Year: 1987
Type: book
Abstract: When did marine glacial conditions develop sufficiently for initiating formation of cold Antarctic Bottom Water in the Antarctic region, particularly in the Weddell Sea? How have bottom and intermediate water temperatures changed in response to Antarctic glacial development?3. What has been the history of oceanic planktonic productivity in the Weddell Sea sector of the Southern Ocean?How is this development linked to the evolution of Antarctic climates and the oceanic environment, particularly the Polar Front? 4. What has been the evolution of the Antarctic planktonic and benthic biota and their biogeographic patterns?How is this linked with the environmental changes?To assist in answering these questions, nine sites were drilled using JO1DES Resolution in the Weddell Sea (Figures 1 and 2; Table 1).These sites form a depth transect for studies of vertical water mass stratification, climatic evolution, and oceanographic history of Antarctica and the surrounding ocean during the late Mesozoic and Cenozoic Approximately 1945 m of sediments and 2 m of igneous rocks were recovered in a total of 22 holes.The cruise comprised 44 operational days and 21 days of transit, between 5 January and 11 March, 1987, beginning in Punta Arenas, Chile, and ending in East Cove, Falkland Islands.SITE 689 (MAUD RISE) Site 689 (W1A) consists of four holes and is located near the crest of Maud Rise (Figures 1, 2, and 3; Table 1) at a water depth of 2080 m.It is isolated from influences of terrigenous sediment transportation from the East Antarctic continent except for wind-blown and ice-rafted components.This site was selected to obtain a high-quality continuously cored (APC/XCB) biogenic sequence through the Upper Mesozoic and Cenozoic in the present-day Antarctic water mass.The quality of the cores is generally excellent, with marked disturbance observed only in the uppermost one or two cores.The hole was abandoned at 297.3 mbsf, an estimated 25-45 m above basement, when progress in drilling cherty layers became extremely slow.The sedimentary sequence (Figures 4 and 5) is exclusively pelagic, biogenic in origin, and ranges in age from middle Campanian to earliest Maestrichtian (~75 Ma) at the base to Pleistocene at the top.The preliminary biostratigraphy and magnetostratigraphy indicate the presence of brief sedimentary hiatuses or highly condensed sequences throughout the section.These breaks represent time intervals in the lower Paleocene (upper Danian-calcareous nannofossil Zones CP2 and CP3); upper Paleocene to lower Eocene; uppermost Oligocene to lowermost Miocene; upper Miocene (about 9 to 6 Ma); and upper Pliocene to Pleistocene.Site 689 provides a biostratigraphic sequence that, in conjunction with Site 690, will form the southernmost anchor for Atlantic biostratigraphic, biogeographic and isotopic stratigraphic studies.This is the first sequence cored in the Antarctic that provides a late Mesozoic through Cenozoic calcareous nannofossil and planktonic foraminiferal biostratigraphy.Mixed assemblages of calcareous and siliceous microfossils from the late Eocene through the Neogene have allowed the first bioβtratigraphic intercalibration to be carried out between these groups in the Antarctic Jan.
Authors: P.F. Barker, J.P. Kennett, S.O. O'Connell
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Life below water
Open Access status: gold
OpenAlex ID: W2483173564