New biostratigraphic data from Cretaceous strata of the Eagle Plain region, northern Yukon: Reassessment of age, regional stratigraphic relationships, and depositional controls

Abstract

Abstract Cretaceous strata of the southern Eagle Plain region, northern Yukon Territory, have been assigned previously to the Whitestone River Formation and overlying Eagle Plain Group, and contain possible reservoir and potential source rock strata. Age control for most of these strata has been limited due to sparse fossil finds and contradicting biostratigraphic ranges. Molluscan, foraminiferal, and palynological data obtained recently from the Parkin, Fishing Branch, Burnthill Creek, and Cody Creek formations in the outcrop area of southern Eagle Plain constrain the age of these units as Albian to Cenomanian, or possibly earliest Turonian. Detrital zircon data collected from the Cody Creek Formation are consistent with the latest Albian to Cenomanian age obtained for the formation using palynology. Grenvillian, Paleozoic, Jurassic, and Cretaceous ages within the zircon assemblage are consistent with derivation from local sources. Mudstone-dominated strata of the Parkin Formation of the lower Eagle Plain Group are lithologically similar to strata of the underlying Whitestone River Formation and the unconformity between them, although not resolvable biostratigraphically, is interpreted to sit within the mid-Albian. The regionally-recognized Late Albian unconformity event is represented in southern Eagle Plain Basin by the transition from marine to non-marine deposition, reflected in progradation of coarse clastics of the Burnthill Creek and Cody Creek formations into the basin. This event corresponds with progradation of the Monster Formation alluvial/fluvial system to the southwest of Eagle Plain. The transition also corresponds to development of a paleosol horizon in the Peel Plateau region to the east of Eagle Plain. Whereas marine conditions returned in that region during the Cenomanian, the southern Eagle Plain region remained subaerially exposed. The paleoshoreline of the Western Interior Seaway remained further east during the Turonian, as documented by prograding shoreface deposits of the Trevor Formation in the Peel Plateau region. Sequence boundaries as documented within the Whitestone River, Parkin, and Fishing Branch formations relate to Albian sea level lowstands that separated the major inundation phases of the Western Interior Sea.