Annual Report 2011-2012 - Birbal Sahni Institute of Palaeobotany

EBIRBAL SAHNI INSTITUT
Annual Report 2011-2012
Sponsored Projects
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OF PALAEOBOTANY
Project—Analysis of palaeovegetation and
palaeoclimate of hominin bearing Quaternary
sediments of central Narmada Valley, M.P.
(Sponsored by DST, New Delhi, No. SR/S4/ES/138/2005)
A Ph.D. Thesis incorporating the pollen data
generated from the sediments is documented by PV. The
project completion report has been finalized and submitted
to the funding agency.
www.bsip.res.in
M.R. Rao & Poonam Verma
Project—Quaternary sedimentary records of Baroda
Window, Mainland Gujarat: A multidisciplinary
approach (Sponsored by DST, New Delhi, No. SR/S4/
ES-21/ Baroda Window/P1/ 2005)
The water samples from the Mahi River Basin have
been analyzed for their physiochemical and biological
(diatoms) parameters. Overall, the water samples are
slightly alkaline (pH-7.11-7.97) with low salinity values
(136-468 ppm). The TDS values (181-544 ppm) and
overall ionic concentration indicate direct control of local
lithology in determining the water chemistry. Relatively
higher concentration of elements such as Ca, Fe, Mn, Ni
etc in samples collected from the Deccan basalt dominated
areas compared to regions dominated by felsic rocks
corroborates the lithologic control. The distribution of
diatoms population shows dominance of fresh water
pennate forms represented by Navicula spp., Navicula
viridula, Pinnularia spp., Gyrosigma sp., Synedra
capitata, Cymbella spp., Stauroneis spp. and Cocconeis
sp. while the centric forms are marked by occasional
occurrences of Cyclotella sp. only. The diatom population
shows significant variation in water bodies of upper and
lower reaches of the Mahi River. Multivariate canonical
correspondence analysis (CCA) was carried out to
establish a relationship between physico-chemical
properties and diatom population. The CCA result indicates
that the EC, HCO 3
-, K+ , NO 3
-
and F - are the major
chemical variables that influence the diatom distribution
in the region. Besides, the contemporary diatom
assemblages of different water bodies of upper and lower
Mahi River Basin provide recent analogs which can
further be applied on much older Pleistocene and
Holocene successions for precise palaeoenvironmental
and palaeoclimatic interpretations.
The hydro-geochemical study of surface and subsurface
water of Mahi River basin was undertaken to
assess the major ion chemistry, solute acquisition
processes and water quality in relation to domestic and
irrigation uses. The analytical results show the mildly acidic
to alkaline nature of water and dominance of Na + and
Ca 2+ -
in cationic and HCO 3
and Cl - in anionic composition.
In general, alkaline earth elements (Ca 2+ +Mg 2+ ) exceed
alkalis (Na + +K + ) and week acids (HCO 3-
) dominate over
2+
strong acids (SO 4
+Cl - ) in majority of the surface and
groundwater samples. Ca 2+ -Mg 2+ -HCO 3-
is the dominant
hydrochemical facies both in surface and groundwater
of the area. The weathering of rock forming minerals
mainly controlled the solute acquisition process with
secondary contribution from marine and anthropogenic
sources. The higher concentration of sodium and dissolved
silica, high equivalent ratios of (Na + +K + /TZ + ), (Na + +K + /
Cl - ) and low ratio of (Ca 2+ +Mg 2+ )/(Na + +K + ) suggest that
the chemical composition of the water is largely controlled
by silicate weathering with limited contribution from
carbonate weathering and marine and anthropogenic
sources. Kaolinite is the possible mineral that is in
equilibrium with the water, implying that the chemistry of
river water favors kaolinite formation. Assessment of
water samples for drinking purposes suggests that the
majority of the water samples are suitable for drinking.
At some sites concentrations of TDS, TH, F - -
, NO 3
and
Fe are exceeding the desirable limit of drinking. However,
these parameters are well within the maximum permissible
limit except for some cases. To assess the suitability for
irrigation, parameters like SAR, RSC, %Na, MH, KR
and PI were calculated. In general, both surface and
groundwater is of good to suitable category for irrigation
uses except at some sites where high values of salinity,
%Na, RSC, KR and MH restrict its uses.
In order to understand the texture, mineralogy,
major and trace element compositions including REE of
the sediments deposited in the lower reaches by the Mahi
River, a ~8.5 m thick fluvial sediments deposited in tidal
flat-estuarine condition near Mujpur was studied in detail
for the provenance characterization and understanding
surface geological processes. The sediment samples are
predominantly of fine sand to silt (lower 5 m); coarse
sand increases up the profile. Quartz + feldspar +
pyroxene + rock fragments + minor calcite + smectite +
illite ± chlorite constitute the bulk mineralogy. Comparable
CIA (45-60 vs. 50) of bulk samples and the upper
continental crust (UCC), and presence of feldspar and
smectite suggest that tectonically active Mahi catchment
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