West 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 years. 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, owing to difficulties encountered 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 1,300 feet. Uvigerina subperegrina and Cyclammina sp. in the channel fill attest to this depth during the time of deposition of the Rosedale Sandstone.

The ecology of the foraminifer Epistominella "Pulvinulinella" gyroidinaformis in the lower Fruitvale Shale, the regional stratigraphy suggesting little or

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no uplift, and the comparatively short time interval between cutting and filling indicate that erosion was not effected in the subaerial environment; therefore the channel was eroded entirely in the marine environment at a depth greater than 1,500 feet.

Cores from the Rosedale Sandstone exhibit many characteristics analogous to turbidites. Turbidity currents or gravity flows of sediment caused the erosion. Downcutting was facilitated by the poor induration of the lower Fruitvale Shale.

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