Causes and climatic effects of carbon sequestration during global warming/oceanic anoxia events in the Cretaceous and Neogene – a synthesis

This study aims at investigating the impact of potential climatic drivers such as enhanced volcanic CO2 emissions and cyclic changes of Earth’s orbital parameters, as well as the associated interaction of biogeochemical processes on the distribution and intensity of widespread ocean dys/anoxia in the geological past, focusing on the Cretaceous (144 – 65 Ma). By using a suite of geochemical proxies (Tex86, Mg/Ca, δ18O, δ13C, Nd and Os iostopes, P, Mo isotopes (with A6) and micropaleontological proxies (with B7), time series data and numerical models (box modelling, earth system modelling (UVic), with B1) we focus on the controls on oceanic oxygen conditions and aim to decode the triggering mechanisms for major oceanic dys/anoxic events in the Cretaceous (OAE1a, 2). This understanding will ultimately improve the prediction of the long-term evolution of dissolved oxygen concentrations in the future ocean.

Key questions focus on the effect of massive CO2 emissions and whether these were a common trigger during major low oxygen events such as OAE1a and OAE2. This includes the amplitude, duration, orbital modulation and phase relationships of anoxia/dysoxia, nutrient (in particular phosphate) cycles, carbon sequestration and δ13C changes. A comparable timeline of events has been identified for the Miocene Monterey Event (~17-13.5 Ma) where ongoing studies indicate similar forcing mechanisms and biogeochemical responses under lower pCO2 conditions of about 300-500 ppm. We will integrate these chronologically well- constrained data sets and conceptual advances to improve the timing of events for the Cretaceous OAEs and to assess the response of the ocean/climate system to global warming under differing pCO2 boundary conditions.

The ultimate goal is to improve our understanding of the underlying endogenic and exogenic physical processes and the biogeochemical interaction (using transfer functions from B5) driving widespread bottom water dys- and anoxia during times of global warmth in the past and in the future. This project will yield significant insights into the rates of change of oceanic oxygen concentrations in response to varying climate and atmospheric pCO2.

Flögel, S., K. Wallmann and W. Kuhnt (2011) Cool episodes in the Cretaceous – exploring the effects of physical forcing on Antarctic snow accumulation. Earth Planet. Sc. Lett., 307, 279- 288. doi: 10.1016/j.epsl.2011.04.024

Flögel, S., K. Wallmann, C.J. Poulsen, J. Zhou, A. Oschlies, S. Voigt and W. Kuhnt (2011) Simulating the biogeochemical effects of volcanic CO2 degassing on the oxygen-state of the deep ocean during the Cenomanian/Turonian Anoxic Event (OAE2). Earth Planet. Sc. Lett., 305, 371-384, doi: 10.1016/j.epsl.2011.03.018

Flögel, S., M. Moullade and W. Kuhnt (2010) Drilling of Early Cretaceous Oceanic An-oxic Event 1a in Southern France. Scientific Drilling, 9, 20-22, doi: 10.2204/

Holbourn, A., W. Kuhnt, K.G.D. Kochhann, N. Andersen and K.J.S. Meier (2015) Global perturbation of the carbon cycle at the onset of the Miocene Climatic Optimum. Geology, doi: 10.1130/G36317.1

Holbourn, A.E., W. Kuhnt, M. Lyle, L. Schneider, O. Romero and N. Andersen (2014) Middle Miocene climate cooling linked to intensification of eastern equatorial Pacific upwelling. Geology, 42(1), 19-22, doi: 10.1130/G34890.1

Holbourn, A.E., W. Kuhnt, M. Schulz and H. Erlenkeuser (2005) Impacts of orbital forcing and atmospheric CO2 on Miocene ice-sheet expansion. Nature, 438(7067), 483-487, doi: 10.1038/nature04123

Lorenzen, J., W. Kuhnt, A. Holbourn, S. Flögel, M. Moullade and G. Tronchetti (2013) A new sediment core from the Bedoulian (Lower Aptian) stratotype at Roquefort-La Bédoule, SE France. Cretaceous Res., doi: 10.1016/j.cretres.2012.03.019

McAnena, A., S. Flögel, P. Hofmann, J.O. Herrle, A. Griesand, J. Pross, H.M. Talbot, J. Rethemeyer, K. Wallmann and T. Wagner (2013) Atlantic ocean cooling and marine biotic crisis in the mid-Cretaceous. Nat. Geosci., doi: 10.1038/NGEO1850

Wallmann, K. (2014) Is late Quaternary climate change governed by self-sustained oscillations in atmospheric CO2? Geochim. Cosmochin. Acta, 132, 413-439 doi: 10.1016/j.gca.2013.10.046

Wallmann, K., G. Aloisi (2012) The Global Carbon Cycle: Geological Processes, in Fundamentals of Geobiology (Eds. A. H. Knoll, D. E. Canfield, K. O. Konhauser), Blackwell Publishing Ltd., 20-35



Prof. Wolfgang Kuhnt                Prof. Klaus Wallmann
Tel.: +49 431 880 2924             Tel.: +49 431 600 2287
wk(a)                   kwallmann(a)