Timing of magmatism, basin formation, and tilting at the west edge ofthe Colorado River extensional corridor; results from single-crystal(super 40) Ar/ (super 39) Ar geochronology of Tertiary rocks in theOld Woman Mountains area, southeastern California
Miller, Jonathan S; Heizler, Matthew T; Miller, Calvin F (1998) Timing of magmatism, basin formation, and tilting at the west edge ofthe Colorado River extensional corridor; results from single-crystal(super 40) Ar/ (super 39) Ar geochronology of Tertiary rocks in theOld Woman Mountains area, southeastern California. Journal of Geology, vol.106, no.2, pp.195-209, Mar 1998
| Authors | Miller, Jonathan S; Heizler, Matthew T; Miller, Calvin F |
|---|---|
| Year | 1998 |
| Title | Timing of magmatism, basin formation, and tilting at the west edge ofthe Colorado River extensional corridor; results from single-crystal(super 40) Ar/ (super 39) Ar geochronology of Tertiary rocks in theOld Woman Mountains area, southeastern California |
| Source | Journal of Geology, vol.106, no.2, pp.195-209, Mar 1998 |
| Publisher | University of Chicago Press, Chicago, IL, United States (USA) |
| ISSN | 0022-1376 |
| GeoRef | 1998-032596 |
| Keywords | absolute age; Ar/Ar; basins; California; Cenozoic; Colorado Riverbasin; dates; detachment faults; extension; faults; igneous rocks;isochrons; Little Piute Mountains; magmatism; Miocene; Neogene;neotectonics; Old Woman Mountains; Piute Mountains; San BernardinoCounty California; sedimentary basins; sedimentation; Ship Mountains;single-crystal method; southeastern California; Southern California;tectonics; Tertiary; tilt; United States; volcanic rocks; volcanism |
| DOI | 10.1086/516016 |
Abstract
Tertiary basin development, volcanism, and structural tilting at thewest edge of the Colorado River extensional corridor is examined usingsingle-crystal (super 40) Ar/ (super 39) Ar ages from volcanic rocksin Ship, Piute, Little Piute, and northern Old Woman Mountains (OldWoman Mountains area). Complications in age determination resultingfrom xenocrystic contamination and common excess trapped Ar arereadily circumvented using single-crystal analysis. Preferred agesindicate that the two thickest sections of Tertiary strata, in theShip and Little Piute Mountains, were deposited between about 19-19.5Ma and 17 Ma. The earliest Tertiary magmatism in the area is recordedby a 21 Ma dike from the northern Old Woman Mountains, but no volcanicunits older than 19.3 Ma have been dated. This earliest dikingcorrelates with the initial phases of volcanism to the east in theColorado River trough. Westward tilting of the Little Piute Mountainsoccurred after 17.8 Ma (uppermost tuff), and final westward tilting ofthe Piute Mountains occurred after 18.4 Ma (Peach Springs Tuff) andbefore 16.6 Ma flat-lying dacite. Major rotation of strata in theseareas overlaps a major period of detachment faulting recognized inranges in the Colorado River trough. Basins in the Old Woman Mountainsarea have stratigraphic thicknesses comparable to those observed inthe Colorado River, but unlike basins in the Colorado River trough, anappreciable period of sedimentation preceded volcanism in the OldWoman Mountains area. Differences in sedimentation history and timingof volcanism between the two areas are related to differences in themagnitude of extensional strain and possibly the position of theregional mantle thermal anomaly giving rise to magmatism in theColorado River extensional corridor. West tilting of strata in thenorthernmost Piute Mountains, Goffs Butte occurred after 10.6 Ma andis the youngest documented tilting in the region at this latitude.