57 Drill, Drill, Drill! A Tribute to USGS Drillers Eugene "Big Gene" Cobbs, Eugene "Little Gene" Cobbs, III, and Jeff Grey, and Their Contributions to Geologic Research East of the Mississippi River (Posters)

Sunday, 22 March 2020
8:00 AM - 12:00 PM
Grand Ballroom A–D

NORTH CAROLINA SHELF SHOWS EVIDENCE OF INCREASED TERRIGENOUS FLUX DURING THE CENOMANIAN-TURONIAN OCEANIC ANOXIC EVENT 2

Paper number: 57-3
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Decades of warming oceans and increased terrigenous nutrient flux are causing a decline in dissolved oxygen in the world’s marine ecosystems, particularly on continental margins. To better understand the oceanographic processes that promote the development of anoxia on the shelf, it is necessary to look to the past. One of the best examples of widespread oceanic anoxia driven by eutrophication is the mid-Cretaceous Oceanic Anoxic Event 2 (OAE2), which spans the Cenomanian-Turonian boundary. Although numerous records exist of extensive mid Cretaceous black shales in the abyssal North Atlantic, equivalent records on the shelf are rare. Presently, the only published OAE2 record for the North Atlantic Coastal Plain is from the Bass River Core in New Jersey. Shelf sediments along the northwestern Gulf of Mexico record maximum carbon burial either before or after OAE2, driven primarily by local changes in sea level. It is unclear if these trends are limited to the Gulf Coastal Plain or if sea level change drove organic carbon burial on the North Atlantic shelf as well. Here, we present the carbon isotope and organic carbon data from the Clubhouse Formation of the North Carolina Coastal Plain recovered from the Hope Plantation (BE-110) and Smith Elementary School (CR-675) cores drilled by the U.S. Geological Survey in the 2000s. The Clubhouse Formation consists of glauconite-rich clayey, silty sand deposited in an inner neritic or estuarine environment and most likely represents one transgressive-regressive cycle with parasequences representing higher-order sea-level changes. Our preliminary work shows that the lower part of the study interval is in late Cenomanian calcareous nannofossil Zone CC10a, whereas the upper part is in early Turonian Zone CC10b. Foraminifera are not preserved in either core. A clear carbon isotope excursion marks OAE2 in both cores, and C/N ratios show an increased flux of terrestrial organic matter during the event, corroborating similar results from the Bass River core. OAE2 is essentially unstudied on the US Coastal Plain between New Jersey and Mississippi, and this new work fills an important gap in our understanding of how the western Atlantic margin responded to this important event.

Geological Society of America Abstracts with Programs. Vol. 52, No. 2

doi: 10.1130/abs/2020SE-344883

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