T237 Insights from Microfossils and Their Modern Analogs: From Traditional and Emerging Approaches, to Critical Re-Evaluations (Posters)

Wednesday, 18 October 2023
8:00 AM - 5:30 PM
Hall B

COMPARISON OF CALCAREOUS NANNOFOSSIL ASSEMBLAGES, BIOSTRATIGRAPHY AND GEOCHEMISTRY ACROSS THE PETM FROM THREE CORES IN THE SOUTHERN SALISBURY EMBAYMENT OF MARYLAND AND VIRGINIA, USA

Paper number: T237-3
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

The Paleocene/Eocene Thermal Maximum (PETM) was a global event that occurred ~56 Ma and was characterized by an initial short negative carbon-isotope excursion (<10,000 years duration) and high global temperatures. Previous studies of cored material in the Salisbury Embayment (US mid-Atlantic Coastal Plain) have documented this event in the upper Paleocene and lower Eocene sediments. Spatial variation in micropaleontological data of these sediments is important for understanding the regional environmental change and biotic response to PETM forcings on the shelf, but those data have previously been limited to cores from New Jersey and Maryland. Here we present lithology, calcareous nannofossil biostratigraphy and geochemistry of the Surprise Hill core, which was drilled by the Virginia Department of Environmental Quality in Northumberland County, Virginia, USA. The Paleocene-Eocene sequence in this core comprises three depositional units in ascending order: the Aquia Formation (~20 ft thick, glauconite-rich sand), the Marlboro Clay (~45 ft thick, light gray massive clay), and the Nanjemoy Formation (~80 ft thick, glauconite-rich sand). All units also include calcareous nannofossils and foraminifera. We compared calcareous nannofossil datums to those reported in the South Dover Bridge and Howards Tract cores from Maryland, including the first occurrence (FO) of Discoaster multiradiatus (56.01 Ma) in the upper Aquia Formation, the FO of Discoaster salisburgensis var. anartios and FO of Rhomboaster spp. (54.99 Ma) in the lower Marlboro Clay, and the FO of Tribrachiatus orthostylus (53.67 Ma), FO of Discoaster lodoensis (52.64 Ma), last occurrence (LO) of T. orthostylus (50.66 Ma), FO of Discoaster sublodoensis with five rays (48.96 Ma) and LO of D. lodoensis (48.37 Ma) in the Nanjemoy Formation. A dissolution zone (2.8 ft thick) is recorded in the basal Marlboro Clay, consistent with global patterns of dissolution in response to rapid injection of carbon into surficial Earth systems at the PETM onset. Correlation between the geochemistry and calcareous nannofossil assemblages of the Surprise Hill, Howards Tract and South Dover Bridge cores allows for a greater understanding of the paleoenvironmental differences that existed in the Salisbury Embayment during the PETM and through the early Eocene.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-391171

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