Early to Middle Holocene Coastal Dune and Estuarine Deposition, Santa Maria Valley, California

Knott, Jeffrey R.; Eley, Donald S.

doi:10.2747/0272-3646.27.2.127

Cited by 12 publications

(17 citation statements)

References 20 publications

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“…Paleo-dune sand supply in the Santa Maria dune sheet has been 14 C dated to latest-Pleistocene time (~29-23 ka) (Orme, 1992) and to latest-Holocene time (< 3.5 ka) (Knott and Eley, 2006). The Pleistocene migratory dune deposits at the south end of the Santa Maria dune sheet were reportedly related to marine sand sources, though interpretations of specific sand supply origins differ from 1) supply during marine regression and river valley incision to 2) supply during glacial marine low-stands (Orme, 1992).…”

Section: Late-quaternary Sand Depositsmentioning

confidence: 99%

“…Standard penetration test (SPT) values or blow counts per 15 cm drive intervals, ASTM Standard Guide D5434-12 (ASTM, 2017), from reported borehole records, are used to supplement the pocket penetrometer data in extended (deeper) geotechnical borehole sections. V3 3859210 719340 45 S2 3889980 715820 10 V4 3857700 720800 85 S3 3888930 718119 30 V5 3857700 721800 70 S4 3888400 717620 20 V6 385700 722900 110 S5 3887280 719180 25 V7 3854780 721430 60 S6 3887180 718590 20 V8 3853980 724040 120 S7 3886960 720850 50 V9 3853700 720830 65 S8 3885590 717150 15 V10 3853600 724320 Knott and Eley (2006). Site OR is combined from Orme (1992) Mussel Rock gully sites B and E. Section site coordinates are in UTM meters (rounded to the nearest 10 m).…”

Section: Mapping the Migratory Paleo-dune Depositsmentioning

confidence: 99%

“…Minor amounts of direct river sand supply to the southern beaches, however, likely occurred in latest-Holocene time. Though not observed in the beach sand mineralogy, some through-put of Santa Maria River and Santa Ynez River sand to the adjacent beaches is inferred from 1) late-Holocene aggradation of the lower river valley fills (Knott and Eley, 2006) and 2) river mouth breaching of beach berms during infrequent events of river flooding (Inman and Jenkins, 1999;Stillwater Sciences and Kear Groundwater, 2012). Sand source indicators, including light-mineral lithic fragment abundance (%) and heavy mineral rounding (angular=1 to well-rounded=5), of sand grains in the mL to fU (175-350 µm) size range in river, beach, and representative paleo-dune samples.…”

Section: Sources Of Modern Beach and Paleo-dune Sandmentioning

confidence: 99%

“…Over-steepened eolian sand ramps extend from the modern beach to bluff tops, reaching 150-160 m elevation at sites S35 and S38 between Mussel Rock and Point Sal, at the southern end of the Santa Maria dune sheet. Morphostratigraphic sites (S) (this article) and selected subsurface section sites, including OR (Orme, 1992) and TM and F5 (Knott and Eley, 2006) are shown in the Santa Maria dune sheet. Near surface deposits are designated Holocene dune (black square) and Pleistocene dune (black circle), Pleistocene beach platform (black rectangle) and Pleistocene alluvium (black inverted triangle).…”

Section: Extent and Thickness Of Migratory Paleo-dune Deposits In Thementioning

confidence: 99%

“…At smaller spatial scales, the landward extents of the Santa Maria and Vandenberg dune sheets are influenced by local topographic features. For example, the Santa Maria dune sheet is split into the north and south sides of the wide Santa Maria River Valley (Figure 2), which was deeply incised to at least 30 m depth (-30 m elevation MSL) during the last marine low-stand, and then back-filled by alluvial deposits during the Holocene marine transgression (11-0 ka) (Knott and Eley, 2006).…”

mentioning

confidence: 99%

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Origins of The Santa Maria And Vandenberg Coastal Dune Sheets (~100-0 ka) Under Changing Sea Levels, Shoreline Orientations and Wave Directions: Long-Term Records of Coastal Sand Supply in South-Central California, USA

