Heat flow and tectonics of the Ligurian Sea basin and margins
Heat flow, tectonic subsidence and crustal thickness distributions in the Ligurian Basin are best explained by asymmetric lithospheric thinning mechanisms. Over 150 heat flow measurements are made on several transects between Nice, France and Calvi, Corsica on continental slope and rise settings. Thermal gradient determinations are improved using an optimization technique. Piston core data and surface sediment 3.5 kHz reflectivity patterns help constrain thermal conductivity obtained from over 100 in situ stations. Plio-Quaternary stratigraphy is revised using new seismic reflection profiles: a boundary fault system associated with postrift margin uplift, a Pleistocene-age Var Fan construction, and recent diapirism of Messinian salt are indicated. After assessing local thermal disturbances (mass-wasting, microtopography, and salt refraction), positive heat flow corrections are made for multi-lithologic sedimentation histories and glacial paleotemperatures. Using boundary-layer cooling models, equilibrium heat flow estimates support geologic evidence for Oligocene and early Miocene rifting. Heat flow maxima correlate well with two "oceanic" sub-basins, suggesting that the southeastern trough near Corsica is ~5 Myr younger, consistent with the southeastern progression of volcanism and back arc rifting in the Western Mediterranean. Tectonic subsidence-crustal thickness trends indicate lithospheric stretching, with heat flow supporting asymmetric sub-crustal lithospheric thinning during the conjugate margin formation.
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Massachusetts Institute of Technology and Woods Hole Oceanographic Institution