Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, Jan 28, 2016
Accumulations of sediment beneath the Antarctic Ice Sheet contain a range of physical and chemica... more Accumulations of sediment beneath the Antarctic Ice Sheet contain a range of physical and chemical proxies with the potential to document changes in ice sheet history and to identify and characterize life in subglacial settings. Retrieving subglacial sediments and sediment cores presents several unique challenges to existing technologies. This paper briefly reviews the history of sediment sampling in subglacial environments. It then outlines some of the technological challenges and constraints in developing the corers being used in sub-ice shelf settings (e.g. George VI Ice Shelf and Larsen Ice Shelf), under ice streams (e.g. Rutford Ice Stream), at or close to the grounding line (e.g. Whillans Ice Stream) and in subglacial lakes deep under the ice sheet (e.g. Lake Ellsworth). The key features of the corers designed to operate in each of these subglacial settings are described and illustrated together with comments on their deployment procedures.
Leg 124 of the Ocean Drilling Project drilled Sites 767 and 770 in the northern Celebes Sea, reac... more Leg 124 of the Ocean Drilling Project drilled Sites 767 and 770 in the northern Celebes Sea, reaching late middle Eocene basaltic basement at both sites. Major shifts in sediment provenance record the changing tectonic setting of the basin. From late middle Eocene into early Miocene time pelagic sedimentation prevailed, with little influence from continental or volcanic arc sources. A major continental influence is first documented in middle Miocene time as a thick sequence of quartzose, mud-rich turbidites accumulated on the deeper basin floor, possibly in response to middle Miocene orogeny in northern Borneo. Terrigenous turbidite deposition waned during the late Miocene as active arc volcanism began to contribute significant amounts of hemipelagic sediment and ash layers, which have remained the dominant basinal sediment to the present. Although the Celebes Sea is now nearly surrounded by volcanic arc terranes, the absence of volcaniclastic sediment in the Eocene to early Miocene section suggests that the basin did not form by back-arc spreading.
Holes were drilled at three Sites in the Sulu Sea on Ocean Drilling Program Leg 124. Site 768 lie... more Holes were drilled at three Sites in the Sulu Sea on Ocean Drilling Program Leg 124. Site 768 lies in the deeper part of the SE sub-basin and Sites 769 and 771 lie on the flanks of the Cagayan ridge. The results indicate that the Sulu Basin originated in the late early Miocene (c.18.8 Ma) in a backarc setting. The Cagayan Ridge was a site of early to early middle Miocene arc volcanism with the deposition of a thick sequence of andesitic to basaltic volcaniclastic deposits. In the basin center an early Miocene pelagic sequence is interrupted by a thick unit of rhyolitic to dacitic pyroclastic flows. Middle to late Miocene sedimentation is more continental in character with thick quartz-rich turbidites in the basin center. Only the hemipelagic claystone related to these terrigenous turbidites were deposited on the Cagayan Ridge. A decrease in the supply of clastic detritus from arc and continental sources and a change in the level of the carbonate compensation depth in the upper Pliocene resulted in pelagic carbonate deposition throughout the late Pliocene and Pleistocene.
Prior to rotary coring, a range of soft-sediment coring tools were deployed to recover the sedime... more Prior to rotary coring, a range of soft-sediment coring tools were deployed to recover the sediment-water interface and the upper few metres of strata, whose integrity was threatened by embedment of the sea riser for drilling of the ANDRILL (AND)-1A/1B holes. These coring options ...
Here we present an initiative for the International Polar Year in 2007/08 to directly investigate... more Here we present an initiative for the International Polar Year in 2007/08 to directly investigate the subglacial environment and geology of Antarctica and Greenland, representing a new frontier in ice sheet research, and a proposal to develop the technology - a hydro-mechanical drill - necessary to obtain rock and sediment samples from beneath deep glacier ice. The Antarctic continent is
Some glacial sediment samples recovered from beneath the West Antarctic ice sheet at ice stream B... more Some glacial sediment samples recovered from beneath the West Antarctic ice sheet at ice stream B contain Quaternary diatoms and up to 10(8) atoms of beryllium-10 per gram. Other samples contain no Quaternary diatoms and only background levels of beryllium-10 (less than 10(6) atoms per gram). The occurrence of young diatoms and high concentrations of beryllium-10 beneath grounded ice indicates that the Ross Embayment was an open marine environment after a late Pleistocene collapse of the marine ice sheet.
Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years1, but... more Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years1, but only recently have these subglacial aqueous environments been recognized as microbial ecosystems that may influence biogeochemical transformations on a global scale2, 3, 4. Here we present the first geomicrobiological description of water and surficial sediments obtained from direct sampling of a subglacial Antarctic lake. Subglacial Lake Whillans (SLW) lies beneath approximately 800 m of ice on the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and evolving subglacial drainage network5. The water column of SLW contained metabolically active microorganisms and was derived primarily from glacial ice melt with solute sources from lithogenic weathering and a minor seawater component. Heterotrophic and autotrophic production data together with small subunit ribosomal RNA gene sequencing and biogeochemical data indicate that SLW is a chemosynthetically driven ecosystem inhabited by a diverse assemblage of bacteria and archaea. Our results confirm that aquatic environments beneath the Antarctic ice sheet support viable microbial ecosystems, corroborating previous reports suggesting that they contain globally relevant pools of carbon and microbes2, 4 that can mobilize elements from the lithosphere6 and influence Southern Ocean geochemical and biological systems7.
During ODP Leg 124, late middle Eocene to Quaternary sediment sequences were recovered from 13 ho... more During ODP Leg 124, late middle Eocene to Quaternary sediment sequences were recovered from 13 holes drilled at five sites in the Celebes and Sulu basins. Paleomagnetic measurements and biostratigraphic studies using calcareous nannofossils, planktonic and benthic foraminifers, radiolarians, and diatoms were completed and summarized here. Two Neogene sediment sections recovered in the Sulu Basin yielded excellent core recoveries and magnetic reversal records, allowing direct magnetobiostratigraphic correlations for the Pliocene and Quaternary at Site 768 and for the middle Miocene to Quaternary at Site 769. The interpolated ages of biohorizons are not consistent between sites and only a few of them are in good agreement with previous calibrations. The differences may be the results of redeposition by turbidity currents and selective dissolution of key fossils.
... 3. Material and methods. Trigger cores (TC) and piston cores (PC) from the polar research shi... more ... 3. Material and methods. Trigger cores (TC) and piston cores (PC) from the polar research shipNathaniel B. Palmer (NBP) cruises of 94-01 and 95-01 in the Ross Sea were selected for analysis (Fig. ... 12, Actinocyclus actinochilus (Ehrenb.) Simonsen, Pliocene–Recent. ...
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, Jan 28, 2016
Accumulations of sediment beneath the Antarctic Ice Sheet contain a range of physical and chemica... more Accumulations of sediment beneath the Antarctic Ice Sheet contain a range of physical and chemical proxies with the potential to document changes in ice sheet history and to identify and characterize life in subglacial settings. Retrieving subglacial sediments and sediment cores presents several unique challenges to existing technologies. This paper briefly reviews the history of sediment sampling in subglacial environments. It then outlines some of the technological challenges and constraints in developing the corers being used in sub-ice shelf settings (e.g. George VI Ice Shelf and Larsen Ice Shelf), under ice streams (e.g. Rutford Ice Stream), at or close to the grounding line (e.g. Whillans Ice Stream) and in subglacial lakes deep under the ice sheet (e.g. Lake Ellsworth). The key features of the corers designed to operate in each of these subglacial settings are described and illustrated together with comments on their deployment procedures.
Leg 124 of the Ocean Drilling Project drilled Sites 767 and 770 in the northern Celebes Sea, reac... more Leg 124 of the Ocean Drilling Project drilled Sites 767 and 770 in the northern Celebes Sea, reaching late middle Eocene basaltic basement at both sites. Major shifts in sediment provenance record the changing tectonic setting of the basin. From late middle Eocene into early Miocene time pelagic sedimentation prevailed, with little influence from continental or volcanic arc sources. A major continental influence is first documented in middle Miocene time as a thick sequence of quartzose, mud-rich turbidites accumulated on the deeper basin floor, possibly in response to middle Miocene orogeny in northern Borneo. Terrigenous turbidite deposition waned during the late Miocene as active arc volcanism began to contribute significant amounts of hemipelagic sediment and ash layers, which have remained the dominant basinal sediment to the present. Although the Celebes Sea is now nearly surrounded by volcanic arc terranes, the absence of volcaniclastic sediment in the Eocene to early Miocene section suggests that the basin did not form by back-arc spreading.
