Older metavolcanic rocks
Older metavolcanic rocks
Late Jurassic to Late Triassic, ~150-233 Ma
Occurs in Ritter Range, Mount Goddard, and Oak Creek roof pendants. In the eastern Ritter Range roof pendant, highly varied unit composed of metamorphosed crystal-lithic tuff, metarhyolite to metabasalt pyroclastic units, tuff breccia, tuffaceous sandstone and siltstone, thin-layered calcareous tuffaceous rocks, marble, slate, rare conglomerate, and mafic flows and hypabyssal intrusives. Kistler and Swanson (1981) report two whole rock Rb-Sr isochron ages of ~185 Ma from the unit in this area, and Huber and Rinehart (1965) reported Early Jurassic pelecypod fossils.  However, detailed studies by Barth and others (2018) and Attia and others (2020) reveal a pattern of zircon U-Pb ages ranging from ~152-233 Ma (plus one outlying age of ~101 Ma) that suggest tightly folded Triassic and Jurassic rocks, plus a narrow infolded layer of the overlying Cretaceous metavolcanics (unit SHKOV) too small to show at scale. In the western Ritter Range pendant, this unit is largely metamorphosed pyroclastic strata with interlayered flow rock and hypabyssal intrusives, with zircon U-Pb ages of ~150-158 Ma (plus an outlier age of ~102 Ma that indicates an infolded or infaulted body of the overlying Cretaceous metavolcanic rocks; Attia and others, 2020). In Mount Goddard and Oak Creek roof pendants, chiefly metamorphosed rhyolite to dacite ash-flow tuff, andesite, and basalt volcaniclastic rocks and flows. Local metaandesite and metabasalt flows, and local thin layers of pelitic schist, calc hornfels, and minor quartzite. In the Oak Creek pendant, this unit has yielded zircon U-Pb ages of ~165-166 Ma (Saleeby and others, 1990), whereas in the Goddard roof pendant ages are ~131-159 Ma (Chen and Moore, 1979; Tobisch and others, 1986). This unit also crops out in the Alabama Hills, where it is locally schistose metatuff, meta-volcanogenic sedimentary rocks, and lesser meta-volcanic flow rock, which has yielded minimum U-Pb ages of ~167 Ma and ~170 Ma (Dunne and Walker, 1993; Dunne and others, 1998), along with small bodies of similar metatuff to the west along the east edge of the Mount Whitney 15’ Quadrangle, near Mount Bago in the southwestern part of the Mountt Pinchot 15’ Quadrangle, and to the south at Braley Creek in the Olancha 15’ Quadrangle.
Unit is highly metamorphosed and multiply deformed with minor and major isoclinal folds. Locally contains narrow bands of mylonite schist. Unit is broadly coeval with metavolcanic rocks of High Sierra terrane but contains quite different stratigraphy. Unit faulted against High Sierra terrane to east along Gem Lake fault (Gem Lake shear zone of Green and Schweickert, 1995). Also faulted against the Owens terrane to east, though note that unit SCGG intrudes the Owens terrane in the Oak Creek pendant. Unit stratigraphically underlies Monarch arc (unit SHKOV, SHKOG, Gmw, and Gbvc) that is only weakly schistose with primary textures predominant. The Early to Late Jurassic part of this unit is magmatically linked to roughly coeval shallow intrusive rocks (unit SCGG) and the Palisade Crest Intrusive Suite (unit Gpc), which, together with coeval rocks in the High Sierra terrane (unit HSV) make up the Goddard arc.  Triassic and earliest Jurassic rocks in this unit, along with coeval rocks in the High Sierra (unit HSV) and Twin Lakes (unit TL) terranes and the Scheelite Intrusive Suite, make up the High Sierra arc