GEOLOGIC AND STRATIGRAPHIC MAPPING OF SHEEP ROCK AT JOHN DAY FOSSIL BEDS NATIONAL MONUMENT, OREGON

The John Day Basin of Oregon contains a rich sequence of beds spanning nearly 40 million years of time, from the mid Eocene to the late Miocene. These fossil horizons document dramatic changes in climate, floras, and faunas. Crucial to the progress of the paleontological efforts of John Day Fossil Beds National Monument is a thorough understanding of the stratigraphy of the major fossil-bearing localities; namely, Sheep Rock, Blue Basin, and Foree. These areas are prospected regularly by the park’s paleontology staff, and yield large numbers of scientifically significant specimens from the Oligocene and early Miocene. Accurate and up-to-date geologic maps of these areas would serve as a valuable addition to the understanding of the park’s geological and paleontological resources.

As a part of a GeoCorps America research project, a geologic map and various cross sectional photo points have been created for Sheep Rock, which is comprised of strata from the Turtle Cove and Kimberly Members of the John Day Formation. The geologic map displays, in detail, 16 subunits of the Turtle Cove Member, which consists primarily of volcaniclastic paleosols, along with multiple air flow and welded ash flow tuffs. The region lies in an extensional zone and contains several normal and vertical faults, which have displaced the stratigraphy to various degrees throughout the area. The map explanation includes field descriptions of the units, which have yet to be formally documented. Geographic Information Systems (ArcGIS) technology will allow for 3-D viewing of the digitized maps and photo points, along with GPS correlation with the data used by the paleontologists at collection sites. These resources will be utilized by the existing park staff, future seasonal employees, and park visitors.