Abstract

Detailed mapping of part of the Othris (=sub-Pelagonian) zone in east-central Greece has revealed the existence of a stack of thrust sheets of Early Cretaceous age. These have emplaced ophiolites onto a formerly stable Mesozoic continental margin from an ocean that lay to the west of the Pelagonian zone. Systematic facies changes from one thrust sheet to the next overlying thrust sheet suggest that the ophiolites originally formed part of an ocean adjacent to the inferred continental margin and were laterally continuous with it. Thus the ophiolites are regarded as parts of a tectonically emplaced marginal oceanic strip (this does not imply they were parts of a “marginal ocean basin” in the sense of Karig).

It is speculatively suggested that prior to emplacement the mantle underneath this marginal strip had been serpentinized and raised to a much higher level. Such a process would overcome one of the problems of ophiolite emplacement–the necessity to postulate uphill movement of heavy oceanic crust and upper oceanic mantle. Serpentinization is attributed to water freed by dehydration reactions in a slab sinking beneath the marginal oceanic strip from a trench initiated at some distance from the continental margin.

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