Abstract
Abstract. There is growing interest in the scientific community in reconstructing the paleoceanography of the Southern Ocean during the Oligocene–Miocene because these time intervals experienced atmospheric CO2 concentrations with relevance to our future. However, it has remained notoriously difficult to put the sedimentary archives used in these efforts into a temporal framework. This is at least partially due to the fact that the bio-events recorded in organic-walled dinoflagellate cysts (dinocysts), which often represent the only microfossil group preserved, have not yet been calibrated to the international timescale. Here we present dinocyst ranges from Oligocene–Miocene sediments drilled offshore the Wilkes Land continental margin, East Antarctica (Integrated Ocean Drilling Program (IODP) Hole U1356A). In addition, we apply statistical means to test a priori assumptions about whether the recorded taxa were deposited in situ or were reworked from older strata. Moreover, we describe two new dinocyst species, Selenopemphix brinkhuisii sp. nov. and Lejeunecysta adeliensis sp. nov., which are identified as important markers for regional stratigraphic analysis. Finally, we calibrate all identified dinocyst events to the international timescale using independent age control from calcareous nanoplankton and magnetostratigraphy from IODP Hole U1356A, and we propose a provisional dinoflagellate cyst zonation scheme for the Oligocene–Miocene of the Southern Ocean.
Highlights
There is a growing need to better understand the dynamics of the Antarctic cryosphere and the paleoceanography of the Southern Ocean during the Oligocene and Miocene, in view of the apparent similarity between Oligocene and Miocene atmospheric CO2 concentrations and those of the near future (e.g. Zhang et al, 2013)
We present dinocyst ranges from Oligocene–Miocene sediments drilled offshore the Wilkes Land continental margin, East Antarctica (Integrated Ocean Drilling Program (IODP) Hole U1356A)
Many sedimentary successions from the Southern Ocean lack the calcareous microfossil groups conventionally used for biostratigraphic age control, which stresses the need to utilise the stratigraphic potential of non-calcareous microfossils
Summary
There is a growing need to better understand the dynamics of the Antarctic cryosphere and the paleoceanography of the Southern Ocean during the Oligocene and Miocene, in view of the apparent similarity between Oligocene and Miocene atmospheric CO2 concentrations and those of the near future (e.g. Zhang et al, 2013). There is a growing need to better understand the dynamics of the Antarctic cryosphere and the paleoceanography of the Southern Ocean during the Oligocene and Miocene, in view of the apparent similarity between Oligocene and Miocene atmospheric CO2 concentrations and those of the near future The vast majority of our understanding of Oligocene–Miocene ice-sheet dynamics and paleoceanography in the high southern latitudes is derived from marine sedimentary archives. A major challenge when employing these archives is to establish accurate age control. Many sedimentary successions from the Southern Ocean lack the calcareous microfossil groups conventionally used for biostratigraphic age control, which stresses the need to utilise the stratigraphic potential of non-calcareous microfossils. For successions from the southern high latitudes, organic microfossils have repeatedly been shown to represent a use- Siliceous microfossils have provided an excellent stratigraphic framework for the Neogene of the Southern Ocean (Cody et al, 2008); they are prone to dissolution when buried below the diagenetic front of opal, which tends to limit their applicability to deeply buried strata (DeMaster, 2003).
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