WORLD SCIENCE ISSN 2413-1032 26 № 12(28), Vol.1, December 2017 http://ws-conference.com/ THE ROLE OF CLAY WITH RHEOLOGICAL PROPERTIES ON GOBUSTAN AND ABSHERON DEPRESSIONS IN THE STRUCTURAL FORMATION AND MUD VOLCANOES Nasibova G. Azerbaijan, Azerbaijan State Oil and Industrial University Abstract. Settlement layer in Gobustan and Absheron depressions is famed for high clay alteration (up to 70 %) and high thickness (up to 19 km). As these depressions are located on south- east hill-side of Greater Caucasus collision, positive structural traps which is spread therein are considerable clay diapirs. Since arch portion of these structures has complicated with cross breaks, rheologically active clay mass with associating fluids reach the earth surface and exudates to the atmosphere in the form of mud volcano by crumb formation on cross breaks with high power potential. Therefore, most structures have complicated with mud volcanoes. Gobustan and Absheron depressions cover large area on south-east part of Greater Caucasus. Majority of cone-shaped, brachyfold diapir folds have developed within this depression, most of which have complicated with mud volcanoes. The formation of clay diapirism and volcanism is caused by thickness and high clayiness of the settlement layer, availability of incompletely consolidated active clay mass in crosses, and subjection to high shrinkage. Keywords: mud volcanoes, Absheron depressions, Gobustan,rheological activity clay, Miocene. The most part of Azerbaijan is composed of South Caspian mega-depression located in the centre of Alpine-Himalayan mountain chains. Gobustan and Absheron depressions, which are a subject research, cover north-west part of Southern Caspian mega-depression. According to correlation schemes of normal-lithological- stratigraphical crosses in this sedimentation area, we may conclude that, depression is characterized by high clayiness (up to 70 %) and high thickness (up to 24 km). Since it is surrounded by Greater Caucasus, Smaller Balkhan, Greater Balkhan, Kopetdagh collisions, the area is subject to shrinkage tension (N.R.Narimanov, etc., 2014,(3-4)). As, such a litho-facial, tectonic and geodynamical condition is very suitable for clay diapirism, mud volcanoes and oil-generation, more than 1/3 of mud volcanoes of the world have developed in Azerbaijan, including Gobustan and Asheron depressions (A.A.Aliyev, et., 2009). The formation of local arched districts is related to all three mechanisms (longitudinal bending mechanism, lateral bending mechanism and flow mechanism) of fold generation. Level of clayiness of settlement, tectonical breaks also affect on morphology of folds during their development. Weakly-developed types of clay diapirs with power potential of core which is composed of unconsolidated clay in crypto-diapirs do not allow it to overcome the layers and emerge on earth surface. Such kind of buried arches emerge as a fold on settlement layer. Several buried arches such as Duvanni arch in Gobustan, Buzovna-Mashtaga, Gala and Turkan arches have developed in Absheron. As these arches have been weakly complicated with breaks, they are famed for high impermeability as a trap. As distinct from crypto-diapirs, power potential of clay diapirs allows them to exude on earth surface. Gungormaz in Gobustan, Bibiheybat, Shabandagh in Absheron are clay diapirs. In case compacted type of folds with core consisted of unconsolidated clay has high power potential, they become complicated with mud volcano on last phase of development. Rheological activity of clay is increased by decrease of its density and dynamic viscosity when liquid and gas organic matters in its content are converted into hydrocarbons. In fact, if arched part of developing fold is complicated with system of breaks, rheologically active clay mass with high power potential and associating fluids reach earth surface by crumb formation in break crossing with high power potential and exudate in the form of volcano to the atmosphere. In case Crumb zone generated by crossing breaks is developed under unconsolidated clay layer, high pressure natural gas might be accumulated in this zone. During the mud volcano formed on such crumb zone, on contrary to other mud volcanoes, big volume of gas exudates to the atmosphere. Unconsolidated clay characterized by high rheological activeness which causes formation of mud volcanoes might not be considered as a base of volcano. From this point, the base of mud volcanoes developed in Gobustan and Absheron depressions is composed of Miocene -Miocene deposits (Maikop series, Middle and Upper Miocene) (Fig. 1).