Late Cretaceous-Paleocene Extensional Collapse and Disaggregation of the Southernmost Sierra Nevada Batholith

Abstract

Geobarometric studies have documented that most of the metasedimentary wall rocks and plutons presently exposed in the southernmost Sierra Nevada batholith south of the Lake Isabella area were metamorphosed and emplaced at crustal levels significantly deeper (~15 to 30 km) than the batholithic rocks exposed to the north (depths of ~3 to 15 km). Field and geophysical studies have suggested that much of the southernmost part of the batholith is underlain along low-angle faults by the Rand Schist. The schist is composed mostly of metagraywacke that has been metamorphosed at relatively high pressures and moderate temperatures.

Salinia revisited: a crystalline nappe sequence lying above the Nacimiento fault and dispersed along the San Andreas fault system, central California

“…a mélange of lithostratigraphic units that have resulted from tectonic deformation). The Salinian basement consists of highly shattered detachment sheets, a series of allochthonous sheets, or nappes (Wood and Saleeby 1997;Chapman et al 2010, figure 2). It can be argued that the limit of resolution of the basement beneath the Maricopa embayment ( Figure 9A) is owing to the structural and stratigraphic complexity of these shattered tectonostratigraphic units or detachment sheets -the structural and stratigraphic complexity of the mélange of these nappes largely defines the boundaries of the eastern boundary of Salinia.…”

“…There is no root zone for a Pastoria thrust in the resolved native area of its upper plate, just a mid-crustal hole that was exhumed rapidly at ca. 85 Ma , figure 9) with structural overprints that are typical of exhumed lower plate source areas for large detachment sheets (Wood and Saleeby 1997). The fault has been considered a thrust fault (May 1989;Pitchett and Saleeby 1993;Kellogg et al 2008) and/or a regional latest Cretaceous, extensional detachment fault (Wood and Saleeby 1997; Basement dextral offset appears to greatly exceed late Cenozoic sinistral offset -critical for palinspastic restoration of the basement.…”

“…85 Ma , figure 9) with structural overprints that are typical of exhumed lower plate source areas for large detachment sheets (Wood and Saleeby 1997). The fault has been considered a thrust fault (May 1989;Pitchett and Saleeby 1993;Kellogg et al 2008) and/or a regional latest Cretaceous, extensional detachment fault (Wood and Saleeby 1997; Basement dextral offset appears to greatly exceed late Cenozoic sinistral offset -critical for palinspastic restoration of the basement. The White Wolf fault has also been considered to be a sinistral fault [Stein and Thatcher (1981), late Miocene to Quaternary movement; Ross (1986Ross ( , 1989) with a SE dip; Bartow (1991); Bawden (2001) with a 75 • SW dip; Saleeby et al 2007, figure 1, and E side-up (Nadin and Saleeby 2010)].…”

“…The northern margin of Salinia, as shown in Figure 2B, corresponds to a well-mapped detachment system named the Jawbone Canyon-Blackburn Canyon faults (Wood and Saleeby 1997;. Southern Great Valley strata bury the northeastern margin of Salinia ( Figure 2B), and Salinia is interpreted as the trailing edge of a single massive, or series, of detached extensional nappe(s).…”

Lithospheric mantle duplex beneath the central Mojave Desert revealed by xenoliths from Dish Hill, California

“…In this scenario, the high-e Nd peridotite suites identified beneath Dish Hill would be representative for individual slab fragments successively attached to the continent. [Carl et al, 1991;Applegate and Hodges, 1995;Wood and Saleeby, 1998;Wells et al, 2005]. Stage 3 illustrates final slab removal, possibly triggered by break off upon slab window initiated at $28-30 Ma.…”