Provenance investigation from sedimentary petrography of the Upper Cretaceous deep marine low density turbidites of the Tanjero Formation around Arbat, northeastern Iraq


Abstract: Deep marine low density turbidites of the Upper Cretaceous Tanjero Formation were studied in terms of their petrographic composition to deduce the provenance of the unit around Arbat, northeastern Iraq. Petrographic works based on modal analysis of the clastic rock fragments and released single minerals in silt, fine to coarse grained sandstone, and, in very small quantities, pebbly sandstone show that these turbidites are mainly composed of sedimentary rock fragments such as carbonate, microcrystalline and cryptocrystalline quartz bearing siliceous sedimentary cherts, Radiolaria bearing cherts, and released Radiolaria fossils from the cherts during a short distance transportation. Quartz and feldspar ratios in the whole thin sections are below two percent. The turbidite siltstones and sandstones are litharenite (calclithite) in composition, indicating sedimentary source rocks mainly consisting of carbonate rocks, Radiolaria, and chert-rich limestone. There is no significant petrographic variation across the clastic succession of the area. The composition of the clastic rocks suggests a recycled sedimentary source. Likewise, the QtFL ternary diagram suggests that the sediments are derived from a lithic recycled provenance, which indicates not only the Lower Cretaceous deep marine Qulqula (radiolarian) Formation as in the previous provenance works but also another deep marine unit, the Lower Cretaceous Balambo Formation, and a shallow water Lower Cretaceous Qamchuqa formation.

Keywords: Tanjero Formation, petrography, provenance, Arbat, northeastern Iraq

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