022181   Karmakar S;Alam M M (Bangladesh Meteorological Dep, , Dhaka, Bangladesh) : Instability of the troposphere associated with thunderstorms nor' westers over Bangladesh during the pre-monsoon season. Mausam 2006, 57(4), 629-38.

The study is an attempt to study different stability indices in relation to the occurence of nor' westers in order to find out the critical values of different indices favourable for the formation of thunderstorms and severe thunderstoms in Bangladesh. Computations have also been made for the stations in and around Bangladesh for studying the spatial distribution of the stability indices. The critical values of Showalter Stability Index (SI), Lifted Index (LI), Dew-point Index (DPI), Dry Instability Index (D1I), Cross Total Index (CT), Vertical Total Index (VT), Total Totals Index (TT), Energy Index (EI), SWEAT Index (SWI) and K-Index (KI) at 0000 UTC over Dhaka may be taken as ≤ + 3° C, ≤0° C, ≤ -3° C, ≤ 0° C, ≥ 16° C, ≥ 24° C, ≥ 40° C, -6 Joule/gm, <62>200 and <62>34° C respectively for the nor' westers to occur in Bangladesh. The spatial distribution of different Stability Indices reveals that maximum negative values of SI, LI, DPI, DII and EI lie over the eastern Madhya Pradesh, Bihar, West Bengal and adjoining Bangladesh indicating the highly unstable area. The negative areas of the indices in combination with the low pressure area over Bihar, West Bengal and adjoining Orissa and Bangladesh as well as the cyclonic circulation up to 3-4 km or above are favourable for the occurrence of nor' westers in Bangladesh. Maximum values of CT, VT, SWI, KI and TT exist over eastern Madhya Pradesh, Bihar, West Bengal and adjoining Bangladesh indicating the highly unstable area. Normally, nor' westers have been found to occur at the northeastern or eastern part of the area of maximum instability.

10 tables, 3 illus, 14 ref

022180   Kane R P (NO, Instituto Nacional de Pesquisas Espaciais - INPE Caixa Postal 515, 12245-970 - Sao Jose dos Campos, SP, Brazil) : Spectral characteristics of atlantic seasonal storm frequency. Mausam 2006, 57(4), 597-608.

The time series of the various indices of Atlantic storm activity (number of named storms, hurricanes, etc.) for 1900-2000 were subjected to spectral analysis by MEM (Maximum Entropy Method) and amplitudes of the periodicities were obtained by MRA (Multiple Regression Analysis). For recent data (1950 onwards), significant periodicities were in the quasi-biennial, quasi-triennial regions and also in higher regions, including decadal. In the QBO region (2-3 years), storm indices had peaks near 2.40 and 2.85 years, similar to 2.40 years of 50 hPa low latitude zonal wind and 2.40 and 2.85 years of ENSO (El Nino/Southern Oscillation) phenomenon. In the QTO region (3-4 years), storm indices and ENSO had common peaks near 3.5 years. In higher periodicity regions, storm indices had peaks at 4.5-5.5, 8-9, 11-12 and 14-15 years, while ENSO had peaks at 7.4 and 12-14 years. In the multi-decadal range, storm peaks were at 28-34, 40, 50-53, 61-63, <126>70 and <126>80 years (but different for different indices), which matched with similar peaks in land and sea surface temperatures. Some indices had large uptrends, <126>50% in 90 years.

2 tables, 3 illus, 46 ref

022179   Johan Devadas D;Subba Rao N;Thirupathi Rao B; Srinivasa Rao K V;Subrahmanyam A (Geology Dep, Andhra Univ, Visakhapatnam-530 003) : Drainage characteristics of the sarada river basin, Andhra Pradesh for watershed management. J Indian Acad Geosci 2006, 49(1), 1-6.

Morphometric analysis has been carried out to assess the drainage characteristics of Sarada river basin, Andhra Pradesh for watershed management. The drainage pattern of the basin is mostly dendritic to sub-dendritic in nature. The bifurcation ratio suggests that the drainage pattern is not much distorted by geological structures. The circularity ratio indicates early to late mature topography. The elongation ratio reveals that the basin has strong relief with steep slopes. The drainage density shows that the basin is coarse drained with permeable strata. Since the basin has steep slopes and plain lands, with permeable strata the streams occurring at topographic-lows may be used for construction of artificial recharge zones for augmenting the groundwater conditions.

2 table, 4 illus, 9 ref

022178   Himabindu D;Ramadass G (Centre of Exploration Geophysics, Osmania Univ, Hyderabad-500 007) : Helium survey for seismo-tectonic studies in the Cuddapah basin. J Indian Acad Geosci 2006, 49(1), 33-7.

The applicability of helium surveys in indicating permeable zones associated with faults is well known. Systematic observations of anomalous helium flow along with other gases emanating from seismic zones might therefore be used to delineate earthquake prone zones. In the present paper an attempt is made to bring forth a qualitative relationship between anomalous helium emanations and geophysical anomalies in the Cuddapah basin, thereby arriving at some broad conclusions about the usefulness of helium surveys in conjunction with other geophysical surveys in determining the seismicity of the area as governed by its tectonic framework.

1 table, 2 illus, 20 ref

022177   Gupta P K;Sri Niwas;Chaudhary N (Earth Sciences Dep, Indian Institute of Technology Roorkee, Roorkee-247 667) : Fast computation of Hankel transform using orthonormal exponential approximation of complex kernel function. J Earth Syst Sci 2006, 115(3), 267-76.

The computation of electromagnetic (EM) fields, for 1-D layered earth model, requires evaluation of Hankel Transform (HT) of the EM kernel function. The digital filtering is the most widely used technique to evaluate HT integrals. However, it has some obvious shortcomings. Presents an alternative scheme, based on an orthonormal exponential approximation of the kernel function, for evaluating HT integrals. This approximation of the kernel function was chosen because the analytical solution of HT of an exponential function is readily available in literature. This expansion reduces the integral to a simple algebraic sum. The implementation of such a scheme requires that the weights and the exponents of the exponential function be estimated. The exponents were estimated through a guided search algorithm while the weights were obtained using Marquardt matrix inversion method. The algorithm was tested on analytical HT pairs available in literature. The results are compared with those obtained using the digital filtering technique with Anderson liters. The field curves for four types (A-, K-, H- and Q-type) of 3-layer earth models are generated using the present scheme and compared with the corresponding curves obtained using the Anderson scheme. It is concluded that the present scheme is more accurate than the Anderson scheme.

2 tables, 11 illus, 20 ref

022176   Gadgil S (NO, Centre for Atmospheric & Oceanic Studies, IISC, Bangalore-560 012) : The Indian monsoon. Resonance 2007, 11(8), 8-9.

