0.
18)
0.30
(0.
07)
1.26
(0.
07)
0.09
(0.
03)
4.29
(0.
18)
3.51
(0.
19)
0.11
(0.
03)
214.
75 (
0.91
)U
A
F23
73.0
9 (0
.24)
0.33
(0.
04)
14.3
2 (0
.13)
2.78
(0.
10)
0.31
(0.
05)
1.26
(0.
05)
0.08
(0.
03)
4.28
(0.
16)
3.44
(0.
07)
0.11
(0.
03)
254.
35 (
0.56
)U
A
DR
-19
71.9
0.34
14.5
2.82
0.33
1.15
0.07
5.3
3.5
0.11
3.6
(1)
Bed
QC
2472
.87
(0.2
5)0.
33 (
0.02
)14
.45
(0.1
0)2.
66 (
0.07
)0.
30 (
0.05
)1.
20 (
0.04
)4.
56 (
0.14
)3.
53 (
0.08
)0.
11 (
0.03
)10
5.25
(1.
65)
WS
U
F24
72.2
2 (0
.26)
0.31
(0.
03)
14.3
0 (0
.17)
2.74
(0.
08)
0.30
(0.
03)
1.25
(0.
05)
0.07
(0.
03)
5.13
(0.
12)
3.55
(0.
08)
0.11
(0.
03)
145.
05 (
1.49
)U
A
DR
-20
72.1
0.33
14.4
2.80
0.32
1.15
0.07
5.2
3.5
0.11
4.2
(1)
New
berr
y -
9920
C73
.04
(0.1
4)0.
31 (
0.03
)14
.37
(0.0
7)2.
60 (
0.07
)0.
32 (
0.03
)1.
15 (
0.04
)4.
56 (
0.15
)3.
52 (
0.07
)0.
12 (
0.02
)20
4.57
(2.
88)
WS
U
Bed
RC
2574
.01
(0.4
1)0.
22 (
0.01
)14
.13
(0.3
0)2.
05 (
0.14
)0.
12 (
0.02
)0.
79 (
0.07
)4.
71 (
0.33
)3.
86 (
0.19
)0.
12 (
0.01
)10
4.99
(0.
89)
WS
U
E47
74.6
6 (0
.22)
0.20
(0.
03)
13.9
4 (0
.10)
2.14
(0.
12)
0.13
(0.
04)
0.82
(0.
05)
0.07
(0.
04)
4.09
(0.
15)
3.81
(0.
10)
0.13
(0.
02)
224.
20 (
0.70
)U
A
F25
74.4
4 (0
.37)
0.21
(0.
04)
13.9
7 (0
.14)
2.17
(0.
20)
0.13
(0.
04)
0.82
(0.
06)
0.07
(0.
02)
4.27
(0.
27)
3.81
(0.
11)
0.12
(0.
02)
244.
97 (
1.04
)U
A
DR
-21
73.6
0.24
14.0
2.12
0.12
0.68
0.06
5.1
3.9
0.12
3.7
(1)
(con
tinue
d)
on April 8, 2012geosphere.gsapubs.orgDownloaded from
Kuehn and Negrini
408 Geosphere, August 2010
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE (
cont
inue
d)
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
R1
C28
, C29
, C30
72.5
8 (1
.18)
0.54
(0.
06)
14.3
5 (0
.53)
2.57
(0.
28)
0.57
(0.
13)
1.96
(0.
30)
4.38
(0.
26)
2.91
(0.
24)
0.14
(0.
03)
365.
08 (
1.79
)W
SU
E48
71.9
7 (1
.33)
0.61
(0.
07)
14.4
1 (0
.68)
3.04
(0.
33)
0.56
(0.
08)
2.29
(0.
40)
0.06
(0.
03)
4.01
(0.
25)
2.91
(0.
19)
0.14
(0.
02)
113.
47 (
1.64
)U
A
F26
70.2
4 (1
.63)
0.66
(0.
09)
14.6
9 (0
.39)
3.49
(0.
61)
0.72
(0.
24)
2.61
(0.
54)
0.05
(0.
02)
4.70
(0.
19)
2.73
(0.
25)
0.11
(0.
02)
105.
11 (
2.33
)U
A
Bed
R2
- po
p. 1
E49
57.6
2 (0
.79)
1.61
(0.
16)
14.8
5 (0
.41)
8.90
(0.
27)
3.79
(0.
23)
7.27
(0.
26)
0.16
(0.
03)
4.39
(0.
31)
1.32
(0.
27)
0.09
(0.
03)
121.
65 (
2.65
)U
A
F27
58.9
81.
5314
.62
8.26
3.53
5.69
0.09
5.29
1.88
0.12
23.
85U
A
Bed
R2
- po
p. 2
C31
61.9
7 (0
.60)
1.60
(0.
17)
14.3
6 (0
.15)
7.61
(0.
21)
2.32
(0.
35)
4.96
(0.
45)
0.15
(0.
00)
4.54
(0.
09)
2.36
(0.
18)
0.13
(0.
03)
40.
05 (
0.52
)U
A
E49
62.3
01.
6614
.32
7.63
2.20
4.66
0.13
4.70
2.25
0.15
3
3.08
UA
F27
62.0
8 (0
.57)
1.64
(0.
10)
14.5
5 (0
.42)
7.48
(0.
23)
2.24
(0.
23)
4.95
(0.
54)
0.10
(0.
03)
4.50
(0.
18)
2.33
(0.
39)
0.12
(0.
02)
133.
20 (
2.83
)U
A
Bed
R3
C33
63.1
8 (0
.90)
1.64
(0.
04)
15.2
5 (0
.39)
5.28
(0.
22)
2.05
(0.
24)
3.87
(0.
45)
4.40
(0.
22)
4.19
(0.
32)
0.14
(0.
02)
75.
29 (
0.89
)W
SU
E50
62.7
1 (0
.76)
1.66
(0.
08)
15.2
8 (0
.32)
5.61
(0.
39)
2.07
(0.
21)
4.02
(0.
37)
0.12
(0.
03)
4.57
(0.
28)
3.81
(0.
32)
0.14
(0.
04)
103.
03 (
1.79
)U
A
Bed
SC
3474
.75
(0.4
9)0.
20 (
0.02
)13
.82
(0.2
2)1.
79 (
0.13
)0.
14 (
0.02
)0.
67 (
0.07
)4.
61 (
0.14
)3.
89 (
0.08
)0.
14 (
0.02
)9
6.05
(0.
83)
WS
U
E51
75.4
5 (0
.30)
0.19
(0.
04)
13.5
8 (0
.13)
1.76
(0.
07)
0.13
(0.
02)
0.66
(0.
04)
0.06
(0.
03)
4.16
(0.
17)
3.88
(0.
08)
0.13
(0.
02)
193.
68 (
0.53
)U
A
F28
74.7
2 (0
.31)
0.19
(0.
05)
13.5
2 (0
.20)
1.82
(0.
08)
0.11
(0.
02)
0.64
(0.
03)
0.05
(0.
02)
4.77
(0.
19)
4.03
(0.
12)
0.15
(0.
03)
185.
22 (
0.50
)U
A
DR
-22
74.4
0.19
13.6
1.86
0.14
0.61
0.05
5.0
4.0
0.12
3.6
(1)
984F
75.4
4 (0
.22)
0.18
(0.
02)
13.7
6 (0
.11)
1.72
(0.
05)
0.14
(0.
01)
0.63
(0.
02)
4.10
(0.
23)
3.91
(0.
06)
0.12
(0.
02)
524.
35 (
0.67
)(8
)
Bed
TC
35B
75.2
5 (0
.19)
0.18
(0.
02)
13.5
6 (0
.12)
1.66
(0.
02)
0.13
(0.
02)
0.59
(0.
02)
4.35
(0.
09)
4.11
(0.
22)
0.16
(0.
01)
105.
98 (
0.60
)W
SU
E52
B75
.57
(0.2
4)0.
18 (
0.04
)13
.45
(0.1
0)1.
74 (
0.08
)0.
13 (
0.01
)0.
63 (
0.03
)0.
05 (
0.03
)4.
13 (
0.18
)3.
99 (
0.29
)0.
14 (
0.03
)20
4.27
(0.
93)
UA
F29
A, F
29B
74.9
3 (0
.30)
0.18
(0.
03)
13.3
8 (0
.18)
1.74
(0.
07)
0.12
(0.
03)
0.62
(0.
03)
0.05
(0.
03)
4.83
(0.
14)
4.03
(0.
12)
0.13
(0.
03)
235.
60 (
0.91
)U
A
DR
-23,
DR
-24
74.8
0.18
13.5
1.68
0.12
0.52
0.06
4.9
4.1
0.13
4.0
(1)
984G
575
.47
(0.1
7)0.
16 (
0.02
)13
.59
(0.1
1)1.
53 (
0.04
)0.
12 (
0.01
)0.
53 (
0.02
)4.
48 (
0.13
)3.
99 (
0.05
)0.
13 (
0.02
)36
(8)
Bed
T0.
5F
3074
.83
(0.2
2)0.
17 (
0.04
)13
.41
(0.1
6)1.
71 (
0.08
)0.
12 (
0.03
)0.
59 (
0.03
)0.
08 (
0.03
)4.
75 (
0.19
)4.
22 (
0.21
)0.
13 (
0.02
)16
6.41
(1.
27)
UA
Bed
T1
C36
75.6
2 (0
.16)
0.16
(0.
02)
13.4
9 (0
.06)
1.57
(0.
05)
0.12
(0.
02)
0.55
(0.
01)
4.25
(0.
10)
4.09
(0.
07)
0.14
(0.
01)
106.
58 (
0.54
)W
SU
E53
75.8
6 (0
.21)
0.16
(0.
03)
13.3
4 (0
.10)
1.62
(0.
07)
0.10
(0.
02)
0.57
(0.
03)
0.07
(0.
04)
4.15
(0.
17)
4.00
(0.
13)
0.14
(0.
02)
184.
10 (
0.49
)U
A
F31
74.9
8 (0
.23)
0.16
(0.
04)
13.3
9 (0
.18)
1.65
(0.
08)
0.10
(0.
02)
0.57
(0.
03)
0.05
(0.
03)
4.76
(0.
19)
4.20
(0.
25)
0.13
(0.
03)
166.
10 (
1.09
)U
A
Bed
U -
pop
. 1F
N-C
U lo
wer
55.0
8 (0
.81)
1.40
(0.
16)
15.8
0 (0
.83)
8.98
(0.
54)
4.78
(0.
83)
8.48
(0.
59)
4.37
(0.
19)
1.03
(0.
12)
0.07
(0.
02)
112.
14 (
0.59
)W
SU
E55
53.8
3 (0
.94)
1.36
(0.
13)
15.5
8 (0
.63)
9.04
(0.
24)
5.48
(0.
46)
9.27
(0.
45)
0.15
(0.
06)
4.33
(0.
23)
0.89
(0.
16)
0.06
(0.
02)
60.
67 (
0.30
)U
A
Bed
U -
pop
. 2E
5556
.68
(0.4
5)1.
84 (
0.06
)14
.79
(1.0
8)10
.62
(0.3
6)3.
29 (
0.18
)7.
00 (
0.31
)0.
20 (
0.02
)4.
11 (
0.53
)1.
39 (
0.14
)0.
06 (
0.03
)6
2.69
(0.
98)
UA
Bed
VC
3773
.59
(0.3
0)0.
22 (
0.02
)14
.30
(0.1
9)2.
45 (
0.10
)0.
19 (
0.02
)1.
19 (
0.06
)4.
40 (
0.17
)3.
53 (
0.13
)0.
13 (
0.01
)10
5.85
(0.
82)
WS
U
E56
73.8
7 (0
.62)
0.23
(0.
05)
14.2
3 (0
.22)
2.61
(0.
21)
0.18
(0.
05)
1.30
(0.
14)
0.08
(0.
04)
4.08
(0.
18)
3.30
(0.
17)
0.12
(0.
02)
213.
81 (
0.74
)U
A
DR
-25
72.9
0.23
14.2
2.52
0.17
1.07
0.06
5.2
3.5
0.11
4.0
(1)
FN
-C V
74.4
3 (0
.20)
0.22
(0.
01)
14.3
4 (0
.10)
2.42
(0.
06)
0.17
(0.
02)
1.15
(0.
06)
3.71
(0.
20)
3.45
(0.
11)
0.12
(0.
02)
20(8
)
Tule
lake
T11
93
(32.
28 m
)73
.50.
2214
.32.
350.
151.
110.
074.
83.
486.
01(4
), (
5), (
6)
New
berr
y -
978D
74.1
3 (0
.44)
0.24
(0.
03)
14.0
9 (0
.18)
2.54
(0.
17)
0.17
(0.
04)
1.07
(0.
11)
4.51
(0.
42)
3.16
(0.
07)
0.08
(0.
03)
109
(8)
New
berr
y -
0004
F
(Qaf
3) p
umic
e73
.89
(0.4
6)0.
24 (
0.02
)13
.89
(0.1
5)2.
54 (
0.22
)0.
18 (
0.03
)1.
12 (
0.10
)4.
74 (
0.76
)3.
30 (
0.24
)0.
10 (
0.02
)33
(8)
New
berr
y -
0004
F
(Qaf
3) a
sh73
.34
(0.3
1)0.
25 (
0.02
)13
.92
(0.0
8)2.
61 (
0.11
)0.
17 (
0.03
)1.
11 (
0.09
)5.
20 (
0.18
)3.
30 (
0.11
)0.
10 (
0.01
)12
(8)
(con
tinue
d)
on April 8, 2012geosphere.gsapubs.orgDownloaded from
250,000-year tephra record from Summer Lake
Geosphere, August 2010 409
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE (
cont
inue
d)
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
WF
N-C
W1
77.7
0 (0
.42)
0.10
(0.
01)
13.4
4 (0
.37)
0.88
(0.
03)
0.23
(0.
04)
1.50
(0.
17)
3.45
(0.
17)
2.60
(0.
16)
0.09
(0.
02)
116.
52 (
1.45
)W
SU
C38
77.2
2 (0
.31)
0.09
(0.
02)
13.7
1 (0
.10)
0.90
(0.
03)
0.26
(0.
02)
1.57
(0.
09)
3.63
(0.
17)
2.55
(0.
09)
0.07
(0.
03)
97.
98 (
1.09
)W
SU
E57
77.4
1 (0
.25)
0.09
(0.
03)
13.6
9 (0
.10)
0.95
(0.
06)
0.22
(0.
03)
1.58
(0.
04)
0.04
(0.
02)
3.43
(0.
23)
2.51
(0.
13)
0.06
(0.
03)
205.
54 (
1.11
)U
A
Bed
OO
F32
76.7
2 (0
.31)
0.11
(0.
02)
13.4
9 (0
.26)
1.01
(0.
12)
0.27
(0.
06)
1.60
(0.
05)
0.04
(0.
02)
4.11
(0.
16)
2.60
(0.
19)
0.06
(0.
03)
67.
24 (
1.11
)U
A
RC
-26
76.5
0.10
14.0
0.94
0.24
1.43
0.03
4.2
2.5
0.07
5.1
(1)
Bed
XC
3956
.70
(0.3
0)1.
15 (
0.03
)16
.97
(0.1
5)7.
45 (
0.15
)4.
67 (
0.12
)7.
56 (
0.16
)4.
35 (
0.14
)1.
07 (
0.04
)0.
07 (
0.01
)12
2.67
(0.
45)
WS
U
Bed
Y -
pop
. 1C
4057
.67
(0.9
0)1.
56 (
0.08
)16
.03
(0.7
3)8.
71 (
0.36
)3.
34 (
0.33
)6.
86 (
0.35
)4.
56 (
0.28
)1.
20 (
0.09
)0.
08 (
0.01
)8
1.92
(0.
84)
WS
U
E59
59.2
2 (1
.50)
1.71
(0.
14)
14.5
7 (0
.86)
9.45
(0.
60)
2.60
(0.
43)
6.12
(0.
81)
0.18
(0.
04)
4.50
(0.
18)
1.55
(0.
23)
0.09
(0.
03)
120.
16 (
0.56
)U
A
Bed
Y -
pop
. 2C
4064
.67
(0.2
7)1.
13 (
0.03
)15
.67
(0.1
2)5.
76 (
0.11
)1.
66 (
0.02
)4.
11 (
0.13
)5.
03 (
0.47
)1.
88 (
0.28
)0.
09 (
0.02
)4
2.37
(1.
11)
WS
U
E59
64.9
1 (0
.22)
1.11
(0.
03)
15.6
5 (0
.15)
5.84
(0.
17)
1.60
(0.
05)
4.02
(0.
08)
0.13
(0.
02)
4.69
(0.
14)
1.96
(0.
