Cenozoic Paleoceanography in the Southwest Pacific Ocean, Antarctic Glaciation, and the Development of the Circumantarctic Current

Abstract

Cenozoic deep-sea sedimentation in the southwest Pacific area was controlled by large changes in the patterns of bottom-water circulation and erosion. The circulation patterns were largely controlled by

Geologic Evolution, Sedimentation, and Paleoenvironments of the Angola Basin and Adjacent Walvis Ridge: Synthesis of Results of Deep Sea Drilling Project Leg 75

“…ago). The late Miocene to early Plio- cene also was a time of major increases in upwelling and organic productivity at the Antarctic convergence (Kennett et al, 1974) due to increased bottom-water circulation related to the development of an Antarctic ice sheet that was much thicker than at present (Shackleton and Kennett, 1974a). We did not recover sediments old enough at Site 532 to determine whether upwelling did indeed begin ca.…”

“…This unconformity apparently was due to the combination of (1) extensive development of shelf ice on Antarctica and concomitant generation and vigorous flow of cold bottom-water leading to development of modern thermohaline circulation Savin et al, 1975;Kennett et al, 1974;Shackleton and Kennett, 1974a;Boersma andShackleton, 1977a and1977b;McCoy and Zimmerman, 1977;van Andel et al, 1977); (2) increased north-south temperature gradients caused by major cooling at high latitudes; (3) stronger circum-polar flow resulting from the complete separation of Antarctica and Australia by later Eocene (Kennett et al, 1974); and (4) a sharp drop in sea level during the Eocene (Fig. 2).…”

“…Active bottom currents with deep-sea erosion (Kennett et al, 1974); high productivity and accumulation of CaCθ3 in the Pacific. Major global cooling; sharpening of latitudinal temperature gradients; extensive production of sea ice on Antarctica; development of present thermohaline deep-water circulation; abrupt increase in depth of CCD world wide (except in Angola Basin) (Heath, 1969;van Andel and Moore, 1974;Berger,1981;Kennett et al, 1974;van Andel et al, 1977) Shoaling of the CCD Maximum depth of the CCD middle Eocene to middle Oligocene section ( Fig.…”

Advances in New Zealand oceanography, 1967–91

“…Around New Zealand, magnetometers towed between Lyttelton and Antarctica showed the same magnetic stripes that recorded the opening of the southern ocean (Christoffel & Falconer 1972), and hence the birth of the Southern Ocean Circulation and the science of palaeoceanography (Kennett et al 1975). In the Tasman Sea, the stripes were clearly old and difficult to correlate (van der Linden 1969) but ultimately provided evidence that New Zealand and all its surrounding plateaus had rifted away from the super-continent of Gondwana 80-60 million years ago (Hayes &Ringis 1973).…”

South Georgia and Gondwana's Pacific Margin: Lost in translation?

“…By hindering deep water connectivity along the way until 22e17 Ma (Barker, 2001), South Georgia could have played a role in Miocene changes to Antarctic glaciation by acting as the physical arbiter on the onset of Antarctic circumpolar oceanic circulation. This circulation has been suggested as necessary for the onset of continental-scale glaciation of Antarctica, which brought with it a range of global changes (Kennett et al, 1975). Early-onset alternatives leave South Georgia closer to its present-day position, permitting shallow Pacific-to-Atlantic water exchange to play a role in fundamentally changing oceanic circulation patterns in such a way that carbon sequestration sites shifted offshore at around 50 Ma, a change that is suggested to have initiated the long Cenozoic decline in atmospheric CO 2 concentration, and with it global temperature (Eagles et al, 2006).…”