HEAT-FLOW IN THE GREAT-PLAINS OF THE UNITED-STATES

Anomalous high heat flow previously reported for the Great Plains is inconsistent with the tectonic setting and requires re-examination. Forty-six new heat flow measurements, 12 revised heat flow values, and several hundred geothermal gradient measurements indicate extensive geothermal anomalies with heat flows ranging from 80 to 140mW m-2 in the northern and central Great Plains. Heat flow in the Great Plains outside the geothermally anomalous regions ranges from 40-60mW m-2. The heat flow anomalies result from the thermal effects of regional groundwater flow where it moves upward either within a dipping aquifer or by cross-formational flow through fractures. The gravitational driving force for the groundwater flow derives from the eastward sloping surface of the Great Plains, and the locations of the geothermal anomalies are determined by the structures of the aquifers and the crystalline basement rocks. -from Author