010477   Bidokhti A A A;Gharaylou M;Pegahfar N; Sabetghadam S;Rezazadeh M (Institute of Geophysics, Tehran Univ, Tehran-14155-6466, Iran, Email: gharaylo@ut.ac.ir) : Characteristics of exttreme dust events observed over two urban areas in Iran. J Earth Syst Sci 2016, 125(2), 431-42.

Determination of dust loading in the atmosphere is important not only from the public health point of view, but also for regional climate changes. The present study focuses on the characteristics of two major dust events for two urban areas in Iran, Kermanshah and Tehran, over the period of 4 years from 2006 to 2009. To detect extreme dust outbreaks, various datasets including synoptic data, dust concentration, reanalysis data and numerical results of WRF and HYSPLIT models were used. The weather maps demonstrate that for these events dusts are mainly generated when wind velocity is high and humidity is low in the lower troposphere and the region is under the influence of a thermal low. The event lasts until the atmospheric stability prevails and the surface wind speed weakens. The thermal low nature of the synoptic conditions of these major events is also responsible for deep boundary layer development with its thermals affecting the vertical dust flux over the region. Trajectory studies show that the dust events originated from deserts in Iraq and Syria and transported towards Iran. The main distinction between the two types of mobilizations seems to affect the dust concentrations in the Tehran urban area.

8 illus, 4 tables, 55 ref

010476   Ballav S;Pata P K;Sawa Y;Matsueda H;Adachi A; Onogi S;Takigawa M;De U K (School of Environmental Studies, Jadavpur Univ, Kolkata-700 032, Email: srabanti_ballav@yahoo.co.in) : Simulation of CO₂ concentrations at Tsukuba tall tower using WRF-CO₂ tracer transport model. J Earth Syst Sci 2016, 125(1), 47-64.

Simulation of carbon dioxide (CO₂) at hourly/weekly intervals and fine vertical resolution at the continental or coastal sites is challenging because of coarse horizontal resolution of global transport models. Here the regional Weather Research and Forecasting (WRF) model coupled with atmospheric chemistry is adopted for simulating atmospheric CO₂ (hereinafter WRF-CO₂) in nonreactive chemical tracer mode. Model results at horizontal resolution of 27 x 27 km and 31 vertical levels are compared with hourly CO₂ measurements from Tsukuba, Japan (36.05øN, 140.13 oE) at tower heights of 25 and 200 m for the entire year 2002. Using the wind rose analysis, we find that the fossil fuel emission signal from the megacity Tokyo dominates the diurnal, synoptic and seasonal variations observed at Tsukuba. Contribution of terrestrial biosphere fluxes is of secondary importance for CO₂ concentration variability. The phase of synoptic scale variability in CO₂ at both heights are remarkably well simulated the observed data (correlation coefficient <62>0.70) for the entire year. The simulations of monthly mean diurnal cycles are in better agreement with the measurements at lower height compared to that at the upper height. The modelled vertical CO₂ gradients are generally greater than the observed vertical gradient. Sensitivity studies show that the simulation of observed vertical gradient can be improved by increasing the number of vertical levels from 31 in the model WRF to 37 (4 below 200 m) and using the Mellor-Yamada-Janjic planetary boundary scheme. These results have large implications for improving transport model simulation of CO₂ over the continental sites.

10 illus, 1 table, 36 ref

010475   Asfahani J;Al-HENT R;Aissa M (Atomic Energy Commission, , P.O. Box 6091, Domascus, Syria, Email: cscientific@aec.org.sy) : Favourable uranium-phosphate exploration trends guided by the application of statistical factor analysis technique on the aerial gamma spectrometric data in Syrian desert (Area-1), Syria. J Earth Syst Sci 2016, 125(1), 203-16.

A scored lithological map including 10 radiometric units is established through applying factor analysis approach to aerial spectrometric data of Area-1, Syrian desert, which includes Ur, eU, eTh, K%, eU/eTh, eU/K%, and eTh/K%. A model of four rotated factors F1, F2, F3, and F4 is adapted for representing 234,829 data measured points in Area-1, where 86% of total data variance is interpreted. A geological scored pseudo-section derived from the lithological scored map is established and analyzed in order to show the possible stratigraphic and structural traps for uranium occurrences associated with phosphate deposits in the studied Area-1. These identified traps presented in this paper need detailed investigation and must be necessarily followed and checked by ground validations and subsurface well logging, in order to locate the anomalous uranium occurrences and explore with more confidence and certitude their characteristics as a function of depth.

7 illus, 6 tables, 28 ref

010474   Anand S P;Erram V C;Patil J D;Pawar N J;Gupta G;Suryavanshi R A (Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai-410 218, Email: aerospl@yahoo.co.uk) : Structural mapping of Chikotra river basin in the deccan volcanic province of Maharashtra, India from ground magnetic data. J Earth Syst Sci 2016, 125(2), 301-10.

Ground magnetic data collected over Chikotra River in the peripheral region of Deccan Volcanic Province (DVP) of Maharashtra located in Kolhapur district was analysed to throw light on the structural pattern and distribution of magnetic sources within the basin. In order to isolate the magnetic anomalies showing varying trend and amplitude, several transformation operations including wavelength filtering, and upward continuation has been carried out on the reduced to pole anomaly map. Qualitative interpretation of these products help identify the distribution of magnetic sources, viz., the Deccan basalts, dolerite intrusives and older greenstone and schist belts in the subsurface. Present study suggests that the Chikotra basin is composed of three structural units; a NE-SW unit superposed on deeper NW-SE unit with randomly distributed trap flows on the surface. One of the major outcome of the present study is the delineation of almost 900-m thick Proterozoic Kaladgi sediments below the Deccan trap flows. The NE-SW magnetic sources may probably represent intrusives into the Kaladgi sediments, while the deeper NW-SE trends are interpreted as the northward extension of the Dharwars, underneath the Deccan lava flows, that forms the basement for the deposition of Kaladgi sediments.

7 illus, 30 ref

009532   Odoh B I;Ezeh H N;Egboka B C E;Ezeh V O (Geological Sciences Dep, Nnamdi Azikiwe Univ, Awka, Nigeria, Email: lifeaquifer2000@yahoo.co.uk) : Hydrogeochemical properties of groundwater in part of Abakaliki city, southeastern Nigeria. J envir Sci Engng 2014, 56(3), 269-76.

This study is aimed at providing useful information about the hydrochemistry of some parts of Abakaliki city for proper understanding of the groundwater quality. Twelve representative groundwater samples from water boreholes/wells in the study area were analyzed for their hydrogeochemical properties : pH, Electrical Conductivity (EC), Turbidity, Total Dissolved Solids (IDS), Total Hardness (TH), COD, Ca^{2+, Mg2+, Na+, K+, HCO-₃, SO2-₄, Cl-, NO-₃, and CO2-₃. Aquifers in the study environment were located in the fractured shales of Abakaliki Formation. The composition of the major ions outlined the relationships between the aquifer chemistry. Strong positive correlations exist between EC-TDS, Na+-TDS, Mg2+-SO₄2+ and Ca2+-SO₄2+. Piper trilinear diagram has also been utilized in data interpretation and to classify the hydrogeochemical facies. Majority of the analyzed samples were characterized by the dominance of Ca2+, Mg2+, SO_42- and Cl- and the Piper trilinear diagram indicated two water types : Ca (Mg)-Cl and Ca-Mg-Na-Cl-SO₄ water types. Na/Cl ratio ranging from 0.12 to 0.73 (all below 1.0) with a mean of 0.55 inferred fresh water existence. Results of this study generally showed that the analyzed groundwater samples pose no threat to human consumption, health and environment since the concentrations of the physico-chemical parameters were within the WHO standards.}

4 illus, 3 tables, 27 ref

009531   Nayak B;Meyer F M (Mineral Preocessing Div, CSIR-National Metallurgical Laboratory, Jamshedpur-831 007) : Manganilmentite in the Magnetic ore body from Pokphur area of Nagaland, North East India and the possibility of Microdiamonds in the Ophiolites of Indo-Myanmar ranges. Curr Sci 2017, 112(1), 155-60.

Manganilmenite is found to be associated with the magnetite ore body of Pokphur area in the Nagaland ophiolites, North East India. There is perhaps no earlier description of the mineral from the Indian subcontinent. It occurs as an accessory mineral with magnetite and Fe-chlorite (chamosite). Electron probe micro-analytical data reveal that the mineral contains 5.6-8.5 wt% MnO and traces of MgO, ZnO and Cr₂O₃, while the TiO₂ content remains within narrow limits of 50-53 wt%. The calculated pyrophanite end-member varies from 13% to 18%. Although the magnetite body of Pokphur has been reasonably proved to be a hydrothermally altered product of basic and ultrabasic igneous rocks, and most of the minerals in the magnetite body are supergene in nature, different end-member compositions of mangan-ilmenite indicate that it has originally crystallized with the basic suite of rocks and has survived the alteration process with only marginal effects. Since manganilmenite has been considered as a diamond indicator mineral and ophiolites are a newly documented host of microdia-monds elsewhere in the world, the presence of manganilmenite in the Pokphur; magnetite hints towards occurrence of microdiamonils in the ophiolite suite of rocks of the Indo-Myanmar Ranges.

2 illus, 1 table, 34 ref

009530   Kavousi K;Nejadsattari T;Asri Y;Ejtehadi H; Khavari-Nejad R A (Biology Dep, Science and Research Branch, Islamic Azad Univ, Hesarak-147789855, Tehran, Iran, Email: nejadsattari_t@yahoo.com) : Effect of glacial retreat on floral distribution and/or displacement in Khersan glacier, central Alborz mountain range, Iran. Ambient Sci 2016, 3(2), 75-9.

