174-5 Pick your poison: environmental change and paleoecology in the Late Cretaceous WIS

Session: Environmental Instability During Greenhouse Periods: Impact on Terrestrial and Marine Ecosystems

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The Late Cretaceous Western Interior Seaway (WIS) and Gulf Coastal Plain (GCP) of North America offer an excellent record of marine invertebrate responses to Greenhouse environmental changes across taxonomic, temporal, and geographic scales. Three styles of environmental change during this interval forced paleoecological and ultimately macroevolutionary responses from WIS/GCP fauna: the excess warmth of the Cenomanian-Turonian boundary global anoxic event (OAE2), cooling and regression of the late Campanian-Maastrichtian, and the rapid and extreme end-Cretaceous (KPg) mass extinction.  Molluscan records are abundant and well-studied in this context and provide evidence of paleoecological response to these different potential “poisons” (warmth/anoxia, cooling/sea level change, volcanism/asteroid impact) in the form of changes in the size and geographic structure of taxonomic and functional diversity as well as by changes in macroecological traits like abiotic niches. Investigations have uncovered some expected patterns – such as change in functional diversity lagging taxonomic diversity, and stability in abiotic niche dimensions across many potentially poisonous environmental changes. However, some patterns are less obvious – such as the lack of extinction resistance that larger abiotic niche tolerances seem to provide under other poisons. Connecting this work to coeval global patterns of diversity and biogeography highlights the importance of geographic and temporal scales in interpreting the paleoecological fallout of these environmental changes. That said, real difficulties remain in robust testing of Earth-life interactions in deep time, especially when tied to niche dynamics. A particular challenge is linking the scale of paleoecological tests to the scale of existing data when, for example, delineation of generic-level niches is most feasible, but may not well-characterize species-level niches when adequate data exists for comparison. This has lasting consequences in identifying how potentially poisonous environmental changes affect species’ survivorship and interesting macroecological patterns like phylogenetic niche conservation in fossil clades.

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

doi: 10.1130/abs/2025AM-10857

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