Geochemistry of the Cretaceous-Tertiary (K-T) boundary interval: south-central Saskatchewan and Montana

Abstract

The Cretaceous-Tertiary (K-T) boundary interval in the Canadian Continental Drilling Program Cretaceous-Tertiary (K-T) Boundary Project Wood Mountain and Wood Mountain Creek core holes along with the Wood Mountain Creek and Rock Creek east A outcrop localities, south-central Saskatchewan, were analyzed using either neutron activation analysis or laser ablation - inductively coupled plasma - mass spectrometry. The claystone towards the base of the Landscape coal zone in the Wood Mountain core hole which coincides with a floristic extinction event was found to have enhanced iridium values, confirming it to be the boundary claystone. Four layers, sub-hackly, hackly, satiny, and laminated, in ascending stratigraphic order, recognizable as part of the boundary claystone in south-central Saskatchewan, are considered to be correlative to previously documented layering in midcontinental United States. Present results indicate both a uniqueness and possible common genesis of these layers. The hackly and satiny claystones have relatively low iridium abundances in comparison to the laminated shale. This pattern is regional in extent and therefore the geochemistry of these layers is accepted as a primary characteristic. Anomalous iridium abundances occur beyond the boundary claystone interval, requiring an explanation more complex than post-depositional chemical migration. As a generalization, the Cyathidites spore spike first occurs in the satiny claystone.