| mountain belts | |||||||||
| Along a NNW to SSE section the Alps reveal four orogenic segments: The foredeep: Sediments eroded from internal zones accumulate into a Molasse basin. This basin cover auchtonous sedimentary sequences lying on top of the European basement. By and large the foredeep is devoid of any deformation beside flexural subsidence. The foreland: In this segment pre-orogenic sedimentary sequences are scrapped off the European basin. Deformation style is characterized by a combination of folds and thrusts whose vergence is inherited from that of the subduction zone. The metamorphic grade increases toward the hinterand up to the amphibolite facies. The basement is affected by reverse faults that merge with decollemnt in the sedimentary pile. Hinterlan accretated terranes: This is were exotic terranes (micro-continents) are staked into complexely deformed crustal piles. Tectonic klippes and windows reveal large horizontal displacement of allochtonous crustal nappes. Thrusts of opposite vergence are indicative of hyper collision during which the mountain belt develop a more symmetric geometry, with strike-slip faults parallel to the belt accommodating part of the convergence. Metamorphic facies increases up to granulite and eclogite facies. Hinterland thrust and fold belt: This segment seats on the overriding plate whose flexure creates the space for the accummulation of a thick syn-orogenic sedimentary sequences. The sedimentary pile is involved into a fold and thrust belt verging in a direction opposite to that of the original subduction. |
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| --------Foredeep------->> | <<---------Foreland Thrust and Fold Belt--------->> | <<---------Hinterland accretated terranes and crustal nappes--------->> | <<----Hinterland T&F belt- | ||||||
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| @ R. Marchant (Univ. Lausanne) | |||||||||
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