Holbourn, Ann, Kuhnt, Wolfgang, Simo, J. A. and Li, Qianyu Y. (2004) Middle miocene isotope stratigraphy and paleoceanographic evolution of the northwest and southwest Australian margins (Wombat Plateau and Great Australian Bight). Palaeogeography Palaeoclimatology Palaeoecology, 208 (1-2). pp. 1-22. DOI 10.1016/j.palaeo.2004.02.003.

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Abstract

The benthic stable isotope record from ODP Site 761 (Wombat Plateau, NW Australia, 2179.3 in water depth) documents complete recovery of the middle Miocene delta(13)C excursion corresponding to the climatic optimum and subsequent expansion of the East Antarctic Ice Sheet. The six main delta(13)C maxima of,the "Monterey Excursion" between 16.4 and 13.6 Ma and the characteristic stepped increase in delta(18)O between 14.5 and 13.9 Ma are clearly identified. The sedimentary record of the shallower ODP Sites 1126 and 1134 [Great Australian Bight (GAB), SW Australia, 783.8 and 701 in water depth, respectively] is truncated by several unconformities. However, a composite benthic stable isotope curve for these sites provides a first middle Miocene bathyal record for southwest Australia. The delta(18)O and delta(13)C curves for Sites 1126 and 1134 indicate a cooler, better-ventilated water mass at similar to 700 m water depth in the Great Australian Bight since approximately 16 Ma. This cooler and younger water mass probably originated from a close southern Source. Cooling of the bottom water at similar to 16 Ma started much earlier than at other sites of equivalent paleodepths in the central and Western parts of the Indian Ocean. At Site 761, the delta(18)O curve shows an excellent match with the global sea level curve between similar to 11.5 and 15.1 Ma, and thus closely reflects changes in global ice volume. Prior to 15.1 Ma, the mismatch between the delta(18)O curve and the sea level curve indicates that delta(18)O fluctuations are mainly due to changes in bottom water temperature. (C) 2004 Elsevier B.V. All rights reserved.

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