1996-97 - Birbal Sahni Institute of Palaeobotany

BSIP
Research
Projects and Programmes
PROJECT 1
Programme 1.1
ANTIQUITY. RADIATION AND EVOLUTIONARY PAT­
TERNS OF EARLY LIFE
Palaeobiology of Vindhyan Basin
P.K. Maithy
& R. Babn
The cherts belonging to Nagod Limestone Formation. Bhander Group exposed
at Bainkuyian in Madhya Pradesh were studied. A rich assemblage of previously
unrecorded organic-walled microfossils is identified. The forms belong to algae and
acritarchs. The characteristic acritarchs are Nucellosphaeridium. Margominuscula.
Pulvinomorpha. Octaedryxium, Archaeohystrichosphaeridium, Cymatiosphaeraides and
a new chlorophycean form. Oncolites from the Nagod Limestone Formation were
investigated in thin section. A dominant assemblage of tubular cyanophycean forms
was assigned to the form genera Eomycetopsis and Gunilintia. Possibly the septation
may be due to diagenesis. Besides. the Chroococcacean forms are being represented
by solitary sphaeroids Huronispora. paired form Eosynechococcus and the colonial
form Eoentophysalis.
A systematic analysis of the biota and ichnofossils of the Vindhyan has shown
that it represents the upper part of Neoproterozoic sequence. The oldest bed of the
Bhander Group. Ganurgarh Shale Formation. outcroping at Mid Ghat Railway Station.
Bhopal District. Madhya Pradesh is dominated by acritarchs. large sized leiosphaerids.
Nucellosphaeridium. processed form Cymatiosphaeraides and tubular Vendian marker
form Polytrichoides. The subsequent overlying Lower Bhander Limestone Formation
has diversified biota. The organic-walled microfossils show predominance of
Gloeocapsomorpha, Sphaeracollgregus, Caryosphaeroides and large sheaths indicating
presence of ?Vendotaenids. The oncolites show dominant presence of
Eoentophysalidaceae and tubular sheaths. An important Vendian macrofossil - Sekwia
is also now known from this formation, besides problematic trails. Occurrence of trace
fossils and dubiotraces are also known from the Lower Bhander Sandstone exposed
around Madhya Pradesh. Sirbu Shale preserves broad aseptate tubular filaments.
acritarchs. commonly large sized leiosphaerids with small process (viz ..
Baltisphaeridillm), and the remains of endosporulating Sphaerocollgreglls. From the
youngest bed of ))holpura Shale Formation exposed near Lakheri Town. comparable
form of Melallocyrillillll1 is recorded. This bed also preserves discoid impressions
comparable to Neoproterozoic sponges. Analyses of the overall assemblages indicate
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