Magnetostratigraphic calibration of Southern Ocean diatom datums from the Eocene-Oligocene of Kerguelen Plateau (Ocean Drilling Program sites 744 and 748)

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doi: 10.1016/S0031-0182(03)00397-3
Author(s): Roberts, Andrew P.; Bicknell, Simon J.; Byatt, Joanne; Bohaty, Steven M.; Florindo, Fabio; Harwood, David M.
Author Affiliation(s): Primary:
University of Southampton, School of Ocean and Earth Science, Southampton, United Kingdom
Stanford University, United States
Geoscience Australia, Australia
University of California at Santa Cruz, United States
University of Nebraska, United States
Volume Title: Antarctic Cenozoic palaeoenvironments; geologic record and models
Volume Author(s): Florindo, Fabio, editor; Cooper, Alan K.; O'Brien, Philip E.
Source: Palaeogeography, Palaeoclimatology, Palaeoecology, 198(1-2), p.145-168; ANTOSTRAT symposium; The geologic record of the Antarctic ice sheet from drilling, coring and seismic studies, Erice, Italy, Sept. 2001, edited by Fabio Florindo, Alan K. Cooper and Philip E. O'Brien. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-0182 CODEN: PPPYAB
Note: In English. 60 refs.; illus., incl. 3 tables, sketch map
Summary: Ocean Drilling Program holes 744A and 748B represent key sections for calibration of Southern Ocean Eocene-Oligocene biostratigraphic zonations. Sites 744 and 748 were above the carbonate compensation depth throughout this time interval and contain good planktonic foraminiferal, calcareous nannofossil, and diatom biostratigraphic records. In particular, the Southern Ocean diatom biostratigraphic zonation for the Oligocene critically hinges on calibration of these two holes. Previous low-resolution magnetostratigraphic studies at these sites were hampered by limited sampling and technical difficulties, which prompted our high-resolution reinvestigation of the magnetostratigraphy. Magnetic polarity zonations for holes 744A and 748B were constructed after inspection of vector component plots at 1-cm stratigraphic intervals from continuous u-channel measurements. The magnetizations are generally stable and a robust polarity stratigraphy has been obtained for both holes. The increased resolution of our study and identification of persistent secondary overprints, which were not recognised in previous studies, suggests that the previously published interpretations need to be revised. Our magnetostratigraphic interpretations for both holes are constrained by foraminiferal and calcareous nannofossil datums, as well as by Sr isotope ages. We have calibrated four diatom datums, which are synchronous at the two studied sites, to the geomagnetic polarity timescale, including the first occurrence (FO) of Lisitzinia ornata (27.8 Ma), the FO of Rocella vigilans var. B (27.8 Ma), the FO of Cavitatus jouseanus (30.9 Ma) and the FO of Rhizosolenia oligocaenica (33.8 Ma). The synchroneity of these datums suggests that diatom biostratigraphy has considerable potential for Palaeogene biostratigraphic correlation in the Southern Ocean. Although the ages of some datums are obscured by an unconformity in Hole 744A, our age model from Hole 748B suggests age estimates for the last common occurrence of Rocella vigilans var. A (∼29.0 Ma), the FO of Rocella vigilans var. A (30.0 Ma) and the FO of Rhizosolenia antarctica (33.2 Ma). It should also be noted that the last occurrence of the calcareous nannofossil Chiasmolithus altus occurs in Chron C8r rather than C8n in our revised magnetostratigraphic interpretation, which indicates that this datum is not diachronous between low and mid latitudes as had previously been suggested. Significant unconformities are documented in both holes, in the middle Oligocene and in the middle late Oligocene, respectively, which probably resulted from periods of enhanced circumpolar deep-water circulation. Abstract Copyright (2003) Elsevier, B.V.
Year of Publication: 2003
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Biostratigraphy; Biozones; Calibration; Cenozoic; Chemical remanent magnetization; Correlation; Diatoms; Eocene; Eocene-Oligocene boundary; Foraminifera; Invertebrata; Kerguelen Plateau; Leg 119; Leg 120; Lower Oligocene; Magnetization; Magnetostratigraphy; Microfossils; Nannofossils; ODP Site 744; ODP Site 748; Ocean Drilling Program; Oligocene; Paleo-oceanography; Paleocirculation; Paleogene; Paleomagnetism; Plantae; Protista; Remanent magnetization; Southern Ocean; Stratigraphic boundary; Tertiary; Unconformities; Upper Eocene; Viscous remanent magnetization
Coordinates: S613440 S613439 E0803528 E0803527
S582627 S582627 E0785854 E0785853
Record ID: 2003073063
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands