Мурманская МИЛЯ. 2018 г. №4.

EXPLORATIONS 70 in the North Chukchi Trough as well as on the identification of the last Brookian BU, lower Cre­ taceous LCU and upper Jurassic JU uncon­ formities in the sedimentary cover as well as on the established fact of continuous track­ ing of BU, LCU и JU from the North Chukchi Trough to the Vilkitsky Trough and Podvod- nikov Basin based on the AR1401 seismic line data. Thus the pre-Cainozoic section is represented by four seismic and stratigraph­ ic sequences (SSS-3, 4, 5, 6). SSS-3 is limited by unconformities pCU and BU. The lower Brookian sequence is as­ sociated with the last stage of magmatism HALIP (80-90 mln years) and includes ter­ rigenous deposits (aleurolites, sandstones) of the Aptian to Albian age and the upper Cretaceous. The seismic facies of sequen­ ces have the features of lateral accreation of paleoshelf in the North Chukchi Trough and avalanche sedimentation in terms of shal­ low sea in the Vilkitsky Trough and the Pod- vodnikov Basin. The SSS-3 thickness varies from 3,000-5,000 m on the shelf in the area of clinoforms spreading (lateral accreation of paleoshelf) up to «1,000 m in the Vilkitsky Trough and up to 100-300 m to the extent of complete pinch-out in the Podvodnikov Ba­ sin. The adjusted to the reflected and diving P-waves values of interval velocities in SSS-3 in the North Chukchi Trough vary in the range of 3.8-3.9 km/sec, in the Podvodnikov Basin the values are equal to 3 .5-3.7 km/sec. SSS-4 is limited by unconformities BU and LCU. The sequence had developed during the first stage of magmatism HALIP (130-120 mln years) and includes terrigenous deposits of the lower Cretaceous (K1h-br). The sequence internal structure is common for terrigenous deposits. According to the data obtained by drilling on the Alaska shelf it comprises most­ ly shale rocks, aleurolites and sandstones. The sequence thickness in the North Chukchi Trough and in the Vilkitsky Trough doesn’t ex­ ceed 300-400 m. The sequence is pinching out in the northern and western parts of the Podvodnikov Basin. The adjusted to the re­ flected and diving P-waves values of interval velocities in the sequence vary from 3.9-4.0 km/sec in the North Chukchi Trough, to 3.8 km/sec in the Podvodnikov Basin. SSS-5 is limited by LCU (or BU+LCU) and JU unconformities and include the upper Ju­ rassic to the lower Cretaceous terrigenous deposits (J3-K1b-v), generally represented by shale rocks and sandstones. The se­ quence is characterized by seismic facies of avalanche sedimentation, it’s synchronized with the rift sequence on the Alaska shelf, separating the Brookian structural level from the Ellesmerian one. In the North Chukchi Trough as part of the sequence the high velocity deposits (up to 4.5 km/sec) were identified with thickness of «2,000 m maxi­ mum. In the area of transition from the North Chukchi Trough to the Podvodnikov Basin, in the saddle area the sequence thickness re­ duces up to 800-1000 m maintaining almost the same within the limits of the whole basin. In the Podvodnikov Basin SSS-5 is featured by the values of P-waves interval velocities equal to 3.8-4.0 km/sec. SSS-6 is limited by JU unconformity and by the acoustic basement (AB). The Elles- merian sequence includes the early and late Jurassic deposits and probably even more ancient sediments (P3-J2). The sequence internal structure is featured by the fragmen­ tary stratification common for poorly strati­ fied terrigenous deposits. The sequence thickness in the depocentre of the North Chukchi Trough reaches «6,000 m with the interval velocity of P-waves from 4.8 to 5.8 km/sec. The sequence continuously extends to the Vilkitsky Trough where its’ thickness in the depocentre reduces to «4,000 m and the adjusted values of the P-waves interval velocities reduce to 4 .1-4.3 km/sec. SSS-6 is not traced beyond the limits of the Vilkitsky Trough and the Chukchi Basin. All the seismic stratigraphic sequences are continuously traced from the shelf North Chukchi Trough to the Vilkitsky Trough, the Podvodnikov Basin to the Chukchi Basin and the upper of them - to the Makarov Basin, the Lomonosov Ridge, Mendeleev High and Chukchi Plateau. Continuous tracking of sedimentary sequences from the shelf to the adjacent deep water area allows making a conclusion about the common development history of structures of the East Arctic conti­ nental margin and the province of the Central Arctic underwater highs. In conclusion it should be emphasized that on August 10, 2014 first in the world in the North Pole region there was performed the integrated geophysical exploration includ­ ing CMP reflection seismic (using 6000 m streamer along with reflection and refraction sounding), bottom relief survey and gravity survey. The surveys were solely performed by the efforts of Russian experts on the basis of innovative geophysical system developed by JSC MAGE. Arthur Chilingarov managed to take a look at the ocean bottom in the North Pole region in the day. And expedi- MURMANSK MILE • 4-2018