Sedimentary Basin Reconstruction and Tectonic Development of Paleocene-Eocene Succession, Southern Iraq, by Geohistory Analysis

Abstract

The Paleocene-Early Eocene sequence is represented by Aliji and Umm Er Radhuma formations, while the Middle-Late Eocene sequence is represented by Jaddala and Dammam formations. The Rus Formation has been described and its basin was analyzed separately because it was deposited during the regression period (Middle Eocene), which is a transitional period between these two cycles. 
 This study includes analysis of the geohistory of this succession, interpretation of the changes of the accumulation, and calculation of subsidence rates. The results were compared with the space available to explain the basin development. The study site included the boreholes of Garraf-84 and 92, Halfaya-1, Nasirya-13 and 40, and Noor-5 at the Mesopotamian Block, in addition to the Ratawi-8, Tuba-15, Rumaila-217, Zubair-45, and West Qurna-60 at the Basra Block.
 The Aliji basin was characterized by the decrease in accommodation values to the northeast direction and the increase in all the other parts of the study area. A comparison of the setting of this basin with the Umm Er Radhuma basin gives a clear evidence of the tectonic impact coming from the northeast. During the Middle Eocene stage, we notice that the basin was affected by comprehensive uplifting processes. This led to the generation of a very shallow basin (Rus basin) with the exposure of the northern part of the basin during the regression stage.
 The Middle-Late Eocene basin is represented by a transgression stage with high subsidence, where the sea level had been raised and covered the northeastern and eastern parts of the studied area by deep sea deposits (Jaddala Formation). While the other parts of the study area were characterized by shallow sediments of Dammam Formation. This period ended with a clear tectonic uplift occurring in the northeastern parts and decreasing towards the southwest. This confirms the reactivation of the tectonic action from the northeast, represented by the continental collision.
 All these sources of evidence indicate that the study area is divided into a northern part and a southern part. Both of these parts are separated by a major tectonic lineament extending from the West Qurna oil field to the Nasiriya oil field, which confirms the presence of the tectonic boundary between the Mesopotamian block and the Basra block. In addition, there exists a secondary tectonic boundary that divides the Mesopotamian block into two parts, the first is to the east and the other is to the west. The results showed that the eastern side was most affected by the collision of the Iranian Plate with the Arabian Plate, which led to its uplift, while the western side was less affected by this tectonics evidence.

Stratigraphy and Basin Development of the Oligocene-Early Miocene Succession, Southeastern Iraq

“…This period ended with a clear tectonic uplift occurring in the northeastern part and decreasing towards the southwest. This confirms the reactivation of the tectonic action from the northeast represented by the continental collision [15,16]. The second sedimentary cycle, Early Miocene Epoch (Aquitania), represents Euphrates Limestone Formation.…”

Microfacies analysis and sequence stratigraphy of Oligocene formations within Bai Hassan oil field, Northern Iraq

“…The Middle-Late Eocene basin is represented by a transgression stage with high subsidence, where the sea level had been raised and covered the northeastern and eastern parts of the Mesopotamian basin by deep-sea deposits (Jaddala Formation) [17]. This succession was underlying the Oligocene which was described by [18] as marly limestone with planktonic foraminifera in the southeastern part of the Mesopotamian basin center during the transgressive and highstand conditions.…”

Paleoclimatic Insights on the Paleocene-Eocene Thermal Maximum in Central Iraq, Based on Calcareous Nannofossils, Ostracoda and Geophysical Data

“…The present study relied on samples collected from a subsurface section, and it was supplemented by some geophysical well logs data of Balad 8 well in central Iraq (Figure 1). The formations mainly investigated, Aaliji and Jadalah Formations (Paleocene and Eocene age), are regarded as significant geological epochs in Iraq and have attracted the attention of many researchers such as [1,2]. The Aaliji Formation was described for the first time in NW Syria (latitude 36° 29' 25" North, longitude.…”

“…Later in Iraq, a supplementary type section locality was chosen at Kirkuk-109 well (latitude 35° 33' 08 North and longitude 44° 18' 55" East), with a depth range 2487-3035 feet), the thickness of 548 feet (167 m) [3]. The first description of the Jaddala Formation was done by Henson (1940) in [1]. The type section is situated close to the Jaddala village at Sinjar, NW Iraq, with an age of lower M. Eocene -L.Eocene.…”