High Sierra terrane, oceanic and continental-rise sedimentary and volcanic rocks
High Sierra terrane, oceanic and continental-rise sedimentary and volcanic rocks
Late Triassic(?) to Mississippian(?) (Silurian(?)
Occurs in the Paiute Meadows, Saddlebag Lake, Mount Dana, and Ritter Range roof pendants. In the Saddlebag Lake and Mount Dana roof pendants, unit consists of highly deformed and thrust-imbricated deep-marine to continental-rise rocks. Major lithologies are chert, phyllite, siltstone, quartzite, conglomerate, arkosic sandstone, minor limestone, local volcaniclastic sandstone, and pillow basalt. In the eastern Ritter Range pendant, unit consists of a highly-deformed sequence of black chert, siliceous argillite and slate, and minor calc-silicate hornfels. Unconformably overlain by unit HSV. In the Ritter Range pendant, unit is named the chert-argillite unit (Green and others, 1997). In the Mount Dana and Saddlebag Lake roof pendants, unit is named the Lewis sequence (Kistler, 1966). In the Saddlebag Lake pendant, unit is correlated by Schweickert and Lahren (1993, 2006) with the Candelaria, Diablo, and Palmetto Formations in the Roberts Mountain allochthon. This correlation is precluded by late Paleozoic fossils (Brook and others, 1979) and Late Triassic detrital zircon MDAs. The upper part of this unit may correlate with the coeval and stratigraphically similar Late Triassic sedimentary member of the Walker Lake terrane (unit WLS) to the north.
In the easternmost Paiute Meadows pendant, Chesterman (1975) mapped this unit as interleaved metavolcanics and metasediments of the Virginia Lakes sequence, along with serpentinite and diorite. Cao (2016) reports a detrital zircon MDA of ~355 Ma from these rocks. In the Saddlebag Lake pendant, Brook and others (1979) report a fossil assemblage from marble interbedded in chert suggestive of a Mississippian age. Farther south, near Tioga Pass, Ardill and others (2020) report a detrital zircon MDA of ~435 Ma (Silurian) from metachert-argillite of this unit. In the Ritter Range pendant, Attia and others (2020) report zircon U-Pb ages of ~216 and ~233 Ma from hypabyssal volcanic rocks that plot within this unit, although near the margin with, and probably part of, the overlying unit (HSV). Brook and others (1979) report fossils from chert in this area suggestive of a Mississippian age.