Sedimentology and taphonomy of the Oldman Formation (Campanian), Dinosaur Provincial Park, Alberta (Canada)

Abstract

Sediments of the Upper Cretaceous (Campanian) Oldman Formation at Dinosaur Provincial Park, Alberta, have yielded an exceedingly rich fauna of dinosaurs. These fluviatile sediments show characteristics of both meandering and braided channels. Fossil molluscs, plants, and diverse salamanders indicate that Oldman sediments were deposited in fresh water, and the very sparse agglutinated Foraminifera recovered fail to controvert this conclusion. Annual growth rings in wood and vertebrate of Champsosaurus demonstrate that the climate was seasonal, and current botanic interpretations suggest that the climate was an equable, warm temperate one. Dinosaurian remains represent all stages of disarticulation from complete skeletons to isolated bones. They are common in channel sediments and rare in overbank deposits, suggesting that the animals preserved died in the water of channels. The persistence of the characteristics sedimentary association of fossils over a 200 ft. stratigraphic interval demonstrates that regular, not catastrophic events determined the preservation of individuals. Stages of progressive decomposition of dinosaurs are inferred from the condition of fossils collected from the Park. Disarticulated small bones occur at interfaces between mudstone and sandstone in which the sandstone lies above the mudstone, and also in intraformational conglomerates. Ceratopsians are identified as dwellers of the swampy lowlands along with hadrosaurs. Hadrosaurs, ceratopsians, and possibly even carnosaurs spent significant portions of their daily lives in water. These dinosaurs did not breed in “uplands”, but possibly in dry areas lateral to the streams.