During past few decades, worldwide various ecological alterations have been experienced after treat and decreasing of glaciers. Notable changes have been traced in Khersan glacier, Central Alborz of Iran by monitoring since 2013 to 2015. According to our studies, Khersan glacier surface reduced since 1991 and this significant reduction led to many ecological alterations. Species elimination close to the glacier, displacement of various flora from sub-Alpine to Alpine and Nival area including changes in floral frequency are notable alterations taken during glacier retreat. A large number of studies in Khersan glacier area since last two centuries have evidenced complete elimination of 6 plant species. Displacement of 16 plant species during recent years revealed that such species after retreat either found a new location for the establishment or got eliminated. Besides natural changes, the glacier area was also affected by man-made developments. Perhaps new condition puts many plant species in conservation level which need proper care programs. In this study multidimensional scaling model (MDS) is used to show the Nival areas where gpecies are under much stress. Proper evidence has been tried to put forward for describing such changes.

6 illus, 2 tables, 15 ref

009529   Gharib-Gorgani F;AshjaArdalan A;Mohammad-Reza E;Seyed-Jamal S;Abdollah Yazdi (Geology Dep, North Tehran Branch, Islamic Azad Univ, Tehran, Iran, Email: gharib.s91@gmail.com) : Petrology of Mg-bearing meta ophiolite complexes of Qaen-Gazik, Eastern Iran. Ambient Sci 2017, 4(1), 1-6.

The ophiolitic complex that studied in this piece of work is the part of an ophiolite ring surrounding Central Iran, emplaced during the Mesozoic related to divisions of Young Tethys types. According to the point analyses performed on the plagioclases and pyroxenes, all pyroxenes of the area are of high-Ca augite type. From labradorite to anorthite, plagioclases are the most dominant phenocryst in all rocks of the area. According to geochemical diagrams, it was concluded that the studied ophiolite complex is of harzburgite type (H-type) and its emplacement model corresponds with a cordilleran model of ophiolite emplacement. Although this ophiolite is of Tethys types, thus it could be stated that most of the parts of ophiolite sequence of the area were undergone metamorphism. Thus according to metamorphism of parts of basal peridotites of the ophiolite, metamorphosed ophiolite is an ideal name for this ophiolite suite.

7 illus, 23 ref

009528   Farahi M;Jehantigh H (NO, Higher Educational Complex of Saravan, Iran, Email: mohsen.farahi62@gmail.com) : Estimation of dusty days using the model of time series A case study of hormozgan province. Ambient Sci 2016, 3(1), 43-8.

Dust storm is one of the climatic hazards in the arid and semi-arid regions. Southern Iran with its hot and dry climate is more likely affected by the adverse consequences of dust storms due to the proximity to the dusty deserts of Saudi Arabia and Iraq, on one hand, and the synoptic situation for the occurrence of the dust storms in the Persian Gulf, on the other hand. In this study, the frequency of dusty days in Hormozgan Province was investigated and predicted. To this end, data were collected from the three synoptic stations in Bandar Abbas, Bandar Lengehand Bandar-e Jaskfrom the Iran Meteorological Organization during the statistical period of 1968-2008. Then, using the non-seasonal ARIMA (p, d, q), were analyzed in i6Minitab and the frequency of the dusty days in the region were predicted. Results of the study show that the ARIMA (1, 1, 1) noc was the most appropriate pattern for predicting the frequency of dusty days in Hormozgan Province. The results showed that the predictions for Bandar-e Jask, compared to those of Bandar Abbas and Bandar Lengeh are more accurate in terms of continuous increasing; trend and the interval stability of the time series prediction and the smaller difference between the observed values with the predicted values.

3 illus, 18 ref

009527   Bhaandari R K (Forum on Engineering Interventions for Disaster Mitigation, Indian National Academy of engineering, Gurgaon-122 018, Email: rajmee@yahoo.com) : Dark clouds of disaster over Uttarkhand and the silver lining. Curr Sci 2017, 112(1), 29-30.

009526   Ashiagbor G;Forkuo E K;Laari P;Abbeyir R (Geomatic Engineering Dep, Kwame Nkrumah Univ of Science & Technology, Kumasi, Ghana, Email: eforkuo.soe@knust.edu.gh.com) : Modelling soil erosion in the Densu river basin using RUSLE and GIS tool. J envir Sci Engng 2014, 56(3), 247-54.

Soil erosion involves detachment and transport of soil particles from top soil layers, degrading soil quality and reducing the productivity of affected lands. Soil eroded from the upland catchment causes depletion of fertile agricultural land and the resulting sediment deposited at the river networks creates river morphological change and reservoir sedimentation problems. However, land managers and policy makers are more interested in the spatial distribution of soil erosion risk than in absolute values of soil erosion loss. The aim of this paper is to model the spatial distribution of soil erosion in Densu River Basin of Ghana using RUSLE and GIS tools and to use the model to explore the relationship between erosion susceptibility, slope and land use /land cover (LULC) in the Basin. The rainfall map, digital elevation model, soil type map, and land cover map, were input data in the soil erosion model developed. This model was then categorized into four different erosion risk classes. The developed soil erosion map was then overlaid with the slope and LULC maps of the study area to explore their effects on erosion susceptibility of the soil in the Densu River Basin. The Model, predicted 88% of the basin as low erosion risk and 6% as moderate erosion risk, 3% as high erosion risk and 3% as severe risk. The high and severe erosion areas were distributed mainly within the areas of high slope gradient and also sections of the moderate forest LULC class. Also, the areas within the moderate forest LULC class found to have high erosion risk, had an intersecting high erodibility soil group.

8 illus, 1 table, 27 ref

008547   Singh R V;Sarbajna C;Basu H;Vekateshwarlu M; Banerjee R;Singh Y;Verma M B (Atomic Directorate for Exploration And Research, Atomic Energy Dep, Srisailam, Hyderabad, Email: rvsingh.amd@gov.in) : Geochemical characterisation of quartzites of the of the Srisailam, Banganapalle and Paniam formation from the northern part of the Cuddapah basin, Telegana and Andhra Pradesh. J appl Geochem 2017, 19(1), 34-43.

Geochemical analysis of non-mineralised quartzites (n=25) was carried out for characterization of the Srisailam, Banganapalle and Paniam Formations from the northern part of the Cuddapah Basin covering parts of Telangana and Andhra Pradesh, as the chemical composition of terrigenous sediments is a good indicator of provenance, degree of weathering, transportation, and diagenesis. The geochemical data indicate variable degree of maturity of these quartzites. The quartzites of Srisailam Formation grade from subfeldspathic arenite to quartz-arenite and exhibit medium to high mineralogical maturity. They also indicate the presence of chloritic matrix/cement, and minor carbonate (dolomite) cement. In contrast, the quartzites of Banganapalle Formation show a considerably high degree of mineralogical maturity, while those of the Paniam Formation are mineralogically the most mature. Petromineralogical studies have also revealed that the Paniam quartzites being devoid of feldspars, clay matrix, are typical quartz-arenite. The geochemical data indicate a gradual increase in mineralogical maturity of these quartzites ranging from the Srisailam Formation (67.20-98.60% SiO₂) through Banganapalle Formation (86.31-98.67% SiO₂) to the Paniam Formation (96.66-98.99% SiO₂). Quartzites from all these formations show a considerably low abundance of most of the trace elements. The gradual decrease of Rb and Ba in successively younger formations indicates depletion of K-feldspar and/or clay matrix, which reflects a relative increase in mineralogical/textural maturity. Further, the gradual decrease of TiO₂ and Zr indicates hydraulic sorting of heavy minerals (anatase/rutile and zircon respectively) during recycling/reworking. TiO₂/Zr ratio in these quartzite samples ranges from 4 to 75 (majority 14-31) indicating derivation of the precursor sediments from dominantly felsic to subordinate intermediate igneous source rocks. SiO₂ vs. (Al₂O₃+K₂O+Na₂O) plot indicates generation of the sediments under a dominantly semi-humid palaeoclimatic condition.

4 illus, 3 table, 28 ref

008546   Singh R V;Banerjee R;Verma M B (NO, Atomic Minerals Directorate For Exploration and Research, MD Complex, Begumpet, Hyderabad, Email: rvsingh.amd@gov.in) : Geochemistry of basement granitiods, Chenchu colony area, Guntur district, Andra Prdesh. J appl Geochem 2017, 19(1), 96-110.

