Heat flow and tectonics of the Ligurian Sea basin and margins

Jemsek, John P.

doi:10.1575/1912/4342

Cited by 5 publications

(2 citation statements)

References 194 publications

(489 reference statements)

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“…JEMSEK (1988) reported several pieces of evidence for the climatic history in the entire Mediterranean basin. Figure 3 shows the climatic model we propose, based on these data, together with the expected change in heat flux within the depth range of Ratio between observed temperature gradient and equilibrium temperature gradient (C obs /C) at the surface for a sediment layer of two thickness h s as a function of the deposition time.…”

Section: Surface Thermal Constraintsmentioning

confidence: 99%

Thermal Structure of the Ionian Slab

Pasquale

Verdoya

Chiozzi

2005

Pure appl. geophys.

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We propose a thermal model of the subducting Ionian microplate. The slab sinks in an isothermal mantle, and for the boundary conditions we take into account the relation between the maximum depth of seismicity and the ''thermal parameter'' L th of the slab, which is a product of the age of the subducted lithosphere and the vertical component of the convergence rate. The surface heat-flux dataset of the Ionian Sea is reviewed, and a convective geotherm is calculated in its undeformed part for a surface heat flux of 42 mW m )2 , an adiabatic gradient of 0.6 mK m )1 , a mantle kinematic viscosity of 10 17 m 2 s )1 and an asthenosphere potential temperature of 1300°C. The calculated temperature-depth distribution compared to the mantle melting temperature indicates the decoupling limit between lithosphere and asthenosphere occurs at a depth of 105 km and a temperature of 1260°C. A 70-km thick mechanical boundary layer is found. By considering that the maximum depth of the seismic events within the slab is 600 km, a L th of 4725 km is inferred. For a subduction rate equal to the spreading rate, the corresponding assimilation and cooling times of the microplate are about 7 and 90 Myr, respectively. The thermal model assumes that the mantle flow above the slab is parallel and equal to the subducting plate velocity of 6 cm yr )1 , and ignores the heat conduction down the slab dip. The critical temperature, above which the subduced lithosphere cannot sustain the stress necessary to produce seismicity, is determined from the thermal conditions governing the rheology of the plate. The minimum potential temperature at the depth of the deepest earthquake in the slab is 730°C.

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Section: Surface Thermal Constraintsmentioning

confidence: 99%

Thermal Structure of the Ionian Slab

Pasquale

Verdoya

Chiozzi

2005

Pure appl. geophys.

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“…The sedimentary correction rate has been made on the basis of Lucazeau and Le Douaran's (1985) model which demonstrated for the adjacent Gulf of Lion that sediments absorb up to 30% of the surface heat flux. Palaeoclimatic variations have been evaluated through Jemsek's (1988) model, implying an increase of 8-10 mW m-2 of heat flux.…”

Section: Heat-flux and Structural Datamentioning

confidence: 99%

Types of crust beneath the Ligurian Sea

Pasquale¹,

Verdoya²,

Chiozzi³

1994

Terra Nova

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The structural setting beneath the Ligurian Sea resuJts from several tectonic events reflected in the nature of the crust. The central‐western sector, called the Ligurian basin, is part of the northwestern Mediterranean. It is a marginal basin that was generated in Oligocene‐Miocene time by subduction of the Adriatic plate beneath the European plate and by the eastward drift of the Corsica‐Sardinia block. The eastern sector belongs to the Tyrrhenian basin system and is characterized by extensional activity which since Tortonian time superimposed an earlier compressional regime. Our effort has been addressed in particular towards simplifying the complex nature of the crust of the Ligurian basin by modelling its genesis using uniform extension and sea‐floor depth variation with age. In the rift stage of the basin's evolution, the initial subsidence reaches the isostatic equilibrium level of the asthenosphere by a thinning factor of 3.15. The additional passive process, corresponding to the cooling of the lithosphere since 21 Ma, leads to a total tectonic subsidence of 3.4 km, representing the boundary of the extended continental crust. For values up to 4.1 km a transitional‐type crust is expected, whereas for higher tectonic subsidence values a typical oceanic crust should exist. After setting these constraints, the boundaries of the different crust types have been drawn based on total tectonic subsidence observations deduced from bathymetry and post‐rift sediment thickness. Although there is a general agreement with the previous reconstructions deduced from other experimental data, the oceanic realm has wider extent and more complex shape. The northernmost part of this realm shows crust of sub‐oceanic type altemating basement highs with lower subsidence values. The observed surface heat flux is consistent with the predicted geothermal held in the Alpine‐Provençal continental margin and in the oceanic domain. However, a characteristic thermal asymmetry is clearly visible astride the basin, due to the enhanced heat flux of the Corsica margin. Even if the uniform extension model accounts well at a regional level for the present basement depth, a remarkable tectonic subsidence excess has been found in the Alpine‐Provençal continental margin. This evidence agrees with the reprise in compression of the margin; the direction of the greatest principal stress is N120°E on average.

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