A Caltech Library Service

Late Jurassic dike swarms in the southwestern Sierra Nevada Foothills terrane, California: Implications for the Nevadan orogeny and North American plate motion

Wolf, Michael B. and Saleeby, Jason B. (1995) Late Jurassic dike swarms in the southwestern Sierra Nevada Foothills terrane, California: Implications for the Nevadan orogeny and North American plate motion. In: Jurassic Magmatism and Tectonics of the North American Cordillera. Special papers (Geological Society of America). No.299. Geological Society of America , Boulder, CO, pp. 203-228. ISBN 9780813722993.

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item:


A previously unrecognized sheared dike swarm has been identified in a southern fragment of the western Foothills terrane—the Owens Mountain area of the western Sierra Nevada foothills, northeast of Fresno, California. It may be the southern extension of the Bear Mountains fault zone. The dike swarm, sheeted in places, consists predominantly of tonalitic tabular bodies and coeval, mutually cross-cutting tonalitic and mafic dikes. Textures and fabrics within the dike swarm range from partially recrystallized igneous to strongly deformed metamorphic tectonites, implying that dike emplacement occurred during ductile deformation. Mylonitization has transposed layering parallel to foliation and has greatly thinned many of the dikes. Layering and foliation dip subvertically and strike NNW–SSE. Post-tectonic annealing has destroyed most microscopic shear indicators, but macroscopic intrafolial folds are common and have steeply southeast-plunging fold axes and S-fold geometries that may indicate a sinistral sense of shear. Age data (U-Pb zircon) from the tonalites reveal that emplacement and crystallization occurred over a 7-m.y. period, from 155 Ma to 148 Ma, at an estimated depth of 10 km (from AlTotal in hornblendes). A correlation between age and degree of deformation and recrystallization of the tonalites implies syntectonic dike emplacement. Intrusion began within 5 m.y. of deposition of the strata into which the dikes were emplaced. Granitic dikes that cut the complex at 123 Ma are nondeformed. The duration of the Nevadan orogeny is shown to have lasted from Late Jurassic to Early Cretaceous (160–137 Ma and possibly to 123 Ma) and thus is more protracted that has been postulated. The regional tectonics of the Owens Mountain and other Cordilleran dike swarms can be related in a broad dynamic sense to the absolute motion of North America by using the apparent polar wander (APW) analysis of May and Butler (1986). The Nevadan orogeny may be the manifestation of drastic changes in magnitude and direction of North American motion (from ~45 km/m.y. to the NNE to ~200 km/m.y. to the NW; May and Butler, 1986). The Late Jurassic dike swarms record a complex pattern of sinistral-sense transtension-transpression that may have developed at the J2 APW cusp (ca. 150 Ma; see May and Butler, 1986) and during subsequent, rapid northwestward acceleration of North America.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Additional Information:© 1995 Geological Society of America. Manuscript accepted by the Society September 23, 1994. This work was supported by NSF grants EAR 8904063 and EAR 9105692. The field work could not have been done without the permission and hospitality of the many ranch owners in the area, especially Morgan Blasingame. The field work was supported in part by Penrose and Sigma Xi grants. The mapping in the present study was based in part on reconnaissance work done by Bill Power (unpublished data, 1980). Mahmood Chaudhry helped with the zircon separation procedures, Yigal Erel helped with DCP analyses, and Joe Kirschvink helped with Figure 10 projections. Reviews by Scott Paterson and Doug Walker greatly improved the manuscript.
Funding AgencyGrant Number
NSFEAR 8904063
NSFEAR 9105692
Geological Society of America Penrose Bequest Research GrantsUNSPECIFIED
Sigma-Xi Grants in Aid of ResearchUNSPECIFIED
Series Name:Special papers (Geological Society of America)
Issue or Number:299
Record Number:CaltechAUTHORS:20140904-134127101
Persistent URL:
Official Citation:Michael B. Wolf and Jason B. Saleeby Late Jurassic dike swarms in the southwestern Sierra Nevada Foothills terrane, California: Implications for the Nevadan orogeny and North American plate motion Geological Society of America Special Papers, 1995, 299, p. 203-228, doi:10.1130/SPE299-p203
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49248
Deposited By: Tony Diaz
Deposited On:05 Sep 2014 23:29
Last Modified:10 Nov 2021 18:41

Repository Staff Only: item control page