Understanding the nature of the variation in the rainfall that occurs on different spatial scales (from that of a station or a taluk to that of the entire country) and on different time scales (from days to months, to the whole season, to inter-annual and longer), unraveling the underlying mechanisms and hence predicting the variation is the central problem of monsoon meteorology. Attempts to address the 'how and why' of the Indian monsoon. I begin with a brief discussion of what we know about the nature of the observed variability of the rainfall on different regional and time-scales. What we understand about the physics of the monsoon and its variability will be considered in the next part. Finally I consider why we are not able to predict it better than we do and the challenges to be met for substantive improvement in understanding and prediction of the monsoon.

10 illus, 4 ref

022175   Fernandes L;D'Souza F;Matondkar S G P;Bhosle N B (NO, National Institute of Oceanography, Dona Paula, Goa-403 004, India, Email: bhosle@nio.org) : Amino sugars in suspended particulate matter from the Bay of Bengal during the summer monsoon of 2001. J Earth Syst Sci 2006, 115(3), 363-70.

Amino sugars (AS) are important constituents of organic matter. However, very little is known about their cycling in marine waters. In this research, author assessed the distribution and cycling of these compounds in waters of the Bay of Bengal. For this purpose, samples of suspended particulate matter (SPM) were collected from 8 depths (surface to 1000 m) at 6 locations during the 166th cruise of the ORV Sagar Kanya in the Bay of Bengal in July/August 2001. The SPM samples were analysed for particulate organic carbon (POC), particulate nitrogen (PN) and AS concentrations and composition. The AS varied between 0.4 and 17.5 nmol/l. Concentrations were high in the surface waters and generally decreased with increasing depth. AS concentration decreased from the south to north. AS accounted for 0.01 to 0.71% and 0.05 to 2.37% of POC and PN, respectively. Rapid decrease in AS-C% and AS-N% with depth indicates that these compounds were preferentially degraded relative to bulk POC and PN. The composition of AS suggests that glucosamine (GLU-N) and galactosamine (GAL-N) were present in the surface SPM samples, and their abundance decreased from surface downwards. Relatively, low values of GLU-N/GAL-N ratio indicate that the organic matter was mostly derived from the detritus of micro-organisms. The data suggest that chitin, a polymer of the glucosamine produced by many marine organisms was not the major source of AS in the Bay. Rapid cycling of these compounds indicates their importance in the cycling of nitrogen in marine waters.

1 table, 4 illus, 41 ref

022174   Dimri A P;Mohanty U C;Azadi M;Rathore L S (Snow and Avalanche Study Establishment, , Chandigarh) : Numerical study of western disturbances over western Himalayas using mesoscale model. Mausam 2006, 57(4), 579-90.

A non-hydrostatic version of the Penn State University - National Center for Atmospheric Research (PSU-NCAR), US, Mesoscale Model (MM5) is used to simulate the characteristic features of the Western Disturbances (WDs) occurred over the Indian region during winter. In the study sensitivity eight experiments are carried out by using two planetary boundary layer schemes, viz., Blackadar and Hong-Pan, and four convection parameterization schemes, viz., Kuo, Grell, Kain Fristch and Betts-Miller, with 60 km horizontal model resolution. And also the role of horizontal model resolution and topography is studied by carrying out six experiments based on two factors: horizontal model resolution of 30 km, 60 km and 90 km with assumed no topography and normal topography. For this study two active WDs are chosen which yielded extensive precipitation over western Himalayas, WD from 18 to 21 January 1997 is chosen for study one and WD from 20 to 25 January 1999 is chosen for experiment two. National Center for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR), US, reanalyzed data is used for initial and boundary conditions. It is found that the performance of combination of the Hong-Pan and Betts-Miller as planetary boundary layer and cloud convection parameterization schemes respectively is best compared to the other combinations of schemes used in this study.

1 table, 7 illus, 15 ref

022173   Das S;Ashrit R;Moncrieff M W (National Center for Medium Range Weather Forecasting, , Noida-201 307) : Simulation of a Himalayan cloudburst event. J Earth Syst Sci 2006, 115(3), 299-313.

Intense rainfall often leads to floods and landslides in the Himalayan region even with rainfall amounts that are considered comparatively moderate over the plains; for example, 'cloudbursts', which are devastating convective phenomena producing sudden high-intensity rainfall (<126> 10 cm per hour) over a small area. Early prediction and warning of such severe local weather systems is crucial to mitigate societal impact arising from the accompanying flash floods. Author examines a cloudburst event in the Himalayan region at Shillagarh village in the early hours of 16 July 2003. The storm lasted for less than half an hour, followed by flash floods that affected hundreds of people. We examine the fidelity of MM5 configured with multiple-nested domains (81, 27, 9 and 3km grid-resolution) for predicting a cloudburst event with attention to horizontal resolution and the cloud microphysics parameterization. The MM5 model predicts the rainfall amount 24 hours in advance. However the location of the cloudburst is displaced by tens of kilometers.

15 illus, 22 ref

022172   Chauhan O S;Vogelsang E (NO, National Institute of Oceanography, Dona Paula, Goa-403 004) : Climate induced changes in the circulation and dispersal patterns of the fluvial source during late quaternary in the middle Bengal Fan. J Earth Syst Sci 2006, 115(3), 379-86.

From a transact along 15°N latitude in the middle Bengal Fan, temporal and spatial variations in the granulometric parameters and clay minerals in 14C dated box cores from the eastern, the central and the western regions were studied to determine climate induced changes in the hydrography. Clay assemblages have spatial and temporal changes and are markedly different in the eastern and the western bay. From a high abundance of the clay smectite, which has its major source in the Deccan Basalt in peninsular India, it is inferred that the western bay is predominantly a depocenter of 'peninsular sources'. The eastern and the central regions of the bay, however, mostly receive sediments of the 'Himalayan source'. Related to unstable climate, the reported dominant illite chlorite (I + C) assemblage in the eastern region of the bay (I + C <62> 60% smectite <60>15%), between 18 and 12.6ka BP, points to a predominant supply from the Himalayan sources through equatorwards dispersal by the winter hydrography. Higher smectite, and reduced clays of the Himalayan sources (smectite <62>25%; I + C <62> 45%) are reported also after 12.5 ka BP from the eastern bay. These are interpreted as evidences of an intensified SW monsoon and associated change in the dispersal pattern by stronger summer monsoon hydrography which supports across bay dispersal by anticyclonic gyre. The influence of climate on hydrographic changes is consistent during the short events of arid climate (weak NE monsoon) in Holocene in core 31/1 (western bay), in which the enhanced contents of the clays of the Himalayan sources are observed (smectite <60> 40% I + C <62> 50%). These findings have implications for climate regulated influence of fluvial processes over the areas, hitherto, considered unaffected by the Indian peninsular fluvial sources.

1 table, 5 illus, 27 ref

022171   Chapla J;Dasaratha Ram G;Babu Rao N (Botany Dep, Univ College for Women, Koti, Hyderabad-500 195) : Trace element contamination in groundwater of Patancheru industrial area, Medak district, Andhra Pradesh, India. J Indian Acad Geosci 2006, 49(1), 45-8.

