Abstract

W. of Bakersfield in the Great Valley of California, 8 wells drilled below the upper Miocene-middle Miocene boundary penetrated an anomalous sequence of middle late Miocene (middle Mohnian) sediments, principally sandstones. These coarse sediments, within the widespread lower Fruitvale Shale of early late Miocene age (early Mohnian), are interpreted to be fill within an early?-middle late Miocene submarine canyon eroded and filled during a time interval of about 700,000 yr. The names, Rosedale Channel and Rosedale Sandstone, are proposed, respectively, for the canyon and the fill. Electric log correlations, microfossil data, and sedimentary characteristics are used for interpretation. Only a remnant of the originally more extensive canyon is described, because of difficulties in the recognition of the headward and seaward extensions. Seismic data are inadequate for recognition. Microfossils show that filling occurred entirely in the marine environment in a depth of water probably greater than 1300 ft. Uvigerina subperegrina and Cyclammina sp. in the channel fill attest to the depth during the time of deposition of the Rosedale Sandstone. Erosion was effected also, entirely in the marine environment, at depths similar to that of the Rosedale Sandstone. The ecology of the Foraminifera in the Rosedale Sandstone and of the foraminifer Epistominella "Pulvinulinella" gyroidinaformis in the eroded lower Fruitvale Shale shows no uplift of the ocean floor to permit subaerial cutting of the Rosedale Channel. Cores from the Rosedale Sandstone show many characteristics analogous with turbidites. Turbidity currents or gravity flows cause the erosion. Downcutting was facilitated by the poor induration of the lower Fruitvale shale.

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