Мурманская МИЛЯ. 2018 г. №4.

EXPLORATIONS Fig. 2. The basement structural and tectonic scheme. Key-words: I - The Alexandrovskaya high zone, I 1 - the Franz Victoria regional step, I 2 - the Alexandrovskaya regional step; II - The North Barents trough, II1 - the North Barents syneclise, II 2 - the East Barents syneclise, II 3 - The Albanovsko Gorbovsky trough, II 4 - the W estern Fobos trough; III - The Prednovozem elskaya structural area, III 1 - the Sedov trough, III 2 - the Cape Zhelaniya high. 34 Рис. 2. Структурно-тектоническая схема по фундаменту. Условные обозначения: I - АЛЕКСАНДРОВСКАЯ ЗОНА ПО ДНЯТИЙ, I 1 - Региональная ступень Ф ранц-Виктория, I 2 - Александровская региональная ступень; II - СЕВЕРО- БАРЕНЦЕВСКИЙ ПРОГИБ, II 1 - Северо-Баренцевская синеклиза, II 2 - Восточно-Баренцевская синеклиза, II3- Альбановско- Горбовский порог, II 4 - Прогиб Западный Фобос; III - ПРЕДНОВОЗЕМЕЛЬСКАЯ СТРУКТУРНАЯ ОБЛАСТЬ, III 1 - Прогиб Седова, III 2 - Поднятие Мыса Ж елания Before the 2000s the geological and geophysical data on the structure of the northern part of the Barents Sea had been based on the gravity and magnetic fields parameters obtained as the result of areal airborne survey and two-dimensional shipboard surveys performed by such institutions as Central Scientific Research Institute of Geodesy, Aerial Survey and Cartography, Scientific- Research Institute of Geology of the Arctic, Polar Marine Geosurvey Expedition of Scientific Production Association Sevmorgeologiya and Complex Marine Arctic Geological Expedition. In 1978 - 1989 MAGE PGA Sevmorgeologiya had performed shipboard gravity survey of the Barents Sea at a scale of 1:1.000.000 which became the base for composing of the sheets of the USSR State Gravity Map and the structural tectonic classification of the Barents Sea waters in whole. Available seismic information was extremely poor limited to several reconnaissance lines shot by 2D CMP method, refraction method and wide-angle seismic profiling performed by MAGE, SMNG and PGA Sevmorgeo. The Nagurskaya, Kheis and Severnaya stratigraphic wells (Fig. 1) were drilled by Volgokamskgeologia trust on the islands of Franz Josef Land in 1977 - 1981. The sedimentary cover stack and the folded basement upper part were uncovered. The nearest offshore wells namely the Pakhtusovskaya well and the Vernadskaya well have become available for geological correlation by means of direct transfer of correlation over the seismic lines. The East Barents megatrough on the whole and particularly its’ northern part are considered the unique shelf sedimentary basin. The trough reaches thickness up to 20 km. Regarding the stratigraphic range the sedimentary cover represents Paleozoic and Mesozoic fill with almost no Cainozoic interval. In the history of the Paleozoic and Mesozoic sedimentary basin development three phases of tectonic stabilization can be clearly featured after which the basin persistent subsidence has stayed within its’ present boundaries. The cause of this subsidence has stayed unclear for the rifting features which are usually associated with thick sedimentary formations are not observed in post mid-Devonian strata at least. Admittedly, the proven oil and gas potential doesn’t coincide with the scale of the sedimentary basin and is limited to the gas and condensate content. The Alexandrovskaya high zone, the North Barents syneclise, the Prednovozemelskaya structural area from west to east are considered the basic tectonic elements distinguished at the sedimentary cover bottom. The south-west closure of the East Barents syneclise appears in the north-east. The Albanovsko Gorbovsky trough is a boundary structure between syneclises (Fig.2.3). 2D seismic section do not show the basement stacks in the North Barents syneclise and at the Albanovsko Gorbovsky trough, but according to the data of the refraction survey and the integrated modelling with the involvement of anomalous gravity and magnetic fields the depth of its’ cover is estimated at 16 km/2,3,4,5/. The lower part of the sedimentary cover is featured by the early mid-Paleozoic geoseismic sequence (GS), which rests with angularity on the heterogeneous platform surface and is limited by the erosional surface III2 at the top. The top of this sequence varies from 4,500 to 16,000 m, and it is from 1,000 to 6,000 m thick. It is most prominent in the trough-shaped depressions in the marginal parts of the sedimentary basin and less certain in the depocentre. The upper Devonian to m id-Perm ian GS rests with angularity over the bedding of the lower mid-Paleozoic GS sediments and is traceable throughout the basin. The GS thickness in the northern part of the Barents MURMANSK MILE • 4-2018