Twenty groundwater samples were collected from Patancheru Industrial area, Medak district of Andhra Pradesh from bore wells during summer season and analysed for trace elements like Fe, Cd, Ni, Zn, Pb, Cr, As and Hg. The study indicated that the groundwater is contaminated with trace elements like Cr and Fe. Necessary steps should be taken to curtail the indiscrimate dumps of effluents, hazardous wastes on land and deep well injections of effluents to conserve and restore the ground water resources for future generations.

8 tables, 2 illus, 7 ref

022170   Chandra Sekhar Rao G;Anji Reddy M (NO, Jawaharlal Nehru Technological Univ, Institute of Science and Technol, Kukatpally, Hyderabad-500 072) : Environmental sensitivity assessment of Erimulli Vagu catchment, Musi river basin, A P. J Indian Acad Geosci 2006, 49(1), 11-20.

Study is aimed at predicting the possible environmental impacts due to industrial operations and suggesting environmental safeguards to ensure environmentally sustainable development. This entails reliable baseline data on geology, geo-morphology, hydrogeology, land, air, water - besides attribute data on socio-economic conditions. The study lead to the identification of three industrial sites based on parameters like infrastructure, water availability, nearness to the sensitive area and land availability. The study highlights that there is no scope for setting the water polluting industries due to low surface water flow. Due to high risk of surface water pollution potential, only low surface water polluting industries can be proposed. Based on the High, Medium and Low risk areas for air and surface water polluting activities three development zones have been delineated.

8 tables, 14 ref

022169   Bastia R;Chakraborty S K;Guha J;Mishra B; Gupta P (Reliance Industries Ltd, , Mumbai, Email: ravi_bastia@ril com) : Submarine canyon and deep-water depositional setting in offshore bengal basin. J Geophys 2006, 27(3), 15-26.

Bengal Basin is located along the north east coast of India having an offshore continuation covering approximately an area of 40,000 km² in the Indian waters within the Bay of Bengal. Thick Neogene sedimentary sequence in the study area located in the southern part of offshore Bengal Basin was fed by the Ganges, Brahmaputra, Mahanadi, Subarnarekha, Baitarani and Brahmani rivers. The sediments in the present day shelf area exhibit a complex depositional history with unique juxtaposition of shallow water deltaic sediments and deep water sediments in the form of incised canyons filled up with deep water channel-levee complex deposits. A detailed study was carried out on the morphology and architecture of the deep water depositional elements in this area utilizing around 4000 1km 2D seismic, 1786 km² of 3D seismic and data from 12 drilled wells. Study of special seismic attributes such as spectrally decomposed amplitude and 'sweetness', etc corroborated by wire-line log, mud log and bio-stratigraphic data from the drilled wells lead to the understanding of a depositional mode comprising of the following elements and environments with characteristic morphology and architecture. Shelfal Canyon cut and fill sequences with geometries like - simple "V" shaped cuts with fills in the form of low to moderate sinuous channels or complex canyon ci t and fills"showing multiple canyon cuts caused by mass-wasting with intervening fills in the form of deep water to sub-aerial channels and deltaic progradational deposits. The correct understanding of the complex clastic reservoir architecture in the above depositional setup leads to successful exploration of hydrocarbon entrapped in these reservoirs.

1 table, 10 illus, 18 ref

022168   Bandyopadhyay B K;Charan Singh (India Meteorological Dep, , New Delhi-110 003) : Cyclone track forecast by combining persistence, climatology and synoptic method. Mausam 2006, 57(4), 619-28.

Tropical cyclones are deadly natural disasters. They came large loss of lives and properties. After the landfall, the main damages from cyclones are due to strong winds and storm surges. The forecast of, landfall point is most important to forecasters as well as the agencies who are engaged to take safety measures or rehabilitation works. An attempt has been made to forecast point and time of landfall. Personnel computer based, track forecast models are already in use, in India Meteorological Department's (IMD) different forecasting offices. The existing model requires cyclone track climatology of the basin and past positions of cyclones. Generally pressure falls along the coast, 24 to 36 hours in advance of cyclone's landfall. This parameter, in combination with other two, with equal weightage i.e., 1/3 (Persistence + Climatology + Pressure change) have been used for track forecasting in this study. Results are comparatively superior to the results obtained only by using climatology and persistence. When the system is within 12 to 24 hour prior to landfall, the 24 hour pressure change becomes more important than Climatology and Persistence and 12 hour prior landfall the hourly pressure change helps in pinpointing the landfall point.

4 tables, 8 illus, 10 ref

022167   Balachandran S;Asokan R;Sridharan S (Regional Meteorological Centre, , 50 (New 6) College Road, Chennai-600 006) : Global surface temperature in relation to northeast monsoon rainfall over Tamil Nadu. J Earth Syst Sci 2006, 115(3), 349-62.

The local and teleconnective association between Northeast Monsoon Rainfall (NEMR) over Tamil Nadu and global Surface Temperature Anomalies (STA) is examined using the monthly grid-ded STA data for the period 1901-2004. Various geographical regions which have significant tele-connective signals associated with NEMR are identified. During excess (deficient) NEMR years, it is observed that the meridional gradient in surface air temperature anomalies between Europe and north Africa, in the month of September is directed from the subtropics (higher latitudes) to higher latitudes (subtropics). It is also observed that North Atlantic Oscillation (NAO) during September influences the surface air temperature distribution over north Africa and Europe. Also, the NAO index in January shows significant inverse relationship with NEMR since recent times. The central and eastern equatorial Pacific oceanic regions have significant and consistent positive correlation with.NEMR while the western equatorial region has significant negative correlation with NEMR. A zonal temperature anomaly gradient index (ZTAGI) defined between eastern equatorial Pacific and western equatorial Pacific shows stable significant inverse relationship with NEMR.

7 illus, 23 ref

022166   Babu Lal (Geophysics Div, Geological Survey of India, , Western Region, Jaipur) : Exploration on potash deposit by magnetic and deep electrical resisitivity methods in Nagaur basin, Thar desert, India. J Geophys 2006, 27(3), 47-51.

The regional magnetic (vertical field) and Deep Resistivity Sounding (DRS) surveys conducted in parts of Bikaner district, Rajasthan have brought out structural configuration of the basin and disposition of the Jodhpur sandstone group critical for the exploration of potash-rich deposits. Spectral analysis carried out for 80Km long magnetic profile has yielded three interfaces. The paramagnetic Jodhpur sandstone group overlain by diamagnetic halite is the shallowest magnetic interface while other two deeper interfaces are for granitic and basaltic horizon. The resistive bottom layer obtained in DRS also invariably corresponds to the Jodhpur sandstone group, which forms the floor of evaporite and provides important information for planning exploratory drilling. Magnetic survey has revealed the presence of an N-S trending 'high' located at northeast of Bikaner, suggestive of a ridge type structure, which acts a barrier resulting in the development of Bikaner sub-basin having potash deposit. Further magnetic survey has brought out E-W trending successive step fault with northerly downthrown side. This indicates the deepening of basin towards north. Significantly, Jodhpur formation group has been identified at depth by DRS with indication of halite dominated evaporite in Kalu-Hansera area lying northern parts of the survey area. Geophysical results supported by drilling indicated potash deposits in the deeper part of the basin.

