Geochemical measurements of the Tasmanian Gateway from ODP Hole 189-1172A

• Main Authors: Stickley, Catherine E, Brinkhuis, Henk, Schellenberg, Stephen A, Sluijs, Appy, Röhl, Ursula, Fuller, Michael D, Grauert, M, Huber, Matthew, Warnaar, Jeroen, Wiliams, Graham L
• Format: Dataset
• Language: English
• Published: PANGAEA 2004
• Subjects: 189-1172A; Carbon; organic; total; Carbonates; Coulometry; DEPTH; sediment/rock; DRILL; Drilling/drill rig; Grain size; mean; Isotope ratio mass spectrometry; Joides Resolution; Leg189; Ocean Drilling Program; ODP; Tasman Sea; δ13C; carbonate; δ18O; Antarc*; Antarctic; Antarctica
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.742605; https://doi.org/10.1594/PANGAEA.742605

Tectonic changes that produced a deep Tasmanian Gateway between Australia and Antarctica are widely invoked as the major mechanism for Antarctic cryosphere growth and Antarctic Circumpolar Current (ACC) development during the Eocene/Oligocene (E/O) transition (34-33 Ma). Ocean Drilling Program (ODP) Leg 189 recovered near-continuous marine sedimentary records across the E/O transition interval at four sites around Tasmania. These records are largely barren of calcareous microfossils but contain a rich record of siliceous- and organic-walled marine microfossils. In this study we integrate micropaleontological, sedimentological, geochemical, and paleomagnetic data from Site 1172 (East Tasman Plateau) to identify four distinct phases (A-D) in the E/O Tasmanian Gateway deepening that are correlative among ODP Leg 189 sites. Phase A, prior to 35.5 Ma: minor initial deepening characterized by a shallow marine prodeltaic setting with initial condensation episodes. Phase B, 35.5-33.5 Ma: increased deepening marked by the onset of major glauconitic deposition and inception of energetic bottom-water currents. Phase C, 33.5-30.2 Ma: further deepening to bathyal depths, with episodic erosion by increasingly energetic bottom-water currents. Phase D, <30.2 Ma: establishment of stable, open-ocean, warm-temperate, oligotrophic settings characterized by siliceous-carbonate ooze deposition. Our combined evidence indicates that this early Oligocene Tasmanian Gateway deepening initially produced an eastward flow of relatively warm surface waters from the Australo-Antarctic Gulf into the southwestern Pacific Ocean. This "proto-Leeuwin" current fundamentally differs from previous regional reconstructions of eastward flowing cool water (e.g., a "proto-ACC") during the early Oligocene and thereby represents an important new constraint for reconstructing regional- to global-scale dynamics for this major global change event.