ground penetrating radar assisted saturation and permeability estimation in bimodal systems near surface investigations often require characterization of vadose zone hydraulic parameters conventional sampling or borehole techniques for estimating these parameters are costly time consuming and invasive all of which limit collection of hydrogeological data at a spacing needed for detailed site characterization incorporation of two or three dimensional densely sampled geophysical data with conventional hydrological data increases the amount of data available for the characterization and thus has the potential to significantly improve the hydraulic parameter estimates over those obtained from borehole data alone the hydraulic estimation procedure can be greatly improved by incorporating dielectric information potentially available from ground penetrating radar gpr a noninvasive high resolution geophysical method the procedures for collecting and processing gpr data in the format needed for the proposed estimation technique are relatively new and still a topic of research our method requires as a starting point the ability to estimate dielectric constants from gpr data numerical experiments were performed to investigate the general utility of the gpr assisted estimation technique under a range of conditions three bimodal systems were investigated each system being composed of a sand facies together with another facies with a larger clay volume fraction each facies was defined using characteristic values of clay content porosity and permeability using dielectric information and petrophysical relations degree of saturation and intrinsic permeability values at each location within the three systems were identified for bimodal systems a dielectric constant measurement corresponds to two possible values of saturation and intrinsic permeability at each location single values of saturation and intrinsic permeability were estimated from these values using the principle of maximum likelihood results from case studies demonstrate that a combination of gpr data with conventional borehole data significantly improves the estimates of saturation and has the potential to improve the estimates of permeability over those obtained from well bore data alone the proposed method should be especially advantageous for vadose zone characterization in areas favorable for gpr data acquisition where detailed hydraulic parameter information is required but the drilling of numerous boreholes is prohibited

late quaternary climate variability and vegetation response in ziro lake basin eastern himalaya a multiproxy approach abstract pollen phytolith and stable carbon isotopic records provide new insights into the palaeoenvironmental and palaeoclimatic changes in ziro lake basin sub himalayan arunachal pradesh india since pre lgm time phytoliths record a minor change in grass woodland cover and appear to be more sensitive than pollen grains to climate fluctuations both pollen and non pollen palynomorph data suggest prevalence of a dense c3 species dominated moist semi evergreen forest in the area until the lgm which shows conformity with 13c data the phytolith assemblage indicates an alteration in forest cover with expansion of c4 grasses during the lgm the study further indicates a climatic amelioration with intensification of south west monsoon during 10 2 3 8 ka and an expansion of forest cover after 3 8 ka there was a rising trend of dryness shrinkage in forest cover and a slight increase in c4 species while c3 plants dominated ecosystem variability also points towards a hydrological transformation in the area since pre lgm time application of coexistence approach on pollen data reveals that prior to the lgm the mean annual temperature and mean annual precipitation were approximately 19 3 0 001 c and 1925 15 mm respectively between 10 2 and 3 8 ka mat was about 19 4 0 5 c while map was 1901 41 3 mm between 3 8 and 1 2 ka and onwards a slight increase in mat 0 3c was observed with further decrease in map to 1861 33 4 mm during pre and post lgm times mat was more or less similar in the ziro lake basin which increased gradually after 3 8 ka and was 1 2 c higher than today prior to the lgm map was higher than the present day by 94 mm between 10 2 and 3 8 ka by 70 mm and since 3 8 ka onwards by 30 mm showing a tendency of gradual decline suggesting a consequent increase in dryness