07)
0.09
(0.
02)
80.
33 (
0.50
)U
A
Bed
Z -
pop
. 1C
4157
.63
(0.6
9)1.
93 (
0.10
)14
.10
(0.6
2)10
.57
(0.4
7)3.
65 (
0.58
)6.
60 (
0.34
)4.
22 (
0.20
)1.
26 (
0.14
)0.
06 (
0.01
)10
2.69
(0.
66)
WS
U
E60
56.9
5 (0
.66)
1.69
(0.
17)
15.1
8 (0
.69)
10.1
8 (0
.57)
3.31
(0.
54)
6.64
(0.
52)
0.18
(0.
02)
4.68
(0.
49)
1.14
(0.
14)
0.06
(0.
01)
100.
52 (
0.93
)U
A
F34
57.7
2 (1
.68)
1.70
(0.
22)
14.7
4 (0
.82)
10.1
8 (0
.49)
3.08
(0.
64)
6.50
(0.
65)
0.17
(0.
03)
4.44
(0.
55)
1.38
(0.
47)
0.08
(0.
03)
132.
94 (
3.35
)U
A
Bed
Z -
pop
. 2C
4166
.32
(0.0
5)1.
05 (
0.01
)15
.64
(0.1
3)5.
23 (
0.04
)1.
26 (
0.03
)3.
36 (
0.10
)4.
87 (
0.19
)2.
17 (
0.03
)0.
09 (
0.00
)4
2.68
(1.
02)
WS
U
E60
66.2
9 (0
.39)
1.02
(0.
09)
15.6
9 (0
.26)
5.20
(0.
31)
1.13
(0.
13)
3.49
(0.
19)
0.12
(0.
03)
4.72
(0.
38)
2.24
(0.
26)
0.09
(0.
02)
70.
55 (
0.99
)U
A
Bed
AA
C42
56.6
0 (0
.40)
1.67
(0.
08)
14.6
6 (0
.68)
10.1
1 (0
.50)
3.82
(0.
41)
7.64
(0.
39)
4.05
(0.
22)
1.37
(0.
15)
0.08
(0.
01)
93.
19 (
0.72
)W
SU
E61
56.4
1 (0
.69)
1.69
(0.
07)
14.2
4 (0
.20)
10.6
5 (0
.69)
3.60
(0.
29)
7.39
(0.
51)
0.18
(0.
04)
4.32
(0.
36)
1.44
(0.
39)
0.08
(0.
02)
180.
20 (
0.77
)U
A
Bed
AA
1 (m
afic
)C
45A
, C45
B56
.31
(0.7
1)1.
62 (
0.08
)16
.42
(0.1
7)8.
93 (
0.52
)3.
49 (
0.07
)7.
14 (
0.30
)4.
81 (
0.13
)1.
25 (
0.23
)0.
03 (
0.03
)5
1.78
(0.
56)
WS
U
E62
B55
.55
(0.8
1)1.
56 (
0.08
)16
.34
(0.2
4)9.
29 (
0.61
)3.
42 (
0.28
)7.
54 (
0.36
)0.
14 (
0.04
)5.
07 (
0.33
)1.
01 (
0.11
)0.
07 (
0.03
)7
0.51
(0.
70)
UA
F35
, F36
56.0
5 (0
.78)
1.56
(0.
07)
16.6
6 (0
.20)
9.39
(0.
42)
3.28
(0.
19)
7.10
(0.
35)
0.15
(0.
03)
4.69
(0.
18)
1.06
(0.
07)
0.08
(0.
02)
171.
44 (
0.89
)U
A
SP
G-A
10-
4, 1
1-1
56.5
4 (0
.50)
1.61
(0.
06)
16.4
7 (0
.14)
8.93
(0.
39)
3.49
(0.
11)
7.00
(0.
18)
4.80
(0.
19)
1.07
(0.
06)
0.09
(0.
01)
132.
07 (
0.85
)W
SU
She
vlin
Par
k Tu
ff -
253B
-E, U
A15
3055
.70
(0.6
8)1.
77 (
0.09
)16
.31
(0.1
7)9.
29 (
0.49
)3.
44 (
0.14
)6.
95 (
0.27
)0.
16 (
0.02
)5.
28 (
0.27
)1.
05 (
0.14
)0.
07 (
0.01
)77
1.69
(0.
52)
WS
U, U
A
(9)
Bed
AA
1 (s
ilici
c)C
45A
, C45
B69
.09
(0.2
9)0.
72 (
0.03
)15
.44
(0.1
0)3.
52 (
0.12
)0.
80 (
0.03
)2.
28 (
0.04
)5.
53 (
0.14
)2.
50 (
0.13
)0.
10 (
0.08
)6
2.23
(1.
03)
WS
U
E62
B69
.84
(0.3
0)0.
69 (
0.03
)15
.30
(0.2
1)3.
53 (
0.15
)0.
77 (
0.06
)2.
32 (
0.14
)0.
14 (
0.04
)4.
97 (
0.16
)2.
31 (
0.11
)0.
13 (
0.03
)6
2.67
(1.
17)
UA
F35
, F36
68.3
9 (0
.39)
0.70
(0.
05)
15.4
2 (0
.18)
3.72
(0.
21)
0.80
(0.
09)
2.37
(0.
20)
0.11
(0.
03)
5.96
(0.
24)
2.37
(0.
18)
0.15
(0.
03)
134.
71 (
1.83
)U
A
SP
G-A
10-
4,11
-169
.56
(0.4
8)0.
72 (
0.03
)15
.50
(0.1
2)3.
46 (
0.13
)0.
83 (
0.06
)2.
26 (
0.11
)5.
20 (
0.30
)2.
31 (
0.05
)0.
16 (
0.02
)18
3.49
(1.
10)
WS
U
She
vlin
Par
k Tu
ff -
253B
-E69
.18
(0.5
7)0.
70 (
0.05
)15
.24
(0.1
7)3.
44 (
0.18
)0.
84 (
0.12
)2.
07 (
0.20
)6.
04 (
0.15
)2.
37 (
0.09
)0.
12 (
0.02
)25
WS
U, (
9)
Bed
AA
1 (b
ulk)
C45
A, C
45B
62.2
9 (5
.52)
1.22
(0.
41)
15.9
7 (0
.46)
6.35
(2.
33)
2.25
(1.
17)
4.89
(2.
13)
5.12
(0.
42)
1.86
(0.
56)
0.06
(0.
06)
201.
70 (
0.91
)W
SU
E62
B62
.36
(5.9
1)1.
16 (
0.36
)15
.90
(0.5
0)6.
59 (
2.47
)2.
06 (
1.10
)4.
99 (
2.15
)0.
14 (
0.04
)5.
07 (
0.26
)1.
64 (
0.54
)0.
10 (
0.04
)21
1.37
(1.
34)
UA
F35
, F36
61.4
1 (5
.39)
1.22
(0.
39)
16.2
2 (0
.73)
6.88
(2.
49)
2.18
(1.
09)
4.98
(2.
06)
0.14
(0.
04)
5.24
(0.
59)
1.63
(0.
58)
0.11
(0.
04)
422.
61 (
1.92
)U
A
SP
G-A
10-
4,11
-1
63.7
4 (6
.19)
1.12
(0.
43)
15.9
6 (0
.51)
5.86
(2.
59)
2.00
(1.
26)
4.36
(2.
25)
5.07
(0.
33)
1.76
(0.
59)
0.12
(0.
04)
372.
70 (
1.21
)W
SU
She
vlin
Par
k Tu
ff -
253B
-E, U
A15
3059
.63
(5.1
1)1.
46 (
0.41
)16
.07
(0.4
6)7.
50 (
2.27
)2.
68 (
1.02
)5.
52 (
1.88
)5.
56 (
0.46
)1.
41 (
0.54
)0.
09 (
0.02
)15
8W
SU
, UA
(9
)
AA
2F
3771
.74
(0.4
6)0.
51 (
0.05
)14
.55
(0.2
4)2.
72 (
0.13
)0.
44 (
0.07
)1.
40 (
0.17
)0.
08 (
0.03
)5.
60 (
0.11
)2.
84 (
0.14
)0.
12 (
0.02
)13
6.13
(0.
56)
UA
Bed
BB
C47
58.0
9 (1
.18)
1.50
(0.
03)
16.3
5 (0
.15)
8.44
(0.
63)
3.22
(0.
28)
6.40
(0.
50)
4.69
(0.
22)
1.25
(0.
15)
0.05
(0.
03)
101.
55 (
0.65
)W
SU
E63
58.1
8 (0
.83)
1.65
(0.
20)
15.3
9 (0
.91)
9.35
(0.
66)
2.71
(0.
42)
6.26
(0.
45)
0.15
(0.
03)
5.04
(0.
38)
1.20
(0.
25)
0.06
(0.
03)
141.
62 (
0.95
)U
A
(con
tinue
d)
on April 8, 2012geosphere.gsapubs.orgDownloaded from
Kuehn and Negrini
410 Geosphere, August 2010
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE (
cont
inue
d)
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
BB
1C
47-2
56.6
3 (1
.26)
1.69
(0.
12)
15.4
8 (0
.40)
8.96
(0.
53)
4.28
(0.
62)
7.57
(0.
52)
4.14
(0.
30)
1.20
(0.
08)
0.05
(0.
01)
103.
12 (
1.02
)W
SU
Bed
CC
C48
58.1
9 (0
.43)
1.79
(0.
12)
14.1
1 (0
.49)
10.1
7 (0
.41)
3.06
(0.
19)
6.92
(0.
39)
0.18
(0.
04)
4.27
(0.
43)
1.23
(0.
19)
0.07
(0.
03)
142.
42 (
2.64
)U
A
Bed
DD
C49
70.5
2 (0
.14)
0.58
(0.
03)
15.4
8 (0
.07)
3.12
(0.
04)
0.66
(0.
03)
1.93
(0.
02)
5.34
(0.
13)
2.25
(0.
05)
0.13
(0.
01)
92.
47 (
1.43
)W
SU
E65
(m
ixtu
re?)
71.1
8 (0
.49)
0.58
(0.
04)
15.1
9 (0
.13)
3.24
(0.
14)
0.59
(0.
05)
1.95
(0.
11)
0.13
(0.
03)
4.71
(0.
30)
2.29
(0.
08)
0.13
(0.
02)
193.
69 (
1.07
)U
A
F38
69.9
2 (0
.19)
0.57
(0.
04)
15.2
5 (0
.14)
3.30
(0.
07)
0.61
(0.
03)
1.97
(0.
06)
0.11
(0.
03)
5.84
(0.
12)
2.31
(0.
07)
0.12
(0.
03)
205.
30 (
1.35
)U
A
DR
-37
69.5
0.60
15.6
3.20
0.62
1.89
0.11
6.1
2.3
0.11
2.8
(1)
DR
-37
69.6
30.
6015
.60
3.08
0.62
1.90
0.11
6.14
2.32
(5),
(6)
Prin
gle
Falls
K70
.02
0.51
15.3
93.
290.
581.
920.
105.
832.
36(5
), (
6)
Bed
DD
1C
5057
.51
(0.1
2)1.
58 (
0.08
)14
.90
(0.2
8)9.
31 (
0.16
)4.
09 (
0.12
)7.
36 (
0.15
)4.
10 (
0.21
)1.
09 (
0.13
)0.
07 (
0.01
)10
2.69
(0.
89)
WS
U
Bed
EE
C51
71.5
3 (0
.25)
0.49
(0.
01)
15.2
0 (0
.14)
2.92
(0.
07)
0.52
(0.
02)
1.67
(0.
05)
5.18
(0.
24)
2.35
(0.
06)
0.13
(0.
02)
104.
50 (
1.98
)W
SU
E66
71.6
9 (0
.48)
0.48
(0.
04)
15.0
9 (0
.21)
3.06
(0.
17)
0.49
(0.
08)
1.72
(0.
11)
0.11
(0.
03)
4.83
(0.
31)
2.39
(0.
14)
0.14
(0.
02)
185.
51 (
1.28
)U
A
F39
70.9
4 (0
.26)
0.50
(0.
05)
15.0
8 (0
.17)
2.98
(0.
10)
0.47
(0.
05)
1.66
(0.
10)
0.10
(0.
03)
5.77
(0.
14)
2.36
(0.
08)
0.14
(0.
02)
344.
42 (
1.46
)U
A
DR
-38
70.4
0.50
15.5
2.86
0.46
1.54
0.09
6.1
2.4
0.11
2.9
(1)
DR
-38
70.5
90.
5015
.51
2.75
0.46
1.54
0.09
6.14
2.42
(5),
(6)
Prin
gle
Falls
H70
.77
0.51
15.0
92.
960.
491.
690.
105.
972.
42(5
), (
6)
Bed
EE
1
Bed
EE
2
C52
55.5
4 (0
.43)
1.40
(0.
08)
15.6
2 (0
.30)
9.23
(0.
19)
4.85
(0.
41)
8.07
(0.
13)
4.35
(0.
15)
0.86
(0.
09)
0.07
(0.
01)
102.
25 (
0.38
)W
SU
C53
73.9
1 (0
.20)
0.28
(0.
02)
14.3
7 (0
.13)
1.96
(0.
04)
0.44
(0.
04)
2.02
(0.
05)
3.75
(0.
13)
3.10
(0.
09)
0.17
(0.
03)
106.
67 (
2.31
)W
SU
Prin
gle
Falls
E
(PF
-88-
E1,
T17
3-6)
73.8
0 (0
.62)
0.26
(0.
05)
14.4
9 (0
.13)
1.92
(0.
07)
0.42
(0.
03)
2.00
(0.
04)
0.04
(0.
03)
4.04
(0.
11)
3.03
(0.
05)
84.
57(5
), (
7)
Prin
gle
Falls
E
(PF
-88-
E2,
T16
9-2)
73.5
7 (0
.60)
0.26
(0.
05)
14.6
4 (0
.52)
1.93
(0.
07)
0.43
(0.
04)
2.06
(0.
03)
0.04
(0.
02)
3.96
(0.
10)
3.11
(0.
05)
154.
51(5
), (
7)
Ben
ton
Cro
ssin
g (M
7810
)73
.47
0.30
14.5
22.
050.
432.
110.
044.
073.
01(5
)
Ben
ton
Cro
ssin
g (K
RL1
0779
A)
73.5
20.
2614
.59
1.97
0.44
2.08
0.03
4.04
3.06
(5)
Pao
ha Is
land
[P
AO
H-3
(1)]
72.9
60.
2715
.01
1.98
0.40
2.08
0.03
4.25
3.01
(5)
Pao
ha Is
land
[P
AO
H-3
(2)]
74.0
00.
2813
.99
2.04
0.45
2.10
0.04
3.90
3.20
(5)
Car
p A
sh-1
4 (T
352-
1)73
.59
(0.5
1)0.
25 (
0.04
)14
.37
(0.1
7)1.
90 (
0.07
)0.
41 (
0.01
)2.
04 (
0.03
)0.
04 (
0.03
)4.
31 (
0.11
)3.
09 (
0.06
)7
5.57
(7)
Bed
EE
3 -
pop.
1E
6770
.79
(0.5
8)0.
57 (
0.07
)15
.22
(0.1
7)3.
47 (
0.24
)0.
57 (
0.06
)2.
01 (
0.09
)0.
11 (
0.02
)4.
78 (
0.49
)2.
35 (
0.10
)0.
13 (
0.02
)9
3.87
(1.
81)
UA
Bed
EE
3 -
pop.
2E
6773
.84
0.26
14.3
72.
090.
402.
180.
093.
642.
950.
173
5.26
UA
Bed
FF
C54
70.1
3 (0
.64)
0.61
(0.
03)
15.5
0 (0
.33)
3.42
(0.
09)
0.69
(0.
08)
1.99
(0.
14)
5.18
(0.
19)
2.35
(0.
09)
0.14
(0.
02)
103.
66 (
1.39
)W
SU
E68
70.3
4 (0
.28)
0.60
(0.
06)
15.4
1 (0
.40)
3.57
(0.
15)
0.64
(0.
05)
2.12
(0.
15)
0.10
(0.
03)
4.82
(0.
41)
2.27
(0.
11)
0.14
(0.
03)
155.
68 (
1.04
)U
A
DR
-39
69.1
0.64
15.5
3.48
0.65
2.01
0.10
6.1
2.3
0.12
2.2
(1)
Bed
FF
1 -
pop.
1E
68.5
70.4
0 (0
.58)
0.60
(0.
04)
15.5
5 (0
.25)
3.45
(0.
20)
0.59
(0.
11)
2.16
(0.
23)
0.11
(0.
04)
4.71
(0.
39)
2.29
(0.
11)
0.15
(0.
03)
114.
