Research Article Sedimentology, depositional environment and classifcation of Karkheh River’s Delta, West of Khuzestan Plain (SW of Iran) Ahmad Abyat1 · Ali Azhdari1 · Amir Feghhi2 · Mohammd Judaki3 Received: 26 July 2020 / Accepted: 21 December 2020 © The Author(s) 2021 OPEN Abstract 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 classifcation, 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 classifca- tion, Karkheh Delta is placed in fne-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 classifcation, in Karkheh delta, silty clay, clay silt, silt, sandy silt and clay-silt-sand were identifed. Also, channel, food plain, crevasse, levee and sabkha depositional environ- ments could be recognized in this delta. Keywords Delta · Karkheh · Khuzestan plain · Karkheh -e- nor · Depositional environment 1 Introduction The identifed deltas in Khuzestan Plain are Karoon, Karkheh, Jarrahi and Zohreh Deltas [2, 3]. In this research, Khuzestan Plain is one of sub-areas of Zagros Basin located sedimentology, depositional environment and classif- in southwest Iran. Top of this plain is covered by coarse- cation of Karkheh Delta in west of Khuzestan Plain were grained alluvial sediments in north and fne-grained in studied. Karkheh Delta is located in west of Khuzestan south. The Lower Khuzestan plain, forming the eastern and between northern latitude of 31° 25′ 30″–31° 47′ 42″ extension of the Mesopotamian Plain, is bordered in the and eastern longitude of 47° 49′ 30″–48° 12′ 01″. Head of north and east by the foothills of the Zagros Mountains this delta is in Susangerd city, ends to Hor Al-Azim marsh [10]. and geographically is limited between Susangerd, Bostan, The known continental Quaternary depositional envi- Rofaieh and Howeyzeh. Since in this article, type determi- ronments in Khuzestan Plain involve alluvial fans, fuvial, nation of Karkheh Delta in conventional classifcation is aeolian sands, deltas, sabkhas and lagoons [2]. Delta is one an aim, it is necessary to say a summary about diferent of transitional depositional environment which has a tri- types of deltas classifcation. So far deltas are classifed in angular shape such that its head towards the river and its diferent ways. The most important classifcation was done base towards the sea, gulf, lagoon or lake. by Galloway [7] in which deltas based on type of process * Ahmad Abyat, [email protected] | 1Geological Survey of Iran, Ahwaz, Iran. 2Department of Petroleum Engineering, Islamic Azad University, Omidieh brunch, Omidieh, Iran. 3Geological Survey of Iran, Tehran, Iran. SN Applied Sciences (2021) 3:140 | https://doi.org/10.1007/s42452-020-03991-6 Vol.:(0123456789) Research Article SN Applied Sciences (2021) 3:140 | https://doi.org/10.1007/s42452-020-03991-6 are divided into three groups, river-dominated, wave- gr. of sediment were taken from the surface to depth of dominated and tide-dominated. Based on the activity of 30 cm. About 250 gr. of each sample was sent to the lab the deltas are divided into two types: active and inactive for sediment sizing, for which wet shaker sieve and laser deltas. Deltas can be also classifed according to sediment particle sizer devices were used. Since the most of sam- transportation and deposition; constructive and decon- ples were fne-grained, Shepard [17] method was applied structive deltas. Orton and Reading [16] mentioned the for denomination. Shepard [17] classifcation excels Folk role of sediments size on delta classifcation and based (1974) classifcation for fne-grained sediments. This clas- on this, four groups were made,fne-grained (muddy), fne sifcation uses SEDPLOT and GSSTAT softwares. At the end, sand, gravelly sand and gravel. the fnal map of Karkheh Delta and its neighboring envi- So far, several studies were done about deltas of earth, ronments was drawn using Google Earth and ArcGis 10.3. most 6important of which are Galloway [7], Wright [18], In order to analyze changes in Karkheh Delta’s area, sat- Orton and Reading [16], Coleman and Huh [16], Kuenzer ellite images came in use. Progression and regression of et al. [13], Petropoulos et al. (2015) and Zheng et al. [19]. deltas can be studies via maps and aerial images in defned However, few studies about sedimentology, depositional time intervals (Bird) [5]. Satellite Images Landsat 1-5MSS, environment and area changes of Karkheh