Isostasy and paleotemperatures in the Southern Tyrrhenian Basin,Mediterranean Sea |
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| Authors: | V Pasquale P Chiozzi M Verdoya |
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| Institution: | (1) Dipartimento per lo Studio del Territorio e delle sue Risorse, Settore di Geofisica, Università di Genova, Viale Benedetto XV, 5, 16132 Genova, Italy |
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| Abstract: | The present-day basement depth of the seafloor in the absence of sediment loading was inferred along a traverse crossing the
Southern Tyrrhenian Basin. A correction for sediment loading was proposed on the basis of density, seismic velocity and porosity
data from selected deep boreholes. The empirical relation between sediment correction and seismic two-way travel time was
extrapolated downward by applying the Nafe–Drake curve and a specific porosity–depth relation. The sediment loading response
of the basement calculated for flexural isostasy is on average about one hundred meters lower than results for local isostasy.
A pure lithosphere extensional model was then used to predict quantitatively the basement subsidence pattern on the margins
of the basin. The basement depth is consistent with uniform extension model predictions only in some parts of the margins.
The observed variability in the region of greatest thinning (transition from continental to oceanic crust) is attributable
to the weakening effect caused by diffuse igneous intrusions. Subsidence of the volcanic Calabrian–Sicilian margin is partly
accounted for by magmatic underplating. The comparison of the calculated subsidence with an oceanic lithosphere cooling model
shows that subsidence is variable in some areas, particularly in the Marsili Basin. This argues for a typical back-arc origin
for the Tyrrhenian Basin, as a result of subduction processes. By taking into account the geodynamic setting, stratigraphic
data from the deepest hole and the terrestrial heat flow, we reconstructed the paleotemperatures of cover sediments. The results
suggest that low temperatures generally have prevailed during sediment deposition and that the degree of maturation is expected
not to be sufficient for oil generation processes. |
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| Keywords: | Subsidence Extension tectonics Airy isostasy Lithosphere flexure Paleotemperature Tyrrhenian Sea |
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