In the Rumaila oilfields in southern Iraq, the Zubair Formation was deposited in a shallow environment as three main facies, delta plain, backshore, and delta front depositional conditions indicating a transition from delta front and delta plain to a highstand level due to the finning upward mode. The facies of the Zubair clasts show well-sorted quartz arenite sandstone, poorly sorted quartz arenite sandstone, clayey sandstone that has not been properly sorted, sandy shale, and shale lithofacies. The minor lithofacies were identified using well-logging methods (gamma ray, spontaneous potential and sonic logs) and petrography. The Zubair clasts are of transition environment that appears to be transported from freshwater and deposited in a marine environment forming many fourth-order cycles reflect sea level rise fluctuations and still-stand under tectonics developed the sequence stratigraphy. A misalignment between relative sea-level and sediment supply caused asymmetry sedimentary cycles. A shallower environment of shale-dominated rocks rich in organic matter and pyrite were exposed. The basinal shale of Ratawi at the Zubair bottom and the shallow carbonate of Shuaiba emplace on the Zubair represent the beginning of the delta build up (delta front and delta plain) to a highstand stage.

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A surface section of the Gercus Formation (Middle-Late Eocene) was studied in Berafat area, Dohuk Governorate, Northern Iraq. The Gercus Formation consists of a mixed siliciclastic sediments, evaporates and carbonate sequences in the studied region, predominantly in the upper and middle parts. Nevertheless, it usually consists of upward-fining carbonate-rich sandstone cyclothems, marl, conglomerate and siltstone along with a gypsum lens and thin micrite carbonate beds.  The Gercus Formation was deposited in delta and delta front of occasionally depositional environment which is represented by red-brown claystone and reddish-brown mudstone lithofacies. Cross bedded  pebbly sandstone, trough cross-bedded sandstone  and laminated cross-bedded sandstone lithofacies are deposited in braided delta  environment. Marl lithofacies and gypsum lithofacies are deposited in intertidal and supratidal environments. The sea level fluctuation caused the river base level to occasionally rise and fall. In addition, the process changed from erosion to deposition, while the grain size also changed at different environments from gravel to sand and clays. The Gercus succession of northern Iraq was developed during the Middle-Late Eocene in an active margin basin, where the last stage closure of the New-Tethys and its collision with the Eurasian plate took place between the northeastern Arabian plate. It caused major episodes of uplifts and subsidence along with base level variations due to eustatic ups and downs. Within Gercus Formation, several fourth order cycles can be recognized, reflecting generally asymmetrical cycles, as well as the difference between sediment supply and accommodation space.

A surface section of the Fatha Formation (Middle Miocene) was studied in the Shaqlawa area, Erbil, Northern Iraq. It consists of siliciclastic silt, evaporates, and carbonates in a mixed siliciclastic silt composition. The Fatha Formation in the study area can be divided into two members of variable thickness based on rocky differences. Depositional settings ranged from shallow open-marine and restricted-hypersaline to supratidal and continental (sabkha, fluvio-deltaic, and exposure). It is bounded below by a type one sequence boundary above the Eocene Pila Spi Formation and marked by conglomerates. The upper sequence boundary with the Injana Formation is conformable. Thirteen sedimentary facies were distinguished in the Fatha Formation within the Shaqlawa region of northern Iraq and include sandstone to mudstone, wavy bedded sandstone to mudstone, Flaser bedded sandstone to mudstone, Marl, sandstone, cross lamination sandstone, Trough cross bedded sandstone, Planar cross bedded sandstone, marly limestone lithofacies, bioclastic grainstone to packstone microfacies, bioclastic lime mudstone to wackestone microfacies, lime mudstone-wackestone microfacies, and gypsum lithofacies. The depositional environment of the formation was inferred based on the facies association concepts. The succession formation can be divided into several third-order cycles, which reflect fluctuations in the relative sea-level rise. High-frequency cycles of transgressive System Tract and Highstand System tract. Fundamental to the evolution of the sequence, in this case, is the local tectonic component.

The Mauddud Formation is Iraq’s most significant and widely distributed Lower Cretaceous formation. This Formation has been investigated at a well-23 and a well-6 within Ratawi oil field southern Iraq. In this work, 75 thin sections were produced and examined. The Mauddud Formation was deposited in a variety of environments within the carbonate platform. According to microfacies analysis studying of the Mauddud Formation contains of twelve microfacies, this microfacies Mudstone to wackestone microfacies, bioclastic mudstone to wackestone microfacies, Miliolids wackestone microfacies,Orbitolina wackestone microfacies, Bioclastic wackestone microfacies, Orbitolina packstone microfacies, Peloidal packstone microfacies, Bioclastic packstone microfacies, Peloidal to Bioclastic packstone microfacies, Bioclastic grainstone microfacies, Peloidal grainstone microfacies, Rudstone microfacies. Deep sea, Shallow open marine, Restricted, Rudist Biostrome, Mid – Ramp, and Shoals are the six depositional environments in the Mauddud Formation based on these microfacies.