Triassic plutonism in southern California: Southward younging of arc initiation along a truncated continental margin

A. P. Barth; R. M. Tosdal; J. L. Wooden; K. A. Howard

doi:10.1029/96tc03596

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Triassic plutonism in southern California: Southward younging of arc initiation along a truncated continental margin

A. P. Barth·R. M. Tosdal·J. L. Wooden·K. A. Howard

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Abstract

Earliest Cordilleran magmatism in the southwestern United States is recorded by a belt of Triassic plutons that intrude Proterozoic basement of the Mojave crustal province and its cratonal/miogeoclinal cover. The belt extends from the western Mojave Desert through the Transverse Ranges to the Colorado River trough. Triassic plutons are predominantly alkali-calcic, Fe- and Sr-enriched quartz monzodiorites and monzonites. The northern part of the belt is composed of two older plutonic suites (241–231 Ma) which are high K to shoshonitic; the southern part of the belt is a younger (218–213 Ma), sodic-alkalic suite. The plutonic record in southern California suggests a short-lived, southward younging continental margin arc setting for emplacement of Triassic plutons, superimposed on a continental margin modified by sinistral transform faulting. Triassic plutonism in this region was followed by a magmatic lull prior to the onset of voluminous Middle to Late Jurassic Cordilleran arc magmatism.

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Source-reported bounding extent: 32.94733586270739° to 35.30646365617464° latitude; -117.9319179036895° to -115.16683761313497° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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A. P. Barth, R. M. Tosdal, J. L. Wooden, K. A. Howard. 1997. Triassic plutonism in southern California: Southward younging of arc initiation along a truncated continental margin. https://doi.org/10.1029/96tc03596

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