Lamont-Doherty geophysical program On Eltanin ...
References Gordon, A. L. 1971a. Eltanin Cruise 44. Antarctic Journal of the U.S., VI (1) : 16-18. Gordon, A. L. 1971b. Antarctic polar front zone. Antarctic Research Series, 15: 205-222.
Gordon, A. L. In press a. Spreading of Antarctic Bottom Water, II. In: Studies in Physical Oceanography: A Tribute to G. Wiist on his 80th Birthday. New York,
Gordon and Breach. Gordon, A. L. In press b. Interaction of the Antarctic Circumpolar Current and the Macquarie Ridge. Antarctic Research Series.
Jacobs, S. S., P. M. Bruchhausen, and E. B. Bauer. 1970a. Eltanin Reports, Cruises 32-36. Palisades, New York, Lamont-Doherty Geological Observatory. Jacobs, S. S., A. F. Amos, and P. M. Bruchhausen. 1970b. Ross Sea oceanography and Antarctic Bottom Water forma tion. Deep-Sea Research, 17(6) : 935-962.
Lamont-Doherty geophysical program On Eltanin Cruises 44, 45, 47, and 47A R. E. HOUTZ
Lamont-Doherty Geological Observatory Columbia University The Lamont-Doherty geophysics group aboard Eltanin achieved 98 percent coverage of the total ship's track with underway geophysical data. The data include seismic, magnetic, and gravity measurements. The seismic system includes two heavy-duty Rix air compressors to drive a Lamont-Doherty airgun sound-source. The signal is received by a towed hydrophone array that is assembled aboard. The signal is recorded on a Lamont-Doherty drum recorder and an E PC Laboratories continuous recorder. Expendable radio sonobuoys are launched to record wide-angle reflection and refraction data to measure sound speed in the sediments and upper crustal layers. The sonobuoys are provided by the U.S. Navy as surplus items. The signal is received with a Communications Electronics FM receiver and played out on the seismic recorder. The gravity system includes an Askania gravi meter mounted on an Anschutz gyro-table, a small Lamont-Doherty analog computer, and recorders. The magnetics data are sensed and recorded by Varian equipment. The sensor is towed about 200 m astern. Precession frequencies are counted and converted to analog and digital tape punch recordings. In addition to recording geophysical data, the geophysics group also has responsibility for digitizing topographic data, computing the ship's adjusted track, and reconciling this information with the primary gophysical data. These tasks are performed with a shipboard IBM 1130 computing system. September—October 1971
Cruise 44 was a hydrographic cruise with underway geophysics data acquired between stations. The Macquarie Ridge and Solandcr Trough south of New Zealand were studied in detail. An east-west crossing of a major fracture zone at 58°S. and a crossing of the Southeast Indian Rise at 120°E. provided fundamental geophysical data relating to seafloor spreading and plate tectonics. Submarine geology and piston-coring were emphasized during Cruise 45, with underway geophysics data being obtained between stations. Seismic data were consulted frequently during the coring operations to judge penetrability and to identify areas of geologic interest. Additional crossings of the Southeast Indian Rise, the Diarnantina Fracture Zone, and the Natural iste Plateau were completed. Cruise 47, although multidisciplinary, was the first comprehensive geophysical survey of the Kerguelen Plateau south to the Antarctic Circle. Profiler data revealed complex tensional faulting and very thick sediments (1 to 2 km near the crest of the plateau). Sonobuoys achieved penetration through 4 km of sediment in the Enderby abyssal plain. A prominent sediment ridge and numerous slump features exist along the eastern edge of the plateau. A short geophysical cruise was carried out in the south-central Tasman Sea. This part of the Tasman is a problem area in terms of plate tectonics, and the numerous trans-Tasman crossings (one-half degree apart in latitude) will provide geophysical data for at least a partial solution.
