Late Quaternary landscape development along the Rancho Marino coastal range front (south-central...

JOURNAL OF QUATERNARY SCIENCE (2009) 24(7) 728–746Copyright � 2008 John Wiley & Sons, Ltd.Published online 16 December 2008 in Wiley InterScience
(www.interscience.wiley.com) DOI: 10.1002/jqs.1243
Late Quaternary landscape development alongthe Rancho Marino coastal range front (south-central Pacific Coast Ranges, California, USA)MARTIN STOKES1* and ANTONIO F. GARCIA21 School of Earth, Ocean and Environmental Sciences, University of Plymouth, Plymouth, UK2 Physics Department, California Polytechnic State University, San Luis Obispo, California, USA

Stokes, M. and Garcıa, A. F. 2009. Late Quaternary landscape development along the Rancho Marino coastal range front (south-central Pacific Coast Ranges, California,USA). J. Quaternary Sci., Vol. 24 pp. 728–746. ISSN 0267-8179.

Received 29 August 2007; Revised 27 August 2008; Accepted 14 September 2008

ABSTRACT: LateQuaternary landscape development along the RanchoMarino coastal range front inthe central-southern Pacific Coast Ranges of California has been documented using field mapping,surveying, sedimentary facies analysis and a luminescence age determination. Late Quaternarysediments along the base of the range front form a single composite marine terrace buried by alluvialfans. Marine terrace sediments overlie two palaeoshore platforms at 5m and 0m altitude. Correlationwith the nearby Cayucos and San Simeon sites links platform and marine terrace development to the125 ka and 105 ka sea-level highstands. Uplift rate estimates based on the 125 ka shoreline angle are

�1 �1
0.01–0.09m ka (mean 0.04m ka ), and suggest an increase in regional uplift along the coasttowards the NWwhere the San Simeon fault zone intersects the coastline. Furthermore, such low ratessuggest that pre-125 ka uplift was responsible for most of the relief generation at Rancho Marino. Thecoastal range front landscape development is, thus, primarily controlled by post 125 ka climatic andsea-level changes. Post 125 ka sea-level lowering expanded the range front piedmont area to a width of7.5 km by the 18 ka Last Glacial Maximum lowstand. This sea-level lowering created space for alluvialfan building along the range front. A 45� 3 ka optically stimulated luminescence (OSL) age provides abasal age for alluvial fan building or marks the time by which distal alluvial fan sedimentation hasreached 300m from the range front slope. Fan sedimentation is related to climatic change, withincreased sediment supply to the range front occurring during (1) glacial period cold stage maximaand/or (2) the Late Pleistocene–Holocene transition, when respective increases in precipitation and/orstorminess resulted in hillslope erosion. Sea-level rise after the 18 ka lowstand resulted in range fronterosion, with elevated localised erosion linked to the higher relief and steeper slopes in the SE. Thisstudy demonstrates that late Quaternary coastal range front landscape development is driven byinterplay of tectonics, climatic and sea-level change. In areas of low tectonic activity, climatic and sea-level changes dominate coastal landscape development. When the sea-level controlled shoreline is inclose proximity to the coastal range front, localised patterns of sedimentation and erosion are passivelyinfluenced by the pre-125 ka topography. Copyright # 2008 John Wiley & Sons, Ltd.
KEYWORDS: marine terraces; shore platforms; alluvial fans; sea-level change; climate change.

Introduction

The Pacific Coast Ranges (Fig. 1) are a major physiographicprovince of the western United States. They occupy aninterplate tectonic setting whose topographic development islinked to the ongoing strain accommodation between thePacific and North American plates (Lettis and Hanson, 1991).Topographic development of the southern Pacific Coast Rangesis considered to be young and rapid, with uplift occurring

* Correspondence to: M. Stokes, School of Earth, Ocean and EnvironmentalSciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK.E-mail: [email protected]

almost wholly during the late Quaternary (Page et al., 1998).Evidence for spatial and temporal variations in topographicdevelopment have been derived from: (1) Plio–Pleistocenesediments that document erosion from uplifted blocks anddeposition in basins around the relief margins (Christensen,1965) (Fig. 1); and (2) flights of late Quaternary erosionalmarine strandlines and marine terrace depositional landforms(e.g. Lajoie et al., 1991).

The late Quaternary landform record has received particularattention within the literature, where spatial and temporalpatterns of the marine terrace record and its integration withglobal late Quaternary sea-level curves have been used (1) forseismotectonic purposes, to quantify local and regional upliftrates (Hanson et al., 1992, 1994; Muhs et al., 1992; Orme,

Figure 1 (A) The Pacific Coast Ranges and their relationship to the major physiographic provinces of California. (B) Regional bedrock geology andprincipal tectonic structures of the southern Pacific Coast Ranges (modified from Page et al., 1998)

COASTAL RANGE FRONT LANDSCAPE DEVELOPMENT, CALIFORNIA 729

1998) and (2) for climatic reasons, to quantify patterns anddurations of late Quaternary palaeoclimate and eustaticchanges (Muhs, 1992;Muhs et al., 2002). Detailed stratigraphicand absolute age datasets are limited to three areas within thecentral-southern Pacific Coast Ranges: along the flanks ofthe San Luis Range, and at Cayucos and San Simeon (Fig. 1).The San Luis Range and San Simeon areas contain flights ofmarine terraces spanning the late Quaternary that cross activefault structures (Hanson et al., 1992, 1994; Lettis and Hanson,1992). In contrast, Cayucos is tectonically quiescent and isdominated by a well-developed last interglacial marine terrace(Muhs et al., 2002).Adjacent to these sites are extensive stretches of coastline

(e.g. Cambria-Point Estero: Fig. 2(A)) that contain fragmentedremnants of marine terrace landforms. Some of these have beenreconnaissance mapped (e.g. Weber, 1983) but have typicallylacked detailed investigation due to the absence of marineterrace flights, instead comprising a single marine terrace levelbut one lacking material suitable for U-Series dating. Marineterrace ages in these areas are based upon height correlationwith the adjacent dated sites, with 125 ka being the mostcommonly cited age.The lack of detailed investigation is surprising as such areas

could provide important insights into local–regional upliftvariations as well as providing evidence for climate-eustaticrelated landscape change. A commonly cited problem is thatthe marine terraces are destroyed by erosion or that their fossilsea cliff (shoreline angle/strandline), that is typically used as apalaeosea-level datum, is buried by aeolian, alluvial fan orslope colluvial deposits (e.g. Weber, 1983; Hanson et al.,1994).The purpose of this study is twofold: (1) to document the late

Quaternary landscape development along the coastal rangefront at Rancho Marino, near Cambria (Fig. 2); and (2) to

Copyright � 2008 John Wiley & Sons, Ltd.

produce a model of coastal range front landscape developmentthat integrates interplay between late Quaternary tectonic,climatic and sea-level forcing mechanisms.Rancho Marino occupies an important location midway

between the well-studied San Simeon and Cayucos sites (Figs 1and 2). Shore platform, marine terrace and alluvial landformsare developed along the base of a NW–SE orientated linearcoastal range front that gains in relief and slope steepnesstowards the SE (Fig. 3). This landscape is documented throughfield-based mapping, surveying, sedimentary facies analysisand an optical luminescence age determination. Resultsprovide an insight into the timing and patterns of (1) localand regional late Quaternary uplift, (2) climate-related sea-level changes and their relationship to accommodation spacecreation for range front sedimentation and erosion, and (3)climate-related changes in sediment supply and its relationshipto alluvial fan building.

Geological setting

Rancho Marino occupies the NW end of a small, NW–SEorientated range of low-relief hills along the coast between thesettlements of Cambria and Cayucos (Figs 1 and 2). Regionally,this topography forms some of the foothills to the Santa LuciaMountains, the principal mountainous relief within thesouthern Pacific Coast Ranges (Fig. 1). The Rancho Marinoridge crest, range front slopes, modern sea cliff and shoreplatform areas comprise an Upper Cretaceous series ofFranciscan Complex sedimentary rocks that form part of the‘Cambria Slab’ (Fig. 2) (Hsu, 1969; Hall, 1974; Smith et al.,1979). This bedrock is characterised by an interbedded

J. Quaternary Sci., Vol. 24(7) 728–746 (2009)DOI: 10.1002/jqs

Figure 2 (A) The Rancho Marino study area and its relationship to the ‘Cambria slab’, major fault structures and nearby locations of late Quaternarysedimentation referred to within the text. (B) Geology and geomorphology mapping results. Study area geographic subdivisions and locations ofsedimentary logging and palaeoshore platform referred to within text, figures and tables

Figure 3 View NW along the Rancho Marino range front illustratingthe linear nature of the range front slope and the alluvial fan, marineterrace and coastal cliff landforms that are developed along it (see Fig. 2for location)


730 JOURNAL OF QUATERNARY SCIENCE

sandstone, shale and mudstone sequence with dominantfeldspar-rich detrital grain content (Hall, 1974; Smith et al.,1979). The sequence dips towards the east between 358 and 708and locally is arranged into a series of minor tight fold structures(Hall, 1974). Overlying the Cretaceous bedrock along the baseof the range front is a thin veneer (�25m) of late Quaternarysediments organised into marine terrace and alluvial fanlandforms that form the focus of this study.

