Bureau of Economic Geology


Detrital mixing on broad continental shelves: U-Pb and Lu-Hf detrital zircon provenance of the Pleistocene-Holocene Bering Sea and its margins

March 12, 2021 9:00 AM

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Presenter

Dr. Matthew Malkowski
Acting Assistant Professor
Department of Geological Sciences
Stanford University

Abstract

Continental shelves occupy a critical region of siliciclastic source-to-sink systems as they control the transfer of terrestrially derived material to the deep-sea. The degree to which sediment is sequestered, mixed, and homogenized during transfer across continental shelves has important implications for interpreting tectonic and climatic terrestrial signals from deep-sea detrital records. This investigation uses the vast Bering Sea shelf to examine the degree of mixing across a broad shelf, and to test the hypothesis that sea-level lowstands yield more efficient and direct sediment transfer from riverine sources to the deep Aleutian Basin compared to highstands, when sediment is sequestered and mixed on the shelf. A comparison of Holocene and surficial sediment with Pleistocene deposits suggests that detrital provenance signatures (detrital zircon U-Pb ages and Lu-Hf compositions) in deep-marine deposits outward of broad transfer zones may remain well-mixed regardless of sea level. However, if riverine sources are sufficiently distinct, well-mixed shelfal and deep-water deposits can be quantitatively ‘un-mixed’ to reliably characterize sediment sources.

Matthew Malkowski

University of Texas at Austin

University of Texas

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