Studies of Eltanin dredged rocks N. D. WATKINS
Graduate School of Oceanography University of Rhode Island Examination of Eltanin-dredged rocks from the collection up through Cruise 27 has now been completed. The following constitutes the results obtained: Paleomagnetic, petrological, and geochemical properties. Watkins et al. (1970) used a large pillow basalt fragment taken during Cruise 5 from a seamount in the Drake Passage to demonstrate the effect of rapid quenching on the magnetic and opaque mineralogical properties of submarine basalts. Watkins and Paster (1971) used basalt samples from Cruises 5, 15, 21, 24, and 25 as part of an extensive investigation of the magnetic and petrological properties of submarine igneous rocks. Watkins and Gunn (1971) have included measurements of the magnetic properties in an analysis of dredged rocks from the Macquarie Ridge collected during Cruises 16, 26, and 27. 167
Composition of the dredge hauls. The variation in distribution of the various rock types recovered, which are dominantly ice-rafted in origin, has been examined using trend-surface analysis. It was shown that the Scotia Sea materials were derived mainly from the Weddell Sea and the east coast of the Antarctic Peninsula (Watkins and Self, 1971). Similar methods have been used to analyze the possible source regions, and to delineate areas of probable in situ fractions, in the subantarctic regions of the South Pacific (Watkins and Self, in press). No further studies of the Eltanin-dredged rocks are planned by the author. References Watkins, N. D., T. Paster, and J . Ade-Hall. 1970. Variation of magnetic properties in a single deep-sea pillow basalt. Earth and Planetary Science Letters, 8: 322-328.
and B. M. Gunn. 1971. Petrology, geochemistry, and magnetic properties of some rocks dredged from the Macquarie Ridge. New Zealand Journal of Geology and Geophysics, 14: 153-168.
and T. Paster. 1971. The magnetic properties of igneous rocks from the ocean floor. Royal Society of London. Philosophical Transactions. A, 268: 507-550. and R. Self. 1971. An examination of the Eltanin dredged rocks from the Scotia Sea. Antarctic Research Series, 15: 327-343.
and R. Self. In press. A description of the Eltanin dredged rocks from high latitudes of the South Pacific.
Proceedings of the Second Conference on Antarctic Geology and Geophysics, Oslo, August, 1970.
Marine origin of sands in the Weddell Sea JOHN
Department of Geology Florida State University In 1969, as part of the International Weddell Sea Oceanographic Expedition, sea-bottom cores were obtained near Berkner Island that contained thick units of sand. Similar sands were first collected and described by W. H. Littlewood in 1957. Size analysis and electron microscope studies led Rex et al. (1970) t9 conclude that nearby sands represent ancient dune and beach deposits. This conclusion was based on the presence of Eolian surface features on individuai grains, characteristic size and sorting values, and paucity of rock flour in the sands. Rex et al. (1970, p. 3466) suggest that these sands were "exposed at th surface during an interglacial period when the antarctic land surface stood approximately 300 in with respect to sea level, than it does today." Five cores taken during the 1969 cruise penetrated sands in this area. Maximum penetration was 312 cm in core G-12, taken at 252 in depth near the ice shelf. Cores G-8, G-11 5 G-13, and G-16 were collected on the slope at 512, 585, 659, and 1,033 meters, respectively (see fig.). These cores contain sand bodies ranging in thickness from 15 to 75 cm. Sands are moderately to well sorted, fine- to medium-grained, and exhibit both Eolian and glacial surface textures. Graded bedding, the presence of a small, mixed shallow and deep water fauna, and diminution in grain size away
Weddell Sea oceanographic research 1971 L. R. A. CAPURRO
60W
168
40W
20W
BATHYMETRY COURTESY OF DR. THOR KVINGE 6OS
Department of Oceanography Texas A&M University During January and February 1971, 22 oceanographic stations were occupied in the Weddell Sea aboard the icebreaker General San Martin as a continuation of the systematic survey initiated during the International Weddell Sea Oceanographic Expedition. Physical and chemical measurements were carried out at each of the stations. The data have already been processed and are being analyzed together with information collected during the previous years. Current measurements were made while the ship was docked to the fast ice of the Filchner Ice Shelf, at General Belgrano Base. The measurements were made with Richardson current meters at a depth of 50 m and with surface float during a period of 12 hours. The ice conditions hampered this work. This work has been carried out jointly with the Argentine Hydrographic Office.
B. ANDERSON
OO N000
. - p
AO°
c:,
%J WEDDELL SEA
65S
1 /
111
cp
7OS
0
100
SOUNDING: IN METERS
00
.......:LOCATION OF CORES
5OW
3OW
Locations of cores taken from the Weddell Sea in 1969 and 190 that contained sand. Sand bodies were 15 to 166 cm thick.
