16-2 Foraminiferal Assemblages and Diversity of the Calvert Formation at Sandtown, Delaware

Session: From Thin Section to Outcrop: Exploration of Undergraduate Research (Posters)

Presenting Author:

Authors:

Abstract:

Foraminiferal species shift as marine environment changes, reflecting past behaviors and acting as paleoceanographic proxies. This study aims to identify and analyze the diversity patterns of foraminiferal assemblages within the Calvert Formation at Sandtown, Delaware. A section of the lower and middle Calvert retrieved from a borehole at Sandtown reveals mostly shelly, fine to medium sand with two thin breaks of shelly silt, underlain by dark brown, bioturbated micaceous silt with fewer shells at the basal Miocene. The Calvert Formation, deposited during the Miocene Climatic Optimum (17–14.8 Ma) and the Middle Miocene Climate Transition (14.8–13.8 Ma), is well studied at the Calvert Cliffs in Maryland and Pollack Farm Fossil Site in Delaware. Prior studies of the Calvert in Delaware indicate early to middle Miocene ages from about 21 to 15.8 Ma using Strontium age dating and nannofossil, radiolarian, foraminiferal, and dinoflagellate biostratigraphy. The Stichocorys wolffii Zone characterizes the late early Miocene (estimated at 17.3 to 19.2 Ma) and is consistent with both marine and terrestrial fossils to form a global biostratigraphic zone at Pollack Farm. Assessing and integrating foraminiferal data from Sandtown, Delaware will provide greater detail of a regional site that can be integrated into the larger geographic picture, expanding on previous studies.

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.