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Earth Science India Volume-3(II),
2010 |
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Excitation of Hard Rock Aquifers in Southern Peninsular India Associated
with the 2004 Sumatra Earthquake
D. Muralidharan,
Rolland Andrade, R. Rangarajan and U. Sathyanarayana |
|
Emergence of
springs at surface or in shallow pits reported from discrete locations
during the month of January 2005 in the southern Indian peninsular
shield area had been an interesting post geo-hydrological phenomenon to
investigate. Such freak incidences at places in the interior parts of a
continental shield area were reported for the first time. Its
connectivity with the 2004 mega thrust great (Mw 9.3) Sumatra earthquake
and its multiple aftershocks are studied and analyzed. Resistivity 2D
imaging and its hydrogeological modulations revealed perched aquifer
conditions at shallow depth (<10 m). There is no geological or
geophysical evidence of structurally controlled upward rise of deep
groundwater in the area. Electrical conductivity of the emergent spring
water and that of deeper (depth >50 m) groundwater support that the
spring water is originated due to local effect by the 2004 mega thrust
earthquake. The emergence of spring is attributed to ground movement and
squeezing of pores in the saturated zone at shallow depth due the mega
thrust Sumatra earthquake. |
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Effect of Depth on the Thermal Signature of Buried Metallic Object
J. A. Olowofela1, O. D.
Akinyemi1, R. Bello1 and A. A. Alabi |
|
The use of thermography for land mine detection has become a topic of
great interest in recent years. The thermal properties and burial depth
of the buried object also play a role in the thermal signature at the
surface. The objective of this contribution is to determine the effect
of burial depth on thermal signature of buried metallic object. The
object used in this work is steel material buried at depth ranging from
1cm to 50cm. The two buried objects used in this work are steel of 12cm
x 12cm surface area with thicknesses of 0.5cm and 3cm respectively. The
soil where the objects were buried is mainly sandy. Soil above the
buried objects and below it is assumed to be the same type of soil. This
work was carried out in Abeokuta, Ogun State, Nigeria. There was a
remarkable phase shift which increased with burial depth. A change in
burial depth from 1cm to 10cm caused the maximum positive peak to shift
from 46.50C to 38.00C and a change in burial depth from 40cm to 50cm,
caused the maximum peak to shift from 30.00C to 29.00C. The burial depth
of the buried objects has effect on the amplitude of the temperature at
the surface and thus its thermal signature. It was also observed that
the thickness of the buried objects has a significant effect on its
thermal signature. |
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First Report of Spheroidal Rhyolite from Nakora area of Malani Igneous
Suite, Northwestern Peninsular India
G. Vallinayagam and Naresh
Kumar |
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Occurrence of rhyolite with spheroidal structure is being reported first
time in the Neoproterozoic Malani Igneous Suite (MIS) of Northwestern
Peninsular India. MIS consists predominantly of felsic volcanic rocks,
felsic plutonic rocks and minor amount of mafic rocks. A spheroidal
rhyolite that is shaped like a sphere but is not perfectly round,
especially an ellipsoid that is generated by concentric shells of
different colours with different compositions revolving around one of
its axes. The spheroidal rhyolite is exposed in an area of 200 sq.m.
radius in the Nakora area. It is pale yellow to light brown colour, fine
grained and consists essentially of quartz, alkali feldspar with
accessories of altered ferromagnesian (arfvedsonite) and iron oxides
(hematite and magnetite). Spheroidal structure is up to 5 m dimension
and shows large number (up to 70) of concentric shells in a few cm
thickness surrounding a nuclei. Nakora rhyolites display different hues
viz.
dark brown, light pink and pink but dark brown rhyolite
is associated with pink colour spheroidal rhyolite where their contact
is sharp. Geological setting and the petromineralogical characters of
spheroidal rhyolite suggest that at early magmatic processes, the
supersaturated liquid crystallized rapidly into relatively differential
density silicate liquid phases and growth of crystals lead the formation
of spheroidal structure in the studied rhyolite. |
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Study of Porosity Loss Due to Compaction in the Cretaceous Upper Bima
Sandstone, Upper Benue Trough, N.E. Nigeria
N.K. Samaila and G.P. Singh |
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Present paper entails the study carried out on the fluvial Cretaceous
Upper Bima Sandstone of the Upper Benue Trough. Compositional and
textural changes due to diagenesis have altered the reservoir properties
of the formation. Modal analyses reveal that these sandstones comprise
of 71.21% quartz, 18.66% feldspars and 10.05% rock fragments. The
average compactional porosity loss (COPL), cementational porosity loss (CEPL),
and compaction index (ICOMPACT) in the Upper Bima Sandstone have been
computed as 13.77%, 3.05% and 0.82 respectively. The sum of these values
subtracted from the original porosity indicates that the initial
porosity of the formation has been reduced to 18.18%. A cross plot of
COPL versus CEPL shows that compaction is responsible for reducing the
initial porosity of the
sediments. |
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Use of Bulk Sample and Hot Acids in Stream Sediment Survey for Gold
K. Bheemalingeswara |
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Fifteen bulk stream sediment samples (minus 0.59mm size) from an area
known for gold mineralization in Ramagiri Gold Fields, India are tested
for gold. In addition, different size fractions (-0.590 + 0.259; -0.259
+ 0.177 and -0.177) of the stream sediment are also analysed for gold.
The data when compared suggests that the bulk samples data not only
tally well with the previous stream sediment survey data but also
provide additional anomalies for gold. The method suggested in this
paper is bulk leach extractable gold (BLEG) using hot aqua regia and
methyl isobutyl ketone solvents (MIBK-AR). The bulk leach extractable
gold data of the new method seems do not suffer from iron oxide
coatings, nugget effects, invisible gold etc. as compared to the data of
different size fractions (coarse/ fine size fractions) of stream
sediment sample. Hence it provides near total values for gold present in
the sample. The proposed method differs from the widely used BLEG in
terms of hot aqua regia treatment in place of cold cyanide solution. The
procedure suggested in this paper is simple to use and it provides an
alternative to the commonly used coarse/finer fractions or BLEG (using
cyanide) methods in stream sediment surveys for Au particularly in areas
where oxide/hydroxide coatings are conspicuous. |
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Thunderstorms/Lightning Generated Sprite and Associated Phenomena
Devendraa Siingh, Sanjay
Kumar and A. K. Singh |
|
The study of the thunderstorms has advanced rapidly during the past
century and lots of efforts have been made towards the understanding of
lightning, thunderstorms and their associated optical phenomena such as
sprites, elves, blue get etc. Even though, thunderstorms and lightning
are well understood, but our knowledge on sprites and associated
phenomena, is limited. In this paper, we review the distribution of
thunderstorm/lightning and their association with optical emissions.
Detailed discussions on lightning generated sprites and various natural
phenomena associated with them are also included. Recent results in this
emerging field are summarized. |
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Earth Science India Volume-3(I),
2010 |
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First Report of the Late Pleistocene Fossil Lizards from Narmada Basin,
Central India
Moulishree Joshi and B. S.
