A geologic perspective on the Miocene evolution of the Antarctic circumpolar current system

Author(s): Rack, Frank R.
Author Affiliation(s): Primary:
Ocean Drilling Program, College Station, TX 77845, United States
Other:
Lamont-Doherty Geological Observatory, United States
Volume Title: Geological perspectives on global change
Volume Author(s): Anderson, Duwayne M., editor; Eaton, Gordon P.
Source: Tectonophysics, 222(3-4), p.397-415; Geodynamics Research Institute symposium on Geological perspectives on global change, College Station, TX, April 25-26, 1991, edited by Duwayne M. Anderson and Gordon P. Eaton. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0040-1951 CODEN: TCTOAM
Note: In English. 115 refs.; illus. incl. 1 table, sketch maps
Summary: The dominant geologic feature of pelagic sediment accumulation patterns at intermediate water depths in the Southern Ocean is the sequential northward migration and replacement of a calcareous ooze sedimentary facies by a siliceous ooze facies, following the Late Oligocene opening of the Drake Passage and the subsequent initiation of the Antarctic circumpolar current. Closely spaced whole-core measurements of bulk density are evaluated for four sites drilled in the Southern Ocean during Ocean Drilling Program (ODP) legs 113 (sites 689 and 690) and 120 (sites 747 and 751). These sites are all located on submarine rises in open-ocean (pelagic) depositional environments south of the Polar Front, a major oceanographic and sedimentologic boundary. High-resolution profiles of bulk density are used to correlate between adjacent drill holes on the Maud Rise, where multiple overlapping sedimentary sequences were recovered using the advanced hydraulic piston core barrel (APC). Stratigraphic age models have been applied to the bulk-density data to provide a temporal framework for a discussion of the sedimentologic basis for paleoceanographic interpretations and also to constrain future acoustic research studies. The Early to Middle Miocene intervals at sites 689 and 690 are marked by distinct sequences of meter scale, alternating carbonate and siliceous units separated by several proposed stratigraphic hiatuses. At least six dissolution/productivity events are identified in the Middle to Late Miocene on the Maud Rise, and others are noted at the ODP sites on the Kerguelen Plateau. The downhole profiles are used to identify the "density signature" and position of sediment facies changes and proposed stratigraphic hiatuses in sediment cores of Late Oligocene to Late Miocene age, based on the reversals, inflections and discontinuities in the downhole bulk-density trends. An analysis of the observed bulk-density trends at these sites is combined with a review of other tectonic, sedimentologic, oceanographic and modeling studies to develop a hypothesis for explaining the observed sediment accumulation patterns at intermediate water depths of the Southern Ocean.
Year of Publication: 1993
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Antarctic Ocean; Antarctic circumpolar current; Cenozoic; Clastic sediments; Density; Drake Passage; Gamma-ray methods; Indian Ocean; Kerguelen Plateau; Leg 113; Leg 120; Lithostratigraphy; Marine sediments; Maud Rise; Microfossils; Miocene; Nannofossils; Neogene; ODP Site 689; ODP Site 690; ODP Site 747; ODP Site 748; ODP Site 751; Ocean Drilling Program; Ooze; Paleo-oceanography; Paleocirculation; Paleocurrents; Pelagic sedimentation; Plantae; Porosity; Sedimentation; Sediments; Southern Ocean; Tertiary; Thallophytes; Weddell Sea; Well-logging
Coordinates: S643101 S643100 E0030600 E0030559
S650938 S650937 E0011218 E0011218
S544841 S544840 E0764739 E0764738
S582627 S582627 E0785854 E0785853
S574334 S574333 E0794854 E0794853
Record ID: 1993020983
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands