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Johns Hopkins University Office: 230 Olin Hall |
Summary:
I am currently working on two exciting projects that fall out of my ideas on secular changes in seawater chemistry. Steve Stanley and I have uncovered some spectacular temporal correlations between changes in seawater chemistry and periods of massive reef-building and sediment production dominated alternately by aragonitic then calcitic organisms. The famous White Cliffs of Dover are an example of the great coccolith calcite chalks that gave the name to the Cretaceous period. The explanation for this period of spectacular "hypercalcification" by calcitic nannoplankton can now be understood in the light of changes in seawater chemistry that affected the kind of CaCO3 polymorph that will most easily precipitate from seawater of a given Mg/Ca ratio.
Tim Lowenstein of Binghamton University and I are starting a major project to try to recover chemical compositions of ancient seawaters from fluid inclusions in halite crystals from marine evaporites. Tim and his students have perfected a method of chemically analyzing very small frozen fluid inclusions (<50µ) in a new Environmental SEM. This is the first time that the inclusions in primary chevron halites can be accurately measured. We can recover the parent seawater chemistry by forward modelling using a brine evaporation computer program.
On another front I am working with Bob Demicco, also of Binghamton University, on 2-D and 3-D modeling of shallow water platform carbonate deposition in the hope of discovering ways to distinguish among the many possible mechanisms that can produce high frequency depositional cycles. We will be collaborating with former student Linda Hinnov who is now an associate research scientist in E&PS.