Assembling and Disassembling California: A Zircon and Monazite Geochronologic Framework for Proterozoic Crustal Evolution in Southern California

Abstract

The Mojave province in southern California preserves a comparatively complete record of assembly, postorogenic sedimentation, and rifting along the southwestern North American continental margin. The oldest exposed rocks are metasedimentary gneisses and amphibolite, enclosing intrusive suites that range from tonalite and quartz monzodiorite to granite with minor trondhjemite. Discrete magmatic episodes occurred at approximately 1790-1730 and 1690-1640 Ma. Evidence from detrital and premagmatic zircons indicates that recycling of 1900-1790 Ma Paleoproterozoic crust formed the unique isotopic character of the Mojave province. Peak metamorphic conditions in the Mojave province reached middle amphibolite to granulite facies; metamorphism occurred locally from 1795 to 1640 Ma, with widespread evidence for metamorphism at 1711-1689 and 1670-1650 Ma. Structures record early, tight to isoclinal folding and penetrative west-vergent shear during the final metamorphic event in the west Mojave province. Proterozoic basement rocks are overlain by siliciclastic-carbonate sequences of Mesoproterozoic, Neoproterozoic, and Cambrian age, recording environmental change over the course of the transition from stable Mojave crust to the rifted Cordilleran margin. Neoproterozoic quartzites have diverse zircon populations inconsistent with a southwest North American source, which we infer were derived from the western conjugate rift pair within Rodinia, before establishment of the miogeocline. Neoproterozoic-Cambrian miogeoclinal clastic rocks record an end to rifting and establishment of the Cordilleran miogeocline in southern California by latest Neoproterozoic to Early Cambrian time.

Detrital zircon provenance and paleogeography of the Pahrump Group and overlying strata, Death Valley, California

“…Informal units KP1-KP4 from Prave, 1999;MacDonald et al (2013). Basement age constraints from Lanphere et al (1964), Labotka et al (1980), Barth et al (2001Barth et al ( , 2009, and Iriondo et al (2004). Ediacaran-Cambrian boundary from Corsetti and Hagadorn (2000).…”

“…Four unconformity-bounded tectonostratigraphic packages have been previously described. The Crystal Spring Formation represents the oldest package, constrained in age by underlying basement (1760-1400 Ma; Wasserburg et al, 1959;Labotka et al, 1980;Barth et al, 2001Barth et al, , 2009. It is intruded by diabase sills, which yield U-Pb baddeleyite ages of 1087 ± 3 Ma and 1069 ± 3 Ma (Heaman and Grotzinger, 1992).…”

“…Detailed provenance analysis from early studies was significantly hindered by small datasets and an incomplete understanding now available of the complexity of the surrounding basement provinces (e.g. Barth et al, 2009;Strickland et al, 2013;Holland et al, 2013). Overall, the data presented herein dramatically expand the understanding of the provenance history for Mesoproterozoic through Neoproterozoic time along the southwestern margin of Laurentia, in the period leading to the development of the Cordilleran passive margin (e.g.…”

“…"2400-2700 Ma DZ paragneiss" refers to detrital zircons of this age derived from supracrustal paragneisses (from Barth et al, 2009;Doe et al, 2012;Strickland et al, 2013;Holland et al, 2013). and Miller, 1990;Karlstrom and Humphreys, 1998;Barth et al, 2000;Bryant et al, 2001;Coleman et al, 2002;Barth et al, 2009;Nelson et al, 2011;Karlstrom and Williams, 2012;Strickland et al, 2013). Similar ages are known from both the Yavapai and Mazatzal crustal provinces (see Fig.…”

“…5). This age is representative of local Mojave Province basement (Wasserburg et al, 1959;Wooden and Miller, 1990;Karlstrom and Humphreys, 1998;Barth et al, 2000;Bryant et al, 2001;Coleman et al, 2002;Barth et al, 2009;Nelson et al, 2011;Karlstrom and Williams, 2012;Strickland et al, 2013), yet this system must have received input from a quartzite unit, as a majority of the clasts present in the basal conglomerate are composed of metasedimentary quartzites. Several quartzite units with similar detrital zircon age-spectra are reported across the Mojave Province (e.g.…”