Evidence for Mojave-Sonora megashear—Systematic left-lateral offset of Neoproterozoic to Lower Jurassic strata and facies, western United States and northwestern Mexico

Abstract

Major successions as well as individual units of Neoproterozoic to Lower Jurassic strata and facies appear to be systematically offset left laterally from eastern California and western Nevada in the western United States to Sonora, Mexico. This pattern is most evident in units such as the "Johnnie oolite," a 1-to 2-m-thick oolite of the Neoproterozoic Rainstorm Member of the Johnnie Formation in the western United States and of the Clemente Formation in Sonora. The pattern is also evident in the Lower Cambrian Zabriskie Quartzite of the western United States and the correlative Proveedora Quartzite in Sonora. Matching of isopach lines of the Zabriskie Quartziteand Proveedora Quartzite suggests ~700-800 km of left-lateral offset. The offset pattern is also apparent in the distribution of distinctive lithologic types, unconformities, and fossil assemblages in other rocks ranging in age from Neoproterozoic to Early Jurassic. In the western United States, the distribution of facies in Neoproterozoic and Paleozoic strata indicates that the Cordilleran miogeocline trends north-south. A north-south trend is also suggested in Sonora, and if so is compatible with offset of the miogeocline but not with the ideas that the miogeocline wrapped around the continental margin and trends east-west in Sonora. An imperfect stratigraphic match of supposed offset segments along the megashear is apparent. Some units, such as the "Johnnie oolite" and Zabriskie-Proveedora, show almost perfect correspondence, but other units are signifi cantly different. The differences seem to indicate that the indigenous succession of the western United States and offset segments in Mexico were not precisely side by side before offset but were separated by an area-now buried, eroded, or destroyed-that contained strata of intermediate facies.

Arc and Slab-Failure Magmatism in Cordilleran Batholiths II – The Cretaceous Peninsular Ranges Batholith of Southern and Baja California

“…This conclusion, coupled with the likelihood that fragments of Laurentia such as the Antler platform of the Great Basin region and Caborca terrane in Sonora (Ketner 1986;Gastil et al 1991;Stewart 2005;Hildebrand 2009Hildebrand , 2013Premo et al 2010) were probably derived from the southwest corner of Laurentia in what is the present day Mexico region and incorporated within the Cordilleran Ribbon Continent, possibly during the transition from Pangea B to A (Irving 1977(Irving , 2004Kent and Muttoni 2003), serves to complicate correlations and detrital zircon studies. Terranes derived from the southwest corner of North America should contain North American flora and fauna, but also large quantities of Grenville age zircon reflecting their proximity to that belt, which was rich in Grenvillian basement (Hoffman 1989).…”

“…12) and the thrust beltcontains distinctive Neoproterozoic and Paleozoic strata that are a detailed match for strata found today in eastern California-western Nevada (Stewart 2005) and in the San Bernardino Mountains near Los Angeles (Cameron 1982;Stewart et al 1984). Crystalline basement is also exposed within the terrane west of the thrust belt in Sonora, where it comprises 1725-1696 Ma orthogneiss, tabular granitoid bodies (Nourse et al 2005), and anorthositic complexes dated at around 1100 Ma (Espinoza et al 2003).…”

Arc and Slab-Failure Magmatism in Cordilleran Batholiths I – The Cretaceous Coastal Batholith of Peru and its Role in South American Orogenesis and Hemispheric Subduction Flip

“…earlier at 100 Ma, and a bit farther west than the Laramide deformational front, the Santiago GEOSCIENCE CANADA Peak-Alisitos arc of the Peninsular Ranges batholith -built upon a varied basement, ranging in age from Proterozoic to Jurassic (Shaw et al 2014;Premo et al 2014;Kistler et al 2014), and torn from the western margin of the ribbon continent at about 140 Ma (Lawton and McMillan 1999;Mauel et al 2011;Peryam et al 2012) -collided with a west-facing Lower Cretaceous carbonate platform, known as the Guerrero-Morelos platform in the south and the Sonoran shelf in the north (LaPierre et al 1992;Monod et al 1994;González-Léon et al 2008). Because the basement within the arc terrane contained fragments of crust, such as the Antler platform and Caborca terrane (Ketner 1986;Gastil et al 1991;Stewart 2005;Hildebrand 2009Hildebrand , 2013Premo et al 2010), derived from the ribbon continent, and ultimately from the 'lost' SW corner of North America, possibly during the transition from Pangea B to A (Irving 1977;Kent and Muttoni 2003;Irving 2004), make arguments tying the Guerrero superterrane to North America prior to the Laramide non-definitive. Terranes derived from this part of Laurentia should contain large quantities of Grenville age zircon grains reflecting their proximity to that belt, which was rich in Grenvillian basement (Hoffman 1989).…”

The Triassic/Jurassic boundary and the Jurassic stratigraphy and biostratigraphy of northern Sonora, northwest Mexico

“…R. suessi of the Crickmayi Zone . Sequence X overlies to sequence IX with an erosional surface of at least 10 m in a lateral distance of less than 1 km that forms the Triassic-Jurassic contact in this locality , 2005 and references therein). The lowermost part of sequence X consists of a 2 to 2.4 m thick, base-erosive, coarse-grained to pebbly sandstone ( Figure 9F) that grades to its upper part to calcareous sandstone with bivalves, belemnoids, cephalopods and the ammonite Sunrisites sunrisesnsis.…”

“…In most of this region, these basement rocks are overlain by miogeoclinal carbonate and siliciclastic strata from Neoproterozoic to Paleozoic ages (Stewart, 2005). Some of the main events that affected this region and shaped the Mesozoic history include truncation of the Proterozoic and Paleozoic rocks in a northwest-southeast direction during the late Paleozoic (Stevens et al, 2005 and references therein).…”