Kotlia |
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The fossil agamid lizards are reported from a Late Pleistocene locality
(ca.0.74 ka in age) in the Narmada valley, central India. Although the
fossil material is scanty, it is described keeping in view that, the
fossil lizards are barely studied from south Asia, and secondly, this is
the only report of fossil lizards from the Narmada valley. With the help
of the jaw fragments and isolated teeth, the material is assigned to a
new species,
Agama schleichi
sp.nov. The
presence of lizards indicates dry/arid to semi-arid oscillations within
otherwise warm/humid climatic conditions in the Narmada basin around the
time of the
Homo erectus,
the only known
Homo
from India. |
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Microstructures of the Zanskar Shear Zone
Soumyajit Mukherjee |
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Thin-section studies of the rocks of the Zanskar Shear Zone led to
document a top-to-SW ductile shearing; a top-to-NE shearing and finally
a top-to-NE (down) shearing. Shape asymmetry and cleavage orientations
of mineral fish reliably give the latter two shear senses. Although some
of the fish reveal different phases of shearing, their specific
orientations indicates simple shear. Type-1 flanking microstructures
indicate the earliest top-to-SW shear. Boudins denote extension along
the main foliation. Intrafolial folds demonstrate a top-to-NE shearing.
A top-to-SW brittle shear is displayed by asymmetric trapezoid-shaped
minerals. The brittle planes cut across rigid minerals. As in other
shear zones, micas are found to be most susceptible to deformation. |
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Distribution of Mangroves along the Red Sea Coast of the Arabian
Peninsula: Part-I : the Northern Coast of Western Saudi Arabia
Arun Kumar, M. Asif Khan and
Abdul Muqtadir |
|
Historical Landsat Enhanced Thematic Mapper (ETM) data of the years 2000
and 2001 were used to numerically illustrate the distribution of
mangroves that occur along the northern Saudi Arabian Red Sea coast from
Sharm Zubair in the north to Al-Lith in the south. The distribution of
mangroves is patchy and they do not occur as a continuous forest and are
generally restricted to the low energy quieter environments like bays,
narrow channels, and inland faces of offshore islands. However, they
also occur in the intertidal environments. At certain locations they
occupy very small area that could indicate depletion of mangroves. Due
to rapid urbanization and industrialization of this region, traditional
land use is changing and adversely impacting sustenance and growth of
mangroves. There should be an inclusive policy that promotes economic
development and protects mangroves also; this can be achieved as shown
by Khan and Kumar (2009) on certain locations along the Arabian Gulf
coast. |
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Scaling Spectral Analysis: A New Tool for Interpretation of Gravity and
Magnetic Data
A.R. Bansal and V.P. Dimri |
|
The scaling spectral method for gravity and magnetic data is found
useful for finding the depth values and statistical properties of the
source distribution. The depth values calculated by scaling spectral
method are close to the realistic values whereas white noise assumption
of sources result in overestimations. The scaling spectral method has
been applied to many parts of the world. The power spectrum
corresponding to low wave number may be dominated by scaling properties
alone rather than the depth values. The scaling distribution is useful
for gridding the datasets, delineating the lithological units and
enhancing the information of sources. The long non-stationary profiles
and larger areas may be divided into piecewise stationary profiles
before applying the scaling spectral method. The values of scaling
exponents from the field as well source indicate 3- D distribution of
susceptibility and density. |
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Use of Meridional Wind Index at East Coast of India for Monitoring
Drought and Flood Monsoon Conditions over Indian Region
S. S. Dugam |
|
In this paper, the relationship between daily meridional winds (v) at
200 hPa taken from NCEP/NCAR, over the domain (15°N to 25°N and 80°E to
95°E) at east coast of India and daily rainfall during the Indian Summer
Monsoon (June-September) has been studied. Analysis is carried out for
fifty three (1951-2003) years of data. The twenty days composite
rainfall and meridional wind for the 10 drought and 8 flood monsoon
years have been analyzed. The twenty days variations of the southerlies
(northerlies) meridional wind in the upper troposphere during the
monsoon at east coast the of India and twenty days rainfall activity
goes hand in hand in drought (flood) monsoon years. From the analysis,
it is observed that during the drought (flood) years southerlies
(northerlies) persist over this domain in monsoon season.
|
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Study on Bromide in Groundwater in Parts of Nalgonda District, Andhra
Pradesh
K. Brindha and L. Elango |
|
The quality of groundwater is under constant threat due to urbanization.
The purpose of this study is to understand the seasonal and temporal
variations with special reference to bromide in groundwater and to
determine the reasons behind the presence of this ion in groundwater.
This study area is located at a distance of about 135 km towards ESE
direction from Hyderabad. The concentration of bromide in groundwater of
the study area was analyzed by collecting the groundwater samples from
forty six wells once every two months from March 2008 to January 2009.
Groundwater level and pH were measured in the field. The concentration
of the minor ion namely bromide was determined by analyzing the
groundwater samples in the laboratory using ion chromatograph. The
bromide concentration ranged from below detection limit to 5.5 mg/l.
The permissible limit for bromide in drinking water according to Indian
standards specification is not mentioned. However, literature based on
toxicity data puts forth 1 mg/l as the maximum admissible level of
bromide. In this study, only a few groundwater samples had concentration
of bromide above this limit. It is evident from this study that the
groundwater quality is good with respect to bromide in this region. By
the proper use of fertilizers and pesticides for agriculture, the
groundwater quality can further be maintained in its current form or can
be improved. |
Earth Science India Volume-2(IV),
2009
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Surface ozone
pollution during the festival of Diwali, New Delhi, India
Nandita D. Ganguly
|
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Pollution
from carbon monoxide, nitrogen dioxide, sulphate and suspended
particulate matter due to ignition of fireworks during the festival of
Diwali is well established. Although surface ozone exhibits high natural
variability throughout the year, any short term enhancement in ozone
levels coupled with high level of pollutants during Diwali might prove
to be deadly for a large number of elderly people and children with
heart and respiratory ailments. Despite this fact, very little study on
surface ozone pollution during the festival of Diwali has been reported
from India so far. In the light of these observations, the changes in
ozone concentration observed during Diwali at New Delhi in India have
been studied to determine the amount and possible causes of ozone
pollution apart from pollution due to ignition of fireworks. Compared to
the normally observed ozone levels, the ozone concentration was higher
during Diwali. The ozone levels were found to be higher in 2006 compared
to 2004, and exceeded the ambient air quality standard for three hours.
The results are discussed in light of enhanced vehicular traffic and
emission of ozone precursor gases from fireworks, transport of ozone and
climatic conditions during Diwali.
|
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Time Lapse (4D) Seismic: Some Case Studies
N. Vedanti1,
A. Pathak2, R.P.Srivastava1 and V.P.Dimri1
|
|
We present advances in Time Lapse
3D seismic (also known as 4D seismic) and its application in oil
industry. Over the years the technique has proved its potential and now
it is aggressively used in most of the oil companies. We have covered
the topic from the basic 4D analysis based on data differencing to the
modern inversion based separate analysis of all the time lapse volumes.
The paper covers all the aspects of 4D seismic data analysis including
feasibility study, acquisition, and processing issues. Further, we
present several successful case studies of 4D seismic. |
|
Appication of Magnetotelluric Technique in selection of Earth Electrode
Sites for HVDC Transmission Systems: An example from NE India
A. Manglik, S.K.
Verma, R. P. Sasmal, and D. Muralidharan
|
|
The use of HVDC (High Voltage Direct Current) technology for
transmission of bulk electrical power over long distances is more
economical as compared to transmission in AC mode as the transmission
losses in HVDC system are significantly lower. Besides, HVDC
transmission has other advantages such as
controllability, improved power system stability, and power modulation
control. HVDC systems are designed to operate in bipolar mode, monopolar
metallic return and monopolar ground return modes. A HVDC system
requires specially designed earth electrode stations associated with the
converter terminals of the HVDC transmission system.
The earth electrodes provide
an earth return circuit, facilitating the flow of current into the
ground at the electrode stations.
The design parameters of earth electrodes require consideration of the
electrical conductivity structure of the subsurface in and around ground
electrode sites. For a proper design, it is important to ensure that the
site selected for the ground electrode has low near-surface resistivity.
