100-2 Ediacaran-Cambrian boundary of North Carolina: New U-Pb constraints for faunal turnover

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The latest Ediacaran period represents a critical geobiological transition with the emergence of the first macroscopic eukaryotic life, the Ediacaran fauna, and their abrupt disappearance before the Cambrian “explosion”. The Ediacaran-Cambrian (E-C) boundary outcrops in two main regions within the United States; the Great Basin region (NV, CA) and the Southeastern region (NC, SC). While the E-C boundary in the Great Basin is widely studied, the boundary in the Southeast has received less attention. Nevertheless, it may offer important insight into the timing of Ediacaran-Cambrian faunal change. 

The Carolina terrane includes sedimentary and volcanic rock that spans the Ediacaran. Within NC, the youngest stratigraphic succession is known as the Albemarle Group. It comprises four main stratigraphic units from oldest to youngest, the Uwharrie, Cid, Floyd Church, and Yadkin Formations. Ediacaran fossils (Pteridinium, Swartpuntia, and Aspidella) have been identified from both the Cid and Floyd Church Formation. Previous age constraints (~540 Ma) from the Flat Swamp volcanic member of the upper Cid Formation place the E-C boundary within the uppermost Cid or lower Floyd Church Formations, indicating the presence of Ediacaran organisms close to the boundary. To improve correlation of these fossils with the rest of the global geologic timescale and to better identify the stratigraphic position of the E-C boundary within the Albemarle Sequence, we are constructing a new age model using U-Pb CA-ID-TIMS dates from interbedded volcanic units. Here we present initial geochronologic data from these efforts.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9525

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