65 (
1.86
)U
A
Bed
FF
1 -
pop.
2E
68.5
72.3
70.
7414
.47
3.39
0.36
1.57
0.08
4.28
2.58
0.16
34.
88U
A
(con
tinue
d)
on April 8, 2012geosphere.gsapubs.orgDownloaded from
250,000-year tephra record from Summer Lake
Geosphere, August 2010 411
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE (
cont
inue
d)
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
GG
C55
C70
.83
(0.3
9)0.
51 (
0.08
)15
.28
(0.1
2)3.
26 (
0.18
)0.
56 (
0.04
)1.
78 (
0.05
)5.
16 (
0.16
)2.
48 (
0.13
)0.
15 (
0.01
)10
4.22
(1.
13)
WS
U
E69
A, E
69D
, E69
F71
.29
(0.6
3)0.
53 (
0.08
)15
.06
(0.2
6)3.
50 (
0.27
)0.
51 (
0.07
)1.
83 (
0.15
)0.
10 (
0.03
)4.
61 (
0.29
)2.
42 (
0.12
)0.
14 (
0.02
)52
4.57
(1.
56)
DR
-40
69.3
0.59
15.4
3.45
0.59
1.86
0.11
6.1
2.4
0.12
3.6
(1)
DR
-40
69.5
60.
5915
.43
3.32
0.55
1.87
0.11
6.15
2.42
(5),
(6)
Prin
gle
Falls
D (
1)70
.34
0.51
15.2
83.
260.
511.
770.
125.
732.
48(5
)
Prin
gle
Falls
D (
2)70
.21
0.47
15.6
73.
270.
501.
810.
105.
512.
46(5
), (
6)
Pao
ha Is
land
(P
I-O
R)
70.6
40.
5314
.90
3.30
0.55
1.80
0.13
5.67
2.48
(5)
Prin
gle
Falls
D
(980
LF-8
)70
.43
(0.5
7)0.
57 (
0.06
)15
.33
(0.1
8)3.
42 (
0.19
)0.
63 (
0.08
)1.
85 (
0.15
)5.
22 (
0.32
)2.
40 (
0.08
)0.
15 (
0.02
)24
2.21
(1.
22)
(8)
New
berr
y -
9917
C
(hig
her
silic
a pa
rt)
70.2
9 (0
.55)
0.60
(0.
04)
15.2
1 (0
.21)
3.45
(0.
21)
0.59
(0.
09)
1.97
(0.
09)
5.37
(0.
32)
2.41
(0.
08)
0.10
(0.
03)
135.
59 (
0.87
)(8
)
New
berr
y -
9917
C
(ove
rall)
69.5
1 (0
.60)
0.64
(0.
04)
15.4
2 (0
.24)
3.62
(0.
26)
0.72
(0.
10)
2.22
(0.
17)
5.46
(0.
25)
2.31
(0.
11)
0.11
(0.
02)
845.
67 (
1.74
)(8
)
Bed
GG
1C
5657
.13
(0.4
8)1.
62 (
0.09
)14
.75
(0.5
1)9.
61 (
0.32
)3.
75 (
0.16
)7.
64 (
0.25
)4.
23 (
0.36
)1.
19 (
0.34
)0.
09 (
0.02
)6
1.95
(0.
71)
WS
U
Mea
n57
.11
(0.3
5)1.
60 (
0.06
)14
.32
(0.2
2)10
.54
(0.2
3)3.
59 (
0.16
)7.
35 (
0.43
)0.
18 (
0.04
)4.
09 (
0.24
)1.
15 (
0.22
)0.
08 (
0.02
)11
-0.2
3 (0
.75)
UA
Bed
HH
C57
73.3
9 (0
.17)
0.29
(0.
02)
14.5
8 (0
.12)
2.55
(0.
06)
0.26
(0.
03)
1.14
(0.
04)
4.84
(0.
15)
2.82
(0.
08)
0.14
(0.
03)
106.
21 (
0.65
)W
SU
E70
73.7
4 (0
.33)
0.29
(0.
04)
14.4
1 (0
.17)
2.69
(0.
08)
0.23
(0.
04)
1.19
(0.
07)
0.09
(0.
03)
4.39
(0.
31)
2.82
(0.
07)
0.13
(0.
02)
224.
68 (
1.15
)U
A
Bed
IIC
5873
.07
(0.6
8)0.
30 (
0.03
)14
.69
(0.1
9)2.
67 (
0.13
)0.
28 (
0.03
)1.
24 (
0.10
)4.
79 (
0.49
)2.
82 (
0.20
)0.
13 (
0.03
)9
5.82
(1.
57)
WS
U
E71
73.0
6 (0
.31)
0.33
(0.
05)
14.6
1 (0
.17)
2.97
(0.
11)
0.28
(0.
03)
1.29
(0.
07)
0.10
(0.
03)
4.47
(0.
17)
2.76
(0.
10)
0.13
(0.
03)
224.
44 (
1.24
)U
A
DR
-35
71.7
0.35
14.6
2.83
0.28
1.22
0.08
5.9
2.8
0.11
3.0
(1)
DR
-35
71.9
00.
3514
.68
2.73
0.28
1.22
0.08
5.94
2.82
(5),
(6)
Prin
gle
Falls
S72
.31
0.33
14.6
92.
810.
261.
250.
095.
412.
84(5
), (
6)
Bed
II1
C58
-274
.27
(0.3
4)0.
19 (
0.02
)14
.29
(0.1
5)2.
07 (
0.08
)0.
19 (
0.03
)0.
99 (
0.06
)4.
49 (
0.20
)3.
36 (
0.30
)0.
14 (
0.02
)13
5.71
(1.
56)
WS
U
F41
74.4
2 (0
.58)
0.19
(0.
06)
13.9
4 (0
.26)
1.98
(0.
18)
0.15
(0.
03)
0.92
(0.
09)
0.06
(0.
03)
5.08
(0.
14)
3.15
(0.
11)
0.12
(0.
03)
293.
68 (
0.85
)U
A
Bed
JJ
(maf
ic)
C59
B, C
59C
, C
59D
- m
afic
58.1
1 (0
.39)
1.48
(0.
03)
16.4
4 (0
.12)
8.36
(0.
25)
3.02
(0.
10)
6.45
(0.
22)
4.53
(0.
25)
1.52
(0.
08)
0.08
(0.
01)
83.
21 (
0.63
)W
SU
F40
- m
afic
58.1
4 (0
.26)
1.61
(0.
07)
16.2
9 (0
.20)
8.70
(0.
09)
2.90
(0.
03)
6.23
(0.
28)
0.16
(0.
01)
4.49
(0.
11)
1.41
(0.
06)
0.07
(0.
03)
40.
80 (
0.82
)U
A
RC
- m
afic
58.4
6 (0
.46)
1.52
(0.
08)
16.2
9 (0
.45)
8.38
(0.
52)
2.96
(0.
28)
6.22
(0.
32)
4.76
(0.
31)
1.34
(0.
12)
0.08
(0.
01)
281.
75 (
0.73
)W
SU
, (9)
DR
-30
- m
afic
57.8
1.60
16.4
8.68
3.05
6.19
0.15
4.5
1.5
0.08
0.3
(1)
DR
-30
- m
afic
58.0
61.
6016
.44
8.37
3.07
6.21
0.15
4.57
1.52
(5),
(6)
Bed
JJ
(sili
cic)
C59
B, C
59C
, C
59D
- s
ilici
c74
.21
(0.2
7)0.
19 (
0.02
)14
.37
(0.0
7)2.
01 (
0.11
)0.
17 (
0.03
)0.
95 (
0.04
)4.
69 (
0.22
)3.
26 (
0.22
)0.
15 (
0.02
)9
6.91
(1.
88)
WS
U
E72
- s
ilici
c74
.72
(0.2
9)0.
19 (
0.02
)14
.13
(0.1
7)2.
11 (
0.14
)0.
14 (
0.03
)0.
99 (
0.05
)0.
07 (
0.03
)4.
33 (
0.13
)3.
19 (
0.16
)0.
13 (
0.02
)15
4.58
(1.
15)
UA
F40
- s
ilici
c74
.16
(0.4
2)0.
19 (
0.04
)13
.98
(0.1
9)2.
06 (
0.14
)0.
14 (
0.04
)0.
94 (
0.08
)0.
06 (
0.03
)5.
13 (
0.23
)3.
19 (
0.13
)0.
15 (
0.03
)26
5.88
(1.
17)
UA
RC
- s
ilici
c74
.55
(0.3
3)0.
21 (
0.05
)14
.18
(0.2
1)2.
13 (
0.15
)0.
18 (
0.04
)0.
95 (
0.11
)4.
56 (
0.18
)3.
10 (
0.15
)0.
14 (
0.02
)25
4.19
(0.
98)
WS
U, (
9)
DR
-30
- si
licic
73.3
0.20
14.5
2.13
0.16
0.96
0.05
5.6
3.0
0.14
5.8
(1)
DR
-30
- si
licic
73.4
40.
2014
.48
2.05
0.16
0.96
0.05
5.63
3.02
(5),
(6)
Wal
ker
Lake
5-4
2A
(141
.9m
)73
.63
0.17
14.3
22.
070.
170.
980.
065.
543.
05(5
), (
6)
Pao
ha Is
land
, PI-
GB
W-B
74.3
60.
2213
.98
2.07
0.18
0.99
0.08
5.09
3.03
(5)
Pao
ha Is
land
, PI-
GB
W-G
74.4
30.
1913
.93
2.08
0.17
0.99
0.09
5.08
3.03
(5)
(con
tinue
d)
on April 8, 2012geosphere.gsapubs.orgDownloaded from
Kuehn and Negrini
412 Geosphere, August 2010
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE (
cont
inue
d)
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
JJ
(sili
cic)
(c
ont.)
Pao
ha Is
land
, PI-
GB
W-W
74.2
60.
1814
.09
2.10
0.17
1.00
0.08
5.09
3.03
(5)
Pao
ha Is
land
, P
OA
H-1
73.0
40.
1914
.94
2.06
0.15
1.00
0.07
5.57
2.98
(5)
Bed
JJ
(bul
k)C
59B
, C59
C,
C59
D -
bul
k66
.53
(7.6
9)0.
81 (
0.62
)15
.39
(1.0
0)5.
00 (
3.04
)1.
48 (
1.36
)3.
53 (
2.63
)4.
73 (
0.35
)2.
41 (
0.85
)0.
12 (
0.04
)20
4.65
(2.
55)
WS
U
E72
- b
ulk
73.7
9 (1
.87)
0.25
(0.
12)
14.3
6 (0
.46)
2.45
(0.
66)
0.23
(0.
19)
1.22
(0.
47)
0.08
(0.
04)
4.46
(0.
32)
3.03
(0.
33)
0.13
(0.
02)
204.
07 (
1.42
)U
A
F40
- b
ulk
71.9
6 (5
.38)
0.38
(0.
48)
14.3
3 (0
.83)
2.93
(2.
23)
0.50
(0.
92)
1.63
(1.
77)
0.08
(0.
04)
5.07
(0.
31)
2.98
(0.
62)
0.14
(0.
05)
325.
38 (
2.19
)U
A
RC
- b
ulk
66.8
3 (7
.63)
0.84
(0.
63)
15.2
2 (1
.04)
5.10
(3.
00)
1.48
(1.
34)
3.46
(2.
52)
4.71
(0.
28)
2.26
(0.
85)
0.11
(0.
04)
642.
99 (
1.41
)W
SU
, (9)
Bed
JJ0
.2C
6073
.88
(0.3
1)0.
17 (
0.02
)14
.45
(0.1
0)2.
04 (
0.14
)0.
19 (
0.04
)0.
91 (
0.03
)5.
07 (
0.22
)3.
16 (
0.10
)0.
13 (
0.02
)10
8.76
(1.
12)
WS
U
E72
.574
.75
(0.2
6)0.
18 (
0.04
)14
.10
(0.1
3)2.
08 (
0.08
)0.
15 (
0.03
)0.
97 (
0.04
)0.
06 (
0.04
)4.
39 (
0.19
)3.
19 (
0.10
)0.
12 (
0.02
)24
4.70
(1.
03)
UA
Bed
JJ0
.4E
7365
.67
(1.4
5)0.
92 (
0.12
)15
.98
(0.4
9)4.
72 (
0.54
)1.
38 (
0.33
)3.
75 (
0.70
)0.
11 (
0.05
)4.
49 (
0.42
)2.
84 (
0.55
)0.
13 (
0.06
)16
2.94
(3.
11)
UA
Bed
JJ0
.6E
7464
.95
(2.9
5)0.
87 (
0.17
)15
.94
(0.4
4)5.
12 (
1.30
)1.
58 (
0.47
)4.
28 (
1.10
)0.
11 (
0.04
)4.
56 (
0.48
)2.
50 (
0.61
)0.
10 (
0.03
)18
0.98
(1.
81)
UA
Bed
JJ1
C62
74.9
8 (0
.67)
0.16
(0.
04)
13.9
7 (0
.34)
1.77
(0.
22)
0.13
(0.
03)
0.80
(0.
13)
4.70
(0.
12)
3.36
(0.
16)
0.14
(0.
01)
126.
37 (
0.64
)W
SU
96-1
9 (p
roxi
mal
B
end
Pum
ice)
75.1
6 (0
.21)
0.14
(0.
02)
13.8
0 (0
.07)
1.76
(0.
03)
0.12
(0.
04)
0.79
(0.
02)
4.70
(0.
16)
3.36
(0.
07)
0.17
(0.
02)
104.
53 (
0.71
)W
SU
SP
G-A
12-
575
.68
(0.2
6)0.
13 (
0.03
)13
.66
(0.1
1)1.
58 (
0.08
)0.
11 (
0.02
)0.
68 (
0.04
)4.
56 (
0.12
)3.
45 (
0.11
)0.
14 (
0.02
)14
5.76
(0.
60)
WS
U
C62
- b
ulk
74.6
0 (0
.81)
0.16
(0.
04)
13.6
4 (0
.36)
1.93
(0.
23)
0.13
(0.
03)
0.89
(0.
16)
0.07
(0.
04)
5.15
(0.
21)
3.30
(0.
17)
0.13
(0.
02)
545.
50 (
1.09
)U
A
C62
- lo
wer
sili
ca
popu
latio
n74
.00
(0.2
5)0.
17 (
0.03
)13
.90
(0.1
4)2.
10 (
0.08
)0.
15 (
0.02
)1.
01 (
0.05
)0.
08 (
0.04
)5.
26 (
0.15
)3.
19 (
0.09
)0.
13 (
0.02
)33
5.52
(1.
26)
UA
C62
- h
ighe
r si
lica
popu
latio
n75
.55
(0.3
0)0.
13 (
0.04
)13
.22
(0.1
5)1.
66 (
0.08
)0.
10 (
0.02
)0.
70 (
0.06
)0.
06 (
0.03
)4.
97 (
0.17
)3.
48 (
0.11
)0.
13 (
0.03
)21
5.46
(0.
76)
UA
SP
G-A
12-
575
.63
(0.2
7)0.
13 (
0.03
)13
.14
(0.1
8)1.
62 (
0.09
)0.
09 (
0.02
)0.
70 (
0.08
)0.
05 (
0.03
)4.
90 (
0.14
)3.
58 (
0.16
)0.
14 (
0.03
)43
5.84
(0.
68)
UA
96-1
9 (p
roxi
mal
B
end
Pum
ice)
74.9
5 (0
.18)
0.14
(0.
03)
13.5
1 (0
.12)
1.82
(0.
06)
0.12
(0.
02)
0.81
(0.
04)
0.07
(0.
03)
5.10
(0.
12)
3.32
(0.
08)
0.17
(0.
03)
534.
60 (
0.84
)U
A
98-5
5-E
474
.95
(0.2
4)0.
15 (
0.04
)13
.42
(0.2
4)1.
84 (
0.06
)0.
12 (
0.02
)0.
80 (
0.04
)0.
08 (
0.04
)5.
12 (
0.24
)3.
34 (
0.13
)0.
17 (
0.02
)47
6.25
(1.
11)
UA
97-6
375
.06
(0.1
9)0.
14 (
0.03
)13
.20
(0.1
4)1.
88 (
0.07
)0.
12 (
0.03
)0.
81 (
0.04
)0.
08 (
0.03
)5.
25 (
0.15
)3.
28 (
0.09
)0.
18 (
0.03
)40
7.58
(1.
24)
UA
03-0
1 (T
umal
o tu
ff)74
.97
(0.1
7)0.
14 (
0.04
)13
.42
(0.1
4)1.
81 (
0.07
)0.
12 (
0.02
)0.
81 (
0.04
)0.
08 (
0.04
)5.
12 (
0.13
)3.