It is also necessary to ensure that the ground currents penetrate deep
into the earth so that the grounding resistance/ potential rises in the
vicinity of the electrode are within acceptable limits ensuring that the
ground currents do not cause corrosion of buried pipelines and do not
enter the neutrals of transformers installed in the close vicinity of
the electrode station. Investigations using artificial source methods
such as deep resistivity sounding pose logistic problems for these
target depths. Magnetotelluric method is a very useful tool especially
for the delineation of the electrical conductivity of the deep structure
(up to 10 km depth) around the earth electrode site. We have carried out
detailed investigations of some potential HVDC ground electrode sites
employing magnetotelluric method to assess the suitability of these
sites for the construction of Earth Electrode stations for India’s first
±800 kV, 6000MW HVDC multi-terminal transmission systems. MT method has
been found to be a very useful tool for this purpose. |
|
Wavelet Analysis of Geophysical Time Series
Ashutosh Chamoli
|
| Wavelet analysis has emerged as a
potential tool for spectral analysis due to the time-frequency
localization which makes it suitable for complex and nonstationary
signals. In this paper, the strength of wavelet analysis is illustrated
by three studies for (1) estimation of Hurst coefficient (2) ocean
bathymetry data (3) gravity anomaly. The self affine behaviour is
characterized by Hurst exponent and the application of wavelet transform
is recommended for its estimation. Particularly, the bathymetry data can
give important information related to the behavior of the crust and its
correlation with other regions. The major thrust zones are delineated by
transforming the gravity anomaly along Kiratpur-Leh-Panamik transect (~
580 km) across NW Himalaya to wavelet domain. |
|
Active Tectonics in the Outer Himalaya: Dating a Landslide Event in the
Kumaun Sector
Rameshwar Bali,
A.R.Bhattacharya and T.N.Singh
|
|
Of the entire Himalayan terrain, the Outer Himalaya is believed to show
excellent signatures of active tectonics. The Main Boundary Thrust (MBT)
that separates the Outer and Lesser Himalayas has a recorded history of
tectonic activities in the recent past. The present study incorporates
an additional example of a major landslide event, the Amiyan landslide,
associated with the MBT that passes through the toe of this landslide.
The Amiyan landslide is one of the biggest debris slides in the Central
Himalayan region. Two prominent fault scarps running almost transverse
to the MBT have developed during the last 15 years. The slide has been
increasing in size at regular intervals from an earlier 0.02 sq km in
1968 to 0.05 sq km till 1992. Thereafter, the process of continuous
reactivation of the MBT and the formation of fault scarps has resulted
in about 12-fold increase of the slide. Such a topographical
adjustment in response to active tectonics in this segment of the
Himalaya suggests that the Outer Himalaya is possibly a major locale of
present-day stress release in the Himalayan region. The results of this
work have significant bearing on the seismotectonic, environmental,
ground stability and the related aspects in the Himalayan domain. |
|
Terrestrial Impact Structures and their Confirmation: Example from Dhala
Structure, central India
J. K. Pati, K.
Prakash and R. Kundu
|
|
Although seventy percent of the Moon surface area is covered by
meteoritic impact structures only 176 confirmed impact structures known
on Earth hitherto. In India, the recently discovered Dhala impact
structure, M.P. and the Lonar crater, Maharastra are the only two
confirmed impact structures. The simple, complex and multi-ring impact
structures are confirmed on the basis of mesoscopic and microscopic
shock metamorphic features besides the physical and/or chemical
signature(s) of the impactor (meteorite). The role of bolide impacts in
the formation of mineral deposits and playing a crucial role in some of
the major mass extinction events is also well known. The impact
cratering process is considered responsible for the planetary evolution,
landscape modification, and the presence of water and life on Earth. |
|
Earth Science
India
Volume-2(III), 2009
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|
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Temperature is an
important parameter that controls various tectonic processes. Therefore,
estimation of the thermal structure of crust/ lithosphere is required
for understanding a variety of geological, geophysical and geochemical
problems. Characterization of thermal structure for thermally
equilibrated continental crust requires reliable models of radiogenic
heat sources distribution and thermal conductivity, a parameter that
determines how fast the Earth looses its internal heat. Geophysical
mapping of the structure of Indian continental crust and measurement of
radiogenic heat sources concentration for various crustal rocks have
enabled development of realistic models of radiogenic heat sources
distribution. Thermal conductivity can be determined either by using ab-initio
calculations of quantum mechanics or by measuring it experimentally.
Recent results of laboratory measurements have provided a reliable
working model of thermal conductivity for crust-forming minerals and
rocks. In this model, thermal conductivity depends on temperature, thus
making the governing heat conduction equation non-linear. We have used
this model of thermal conductivity and available heat flow and
radiogenic heat generation data to obtain the depth distribution of the
temperature for some provinces of the Indian shield. |
| |
|
Gravity and magnetic surveys were conducted in an area about 5000 km²
covering offshore region of the Qamar basin in the eastern part of
Yemen. An attempt is made to address the gravity and magnetic signatures
in term of structural features. In addition, seismic section
(NIM-QAM-92-201) compiled by Nimir services limited, 1992 were used to
illustrate subsurface structures in sedimentary sequences. Combined
gravity and magnetic modeling along section QAM-92-201 by Geomodel 2.5D
inversion technique suggest the thickness of sediment to vary from 3.2
to 5.3 km in the Qamar basin (offshore), and the basement rocks are
divided into blocks because of existence of several faults extending
from basement rocks to sedimentary rocks owing to strong tectonic
activities. So the study area may be divided into several major blocks
along the Qamar Gulf. It can be concluded that the sedimentary processes
were affected by basement tectonics as
revealed by the seismic
section. |
|
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Rock mass are generally considered to be the most heterogeneous, complex
and unpredictable geomaterials. It is difficult to fully understand its
behavior under various loading conditions. In the present paper, an
attempt has been made to calculate the maximum stresses at the crack
tips (6m) after fracture developed in a rock specimen. Rock specimen was
subjected to loading on servo-controlled auto feedback stiff testing
system under compressional mode in a Brazilian cage. The fractured rock
surface was considered for the determination of stresses all along the
crack tips. The specimens were prepared and tested as per International
Society of Rock Mechanics specifications for tensile strength
determination. The specimen was placed under the Brazilian cage and
subjected to compressional loading till it develop failure. The fracture
mode followed the Griffith failure criteria. Various researchers have
tried to calculate the stress at various point along the fracture plane
and established relation with other physicomechanical properties, which
is time taking and tedious job. In the present paper, a technique has
been suggested to calculate maximum stresses at crack tips in a simple
manner. The results can be used to establish the damage characteristic
of the rock mass for improving safety and stability of existing
structures and further help to improve production and productivity in
mining and civil engineering constructions. |
|
|
Development of urban infrastructure along the west coast of the Arabian
Gulf has caused major disturbance to the coastal environment and
mangrove ecosystem during the past 40 years. The mangrove forests along
this coastline have particularly been adversely impacted in most areas.