Chenchu colony area, Guntur district, Andhra Pradesh, is targeted for sub-surface exploration based on favourability criteria for Proterozoic unconformity-related fracture-controlled uranium mineralisation. Geologically, Neoarchaean to Palaeoproterozoic granitoids form basement for the overlying Neoproterozoic Kurnool Group of sediments (Banganapalle and Narji Formations). These granitoids are substantially reactivated in nature as evident from the presence of fractures/faults, mafic dykes and quartz/quartzo-feldspathic veins. Geochemically, they (n=17) show wide variation in SiO₂ (68.12-76.65%), Al₂O₃ (11.34-17.29%), K₂O (4.30-9.96%), Na₂O (0.21-3.14%) and CaO (0.08-3.87%) contents while two highly altered and radioactive granitoids (171 and 445 ppm U) exhibit comparatively low average abundance of SiO₂ (64.54%) and high abundance of Al₂O₃ (18.56%) and K₂O (7.96%). Total alkali content of these granitoids varies from 7.13 to 10.17% with an overall predominance of potassium over sodium. They belong to granite-adamellite suite and exhibit a predominant peraluminous nature (A/CNK: 1.01-1.87; except for three samples with values of 0.67-0.95), signifying derivation of the magma from sedimentary or supracrustal sources with S-type signature. This is further substantiated by low sodium (<60> 3.2% Na₂O) and high potash (<126>5% K₂O) contents as well as sample plots in Altherr's diagram [mol CaO/(MgO+FeOt) vs mol Al₂O₃/(MgO+FeO^{t)], indicating generation of these granitoids by partial melting of metapellitic (crustal) sources. Petrographic evidences viz., presence of K-feldspar (orthoclase, microcline), both varieties of mica (muscovite and biotite), monazite and apatite support the above observation. In Rb-Nb+Y and Nb-Y tectonic discrimination plots, these granitoids straddle in the fields of volcanic arc granite (VAG) and syn-collision (syn-COLG), signifying evolution in subduction-related arc magmatism in a collisional environment, which is further corroborated by sample plots in syn-collision field in R1-R2 diagram. Such reactivated S-type granitoids with high intrinsic uranium (19ppm U) form a potential and fertile source, which may lead to uranium mineralisation under favourable conditions in an unconformity proximal setup.}

8 illus, 2 table, 51 ref

008545   Sharma K A;Maibam B (Earth Science Dep, Manipur University, Canchipur, Imphal, Email: bmaibam@yahoo.com) : Mineralogical and geochemical study of Rodingites of Indo-Myanmar ophiolite Belt, North Eastern India. J appl Geochem 2017, 19(1), 28-33.

Rodingites associated with serpentinised ultramafic rocks from the Indo-Myanmar Ophiolite Belt are studied. The rocks occur as irregular pods and lenses, and as veins and blocks in studied serpentinized zones, as well as alluvium placer and also as in situ bodies in the area. They comprise of a metasomatic assemblage formed due to serpentinisation/alteration of lherzolite, a harzburgite, gabbro and dolerite dykes. The mineral assemblage of the studied samples is grossular garnet, vesuvianite, idocrase, diopside, tremolite, actinolite, chlorite, albite, prehnite, pyrophyllite and sphene (titanite). Though characterized by high CaO and Al₂O₃ contents they are lower in MgO and SiO₂. Based on geochemistry and petrographic evidence the Indo-Myanmar ophiolite seems to have formed from different protoliths.

2 ilus, 2 table, 21 ref

008544   Prabhakar G;Sudheer Kumar M;Reddy K S;Mondal N C (Geology Dep, University College of Science, Saifabad, Osmania Univ, Hyderabad, Telangana, Email: project-prabhakar@yahoo.co.in) : Assessment of groundwater quality from phreatic aqifer around opencast coal mining areas of Kothagudem, Manguru and Sattupally in Khammam district, Telangana State. J appl Geochem 2017, 19(1), 76-87.

Thirty groundwater samples were collected from phreatic aquifers during post-monsoon season (December, 2013) around the three different opencast coal mining areas of Kothagudem, Manuguru and Sattupally in Khammam district, Telangana State. The American Public Health Association (APHA, 1995) standard methods were followed for analyzing concentrations of the physicochemical parameters pH, EC, TDS, TH, Ca^{2+, Mg2+, Na+, K+, HCO-₃, SO2-₄, Cl-, NO-₃ and F. The results of these parameters were interpreted with the help of Piper, Gibbs and Wilcox diagrams along with correlation matrix. Results indicate that alkaline earth's Ca2+ + Mg2+ exceed alkalies Na+ + K+ while the weak acids CO-₃+ HCO-₃ exceed the strong acids SO2-₄ + Cl-. The quality of groundwater is governed by rock dominance with no significant dominance by precipitation and evaporation. From correlation matrix, the highest correlation is found between EC and TDS with a correlation coefficient of 0.59. Further, suitability of groundwater for irrigation was examined with reference to different irrigation indices like electrical conductivity (EC), total dissolved solids (TDS), sodium percent (SP), sodium adsorption ratio (SAR), residual sodium carbonate (RSC) and Kelly's ratio (KR). It indicates that groundwater quality has EC value in about 77% of the samples under high salinity category while sodium percent (SP) value in 67% of the samples fall under excellent to permissible category. The RSC and KR values in about 73% samples and 53% samples, respectively, fall are in the safe category for irrigation purpose. Due to high concentration of fluoride (<60> 1.5 mg/l), the groundwater quality is not suitable for drinking purposes around these opencast mining areas.}

4 illus, 7 table, 34 ref

008543   Powshi V;Sreekesh S (Centre for the Study of Regional Developement, Jawaharlal Nehru Univ, New Delhi) : Assessment od soil nutrients across crop and depth variations in Chulliar-Ikshumathi sub-watershed of Gayathripuzha, Kerala. J appl Geochem 2017, 19(1), 88-95.

Soil nutrients are vital for plants. Excessiveor deficit soil nutrients have a negative impact on the growth of plants. Present study has analyzed variations in macronutrients such as nitrogen, phosphorus, and potassium content in the soil from areas having different crop cover. The study was carried out in Chulliar-Ikshumathi sub-watershed of Gayathri sub-basin, in Kerala. The soil samples were collected from 44 locations under different crop cover conditions. At each site samples were collected from 0 to 10, 10 to 20 and 20 to 30 cm depths, after removing the superficial litter and other organic matter from the top soil. Standard soil chemical analysis methods were employed to determine the nutrient status and statistical analysis was carried out to understand the nutrient status under different crop cover conditions as well as variations with depth. The latter analysis would also help to understand nutrient movement under tropical humid conditions. It has been observed that the nutrient concentration is more under banana and vegetable plants which are the annual and seasonal crops respectively. In general nutrient concentration significantly reduces with depth. It is also found that nutrient level is relatively lower under perennial crops than the seasonal or annual crops. Extensive use of chemical fertilizers is the reason for such high nutrient levels in those areas. The nutrient status is comparable in the fields where chemical fertilizers have been used as well as those that are chemical fertilizer free.

4 illus, 3 table, 25 ref

008542   Mathur N (Centre of Excellence for Studies, Oil India Limited, Rukminigam, G.S Road, Guwahati, Assam, Email: nmathur@oilindia.in) : Orgin, maturity and biodegradation of natural gases from upper Assam, India. J appl Geochem 2017, 19(1), 1-20.

The Upper Assam Basin is a Tertiary sub-basin of the Assam-Arakan Geological Province in north-east India. Hydrocarbons occur in the Upper Palaeocene, Lower Eocene, Oligocene and Miocene reservoirs in the basin. The isotopic (δ^{13C) and molecular composition of natural gases from reservoirs of the Upper Assam Basin indicates the presence of two types of gases. Pristine thermogenic gases ("Group I"), generated from humic organic matter, with possible contribution from algal organic matter and occurring in deeper reservoirs. Although they are not biodegraded, low δ13C values for methane suggest that microbial methane has been added to these gases, probably due to anaerobic biodegradation of oil (methane being a major end-product). By contrast, gases from shallow reservoirs are biodegraded ("Group II"). In these gases, methane is isotopically light, suggesting that significant amount of 13C-depleted methane has been mixed with the thermogenic (and biodegraded) gases. The microbial methane generation is again likely associated with biodegradation of oil in the reservoirs. The pristine thermogenic gases ("Group I") were generated from a mid-to late oil window maturity source (vitrinite reflectance <126>0.8% to 1.2% Ro). The altered composition of the shallow reservoirs gases ("Group II") does not allow for an unambiguous assessment of their maturity, which should however not exceed <126> 1.2% Ro, similar to that of the un altered thermogenic gases. The following multi-step charging history is proposed for the Upper Assam reservoirs, based on geochemical data discussed in this work and supported by petroleum system models for the region: a) charging of the first oil in the reservoir when the reservoir temperature is low enough to permit bacterial activity, b) biodegradation of oil and generation of secondary microbial methane via methanogenesis, c) input of fresh charge of oil and thermogenic gas in the reservoir and d) biodegradation of oil and gas, if the reservoir temperature still permitted bacterial activity.}

11 illus, 2 table, 28 ref

008541   Kamlesh Kumar;Banerjee R;Malpe D B (NO, Atomic Minerals Directorate for Exploration and Research, Western Region, Jaipur, Email: kamleshkuamar.amd@gov.in) : Geochemsitry and petrogenesis of arenites and shales of Tirathgarh formation of Indravati basin, Burgibhata area, Bastar district, Chhattisgarh. J appl Geochem 2017, 19(1), 56-75.

Tirathgarh Formation constituting the basal part of Indravati Group rests unconformably over a basement consisting mainly of the Palaeoproterozoic Darba Granite. This formation comprises predominantly arenites with intercalation of shales. Geochemical and petrogenetic studies have been carried out on borehole and surface samples collected from Burgibhata area. In general arenites of Tirathgarh Formation are charactersed by higher SiO₂ (94.02%) content and lower content of TiO₂(0.06%), Al₂O₃(3.16%), FeOT(1.34%), MgO (0.14%), MnO (0.01%), CaO (0.05%), Na2O (0.36%), K₂O (0.68%) and P₂O₅ (0.02%) as compared to the values of Upper Continental Crust (UCC). Among the trace elements V, Cr, Co, Ni, Cu, Zn, Pb, As and U contents are higher than the values of UCC while Rb, Ba, Sr, Zr, Nb, Ce, Y and Ga are less than the UCC concentrations. Shales of the area are charactersed by lower content of SiO₂ (60.43%), TiO₂ (0.90%), MgO (1.37%), CaO (0.10%), Na2O (0.82%) and P₂O₅ (0.07%) with a higher content of Al₂O₃ (22.36%) and K₂O (6.59%) in comparison to Post Archaean Average Shale (PAAS). Further in comparison to PAAS, these shales contain higher concentration of V, Cr, Co, Ni and Rb and lower concentration of Cu, Zn, Sr, Zr, and Ba. Provenance for these sediments are the granites and quartzite bearing metasediments of Bengpal Group derived under strong chemical weathering and a humid climatic condition. Sedimentation processes took place in a shallow shelf with relict shoreline environment in the passive margin tectonic setting.