high resolution characterization of vadose zone dynamics using cross borehole radar characterization of the dynamics of moisture migration in the unsaturated zone of aquifers is essential if reliable estimates of the transport of pollutants threatening such aquifers are to be made electrical geophysical investigation techniques such as ground penetrating radar offer suitable methods for monitoring moisture content changes in the vadose zone moreover these tools permit relatively large measurement scales appropriate for hydrological models of unsaturated processes and thus they offer a distinct advantage over conventional measurement approaches ground penetrating radar when applied in transmission mode between boreholes can provide high resolution information on lithological and hydrological features the technique may be applied in tomographic mode and in a much simpler vertical profile mode both modes of measurement have been utilized using two boreholes 5 m apart located at a field site in the uk sherwood sandstone aquifer radar transmission measurements have been used to characterize the change in moisture content in unsaturated sandstone due to controlled water tracer injection continual monitoring of cross borehole radar measurements over an 18 month period has also permitted determination of travel times of natural loading to the system and has revealed the impact of subtle contrasts in lithology on changes in moisture content over time the time series of inferred moisture contents show clearly wetting and drying fronts migrating at a rate of approximately 2 m month 1 throughout the sandstone

monsoon fluctuations in two 20 000 yr b p oxygen isotope pollen records off southwest india abstract two marine pollen diagrams for sediments off the southwest coast of india provide a 20 000 yr history of the nearby continental vegetation determined by the monsoon climate within the framework of the isotopic stratigraphy two important phases of the evolution of the monsoon climate are a very arid period about 22 000 18 000 yr b p and a very humid period culminating at 11 000 yr b p the very arid period corresponds to the lowest pollen representation of mangrove vegetation which is used here as an indirect indicator of monsoonal runoff this aridity is due to a very weak southwest airflow a great reduction of summer monsoonal rainfall and reduced runoff of the western ghats rivers the extension of the monsoon over india after the last glacial maximum has been a gradual process following the northward progression of the intertropical convergene zone the very humid period corresponding to the highest pollen representation of mangrove vegetation and the heaviest summer rainfall is a climatic response to the maximum summer insolation of the northern hemisphere at 11 000 yr b p

radar reflections from sedimentary structures in the vadose zone ground penetrating radar gpr is a suitable technique for imaging sedimentary structures in the vadose zone because small texture related capillary pressure variations lead to changes in water content and electromagnetic properties to study exactly how gpr reflections are generated by sedimentary structures gpr profiles of an aeolian sedimentary succession are combined with measurements of textural electromagnetic and water retention characteristics from a trench time domain reflectometry indicates that small variations in texture in the high angle dune sediment are associated with changes in water content synthetic modelling shows that these changes cause clear gpr reflections in an experimental approach to estimate the radar response of structures below the wave resolution i e features smaller than 4 variations in grain size distribution and porosity in a thin section were used to reconstruct water retention curves and impedance models of the thinly layered sediment synthetic radar records calculated from the impedance models show that reflections from the studied subcentimetre scale structures are composites of interfering signals although these low amplitude interfering signals will commonly be overprinted by more prominent reflections they may cause reflection patterns that change with frequency and do not represent primary bedding

tectono climatic signatures during late quaternary in the yunam basin baralacha pass upper lahaul valley india derived from multi proxy records abstract this study provides evidence of the monsoon record over the past 25 ka from the kilang sarai palaeolake which is located in nw himalaya in the rain shadow zone of the indian summer monsoon ism the multi proxy study by using geomorphology carbon isotopes mineral magnetism clay mineralogy and elemental chemistry of a 8 m thick laminated lacustrine sediments indicates that the area experienced fluctuating precipitation conditions during the last 25 ka the time period between 12 and 5 ka bp can be regarded as a very wet interval of the last glacial to mid holocene due to a combined effect of ism and westerlies followed by aridity after 5 ka bp tectonic triggers may have caused the development of terraces and closure of lake at the millennial time scale a correlation of precipitation and vegetational changes between our data and other records from similar geographical settings suggests that kilang sarai basin responded to periods of strengthening in precipitation during the last glacial to early holocene