Temporal Landsat MSS images of 1972-1973 and Landsat ETM images of
1999-2001 were used to detect changes in mangrove forests at 10 sites
along the Arabian Gulf coast. The temporal changes in the mangrove
covered areas were calculated using geometrically registered and
radiometrically corrected historical Landsat images. Region masks were
employed to isolate the unwanted area from the images. Normalized
Difference Vegetation Indices (NDVI) were computed from the satellite
images. The analysis of satellite images revealed massive losses of
mangrove forests at six sites due mainly to the infrastructure
development of coastal areas. The depletion of mangrove forests has been
uneven in the region. Out of ten sites six sites showed varying degrees
of reduction but in four sites 4, 8, 9 and 10 area covered by mangrove
forests actually increased despite urban development. This was because
areas of mangrove stands were left undisturbed during the development
process. Although there are laws to protect mangrove forests in the
region but they are not implemented effectively. This study shows the
urgent need to protect mangrove ecosystem and consequently coastal
marine habitats of region’s flora and fauna and natural protection from
erosion from waves and currents. |
|
|
Assessment of groundwater prospects has been carried out for the Morar
river basin in Gwalior district, Madhya Pradesh. Groundwater prospect of
the basin has been delineated from the satellite data by the integration
of geology, geomorphology, lineament and slope and classified as
Excellent to poor groundwater potential zones using GIS. The results
obtained from remotely sensed data cross checked with the bore well
yield data and found in good agreement. This depicts the positive
prospective zones in the study area for exploration of groundwater in
future. Water level fluctuation map prepared from the pre- and
post-monsoon water level data do not show any significant change except
at some locations in alluvial area Net groundwater availability also
calculated is about 63.634 MCM. The calculated annual draft of
Groundwater from dug wells and tube wells for all users is 70.051 MCM
revealing a deficit in groundwater storage in the Basin. |
|
|
This study is an attempt to analyse and highlight the present state of
forests in Kashmir, which are under tremendous anthropogenic pressure.
Extensive deforestation has resulted in harmful impacts on the overall
environment especially on the health of the soil. The detailed studies
were carried out in Kahmil Watershed of the Kashmir valley using
Geo-spatial tools. The data of the Year 1974-75 and 2000 were used and
changes in forest categories viz-a-viz soil erosion status have been
analysed. The analysis revealed that the Kahmil watershed situated in
the Kashmir valley is undergoing large scale deforestation. There has
been a total loss of about 848 hectares of forest cover in about three
decades. The most startling fact is the change in terms of density
classes, where the change percentage is quite high. This deforestation
has resulted in accelerated soil erosion. The area which was under the
Moderate erosion class has reduced and that soil has further degraded
and shifted to Moderate to severe class of erosion. Necessary remedial
measuresshould be taken to check this deforestation and consequent soil
erosion. |
|
|
Bhuban Formation, Surma Group (Lower-Middle Miocene) of Aizawl, Mizoram
are rich in mega-invertebrate fossils including decapods. This paper
describes six genera and five species of decapod fossils viz., Calappa
protopustulosa Noetling, Ebalia tuberculata Noetling, Typilobus
granulosus Stoclizka, Neptunus sindensis Stoliczka, Xantho sp. and
Palaeocarpilius rugifer Stoliczka from Aizawl area, out of which the
last two are being reported for the first time from the Miocene
succession of Mizoram. These decapods and the associated bivalves,
gastropods, echinoids and fish teeth indicate Aquitanian - Burdigalian
age for the fossil yielding beds and the existence of an open shallow,
warm sea with fluctuations from inner neritic to littoral water with
depth <45m meter. |
|
|
Monitoring of hydrological data is pre-requisite for systematic and
scientific designing of sub-surface drainage system for control water
logging and salinity. In the present study, field experiments were
conducted to determine various soil hydrological and physico-chemical
properties (soil texture, color, permeability, infiltration, soil
moisture characteristics, dry density, total dissolved solids, SAR,
etc.) under saline soils around Gohana tehsil. The majority of the area
is represented by silt loam texture with varying soil color having
dominance of yellowish brown in top layer. The in-situ permeability was
measured using Guelph Permeameter in the field and its values were found
to vary from 0.01 to 0.69 m/d for silt loam. The SAR of the soil
generally varied from 0.5 to 54. The infiltration data of area was
fitted with Kostiakov’s type cumulative infiltration function (Y=a*tb)
and its coefficient of determination (r2) varied from 0.956 to 0.998.
The present data would be useful in planning of on farm land and water
management strategies ultimately for enhancing the productivity of the
land. |
Earth Science India
Volume-2(II), 2009 |
Comparison of the accuracy of SST estimates by
artificial neural networks (ANN) and
other quantitative
methods using radiolarian data from the
Antarctic and Pacific Oceans
Shyam M. Gupta and Björn A.
Malmgren |
The quality of quantitative estimates of sea surface water temperatures
(SSTs) is evaluated for different techniques, Imbrie-Kipp transfer
functions (IKTF), the modern analog technique (MAT), weighted-averaging
partial least squares (WAPLS) regression, the maximum likelihood (ML)
method, and artificial neural networks (ANNs), based on radiolarian
faunal abundance data from surface sediments from the Antarctic and
Pacific Oceans. Recent studies have suggested that ANNs may represent
one of the most optimum procedures for estimates of paleo-SSTs. We,
therefore, employed ANNs together with these other methods to estimate
SSTs during February-April (TFA) and August- October (TAO) at a mean
water depth of 40 m, wherein radiolarian abundances generally coincide
with chlorophyll-a maximum. We used CLIMAP’s modern Antarctic
radiolarian core top data and Pisias et al.’s Pacific Ocean core top
data for the analyses. A portion of the datasets (75%) was used for
training of ten ANNs per season, and estimates of error rates
(root-mean-square-errors of prediction, RMSEPs) were made from the
remaining observations, constituting an independent holdback (HB) set.
The same training and HB sets were used for estimates of RMSEPs for the
other methods. For the ANNs the RMSEP in the Antarctic Ocean dataset is
as low as ~1.3oC for both TFA and TAO. In comparison, RMSEPs for the
other techniques for TFA are higher in ranging between 1.8 and 2.0°C,
whereas those for TAO are similar (1.4-1.5°C). Correlation coefficients
(r:s) between observed and predicted SSTs using the ANNs are 0.97 for
both seasons. In the Pacific Ocean dataset, RMSEPs derived from the ANNs
are considerably lower for both seasons, 1.5°C for TFA (1.8-2.2°C for
the other methods), and 1.4°C for TAO (the other methods 1.7-1.9°C).
ANN-derived correlation coefficients (r:s) between observed and
predicted SSTs are 0.98 for both TFA and TAO in the Pacific Ocean.
Comparison of residual (estimated-observed) SST maps suggests that MAT
and ANN produced lesser geographic trends than those of the other
methods. |
|
Radon Time Series and Earthquake Signals—a Study by
SSNTD at Matigara (Darjeeling), India
Dipak Ghosh, Argha Deb, Subrata Haldar, Swarup Ranjan Sahoo, Rosalima
Sengupta |
A survey of radon concentration in the soil gas in order to get
premonitory signal of arthquakes is being carried out by us since last 4
years in Kolkata, West Bengal, India—which is known to be situated at
non-active fault zone and since last 2 years in an active fault
zone—Jalpaiguri (26A32BN, 88 A46BE), West Bengal. In extension of our
work we have started the experiment in another active fault zone:
Matigara, Darjeeling (26º43' N, 88º23'E), West Bengal, India, to have
more confirmatory signal. We present the description of signal of the
terrestrial gas 222Radon observed for a period of more than one year at
a depth of 70 cm in the soil using passive detector –Solid State Nuclear
Track Detector (SSNTD). The time series of radon shows a distinctive
anomalous fluctuation prior to seismic events that ccurred within 1000
km from the measuring site. The results are obtained at two fault zone
sites are compared and the present analysis provides further evidence in
favour of using radon signal as a precursor of earthquake. |
|
Sun-Earth-cosmic connection to understand early
warning of Earthquakes
Saumitra Mukherjee |
Muon detector has the potential to function as Nano Sensor to infer
possible earthquake in earthquake prone areas. It has been observed that
30 to 36 hours before the occurrence of the earthquake the magnetic
field (Kp) and electron flux (E-flux) of the Sun-Earth environment
changes. Using Sun-Observatory-Heliospheric Observatory (SOHO) satellite
data it is possible to monitor the fluctuation every 15 minutes
interval. It has been observed that before the occurrence of earthquake,
nanoparticle (muon) intensity reduces, while the atmospheric temperature
rises along with the increase in Kp and E-flux values. After the
earthquake the atmospheric temperature falls suddenly with the rise in
cosmic rays and fall in Kp and E-flux values. It has been planned by
IHY, NASA and UNBSS (United Nations Basic Space Sciences) to design and
install basic hybrid SEVAN (Space Environment Viewing and Analysis
Network) in 14 locations across the world. Cosmic Ray Division
laboratory of Armenia will supply photomultiplier of similar standards
to all these 14 locations including Jawaharlal Nehru University, New
Delhi, India. These detectors will record and correlate the intensity of
cosmic ray data to predict various environmental perturbations including
earthquake. Based on this plan it was attempted to correlate Kp, Eflux
and chages in environment in different locations across the world with
variation of cosmic rays collected from existing muon detectors. |
|
Microscopic examination of concrete with and
without corrosion inhibitor
B.N. Singh, P.P. Abhilash, V. Kumar and M.A. Quraishi |
The present paper addresses the mineral constituents and microstructural
behaviour of concrete with and without corrosion inhibitor (i.e.
