EVIDENCE FOR CONTINENTAL SUBSIDENCE IN NORTH-AMERICA DURING LATE CRETACEOUS GLOBAL SUBMERGENCE

The widespread Late Cretaceous transgression is one of the best documented episodes of world-wide continental submergence, yet its cause or causes remain elusive. Subsidence of continents, rise of sea level, or a combination of both are plausible hypotheses, but testing them is difficult because the effects of sea level rise and continental subsidence are similar- that is, transgressive deposits. One solution to the problem can be derived from comparison of actual sediment thicknesses with those calculated as possible from a maximum sea level rise. A sea level rise of about 310 m is required to flood the area submerged in Late Cretaceous time. However, the maximum thickness of a transgressive deposit produced by a 310-m rise of sea level is only about 700 m. In North America, nearly 50 percent of the area flooded during Late Cretaceous time contains strata thicker than 700 m; this indicates the important role of continental subsidence during the Late Cretaceous submergence. © 1976 Geological Society of America.