The microbial carbonates and geochemistry theme is addressed in three projects.

The first project studies the diverse organosedimentary deposits in the Salar de Atacama

in Chile to unravel the dynamic biogeochemical processes in the geological record. The

second project aims to elucidate the effect of microbial communities in diagenetic processes

in skeletal grains. To reach this goal, in vitro incubation experiments will be conducted with

skeletal grains in the presence and absence of microbial marine communities. The third

project is using the vast sample base from the Neuquén basin to measure organic and

inorganic carbon variations. Key questions to be answered is if changes in δ13C values

proximal and/or distal behave correlative within the Neuquén Basin and their reliability as

global climate proxies.

In the diagenesis theme, we plan to assemble a petrographic data base in carbonates

with examples of all diagenetic environments. Starting point of this new initiative is our

petrophsyical data base where each of the measured samples has a digital image with the

diagenetic information.

Our research effort in carbonate contourite depositional systems continues with

updating the carbonate contourite data base and with a project that investigates the

importance of current deposition on continental and carbonate margin stratigraphy. The

ultimate goal of this ongoing project is a sequence stratigraphic model that incorporates

the facies both current and sea-level controlled deposits.

Project Objectives:

• Characterize the mineralogical and sedimentological compositions of diverse organosedimentary deposits in the Salar de Atacama.

• Assess how variations in facies characteristics of organosedimentary deposits influence trace element enrichments and stable isotope fractionation patterns.

• Develop a conceptual model using facies-specific elemental partition coefficients and isotope fractionation factors to improve the interpretation of biosignatures over geological time.

Project Objectives:

• To elucidate the effect of microbial communities in diagenetic processes that lead to the cementation of skeletal grains.

• Toward this end, in vitro incubation experiments will be conducted with skeletal grains in the presence and absence of microbial marine communities.

• To determine whether microbial exudates of exopolysaccharide substances (EPS) influence agglutination and early cementation of skeletal grains.

• To document the development of inter/intragranular cements and identify textural forms and mineral microstructure composition of early marine cementation areas using petrographic thin-sections and SEM/EDS.

Project Objectives:

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

• Reevaluate the reliability of carbon isotopic values (δ13Ccarb and δ13Corg) for reconstructing Late Jurassic–Early Cretaceous climatic signals.

• 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.

• Assess the impact of diagenetic processes and localized sedimentary influences on δ13C records.

• Integrate legacy ocean drilling core data (NSF Proposal) to understand and resolve existing discrepancies and enhance the reliability of carbon isotopic values to understand global climate of the past.

Project Objectives:

• Measure the δ13C values of intestinal fluid and ichthyocarbonate.

• Calculate the fractionation factor (ε) for ichthyocarbonate formation.

• Assess the relationship of ε with mol%MgCO3 content.