calcium stearate) observed under petrological microscope.
Mineralogically and texturally, these concretes are largely similar but
microstructurally they are quite distinct. The concrete samples without
calcium stearate are characterized by the occurrence of microcracks,
voids and carbonation leading to lower the strength and durability of
concrete. However, these features are less abundant in the concrete with
calcium stearate. The microcracks and voids are infilled with
cementitious materials, if calcium stearate is used as admixture.
Therefore, the use of calcium stearate in concrete can enhance the
strength and durability properties of concrete. |
|
Possibility of artificial recharge in overdeveloped
miniwatersheds: A RS-GIS approach
Bhagyashri C. Maggirwar and Bhavana N. Umrikar |
The stress on groundwater has become a point of concern for planners and
researchers. The groundwater pumping is exceeding the recharge due to
increased dependency on roundwater to cater the needs of the growing
population. Therefore, the assessment of groundwater potential and scope
for artificial recharge in the overdeveloped watersheds is very crucial.
GV-41 5/8 and 6/8 miniwatersheds are such overdeveloped areas where the
groundwater occurring in unconfined / semi confined shallow aquifer
needs to be augmented by undertaking suitable artificial recharge
structures in order to ensure economically viable yields of wells
vis-à-vis increase the groundwater availability on sustained basis. For
the purpose of assessment of groundwater potential in GV-41 5/8 and 6/8
miniwatersheds, detailed hydrogeological surveys were carried out in
Aurangabad District, Maharashtra and the database was also used to find
out the feasibility of artificial recharge structures. The present study
is an attempt to find out the possibility of artificial recharge
considering the existing water harvesting structures using Remote
Sensing and Geographical Information System techniques (RS - GIS). |
|
Assessment and impacts of surface water
environment in and around Jabalpur
city, Madhya
Pradesh, India
Medha Jha and Sanjay Tignath |
The physical, chemical and biological characteristics of surface water
in and around Jabalpur city, M.P. have been studied to evaluate the
suitability of water for irrigation and domestic uses. Samples of water
were collected from various localities such as Narmada and Pariyat water
supply system, various ghats of Narmada river, various tals and tanks,
main drains of the city such as Omti nala and Moti nala and were
analyzed for pH, electrical conductivity, temperature, dissolved oxygen,
five days Biological oxygen demand , fecal coliform , turbidity, total
solids, nitrates and phosphates.Water quality indices “WQI” developed in
1970 by the U.S. National sanitation foundation were calculated for
these water samples. The results conclude that the water quality of
water supply systems, various ghats of Narmada River is of medium
quality and can be used for domestic use after suitable treatment. The
water quality of various tanks and drains falls in the range of bad
quality waters by index rating and can be used for irrigational purposes
.This study is helpful to environmental planning and pollution control
measures applicable to the area. |
|
Hydro-meteorological disasters and climate change:
conceptual issues and data needs for
integrating
adaptation into environment -
development framework
Anil K. Gupta, Sreeja S. Nair and Vinay K. Sehgal |
Integrating Risk Reduction to the Environment and Development Framework
at local and regional levels has now emerged as the core strategy for
minimizing hazards and managing disasters. This strategy calls for a
‘paradigm shif by treating disaster management and climate change as
developmental issues interlinked to each other and requiring common
management approaches’. Disaster management comprises of (1) disaster
risk management and (2) emergency organization for protecting natural,
built and socio-economic environments from impacts at temporal and
spatial scales. Damage and losses due to extreme events depend upon the
magnitude and intensity of hazardous event along with the vulnerability
of population, habitat, resources, and developmental settings, as
against the capacity to withstand the risk. Designing the approach for
convergence of Climate Change Adaptation and Disaster Risk Reduction (DRR)
and mainstreaming towards development, it required an analysis of
various components of environment-development complex that are to
be put into adaptation agenda. Availability of suitable, accurate and
proper data is crucial for any assessment, planning or decision task.
The present paper presents an effort of cross-sectional probe into
various conceptual issues relating to hydro-meteorological disasters,
climate-change impacts and disaster risks, issues for adaptation nd
convergence, disaster risk reduction framework in India and examples of
data needs at different stages for their better management.
|
|
Earth Science India Volume-2(I),
2009
|
|
Radiolarian abundance - a monsoon proxy responding to the Earth’s
orbital forcing: Inferences on the mid-Brunhes climate shift
Shyam Murti Gupta |
Radiolarian fluxes from the sediment traps moored in the
southern Bay of Bengal suggested that radiolarians were invariably
higher at times of higher sea surface temperature (SST >28oC) and
moderately lower salinity (~33.5 psu) during the summers of 1991-93. It
implied that higher SSTs due to summer heat and lower salinity due to
rains might have affected the radiolarian fluxes during the monsoon.
