USGS Open-File Report 94-588
Paleoclimatic Implications of a Late Neogene Antarctic Marginal Marine Record
- Scott E. Ishman
- U.S. Geological Survey, Reston, VA
The Antarctic margin provides us with the best opportunity to construct an
ice proximal paleoenvironmental record for Antarctica. Dry Valley
Drilling Project Cores 10 (DVDP 10) (77°34'43''S, 163°30'42" E) and 11
(DVDP 11) (77°35'24.3" S, 163°24'40.3" E) in Taylor Valley contain the most
complete late Miocene through Recent glacial and glacio-marine sedimentary
sequence recovered from the Victoria Land margin, Antarctica.
Sedimentologic, paleontologic, and paleomagnetic data have been employed
in deciphering the chronology, depositional environments, and
paleobathymetry from these late Neogene sediments placing limitations on
depositional models constructed for the Ross Sea from seismic
stratigraphic records. The presence of diamictons containing abundant and
well preserved benthic foraminifers interbedded with siltstones and
sandstones containing benthic foraminifer and diatom assemblages indicate
fluctuating oceanographic conditions in a polar fjord setting. Paleodepth
estimates of 600 mbsl for these sediments requires uplift rates on the
order of 100 m/m.y., constraining the timing and uplift of the Dry Valley
block of the Transantarctic Mountains (Ishman and Rieck, 1992).
The Southern Ocean record provides a link between Antarctica and global
records. Ocean Drilling Program (ODP) Site 704 (47° S, 7° E), South
Atlantic Ocean, provides one of the most complete Pliocene-Pleistocene
transition sequences in the Southern Ocean (Ciesielski, P.F., et al.,
1988). Stable isotopic records from ODP Hole 704A (Hodell and Venz, 1992)
show changes from the Pliocene through early Pleistocene. Benthic
foraminifers from ODP Hole 704A show deep water fluctuations throughout
this time. The fluctuations observed in the faunal and isotopic records
are related to significant ice volume and temperature changes.
Correlation between the DVDP record and Hole 704A isotopic records show
close correlation between the negative excursion in the benthic isotopic
record and the Pliocene ice volume minimum. A positive shift in the
middle to late Pliocene isotopic record indicates deteriorating climatic
conditions in the Southern Ocean accompanied by a shift in the benthic
foraminifer assemblage from a northern component deep water assemblage to
a Southern Ocean deep water assemblage.
References Cited:
- Ciesielski, P.F., et al., 1988, Leg 114. Proceedings of the Ocean Drilling Program Initial Reports, v. 114, 815 p.
- Hodell, D.A. and Venz, K., 1992,Toward a high-resolution stable isotopic record of the Southern Ocean during the Pliocene-Pleistocene (4.8 to 0.8 MA): Antarctic Research Series, v. 56, p. 265-310.
- Ishman, S.E. and Rieck, H.J., 1992, A late Neogene Antarctic glacio-eustatic record, Victoria Land basin margin, Antarctica: Antarctic Research Series, v. 56, p. 327-347.
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