Shedding Further Light on Upper Cretaceous – Neogene Subsurface Lithostratigraphy of Southwestern Iraq

Y. Tamar-Agha, Mazin; E.A. Al-Sagri, Khedar

	Shedding Further Light on Upper Cretaceous – Neogene Subsurface Lithostratigraphy of Southwestern Iraq
Iraqi Journal of Science
Article 1, Volume 56, Issue 1, 2015, Pages 798-827
Authors
Mazin Y. Tamar-Agha; Khedar E.A. Al-Sagri
Abstract
Exploratory activities carried out by oil companies in the latter half of the past century proved the existence of voluminous reserve of oil and gas in the southwestern area of Iraq. In view of this, it seemed more than prudent to add a new knowledge to that currently existing about the subsurface lithostratigraphy of this area. As a first step in fulfilling this mission, this paper will attempt to do so by covering the time interval from the Upper Cretaceous to the Neogene. In turn, this effort had entailed both the description of about 4707 metres of fully recovered cores, plus the subjection of more than 4000 samples to existing petrologic analyses. Findings worth mentioning does include the observation that with the exception of the Paleogene sequence, the Upper Cretaceous and Neogene sequences are no different from those found in other parts of southern Iraq. For instance, the Upper Cretaceous sequence is found to be consisted of the common Hartha, Qurna, and Tayarat Formations. The same could be said about the Neogene sequence which is found to be again made of the common Ghar, Euphrates, Fatha, and Zahra Formations. In contrast, the Paleocene – Lower Eocene sequence lithology is found a bit different from those commonly encountered in other parts of southern Iraq. This difference emanates from the intense sulphidzation as manifested in the common occurrence of anhydrite, gypsum, and vanished evaporite being observed through the lower Paleogene sediments of south west, Iraq. Because this phenomena exhibits strong vertical as well as lateral variation, this sequence is divided into an intensely evaporitic portion, which is introduced in this article under the name of the Jerishan Group (Paleocene - Lower Eocene), inclusive of Umm Er Radhuma, Rus, Jil/Rus, and Jil Formations. The latter formation is recently introduced stratigraphic rock unit representing the non-evaporitic equivalent for the Rus Formation. The less evaporitic portion (the Dammam Formation) of the Paleogene was found to be the same as the ones found in other parts of the south Iraq, Kuwait and Saudi Arabia.
Keywords
Stratigraphy; Southern Iraq; Upper Cretaceous; Paleogene; Neogene

Statistics Article View: 73 PDF Download: 53