Parasequence geometry and facies architecture in the upper Cretaceous Point Lookout Sandstone, Four Corners platform, southwestern Colorado

Abstract

-In the Upper Cretaceous Point Lookout Sandstone in southwestern Colorado, the presence of distinctly different scales of transgressive deposits defines a hierarchy of high-frequency, nearshore-marine transgressive-regressive cycles. The two cycle scales, parasequences and parasequence sets, are delineated on the basis of thickness and lithologic characteristics of the transgressive deposits at inner-shelf and back-barrier positions. This observation is contrary to most previous work on cycles at this scale, which suggests that the stratigraphic record is composed of regressive strata with the transgressive portion of the cycle being represented only by a surface of erosion or nondeposition. Here, we recognize that both regressive and transgressive deposits are important components of the cycle stratigraphy.