--> Abstract: Tertiary Sedimentation in the Sacramento Pass Basin, East-Central Nevada: Implications for the Evolution of Extensional Detachment Faults in the Basin and Range, by C. M. Martinez; #90925 (1999)

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MARTINEZ, CYNTHIA M., Stanford University, Dept. of Geological and Environmental Sciences, Stanford, CA

Abstract: Tertiary Sedimentation in the Sacramento Pass Basin, East-Central Nevada: Implications for the Evolution of Extensional Detachment Faults in the Basin and Range

The Sacramento Pass basin, east-central Nevada, is a Miocene-age basin formed above a low angle detachment fault near the Snake Range metamorphic core complex. Sediments in the basin include alluvial fan/playa lake facies of conglomerate and lacustrine limestone and marl interfingered with brecciated paleozoic rock-avalanche deposits. Sedimentation began after 30.77 +/- 0.18 Ma (40Ar/39Ar dating of biotite from a rhyolite flow at the base of the section). The age of deposition of the breccia sheets, constrained by rhyolite tuff layers in the section below and above them, is younger than 20.70 +/- 0.18Ma and older than 20.99 +/- 14Ma (40Ar/39Ar dating of biotite). Within error, this shows that rapid implacement of the breccia sheets is coincident with the beginning of a period of slip from 20-16 Ma along the incipient Snake Range decollement (Lee, 1995). Miller, et al. (1999) indentify the period rapid slip at about 17 Ma, from apatite fission track thermochronology studies of the footwall.

Palinspastic reconstruction of the Sacramento Pass basin reveals that its basin geometry does not differ in a significantly from that of basins developed adjacent to high angle faults. The strata show slight fanning of dips towards the basin-bounding fault, with interfingering of coarse clastic and fine-grained facies close to the fault. Though distal exposure of the basin is not available, these relations suggest that the basin may have originated as a high-angle fault bound basin. The low angle geometry of the bounding fault and subsequent exposure of the basin could have occurred during later deformation as a product of continued uplift and deformation in the region. 

AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid