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Metadata
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ID
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T-1-69-BS
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Also Known As
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69ANC
TT042
Cruise_42
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Abstract
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Chief Scientist: Joe Creager. Geological and Geophysical
data (sparker, airgun, echosounder, VanVeengrab, Shipekgrab,
gravitycore, transmissometer) of field activity T-1-69-BS in
Chukchi Sea-Bering Sea continental shelf, between St. Matthew
and St.Lawrence Island and Alaska from 08/19/1969 to
09/12/1969
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Project/Theme
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Chukchi Sea - Bering Sea Continental Shelf
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Chief Scientist
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Joe Creager
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Activity Type
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Geological and Geophysical
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Platform
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Thomas G. Thompson
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Area of Operation
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Chukchi Sea-Bering Sea continental shelf, between St. Matthew and St.
Lawrence Island and Alaska
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Location map
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Bounding Coordinates
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65.75000
160.25000 -155.25000
50.25000
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Dates
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08/19/1969 (JD 231) to 09/12/1969 (JD 255)
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Analog Materials
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list
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Index map
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Crew
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Joe Creager
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Chief Scientist, Univ of WA
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Mark Holmes
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Cruise Leader, Univ of WA
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E. Baker
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Radio Operator, Univ of WA
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S. Barnes
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Scientific Watch and Photographer, Univ of WA
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K. Duff
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Scientific Watch, Univ of WA
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R. J. Echols
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Coring Watch and Recorder, Univ of WA
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J. Kummer
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Scientific Watch, Univ of WA
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D. R. Morrison
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Coring Supervisor, Univ of WA
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R. Nishimori
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Scientific Watch, Univ of WA
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R. W. Roberts
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Watch Chief, Univ of WA
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N. Silverberg
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Watch Chief, Univ of WA
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C. S. Smyth
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Scientific Watch and Computer Operator, Univ of WA
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J. Svensson
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Scientific Watch, Univ of WA
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R. Sylwester
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Electronic Technician, Univ of WA
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N. Varney
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Scientific Watch, Univ of WA
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K. Von Bock
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Watch Chief, Univ of WA
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V. Walsh
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Scientific Watch, Univ of WA
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Equipment Used
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sparker
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airgun
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echosounder
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VanVeengrab
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Shipekgrab
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gravitycore
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transmissometer
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Purpose
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To provide the field collections
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necessary to interpret the stratigraphic history of the sediments
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deposited during a major marine transgression across a continental
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shelf-coastal plain complex. The area represents an excellent model
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for the study of transgressive sedimentary sequences because of its
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simplicity in sediment thickness, age, and marker horizons. The
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sediment, predicted to average no greater than 10 to 15 m, can be
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collected fully with presently available coring equipment where the
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sediment is soft, and yet it is thick enough to provide detail of
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sedimentologic events over the 20,000-year Holocene transgression.
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Because of the importance of the area covered by this cruise to the
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studies of the Bering Land Bridge and the migration of man to the
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New World, it is hoped that it will be of use in interpreting the
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paleotopography of the land bridge surface and the times of
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inundation.
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Information to be Derived
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Summary
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Shallow-penetrating continuous seismic profiling (using a 3.5-khz
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system, 150-joule sparker, and 1000- and 2000-joule air guns) and precision echo
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sounding were planned to permit continuous monitoring of the changing thickness
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of unconsolidated sediment. The 3.5-khz system was never successfully operated
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because of malfunctioning of the equipment as supplied by the manufacturer. The
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air gun was operated over about half of the total track, and the 150-joule
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sparker was operated almost continuously. The precision echo-sounding system was
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operated continuously. Continuous reduction of the data permitted tentative
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location of buried Pleistocene drainage channels. A great deal of reduction and
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interpretation remains, however, because the upper 15 m of the sediments
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contained as many as six reflectors in some areas. Wherever the subbottom
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reflectors indicated a thickened section of unconsolidated sediment, the bottom
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was cored at least to the first major reflector and, where possible, through a
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number of reflectors. As was the case during past cruises, the suspected
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interfluves were covered by thinner sediment layers that were significantly more
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difficult to core. The area east of 172 degrees W was apparently covered by more
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recent coarser grained sands and silts, which make coring difficult and which
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reduce the amount of subbottom penetration of acoustic energy. The buried
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channels detected in the western part of the survey area were cored; the length
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of the piston core barrel was varied at each station until maximum penetration
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was attained. Additionally Van Veen or Shipek grab samples and gravity cores
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were obtained at no greater than 56-km intervals along the cruise track.
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Transmissometer measurements of suspended sediments were made along the leg
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between Nunivak and Northeast Cape, St. Lawrence Island. One 20-foot piston core
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assembly and one transmissometer were lost. Approximately 7200 km of track were
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run, with the precision echo sounder continously in use. Approximately 4700 km
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of sparker profiles and 2200 km of air-gun profiles were made.158 stations were
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occupied, with grab samples collected at all stations and gravity cores
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collected at 92 stations. Piston cores were collected at 44 stations.
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Notes
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Cruise conducted by the University of Washington
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Department of Oceanography, Seattle, Washington. Information is
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from the "Preliminary Report RV Thomas G. Thompson Cruise 42" by
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J.S. Creager and D.A. McManus, M69-80, September 1969
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Got Help?
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For T-1-69-BS, we would appreciate any information on -- contract, days at sea, dive count, funding, information specialist, kms of navigation, national plan, NGDC Info, organization, owner, ports, project number, publications, scanned materials, seismic description, station count, station description, submersible, tabulated info.
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