Records of Be-10, Be-9, mineralogy and grain size were obtained from two cores collected by the Polarstern Expedition 1991 in the southern Nansen Basin (Core 2213-6) and the Yermak Plateau (Core 2208-2). The accumulation of sediments examined started from about 350 ka (BP), and includes relatively well defined trends of Be isotopes coincident with interglacial/glacial climatic cycles. Sediment accumulation rates (g/cm(2) ka) were higher during glacial periods and our estimates of 1.0 and 2.5 cm/ka sedimentation rates during the Holocene agree with other estimates for the southern Nansen Basin and the Yermak Plateau, respectively. The variations in Be-10 concentration (atoms/g) and flux (atoms/cm(2) ka) are inverse to sediment flux, where high Be-10 concentration and flux are associated with generally low sedimentation/accumulation rates during interglacial periods. We hypothesize that climate plays an important role in Be-10 records from the Arctic sediments, reflecting the intensity and distribution of the ice mass on land and the ocean. (C) 1997 Elsevier Science B.V.
The first seismic reflection data from the shallowest part of the submarine Lomonosov Ridge north of Arctic Canada and North Greenland comprise two parallel single channel lines (62 and 25 km long, offset 580 m) acquired from a 10 day camp on drifting sea ice. The top of southern Lomonosov Ridge is bevelled (550 m water depth) and only thin sediments (< 50 ins) cover acoustic basement. We suggest erosion of a former sediment drape over the ridge crest was either by a grounded marine ice sheet extending north from Ellesmere Island and/or deep draft icebergs. More than 1 km of sediments are present at the western entrance to the deep passage between southern Lomonosov Ridge and the Lincoln Sea continental margin. Here, the uppermost part (+0.3 s thick) of the section reflects increased sediment input during the Plio-Pleistocene. The underlying 0.7 s thick succession onlaps the slope of a subsiding Lomonosov Ridge. An unconformity at the base of the sedimentary section caps a series of NW-SE grabens and mark the end of tectonic extension and block faulting of an acoustic basement represented by older margin sediments possibly followed by minor block movements in a compressional regime. The unconformity may relate to termination of Late Cretaceous deformation between Lomonosov Ridge and Alpha Ridge or be equivalent to the Hauterivian break-tip unconformity associated with the opening of the Amerasia Basin. A flexure in the stratigraphic succession above the unconformity is most likely related to differential compaction, although intraplate earthquakes do occur in the area. (c) 2005 Elsevier B.V. All rights reserved.
Seismic reflection data from drifting ice stations and an icebreaker survey document the presence of a submarine fan along the east flank of the Lomonosov Ridge in the Amundsen Basin, Arctic Ocean. The fan extends from a source area at the North Greenland and Canadian Arctic continental margin to the North Pole. The fan probably developed in response to the combined effect of increased glacial sediment input during the Plio-Pleistocene and topographically confined transport of glacial debris in the deep sea passage between Lincoln Sea margin and the southern end of the Lomonosov Ridge. (C) 2004 Elsevier B.V. All rights reserved.
A total of seven arcuate transverse troughs 5-6 km wide, 7-9 km long and 150-200 m deep are present on both sides of the crest of the central part of Lomonosov Ridge, Arctic Ocean. The troughs occur within a restricted ridge length of ca. 65 km. Trough morphology and disrupted, piecewise continuous sub-bottom reflections down to a common stratigraphic horizon below the troughs indicate lateral spread of progressively disintegrating sediment blocks above a glide plane. Lomonosov Ridge is aseismic, but the spatially restricted mass waste occurrences suggest sediment instability induced by earthquake loading. Another possibility is a pressure wave from a possible impact of an extraterrestrial object on Alpha Ridge about 500 km away. The slide event(s) is likely to be pre-late Pleistocene as sediment deposition within one of the slide scars appears continuous over the last c. 600 ka. (c) 2007 Elsevier B.V. All rights reserved.
A sediment record from the practically unknown southernmost part of the Lomonosov Ridge off North Greenland/Ellesmere Island has been studied. GreenICE core 10 encompasses marine isotope stages (MIS) 7-1 and reveals changing paleoceanographic conditions and land-ocean connections during the last two glacial-interglacial cycles. The isotope record of planktic foraminifera Neogloboquadrina pachyderma (s) show large similarities to other Arctic Ocean key records, supporting that the pattern reflect over-regional changes of the halocline structure. The relatively low delta O-18 values of subpolar foraminifera Turborotalita quinqueloba in the last interglacial unit support that the specimens represent local production, related to warm interglacial conditions and a reduced sea ice cover in the interior Arctic Ocean. Enhanced deposition of coarse ice-rafted debris took place during the MIS 8/7 transition, periods of MIS 6, MIS 6/5 transition, MIS 5d, MIS 4, and late MIS 3 (30-40 C-14 kyr BP). In MIS 2, IRD flux was low in the area. The IRD contains detrital carbonate similar to other Amerasia Basin records. The occurrence of fine-grained, calcite-rich detrital carbonate layers at glacial-interglacial transitions, seems unique to this area. We suggest that detrital carbonate was transported and deposited from nepheloid flows during deglaciations of Ellesmere Island, when the Atlantic Water boundary current along the continental margin was gaining strength. (c) 2007 Elsevier B.V All rights reserved.