Models of marine transgression —Example from Lower Cretaceous fluvial and paralic deposits, north-central Kansas

Abstract

Transgression of the Early Cretaceous Kiowa sea in north-central Kansas led to deposition and preservation of fluvial, estuarine, and lagoon or bay deposits behind Kiowa barrier systems. The fluvial, estuarine, and part of the lagoon or bay deposits compose the Longford Member of the Kiowa Formation. The member is thickest in broad valleys that were eroded into Permian bed rock prior to deposition of the Cretaceous strata. Overlying Kiowa beds include open-sea deposits of shale., and barrier-system deposits of sandstone. Transgression was not accompanied by near-shore erosion of barrier, paralic, or fluvial deposits, nor by development of transgressive disconformities within the transgressive sequence, nor by deposition of transgressive sand sheets. Progradational pulses that might account for the generation and preservation of the barrier, paralic, and fluvial deposits are not apparent in the Longford-Kiowa record. An upward gradation from fluvial deposits at the base of the member to lagoonal deposits at the top and an apparently scattered distribution of Kiowa open-sea and barrier deposits above the member indicate that rising sea level or basin subsidence was accompanied by vertical growth, eventual submergence, and stepwise landward shift of barrier systems across expanding lagoons or bays.