Rancho Marino occurs within the coastal Franciscanseismotectonic domain of Clark et al. (1994). This regioncomprises a series of linked strike–slip and reverse/thrust faultsthat form part of the San Andreas transform zone, a region thataccommodates the transpressive motion between the NorthAmerican and Pacific plates (Clark et al., 1994). Offshore fromRanchoMarino is the San Gregorio–Hosgri fault zone (Fig. 1), amajor NNW–SSE to NW–SE orientated strike–slip fault thatforms the western margin of the seismotectonic domain (Clarket al., 1994; Jennings, 1994; Hanson et al., 1995; Dickinsonet al., 2005). This structure comes onshore in the San Simeonregion (Figs 1 and 2) where displacement of late Quaternarymarine terraces have been used to quantify fault-related surfaceuplift and fault slipmovements (Hanson et al., 1994). Inland lies



the Cambria Fault (Fig. 2), a NW–SE orientated reverse faultwith Rancho Marino forming the hanging wall block (Hall,1974; Jennings, 1994). The topographic relief of RanchoMarino probably relates to block uplift between the SanGregorio–Hosgri and Cambria faults.Evidence for regional late Quaternary block uplift is derived

from the marine terrace record where the widespread 125 kamarine terrace has been used to calculate differential upliftrates along the coast at San Simeon (<0.27m ka�1) andCayucos (0–0.14m ka�1) (Muhs et al., 1992; Hanson et al.,1992, 1994; Orme, 1998). Block uplift is accommodated alongrange front bounding faults (e.g. San Luis Range: Lettis andHanson, 1992). However, the Rancho Marino range front lacksfaulting evidence despite its linear appearance suggesting apassive tectonic origin for its topographic configuration.

Methods

Approach and techniques overview

Late Quaternary landscape development along the RanchoMarino coastal range front was recorded using field-basedmapping, sedimentary facies analysis, surveying techniquesand an optical luminescence age determination. Data arepresented in relative stratigraphic order. Map results arepresented first to establish types and distribution of landforms.Shore platforms and overlying deposits are recorded in graphicsedimentary logs from which a relative stratigraphic frameworkis established and relationships to late Quaternary sea-levelchanges are assessed. Sedimentary deposits are described usinga sedimentary facies analysis approach in order to establish theprincipal sedimentary processes, depositional settings andchanges in depositional environment. Surveying results areused to tie the graphic logging results and related stratigraphicfeatures (e.g. shore platforms and shoreline angles) to UnitedStates Geological Survey (USGS) topographic map height data.The range front surface morphology was documented bysurveying marine terrace and alluvial fan surfaces and theirincised stream channels. A chronology for landscape devel-opment is established by correlation of landforms with adjacentwell-known sites at Cayucos and San Simeon. An opticalluminescence age provides an absolute age indication to assessthe timing of alluvial fan building along the range front. Shoreplatform and marine terrace height data together with thelandscape chronology are then used to calculate rates oftectonic uplift along the range front. Data are then collectivelydiscussed in terms of late Quaternary environmental controlsincluding tectonics, climate and sea-level change from which amodel for late Quaternary coastal range front landscapedevelopment is constructed.To simplify data presentation and discussion the study area

has been arbitrarily subdivided into three equal geographicalregions: NW, central and SE (Fig. 2). Field mapping, logging,surveying and sediment description methods are describedbelow. Additional methods, including inland projection ofshore platforms to provide estimates of shoreline angle heights,sampling for optical luminescence dating, laboratory lumines-cence age determination and quantification of uplift rates aregiven within relevant data sections for ease of reference.

Mapping

Field mapping of the bedrock geology and landforms wasconducted using a compass, a handheld global positioning


system (GPS) with an x–y coordinate accuracy of ��1m and50m tape measures. Features were mapped onto 1:12 000enlargements of the USGS (1979) 1:24 000 topographic mapand Golden State Aerial Surveys �1:20 000 colour verticalaerial photography taken in 1995.

Graphic sedimentary logging and surveying

Coastal cliffs along the length of the study area coastlineprovide excellent exposures through shore platform, marineterrace and alluvial fan landforms. Fifteen sites were selectedfrom which graphic logs were constructed using a scale of 1mof section to 1 cm of log. The graphic logs were surveyed toUSGS topographic map height data using a handheld Abneylevel, 50m tape measures and GPS. Surveying involved theconstruction of a temporary network of benchmarks over therange front landscape that were then tied to the USGStriangulation station/vertical angle bench mark (358 310

46.2400 N, 1218 40 13.6200 W) with an accuracy of �0.5m to1m. Survey height data were then used to assess and quantifyerosional and depositional landform stratigraphic relationshipsalong the range front.

Sedimentary facies analysis

Sedimentary deposits were described and interpreted using afacies analysis approach that integrates standard sedimentcharacteristics including lithology, textures (grain size, shape,roundness, sorting, sedimentary structures, grain fabrics etc.),composition and sediment body geometries. Facies thicknessand lateral distribution were recorded in graphic sedimentarylogs (previous subsection). Facies were interpreted in terms of asedimentary process and then grouped accordingly into a faciesassociation that reflected the overall depositional setting ofdeposits. Vertical and lateral changes in facies associationswere then used to document relative temporal changes indepositional environment.

Coastal range front geomorphology

Rancho Marino encompasses a �3 km long and up to 1.5 kmwide area defined by the coastal part of Cambria town (NW),the range ridge crest (NE) and the modern shoreline (SW)(Fig. 2). This coastal landscape can be subdivided into ridgecrest, range front slope, range front base, coastal cliff andoffshore components (Figs 3 and 4).The range front comprises a linear NW–SE orientated

topography with a ridge crest that gains relief from 110m inthe NW to 211m in the SE. The change in relief heightcoincides with the range front slope becoming progressivelymore rugged and steep, with USGS (1979) topographic contourdata revealing mean range front gradients changing from 0.1 inthe NW to 0.36 in the SE.The range front slopes comprise rounded interfluves and

small ephemeral streams and gullies developed into Cretaceousbedrock that collectively form small drainage basins (areas<0.24 km2) to range front alluvial fans (Fig. 4). The interfluvesare characterised by either bare Cretaceous sandstone bedrock,with a highly jointed and fractured appearance, or by thinveneers of soil or weathered sandstone clasts. In proximal areas


Figure 4 Oblique aerial views along the Rancho Marino range front(California Coastal Survey, 2008). NW region, large fan (A) and exten-sive marine terrace. Central region, dissected smaller fan (E) andmarineterrace fragments. SE region, dissected and foreshortened fans (G). SeeFig. 2 for locations. Images used with permission from the CaliforniaCoastal Records Project, 2008. Copyright � 2002–2007 Kenneth &Gabrielle Adelman, www.californiacoastline.org


close to the ridge crest, the ephemeral stream channels andgullies are developed into bedrock. Downstream, the rangefront slope channels are infilled with sediment, some of whichreveal clear elongated debris flow lobe morphologies.Channels often cut down through this sediment (Figs 3and 4), with channel margins showing localised undercuttingand channel long profiles showing step-like features interpretedas knick points (Fig. 5). The range front slopes lack evidence forrecent erosion, comprising well-vegetated Monterey pine andcoastal oak forest and coastal scrub vegetation (Figs 3 and 4).Late Quaternary sediments occupy the base of the range front

slope, occurring as marine terrace and alluvial fan landformswith a vegetation cover of coastal terrace prairie and nativegrasses/flowers (Figs 3 and 4). Mapping (Fig. 2) and surveying(Fig. 5) of these sediments reveals the presence of a single, low


gradient (0.05), seaward-dipping marine terrace surface. In theNW the marine terrace surface is up to 300m wide, becomingnarrower, fragmentary and absent along the range front to theSE (Figs 2 and 4). In the NW and central regions, the inner,landwards edge of the marine terrace surface occurs consist-ently at an altitude of �þ25m forming a change or break inslope along the range front (Fig. 2).

The mapping results reveal 11 alluvial fan-shaped lobes ofsediment, sourced from streams that emerge from point sourcesalong the range front slope (Fig. 2). In the NW and part of thecentral region, the fans have a well-preserved morphology(Fig. 2) comprising a single surface that builds out onto themarine terrace (Fig. 5). These fans are moderately large (e.g. fanarea¼ 0.24 km2) and have low mean surface gradients (0.1)that closely approximate to the marine terrace surface gradient(0.05) (Fig. 5).

Within central and SE regions the fans begin to lose theirmorphology through coastal sea cliff erosion, becomingprogressively smaller (e.g. area¼ 0.15 km2) and steeper(gradient¼ 0.8) (Figs 2,4 and 5). In the SE region only, proximalfragments of fan lobes with small areas (0.1–0.05 km2) arepreserved (Figs 2 and 4). Collectively, the smaller fans andfragments in the central and SE regions comprise a singlesurface that correlates well with the surface of the larger, better-preserved fans in the NW region. However, subtle slopemorphology changes suggest the presence of some older fansurface fragments (Fig. 2).

Alluvial fan surfaces are dissected by single stream channelsthat are the downstream continuation of the previouslydescribed range front slope channels and gullies. The fanchannels cut down through fan and marine terrace sediments.Only in distal reaches, either at or within close proximity to thecoastal cliff, do channels cut down into Cretaceous bedrock.Fan channels show spatial variations of incision pattern. In theNW, incision is negligible to small, with low channel gradientsof�0.05 mimicking the most landward gradients of inner shoreplatform levels (0.04: Bradley and Griggs, 1976) (Figs 4 and 5).Towards the SE, incision increases, with steeper channels(gradient¼ 0.2) cut down by 3–5m into fan surfaces (Figs 4and 5). Surveying of channels (Fig. 5) commonly reveals astepped long profile where channel knick points have formed.Knick points are particularly evident within fans of the centraland SE regions and show some discrete groupings into ‘knickzones’ (Fig. 5).

The marine terrace and alluvial fan landforms are truncatedby a steep to vertical coastal cliff up to 25m high. Erosion isevident along the length of this coastal cliff, characterised bygully erosion, rotational landslide complexes and slumpingwithin marine terrace and alluvial fan deposits (Fig. 6), andstream channel margins of entrenched fans. Local studies oferosion rates are lacking, with only regional estimates availablederived from short-term monitoring of fine-grained fluvialsediment inputs into near-shore coastal settings (Griggs andHein, 1980) and longer-term late Cenozoic denudationestimates using apatite (U–Th)/He ages (Ducea et al., 2003).

Offshore, a low-gradient shore platform exists with bathy-metric contours that parallel the Rancho Marino range front(USGS, 1979). Within 1.6 km of the modern shoreline, offshoretopographic gradients vary between 0.02 and 0.04 (USGS,1979) and are therefore typical of inshore platform segmentsobserved in other areas of the Coast Range shoreline (Bradleyand Griggs, 1976).

