Chemostratigraphic documentation of a complete Miocene intermediate-depth section in the Southern Ocean: Ocean Drilling Program Site 1120, Campbell Plateau off New Zealand |
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| Authors: | Atsushi Ando Boo-Keun Khim Takanori Nakano Hiroyuki Takata |
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| Institution: | 1. Utrecht University, Paleomagnetic Laboratory ‘Fort Hoofddijk’, Budapestlaan 17, 3584 CD Utrecht, the Netherlands;2. University of Belgrade, Faculty of Mining and Geology, Serbia;3. Natural History Museum Vienna, Geological-Paleontological Department, Austria;4. University of Zagreb, Faculty of Mining, Geology & Petroleum Engineering, Croatia;5. Geological Survey of the Federation of Bosnia and Herzegovina, Bosnia and Herzegovina;1. U.S. Geological Survey, MS910, Menlo Park, CA 94025, USA;2. Evolution Applied Ltd., 50 Mitchell Way, Upper Rissington, Cheltenham GL54 2PL, UK;1. Geology and Palaeogeography Unit, Faculty of Earth Sciences, University of Szczecin, ul. Mickiewicza 18, 70-383 Szczecin, Poland;2. Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton SO14 3ZH, UK;3. School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, UK;4. Department of Earth and Atmospheric Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588-0340, USA |
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| Abstract: | An integrated chemostratigraphic (87Sr/86Sr, δ13C and δ18O) study of benthic foraminifera is presented for a 210 m-thick, intermediate depth (upper/middle bathyal transition), Miocene nannofossil ooze section of Ocean Drilling Program Site 1120, Campbell Plateau off New Zealand. Our results indicate that new 87Sr/86Sr, δ13C and δ18O profiles are wholly consistent with their respective Miocene reference curves. These observations facilitate identification of a total of five reliable chemostratigraphic datums, which are based on the fundamental structural changes in the 87Sr/86Sr curve and paired simultaneous δ13C and δ18O events. The resultant age–depth relationship clearly shows that the Miocene (20–5 Ma) biopelagic sedimentation on the Campbell Plateau was essentially continuous at a moderate to high, linear sedimentation rate (17.5 m/m.y. with an exception of the uppermost 13 m). Our findings do not support the shipboard biostratigraphic age model, which assumes that the critical early–middle Miocene transition was interrupted by a major hiatus (<~3 m.y.). Because of its unique bathymetric setting at a paleowater-depth of ~ 600 m, which is among the shallowest of the coeval isotopically studied deep-sea sections in the South Pacific/Southern Ocean, Site 1120 will serve as a reference section for surveying the evolution of intermediate-water paleoceanography in the Southern Hemisphere across the middle Miocene climatic transition. |
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