1 table, 8 illus, 10 ref

022165   Abdulla F;Assad T A (Civil Engineering Dep, Science & Technology Univ Jordan, P. O Box 3030, Irbid-221 10 Jordan) : Modeling of groundwater flow for mujib aquifer, Jordan. J Earth Syst Sci 2006, 115(3), 289-97.

Jordan is an arid country with very limited water resources. Groundwater is the main source for its water supply. Mujib aquifer is located in the central part of Jordan and is a major source of drinking water for Amman, Madaba and Karak cities. High abstraction rates from Mujib aquifer during the previous years lead to a major decline in water levels and deterioration in groundwater quality. Therefore, proper groundwater management of Mujib aquifer is necessary; and groundwater flow modeling is essential for proper management. For this purpose, Modflow was used to build a groundwater flow model to simulate the behavior of the flow system under different stresses. The model was calibrated for steady state condition by matching observed and simulated initial head counter lines. Drawdown data for the period 1985-1995 were used to calibrate the transient model by matching simulated drawdown with the observed one. Then, the transient model was validated by using drawdown data for the period 1996-2002. The results of the calibrated model showed that the horizontal hydraulic conductivity of the B2/A7 aquifer ranges between 0.001 and 40m/d. Calibrated specific yield ranges from 0.0001 to 0.15. The water balance for the steady state condition of Mujib aquifer indicated that the total annual direct recharge is 20.4 x 10⁶m³, the total annual inflow is 13.0 x 10⁶ m³, springs discharge is 15.3 x 10⁶ m³, and total annual outflow is 18.7 x 10⁶ m³. Different scenarios were considered to predict aquifer system response under different conditions. The results of the sensitivity analysis show that the model is highly sensitive to horizontal hydraulic conductivity and anisotropy and with lower level to the recharge rates. Also the model is sensitive to specific yield.

1 table, 9 illus, 6 ref

021327   Singh J P;Verma N;Mishra T P (Zoology Dep, K.S. Saket P.G. College, Ayodhya, Faizabad, U.P.) : Physico-chemical characteristics of darban lake (Ambedkar Nagar, (Uttar Pradesh): temperature and alkalinity. J advd Zool 2006, 27(2), 98-100.

In the present investigation temperature and total alkalinity with pH data of the Darban lake, were collected from littoral and benthic zones for a period of twelve months from July 2004 to June 2005. pH has been an important index in determining the ecological condition of this lake. Eutrophic lakes like Darban have calcareous as well as non calcareous water with high pH effecting alkalinity.

1 table, 12 ref

021326   Singa Raju V;Shah B M (Geological Survey of India, , Hyderabad-500 068, Email: v_singaraju@yahoo.com) : Holocene marine transgression in the Eleru delta, East Godavari district, Andhra Pradesh. J Geol Soc India 2006, 67(5), 605-8.

Thick sequence of Upper Pleistocene and Holocene litho-assemblages (50 m) are recorded while evaluating the Quaternary geology of the Eleru delta. Classified under fluvial, marine and aeolian facies, these sediment assemblages indicate the transgressive and regressive phases in the process of coastal evolution. The marine regressive phase is indicated by predominant fluvial sediment characteristics in these assemblages during Upper Pleistocene times. The sediment characteristics of the channel-fill deposits are suggestive of prevalence of aggraded fluvial channels that might be consequent to the rise in the sea level, subsequent to the last glacial maximum (18000 years B.P). The sea level reached its peak during climatic optimum (6500 years B.P). The landward geomorphological observations suggest a palaeo-shoreline which existed at around 2.5 km away from the present coastline. However, the present systematic evaluation of the sediment parameters and microfossils in the coastal litho-assemblages brought to light a palaeo-coastline extending even beyond 4 km from the present coastline. This transgressive marine phase is typified by the consistent predominance of organic matter-rich, greyish black silty clays right up to the inferred coastline. The marine micro-fauna, represented by benthic and planktonic foraminifera, ostrocods and pteropods, in these clays further strengthens this observation. The recurrence of dominant fluvial processes along the coast might be due to subsequent gradual recession of the sea. The presence of the palaeo-beach ridges and present beach ridge marks the standstill points in the upper Holocene coastal evolution.

1 illus, 4 ref

021325   Satyanarayanan M;Balaram V;Gnaneshwar Rao T; Dasaram B;Ramesh S L;Mathur R;Drolia R K (Geochemistry Div, National Geophysical Research Institute, Uppal Road, Hyderabad-500 007, Email: icpmslabngri@rediffmail.com) : Determination of trace metals in seawater by ICP-MS after preconcentration and matrix separation by dithiocarbamate complexes. Indian J Mar Sci 2007, 36(1), 71-5.

Rapid single extraction procedure using dithiocarbamate complexing agent in methyl-isobutyl ketone (MIBK) organic phase and acid exchange back-extraction is described for the simultaneous quantitative preconcentration of Fe, Mn, V, Cr, Ni, Co, Cu, Zn, As, Mo, Cd, Pb and U in seawater followed by its determination by inductively coupled plasma mass spectrometry (ICP-MS). This method gives quantitative recoveries for all above metals at pH 4.1-6.4. A matrix matching seawater certified reference material (CRM), NASS-5, was used for calibration so as to minimize the matrix and other associated effects. Blanks and detection limits were in ng/1 range. The method gives a recovery of 94-100% for 100 ml sample, facilitating the rapid and interference-free analysis of seawater samples. Excellent agreement was obtained with the certified values of another seawater CRM, CASS-4, when it was analyzed as an unknown. The major advantage of this procedure is that rapid analysis can be performed for a wide range of metals from relatively small samples.

4 tables, 24 ref

021324   Rao K N (Geo-Engineering Dep, Andhra Univ, Visakhapatnam-530 003) : Coastal morphodynamics and asymmetric development of the Godavari delta: implications to facies architecture and reservoir heterogeneity. J Geol Soc India 2006, 67(5), 609-17.

