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Videotapes from 23 camera stations in the northern Bering Sea provide a unique view of the formation and modification of primary sedimentary structures in the marine environment. The study area is a shallow-water (<35 m) ridge and swale terrane located west of Seward Peninsula and south of Bering Strait, Alaska. Strong, north-flowing, unidirectional currents of Alaskan coastal water dominate the region. Ancillary information collected at each station includes bottom samples, surface-to-bottom current-meter and light-transmission data, and high-resolution seismic reflection and sidescan sonar records.
Ridges exhibit 5 to 10 m of relief and are mantled by fine to medium, moderately well-sorted detrital sand. Bed forms observed on ridge crests and flanks include wave and current ripples and two populations of sand waves (^lgr^cong15 m and ^lgr^cong200 m). Videotapes recorded atop sand ridges show modification of ripples in response to oscillatory bottom currents. Observations of
small bottom-dwelling fish escaping from bottom ripples provide evidence of penecontemporaneous bioturbation of sedimentary structures. Ripple migration and bottom transport of many starfish occur as a result of strong (>25 cm/sec) bottom currents. Swales between sand ridges are covered predominantly with mud, generally devoid of bed forms, and contain local patches of shell accumulations. Current speeds are reduced (<15 cm/sec) and strongly asymmetric in the swale areas. The videotapes show the transport of fine-grained sediment and organic material in suspension and the formation of burrows, trackways, and trails by benthic organisms (crabs, worms, and shrimp).
The information conveyed by these videotapes is useful for interpreting primary sedimentary structures in adjacent lithofacies of ancient epicontinental-shelf deposits.
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