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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 64 (1980)

Issue: 5. (May)

First Page: 797

Last Page: 797

Title: Geologic and Structural History of Zagros Foldbelt, Iran: ABSTRACT

Author(s): P. Verrall

Article Type: Meeting abstract

Abstract:

The earliest discernible event in the Zagros area, which is structurally the northern part of the Arabian continental block, was the deposition of the Infracambrian Hormuz salt, presumably in a rift basin with a north-south boundary on its west side. The overlying shallow-marine miogeoclinal shale-carbonate sequence through the Cambrian is overlian by deeper water Ordovician and Silurian shales, representing a progressive foundering of the rift margin. A second rift event, oriented along the present northern margin of the Zagros foldbelt, began in the pre-Permian, represented by a significant angular unconformity at the base of the shelfal, largely carbonate, Permian to Late Cretaceous sequence.

Sharp change from carbonate to marl deposition along this margin in the latest Cretaceous suggests rapid deepening associated with arrival at a north-dipping oceanic subduction zone, which almost immediately thrust melange and ophiolites up over the edge of the shelf. This entire ensemble has been colliding with the Central Iranian Block along a second north-dipping subduction zone since the Miocene, resulting in essentially concentric folding of the Infracambrian to Miocene shelf sequence, largely upon a basal detachment within the Infracambrian Hormuz salt but also involving the basement in north-dipping thrusts and in tear faulting, and involving the salt in numerous compressionally induced diapiric structures. The syntectonic, evaporitic, Miocene-Pliocene Fars Group rocks represen deposition in a basin restricted by the actual collision event. They are involved in the Zagros folding, and also in enormous, southward directed gravity glides down the regional topographic gradient resulting from the orogeny. The huge oil and gas traps of the area are within the concentric Zagros fold structures, in strata ranging from Permian to Miocene in age.

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Copyright 1997 American Association of Petroleum Geologists