108 The Cretaceous-Paleogene (K-Pg) Boundary Interval: From Large-Scale Geological Events to Mass Extinction Mechanisms (Posters)

The Cretaceous-Paleogene boundary interval witnessed extreme geological events: the Chicxulub impact and Deccan Traps volcanism, and a biological catastrophe. New proxy-records, coupled with numerical modelling, unravel the mechanisms driving the environmental change and mass extinction.

Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Two Stages of Macroinvertebrate Recovery from the End-Cretaceous Mass Extinction at Brazos, TX U.S. Gulf Coastal Plain.

Paper number: 108-1
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Useful information on how ecosystems respond to rapid environmental changes can be better understood by analyzing the marine invertebrate fossil record. The end-Cretaceous mass extinction event (66 Mya) is the most recent such extreme taxonomic and ecological event to affect the modern fauna inhabiting marine shelf ecosystems. Studies of shallow marine ecosystems across the globe have shown variable effects on functional ecology and diversity in the extinction aftermath, demonstrating the need for high-resolution, multi-proxy, regional studies. Previous research on Cretaceous-Paleogene boundary (KPB) marine invertebrate fossil record preserved throughout the U.S. Gulf Coastal Plain, specifically along the Brazos River in Texas, documented an increase in deposit feeders and carnivores in the post extinction assemblages followed by a return of suspension feeders within ~100 kyr. 

The fossiliferous sections from the Brazos River, TX record late Maastrichtian (last 140 kyr of the Cretaceous) Corsicana Formation mudstones, overlain by a series of event deposits with evidence of impact-related features such as spherules and iridium concentrations and physical structures including large rip-ups clasts and hummocky cross stratified sandstones interpreted as evidence for post-impact debris flows and tsunamis. Danian mudstones and siltstones of the Kincaid Formation record the earliest Paleogene (P0 to P1a foraminifera zones). Bulk samples, to control for specimen abundance, were collected at 0.25m to 0.5m intervals from 1 meter of the Corsicana Fm. and 4 meters of the Kincaid Fm. To enhance previous interpretations of the functional diversity shifts observed at Brazos we characterized species richness, diversity, abundance, functional ecology, body size, preservation style, and estimated metabolic energy of the benthic marine invertebrate assemblages across the KPB. Preliminary results find both detritivores and suspension feeders in the early Danian, potentially a survival strategy for low primary productivity input, followed by deposits dominated by suspension feeding oysters within the P1a zone, interpreted as sufficient primary production recovery within ~100kyr of the KPB. Comparisons with other KPB U.S. Gulf Coast Plain sites will ultimately be made to enhance understanding of regional patterns in the diversity, functional ecology, and body size recovery of marine invertebrate macrofauna assemblages.

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

doi: 10.1130/abs/2025AM-413107

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