Abstract

One of the major oil-impregnated sandstone deposits in the United States is present on the Circle Cliffs uplift in an unnamed sandstone unit in the middle portion of the Triassic Moenkopi Formation. The deposit occurs on the west and east flanks of the uplift and is separated by an irregular barren area where the sandstone sequence is thin or absent by non-deposition or has been removed by erosion across the topographic and structural crest of the fold.

Based on reconnaissance mapping, the deposit contains 1.3 billion barrels of oil in place, 860 million on the east flank and 447 million on the west flank. Much of the reservoir sandstone is fine-grained clayey and micaceous and would present formidable problems in mining and extraction.

Smaller occurrences are found in sandstone lenses in the Shinarump Member of the Chinle Formation (Triassic) at White Canyon Flat and in the south part of Muley Twist Canyon. Thin vuggy beds in the Kaibab Limestone (Permian) locally contain small amounts of liquid oil at various localities on the crest of the anticline, and the uppermost part of the White Rim Sandstone Member of the Cutler Formation (Permian) also contains minor amounts of oil.

The east flank deposit is mostly within the Capitol Reef National Park, and the west flank deposit is in an area proposed for wilderness or reserved status by environmental groups.