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Analysis of approximately 700 km of high-resolution 3.5-kHz seismic profiles taken aboard the R/V Endeavor during the summer of 1980 indicates several distinct and sometimes puzzling features on the floor of the northern Hatteras Abyssal Plain. The basic pattern of echo character is perpendicular to rather than parallel with the axis of the plain, extending in bands across the plain almost to the Bermuda Rise. This banding may be the result of very low-relief fans extending across the basin from entry points at the Hatteras, Wilmington, and perhaps Hudson Canyon mouths. A series of terracelike features slopes gently seaward to form the western boundary between the abyssal plain and lower continental rise hills. Each terrace has a length of 5 to 10 km and an approximate re ief of 5 m at its seaward boundary. Whether this 50-km wide boundary zone has been formed by boundary currents, intraformational faulting, or fan development is not clear. Distinct lensoidal deposits 200 to 500 m long and less than 5 m thick are sparsely distributed west of the Hatteras Canyon mouth. These acoustically transparent lenses lie in shallow channels and closely resemble debris-flow deposits; however, their small size and sparse distribution do not suggest that they are laterally continuous. These anomalous sedimentary features will be more intensively studied during the summer of 1981.
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