Delta have Landsat 5 TM, Landsat 7 ETM and Landsat 8 (from 1973 to been done. In terms of sedimentology and depositional 2016) were used. Based date of images is June, since in environment, Abyat et al. [1] and then Abyat et al. [2, 3] did this time there is no mendacious input (unexpected winter the frst research on this delta. Moreover, Abyat et al. [2, rain) and therefore real delta’s area is seen. Specifcations 3] performed some research about depositional environ- of the received images are shown in Table 1. ENVI 5.3 soft- ments of Late Quaternary in Khuzestan Plain. ware was used to process the images. The band combina- tions used to separate aquatic area of Hor Al-Azim marh from the delta in this research are shown in Table 1. Finally, 2 Method of study using ArcGIS 10.3 software, delta limits during diferent years was identifed and its area was calculated. This research is a part of the study done on the Quater- nary depositional environment of Khuzestan Plain. In the beginning step, data like reports, articles, topographical 3 Discussion and results and geological maps, aerial images etc. were gathered. Then, using satellite images, topographical and geologi- As mentioned before, Karkheh Delta is located between cal maps, Karkheh Delta and the near depositional envi- Dasht -e- Azadegan and Howeyzeh cities and begins as ronments were distinguished. In the next step, feld sam- Karkheh river branches in Susangerd city. Like Jarrahi pling was planned. In this research, 25 samples were taken Delta, Karkheh Delta also enters into a marsh named from Karkheh Delta (Fig. 1). In sampling stage, almost 2500 as Hor Al-Azim or Hor Al-Howeyzeh. Catchment basin Fig. 1 Location of the study area and samples taken Vol:.(1234567890) SN Applied Sciences (2021) 3:140 | https://doi.org/10.1007/s42452-020-03991-6 Research Article Table 1 Description of landsat data used in this study of 879 km2. The full triangular shape of this delta shows Platform/Sensor Source Year Path/Row that waves and tides lack any impact on its formation. This delta from northeast limits to Fars Group outcrop in L1-5/MSS USGS 1973 178/39 Band-e-Karkheh anticline and its alluvial fans, from north USGS 1977 179/38 to Om-Al-Debes sand dunes, from southeast to Karkheh L5/TM USGS 1985 flood plain, from south to Karoon west sabkha and from USGS 1990 west to Hor Al-Azim marsh (Fig. 3). USGS 1993 Three main channel belts of the Karkheh were identi- USGS 1998 fied (labelled Kh1, Kh2 and Kh3) by Heyvaert et al. [10]. USGS 2000 Abyat et al. [1] divided Karkheh river channel into three L7/ETM USGS 2004 165/39 intervals which the third one (Hamidiyeh to Hor Al-Azim) USGS 2007 166/38 is placed in Karkheh Delta. In this interval, Karkheh is a USGS 2010 combination of straight and meandering shapes. From USGS 2012 Hamidiyeh Dam towards Bostan, Karkheh Channel USGS 2014 almost has a straight path after which the river contin- L8/OLI USGS 2016 ues in a slight meandering shape to Hor Al-Azim marsh. This section is highly branched and in fact is the Karkheh Delta. The main channel of Karkheh delta is Kh3b which of Karkheh river has an area of 51,643 km2. Average of forms northeast-southwest side of this delta, starts from Karkheh river flow rate in Hamidiyeh Station in recent Susangerd, continues to Bostan City and finally enters 62 years is 134.2 m 3/s. Karkheh delta has a triangular into the marsh. The other channels of this delta are Kh2b, shape and its base is almost smooth (Fig. 2). Height of Kh2c, Kh2d and Kh3c. unlike the Karoon Delta and like this triangle is 37 km, its base is 41 km and has an area Fig. 2 The Landsat 8 satellite image of the Karkheh Delta and adjacent environments Vol.:(0123456789) Research Article SN Applied Sciences (2021) 3:140 | https://doi.org/10.1007/s42452-020-03991-6 Fig. 3 Karkheh Delta and adjacent environments of this Delta Jarrahi Delta, this delta is intensively branched (Abyat and is smaller than the northern delta. The approximate et al.) [2, 3] with many branches (Fig. 4). length (without considering curve sections) of Kh2c is In a large-scale view regarding the main existing chan- 20 km. The base of this delta from tongues of two chan- nels, Karkheh Delta can be divided to two deltas; northern nels is almost 20 km long and has an approximate area delta named as Karkheh Delta and southern delta named of 312 km2.