1995-96 - Birbal Sahni Institute of Palaeobotany

BSIP
Objective 'To carry out morphotaxonomic study of recorded palynotaxa
To determine stratigraphically significant palynotaxa and
their application in zonation, correlation and dating
To infer palaeoclimate and environment of deposition
To trace botanical affinity and evolutionary lineages of studied
palynotaxa
A palynofloral assemblage, comprising 30 genera and 48 species, has been recorded
from the Tura Formation (Palaeocene) exposed in Nongwal Bibra area in East
Garo Hills District.Two palynozones have been recognized. The lower is dominated by
angiospermous pollen (79 %), viz., Proxapertites spp., Tricolporopollis spp.,
Granustephanocolpites cooksoniae, Palmidites spp., Tricolpites matanomadhensis, etc.
followed by pteridophytic spores (7.5 %) and fungal remains (13.5 %), whereas the upper
palynozone is dominated by pteridophytic spores (76 %), viz., Lycopodiumsporites spp.,
Dandotiaspora sp., Foveosporites triangulus, Todisporites spp., etc. followed by angiospermous
pollen (15 %) and fungal remains (9 %). The palynoflora indicates prevalence of
tropical-subtropical climate, luxuriant growth of wet-evergreen forest in the vicinity ofthe
area and near-shore, shallow marine environment of deposition. Based on close similarity of
the present assemblage with those recorded from parts of the Tura Formation (Garo Hills),
Cherra Formation (Khasi Hills), Therria Formation (Jaintia Hills), Mikir Formation (North
Cachar Hills), subsurface Palaeocene sediments of Bengal Basin and Matanomadh
Formation (Kutch), a Palaeocene age has been assigned to the studied sequence.
Maceration of samples from the Palaeocene-Eocene sediments ofTura-Dalu Road
Section (West Garo Hills) has been done and is being continued. Study of palynoflora from
the Siju Limestone and Rewak formations of Siju-Baghmara Road Section has bccn
taken up.
R.K. Saxena, S.K.M. Tripathi & Vandana Prasad
A rich palynological assemblage has been recorded from the Boldamgiri Formation
(Early Miocene) exposed in the type area-Boldamgiri, on Adugiri-Purakhasia Road,
in West Garo Hills District. The assemblage is dominated by pteridophytic spores,
followed by gymnospermous and angiospermous pollen. Besides, a good number of dinoflagellate
cysts and fungal remains have also been recorded. The important paJynotaxa of
the assemblage are: Lygodiumsporites, Pteridacidites, Osmundacidites, /ntrapunctisporis,
Striatriletes, Foveotriletes" Cheilanthoidspora, Polypodiaceaesporites, Pinuspollenites,.
Abiespollenites, Spinizonocolpites, Plumbaginaceaepites, Meyeripollis,
Echistephanocolpites, Polyadopollenites, Proteacidites, Chenop'odipollis and Malvacearumpollis.
Representation of dinoflagellate cysts and pollen of mangrove and back-mangrove
and coastal elements suggests a near-shore environment of deposition. Present day
distribution of various plant families and abundance of pteridophytic spores and fungal
remains indicate tropical-subtropical (wann-humid) climate. The assemblage also contains
reworked Permian pollen, e.g., Parasaccites, Plicatipollenites, etc. which might have
bcen derived from the Lower Gondwana sediments developed in the West Garo Hills, near
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