Climate in the study area is characterised by warm, drysummers and cooler, wetter winters (California Climate DataArchive, 2008). Mean annual precipitation varies from 50 to40 cm, with delivery by North Pacific storms during the winter(Raphael and Mills, 1996; Mitchell and Blier, 1997). Major


Figure 5 Examples of surface profiles withmean gradients of alluvial fan andmarine terrace landforms and stream channel incision fromNW, centraland SE regions. See Fig. 2 for fan locations


storm waves break in water depths of 7–12m suggesting thatinner shore platforms are formed via storm-wave surf zoneprocesses (Bradley and Griggs, 1976).

Figure 6 Gully and landslide styles of sea cliff erosion in the SE of thestudy area (site 15: Fig. 2), with view looking towards the SE


Palaeoshore platforms and shoreline angles

Late Quaternary sediments at Rancho Marino overlie erosionsurfaces cut into Cretaceous bedrock, truncating bedrockbedding and fold structures (Fig. 7). Surfaces can be tracedlaterally along the modern coastal cliff line, often over severaltens of metres, and display an undulating form of up to 1mrelief, or rare, highly localised relief of up to 2m. Theundulating topographic variations (�1m) reflect changes inbedrock lithology, with lows coinciding with finer-grainedunits, and highs with sandstones. Highly localised relief (�2m)corresponds to degraded sea stacks. Platform elevations rangedfrom 0 to 7.4m above sea level (Table 1). These erosionsurfaces are interpreted as palaeoshore platforms (terminologyafter Weber, 1983) cut by wave action during variations in LateQuaternary sea level (e.g. Lambeck and Chappell, 2001).Bradley and Griggs (1976) in their study of modern andPleistocene palaeoshore platforms in central California showedthat platforms comprise (1) a 300–600mwide, slightly concaveinshore segment with gradients of 0.02–0.04 and (2) a flatteroffshore segment with gradients of 0.007–0.017. At RanchoMarino the coastal cliff sites where the palaeoshore platformsare located are in close proximity (<300m) to the main range


Figure 7 (A) ‘Upper’ (125 ka) palaeoshore platform (arrowed) at�5m altitude truncatingUpper Cretaceous bedrock fold structures (Site 6: Fig. 2). (B)Fossil sea cliff (fsc), ‘lower’ palaeoshore platform (psp) and shoreline angle (fsa: black arrow 1) of 105 ka highstand at�2.1 m altitude. Modern sea cliffand shore angle (black arrow 2). Backpack for scale. Inset provides an oblique view schematic representation of Fig. 7(B)


front slope (Fig. 2) and would therefore correspond to thelandward margin of Bradley and Griggs’ (1976) inshoreplatform segment.Evidence for a landward limit of palaeoshore platform

development, the strandline, whose geometrical relationshipwith a fossil sea cliff is termed the shoreline angle, can onlyclearly be observed at site 4 (Figs 2 and 7(B)). Shoreline anglesare important as they are a sea-level index point that, togetherwith other data (e.g. dated marine terrace deposits), can belinked to palaeosea-level positions, which in turn can be usedto quantify surface uplift rates. At site 4, a shoreline angle ispresent at þ2.1m and appears to be genetically related to alow-level platform at 0m that is recorded at the nearby andadjacent site 3 (Fig. 2). This low-elevation shoreline angle islocally backed by a small sea cliff (<3m) and links to a


degraded and highly fragmented platform that can be tracedalong the coast and offshore (Fig. 7(B)). The shoreline angle canbe traced laterally several tens of metres along the coast to thesouth-east as a strandline before being buried by alluvialsediments.

All other sites along the coastline are characterised by ahigher-elevation palaeoshore platform with a mean altitude of5.27m, minimum altitude of 3.85m and maximum altitude of7.4m (Table 1). The height variation of up to �2m from themean palaeoshore platform altitude can be explained bythe previously mentioned changes in bedrock lithology and thelocalised presence of fossil sea-stack remnants.

Estimations of the altitudes of the higher platform shorelineangles were undertaken using a trigonometric projectionmethod based on a right-angled triangle (Fig. 8). The base of


Table 1 Upper and lower palaeoshore platform locations, height data and projected altitudes of upper platform 125ka shoreline angles

Platform levelassignment

Region(see Fig. 2)

Site number(see Fig. 2)

Location coordinates:latitude and longitude

Platformheight (m)

Horizontal distanceto range front break

of slope (m)

Projected shoreline angleheight (m) 0.04 gradient

(2.298) (see Fig. 8)

Lower Central 3 358 32.0440 N, 1218 05.1760 W 0 289 N/ACentral 4 358 32.0200 N, 1218 05.0390 W 2.1 175 N/A

Higher NW 1 358 32.3470 N, 1218 05.4780 W 6.4 260 16.8NW 2 358 32.1590 N, 1218 05.2380 W 5.3 261 15.7Central 5 358 31.9660 N, 1218 04.9830 W 5.9 187 13.4Central 6 358 31.8740 N, 1218 04.8340 W 4.75 122 9.6SE 7 358 31.7890 N, 1218 04.8010 W 6.4 142 12.1SE 7 358 31.7590 N, 1218 04.7350 W 7.4 127 12.5SE 9 358 31.7410 N, 1218 04.7030 W 5.9 124 10.9SE 10 358 31.6800 N, 1218 04.6690 W 4.2 118 8.9SE 11 358 31.6590 N, 1218 04.6430 W 3.85 112 8.3SE 12 358 31.5890 N, 1218 04.5880 W 5.55 134 10.9SE 13 358 31.5690 N, 1218 04.5510 W 4.7 63 7.2SE 14 358 31.4580 N, 1218 04.4910 W 3.95 128 9.1SE 15 358 31.4220 N, 1218 04.4390 W 4.2 98 8.1


the main range front slope occurs at þ25m altitude and marksthe most landward limit of where marine terrace sedimentswere mapped (Fig. 2). We propose that the fossil sea cliffassociated with the higher palaeoshore platform is buriedbeneath this landward limit of marine terrace sediments. Thetrigonometric projection involved measuring the horizontaldistance from each coastal cliff site to the þ25m altitudeposition, to provide the adjacent value of the right-angletriangle (Table 1 and Fig. 8). Given the close proximity of thecoastal cliff sites to the main range front slope at þ25m (83–261m: Table 1), we used the higher 0.04 platform gradientvalue of Bradley and Griggs (1976) that is typical of the mostlandward portions of inner platform segments. The 0.04platform gradient was converted into a slope of 2.298 usingarc tangent. The slope and adjacent right-angle triangle valueswere then used to calculate the length of the opposite. Theopposite values were then added to the height of theirrespective palaeoshore platform to provide the altitude estimateof the shoreline angle. Results show that projected higherpalaeoshore platform shoreline angle altitude estimates rangefrom 7.1m to 16.8m, with a mean altitude of 10.9m (Table 1).These altitude results are subject to the �0.5–1m surveyingaccuracy outlined previously (‘Graphic sedimentary loggingand surveying’).In summary, two platform levels can be identified at Rancho

Marino: (1) a rare lower platform at 0m altitude linked to a

Figure 8 Trigonometric projection method used to estimate altitudes of thexplanation


shoreline angle at 2.1m; and (2) a more common upperplatform with a mean altitude of 5.27m, linked to a projectedmean shoreline angle at 10.9m (Table 1). The regionalstratigraphic relationships of these platforms and their shorelineangle altitudes are discussed below (‘Landscape correlationand chronology’).

Range front sediments, process andenvironments

Overlying the shore platforms are a sequence of lateQuaternary clastic sediments. These sediments are exposedin the coastal cliff and distal alluvial fan stream channelmargins, varying in thickness from 3m in the NW to 20m in theSE.

Marine terrace sediments

These facies comprise gravel and sand units that can be tracedalong the entire length of the study area coastline formingthe basal component of the late Quaternary sedimentary

e upper palaeoshore platform (125 ka) shoreline angles. See text for


Figure 9 Examples of graphic sedimentary logs of marine terrace and alluvial fan sediments that overlie the lower and upper palaeoshore platforms(see Fig. 2 for locations). Upper palaeoshore platform logs illustrate changes in facies occurrence and thickness along the coast (NW–SE)


succession (Fig. 9). The sediments form composite units of 0.5–4.5m (1.5m mean) thickness with a brown coloration(weathered surface¼ 7.5YR 6/4 light brown; fresh¼ 7.5YR 4/6 strong brown).

Coarse rounded gravels

Coarse gravels dominate the lowermost part of the sedimentarysequence (e.g. Fig. 10(A) and (B)) forming units from 0.5 to2.7m thick (1m mean) that can be traced along the entirelength of the study area (Fig. 9). Thicker gravel units (>1m) tendto occupy pronounced localised topographic lows within theCretaceous bedrock (Fig. 10(B)), while thinner units (<1m) arelaterally persistent, often traceable over near-horizontalsurfaces for several tens of metres. The gravels compriserounded to subrounded boulder and cobble sized clasts (meanDmax¼ 0.3m) of locally derived Cretaceous sandstone,siltstone and mudstone composition (Fig. 10(B)). Gravels either


lack organisation or show a weak horizontal stratification, withthe long axis of larger clasts arranged horizontally or withlandward imbrication. Sorting is generally moderate to poor,with larger clasts supported within a matrix of clay-rich sand.Cobble clasts of sandstone sometimes show rare circular pittingof up to 2 cm wide and 1 cm deep (Fig. 7(C)).

