Publication Date:
2022-05-27
Description:
© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wehmiller, J. F., Brothers, L. L., Ramsey, K. W., Foster, D. S., Mattheus, C. R., Hein, C. J., & Shawler, J. L. Molluscan aminostratigraphy of the US Mid-Atlantic Quaternary coastal system: implications for onshore-offshore correlation, paleochannel and barrier island evolution, and local late Quaternary sea-level history. Quaternary Geochronology, 66, (2021): 101177, https://doi.org/10.1016/j.quageo.2021.101177.
Description:
The Quaternary record of the US Mid-Atlantic coastal system includes onshore emergent late Pleistocene shoreline deposits, offshore inner shelf and barrier island units, and paleovalleys formed during multiple glacial stage sea-level lowstands. The geochronology of this coastal system is based on uranium series, radiocarbon, amino acid racemization (AAR), and optically stimulated luminescence (OSL) methods. We report over 600 mollusk AAR results from 93 sites between northeastern North Carolina and the central New Jersey shelf, representing samples from both onshore cores or outcrops, sub-barrier and offshore cores, and transported shells from barrier island beaches. AAR age estimates are constrained by paired 14C analyses on specific shells and associated U-series coral ages from onshore sites. AAR data from offshore cores are interpreted in the context of detailed seismic stratigraphy. The distribution of Pleistocene-age shells on the island beaches is linked to the distribution of inner shelf or sub-barrier source units. Age mixing over a range of time-scales (~1 ka to ~100 ka) is identified by AAR results from onshore, beach, and shelf collections, often contributing insights into the processes forming individual barrier islands. The regional aminostratigraphic framework identifies a widespread late Pleistocene (Marine Isotope Stage 5) aminozone, with isolated records of middle and early Pleistocene deposition. AAR results provide age estimates for the timing of formation of the three major paleochannels that underlie the Delmarva Peninsula: Persimmon Point paleochannel ≥800 ka; Exmore paleochannel ~400–500 ka (MIS 12); and Eastville paleochannel 〉 125 ka (MIS 6). The results demonstrate the value of synthesizing abundant AAR chronologic data across various coastal environments, integrating multiple distinct geologic studies. The ages and elevations of the Quaternary units are important for current hypotheses about relative sea-level history and crustal dynamics in the region, which was likely influenced by the Laurentide ice sheet, the margin just ~400 km to the north.
Description:
This project was funded through a cooperative agreement with the Bureau of Ocean Energy Management of the U.S. Department of the Interior, Offshore Sand Resources for Coastal Resilience and Restoration Planning: M14AC00003 and M16AC00001. We thank J. Waldner (BOEM) for support and encouragement during this project. We also thank S. Howard and K. Luciano, South Carolina Geological Survey, and numerous colleagues in both the Mid-Atlantic and Southeast Atlantic BOEM ASAP projects, active from 2015 through 2019. This paper is contribution #3999 of the Virginia Institute of Marine Science, William & Mary. Partial support was also provided to Hein by the Mid-Atlantic Sea Grant program (NOAA) award numbers R/71856G and R/71856H and a Virginia Sea Grant (NOAA) Fellowship award NA18OAR4170083 supported Shawler. JFW acknowledges support from the University of Delaware Retired Faculty Research Program.
Keywords:
Quaternary sea-level
;
Delmarva peninsula
;
US Mid-Atlantic shelf
;
Paleovalley
;
Amino acid racemization
;
Geochronology
;
Age-mixing
;
Seismic stratigraphy
;
Mollusks
Repository Name:
Woods Hole Open Access Server
Type:
Article
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