Base-Level Buffers and Buttresses: A Model for Upstream Versus Downstream Control on Fluvial Geometry and Architecture Within Sequences

摘要

The effects of downstream base-level control on fluvial architecture and geometry are well explored in several broadly similar sequence-stratigraphic models. Cretaceous Dakota Group strata, U.S. Western Interior, have characteristics reflecting combined downstream and upstream base-level controls that these models cannot address. Particularly, three layers of amalgamated channel-belt sandstone within this group thicken and are continuous for distances ( 300 km) along dip that stretch the reasonable lengths for which these models are intended to apply. As well, architecture in up-dip reaches records repeated valley-scale cut-and-fill cycles. This contrasts with equivalent strata down dip which record channel-scale lateral migration with no such valley-scale cycles apparent.