Organisational Structure - Birbal Sahni Institute of Palaeobotany

Birbal Sahni Institute of Palaeobotany
sp., Rhizomaospora sp., etc. with few Tertiary forms,
like Striatriletes susannae, Polypodiaceaesporites
sp., Pinuspollenites sp., Abiespollenites sp., besides
some fungal forms, mainly Frasnacritetrus sp. The
distribution of the families in the assemblege indicates
a tropical to subtropical climate during the deposition
of the sediments. Presence of reworked Permian
palynofossils indicates that the Lower Gondwana
sediments were extensively developed in the region
and were the source rocks for these younger Tertiary
sediments. Presently, the Permian sediments are well
exposed to the north of the studied localities. Field
work was undertaken to collect palynological samples
from Itanagar-Naharlagun Road section and Likabali-
Garu-Along Road section. About 114 rock samples
and about 36 fossil woods were collected from in
and around Likabali, West Siang district.
G.K. Trivedi
Project 8: Tertiary floristics of peninsular India
Component 1: Tertiary floral diversity in North-East India
Recorded rich palynofloral assemblages from the
Siju and Rewak formations (Middle-Late Eocene)
exposed in a stream section at Jenggitchakgre and
along Tura-Dalu Road in West Garo Hills
(Meghalaya). Dinoflagellate cysts and acritarchs
dominate the Siju palynoflora, whereas the Rewak
palynoflora is mainly represented by spores-pollen
followed by fungal remains and dinoflagellate cysts.
Predominant palynotaxa of the assemblage are
Achomosphaera alcicornu, A. ramulifera,
Homotryblium floripes, H. tenuispinosum,
Operculodinium centrocarpum, O. major,
Cordosphaeridium fibrospinosum, etc. The
palynoflora indicates prevalence of tropical (warmhumid)
climate and presence of mangrove elements
along the shore. It has been interpreted that the Siju
Formation was laid down over the unstable shelf in a
shallow sea. The dominance of terrestrial elements
and decrease of dinocysts indicates a regressive phase
during the sedimentation of the Rewak Formation.
The palynoflora have been compared with the Eocene
assemblages recorded from various sedimentary
basins of India. Representation of Areoligera
undulata, Areosphaeridium arcuatum, Homotryblium
floripes, Distatodinium ellipticum, etc. suggests a
Middle Eocene age for the Siju Formation. The
overlying Rewak Formation is dated as late Eocene
on the basis of palynofossils. Chemical processing
of the samples from the Boldamgiri/ Baghmara
Formation has also been taken up.
R.K. Saxena & S. Sarkar
Fossil fruit of Sterculia villosa from Oligocene sediments of Makum Coalfield, Assam X 1 Modern fruit of Sterculia villosa X 1
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