Cache Peak Volcanics
Cache Peak Volcanics
middle(?) to early Miocene
Consists of hypabyssal intrusions, pyroclastic flow and fall deposits, and lava flows, interbedded with lesser arkosic to volcaniclastic sedimentary strata in the Tehachapi Mountains in southern map area.
Hypabyssal intrusions consist of dikes, plugs, sills, and domes, which intrude basement units, the Witnet Formation (map unit wit), and lower sections of the Cache Peak Volcanics sequence (e.g., Dibblee, 1967; Saleeby and Saleeby, 2019).
Volcanic deposits consist of pyroclastic flow and fall deposits (some with pumice lapilli), lava flows (some vesicular and amygdaloidal), and volcanic breccias (e.g., Quinn, 1987; Saleeby and Saleeby, 2019). Compositions range from basalt to rhyolite, with silicic compositions primarily in the volumetrically dominant pyroclastic deposits.
Sedimentary strata are commonly tuffaceous and consist of arkosic to volcanic lithic sandstone, pebble to cobble conglomerate, siltstone, mudstone, and minor local (basal?) sedimentary breccia (e.g., Dibblee, 1967; Quinn, 1987).
Proportions of hypabyssal intrusions, extrusive volcanics, and sedimentary strata vary across mapped locations, with intrusive units dominant in the proximal northern area, sedimentary strata dominant in the distal southwestern area (where they are mapped as kin and bop), and volcanics dominant in the intervening region. Volcanics are interbedded with the Kinnick Formation (map unit kin) and lower(?) Bopesta Formation (map unit bop). The boundaries between this unit and the distal map units kin and bop are gradational rather than discrete, though depicted as lines on the map.
Lower to central part of section is intruded by an 18.63 ± 0.55 Ma dacite dike and includes two ash-flow tuffs with Ar-Ar plagioclase dates of 18.34 ± 0.20 Ma and 17.57 ± 0.13 Ma (Saleeby and Saleeby, 2019).