36 (
0.09
)0.
17 (
0.03
)52
4.06
(0.
91)
UA
Bed
KK
C63
B, C
63D
65.8
1 (3
.35)
0.84
(0.
18)
16.0
9 (0
.64)
4.51
(1.
23)
1.53
(0.
57)
3.68
(1.
16)
4.70
(0.
60)
2.73
(0.
88)
0.11
(0.
02)
173.
66 (
2.15
)W
SU
E75
65.8
4 (2
.11)
0.85
(0.
08)
15.8
6 (0
.32)
4.74
(0.
84)
1.38
(0.
38)
3.94
(0.
78)
0.11
(0.
03)
4.69
(0.
31)
2.49
(0.
28)
0.11
(0.
03)
181.
53 (
1.91
)U
A
F42
67.0
7 (2
.62)
0.79
(0.
10)
15.2
2 (0
.44)
4.35
(1.
02)
1.27
(0.
56)
3.55
(0.
98)
0.09
(0.
04)
4.94
(0.
42)
2.60
(0.
39)
0.11
(0.
02)
123.
68 (
2.93
)U
A
Ant
elop
e W
ell t
uff
[194
-M(2
)A]
66.1
3 (3
.71)
0.88
(0.
20)
15.4
9 (1
.11)
4.57
(1.
39)
1.31
(0.
55)
3.61
(1.
20)
0.08
(0.
04)
5.42
(0.
99)
2.52
(1.
34)
0.02
(0.
03)
431.
94 (
1.55
)W
SU
,UA
DR
-33
63.0
0.99
16.3
5.82
1.98
4.75
0.11
4.8
2.1
0.10
(1)
DR
-33
63.1
90.
9916
.38
5.61
1.99
4.76
0.11
4.85
2.12
10(5
), (
6), (
7)
Ant
elop
e W
ell t
uff
(194
M a
, b, a
nd c
)66
.34
0.87
15.6
84.
361.
383.
680.
074.
912.
72(5
), (
6)
Wal
ker
Lake
4-5
7 (1
54.4
m)
64.5
60.
8615
.97
4.99
1.78
4.57
0.10
4.99
2.19
(5),
(6)
Tule
lake
T-2
023S
(5
3.07
–53.
13 m
)63
.98
0.97
16.4
15.
322.
004.
470.
094.
582.
18(5
), (
6)
Tule
lake
612
84-1
4 (T
81-8
)63
.32
(0.5
7)0.
96 (
0.08
)16
.32
(0.4
8)5.
52 (
0.17
)2.
11 (
0.08
)4.
85 (
0.09
)0.
11 (
0.02
)4.
66 (
0.13
)2.
14 (
0.04
)8
5.44
(7)
Car
p A
sh-1
5 (T
352-
2)63
.12
(0.4
3)0.
88 (
0.06
)16
.40
(0.2
0)5.
69 (
0.25
)2.
11 (
0.15
)4.
89 (
0.22
)0.
11 (
0.03
)4.
73 (
0.23
)2.
06 (
0.11
)15
1.50
(0.
52)
(7)
(con
tinue
d)
on April 8, 2012geosphere.gsapubs.orgDownloaded from
250,000-year tephra record from Summer Lake
Geosphere, August 2010 413
TAB
LE 2
. ME
AN
GLA
SS
CO
MP
OS
ITIO
NS
BY
BE
D A
ND
SA
MP
LE (
cont
inue
d)
Bed
Sam
ple
SiO
2T
iO2
Al 2O
3F
eOt
MgO
CaO
M
nO
Na 2O
K2O
Cl
nH
2Od
Lab
or R
ef
Bed
KK
1C
6457
.23
(1.7
5)1.
82 (
0.19
)15
.43
(0.9
3)9.
66 (
0.65
)3.
97 (
0.70
)6.
20 (
0.91
)4.
49 (
0.25
)1.
15 (
0.17
)0.
05 (
0.01
)12
2.40
(0.
68)
WS
U
E76
58.2
3 (1
.41)
1.80
(0.
17)
14.8
0 (0
.52)
9.87
(0.
18)
3.16
(0.
62)
5.78
(0.
93)
0.18
(0.
04)
4.89
(0.
38)
1.21
(0.
23)
0.06
(0.
02)
140.
72 (
1.23
)U
A
Bed
LL
C65
66.9
9 (0
.89)
0.75
(0.
08)
16.1
3 (0
.17)
3.37
(0.
31)
1.30
(0.
19)
3.58
(0.
37)
4.99
(0.
15)
2.71
(0.
20)
0.18
(0.
02)
123.
46 (
2.23
)W
SU
F43
68.5
1 (1
.52)
0.65
(0.
10)
15.3
9 (0
.46)
3.04
(0.
42)
1.07
(0.
21)
3.18
(0.
57)
0.05
(0.
03)
5.03
(0.
22)
2.89
(0.
31)
0.20
(0.
04)
124.
66 (
2.64
)U
A
DR
-34,
DR
-15
66.7
0.80
16.2
3.55
1.33
3.61
0.08
4.9
2.7
0.16
1.4
(1)
Bed
LL1
C66
61.3
5 (0
.44)
0.89
(0.
02)
17.6
0 (0
.19)
5.05
(0.
12)
2.61
(0.
21)
5.66
(0.
20)
4.94
(0.
09)
1.78
(0.
12)
0.12
(0.
02)
102.
80 (
0.42
)W
SU
F44
61.8
5 (1
.41)
0.84
(0.
06)
17.2
2 (0
.60)
5.38
(0.
36)
2.30
(0.
51)
5.53
(0.
50)
0.07
(0.
02)
4.95
(0.
26)
1.74
(0.
11)
0.12
(0.
02)
91.
94 (
1.72
)U
A
Bed
LL2
C67
76.5
0 (0
.18)
0.20
(0.
02)
12.9
4 (0
.07)
1.67
(0.
05)
0.11
(0.
02)
0.65
(0.
02)
4.18
(0.
10)
3.66
(0.
14)
0.10
(0.
02)
116.
30 (
0.48
)W
SU
Bed
MM
C68
57.1
6 (0
.55)
1.64
(0.
12)
14.8
9 (0
.34)
9.11
(0.
44)
4.03
(0.
32)
7.50
(0.
36)
4.32
(0.
28)
1.25
(0.
19)
0.09
(0.
02)
122.
16 (
0.70
)W
SU
Bed
MM
1C
6953
.25
(0.4
5)2.
29 (
0.19
)14
.74
(0.1
6)10
.73
(0.3
7)4.
66 (
0.28
)8.
47 (
0.36
)4.
62 (
0.31
)1.
19 (
0.15
)0.
05 (
0.01
)11
2.87
(0.
82)
WS
U
Bed
NN
C70
A, C
70B
69.7
3 (0
.27)
0.64
(0.
03)
15.1
7 (0
.09)
3.49
(0.
10)
0.70
(0.
06)
2.29
(0.
08)
4.92
(0.
13)
2.96
(0.
19)
0.10
(0.
02)
124.
53 (
0.70
)W
SU
DR
-70
70.2
5 (0
.33)
0.65
(0.
02)
15.1
1 (0
.13)
3.48
(0.
09)
0.69
(0.
04)
2.31
(0.
11)
4.61
(0.
28)
2.81
(0.
08)
0.09
(0.
02)
214.
37 (
0.95
)W
SU
DR
-70
69.8
0.68
15.1
3.56
0.67
2.16
0.09
5.1
2.7
0.09
1.3
(1)
DR
-70
69.9
70.
6815
.13
3.42
0.67
2.17
0.09
5.14
2.72
(2)
Col
umbi
a C
anal
(B
PT-
CC
)69
.60
0.67
15.3
73.
340.
722.
130.
135.
722.
31(2
)
New
berr
y -
9881
C70
.30
(0.2
5)0.
65 (
0.03
)15
.10
(0.1
4)3.
46 (
0.09
)0.
71 (
0.03
)2.
32 (
0.12
)4.
57 (
0.23
)2.
79 (
0.05
)0.
09 (
0.01
)53
4.69
(1.
29)
WS
U
New
berr
y -
Qdt
-Q
to69
.97
(0.3
8)0.
64 (
0.05
)15
.08
(0.1
3)3.
40 (
0.22
)0.
73 (
0.08
)2.
28 (
0.15
)4.
96 (
0.15
)2.
86 (
0.11
)0.
07 (
0.02
)51
(8)
Site
E, t
renc
h 5
E78
74.7
8 (1
.34)
0.32
(0.
10)
13.8
9 (0
.51)
1.90
(0.
22)
0.34
(0.
11)
1.45
(0.
33)
0.05
(0.
02)
4.13
(0.
38)
3.01
(0.
26)
0.14
(0.
04)
184.
12 (
1.55
)U
A
Gla
ss s
tand
ard
UA
583
174
.76
(0.2
4)0.
07 (
0.03
)13
.28
(0.1
3)1.
58 (
0.09
)0.
05 (
0.03
)0.
73 (
0.04
)0.
07 (
0.03
)4.
05 (
0.17
)5.
06 (
0.13
)0.
35 (
0.03
)57
31.
78 (
0.87
)U
A
Gla
ss s
tand
ard
UA
583
1 (C
CN
M21
1)74
.83
(0.1
7)0.
07 (
0.02
)13
.25
(0.1
1)1.
57 (
0.06
)0.
05 (
0.02
)0.
74 (
0.03
)4.
06 (
0.10
)5.
09 (
0.07
)0.
34 (
0.04
)24
91.
41 (
0.61
)W
SU
N
ote:
Sta
ndar
d de
viat
ions
of t
he n
orm
aliz
ed v
alue
s ar
e gi
ven
in p
aren
thes
es, s
tand
ard
devi
atio
ns o
f the
unn
orm
aliz
ed v
alue
s ar
e la
rger
; FeO
t is
tota
l iro
n ox
ide
as F
eO; n
—nu
mbe
r of
ana
lyse
s; H
2Od
is
estim
ated
wat
er b
y di
ffere
nce;
Lab
—la
bora
tory
. UA
— U
nive
rsity
of A
lber
ta; W
SU
—W
ashi
ngto
n S
tate
Uni
vers
ity. W
L—W
etla
nd L
evee
. Ref
—re
fere
nces
: (1)
Dav
is (
1985
), (
2) S
arna
-Woj
cick
i et a
l. (1
989)
, (3)
Bus
acca
et
al.
(199
2), (
4) R
ieck
et a
l. (1
992)
, (5)
Her
rero
-Ber
vera
et a
l. (1
994)
, (6)
Neg
rini e
t al.
(199
4), (
7) W
hitlo
ck e
t al.
(200
0), (
8) K
uehn
and
Foi
t (20
06),
(9)
WS
U d
ata
prov
ided
by
Ric
hard
Con
rey(
2002
, per
sona
l co
mm
un.)
, (10
) WS
U d
ata
prov
ided
by
Fran
klin
Foi
t (20
07, p
erso
nal c
omm
un.)
; pop
.—po
pula
tion;
UA
831
is a
lso
know
n as
CC
NM
-211
at W
SU
. No
corr
ectio
ns h
ave
been
app
lied
to th
e re
port
ed g
lass
sta
ndar
d va
lues
. Dat
a po
ints
that
app
ear
as o
bvio
us o
utlie
rs o
n bi
varia
te p
lots
are
not
incl
uded
in th
e sa
mpl
e or
pop
ulat
ion
mea
ns. S
ee T
able
S4
(see
text
foot
note
1)
for
com
plet
e E
PM
A (
elec
tron
pro
be m
icro
anal
ysis
) da
ta.
Sel
ecte
d lit
erat
ure
data
are
als
o in
clud
ed to
faci
litat
e di
scus
sion
(se
e te
xt).
The
se a
re d
esig
nate
d by
num
eric
al r
efer
ence
s in
the
far
right
col
umn.
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Kuehn and Negrini
414 Geosphere, August 2010
Some modest differences are apparent between the data sets produced in the two laboratories. For mafi c tephras, FeO values tend to be ~0.5–1 wt% higher in the UA data (Table 2), probably due to the use of different Fe standards. There also are some differences in Na
2O and SiO
2 values that vary from sample
to sample, and these are likely due to variations in Na migration resulting from the different beam currents.
To compare compositional values of dif-ferent samples and evaluate potential cor-relations, two approaches were used: (1) the similarity coeffi cient of Borchardt et al. (1971, 1972), and (2) bivariate plots combining both unknowns and reference data. The similar-ity coeffi cient (SC), a simple ratio between concentrations, was employed in the same manner used in Kuehn and Foit (2006). This includes differential weighting of the various oxides to refl ect differences in analytical preci-sion. Higher SC values indicate more similar compositions, and identical values result in an SC of 1.0. Repeated analysis of the same homogeneous tephra on the same instrument typically results in similarity coeffi cients of 0.97–0.99 between sample means, thus SCs >0.97 are considered good evidence for corre-lation. Comparison of less homogeneous sam-ples and comparison of analyses of the same tephra performed at different laboratories com-monly results in lower similarity coeffi cients. An SC of 0.92 typically is considered the low-est acceptable value for correlation (Froggatt, 1992), provided that other signifi cant and com-pelling evidence is available. For composition-ally heterogeneous samples with well-defi ned end members, it is possible to use the SC to compare the end-member compositions sepa-rately. Similarly, the individual populations in bimodal and polymodal samples may also be treated separately.
For heterogeneous samples, bivariate plots are generally superior to the SC for evaluat-ing potential correlations because plots allow full examination of multiple populations, com-positional ranges, covariation trends, and the relative frequencies of different glass compo-sitions. Even in more homogeneous samples, bivariate plots sometimes reveal subtle varia-tions that can be important for testing correla-tions. Plots are typically less useful when com-paring to published data, because the individual data points used to calculate the mean values are often not reported. In this study, bivariate plots were used extensively to test correlations between the outcrop localities. Where the nec-essary reference samples or reference data sets were available, bivariate plots were also used to evaluate distal correlations.
TEPHRA BEDS AND STRATIGRAPHY
At least 88 visible tephra beds are preserved in 18.4 m of lacustrine sediments at the C, E, and F outcrop locations along the Ana River (Fig. 6; Table 1). Most consist of particles of silt to fi ne or medium sand size, but several contain coarser grains, including three beds that contain small pumice lapilli. Table 1 summarizes the thickness, particle size, and outcrop color for each tephra bed, along with the silica content of the glass. Silica ranges are provided for samples in which observed variability noticeably exceeds analyti-cal error. For the remaining samples, observed variability is largely a function of analytical error, so approximate mean values are provided instead. Photographs of most of the numerous tephra beds are available in Figures S1–S38 in the Supplemental Figure File2. Names for previ-ously known tephra beds and designations for new beds follow the scheme of Allison (1945) and Davis (1985). The six tephra layers desig-nated only by number were named by Allison (1945) in his description of the top few meters of section. Davis (1985) included these designa-tions in his nomenclature and named additional tephra from the top of the section down using the alphabet. After the fi rst 26 he used double letters (e.g., tephra Z is followed by AA). When new tephra beds were found between previously identifi ed beds, he added sequential numbers after the name of the upper tephra (e.g., T1 is the name of the tephra found between tephras T and U). Note that several tephra beds described here have more familiar names based on correlatives studied elsewhere. For examples, tephra 12 is correlative to the Mount St. Helens Cy tephra, also known farther south in the Great Basin as the Marble Bluff bed (Davis, 1985).
The youngest recognized tephra at Summer Lake, the Mazama tephra from Crater Lake, is present as pale yellow to brown lapilli and ash in surfi cial dune sediments that unconformably overlie the lacustrine deposits (Davis, 1985). The youngest water-lain tephra beds (D–A) and the youngest lacustrine sediments found along the Ana River are known only from the top of site E. Here, the sequence is inclined slightly to the west, and it is possible that even younger beds may be present to the west of the canyon expo-sures beneath surfi cial sediments. The oldest deposits exposed in canyon outcrop are found at the bottom of site C and adjacent areas. Here,
2Supplemental Figure File. PDF fi le of 38 supple-mental fi gures. If you are viewing the PDF of this paper or reading it offl ine, please visit http://dx.doi.org/10.1130/GES00515.S2 or the full-text article on www.gsapubs.org to view the supplemental fi gure fi le.
tephra bed NN is present several centimeters below the surface of the Ana River (Figs. 6 and S4 [see footnote 2]; Table S1 [see footnote 1]).
Stratigraphic relations are not entirely certain for a small number of beds. Stratigraphic rela-tions between JJ0.6 and JJ1, for example, are not known directly as they have not been found together (although based on their relative posi-tions between beds JJ and KK as shown in Fig. 6, it is suspected that JJ0.6 is younger than JJ1). Similarly, the age of EE3 in relation to EE1 and EE2 is unclear, as EE3 was found only at site E, and EE1 and EE2 were observed only at site C.
