Nature of the crust beneath northwest Basin and Range province from teleseismic receiver function data

Abstract

[1] We utilized teleseismic receiver function techniques complemented by active source refraction seismology to study the crustal structure and continental rift processes responsible for the development of the northwest corner of the Basin and Range province in northwest Nevada. Our passive seismic array of 28 short-period stations, spanning 70 km west to east, and 5 broadband USArray transportable array stations that extended our aperture to 230 km provided data on crustal properties independent of the results of our active source refraction experiment. Combining data from the two experiments provides better constraints on Moho depth, V p /V s ratio, and the structure and composition of the crust beneath the northwestern Basin and Range province than possible from either experiment alone. Our new data indicate Moho depths that vary from 29.5 on the east to 36.5 km in the west along the passive source array and V p /V s ratios that systematically span a wide range from 1.68 to 1.83. Velocity modeling of data collected from the 300 km, wide-angle refraction/reflection survey provides comparable Moho depths of 32-37 km under the same region. Decreasing V p /V s is correlated with decreasing crustal thickness, with V p /V s ratio > 1.80 in northeast California and V p /V s < 1.74 in the thinner crust of the Basin and Range province. We associate the high V p /V s of northeast California with mafic additions to the crust during formation of the Modoc Plateau in a region of accreted Paleozoic island arc terrans similar to those exposed in the eastern Klamaths and northwestern Sierra Nevada. Unusually low V p /V s in conjunction with low absolute V p and V s is observed beneath the central part of our array and may be due to the roots of the Sierra Nevada batholith, now dismembered by Basin and Range faults. Back azimuthal stacking of our receiver function data suggests a northwest oriented crustal anisotropy fast direction beneath this region, parallel to the northwest to southeast oriented Cenozoic extension experienced by the Basin and Range province and suggestive of a similar flow direction in the middle to lower crust.

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“…Both controlled source and earthquake investigations identifi ed crust >35 km thick in the portion of the Basin and Range near the northwestern corner of Nevada, the crust thinning to ~30 km to the east away from the western margin of the province (Lerch et al, 2007;Gashawbeza et al, 2008). These studies in the northwestern portion of the Basin and Range did not identify the same discrete zone of high velocities that was reported to the south by Catchings and Mooney (1991).…”

Depths and temperatures of <10.5 Ma mantle melting and the lithosphere‐asthenosphere boundary below southern Oregon and northern California

“…[] also examined two stations in the Modoc Plateau that yield Moho depths of 35–36 km, a nearly identical result to that of Gashawbeza et al . [], who investigated the Modoc Plateau and areas to the east in the Great Basin. Scattered wave inversion images from a 2‐D teleseismic migration [ Chen et al ., ] also image a prominent Moho at 35 km below the HLP and thickening to 45 km beneath the Owyhee Plateau to the east.…”

“…To calculate the depth and temperature of melt extraction from the mantle for the primitive basaltic lavas, we use a new model for melting variably depleted and metasomatized upper mantle calibrated with plagioclase and spinel lherzolite melting experiments [ Till et al ., ]. The calculated depths of melt extraction are then compared to the location of the Moho and the lithosphere‐asthenosphere boundary (LAB) in the region as constrained by teleseismic receiver function data [ Gashawbeza et al ., ; Eagar et al ., ], Rayleigh wave tomography [ Wagner et al ., ], and seismic refraction surveys [ Leaver et al ., ; Zucca et al ., ], in order to place new constraints on the thickness of the mechanical lithosphere.…”

Multistage Cenozoic extension of the Albion–Raft River–Grouse Creek metamorphic core complex: Geochronologic and stratigraphic constraints

“…1A) is a broad, active continental rift, characterized by northward-striking normal fault blocks formed by east-west extension, a lower crust with subhorizontal seismic refl ectivity, and a sharp Moho at a uniform depth of 28-32 km (e.g., Klemperer et al, 1986;Hauser et al, 1987;Catchings and Mooney, 1991;Catchings, 1992;Gashawbeza et al, 2008). These present-day characteristics are the result of a protracted history of both magmatism and deformation, the details of which elusive and controversial.…”