25th International Meeting on Organic Geochemistry IMOG 2011

P-268
Hydrocarbon molecular markers in the upper Cenozoic
sediments of the Arctic megabasin: distribution, genesis &
sources
Vera Petrova
Federal state enterprise ―Academician I.S. Gramberg All-Russia Research Institute for Geology and Mineral
Resources of, St.Petersburg, Russian Federation (corresponding author:petrovavi@mail.ru)
The investigation purpose and idea is to determine
the distribution patterns of hydrocarbon molecular
markers in the sediments of different geostructural
areas of the Eurasian Arctic megabasin in a context of
general geochemical ways of dispersed organic
matter (DOM) transformation and to identify their
indicator functions. This brief is based on the
materials of VNIIOkeangeologiya electronic database
(>2500 bottom stations), formed during long-term
(1980-2008) geological and geochemical studies of
the Russian sector of the Arctic Ocean water areas.
The scale of expeditionary work (regional,
subregional, local) and a wide range of used
analytical methods (bituminology, physical-chemistry,
gas chromatography-mass spectrometry) allowed to
characterize the Pleistocene-Holocene sedimentary
DOM and identify the main factors controlling the
geochemical background formation of the different
litho-facial zones of the region: from estuarine-deltaic
to abyssal. Analysis of hydrocarbon molecular
markers (123 bottom stations, >1000 samples) of the
Holocene-quaternary sediments from the Arctic
Ocean Eurasian sector has revealed their basic
compositional and lateral distribution patterns. The
geohopanes and geosteranes are almost absent in
river and estuarine sediments and only the
components characteristic for the earliest stages of
biogenic OM transformation (hopanols, hopenes,
sterols) have been recorded. Moreover, the chemical
taxones which often mark the specific types of higher
terrestrial plants - D-Friedoolean- 14-ene (gen.
polipodium) and Olean-12-ene (angiosperms) and
miss in the shelf and deep-sea sediments have been
identified.
Both bio- and geoisomers have been fixed in the
terpenoid composition of the offshore sediments.
However the geoisomers structure reflects the low
diagenetic level of DOM transformation. The share of
biological taxones in continental slope sediments is
naturally decreasing to the pelagic region and in the
abyssal zone they haven‘t been detected.
Cadalen and abietic acid transformation products
such as reten, tetrahydroreten, dihydroabietan have
been identified in the aromatic biomarkers
composition of the studied sediments.
On the sea-river transect a consistent increase of
abietan aromatization level, wich agrees with the
postsedimentary DOM transformation trend, have
been fixed.
Reconstruction of the late Cenozoic sedimentation
process was carried out using materials of the
sediment core columns and shallow (12 m) wells
complex study and included seismo-acoustic,
paleomagnetic, biostratigraphic, palynological and
organic-geochemical studies. The result revealed the
characteristic features of the lipid biomarker
composition of the Arctic shelf upper Pleistocene-
Holocene and Eopleistocene-Pliocene sediments.
Thus, the comparative study of the Arctic
megabasin multifacial sediments evaleates the
contribution of different sources (river run-off, turbidity
flows, ocean currents, subaqueous erosion and
redeposition of bedrocks) to the formation of loose
sedimentary cover. In particular, the leading part of
terrigenous material in the Late Cenozoic sediment
composition of the shelf and deep Arctic Basin
including the North Pole area has been shown during
the investigation. At the same time, a complex study
of organic-geochemical and geology-geophysical
parameters of bottom sediments made it possible to
surely identify and characterize the glacial/deglacial
and transgressive-regressive stages of the Late
Cenozoic sedimentation process.
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