Sands

Coarse to medium sands with a reddish-orange colourcommonly overlie the cobble–boulder gravel units, displayingeither sharp or gradational basal contacts (Fig. 10(A)). The sandsform laterally persistent units that range in thickness from 0.5 to2.8m (1.1m mean) (Fig. 9). Their occurrence is variablethroughout the study area, being common and often thicker inthe NW and central regions, particularly around Site 3 (Figs 2and 9) and becoming less common and ultimately absenttowards the SE (Fig. 9). This distribution appears to coincide


Figure 10 (A) Typical section of coastal marine sediments (Site 3: Fig. 2) showing Cretaceous bedrock (0), overlain by coarse rounded gravels (1) andwell-sorted sands (2). Upper parts of the section comprise distal alluvial fan sediments (3) and soil (4). Arrow denotes OSL sampling site. Backpack forscale. (B) Cobble–boulder dominated coarse rounded gravels infilling a pronounced topographic relief within the Cretaceous bedrock (Site 5). (C)Mollusc borings (arrowed) on Cretaceous sandstone clast (Site 3). (D) Lens of pebble–gravel clasts within the well-sorted sand facies (Site 3)


with the proximity of the coastal cliff site where facies werelogged in relation to the main range front slope (Table 1). Sitescloser to the range front (<125m) tend to lack sands, while sitesfurther away (125–289m) contain sands (Fig. 9).The sands are typically moderately to poorly sorted and

are either massive or show weak horizontal bedding. Many ofthe sand units contain discrete, laterally impersistent lensesof weakly stratified subrounded to rounded pebbles(Fig. 10(D)) and rare larger cobble–boulder clasts (meanDmax¼ 0.1m). Many clasts show landward imbrication andsome clasts again reveal evidence for concentrations ofcircular surface pitting. The marine terrace sands grade upinto alluvial fan clay-rich sands and silts (‘Alluvial sandsediments’, below).

Process and environment interpretations

The gravels and sands are interpreted to be the product of high-energy wave processes within a rocky shoreline region inwhich marine terrace construction has occurred. Changes ingravel and sand thickness reflect deposition onto a highlyvariable local bedrock topographic relief, characterised byerosional sea stacks between which discontinuous pocket sandbeach sedimentation occurs (Muhs, 1987). Coastal shellmaterial is lacking from the deposits but the circular pittingon clasts corresponds to mollusc borings typical of littoral zoneregions (Taylor and Wilson, 2003). Landward imbrication ofgravel sediments reflects clast configuration by breaking wavewash energy. Matrix support of larger clasts by clayey sands


corresponds to infilling of open framework gravels (e.g. Bluck,1967) and to the in situ breakdown of feldspar-rich Cretaceoussandstones. The gravels correspond to a coarse-grained beachdeposit formed by combinations of storm wave processes andwave erosion of the sea cliff and sea stacks. The overlying sandscorrespond to a finer-grained beach deposit, with theinterbedded gravel lenses corresponding to infrequent stormsedimentation or reworking of alluvial fan sediment inputs.Sands of aeolian origin have been reported as a component ofmarine terrace sediments in the Cambria, San Simeon andSanta Maria Basin areas (e.g. Weber, 1983; Orme, 1992).However, the large grain size, absence of cross-stratification,root bioturbation or rhizolith structures suggests that aeoliansands are not evident at Rancho Marino.The stratigraphic arrangement of gravels overlain by sands

and the dominance of gravels at sites in closest proximity to therange front slope can be accounted for by marine terraceformation models. Platform erosion and sea cliff developmentare considered to occur during rising sea level (Bradley andGriggs, 1976). Marine terrace building is thought to occurduring the sea-level highstand/stillstand and during sea-levelfall when seaward beach sedimentation and progradationoccurs (Bradley, 1957; Bradley and Griggs, 1976; Muhs et al.,2002). Thus, at RanchoMarino the coarse gravels are depositedfirst as a high-energy rocky shoreline and/or storm beach lagduring the initial stages of marine terrace building, reworkingthe coarse material eroded during sea-level rise-related plat-form and sea cliff erosion. Sands are then deposited underprogressively lower energy conditions further away from therange front slope, firstly infilling the coarse beach gravel lagsand then building seawards.


Figure 11 (A) Alluvial fan sediments exposed within the SE region (Site 10: Fig. 2), comprising clay rich sands and silts (3) interbedded with coarsegravels (4) and capped by a soil (5). The fan sediments overlie a thin veneer of coastal marine sediments (2) developed onto a shore platform cut intoCretaceous bedrock (1). (B) Clay-rich sands and silts overlain by coarse gravels and soil at Site 16. (C) Imbricated, clast-supported coarse gravels withweak normal grading (Site 12). Pencil for scale (arrowed). (D) Poorly sorted, matrix-supported coarse gravels (Site 12). Notebook for scale (arrowed)


Alluvial fan sediments

These facies dominate the late Quaternary sedimentarysuccession along the Rancho Marino range front, comprisingclay-rich sands and silts, interbedded with less common coarseangular gravels (Fig. 11(A)). The facies are exposed along theentire length of the coastline, forming composite units of 0.6 to18.4m (6.6m mean) thickness, with thicker successionsexposed towards the southern end of the study area (Fig. 9).

Clay-rich sands and silts

The clay-rich sands and silts have a yellow to beige colouration(Munsell colour: weathered¼ 10YR 6/4 light yellowish brown,fresh¼ 10YR 4/4 dark yellowish brown). Exposures of thesesediments typically display surface weathering, with a crackedprismatic structure, grey mottling and slumping, together withcommon rill and gully erosion (Figs 6 and 11(B)). The contactbetween these sediments and the underlying beach sands andgravels is gradational (e.g. Fig. 10(A)). Sediments form laterallypersistent units ranging in thickness from 0.3 to 7m (Fig. 9). Thesediments are massive, lacking any evidence for bedding orcross-stratification.

Poorly sorted coarse gravels

These gravels form composite units up to 3m thick that aregenerally arranged into laterally persistent, sheet-like units


(Fig. 11(C) and (D)) that display crude horizontal bedding.Individual beds vary from 0.2 to 1m thick and typicallycomprise subrounded to angular gravel to cobble-sized clasts(mean Dmax¼ 0.16m) that display both clast (Fig. 11(C)) andmatrix support (Fig. 11(D)). Clast-supported varieties fineupwards, with individual clasts displaying a crude imbricationtowards the west. Matrix-supported varieties are typicallymassive with no grading. Less common are gravel beds up to1.8m thick comprising poorly sorted, angular cobble andboulder-sized clasts (mean Dmax¼ 0.35m) supported within agravel to clay matrix. These coarser-grained gravels can displayrare channelised geometries forming gentle, open V-shapedforms that cut down by 1–2m into underlying clay-rich sandsand silts.

Interpretations

The facies correspond to range front alluvial fan deposition. Thecommon occurrence of laterally persistent gravels with sheet-like geometries suggests deposition by unconfined flows.Gravels with smaller grain sizes that display clast support, weakimbrication and normal grading are the product of sheetflooddeposition (Blair, 1987). Coarser-grained gravels that arematrixsupported and lack of internal organisation correspond todeposition by debris flow processes (Wells and Harvey, 1987).The occurrence of rare gravel-filled channels probablycorresponds to the infilling of fan channel streams. The clay-rich sands and silts probably correspond to alluvial mudflowprocesses (Bull, 1977), via the reworking of alluvial fancatchment area soils, with clays formed via the breakdown of



the common feldspar component of the Cretaceous bedrock.The grey mottling reflects localised waterlogging and gley-likesoil development within the clay-rich mudflows (Wright andAllen, 1989).Variations in the proportions of gravel and clay-rich sand and

silt fan sediments throughout the study area reflect differentdegrees of coastal cliff erosion into the Rancho Marino rangefront. The dominance of clay-rich sands and silts in the northrelates to exposures through more distal fan settings. Theincrease in gravels towards the south relates to exposures inproximal to mid fan settings. Indeed, sedimentary logs from thesouth-east region (Sites 10–13; Fig. 2) all show crude cyclicalluvial fan sedimentation patterns with a number of stackedcoarsening upwards sequences (e.g. Fig. 9). These sedimentaggradation patterns can be attributed to alluvial fan prograda-tion, revealing either an internal (intrinsic) alluvial fan systembehaviour of lobe switching or an external (extrinsic) drivingmechanism from variations in sediment supply and accom-modation space such as tectonism, climate change or eustacy(Harvey et al., 2005, and references therein).

Soil

The uppermost part of the sedimentary succession is capped bya dark-grey sandy silt soil (weathered surface¼ 2.5Y 3/1 verydark grey; fresh¼ 2.5Y 2.5/1 black) (Fig. 11(A)). The soil forms a0.4–1.2m (mean¼ 0.7m) thick unit that can be traced alongthe entire length of the study area coastal exposure and inlandalong the upper parts of the alluvial fan stream channelmargins (Fig. 9). There is a gradational boundary in terms ofgrain size and coloration between the soil and the underlyingalluvial fan sediment (Fig. 11(B)). The soil is typically massiveand generally well sorted, although does contain relativelycommon ‘floating’ gravel- to pebble-sized angular clasts ofFranciscan sandstone. Surface exposures of the sandy silt reveala blocky, prismatic-like weathering structure. Soil maps of theregion describe the soil type as a sandy clay with a deepdevelopment and moderate drainage (USDA Soil ConservationService, 1979).

Landscape correlation and chronology

Introduction

Landform correlation and chronologies for landscape devel-opment within the central-southern Pacific Coast Ranges haveemployed a range of relative and absolute dating techniquesthat have typically targeted marine terrace landforms using (1)their surface expression and elevation, (2) their depositsincluding sediment characteristics and fossil content, and (3)their underlying palaeoshore platforms and strandlines/shore-line angles. Relative stratigraphic frameworks have beenproposed principally by correlation of palaeoshore platformand marine terrace landforms to palaeosea levels (e.g. Hansonet al., 1994) based upon their altitudinal spacing (e.g. Bull,1985). Studies of global late Quaternary eustatic variationsfrom key sites around the world (e.g. Bermuda, Bahamas, PapaNew Guinea, California: see Hanson et al., 1994, andreferences therein) suggest palaeosea-level highstands at ca.125, 105, 80 and 60 ka. However, the altitudinal manifestationof these palaeosea levels can vary locally depending upon localtectonic conditions (e.g. Lajoie, 1986). For the central-southern


Pacific Coast Ranges the following palaeosea-level altitudeshave been proposed: 125 ka¼þ6m; 105 ka¼�2m� 2m;80 ka¼�5m� 2m; 60 ka¼�24m and 20–18 ka¼�120m(Hanson et al., 1994, and references therein). The ages of thesepalaeosea levels have been confirmed via the application ofabsolute age determinations, primarily by U-Series techniquesapplied to fossil shell, coral and bonematerial containedwithinmarine terrace sediments (e.g. Muhs et al., 1992, 2002). Lesscommon absolute dating techniques including amino acidracemisation of fossil shell material and corals (e.g. Wehmiller,1992) as well as thermoluminescence dating of estuarinesediments (e.g. Berger and Hanson, 1992) have also beenundertaken to varying degrees of success.

