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Interpretation
of Gravity and Aeromagnetic Anomalies in the Gongola Arm of
the Upper Benue Trough, NE Nigeria
--
E M Shemang
Gravity
and magnetic investigations are undertaken to determine the
structure in the Gongola arm of the Upper Benue Trough. The
area is characterized by negative Bouguer anomalies ranging
from -75 to -10 mGal. The residual gravity anomalies range
from -28 to +20 mGal. Results of 2.5-D modeling of the residual
gravity anomalies along selected profiles reveal the presence
of horst and graben structures. Some of these grabens are
as wide as 80 km and are filled by sediments as thick as 4.8
km. The interpreted results also suggest the presence of basic
intrusives (of density about 2800 kg m-3) as shallow
as 0.5 km extending upto 8 km. Magnetic data interpretation
along some profiles coinciding with interpreted gravity profiles
also reveal the existence of high magnetic susceptibility
rocks (about 0.0476 SI units) of basic to ultrabasic composition
at 7 to 8 km depth. A prominent magnetic lineament identified
was interpreted in terms of a geosuture zone at depth beneath
the Gongola Arm of the Benue Trough.
© 2007 IUP . All Rights Reserved.
The
Effect of Tsunami on the Placer Mineral Distribution in the
Beaches between Tuticorin and Ovari, Tamil Nadu, India
-- Suresh Gandhi M,
Vetrimurugan
E,
Angusamy N and Victor Rajamanickam G
Placer
mineral studies before and after the tsunami were undertaken
systematically along the coastal region from Tuticorin to
Ovari, Tamil Nadu. Different size grades of heavy minerals
show a similar trend of concentration from +70 to +200 mesh,
except at +80 and +170 mesh size grades before the event.
After the tsunami, a shift in the modality to a slightly coarser
grade is noticed in all the beaches at stations Ovari and
Manappad. An increasing trend of heavy mineral concentration
was noticed after the tsunami at Tuticorin south, Tuticorin
north, Manappad and Ovari. Depletion of placers in other regions
is attributable to the beach configurations. At Ovari, a higher
percentage of heavy minerals may be attributed to the deposition
of tsunamigenic sediments towards the shore region. SEM studies
show the internal surface features for different minerals.
The present study has disclosed a higher concentration of
garnets and zircons after the tsunami.
© 2007 IUP . All Rights Reserved.
Application
of GPS for Monitoring Land Subsidence
-- Parul Patel and Madhav N Kulkarni
This
paper deals with the monitoring of land subsidence using Global
Positioning System (GPS) in the South Gujarat, India. In this
area, hydrocarbon is being extracted since many years. It
has been established that hydrocarbon extraction is one of
the main causes of subsidence over the study area. Land subsidence
studies have been carried out by the GPS team of Indian Institute
of Technology Bombay, with dual frequency GPS receivers. A
total of nine field campaigns have been completed. The collected
GPS data have been processed in post-processing mode, using
scientific GPS data processing software with precise ephemeris.
To achieve millimeter (mm) level accuracy, ionospheric correction
and tropospheric corrections were estimated and applied during
data processing. Statistical testing was done to check the
significance of the GPS data. The results of statistical testing
confirm that there is significant subsidence within the reservoir
boundary, rather than outside the boundary.
© 2007 IUP . All Rights Reserved.
Landscape
Modification in Chilika Lagoon Area, East Coast of India:
A Remote Sensing and GIS-based Study
--
Kali C Sahu
This
paper reports the results of a case study undertaken in the
Chilika catchment area, located at the east coast of India,
and focuses on the assessment of: (1) spatial distribution
of land use/land cover patterns, and (2) change detection
using IRS 1A LISS-I of April 1989 and IRS 1D LISS-III of May
2002. The change in the built-up area is 3.006 km2
from 1989 to 2002. The agricultural land has been increased
by 5.963 km2 during the 13 years. The total forest
cover was estimated to be 348.128 km2 in the year
1989, and 350.081 km2 in the year 2002. Change
in the wastelands, mostly scrublands, has shown a decreasing
trend. In the Chilika catchment area, there has been a decrease
of 27.025 km2 in the scrublands due to agriculture
and plantation. The principal observation reveals that there
is a positive sign for the restoration of the Chilika lagoon.
© 2007 IUP . All Rights Reserved.
Study
of Coastal Water Pollution in Sundarban
--
Dip Narayan Ganguly,
Anirban Mukhopadhyay,
Rahul
K Pandey and Debashish Mitra
Sundarban
delta is one of the most dynamic ecosystems of the world.
Several river channels criss-cross the Sundarban delta and
bring with them, tons of suspended sediments, nutrients, and
polluting substances from terrestrial sources, and play a
major role in India's biggest mangrove ecosystem. This paper
deals with the multitemporal study of different water quality
parameters (nitrate, phosphate, heavy metal, and suspended
sediment concentration) of this zone. Distribution of different
water quality parameters was determined by using the data
set collected from 17 sampling stations distributed between
Hooghly and Matla estuary. Sampling of water was done during
the early pre-monsoon seasons (March-April) of both 1998 and
2004. Interpolation technique (inverse distance weightage)
was used to carry out spatial analysis of water quality distribution
in this area, and a spatial distribution map of several water
quality parameters was generated. Finally, a pollution map
of Sundarban coastal water between 1998 and 2004 was prepared,
giving weightage to various parameters using Arc-GIS software,
and an increase of pollution level was detected within the
area.
© 2007 IUP . All Rights Reserved.
GIS
Technology-based Geohazard Zonation and Advance Warning System
for Geohazard Mitigation and Information Dissemination towards
Relief and Rescue Operations
--
Mu. Ramkumar and R Neelakantan
GIS
Technology could play a major role in disaster mitigation
and management. The authors advocate that linking the GIS-based
warning system with administrative machinery could save precious
lives, minimize economic loss and protect infrastructure.
Hence, this paper proposes a GIS technology-based conceptual
model, which, on operationalization, may be extremely helpful
in disaster management.
© 2007 IUP . All Rights Reserved.
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