Several tephra beds have conspicuous internal layering, including beds 2, GG, and JJ (Table 1). The bottom of tephra 2 typically consists of two 8–10-mm-thick upward-fi ning layers (Fig. S30 [see footnote 2]). These are overlain by multiple thin layers that consist of tephra mixed with a lesser amount of silt; this in turn is capped by a lighter colored, 2–3-mm-thick tephra layer. A possible explanation for this pattern is two pulses of the same eruption followed by a short time for reworking and redeposition followed by an additional eruption of the same magma. Tephra GG typically has a 1 cm white base that is overlain by alternating lighter and darker gray layers. At site C, the base of tephra JJ is a pre-dominantly white, 1-mm-thick layer consisting of silt- to very coarse sand–sized pumiceous ash. Above this is a 2-mm-thick layer that con-tains a mixture of dark gray, medium- to coarse sand–sized grains and white, lower density grains of coarse to very coarse sand size. Above this is a 1-cm-thick layer of orange to dark gray color that consists largely of the darker tephra. The uppermost layer consists of 2 mm of silt-sized gray ash.
The host sediments for the Summer Lake tephra beds typically also contain signifi cant tephra glass. This likely results from a combina-tion of reworking together with the signifi cant input of tephra to the basin from the Cascade
Figure 6 (Continued on following pages). Tephrostratigraphy for sites C, E, and F. Thicker beds are shown to scale (angled shading). Arrows between columns indi-cate correlations between sites. Dotted and dashed lines indicate selected carbonate (tufa) beds. Dotted lines indicate selected sand beds. Short dotted lines at the top left of each column indicate the local datums (local zero depth) used for Tables 3 and S1–S3 (see footnote 1). Selected correlations to named beds that are known outside of the Summer Lake basin and selected ages are indicated adjacent to short arrows.
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Geosphere, August 2010 415
Site E
B1
D
B
A
C
E
I1
H0.2
B2
St. Helens Mp
M
R3
N
C2
C1
H1H2
Site C
F
12
1818
G
H
864
2
I
J
H2
H0.2
Trego Hot Springs
K
OPQR
R1
S
L
major unconformity
T
VU
T1
Wono
Pumice Castle
E1 E1
H1
H3
J3
L1
N2
R2R3
Site F
F
12
G
H
864
2
I
J
H0.4
F1
O
QR
S
majorunconformity
T
T1
G1
J1
J3
K
N (N1)
P
T0.5
minorunconformity ?
L
1
2
3
4
5
6
7
8
9
0
Depth (m)
H0.4
J1J2
J2
R1R2
Mt. St. Helens Cy
minor unconformity ?
Ice Quarry
9912D
9920C
984F984G5
978D/0004F
minor unconformity ?
minorunconformity ?
Correlated Units
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Kuehn and Negrini
416 Geosphere, August 2010
U
Y
GG
JJ0.6
HH
EE3
II
Ana River
FF
JJ 0.4
V
X
Z
BB
DD
FF
HH
JJ
KK
LL
AA
CC
EE
GG
II
II1
Y
W
JJ1
LL1
LL2
MM
Pringle Falls K
Pringle Falls H
Pringle Falls D
Pringle Falls S
Ana RiverNN
Shevlin Park Tuff
BB1
DD1
EE1EE2
GG1
JJ0.2JJ0.4
KK1
MM1
AA1
W (OO)
AA1
DD
KK
EE
KK1
JJII1
Z
LLLL1
Ana River
9
10
11
12
13
14
15
16
17
18
AA2
FF1
JJ 0.2
Pringle Falls E
VV
Antelope Well tuff
U978D/0004F
9881C,Qdt-Qto
minor unconformity ?
minorunconformity ?
LL3?
Figure 6 (Continued).
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250,000-year tephra record from Summer Lake
Geosphere, August 2010 417
volcanic arc, some of which is too disseminated to form visible beds. Pure samples were diffi -cult to obtain for some of the thinner beds, and the resulting EPMA data sets contain a chaotic mixture of glass compositions (Table S4 [see footnote 1]). These mixtures are likely to rep-resent a combination of primary deposition (the visible tephra bed) and reworked tephra (from the host sediments). In many cases, samples that appear to contain a signifi cant reworked tephra component also contain some shards with ele-vated K
2O and low Na
2O values (Table S4 [see
footnote 1]), features that are common in glass that has undergone alkali exchange (Shane, 2000). This altered glass may possibly derive from Miocene and Pliocene tuffs and tuffaceous sediments (Walker, 1963; Travis, 1977) exposed in the Winter Ridge escarpment that bounds the western side of the basin (Fig. 2).
Although the lake sediments consist predomi-nantly of silt and clay, signifi cant sand is present. This consists largely of ostracode valves, and several sand beds composed almost entirely of ostracodes are present (Tables S1–S3 [see foot-note 1]). Also present in the sequence are several continuous or semicontinuous carbonate beds (tufas) and several beds with hard or soft carbon-ate nodules. A few of the more prominent tufas and sand beds are useful for correlation (Fig. 6).
Previous work (Davis, 1985; Davis, in Erbes, 1996, and in Negrini et al., 2001; Negrini and Davis, 1992; Erbes, 1996; Langridge, 1998; Negrini et al., 2000) documented two signifi -cant unconformities in outcrop and core and suggested several additional minor unconfor-mities or hiatuses. As these sometimes appear to vary laterally in their character (i.e., between disconformity and angular unconformity), we describe them in nonspecifi c terms. At site C, the main unconformity is marked by several cen-timeters of sand over a tufa bed and is located below tephra beds L and L1 at a depth of 5.83 m (Figs. 3, 6, and S1 [see footnote 2]; Table S1 [see footnote 1]). At site F, the same unconformity is marked by as much as 22 cm of cross-bedded sand on top of a thin layer of ooids and a discon-tinuous tufa located at a depth of ~4.8 m below tephra bed L (Figs. 5, 6, and S1 [see footnote 2]; Table S3 [see footnote 1]). At site E, thick sand and tufa layers are absent, and the location of the equivalent unconformity is assigned to an abrupt transition at 6.83 m from fi ner silt and clay to coarser silt that is overlain by a thin ostracode sand (Figs. 4 and S1 [see footnote 2]; Table S2 [see footnote 1]). The same unconformity is also known from the WL core and is probably related to a lowstand during marine oxygen isotope stage 5 (Cohen et al., 2000; Negrini et al., 2000).
Davis (1985) described a second major unconformity at site F that is marked in our exca-
vation by conspicuous cross-bedded sands and tufa below tephra bed T1 at a depth of 7.06 m (Figs. 5, 6, and S2 [see footnote 2]; Table S3 [see footnote 1]). Davis (1985) interpreted the fi ve tephra beds that he found below this uncon-formity to be older than tephra NN, which is found at the base of site C, and so gave them designations SS–OO. Based on the fi eld char-acter of these beds in our deeper excavation and the tephra glass compositions, we reinterpret the beds below Davis’s lower unconformity as cor-relative to tephra layers found at sites C and E (e.g., beds OO and W are equivalent) (Fig. 6). This removes most of the time gap associated with Davis’s earlier interpretation.
A prominent thick sandy bed, but no tufa, is also present beneath bed T1 at site E at a depth of 9.54 m in a stratigraphic position equivalent to Davis’s (1985) lower site F unconformity (Figs. 6 and S2 [see footnote 2]; Table S2 [see footnote 1]). At site C an apparently correla-tive sandy interval is present beneath bed T1 at 8.99 m, but is much less prominent (Figs. 6 and S2 [see footnote 2]; Table S1 [see footnote 1]). At site C, a distinct repeating paleomagnetic waveform continues across this interval and further argues against a signifi cant gap in time (Negrini et al., 1994).
An additional unconformity was observed higher in the section at site E, where disrupted beds K and L are truncated by sandy sediments and a tufa at a depth of 6.45 m (Figs. 6 and S3 [see footnote 2]; Table S2 [see footnote 1]). Equivalent sand and tufa beds are also present 10–15 cm below bed J3 at sites C and F (at total depths of 5.06 and 4.05 m, respectively), so the same unconformity might exist there as well (Fig. 6; Tables S1 and S3 [see footnote 1]). A few centimeters higher and just below bed J3 is an abrupt transition from silty to sandy sedi-ments that may mark a second unconformity in this interval (Figs. 6 and S3 [see footnote 2]; Tables S1–S3 [see footnote 1]). Davis (in Erbes, 1996) and Erbes (1996) suggested a possible unconformity and soil horizon associated with sand and tufa beds ~0.6 m below tephra bed LL1 at site C (Fig. 6; Table S1 [see footnote 1]).
Variations in lake level (Negrini et al. 2000; Cohen et al., 2000) are clearly apparent in the fi eld. Deeper water intervals are associated with fi ner sediments that are often fi nely laminated and tend to develop a blocky texture. These deeper water sediments on occasion contain isolated pebbles that may represent dropstones, suggest-ing that deeper water intervals are times associ-ated with colder climates. Shallower intervals are associated with lower clay contents and higher sand contents, and may be associated with tufas, unconformities, and sand beds containing ostra-codes coated with carbonate and/or iron oxides.
CORRELATIONS AND AGES
Age control for the Summer Lake area sedi-ments is derived from the correlation of tephra beds and paleomagnetic variations to other dated records plus a limited number of radiometric dates on the Summer Lake deposits (Table 2). On this basis, age-depth models have been con-structed for the upper sediments (Negrini and Davis, 1992; Zic et al., 2002) and the entire outcrop sequence (Negrini et al., 2000). For the uppermost ~5 m, the chronology is well con-strained, but there is considerable uncertainty in the ages of the middle to lower portions of the outcrop sequence.
The uppermost correlated tephra is the Mazama tephra from Crater Lake, Oregon. Mazama tephra is present in surfi cial sedi-ments that unconformably overlie the lake beds (Davis, 1985), and thus provides a minimum age for the youngest lacustrine sediments. Mazama tephra has a weighted mean radiocarbon age of 6730 ± 40 14C yr B.P. (7470–7620 calendar yr B.P.) (Hallett et al., 1997), and Zdanowicz et al. (1999) reported an essentially equivalent age of 7627 ± 150 cal yr B.P. based on identifi cation of Mazama tephra in the GISP2 (Greenland Ice Sheet Project) core.
Other previously correlated units in the upper portion of the section include bed D (Mount St. Helens Mp); bed 18 (Trego Hot Springs tephra); bed E1 (Tulelake T2438); bed F (Wono tephra); bed G (9715K, found at but not originating from Newberry Volcano); bed 12 (Mount St. Helens Cy); 8, 6, and 4 (beds of the Pumice Castle set); and bed 2 (Ice Quarry tephra) (Davis, 1985; Rieck et al., 1992; Negrini et al., 2000; Kuehn and Foit, 2006) (Fig. 6; Tables 2, S2, and S3 [see footnote 1]). All of these beds except E1 and G have associated dates by 14C, thermolu-minescence (TL), or K-Ar methods (Figs. 6–8; Table 3). The Trego Hot Springs and Pumice Castle beds originate from Crater Lake (Davis, 1985). The Ice Quarry tephra originates from Newberry Volcano (Kuehn, 2002; Kuehn and Foit, 2006). Beds G and F (Wono tephra) cor-relate to coarser deposits in the vicinity of New-berry Volcano to the north (Kuehn, 2002, Kuehn and Foit, 2006) (Fig. 1; Table 2).
The glass in bed B1 is similar in composition (SCs of 0.97) to proximal Llao Rock tephra fall deposits at Crater Lake (Table 2) that preceded the climactic Mazama tephra by 100–200 yr (Bacon and Lanphere, 2006). B1, however, is too old to directly correlate with the Llao Rock deposit, but the strong compositional similarity may be interpreted to suggest Mount Mazama (Crater Lake) as the likely source.
Bed I, newly analyzed herein, is very similar in glass composition (SCs to 0.99) to the much
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Kuehn and Negrini
418 Geosphere, August 2010
0.0
1.0
2.0
3.0
4.0
5.0
52.0 56.0 60.0 64.0 68.0 72.0SiO2
MgO
1.0
3.0
5.0
7.0
9.0
2.0 4.0 6.0 8.0 10.0 12.0FeO
CaO
AShevlin Park Tuff reference
Bed AA1
0.0
2.0
4.0
6.0
8.0
1.0 3.0 5.0 7.0 9.0FeO
CaO
Bed JJ
Bed II1
Bed JJ0.2
0.0
1.0
2.0
3.0
56.0 60.0 64.0 68.0 72.0 76.0SiO2
MgO
0.0
0.1
0.2
0.3
72.0 74.0 76.0 78.0SiO2
MgO
Bend pumice, Tumalo tuff reference
Bed JJ1
0.4
0.6
0.8
1.0
1.2
1.3 1.7 2.1 2.5FeO
CaO
B
C
0.25
0.0073.0 75.01.75 2.25
1.25
0.75
Figure 7 (Continued on following page). Plots of probe data for selected Summer Lake beds and reference samples.
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250,000-year tephra record from Summer Lake
Geosphere, August 2010 419
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
70.0 72.0 74.0 76.0SiO2
MgO
0.5
0.9
1.3
1.7
2.1
1.2 1.6 2.0 2.4 2.8 3.2 3.6FeO
CaO
Beds II1, JJ, JJ0.2
Bed JJ1
0.0
2.0
4.0
6.0
1.0 2.0 3.0 4.0 5.0 6.0 7.0FeO
CaO
Antelope Well tuff referenceBed KK
0.0
1.0
2.0
3.0
60.0 64.0 68.0 72.0 76.0SiO2
MgO
D
E
Figure 7 (Continued).
bed AA1 - Shevlin Park tuff(primary graded bed)
bed AA1 - Shevlin Park tuff(primary graded bed)
laminated,redeposited tephra
laminated,redeposited tephra
Site CSite C
Figure 8. Photograph of bed AA1 (correlated to Shevlin Park Tuff) at site C.
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Kuehn and Negrini
420 Geosphere, August 2010
TAB
LE 3
. AG
E C
ON
TR
OL
FO
R T
HE
SU
MM
ER
LA
KE
OU
TC
RO
P S
EQ
UE
NC
E
Dat
ed b
ed o
r ho
rizon
Cor
rela
tive
unit
Age
and
1σ
erro
r (k
a)M
etho
dA
ge r
efer
ence
Not
es
Maz
ama
teph
ra7.
545
± 0
.075
radi
ocar
bon
Hal
lett
et a
l. (1
997)
Wei
ghte
d m
ean
age
of 6
730
± 4
0 14
C y
r B
.P. (
7470
–762
0 ca
lend
ar y
r B
.P.)
Teph
ra in
GIS
P2
core
Maz
ama
teph
ra7.
627
± 0
.150
posi
tion
in c
ore
Zda
now
icz
et a
l. (1
999)
Gre
enla
nd Ic
e S
heet
Pro
ject
2 (
GIS
P2)
cor
e ha
s an
ann
ually
cou
nted
chr
onol
ogy
(Mee
se e
t al.,
199
7)B
ed A
18.2
pale
omag
netic
cor
rela
tion
Neg
rini a
nd D
avis
(19
92),
N
egrin
i et a
l. (2
000)
Est
imat
ed a
ge o
f bed
A b
ased
on
pale
omag
netic
cor
rela
tion
to r
adio
carb
on-d
ated
W
ilson
Cre
ek r
ecor
d (p
luvi
al L
ake
Rus
sell)
with
adj
ustm
ent f
or r
evis
ed a
ge o
f Won
o te
phra
Mou
nt S
t. H
elen
s M
pB
ed D
~22.
9ra
dioc
arbo
nC
lynn
e et
al.
(200
9)T
hree
cal
ibra
ted
radi
ocar
bon
ages
from
pro
xim
al M
ount
St.
Hel
ens
set M
dep
osits
su
gges
t an
age
of 2
2.2–
23.6
ka.
Indi
vidu
al a
ges:
19,
670
± 6
0 14
C y
r B
.P.
(23,
590
+
120,
–150
cal
yr
B.P
.), 1
8,56
0 ±
180
14C
yr
B.P
. (22
,170
+ 1
90,–
240
cal y
r B
.P.)