Relative dating and correlation of RanchoMarino marine terraces

Field mapping and survey data show two palaeoshore platformheight groupings and a single marine terrace landform surfaceat Rancho Marino (Figs 2 and 5; Table 1). These marine terracecomponents can be correlated with the well-studied marineterraces at nearby San Simeon and Cayucos.At San Simeon, �15 km to the north-west of Rancho Marino

(Figs 1 and 2), well-developed flights of marine terraces havebeen mapped by numerous authors (e.g. Weber, 1983; Hansonet al., 1994). The number of terraces and the altitudes of theirplatforms and shoreline angles vary considerably dependingupon the proximity to the San Simeon fault zone. Three lowterraces are present in the San Simeon area referred to as thePoint, San Simeon and Tripod Terraces by Hanson et al. (1994).Only the San Simeon and Tripod terraces are present north-eastof the San Simeon Fault Zone. Here, the San Simeon terracecomprises rare and isolated fragments with a shoreline angle at5–7m altitude, while the Tripod terrace is extensive and has ashoreline angle at 23–26m (Hanson et al., 1994). The regionalmapping of Weber (1983) mapped the San Simeon and Tripodterraces together as a single composite landform called thePiedras Blancas terrace, underlain by two palaeoshore plat-forms (called San Simeon and Tripod).At Cayucos, �15 km to the south-east of Rancho Marino

(Figs 1 and 2), an extensive lower marine terrace surface ispresent. The single palaeoshore platform of this terrace occursat up to 5m altitude and can be linked to a shoreline angleelevation of �7–8m (Muhs et al., 2002).The configuration of a single marine terrace surface and two

underlying platforms at Rancho Marino has some similaritieswith the San Simeon and Cayucos areas. The single loweremergent marine terrace surface appears to correlate regionallybetween San Simeon (NE of fault), Rancho Marino andCayucos. Several authors have already noted this regionalextent (e.g. Weber, 1983; Muhs et al., 1992; Orme, 1998). Therelationships of platforms underlying the lowermost emergentterrace are more problematic. Correlation between therespective San Simeon (SS) and Tripod (T) platforms from thePiedras Blancas terrace at San Simeon and the Rancho Marinolower (RML) and upper (RMU) platforms seems reasonable butthe height difference between the respective shoreline anglealtitudes is at least double (RML¼ 2m, SS¼ 5–7m;RMU¼ 11m; T¼ 23–26m). At Cayucos only a single platformis present underneath the lowest emergent marine terrace.However, the heights of this platform (�5m) and its shorelineangle (�7–8m) are in closer agreement to the mean upperplatform (5.27m) and shoreline angle altitude (10.9m) atRancho Marino. Integration of absolute dating from the



correlative marine terraces at San Simeon and Cayucos couldhelp reconcile these issues and is subsequently considered.

Absolute dating and correlation of RanchoMarino marine terraces

An absolute chronology for landscape development at RanchoMarino is challenging owing to an absence of fossil materialthat has frequently been used for uranium-series dating ofmarine terrace sediments at nearby sites (e.g. Muhs, 1992;Hanson et al., 1994; Muhs et al., 2002). Much of this U-seriesdating has been undertaken using fossil material sampled fromthe regionally extensive Piedras Blancas/Cayucos marineterrace at the San Simeon and Cayucos sites, typically yieldingan age of ca. 125 ka (Veeh and Valentine, 1967; Hanson et al.,1994; Muhs et al., 1992, 2002). If the relative stratigraphiccorrelation between the lowermost emergent terraces atCayucos, San Simeon (Piedras Blancas terrace) and RanchoMarino is correct (see previous subsection), then the RanchoMarino marine terrace is also ca. 125 ka, linking marine terraceformation here to the Marine Isotope Stage (MIS) 5e sea-levelhighstand (e.g. Muhs et al., 1992). Reconciling the lower andupper palaeoshore platforms that underlie the marine terracesediments is straightforward, with the development of the upperplatform during the 125 ka highstand when sea level was þ6maltitude. Development of the lower platform can be linked tothe 105 ka (MIS 5c) highstand, when sea level was �2� 2maltitude.Recent dating on corals from the Cayucos terrace by Muhs

et al. (2002) has revealed a mixture of 120 and 105 ka ages.These ages have been explained by a recapturing of the 125 katerrace during the 105 ka highstand due to the low to negligibleuplift that occurred at Cayucos between 125 and 105 ka. Theages and model of marine terrace development at Cayucosreinforce the correlation of the upper and lower platforms atRancho Marino, respectively, with the 125 and 105 kahighstands and also support the notion that the Rancho Marinomarine terrace is a composite landform.

Luminescence dating

The determination of the 125–105 ka age of the RanchoMarinomarine terrace by correlation with the San Simeon and Cayucossites provides a useful stratigraphic marker to assess the timingof landscape development along the Rancho Marino rangefront. However, the chronology of the overlying alluvial fansediments and range front erosion is less clear. In order toimprove the overall landscape chronology an opticallystimulated luminescence date was derived from sands thatoverlie the 105 ka platform at site 3 (Figs. 2 and 10(A)). The

Table 2 Analytical data used for optical dating and dating results. Waterlaboratory; its uncertainty gives the assumedmaximum fluctuation of the wateU, Th and K concentrations are determined by low-level gamma spectrometrydetermined from the mean burial depth of the sample; Deffective is the total dosfrom 21 accepted aliquot data. All data are given with 1s error limits

Samplecode (LV)

Watercontent (%)

Grainsize (mm)

U(mg g�1)

Th(mg g�1)

237 15�5 150–250 1.31�0.05 6.66�0.41 0.6


sample was obtained from sand at 0.9m above the �0mplatform, in the transition zone between marine terrace anddistal alluvial fan sand/clayey sand facies (Fig. 10(A)).

Following standard optically stimulated luminescence (OSL)laboratory preparation (sieving, carbonate dissolution, organicmatter removal, density separation of heavy minerals andquartz grain isolation, surface etching of quartz grains andmounting etc.), aliquots of 3mm size were made and thenanalysed on a Risø TL/OSL reader using a single aliquotregenerated dose method of Murray and Wintle (2000). Thesample yielded a reasonable-quality OSL age of 45� 3 ka(Table 2).

The 45� 3 ka age equates to MIS 3, a time of full glacialconditions when polar ice volumes were expanding andpalaeosea level was greater than �24m and falling (Hansonet al., 1994). This age can be interpreted in two ways:

1. th

conr coan

e ra

K(%

7�

at distal alluvial fan sediments were burying the 125–105 ka marine terrace along the Rancho Marino range frontby 45 ka, infilling the space created along the range front assea level dropped in relation to global climatic cooling;

2. th
at the 105 ka age of the lower palaeoshore platform atRancho Marino has been misinterpreted and in fact theplatform and overlying marine terrace sediments are con-siderably younger. The 45 ka OSL age is similar to U-seriesdates of 46� 2 ka and 49� 4 ka derived from a weatheredmammalian bone in the Qp terrace at San Simeon (Hansonet al., 1994). These U-series ages would link the Qp terraceto the 60 ka palaeosea-level highstand at �24m. However,the Qp terrace palaeoshore platform and shoreline angleheights occur at 6.4–8.5m and reflect high uplift rates linkedto the nearby San Simeon fault to account for such altitudes(Hanson et al., 1994).
The 45� 3 ka OSL age can therefore most simply be inter-preted as corresponding to distal alluvial fan sedimentationalong the Rancho Marino range front. However, to test thismodel and to further assess the role of tectonism along the rangefront, we have calculated uplift rates along the range frontaccordingly (next section).

Tectonic uplift at Rancho Marino

Inferred uplift rate methods as defined by Bull (1985) havetypically been employed for sites along the Pacific Coast ofNorth America using the125 ka/MIS 5e shoreline angle (Muhset al., 1992; Hanson et al., 1994; Orme, 1998). This methodinvolves subtracting the marine terrace shoreline angle altituderelative to modern sea level from the shoreline angle altitude ofglobal palaeosea level at 125 ka (þ6m). The corrected height isthen divided by the age of the marine terrace, with the resultantnumber being expressed as metres of uplift per thousand years.

tent indicates the moisture measured when sample arrived in thentent. Grain size indicates the quartz grain size used for OSL dating.d used to calculate the total dose rate; Dcosm is the cosmic dose ratete corrected for water absorption; De is the equivalent dose resulting

)Dcosm

(Gy ka�1)Deffective

(Gy ka�1)De

(Gy)Age

(�1s, ka)

0.03 0.190� 0.009 1.44�0.03 65.4� 4.7 45� 3



We applied this method to the projected 125 ka shorelineangle altitudes linked to the upper palaeoshore platform atRancho Marino. Results show that estimates of uplift rate rangefrom 0.01 to 0.09m ka�1, with amean of 0.04m ka�1 (Table 1).These results suggest low uplift rate estimates in the RanchoMarino area and are consistent with values of 0.017–0.042m ka�1 calculated by Weber (1983) along the coastlinein the Cambria region. The low uplift rates at Rancho Marinocontrast with high values in the San Simeon region (0.12–0.27m ka�1: Hanson et al., 1994; 0.13–0.27m ka�1: Orme,1998) and in closer agreement to the low/negligible valuesrecorded at Cayucos (0–0.14m ka�1: Muhs et al., 1992;0m ka�1: Orme, 1998).We then applied the same uplift calculation method to the

2.1m altitude shoreline angle associated with the lowerplatform at Rancho Marino (Fig. 2 and Table 1). The 2.1maltitude was corrected using the 125 ka (þ6m), 105 ka (�5m)and 60 ka (�24m) sea-level positions, yielding respectiveresults of �0.03, 0.07 and 0.43m ka�1. Although calculatedusing a single data point, the 105 ka uplift rate of 0.07m ka�1

appears reasonable and consistent with the mean 0.01–0.09m ka�1 range calculated for the upper platform shorelineangles using the 125 ka age. The uplift values using the125 and 60 ka ages, respectively, indicate subsidence orexceptionally high uplift rates, both of which are inconsistentwith known uplift patterns within the San Simeon to Cayucosregion (e.g. Hanson et al., 1994; Orme, 1998). The low upliftrate therefore helps to support the fact that the 45 ka OSL agecorresponds to distal alluvial fan sedimentation over the 105 kaplatform and marine terrace (see ‘Luminescence dating’,above).

