Salt basins in Oman contain a well-preserved sedimentary sequence of Late Neoproterozoic-Early Cambrian age. More specifically, the evaporite-carbonate sequences of the Ara Group in Oman provide a complete record of sedimentary, biological and geochemical events at the boundary. Some key observations include:

Platform carbonates are significant hydrocarbon reservoirs; microbial reefs within the carbonates contain some of the earliest metazoan fossils (Cloudina and Nama- calathus).

The carbonates record a prominent negative carbon isotopic excursion and an unusual enrichment of uranium. Coeval ash beds have been dated at MIT's geochronology laboratory. The dates confirm the correlation with the global carbon isotopic excursion at the Precambrian/Cambrian boundary.

Evaporites of the Ara Group are characterized by heavy sulfur isotopes, comparable to observations from other evaporite basins of that period.

During deposition of the platform carbonates, the surrounding basinal areas were probably characterized by largely anoxic water masses. The basins filled with organic-rich cherts (Athel silicilyte) that are important hydrocarbon source rocks. Anoxic waters may have flooded platform areas periodically.

These observations suggest profound biological and geochemical changes. Our current research focuses on the processes behind these changes and how they are linked to each other. The main research areas are:

Redox-sensitive trace metals and organic carbon isotopes are analyzed in order to understand the redox conditions in platform carbonates and organic-rich basinal cherts. They can also be helpful in tying together the geochemical archives from platform and basin locations. Collaboration with Ed Boyle of MIT.

Analysis of Re-Os isotopes in the organic-rich cherts as an additional archive of redox conditions and for radiometric dating. Collaboration with Greg Ravizza and Bernhard Peucker-Ehrenbrink, Woods Hole Oceanographic Institution.

The geochemical signature of organic compounds should reflect biochemical processes in the water column. Collaboration with Roger Summons of MIT.

In addition, the fabrics and the metazoan component of the microbial carbonate reefs are studied to better understand how they reflect the changes recorded by the various geochemical archives. Fabrics are also compared to coeval microbial reefs in Namibia.