Paleocurrents and Shoreline Orientations in Green River Formation (Eocene), Raven Ridge and Red Wash Areas, Northeastern Uinta Basin: REPLY

Paleocurrent data from ripple marks and cross-stratification are related to orientations of shorelines and sandstone-body trends in the lacustrine and fluvial setting of the Green River Formation (Eocene) in the Red Wash field and the adjacent outcrops along Raven Ridge in Utah and Colorado. At 11 localities along Raven Ridge, the northeastern margin of the Uinta basin, 125 paleocurrent directions were measured from cross-stratification and asymmetrical ripple marks in the Douglas Creek and Garden Gulch Members and the lower part of the Parachute Creek Member. Vertical stratigraphic variation of paleocurrent directions at each locality is small, indicating that the over-all current system was stable. A plot of measurements of 84 asymmetric and 68 symmetric ripple marks shows that their distribution is similar, which is interpreted to be the result of their formation by the same current system. Based on arcs of azimuths, there is essentially no difference between paleocurrent directions from cross-stratification and from ripple marks. The dominant paleocurrent directions are toward the north, south, and southeast. Of all observations, 25 per cent range from 331° to 30°, and 51 per cent range from 121° to 210°. The shorelines in the northeastern Uinta basin area are interpreted to have been generally at right angles to the dominant paleocurrent directions. Therefore, essentially all of the shorelines had bearings of 31° to 120°. An arc of 61°-90° would contain about 40 per cent of the bearings of the shorelines, based on the paleocurrent data. Trends of single sandstone bodies, the total footage of sandstone, sandstone plus siltstone, and net sandstone in the Red Wash field, and the trends of major facies in the northeastern Uinta basin support the generalizations about the orientations of shorelines and sandstone-body trends.