JURASSIC INTRUSIVES OF THE COYOTE MOUNTAINS, WESTERN SALTON TROUGH, SOUTHERN CALIFORNIA AND THEIR RELATIONSHIP TO THE NAZAS ARC OF NORTHERN MEXICO

Abstract

Zircon U/Pb dates from several granitic intrusives found in the Coyote Mountains (CMs) range from 164.1 Ma to 138.9 Ma. The CMs magmatic activity is too early to be associated with the Cretaceous magmatic activity of the Peninsular Ranges Batholith (~128-92 Ma) (Hildebrand and Whalen, 2014b and references therein) but is in the age range of the magmatic activity associated with the Jurassic part of the Nazas Arc in northern Mexico (State of Sonora). The Nazas Arc in Sonora is comprised of two episodes of tectonic activity: an earlier episode from ~ 275 to 221 Ma and a second (Jurassic) episode from ~190 to 150 Ma. (González-León et al., 2017 and references therein). The earliest normal faulting that represents a possibly detachment below the CMs is older than ~17 Ma: an age consistent with early Miocene extensional tectonics of the Basin and Range in Sonora. Extensional tectonics and subsidence continue to affect the CMs until the start of right-lateral transtensional faulting and uplift associated with the reorganization of the San Andres Fault System at ~1.1 Ma (Steely et al., 2009). With extension of the Basin and Range in Sonora, followed by right-lateral transtensional faulting, the CMs left Sonora and arrive in the western Salton Trough, next to the Peninsular Ranges Batholith (Morgan and Morgan, 2018b). González-León, C. M., Stanley, Jr., G.D., Lawton, T. F., Pálfy, J., Hodges, M. S., 2017, The Triassic/Jurassic boundary and the Jurassic stratigraphy and biostratigraphy of northern Sonora, northwest Mexico: BOL. SOC. GEOL. MEX., VOL. 69, NO. 3, P. 711 ‒ 173. Morgan, G, J., and Morgan, J. R., 2018b, Extensional Tectonics, a Slab Window and the arrival of the Gulf of California about 17Ma, while the Coyote Mountains of southern California, USA undergo 90° clockwise rotation in Sonora, Mexico: Geological Society of America Abstracts with Programs. Vol. 50, No. 5, ISSN 0016-7592. Steely, A. N., Janecke, S. U., Dorsey, R. J., and Axen, G. J., 2009, Early Pleistocene initiation of the San Felipe fault zone, SW Salton Trough, during reorganization of the San Andreas Fault System: Geological Society of America Bulletin, v. 121, P. 663-687.