Datapages, Inc.Print this page

Aptian Organic-Rich Intrashelf Basin Creation in the Dezful Embayment (Kazhdumi and Dariyan Formations, Southwest Iran)

Frans S.P. van Buchem1, D. Baghbani2, Luc-Georges Bulot3, M. Caron4, Fabrice Gaumet1, A. Hosseini2, A. Immenhauser5, F. Keyvani2, R. Schroeder6, V. Vedrenne1, and Benoit Vincent1
1 Institut Français du Pétrole, Rueil-malmaison, France
2 Exploration Department, NIOC
3 Université de Provence, France
4 University of Fribourg,
5 Bochum University,
6 Senckenberg Museum

In the Zagros Mountains of SW Iran a well developed Mid Cretaceous succession is exposed in a number of giant anticlinal structures. In these first class outcrops the evolution from a regional shallow water carbonate platform (Hauterivian to Barremian) to the initiation and development of an intrashelf basin (Aptian) is documented.

A high resolution time framework, based on the integration of biostratigraphic, chemostratigraphic and sequence stratigraphic data, allows to characterise step by step the geometrical and ecological evolution of this system. The Hauterivian/Barremian shallow water carbonate platform was a very flat, layer cake organised system, with meter to decameter scale cycles that can be followed over several hundreds of kilometers. Sedimentation was mixed, with the influx of clays shed of the Arabian shield. In early Aptian times (Deshayesi ammonite zone) a reorganisation took place, initiating an intrashelf basin in the Dezful Embayment, that led to very distinct lateral facies changes. The shallow water deposits contain rudists in the lower part, often overlain by thick packages of Orbitolina dominated facies. In the organic-rich intrashelf basin, a pelagic fauna is found of ammonites, pelagic foraminifera and Radiolaria. Around the margin, prograding packages of Orbitolina-dominated facies interfinger with the pelagic facies.

The creation of this early Aptian intrashelf basin is not only time equivalent with the Formation of other intrashelf basins on the Arabian Plate (Bab basin), but probably also with similar sedimentation patterns in Mexico and Texas.