INAUGURATION OF A SCIENTIFIC DRILLING PROGRAM INVESTIGATING THE LITHOLOGY AND STRATIGRAPHY OF NEOGENE STRATA OF THE CENTRAL HIGH PLAINS AQUIFER IN WESTERN KANSAS

The High Plains-Ogallala Drilling Program (HPODP) is dedicated to advancing scientific understanding of the sedimentary facies, stratigraphic framework, and chronostratigraphy of the Ogallala Formation and overlying units of the central High Plains aquifer. These properties control aquifer geometries and are derived from the formative processes and depositional histories of water-bearing and confining strata. The aquifer is under increasing developmental stress and groundwater management will depend on accurate characterization of aquifer materials and their stratigraphic framework. Quality stratigraphic information from the Ogallala, however, has been impossible to retrieve due to unconsolidated and saturated intervals of the aquifer. The recent purchase of a rotary-vibratory drill rig by the Kansas Geological Survey provides, for the first time, a means of collecting intact cores from the Ogallala Formation. Major scientific questions that the HPODP will address include: 1) What are the sedimentary facies, depositional environments, and ages associated with areas of high and low relative permeability? 2); Is there a coherent δ¹³C and δ¹⁸O chemostratigraphy that can be used to partition and correlate units?; 3) Do sedimentary facies control the age and chemistry of ground waters sufficiently to produce a recognizable stratified succession of pore fluids?; 4) Are there detectable changes that correspond to such proposed major paleoclimate events as the Middle Miocene Climate Transition, the mid-Pliocene Warm Period, or the onset of Late Pliocene glaciation? Cores will undergo lithologic, spectral gamma-ray, and magnetostratigraphic analyses; core materials and fluids will be analyzed for stable isotopes; and appropriate materials will be analyzed for tephrochronologic, optically stimulated luminescence, magnetic polarity, and U/Pb dating to test permissible interpretations of stratigraphic correlation and hydrostratigraphic architectures. This research has global import because aquifers in heterolithic successions of continentally derived sediments are under developmental stress in many parts of the world. The cores will be curated at the Kansas Geological Survey and will provide additional research opportunities for the larger earth sciences community.