Regional geology, sedimentology and sequence stratigraphic framework of the Albian Pense formation, southwestern Saskatchewan

A detailed study of the sedimentology and stratigraphy of the middle to lat e Albian Pense Formation was undertaken in southwestern Saskatchewan (Twp. 1-20, Rge. 10-22W3). Shallow-marine shelf sandstones and shales of the Pens e Formation overlie either pre-existing interfluve deposits of the Success S2 Formation (fluvial), or valley-fill deposits of the Chokecherry Creek (s ubtidal, estuarine) or Atlas (non-marine, valley-fill) members of the Cantu ar Formation all within the Mannville Group. The base of the Pense Formatio n represents a transgressive surface of erosion but may also be a sequence boundary. A transgressive systems tract is identified, culminating in depos ition of a condensed section historically identified as the Index Horizon A bove the Cantuar Marker (IHACM). The IHACM represents sediments deposited d uring maximum marine inundation of the Pense transgression. The IHACM is ch aracterized by nonbioturbated shale having elevated total organic carbon co ntent and hydrogen indices. Five coarsening-upward/fining-upward cycles are mapped within the Pense Formation above the IHACM. The lowermost of these sandstone/shale cycles is interpreted to be the result of a forced regressi on. Incised valley deposits occur in Cycles R3 and R5 in the northeast. The shelfal sandstone bodies of the Pense Formation are dominantly quartzose, storm-dominated, originated from sources outside and to the north and north east of the study area, and were probably transported to this region by lon gshore shelf processes.