The Godavari delta on the east coast of India exhibits wave-influenced morphologies by the presence of a number of spits and barrier islands at its two active distributary lobes of the Gautami and the Vasishta. The most prominent of them is the 21-km-long Kakinada spit, which in its initial stages in the late nineteenth century had even deflected the Gautami course. As a result, the Gautami has built an extensive bayhead delta behind the spit. The 1965 satellite imagery showed several other smaller spits, especially at the southwestern side of the Gautami mouth and the northeastern side of the Vasishta, whereas barrier islands that are welded to the main coast by the backbarrier mudflats occur on the other sides of the mouths. A comparison of a series of satellite imagery showed that the 15-km-long shoreline in the central part of the delta in between the Gautami and the Vasishta lobes retreated landward by about 500 m during the past four decades. The material eroded from this part, presumably, drifted in both the directions - northeastward toward the Gautami and southwestward toward the Vasishta. As the river effluent plumes act like groynes, the material drifted alongshore from the central part toward both the lobes is deposited at the respective updrift sides of the distributary mouths forming into spits, whereas the river-borne sediments are deposited at the downdrift sides, initially as bars that emerge as barrier islands, followed by the backbarrier-bay-filling with riverine muds. The presence of closely spaced beach ridges on the updrift side, and wide mudflats interspersed with narrow sand bodies on the downdrift side, that especially characterize the Vasishta lobe, indicate asymmetry of the sedimentation processes and facies architecture. The likely occurrence of better quality reservoir facies on the updrift side than on the downdrift side, besides the presumable shore-parallel than shore-normal prodelta clinoforms of the bayhead delta in the Kakinada Bay reflect the possible reservoir heterogeneity in the Godavari sedimentary basin, considering that similar asymmetries possibly prevailed in the geological past.

6 illus, 13 ref

021323   Ramasamy S M;Saravanavel J;Selvakumar R (Centre for Remote, Sensing School of Geosciences, Bharathidsan Univ, Tiruchirappalli-620 023, Email: smrsamy@gmail.com) : Late holocene geomorphic evolution of Cauvery delta, Tami Nadu. J Geol Soc India 2006, 67(5), 649-57.

Present day flow of Cauvery river is confined to the northernmost rim of the delta as river Coleroon. On the basis of the archaeological, epigraphic and historical data analysed earlier and the¹⁴C dating carried out recently, the authors infer that the age of the delta may vary from 2300 Y.B.P. (Years Before Present) to 750 Y.B.P. and the age of the palaeochannels are also younging from 2300 Y.B.P. in the south to 750 Y.B.P. in the north. In the southern part of the Cauvery delta, the Mio-Pliocene Sandstone of Pattukottai-Mannargudi area is undergoing upliftment along N-S faults. On the basis of the rapid land progradation during 6085±233 Y.B.P. - 1020±80 Y.B.P. in Vedaranniyam coast, it is visualized that the Mio-Piiocene Sandstone must be undergoing upliftment significantly since 6100 Y.B.P. onwards. On the basis of the occurrence of older palaeochannels in the south, the gradual younging palaeochannels towards the north and the land emergence in the south of the Cauvery delta in Pattukottai - Mannargudi area, it is concluded that the distributary drainages of river Cauvery would have become sequentially defunct/shifted from south to north and finally the mother channel Cauvery also would have been pushed towards north to reach the present tract of Coleroon river. The thinner palaeochannels in the south and the gradual wider palaeochannels in the north of the delta further indicate that as the land was already undergoing emergence in the south even before the river Cauvery had entered into Thanjavur plains, the river could not comfortably spread its distributaries in the south. Hence, the southern distributaries, after a brief flow, would have started drying sequentially from south to north during 2300-750 Y.B.P. thereby the floodwater of each of the southern distributary channel would have been pushed to its successive northern counterpart, i.e. the southern distributary (say 1), pushing its water to its immediate northern counterpart (say 2), then the combined flow of 1 and 2 pushing the water to 3 and so on. The anomalous eyed drainage and its modifications during the last 50-60 years and compressed meanders in Coleroon river, deflected drainages in Palam Cauvery, truncation and punctuation of beach ridges by the E-W faults along the N-S coast and such faults acting as pathways for the sub parallel creeks indicate vibrant Late Holocene geological history predominated by the tectonic movements in Cauvery delta.

3 illus, 30 ref

021322   Ramasamy S M (Centre for Remote, Sensing School of Geosciences, Bharathidasan Univ, Khajamalai Campus Tiruchirappalli-620 023, Tamil Nadu, Email: smrsamy@gmail.com) : Holocene tectonics revealed by Tamil Nadu delta, India. J Geol Soc India 2006, 67(5), 637-48.

Overall geological histories of the Quaternary deltas of all over the world have been studied considerably, to understand the evolution, eustatic - isostatic changes, land - ocean interactive phenomenon, resources, environment etc. But tectonic signatures of these deltas have been less studied, though these have significance in understanding the natural resources, environment and evaluation of natural disasters. In this context, as the state of Tamil Nadu is a low easterly gradient plain, all the easterly flowing rivers have developed well evolved geomorphic features related to youthful, mature and old stages. Such old stages of the rivers are marked by the spectacular development of deltas. These deltas of Tamil Nadu have been studied in detail for understanding the tectonics with the help of visibly seen tectonic and geomorphic features in satellite based remote sensing and ground based data sets. The study has revealed that the upper age limit/ages of these deltas are probably of Middle to Late Holocene and the various tectonic and geomorphic anomalies observed in these deltas obviously indicate the tectonic processes/phenomena that prevailed during Middle Holocene - till date. The Proto Cauvery delta of Chennai region is witnessing ongoing NE-SW sinistral, NW-SE dextral and E-W vertical tectonic activities. The streams in Ponnaiyar delta are showing persistent southerly migration due to the probable ongoing land subsidence along NE-SW faults in the southern part of the delta. The Cauvery river which has originally developed a broad bird-foot shaped - arcuate delta, has undergone a phase of anticlockwise rotational migration and stabilized in the northern rim of the delta as Coleroon river during 2300-750 Y.B.P. due to the ongoing tectonic emergence in the south of the delta almost since the last 6000 years or so. The Vellar river, in deltaic regime, shows northerly migration due to E-W grabening in the northern part of the delta. Vaigai and Manimuttar rivers are again migrating northerly in their deltaic regions due to the probable land arching to the south of their present day flow. Thus, the paper discusses the post deltaic/Middle - Late Holocene geological processes of Tamil Nadu deltas which are predominated by tectonic activities.

7 illus, 41 ref

021321   Rajesh Kannah T;Natarajan R (Mechanical Engineering Dep, P.R. Engineering College, Thanjavur-613 403, Email: rajeshkannah99@hormail.com) : Hydrodynamics of external turret moored FPSO system. Indian J Mar Sci 2007, 36(1), 27-34.

Dynamic behavior of a 1:100 scale model of 140000 DWT turret moored FPSO system for three operating conditions, i.e., 40% DWT, 7037 DWT and 100% DWT with three hawser lengths, i.e., 15%, 20%and 25% of the length of FPSO is discussed in this paper. The model tests were conducted in the 2 m wide wave flume under regular waves for the wave frequencies ranging from 0.55 Hz to 1.25 Hz in steps of 0.04 Hz at a water depth of 1 m for head sea condition. The motion response was measured using rotary type potentiometers. The mooring and hawser line forces were measured using specially fabricated ring type load cells. The test results of the forces and motion response were analyzed for the three hawser lengths at three operating conditions. From the analysis of the results, it is found that the tension in the forward mooring line is more than the tension in the aft mooring line for all loading conditions and hawser lengths. It is also observed that the tension of the forward mooring line decreases with increase in hawser length. The mooring tension is maximum for all hawser lengths at the full load condition.

