Detailed geological studies on mine workings, trenches excavated for civil structures, and traverses at closer intervals help to document the micro-scale lithological, sedimentary structural and facies interpretations, resulting in improving our understanding of the cyclic deposits. In the paper, "Cyclic Fine-Grained Deposits with Polymict Boulders in Olaipadi Member of the Dalmiapuram Formation, Cauvery Basin, South India: Plausible Causes and Sedimentation Model", Mu Ramkumar examines the new exposures confined to the Olaipadi member of Dalmiapuram formation exposed along NE-SW trending margin of the Cauvery basin, and documented the sedimentary textural, structural and lithofacies characteristics, contact relationships, facies association and tectonic structures. The study indicates that the sedimentation of Olaipadi deposits was initiated by the hyperpycnal flow, following faulting and upliftment of former shelf and coastal regions that led to gravity flow of fractured and unstable fault scarp blocks, resulting in turbidite deposition in the adjacent deeper regions of sea. General grading of the beds from bottom to top of the member also suggests retrogradation of the member from proximal to distal parts of fan, indicating either sinking of the basin or sea level increase or both. It also indicates general smoothening of the depositional topography, concomitant with denudation of drainage basin and reduction of feeder channel gradient.

Knowledge of geotechnical status of an area is a prerequisite to develop a modern sustainable urban area. In the paper, "Geotechnical Mapping of the Jamalpur Municipality and Surrounding Areas, Bangladesh", A S M Shafiul Azam and Sohail Kabir have prepared a geotechnical zonation map using geomorphological map, subsurface lithology, geotechnical properties of different geomorphic units and clay mineralogy. The area is neotectonically active as evidenced by possible fault, sharp lithologic variation and elevation difference. The study categorized the region into four major zones-A, B, C and D. Zone-A is the best possible zone for engineering construction, whereas Zone-D is the worst area for any kind of construction. Zone-B could be used for construction with suitable modification. Such detailed studies would be helpful in any small-sized municipality development planning.

In magnetic exploration one tries to identify the variations in the magnetic field caused by the changes in the subsurface geologic structure. Within a given area, varying intensities of the magnetic anomalies are thought to reflect the degree or amount of geochemical alteration having taken place and the percentage by volume of magnetic or nonmagnetic minerals produced. In the paper, "Structural Inferences from Total Magnetic Intensities in the Gadag Region: A Case Study", Veeraiah B, Himabindu D and Ramadass G have determined the structural fabric of the Gadag region (Karnataka) through 2-D total field magnetic intensity observations made over an area of approximately 2,750 Sq Km in the geologically and tectonically interesting Gadag region. Several tectonic featuresdeep-seated faults and magnetic linears in the regionwere identified. From the trend of the contours, major features delineated include the NW-SE trending Gadag schist belt and the Chitradurga thrust fault, which is found to be limited by a major NE-SW fault. The delineation of the intracrustal magnetic interface and forward modeling of the results indicated that Banded Iron Formation (BIF) occurred at depths ranging from 300 to 1,300 m.

The use of remote sensing in hydrogeomorphological mapping for water resource management is gaining importance in the present day world. Water, being the most vital requirement of the mankind and available surface water resources being inadequate to meet the requirements for different purposes, the search for subsurface water has been on the increase. In the paper, "Hydrogeomorphological Mapping for Groundwater Prospects Using Remote Sensing Data: A Case Study of a Part of Bhind District, Madhya Pradesh", the authors, Vineesha Singh and Khare, studied the groundwater prospects in the region using the data obtained from IRS-1B LISS II data. The geology, geomorphology and lineament information along with other collateral data have been analyzed and integrated to evaluate the groundwater prospective geomorphic units. The analysis indicated that the groundwater conditions are excellent to very good in Alluvial plain, moderate to good in pediplain; good in buried pediplain; and poor to very poor in pediment and structural hills.

Koyna Dam is one of the largest dams in Maharashtra, India. The uniqueness of the Reservoir Induced Seismicity (RIS) at Koyna is attributed to the high pore pressure build-up rate caused by the hydraulic head of the impounded water and due to the high strain energy density in the region. After the 1967 major earthquake, which almost razed the dam, the region continued to experience several earthquakes of M>4.0 even after 40 years of its impoundment. Even though the debate about the safety of the dam has been continuing, no direct evidence could be obtained so far. In the paper, "Monitoring the Coseismic Movement of Koyna Dam Using GPS", Nisha Radhakrishnan, Madhav N Kulkarni and Kamal Sakr have recorded for the first time in India, coseismic displacement of a dam body using GPS data recorded during the time of occurrences of a felt earthquake and its aftershock. The analysis of the data collected just before and after the earthquake occurrences showed a displacement in the North-West direction with a certain magnitude of deflection. After the occurrence of the earthquakes, the dam was observed to attain its original position by shifting in the opposite direction (S-E) with the same degree of deflection as observed during the time of the earthquakes. The return of the dam to its original position after the earthquakes reflects the high response value of the dam foundation, indicating that the dam body is stable and not affected by the earthquakes. This could be attributed to the reason that the dam did not suffer much damage due to the earthquake of M 6.3 of 1967.

- S V Srirama Rao
Consulting Editor