Times are displayed in (UTC-06:00) Mountain Time (US & Canada) Change

292-10 Prolonged Terrestrial Ecosystem Instability Following the Cretaceous-Paleogene Mass Extinction in Western North America

Session: New Advances in Mesozoic Paleontology, Stratigraphy, and Paleogeography of the Western Interior of North America (Part I)

Presenting Author:

Andrew Flynn

Authors:

Flynn, Andrew G.¹, Milligan, Joseph N. ², Peppe, Daniel J.³, Geng, Jie⁴, Secord, Ross⁵, Williamson, Thomas⁶, Brusatte, Stephen⁷, Shelley, Sarah⁸, Munyaka, Venanzio⁹r> (1) Department of Geological Sciences, New Mexico State University, Las Cruces, NM, USA, (2) Environmental Science & Studies Department, Washington College, Chestertown, MD, USA, (3) Baylor University, Waco, TX, USA, (4) University of Michigan, Ann Arbor, MI, USA, (5) University of Nebraska-Lincoln, Lincoln, NE, USA, (6) New Mexico Museum of Natural History and Science, Albuquerque, NM, USA, (7) University of Edinburgh, Edinburgh, United Kingdom, (8) University of Lincoln, Lincoln, United Kingdom, (9) University of Notre Dame, Notre Dame, IN, USA,

Abstract:

Early Paleocene floral and faunal communities were substantially restructured as a result of the Cretaceous-Paleogene mass extinction approximately 66.0 Ma. While events immediately adjacent to the Cretaceous-Paleogene (K-Pg) boundary have been widely studied, comparatively little research has looked at long-term patterns in terrestrial ecosystem recovery during the early Paleocene. The San Juan Basin (SJB), located in northwestern New Mexico, preserves exceptional, diverse, and geochronologically well-constrained early Paleocene floral and faunal records, making it an ideal location to investigate long-term recovery of early Paleocene terrestrial ecosystems. Here we present a high-resolution record of early Paleocene terrestrial ecosystem instability during the first ~1.5 Myr of the Paleocene using plant and vertebrate fossils coupled with bulk organic carbon δ¹³C and reconstructed leaf area index from the SJB.

Plant and vertebrate macrofossils in the SJB were collected from the lower Paleocene Ojo Alamo Sandstone and lower Nacimiento Formation spanning the first ~1.5 Myr of the Paleocene. Floral extinction, origination, and net diversification rates were estimated using the Pradel capture-mark-recapture (CMR) model from 66.0-64.5 Ma with 150 Kyr timesteps. Two early Paleocene intervals of decreasing floral diversity were identified: a lower interval of ~25% diversity decrease at ~65.5 Ma and an upper interval of ~40% decreased diversity at ~64.8 Ma. Two short intervals of rapid floral diversification were also identified at ~65.3 and ~64.6 Ma. The onset of both intervals of decreasing floral diversity are coeval with -1.5 to -2.5 ‰ bulk organic carbon δ¹³C excursions and a decrease in forest canopy density reconstructed from paleo-leaf area index. Both intervals of floral extinction immediately precede the first appearance Puercan 3 (Pu3) and Torrejonian 1 (To1) mammalian assemblages, respectively, in the SJB, suggesting coupled floral and faunal turnover.

We also applied the Pradel CMR model to coeval macrofloras from the Denver Basin (DB), Colorado and the Williston Basin (WB), North Dakota and Montana, respectively. The floral diversity patterns estimated from the DB and WB indicate intervals of increasing and decreasing floral diversity that are contemporaneous with the same intervals identified in the SJB. This suggests a regional driver in patterns of floral diversity change during the early Paleocene in western North America, reflecting prolonged terrestrial ecosystem instability following the K-Pg mass extinction.

Prolonged Terrestrial Ecosystem Instability Following the Cretaceous-Paleogene Mass Extinction in Western North America

Description

Session Format: Oral

Presentation Date: 10/14/2026

Presentation Start Time: 10:15 AM

Presentation Room: CCC, Bluebird Ballroom 3A

Back to Session