12 illus, 5 table, 23 ref

008540   Inbakandan D;Sumit Raj;Kumar C;Venkatesan R; Khan S A (Centre for Ocean Research, Sathyabama Univ, Chennai-600 119, Email: inbakandan@gmail.com) : Virtual screening of marine natural antifoulant: in silico approach to screen antifouling metabolites from marine sponges. Indian J Geomar Sci 2016, 45(8), 1042-8.

A molecular docking analysis was carried out followed by Molecular Dynamics (MD) simulation studies on the metabolites from various marine sponges in order to identify their metabolites being potent inhibitors towards biofouling. The docking analysis reveals that the metabolites from a marine sponge Acanthodendrilla sp. and Agelas cf. mauritiana may act as potent antifouling agents with the docking scores ranging from 68 to 123 for the metabolites. Chemical structure of the most active ligand was converted into a feature-shaped query. This query was used to align molecules to generate statistically valid lead compound.

7 illus, 1 table, 18 ref

008539   Hoda S Q;Krishnamurthy P (NO, Fomerly Atomic Minerals Directorate for Exploration and Research, Hyderabad, Email: hoda-sq@yahoo.com) : Geochemistry, mineralogy and economic aspects of phosphatic rock of the Samchampi alkaline-carbonatite complex, Assam, North East India. J appl Geochem 2017, 19(1), 21-7.

Four discontinuous lensoid bodies of secondary phosphatic rock (0.433 sqkm) occur along the curvilinear fault zone in the dominantly soil covered Samchampi Alkaline-Carbonatite Complex (SACC) that was emplaced in close proximity to the Kalyani lineament during the upper Cretaceous (109Ma) in the Mikir Hills massif of Assam. Petrographic studies indicate that fine-grained flourapatite is the dominant phosphate mineral set in a ground mass of calcite and francolite. Crandallite, pyrochlore, magnetite, ilmenite, goethite, biotite and zircon occur as accessory minerals. Major and minor oxides show a wide range of P₂O₅(31.49-38.0%), CaO (41.70-54.73%), Fe₂O₃(1.40-11.16%), and Al₂O₃(0.53-4.47%) and SiO₂(0.64-7.24%). Trace element analysis including REE indicate high REE (1518ppm), U₃O₈ (223 ppm), Nb (168 ppm), Y (69 ppm) and Zr (674 ppm). Electron Microprobe studies have revealed the presence of mineral phases such as apatite, crandallite, pyrochlore that account for the chemical constituents like P, REE, U, Nb and Y in the rock. A moderate reserve of 15 million metric tons of phosphatic ore averaging 35% P₂O₅ has been estimated under the resources category down to a depth of 15m. Thus, the phosphatic rock of Samchampi Complex could become a potential source for production of phosphoric acid together with uranium and rare-earth elements as by-products. They can be extracted economically by using a combination of froth flotation to remove calcite and silica as gangue and hydrometallurgical treatment of the beneficiated ore.

6 illus, 4 table, 11 ref

008538   Harini P;Manikyamba C;Dinesh Kumar S; Durgaprasad M;Nandan M J (NO, CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad, Email: ngriharini@gmail.com) : Geographical Information System based morphometric analysis of Krishna River basin. J appl Geochem 2017, 19(1), 44-55.

In this paper, an attempt has been made to study and characterize the drainage morphometry of Krishna River Basin to evaluate the hydro-geological characters where the quantitative outcomes act as one of the constructive input for the water resource management and planing. Remote sensing data is significant for the extraction of river basin and its stream networks through Shuttle Radar Topography Mission (SRTM) DEM. Geographical Information System (GIS) is used in evaluation of Linear, Areal and Relief aspects of the river basin. The drainage area of Krishna River Basin is 2, 58, 791 km^{2 and shows a dendritic drainage pattern. The stream network of the basin is mainly controlled by slope and geological conditions of the area. The study area is designated as eighth order basin with a drainage density of 0.32km/km2. The increase in stream length ratio from lower to higher order shows that the drainage basin has reached a mature geomorphic stage. The study reveals that the basin is elongated in shape. Low order streams are mostly dominating the basin and the calculated mean bifurcation ratio of the entire basin is 1.84 indicating that the river is not much influenced by geological structures. The results observed from this work would be very useful in drainage basin development and management of water resource.}

8 illus, 9 table, 40 ref

008537   Gokulakrishnan R;Ravikumar S (Oceanography and Coastal Area Studies, School of Marine Sciences, Alagappa Univ, Thondi-623 409, Email: ravibiotech20132@gmail.com) : Assessment of seagrass biomass and coastal land forms along palk strait. Indian J Geomar Sci 2016, 45(8), 1035-41.

Present study was made an attempt to assess the onshore seagrass biomass and off shore seagrass deposition. Maximum total biomass of Cymodocea serrulata (571.2±78.94 g.dry wt/m^{2) and Syringodium isoetifolium (240 ± 24.92 g.dry wt/m2) were recorded in Thondi during the month of December-2011. Maximum total biomass of Halodule pinifolia (145.6 ± 57.41 g.dry wt/m2) and Halophila ovalis (142.4 ± 21.83 g.dry wt/m2) were recorded in Manamelkudi during the month of December-2011. Several seagrass parameters viz., above ground biomass, below ground biomass, canopy height, percentage coverage, above and below ground biomass ratio were also examined in this study. Maximum deposition of Cymodocea serrulata (10.73±0.08 Kg.dry wt/m2) and Syringodium isoetifolium (7.93±0.03 Kg.dry wt/m2) were recorded at Thondi coastal area during the month of May-2012. The survey provides enormous information on the seagrass biomass and seagrass deposition along the Palk Strait coast.}

9 illus, 2 tables, 14 ref

008536   Das S;Giri S;Das I;Chanda A;Akhand A; Mukhopadhyay A;Maity S;Hazra S (School of Oceanographic Studies, Jadavpur Univ, 188, Raja S.C. Mullick Road, Kolkata-700 032, Email: sourav.bioptics@gmail.com) : Tide induced annual variability of selected physico-chemical characteristics in the northern Bay of Bengal (nBoB) with a special emphasis on tropical cyclone-phailin, 2013. Indian J Geomar Sci 2016, 45(8), 952-9.

Daily monitoring (in the day time) of sea surface temperature (SST), sea surface salinity (SSS), pH and weekly measurement of dissolved oxygen (DO) were carried out in the northernmost sector of the Bay of Bengal for the first time, covering roughly an area of <126>750 sq. km throughout an annual cycle from 1st June, 2013 to 31st May, 2014. SSS, pH and DO maintained a higher and lower value during the highest high tide (HHT) and lowest low tide (LLT) hours respectively, throughout the year, except in some weeks of monsoon. But SST did not follow any such type of tide influence trend. The strong physical forcing and high energy tidal surges caused by the tropical cyclone (Phailin) increased the SSS, pH and DO by 33.11%, 3.73% and 40% respectively. In contrast, a massive cooling in SST by 15.38% was observed. Though SST returned to normal range within one week, DO and SSS took almost 10 days to reach equilibrium. However, tropical cyclone poses a short term strong impact on the physico-chemical properties and ecology of the shallow continental shelf coastal water.

7 illus, 2 tables, 36 ref

008535   Akbari P;Sadrinasab M;Shegini V;Siadatmousavi M (NO, Khorramshar Univ of Marine Science and Technology, Khorramshar, Iran, Email: pakbari91@yahoo.com) : Tidal constituents in the persian guld, gulf of Oman and Arabian sea: a numerical study. Indian J Geomar Sci 2016, 45(8), 1010-16.

In this study, a three-dimensional coastal ocean model (FVCOM) is used in barotropic mode to simulate tidal amplitudes in the Persian Gulf, Gulf of Oman and Arabian Sea. Finite volume method is applied for solving hydrodynamic equations on an unstructured triangular mesh grid. Amplitudes and phases of 8 main tidal constituents are prescribed along the southern open-ocean boundary. To assess the model performance, the model results were compared with observational evidences. Amplitudes of tidal components observed at 9 tidal gauges in the region confirm the results of harmonic analysis performed on model outputs. Hence, it can be concluded that the amplitudes of 8 tidal components are well predicted by the model. Moreover, amphidromic points are accurately predicted from model results for these components. Also M₂ and K₁ are determined respectively as major semi-diurnal and diurnal constituents in entire domain. Finally, the tidal regime is classified by employing the form factor F in this area.

10 illus, 4 tables, 17 ref

007434   Palanichamy A (Geography Dep, Madurai Kamaraj Univ, Madurai) : Assessment of rainfall and groundwater for agriculture of Tiruchirappalli district, Tamil Nadu, using geospatial technology. Int J latest Technol Mgmt appl Sci 2016, 5(8), 40-52.

