THE STATUS OF GEOLOGIC MAPPING IN OKLAHOMA

As part of the STATEMAP component of the USGS's National Cooperative Geologic Mapping Program, the Oklahoma Geological Survey has been undertaking a 2-part mapping program consisting of: 1) a series of 1:100,000-scale reconnaissance geologic maps of the entire State that will become the foundation for a new 1:500,000-scale geologic map of Oklahoma; and 2) detailed 1:24,000-scale geologic maps of metropolitan areas, which helps identify potential engineering and environmental hazards in rapidly growing urban areas. Detailed mapping of 25 7.5´ quadrangles in the Oklahoma City Metro Area (OCMA) has just been completed and made available to the public. This project has led to significant changes in the distribution and extent of Quaternary alluvial deposits, particularly those associated with the North Canadian River drainage system, as well as led to a better understanding of the geometry of the Garber-Wellington aquifer. For the most part, terrace deposits are smaller in areal extent than what was previously mapped; this will have considerable impact on potential sand and gravel operations as well as on the potential use of alluvium-based aquifers for agricultural enterprises. The distribution of these terrace deposits also allows for better understanding of Quaternary base-level changes that have occurred along the North Canadian River. Detailed mapping of the Garber and Wellington Formations in the OCMA has led to better delineation of the surface and subsurface occurrences of these important water-bearing units. This will aid in more effective land-use for municipal and residential development, and allow for better cost-effective measures in setting depth of casing of oil and gas drill holes. Currently ten 1:100,000-scale reconnaissance maps in western Oklahoma have been completed. This project also has led to better delineation of different types of Quaternary deposits compared to previous 1:250,000-scale maps, particularly by differentiating between vegetated dune and wind-blown sheet sand deposits, and between high and low fluvial terrace deposits. Greater accuracy in locating the eastern extent of the Ogallala aquifer has also been achieved.