DETRITAL ZIRCONS FROM CRETACEOUS MIDCONTINENT STRATA REVEAL AN APPALACHIAN MOUNTAINS-CORDILLERAN FORELAND BASIN CONNECTION

U-Pb ages (n=403) of detrital zircons from the Dakota Formation in western Iowa and eastern Nebraska provide evidence for westward-flowing fluvial systems that stretched from the Appalachian highlands to the western United States Cordilleran foreland basin during Albian-Cenomanian time. Approximately 78% of detrital zircon grains match the ages of Grenvillian (1.3-1.0 Ga), Pan-African (750-500 Ma), and Paleozoic (500-310 Ma) bedrock sources located within the present-day Appalachian Mountains. The presence of minor detrital zircon grains of Paleoproterozoic (2.5-1.5 Ga) or Archean age (>2.5 Ga) indicates that northern source regions in Minnesota, Wisconsin, and Canada did not contribute a significant volume of sediment as had been previously interpreted. Based on similarities between detrital zircon signatures in the midcontinent strata and time-equivalent Cordilleran foreland basin strata, Appalachian sources may have contributed a previously unrecognized volume of sediment to the Albian-Cenomanian foreland basin system. Sediment flux from the Appalachian region to the Cordilleran foreland basin during middle Cretaceous time may be related to increased uplift and exhumation due to passage over a mantle plume track.