October, 2015

October, 2015   ||  Volume 19 No.4



Thermal evolution of Indian cratonic lithosphere

R N Singh

CSIR-National Geophysical Research Institute, Hyderabad 500007
e-mail : rnsingh@ngri.res.in


Thermal evolution of the Indian cratonic lithosphere can be deciphered by using the heat conduction equation with the thermal properties and other related information, such as heat flow values and pressures, temperatures and ages derived from rocks of various terrains. Some thermal causes reflect changes in the surface and basal boundary conditions and some others reflect input of heat inside the lithosphere as a result of magmatic or tectonic events. The later processes can be posed as initial value problem of the heat conduction equation. Surface heat flow and heat generation data are used to infer the present thermal structure of the Indian cratonic lithosphere. Metamorphic pressure and temperature data have been used to construct the paleogeotherms. Formation of the Cudappah basin is ascribed to thermal perturbation of the lithosphere. Formation of charnockites has been ascribed to thermal perturbation by flux of CO2 from mantle depths, or uplift and erosion of thrust sheets emplaced on the lithosphere or a combination of both. The few problems of the Indian cratonic lithosphere, which have been addressed as initial/boundary problems or changes in the heat sources or addition of advection term in the heat conduction equation are described in this review.


Geological and Geotechnical Characterisation of Ramagundam Opencast-II of Singareni Collieries using Geophysical Logs

G. Uday Bhaskar*1, A. Srinivasa Rao2, G. V. S. Prasad2 and B. Shravan Kumar3

1DGM (Geophysics), Exploration Division, SCCL, Kothagudem 507 101, 2Superintending Geophysicist, 3Senior Geophysicist, Exploration Division, SCCL, Godavarikhani – 505 214
*Corresponding Author: udaybhaskar_g@yahoo.com

Deep and large opencast coal mines of 400m to 450m depth are considered important to increase the coal production of India. Planning and managing such large open pits depends upon a thorough understanding of geological and geotechnical aspects of the rock strata comprising the overburden column. The experiences of Singareni Collieries Company Limited (SCCL) located in Telangana, India document borehole geophysical logging as an effective means to generate a continuous description of geological and geotechnical strata features from the surface to total drilled depth. Conventional geophysical logs are used to identify the basic lithologies and construct geological maps of overburden strata. The uniaxial compressive strength (UCS) of sandstones is empirically estimated by correlating P wave velocities (Vp) obtained from sonic logs with the laboratory determined UCS value. Acoustic images help determine the location and trend of fractures and minimum horizontal stress directions. Together, these data provide the basis for characterisation of the rock mass and form the foundation for the effective design of stable pit walls in deep sedimentary strata. This paper presents usage of different geophysical logs at the proposed deep pit at Opencast-II Expansion Project of Ramagundam, SCCL.


Recharge rate in a carbonate rock covered watershed in Kurnool district, Andhra Pradesh, India using Tritium injection and Soil Water Balance methods
Farooq Ahmad Dar*, R. Rangarajan, D. Muralidharan and Shakeel Ahmed
CSIR-National Geophysical Research Institute, Uppal Road Hyderabad, 500007
*Corresponding Author: farooq.dar1@gmail.com

Groundwater in the carbonate aquifers of the southern Andhra Pradesh, India has approached to stress level as water table has declined due to increasing groundwater draft, low to moderate rainfall, less availability or absence of surface water sources and semi-arid climate. In Kallugotla watershed of Kurnool district, groundwater is overexploited for irrigation and static water level exhibit declining trend. In order to manage the aquifers for sustainable water supply, understanding and accurate assessment of groundwater recharge is necessary. Two approaches, namely soil water balance and injected tritium tracer methods were used to estimate the recharge. Tritium injection method yields 14.5 %, while soil water balance indicates 13.5% of annual rainfall as recharge. Daily and monthly recharge variability is highly dependent on soil properties and climatic parameters. The research study demonstrated that the recharge could be estimated over a watershed/sub-basin area by integrating spatial tritium injected estimates and soil water balance method.

