25th International Meeting on Organic Geochemistry IMOG 2011

P-474
Paleosalinity significance of the occurrence and distribution of
MTTCs in the Nenjiang Formation of Upper Cretaceous in
Songliao Basin, China
Li Wang 1,2 , Zhiguang Song 1 , Qin Yin 1,2 , Jiangtao Guo 1,2
1 Guangzhou Institute of Geochemistry, Chinese Academy of Sciences,, Guangzhou, China, 2 Graduate
School of Chinese Academy of Sciences, Beijing, China (corresponding author:zsong@gig.ac.cn)
A group of methylated-2methyltrimethyltridecylchromans
(MTTCs) is identified
in the core samples of Member 1 (K2n 1 ) and Member
2 (K2n 2 ) of Nenjiang Formation of Upper Cretaceous
from SK-l drilling borehole of Songliao Basin. This is
the first time that these compounds are reported from
the sediments older than Tertiary in China. Their
composition and distribution are mainly indicative of
the redox and salinity conditions of depositional
environments. Among these MTTCs, δ-MTTC is found
in relative abundant in enhanced salinity and reduced
environment, but absent in oxic and much less salinity
environment, while α-MTTC appears to be a nonsalinity
dependent compound and presents in all
environments. It is also found that α-MTTC/γ-MTTC
(α/γ) ratio has similar salinity indication as that of α/δ
ratio but is more widely applicable. The combination
of all related index and biomarkers suggest that the
massive lacustrine petroleum-prone source rocks
within K2n 1 member were likely developed under a
stratified water column environment with the reduced
and enhanced salinity of bottom water layer, which
was associated with a much less salinity top layer of
water(fresh to brackish). Finally, this study suggests
that the MTTC compounds were formed abiotically
from the precursors that originated from various
species of algae under a broad range of redox and
salinity depositional conditions.
Key words: MTTCs; depositional environment;
paleosalinity; Nenjiang formation; Songliao Basin
Acknowledge: This research was supported by
NSFC project of 40973033 and State ―973‖ Project
(2006CB701404)
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