ABSTRACT: Evolution of the San Juan Basin, Colorado, and New Mexico Basin Analysis Case Study

Jennie L. Ridgley, A. Curtis Huffman, Jr.

During 1985 to 1989, the U.S. Geological Survey conducted a basin analysis study that investigated the sedimentological and structural history of the San Juan basin and vicinity. The San Juan basin is a large asymmetric basin in southwest Colorado and northwest New Mexico near the southeastern edge of the Colorado Plateau. It formed as a result of northeast-directed compression coupled with a slight northeastward shift of the Colorado Plateau during the Late Cretaceous to Oligocene Laramide orogeny. Although the basin assumed its final configuration during the Laramide orogeny, regional stratigraphic and sedimentologic studies show that uplifts active during the Laramide orogeny were also active in the geologic past. Analysis of 1000 mi of reflection seismic data defines rectilinear pattern of northwest- and northeast-trending faults that involved the Precambrian basement in basin development. Middle Pennsylvanian to Late Permian, Middle to Late Jurassic, Early Cretaceous, Late Cretaceous-Oligocene, and Miocene were major times of movements on the faults and/or bounding uplifts.

Preserved Mesozoic and older sedimentary rocks in the basin accumulated as part of widespread regional depositional systems. Pennsylvanian strata, consisting of a thick sequence of clastic and carbonate rocks, and evaporites deposited in both open and restricted marine environments contain significant oil and gas resources. Mesozoic strata deposited in a variety of widespread continental and marine environments host 50% of the country's uranium reserves. Five marine transgressive-regressive cycles during the Cretaceous resulted in a thick sequence of intertonguing marine and continental rocks containing large resources of coal, oil, and gas.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990