1994-95 - Birbal Sahni Institute of Palaeobotany

BSIP
Ring counts in the Skeleton Plots show that tree-age of Larix grijfithialla ranges
from 100-250 years, Taxus baccata 150-380 years, and 150-530 years in Tsuga brwlOllialla.
Dating of these tree-ring sequences to the calendar year of their formation is in progress.
S.P.IV
A. Bhattacharyya, R.R. Yadav & Vandana Chaudhary
Palaeo biological investigations across Archaeozoic-Early
Proterozoic transition (OST NO. ESS/CAlA4-09/93)
Objective
To identify orgallic-walled microfossils. their sy"ge"icity alld
biogellicity from Archaean and Early Proterozoic
Identification of benthic and planktollic biota alld their comparison
with extant forms
Significallce of biota ill metallogellesis
Organosedimentary struC/ltres-stromatolite morphology. etc.
associated with stroma­
Study of orgallic walled microfossils
tolites
Significance of stromatolites in biostratigraph)\ basin analysis.
etc.
Two sections in Noamundi-Barbil area, Orissa were identified which show good
development of carbonate facies underlying the Iron-Manganese ore-bearing horizon. One
section is near Bhadrasahi in the Kasia Mine and other at Nadidih about 10 km from the
Kasia Mine area. The Kasia Mine area shows ca 80 m thick carbonate sequence with
intercalated snales and black bedded cherts. Thc tnickness ofcnClt bands varies from a few
mm to 2 m with colour varying from light grey to black. The lower part of the carbonate
sequence is devoid of cyanobacterial mat horizon but the upper part snows excellent preservation
of mat horizon. A few bands show development of Strati/era type mats but some
also snow columnar, non-branching stromatolites. The height of the stromatolite columns
is up to few ems. The upper part is overlain by Hematite-Jasper-bearing horizon which is
mined for iron and manganese ores. A lithostratigraphic succession is established for Kasia
Mine area and entire 80 m thick carbonate sequence is divided into 5 informal units. The
Nadidih section shows an exposure mea~uring a few meters only. A detailed sampling is
done in both the areas for the study of stromatolites and microbiota. More than 100 thin
sections were prepared and studied for lhe presence of rnicrobiota.
For organic-walled microfossils each slide was scanned under the petrological microscope
with lOa x objective. Majority of lhe slides are non-fossiliferous but some
show poorly developed microfossils. However, in lhree slides fairly well developed
microbiota has been recorded whicb shows following morphotypes :
(a) Solitary cells (1-6lJ111 size) with sheath encompassing individual cells. Some cells
show ornamented outer wall also,
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