Coastal range front landscape development

Introduction

Table 3 presents a summary of the timing, styles and patterns oflandscape development along the Rancho Marino range frontusing key data presented in this paper. The estimated low ratesof tectonic uplift (mean¼ 0.04m ka�1) suggest that lateQuaternary landscape development has been primarilygoverned by climate-related sea-level changes and climaticcontrols on range front weathering, sediment supply, sedimentprocesses and depositional styles. The timing of key stages oflandscape development are organised to reflect major changesof global sea-level positions at 125 ka (þ6m); 105 ka(�2� 2m); 80 ka (�5m), 60 ka (�24m), 18–20 ka (�120 to�160m) and 10–0 ka (�0m). These sea-level positions withrespect to their distance from the main range front slope areimportant as they provide a local base level and a control onrange front accommodation space that collectively influencerange front sedimentation and erosion patterns. Figure 12 is atopographic profile of the Rancho Marino range front and itsoffshore region. Key sea-level positions are plotted on thisprofile to demonstrate the base level and accommodationspace landscape controls. In other words, Fig. 12 illustratesspatially and temporally where shore platform cutting, marineterrace development and alluvial fan formation occurred inrelation to the main range front slope. An annotated inset of aglobal sea-level curve by Lambeck and Chapell (2001) isincluded in Fig. 12 so as to show the patterns and timing ofglobal sea-level change and how they relate to the key stages ofthe development of the Rancho Marino landscape.


Pre-125 ka landscape development: reliefgeneration

Low rates of tectonic uplift at Rancho Marino suggest that therange front topographic configuration was conceived prior to125 ka. There are no major changes in bedrock lithology andstructure in the study area (Hall, 1974). Therefore, the increasein relief (110–211m) and steepening of range front slope (0.1 to0.361 gradient) from NW to SE probably reflects differentialpatterns of tectonic uplift and denudation over a longer LateCenozoic timescale linked development of the Santa LuciaMountains (e.g. Ducea et al., 2003). This pre-125 ka reliefconfiguration exerts a passive control on the late Quaternarylandform development by producing (1) large alluvial fans inthe NW associated with the lower and less steep relief and (2)small alluvial fans in the SE associated with the higher andsteeper relief. Furthermore, this relief configuration becomesvery significant when the late Quaternary landforms are erodedduring the post 18 ka sea-level rise (see ‘The 80–18 kalandscape development’, below).

The 125–105 ka landscape development

125ka corresponds to MIS 5e and marks the peak sea-levelaltitude of þ6m during the last interglacial (Fig. 11). Followingthemarine terrace formationmodel of Bradley andGriggs (1976),the upper palaeoshore platform (mean altitude¼ 5.27m) and seacliff (mean projected altitude¼ 10.9m) (Figs. 7(A) and 9; Table 1)formed during the MIS 5e sea-level rise and highstand. Rangefront alluvial fans that may have existed prior to 125 ka wouldhave been eroded and foreshortened by the rising sea level.Field evidence for ‘older’ alluvial fan deposits that may haverelated to this stage of landscape development is limited to rarefragments of proximally located higher and older alluvial fansurfaces (Fig. 2). During the MIS 5e highstand, sea leveloccupied its most landward limit, with <100m of space (basedupon most proximal occurrences of the upper platform:Table 1) between the highstand and the main range frontslope. This would have limited space for alluvial fansedimentation. Marine terrace sedimentation and seawardbuilding of the landform occurred during the ensuing sea-levelfall during MIS 5d (Fig. 12(A)), forming much of the extensivesingle marine terrace surface of up to several hundred metreswide (Fig. 5) that dominates the NW and central regions ofRancho Marino (Figs. 2 and 3).The next sea-level rise during MIS 5c and its highstand at

105 ka with an altitude of �2� 2m (Fig. 12(A)) eroded into the125 ka marine terrace. This formed the lower palaeoshoreplatform (0m altitude) and a new sea cliff at þ2.1m (Fig. 7(B))�175m from the range front slope (Table 1). Marine terraceconstruction following the MIS 5c/105 ka highstand andensuing sea-level fall simply built out from the 125 ka terraceforming a single composite terrace landform. Variations in lateQuaternary uplift along the coast from Cayucos to San Simeonresulted in the formation of a composite 125–105 ka terrace inthe Cayucos and Rancho Marino areas, with distinct 125 and105 ka platforms forming at Rancho Marino because of theslightly higher uplift rate. At San Simeon the higher uplift rateshave enabled a clear separation of the 125 and 105 ka platformsand their overlying marine terraces to develop.

The 80–18 ka landscape development

Following the MIS 5c/105 ka highstand at �2� 2m, sea levelhas fluctuated but followed an overall lowering trend


Tab

le3

SummaryofRan

choMarinosedim

entation/erosionpatternsan

dtheirrelationship

toclim

atech

angesan

deu

static

base-leve

lac

tivity

duringthelate

Quaternary.

Seetext

forfuller

explanationan

dFig.

12for

grap

hic

representation

MarineIsotope

Stag

ePalaeosea-leve

laltitude

Distance

from

range

frontbreak

ofslope

Ran

gefrontsedim

entation

and

erosion

patternsan

dtheirrelationship

totectonics,

sea-leve

lch

angesan

dclim

ate(numbersin

paren

theses

approximateto

sea-leve

lcu

rvepositionsin

Fig.

12(B))

Holocene

2–1

0m

N/A

Differential

range

fronterosionpatternslinkedto

risingsealeve

ldueto

variationsin

range

frontrelief

(1)

NW

–lower

andless

stee

prelief!

seaclifferosionan

dminorterrac

e/fanincision

SE–higher

andstee

per

relief!

majorseaclifferosionan

dterrace/fanincision

Risingsealeve

lerodes

into

range

frontalluvial

fantoeregions(1)

Possible

fanbuildingduring14–9

kadueto

increa

sedstorm

activity

lead

ingto

hillslopeinstab

ilityan

ddeb

risflow

activity

byco

lluvial

hollow

excava

tion(2)

Risingsealeve

lex

cava

tesoffshore

platform

region(3)

18–2

0ka

2�120m

7.5km

LastGlacial

Maxim

um

sea-levellowstan

dan

dgrea

testpiedmontarea

exposure

(4)

60ka

3�24m

1.3km

45ka

OSL

age–sugg

eststhat

fanbuildingreac

hed

�300m

from

range

fronta

nd/orsugg

estsabasal

ageforrange

frontfan

building(5)

Shore

platform

cuttingan

dmarineterracedevelopmen

t(6)

80ka

5a

�5m�2m

<500m

Shore

platform

cuttingan

dmarineterracedevelopmen

t(7)

Ran

choMarinorange

frontbec

omes

disco

nnec

tedfrom

eustatic

base-leve

lfall

Possible

ongo

ingfansedim

entationas

more

spac

ecrea

tedalongrange

fronta

ndsedim

entsupply

isincrea

seddueto

increa

sedglac

ial-

clim

ateprecipitation(8)

105ka

5c

�2m�2m

<200m

Possible

fanbuildingas

spac

ecrea

tedalongrange

frontdueto

sea-levelfall(8)

Marineterracesedim

entationinto

distalpartsof125ka

terrac

eform

ingaco

mposite

marineterracelandform

(9)

Risingsealeve

lerodes

into

125ka

marineterracean

dcu

tslower

palae

oshore

(0m)platform

andshorelinean

gle(2.1m)(10)

125ka

5e

þ6m

<100m

Marineterracesedim

entationan

dseaw

ardbuildingduring/post

highstan

d(11)

Risingsealeve

lcu

tsupper

palae

oshore

platform

anderodes

range

frontfans(12)

Pre-125ka

N/A

N/A

N/A

Tec

tonic

upliftan

dden

udationlead

ingto

contemporary

topograp

hic

configu

rationofRan

choMarino

Copyright � 2008 John Wiley & Sons, Ltd. J. Quaternary Sci., Vol. 24(7) 728–746 (2009)DOI: 10.1002/jqs


