Hydrocarbon Possibilities in Yuma Area, Arizona

Daniel J. Brennan

Fault block mountains and broad valleys characterize the Yuma area, southwestern Arizona. Fewer than 20 oil tests have been drilled in an area of over 450 mi². Recently released reflection data, integrated with earlier work and with data from oil and gas tests and water wells, reveal a complex geologic history.

The Algodones fault zone, part of the San Andreas system, cuts across the area in a northwesterly direction. Movement, believed to be right lateral, may have originated before the Cenozoic and is probably continuing. Cenozoic extensional faulting added the basins and ranges. Several thousand feet of continental clastics and basic volcanics accumulated. A Miocene-Pliocene marine incursion deposited up to several thousand feet of older marine Bouse Formation marine shales and sandstones and a transition zone of interbedded marine and continental sediments. Colorado River sediments have subsequently accumulated to a thickness of up to 4,000 ft. Geophysical data suggest a total thickness in excess of 15,000 ft. No well in a basin has yet penetrated the entire section.

Post-Bouse folding is evident on some seismic lines. On those lines, the Colorado River sediments appear to be undeformed. Folds observed may be due to continuing activity along the Algodones fault or to relaxation of forces that formed the basins and ranges.

Petroleum possibilities are related to the presence of marine and transitional wedges of shale and sandstone. Traps present may include sandstone pinch-outs and fault-and-fold closures.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.