The Origin of Tar Al-Say'ed and Tar Al-Najaf, Karbala-Najaf Vicinity
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Journal of Civil Engineering and Architecture 9 (2015) 446-459 doi: 10.17265/1934-7359/2015.04.008 D DAVID PUBLISHING The Origin of Tar Al-Say’ed and Tar Al-Najaf, Karbala-Najaf Vicinity, Central Iraq Varoujan K. Sissakian1, Mawahib F. Abdul Jab’bar2, Nadhir A. Al-Ansari3 and Sven Knutsson3 1. Private consultant geologist, Erbil 14006, Iraq 2. State Company of Geological Survey and Mining, Baghdad 14001, Iraq 3. Department of Civil, Environmental and Natural Resources Engineering, Lulea University of Technology, Lulea 97187, Sweden Abstract: In central part of Iraq within the vicinity of Karbala-Najaf, two cliffs called “Tar Al-Say’ed” and “Tar Al-Najaf” form conspicuous geomorphological forms between the Mesopotamia Plain and the Western and Southern Deserts. The top surface between the two cliffs (tars) is covered by alluvial fan sediments, laid down by Al-Khir Valley when merging in a large depression due to the drop in the gradient of the valley. Consequently, the depression was divided into two parts, to the left is called Al-Razzazah Depression, whereas to the right is called Bahir Al-Najaf. This affected the course of the River Euphrates. The deposition stopped due to an uplift movement which caused the elevation of the two cliffs which are covered by alluvial fan sediments. The two cliffs had and are still suffering from retreating, due to lateral erosion by wave actions in Al-Razzazah Depression. Springs located along a straight line, sag pond, deflected drainage, shutter ridges and pressure ridges can be noticed in the area. The age of both cliffs is estimated to be upper Late Pleistocene—early Holocene. Key words: Neotectonic, erosional cliff, alluvial fan, Pleistocene, Iraq. 1. Introduction is originated from Al-Khir Valley, with SW-NE trend, starting from the Saudi Arabia, being one of the largest Tar Al-Say’ed and Tar Al-Najaf are two valleys in the Iraqi Southern Desert (Fig. 1) [1]. To the conspicuous geomorphological outstanding features in left of Tar Al-Najaf is the Al-Razzazah Depression, or Karbala-Najaf vicinity (Fig. 1). “Tar” is a local name Lake Milih into which excess water from the Euphrates for a cliff. Tar Al-Say’ed and Tar Al-Najf form River is diverted by a controlled escape channel or elongated and steep cliffs with NE-SW and NW-SE canal. The lake is rather shallow and water levels change trends, respectively, meeting at appoint called with the seasons. The lake was created in 1969 when a “Al-Lisan” area, which forms the head of a triangle Spanish contractor built a drainage canal to divert the formed by the two cliffs, whereas the base of the annual floodwaters of the Euphrates River into the triangle is a flat area, forming the boundary between desert to prevent flooding across southern Iraq [2]. the flat Mesopotamia Plain and gently sloping plain of A number of researchers had executed some work on the Karbala-Najaf Alluvial Fan. the studied area and its surroundings, but none of them The length of Tar Al-Say’ed and Tar Al-Najaf is dealt with the origin of the two cliffs. Most related 105.1 km and 103.4 km, respectively. They form the studies are mentioned hereinafter: boundaries of a large alluvial fan with typical delta Ghalib [1] mentioned that the area covered by the shape and flat top, and the length of the top covered the two cliffs is built-up by the Dibdibba Formation, alluvial fan is 64 km, with coverage area of 2761 km2. It representing a very large alluvial fan; Hamza [3], in the geomorphological map of Iraq, Corresponding author: Nadhir A. Al-Ansari, professor, mentioned the presence of gypcrete covering the research fields: water resources and environmental engineering. E-mail: [email protected]. involved area, but did not refer to the alluvial fan; The Origin of Tar Al-Say’ed and Tar Al-Najaf, Karbala-Najaf Vicinity, Central Iraq 447 Fig. 1 Landsat 7 image of Karbala-Najaf Plateau, top covered by gypcrete. Barwari et al. [4], in the Quaternary Sediments Al-Khateeb and Hassan [6] carried out detailed Map of Iraq, also referred to the gypcrete that covers geological mapping in the involved area, and they the top surface area, without referring to the origin of defined the exposed geological formations; the cliffs; Fouad [7-9] and Fouad and Sissakian [10] did not Sissakian and Ibrahim [5], in the geological mention about the origin of the two cliffs when hazards map of Iraq, mentioned about the gypcrete reporting about the structural and tectonic evolution of covering the top surface area and about the active mass the Iraqi Western Desert and the Mesopotamia movements acting along the two cliffs, without Foredeep, respectively, neither mentioned about the referring to their origin; presence nor otherwise surface faults, near