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Oxygen-isotope and paleomagnetic stratigraphy of Pacific core V28-239 late pliocene to latest pleistocene
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Oceanographic Abstracts
SERGEANT D. E., 1976. History and present status of populations of harp and hooded seals. BioL Conserv., 10 (2): 95-118. The biology of harp (Pagophilus groenlandicus Erxleben) and hooded (Qestophora cristata Erxleben) seals is described. These abundant species inhabit the seasonally-shifting pack ice of the North Atlantic. Intensive hunting over 150 years depleted but did not exterminate three harp seal populations, which initially may have totalled some 9 million animals and may now total some 3 millions. All are now hunted under quotas and other restrictions. One population is rising and the other two, while probably still declining slowly, are probably close to stability. Knowledge of hooded seals is less advanced; one of three major sub-populations has only recently been rediscovered after 150 years. These populations are more closely interconnected than populations of harp seals, and management of hooded seals seems likely to need a wider framework than exists at present SESSIONS M . H . , T. P. BARNETT and W, S. WILSON, 1976. The airborne expendable bathythermograph. Deep-Sea
Res., 23 (8): 779-782. The Airborne Expendable Bathythermograph (AXBT) system is described. Results of extensive calibrations and field tests are presented. It is shown that with proper calibration these devices are a useful oceanographic research tool with temperature accuracies of a few tenths of a degree Celsius. SHACKLETON N . J . and N. D. OPDYKE, 1976. Oxygen-isotope and paleomagnetic stratigraphy of Pacific core V28-239 Late Pliocene to latest Pleistocene. Mem. Geol. Soc. Am., 145: 449-464. V28-239 core from cruise 28 of R/V Vema preserves a detailed oxygen-isotope and paleomagnetic record for all of the Pleistocene Epoch. The entire 21-m-long core has been analyzed at 5-cm intervals, Glacial stage 22, above the Jaramillo magnetic event, may represent the first major Northern Hemisphere continental glaciation of middle Pleistocene character. Prior to this, higher frequency glacial events extend to near the level of the Olduvai magnetic event. Glacial events of less regular frequency extend to the bottom of the core, which represents late Pliocene time. Fluctuations in carbonate dissolution intensity occur throughout the core with a similar frequency to the oxygen-isotope fluctuations. SOMAYAJULU B. L. K. and H. CRAIG, 1976. Particulate and soluble 85. Also in: Earth planet. Sci. Letts, 32 (2): 268-276.
21°pb activities in the deep sea. GEOSECSPubL,
Particulate and soluble 21o Pb activities have been measured by filtration of large-volume water samples at two stations in the South Atlantic. Particulate phase 21°Pb (caught by a 0.4-/am filter) varies from 0.3% of total 21°Pb in equatorial surface water to 15% in the bottom water. The "absolute activity" of 2~°Pb per unit mass of particulate matter is about 10 7 times the activity of soluble 21o Pb per unit mass of water, but because the mass ratio of particulate matter to water is about 10 -s, the particulate phase carries only about 10% of the total activity. In Antarctic surface water the particulate phase carries 40% of the total 2~°Pb activity: the absolute activity of this material is about the same as in other water masses and the higher fraction is due to the much larger concentration of suspended matter in surface water in this region. In the equatorial Atlantic the particulate phase 21o Pb activity increases with depth, by a factor of 40 from surface to bottom and by a factor of 4 from the Antarctic Intermediate Water core to the Antarctic Bottom Water. This increase with depth is predicted by our previously proposed particulate scavenging model which indicated a scavenging residence time of 50 years for 210 Pb in the deep sea. A scavenging experiment showed that red clay sediment removes all the 21°Pb from seawater in less than a week. The Antarctic particulate profile shows little or no evidence of scavenging in this region, which may be due to the siliceous nature of the particulate phase in circumpolar waters. Our previous observation that the 21°Pb/226 Ra activity ratio is of the order of 0.5 in the deep water is further confirmed by the two South Atlantic profiles analyzed in the present work. SOPER N . J . , C. DOWNIE, A. C. HIGGINS and L. 1. COSTA, 1976. Biostratigraphic ages of Tertiary basalts on the east Greenland continental margin and their relationship to plate separation in the northeast Atlantic. Earth planet. ScL Letts, 32 (2): 149-157. Palynohigical evidence indicates that the 4 - 5 X 10 s k m a pile of tholeiitic basalts on the central east Greenland coast was erupted in latest Palaeocene (late Landenian) and earliest Eocene (early Ypresian) time. Assignment of a precise numerical age of this interval is not yet possible, but it is evident that the eruptive episode was completed within about 3 m y. The effusion rate was at least an order of magnitude faster than the current Icelandic rate. Marine horizons at the base and top of the pile show that its build-up was accompanied by concomitant crustal depression. It is argued that this major volcanic episode marks tire initiation of plate separation between Greenland and northwest Europe. Implications with regard to spreading chronology and the magnetic polarity time scale are discussed.
