The Upper Cretaceous paralic to nonmarine Horseshoe Canyon Formation (HCFm) of southern Alberta is divided into seven mappable members: Strathmore, Drumheller, Horsethief, Morrin, Tolman, Carbon, and Whitemud (bottom to top). This subdivision, based on combined outcrop and subsurface analyses, reflects lithostratigraphic variations related to changes in sea level (previously recognized) and newly documented changes in climate, volcanism, and orogenesis in an evolving foreland basin. Million-year-scale cycles of orogenesis resulted in changes in sediment supply and rates of subsidence in the basin and are interpreted in the context of a simple, two-phase foreland-basin sequence stratigraphic model: (i) overthrust loading resulting in reduced rates of sediment supply and subsidence in the most distal portions of the Alberta foredeep (our field area); (ii) tectonic quiescence leading to increased rates of sediment supply and subsidence during proximal-foredeep rebound. During the first ∼2.5 Ma of its history (Strathmore and Drumheller members), the HCFm was tectonically and climatically "stable", and depositional style and stratigraphic architecture were influenced by vertical aggradation and modest progradation of shorelines. During the remaining ∼4.5 Ma (Horsethief, Morrin, Tolman, Carbon, and Whitemud members), there were more complex and frequent changes in climate, volcanism, orogenesis, landscape weathering, and soil formation. Understanding this previously unrecognized complexity is critical for correctly assessing hydrocarbon resource distributions and biostratigraphic and taphonomic patterns.Résumé : La Formation de Horseshoe Canyon (HCFm) du sud de l'Alberta est divisée en sept membres cartographiables : Strathmore, Drumheller, Horsethief, Morrin, Tolman, Carbon et Whitemud (du bas vers le haut). Cette subdivision, basée sur une combinaison d'analyses de roc affleurant et de roc sous la surface, reflète les variations lithostratigraphiques relatives aux changements du niveau de la mer (reconnus antérieurement) et les nouveaux changements documentés de climat, de volcanisme et d'orogenèse dans un bassin d'avant-pays en constante évolution. Des cycles de millions d'années d'orogenèse ont produit des changements dans l'apport de sédiments ainsi que dans les taux de subsidence du bassin; ces cycles sont interprétés dans le contexte d'un modèle stratigraphique simple de séquence à deux phases de bassin d'avant-pays : (i) un chargement par chevauchement qui réduit les taux d'apport de sédiments et de subsidence dans les portions les plus distales de l'avant-fosse de l'Alberta (notre secteur); (ii) une quiescence tectonique qui mène à un accroissement des taux d'apport de sédiments et de subsidence lors du soulèvement de l'avant-fosse proximale. Au cours des premiers ∼2,5 Ma de son histoire (les membres Strathmore et Drumheller), la HCFm était tectoniquement et climatiquement stable; le style de déposition et l'architecture stratigraphique étaient influencés par une aggradation verticale et une légère progradati...

In 1916, a centrosaurine dinosaur bonebed was excavated within the Campanian−aged deposits of what is now Dinosaur Provincial

An exceptionally preserved subadult specimen (JRF 115H) of a hadrosaurid, Brachylophosaurus canadensis, from the Judith River Formation near Malta, Montana, contains abundant plant fragments concentrated within the body cavity. We examined the taphonomy of the carcass and analyzed the gut-region material to test whether the organic remains represent fossilized gut contents. The dinosaur was buried in a fluvial channel setting, and the excellent articulation, integument impressions, and lack of scavenging indicate rapid burial. The organic material occupies a volume of at least 5750 cm 3 , and comparable material is not found outside the carcass. The carcass contents include ϳ63% clay, ϳ16% undetermined matrix, ϳ12% organic matter, and ϳ9% larger inorganic clasts-mostly 50-100 m quartz grains. Most of the organics appear to be mm-scale leaf fragments. The most parsimonious explanation for the presence and composition of the gut-region material is that much of the plant fossils represent reworked brachylophosaur ingesta influenced by flowing water that entered through openings in the carcass and introduced clay. The evidence strongly suggests that the hadrosaurid ate significant quantities of leaves and processed them into small pieces. This study provides baseline information for analyzing other cases of putative gut contents in herbivorous dinosaurs.

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