25th International Meeting on Organic Geochemistry IMOG 2011

P-076
Lanostanes as the new biomarkers from organic matter of
Cambrian black shales in the Siberian platform
Tatyana Parfenova
Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russian Federation
(corresponding author:parfenovatm@ipgg.nsc.ru)
Lanosteroids are tetracyclic triterpenoids
containing, unlike steroids, additional methyl
substituents at the C4 and C14 atoms of the A- and Ccycles.
Only a few identifications of lanosteroids in the
Cenozoic organic matter (OM) are known [1, 2, 7, 9].
This study deals with the collection of limestones of
the Lower Cambrian Sinskaya (Sinyaya) Formation.
The samples of OM-enriched rocks were obtained
from a section of the Sinyaya River at the northern
slope of the Aldan anteclise [8]. It is known that the
rocks of the Sinskaya Formation are considered as a
potential oil-producing rocks [4, 5, 8, etc.]. In m/z 217
chromatograms, С27–С30 steranes were identified.
The analysis has shown that their contents vary from
25 to 37% for С27, from 8 to 13% for С28, from 49 to
62% for С29, and from 1 to 4% for С30 for total of
steranes. During the studies of diasteranes, two
peaks of unknown compounds were found in the
m/z 259 chromatograms of 22 samples. The spectra
of these compounds are identical and coincide with
the С30 lanostane spectrum. The latter compound was
identified by the molecular mass М equal to 414, М –
15 = 399, and a high intensity of the ions (259, 190,
231, and 274) [2, etc.]. The lanostanes have not yet
identifies in Proterozoic and Phanerozoic oils and
scattered OM of Eastern Siberia [4, 6, etc.]. The
complementary studies of OM from the Kuonamka
formation (a facial analogue of the Sinskaya
sediments [5]) showed the absence of lanostanes.
The lithological, paleontological, and geochemical
studies showed that the OM of carbonaceous rocks of
the Sinskaya Formation was accumulated in the
marine basin with an excess of hydrogen sulfide in
carbonate sediments and, probably, in near-bottom
waters [3, 5, 8, etc.]. It was found that the lanostanecontaining
dolomite claystones were formed in a lake
of increased water salinity [2]. The studies of oils in
Wubei province revealed the lanostane sulfides [9].
The authors think that these oils have been derived
from Paleocene evaporite sediments. The evaporites
were accumulated under reductive conditions of
saline lakes. The lanostanes of Pietralunga (Italy)
were extracted from the lipids of Miocene marine
limestones [1]. The OM was preserved owing to the
rapid transformation of oxidizing conditions into
reducing ones.
Conclusions. 1. This report describes the first
occurrence of lanostanes in the Cambrian OM. 2.
Lanostane compounds could be markers for
carbonate or carbonate-containing rocks of lacustrine
or marine basins and for reducing conditions in
diagenesis. 3. The identification of these biological
markers in naphthides of the northern slope of the
Aldan anteclise should be a strong evidence of
realization of generative potential of oil-producing
rocks in the Sinskaya Formation.
This study was supported by the Russian Foundation for
Basic Research ( no. 10-05-00705, 11-05-0034), by the
Leading Scientific Schools Grant of the President of the
Russian Federation (grant no. NSh-6244.2010.5).
References
[1] Birgel D., Peckmann J., Org. Geochem. 39, 1659-
1667 (2008).
[2] Chen J.H., Philp R.P., Fu J.M., et al., Geochim.
Cosmochim. Acta 53, 2775-2779 (1989).
[3] Ivantsov A.Yu., Zhuravlev A.Yu., et al.,
Palaeogeogrh., Palaeoclimat., Palaeoecol 220, 69-88
(2005).
[4] Kashirtsev V.A., ―Organic Geochemistry of
Naphthides of the East Siberian Platform― (Yakutsk, 2003)
[in Russian].
[5] Kontorovich A.E. ―Geochemical Methods of
Quantitative Forecasting for Oil-and-Gas content‖, in
Proceedings of the Siberian Research Institute of Geology,
Geophysics and Mineral Resources, V. 229 (Moscow, 1976)
[in Russian].
[6] Kontorovich A.E., et al., Dokl. Earth Sciences 403,
754-759 (2005).
[7] Murae T., Naora M., Hosokawa K., et al.,
Geochim. Cosmochim. Acta 54, 3253-3257 (1990).
[8] Parfenova T.M., Pushkarev M.S., Ivanova E.N.,
Dokl. Earth Sciences 430,129-133 (2010).
[9] Peng. Ping‘an, A. Morales-Izquierdo, Jiamo Fu et
al., Org. Geochem. 28, 125–134 (1998).
220