ABSTRACTThin-section (micromorphological) analysis of samples from the upper 1.5 m of a core obtained in 2007 from Anderson Pond, Tennessee reveals a coherent 15,000 yr record of late Pleistocene to Holocene climate change supporting interpretations from previous pollen and charcoal records from the site, paleoclimate records from correlative floodplains, as well as a high-resolution speleothem record from Raccoon Mountain Cave, Tennessee. The Holocene record at Anderson Pond is highly condensed due to low sedimentation rates, episodes of erosion, and soil formation during subaerial exposure of this sinkhole lake. Legacy sediments recording Euro- and Native American(?) disturbance dominate the upper 60 cm of the core (<1682 cal yr BP) and are characterized by mixed, darker-colored and coarser-grained deposits containing high charcoal, reworked soil aggregates and medium- to coarse detrital quartz sand grains, which sharply overlie finer-grained and lighter-colored, heavily rooted Middle and Early Holocene sediments. Middle Holocene sediments (73-89 cm) record extensive warm-dry subaerial soil conditions during the Middle Holocene Thermal Maximum (6037-8361 cal yr BP), manifested by birefringent illuviated clay lining root pores and lining ped faces, with partially dissolved siliceous sponge spicules and diatoms, and also contain the high charcoal concentrations. Late Pleistocene sediments (100-150 cm) are very dark-colored and very organic-rich recording open-water conditions, and include abundant organic grains (fresh to partially decomposed plant tissues, pollen, spores, seeds) as well as “siliceous aggregate” grains at 121-148 cm (13,951-14,358 cal yr BP). These distinctive siliceous aggregate grains are medium- to coarse silt-sized and consist of very fine- to fine-silt-sized quartz grains that are cemented by amorphous silica; they are interpreted as recording fire processes and production of wood ash, and formed when loessal silt and biogenic silica were admixed with the ash within the lacustrine basin. Although not commonly used in late Quaternary lacustrine paleoclimate studies, we advocate a multi-analytical approach involving use of thin sections, in addition to more standard methods which emphasize pollen and charcoal, because of enhanced resolution of depositional and pedogenic processes.

Can micromorphology enhance paleoenvironmental interpretations?

DRIESE, Steven G.1, HORN, Sally P.2, BALLARD, Joanne P.2, LI, Zheng-Hua3 and BOEHM, Mathew S.2, (1) Terrestrial Paleoclimatology Research , Dept. of Geology, Baylor Univ., One Bear Place #97354, Waco, TX 76798-7354, (2) Dept. of Geography, Univ. of Tenn., Knoxville, TN 37996-0925, (3) Earth & Environ. Sci. Div., Los Alamos Nat. Lab., P.O. Box 1663, MS J535, Los Alamos, NM 87545

2. Study Area: Anderson Pond Sinkhole Lake

4.1 Whole Thin-section Microscopy:

5. Summary with age-depth model

3. Methods: thin-section micromorphology of new Anderson Pond core collected in 2007 by Jackson and co-workers (Liu et al., 2013) using PPL, XPL and UVf.

6. Conclusions:1)Micromorphology is an under-utilized, but very useful, method for independently assessing paleoenvironmental records of Quaternary lakes, supporting charcoal and pollen studies.2)Legacy sediments (Late Holocene), buried soil (Middle Holocene), and siliceous aggregate grains (Late Pleistocene) observed in thin sections record specific climate and geomorphic conditions at Anderson Pond, Tennessee.

7. Acknowledgments: The authors wish to thank Steve Jackson (U. WY) for allowing use of Anderson Pond core 2007 for this study. The authors gratefully acknowledge support of NSF EAR-0823131 awarded to SGD and EAR-0822824 awarded to SPH and Z-HL for research on Late Pleistocene-Holocene paleoclimate reconstructions in the southern Appalachian region.

Ballard, J.P., 2015. Evidence of Late Quaternary fires from charcoal and siliceous aggregates in lake sediments in the eastern U.S.A. Ph.D. Thesis, University of Tennessee, Knoxville.Ballard, J.P., Horn, S.P., Li, Z.-H., in review. A 23,000-year microscopic charcoal record from Anderson Pond, Tennessee.

Submitted to Palynology.Delcourt, H.R., 1978. Late Quaternary vegetation history of the Eastern Highland Rim and adjacent Cumberland Plateau of

Tennessee, Ph.D. Thesis, University of Minnesota, Minneapolis.Delcourt, H.R., 1979. Late Quaternary vegetation history of the eastern Highland Rim and adjacent Cumberland Plateau of

Tennessee. Ecological Monographs 49, 255-280.Driese, S.G., Li, Z.-H., McKay, L.D., 2008. Evidence for multiple, episodic, mid-Holocene Hypsithermal recorded in two soil

profiles along an alluvial floodplain catena, southeastern Tennessee, USA. Quaternary Research 69, 276-291.Liu, Y., Andersen, J.J., Williams, J.W., Jackson, S.T., 2013. Vegetation history in central Kentucky and Tennessee (USA) during the last glacial and deglacial periods. Quaternary Research 79, 189-198.Reimer, P.J., et al., 2013. INTCAL13 and MARINE13 Radiocarbon age calibration curves 0–50,000 years cal BP. Radiocarbon 55(4), 1869–1887.Reimer, P.J., Brown, T.A., Reimer, R.W., 2004. Discussion: reporting and calibration of post-bomb 14C data. Radiocarbon 46

(3), 1299–1304.Stuiver, M., Reimer, P.J., 1993. Extended 14C database and revised CALIB radiocarbon calibration program. Radiocarbon 35

(1), 215–230.

1. Background:

4.4 Siliceous aggregate grains 121-148 cm (13,950-14,400 cal yr BP) = period of extensive fires generating wood ash + loessal silt

4.3 Paleosol, subaerial exposure and soil development: 73-89 cm (6050-8361 cal yr BP) = Middle Holocene Thermal Maximum

4.2 Legacy sediments: Late Holocene, 0-60 cm (-57 to1682 cal yr BP) = Anthropogenic (European and Native American influences)

Original AP-76 Anderson Pond core described and 14C-dated by H. Delcourt (1979)

48-52 cm depth

59-63 cm depth

Medium- to coarse- monocrystalline quartz sand grains (PPL)

Reworked soil aggregate grains (pedoliths) (PPL)

Freshwater diatoms and sponge spicules (PPL)

Partially decayed plant tissues, spores and algal remains (UVf)

76-82 cm depth

88-94 cm depth

Root traces and bioturbation (PPL)

Macro- and micro-charcoal grains (PPL)

Illuviated clay lining root pore (PPL)

Illuviated clay lining root pore (XPL)

121-125 cm depth

133-137 cm depth

(PPL) (XPL)

138-141 cm depth

Laboratory experiments by Ballard (2015) demonstrate environmental conditions for formation of siliceous aggregates (Ballard et al., manuscript in preparation).

100 μm

100 μm100 μm

100 μm1.0 mm1.0 mm

1.0 mm 200 μm

2.0 mm

2.0 mm

200 μm 200 μm 200 μm

200 μm 200 μm200 μm

100 μm 100 μm

50 μm 50 μm

50 μm 50 μm

(PPL) (XPL)

= UT-K date = WY date

1976 AD -10 + 100 yr BP