16 Paleontology of North America
Added from Discipline submissions.
Monday, 9 March 2026
1:30 PM - 4:30 PM
RCC, 106
Faunal Turnovers and Community Stasis of Ostracod Communities in the Upper Cretaceous of the Northern Gulf Coastal Plain
Paper number: 16-2
Program: Technical Sessions
Time: 2:00 PM – 2:15 PM
Authors
Abstract
Information from 353 samples, 108 sections and 268 species of ostracods and planktonic foraminifera from the northern Gulf Coastal Plain of Tennessee-Mississippi-Alabama was analyzed using the heuristic Constrained Optimization (CONOP) algorithm. This analysis produced an ordinal scale of 544 events spanning the Santonian-Maastrichtian, a ~20-million-year interval that averages one event per 36,764 years. Extracting ostracod first and last occurrences from the composite sequence enables reconstruction of species richness through time and reveals several pronounced diversity trends.
During the Santonian, as sea level encroached on eastern Alabama, ostracod species richness was low (approximately 10 species) and associated with lagoonal environments. Near the Santonian-Campanian boundary, regional flooding introduced many new species, increasing to about 55 species. Subsequently, species origination and extinction rates were low, resulting in a relatively constant diversity and remarkably stable community through the lower Campanian. A pronounced spike in diversity, reaching up to 72 species, occurred not far below the Arcola Limestone that was followed by a spike in extinctions above the Arcola. This spike and collapse pair defines the Lower Campanian Turnover.
Origination and extinction rates then remained low to near the mfs of the overlying sequence in the middle Campanian, indicating another interval of community stability. This stability was followed by a second pair of spikes in origination and extinction rates that define the Upper Campanian Turnover. From the late Campanian onward, diversity remained relatively steady until the end-Cretaceous mass extinction that eliminated all remaining Cretaceous species.
Geological Society of America Abstracts with Programs. Vol. 58, No. 1
doi: 10.1130/abs/2026SE-411714
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