Document: MAT-3-41-12

Quantitative analyses of late Cretaceous benthic marine communities: Spatial and temporal variation.

KOSNIK, M.*

University of Chicago, Chicago, IL 60637, USA ¹

Abstract:
Work extending back decades by Sohl and Koch produced taxonomically standardized and tightly age-correlated samples of marine molluscs from the Maastrichtian (Haustator bilira zone, 67-65 Ma) of the Atlantic and Gulf Coastal Plain, USA. Pursuing a question first by posed by C. Koch, I reanalyzed this dataset using both taxonomic and eco-morphological classifications to characterize variation in mollusc diversity and abundance among assemblages and lithologies. My question was simple: Given the variation among samples collected within narrowly defined areas, could I detect statistically significant variation in species richness and composition within the much larger area stretching from Texas to New Jersey? Sampling intensity was standardized using rarefaction and multiple units of sampling (i.e., equivalent number of occurrences, samples, and/or specimens) were contrasted. All pairwise comparisons among areas were conducted and tested against bootstrapped resampling distributions of appropriate combined area samples. Substantial and significant variation from area to area was documented. Using spatial variation in the H. bilira zone as a guide, temporal trends in Late Cretaceous benthic marine communities are examined by comparing other Late Cretaceous faunas to the Sohl and Koch dataset. Comparing changes in taxonomic composition with changes in eco-morphological composition suggests that eco-morphological composition is relatively stable despite changes in taxon composition.

Keywords: Cretaceous, Atlantic and Gulf Coastal Plain, Paleoecology, eco-morphological groups, rarefaction, spatial and temporal variation

This abstract is being presented at: 1:15 PM in session:
Oral Session #32: Paleoecology.