25th International Meeting on Organic Geochemistry IMOG 2011

O-06
Eocene out-of-India dispersal of Asian dipterocarps
Suryendu Dutta 1 , Suryakant Tripathi 2 , Monalisa Mallick 1 , Runcie Mathew 1 , Paul
Greenwood 3 , Mulagalapalli Rao 2 , Roger Summons 4
1 Indian Institute of Technology Bombay, Mumbai, India, 2 Birbal Sahni Institute of Palaeobotany, Lucknow,
India, 3 The University of Western Australia, Perth, Australia, 4 Massachusetts Institute of Technology,
Cambridge, United States of America (corresponding author:s.dutta@iitb.ac.in)
Dipterocarpaceae comprise large trees that dominate
the canopy of lowland equatorial forests. They
typically contribute to 30% of the total basal area of
typical lowland evergreen forests in southeast Asia
and play a dominant role in Asian rain forest ecology.
Two opposing hypotheses have been proposed to
explain the origin of the Asian dipterocarps. Some
hypothesize that the family originated in Southeast
Asia, most probably from West Malaysia in the late
Mesozoic (Lakhanpal, 1970) and migrated into India
during the late Cenozoic Era. The occurrence of
bicadinanes diagnosic of Dipterocarpaceae resins in
late Cenozoic fluvio-deltaic oils from across SE Asia
(Dutta et al., 2009) represented a further connection
with this age. Others suggest that Dipterocarpaceae
have a Gondwanan origin and reached Asia by rafting
on the Indian plate (Ducousso et al., 2004).
The earliest dipterocarp fossils recorded in SE Asia
come from Oligocene (34-23 Ma) sediments of
Borneo (Muller, 1981). Here, we report an occurrence
of Asian dipterocarps from approximately 53 Ma
sediments from western India based on fossil resin
chemistry and palynological data. Early Eocene
lignites, carbonaceceous shales and resins were
collected from the Cambay, Kutch and Rajasthan
basins of Western India. Cadalene based C15 bicyclic
sesquiterpenoids and their dimer bicadinanes were
consistently identified as the major pyrolysis products
(Figure 1) from all Early Eocene resins identifying
them as angiosperm Dipterocarpaceae-sourced
dammar (Class II) resins (Dutta et al., 2009). We have
also recovered angiosperm pollen grains which show
close affinity with modern pollen of Dipterocarpus
indicus.
An important implication of the present finding is that
Asian dipterocarps must have originated in
Gondwana and dispersed out-of-India into Asia once
the land connection between Indian and Asian plate
was well established during the middle Eocene (49-41
Ma). Moreover, the present study supports the
hypothesis which suggests that many angiosperms
did not originate in the SE Asian region, but dispersed
into the area from western Gondwanaland.
References
Ducousso, M., Bena, G., Bourgeois, C., Buyck, B.,
Eyssartier, G., Vincelette, M., Rabevohitra, R.,
Randrihasipara, L., Dreyfus, B., Prin, Y., 2004.
The last common ancestor of Sarcolaenaceae
and Asian dipterocarp trees was ectomycorrhizal
before the India-Madagascar separation, about
88 million years ago. Molecular Ecology 13, 231-
236.
Dutta, S., Mallick, M., Bertram, N., Greenwood, P.F.,
Mathews, R.P., 2009. Terpenoid composition
and class of Tertiary resins from India.
<strong>International</strong> Journal of Coal Geology 80, 44–50.
Lakhanpal, R.N., 1970. Tertiary floras of India and
their bearing on the historical geology of the
region. Taxon 19, 675-694.
Muller, J., 1981. Fossil pollen records of extant
angiosperms. Botanical Review 47, 1-142.
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