Iraqi National Journal of Earth Science

Abstract

Interpretation of Paleofacies maps was used as a tool to prove that Mosul fault was active since Middle Jurassic or even earlier. This fault extends from the Turkish border to the Lower Zab tributary of the Tigris River dividing the region into Mosul and Sinjar blocks. The sedimentary facies were used as indicators for the fault extension and its vertical displacements. They showed that Sinjar block was uplifted until Cretaceous when the two blocks were at almost a same elevation. Such a situation was remained until Middle Eocene.
During this epoch, the collision between Arabian and Eurassian plates resulted in a relative uplift of the Mosul block and the deposition of the continental Gercus Fm. In the mean time, a thick deposition of the basinal Jaddala Fm. was dominating the subsided Sinjar block. The Mosul block persisted the extremely uplifting until end of the Oligocene. The Early Miocene was characterized by the up- and downward movements of Sinjar block. This was also manifested by the facies alternations of both basinal and lagoonal types although in general the Sinjar block was relatively uplifted. During the Middle Miocene, the deposition of the Jeribe Fm. on the Sinjar block side may indicate that the Mosul block was in a higher position. In Late Miocene the Injana Fm. covered both blocks revealing that their elevation might be on the same level. However, later and according to the presence of the Bakhtiari Fm. the Sinjar Block seemed to be slightly in a higher position.
The paleostress analysis showed that the Mosul fault might be sinistral strike-slip at the extension phase of the Alpine orogeny (Triassic- Upper Cretaceous) then later it was becoming dextral strike-slip during the compression phase from Upper Cretaceous till now. As a result the present day may expose the risk of the fault displacement. Some fractures of such displacement were recorded on the
Al-Shohada' Bridge (the 3rd bridge over the Tigris River) of the Mosul city, which are indicating the existence of the dextral strike-slip neotectonics within the city of Mosul. So it is highly recommended to take such a risk into consideration, particularly when constructing large projects in future.