IRAQI BULLETIN OF GEOLOGY AND MINING
مجلة الجيولوجيا والتعدين العراقية
ISSN 1811 - 4539
البحوث المنشورة تعليمات النشر للمؤلفات اهداف ومجال النشر هيئة التحرير
GEOMORPHOLOGY OF THE MESOPOTAMIA PLAIN
Sabah Y. Yacoub
Received: 23/ 07/ 2009, Accepted: 25/ 03/ 2010
Key words: Mesopotamia Plain, Marshes, Alluvial fans, Sand dunes, Holocene, Marine sediments
(p. 7 – 32)
ABSTRACT
The present study is a review of the geomorphology of the Mesopotamia Plain. It depends on the data obtained from the regional geological survey project of the plain, which has been carried out during the years 1977 through 1981 by GEOSURV's geological staff.
The Mesopotamia Plain is vast lowland, which has clearly defined physiographic boundaries with the Low Folded Zone, in the northern and eastern sides and the Western Desert and Al-Jazira Area, in the western side.
The Mesopotamia Plain is considered as a huge aggradational (accumulational) geomorphologic unit, where the fluvial, lacustrine, and Aeolian landforms prevail. Estuarine and marine forms also exist, but these are restricted to the extreme southeastern reaches of the plain. However, the degradational (erosional) landforms are developed, but these are not well expressed. The geomorphic units are classified according to origin, geomorphic position, and lithology. Some of the units involve different geomorphic features, which are described with some details taking in consideration their order and importance.
The main geomorphologic units of the aggradational fluvial origin are: Terraces, alluvial fans, sheet run-off plain, flood plains of major rivers and their distributaries, shallow depressions, marshes and lakes, and sabkhas. The tidal flat is the only marine aggradation form. The Aeolian forms are: Nabkhas, sand sheets and sand dunes, in addition to anthropogenic forms. The degradation geomorphic features are: Erosional cliffs, margins of flood stages and bad land, which are developed due to the lateral erosion and vertical incision of rivers and streams, wind deflation and tidal channels (creeks), which are resulted due to marine tides action.
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TECTONIC AND STRUCTURAL EVOLUTION OF THE MESOPOTAMIA PLAIN
Saffa F.A. Fouad and Varoujan K. Sissakian
Received: 27/ 9/ 2010, Accepted: 29/ 12/ 2010
Key words: Mesopotamia, Foredeep, Mesopotamia Plain, Iraq
(p. 33 – 46)
ABSTRACT
The geological setting of the Mesopotamia Plain, which is a part of the Mesopotamia Foredeep within the tectonic framework of Iraq, has been reviewed and redefined according to the modern concepts of foreland basins, and new structural boundaries are introduced. The Mesopotamia Plain of the central part of Iraq is a large subsiding basin covered by thick Quaternary sediments of the Tigris and Euphrates Rivers with their tributaries and distributaries. It has been receiving pre-Quaternary sediments from the adjacent rising mountains, in the north, northeast and east, and from the Inner Platform, in the west and south, too.
The Mesopotamia Plain is an epicontinental basin formed above an earlier platformal and marginal basin. Accordingly, the Phanerozoic stratigraphic sequence of the basin can be broadly categorized into three major tectono-stratigraphic assemblages; Cambrian – Early Permian intraplate assemblage, Late Permian – Middle Cretaceous Neo-Tethys passive margin assemblage, and Late Cretaceous – present foreland basin assemblage.
The Mesopotamia Plain is a mobile tectonic zone and contains several buried structures including folds, faults and diapiric structures. Recent tectonic activity of some of these structures is recorded through their effects on the Quaternary stratigraphy and present geomorphological landforms, such as abandoned river channels, active and inactive alluvial fans and topographic expressions of some active subsurface anticlines, all together indicating Neotectonic activity of the plain.
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STRATIGRAPHY OF THE MESOPOTAMIA PLAIN
Sabah Y. Yacoub
Received: 08/ 08/ 2010, Accepted: 30/ 01/ 2011
Key words: Quaternary Sediments, Mesopotamia, Tigris and Euphrates, Pleistocene, Holocene
(p. 47 – 82)
ABSTRACT
The current study is a stratigraphic review of the Quaternary sediments of the Mesopotamia Fluvial Basin, which is essentially based on the data obtained from the regional geological survey carried out during 1975 – 1981, by the staff of GEOSURV. Many boreholes were drilled, the acquired data forms essential part of the present study.
The Mesopotamia Fluvial Basin is an integral part of the Zagros Fold – Thrust Belt, which is developed as a result of the last phase of Alpine Orogeny during Pliocene – Early Pleistocene. It represents the area bordered by the uplifted Low Folded Zone, to the east and northeast, and the eastern margin of the Inner (Stable) Platform of the Arabian Shelf, to the west and southwest. At present day, the basin is totally covered by the Quaternary sediments, which are in some margins bounded by limited exposed Tertiary formations that extend beneath the thick Quaternary sediments, within the basin.
Most of the stratigraphy of the Quaternary sediments has not been precisely determined due to the lack of accurate dating. However, relative ages of the main stratigraphic divisions, are suggested depending upon the stratigraphic correlation and their correspondence with global geological events; such as climatic changes. Three main stratigraphic subdivisions are recognized based on their relative ages; namely: Pleistocene, Late Pleistocene – Early Holocene, and Holocene.
