Journal of Earth Sciences and Geotechnical Engineering

Factors Controlling the Karstification Process in the Fatha Formation in Iraq

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• Abstract

   

  The Fatha Formation (ex-Lower Fars) is Middle Miocene of age and consists of cyclic sediments, each ideal cycle consists of marl, limestone and gypsum. However, in the upper half part of the formation, reddish brown claystone occur in the cycles. Moreover, in the uppermost part of the formation, fine reddish brown siltstone and claystone occur in the cycles too. The formation is divided into two members depending on the lithological constituents. Lower Member and Upper Member, the former is characterised by the absence of red clastic in the cycles and presence of thick gypsum beds, whereas the latter is characterised by the presence of fine red clastic with subordinate limestone beds. The Fatah Formation covers considerable parts of the Iraqi territory, especially in the central western part and the central northern part too. In the former area, the formation usually crops out in a horizontal beds, whereas in the latter area; it is exposed in the limbs of anticlines and occasionally in their cores. The Fatha Formation is one of the main problematic geological formations in Iraq. Due to intense karstification, the rocks of the formation have caused severe damages to the constructed structures built on its exposure areas. This article deals with the factors controlling the karstification process in the rocks of the Fatha Formation and shade light why karstification is not distributed over all the exposure areas of the formation in Iraq. The study concluded that the main factors that control the karstification process in the Fatha Formation are lithological and tectonic factors.