The Impact of Tectonic Setting on Distribution of Kolosh Formation during Paleocene –Lower Eocene in Northern Iraq

Rabeea Znad,Ibrahim Aljumaily

doi:10.33899/earth.2019.170264

Abstract

This study covered most of Kolosh Formation exposure areas in northern Iraq. Description of the lithology and measuring the actual thickness of the Formation from exposures and well logs were performed. The isopach map of the Formation was constructed. The sedimentation of the Formation was affected by the tectonic activity of the northeastern edge of the Arabian plate during the closure of the Neo-Tethys Ocean. The tectonic setting outlined the depozone of foreland basin system and controlled the variation of the deposits of the Kolosh Formation along the orogenic front (It revealed that there are more than one basin of deposition). The deviations of the depocenters of the Kolosh deposit basins from the current folds are depicted. The counterclockwise rotation of Arabian plate and its oblique collision with Iranian plate as well as the rejuvenation of the basement faults during the peak of the orogeny might cause such deviation.

Highlights

Kolosh Formation is one of the widely distributed clastic sediments throughout northern Iraq
The present study identified some lineaments extending regionally (Fig. 7A, marked in red) which correspond roughly with the general boundaries of the fore-bulge depozone
The second main lineaments represent the northeastern boundary of Duhok-Kand basin (Fig. 7A&B) extending from west of Khabour River to the western part of the Galy Dhe, and passing through the western part of the Gara anticline, close to Galy Besari, it deviates towards Galy Qeer (Shaikhan anticline), and its effect diminishes towards Aqra anticline

Summary

INTRODUCTION

Kolosh Formation is one of the widely distributed clastic sediments throughout northern Iraq. The distribution of these deposits reflects the dynamic tectonic setting of Arabian northeastern edge during its subduction under Iranian plate and initiation of foreland basin system during late Cretaceous. The formation consists of rhythmic alternation of thin sandstone, siltstone, marlstone, and less common conglomerate and limestone with calcareous silt shale inter-layers. Pebbles are mainly limestone and chert, spherical in shape, sorted and rounded They are poorly cemented with sandy and clayey materials, and occasionally bituminous. In Shaqlawa area, there is an increase in dark shale upward the section, with bituminous saturated sandstone beds and abundance of trace fossils and sedimentary structures (Fig. 3). Friable, wetted sometimes, (fine to coarse grain) Sedimentary structures, bituminous matter

A BB B B

CONCLUSIONS