Stratigraphy and Structure of the Iranian Makran

Burg, Jean-Pierre ¹
(1)Earth sciences, Geologisches Institut, ETH-Zurich, Zurich, Switzerland.

Four main tectono-stratigraphic provinces were distinguished in the central Makran Accretionary Wedge, in southern Iran: North-, Inner, Outer and Coastal Makran. North Makran is dominated by mafic to intermediate igneous rocks, tectonic mélanges and Cretaceous deep-water marine sediments. Upper Cretaceous shallow-water limestone unconformably covers Lower Cretaceous sediments and igneous rocks. The oldest turbiditic sequences are Late Cretaceous. Lower Eocene deep-marine sediments grade into deeper marine Eocene turbidites that show a general thickening- and coarsening-upward trend, becoming more terrigenous and proximal during Early-Late Oligocene. This suggests progradation of submarine fans, followed by more distal deposition during the Late Oligocene. Pro-delta turbidites grade up-section into Lower Miocene sandstones deposited on a shelf dominated by waves and tidal currents. The Lower Miocene sediments are mainly marls with gypsum deposited in basins with restricted circulation. These deposits grade laterally into bioclastic sandstones and marls and coral limestones bordering the basin. The passage from the Lower to Middle Miocene is not observed but the Middle Miocene starts with deep-marine turbidites and grade up-section into shallower facies. Coastal Makran exposes sediments mostly younger than the Late Miocene. These sediments represent a wedge-top basin with a shallowing-upwards sequence from slope marls to coastal and continental deposits. All provinces, Coastal Makran excepted, are covered unconformably by a large, Tortonian (11.6-9.6 Ma) olistostrome. A series of analogue experiments tested the influence of erosion and deposition on the deformation style of the wedge. Sudden mass redistribution caused a change of thrusting pattern, with thrusting jumping to the front of the resedimented load. Striking differences in deformation style and intensity observed in the Iranian Makran are explained by the mass-redistribution caused by the Late-Miocene olistostrome.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.