Geophysical framework of northern end of Gulf of California structural province
- Others:
- Van Andel, Tjeerd H.
- Shor, George G.
Abstract
More than 3,000 gravity observations in the Northern Gulf province, including an underwater gravity survey of the Salton Sea, show the over-all trend of isogal contours to be northwest, parallel to the tectonic pattern dominated by the San Andreas fault system. Contours northeast of the trough trend east, probably reflecting Transverse Range structures in this area. A prominent and linear gradient of 5 mgal/km marks the Banning-Mission Creek fault in the Coachella Valley but dies out southeastward at about the same point the surface trace disappears. The San Jacinto fault zone is characterized by a series of maxima and minima that tend to confirm continuity of this fault zone to the Gulf of California. A 15-20 mgal maximum over the Obsidian Buttes suggests a large anomalous mass at depth, or may be related to contemporaneous metamorphism of the Tertiary sedimentary section that has recently been observed in nearby steam wells. The regional gravity gradient indicates a crustal thickening northwest from the Gulf of California; inferred crustal thicknesses are 32 km at the International Border and 40 km at San Gorgonio Pass. Ten seismic refraction profiles in the Imperial and Coachella Valleys indicate several throughgoing velocity zones, but we are unable to correlate these with known stratigraphic units. The maximum thickness of sediments in the trough appears to be about 6.4 km (21,000 ft) just south of the International Border, with basement becoming shallower both to the north and south. The Salton trough has many geophysical and structural similarities to the Dead Sea rift, but the markedly en echelon pattern of major faults in the Salton trough and Gulf of California appears unique. A particular problem is presented by their orientation, which would suggest left-lateral displacement across the zone rather than the right-lateral displacement that is known to characterize at least the northern end of the province.
Additional Information
© 1964 American Association of Petroleum Geologists. Manuscript received, June 25, 1963. The gravity measurements in Mexico were made in collaboration with the Instituto de Geofísica, Universidad Nacional Autónoma de México, through the participation of Ing. Julio Monges C. We are indebted to Dr. Lucien LaCoste of LaCoste and Romberg for supplying the underwater gravimeter, and to Aerial Control, Inc., and Pacific Air Industries for the use of their Tellurometers. Dr. Frank Press helped supervise most of the work reported herein, and Dr. Charles Helsley was particularly helpful in the field program. Others who assisted us in the field include S. Alexander, D. Harkrider, J. Healy, A. Ibrahim, R. Phinney, and L. Teng. Most of this work was supported by National Science Foundation Grant G-19778 and by the American Petroleum Institute.Attached Files
Published - Allen_1964p126.pdf
Supplemental Material - Map.PDF
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Additional details
- Eprint ID
- 49926
- Resolver ID
- CaltechAUTHORS:20140923-093145767
- NSF
- G-19778
- American Petroleum Institute
- Created
-
2014-09-23Created from EPrint's datestamp field
- Updated
-
2023-06-26Created from EPrint's last_modified field
- Series Name
- Memoir (American Association of Petroleum Geologists)
- Series Volume or Issue Number
- 3
- Other Numbering System Name
- Caltech Division of Geological and Planetary Sciences
- Other Numbering System Identifier
- 1139