Incision and filling of a lowstand valley: late Albian Viking Formation at Crystal, Alberta, Canada

Crystal field in the Albian Viking Formation represents the fill of a lowstand incised valley at least 55 km long, 7-12 km wide, and up to 32 m deep. The valley trends south-north, with a smaller arm trending east-west; the open sea lay to the north and east. The valley cuts into five regionally extensive sandier-upward successions of open marine bioturbated mudstones and sandstones. There were two separate episodes of valley filling. The base of Valley 1 represents an original fluvially formed sequence boundary completely modified by marine transgression, whereas the base of Valley 2 is a fluvial cut sequence boundary in the south and a marine-modified sequence boundary in the north. The sandbodies within the valley are poorly connected as reservoirs. -from Authors