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Geochemistry and Geobiology

In the geochemistry and geobiology theme, the focus is twofold. The first is to maintain

a leading role amongst scientific laboratories using the clumped isotope method. The stable

isotope laboratory (SIL) is one of only two laboratories that can measure the Δ48 proxy and

apply it to various aspects of carbonate geochemistry. The second focus is understanding

microbial carriers and biosignatures in microbialites. Both are important for identifying

microbial origin of ancient carbonates.

Current Projects

The Carbon Isotopic Composition of Proximal and Distal Sediments in the Vaca Muerta


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Investigators: Ralf J. Weger, Gregor P. Eberli, and Peter K. Swart

Project Objectives:

  • Evaluate the ability to use δ13C values from organic material to correlate between different sections within the basin, located kilometers apart, in both proximal and distal positions.

  • Re-validate that the δ13C values of organic material (δ13Corg) are unrelated to changes in the total organic content.
  • Confirm that δ13C values of organic material can be used to correlate coeval sections within a basin more accurately than the δ13C values of carbonate.


The Delineation of the Mixing Zone Using Clumped Isotopes


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Investigators: Peter K. Swart and Chaojin Lu

Project Objectives:

  • The Δ47 values of carbonates, affected by freshwater and marine fluids, can beused in conjunction with the δ18O values of the carbonates (δ18Ocarb) to determine the δ18Ofluid values of the diagenetic fluids.

  • These data show that the zone of covariance between δ13Ccarb and δ18Ocarb values, previously interpreted as representing diagenesis within the zone of mixing between fresh and marine fluids, takes place largely within the freshwater phreatic zone. The purpose of this work is to refine the hypotheses previously suggested.


The Use of Δ47 and Δ48 Disequilibrium in Understanding Dolomite Formation


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Investigators: Chaojin Lu and Peter K. Swart

Project Objectives:

  • To investigate the utility of dual clumped isotope thermometry (Δ47 and Δ48) to understand the processes of dolomitization.

  • To use Δ47 and Δ48 values to decipher the kinetic isotopic effects during microbial induced dolomitization.



Origin of Δ47 and Δ48 Disequilibrium in Carbonate Minerals


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Investigators: Peter K. Swart and Chaojin Lu

Project Objectives:

  • The combination of Δ47 and Δ48 proxies can be used to ascertain whether carbonates are deposited close to equilibrium or if they are affected by kinetic influences.


Clumped Isotope Evidence on the Origin of the Marinoan Cap Dolostone


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Investigators: Chaojin Lu, Jiuyuan Wang, Matthew Hurtgen, and Peter K. Swart

Project Objectives:

  • Examine whether reordered dolomite and calcite can preserve the primary oxygen isotopic composition of formation fluids.

  • Decipher the formation process of the Marinoan cap dolostone (primary versus diagenetic origins).


Impacts of the Microbialite Evolution on Chemical Biosignatures


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File Size:395KB


Investigators: Clément G. L. Pollier, Brooke E. Vitek, Erica P. Suosaari, R. Pamela Reid, and Amanda M. Oehlert

Project Objectives:

  • Determine which elements are transferred from microbial organic matter into carbonate minerals during early taphonomy.
  • Develop a workflow to constrain the preservation mechanism of chemical biosignatures within microbialite systems.


Peloids as Microbial Carriers for Organomineralization in Ooids


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File Size:399KB


Investigators: Mara R. Diaz and Gregor P. Eberli

Project Objectives:

  • To test the hypothesis that peloids, which form the majority of nuclei in ooids, carry the microbial communities for organomineralization in ooids.
  • To compare the organic and mineral composition within peloidal nuclei of ooids and fecal pellets by integrating RAMAN spectroscopy for the characterization of biomolecules (e.g. lipids and carbohydrates) and SEM/EDX for the mineral phases.




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