, and
19
,160
± 2
50 1
4C y
r B
.P. (
22,6
20 +
520
,–21
0 ca
l yr
B.P
.)B
ed 1
8–Tr
ego
Hot
Spr
ings
24.8
± 1
.0w
eigh
ted
mea
nW
eigh
ted
mea
n of
ther
mol
umin
esce
nce
and
calib
rate
d ra
dioc
arbo
n ag
es b
elow
Bed
18
Treg
o H
ot S
prin
gs23
.5 ±
2.5
ther
mol
umin
esce
nce
Ber
ger
(199
1)
Dat
e on
sam
ple
of b
ed 1
8 te
phra
col
lect
ed a
t site
ETr
ego
Hot
Spr
ings
Bed
18
25.0
± 1
.1ra
dioc
arbo
nZ
ic (
2001
)23
,200
± 3
00 1
4C y
r B
.P. a
ge o
f Ben
son
et a
l. (1
997)
, cal
ibra
ted
and
rese
rvoi
r co
rrec
ted
Won
oB
ed F
29.1
± 0
.9ra
dioc
arbo
nZ
ic (
2001
), Z
ic e
t al.
(200
2)27
,300
± 3
00 1
4C y
r B
.P. a
ge o
f Ben
son
et a
l. (1
997)
, cal
ibra
ted
and
rese
rvoi
r-co
rrec
ted
Bed
FW
ono
29.7
pale
omag
netic
cor
rela
tion
to G
ISP
2Z
ic (
2001
), Z
ic e
t al.
(200
2)M
odel
age
for W
ono
teph
ra in
B&
B (
Bed
&B
reak
fast
) co
re b
ased
on
corr
elat
ion
of
pale
omag
netic
var
iatio
ns w
ith G
ISP
2 18
O r
ecor
dM
ono
Lake
exc
ursi
on30
.5 ±
1.3
pale
omag
netic
cor
rela
tion
Zic
(20
01),
Zic
et a
l. (2
002)
Age
of M
ono
Lake
exc
ursi
on (
MLE
) in
rad
ioca
rbon
-dat
ed W
ilson
Cre
ek r
ecor
d (p
luvi
al L
ake
Rus
sell)
(N
egrin
i et a
l., 2
000)
cor
rect
ed fo
r re
vise
d (c
alib
rate
d, r
eser
voir
corr
ecte
d) a
ge o
f Won
o te
phra
Mon
o La
ke e
xcur
sion
33.9
± 0
.5pa
leom
agne
tic c
orre
latio
n to
GIS
P2
Zic
(20
01),
Zic
et a
l. (2
002)
, B
enso
n et
al.
(200
3)A
ge fo
r in
clin
atio
n lo
w w
ithin
MLE
in B
&B
cor
e ba
sed
on c
orre
latio
n of
pal
eom
agne
tic
varia
tions
with
GIS
P2
18O
and
36C
l rec
ords
; MLE
is a
lso
reco
rded
at A
na R
iver
site
E
(Neg
rini a
nd D
avis
, 199
2; N
egrin
i et a
l., 2
000)
B
ed 1
2M
ount
St.
Hel
ens
Cy
46.3
± 4
.8th
erm
olum
ines
cenc
eB
erge
r an
d B
usac
ca (
1995
)D
ate
on s
ampl
e of
bed
12
teph
raB
ed 1
2M
ount
St.
Hel
ens
Cy
45.6
pale
omag
netic
cor
rela
tion
to G
ISP
2Z
ic (
2001
), Z
ic e
t al.
(200
2)M
odel
age
for
Mou
nt S
t. H
elen
s C
y te
phra
in B
&B
cor
e ba
sed
on c
orre
latio
n of
pa
leom
agne
tic v
aria
tions
with
GIS
P2
18O
rec
ord
Mou
nt S
t. H
elen
s C
yB
ed 1
2<
47.
43 ±
0.6
radi
ocar
bon
Cly
nne
et a
l. (2
009)
Rad
ioca
rbon
age
42,
950
± 5
60 1
4C y
r B
P (
47.4
2 ±
0.6
0 ka
cal
yr
B.P
.) o
n ch
arco
al
from
the
uppe
r pa
rt o
f lay
er C
b fo
und
belo
w C
y at
Mud
dy R
iver
Qua
rry
Pum
ice
Cas
tleB
ed 6
71 ±
5K
-Ar
Bac
on a
nd L
anph
ere
(200
6)W
eigh
ted
mea
n of
two
date
s on
Pum
ice
Cas
tle d
acite
Bed
2 (
site
C)
67.3
± 7
.2th
erm
olum
ines
cenc
eB
erge
r (1
991)
D
ate
on s
ampl
e of
bed
2 te
phra
col
lect
ed a
t site
C
EM
SH
teph
ra b
edB
ed I
83 ±
8th
erm
olum
ines
cenc
eB
erge
r an
d B
usac
ca (
1995
)D
ate
on lo
ess
10 c
m b
elow
EM
SH
ash
bed
of B
usac
ca e
t a. (
1992
); E
MS
H b
ed is
at
leas
t fro
m th
e sa
me
erup
tive
perio
d as
bed
I an
d is
pos
sibl
y co
rrel
ativ
e (s
ee te
xt)
Bed
N10
2.3
± 1
1th
erm
olum
ines
cenc
eB
erge
r (1
991)
D
ate
on s
ampl
e of
bed
N te
phra
col
lect
ed a
t site
E
Bed
R16
5 ±
19th
erm
olum
ines
cenc
eB
erge
r (1
991)
D
ate
on s
ampl
e of
bed
R te
phra
col
lect
ed a
t site
E
She
vlin
Par
k Tu
ffB
ed A
A1
260
± 1
5A
r-A
r pl
atea
uLa
nphe
re e
t al.
(199
9)D
ate
on p
lagi
ocla
se fr
om p
roxi
mal
She
vlin
Par
k Tu
ff
She
vlin
Par
kTuf
fB
ed A
A1
255
± 7
4A
r-A
r is
ochr
onLa
nphe
re e
t al.
(199
9)D
ate
on p
lagi
ocla
se fr
om p
roxi
mal
She
vlin
Par
k Tu
ff
Prin
gle
Falls
DB
ed G
G22
1 ±
10
Ar-
Ar
plat
eau
Sin
ger
et a
l. (2
008)
Dat
e on
pla
gioc
lase
from
Prin
gle
Falls
D te
phra
; rec
alib
rate
d fr
om H
erre
ro-B
erve
ra e
t al
. (19
94)
Prin
gle
Falls
DB
ed G
G21
1 ±
6.4
Ar-
Ar
isoc
hron
Sin
ger
et a
l. (2
008)
Mea
n of
16
isoc
hron
s fo
r pl
agio
clas
e fr
om P
ringl
e Fa
lls D
teph
ra; m
ean
– 1?
use
d fo
r ag
e-de
pth
mod
elP
ringl
e Fa
lls e
xcur
sion
Bed
GG
218
± 1
4pa
leom
agne
tic c
orre
latio
nS
inge
r et
al.
(200
8)A
ge o
f Prin
gle
Falls
exc
ursi
on in
lava
s of
the
Alb
uque
rque
Vol
cano
es, N
ew M
exic
o,
base
d on
Ar-
Ar
datin
g of
gro
undm
ass
(wei
ghte
d m
ean
of is
ochr
ons
for
six
sam
ples
)P
ringl
e Fa
lls e
xcur
sion
Bed
GG
227
± 8
pale
omag
netic
cor
rela
tion
Hou
ghto
n et
al.
(199
5),
McW
illia
ms
(200
1)A
ge o
f Prin
gle
Falls
exc
ursi
on in
the
Ar-
Ar
date
d M
amak
u ig
nim
brite
, New
Zea
land
Prin
gle
Falls
exc
ursi
onB
ed G
G20
5-22
5pa
leom
agne
tic c
orre
latio
nC
hann
ell (
2006
) E
stim
ated
age
of P
ringl
e Fa
lls e
xcur
sion
in m
arin
e ox
ygen
isot
ope
stra
tigra
phy
of
Oce
an D
rillin
g P
rogr
am S
ite 9
19P
ringl
e Fa
lls D
Bed
GG
142
± 3
3th
erm
olum
ines
cenc
eB
erge
r (2
001)
Dat
e on
sam
ple
of P
ringl
e Fa
lls D
teph
raA
ntel
ope
Wel
l tuf
fB
ed K
K17
1 ±
43A
r-A
rH
erre
ro-B
erve
ra e
t al.
(199
4)D
ate
on p
lagi
ocla
se fr
om p
umic
e co
llect
ed fr
om o
utcr
op o
f the
tuff
Bed
KK
200
± 2
7th
erm
olum
ines
cenc
eB
erge
r (1
991)
D
ate
on s
ampl
e of
bed
KK
teph
ra c
olle
cted
at s
ite C
Bed
LL
160
± 3
5th
erm
olum
ines
cenc
eB
erge
r (1
991)
D
ate
on s
ampl
e of
bed
LL
teph
ra c
olle
cted
at s
ite C
Qdt
-Qto
teph
raB
ed N
N~
300
Ar-
Ar
Don
nelly
-Nol
an e
t al.
(200
4)A
ppro
xim
ate
age
of p
roxi
mal
Qdt
-Qto
teph
ra (
igni
mbr
ite);
9881
C is
pro
babl
y th
e pr
oxim
al te
phra
-fall
equi
vale
nt (
Kue
hn a
nd F
oit,
2006
).
Not
e: A
ges
used
to c
onst
ruct
the
age-
dept
h m
odel
sho
wn
in F
igur
e 10
and
Tab
le 3
are
hig
hlig
hted
in b
old
type
.
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250,000-year tephra record from Summer Lake
Geosphere, August 2010 421
younger bed 12 (Mount St. Helens Cy) found 2–3 m above it (Table 2). It is also similar in composition to a series of tephra beds thought to be of Mount St. Helens origin that are known from Washington and Idaho and that date to ca. 70–120 ka (Busacca et al., 1992; Berger and Busacca, 1995; Bouchard et al., 1998; Whitlock et al., 2000) (Table 2). Based on glass com-positions and estimated ages, the most likely potential correlatives to bed I are Carp Ash-8 and Carp Ash-9 from Carp Lake (Whitlock et al., 2000) (Fig. 1; Table 2) (SCs to 0.97 and 0.95, respectively) and the EMSH ash of simi-lar age from sites KP-1 and WA-5 (Busacca et al., 1992) (Fig. 1; Table 2) (SCs of 0.94–0.95 to sample KP-1D). The EMSH ash, which is found in loess in eastern Washington State, is associ-ated with a TL date of 83 ± 8 ka (Berger and Busacca, 1995) (Table 3), consistent with the position of bed I in the Summer Lake age-depth model in Negrini et al. (2000).
The next lower dated layer is bed N. Bed N and the much thinner bed M just above it were indicated by Davis (1985) to be above the major unconformity at sites C and F. Berger (1991) obtained a TL date of 102.3 ± 11 ka on bed N (Table 3), and this age and the stratigraphic context indicated by Davis (1985) were used in Negrini et al. (2000) to construct an age-depth model. However, new excavations at sites C and F failed to locate the M and N pair in Davis’s (1985) indicated stratigraphic context. Neither are they noted at site C in Davis’s composite section (in Erbes, 1996; Negrini et al., 2001) or in Erbes (1996). A pair of beds matching Davis’s (1985) description of M and N was found in the site E excavation, however, and it is from this locality that Berger (1991) obtained his dated sample.
A similar pair of beds (0.6–0.8 and 6 cm thick) was also sampled during reexamina-tion of the WL core. These are equivalent to
WL-37–1 and WL-37–2 in Negrini et al. (2000). They have the same thicknesses (Table S2 [see footnote 1]), glass composition (Table 2), and relative stratigraphic position as M and N at site E. They also were interpreted in Negrini et al. (2000) as being below the major unconformity that occurs below bed L in the WL core, below bed L at sites C and F, and probably also below bed L at site E (Figs. 6 and S1 [see footnote 2]; Tables S1–S3 [see footnote 1]). Reinterpret-ing beds M and N as being below the uncon-formity requires revision of the published age-depth model (discussed further herein), and also permits the correlation of bed N1 with bed N. Bed N1, located at site F, has the same glass composition (Table 2), the same thickness, and the same particle size range as bed N (Fig. 9; Tables S2 and S3 [see footnote 1]). Bed N1 also has the same stratigraphic relations with the unconformity above and beds O, P, and Q below (Fig. 6). Beds M and N are also similar in glass
bed N1bed N1
Site ESite E Site FSite F
bed Nbed N
bed Nbed N
bed Mbed M bed M?bed M?
bed Mbed M
Site ESite E
Figure 9. Photographs of beds M, N, and N1 at sites E and F. M and N form an easily recognizable set at both site E and in the Wetland Levee core.
on April 8, 2012geosphere.gsapubs.orgDownloaded from
Kuehn and Negrini
422 Geosphere, August 2010
composition to Newberry tephra 9912D and thus are probably correlative (Kuehn and Foit, 2006) (Table 2).
A further implication of correlating N and N1 and reinterpreting the stratigraphic position of the associated unconformity is that it is now clear that beds OO–SS (described from beneath the unconformity at site F by Davis, 1985) need not be older than the base of the site C exposure. Of these beds, Davis (1985) reported a glass composition only for OO. Notably, this compo-sition is very similar to that of bed W (Table 2), suggesting that W and OO are the same bed. In Kuehn and Foit (2006), W was identifi ed at site C as a new bed W1, but the stratigraphic posi-tion relative to carbonate beds above it at site C and the relations shown in the composite mea-sured section of Davis (in Erbes, 1996; Negrini et al., 2001) suggest that this is, in fact, bed W of Davis (1985).
Beds Q, S, T, T1, and V are compositionally similar to tephra beds at Newberry Volcano and are likely correlative (Kuehn and Foit, 2006). The glass composition of bed Q is similar to that of Newberry tephra 9920C; S, T, and T1 are very similar in composition to Newberry tephra beds 984F and 984G5; and V is similar to New-berry tephras 978D and 0004F, which are tephra fall and pyroclastic fl ow deposits, respectively (Kuehn, 2002; Kuehn and Foit, 2006) (Table 2). Bed V has also been previously correlated to tephra bed T1193 found at 32.28 m in the Tule-lake core (Rieck et al., 1992; Herrero-Bervera et al., 1994; Negrini et al., 1994) (Table 2). Consistent stratigraphic relations provide fur-ther supporting evidence for the Summer Lake– Newberry correlations. Beds Q, S, T, T1, and V at Summer Lake occur in the same stratigraphic order as the beds at Newberry Volcano that are interpreted as correlative (Kuehn, 2002).
Bed R was dated by TL. Glass sample SML-1a from bed R at site E provided a TL date of 165 ± 19 ka (Berger, 1991) (Table 3).
Like bed I, bed W is similar in glass com-position to bed 12 (Davis, 1985; Kuehn and Foit, 2006) (SCs of 0.97–0.98) and to the ca. 70–120 ka Mount St. Helens set C–like beds discussed herein (Table 2) (e.g., SCs of 0.96–0.97 to Carp Ash 8). The position of bed W at Summer Lake suggests that it is signifi -cantly older than the inferred ages of these beds and therefore not directly correlative. The strong compositional similarity together with the age relations suggests that bed W represents an ear-lier eruption of Mount St. Helens.
Glass in bed AA1 is very heterogeneous and is somewhat bimodal (Fig. 7A). The two end members average ~56 and 69 wt% SiO
2,
and the overall average is ~62–63 wt% SiO2
(Table 1). The reported mafi c end-member
composition was calculated using data points with SiO
2 <57.3 wt%. The silicic end-member
composition was calculated using data points with SiO
2 >67.4 wt% and with CaO and
FeO <2.9 and <4.3 wt%, respectively (Table S4 [see footnote 1]).
Glass in bed AA1 is strikingly similar to that in proximal Shevlin Park Tuff, a largely bimodal andesitic ash-fl ow tuff found primarily to the west of Bend, Oregon, and erupted from a vent located east of the Three Sisters (Conrey et al., 2002; Sherrod et al., 2004). Lanphere et al. (1999) reported 40Ar/39Ar ages from plagio-clase of 260 ± 15 ka (plateau) and 255 ± 74 ka (isochron) for Shevlin Park Tuff (Table 3). Bed AA1 glass compositions are an excellent match to the compositional range, trend, and largely bimodal frequency distribution of Shevlin Park Tuff (Fig. 7A; Tables 2 and S4 [see footnote 1]). Similarity coeffi cients to proximal refer-ence material are also good, with SCs as much as 0.97 for the silicic end member, to 0.97 for the mafi c end member, and to 0.94 for the bulk composition. Most of the analyses of proximal Shevlin Park Tuff glass presented here are WSU data provided by R.M. Conrey (2002, personal commun.). When it was observed that this initial data set did not fully replicate the most mafi c shards in bed AA1, two of the most mafi c Shev-lin Park clasts identifi ed by X-ray fl uorescence were obtained from R.M. Conrey and analyzed at the UA (Table S4 [see footnote 1]). The addi-tional analyses from these clasts signifi cantly improved the match between the Shevlin and AA1 data sets apparent on bivariate plots and illustrate the importance of obtaining suffi -ciently representative reference material.
