On the Problem of Rift-Related Structures in Yamal-Gydan Province of the South Kara Basin

Yuri Filippovich

As it is generally believed, the West Siberian Mesozoic-Cenozoic Basin or Geosyneclise (WSGS) represents a post-rift depression. As the primary rift structure for the WSGS, the so-called Koltogor-Urengoi 'graben-rift' identified by V.S. Surkov, et al in 1974 has been traditionally considered. The rift dissects the plate in the south-north direction from Kazakhstan to the North Siberian Arch. One of the key indicators of rift-related processes are synchronous (syn-rift) and post-rift sedimentary complexes. The depositional peculiarities of the complexes may represent good markers for definition of the marginal and axial parts of regional extensional basins. In particular, regional facies analysis of the central part of the West Siberian Basin shows that the basin's axial area, throughout the entire Mesozoic period, is associated not with the Urengoi-Koltogorsk zone but with the linear segment where large depression structures develop in the west part of the Western Siberia: Turgaysky trough, Frolov and Nadym depressions (Filippovich, 2007). For the Yamal-Gydan province, which is separated from the mainland Western Siberia with a east-west oriented Messoyakha Arch, localization of the main rift structures is not studied well enough. To find a reasonable solution to this issue, the areal distribution of thicknesses of the Jurassic post-rift depositional sequences and the character of the Late Jurassic – Neocomian noncompensated sedimentation have been analyzed to define the key features of the Mesozoic geodynamics in this sub-basin. The performed studies resulted in the understanding that the dominanting rift-related structure for the Yamal-Gydan province is the Yenisei-Khatanga Basin (Megatrough) whose paleotectonic boundaries are traced through up to the Baydarata monocline (the buried part of Pay-Khoy ridge, Kara Sea Region). It should be noted that the well-expressed frontal character of the joint between these two structures testifies to regional sinistral displacements. The data collected call for a significant revision of the tectonic development history of the north part of the West Siberian Basin, from the structure, composition and age of the basement to regularities in areal and depth distribution of petroleum accumulations in the region.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013