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

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
1:30 PM - 5:30 PM
HBGCC, 304A

The Hell Creek Project: Tracking the Mass Extinction and Biotic Recovery across the K/Pg boundary in eastern Montana, USA

Paper number: 138-1
Program: Technical Sessions
Time: 1:35 PM – 1:55 PM

Authors

Abstract

The geological and paleontological data from the latest Cretaceous and earliest Paleocene are critical for analyzing the Cretaceous-Paleogene (K/Pg) mass extinction, biotic recovery, and related evolutionary and ecological radiations (e.g., mammals, birds, angiosperms). The non-marine sedimentary sequences in western North America from western Canada to southern USA presently provide the best fossil record for investigating these patterns and processes. However, few areas (i) preserve localities in composite or direct superposition, (ii) adequately sample the latest Cretaceous and earliest Paleocene, and (iii) provide accurate placement of the K/Pg boundary as well as an encompassing temporal framework. 

The Hell Creek study area of eastern Montana and regionally within the Williston Basin is an exception. It preserves fossil localities in composite stratigraphic superposition from three North American land mammal “ages” (Lancian, Puercan to the early Torrejonian To1 interval zone) as well as multiple indications of the K/Pg impact event in local sections. A large amount of data has been compiled from the ~3-million-year window represented by these strata, providing a local fossil database and chronostratigraphic framework that has been used in studies of the K/Pg mass extinction and recovery and the ensuing early Paleocene radiations. Since 1972, a multidisciplinary team of researchers has intensively collected and analyzed paleontological and geological data from the Hell Creek area and honed our view of this critical temporal interval to ecologically relevant time scales. Most recently, we have targeted key gaps in fossil sampling, chronostratigraphy, and geological context of the study system to facilitate effective application of novel approaches (e.g., food web modeling) and more rigorously test hypotheses of the K/Pg mass extinction and recovery and the evolutionary and ecological radiations in the Paleocene. Results show that minor biotic changes occurred in the hundreds of thousands of years before the K/Pg, whereas major biotic changes occurred at the K/Pg with the magnitude and selectivity of the extinctions having varied widely across taxa as did the rate of recovery. Current and future research aims to (i) expand the temporal scope by sampling older and younger biotas, (ii) better document and correlate vegetation and paleoclimate records with the vertebrate fossil record, and (iii) expand our view beyond western North America to other areas (e.g., India, Spain, Bolivia, and Colombia).

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

doi: 10.1130/abs/2025AM-413478

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