Abstract

A series of broad, symmetrical undulations, between 40 and 60 cm in wavelength and 2 to 4 cm in amplitude, are exposed on the upper surface of a turbidite bed in the Hatch Formation, Finger Lakes area of New York State. The undulations are 12 cm thick, and occur above a graded basal division. They grade upward with decreasing amplitude into parallel laminae. The crests of the undulations are roughly parallel to the sole mark directions. Grain orientation measurements on ten specimens from one undulation show vector means roughly parallel to the crest of the undulation. They are therefore interpreted as longitudinal, not transverse, features. They are named "short crested antidunes", and are referred to the upper flow regime because they occur gradationally between the graded division and lower division of parallel lamination in the turbidite. The current velocity during formation of the antidunes was of the order of 1.5 to 2 m per second.

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