Dr Cédric M. John
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RESEARCH INTERESTS | SHORT BIOGRAPHY | CURRICULUM VITAE | PUBLICATIONS
Research Interests
Broadly speaking, I am interested in neritic and pelagic carbonates, what they tell us about the history of climate and paleo-fluid flow, and what controls the architecture of carbonate platforms. I am notably keen on applying novel isotopic techniques to carbonate material in order to extract relevant proxy data. My research group is currently working on clumped isotope paleothermometry. This new paleotemperature proxy is very promising, tricky to master, and (let’s admit it) fun to work with. Now is an exciting time to work on clumped isotope because a number of labs are finally able to run the technique (making inter-laboratory calibration possible) and new studies suggest additional interesting kinetic controls on the clumping of heavy isotopes in carbonates.
A major component of my research on paleoclimate is to reconstruct the amplitude of global sea-level variations, and relate this to ice volume, and the stratigraphy and sedimentology of the shelf. My approach to this tricky problem is two-fold: first, to use the stratigraphic record of carbonate systems to reconstruct sea-level based on geometries. Second, to use isotope methods to extract a geochemical signal (oxygen isotope composition of sea-water) that can be converted into a high-resolution sea-level record. Understanding the timing and quantifying the amplitude of sea-level changes is important for three reasons: 1) future sea-level rise linked to anthropogenic greenhouse warming is a threat to millions of people living in coastal area, 2) understanding eustasy in the Cenozoic implies quantifying ice volume, an important parameter in understanding and modelling paleoclimate, and 3) eustasy is one of the major contributor to sediment accommodation variation on continental margins, and by extension plays a major part in controlling the sedimentary architecture of continental margins.
Finally, a completely different aspect of my research interests is to explore the interaction through time between carbonate rocks and the surrounding fluids: this interaction promotes dissolution of the original phases, and/or precipitation of new cement, i.e. carbonate diagenesis. An interesting approach is to link the depositional environment of carbonate platform (climate, eustasy, paleoceanography, biological constraints, etc…) with the diagenetic potential of carbonate rocks, the potential for fracturation, and the resulting fracture network with diagenetic fluid circulation and further modifications of the carbonate rocks. This approach is multidisciplinary, and because diagenesis impacts on the porosity and permeability of carbonate rocks, our research has tremendous implications for oil and gas reservoirs, and for safe carbon capture and storage (CCS) in carbonate rocks.
Current projects that I am involved with include:
- The Qatar Carbonate and Carbon Storage Research Centre, from which we receive funding for five individual projects (Impact of early diagenesis on fracture potential, diagenesis along faults in a salt dome, dolomitization along faults, clumped isotopes applied to carbonate diagenesis, and mechanical stratigraphy of a salt dome).
- The ExxonMobil FC2 alliance, financing our work on flow simulations in carbonate reservoirs
- Reconstructing sea-level and the interplay of sea-level and early diagenesis on the Marion Plateau, offshore Australia. This work is financed in part by the American Chemical Society Petroleum Research Fund.
- Paleoceanography and Paleoclimate of the Messinian stage reconstructed from cores of the Integrated Ocean Drilling Program Expedition 320
- Stable isotope stratigraphy of IODP Expedition 317, focusing on comparing a chemical sea-level record with sequence stratigraphy of the Canterbury basin shelf.