ANTARCTIC JOURNA
Gordon, A. L. In press a. Spreading of Antarctic Bottom Water, II. In: Studies in Physical Oceanography: A Tribute to G. Wiist on his 80th Birthday. New York,
Gordon and Breach. Gordon, A. L. In press b. Interaction of the Antarctic Circumpolar Current and the Macquarie Ridge. Antarctic Research Series.
Jacobs, S. S., P. M. Bruchhausen, and E. B. Bauer. 1970a. Eltanin Reports, Cruises 32-36. Palisades, New York, Lamont-Doherty Geological Observatory. Jacobs, S. S., A. F. Amos, and P. M. Bruchhausen. 1970b. Ross Sea oceanography and Antarctic Bottom Water forma tion. Deep-Sea Research, 17(6) : 935-962.
Lamont-Doherty geophysical program On Eltanin Cruises 44, 45, 47, and 47A R. E. HOUTZ
Lamont-Doherty Geological Observatory Columbia University The Lamont-Doherty geophysics group aboard Eltanin achieved 98 percent coverage of the total ship's track with underway geophysical data. The data include seismic, magnetic, and gravity measurements. The seismic system includes two heavy-duty Rix air compressors to drive a Lamont-Doherty airgun sound-source. The signal is received by a towed hydrophone array that is assembled aboard. The signal is recorded on a Lamont-Doherty drum recorder and an E PC Laboratories continuous recorder. Expendable radio sonobuoys are launched to record wide-angle reflection and refraction data to measure sound speed in the sediments and upper crustal layers. The sonobuoys are provided by the U.S. Navy as surplus items. The signal is received with a Communications Electronics FM receiver and played out on the seismic recorder. The gravity system includes an Askania gravi meter mounted on an Anschutz gyro-table, a small Lamont-Doherty analog computer, and recorders. The magnetics data are sensed and recorded by Varian equipment. The sensor is towed about 200 m astern. Precession frequencies are counted and converted to analog and digital tape punch recordings. In addition to recording geophysical data, the geophysics group also has responsibility for digitizing topographic data, computing the ship's adjusted track, and reconciling this information with the primary gophysical data. These tasks are performed with a shipboard IBM 1130 computing system. September—October 1971
Cruise 44 was a hydrographic cruise with underway geophysics data acquired between stations. The Macquarie Ridge and Solandcr Trough south of New Zealand were studied in detail. An east-west crossing of a major fracture zone at 58°S. and a crossing of the Southeast Indian Rise at 120°E. provided fundamental geophysical data relating to seafloor spreading and plate tectonics. Submarine geology and piston-coring were emphasized during Cruise 45, with underway geophysics data being obtained between stations. Seismic data were consulted frequently during the coring operations to judge penetrability and to identify areas of geologic interest. Additional crossings of the Southeast Indian Rise, the Diarnantina Fracture Zone, and the Natural iste Plateau were completed. Cruise 47, although multidisciplinary, was the first comprehensive geophysical survey of the Kerguelen Plateau south to the Antarctic Circle. Profiler data revealed complex tensional faulting and very thick sediments (1 to 2 km near the crest of the plateau). Sonobuoys achieved penetration through 4 km of sediment in the Enderby abyssal plain. A prominent sediment ridge and numerous slump features exist along the eastern edge of the plateau. A short geophysical cruise was carried out in the south-central Tasman Sea. This part of the Tasman is a problem area in terms of plate tectonics, and the numerous trans-Tasman crossings (one-half degree apart in latitude) will provide geophysical data for at least a partial solution.