Figure 12 (A) Late Quaternary sea-level curve (modified from Lambeck and Chappell, 2001) used to illustrate sea-level changes and theirrelationships to landscape development at Rancho Marino. (B) NE–SW orientated topographic profile passing through the central region of theRancho Marino range front and its offshore region. Profile created using contour data from USGS (1979). The profile illustrates the relationship ofpalaeosea-level shoreline positions to the Rancho Marino range front and highlights the extent of piedmont exposure and space for alluvial fanbuilding. See Table 3 and text for explanation of model


characterised by highstand positions at MIS 5a/80 ka (�5� 5m)and MIS 3/60 ka (�24m) and the Last Glacial Maximum (LGM)MIS 2/20–18 ka lowstand at �120m (Fig. 12(A)). The siteswhere the 80–18 ka shore platform and marine terraces wouldhave developed are currently located in submerged regionsoffshore from Rancho Marino (Fig. 12(B)). Plotting the 80 and60 ka highstands with the 18 ka lowstand positions usingbathymetric contour data against the distance from the RanchoMarino range front slope reveals a progressive increase in thewidth of range front piedmont area (80 ka, 500m; 60 ka,1.6 km; 18 ka, 7.5 km) (Fig. 12 and Table 3).The stratigraphic arrangement of alluvial fan sediments

overlying the 125–105 ka marine terrace sediments along theRancho Marino range front (Fig. 9) suggests that fan buildingoccurred in the space created during the post 125–105 ka sea-level lowering. TheOSL age derived from site 3 at�289m fromthe main range front slope (Figs. 2 and 10(A)) implies that burialby distal alluvial fan sediments did not take place here until ca.45 ka. It is possible that fan building closer to the range frontslope commenced as soon as sufficient space was madeavailable, possibly even coeval or immediately post theMIS 5e/25 ka highstand and its seaward terrace building duringMIS 5d.Alternatively, the OSL age could be considered a basal age forfan sedimentation and that significant fan building along theRancho Marino range front commenced after 45� 3 ka. Fanbuilding is closely related to climatic variations in precipitationand associated vegetation cover that collectively influencebedrock weathering, slope sediment generation and hillslopestability (Harvey et al., 2005, and references therein). MIS 5corresponds to the last interglacial period when climaticconditions and vegetation cover in the Pacific Coast Rangeswere considered to be similar to that of today. The climate wasrelatively warm and dry, supporting a Monterey pine andcoastal oak forest and coastal scrub vegetation on relatively


stable hillslopes (Heusser, 1960, 1995; Johnson, 1977). Thetime that follows MIS 5 is considered a glacial periodcomprising two glacial maxima (MIS 4, ca. 75–60 ka; andMIS 2, 25–11 ka) separated by a warmer interlude (MIS 3, ca.60–25 ka). The cooling trend associated with this glacial periodis believed to have increased precipitation but changedvegetation only a little, with a slightly enhanced coniferousforest cover within lower-relief coastal settings (Johnson, 1977).The increased precipitation is argued by some (e.g. Shlemonet al., 1987) to have resulted in slope instability leading toenhanced debris flow activity and therefore could support fanbuilding at Rancho Marino during glacial time. Although aprecise timing of fan building is unclear, the small size of therange front fans (<0.24 km2) would suggest that they becamequickly disconnected from base level as the sea level loweredduring glacial time.

The 18 ka to recent landscape development

18 ka coincides with the LGM and is characterised by a sea-level lowstand at�120m, with the shoreline some 7.5 km fromthe Rancho Marino range front (Fig. 12(B)). Sea-level risefollowing the lowstand is rapid and is associated with climaticamelioration during the transition from the last glacial into thecurrent interglacial. The warming climate was characterised byperiods of instability. For example, from 14 to 9 ka an increasein landslide and debris flow activity has been recorded alongthe California coast, whereby increased storminess resulted inhillslope denudation via debris flow activity (Reneau andDietrich, 1987; Reneau et al., 1990; Garcıa and Mahan, 2008),leading to (at least) localised stream aggradation throughout thePacific Coast Ranges (Personius et al., 1993; Garcıa and



Mahan, in press).This climatic instability could be responsiblefor fan sedimentation along the Rancho Marino range front,although a more comprehensive age dataset would be requiredto fully explore this model.The rapid rise in sea level from the �120m 18 ka lowstand

(Fig. 12(A)) can be used to explain patterns of erosion along theRancho Marino range front. Sea-level rise from the lowstandtracked landwards over the 7.5 km wide emergent piedmont(Fig. 12(B)). Marine terraces associated with the 60 ka (�24m)and 80 ka (�5m) highstands are sequentially eroded by thelandwards shift in sea cliff position of the rising sea level. Uponreaching the 125–105 ka marine terrace within <500m fromthe range front slope, the topographic configuration of RanchoMarino becomes significant for controlling range front erosionpatterns. Relief and range front steepness increase from NW toSE (Fig. 4) and are coincident with a respective increase incostal cliff erosion and marine terrace/alluvial fan surfacestream incision (Figs. 5 and 6). The rising sea level combineswith the steeper and more rugged slopes in the SE, acceleratinglandscape erosion accordingly. This erosion follows the marineterrace degradation model of Anderson et al. (1999), who showthat emergent marine terraces erode by combinations of seacliff retreat and backwearing of slopes adjacent to incisingstreams. Stream incision within the south-east shows evidencefor episodic sea cliff erosion, whereby knick zone developmentcorresponds to foreshortening of alluvial fan stream channels asbase-level changes are transmitted upstream (Fig. 5).

Conclusions

Late Quaternary landscape development along the RanchoMarino coastal range front in the central-southern Pacific CoastRanges of California has been controlled by an interplaybetween tectonic, climatic and eustatic forcing mechanisms.Pre-125 ka uplift and denudation patterns linked to the lateCenozoic development of the Santa Lucia Mountains wereresponsible for the overall range front topographic configur-ation, characterised by linear NW–SE orientated topographythat becomes progressively higher, steeper and more ruggedtowards the SE.Late Quaternary sediments have accumulated along the base

of the range front slope forming a single marine terracelandform buried by alluvial fans. The marine terrace overliestwo palaeoshore platform levels at �5m (upper platform) and�0m (lower platform). Collectively, platform, marine terraceand alluvial fan development are related to late Quaternaryclimatic and climate-related sea-level changes. Correlationwith the Cayucos and San Simeon sites suggests that platformsdeveloped during sea-level rises culminating in the 125 ka(upper platform) and 105 ka (lower platform) highstands.Genesis of the single marine terrace landform can be attributedto post-125 ka sea-level fall but with sea-level rise at 105 kaeroding into and recapturing the 125 ka terrace, forming acomposite 125–105 ka marine terrace landform. Lowering ofglobal sea level from the peak 125 ka highstand at þ6m,followed by highstands at 105 ka (�2m), 80 ka (�5m), 60 ka(�24 ka) and culminating in a lowstand at 18 ka progressivelyexposed a 7.5 km wide piedmont area adjacent to the RanchoMarino range front.Shoreline angle altitudes associated with 125 ka (10.9m) and

105 ka (2.1m) platforms were used to calculate uplift rateestimates along the RanchoMarino range front. Values of 0.01–0.09m ka�1 (mean 0.04m ka�1) suggest a low uplift rate,supporting the notion of pre-late Quaternary uplift and relief


generation. Integration of RanchoMarino uplift data (low uplift)with Cayucos (negligible uplift) and San Simeon (high uplift)suggests an along-coast increase in uplift rate towards thenorth-west and the San Simeon fault zone.

Alluvial fan building along the base of the range front slope isattributed to a combination of tectonics, sea-level and climaticchanges. Sea-level lowering post the 125 ka highstand providedspace along the range front for alluvial fan building, with fansbecoming disconnected from the falling base level due to theirsmall size. Climate-related changes in slope stability increasedrange front sediment supply, resulting in fan aggradation. Thismay have occurred during glacial cold maxima (e.g. MIS 4/2)and/or during increased climate storminess associated with thePleistocene–Holocene transition. A 45 ka OSL age of sands thatunderlie distal alluvial fan sediments associated with the 105 ka(lower) platform suggests either (1) that fan building reached�300m from the range front slope by 45 ka or (2) provides alower/basal age for range front fan sedimentation, with fanbuilding occurring after 45 ka.

Patterns of range front erosion are related to rising sea levelafter the 18 ka lowstand. Within close proximity to the rangefront slope (�<500m) the passive relief configurationsignificantly influences piedmont geomorphology. Specifically,fans are progressively smaller, steeper and more incisedtowards the south-east and therefore follow the NW to SEtrend of steadily increasing range front relief and slopesteepness.

Acknowledgements Fieldwork was conducted by MS during sabba-tical leave hosted by Cal Poly San Luis Obispo and theUCSB Kenneth S.Norris RanchoMarino reserve. Don Canestro (reserve manager) and hisfamily are thanked for their hospitality during fieldwork. Surveying wasconducted with the support of Jim Webb, Sophie Pierszalowski andAlison Stokes. The OSL date was part funded by the British Society forGeomorphology and analysis was undertaken by Dr Barbara Mauz atthe University of Liverpool OSL laboratory. The California CoastalRecords Project is thanked for permission to use their oblique aerialphoto imagery. Carol Prentice, Don Rodbell and an anonymous refereeare thanked for their helpful review comments.

References

Anderson RS, Densmore AL, Ellis MA. 1999. The generation anddegradation of marine terraces. Basin Research 11: 7–19.

Berger G, Hanson KL. 1992. Thermoluminescence ages of estuarinedeposits associated with Quaternary marine terraces, south-centralCalifornia. In Quaternary Coasts of the United States: Marine andLacustrine Systems, Fletcher CH, Wehmiller JF (eds). SpecialPublication 48. SEPM: Tulsa, Oklahoma; 304–308.

Blair TC. 1987. Sedimentary processes, vertical stratificationsequences, and geomorphology of the Roaring River alluvial, RockyMountain National Park, Colorado. Journal of Sedimentary Petrology57: 1–18.

Bluck BJ. 1967. Sedimentation of beach gravels: examples from SouthWales. Journal of Sedimentary Petrology 37: 128–156.

Bradley WC. 1957. Origin of marine terrace deposits in the Santa Cruzarea, California. Geological Society of America Bulletin 68: 421–444.

Bradley WC, Griggs GB. 1976. Form, genesis and deformation ofcentral California wave-cut platforms.Geological Society of AmericaBulletin 87: 433–449.

Bull WB. 1977. The alluvial-fan environment. Progress in PhysicalGeography 1: 222–270.

Bull WB. 1985. Correlation of flights of global marine terraces. InTectonic Geomorphology: Proceedings, 15th Binghamton Geomor-phology Symposium, Morisawa M, Hack J (eds). Allen & Unwin:Boston, MA; 129–152.



California Climate Data Archive. 2008. http://www.calclim.dri.edu [10August 2008].

