EGU21-11977, updated on 04 Mar 2021
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The rhythmic expression of mid-Cretaceous Oceanic Anoxic Event 2 at IODP Sites U1513 and U1516 (southwest of Australia) 

Sietske Batenburg1, Kara Bogus2, Matthew Jones3, Kenneth Macleod4, Mathieu Martinez1, and Iodp Exp 369 Scientists5
Sietske Batenburg et al.
  • 1Géosciences Rennes, Université de Rennes 1, Rennes, France (
  • 2Camborne School of Mines, University of Exeter, Penryn, United Kingdom
  • 3Dept. Earth & Environmental Sciences, University of Michigan, Ann Arbor, USA
  • 4Department of Geological Sciences, University of Missouri, Columbia, USA
  • 5International Ocean Discovery Program, Texas A&M, College Station, USA

The widespread deposition of organic-rich black shales during the mid-Cretaceous hothouse at ~94 Ma marked a climatic extreme that is particularly well studied in the Northern Hemisphere. The expression of Oceanic Anoxic Event 2 (OAE 2) in the NH was characterised by low oceanic oxygen concentrations, likely caused by the input of nutrients through volcanism and/or weathering in combination with a peculiar geography in which the proto-North Atlantic was semi-restricted (Jenkyns, 2010; Trabucho Alexandre et al., 2010). The extent of water column anoxia outside the North Atlantic and Tethyan domains remains poorly resolved, as few Southern Hemisphere records have been recovered that span OAE 2, and only a portion of those Indian and Pacific Ocean localities experienced anoxia and organic matter deposition (Dickson et al., 2017; Hasegawa et al., 2013).


Here we present new results from IODP Expedition 369 offshore southwestern Australia. Sedimentary records across the Cenomanian-Turonian transition from Sites U1513 and U1516 in the Mentelle Basin (Indian Ocean) display rhythmic lithologic banding patterns. The OAE 2 interval is marked by a dramatic drop in carbonate content and the occurrence of several thin organic-rich black bands. The spacing of dark bands within a rhythmic sequence suggests a potential orbital control on organic matter deposition at our study sites. Time series analyses of high-resolution (cm-scale) elemental data from XRF-core scanning reveal the imprint of periodicities that can be confidently linked to Earth’s orbital parameters. The new OAE 2 records from Sites U1516 and U1513 allow us to i) evaluate existing time scales over the Cenomanian-Turonian transition, and ii) investigate the mechanisms leading to a recurrent lack of oxygen in the Indian Ocean.


Climatic mechanisms translating changes in insolation to variations in organic matter deposition may have included variations in nutrient input from nearby continents and shifts in water column structure affecting local to regional stratification versus deep water formation and advection. Investigating ventilation of the deep sea during the OAE2 interval is of heightened relevance as current global warming is leading to a worldwide expansion of oxygen minimum zones (Pörtner et al., 2019).



Dickson, A.J., et al., 2017. Sedimentology 64, 186–203.

Hasegawa, et al., 2013. Cretaceous Research 40, 61–80.

Jenkyns, H.C., 2010. Geochemistry, Geophysics, Geosystems 11, Q03004.

Pörtner, H.O., et al., 2019. IPCC Intergovernmental Panel on Climate Change: Geneva, Switzerland.

Trabucho Alexandre, J., et al., 2010. Paleoceanography 25, PA

How to cite: Batenburg, S., Bogus, K., Jones, M., Macleod, K., Martinez, M., and Exp 369 Scientists, I.: The rhythmic expression of mid-Cretaceous Oceanic Anoxic Event 2 at IODP Sites U1513 and U1516 (southwest of Australia) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11977,, 2021.


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