THE SEDIMENTOLOGY AND STRATIGRAPHY OF THE LOWER CRETACEOUS CLEARWATER FORMATION AT MARTEN HILLS AND NIPISI, ALBERTA, CANADA

Abstract

The Lower Cretaceous (Albian) Clearwater Formation at Marten Hills and Nipisi in north-central Alberta contain two members (Wabiskaw and the newly proposed Marten Hills Member), which sit disconformably above the sub-Cretaceous unconformity. Both the Marten Hills and Nipisi regions are currently being explored for oil resources; however, the region suffers from a paucity of previous studies. A robust interpretation of paleoenvironmental settings and stratigraphic architecture is required to further delineate the Marten Hills Member of the Clearwater Formation. The Wabiskaw marker bed separates the underlying Wabiskaw Member from the Marten Hills Member and is interpreted to represent a regionally extensive maximum flooding surface. This flooding surface is in turn overlain by a series of subsequent cleaning upwards profiles, each of which is capped by a marine flooding surface and represents transgressive-regressive cycles of the Boreal Seaway. Sedimentologic and ichnologic analysis indicate the presence of a range of depositional settings, from deltaic distributary channels to fully marine offshore environments. Within the study region, the Marten Hills Member consists of six interpreted stratigraphic intervals (Marten A-F) deposited above the Wabiskaw Member. Core and well-log interpretations reveal a series progradational and aggradational shoreline parasequence sets indicative of a wave-influenced shoreline complex. The Nipisi and Marten Hills oil pools are predominantly producing from the Marten B and C intervals (respectively) and represent deposition of marginal marine sandstones associated with a wave- and storm-dominated shoreline. Insights from this thesis provide a foundation for future work to build upon and further evaluate the Marten Hills Member in north-central Alberta.