Water demand always exceeds rainfall, but the water deficit is quite low in the northeast monsoon period. Hence, due to severe water deficit, drought recurs during the southwest monsoon and also in summer months in Tamil Nadu. In recent decades, the exploitation of groundwater has increased greatly particularly for agricultural purpose, because large parts of the country have little access to rainfall due to frequent failures of monsoon. The aim of the study is to asses the status of rainfall and groundwater for agriculture with the following objectives. to analyze the mean rainfall and groundwater level to associate rainfall and water level during wet, dry and normal years. To assess the rainfall and groundwater for different cropping period. The results were effectively portrayed using simple graphs and thematic maps with the aid of open source GIS software. Tiruchchirappalli district, same name is located in the central part of Tamil Nadu between 78ø09'00" - 79ø03'00" east longitudes and 10ø17'00" - 11ø25'00" north latitudes. Where ever the excess rainfall occurrences have observed the groundwater level either goes high or low may caused due to the trend of groundwater utilization over the particular area.

22 illus, 3 tables, 18 ref

007433   Palamarchuk V K;Glinskaya N V;Mischenko O N (Federal State Budgetary Institution, "Academician I.S. Gramberg All-Russian, Scientific Research Institute, 190121, ST.-Petersburg, Russia, Email: palvas@mail.ru) : Way of linking of magnetic fields at the high-precision hydromagnetic surveys carried out on water areas. Asian J Microbiol Biotechnol envir Sci 2016, 18(3), 789-95.

The purpose of this research is to consider various ways of the accounting of variations and linking of results of hydromagnetic survey on water areas providing a high precision of survey. The direct way - according to coastal magnetovariational station (MVS) which is capable to consider variations only as a zero approximation is presented. The indirect way - carries out coordination of the profile magnetic surveys executed on ordinary (workers) and the intersecting routes where, for increase in accuracy, it is offered to carry out except planned, additional intersecting routes on those points where at this time on coastal MVS extreme values of variations were observed. The gradientometric way - by results of gradientometric magnetic survey with two magnetometers restore a magnetic field without variations on a profile and on a difference of observed and restored fields calculate a zero approximation of variations which is used in an indirect way. Linking is offered to be carried out by method of artificial (simulated) secant (intersecting) routes using after the accounting of variations by indirect and gradientometric (direct) ways. Application of these ways allows carrying out sea magnetic survey with a margin error in 1-2 nTl.Summing up the results, it should be noted that the offered way of linking needs to be carried out in the following sequence: 1. Observed data linking realization on ordinary and secant routes, 2. Linking of ordinary and secant routes data on additional intersecting routes, 3. Linking realization along the artificial (simulated) secant (intersecting) routes, 4. Digital model of map creation.Reliability of the offered ways is based on fact that its realization doesn't use the minimization of discrepancies by means of a method of least squares. Therefore, the residual discrepancy serves as criterion of data linking.

3 illus, 5 ref

006439   Wadhawan S K (Former Director General, Geological Survey of India, Kolkata, Email: wadhawansk.leo@gmail.com) : Marine geology and coastal surveys for seabed mapping and mineral resource evaluation in India - an overview. Proc Indian Natn Sci Acad 2016, 82(3), 675-83.

Off-shore geoscientific studies and systematic mapping of the seafloor, both in Exclusive Economic Zone (EEZ) and Territorial Waters (TW) along east and west coasts in India, started with the acquisition of research vessels R. V. Samudra Manthan in 1983 and two coastal vessels in 1984. Since then Marine and Coastal Survey Division in Geological Survey of India has been acquiring geoscientific data on the sea bed sediments, seabed morphology, mineral resources, geochemistry and geophysical parameters. The three vessels have collected thousands of surface and subsurface samples from the Indian and international waters during their past over 30 years of service to the nation. As the seabed mapping/ reconnaissance had been completed for EEZ (23,05,143 km^{2) during the first phase of marine geological mapping and exploration by GSI, the compilation and synthesis of this enormous wealth of geoscientific data is now attempted[63 maps from EEZ and 143 maps from TW]. The second phase of detailed marine geological exploration has been launched as 'National High Resolution Seabed Mapping and Resource Evaluation within EEZ of India and Beyond' during the flagging off of the newly acquired all-weather modern research vessel RV Samudra Ratnakar flagged off on 23rd December, 2013 from the Port of Mangalore. Operational strategies such as marine surveys through progressively closer intervals, systematic ocean bottom probing and sampling, prognostication of natural resources based on conventional methods, conceptual modeling, etc.; are finalized for a focused approach for targeting and prioritizing offshore mineral resources within EEZ of India. Placer heavy mineral resources up to a depth of 1-1.5m thickness from the sea floor on the middle shelf have been identified in an area of 764 sq km with a proven reserve of 108 million tons. On the basis of the delineated OGP (<126>2,40,000 km2) for the present, Focused Offshore Mineral Exploration (FOME) Cruises are planned to be taken up for Rare Earth Elements & Yttrium (REY), Seafloor Massive Sulphides (SMS), phosphorites, lime mud, gas hydrates, carbonate sand etc; onboard R.V. Samudra Ratnakar.}

6 illus, 26 ref

006438   Thamban M;Laluraj C M;Mohan R (NO, ESSO - National Centre for Antarctic and Ocean Research, Headland Sada, Goa-403 004, Email: meloth@ncaor.gov.in) : Antarctic palaeoclimate variability on millennial, centennial and decadal time scales: Indian initiatives during 2010-2015. Proc Indian Natn Sci Acad 2016, 82(3), 685-94.

Palaeoclimatic reconstructions using diverse types of climatic archives and proxies help us in understanding the long term climatic variability and improve our knowledge for climate change perspectives. Globally, the Cenozoic was characterized by the cyclicity of glacial and interglacial fluctuations at regular intervals. Understanding the Antarctic climate variability on millennial, centennial to decadal level is crucial to our knowledge on the role and response of Antarctic ice sheets to the global climate variability. During the period 2010-15, the Indian scientists have used a variety of palaeoclimate records like marine/lake sediment cores and ice cores, mainly from the East Antarctica and its margins. The Indian studies have made significant contributions to the understanding of Antarctic climate variability and the various factors involved. Among the diverse types of studies undertaken, the ice core studies have generated large amount of knowledge basis on the Antarctic climate and its global/ regional linkages. Recent developments in the recovery and study of undisturbed sedimentary records from Antarctic lakes for the first time in the country provide an excellent opportunity to understand the last glacial to Holocene variability with better stratigraphic constraints. Compared to these, deeper sedimentary records from the Antarctic continental margin offer us an important opportunity to study of evolution and dynamics of the Antarctic cryosphere from its inception.

8 illus, 25 ref

006437   Srivastava P;Rau Y;Phartiyal B;Sundriyal Y P (NO, Wadia Institute of Himalayan Geology, 33 GMs Road, Dehradun-248 001, Email: pradeep@wihg.res.in) : Rivers in the Himalaya: responses to neotectonic and past climate. Proc Indian Natn Sci Acad 2016, 82(3), 763-72.

Rivers in Himalaya respond to tectonics and climate of the region on different spatio-temporal scales. Here we present a brief account of Indian contribution, on the study pertaining to the fluvial record from Himalaya during 2011-2015. Total number of papers published in SCI journals and edited books are 64 where authors have mainly focused on the understanding of (i) extreme events and their terrain responses in Himalaya (ii) records of river aggradation-incision and the forcing factors (iii) geomorphic indicators of neotectonic deformation. Emphasis has also been made towards understanding the development of frontal belt of the Himalaya, sediment production, storage and delivery in the wedge.

1 illus, 71 ref

006436   Singh R P;Gupta P K (Land Hydrology Div, Geosciences, Hydrology, Cryosphere Sciences and Applications Group (E, Ahmedabad-388 015, Email: rpsingh@sac.isro.gov.in) : Development in remote sensing techniques for hydrological studies. Proc Indian Natn Sci Acad 2016, 82(3), 773-86.

Observations and modeling of terrestrial water cycle is important for sustainable management of water resources as well as understanding the impact of climate change. Satellites provide an important role in measurements of various dimensions of water cycle components in spatio-temporal domain. Paper reviews the scientific basis and techniques of retrieval of various hydro-meteorological parameters (Rainfall, Soil Moisture, Evapo-transpiration, Groundwater, Water level, Surface Runoff, conjunctive water utilization and Water quality etc.) which are estimated using advanced satellite based instruments (Altimeter, Radar, Optical and Microwave Radiometers). Variability of various hydro-meteorological parameters and recent satellite based observation on flood and hydrological drought condition in selected regions over India is discussed.

12 illus, 55 ref

006435   Singh L;Dalei S N;Bhardwaj A (NO, , ONGC, 7th floor, Core-8, Scope Complex, Lodhi Road, New Delhi-110 003, Email: singh_kavitha@ongc.co.in) : De-risking shallow hazards through pore pressure prediction and special studies - a case study from KG-offshore. Proc Indian Natn Sci Acad 2016, 82(3), 935-43.

Shallow hazards in drilling are caused due to water flow from an over pressured shallow sand encountered at shallow depths below the mudline in deepwater regions of the world. High sedimentation rates and an impermeable mud or clay seal from a condensed section are the main factors contributing to overpressures in shallow water flow sands. If isolated sand bodies are in this shale or mudstone, water from such bodies will not escape easily due to the presence of low-permeability sediments around them. In addition, the high rate of sedimentation from the overburden exerts an enormous pressure on these sediments, causing these isolated bodies containing large amounts of water to be over pressured. The shallow hazards can cause extensive damage to the borehole and pose a great threat to drilling. Their identification/delineation prior to drilling is therefore of utmost importance in reducing risk. The study area has a highly promising Miocene roll structure beneath the shallow hazard zones which warrants probing. Negotiating to this structure through hazardous shallow anomaly already encountered during drilling necessitated for detailed shallow hazard analysis. The area has very limited well data. This limitation in the input data prompted the authors to look for suitable methods to address the issue. An innovative approach to generate pseudo logs from freshly picked seismic velocities was adopted. The pseudo logs were used for carrying out post stack model based inversion. This approach could overcome the limitations of non availability of well data significantly and the generated impedance volume was of optimum quality. The impedance volume could delineate the zones of shallow hazards. The volume was calibrated at the well location indicating low impedance at high pressure zones. This paper describes this innovative/unconventional approach adopted for delineation of these shallow hazards.

