Middle Miocene deepwater paleoceanography in the Southwest Pacific; relations with East Antarctic ice sheet development

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doi: 10.1029/95PA02022
Author(s): Flower, Benjamin P.; Kennett, James P.
Author Affiliation(s): Primary:
University of California, Earth Sciences Department, Santa Cruz, CA, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 10(6), p.1095-1112. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. Data described in this paper are available in digital form at the World Data Center-A for Paleoclimatology, NOAA/NGDC; Internet e-mail; paleo @mail.ngde.noaa.gov. 56 refs.; illus., incl. 3 tables, sketch map
Summary: A suite of middle Miocene Deep Sea Drilling Project sites in the southwest Pacific reveals large-scale changes in deepwater circulation associated with East Antarctic Ice Sheet (EAIS) variations from ∼16.5 to 13.8 Ma. Oxygen and carbon isotopic records based on Cibicidoides benthic foraminifera from a depth transect (sites 590B, 588A, 591B, and 206 from 1200- to 3150-m paleodepth at ∼35°S paleolatitude) and from a meridional transect (sites 588A, 590B, 593, and 594 from 30° to 48°S paleolatitude at intermediate water depth) allow detailed examination of southwest Pacific deepwater circulation from ∼17.5 to 12 Ma. Significantly, intervals of low δ18O from 16.5 to 16.3 Ma and perhaps at 15.7 Ma were marked by similar δ18O values at upper bathyal (∼1200-1500 m; sites 588A and 590B) and midbathyal (∼2100 m; site 591B) water depths. Small vertical δ18O gradients during δ18O minima may indicate warm saline deep water (WSDW) at midbathyal depths in the southwest Pacific during intervals of inferred global warmth and low global ice volume. Increased vertical δ18O gradients after ∼15.6 Ma and especially after 13.8 Ma indicate increased production of Southern Component Water (SCW) in association with EAIS growth. These data are consistent with the hypothesis (Woodruff and Savin, 1989) that major EAIS growth was fostered by diminished meridional heat transport to the high southern latitudes related to the termination of Tethyan Indian Saline Water (TISW) and an increase in SCW production during the early middle Miocene after ∼15.6 Ma. Further, a maximum vertical carbon isotopic gradient of ∼0.8 per mil at 13.6 Ma suggests that Southern Component Intermediate Water (SCIW) production and Pacific Deep Water (PDW) strength were each at a maximum at this time and were critical to major EAIS growth. The establishment of near-modern δ13C and δ18O gradients following major EAIS growth from ∼14.0 to 13.8 Ma marks a major step in the development of the Neogene ocean/cryosphere system. Copyright 1995 by the American Geophysical Union.
Year of Publication: 1995
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Age; Antarctic ice sheet; Antarctica; Benthic taxa; Biostratigraphy; C-13/C-12; Carbon; Carbonate rocks; Cenozoic; Chalk; Clastic sediments; DSDP Site 206; DSDP Site 588; DSDP Site 590; DSDP Site 591; DSDP Site 593; DSDP Site 594; Deep Sea Drilling Project; Deep-water environment; Deglaciation; East Antarctic ice sheet; East Antarctica; Foraminifera; Glacial geology; Glaciation; IPOD; Invertebrata; Isotopes; Leg 21; Leg 90; Lord Howe Rise; Marine sediments; Microfossils; Middle Miocene; Miocene; Neogene; O-18/O-16; Ocean circulation; Ooze; Oxygen; Pacific Deep Water; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Protista; Sedimentary rocks; Sediments; South Pacific; Southern Component Intermediate Water; Southwest Pacific; Stable isotopes; Tertiary; West Pacific
Coordinates: S453129 S211153 E1745653 E1611336
Record ID: 1996050531
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.