Shevlin Park Tuff was previously corre-lated with Summer Lake beds JJ (Gardner et al., 1992; Gardner and Negrini, 2001) and NN (Conrey et al., 2001). Bivariate plots (Figs. 7A, 7B) clearly distinguish Shevlin and JJ. Both the end-member compositions and frequency dis-tributions are substantially different. Bed NN glass is relatively homogeneous in composition, unlike that in Shevlin Park Tuff (Table 2).
Beds DD, EE, GG, and II were previously correlated to a series of beds preserved in lacustrine sediments at Pringle Falls, Oregon (Herrero-Bervera et al., 1994; Negrini et al., 1994) (Figs. 1 and 6). Glass in Summer Lake beds DD, EE, GG, and II are very similar in composition to Pringle Falls beds K, H, D, and S, respectively (Table 2). This set of beds also occurs in the same stratigraphic sequence at both locations.
Pringle Falls D (and thus Summer Lake GG) was also previously correlated to tephra PI-OR at Paoha Island in Mono Lake (Herrero-Bervera et al., 1994) (Fig. 1). In addition, bed GG is very
similar in glass composition to Newberry tephra 9917C (Table 2), and therefore may have origi-nated from Newberry Volcano (Kuehn and Foit, 2006). New bed EE2 is similar in glass compo-sition to Pringle Falls bed E (SC 0.98; Table 2) and is likely correlative. Pringle Falls E was previously correlated to Paoha Island and Ben-ton Crossing in California (Herrero-Bervera et al., 1994; Liddicoat et al., 1998, 1999) (Fig. 1). Whitlock et al. (2000) also noted a strong simi-larity between Pringle Falls E and Carp Lake Ash-14 (Table 2), but preferred an age model that precludes correlation.
Bed GG and its associated magnetic excur-sion provide the most precise age control point in the lower portion of the Summer Lake out-crop sequence. Herrero-Bervera et al. (1994) reported an 40Ar/39Ar plateau age on plagioclase of 227 ± 8 ka from the correlated Pringle Falls D bed. Singer et al. (2008) recalibrated this result to 198 ± 59 ka and 221 ± 10 ka for the isochron and plateau, respectively (Table 3). Singer et al. (2008) also dated an additional sample of Prin-gle Falls D plagioclase by 40Ar/39Ar and reported an age of 211 ± 6.4 ka (mean of 16 isochrons). GG and Pringle Falls D are also both closely associated with the Pringle Falls geomagnetic excursion (Herrero-Bervera et al., 1994; Negrini et al., 1994). It was proposed (Negrini et al., 2000; Negrini, 2002), based on the similarity of subsequent paleomagnetic secular variations, that the Pringle Falls excursion is correlative with a ca. 190 ka excursion found in marine sediment cores (e.g., Henyey et al., 1995). How-ever, the balance of radiometric dating evidence suggests that, instead, the Pringle Falls excur-sion is an older excursion (ca. 220 ka) that has been dated at other locations around the world both with the 40Ar/39Ar method and marine oxygen isotope stratigraphy (e.g., Channell, 2006). The corroborating 40Ar/39Ar ages include an isochron age of 218 ± 7 ka on groundmass (weighted mean of six samples) from the Albu-querque Volcanoes, New Mexico (Singer et al., 2008), and an 40Ar/39Ar age of 227 ± 8 ka on the Mamaku Ignimbrite, New Zealand (Houghton et al., 1995; McWilliams, 2001). Berger (2001) reported a signifi cantly younger TL age of 142 ± 33 ka for Pringle Falls bed D.
Initial EPMA analyses of bed JJ1 and proxi-mal reference material for Bend Pumice ana-lyzed on the same instrument on the same day produced essentially identical mean values, sug-gesting a potential correlation (see WSU results for samples C62 and 96–19, the fi rst two entries associated with bed JJ1 in Table 2). Because of the greater standard deviations in the JJ1 data and dates indicating a much older age for Bend Pumice (Lanphere et al., 1999), additional analyses were obtained to further evaluate the
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250,000-year tephra record from Summer Lake
Geosphere, August 2010 423
possible correlation. The resulting much larger data set on a total of six samples (UA results in Table 2), analyzed consecutively on the same day on the same instrument and including addi-tional reference material, instead revealed sig-nifi cant differences that preclude correlation. Bivariate plots clearly show that glass in the JJ1 sample from site C (C61) is bimodal (Fig. 7C; Table 2). The homogeneous Bend Pumice reference data plots between the two modes (Fig. 7C). The stratigraphically equivalent bed in the SPG-A core yielded only the higher silica mode (Table 2).
Bed KK has been previously correlated to the heterogeneous Antelope Well tuff (also known as Medicine Lake andesite tuff), which erupted from Medicine Lake volcano (Herrero-Bervera et al., 1994; Negrini et al., 1994). Donnelly-Nolan et al. (2008) regarded Antelope Well tuff as the single most important stratigraphic unit at Medicine Lake, as it forms the only widespread marker bed present at the volcano. To further test the correlation with bed KK, an Antelope Well reference sample, 194-M(2)A, was obtained from E. Wan (2007, personal commun.) at the Menlo Park campus of the U.S. Geological Survey and analyzed at WSU by F. Foit (2007, personal commun.). Additional analyses were obtained at the UA. Similar mean values (SC as high as 0.96) are generally supportive of the correlation between KK and Antelope Well tuff (Table 2), but the very similar distributions of glass compositions apparent on bivariate plots (Fig. 7E) are even more compelling and provide strong evidence for correlation. The plots demonstrate that KK and Antelope Well tuff have essentially identical major populations (range, trend, and frequency distribution), and both have similar trace populations of higher silica glass.
Bed KK was previously correlated with tephra in cores from Tulelake and Walker Lake (Herrero-Bervera et al., 1994; Negrini et al., 1994) (Fig. 1; Table 2). Negrini et al. (1994) and Sarna-Wojcicki et al. (2001) noted simi-larities between bed KK and the Wadsworth tephra bed of Davis (1978) (Table 2), but this latter correlation remains uncertain. Whitlock et al. (2000) also noted a similarity to Carp Ash-15 (Table 2), but preferred an age model that precludes correlation.
Several dates are available for bed KK and potentially correlative deposits. Berger (1991) reported a TL date of 201 ± 27 ka on glass in sample SML-21a from Summer Lake site C and a 201 ± 45 ka TL date from glass in sample JOD88B from the possibly correlative Wadsworth bed. Herrero-Bervera et al. (1994) reported 40Ar/39Ar plateau and isochron ages of 171 ± 43 and 149 ± 110 ka, respectively, for
plagioclase obtained from pumice in proximal Antelope Well tuff. All of the ages above over-lap at 1σ error. Older dates associated with the overlying bed GG (ca. 211 ka) favor a bed KK age toward the higher end of the error range associated with the dates discussed above. In contrast, Donnelly-Nolan et al. (2008) con-cluded that the age of the Antelope Well tuff is ca. 180 ka on the basis of a 40Ar/39Ar age, strati-graphic constraints from other (unspecifi ed) dated units, and evidence that the tuff erupted through an ice cap on the volcano (Donnelly-Nolan and Nolan, 1986). One possible solution is an eruption age of 225–230 ka. This is con-sistent with most of the age estimates and with the constraint provided by the ice cap interpreta-tion, because this age range is within a several-thousand-year-long glacial interval indicated by the marine oxygen isotope curve (Martinson et al., 1987). Although this older age is beyond the 1σ error range of the 171 ± 43 ka plateau date on the Antelope Well tuff, it is still within the 95% confi dence interval. Alternatively, the glacial history of the Medicine Lake volcano as suggested by Donnelly-Nolan and Nolan (1986) may not be representative of time-averaged global ice conditions, a supposition that is con-sistent with the relatively low magnetic suscep-tibility of the Summer Lake sediments contain-ing bed KK. Such magnetic properties appear to be indicators of shallow lakes during interglacial times (Negrini et al., 2000). A fi nal alternative is that the correlation between bed KK and Ante-lope Well tuff is incorrect. This, however, would require the existence of an additional major eruption of broadly similar age, with essentially identical major element glass geochemistry, and no known proximal deposits. It would also require the Antelope Well tuff to have not left any recognizable bed at Summer Lake.
Bed LL was dated by TL. Sample SML-5 from bed LL at site C yielded a TL data of 160 ± 35 ka (Berger. 1991). Berger (2001) consid-ered this to be a minimum age due to an unusual dose-response curve produced by the sample.
Bed NN, the lowermost bed in the outcrop sequence, is very similar in glass composition to homogeneous Newberry tephra units 9881C and Qdt-Qto (Table 2) and thus is probably correlative. Units Qdt and Qto are Newberry ash-fl ow tuffs that were mapped separately by MacLeod et al. (1995) and were later correlated on the basis of similar whole pumice composi-tions by J. Donnelly-Nolan (cited in Jensen et al., 2009; see also Kuehn and Foit, 2006), and on the basis of glass compositions (Kuehn, 2002). Newberry tephra 9881C is indistinguish-able in glass composition from the Qdt-Qto fl ow and is likely the tephra fall equivalent (Kuehn and Foit, 2006). We consider earlier correlations
of bed NN with Shevlin Park Tuff (Conrey et al., 2001) and with a preceding tephra fall pre-served at Columbia Canal (Columbia Canyon) (Sarna-Wojcicki et al., 2001) to be less likely. Shevlin Park Tuff is strongly heterogeneous and is an excellent match to bed AA1. Columbia Canal glass is close to NN on most elements, but the reported abundance of K
2O is signifi -
cantly lower (Table 2). Some constraint on the age of bed NN is provided by a 40Ar/39Ar age of ca. 300 ka on plagioclase from Qdt and Qto (Donnelly-Nolan et al., 2004).
Although a large number of mafi c tephra beds is preserved at Summer Lake, some of them containing sand-sized grains, none of them has been correlated to specifi c source vents outside of the basin. In the Fort Rock–Christmas Lake basin, ~40–60 km to the north, are numerous maars, tuff cones, and cinder cones that are regarded as Pliocene– Pleistocene in age (Heiken, 1971). Although these are the closest potential sources, their ages are poorly constrained, and it is uncertain how many of them might be late Pleistocene in age. In contrast, late Pleistocene mafi c vents are well known in the Cascade arc (e.g., Bacon and Lanphere, 2006; Hildreth, 2007). The clos-est Cascade vents are ~90–120 km to the west of Summer Lake (Fig. 1), and are located gen-erally up wind. Cascade arc sources are thus likely to be major contributors of mafi c tephra to the Summer Lake basin.
REVISED AGE-DEPTH MODEL
A revised age-depth model is presented in Figure 10 and Table 4. Above the major uncon-formity (~6.5 m), the model is largely unchanged from that of Negrini et al. (2000) and Zic et al. (2002). In this part of the section, previously discussed glass compositions and the age model suggest that bed B1 originates from an erup-tion of Mount Mazama (Crater Lake) ca. 20 ka (Table 4). Bacon and Lanphere (2006) reported proximal eruptive activity from this time in the form of several rhyodacite domes with 40Ar/39Ar isochron ages of 24 ± 3 and 18 ± 4 ka. The exis-tence of this corresponding activity at Crater Lake suggests that both the correlation and the inferred ages of the uppermost sediments are accurate. The 83 ± 8 ka age of the EMSH ash from Mount St. Helens (Berger and Busacca, 1995), a deposit that is potentially correlative with bed I, is also consistent with the earlier chronologies suggested for the Summer Lake sediments above the major unconformity.
We propose changes to the previously pub-lished age model, below the major unconfor-mity, based primarily on our new interpretation that tephra N and N1 are the same bed, on a
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Kuehn and Negrini
424 Geosphere, August 2010
Negrini et al. (2000)age model
0
5
10
15
0 50 100 150 200 250 300 350
Age (ka)
Com
posi
teD
epth
Sca
lefo
rC
(m)
Site
san
dE
D - Mt St Helens Mp ( C)14
Mazama ( C, GISP2)14
F - Wono ( C)14
Mono Lake excursion (paleomag. correlation to GISP2)12 - Cy , TLMt St Helens ( C )14
6 - Pumice Castle Cy K-Ar( )
2 - Ice Quarry TL( )
I - EMSH TL( )
R TL( )
NN (Ar-Ar)
major unconformity (MIS 5e)
GG - Pringle Falls D Ar-Ar( )
LL (TL)
KK - Antelope Well tuff( )
(TL)Ar-Ar
AA1 - Shevlin Park tuff Ar-Ar( )
N TL( )
18 - Trego Hot Springs , TL( C )14
unconformity ?
?
minor (?) unconformities
minor unconformity?
?
AB-C1C2,D
All tephrabeds
18-E1
F-GG112HH0.28-42
H1,H2H3II1,JJ1,J2J3KLL1
M,NN2-QRR1-R3S-T1
U,V
W
W2X-ZAAAA1,AA2BB,BB1CC-EE
II1-JJ0.4
EE1-II
JJ0.6,JJ1KK,KK1
LL,LL1
LL2
MM,MM1
NN
Figure 10. Age-depth model. Depth scale derived from site E above tephra 18. Site C depth scale used below tephra 18, except between the upper unconformity and bed N, where the site E depth scale is used. Above the upper unconformity, the age model is essentially unchanged from that of Negrini et al. (2000) and Zic et al. (2002). Below the same unconformity, there is considerable uncertainty in the age-depth relations. TL—thermoluminescence; GISP—Greenland Ice Sheet Project; MIS—marine oxygen isotope stage.
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250,000-year tephra record from Summer Lake
Geosphere, August 2010 425
TAB
LE 4
. CO
MP
OS
ITE
DE
PT
H S
CA
LE F
OR
SIT
ES
C A
ND
E, L
OC
AL
DE
PT
HS
OF
BE
DS
FO
R A
LL T
HR
EE
SIT
ES
, AN
D M
OD
EL
AG
ES
FO
R A
LL T
EP
HR
A B
ED
S
Teph
ra la
yers
and
sel
ecte
d ot
her
feat
ures
Dep
th in
com
posi
te
sequ
ence
(m
)Lo
cal d
epth
at s
ite C
(m
)Lo
cal d
epth
at s
ite E
(m
)Lo
cal d
epth
at s
ite F
(m
)M
odel
age
(k
a)*
Teph
ra la
yers
and
sel
ecte
d ot
her
feat
ures
Dep
th in
com
posi
te
sequ
ence
(m
)Lo
cal d
epth
at s
ite C
(m
)Lo
cal d
epth
at s
ite F
(m
)M
odel
age
(k
a)*
Top
of s
ectio
n0
––
–17
.0R
17.
816.
465.
6917
7A
0.21
–0.
21–
18.2
R2
7.85
6.50
5.72
177
B0.
50–
0.50
–19
.8R
37.
916.
56–
177
B1
0.51
–0.
51–
19.9
S8.
186.
836.
0417
9B
20.
53–
0.53
–20
.0T
8.26
6.91
6.14
179
C0.
60–
0.60
–20
.4T
0.5
~8.
27–
~6.
1618
0C
10.
69–
0.69
–20
.9T
18.
296.
946.
1818
0C
20.
95–
0.95
–22
.4m
inor
unc
onfo
rmity
?8.
997.
647.
0618
4D
1.03
–1.
03–
22.9
U9.
187.
83–
186
181.
350.
601.
35–
24.8
V9.
227.
87–
186
E1.
38–
1.38
–24
.9tu
fa9.
568.
21–
189
E1
1.40
0.65
1.41
–25
.1W
9.73
8.38
7.99
190
Tufa
1.69
0.94
1.69
0.00
26.5
tufa
10.4
29.
078.
8019
4F
1.78
1.03
1.87
–1.8
80.
1929
.1X
10.4
69.
11–
194
Tufa
1.85
1.10
1.89
–1.9
3
0.20
29.9
Y10
.49
9.14
–19
4F
11.
861.
111.
90–1
.92
0.21
30.0
Z10
.53
9.18
8.87
195
G1.
891.
141.
95–1
.97
0.25
30.4
AA
10.8
39.
48–
196
Incl
inat
ion
low
in M
LE2.
20–
––
33.9
AA
111
.15
9.80
9.01
198
Tufa
2.25
1.50
2.35
0.40
35.7
AA
211
.17
–9.
0319
9G
12.
161.
412.
220.
4232
.5B
B11
.52
10.1
7–
201
122.
531.
782.
680.
57–0
.60
45.6
BB
111
.54
10.1
9–
201
H2.
892.
143.
09~
0.77
54.1
CC
11.7
010
.35
–20
2H
0.2
3.09
2.34
3.33
–58
.8D
D11
.78
10.4
3~
9.05
202
83.
452.
703.
621.