11 illus, 8 ref

006434   Sharma M;Tiwari M;Ahmad S;Shukla R;Shukla B; Singh V K;Pandey S K;Ansari A H;Shukla Y;Kumar S (NO, Birbal Sahni Institute of Palaeosciences, 53 Univ Road, Lucknow-226 007, Email: mukund_sharma@bsip.res.in) : Palaeobiology of Indian proterozoic and early cambrian successions - recent developments. Proc Indian Natn Sci Acad 2016, 82(3), 559-79.

Many facets of the early biosphere preserved in the Proterozoic and Early Cambrian successions, recorded during 2011- 2015, are reviewed. Recent advancements made in the Precambrian palaeobiology and newer steps recognized in the organismal evolution in the global perspective vis-a-vis significance of Indian records are discussed. The palaeobiological evidence reported from India are chronicled and grouped under seven categories: MISS (Microbially Induced Sedimentary Structure) & stromatolites, acritarchs, OWM (Organic Walled Microfossils), carbonaceous remains, trace-fossils & Ediacaran fossils, stable isotope studies and organic geochemistry. Present article is a continuum of Sharma et al. (2012), provides the status of Precambrian palaeobiological studies in the country, enumerates the importance of Indian records, and enlist unsolved problems and future research directions.

10 illus, 148 ref

006433   Sharma M C;Chand P (NO, Centre for the Study of Regional Development (CSRD), School of Social, Jawaharlal, Email: milap@jnu.ac.in) : Studies on quaternary glaciations in India during 2010-2016. Proc Indian Natn Sci Acad 2016, 82(3), 869-80.

In the recent years, number of studies were carried out to define the timing and extent of Quaternary glaciation throughout the Himalayan region. Such studies have helped to understand the past climate changes and further develop predictive futuristic models. There have been 22 research studies that were carried out during the past six years (2010-2016) with equal contribution from Indian researcher and their international counterparts in terms of research output. Most of these studies have focused on the north-western Himalaya, with only a few studies being carried out in the eastern part. Recently published new glacial succession chronology (Terrestrial Cosmogenic Nuclide (^{10Be TCN), Optically Stimulated Luminescence (OSL), Electron Spin Resonance (ESR) and Radiocarbon (14C)) in these studies provide a synoptic picture of glacial episode for most the Himalayan regions. Major glacial advances occurred during the Last glacial stage and early Holocene, with minor fluctuations during the mid-Holocene. However, recent study suggests contrary to the earlier suggestions that a reasonably large valley glacier expansion occurred during the global Last Glacial Maxmium (LGM), likely in response to global variations in temperature.}

2 illus, 78 ref

006432   Sekhar M;Riotte J;Ruiz L;Jouquet P;Braun J J (NO, , Indian Institute of Science-560 012, Email: sekhar.muddu@gmail.com) : Influences of climate and agriculture on water and biogeochemical cycles: kabini critical zone observatory. Proc Indian Natn Sci Acad 2016, 82(3), 833-46.

In the last decades, globally several small experimental watersheds were set up to study the climate and agricultural influences on water and biogeochemical cycles. Recently, the concept and importance of Critical Zone Observatory (CZO) was made and this resulted in developing such observatories in several countries including a global network of CZOs. The CZOs combine characterization, long term monitoring and modeling to allow understanding of the processes governing water and biogeochemical cycles in a small experimental watershed or network of watersheds. The Kabini CZO too was formed from similar twin experimental watersheds (forested and cultivated) developed during the last decade in the Kabini river basin in the south western part of India. A summary of the salient studies performed on water and biogeochemical cycles under the influence of climate and agriculture during the last ten years in the Kabini CZO are reported here.

12 illus, 37 ref

006431   Saha D;Shekhar S;Ali S;Vittala S S;Raju N J (Central Ground Water Board, MOWR, RD & GR Government of India, Email: shakiriitb@gmail.com) : Recent hydrogeological research in India. Proc Indian Natn Sci Acad 2016, 82(3), 787-803.

The hydrogeological setup of India represents a wide variation, from rugged Himalayan mountainous region in the north, extensive Indo-Ganga-Brahmaputra floodplain and deltaic region in the central and eastern part, aeolian- alluvial deposits in the west, vast basalt flows in the west central part, gently undulating central and southern region underlain by Precambrian crystalline, sedimentary and metamorphic, coastal deposits along the east coast etc. The research on hydrogeology has got special socioeconomic significance because India is now the largest extractor of groundwater in the world. The impact of overexploitation of the resource is surfacing in large parts of the country, in the form of lowering of water level, dwindling yield of well and deterioration in water quality. In recent years, extensive studies have been carried out in this field of geoscience. We have discussed these in different segments, after enumerating the broad hydrological framework of India. The segments are 1. Hydrogeological investigations in Indo-Ganga-Brahmaputra Plains holding one of the potential aquifer systems 2. Groundwater chemistry and contamination issues in Peninsular India 3. Urban hydrogeology 4. Groundwater modeling 5. Ground water exploration 6. Groundwater recharge and associated quality issues 7. Remote sensing and GIS applications 8. Coastal aquifers and 9. Groundwater management. It is observed that the potential groundwater reserve in the Indo-Gangetic basin and the Peninsular part of India has two serious issues: 1. Overexploitation of groundwater mainly in the western and north western parts and also in southern peninsular India in pockets and 2. Groundwater quality deterioration by anomalous concentration of arsenic, fluoride and salinity. The findings of the research will help in understanding the hydrogeological complexities in its entire gamut and also offers insight into the ways for sustainable management of groundwater resource of the country.

155 ref

006430   Saha D;Bhowmik S K;Bose S;Sajeev K (Geological Studies Unit, Indian Statistical Institute, Kolkata-700 108, Email: dsaha@isical.ac.in) : Proterozoic tectonics and trans-Indian mobile belts: a status report. Proc Indian Natn Sci Acad 2016, 82(3), 445-60.

The Archean cratonic nuclei in India are hemmed by Proterozoic mobile belts or fold belts. These mobile belts reveal the tectonic processes that shaped the then craton margin magmatism, sedimentation, metamorphism and deformation of crustal segments, and suturing of the cratonic blocks embedded within the peninsular Indian shield that remained more or less stable since the Cambrian. A loose spatial connection of the Eastern Ghats belt (EGB) along southeastern margin of India, through Chotanagpur granite gneiss terrain and adjoining North Singhbhum fold belt in eastern India, Central Indian tectonic zone, to Aravalli-Delhi mobile belt in northwestern India constitute the trans-Indian mobile belts with tectonic episodes apparently linked to assembly and dispersal of two major supercontinents in the Proterozoic. Beyond southern extremity of the EGB (Ongole domain), the Nellore schist belt and tectonically juxtaposed Nallamalai fold belt in southern India abuts further south against the Southern granulite terrain (SGT) with remnants of Neoarchean inheritance and Neoproterozic remobilization. SGT is a key element in unravelling trans-continental connections of India during the late Neoproterozoic marked by assembly of the Gondwana supercontinent. Despite the apparent first order connection of these belts developed under largely similar global tectonic framework, individual mobile belts show diverse rock association, metamorphic grade and geologic antiquity. In this status report we briefly review these Indian Proterozoic mobile belts and associated fold belts in the light of recently published work bearing on tectonomagmatic, structural, metamorphic and geochronological data and interpretation.

^iia1 illus, 98 ref

006429   Rudraswami N G;Prasad M S (NO, National Institute of Oceanography (Council of Scientific and Industri, Dona Paula, Goa-403 004, Email: rudra@nio.org) : Extraterrestrial components from deep sea sediments of Indian ocean. Proc Indian Natn Sci Acad 2016, 82(3), 653-61.

Two different types of extraterrestrial particulate matter collections were undertaken during the last few years - by using magnets encased in dredges that were dragged along the seafloor and by sieving massive quantities of deep sea sediments from which cosmic spherules were subsequently isolated. Detailed investigations on close to 1000 sectioned cosmic spherules revealed the presence of Pt-group nuggets in all the three basic types of cosmic spherules - all of whom had carbonaceous chondritic meteorites as precursors, thus in a way unifying them. Further, Fe-Ni beads in all types of the investigated cosmic spherules further confirmed this finding. Oxygen isotopes of relict-grains in silicate cosmic spherules suggested chondrules from carbonaceous chondrites to be major contributors. In addition, relict chromite grains and dusty olivines observed in several cosmic spherules suggested that at least 3% of the cosmic material that rains on the earth is sourced from ordinary chondrites. The Australasian microtektites found in the Indian Ocean retained unique microimpact features generated while they were in flight due to inter-particle collisions in the ejecta. This unique phenomenon outlined the importance of the impact process during estimation of cosmic dust fluxes estimated from lunar materials.

4 illus, 32 ref

006428   Rastogi B K (NO, Institute of Seismological Research, Raisan, Gandhinagar-382 009, Email: bkrastogi2@gmail.com) : Seismology in India. Proc Indian Natn Sci Acad 2016, 82(3), 705-25.