5 illus, 6 ref

021320   Mahalik N K (NO, , C-73, H. I. G Duplex, Baramunda Housing Board Colony, Bhubaneswar-751 003) : Study of the morphological features and bore hole cuttings in understanding the evolution and geological processes in mahanadi delta, east coast of India. J Geol Soc India 2006, 67(5), 595-603.

Mahanadi delta is a classical arcuate delta along the east coast of India formed around the confluence of river Mahanadi with the Bay of Bengal in Orissa state. It was formed during the Upper Pleistocene-Holocene period overlying a dark grey shell bearing sequence with a distinct unconformity. The subaerial part of the delta has been the product of sedimentation under fluvial and fluvio-marine environments where a variety of depositional energy systems were operative e.g. river flow, sea waves, tides, littoral drift and wind. A variety of geomorphological features e.g., river channels, point bars, palaeo-channels, natural levees, flood plains, beaches, palaeo-beach ridges, tidal flats, tidal swamps, tidal creeks, spits, bars, lagoons and aeolian sand dunes have been observed and studied. These morphologic features have distinct relation between energy conditions of deposition, sediment make up, typographic level and land use. Three shell bearing marine horizons have been observed in most borehole cuttings of which the bottom most horizon is of pre-Pleistocene age while the rest two are within the deltaic sequence. The bottom most marine horizon is characterised by the presence of iron silicate oolites and Oliva-Glycimeris shell association. Delta building has taken place by shifting of distributary channels and fluctuation of sea level. Four fluvial and marine stages have been identified e.g., Kathjodi-Burdha-Prachi-Debi fluvial stages interacting with four corresponding strand lines. In general the sea was receding during the delta formation except a short transgression during the second stage of the deltaic evolution. The marine marginal part of Mahanadi Delta shows three distinct morphologic makeup: (1) the southwestern sector is characterized by thick wide sandy beaches, (2) the central sector by narrow beach and alternating sequence of parallel paleo-beach ridges and tidal swales and (3) the northern sector by tidal flats and mangrove swamps. This is explained by the role of the prevalent wind in shaping coastal geomorphology. This aspect is very typical of Mahanadi Delta.

6 illus, 3 table, 14 ref

021319   Gadi S D;Rajashekhar K P (Applied Zoology Dep, Mangalore Univ, Mangalore-574 199, Email: subhadragadi@yahoo.com) : Changes in inter-tidal foraminifera following tsunami inundation of indian coast. Indian J Mar Sci 2007, 36(1), 35-42.

To ascertain whether severe Indian Ocean tsunami of 26 December 2004 along the coast of India generated a change in diversity of foraminifera, inter-tidal post- tsunami samples were collected between 3rd and 4th January 2005 and compared with shore samples prior to tsunami, collected during an ongoing survey between 11 and 12th December 2004. A total of 24 sediment samples from different sites were analysed for foraminiferal diversity and also for sediment characteristics. Total foraminiferal number, organic matter and calcium carbonate showed considerable increase in post-tsunami samples. Significant changes in diversity were observed as indicated by Shannon Diversity and Morisita-Horn Similarity indices. As many as 41 species belonging to 20 genera, 14 families and 3 sub-orders were identified from pre-tsunami samples, while 71 species belonging to 34 genera, 17 families and 3 sub-orders were recorded from post-tsunami samples. A marked increase in foraminiferal relicts was observed in post-tsunami samples, suggesting a large-scale transportation of deeper water, offshore sediment to intertidal zone. Thus, geological events may cause abrupt changes in foraminiferal abundance and diversity of sediments.

3 illus, 4 tables, 25 ref

021318   Evren Mazlum R;Seyhan K (Faculty of Fisheries, University of Rize, Main Campus 53100, Rize, Turkey, Email: seyhan@ktu.edu.tr) : Gastric emptying, clearance rate, feeding periodicity and food consumption of the black sea jelly fish, Mnemiopsis leidyi (agassiz). Indian J Mar Sci 2007, 36(1), 59-64.

Feeding physiology of Mnemiopsis leidyi fed on Artemia salina were investigated under laboratory conditions. Multifactorial experimental designs were used to study the factors affecting gastrovascular emptying in M. leidyi. A high correlation was found between number of prey ingested and digestion time. Modelling of gastric emptying time (GET, h.) of M. leidyi fed on A. salina was attempted to describe the effect of animal size, prey number, container volume and temperature on the digestion time. GET= 3.42- 0.00636 W + 0.0121 pN-0.155 V-0.00983 T. The clearance-rate was significantly affected by container volume and the feeding time. Multiple regression was attemped to model clearance rate: CR = 0.366 + 0.377 V-0.197 H. Studying the feeding periodicity over a 24 h period, it was found that under laboratory condition and with readily available prey, M. leidyi feeds continuously except for the early hours of the day. Under such conditions medium size Mnemiompsis (11.36±0.38g) consumed between 1286 and 2741 artemia daily. With the models of gastric emptying time (GET) and clearance rate (CR) presented in this study, quantitative assessment of the predatory impact of the ctenophore Mnemiopsis leidyi on the Black Sea ecosystem can be faciliated.

4 illus, 2 tables, 30 ref

021317   Dineshbabu A P;Manissery J K (NO, Mangalore Research Centre of Central Marine Fisheries Research Institu, Mangalore-575 001, Email: dineshap@rediffmail.com) : Morphometric relationship and growth of the 'ridge back shrimp' Solenocera choprai (decapoda/crustacea) from mangalore (southwest coast of India). Indian J Mar Sci 2007, 36(1), 65-70.

Ridge back shrimp', Solenocera choprai, caught from a depth of 70 to 100 m off Mangalore, has been contributing substantially to the commercial fishery of the coast from 1993 onwards. During 2002, the species formed <62> 50% of the total shrimp landing of Mangalore fisheries harbour (2746 t). Since it is a non-conventional species to commercial fishery, the detailed information about the biology and population characteristics of the species is reported for the first time. The present paper deals with the morphometric relationship like length-weight relationship and carapace length-total length relationship of the species which will be useful in studying the population dynamics of the species. The life span of S. choprai is about 30 months and males and females attain a total length of 66 mm and 83 mm at the end of 12 months, 88 mm and 109 mm at the end of 24 months respectively. The results of the study will help in formulation of strategies for the management of this resource in terms of regulation of mesh size and fishing pressure.

4 illus, 14 ref

021316   Dhana Raju R (NO, , 6-3-124, Hastinapuri, Sainikpuri P. O., Secunderabad-500 094) : Delta region of the east coast of India: a potential target for explorationof heavy minerals. J Geol Soc India 2006, 67(5), 669-74.

