A fundamental problem in extensional tectonics is unraveling- three dimensions-the growth and evolution of half-graben-type basins and their basin-bounding faults. This is a project to analyze the transverse and along-strike variations in basin subsidence through a study of changes in thickness and facies of fixed-period Milankovitch-type lacustrine cycles recorded in six cores to be drilled as part of another NSF-funded research project as well as from correlatable outcrops from other parts of the early Mesozoic Newark rift basin of New York, New Jersey, and Pennsylvania. Such an analysis will also aid in the identification of synsedimentary structures. Variations in cycle thicknesses in a vertical section will be used to constrain the factors affecting the basin's historical (evolutionary) development, including its growth through time. Mass-balance basin filling models, constrained by the known geometry of the basin (based on available seismic reflection profiles) as well as by variations in subsidence, will be constructed to assess the "background" or intrinsic effects of uniform subsidence and extension rates and uniform input rates of sediment and water on generating the basin's stratigraphic record. Deviations of the actual stratigraphy (recorded in the cores) from the filling model's simplified predictions can then be used to assess changes in subsidence and extension rates as well as changes in sediment and water supply. In addition to furthering our understanding of the three- dimensional development of half-graben, this study also will constrain the early rifting history of Pangaea in eastern North America.