Studies of Eltanin dredged rocks N. D. WATKINS
Graduate School of Oceanography University of Rhode Island Examination of Eltanin-dredged rocks from the collection up through Cruise 27 has now been completed. The following constitutes the results obtained: Paleomagnetic, petrological, and geochemical properties. Watkins et al. (1970) used a large pillow basalt fragment taken during Cruise 5 from a seamount in the Drake Passage to demonstrate the effect of rapid quenching on the magnetic and opaque mineralogical properties of submarine basalts. Watkins and Paster (1971) used basalt samples from Cruises 5, 15, 21, 24, and 25 as part of an extensive investigation of the magnetic and petrological properties of submarine igneous rocks. Watkins and Gunn (1971) have included measurements of the magnetic properties in an analysis of dredged rocks from the Macquarie Ridge collected during Cruises 16, 26, and 27. 167
Composition of the dredge hauls. The variation in distribution of the various rock types recovered, which are dominantly ice-rafted in origin, has been examined using trend-surface analysis. It was shown that the Scotia Sea materials were derived mainly from the Weddell Sea and the east coast of the Antarctic Peninsula (Watkins and Self, 1971). Similar methods have been used to analyze the possible source regions, and to delineate areas of probable in situ fractions, in the subantarctic regions of the South Pacific (Watkins and Self, in press). No further studies of the Eltanin-dredged rocks are planned by the author. References Watkins, N. D., T. Paster, and J . Ade-Hall. 1970. Variation of magnetic properties in a single deep-sea pillow basalt. Earth and Planetary Science Letters, 8: 322-328.
and B. M. Gunn. 1971. Petrology, geochemistry, and magnetic properties of some rocks dredged from the Macquarie Ridge. New Zealand Journal of Geology and Geophysics, 14: 153-168.
and T. Paster. 1971. The magnetic properties of igneous rocks from the ocean floor. Royal Society of London. Philosophical Transactions. A, 268: 507-550. and R. Self. 1971. An examination of the Eltanin dredged rocks from the Scotia Sea. Antarctic Research Series, 15: 327-343.
and R. Self. In press. A description of the Eltanin dredged rocks from high latitudes of the South Pacific.
Proceedings of the Second Conference on Antarctic Geology and Geophysics, Oslo, August, 1970.
Marine origin of sands in the Weddell Sea JOHN
Department of Geology Florida State University In 1969, as part of the International Weddell Sea Oceanographic Expedition, sea-bottom cores were obtained near Berkner Island that contained thick units of sand. Similar sands were first collected and described by W. H. Littlewood in 1957. Size analysis and electron microscope studies led Rex et al. (1970) t9 conclude that nearby sands represent ancient dune and beach deposits. This conclusion was based on the presence of Eolian surface features on individuai grains, characteristic size and sorting values, and paucity of rock flour in the sands. Rex et al. (1970, p. 3466) suggest that these sands were "exposed at th surface during an interglacial period when the antarctic land surface stood approximately 300 in with respect to sea level, than it does today." Five cores taken during the 1969 cruise penetrated sands in this area. Maximum penetration was 312 cm in core G-12, taken at 252 in depth near the ice shelf. Cores G-8, G-11 5 G-13, and G-16 were collected on the slope at 512, 585, 659, and 1,033 meters, respectively (see fig.). These cores contain sand bodies ranging in thickness from 15 to 75 cm. Sands are moderately to well sorted, fine- to medium-grained, and exhibit both Eolian and glacial surface textures. Graded bedding, the presence of a small, mixed shallow and deep water fauna, and diminution in grain size away
Weddell Sea oceanographic research 1971 L. R. A. CAPURRO
60W
168
40W
20W
BATHYMETRY COURTESY OF DR. THOR KVINGE 6OS
Department of Oceanography Texas A&M University During January and February 1971, 22 oceanographic stations were occupied in the Weddell Sea aboard the icebreaker General San Martin as a continuation of the systematic survey initiated during the International Weddell Sea Oceanographic Expedition. Physical and chemical measurements were carried out at each of the stations. The data have already been processed and are being analyzed together with information collected during the previous years. Current measurements were made while the ship was docked to the fast ice of the Filchner Ice Shelf, at General Belgrano Base. The measurements were made with Richardson current meters at a depth of 50 m and with surface float during a period of 12 hours. The ice conditions hampered this work. This work has been carried out jointly with the Argentine Hydrographic Office.
B. ANDERSON
OO N000
. - p
AO°
c:,
%J WEDDELL SEA
65S
1 /
111
cp
7OS
0
100
SOUNDING: IN METERS
00
.......:LOCATION OF CORES
5OW
3OW
Locations of cores taken from the Weddell Sea in 1969 and 190 that contained sand. Sand bodies were 15 to 166 cm thick.
ANTARCTIC JOURNA
