-A sedimentological investigation of the Neogene deposits of the Zagros foreland basin in SW Iran reveals a continuous and largely gradational passage from supratidal and sabkha sediments at the base (represented by the Gachsaran Formation) to carbonates and marine marls (Mishan Formation with basal Guri carbonate member) followed by coastal plain and meandering river deposits (Agha Jari Formation) and finally to braided river gravel sheets (Bakhtyari Formation). This vertical succession is interpreted to represent the southward migration of foreland basin depozones (from distal foredeep and foredeep to distal wedge-top and proximal wedge-top, respectively) as the Zagros fold-thrust belt migrated progressively southward towards the Arabian foreland. This vertical succession bears a striking similarity to modern depositional environments and sedimentary deposits observed in the Zagros region today, where one passes from mainly braided rivers in the Zagros Mountains to meandering rivers close to the coast, to shallow marine clastic sediments along the northern part of the Persian Gulf and finally to carbonate ramp and sabkha deposits along the southeastern coast of the Persian Gulf. This link between the Neogene succession and the modern-day depositional environments strongly suggests that the major Neogene formations of the Zagros foreland basin are strongly diachronous (as shown recently by others) and have active modern-day equivalents.

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Karkheh river’s Delta is located in the west of Khuzestan Plain and can be divided into two smaller deltas; northern delta named as Karkheh Delta (including Bostan, Sableh and Neisan Deltas) and southern delta named as Karkheh -e- Noor Delta. Based on Galloway7 classification, Karkheh Delta is river-dominated type (type 1). Considering activity, this delta is divided to two parts; an active part in north and an inactive part in south. Based on Orton and Reading 16 classification, Karkheh Delta is placed in fine-grained (muddy) delta category due to prevailing silt and clay. In terms of sediment transportation and deposition process, this delta is a constructive delta. To recognize changes of Karkheh Delta’s area, Landsat images 5, 7 and 8 were studied and compared using 13 satellite images from 1973 to 2016 which shows an increase in the delta’s area particularly in northern part. In order to study sedimentology of this delta, 25 samples were taken. Sediment sizing analysis results show that silt is the most abundant sediment on average in this delta whereas clay, sand and gravel are in next abundance. Due to Shepard 17 classification, in Karkheh delta, silty clay, clay silt, silt, sandy silt and clay-silt-sand were identified. Also, channel, flood plain, crevasse, levee and sabkha depositional environments could be recognized in this delta.