Evaluating the Baluti Formation at Sararu village, Ora Anticline, Iraqi Kurdistan: a stratigraphic and geochemical approach

M A Maleko,A Y Mohamed,S A Bowden,A N F Edilbi

doi:10.1007/s12517-017-2846-y

M A Maleko, A Y Mohamed + Show 2 more

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https://doi.org/10.1007/s12517-017-2846-y

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Abstract

Here, we report that a lithostratigraphic unit that outcrops at Sararu village, 6 km northeast of Qumri village that had previously been assigned to the Baluti Formation is not Triassic in age and therefore can not be a correlative equivalent of the Baluti Formation. The outcropping unit at Sararu comprises intercalation of calcareous mudstones and limestones, and is indeed lithologically similar to the Baluti Formation (Late Triassic). The Baluti Formation (also known as the Baluti Shale) is known from a typical section found at the Gara Anticline and from many deep drilled oil exploration wells. It is generally composed of alternations of the shales, limestones, dolomites, and dolomitic limestones. It is underlain by the Kurra Chine Formation (Upper Triassic) and overlain by the Sarki Formation (Lower Jurassic). In this study, detailed field observations, an assessment of stratigraphic successions, studies of microfossils such as age-specific planktonic foraminifera (e.g., Globotruncana bulloides), and age-specific biomarkers (oleanane index and C28/C29 regular sterane index) reveal that the lithostratigraphic unit at Sararu village can not be a correlative equivalent of the Baluti Formation, and it is more likely from the Upper Cretaceous. There are a number of Upper Cretaceous formations found in this part of Kurdistan, but based on fossil-type and palaeoenvironmental associations, the Hadiena Formation, from the Upper Cretaceous, is considered as the most likely correlative equivalent to the calcareous mudstone and limestone succession found at Sararu village.

Highlights

The study area is located in the Kurdistan Region of northern Iraq (Fig. 1a)
We present an example of one such case, where distinguishing two lithologically similar units was found to be extremely difficult based on field observations alone; the Baluti within the Gara Anticline and another currently unnamed (X-unit) succession of mudstones and limestones found near Sararu village within the southern limb of the Ora Anticline
The main goal of this study is to provide evidence that the X-unit found at the Ora Anticline can not be the Baluti Formation, as previously proposed

Summary

Introduction

The study area is located in the Kurdistan Region of northern Iraq (Fig. 1a). The studied unit (here after termed the X-unit) is located near Sararu village, 6 km northeast of Qumri village on the main road in Barwari Bala. The outcrops of the X-unit utilized for this study are found on the southern limb of the Ora Anticline (37° 14′ 54.6′′ N, 43° 17′ 51.4′′ E), in the Ora Thrust Zone (Numan 2000; Jassim and Buday 2006) (Fig. 1b). The Baluti Formation outcrops used for this study are found within the core of Gara Anticline, in the highly folded zone (Numan 2000; Jassim and Buday 2006) (Fig. 1b). The depositional environment of the Zor Hauran Formation in the west of Iraq is interpreted to have been similar to that of the Baluti Formation (at Sararu village), and the two formations are tentatively considered to be correlatable (Buday 1980; Jassim and Goff 2006; Aqrawi et al 2010). The Dashtak (Lower-Middle Triassic) and Neyriz (Liassic) formations might be tentatively

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