A statistical analysis of bottom-hole temperatures from oil and gas wells in the northern Mississippi embayment suggests that the geothermal gradient below a depth of 1 km is low (22.2°C/km) and for the New Madrid seismic zone, it is even lower (15.7°C/km). These data support the tentative conclusion of Swanberg et al that ground-water convection is the source of near-surface heat in shallow water wells of the region. Research by Mitchell et al had suggested a high geothermal gradient in the crust and upper mantle beneath the New Madrid seismic zone as a plausible explanation for the lower than average compressional wave velocities observed there. Warmer than normal wells in the northern Mississippi embayment are scattered at random and may be attributed to rand m error in the data. Deep wells in the southern Mississippi embayment are substantially hotter than wells at a comparable depth farther north. The regional geothermal gradient below a depth of 1 km from northern Louisiana to central Mississippi is 26.9°C/km. From central Mississippi to central Alabama, the geothermal gradient (23.1°C/km) is comparable to that of the northern Mississippi embayment.

End_of_Article - Last_Page 1460------------