Oceanographic Abstracts
SERGEANT D. E., 1976. History and present status of populations of harp and hooded seals. BioL Conserv., 10 (2): 95-118. The biology of harp (Pagophilus groenlandicus Erxleben) and hooded (Qestophora cristata Erxleben) seals is described. These abundant species inhabit the seasonally-shifting pack ice of the North Atlantic. Intensive hunting over 150 years depleted but did not exterminate three harp seal populations, which initially may have totalled some 9 million animals and may now total some 3 millions. All are now hunted under quotas and other restrictions. One population is rising and the other two, while probably still declining slowly, are probably close to stability. Knowledge of hooded seals is less advanced; one of three major sub-populations has only recently been rediscovered after 150 years. These populations are more closely interconnected than populations of harp seals, and management of hooded seals seems likely to need a wider framework than exists at present SESSIONS M . H . , T. P. BARNETT and W, S. WILSON, 1976. The airborne expendable bathythermograph. Deep-Sea
Res., 23 (8): 779-782. The Airborne Expendable Bathythermograph (AXBT) system is described. Results of extensive calibrations and field tests are presented. It is shown that with proper calibration these devices are a useful oceanographic research tool with temperature accuracies of a few tenths of a degree Celsius. SHACKLETON N . J . and N. D. OPDYKE, 1976. Oxygen-isotope and paleomagnetic stratigraphy of Pacific core V28-239 Late Pliocene to latest Pleistocene. Mem. Geol. Soc. Am., 145: 449-464. V28-239 core from cruise 28 of R/V Vema preserves a detailed oxygen-isotope and paleomagnetic record for all of the Pleistocene Epoch. The entire 21-m-long core has been analyzed at 5-cm intervals, Glacial stage 22, above the Jaramillo magnetic event, may represent the first major Northern Hemisphere continental glaciation of middle Pleistocene character. Prior to this, higher frequency glacial events extend to near the level of the Olduvai magnetic event. Glacial events of less regular frequency extend to the bottom of the core, which represents late Pliocene time. Fluctuations in carbonate dissolution intensity occur throughout the core with a similar frequency to the oxygen-isotope fluctuations. SOMAYAJULU B. L. K. and H. CRAIG, 1976. Particulate and soluble 85. Also in: Earth planet. Sci. Letts, 32 (2): 268-276.
21°pb activities in the deep sea. GEOSECSPubL,
Particulate and soluble 21o Pb activities have been measured by filtration of large-volume water samples at two stations in the South Atlantic. Particulate phase 21°Pb (caught by a 0.4-/am filter) varies from 0.3% of total 21°Pb in equatorial surface water to 15% in the bottom water. The "absolute activity" of 2~°Pb per unit mass of particulate matter is about 10 7 times the activity of soluble 21o Pb per unit mass of water, but because the mass ratio of particulate matter to water is about 10 -s, the particulate phase carries only about 10% of the total activity. In Antarctic surface water the particulate phase carries 40% of the total 2~°Pb activity: the absolute activity of this material is about the same as in other water masses and the higher fraction is due to the much larger concentration of suspended matter in surface water in this region. In the equatorial Atlantic the particulate phase 21o Pb activity increases with depth, by a factor of 40 from surface to bottom and by a factor of 4 from the Antarctic Intermediate Water core to the Antarctic Bottom Water. This increase with depth is predicted by our previously proposed particulate scavenging model which indicated a scavenging residence time of 50 years for 210 Pb in the deep sea. A scavenging experiment showed that red clay sediment removes all the 21°Pb from seawater in less than a week. The Antarctic particulate profile shows little or no evidence of scavenging in this region, which may be due to the siliceous nature of the particulate phase in circumpolar waters. Our previous observation that the 21°Pb/226 Ra activity ratio is of the order of 0.5 in the deep water is further confirmed by the two South Atlantic profiles analyzed in the present work. SOPER N . J . , C. DOWNIE, A. C. HIGGINS and L. 1. COSTA, 1976. Biostratigraphic ages of Tertiary basalts on the east Greenland continental margin and their relationship to plate separation in the northeast Atlantic. Earth planet. ScL Letts, 32 (2): 149-157. Palynohigical evidence indicates that the 4 - 5 X 10 s k m a pile of tholeiitic basalts on the central east Greenland coast was erupted in latest Palaeocene (late Landenian) and earliest Eocene (early Ypresian) time. Assignment of a precise numerical age of this interval is not yet possible, but it is evident that the eruptive episode was completed within about 3 m y. The effusion rate was at least an order of magnitude faster than the current Icelandic rate. Marine horizons at the base and top of the pile show that its build-up was accompanied by concomitant crustal depression. It is argued that this major volcanic episode marks tire initiation of plate separation between Greenland and northwest Europe. Implications with regard to spreading chronology and the magnetic polarity time scale are discussed.