Aptian to Cenomanian Paleoenvironmental History of the Northern Western Interior Sea: A Core Study From the Eagle Plain, Yukon Territory, Canada

Abstract

The Eagle Plain, located in the Northeastern Yukon Territory, Canada, forms a northern segment of the Cretaceous Western Interior Sea. Its preserved Cretaceous strata document the initial inundation of northwestern Canada by the Polar Sea. Preserved strata are the result of an active structural regime, sea-level fluctuations and changing sediment supply areas. The Cretaceous rocks are unconformably underlain by either Paleozoic or younger Mesozoic formations. Recent paleontological evidence including pollen, foraminifera and macrofossils from outcrop sections in the Eagle Plain suggested that Aptian to Cenomanian aged strata are preserved. This package includes the Whitestone River, Parkin, Fishing Branch, Burnthill Creek and Cody Creek formations. The area became terrestrially exposed during the upper Cretaceous when paleoshorelines moved northward and eastward to the Peel Plateau region. This project takes this new stratigraphy into the subsurface by examining two cores and their foraminiferal assemblages that represent proximal shelf and slope settings. In both regions foraminiferal assemblages are almost entirely dominated by agglutinated taxa and document response to fluctuating sea-level changes during the Albian Stage. The Ellen C-24 core represents a proximal shelf setting where the lower to middle Albian Whitestone River Formation is fully marine with hospitable benthic conditions. The Molar P-34 well represents an offshore setting with increased accommodation space marked by sediment slumping, representing a northwestward deepening of the basin. The deep water setting is evidenced by abundant tubular suspension feeders which are rarer in the Ellen C-24 core. In both settings a marked lithological change from shale to sandstone takes place within the upper Albian Parkin Formation corresponding to a distinct faunal changeover to an impoverished fauna. This shallowing event alludes to a regionally recognizable late Albian sea-level drop that is expressed in the Peel Plateau region as a paleosol, but remains elusive in the lithology of the Eagle Plain. The distinct faunal loss, however, clearly marks a basin change. The Whitestone River Formation documents Aptian/Albian sea-level fluctuations that can be correlated to the Polar Sea and Sverdrup Basin to the North and to southern basins of the Western Interior Sea.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015