Significant progress has been made in understanding the water column and circulation of the mid-Cretaceous Western Interior Sea by utilizing planktic foraminiferal porosity of the species Hedbergella delrioensis as a proxy for water temperature and relative density (Fisher et al., 2003 and Fisher et al., in review). The water column was significantly stratified; thereby inhibiting wind- mixing. Water mass mixing occurred along oceanic-fronts resulting in the formation of endemic Western Interior waters. Fronts may explain the paradox of a stratified, highly productive ocean, where nutrient renewal to the photic zone should have been inhibited due to the density stratification. Mixing along fronts provided nutrients to the central, more normal marine waters, to stimulate and sustain the high primary productivity recorded by the high organic-carbon accumulation found in the strata. Mixing in the Western Interior Seaway produced relatively cool water that was exported out of the sea to the south at depth (Fisher, 2002; Fisher, in review). As the Greenhorn Sea evolved, the strata of the Hartland Shale and Bridge Creek Limestone members indicate that the sea became more stratified by the addition of warmer layers, some of which were produced within the seaway (Fisher, 2002; Fisher, in review). Although much has been learned about the evolution of this important epicontinental sea of the greenhouse Earth, much remains to be learned. Due to the indurated nature of the limestones of the Greenhorn Formation, no examination of the development of Milankovitch cyclicity has been possible using the porosity method. Conducting porosity analyses on foraminifers from the Niobrara Formation is expected to provide data that will assist in understanding how the astronomical orbital cycles may have amplified terrestrial processes such as increased runoff, delivery of detrital material to the sea, and changed the mixing ratio of Tethyan-sourced versus Boreal-sourced waters. This information could prove critical to a greater understanding of the development of Cretaceous source-rock strata. An improved understanding of the Cretaceous greenhouse ocean circulation could also assist in understanding how future climate changes impact Earth. There are three goals to this pilot project: 1) establish a new proxy species adequate for porosity analysis in rocks younger than early Santonian (Hedbergella delrioensis has its global extinction in the early Santonian (Caron, 1985) and therefore would not be available for the entire duration of the Niobrara); 2) determine if there are substantial differences in the temperature and water column stratification in the Niobrara as compared to the Greenhorn; and 3) determine the feasibility of investigating the origin of the bedding couplets found in the Niobrara. Results of the pilot project should not only establish the feasibility of conducting a large-scale geographic and stratigraphic porosity study of the Niobrara Formation and equivalents that can be used to reconstruct circulation of the Niobrara Sea through time; but should provide preliminary results about the origin of couplet formation and provide important insights into the development of the Western Interior Seaway over the longer time-frame of second-order sea-level changes. This research will have an impact on teaching and learning in that the investigation will be carried out by the PI and two undergraduate research assistants over a period of one year beginning in June, 2003. The undergraduate students will be involved in every aspect of the work. All will participate in sampling the Berthoud State No. 4 core at the Denver United States Geological Survey Core Research Center. The students will be involved in all aspects of data collection, including operating the new Environmental Scanning Electron Microscope, interpreting the data and disseminating results in professional presentations and publications. The results of the research will be integrated into the West Chester University Introduction to Oceanography laboratories on paleoceanographic reconstruction and geologic proxies. The strong established record of involving underrepresented groups in research will be continued. The selection for undergraduate research assistants will take into account the under-representation of women and minorities in the Geosciences.
