OAE2 AND THE EASTERN EXTENT OF THE WESTERN INTERIOR SEAWAY IN IOWA

The Western Interior Seaway (WIS) expanded through much of west-central North America during the Cretaceous. The majority of research on the WIS has been conducted along the axis of the basin, or on the western margin proximal to orogenic events and radioisotopically dateable volcanic materials. By comparison, only a handful of studies have focused on the eastern margin of the WIS and the true geographic extent of the seaway remains a matter of debate.

Here, we produced high-resolution carbonate carbon isotope chemostratigraphy from a core drilled in Sioux County, Iowa, that includes Oceanic Anoxic Event 2 (OAE2) in clearly marine, carbonate-dominated strata from western Iowa. Additional cores in Iowa also preserve the Greenhorn Formation in marine strata and demonstrate that the WIS extended at least well into central Iowa during the maximum transgression during the Late Cretaceous.