--> Influences of Episodes of Structural Deformation on Southern Sierra Nevada – Southeastern San Joaquin Basin Source-to-Sink Systems

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Influences of Episodes of Structural Deformation on Southern Sierra Nevada – Southeastern San Joaquin Basin Source-to-Sink Systems


Two major episodes of structural deformation of the southern Sierra Nevada (SSN) and adjacent southern San Joaquin Basin (SSJB) strongly influenced the development of source-to-sink depositional systems. Regional extension of the SSN in the early Miocene led to the consolidation of drainage into a single major channel that entered the SSJB through the newly formed Edison graben. The input of large volumes of sediment into the basin from the graben led to the development of new deltaic, shelf, slope, and basin floor depositional sites. In the model of MacPherson (1978), by late Miocene, uplift on the Bakersfield arch led to the main fluvial conduit switching to the location of the modern Kern River Gorge. However, subsurface mapping in the SSJB and petrographic and detrital zircon study by Saleeby and others (2016) confirm that the Edison conduit remained the primary source of SSJB sediments through the Pliocene Evidence from the SSJB supports a second major regional structural deformation episode in the Pleistocene that is coincident with the primary sediment supply shifting to the modern location of the Kern River. Deposition in the Elk and Buena Vista Hills area of the SSJB was continuous from the Miocene until the middle Pleistocene, and near the top of the section are lakebed deposits in the Tulare Formation about 1.8 to 1.4 Ma in age. Davis (2020) maps these lakebed intervals (and their coarse-grained equivalents) of the Tulare across the SSJB and notes the section younger than the lakebeds exhibits many components that have a structural influence. These components include uplift of Elk and Buena Vista Hills, growth of the Paloma anticline, uplift of the Bakersfield arch, and creation of a deep basin at the south end of the SSJB. Additional structural deformation at this time included the rapid growth of the San Emigdio fold and thrust belt, and the uplift of the basin’s eastern margin. Taken together, the location and style of deformation suggests the development of a new fold and thrust belt – foreland basin – forebulge system, oriented WSW to ENE across the SSJB. Uplift led to the abandonment of the Edison conduit and development of a new major deposition route coincident with today’s Kern River, which in the Pleistocene actively eroded the uplifted sedimentary section on the Bakersfield arch and transported sediments to the foredeep basin at the foot of the fold and thrust belt.