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Peterson, C.D.; Stock, E.; Meyer, J.; Kaijankoski, P., and Price, D.M., 2015. Origins of Quaternary coastal dune sheets in San Francisco and Monterey Bay, central California coast, U.S.A.: Reflecting contrasts in shelf depocenters and coastal neotectonics. The San Francisco and Monterey Bay coastal dune sheets derive from similar origins in the central California coast but differ substantially in size (respectively, ~400 and ~900 km2) and age (respectively, <0.1 and >1.0 Ma). The San Francisco dune sheet is restricted to a short alongshore interval (<20 km) within a relatively straight coastline (150 km in length) that borders a broad shelf (~40 km in width). The Monterey Bay dune sheet is restricted to the Monterey Bay embayment (41 km alongshore length). The embayment includes a very narrow shelf (3-15 km in width), which is dissected by the Monterey Submarine Canyon. Generally low onshore topographic relief (<150 m elevation) likely enhanced inland transgression of Late Pleistocene dune fields in both the San Francisco and Monterey Bay areas. The locations of the dune sheets are directly related to sand accumulations in marine low-stand depocenters that supplied sand to the adjacent dune fields by eolian transport across the emerged inner shelves. The San Francisco shelf depocenter is apparently localized at a midshelf bight (−50 to −100 m elevation) that extends 25 km (east-west) offshore of a paleoriver mouth of a major river system, the Sacramento-San Joaquin River. The Monterey Bay shelf depocenter is bounded alongshore by major headlands and converging paleoshorelines (−30 to −90 m elevation) that effectively trapped littoral sand from small coastal drainages, primarily the Salinas River. High vertical rates of neotectonic deformation in the San Francisco dune sheet (0.4-1.0 mm y−1) limited dune sheet longevity and deposit thickness (5-35 m). Low uplift rates (~0.1 mm y−1) in the central Monterey Bay dune sheet permitted deposit accumulations of up to 250 m thickness. The differences in dune sheet extent, thickness, and age resulted from key differences in localized shelf accommodation space and coastal neotectonic vertical movements. [ABSTRACT FROM AUTHOR]

The identification and correlation of a sequence of Pleistocene beach barriers located within the northern Coorong Coastal Plain, South Australia, is made difficult by long-term subsidence and extensive reworking. Associated shell beds, to all but the last interglacial barrier, are subsurface and not readily accessible. The whole-rock amino acid racemization method was found to be unsuitable for distinguishing age differences of the individual barriers due to the low calcium carbonate content of the sediments, concerns for the leaching or contamination as a result of the comminuted nature of the shelly component, and the potentially high content of reworked sediment. These difficulties prompted an investigation into the applicability of AAR analysis of single foraminifera tests to ascertain whether the relative age of beach barriers could be determined and whether sediment contribution from antecedent barriers could be identified. Foraminifera tests of multiple genera (including Cibicides corticatus and Rosalina bradyi) from numerous modern depositional environments were analyzed to establish aminozones of aspartic acid and glutamic acid D/L values representative of modern/Holocene foraminifera and to assess natural variability of Holocene D/L values between depositional settings. Tests of Lamellodiscorbis dimidiatus , common in the Pleistocene barriers, were analyzed from MIS 5 and MIS 7 sediments and aminozones identified, allowing correlation of non-contiguous barrier features and the identification of reworked foraminifera. Rejection criteria removed, on average, between 25 and 30% of analytical results. The Holocene aminozone for every genus analyzed falls within the same general constraint: D/L values less than 0.40 for aspartic acid and less than 0.20 for glutamic acid. The D/L values of approximately 15% of foraminifera from the modern sediments exceed the Holocene aminozone constraint and the tests are considered reworked. The range of D/L values representative of each interglacial aminozone decreases with age, reflecting the slowing rate of amino acid racemization with time. Pleistocene sediments are found to have a higher percentage of reworked tests. Thermoluminescence dating of the Pleistocene successions was used to evaluate the AAR results. This work illustrates that foraminifera tests are surprisingly robust and can survive potentially multiple phases of deposition and reworking. • AAR analysis of single foraminifer can be used to determine relative age and correlate landscape features. • Robust, reworked foraminifera tests can assist in understanding spatio-temporal patterns of erosion and redeposition. • Previously unanalyzed Cibicides corticatus and Rosalina bradyi tests are shown to be useful in geochronological applications. [ABSTRACT FROM AUTHOR]