The main Pleistocene sediments are represented by river terraces, alluvial fans and fluvial sediments. The Pleistocene – Early Holocene Units include sheet run-off, gypcrete and slope sediments. While the Holocene Units include sediments of different origins, such as fluvial, lacustrine, marine, estuarine, Aeolian and anthropogenic. The Holocene sediments are also found in the modern sedimentary environments of the Mesopotamia Plain.
The presence of Holocene marine sediments (i.e. Hammar Formation) has been confirmed in the Southern Mesopotamia Plain, indicating the influence of marine inundation during early to mid Holocene. Such a marine transgression has reached as far as Amara City, on the eastern side and Nasiriyah City, on the western side, about 200 Km north of the present day northern shoreline of the Arabian Gulf.
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HYDROGEOLOGY OF THE MESOPOTAMIA PLAIN
Hatem K. Al-Jiburi and Naseer H. Al-Basrawi
Received: 06/ 04/ 2009, Accepted: 01/ 07/ 2010
Key words: Mesopotamia Plain, Quaternary aquifer, Groundwater, Transmissivity, Permeability
(p. 83 – 103)
ABSTRACT
The Mesopotamia Plain is characterized, topographically as a flat plain that slopes gently between Baghdad and Basrah, but it is gently undulated in its northern parts. It is totally covered by Quaternary sediments. These sediments are composed of alternation of clay, silty clay, clayey silt, silt, sand and gravel. Fine sediments represent the aquitards, while sand and gravel form the aquifers. These sediments have abrupt lithologic changes, both laterally and vertically, therefore, are considered regionally as a lithologically complex aquifer system. There is a hydraulic continuity within the entire Quaternary aquifer system, but the degree of the continuity differs from place to another, depending on the lithological characteristics of water bearing sediments. It is assumed that, a hydraulic continuity is present between surface water and groundwater aquifers, to some extent. Therefore, effluent and influent river phenomena exist throughout the plain. Moreover, there is a hydraulic continuity between Quaternary aquifer system, in the plain and the underlying pre-Quaternary formations.
The groundwater level fluctuations throughout the Mesopotamia Plain depend, mainly on the natural conditions and to some extent on artificial conditions. Generally, water bearing Quaternary sediments, of the plain are considered quantitatively promising, but the problem is concerned with the quality of the groundwater. High salinity of the groundwater prevails throughout the plain, but the groundwater, which is close to rivers and main irrigation channels may be in better condition for exploitation, particularly where phenomenon of induced seepage of fresh water exists, also in areas along Low Folded Zone, where recharge water zones exist.
The direction of the groundwater flow is towards the center of the Mesopotamia Plain, from all neighboring regions, because the plain represents a regional discharge zone for the whole Mesopotamian Aquifer Mega System of Iraq. The piezometric level of the groundwater is generally inclined from north and northwest (it is < 200 m, a.s.l., near Makhoul Mountain) towards south and southeast (2 m, a.s.l., near Basrah city). The salinity of the groundwater increases generally from the recharge areas towards discharges areas, within the plain. The chemical quality of the groundwater changes from sulphatic to chloridic type from recharge to discharge areas, respectively, being in accordance with the groundwater movement.
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MINERAL RESOURCES AND INDUSTRIAL DEPOSITS IN THE MESOPOTAMIA PLAIN
Mazin M. Mustafa
Received: 30/ 09/ 2009, Accepted: 2/08/ 2010
Key words: Nuba'i Deposits, Glauberite, Salt pan, Gypcrete, Gravels and Sands, Common Clays
(p. 105 – 118)
ABSTRACT
The Mesopotamia Plain represents about 25% of the total area of Iraqi territory; it is a part of Arabian Platform, which is divided into Stable and Unstable Shelves, being a part of the Unstable Shelf. The sediments within the Mesopotamia Plain are fluvial, lacustrine, deltaic and Aeolian in origin. The sediments of each type are intercalated, horizontally and vertically.
The Metalogeny of the Mesopotamia Plain is almost entirely related to the Quaternary sediments, which have a thickness that exceeds 180 m. There is very limited information on the pre-Quaternary economic deposits. The main economic deposits in the Mesopotamia Plain are fluviatile gravel and sand, clay, continental evaporites represented by salt pans and gypcrete, and partly the Aeolian sand. Peat is also recorded in many locations. The gravel and sand are used as a source for building material; they represent river terraces and alluvial fans, range in gravel to sand proportions and composition according to the source and distance of transportation. The Nuba'i, Chlat, Safwan and Chwaibda are the main localities for such deposits. The Aeolian sands are limited in use only in one area as a raw material for cement industry that is in Samawa vicinity.
The clays are of fluvial and fluvio – lacustrine origin and are widely spread in the central and southern parts of the Mesopotamia Plain. According to their use; they are classified into two major groups: one is for brick industry and the other as a raw material for cement industry. Nahrawan deposit is the best example for brick clays and Samawa deposit as for cement industry.
Continental evaporites are mainly represented by salt pans and gypcrete. The salt pans are formed by evaporation of saline water yielded by springs, then evaporate due to sun heating, leaving a veneer crust of salts. Samawa Salt Pan represents the best example for halite mineral production and Shari Salt Pan represents other type of salt minerals; mainly of glauberite. Other small salt pans are distributed in the middle parts of the Mesopotamia Plain. Gypcrete is also formed by evaporation of sulphate water raised by capillary action forming a fibrous texture with clay and sand. This type of deposits is commonly used as a mortar for brick. Peat deposits are recorded within different areas and they may be used as a source for fertilizer.
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