«Geology, geophysics and development of oil and gas fields»

THE ROLE OF DISCONTINUITIES AND UNCONFORMITIES IN THE STUDY OF SEDIMENTARY BASINS (THE EXAMPLE OF THE SOUTH CASPIAN BASIN)

UDC: 550.83
DOI: 10.33285/2413-5011-2021-8(356)-19-24

Authors:

¹ Azerbaijan State Oil and Industry University (ASOIU), Baku, Republic of Azerbaijan

Keywords: sedimentary basins, discontinuities, complex, basin, unconformity, tectonics, sedimentation

Annotation:

This paper discusses the role of discontinuities and unconformities in the study of sedimentary basins on the example of the South Caspian Basin. Sedimentary basins occur in various geological conditions, usually associated with plate tectonic activity. Two main conditions are required for the formation of a sedimentary basin: a sedimentation space and a source of sediment. The sedimentary complex in sedimentary basins is a stratigraphic unit composed of a consonant sequence of geometrically related layers, bounded at the top and bottom by unconformities or corresponding consonant surfaces. In order to identify and accurately correct a sedimentary complex, its boundaries should be established and traced. Such boundaries are usually unconformities caused by unconformities of the section layers placement in relation to the unconformity surface. In addition, the geological age of the rocks above and below the unconformity determines the duration of the sedimentation interruption in the area. This paper examines the details of Early Pliocene age unconformity in the sedimentary cover of the South Caspian mega basin. Several different-age and different-scale tectonic-sedimentary complexes and strata are distinguished. The sedimentary cover of the mega basin is saturated by the surfaces of unconformity and erosion. In the side zones of the South Caspian mega depression mainly three regional (structural) surfaces of unconformity are distinguished by seismic criteria and peculiarities of the wave field. Regional wedging of formations and strata along the natural boundaries of the sedimentation basin and in the wing parts of structures, presence of breaks and unconformities, which caused erosion and tectonic cut of layers, constructive forms of the buried relief and exogenous processes promoted the formation of non-anticlinal oil and gas traps.

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