Tectonics and sedimentation of Oligo-Miocene Vasquez Formation, Soledad basin, southern California
Conference
·
· AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)
OSTI ID:5993625
The nonmarine Oligo-Miocene Vasquez Formation represents the earliest sedimentation within the Soledad basin. Basin analysis of this unit provides important clues to the tectonic regimen during the convergent/transform-margin transition in southern California during the mid-Tertiary. The Vasquez crops out in three separate subbasins or depocenters; from south to north, these are the Vasquez Rocks, Texas Canyon, and Charlie Canyon subbasins. Basaltic-andesitic volcanism and rapid subsidence punctuated the initial rifting event which generated the Vasquez Rocks half-graben and Texas Canyon graben. Small, thick alluvial fans were shed into these two subbasins, with sediment derived via erosion of local plutonic, metamorphic, and volcanic source terranes. A minimum of four discrete uplift events generated development of 250 to 600-m thick, upward-fining alluvial megacycles in both the Vasquez Rocks and Texas Canyon depocenters. In the absence of biostratigraphic control, these allocyclic megasequences provide a tangible means of lithostratigraphic correlation between these separate subbasins. A major uplift and drainage basin reorganization event subsequently modified the Vasquez depositional system, facilitating physical interconnection of the two southern subbasins. The northernmost subbasin, Charlie Canyon, is characterized by a single, thick, upward-coarsening alluvial fan sequence. There are no megacycles or clast suites to suggest interconnection with or evolutionary similarities to the other two depocenters. This sedimentologic uniqueness may support a mid-Tertiary palinspastic reconstruction which places the Charlie Canyon region 80-100 km northwest of its current location. Soledad basin rifting and Vasquez sedimentation are consistent with a tectonic model involving lithospheric extension north of the unstable Mendocino triple junction.
- Research Organization:
- Univ. of California, Los Angeles
- OSTI ID:
- 5993625
- Report Number(s):
- CONF-870606-
- Conference Information:
- Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 71:5
- Country of Publication:
- United States
- Language:
- English
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