english final - Birbal Sahni Institute of Palaeobotany

BIRBAL SAHNI INSTITUTE OF PALAEOBOTANY
Annual Report 2004-2005
Component 2: Analysis of climatic changes based on multi-proxy data during last 1000 years from
peninsular and Himalayan regions
Measured ring width of Cedrus deodara collected from
the Kinnaur and adjoining areas and prepared tree-ring
chronologies from several sites. Also measured ring width from
tree cores of Tectona grandis from the Nilambur (Kerala) and a
chronology, extending from 1813-2003 AD, has been prepared.
The Mean Vessel Area (MVA) chronology of Teak made through
Image Analysis has been analysed further to understand
temporal relationship with climate. The study shows that MVA
of Teak at Hoshangabad, the central part of India exhibits
positive correlation at June, but negative in May with the
precipitation, and with the temperature correlation is negative
in February. However, at the southern part of India,
Parambikulum (Kerala), MVA has positive correlation during
May and negative in February and March with precipitation;
and with temperature, May is found negative.
Pollen analysis made from a 130 cm deep profile (SKYS)
at the left bank of Rukti River, (3500 m masl) Sangla, Himachal
Pradesh covering almost entire Holocene shows that during
early to mid Holocene climate was warm and moist and later, i.e.
since 3000 yrs. B.P it was comparatively drier.
Amalava Bhattacharyya
Project 14: Special Activities
Component 1: Accretionary evolution, tectonics and palaeoclimate in Lahaul-Spiti, Ladakh and
eastern Karakoram regions: Study based on tectonics, geochemistry, sedimentology,
petrography, magnetostratigraphy and palaeobotanical evidences
Finalized a paper based on palynological studies “First
record of Middle-Late Jurassic palynomorphs from
Lamayuru complex, Indus Suture Zone, Ladakh”. It was
observed that Jurassic palynomorphs recovered from Khangral
village were reworked from Zanskar-Lamayuru Complex Tethyan
realm and transported through the Lamayuru to Nindam Basin
during ongoing geodynamic processes operative within the
India-Asia trench forearc subduction complex between
Cretaceous-Palaeocene time span. Another paper “Miocene
palynological assemblage from Nindam Formation, Ladakh
Himalaya and its implication on palaeoenvironment” highlighted
the occurrence of reworked Permian and Mesozoic spore-pollen
and in situ palynomorphs consisting of microthyriaceous,
ascostromata and bisaccate pollen, assignable to Lower
Miocene assemblage. Tropical to sub-tropical climate is
deduced during the deposition of these sediments. The mega
fossil, collected from Hemis Gompa, about 50 km SE of Leh,
Indus Suture Zone ~500 NNE of Gompa, identified as
Amesoneuron hemisiensis, a new fossil palm leaf from Ladakh.
Detailed study is in progress. Maceration of samples from
Chiktan Nala and Fotula areas has been completed.
Quantitative analysis and photodocumentation and compilation
of data are in progress.
Finalized a paper entitled “Quaternary geology, tectonics
and distribution of palaeo- and present- fluvio/glacio lacustrine
deposits in Ladakh, NW Indian Himalaya” study based on field
observations. Shyok river valley, situated in the trans Himalayan
region of NW India, has numerous well preserved fluviolacustrine
Quaternary sediment deposits. Continuous
sedimentation and lowering of the lake base resulted into thick
deposition in the late Quaternary times. Being in the vicinity of
the Karakoram fault, which has a right lateral shift of rate of 10.7
+-0.7 mm/year (Chevalier et al., 2005), it is presumed that tectonic/
seismic activities may have been responsible for blocking the
river flow and thereby transforming into a lake. Later due to
either excessive water/sediment load or tectonic/seismic
activity, the lake water drained out and the region regained its
original river valley status. The coupled effect of continuous
upliftment and river incision has exposed > 1000 m of these
deposits.
Based on seismicity in the region and preliminary data
on geochemistry, mineralogy and mineral magnetic studies of
~50 m thick sequence at different intervals as the entire section
stands out a vertical cliff which is inaccessible and covered by
debris flow with tens to hundreds of meters of boulder beds.
Three levels of soft sediment deformation structures in the
middle part are recorded at ~26,960, ~24,300 and ~21,000 yrs BP
indicative of 3 major seismic tremors in the region, probably
due to the Karakoram fault activation. In general, the sediment
is silty/clayey in nature with rare sandy beds. Quartz, feldspars,
mica with little Illite/chlorite are the major constituents. Poor
sorting and low Chemical Index of Alteration values (CIA ~55-
60) indicate the dominance of mechanical weathering and
nearby source region of the sediment. The presence of
secondary CaCO 3
precipitates at the bottom and top parts and
high magnetic susceptibility values in the top part suggests
intermittent warmer phases.
Finalized another paper “Weathering of rocks in Ladakh
region of India: implications to tectonics and climate”. Freezing
and thawing, diurnal temperature variation and frost action are
the dominant mode of weathering in Ladakh region. Secondary
clay mineral formation is insignificant. Consequently, there is
little chemical change even up to the most weathered stage.
The little variation in chemical distribution is rather related to
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