Tectonic Significance of Gravity and Aeromagnetic Investigations at the Head of the Gulf of California
1972; Geological Society of America; Volume: 83; Issue: 10 Linguagem: Inglês
10.1130/0016-7606(1972)83[3103
ISSN1943-2674
Autores Tópico(s)Methane Hydrates and Related Phenomena
ResumoResearch Article| October 01, 1972 Tectonic Significance of Gravity and Aeromagnetic Investigations at the Head of the Gulf of California JOHN R SUMNER JOHN R SUMNER Department of Geophysics, Stanford University, Stanford, California 94305 AUTHOR'S PRESENT ADDRESS: DEPARTMENT OF GEOLOGICAL SCIENCES, LEHIGH UNIVERSITY, BETHLEHEM, PENNSYLVANIA 18015 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1972) 83 (10): 3103–3120. https://doi.org/10.1130/0016-7606(1972)83[3103:TSOGAA]2.0.CO;2 Article history received: 17 Sep 1971 rev-recd: 01 Mar 1972 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOHN R SUMNER; Tectonic Significance of Gravity and Aeromagnetic Investigations at the Head of the Gulf of California. GSA Bulletin 1972;; 83 (10): 3103–3120. doi: https://doi.org/10.1130/0016-7606(1972)83[3103:TSOGAA]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract To investigate the morphology of an incipient spreading center and associated transform faults, aeromagnetic and gravity surveys were made of the region at the head of the Gulf of California. The Salton Trough and Gulf of California have formed, with inevitable accompanying tectonic complexities, as two large plates of the Earth's crust have moved diagonally apart relative to one another.Reconnaissance geology of the area shows that the ranges, which trend northwesterly approximately parallel to the Salton Trough, contain biotite and hornblende schist, granitic gneiss, granitic rocks, and widely scattered mesa-forming volcanic rocks. The Sierra del Pinacate of Sonora is a Quaternary shield volcano composed of olivine basalt which covers more than 1,500 km2 of the pre-Quaternary terrain.The Bouguer anomaly map constructed from the gravity survey shows that anomalies range from −7 to −35 mgals over bedrock exposures to −40 to −55 mgals over the centers of alluvial basins. Interpretation of the gravity data shows that basins northeast of the Salton Trough trend northwesterly and are from 0.25 to 1.25 km deep. No northeast-trending grabens, which would locate a spreading center, were located by the gravity survey. The total field, residual magnetic map constructed from an aeromagnetic survey ranges from 600γ over basalt and some gneiss to 50γ over the deeper alluvial basins. The magnetic anomalies trend predominantly to the northwest, in reflection of the structural grain in the area. Measurements of susceptibilities and remanent magnetizations of rock samples provide constraints for geologic models constructed from magnetic profiles.Interpretation of the geophysical data indicates that a vertical offset in the basement of ~3 km separates the southeastern extension of the Salton Trough from the area to the northeast. This vertical offset represents the continuation of a strike-slip fault from the northwest. The magnetic data also show that at least two of the basins in Arizona contain extensive buried sheets of basalt. The Pinacate lava field lies at the intersection between an east-northeasterly magnetic trend and the primary northwesterly magnetic trend. The cause of the east-northeasterly cross trend is not known, but could be due to basement deformations not detected by the gravity survey, or basaltic dikes, which intrude along a zone extending from the northern gulf to the Pinacate lava field. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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