Recent seismological research in India can be mainly grouped into study of 1) seismogenesis and seismotectonics of the three regions viz., Himalaya, Andaman-Nicobar subduction zone and the Stable Continental region (SCR); 2) Strong motion study and 3) earthquake prediction. Last few years have witnessed significant change in monitoring of earthquakes through about hundred broadband seismographs in National Network and many more in clusters whose data are brought online to two centers at National Centre for Seismology, Delhi and INCOIS, Hyderabad. Extensive research on reservoir induced earthquakes has culminated into "Deep Crustal Drilling" (DCD) in the Koyna-Warna region down to focal depth to understand the nucleation and generation process of earthquakes.

247 ref

006427   Rao Y J B;Khadke N;Vijaya Kumar T (LAM-MC-ICPMS Facility, CSIR-National Geophysical Research Institute, Hyderabad, Email: yjbhaskarrao@gmail.com) : Research highlights on the evolution of precambrian crust of precambrian crust of peninsular India: constraints from recent zircon U-Pb geochronological results. Proc Indian Natn Sci Acad 2016, 82(3), 489-503.

During the last quadrennial period, (2012-2016), many aspects of the Precambrian geology of the Indian peninsula were revisited by Indian geoscientists and their collaborators with the advantage of modern analytical techniques for geochronology as well as new perspectives on global geodynamics in space and time. Important contributions were made to the Archean and Proterozoic geological evolution of the Dharwar, Singhbhum, Bundelkhand and Bastar cratons, the granulite gneiss terrains, especially the Southern Granulite Terrain (SGT) and the Eastern Ghats Granulite Terrain (EGGT) and also the Proterozoic sedimentary Basins of peninsular India. Significantly, these studies have provided evidence for Paleo- to Eoarchean crustal remnants apart from placing precise age constraints on geological events. Most authors favoured the interpretation of Archean geodynamics in a plate tectonics conceptual framework for the assembly of Indian terranes in the supercontinent reconstructions, as reviewed on the basis of a short compilation of published research articles.

2 illus, 150 ref

006426   Rao V P;Chakraborty P (NO, CSIR-National Institute of Oceanography, Dona Paula-403 004, Email: vprao@nio.org) : Estuarine and marine geology (2011-2015). Proc Indian Natn Sci Acad 2016, 82(3), 625-37.

The estuaries of the Mandovi and Zuari (Ma-Zu) Rivers and Godavari River have been investigated extensively for understanding the sedimentary and bio-geochemical processes during the last 5 years. Estuarine turbidity maximum is a characteristic feature at the mouth of Ma-Zu estuaries, formed by the interaction between tidal currents and river flows during monsoon, and by the re-suspension of bottom sediments by tidal and wind-induced currents during pre-monsoon. Kaolinite and illite, followed by minor goethite, gibbsite and chlorite are present in SPM and sediment of the estuaries. Smectite occurs in traces at river end stations but its contents increased downstream. The ^{87Sr/86Sr ratios of SPM are higher than those in hinterland rocks and laterite soil The Nd isotopic compositions of Ma-Zu estuaries are influenced by the lateritization of source rocks and anthropogenic contribution of ore materials. The major and trace elements in sediments of Ma-Zu estuaries indicate the metals contribution of metals from lateritic formations as well as iron ore. Shale-normalized REE patterns exhibit MREE- and HREE enrichment with positive Ce and Eu anomalies indicative of contamination from iron ore. Stable isotopes of organic matter indicate at least <126>20% terrestrial organic carbon (TOC) to the coastal system during wet season. Chemical speciations studies indicate that the concentrations of non-residual and dynamic metalsediment complexes (which are good indicators of bioavailability) of toxic metals gradually increase with increasing total metal loading in estuarine sediments. Quality and quantity of sedimentary organic matter (SOM) is one of the key factors which play a crucial role in controlling speciation of trace/toxic metal in sediments. The distribution and sources of particulate organic carbon and particulate nitrogen in 27 Indian estuaries during the monsoon indicate higher phytoplankton biomass with deeper photic zone than other estuaries receiving higher suspended matter. Detailed studies on rock-magnetic properties and δ13C_org in sediments off the Krishna-Godavari provide evidence of reductive diagenesis, formation of authigenic sulfides and occurrence of methane in these estuarine sediments and also episodic methane expulsion events.}

2 illus, 42 ref

006425   Rao N V C;Srivastava R K (Geology Dep, Centre of Advanced Study, Banaras Hindu Univ, Varanasi-221 005, Email: nvcr100@gmail.com) : Kikberlites, lamproites, lamprophyres, carbonatites, other Alkaline rocks, and mafic dykes from the Indian shield: glimpses of research (2012-2016). Proc Indian Natn Sci Acad 2016, 82(3), 515-36.

Major highlights of researches carried out on kimberlites, lamproites, lamprophyres, carbonatites, other alkaline rocks and mafic dykes from the Indian shield during 2012-2016 are presented. New findings involving field mapping, petrology, geochemistry (including high quality mineral based in situ isotopic studies) and geophysics have provided remarkable insights on the mode of their occurrence, timing of emplacement, mineralogy and bulk-rock composition, redox conditions, relative contribution of the lithosphere and asthenosphere, as well as their economic potential. Several large-scale geodynamic aspects such as plume-lithosphere interactions, ancient subduction events, layered structure of the sub-continental lithospheric mantle, spatial extent of the Precambrian large igneous provinces and supercontinent configurations could be unraveled from these studies on deep-mantle derived small-volume magmatic rocks.

5 illus, 96 ref

006424   Rajendran C P (NO, Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru-560 064, Email: cprajendran@gmail.com) : Paleoseismology: 2010-2016. Proc Indian Natn Sci Acad 2016, 82(3), 695-704.

We present here an overview of progress in paleoseismological/active fault researches in India during 2010-2016. These studies initiated in the country in early nineties have now expanded in scope and gained further momentum. Moving into a greater variety of morphological settings, several groups of researchers are now involved in defining the fault geometry and the nature of near-surface crustal deformation in various tectonic regimes with a view to constrain the frequency and magnitude of fault activations, thereby contributing to earthquake hazard evaluations. Future challenges would include integrating paleoseismological observations with relevant geophysical inputs and developing physical models of the complete earthquake cycle, ultimately leading to an inventory of active faults.

42 ref

006423   Padhy P K;Arun Kumar;Chandra Y R;Das S K;Jha S K;Advani D R (COD-Shale Gas, Oil & Natural Gas Corporation, Vadodara-390 009, Email: padhy_pk@ongc.co.in) : Shale oil exploration from paleocene-early eocene sequence in Cambay Rift basin, India. Proc Indian Natn Sci Acad 2016, 82(3), 945-63.

Shale gas and oil constitute an important unconventional resource of hydrocarbons stored in organic rich, matured fine grained sedimentary rock. The organic rich source rock, on deep burial, results in conversion of organic matter into oil and natural gas. A major part of the hydrocarbons is expelled, migrated and entrapped in ideal locales constituting conventional accumulations in the basin. The residual quantities retained within the original source rock constitute the unconventional shale gas and oil plays. The gas and oil in shale are held as free hydrocarbons within natural fractures, pore spaces and some gas are stored as adsorbed gas on the organic matter. The shale, characterized by low matrix permeability, requires hydrofracturing for shale gas and oil production. A pilot Shale gas and oil well (Well-X) is drilled in Broach-Jambusar block of Cenozoic Cambay Petroliferous basin is drilled and extensive core has been collected in the Cambay Shale section of Paleocene-early Eocene age. Detailed shale specific geological, minerological, geochemical, petrophysical, geomechanical, desorption and adsorption isotherm studies etc are carried out and are synthesized for prospect evaluation. The Cambay Shale is moderately fissile, silty with presence of occasional fractures. The average Total Organic Content (TOC) is around 2.9wt%. The shale is characterized by high clay (kaolinite and chamosite) content of around 55% with average quartz content around 29%. The shale resistivity is 1.5-4.0 ohm-m. Based on integrated analysis, a zone of 60 m was hydrofractured and it yielded oil (API gravity: 40.0). Transgressive Regressive cycle analysis of the shale section has been attempted for better understanding of the unconventional plays.

15 illus, 27 ref

006422   Mukul M;Singh V (Continental Deformation Laboratory, Earth Sciences Dep, Indian Institute of Technology, Mumbai-400 076, Email: malaymukul@iitb.ac.in) : Active tectonics and geomorphological studies in India during 2012-2016. Proc Indian Natn Sci Acad 2016, 82(3), 727-35.

This article reviews the literature on tectonic geomorphological studies in India published in peer reviewed journals between 2012-2016. The northward drift of the Indian plate and its collision with the Eurasian plate results in compressive stresses in Indian subcontinent. Based on the broad morphotectonic setup the studies are categorised into the Himalaya and the Indian Peninsula. Studies in the Himalaya mainly demonstrate that most of the deformation during Holocene has occurred in the sub-Himalaya and especially along the Main Frontal Thrust (MFT). Evidences of active tectonics is also reported from several parts of the Himalaya which also includes the Main Boundary Thrust (MBT) zone. The impact of active tectonics on the geomorphology along the active faults is also investigated in several areas of the Himalaya. In the Indian Peninsula Narmada-Son fault, Tapti fault and Katrol hill fault are shown to be active on the basis of sedimentological and geomorphological investigations.

28 ref

006421   Mondal A;Narasimhan B;Sekhar M;Mujumdar P P (Civil Engineering Dep, Indian Institute of Technology Bombay, Powai, Mumbai-400 076, Email: pradeep@civil.iisc.ernet.in) : Hydrologic modelling. Proc Indian Natn Sci Acad 2016, 82(3), 817-32.

