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Extension directions in the Colorado River extensional corridor compared to fragmentation of a structurally disrupted caldera in the Sacramento Mountains, southeastern California

December 31, 2020

The northwest trend of the southern Colorado River extensional corridor in the southwestern USA veers northward between 34° and 35° north latitude. The tilt axes of early Miocene west-tilted volcanic strata in the west-central Sacramento Mountains mirror this bend. Steeply dipping early Miocene strata and volcanics north and south of the bend indicate the strong respectively westward to southwestward tilt of detached fault blocks and probably of the detachment fault on which they are  superposed. These fault panels include fragments of the 18.8 Ma Peach Spring Tuff’s (PST) source caldera. The PST occurs in two major detached fault domains in the Sacramento Mountains where outflow facies ignimbrite grades southward into intracaldera facies. The facies transitions, interpreted as part of the PST’s source caldera’s northeastern margin, lie on a northeast extensional azimuth that would restore them to continuity with the Silver Creek caldera in the Black Mountains, AZ, 50 km to the northeast. This extensional vector agrees with some but not other indicators of extension azimuth such as fault striae, ductile lineations, tilt axes, and elongated plutons. The new results imply spatial variability of extension direction and raise questions about the how this variability may relate to the bend in the Colorado River extensional corridor.

Citation Information

Publication Year 2020
Title Extension directions in the Colorado River extensional corridor compared to fragmentation of a structurally disrupted caldera in the Sacramento Mountains, southeastern California
DOI
Authors Keith A. Howard, Charles A. Ferguson
Publication Type Conference Paper
Publication Subtype Conference Paper
Series Title
Series Number
Index ID 70223185
Record Source USGS Publications Warehouse
USGS Organization Geology, Minerals, Energy, and Geophysics Science Center

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