Dynamics of Hamtah Glacier, Lahaul & Spiti district, Himachal Pradesh
S.P. Shukla*1, Rakesh Mishra1 and Alok Chitranshi2
1Glaciology Division, Geological Survey of India, Sector, ‘E’, Aliganj, Lucknow 220024, India
2Regional Training Institute, Geological Survey of India, Sector, ‘E’, Aliganj, Lucknow 220024, India
*Corresponding Author: satyashukla63@gmail.com

Understanding the glacier dynamics is significant for understanding the response of the glacier to the changing climate, i.e., determining how the glaciers change over time in response to a changing climate. It is well known that velocity of the glacier is a function of thickness and gradient of the glacier bed. In addition, the glacier velocity also depends on the availability of the water at the bottom as the basal sliding is considered as the most important factor affecting the dynamics of Himalayan glaciers. In order to understand the impact of changing glacier mass balance and the availability of melt water at the glacier bed, the glacier dynamics of Hamtah glacier, a small valley glacier in Chenab basin, Lahaul & Spiti district, Himachal Pradesh, has been studied. For this purpose the horizontal component of flow movement has been measured, during 2000-01 to 2005-06, using the stake network fixed for the assessment of annual mass balance.
The highest glacier flow velocities were recorded in the highest elevation zones whereas the least flow velocities were observed near the glacier snout. The annual horizontal component of flow velocities recorded successive decline from 2000-01 to 2003-04 with marginal upward trend in 2004-05, followed by decline in 2005-06. This variation in horizontal component of flow velocity was correlated with the mass balance recorded during the observation period. In addition, the annual and summer horizontal component of flow velocity was also compared to comprehend the effect of the increase in water availability at the glacier bed. It has been observed that the annualized summer flow velocities (Um*12) and the annual flow velocities (Ua) deduced from field measured summer flow and annual flow respectively show considerable variations, including during different observational years.

Application of MODFLOW for groundwater Seepage Problems in the Subsurface Tunnels
L. Surinaidu*1, V.V.S. Gurunadha Rao1, M.J. Nandan1, C.S. Khokher2, Yugraj Verma2 and S.K. Choudhary2
1CSIR-National Geophysical Research Institute (NGRI), Hyderabad
2Geotechnical Group, RITES Ltd. Gurgaon
*Corresponding Author: suryangri@gmail.com

The construction of subsurface structures such as Tunnel beneath the water table causes the groundwater seepage into the structure and impacts the stability of the structure. A 2.483 km long railway Tunnel was constructed between Katara and Udhampur in Jammu and Kashmir province of India. It is occupied by alluvium with scanty exposures of sandstone belonging to the Middle Shiwalik group. A huge amount of infiltrated water from the perennial canals and agriculture fields is entering the Tunnel. In addition to this, dry Nala/Palaeo channel across the Tunnel alignment contributes significant groundwater seepage during rainy season. A finite difference based groundwater flow model was constructed using the inferences from hydro-geo-morphological features and geologic lineaments to estimate the groundwater seepage and find out the possible solution. The computed flow model indicated that Tunnel would receive groundwater seepage of 78,133 m3/day. The analysis of the model results revealed that 500 lateral perforated pipes of 5 m in length at an interval of 2 m with an annular space filled with highly permeable geo media can drain out the seepage water. The suggested perforated pipes were successfully installed in the Tunnel. They were effective in draining out the groundwater seepage.

