Source Areas and Paleotectonic Implications of Upper Cretaceous Ohio Creek Member of Mesavarde Group, Piceance Basin, Colorado: ABSTRACT

Abstract

The Ohio Creek member of the Mesaverde Group consists of massive or a series of massive conglomeratic sandstones deposited by several large braided stream systems that drained into the Piceance basin during Campanian-Maestrichtian time. Channel forms and internal bedding features are similar to those in the underlying Mesaverde. However, the Ohio Creek weathers to form a conspicuous white band above the brown sandstones of the Mesaverde and is further distinguished by an increase in pebble content. The distinctive color is due to extensive kaolinization caused by post-Ohio Creek weathering. Paleocurrent data, pebbles, and sandstone lithologies indicate at least two distinct source areas. A western sedimentary source area, probably central Utah, is indicated by deposits along the western margin of the basin. A contribution from the Uncompahgre highland area cannot be ruled out as yet. A sedimentary source area is also indicated to the east and/or southeast. The Sawatch Range area seems to have been the major contributor of coarse material, but a change in pebble lithology could be due to an influx from the southern Park Range. Approximate ages of the Ohio Creek member in published literature are derived from palynomorphs. Scattered data by separate workers indicate that the Ohio Creek in the southern part of the basin is conformable with the underlying Mesaverde, whereas the member could be as young as middle Paleocene in the northeastern basin. End_of_Article - Last_Page 954------------