Abstract
The long-term climate transition from the Cretaceous greenhouse to the late Paleogene icehouse provides an opportunity to study changes in Earth system dynamics associated with large changes in global temperature and atmospheric CO2 levels. Elevated CO2 levels during the mid-Cretaceous supergreenhouse interval (~95–80 Ma) resulted in low meridional temperature gradients, and oceanic deposition during this time was punctuated by widespread episodes of severe anoxia termed oceanic anoxic events, resulting in enhanced burial of organic carbon in conjunction with transient carbon isotope and temperature excursions. The prolonged interval of mid-Cretaceous warmth and subsequent Late Cretaceous–Paleogene climate trends, as well as intervening short-lived climate excursions, are poorly documented in the southern high latitudes. International Ocean Discovery Program (IODP) Expedition 392 aims to drill five sites in the southwest Indian Ocean on the Agulhas Plateau and in the Transkei Basin, positioned at paleolatitudes of 65°–58°S during the Late Cretaceous (100–66 Ma) and in the new and evolving gateway between the South Atlantic, Southern Ocean, and southern Indian Ocean basins. Recovery of basement rocks and expanded sedimentary sequences from the Agulhas Plateau and Transkei Basin will provide a wealth of new data to (i) determine the nature and origin of the Agulhas Plateau and (ii) significantly advance the understanding of how Cretaceous temperatures, ocean circulation, and sedimentation patterns evolved as CO2 levels rose and fell and the breakup of Gondwana progressed. Importantly, Expedition 392 drilling will test competing hypotheses concerning Agulhas Plateau large igneous province formation and the role of deep ocean circulation changes through southern gateways in controlling Late Cretaceous–Paleogene climate evolution.
Highlights
The warmest sustained greenhouse episode of the past ~150 My occurred during the mid-Cretaceous between ~95 and 80 Ma (e.g., Clarke and Jenkyns, 1999; Friedrich et al, 2012; Huber et al, 2002, 2018)
Cretaceous warmth was interrupted by periods of rapid global climate change during oceanic anoxic events (OAEs), which were associated with widespread reduction in basin ventilation and major changes in ocean temperature and circulation (Arthur et al, 1985, 1987; Jenkyns, 2003, 2010; Schlanger and Jenkyns, 1976; Sinninghe Damsté et al, 2010)
Greenhouse climate conditions with CO2 levels approaching those of the Cretaceous–Paleogene interval are envisioned for the near future (e.g., Hay, 2011) calling for action to gain a better understanding of their potential impacts
Summary
The warmest sustained greenhouse episode of the past ~150 My occurred during the mid-Cretaceous between ~95 and 80 Ma (e.g., Clarke and Jenkyns, 1999; Friedrich et al, 2012; Huber et al, 2002, 2018). The southwest Indian Ocean is a key area to retrieve high-quality basement and sedimentary records to test these models and proxy reconstructions concerning the formation of the Agulhas Plateau and the evolution of deep ocean circulation between the Indian and Atlantic Ocean basins. The proposed Expedition 392 drill sites on Agulhas Plateau and Transkei Basin were located at high latitudes during the Late Cretaceous (65°–58°S; Hay et al, 1999; Sewall et al, 2007) and positioned in the gateway between the newly opening South Atlantic, Southern Ocean, and southern Indian Ocean basins. Recovery of basement and sedimentary sequences from this region and comparison with recent results from Naturaliste Plateau drilled during IODP Expedition 369 (Huber et al, 2018) will significantly advance the understanding of large igneous province (LIP) formation and the evolution of ocean temperature, circulation, and sedimentation patterns during the Cretaceous
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