Early Miocene extension in the southern Stillwater Range of west-central Nevada

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5099654

Hudson, M R ^[1]; John, D A; McKee, E H ^[2]

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1. Geological Survey, Denver, CO (United States)
2. Geological Survey, Menlo Park, CA (United States)

Paleomagnetic data, geologic mapping, and K-Ar dating document a short-lived but intense early Miocene period of extension in the southern Stillwater Range of west-central Nevada. Tertiary rocks in this area include (1) intracaldera ash-flow turfs, lavas, and subjacent plutons comprising the [approx]29-Ma Job Canyon caldera and the 25-Ma Elevenmile and Poco Canyon calderas, (2) 25- to 21-Ma post-caldera silicic dikes and domes, and (3) unconformably overlying 15- to 13-Ma mafic to intermediate lavas. An earlier period of extension, however, tilted the 29- to 25-Ma tuffs, lavas, and plutons 60--70 [degree] west and east in the northern and southern parts of the area, respectively. Paleomagnetic directions from these rocks are strongly deflected from an expected Miocene direction in senses appropriate for their tilt. A tilt-corrected mean direction for these rocks, however, suggests that they were also affected by a 42[degree] [+-] 12[degree] component of counterclockwise vertical-axis rotation that may have accompanied tilting. This early deformation was probably concurrent with emplacement of 25- to 21-Ma dikes and domes because uncorrected remanence directions from 14 sites from these rocks are closer to expected directions than the uncorrected directions from the steeply tilted 29- to 25-Ma rocks. High dispersion of site mean directions from the dikes and domes probably reflects their emplacement through much of the early deformation period. Thus deformation was mostly restricted to 25--21 Ma. Most faults that accommodated the deformation are cryptic due to the thick and heterogeneous nature of units in the southern Stillwater Range, but initially they must have dipped steeply and cut deeply to expose as much as 10 km of crustal section.

• OSTI ID: 5099654
• Report Number(s): CONF-9305259--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ALKALI METAL ISOTOPES
ARGON ISOTOPES
CALDERAS
CENOZOIC ERA
DEFORMATION
DEVELOPED COUNTRIES
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FORMATIONS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRATA
GEOLOGIC STRUCTURES
GEOLOGY
GEOMETRY
INCLINED STRATA
ISOTOPE DATING
ISOTOPES
MAGNETISM
MATHEMATICS
MIOCENE EPOCH
NEVADA
NORTH AMERICA
ORIENTATION
PALEOMAGNETISM
POTASSIUM ISOTOPES
TECTONICS
TERTIARY PERIOD
USA