Journal ID : TRKU-30-08-2020-11055
[This article belongs to Volume - 62, Issue - 08]
Total View : 346

Title : Depositional environments and sequence stratigraphy of the Upper Liassic Hussainiyat Formation- Western Iraq

Abstract :

Hussainiyat Formation (Upper Liassic) represents the uppermost of early Jurassic sediments. In the study area, the exposure section was formed in the intra-plate basin within the stable shelf, western Iraq. The main objectives of the study is to identify the lithology, microfacies, and sedimentary environment to interpret the origin of sequences that developed in the study area. The lower unit of Hussainiyat Formation consists from a repeated succession of sandstone, siltstone, and claystone, with relatively high intercalation between them, with common rusty color. Such sequence represents the low stand system tract phase, where the main sediment supplies are river-dependent. The upper unit is divided into four main lithofacies; Floodplain, Channels, Point bar, and Coastal plain facies. The sedimentation in this unite are dominantly of intercalation of varied dolomitized limestone facies, with thin laminations of sand and marl. The main distinguished facies were highly dolomitized mudstones, dolomitic peloidal packstone, and dolomitized grainstone. Three distinct depositional setting can be recognized: restricted marine, lagoon, and Shoal that are interpreted as a carbonate rimmed shelf setting. The exposed sections of the Hussainiyat Formation shows a major 3rd order (D1 and D2) and numbers of 4th order cycles (d1, d2, d3, and d4) these are asymmetrical and shows an upward increase in thickness. This may reflect the imbalance between accommodation and sediment influx for the clastic unit. Whereas the carbonate unit cyclicity shows a more or less balanced situation between the relative sea level rise, accommodation, and accumulation of sediment reflecting a relatively low subsidence

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