Hence, the down core radiolarian-yield in the unit weight as the
percentage abundance may shed light on monsoon-sensitive radiolarian
production through the geological past. It is tested in a well-dated
radiolarian ooze-bearing sediment core collected from the central Indian
Ocean in the southwest of the trap site. Radiolarian tests/g dry bulk
sediment (Rads/g) yield from the sediment samples at every 4750 years
(4.75 ka) time interval (δt) produced a time series for the last 485000
years (485-ka) during the late Quaternary. Rads/g was higher during the
upper last 200-ka record than the lower section of the core implying
higher radiolarian production in the upper part than in the lower part
of the core. Blackman-Tukey and maximum entropy spectral analyses of the
Rads/g time series revealed multiple cycles at ~126-, 95-ka due to the
Earth’s orbital eccentricity, ~54-, 41-, and 31-ka due to axial tilt,
23-, 19-, and 17-ka due to changes in the precession of equinoxes,
besides the 15-, 13- and 11-ka sub- Milankovitch cycles. The spectral
results are further verified by multi-taper method using 90% reshaped
spectrum, adaptive narrowband and high-resolution harmonic signals with
robust noise and the statistical significance test (F-test), and the
>90-99% significant cyclic components are reconstructed to visualize the
variation in their amplitude through time. The reconstructed harmonic
components revealed a conspicuous change in the trend of the amplitudes
of ~95-, 54-, 41-, 31-, 17-, 15-, 13- and 11-ka cycles suggesting an
effect of the mid-Brunhes epoch climate shift at around ~300-350-ka
before present. The results substantiates the existence of multiple
cycles at the eccentricity (126-, and 95-ka), tilt (~54-, 41-, and
31-ka) and precession (23-, 19-, and 17-ka) and sub-orbital bands (~15-,
and 13-ka) as proposed by Berger (1977) in the astronomical data, which
strengthens growing belief of multiple orbital cycles reported from
pollens (Mommersteeg et al, 1995) and the radiolarian
assemblages (Gupta, 2003) suggesting the cyclic changes in the
summer-monsoon productivity during the Late Quaternary in the Central
Indian Ocean sediments. |
|
Seasonal and inter-annual variability of Chlorophyll – a in the Arabian
Sea from SeaWiFS data
Rajeev Mudgal1, Mihir K. Dash2and P. C. Pandey2 |
|
This study utilizes monthly mean chlorophyll – a
concentration (Chl – a) and sea surface temperature (SST) retrieved from
Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Advanced Very High
Resolution Radiometer (AVHRR) respectively. In addition surface wind
vector derived from SeaWinds observations were used in this study. The
Chl – a and the SST data for the period September 1997 to August 2007
were used in the present study. Whereas the wind vector for the period
August 1999 to August 2007 is used. The seasonal and inter-annual
variations in the Chl -a and SST in the Arabian Sea warm pool region
were clearly observed. The winter bloom signatures were seen in the
month of February. One interesting result obtained from the study is,
post 2002 period shows Chl – a maxima in the month of September. High
inter-annual variation in Chl – a and SST were observed during south –
west monsoon months after 2002. The effects of wind stress and SST on
the Chl – a are studied. It is found that the relation between wind
stress induced divergence/convergence of the ocean surface (Cov/Div) and
Chl – a is stronger than that of SST. Exceptionally high anomalous Chl –
a was observed during 2004 and 2006 summer monsoon period due to
increased Cov/Div and low SST during these periods. |
|
Dynamics of a river system– the case of the Kosi river in
north Bihar
Rajiv Sinha
|
The paper presents an account of the Kusaha breach of
the Kosi river which has been widely perceived as a flood event in
the media and scientific circles. It is true that a large area was
inundated after this event but it is important to appreciate that
this inundation was different from a regular flooding event. It is
argued that this event marked a mega-avulsion of the Kosi river.
While the basic mechanism of this avulsion needs a detailed study,
this paper aims to document the avulsion event and speculates the
causative factors of the dynamics of the Kosi in general based on
limited field evidence and available maps. |
Taxonomic placement of a holectypoid echinoid genus Srivastava and
Singh, 2001
D. K. Srivastava
A holectypoid echinoid recorded as indeterminate genus and species
by Srivastava and Singh (2001) from the sediments of middle Eocene
exposed near Bermota, Kachchh (Gujarat), India is redescribed and
identified as Amblypygus pentagonalis Duncan and Sladen,
1883.
|
|
|
|
Earth Science India
Vol.1 (IV), October, 2008 |
|
Granite
Series Evaluation of Early Ordovician Kyrdem Granitoids and
Enclaves, Meghalaya Plateau, Northeast India: Implication on
Oxidation Condition of Interacting Mafic-Felsic Magma System
Santosh
Kumar and Kh. Mohon Singh |
|
Early Ordovician (479±26 Ma) Kyrdem granitoids (KG) and their
enclaves in Meghalaya plateau have been evaluated in terms of
magnetic susceptibility (MS) and whole rock composition in order to
understand the redox condition of comingled mafic and felsic melts.
KG (MS=15.56-31.55×10-3SI) and microgranular enclaves
(ME) (MS=24.47-32.09×10-3SI) are moderately to strongly
oxidized, magnetite series granites formed in a late- to
post-tectonic calc-alkaline, mafic-felsic magma interacting
environment. Oxidizing nature of bulk KG melt was locally reduced to
ilmenite series (0.26×10-3 SI) granite near the margin of
the KG pluton as a result of reaction with pelitic country-rocks
occurred at shallow emplacement level. |
|
New Trends in
Gondwana Palaeobotany
A.K.
Srivastava |
|
Discoveries of insect wings, insect activities in fossil flora and
microbial association with plant fossils have helped to understand
the interrelationship of plants and insects and role of mico-organisms
in Gondwana flora. |
|
Speleothems
from the Himalaya and the Monsoon: A Preliminary Study
V. C.
Tewari |
|
Speleothems (stalagmites, stalactites) have great potential for the
records of past climate, environment and monsoon on a global scale
particularly in the Asian region. Speleothems are found in all parts
of the world and grow continuously through many glacial –
interglacial cycles and their stable isotopic ratios and annual
growth bands are useful for decadal to seasonal variations in
rainfall. Some important speleothems from the Himalayan region such
as Sahastradhara, Dehradun; Brahmakhal, Uttarkashi; Bhagirathi
valley, Garhwal and Mawasmai caves from the Meghalaya have been
studied. In the present paper, the oxygen and carbon isotope ratios
from the Sahastradhara, Brahmakhal, Nagni and Pratapnagar
speleothems and cave drip water has been recorded for the first
time. The significance of speleothems and their relationship with
the monsoon is discussed. |
|
Marine
14C Reservoir Age and Suess Effect in the Indian Ocean
Koushik Dutta |
|
Apparent radiocarbon (14C) ages of marine biogenic
samples that derive their carbon from surface seawater dissolved
inorganic carbon are on the average about 400 years older than
contemporary terrestrial woods or global atmospheric CO2.
This age offset is due to mixing of old carbon from the deep ocean
and is referred to marine 14C reservoir effect. Both
regional and temporal variations of ocean circulation pattern causes
significant spatial and temporal variations in marine 14C
reservoir ages and hence of biogenic surface marine samples.
Knowledge of reservoir age is very important to accurately calibrate
14C-ages of biogenic carbonates and sediment organic
matter from marine sediments that are frequently used in
paleoceanographic studies. Here the concept of marine 14C
reservoir ages and their quantification are discussed and data for
the Indian Ocean region are reviewed. Regional variations of marine
14C reservoir ages and fossil fuel Suess effect for the
Indian Ocean and the South China Sea are analyzed. |
|
Recently
Studied Sedimentary Records from the Eastern Arabian Sea:
Implications to Holocene Monsoonal Variability
Rajesh
Agnihotri and Siby Kurian |
|
Deep insight into exact mechanism(s) controlling past monsoonal
variability on inter-annual to millennial time scales is a
pre-requisite for developing predictive capability of monsoon on
timescales relevant to human life. Reliable monsoon predictions
developed by climate modelers play a crucial role for making
country’s future economic programme. Basic data input to generally
applied monsoon models is instrumental rainfall data, beyond which
search for monsoon variability relies upon proxy records stored in
various natural repositories such as tree rings, corals, cave
deposits, lake and marine sediments. While tree rings, cave deposits
and corals are capable of yielding paleo-monsoonal information on
extremely high temporal resolution, continental margin sediments
depositing in the Arabian Sea have provided relatively coarser but
longer proxy records of monsoonal variability. Here we review some
of such recently studied sedimentary records from precipitation
dominated eastern Arabian Sea in an attempt to comprehend past
monsoonal variability in Indian as well as global context. We also
focus upon different proxies used so far in the Arabian Sea, their
fidelity, limitations and future scope of using novel proxies for a
better understanding of past monsoonal variability especially in the
anthropocene epoch. |
|
Variation in Erythemal UV Dose for Indian Cities as
Observed from Global Ozone Monitoring Experiment Data
Nandita D.
