DATING AND CORRELATION OF THE BALUTI FORMATION, KURDISTAN, IRAQ: Implications for the regional recognition of a Carnian “marker dolomite”, and a review of the Triassic to Early Jurassic sequence stratigraphy of the Arabian Plate

Abstract

The Baluti Formation is a lithostratigraphic unit defined at outcrop in the Zagros foldbelt in Kurdistan, North Iraq, where it consists of a thin, shale‐dominated interval between the thick carbonates of the overlying Sarki and the underlying Kurra Chine Formations. New biostratigraphic results presented in this study confirm that firstly, the Baluti shale marks the top of the Carnian at outcrop; and secondly, that the correlative subsurface shale occurs well above the base of the subsurface‐defined Butmah Formation. As such, the Butmah is not directly correlative to the Sarki as has previously been assumed, and its definition overlaps that of the Baluti and Kurra Chine Formations. These results have regional implications. A distinctive low Gamma Ray dolostone unit in the Kurra Chine A can be correlated across Kurdistan. Similar dolostones are recognised widely across the Arabian Plate and have been considered to be correlative by some workers, but not by others. This study establishes the age of this “Marker Dolomite” as late Carnian on the basis of its position below the Baluti Formation and confirms its regional development. Correlation is demonstrated to the Sefidar Dolomite (Iran), the “Muss”/Mulussa D (Syria), the upper Abu Ruweis Formation (Jordan), the Jilh Formation (Kuwait, Saudi Arabia, Oman), and the upper Gulailah Formation (UAE). Regional sequence stratigraphic studies have assigned the Marker Dolomite to different sequences in different areas. The recognition that it represents a single, regionally‐correlatable event provides the starting point for a sequence stratigraphic review based on regional log correlation and published dating. An updated sequence stratigraphic framework is presented for the Triassic to Early Jurassic, defining additional sequences (e.g. Tr55, Tr90, Tr100, J01, J05) and recognising that significant depositional breaks are associated with SBs Tr60, Tr70, Tr80, Tr100 and J01. The hiatus below Tr80 reflects a Carnian–Ladinian regional high in the Southern Gulf. This represents the barrier between the open Neo‐Tethys and the saltern in which the Carnian evaporites accumulated. The implications for petroleum exploration are discussed in the light of these revisions. There are two established Triassic plays in Iraq and Syria: firstly, in fractured carbonate reservoirs sealed by evaporites and shales, which is productive in both countries; and secondly, in fluvial sandstones sealed by interbedded shales, which is productive in Syria. A key observation regarding the carbonate play is that the main Triassic exploration target in Iraq has been the Kurra Chine B fractured carbonates, located above the main Carnian evaporites; whereas in the Syrian Palmyrides, the main discoveries are generally located below the Carnian evaporites. The sub‐evaporite fractured carbonate play is underexplored in Iraq. With regard to the clastic play, the correlations presented in this study indicate that the Mulussa F and Minjur represent a single clastic pulse, and equivalent sandstones are likely to be ...

Source Rock Evaluation of the Upper Triassic Baluti Formation in Bekhme-1 and Gulak-1 Wells from Akri-Bijeel Block, Kurdistan-Iraq

“…The Baluti Formation has a number of the lateral equivalents within the region. The most correlatable formation in Syria to the Baluti Formation may be the Mulussa-E Formation (Lunn et al, 2019). The Minjur Formation (Upper Triassic-Lower Jurassic) in Kuwait and Saudi Arabia might.be tentatively correlated to the Baluti Formation.…”

“…Within the Iranian part of the Zagros there is not a distinctive rock unit of the Late Triassic age or a clear equivalent to the Baluti Formation. The Dashtak Formation in Iran is a possible lateral equivalent formations to the Baluti Formation ( Lunn et al, 2019).…”

Depositional Environment of the Upper Triassic Baluti Formation in Gara Anticline, Kurdistan Region, North Iraq: Insight from Microfacies and Biomarker Characteristics

“…Based on the ratios of Mg/Ca and Sr/Ca, the shallow marine environment was suggested for Baluti Formation in the Sarki section by Tobia and Mustafa (2019). Lunn et al (2019) suggested late Carnian (Tuvalian)-early Norian age for the Baluti Formation. The Baluti Formation has a number of lateral equivalents within the region that contribute to petroleum systems.…”

Sedimentology of the Baluti Formation (Late Triassic) in the Warte area, northeastern Iraqi Kurdistan region

“…Since the first description of the Baluti Formation by Bellen et al (1959) in it is type section, there have been several published articles on the Baluti Formation in the outcrops of Northern Iraq. This includes the works of Buday (1980), Jassim and Goff (2006), Hanna (2007), Aqrawi, Goff, Horbury, and Sadooni (2010), Al‐Juboury and McCann (2015), Shingaly (2016), Al‐Mashaikie, Abdul‐Razzak, and Naser (2016), Al‐Mashaikie (2017), Al‐Mashaikie and Abdul‐Razzak (2017), Asaad (2019), Asaad and Omer (2019), Lunn, Miller, and Samarrai (2019), Azo, Hanna, and Edilbi (2020), and Asaad and Omer (2020), which have all focused mainly on the stratigraphy, sedimentology and palaeontology of the studied formation. The main aim of this article is a detailed investigation of the sedimentological aspect of the Baluti Formation in the studied section in terms of lithostratigraphy, petrography, diagenesis, mineralogy, facies analysis, and subdivisions, in order to understand further the lateral continuity of its depositional environment in areas that have not been studied previously.…”