Holes were drilled at three Sites in the Sulu Sea on Ocean Drilling Program Leg 124. Site 768 lie... more Holes were drilled at three Sites in the Sulu Sea on Ocean Drilling Program Leg 124. Site 768 lies in the deeper part of the SE sub-basin and Sites 769 and 771 lie on the flanks of the Cagayan ridge. The results indicate that the Sulu Basin originated in the late early Miocene (c.18.8 Ma) in a backarc setting. The Cagayan Ridge was a site of early to early middle Miocene arc volcanism with the deposition of a thick sequence of andesitic to basaltic volcaniclastic deposits. In the basin center an early Miocene pelagic sequence is interrupted by a thick unit of rhyolitic to dacitic pyroclastic flows. Middle to late Miocene sedimentation is more continental in character with thick quartz-rich turbidites in the basin center. Only the hemipelagic claystone related to these terrigenous turbidites were deposited on the Cagayan Ridge. A decrease in the supply of clastic detritus from arc and continental sources and a change in the level of the carbonate compensation depth in the upper Pliocene resulted in pelagic carbonate deposition throughout the late Pliocene and Pleistocene.
Prior to rotary coring, a range of soft-sediment coring tools were deployed to recover the sedime... more Prior to rotary coring, a range of soft-sediment coring tools were deployed to recover the sediment-water interface and the upper few metres of strata, whose integrity was threatened by embedment of the sea riser for drilling of the ANDRILL (AND)-1A/1B holes. These coring options ...
Here we present an initiative for the International Polar Year in 2007/08 to directly investigate... more Here we present an initiative for the International Polar Year in 2007/08 to directly investigate the subglacial environment and geology of Antarctica and Greenland, representing a new frontier in ice sheet research, and a proposal to develop the technology - a hydro-mechanical drill - necessary to obtain rock and sediment samples from beneath deep glacier ice. The Antarctic continent is
Some glacial sediment samples recovered from beneath the West Antarctic ice sheet at ice stream B... more Some glacial sediment samples recovered from beneath the West Antarctic ice sheet at ice stream B contain Quaternary diatoms and up to 10(8) atoms of beryllium-10 per gram. Other samples contain no Quaternary diatoms and only background levels of beryllium-10 (less than 10(6) atoms per gram). The occurrence of young diatoms and high concentrations of beryllium-10 beneath grounded ice indicates that the Ross Embayment was an open marine environment after a late Pleistocene collapse of the marine ice sheet.
Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years1, but... more Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years1, but only recently have these subglacial aqueous environments been recognized as microbial ecosystems that may influence biogeochemical transformations on a global scale2, 3, 4. Here we present the first geomicrobiological description of water and surficial sediments obtained from direct sampling of a subglacial Antarctic lake. Subglacial Lake Whillans (SLW) lies beneath approximately 800 m of ice on the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and evolving subglacial drainage network5. The water column of SLW contained metabolically active microorganisms and was derived primarily from glacial ice melt with solute sources from lithogenic weathering and a minor seawater component. Heterotrophic and autotrophic production data together with small subunit ribosomal RNA gene sequencing and biogeochemical data indicate that SLW is a chemosynthetically driven ecosystem inhabited by a diverse assemblage of bacteria and archaea. Our results confirm that aquatic environments beneath the Antarctic ice sheet support viable microbial ecosystems, corroborating previous reports suggesting that they contain globally relevant pools of carbon and microbes2, 4 that can mobilize elements from the lithosphere6 and influence Southern Ocean geochemical and biological systems7.
During ODP Leg 124, late middle Eocene to Quaternary sediment sequences were recovered from 13 ho... more During ODP Leg 124, late middle Eocene to Quaternary sediment sequences were recovered from 13 holes drilled at five sites in the Celebes and Sulu basins. Paleomagnetic measurements and biostratigraphic studies using calcareous nannofossils, planktonic and benthic foraminifers, radiolarians, and diatoms were completed and summarized here. Two Neogene sediment sections recovered in the Sulu Basin yielded excellent core recoveries and magnetic reversal records, allowing direct magnetobiostratigraphic correlations for the Pliocene and Quaternary at Site 768 and for the middle Miocene to Quaternary at Site 769. The interpolated ages of biohorizons are not consistent between sites and only a few of them are in good agreement with previous calibrations. The differences may be the results of redeposition by turbidity currents and selective dissolution of key fossils.
... 3. Material and methods. Trigger cores (TC) and piston cores (PC) from the polar research shi... more ... 3. Material and methods. Trigger cores (TC) and piston cores (PC) from the polar research shipNathaniel B. Palmer (NBP) cruises of 94-01 and 95-01 in the Ross Sea were selected for analysis (Fig. ... 12, Actinocyclus actinochilus (Ehrenb.) Simonsen, Pliocene–Recent. ...
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