Age of Goose Rock Conglomerate, Wheele and Grant Counties, north-central Oregon

A reconstruction of the geologic history and synthesis of the tectonic history of the Blue Mountains and Columbia Basin require that they know the age of key outcrops. The geological record in this entire area has been largely hidden by a thick blanket of Tertiary volcanic rocks. Only a few erosional inliers are available from which to interpret the pre-volcanic tectonic and sedimentation history. The Goose Rock Inlier, exposed along the John Day River in the Butler basin and Turtle Cove, is one such important outcrop. These exposures, consisting of a few hundred feet of fluvial sandstones and conglomerates, informally called the Goose Rock Conglomerate have received only limited attention from previous workers. Estimates of this unit's age range from Early Cretaceous to early Tertiary, on the basis of lithologic similarities with other named and unnamed formations in the area. The terrestrial nature of these strata and the apparent lack of fossils cause considerable difficulty in correlation with other Cretaceous sequences, which are largely marine. In the absence of scarcity of other fossils, palynology offers a unique alternative for making biochronological and paleoenvironmental interpretations.