India has a coastline of over 7,500 km, with a large delta-region behind it along its East Coast and practically no delta along its West Coast. Scientists of the Atomic Minerals Directorate (AMD) for I Exploration and Research of the Department of Atomic Energy, by their more than 5-decade old reconnoitory surveys and detailed exploration, have identified many dune and beach placer Heavy Minerals (HMs: ilmenite, rutile, monazite, zircon, garnet, sillimanite, etc.) sand deposits along the East Coast in the States of Orissa, Andhra Pradesh and Tamil Nadu. A few big deposits amongst these are being exploited by some Govt. and Private agencies. As these HMs have numerous industrial, including hi-tech, applications with further requirement to establish their additional exploitable resource-base, it is time to explore for concealed deposits in the hitherto unexplored areas. In this backdrop, it is suggested that the delta-region of the East Coast could be a target. Within this, strandplain behind the shoreline' and prograding del as of the Rivers like Mahanadi and Godavari, which are characterized by palaeo-strandlines associated with palaeo-said bodies, all within a zone of <126>30 km inland from the present day shoreline, appear to be potential for such exploratioi . This is supported by AMD's recent identification of notable concentration (2-64 wt.%; average 16 wt.%) of HMs in palaeo-sand ridges in the Paradeep sector of Orissa and of lesser concentration in parts of the Krishna-Godavari delta in Andhra Pradesh. An exploration programme, involving sequentially (a) mapping of the areas of strandplain and prograding deltas within <126>30 km inland from the present day shoreline by high-resolution satellite imageries and aerial photographs, (b) shallow seismic survey, (c) low-flying aero-radiometric/-magnetic surveys, (d) reconnoitory ground survey and sampling, (e) sub-surface exploration, first by reconnoitory and then by exploratory-evaluation drilling and (0 determination of grade, mode and resource of HMs, is proposed for this purpose.

2 illus, 29 ref

021315   Das S (NO, , Central, Ground Water Board, M 901, HM Tambourine, No. 28 Jaraganahalli, J P Nagar 6th Phase, Kanakpura Main Road, Banga, Email: subhajyoti_das@hotmail.com) : Aquifer systems in Mahanadi delta - occurrence, potential and quality characteristics. J Geol Soc India 2006, 67(5), 675-92.

Mahanadi delta occurs on the east coast of India, in the state of Orissa. Groundwater is a major source of fresh water in the area. The permeable sand and gravel layers in the unconsolidated sediments form the potential aquifers, having a cumulative thickness of 15-65 m. Groundwater occurs under both confined and unconfined conditions. The depth to water table varies from less than 2 m to 4 m below ground level. The well yields vary from less than 35 m³/hr in the basin marginal areas in the west to more than 270m³/hr in the coastal plains in the east. K and S values of the deeper aquifers are in the range of 5-330 m/day and 1.75xlO^-2-8.81xlO^-6 respectively. But the aquifers are beset with salinity hazards. The saline and fresh water profile is non-uniform with freshwater overlying/underlying or alternating with saline zones, or with saline water at all depths. However, the ground water quality is in general fresh (EC<60>1600 μS/cm) and suitable for all uses, except in areas having high (salinity, and in localized pockets showing high concentration of iron, fluoride, nitrate and sulphate being injurious to health. The annual groundwater recharge is of the order of 351069 HAM, with gross draft of 39688 HAM. The paper presents the complex hydrogeoloeical set-up in the delta and outlines groundwater development potentials.

8 illus, 6 tables, 24 ref

021314   Bhattacharjee D;Ghosh S K;Roychaudhuri S; Biswas N R (O P E. C. I, Marine Wing, Geologicl Survey of India, Kolkata-700 032) : Quaternary sedimentary environments in ganga prodeltaic region, northern part of bay of Bengal. J Geol Soc India 2006, 67(5), 585-93.

Sedimentological characteristics, fossil contents and geochemical behaviour of the seabed sediments of the inner continental shelf region off Ganga river mouth, Bay of Bengal reveal some aspects of macrotidal deltaic environment. Seabed sediments between 11 m and 45m water depths, covering an area of about 1450 sq km, indicate the presence of three characteristic domains from West to East each having specific features. Relict calcareous/ferruginous concretions, oolites, pellets as well as older skeletal matters of bivalve, gastropod, scaphopod and benthic foraminifera occur in the sediments of western domain at about 20 to 35m water depths. The relict taxa generally show worn out tests and ferruginous coated surfaces. The central domain is made up of sand and sandy clay with common occurrence of foraminifera. Some carbonaceous material and minor disseminated grains of heavy minerals are commonly associated with these sediments. The eastern domain is covered by silt and silty sand, mainly composed of quartz, feldspar, muscovite and biotite, which represent recent sediments of Ganga delta. Gastropod, bivalve, scaphopod, burrows, echinoid spines and benthic foraminifera are abundant in the western, poor in the central and rare in the eastern domain. However, Astrorotalia trispinosa and Astrorotalia-Ammonia are two dominant foraminiferal assemblages in this entire region. They are large and well ornamented in the western part compared to those in the east. The subrounded ill sorted concretions, oolites and pellets along with the above insitu biota in the western domain suggest very shallow sedimentary facies, probably deposited in a littoral condition during the Late Pleistocene time. On the other hand, the composition and nature of sediments and distinct morphological changes of taxa in the eastern domain corroborates that the Ganga delta is under a process of continuous progradation during the Holocene time.

4 illus, 3 table, 30 ref

021313   Bhandari A;Singh S D (Geology Div, Paleontology Laboratory, K. D. M. I. P. E., Oil and Natural Gas Corpo, Dehra Dun-248 195, Uttranchal, Email: bhandarianil88@yahoo.co.in) : Recent Ostracoda from the Deltaic subenvironment and shallow inner shelf, east coast of India. J Geol Soc India 2006, 67(5), 659-68.

Total of 24 ostracode species belonging to 14 genera are recorded from the Krishna River estuary and Gautami-Godavari estuary. The study reveals that the upper estuary is dominated by thin shelled Hemicytheridea andhraensis (Annapurna and Rama Sarma) and few fresh water ostracodes having low frequency (05) and diversity (2-3). The lower estuary ostracodes have some influence of marine ostracodes and comparatively high frequency (50-60) and diversity (08). Ostracodes recorded from the lower estuary are represented 1 by Kallingella mckenziei Jain, Neosinocythere dekrooni (Kingma), Tanella gracilis Kingma, Neomonoceratina inqua (Brady), Phlycetenophora orientalis (Brady) along with Hemicytheridea andhraensis (Annapurna and Rama Sarma). This study will be helpful in understanding and recognizing paleo subenvironment and thus helpful in developing precise paleodepositonal model which will give further lead to hydrocarbon exploration.

2 illus, 1 table, 19 ref

021312   Bastia R;Pankaj Singh;Nayak P (NO, Reliance Industries Ltd., Mumbai-400 709) : Linking Shelf delta to deep water; Krishna-Godavari basin. J Geol Soc India 2006, 67(5), 619-28.