1667
.4D
D1
11.8
510
.50
–20
36
3.47
2.72
3.64
1.19
67.8
EE
11.8
810
.53
~9.
2520
34
3.49
2.74
3.66
1.22
68.3
EE
111
.99
10.6
4–
204
H0.
43.
54–
3.76
1.27
69.6
EE
212
.02
10.6
7–
204
23.
672.
923.
981.
4870
.8E
E3
~12
––
204
San
d an
d tu
fa4.
113.
364.
772.
4475
.1F
F12
.07
10.7
2–
204
H1
4.30
3.55
5.07
–77
.0F
F1
12.0
9–
–20
4H
24.
333.
585.
14–
77.3
GG
12.1
410
.79
–20
5S
and
and
tufa
4.63
3.88
5.35
2.93
80.2
GG
112
.18
10.8
3–
205
H3
4.69
3.94
––
80.8
HH
12.2
410
.89
–20
5I
4.91
4.16
5.56
3.07
82.9
II12
.28
10.9
3–
206
San
d an
d tu
fa5.
134.
385.
773.
2885
.0II1
13.1
211
.77
~9.
8921
1I1
5.18
–5.
82–
85.5
JJ13
.16
11.8
1~
9.91
211
J5.
214.
465.
853.
3285
.8JJ
0.2
13.2
211
.87
–21
1J1
5.44
4.69
6.10
3.63
88.1
JJ0.
413
.25
11.9
0–
212
J25.
464.
716.
343.
6588
.3JJ
0.6
~13
.4–
–21
2J3
5.73
4.98
6.34
3.90
90.9
JJ1
13.4
912
.14
–21
3M
inor
unc
onfo
rmity
?5.
755.
006.
363.
9491
.1K
K13
.81
12.4
610
.19
215
Min
or u
ncon
form
ity?
5.81
5.06
6.45
4.05
–K
K1
13.8
612
.51
10.2
421
5K
6.19
5.44
~6.
49–6
.51
4.36
102
ostr
acod
e sa
nd13
.98
12.6
310
.40
216
L6.
34, 6
.36
5.59
, 5.6
1~
6.46
–6.5
54.
41, 4
.43
104
LL14
.33
12.9
810
.96
218
L16.
505.
75–
–10
5LL
114
.34
12.9
910
.88
218
Maj
or u
ncon
form
ity6.
585.
836.
834.
73–4
.81
105
unco
nfor
mity
?14
.93
13.5
8–
222
M7.
12–
7.37
5.06
?17
2LL
216
.33
14.9
8–
231
N7.
21–
7.46
5.15
173
LL3?
17.6
216
.27
–23
9N
27.
406.
05–
–17
4M
M17
.63
16.2
8–
239
O7.
426.
077.
675.
3217
4M
M1
17.6
416
.29
–23
9P
7.48
6.13
7.72
5.37
175
Ana
Riv
er18
.10
16.7
5–
Q7.
56.
15–
5.39
175
NN
18.3
016
.95
–24
3R
7.70
6.35
7.87
5.57
176
botto
m o
f sec
tion
18.4
017
.05
–24
4 N
ote:
Abo
ve b
ed 1
8, th
e de
pth
scal
e is
bas
ed o
n th
e si
te E
rec
ord.
Bel
ow b
ed 1
8, th
e de
pth
scal
e is
bas
ed o
n si
te C
exc
ept f
or th
e in
terv
al b
etw
een
the
maj
or u
ncon
form
ity a
nd b
ed O
whe
re th
e si
te E
re
cord
is a
gain
use
d. D
epth
s fo
r a
few
bed
s fo
und
only
at s
ite F
are
inte
rpol
ated
into
the
C–E
seq
uenc
e ba
sed
on th
e re
lativ
e po
sitio
ns o
f cor
rela
ted
beds
. Mod
el a
ges
are
base
d on
Tab
le 3
and
Fig
ure
10.
MLE
—M
ono
Lake
exc
ursi
on. F
or p
ositi
on o
f the
MLE
in th
e co
mpo
site
seq
uenc
e, s
ee N
egrin
i et a
l. (2
000)
. *
Age
s ar
e ba
sed
on T
able
2 a
nd th
e ag
e m
odel
sho
wn
in F
igur
e 10
.
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Kuehn and Negrini
426 Geosphere, August 2010
new correlation of bed AA1 with the Shevlin Park Tuff, and on new dates (Singer et al., 2008) associated with correlatives of bed GG and the Pringle Falls geomagnetic excursion.
We have shifted the preferred chronology below the unconformity toward older ages to better honor the numerous and convergent radio-metric ages now associated with the correlative tephra of bed GG and the Pringle Falls geomag-netic excursion. The new chronology also hon-ors the radiometric ages of the Shevlin Park Tuff and Antelope Well tuff, though at the extremi-ties of their 1σ uncertainty estimates. (See the related discussion herein on the Antelope Well–KK correlation.) The resulting chronol-ogy is a plausible, albeit poorly constrained, age model for the lower two-thirds of site C using the limits of the single standard deviation error bars for the 40Ar/39Ar ages on beds GG (Prin-gle Falls D) and KK (Antelope Well tuff) as the key control points. The resulting model has an average sedimentation rate of 16 cm/ka and sug-gests approximate ages of 190 ka for W, 196 ka for Shevlin Park Tuff, 215 ka for Antelope Well tuff, and 218 ka for bed LL (Fig. 8; Table 3). These age estimates are compatible with the iso-chron age for Shevlin Park Tuff (Lanphere et al., 1999), the TL date on bed R (Berger, 1991), and the interpretation of the TL date on bed LL as a minimum age (Berger, 2001). The model does not, however, fi t the TL date on bed N. The N date is signifi cantly younger than that for bed R below it, and lacking any sedimentological evi-dence for an unconformity between these beds, we suggest that the date on N should be inter-preted as a minimum age.
Projecting the model to the base of the section suggests an age of 240–250 ka for bed NN. Con-sidering the signifi cant uncertainties inherent in this model, the suggestion by Davis (in Erbes, 1996; Negrini et al., 2001) and Erbes (1996) of a possible unconformity below bed LL, and the 300 ka approximate age of tephra correlated to bed NN, the base of the sequence could be older.
REPEATED ERUPTIONS FROM INDIVIDUAL SOURCES AND PETROLOGIC INTERPRETATIONS FOR SELECTED BEDS
At Summer Lake, there are many examples of tephra beds that are very similar to others above or below them in the sequence. In many cases, these geochemical similarities can be interpreted to suggest repeated eruptions from the same volcano. Using the overall age-depth model, the relative timing of these events can be considered. In addition, a number of deposits show patterns of heterogeneity that suggest the involvement of zoned magma chambers and/
or multiple magmas. Many examples of both are outlined here, largely in order from older to younger beds.
The compositional heterogeneity observed in bed KK (Fig. 7E) could potentially be explained by either zoned or multiple magmas. Although it is diffi cult to determine which from glass compositions of individual shards alone, the nearly equal frequency distribution along the main trend and smaller compositional range (e.g., compared to AA1 and JJ) could be con-strued as evidence for a zoned chamber. Two diffuse beds, JJ0.6 and JJ0.4, ~40 and 60 cm above KK, contain glass that spans the same compositional range as bed KK. We interpret these beds to be the result of redeposition rather than additional eruptions because erosion and redeposition of the thick underlying KK bed are thought to be more likely than the occurrence of two additional eruptions with exactly the same pattern of heterogeneity.
Glass in bed JJ is strongly heterogeneous with two relatively abundant end-member com-positions and fewer data points between them (Fig. 7B). On a plot of MgO versus SiO
2 (right
side plot of Fig. 7B), the major mafi c compo-nent plots off of the trend formed by the silicic end member and intermediate data points. This pattern could be modeled using a system with three end-member magmas. An alternate model consists of a homogeneous mafi c magma and a zoned intermediate to rhyolitic magma. Three additional beds have glass compositions that are similar to the silicic end member of JJ. These include II1, located ~4 cm above JJ, and JJ0.2, located ~6–8 cm below JJ. II1 and JJ0.2 and glass compositions are indistinguishable from the silicic end member of JJ (Fig. 7B). Assum-ing a constant sedimentation rate, the age model suggests that bed II1 may be ~200 yr younger than JJ and that JJ0.2 may be ~400 yr older. The identical compositions and short time interval are compatible with origin of II1, JJ, and JJ0.2 from three eruptions of the same magma cham-ber, only one of which also involved the erup-tion of mafi c magma. Bimodal bed JJ1, located ~33 cm below JJ and estimated to be older by ~3 k.y., contains glass compositions that plot together with all 3 of the aforementioned beds (Figs. 7B and 7D). The apparent absence of the lower silica component in the stratigraphi-cally equivalent sample from the SPG-A core (Table 2) suggests that the two modes may represent two different eruptions. The small compositional difference between modes could have originated by tapping different portions of a variably evolved magma chamber.
On most bivariate plots, bed AA1 and proxi-mal Shevlin Park Tuff appear to have two prom-inent end members, a more tightly clustered
silicic end member and a somewhat broader mafi c end member with a lower abundance of data points between end members (Fig. 7A). The relative lack of intermediate data points suggests magma mixing. On some plots (e.g., K
2O versus MgO, not shown) there appear to
be two mafi c components, thus suggesting the involvement of three magmas in the eruption. Conrey et al. (2001) came to a similar conclu-sion based on a more comprehensive set of pet-rologic data.
Glasses in beds HH and II are very similar, being distinguished only by small offsets in SiO
2, Al
2O
3, and CaO. On this basis, it is possi-
ble that these derive from the same source. Their relative depths indicate an interval of ~250 yr between them (Table 4).
The glass compositions of beds S, T, and T1 are very similar in composition (Table 2). Thus, these beds could have been erupted from the same magma system. Bed S and T glasses are indistinguishable. The somewhat older T1 is shifted slightly toward higher SiO
2 and
lower CaO and FeO [Table 2; cf. sample E52 (T) with E53 (T1) and C35 (T) with C36 (T1)]. The spacing between beds S and T suggests ~500 yr between them. T and T1 are closer together and probably differ in age by ~200 yr. The silicic glass in bed T0.5 is indistinguish-able from T1, but it is unclear whether this bed represents an additional event or simply rede-posited tephra T1.
Several pairs of compositionally indistin-guishable beds are above S and T, and each of these may also represent a pair of closely spaced eruptions from the same source magma. Included here are beds P and Q, which are prob-ably separated by ~120 yr. Compositionally indistinguishable beds M and N are separated by ~3 cm of sediment, which corresponds to ~200 yr. Glass in bed H0.2 is indistinguishable from that in bed 8 found 30–35 cm below it. The age model suggests that they differ in age by ~6 k.y. (Table 4).
Bed F, correlated to Wono tephra, is hetero-geneous in composition with a 3–4 wt% range in silica (Tables 1, 2, and S4 [see footnote 1]). F and Wono lack clearly defi ned end members; rather, there is a continuous trend with a some-what higher frequency of data points closer to the less silicic end (Kuehn, 2002). Bed F1, which is ~1–4 cm lower and is perhaps 100–200 yr older, is compositionally similar to F and Wono tephra. Bed G, which is ~3 cm below F1 and is perhaps 400 yr older, is relatively homo-geneous in composition, but it plots on the trend line defi ned by F and Wono tephra com-positions. A few Wono clasts found at Newbery Volcano also contain a small fraction of glass with the same composition as tephra G (Kuehn,
on April 8, 2012geosphere.gsapubs.orgDownloaded from
250,000-year tephra record from Summer Lake
Geosphere, August 2010 427
2002). These geochemical relationships imply that G, F1, and F (Wono) derive from the same zoned magma system. Although the exact source these tephras is unknown, Wono tephra has a northward-coarsening particle size distri-bution (Davis, 1985; Kuehn, 2002) and occurs on the northwest fl ank of Newberry Volcano as a 63-cm-thick deposit containing pumice as much as 4 cm in diameter. This distribution pattern suggests an eruptive source somewhere in the general vicinity of the Three Sisters. Beds B and A also contain glass that is similar in composi-tion to bed F, and these may record additional activity at the same source that produced Wono tephra. Bed B is located 1.4 m above bed F and is ~10 k.y. younger. Bed A is 10 cm above bed B and is ~1.6 k.y. younger than B. Bed A contains multiple populations of glass, and it is possible that it contains reworked glass from bed B.
CONCLUSIONS
Collectively, the Summer Lake outcrop and core records represent one of the most com-plete and detailed tephrostratigraphic records of Pleistocene volcanism in western North Amer-ica. As such, this sequence serves as a key refer-ence locality that puts together in a single strati-graphic context multiple beds that are known from many different locations. Thus it serves a critical role in refi ning the Pleistocene teph-rostratigraphic framework for western North America. The expanded catalog of tephra beds provided herein also offers, for example, the potential to tie together paleoclimate records of the Great Basin more precisely than previously.
At least 88 visible tephra beds, 25 of them newly described, are preserved in 18.4 m of lacustrine sediments exposed in outcrop sec-tions along the Ana River. Thicknesses of these beds range from <1 mm to >10 cm. Half of the tephra beds, 44, are characterized by rhyolitic glass, 40 beds contain predominantly basaltic or intermediate glass, and 4 are characterized by wide ranges in glass composition; 23 beds are known from localities outside of the basin, and 20 of these have been connected to specifi c source volcanoes, including Mount St. Helens, Newberry Volcano, Crater Lake, and Medicine Lake volcano. The remaining 65 beds are as yet known only at Summer Lake and therefore provide a unique record of Cascade arc volca-nism. The large number of mafi c tephra beds present at Summer Lake, close to half of the total, indicates that mafi c eruptions contribute signifi cantly to the distal ash fall produced by the Cascade arc. Some of these mafi c eruptions were also suffi ciently powerful to disperse sand-sized tephra ~100 km downwind. Evidence of repeated eruptions of individual sources, many
of which appear to be spaced a few hundred years apart, provides useful information about frequencies of pyroclastic eruptions in the Cas-cade arc.
Two of the compositionally heterogeneous tephras present in the sequence have been cor-related to major ash-fl ow tuff deposits found outside of the basin (AA1 to Shevlin Park Tuff and KK to Antelope Well tuff). By obtaining well-representative proximal reference samples, geochemically analyzing them using the same procedures applied to the Summer Lake tephras, and carefully comparing the data using bivariate plots, robust correlations have been established. Rather than providing a hindrance, the observed heterogeneity in these deposits signifi cantly strengthens the correlations, as it is unlikely that additional eruptions would so closely replicate all of the patterns observed in the data, including the means, compositional ranges, covariation trends, and frequency distributions of different glass compositions.
Our refi ned stratigraphy includes a single major unconformity associated with marine oxygen isotope stage 5e, and there are probably several minor unconformities present as well. From 0 to ~6 m depth, above the major uncon-formity, the age-depth model is relatively well constrained. Age-depth relations for the rest of the section have signifi cant uncertainties, and additional work is critically needed to provide better age control for the lower two-thirds of the sequence. It is possible, however, to construct a reasonable, but still signifi cantly uncertain, age model using the available dates. Our revised age model increases the ages for the lower two-thirds of the sequence by ~20 k.y., and suggests approximate ages of 190 ka for bed W, 198 ka for bed AA1 (Shevlin Park Tuff), and 215 ka for bed KK (Antelope Well tuff), although possibly confl icting age control for the Antelope Well tuff adds uncertainty to our revision. The esti-mated age of bed NN at the base of the section is 240–250 ka, but given the limited age control the actual age could be signifi cantly greater.
ACKNOWLEDGMENTS
Tephra studies at the University of Alberta were supported by a Natural Sciences and Engineering Research Council Discovery grant and an Alberta Ingenuity New Faculty Award to Duane Froese. The School of Earth and Environmental Sciences at Washington State University (WSU) provided instru-ment time for electron probe microanalysis (EPMA) of the site C and Summer Lake Playa site G (SPG) core samples. The Department of Chemistry at Cali-fornia State University, Bakersfi eld, provided cold room storage for the SPG, WL (Wetland Levee), and B&B (Bed and Breakfast) cores. Elmira Wan supplied a reference sample of the Antelope Well tuff, and Franklin Foit provided an analysis of the sample by EPMA at WSU; Foit also provided EPMA data for
proximal Llao Rock tephra. Richard Conrey provided EPMA data for bed JJ and proximal Shevlin Park Tuff. Marty St. Louis of the Summer Lake Wildlife Refuge arranged for the permits necessary to conduct fi eld studies along the Ana River. Bill Cannon of the U.S. Bureau of Land Management, Lakeview District, con-ducted the archaeological examination of the fi eld site needed for the permit process. Careful and compre-hensive comments by two anonymous reviewers led to important improvements in the manuscript.
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