25th International Meeting on Organic Geochemistry IMOG 2011

P-059
Update and review of recent advances in age-related biomarkers
Silvana Barbanti 1 , J. Michael Moldowan 2
1 Integrated Petroleum Expertise Company, Rio de Janeiro, Brazil, 2 Geological & Environmental Sciences,
School of Earth Sciences, Stanford University, Stanford, United States of America (corresponding
author:silvana.barbanti@ipexco.com.br)
Petroleum exploration geologists and basin modelers
have often faced the challenge of defining the age of
petroleum that has not been rigorously correlated to a
source rock. Biomarkers have been applied with
success in many cases due to the high taxonspecificity
of some of these compounds. For example,
24-norcholestanes are more prominent in some oil
samples from Jurassic, Cretaceous, and Tertiary
source rocks than oil from older source rocks, which
is consistent with a possible origination from diatoms
[1]. Triaromatic 24-norcholesteroids are abundant
from Jurassic to Cretaceous and to Tertiary exhibiting
a similar trend to the nordiacholestanes, but also
show more sensitivity in the Jurassic than their
saturate analogs [2]. 24-iso-Propylcholestanes are
particularly abundant in some Ediacaran and
Ordovician oil and extracts [3, 4, 5]. The C28/C29
sterane ratios increase in the Cretaceous or at the
transition between the Jurassic and Cretaceous for
marine oil samples [6, 7]. Marine oils derived from
older than Silurian source rocks show particularly low
non-zero values for C30 sterane and C30 diasterane
indexes indicating that these ratios can be useful for
distinguishing marine oil samples from Silurian and
older [8]. Recent work has demonstrated non-zero
values for these indices in lacustrine oil, albeit orders
of magnitude less than for marine oil of similar age
(Zinniker, personal communication).
The combined application of some biomarkers is an
even more powerful tool for defining the geological
age of oil samples. Triaromatic 4,23,24trimethylcholesteroids
(TA-dinosteroids) and 23,24dimethylcholesteroids
(TA-DMC) are useful
parameters to distinguish oil samples as being
derived either from the Paleozoic or from the
Mesozoic through Tertiary [9, 10]. The combined
application of oleanane and bicadinane indices can
signal Mesozoic and Tertiary ages from the
contributions of terrestrial plants. From the standpoint
of algal taxa, biomarkers most likely based on
different diatoms including the C25-highly branched
isoprenoid (C25-HBI) and the saturate and aromatic
24-norcholestanes are also active in the Mesozoic to
Tertiary time period, while the as yet not fully
understood tricyclic terpanes (however, probably
algal) carve out the Jurassic. Therefore, based on
many taxon specific biomarkers the Triassic, Jurassic,
Cretaceous and Tertiary Periods and the Paleozoic
Era can often be differentiated.
References
[1] Holba, A.G., et al. (1988) Application of 24norcholestanes
for constraining source age of petroleum.
Organic Geochemistry 29, 1269-1283.
[2] Barbanti et al. (2009) New triaromatic steroids with
taxon and age-specificity [abs.], in Proceedings of 24 th Int.
<strong>Meeting</strong> on Organic Geochemistry, Bremen, Germany.
[3] McCaffrey, M.A., et al. (1994) Paleoenvironmental
implications of novel C30 steranes in Precambrian to
Cenozoic age petroleum and bitumen. Geochimica et
Cosmochimica Acta 58, 529-532.
[4] Love, G.D., et al. (2009) Fossil steroids record the
appearance of Demospongiae during the Cryogenian period.
Nature 457, 718-721.
[5] Peters, K.E., Walters, C.C., Moldowan, J.M.
(2005) The Biomarker Guide, 2nd Edition. Cambridge
University Press, Cambridge.
[6] Grantham P.J., Wakefield L.L. (1988) Variations in
the sterane carbon number distributions of marine source
rock derived oils through geological time. Org. Geochem. 12,
61-73.
[7] Moldowan, J.M., Barbanti, S.M., Trindade, L.A.
(2002) A new look at one of the first age-related biomarker
parameters, the C28/C29 sterane ratio [abs.], in Proceedings
of 8 th Latin American Congress on Organic Geochemistry,
Cartagena, Colombia.
[8] Barbanti, S.M. and Moldowan, J.M. (2005)
Relationship between petroleum biomarker composition,
depositional environment and age of the source rock
(revisited) [abs.], in Proceedings. of 22 nd Int. <strong>Meeting</strong> on
Organic Geochemistry, Seville, Spain.
[9] Moldowan, J.M., et al. (1996) Geology 24, 159-
162.
[10] Barbanti S.M., et al. (1999) Analysis and
occurrence of novel triaromatic 23,24-dimethylcholestanes in
geological time [abs.], in Proceedings. of 19 th Int. <strong>Meeting</strong> on
Organic Geochemistry, Istanbul, Turkey, p. 159-160.
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