Florindo, Fabio and Roberts, Andrew P. (2005): Eocene-Oligocene magnetobiochronology of ODP Sites 689 and 690, Maud Rise, Weddell Sea, Antarctica

Leg/Site/Hole:
ODP 113
ODP 113 689
ODP 113 690
Identifier:
2005-013968
georefid

10.1130/B25541.1
doi

Creator:
Florindo, Fabio
Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
author

Roberts, Andrew P.
University of Southampton, United Kingdom
author

Identification:
Eocene-Oligocene magnetobiochronology of ODP Sites 689 and 690, Maud Rise, Weddell Sea, Antarctica
2005
Geological Society of America Bulletin
Geological Society of America (GSA), Boulder, CO, United States
117
1-2
46-66
Magnetostratigraphic studies of Paleogene sediments piston-cored on Maud Rise, Weddell Sea (ODP Sites 689 and 690), are a cornerstone of Southern Ocean Paleogene and Neogene chronostratigraphy. However, parts of previous magnetostratigraphic interpretations have been called into question, and recent reinvestigation of the upper Paleocene-middle Eocene portion of Site 690 suggested that the records might be contaminated by spurious magnetizations, which raises doubts about the reliability of these important records. We undertook a high-resolution magnetostratigraphic study of Eocene-Oligocene u-channel samples from ODP Holes 689B, 689D, 690B, and 690C in order to address these concerns. A pervasive overprint appears to be present below the middle Eocene, which compromises magnetobiostratigraphic interpretations for the upper Cretaceous and lower Paleogene. Nevertheless, our new results provide a robust record of geomagnetic field behavior from 38.5 to 25 Ma and confirm the reliability of these sediments for calibration of biostratigraphic datum events during a crucial phase of earth history when major Antarctic ice sheets developed. Also, comparison of magnetozone thicknesses in multiple holes at the same site indicates that approximately 1.2-1.8 m of the stratigraphic record is missing at each core break, which corresponds to time breaks of 120-360 k.y. Lack of a continuous record within a single hole renders useless spectral analyses for investigating long geomagnetic and paleoclimatic time series. This observation reinforces the need for coring of multiple offset holes to obtain continuous paleoceanographic records. Sedimentary hiatuses have been identified only at the deeper of the two investigated sites (Site 690), which could mark a local response to the onset of the Antarctic Circumpolar Current.
English
Serial
Coverage:Geographic coordinates:
North:-64.3100
West:1.1218East: 3.0600
South:-65.0938

Stratigraphy; Antarctic Circumpolar Current; biochronology; Cenozoic; characteristic remanent magnetization; cores; Eocene; erosional unconformities; Leg 113; magnetization; magnetostratigraphy; marine sediments; Maud Rise; natural remanent magnetization; Ocean Drilling Program; ODP Site 689; ODP Site 690; Oligocene; paleo-oceanography; paleocurrents; Paleogene; paleomagnetism; remanent magnetization; sediments; Southern Ocean; Tertiary; unconformities; Weddell Sea;

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