Ganguly |
|
Variation in
Erythemal UV Dose (EUVD) for five
Indian cities and their expected critical limits has been studied
using the data obtained from Global Ozone Monitoring Experiment (GOME).
The EUVD values are found to be higher and peak earlier at places
located at lower latitudes than at higher latitudes. They are higher
during summer / monsoon compared to winter.
Seasonal variation in EUVD is more pronounced at higher latitudes
compared to lower latitudes. EUVD variations
show a negative correlation with solar activity and
are observed to be
well within the
statistically calculated critical limits for these five Indian
cities. |
|
Use of
Interactions between NAO and MJO for the Prediction of Dry and Wet
Spell in Monsoon Season
S.S.Dugam |
|
The Indian summer monsoon exhibits prominent 30-40 day fluctuations
with “active” periods of heavy rain interrupted by dry periods
i.e. “Breaks”. The circulation anomalies associated with
active/break monsoon cover the entire Indian Ocean remote tropics
and North Pacific Ocean. A prolonged dry/wet period will result in
severe drought/flooding, which have profound influences on the south
Asia water cycle, agriculture and societal activity of more than one
billion people. The atmospheric general circulation models have
great difficulty in simulating the Intra-seasonal oscillation (ISO).
Therefore, it is necessary to study the empirical relationship
between various atmospheric processes, which are responsible for the
ISO. In this paper, the analysis of North Atlantic Oscillation Index
(NAOI) and Madden Julian Oscillation Index (MJOI) on daily scale is
carried out in relation to daily Indian summer monsoon rainfall
(June-September). The analysis is carried out for the period
1979-2001. Since the potential predictability limit for monsoon
break is about 20 days, the 20 days running lag/lead correlation
analysis between the NAOI and MJOI is found out for each year. It is
observed that 20-day lag relationship between NAO and MJO is inverse
and significant (0.1 level) and this relationship remains negative
throughout the break monsoon period and in active phase it reverses.
This twenty days lag relationship between NAO and MJO is potential
predictor for break/ active monsoon conditions over the Indian
region. The analysis is verified for major drought year 2002. |
|
Earth Science India
Vol.1 (III), July, 2008 |
|
Chemical Characteristics of Water Soluble Components
of Fine Particulate Matter,
PM2.5,
at Delhi, India
Suresh Tiwari
, Manoj K. Srivastava
, and Deewan S. Bisht |
|
Aerosol samples in the size range up to 2.5 µ m were collected from
January to December 2005 at New Delhi, India, as a pilot experiment
and analysed for organic [O xalate and Formate ] and inorganic [
Sulfate, Ammonium, Nitrate, Potassium, Chloride, Sodium, Calcium and
Magnesium] chemical components. Initial results show that the annual
mean PM 2.5 concentration was 98.7 µg/m 3 , which varied
between 38 to 285µg/m 3 . The water soluble inorganic fraction
constituted only 9% of PM 2.5 with SO 4 2- , NH 4 + and NO 3 - being
the dominant ions followed by potassium. Annual cycle shows higher
concentration of PM 2.5 during winter season [October to January]
and the lowest during monsoon. It is attributed to the enhanced
production of aerosols and prevailing meteorological conditions. The
PM 2.5 /PM 10
ratio [0.86] coupled with the HySPLIT air-mass back trajectories
indicated that PM 2.5 at was dominated by fine particles,
when the winds passed through the eastern azimuth, where many
industries and major thermal power plants are located. |
|
Cosmic Rays and
Earth's Atmospheric Processes : A review
Devendraa Siingh |
|
The
modulation of cosmic ray flux incident on the Earth's upper
atmosphere by solar activity results in changing the global
electrical properties of the atmosphere, which is, in turn, believed
to affect weather and climate. In this review paper an attempt has
been made to summarize the present understanding of Earth's
atmospheric processes, which are affected by Cosmic rays. |
|
Sediment
characteristics and Heavy Mineral Distribution in Tamiraparani
Estuary and off Tuticorin, Tamil Nadu- SEM Studies
M. Suresh Gandhi, A.
Solai, K. Chandrasekaran and V. Rammohan |
|
The study area Tamiraparani located between latitudes 8° 25? and 9°
13? N, and longitudes 77° 10? to 78° 10? E along the south- east
coast of India. All samples were collected between Pre-monsoon July
2003 and Post-monsoon February 2004 . The heavy mineral assemblage
of the study region is governed by the distribution of different
type of minerals. However, the assemblage is restricted to the
dominance of few selective minerals like garnet (colourless), garnet
(pink), zircon, rutile, chlorite, etc. From the SEM studies, it is
observed that, the grains are sub-angular with various surface
solution features, rounded crescent like pits, straight net like
sutures; v-shaped pits are noticed in pre- and post-monsoon samples.
The coarser nature of the grain may be due to the influence of river
activities. The weathered surface futures also noticed in few
samples. The sediment texture, mineral and SEM studies, clearly
indicate that in pre-monsoon the erosional activities are
predominant than the post-monsoon. In both the monsoons, sediments
transport from river and estuary towards the beach and marine. In
pre-monsoon whatever sediment deposited were transported and shifted
due to longshore current action. But, in the post-monsoon, it is
depositional environment where the sediments deposited due to the
multi-source like riverine and marine influence is observed. |
|
Small-scale deformational structures
as significant shear-sense indicators: An example from Almora
Crystalline Zone, Kumaun Lesser Himalaya
K. K.
Agarwal and R. Bali |
|
Small-scale deformational structures e.g. folds, asymmetric boudins,
thin veins in an en-echelon pattern, small-scale duplex, shear zones
and shear bands are the most common structural elements used as
reliable shear-sense indicators in crystalline rocks. Most of these
structures are observed in the Almora Crystalline Zone (ACZ) in
Kumaun Lesser Himalaya, which is disposed in the form of a huge
asymmetric synform. The shear-sense observed on the northern and
southern flanks is found to be – top to north and top to south
respectively. |
|
SFARF:
Software for Classification of Fourier Shape of the Folds Around
Tamadhaun, District Almora, Uttarakhand
H. Thomas , S.
Sujata and A. Chandel |
|
Fourier (harmonic) analysis is a very simplified graphical method of
plotting fold shapes in two dimensions. The authors have developed
software (SFARF) to directly assign the class of fold shapes on the
basis of the value of the ratio b3 / b1 (Fourier Coefficient). The
various fold forms obtained by the software around Tamadhaun area
reveal that fold developed in quartzite occurring in the study area
is varying in the range between sine-waves and parabolas to almost
sine-wave, whereas the folds which are developed in phyllite and
schist rocks are statistically between sine-waves to almost chevron. |
|
Climate change and
its future impact on the Indo-Gangetic Plain (IGP )
H.S.Saini |
|
The Indo-Gangetic plain (IGP) is an environmentally sensitive,
socially significant and economically strategic domain of India
where landscape, hydrology and fertility are threatened by climate
warming and anthropogenic pressure. Irregular availability of water
is going to be thebiggest hazard in future. In case of increased
water supply, the piedmont zone and river lowlands are threatened by
erosion and sedimentation while in case of decreased water supply,
the upland surface is endangered by salinization, desertification
and drying-up of aquifers. Decline in food production will be the
major problem. In order to make assessments of the environmental
changes, concerted efforts should be initiated to understand the
geological past and model the future. A pre-requisite is to develop
a high resolution history of climate variation and their impact on
landscape and ecology from the geological and historical recordsof
IGP during the past 25 ka. Such data can help in the evaluation of
forecasting scenarios, and thereby assist in developing mitigation
plans regarding the environment. Artificially induced recyclingof
the water can be one of the possible ways to maintain a minimum
availability of water. |
|
Earth Science India
Vol.1 (II), April, 2008 |
|
Lateral
Zonation Around Archean Nucleus of the Dharwar Craton (India): Its
Deformation, Segmentation and Subsequent Breakup
O.P. PANDEY
and
P.K. AGRAWAL
|
|
Regional
scale variation of the nature of geological units across the
earliest evolved regions of the earth may contain fundamental
information about continental evolution. Among the Archean blocks,
the Indian shield appears to possess certain unique geotectonic and
geodynamical characteristics which provide an opportunity to
understand its multi-stage crustal evolution both in space and time.
Our study of the south Indian shield reveals segmentation and a
secular and progressive lateral zonation of the continental
lithosphere around Dharwar nucleus since mid-Archean. However, its
cratonic nucleus seems to have ultimately broken due to successive
crustal remobilization and foundering of the rheologically and
tectonically weak Archean lithosphere. Such weakness were caused by
(i) episodic plume induced tectonothermal events since 2.7 Ga, and
(ii) asthenospheric convective processes associated with a new
rifting phase triggered by Marion plume activity along the India's
western margin at about 90 Ma. The Antongil block of northeast
Madagascar seems to correspond to the broken segment of the western
Dharwar craton. |
|
Some
Observations on the Thrust Geometry of the Siwalik Rocks of the
Outer Himalaya , India
A. R.
Bhattacharya and K. K. Agarwal |
|
The rocks of
the Siwalik Supergroup of the Outer Himalaya have been found to show
a complicated system of thrust geometry in their internal domain.
The structures which the lithic layers commonly show include the
following: duplex, imbricate fan system, thrust propagation
structures, fault propagation folds, pop-up structures, antiformal
stack, snakehead anticline, snakehead duplex, overstep thrust system
and the related types. Occurrence of these structures suggests,
amongst others, the active role, and/or reactivation, of the
anisotropy planes of the rocks during deformation, and that the
deformation was progressive in nature. Development of most of these
structures may have involved addition of mass to the moving thrust
complexes. Presence of the above structures possibly indicates that
the Siwalik strata, in general, may have undergone structural
thickening in their internal domain during the overall deformation
of these rocks. |
|
Brissid echinoid
Eupatagus L. Agassiz, 1847 from the Khuiala Formation, Jaisalmer
district, Rajasthan, India
D. K.
Srivastava and Hukam Singh |
|
The
spatangoid genus Eupatagus L. Agassiz, 1847 is recorded, for the
first time, from the sediments of the Khuiala Formation (Early
Eocene) exposed near Habur, Jaisalmer district, Rajasthan, India.
The specimens are placed in a new species characterised by its
large, oval test with mild frontal sinus; convex aboral surface;
flat oral surface; anteriorly eccentric ethmolytic apical system;
anteriorly eccentric kidney- shaped peristome; long, petaloid
ambulacral petals; longitudinally oval periproct at the posterior
truncation and imperforate, non crenulated tubercles.
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Earth Science India
Vol.1 (I), January, 2008 |
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Basement Rocks of
the Kumaun - Garhwal Himalaya: Some Implications for Himalayan
Tectonics
A. R. Bhattacharya |
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The Himalayan orogenic belt is characterized by the presence of
basement rocks. These rocks got involved in the evolution of the
mountain belt and, as such, have played a great role in the
structural architecture and tectonic framework of the orogen. These
rocks have evolved from depth due to concentration of compressive
stresses generated by plate collision and rose vertically up because
of buoyancy up to the surface and were then pushed southwards over
the less- or un-metamorphosed , younger rocks of the sedimentary
belt of the Lesser Himalaya. In order to make room for such a vast
chunk of the basement, the sedimentary pile had to undergo large
scale deformation sympathetically. As such, the present tectonic
setting, structural architecture and deformation pattern of the
upper crustal rocks of the Himalaya owe much to the rise of the
basement rocks during evolutionary stages of the Himalaya. The paper
examines some aspects of the tectonics and structural framework of
the Himalaya as related to the basement rocks in the Kumaun -
Garhwal sectors. |
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Fluvial
Palaeohydrological Studies in Western India: A Synthesis
Alpa Sridhar
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The river basins of India are important repository of the late
Quaternary hydrological and climatic changes. The long term
(millennial scale) and short term (centennial scale) hydrological
changes in these river basins can be reconstructed through the
records of platform alterations and sediment deposits that occur
during the rare extreme flood events. The status of fluvial
palaeohydrological studies in western India and the future prospects
are discussed in this synthesis. Almost continuous palaeoflood
records spanning two thousand years is available from the bedrock
rivers on western India, whereas older events dating back to ~ 5 ka
have also been documented from the alluvial reaches. Though bedrock
gorges are considered to be ideal sites for the preservation of
palaeoflood deposits and related discharge estimations, the alluvial
reaches of the rivers in western India owing to their unique
geomorphic set up are equally promising. Regime-based
palaeodischarge estimations for the average flows in these alluvial
reaches would be significant in providing a regional history of the
hydrological changes that have occurred in the river basins of
western India. |
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Geothermal Energy
Resources and Their Potential in India
P.N.Razdan,
R.K.
Agarwal and Rajan Singh |
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Geothermal Energy is the vast reservoir of heat energy in the
earth’s interior, whose surface manifestations are the volcanoes,
fumaroles, geysers, steaming grounds and hot springs. About 300
thermal springs are known to occur in India, falling in orogenic
(Himalayan) as well as non-orogenic (Peninsular) province. Thirty
one areas have been examined in detail and finally, shallow drilling
has been done in sixteen areas. The temperatures of these springs
range from 35°C to the boiling point of water. On the basis of
enthalpy characteristics the geothermal systems in India, are
classified into medium (100°C-200°C)-and low enthalpy (<100°C)
geothermal energy resources/systems. Medium enthalpy geothermal
energy systems are associated with younger intrusive granites (as in
Himalayas), major tectonic features/lineaments and rifts and grabens.
The Low enthalpy geothermal energy systems are associated with
Tertiary tectonism and neo-tectonic activity. The primary and most
important aspect of geothermal system is to understand the heat
source and its capacity for exploitation. Studies carried out, so
far, have clearly pointed that adequate geothermal potential in
respect of direct heat utilization and power generation does exist
at several geothermal sites. Reservoir simulation studies have
suggested the possibility of generating over 3 MW electric power in
Puga (J&K) field, if deeper levels are probed at least up to the
depth of 500 m. The paper provides an overview on various geothermal
fields of India and the status of exploration for future studies. |
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Synthetic Minerals
for Electronic Applications
P. S. Anjana, Sherin
Thomas, M. T. Sebastian and J. James |
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Several of the mineral phases used for our
common use are available in nature. However, the purity of the
natural mineral phases, their consistency of properties, structure,
morphology and availability make them unsuitable for large scale
continuous use in electronic and other applications. Therefore,
several inorganic minerals are synthesized to tailor their
properties for specific applications. These minerals, though similar
in their structural characteristics to the naturally occurring
minerals, gives flexibility in controlling their purity, and
crystallographic characteristics. This in turn helps to develop
newer and improved applications like electronic and magnetic devices
for communication. This article has concentrated on of some of the
major synthetic materials used for electronic applications with
special ephasis on their mineralogical aspects, structure,
preparation and uses. The minerals covered include: quartz,
synthetic Berlinite, synthetic Perovskites, synthetic halites,
synthetic pyrites, synthetic rutiles, synthetic pyrochlores,
synthetic spinels, synthetic sphalerites, synthetic wurtzites,
synthetic corundum. |
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