Pacific Section AAPG, SPE and SEPM Joint Technical Conference

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Preliminary Results Of Geologic Mapping Of The Durwood, Alder Creek, And Rincon Roof Pendants, Sierra Nevada Batholith (Fairview Quadrangle), Tulare County, California


USGS -supported geologic mapping of the Fairview 7.5′ quadrangle in southern Tulare County, southern Sierra Nevada mountains, is shedding light on the structure and stratigraphy of three metasedimentary and metavolcanic roof pendants within the batholith, and the nature of the batholith-cover architecture. The ‘Durwood inlier’ is a Mesozoic(?) metavolcanic and metasedimentary roof pendant similar to those in the Erskine Canyon and Mineral King to the south and north, respectively. It is composed of vertically dipping, moderately deformed and weakly metamorphosed (lower greenschist?) sequence of (from bottom up) metapelite, metavolcanic rocks, marble, and quartzite. The metavolcanic sequence is composed of water-reworked felsic tuffs including at least one primary pyroclastic density current deposit (ignimbrite) with andesitic clasts, peperite, and andesitic sheet-like intrusions. The ‘Alder Creek inlier’ is an Upper Paleozoic(?) metasedimentary sequence composed almost entirely of turbidites and hemipelites. The ‘Rincon inlier’ consists of predominantly Paleozoic and some Mesozoic metapelite and marble sequences. All three inliers are characterized by very low to low regional metamorphic grade (lower greenschist), steeply dipping, north-striking foliation, vertical lineations, and localized contact metamorphism from the engulfing batholith (hornfels and garnetiferous skarns). The Rincon inlier's eastern margin corresponds at least in part with the proto-Kern Canyon Fault where it takes the form of an east-verging, high-angle reverse fault with ultracataclasite. Studies of these inliers are improving our understanding of the assembly of the Sierra Nevada batholith and the role of arc-parallel shear zones in controlling down-warping of supracrustal successions.