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The metamorphosed olistostromes and turbidites of Andros Island, Greece, and their tectonic significance

Published online by Cambridge University Press:  01 May 2009

P. Mukhin
P. Mukhin
Affiliation:
Institute of Earth Sciences, The Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel
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Abstract

The blueschists of Andros Island consist of a probable Permian-Eocene metasedimentary rock succession (meta-sandstone, marble, chert), containing large bodies of magmatic rock (serpentinized ultra-mafic rocks, gabbros and granodiorite). The development of a layer-parallel foliation and axial plane cleavage, followed by two phases of intense deformation with recumbent folding, almost completely obliterated the primary bedding and stratigraphic relations in the metamorphic complex. The main features of the geological evolution of Andros, that is, the original environment of deposition and the character and direction of tectonic transport, have been hitherto unclear because of this deformation. The present sedimentological and structural study has led to the discovery of preserved relics of primary sedimentary structures, including graded bedding and chaotic sedimentary breccias. Associated turbidite and olistostromic formations can be recognized at three stratigraphic levels in the Andros Island’s reconstructed column. Some layers of the metasedimentary rocks, having preserved clear signs of the layer’s top and bottom, were also used for the identification of the primary anticlines and synclines among widespread developed recumbent folds. This study has shown that the structural style of the last synmetamorphic recumbent folds with northwest vergence is the same, independent of the direction of the present axial plane dips. This data can be interpreted as a result of monovergent tectonic transport in the last metamorphic event. The analysis of structural relations between primary bedding and first synmetamorphic foliation proves that most of the stratigraphic succession has been preserved in a normal stratigraphic position after the first blueschist and before the second greenschist deformation stage.

Type
Articles
Information
Geological Magazine , Volume 133 , Issue 6 , November 1996 , pp. 697 - 711
Copyright
Copyright © Cambridge University Press 1996

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