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Abstract

AAPG Bulletin, V. 90, No. 1 (January 2006), P. 115-136.

Copyright copy2006. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/07260504096

Polyphase deformation of diapiric areas in models and in the eastern Prebetics (Spain)

Eduard Roca,1 Maura Sans,2 Hemin A. Koyi3

1Grup de Geodinagravemica i Anagravelisi de Conques, Facultat de Geologia, Departament de Geodinagravemica i Geofiacutesica, Universitat de Barcelona, 08028 Barcelona, Spain; [email protected]
2Grup de Geodinagravemica i Anagravelisi de Conques, Departament de Geodinagravemica i Geofiacutesica, Universitat de Barcelona, 08028 Barcelona, Spain; present address: Cal Rovireta, Pacs del Penedegraves, 08729 Barcelona, Spain; [email protected]
3Hans Ramberg Tectonic Laboratory, Department of Earth Sciences, Uppsala University, Villavaumlgen 16, S-75236 Uppsala, Sweden; [email protected]

ABSTRACT

Fingerlike bodies of evaporite rocks have been observed in many regions affected by multiple tectonic phases, such as the Atlas, the Pyrenees, or the Zagros Mountains, where they have been interpreted as fault-plane diapiric injections or collapse-related salt welds. In this article, we suggest a new interpretation of these structures as squeezed diapirs based on detailed structural and sedimentological field data of the Bicorb–Quesa diapir (eastern Prebetics) and offer five analog models, which simulate the polyphase deformation of the eastern Prebetics. In this area, diapirs formed from the Oligocene to Langhian during an extensional Previous HitphaseNext Hit related to the opening of the Valencia Trough. These diapirs were later affected by a Serravallian contractional Previous HitphaseNext Hit, which inverted the preexisting grabens and created new folds and thrusts. The preexisting diapirs were necked and/or squeezed, forming secondary welds with a fingerlike geometry that isolated the diapir bulbs from their source layer. Extrusion of diapiric material was also accelerated during this Previous HitphaseNext Hit, but no new diapirs formed. Finally, the area was again affected by an extensional Previous HitphaseNext Hit during the Tortonian, which reactivated the normal faults and created a new set of diapirs. The new diapirs formed where the overburden was thinner, that is, at the toe of the major reactivated faults. Commonly, these faults coincide with the bounding faults of the major grabens formed during the first extensional Previous HitphaseNext Hit, and therefore, the new diapirs grow close to the location of the squeezed diapirs. The models also show that the faults created during the initial extension prevailed as the main focus for deformation during the polyphase history. Deformation in the overburden and the viscous layer was mainly accommodated along the major grabens formed during the first extensional stage. During shortening, the initial major grabens deformed as complex anticlines, and during the subsequent extensional Previous HitphaseTop, most deformation occurred by the collapse of these anticlines along preexisting faults, fault welds, and the flank of the squeezed diapirs. The source layer is compartmentalized, accumulating and withdrawing material in the same locations (the initial grabens and horst). As a result, the source layer is easily depleted beneath the initial horst, forming primary welds.

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