A relation between continental heat flow and the seismic reflectivity of the lower crust

Deep seismic reflection profiling of the continental crust has found world-wide evidence for prominent reflections from the middle and lower crust. This paper presents evidence for a correlation between the depth to the zone of pronounced reflectivity (the 'reflective lower crust') and the surface heat flow. The highly reflective zone appears to be shallower beneath regions with higher heat flow, suggesting that one condition for the development of the reflective zone is the existence of a sufficiently high temperature in the crust. The data presented in this paper suggest that the highly reflective zone is generally developed only at temperatures higher than 300°-400 °C. This correlation of reflectivity with heat flow implies that crustal reflectivity must be variable on the same time scales on which crustal heat flow is variable. This constraint appears to favour an origin for the lower crustal reflectivity related either to ductile strain banding or to free fluids that may be transient on geologic time scales, rather than to compositional layering or multiple igneous intrusions that are relatively permanent features of the crust.      ARK: https://n2t.net/ark:/88439/y039633 Permalink: https://geophysicsjournal.com/article/6 &nbsp