California Coastal Records Project. 2008. http://www.californiacoas-tline.org/ [10 August 2008].

Christensen MN. 1965. Late Cenozoic deformation in the central Coastranges of California. Geological Society of America Bulletin 76:1105–1124.

Clark DG, Slemmons DB, Caskey SJ, dePolo DM. 1994. Seismotectonicframework of coastal central California. In Seismotectonics of theCentral California Coast Ranges, Alterman IB, McCullen RB, CluffLS, Slemmons DB (eds). Special Paper 292. Geological Society ofAmerica: Boulder, CO; 9–30.

DickinsonWR, DuceaM, Rosenberg LI, GreeneHG, Graham SA, ClarkJC, Weber GE, Kidder S, Ernst WG, Brabb EE. 2005. Net dextral slip,Neogene San Gregorio–Hosgri fault zone, coastal California: geolo-gic evidence and tectonic implications. Special Paper 391. Geologi-cal Society of America: Boulder, CO.

Ducea M, House M, Kidder S. 2003. Late Cenozoic denudation anduplift rates in the Santa Lucia Mountains, California. Geology 31:139–142.

Garcıa AF, Mahan SA. Sediment storage and transport in Pancho RicoValley during and after the Pleistocene–Holocene transition, CoastRanges of central California (Monterey County). Earth Surface Pro-cesses and Landforms (in press).

Griggs GB, Hein JR. 1980. Sources, dispersal, and clasy mineralcomposition of fine grained sediment off central and northern Cali-fornia. Journal of Geology 88: 541–566.

Hall CA. 1974. Geologic map of the Cambria region, San Luis ObispoCounty, California. USGS Miscellaneous Field Studies Map MF-599,scale 1:24 000.

Hanson KL, Lettis WR, Wesling JR, Kelson KI, Mezger L. 1992. Qua-ternary marine terraces, south-central coastal California: implica-tions for crustal deformation and coastal evolution. In QuaternaryCoasts of the United States: Marine and Lacustrine Systems, FletcherCH, Wehmiller JF (eds). Special Publication 48. SEPM: Tulsa,Oklahoma; 323–332.

Hanson KL, Wesling JR, Lettis WR, Kelson KI, Mezger L. 1994. Cor-relation, ages, and uplift rates of Quaternary marine terraces: south-central California. In Seismotectonics of the Central California CoastRanges, Alterman IB, McCullen RB, Cluff LS, Slemmons DB (eds).Special Paper 292. Geological Society of America: Boulder, CO; 45–71.

Hanson KL, Lettis WR, McLaren MK, Savage W, Hall NT. 1995. Styleand rate of Quaternary deformation of theHosgri Fault Zone, offshoreSouth-Central California. USGS Bulletin 1995-BB.

Harvey AM, Mather AE, Stokes M. 2005. Alluvial Fans: Geomorphol-ogy, Sedimentology, Dynamics, Special Publications 251. Geologi-cal Society: London.

Heusser CJ. 1960. Late Pleistocene of North Pacific North America,Special Publication 35. American Geographical Society: New York.

Heusser CJ. 1995. Pollen stratigraphy and paleoecologic interpretationof the 160-K.Y. record from Santa Barbara basin, hole 893A. InProceedings of the Ocean Drilling Program: Scientific Results, Vol.146, Part 2, Kennett JP, Bauldauf JG, Lyle M (eds). 265–279.

Hsu KJ. 1969. Preliminary report and geologic guide to Franciscanmelanges of the Morro Bay-San Simeon area, California. SpecialPublication 35. California Division of Mines and Geology: SanFrancisco, California.

Jennings CW. 1994. Fault activity map of California and adjacent areaswith location and ages of recent volcanic eruptions. CaliforniaDivision of Mines and Geology Data Map Series No. 6, 92 p., 2plates, map scale 1: 750000. Sacramento, California.

Johnson DL. 1977. The late Quaternary climate of coastal California:evidence for an ice age refugium. Quaternary Research 8: 154–179.

Lajoie KR. 1986. Coastal tectonics. In Studies in Geophysics: ActiveTectonics, Usselman TM (ed.). National Academy Press:Washington, DC; 95–124.

Lajoie KR, Ponti DJ, Powell CL II, Mathieson SA, Sarna-Wojcicki SA.1991. Emergent marine strandlines and associated sediments, coastalCalifornia: a record of Quaternary sea-level fluctuations, verticaltectonic movements, climatic changes, and coastal processes. InQuaternary Non-glacial Geology: Conterminous US, Morrison RB(ed.). Geological Society of America: Boulder, CO; 190–203.


Lambeck K, Chappell J. 2001. Sea level change through the last glacialcycle. Science 292: 679–686.

Lettis WR, Hanson KL. 1991. Crustal strain partitioning: implications forseismic hazard assessment inwestern California.Geology 19: 559–562.

Lettis WR, Hanson KL. 1992. Quaternary tectonic influences on coastalmorphology, south-central California. Quaternary International 15/16: 135–148.

Mitchell TP, Blier W. 1997. The variability of wintertime precipitationin the region of California. Journal of Climate 10: 2261–2276.

Muhs DR. 1987. Geomorphic processes in the Pacific Coast andMountain System of central and southern California. In GeomorphicSystems of North America, Graf WL (ed.). Geological Society ofAmerica: Boulder, CO; 560–570.

Muhs DR. 1992. The last interglacial–glacial transition in North Amer-ica: evidence from uranium-series dating of coastal deposits. In TheLast Interglacial–Glacial Transition in North America, Clark PU, LeaPD (eds). Special Paper 270. Geological Society of America:Boulder, CO; 31–51.

MuhsDR, Rockwell TK, KennedyGL. 1992. LateQuaternary uplift ratesof marine terraces on the Pacific Coast of North America, southernOregon to Baja California Sur. Quaternary International 15/16: 121–133.

Muhs DR, Simmons KR, Kennedy GL, Rockwell TK. 2002. The lastinterglacial period on the Pacific Coast of North America: timing andpaleoclimate. Geological Society of America Bulletin 114: 569–592.

Murray AS, Wintle AG. 2000. Luminescence dating of quartz using animproved single-aliquot regenerative-dose protocol. RadiationMeasurements 32: 57–73.

Orme AR. 1992. Late Quaternary deposits near point Sal, south-centralCalifornia: a time frame for coastal dune emplacement. In Quatern-ary Coasts of the United States: Marine and Lacustrine Systems,Fletcher CH, Wehmiller JF (eds). Special Publication 48. SEPM:Tulsa, Oklahoma; 309–315.

Orme AR. 1998. Late Quaternary tectonism along the Pacific coast ofthe Californias: a contrast in style. In Coastal Tectonics, Stewart IS,Vita-Finzi C (eds). Special Publication 146. Geological Society:London; 179–197.

Page BM, Thompson GA, Coleman RG. 1998. Late Cenozoic tectonicsof the central and southern Coast Ranges of California. GeologicalSociety of America Bulletin 110: 846–876.

Personius SF, Kelsey HM, Grabau PC. 1993. Evidence for regionalstream aggradation in the Central Oregon Coast Range during thePleistocene–Holocene transition.Quaternary Research 40: 297–308.

Raphael M, Mills G. 1996. The role of mid-latitude cyclones in the winterprecipitation of California. Professional Geographer 48: 251–262.

Reneau SL, DietrichWE. 1987. Size and location of colluvial landslidesin a steep forested landscape. In Erosion and Sedimentation in thePacific Rim, Beschta RL, Blinn T, Grant GE, Swanson FJ, Ice GG(eds). Publication 165. International Association of HydrologicalSciences: Paris; 39–48.

Reneau SL, Deitrich WE, Donahue DJ, Jull AJT, Rubin M. 1990. LateQuaternary history of colluvial deposition and erosion in hollows,central California Coast Ranges. Geological Society of AmericaBulletin 102: 969–982.

Shlemon RJ, Wright RH, Montgomery DR. 1987. Anatomy of a debrisflow, Pacifica, California. In Debris Flows/Avalanches: Process,Recognition and Mitigation, Costa JE, Wieczorek GF (eds). Reviewsin Engineering Geology 7. Geological Society of America:Boulder, CO; 181–199.

Smith GW, Howell DG, Ingersoll RV. 1979. Late Cretaceous trench-slope basins of central California. Geology 7: 303–306.

Taylor PD, Wilson MA. 2003. Palaeoecology and evolution of marinehard substrate communities. Earth Science Reviews 62: 1–103.

USDA Soil Conservation Service. 1979. Soil Survey of San Luis ObispoCounty. Coastal Part. Map Sheet #4. USDA: Washington, DC.

United States Geological Survey. 1979. Cambria Quadrangle, Califor-nia–San Luis Obispo County 7.5 minute, 1:24 000 topographic mapseries. USGS. Denver, Colorado.

Veeh HH, Valentine JW. 1967. Radiometric ages of Pleistocene fossilsfrom Cayucos, California.Geological Society of America Bulletin 78:547–549.

Weber GE. 1983. Geologic investigation of the marine terraces of theSan Simeon region and Pleistocene activity of the San Simeon Fault



Zone, San Luis Obispo County, California. Technical Report, Con-tract No. 14-08-001-18230.USGS. Denver, Colorado.

Wehmiller JF. 1992. Aminostratigraphy of southern California Qua-ternary marine terraces. In Quaternary Coasts of the United States:Marine and Lacustrine Systems, Fletcher CH, Wehmiller JF (eds).Special Publication 48. SEPM: Tulsa, Oklahoma; 317–321.


Wells SG, Harvey AM. 1987. Sedimentologic and geomorphicvariations in storm-generated alluvial fans, Howgill Fells, northwestEngland. Geological Society of America Bulletin 98: 182–198.

Wright VP, Allen JRL. 1989. Palaeosols in silici-clastic sequences. PRISShort Course Notes. Reading University, Reading, UK.


Late Quaternary landscape development along the Rancho Marino coastal range front (south-central...

Documents

Transcript of Late Quaternary landscape development along the Rancho Marino coastal range front (south-central...