Geophysical Investigations for Delineation of Gondwana Sediments below Deccan Trap beyond the Western Limit of Wardha Valley Coalfields, Yeotmal and Wardha Districts, Maharashtra-a comprehensive analysis of case studies
D.C. Naskar* and D.K. Saha
Geological Survey of India, Geophysics Division, ER, Kolkata, India
*Corresponding Author:dcnaskar@yahoo.com

The present work in Wardha valley in Central India is an effort in identification and evaluation of concealed Gondwana (coal bearing at places), under the Deccan trap cover, using geophysical inputs. The geophysical exploration was done by using magnetic (VF) and electrical surveys in three blocks in and adjoining part of Wardha valley, which hither to was not explored using Geophysical investigations. The presence of drilling data was an added advantage for correlation of geological litho packages vis-à-vis resistivity data interpretation.
The result of Resistivity Sounding (RS) data interpretation shows mainly four interfaces: top soil/alluvium, Deccan trap, Gondwana sediment and basement of high resistivity. The resistivities of trap rock vary from 50-300 Ohm-m, with thickness in the range of 20-210 m. The Gondwana shows resistivity in the range of 6-120 Ohm-m with thickness variation ranges from 76-560 m. The geo-electric section in Block I indicate a fault zone in Mangli-Sindhi segment, due to appreciable large variation in basement depth (871 m and 313 m) in two adjoining RS locations. The geo-electric section in Block II indicates high resistivity basement (461-1628 Ohm-m) at a relatively shallow depth (102-218 m) southwest of Wardha River, whereas the same occurs at a greater depth (329-455 m) northeast of Wardha river. The basement has come up to a level of 75 m in the region immediate northeast of Wardha River. The course of the Wardha River is coincident with a postulated fault plane.
The magnetic map shows the presence of fluctuating high amplitude long wavelength anomalies due to the presence of a thick blanket of trap lying above the Gondwana sediments. These magnetic anomalies did not show the basement configuration appropriately due to an overlying blanket of trap. The highly fluctuating anomalies due to the trap overshadow the basement effect. The map, however, approximately indicates the fault zone through the change in the wavelength character of the magnetic anomalies.

Palaeomagnetic and Rock magnetic investigations on Gadwal “Dike 2”, eastern Dharwar craton, India
M. Venkateshwarlu* and Tarun C. Khanna
CSIR – National Geophysical Research Institute, Hyderabad - 500007
*Corresponding author: mamila_v@rediffmail.com

A rare crustally uncontaminated mafic magmatic dike “Dike 2” of alkaline affinity, which has a visible outcrop length of ~20 km trending NW-SE, transects the Neoarchean Gadwal greenstone terrane in the eastern Dharwar craton, India. Although, the age of the Gadwal schist belt is well constrained, the field relationship between the Dike 2 and the adjacent granitoids suggests a post-Archean age for its emplacement. There is no direct age information available for Gadwal Dike 2. Fifty oriented samples were collected from 10 sites along the strike length of the Dike 2. Rock magnetic studies (IRM and K-T) indicate that the main remanence carrier resides in multidomain Magnetite. Palaeomagnetic results infer a mean direction at Dm=225°; Im= -21° (N=8, α95= 10.3 and k=29.9) and yield a paleo pole at lat.46°S; long.349°E (dp=5.6; dm=10.8). This new pole position indicates an emplacement age of ~2.2 Ga for the “Dike 2”. This pole is in conformity with the poles determined for Cuddapah dykes and those in the peninsular India.

Role of Biogenic Hydrocarbon on the Variability of Total Rainfall Amount over Sundarban, Kaziranga and Gir Forests
S. K. Midya*1, S. Ghosh1, S.C. Ganda1 and G. K. Das2
1Department of Atmospheric Science, University of Calcutta,51/2 Hazra Road,Kolkata-700019,West Bengal, India
2Regional Meteorological Centre, Kolkata
*Corresponding Author:drskm06@yahoo.co.in

A critical analysis of the yearly variation of rainfall with tropospheric ozone for three Indian forest zones, namely, Sundarban in West Bengal, Gir in Gujarat and Kaziranga in Assam has been carried out from 1979 to 2009. The Analysis shows that low temperature of troposphere, presence of sufficient water vapor, and CCN (Cloud Condensation Nuclei) are not sufficient for generating rainfall. From the study the following important results are obtained:
i) The amount of rainfall showed an overall increasing trend with increasing tropospheric ozone concentration for three forest zones of India, over 30 year period.
ii) A few anomalous results are obtained over Gir and Sundarban forest zones, for the years 1982, 1983, 2001, while no such opposite trend has been observed for Kaziranga.
Possible explanation of such varied trend in rainfall amount with tropospheric ozone concentration is presented.

