ABSTRACT

The Bisti Fruitland area contains about 1,870 million tons of subbituminous low-sulfur coal beneath less than 250 ft (76.2 m) of overburden and is the largest undeveloped reserve in the San Juan basin. To aid prudent development of these resources intensive field investigations of the depositional environments of the strata were undertaken east and southeast of the old Bisti Trading Post.

Seventeen measured sections were made in the vicinity of Hunter Wash. The stratigraphic sequence exposed consists of interbedded shales, siltstones, channel sandstones, and coals. Coals are more prominent in the lower part of the sequence. Correlations were facilitated by the presence of a prominent, medium-grained, reddish-brown sandstone. The usefulness of coals for correlation in the study area has not been demonstrated.

The included sequence contains the Fruitland-Kirtland contact with most of the strata in the Fruitland Formation. This contact is approximately 200 ft (61 m) lower in elevation than the Pictured Cliffs Sandstone-Fruitland Formation contact about 5 mi (8 km) southeast. There are possible correlations of the rocks in this area with those of the “fossil forest” near the Split Lip Flats on the southeast.

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