Abstract

The Lower Permian Mount Bayley Formation is a subaqueous evaporite deposit. Exceptional outcrop exposures, located along the eastern margin of the Sverdrup Basin, extend over 160 km on west-central Ellesmere Island.

Packages within the formation consist of shale, fossiliferous carbonate, non-fossiliferous carbonate and anhydrite. The shales are interpreted as flooding deposits during seawater replenishment. Fossiliferous carbonates contain facies assemblages that can be assigned to energy restricted outer-shelf and lagoonal marine environments. Non-fossiliferous carbonates occur as metre-scale packages of laminites, with individual laminae as thin as 100 microns. Anhydrite is present as thick (tens of metres) packages of laminites that are interrupted by a variety of diagenetic features including nodular fabrics and microfolds.

Primary sedimentary structures preserved within the Mount Bayley Formation are almost exclusively laminites. Cycles present are defined by changes in mineralogy, not by changes in sedimentary structures. Thick sequences of laminites point to a relatively deep water depositional environment. The Mount Bayley Formation lacks common shallow water features such as bottom growth fabrics, wave generated structures and evidence for desiccation found in other evaporitic units. Nodular fabrics from several other evaporite units have been interpreted as overprints of primary shallow water fabrics. However, because of excellent exposures, the nodular fabrics developed within the Mount Bayley Formation evaporites can be traced laterally into primary laminites.