Quaternary geology and sedimentation environment of the north-eastern Barents sea

KOSTIN, DA JSC "AMIGE", Russia

The paper is based on the data of shallow seismic reflection survey, shallow boring and sampling which have been carried out by various companies in the northern part of the Barents shelf The area of interest is bounded from the North by the Franz Josef Land and from the South by the Novaya Zemlya.

Quaternary sediments overlie the Mesozoic and Paleozoic rocks with angular and stratigraphic unconformity and form a discontinuous cover. The Quaternary strata are about 10-20 m thick, but in the areas of denudation they may almost thin out. Maximal thicknesses are characteristic for moraine sediments which form the ridges clearly reflected in present-day topography of seabed and for glacial-marine sediments within overdeepened depressions. In the areas of glacial scouring, modem seabed abrasion near the shoreline and inherited highs there is a thinnest cover of the Quaternary sediments, if at all.

On the base of seismic stratigraphy data the Quaternary sediments can be differentiated into three seismic-stratigraphic sequences (SSS) which in turn are subdivided into several seismic units (SU). A generalized section therefore looks as follows (from the foot topwards):

l.SSS-III- Lower - Mid Pleistocene sequence:
a) SU-III-2 - Lower - Mid Pleistocene unit with "dotted" or "spotted" pattern of seismic image without any long lineups (m, mgl-II);
6) SU-III-1 - Lower - Mid Pleistocene unit with chaotic seismic image (gl-II).

2. SSS-II - Upper Neopleistocene sequence:
а) SU-II-6 - Upper Neopleistocene unit with layered or "spotted" pattern occurring as covers or in-fills (m, mglll);
б) SU-II-5 - Upper Neopleistocene (Lower Valday) moraine unit with chaotic seismic record (glib);
в) SU-II-4 - Upper Neopleistocene (Lower Valday) acoustically transparent, sometimes indistinctly layered unit occurring as in-fills or loaf-shaped bodies (gmlll2);
r) SU-II-3 - Upper Neopleistocene (Upper Valday) unit with chaotic seismic pattern forming moraine bodies reflected in the present-day topography (glll4):
д) SU-II-2 - Upper Neopleistocene - Holocene (Upper Valday - Holocene) acoustically transparent "spotted" or indistinctly layered seismic unit occurring as loaf-shaped bodies or in-fills (gmllLrH);
е) SU-II-1 - Upper Neopleistocene - Holocene (Upper Valday - Holocene) acoustically transparent seismic unit forming in-fills (gm, mlll4-Н).

3. S S S - I - Holocene transparent or thinly layered seismic sequence occurring as in-fills (mH).

The specified seismic-stratigraphic units are characterized geologically, their occurrences are outlined laterally.
Cenozoic sedimentation in the area went on in close relation to active forming of oceans within the Norwegian-Greenlandian basin during the Paleogene time and within the Eurasian basin in the Neogene - Antropogene. Besides, there were multiple glaciations of vast areas in the Quaternary time. All these factors caused a significant stratigraphic break which covered the Paleogene. Neogene and Eopleistocene, and made relatively low average thickness of the sedimentary cover and great variety of genetic types of the Quaternary sediments characteristic of the area.

ARCTIC SHELF OIL AND GAS CONFERENCE 2004

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