2002. Litho− and chronostratigraphic relationships of the Santonian–Campanian Milk River Formation in southern Alberta and Eagle Formation in Montana uti− lising stratigraphy, U−Pb geochronology, and palynology. Canadian Jour− nal of Earth Sciences 39

Abstract: U–Pb geochronology, palynology, and lithostratigraphy were employed on the Late Cretaceous rocks in southern Alberta and Montana to solve litho- and chronostratigraphic correlation problems. In the outcrop area around Writing-On-Stone Provincial Park, southern Alberta, the Milk River Formation has a Santonian to possibly very earliest Campanian age and was deposited between 84.5 Ma and 83.5 Ma. In southern Montana, the Eagle Formation was deposited from 83.5 Ma to 81.2 Ma, and contains different lithologies and depositional environments as opposed to southern Alberta. In north-central Montana, the Telegraph Creek Formation and Virgelle and Deadhorse Coulee members are equivalent in depositional environments and time to those of the Milk River Formation in southern Alberta. The upper Eagle member, however, has no time- or facies-equivalent rocks around Writing-On-Stone Provincial Park, but is time equivalent to the Alderson Member of the Lea Park Formation in southeastern Alberta. A hiatus of 2.5 Ma is present between the top of the Milk River Formation in the outcrop area and the basal beds of the Pakowki Formation. The Pakowki transgression occurred at around 81.0 Ma based on a U–Pb zircon age of 80.7 ± 0.2 Ma from bentonite beds just above the bottom of the Pakowki Formation in southern Alberta. This age agrees with previous ages of 80.7 ± 0.6 Ma for the Ardmore Bentonite Beds and 81.0 Ma for the Claggett transgression in southern Montana. Résumé: Afin de résoudre des problèmes de corrélations lithostratigraphiques et chronostratigraphiques, on s’est servi de géochronologie U–Pb, de palynologie et de lithostratigraphie sur des roches du Crétacé tardif du sud de l’Alberta et du Montana. Dans la région des affleurements autour du parc provincial de Writing-On-Stone, au sud de l’Alberta, la Formation de Milk River date possiblement du Santonien au Campanien très précoce et aurait été déposée il y