Facies Anatomy and Early Diagenesis of Carbonate Rocks

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Carbonate sedimentary rocks such as limestone are largely made of marine fossils. These components that formed in ancient marine environments tell us much about the very ancient oceans on our planet and thus the history of our world. The limestones are, furthermore, significant archives of the evolution of marine life, amongst the nation's most prolific hydrocarbon reservoirs, and critical aquifers for fresh water and so human wellbeing. The aim of the science proposed here is to ascertain how marine carbonate sediments form in the ocean today (facies anatomy) and how they are then transformed into rock (early diagenesis) throughout the vastness of geologic time. These findings are then used to decipher global climate change and to generate predictive scientific models that can be used by earth scientists to interpret ancient rocks. The focus is on the most poorly understood of these sediments and rocks, specifically cool-water and high latitude polar marine carbonates and related deposits (heterozoan carbonates), the processes of early chemical alteration both terrestrial and marine that changed them, and the perplexing origin of 1 billion year old Precambrian carbonates.***Much of the planned research will take place on and adjacent to the southern Australian continental shelf, the largest area of cool-water, heterozoan, carbonate deposition in the modern world. Expanding on previous NSERC-supported research in the region, specific questions will be addressed via an integrated field program utilizing extensive onland mapping, sampling, and geochemical analysis, marine research, and computer modeling. Research will focus on shallow marine, marginal marine, and lacustrine depositional systems. Funds are also requested to investigate very ancient limestones, specifically 1) to understand how late Devonian (~380 million year old) warm-water (photozoan) reefs formed just prior to a global extinction event, and 2) to determine, via the nature of carbonate sedimentation, how the global ocean evolved during the Neoproterozoic (~800 million years ago) just before the evolution of complex animals. ***Highly Qualified Personnel (HQP) are an integral part of this science. Graduate and undergraduate students are involved in all aspects of the research both in the field (land and marine) and in the laboratory (petrography and geochemistry). They present their results at scientific meetings and are authors on resulting scientific papers. ***End users of this research are those scientists that research ancient carbonate rocks. Paleontologists, paleoceanographers, and sedimentary geologists utilize the information to unravel the rock record. Canadian geoscientists using comparative reasoning to search for and exploit hydrocarbon reservoirs and mineral deposits, together with researchers monitoring marine environmental change through time must be familiar with details of deposition and early diagenesis to be successful. **