Advances in computational tools and modelling techniques combined with enhanced process knowledge have, in recent decades, facilitated a rapid progress in hydrologic modelling. From the use of traditional lumped models, the hydrologic science has moved to the much more complex, fully distributed models that exude an enhanced knowledge of hydrologic processes. Despite this progress, uncertainties in hydrologic predictions remain. The Indian contribution to hydrologic science literature in the recent years has been significant, covering areas of surface water, groundwater, climate change impacts and quantification of uncertainties. Future scientific efforts in hydrologic science in India are expected to involve better, more robust observation techniques and datasets, deeper process-knowledge at a range of spatio-temporal scales, understanding links between hydrologic and other natural and human systems, and integrated solutions using multidisciplinary approaches.

4 illus, 108 ref

006420   Mishra S K;Phukon J;Bhoktiari P;Rahaman A (Oil & Natural Gas Corporation Ltd., , Jorhat, Assam, Email: mishrasarad75@gmail.com) : Integrated structural analysis of fractured basement reservoir in the South Assam shelf, India. Proc Indian Natn Sci Acad 2016, 82(3), 923-33.

Hydrocarbon potential of fractured basement in South Assam shelf has a complex geological history related to episodic evolution of the basin. In the complex tectonic evolution processes from passive margin to active margin, Precambrian Basement has experienced severe fracturing up to deep level. In the highly fractured Basement, where overlying sedimentary column is thicker with the presence of other favourable components of entrapment model, chances of hydrocarbon success is high. The Borholla Field in the north eastern edge of the study area is fully developed for its hydrocarbon commerciality from Basement in last three decades while recent oil find within fractured Basement in southern part in Khoraghat area has also opened up rest of the Basin for Basement exploration. Application of conventional seismic methods for mapping of natural fracture distribution cannot be conducted directly due to dimension of fracture lying below the seismic resolution (sub-seismic). This paper presents an integrated structural analysis of the prospectivity of basement exploration in the study area.

7 illus, 41 ref

006419   Mishra B (Geology and Geophysics Dep, IIT Kharagpur, Kharagpur-721 302, Email: bmgg@iitkgp.ac.in) : Metallogeny. Proc Indian Natn Sci Acad 2016, 82(3), 505-13.

This article briefly reviews all contributions by Indian geoscientists in the period 2011-2016 in the field Metallogeny. The contributions covered are mainly on deposits and prospects of chromite, PGE, gold and uranium. Very few contributions have been made on base metals. However, experimental sulfide phase equilibrium research, related to metamorphic remobilization of massive sulfides, has been initiated.

51 ref

006418   Mandal N (Geological Sciences Dep, Jadavpur Univ, Kolkata-700 032, Email: nibirmandal@yahoo.co.in) : Chrrent trends of geodynamic research in India: a review of theoretical and experimental studies. Proc Indian Natn Sci Acad 2016, 82(3), 425-34.

This paper presents a review of the geodynamic studies, giving a special emphasis on the recent theoretical and experimental work in India. The geodynamic research has progressed broadly in the three major areas- physical states of Earth's interior, thermo-mechanical processes, and lithospheric slab dynamics. Understanding the physical properties of minerals under extreme pressures and temperatures is one of the major challenges in solid earth geophysics. This review provides an account of the theoretical studies in mineral physics in India, which primarily use ab-initio calculations to characterize the high-pressure behaviour of silicates and oxides, and discusses their implications in predicting geophysical discontinuities. A number of researchers in India are actively engaged in performing physical as well as numerical model experiments to study a range of thermo-mechanical processes, such as plumes in Earth's mantle, subduction of lithospheric slabs in convergent tectonic settings and evolution of the mid-oceanic ridges in divergent tectonic boundaries. This review summarizes the outcome of these studies in the perspective of current research trends in geodynamics.

^iia9 illus, 20 ref

006417   Krishna K S;Raju K A K;Ramprasad T;Chaubey A K;Dewangan P;Yatheesh V (NO, CSIR - National Institute of Oceanography, Dona Paula, Goa-403 004, Email: krishna@nio.org) : Advances in marine geophysical studies of the Indian ocean: contributions from India (2010-2015). Proc Indian Natn Sci Acad 2016, 82(3), 639-52.

Indian scientists carrying marine geophysical research at different Earth Science institutions have made significant advances during the last six years (2012-2015) for understanding evolution of continental margins of India and deep sea regions. The investigations were mostly focused on continental margins of India encompassing deep-water regions, mid-ocean ridges, aseismic ridges and Andaman Sea including the back-arc basin. The studies were aimed at unraveling the tectonic and physical processes associated with evolution of the margins, ocean basins, volcanic structures, etc. In addition, industryrelated research for mapping of energy resources such as gas hydrates and hydrocarbons was also carried out in rifted basins on Eastern Continental Margin of India. The investigations were successfully carried out with integration of several geophysical datasets available at National Institute of Oceanography, India, National Geophysical Data Center, USA and petroleum industries, and by acquiring new geophysical data and geological sampling. In this report we describe major outcomes of the investigations focused on specific geological aspects of the Indian Ocean. Investigations carried out by individual works are also included in the bibliography. Geophysical studies carried out over the Ninetyeast Ridge led to understand how the Kerguelen plume interacted with the spreading centers as well as with the lithosphere during emplacement of volcanic edifices, isostatic compensation mechanisms of the ridge and magma production rates in response to the Indian plate motion. The analyses of seismic data over the 85°E Ridge revealed the internal structure consisting of volcanic plug and several stratigraphic units such as lava-fed deltas and prograding clinoforms. The lava deltas along with intervening erosional surfaces and mass wasting on ridge flanks suggested that the ridge was built by both subaqueous and multiphase submarine volcanism during the late Cretaceous. Study of seismic reflection data of the Eastern Continental Margin of India and adjacent deep-water region revealed two different phases of sediment deposition piled in the Bay of Bengal. The sediment distribution pattern, thickness and the bay architecture unveiled an occurrence of major change in sediment source from the peninsular India to the Bengal Basin at <126>23 Ma as a result of uplift of Himalayas and onset of Asian monsoon system and this eventually led to the commencement and growth of the Bengal Fan. The gas hydrates studies in Krishna-Godavari (KG) offshore basin revealed that the hydrate distribution in the basin is controlled mainly by fault systems. The velocity analysis of sediment strata within the basin suggested occurrence of high concentration of gas hydrate close to the large-scale fault system. Thus, the fault system in KG Basin provides a conducive environment for the migration of methane, which upon entering the hydrate stability zone forms the fracture-filled gas hydrate deposits. Marine geophysical data of both the continental margins of India and western Andaman region were studied for extending the country's limit of the continental shelf beyond the Exclusive Economic Zone. The scientific and technical information extracted from the studies would serve its primary purpose of delineating the outer limits of India's continental shelf beyond 200 nautical miles. The teleseismic studies of the back-arc basin, Andaman Sea revealed that the back-arc spreading fabric is undergoing readjustment to be in equilibrium with the current plate motions. A passive Ocean bottom seismometer (OBS) experiment in the back-arc basin recorded several events including teleseismic, microseismic and local events. Geological and geophysical studies over the Carlsberg and Central Indian Ridges have brought out finer scale segmentation of the ridge system and delineated zones of magmatic and sparsely magmatic sections of the ridges. The water column and deep-tow investigations carried out over the Carlsberg Ridge provided evidences for a prominent plume signatures emanating from a seafloor hydrothermal vent system. A model for the early opening of the Arabian Sea for the period 88 to 56.4 Ma is proposed with the consideration of the Gop and Laxmi Basin spreading centers as two arms of a triple junction and Narmada Rift on the Indian peninsula in the east as third arm of the triple junction. The reconstruction model did provide a new view on dispersals of Madagascar, Seychelles and India, during their early drift period, wherein the Laxmi Ridge and the Laccadive Plateau have been accommodated as intervening continental slivers.

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006416   Kale V S (Advanced Centre for Water Resources Development & Management [ACWADAM], , Sus Road, Pune-411 029, Email: dr.vivekale@gmail.com) : Proterozoic basins of peninsular India: status within the global proterozoic systems. Proc Indian Natn Sci Acad 2016, 82(3), 461-77.

This compilation is intended to present a snap-shot of the current status of the knowledge on the Proterozoic sediments and tectonic events that are preserved in Peninsular India; on the backdrop of the growing understanding of global events and environmental evolution during that period. Proterozoic sediments in Peninsular India are found in two contrasting categories of basins. Narrow linear intercratonic belts host terrigenous and marine sediments, often interbedded with volcanics and volcaniclastics; that are deformed, metamorphosed and occasionally intruded by granitic bodies. These belts abut with a tectonic contact with wide, unmetamorphosed platform sediments from epicratonic basins with limited igneous activity associated within them; clubbed as the Purana Basins of Peninsular India. Although traditionally the former (mobile belts) were considered to be older and different from the latter, emerging geochronological data demonstrates that they were coeval products of basins evolving adjoining each other in diverse tectonic setting. Available knowledge on these basins is summarised within the framework of the emerging understanding of the Proterozoic geohistory punctuated by assembly and break-up of supercontinents, progressive oxygenation of the atmosphere, changes in the sea-water chemistry; establishment of the continental free-board and the generic environments that laid the foundation of biotic evolution. Although significant advances have been made in the last decade in the knowledge of these sediments, much more is required to achieve the desired precision and resolution.

4 illus, 149 ref