Peterson¹,

Ryan²,

Meyer³

et al. 2017

JGG

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Two large coastal dune sheets, including the Santa Maria dune sheet and Vandenberg dune sheet, have been analyzed for late-Quaternary distributions, ages and volumes of dune sand deposition. Six new thermoluminescence (TL) ages establish the age range of dune sand deposition from >106±21 ka to <4.1 ka in the study area. Seven late-Pleistocene TL and 14 C dated mid-depth samples (≤30 m depth subsurface), yield a mean of 33 ka for the late-Pleistocene dune deposits. Both TL and 14 C dated Holocene dune deposits establish a transition from weathered middle-Holocene dune deposits to unweathered latest-Holocene dune deposits after 4 ka. Marine sand supply to the large dune sheets occurred by 1) cross-shelf eolian transport during late-Pleistocene marine low-stands (70-13 ka), 2) shoreward wave transport during slowing of the Holocene marine transgression (9-5 ka), and 3) longshore littoral transport during the latest-Holocene marine high-sand (3.5-0 ka). Measured and dated dune deposit sections (n=66, ranging from 2 to 60 m depth) demonstrate substantial differences in preserved sand volumes between the two adjacent dune sheets, Santa Maria (~ 2,300x10 ). Asymmetric distributions of dune deposit volumes between and within the dune sheets show that long-term sand supply was locally controlled by paleo-shoreline orientations relative to corresponding deep-water wave propagation directions (260-290° TN) from the North Pacific Low Pressure Area. Recently declining sand supplies and/or -trapping efficiencies in the dune sheet littoral subcells led to ongoing shoreline retreat (≥ 200 m) and under-cutting of late-Holocene eolian sand ramps at the south ends of the Santa Maria and Vandenberg dune sheets. The termination of transgressive cross-shelf sand supply and locally variable longshore retention of littoral sand confirm previously reported framework models of regional coastal sand supply. Such models help to identify shorelines that are most susceptible to future beach erosion from predicted sea level rise following ongoing global warming.

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Section: Late-quaternary Sand Depositsmentioning

confidence: 99%

Section: Mapping the Migratory Paleo-dune Depositsmentioning

confidence: 99%

Section: Sources Of Modern Beach and Paleo-dune Sandmentioning

confidence: 99%

Section: Extent and Thickness Of Migratory Paleo-dune Deposits In Thementioning

confidence: 99%

mentioning

confidence: 99%

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Origins of The Santa Maria And Vandenberg Coastal Dune Sheets (~100-0 ka) Under Changing Sea Levels, Shoreline Orientations and Wave Directions: Long-Term Records of Coastal Sand Supply in South-Central California, USA

Peterson¹,

Ryan²,

Meyer³

et al. 2017

JGG

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Origins of late- Pleistocene coastal dune sheets, Magdalena and Guerrero Negro, from continental shelf low-stand supply (70–20 ka), under conditions of southeast littoral- and eolian-sand transport, in Baja California Sur, Mexico

et al. 2017

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Shallow morpho-stratigraphic sections (n = 11) in each of two large coastal dune sheets including the Magdalena (7000 km 2) and Guerrero Negro (8000 km 2) dune sheets, from the Pacific Ocean side of Baja California Sur, Mexico, have been analyzed for dune deposit age. The shallow morphostratigraphic sections ($2-10 m depth) include 11 new TL and 14C ages, and paleosol chronosequences, that differentiate cemented late Pleistocene dune deposits (20.7 ± 2.1 to 99.8 ± 9.4 ka) from uncemented Holocene dune deposits (0.7 ± 0.05 to at least 3.2 ± 0.3 ka). Large linear dune ridges (5-10 m in height) in the dune sheet interiors trend southeast and are generally of late Pleistocene age ($70-20 ka). The late Pleistocene dune deposits reflect eolian transport of marine sand across the emerged continental shelf (30-50 km southeast distance) from low-stand paleo-shorelines (À100 ± 25 m elevation), which were locally oriented nearly orthogonal to modeled deep-water wave directions ($300°TN). During the Holocene marine transgression, onshore and alongshore wave transport delivered remobilized shelfsand deposits to the nearshore areas of the large dune sheets, building extensive barrier islands and sand spits. Submerged back-barrier lagoons generally precluded marine sand supply to dune sheet interiors in middle to late Holocene time, though exceptions occur along some ocean and lagoon shorelines. Reactivation of the late Pleistocene dune deposits in the dune sheet interiors lead to generally thin (1-3 m thickness), but widespread, covers of Holocene dune deposits (0.41 ± 0.05 to 10.5 ± 1.6 ka). Mechanical drilling will be required to penetrate indurated subsoil caliche layers to reach basal Pleistocene dune deposits.

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Holocene coastal dune fields used as indicators of net littoral transport: West Coast, USA

et al. 2010

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Early to Middle Holocene Coastal Dune and Estuarine Deposition, Santa Maria Valley, California

Cited by 12 publications

References 20 publications

Origins of The Santa Maria And Vandenberg Coastal Dune Sheets (~100-0 ka) Under Changing Sea Levels, Shoreline Orientations and Wave Directions: Long-Term Records of Coastal Sand Supply in South-Central California, USA

Origins of The Santa Maria And Vandenberg Coastal Dune Sheets (~100-0 ka) Under Changing Sea Levels, Shoreline Orientations and Wave Directions: Long-Term Records of Coastal Sand Supply in South-Central California, USA

Origins of late- Pleistocene coastal dune sheets, Magdalena and Guerrero Negro, from continental shelf low-stand supply (70–20 ka), under conditions of southeast littoral- and eolian-sand transport, in Baja California Sur, Mexico

Holocene coastal dune fields used as indicators of net littoral transport: West Coast, USA

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