GEOMORPHOLOGY

Ala,; A. Ma, Khaldoun

	GEOMORPHOLOGY
Iraqi Bulletin of Geology and Mining
Article 1, Volume 0, Issue 2, 2017, Pages 1-33
Authors
; Khaldoun A. Ma
Abstract
This study deals with defining the landforms, morphogenetic processes and climatic fluctuations during the continental phases through the Tertiary and Quaternary periods, based on the available data obtained from the geological studies in the Iraqi Southern Desert. The study reveals that the present surface of the Southern Desert is attributed to rejuvenated plateau, which originated from influence of the destruction and construction processes, during two continental phases. The first phase, which commenced after the Oligocene Uplift, formed the older plateau. It is characterized by prevailing of denudation processes in a semiarid climate; as well, beginning of subterranean hallows and caves. The second phase, which started after the last Alpine movements, included the Pliocene and Quaternary Periods, formed the younger plateau. It is characterized by climatic fluctuations between wet – arid and semiarid, which induced denudations in places and depositions in others. Twenty four landform assemblages, related to seven morphogenetic groups of variable origins, are distributed on three physiographic units, named: Al-Hijara, Al-Dibdibba and the Periphery. Each unit has specific landform assemblages, which reflect effect of the structure, lithology and climate. Moreover, the exterior part of the younger plateau suffered from depressing due to influence of erosional process along the Euphrates Fault Zone, which modified later on to foot basin, due to supply of a clastic sediments from the elevated parts of the plateau, during the Pleistocene and early Holocene. In addition to polygenetic accumulations referred to evaporation, Aeolian, estuary and floods of Euphrates River. This phase was witnessed the development of two types of lakes: collapse lakes (in the elevated part) and seepage lakes (in the depressed part). The former is filled by clastic sediments of Zahra Formation, whereas the latter is filled by salt accumulations, excluding Sawa Lake. The underground drainage system was active and originated network of passages and chambers since Oligocene to Recent time. While the surface drainage system was active and originated sub parallel rivers, which were running towards NE since Late Pleistocene to early Holocene and became dry later on, due to climatic changes. The study revealed that the formed landforms, by the present semiarid climate contributed in the protection of the area by desert pavement, excluding the karstified areas (Limestone pavement) that served as passageways for rainwater. Consequently, new geomorphological map for the Iraqi Southern Desert is constructed based on the achieved data.

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