Variations in Atmospheric Structure and Wave Activity in Changing Monsoon Conditions over Mahabubnagar, as observed during Caipeex-2011
S. G. Narkhedkar*, S. P. Ghanekar, Asha Nath, P. P. Leena, M. D. Chipade, S. D. Bansod, K. K. Dani and Sunil Sonbawane
Indian Institute of Tropical Meteorology, Pune – 411 008, India.
*Corresponding Author: narkhed@tropmet.res.in

Upper-air radiosonde observations, taken during “Cloud Aerosol Interaction and Precipitation Enhancement EXperiment” (CAIPEEX) at Mahabubnagar (16.73°N, 77.98°E) under Integrated Ground Observation Campaign (IGOC) during the second half of southwest monsoon of 2011 have been analysed. Various weather data taken from India Meteorological Department as well as NCEP/NCAR reanalyzed upper-air wind data for the months August and September of 2011 have also been used in the study. Intra-seasonal variation of monsoon, during the period of experiment, has been studied. Using the field observations taken under IGOC, an attempt is made to investigate dynamical and thermal structure and also wave activities in relation to prevailing monsoon conditions over the station. Auto-correlation analysis has been carried out to identify the dominant modes associated with the monsoon variations observed over the station. Various wave characteristics have been extracted. The study has indicated the presence of gravity waves over this tropical station, during monsoon period. It is inferred that the wind shear and tropical convection associated with weather disturbances are possible sources of excitation of such waves over the location.

Sensitivity study of Matched Field Processor and Geoacoustic Inversion with combined BMV processor
Sanjeev Naithani*1, P.V. Hareesh Kumar1, Rao Tatavarti2 and Y. Satyanaryana1
1Naval Physical and Oceanographic Laboratory, Thrikkakara, Kochi, India
2Now in Gayatri Vidya Parishad College of Engineering, Visakhapatnam, India
*Corresponding Author: sannaithani@gmail.com

Estimation of geoacoustic parameters via Matched Field Inversion is controlled by many factors. This study presents the performance of Bartlett and Minimum Variance processors with respect to sensitivity of geoacoustic parameters, acoustic frequencies and signal to noise ratio. The cost function of processors is studied by assuming a geoacoustic model. Subsequently, it is proposed to use both the processors in tandem as they complement each other. The performance of Bartlett and Minimum Variance processors individually is compared with the tandem use of both the processors through geoacoustic inversion with Genetic Algorithm. The inversion results show that the joint usage of both the processors gives better estimates and can be used for matched field geoacoustic inversion.

An over view of Irrigation Tanks Rehabilitation in semi arid hard rock terrain
Former Scientist G & Emeritus Scientist, CSIR-NGRI, Hyderabad-500 007
e-mail: parvatarreddy@gmail.com

Tank rehabilitation presently in vogue, in many states of India and neighbouring Sri Lanka, needs a holistic approach involving scientific planning and execution and people`s participation to save the tank and meet basic objective of providing water for irrigation. The article brings into focus the essential inputs to make the initiative successful. The main inputs include specialists’ reports on successful and failed initiatives in Karnataka, Tamilnadu, Pondicherry states and Sri Lanka. Needed procedural changes are also outlined to make tank rehabilitation under Mission Kakatiya Project, Telangana state effective and long lasting.

News and views at a glance

Book Review
Seismic Activity - Indian Scenario