East Siberian Sea Rift System: Results of 2D Seismic Interpretation

Maria Kamaeva

East Siberian Sea shelf is the largest and the least studied part of East Arctic Shelf. This area attracts attention because of possible similarity of structure and origin to US Chukchi Sea that is known as oil-gas bearing area. Our researches in structure and stratigraphy are based on seismic interpretation and available onshore and offshore data. More than 50 seismic lines were interpreted. The seismic lines across East Siberian Sea represent layered reflection package that is referred to sedimentary cover, overlaying chaotic reflection pattern, defined as an acoustic basement. Four main angular unconformities are observed. Ages of all unconformities are being specified now, but probably they are Mid-Aptian, Top Cretaceous, Top Eocene and Top Miocene. These unconformities divide sedimentary cover into four seismic complexes: synrift complex 1, synrift complex 2, postrift complex 2, postrift complex 2. Boundaries between seismic complexes match such important regional events as Cenozoic stretching episode, Top Cretaceous local inversion further transtention, Early Oligocene erisional event, Top Miocene inversion respectively. For East Siberian Sea Basin formation of sedimentary cover started at Late Aptian, postdating the Verkhoyansk-Brookian orogeny. Mid-Aptian – Late Cretaceous period was characterized by extention and rifting that caused development of the first seismic complex (synrift complex 1). On seismic lines this complex is recognized as a pattern of sub-parallel and divergent reflections, thickness varies from 0 up to 3 km. Eocene seismic complex is also synrift, it formed due to rifting and transtention after Top Cretaceous local basin inversion. On seismic lines it consists of sub-parallel and divergent reflections, thickness is up to 1.5 km. Oligocene-Miocene seismic complex is already postrift, it’s peak thickness is 0.75 km. The main feature of this complex is clinoform structure of it’s part. Clinoforms were observed at several seismic lines at Central part of East Siberian Sea, they fall in north-north-west direction. Clinoforms can probably be dated as Miocene. The upper part of the sedimentary cover is Pliocene-Quaternary seismic complex, postrift complex 2. This period of sediment accumulation was characterized by quiet subsidence, thickness of sediments is not significant – not more than 0.6 km. Total thickness of sedimentary cover varies noticeably in within East Siberian Sea Basin. In some places basement comes really close to the sea bottom, in submerged areas, especially rifts, sedimentary cover attains thickness about 6 km.

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