Dinosaur geo-engineers changed carbon storage of sediments

[Tom Goreau]

• Article
• Open access

• Published: 15 September 2025

Dinosaur extinction can explain continental facies shifts at the Cretaceous-Paleogene boundary

• Lucas N. Weaver, 
• Thomas S. Tobin, 
• Courtney J. Sprain, 
• Paige K. Wilson Deibel, 
• Vera A. Korasidis, 
• Mónica R. Carvalho, 
• Pim Kaskes & 
• Isabel M. Fendley 

Communications Earth & Environment volume 6, Article number: 712 (2025) 

Abstract

Continental Cretaceous-Paleogene boundary sections are best known from North America, where they invariably exhibit a marked shift in sedimentary facies at or very near the boundary level. Uppermost Cretaceous strata typically reflect water-logged soils and unstable meandering-river deposits, whereas lowermost Paleogene strata typically reflect coal swamps and broad, stable meander-belt deposits. Causal links between facies shifts at the Cretaceous-Paleogene boundary and the end-Cretaceous mass extinction have been largely dismissed. Here, we present five new Cretaceous-Paleogene boundary sections identified via iridium anomalies in the Bighorn and Williston basins and assess the sedimentological changes that occur at North American Cretaceous-Paleogene boundaries. We hypothesize that the geographically widespread Cretaceous–Paleogene facies shifts were driven by the extinction of dinosaur megafauna. Large-bodied dinosaurs likely promoted open vegetation structure, prompting fluvial avulsion and clastic sediment input to distal floodplains. After the end-Cretaceous mass extinction, dense forests could establish, stabilizing meander belts and starving the floodplain of clastic sediment, favoring the accumulation of organic-rich strata. More empirical data are needed, but facies change in continental Cretaceous-Paleogene boundary sections suggests dinosaurs were ecosystem engineers that promoted habitat openness in the Late Cretaceous, and their extinction likely led to a dramatic reorganization of ecosystem structure in the earliest Paleogene.

 

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