Krishna-Godavari basin located on the east coast of India represents a complete depositional setting with well defined shelf to shelf edge delta to deep water. This basin has a lateral stretch of about 500 km and extends more than 200 km from the coast into the deep sea. This basin has been fed dominantly by Krishna and Godavari river systems along with numerous tributaries. The area is adequately covered by several vintages of 2D and focused 3D seismic data which has been primarily used for subsurface imaging. Further the depositional units have been identified by interpreting seismic stratal pattern and the facies distribution in a sequence stratigraphic framework. This is supplemented by information from wireline logs and cores. The gradational facies pattern, sequence boundary, transgressive surface, maximum flooding surface, channel architecture etc. have been demonstrated in selected seismic sections for developing the concept. Linkng the depositional elements from shelf to deep water in a sequence stratigraphic framework for this basin is a good guide for hydrocarbon exploration.

16 illus, 7 ref

021311   Bastia R;Chakraborty S K;Mishra B S (NO, Reliance Industries Ltd., Mumbai) : Depositional architecture of mio-pliocene sequences in offshore Bengal basin. J Geol Soc India 2006, 67(5), 575-83.

Detailed study was carried out on the morphology and architecture of the different depositional elements and units utilizing different vintages of 2D/3D seismic and data from drilled wells. Geo-Body mapping and attribute studies reveal finer details of the complex system. Special seismic attributes such as spectrally decomposed amplitude, waveform classifier and 'sweetness' (amplitude by square root of frequency) were quiet helpful in understanding the morphological details of the system. The following depositional elements have bee I brought out. Delta-Distributary channel complex associated with incised valley and tidal inlets. Shelfal Canyon cut and fill sequences: Simple canyon fills: Simple "V" shaped cuts with fills in the form of low to moderate sinuous channels. Complex Canyon cut and fills: Numerous, repeated canyon cuts caused by mass-wasting with intervening fills in the form of deep water to sub-aerial channels and deltaic progradational deposits. Deep-Water Channel Complex: Fed by large canyon up-dip. These depositional elements do not form part of the canyon fill, but occur down-dip. The sand and silt lithological distribution in the above depositional complexes form the predominant hydrocarbon reservoir units. The numerous reservoir bodies within the above units of varying lateral and vertical extents, are expected to hold the future exploration potential in this frontier basin.

22 illus, 11 ref

021310   Balaji R;Sannasiraj S A;Sundar V (Ocean Engineering Dep, Indian Institute of Technology Madras, Chennai-600 036, Email: sasraj@iitm.ac.in) : Physical model studies on discus buoy in regular, random and double peak spectral waves. Indian J Mar Sci 2007, 36(1), 18-26.

Experimental investigation was carried out to study the motion characteristics of a data buoy under regular as well as uni-modal and bimodal sea states. For the present study, the 2.2 m diameter discus shaped data buoy of India's National Data Buoy Programme (NDBP) was scale modeled and, its heave and pitch motions were measured by two methods using potentiometers and motion capturing non contact infra-red cameras. The response amplitude operators obtained through the present experiment are proved to be predicting the different ranges of sea states well. The details of the model, instrumentation, testing conditions and the response amplitude operators for heave and pitch as a function of excitation frequency are presented and discussed in this paper.

10 illus, 10 ref

021309   Babu P V L P (NO, , 218, Lakshmi Apts., 6-1-1 Padmaraonagar, Secunderabad-500 025) : On the ancient delta of India. J Geol Soc India 2006, 67(5), 569-74.

Sedimentary basins of India have been geologically, geophysically and gepchemically surveyed for a long time. In the course of these studies several deltaic sedimentary units are identified in the surface and subsurface areas of these sedimentary basin Ancient deltas are recognized in the subsurface by the presence of thick clastic sequences showing repeated cycles of upward coarsening grain size, each cycle should begin at the base with a marine shale which passes up through silts into coarser freshwater channel sands at the top. Deltaic sequence from land to sea is represented by fluviatile coastal plain, lagoonal and tidal flat complex, barrier island and offshore marine shelf Ancient Deltas are identified in several sedimentary basins of India. Jurassic to Cretaceous, Paleocene to Miocene times witnessed deltaic conditions of deposition in Jaisalmer, Kutch, Saurashtra, Cambay basins on the western part of India and Cauvery, Krishna, Godavari, Mahanadi and lower Ganga basins on the eastern part of lndia. Marine shales (potential source rocks) which interfinger upslope with sandstones (potential reservoirs) in deltaic sequences (cyclically repeated) are significant in oil exploration.

1 illus, 7 ref

021308   Anand Rao M;Ramamurthy S;Shah B M;Hanumantha Rao V (Geological Survey of India, , Hyderabad, Email: anandamrao@yahoo.com, ramasoma@yahoo.com) : Recent morphological changes along the Krishna delta shoreline. J Geol Soc India 2006, 67(5), 629-35.

Geomorphic expression of the variety of landform units exposed in the Krishna Delta is a manifestation of complex interplay of riverine and marine processes in space and time. The dominance of fluvial processes is largely responsible for the progradation of the delta. This is evidenced by the presence of a series of palaeo-delta lobes and strand plains across the deltaic plain. Systematic study of geomorphic maps, aerial photographs, toposheets spanning a period of eight decades and satellite images (IRS- 21D) indicates operation of highly dynamic nature of coastal processes. Superimposition of data sets of different periods, clearly exhibits remarkable changes in the configuration of the lower deltaic plain. It is observed that towards the eastern margin and in close proximity to the easternmost distributary a substantial part of about 1.5 km has been eroded away. At the same time the western part of the lower deltaic plain shows accretion. There is an enlargement and further westward growth of the spit. The width of the spit which was approximately 120m during the 1920s had grown to 620m in the 1970s and in the year 2001 its width is around 1km. Another spit with bars enclosing a lagoon, which is a new development, was observed. Impact and possible causes of the changes in the deltaic region on environment are also discussed. The attempt here is to highlight only the morphological changes along the delta coast.

4 illus, 3 tables, 15 ref

020363   Vivekanandan N (Central Water and Power Res Station, , Pune-411 024) : Intercomparison of evaluation of low-flow characteristics of streams using statistical modelling approach. Mausam 2006, 57(2), 291-300.

Low-flow characteristics of streams are used in planning and design of water supplies, analysing environmental and economic impacts, modelling stream water quality, regulating instream uses, and improving the general level of understanding of natural and regulated stream systems. Statistical modelling approach involving standard probability distributions of Box-Cox Transformation, Lognormal, Log Pearson Type III and Pearson Type III and Weibull are used to determine low-flow characteristics for different return periods for three different river basins, namely, Mahanadi, Godavari and Narmada. Chi-square (χ<^>2) test is used for comparison of low-flow characteristics of different stream. The paper presents that Lognormal, Weibull and Pearson Type III distributions are found to be suitable for determination of low-flow characteristics for rivers Narmada, Mahanadi and Godavari respectively. Low-flow frequency curves are also developed and presented.