Carbonate platform development responding to tectonic, oceanographic, and biotic transitions

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To understand the potential impact of "global change" in today's world, it is necessary to appreciate the character and rate of environmental change itself; to understand if an environment can resist change; and, to understand if change is reversible (i.e., the environment recovers). Modern earth systems provide only a "temporal snapshot" of the environment. Missing is the historical framework. The geologic record (in outcrops, quarries, and drill cores) is such an archive, and, when incorporated with data from modern systems, provides the only sound basis for public understanding of the potential dynamics of the Earth system. Two geologic settings very sensitive to local and global external environmental pressures are tropical- and temperate-latitude carbonate shelves. Production of carbonate sediment (whether by inorganic or biological means) is sensitive to subtle physical and geochemical changes in the ocean water. Seafloor sediments along these modern shelves are often viewed to be the "barometers" of the Earth's health. The proposed research will examine three ancient carbonate shelves of different ages; in million years, ~570 (Uruguay), ~440 (Ontario) and ~25 (New Zealand). Each records different, and in two cases changing, frameworks of tectonism, paleoclimate, oceanography, and biotic evolution during shelf development. By examining environmental change as documented by the history of sedimentation and the paleontological record, the research will help better understand how these types of shelves can respond to competing environmental pressures, the rates of change, and what sets of pressures are dominant in suppressing or augmenting environmental change. The work will be transferable to help understand modern day depositional systems. In addition, two of the platforms (Uruguay, Ontario), will provide information about how the earth system responded to prominent environmental crisis associated with oceanographic and biotic transitions. The Ontario platform will also provide information about the history of long-lived (600 million year) tectonism along a fault system within the otherwise stable Canadian Shield.