Oil-impregnated intervals, up to 75 ft thick within a stratigraphic interval of about 250 ft in the Garden Gulch and Parachute Creek Members of the Green River Formation (Eocene), are exposed in beds that dip gently northward in the P. R. Spring area of the southeast Uinta basin, Utah. Reserve estimates indicate that there may be about 3.7 billion bbl of oil in place.

It is necessary to distinguish lacustrine from fluvial sandstone in these intertonguing beds because most of the oil is in lacustrine sandstone. Paleocurrent study indicates that paleocurrent patterns can be used for these distinctions. A total of 308 paleocurrent measurements was made at 13 localities in the P. R. Spring area; 123 from sandstone beds of fluvial origin and 185 from lacustrine sandstone bodies.

Of 9 fluvial paleocurrent patterns, 7 indicate that streams flowed northward into Lake Uinta in the P. R. Spring area. The considerable scatter in the paleocurrent measurements suggests that the streams had low gradients and were meandering. Many of the fluvial sandstone bodies are oriented approximately north-south and contain northward-inclined foreset laminae.

Of 10 lacustrine paleocurrent patterns, 9 have significant intervals in the south half of the compass. These directions are interpreted to be dominantly the result of onshore lake currents. The shorelines of Lake Uinta probably trended northeast through much of the P. R. Spring area, but on the northeast, shorelines were oriented northwest-southeast.

The paleocurrent patterns of fluvial and lacustrine sandstone are both unimodal. The environments can be differentiated, however, on the basis of paleocurrent orientations; the fluvial currents flowed northward; the lacustrine currents were southerly.

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