Late Cretaceous Syn-depositional mass transport deposits in the turbidites of Zagros Orogenic belt: examples in the Maastrichtian Tanjero formation, Kurdistan region, NE-Iraq

Abstract

In the northeast Iraq, the Maastrichtian turbidite deposits, as a Tanjero Formation, consist of very thick succession of sandstones, conglomerates, and calcareous shales. It deposited in a deep and coastal areas of the Early Zagros Foreland basin which is generated after the radiolarites and limestone obductions during Maastrichtian. The foreland basin was bounded from northeast by newly uplifted and highly elevated active terrestrial land from which voluminous amount of the siliciclastic sediments and carbonates transported to the different parts of the foreland basin. In the studied area, two types of lenticular bodies of synsedimentary mass transport deposits (MTDs) are recorded in the turbidite succession and studied in three outcrop sections about 70 km far from each other. The first type is deposits of coarse grain debris flow, characterized by bad sorting, mud supporting, chaotic internal structures, and bearing angular blocks of olistoliths which reveal instable tectonic setting of the basin. The second is Maastrichtian slump debris within sandstone bedsets (succession) which are extremely deformed, wildly fragmented to blocks of olistoliths and boulders. These deformed bedsets are squeezed between intact and unreformed strata of the lower part of the Tanjero Formation. The slump deposits contain folded sandstone beds and their attitudes indicate, on the stereonet, the southwest transport of the slump deposits. This direction is detected from trends of four fold axes included in the slump debris. The fold axes are extending northeast-southeast which indicate the gravitation stress was in the southwest direction. This study includes a first record of the catastrophic submarine coarse grain debris flow, slumping, and olistolith deposition in the Zagros orogenic belt that uncovers important tectonic setting processes and paleogeographic configuration of the Zagros Collisional Belt during Maastrichtian.