2025-09-15 ミシガン大学
Web要約 の発言：
Luke Weaver and his coauthors examined several locations throughout the western United States to investigate the sudden change in geologic layers before and after dinosaurs became extinct. Image credit: Luke Weaver/University of Michigan
＜関連情報＞
- https://news.umich.edu/your-ecosystem-engineer-was-a-dinosaur/
- https://www.nature.com/articles/s43247-025-02673-8
白亜紀-第三紀境界における大陸相の変化は恐竜絶滅で説明可能 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 Published:DOI:https://doi.org/10.1038/s43247-025-02673-8
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.
