Late Oligocene-Miocene proto-Antarctic circumpolar current dynamics off the Wilkes Land margin, East Antarctica

• Published in: Global and Planetary Change
• Main Authors: Evangelinos, Dimitris, Escutia, Carlota, Etourneau, Johan, Hoem, Frida S., Bijl, Peter K., Boterblom, Wilrieke, van de Flierdt, Tina, Valero, Luis, Flores, José Abel, Rodríguez-Tovar, Francisco Javier, Jiménez Espejo, Francisco J., Salabarnada, Ariadna, López-Quirós, Adrián
• Other Authors: Ministerio de Ciencia e Innovación (España), European Commission
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier BV 2020
• Subjects: Antarctic; East Antarctica; Southern Ocean; Wilkes Land; Antarc*; Antarctica; Ice Sheet
• Online Access: http://hdl.handle.net/10261/224299; https://doi.org/10.1016/j.gloplacha.2020.103221; https://doi.org/10.13039/501100000780; https://doi.org/10.13039/501100004837

At present, the Southern Ocean plays an important role in the global climate system and in modern Antarctic ice sheet dynamics. Past Southern Ocean configurations are however poorly understood. This information is yet important as it may provide important insights into the climate system and past ice-sheet behavior under warmer than present day climates. Here we study Southern Ocean dynamics during the Oligocene and Miocene when reconstructed atmospheric CO concentrations were similar to those expected during this century. We reconstruct snapshots of late Oligocene to earliest Miocene (~24.2–23 Ma) paleoceanographic conditions in the East Antarctic Wilkes Land abyssal plain. For this, we combine marine sedimentological, geochemical (X-ray fluorescence, TEX,), palynological and isotopic (ε) records from ocean sediments recovered at Deep Sea Drilling Project (DSDP) Site 269. Overall, we find that sediments, delivered to the site by gravity flows and hemipelagic settling during glacial-interglacial cycles, were persistently reworked by a proto-Circumpolar Deep Water (CDW) with varying strengths that result from climatically controlled frontal system migrations. Just prior to 24 Ma, terrigenous input of predominantly fine-grained sediments deposited under weak proto-CDW intensities and poorly ventilated bottom conditions dominates. In comparison, 24 Ma marks the start of episodic events of enhanced proto-CDW current velocities, associated with coarse-grained deposits and better-ventilated bottom conditions. In particular, the dominance of P-cyst and low Calcium (Ca) in the sediments between ~ 24.2 Ma and 23.6 Ma indicate the presence of an active open ocean upwelling associated with high nutrient conditions. This is supported by TEX-derived sea surface temperature (SST) data pointing to cool ocean conditions. From ~ 23.6 to 23.2 Ma, our records reveal an enrichment of Ca in the sediments related to increased calcareous microfossil preservation, high amounts of G-cysts and increasing TEX-SSTs. This implies warmer ...