the two 448 The Origin of Tar Al-Say’ed and Tar Al-Najaf, Karbala-Najaf Vicinity, Central Iraq cliffs, except the active Abu Jir-Euphrates Tectonic geological reports, historical and relevant Zone; scientific published articles were reviewed to get an Yacoub [11] did not mention about the origin of idea about the origin of the two cliffs. Some structural the cliffs during reporting about the geomorphology of data were also reviewed to elucidate the relation the Mesopotamia Plain. between the subsurface geology and the existing two The aim of this study is to explain the origin of the cliffs. two cliffs and discuss their evolution, using mainly Within GIS (Geographic Information System) and Landsat, Google Earth and DEM (digital elevation DEM applications, spatial analysis and hydrological model) images, with collaboration of field and tools of ArcGIS were used to prepare many maps for historical data. the studied area, such as elevation map and slope map in addition to 3D image. The simplest morphological 2. Materials and Method analysis involved the study of the elevation data. In the To achieve the aim of this study, the following present approach, DEMs (Fig. 2) were displayed for materials were used: visual inspection as grey-scale images, 3D surface geological maps (scale of 1:100,000, 1:250,000 views and shaded relief models or as combinations of and 1:1,000,000); these. The shaded relief model was a key component topographical maps (scale of 1:100,000 and throughout this study because it was the most suitable 1:250,000); terrain model for the recognition and interpretation of Google Earth, DEM and satellite images (Fig. 2); complex morphological features. Vertical exaggeration relevant published articles and theses. of elevations was used to enhance the study of subtle The geological and topographical maps with the features in flat basin areas, and cross-sections were Google Earth, DEM and satellite images were used to generated along topographical sections to study slope recognize the present indications of the origin of the and slope curvature conditions using 3D analyst two cliffs. Field description points in different extension. Fig. 2 DEM image showing the studied area. The Origin of Tar Al-Say’ed and Tar Al-Najaf, Karbala-Najaf Vicinity, Central Iraq 449 3. Geological Setting part of the studied area. The presence of tens of springs is good indication for this active tectonic zone. The geology of the involved area is described briefly hereinafter. It includes: geomorphology, structure and 3.3 Stratigraphy tectonics, stratigraphy and hydrogeology depending on The exposed geological formations and present Refs. [6, 12-15]. Quaternary sediments (Fig. 3) are briefly mentioned, 3.1 Geomorphology hereinafter. 3.3.1 Dammam Formation, Upper Member (Late The two cliffs are the most significant Eocene) geomorphological feature in the involved area, forming Only the upper member of the Dammam Formation erosional ridges suffering from different types of mass is exposed in the studied area. The upper member movements. In between the ridges, the area is covered consists of thickly bedded limestone: some beds by a very large alluvial fan of one stage [16], developed include small nummulites, with marl intercalations and by Al-Khir Valley, and the apex of the fan is at very rare chert lenses. Al-Lisan area. The gravels of the fan range in size from 3.3.2 Euphrates Formation (Early Miocene) 1~2 cm, with a thickness varying from 8~14 m, The formation consists of basal conglomerate and/or composed mainly by silicates and carbonates [6]. Top breccia, followed upwards by fossiliferous limestone, of the alluvial fan is a flat area sloping NE wards, dolostone with some marl intercalations. The pebbles covered by thick gypcrete with a high percentage of of the conglomerate are derived from the underlying fine sand. Dammam Formation, the size of the pebbles ranges Large valleys run on both sides of the fan, those on from < 0.1~1.5 m. the left side drain in the Razzazah depression, whereas 3.3.3 Nfayil Formation, Lower Member (Middle those on the right side drain in Bahr Al-Najaf Miocene) depression (also called Bahr Al-Milih). Both Only the lower member of the Nfayil Formation is depressions are very wide. The latter is shallow almost exposed in the studied area. The upper member dry, except in the rainy seasons. Whereas, the former consists of three sedimentary cycles. Each cycle includes water derived from the Euphrates River and consists of green marl overlain by limestone. The tens of springs. Both depressions are bounded by limestone of the second cycle includes large oyster sabkha sediments. shells. 3.3.4 Dibdibba Formation (Pliocene-Pleistocene) 3.2 Tectonics and Structure The formation consists of coarse and white The involved area is located within the Inner sandstone and rare conglomerate.