neotectonically triggered instability around the palaeolake regime in central kumaun himalaya india mass wasting often results from the combined effect of tectonic and climate processes it has not only resulted in human casualties on large scale but has also ruined agricultural land and disrupted hydro power projects and other governmental as well as private property despite the belief that prevention is inevitably better than cure decrease in future hazards requires proper dissemination of knowledge to the himalayan inhabitants considering this we investigated a part of kumaun himalaya to understand the cause of cloud burst induced mass movements along the saryu river that took place on 18th august 2010 and subsequently on 12 14th september 2012 a number of quaternary faults e g dulam fault df dulam gadhera fault dgf and vongarh gason fault vgf in the zone of a major thrust berinag thrust in the studied sector are invariably active as evident by various geomorphic features e g saw cutting of host rocks immature topography deflecting river courses ponding of ancient drainage development of cascades formation of unpaired fluvial terraces and series of triangular fault facets the fragile lithology deep v shaped valleys accelerating erosion and incision with higher uplift due to tectonic upheaval along the active faults are also responsible for rainfall induced catastrophes in the region additionally morphometric analysis reveals that the saryu basin is elongated and tilted further the tectonic tilting and moderate to coarse drainage density may possibly be responsible for quicker runoff amplified erosion and subsequently increased flooding around the study area we infer that the area is not only controlled by topography but may also have been affected by the hydraulic factors such as climate in addition the drainage is dominated mostly by first order streams which seem to be indicative of higher chances of flooding as most of the water is concentrated in a single channel during monsoon season we believe that the similar studies done in the other sectors will be helpful in reducing not only the huge loss of life but may also help in protecting ongoing and huge hydropower and other developmental projects in this newly born state

a review of lacustrine paleomagnetic records from western north america 0 40000 years bp abstract a review of 16 lake sediment paleomagnetic records from western north america spanning time intervals over the last 40 000 yr bp provides evidence that many of these lacustrine records have recorded geomagnetic secular variation with wavelengths on the order of a few hundred years the younger studies 0 13 300 yr bp show general morphologic agreement among inclination records but most of the declination records are difficult to correlate among the older records there are major disagreements over the existence of the mono lake excursion specifically five studies contain evidence for the excursion but six studies do not show any record of it because errors in radiocarbon dating will distort down core time scales the younger records were rescaled with time scales that were constructed from extremal correlations of long wavelength 1000 2000 yr high amplitude 10 20 inclination features with these new time scales the excellent temporal and morphologic agreement between the fish lake oregon and blue lake idaho declination records confirms the existence of errors in the radiocarbon time scales the lack of agreement among the other rescaled declination records indicates that the records have been distorted or altered by sedimentary and geologic processes and or by sampling measuring and data analysis procedures in terms of the regional geomagnetic record fish lake and blue lake present a 3300 yr master curve of secular variation for northeastern oregon and southwestern idaho the lack of correlation among the other records however prevents us from drawing definite conclusions about the areal variation of the geomagnetic field in western north america over the past 40000 yr bp

late pleistocene paleomagnetic secular variation from the sea of galilee israel 1 stable magnetization of laminated lacustrine lisan formation show typical paleomagnetic secular variation and a possible geomagnetic field excursion 14c ages from the top and assumed 0 9 mm yr deposition rate constrain the recorded section between 29 28 ka and 22 23 ka samples were recovered from two trenches at the southwestern shore of the sea of galilee a graben within the dead sea transform system the angle between the two site mean directions is 21 but retilting the beds to horizontal reduces it to 7 indicating pre folding probably depositional magnetization aberrations of field directions at one locality where vgps deviate 40 from the geographic north and low nrm intensities between 29 28 ka and 25 24 ka are contemporaneous with the mono lake excursion if the correlation is correct the new data support the hypothesis that the excursion was global justifying its utilization as a chronological datum

paleomagnetic evidence for long term 104 year memory and periodic behavior in the earth s core dynamo process a new paleomagnetic secular variation psv record from the late quaternary wilson creek beds of mono lake california contains a distinctive periodic vector waveform that follows and is almost certainly related to the mono lake excursion a comparison of all published psv results from the wilson creek beds suggests that the magnetic field at mono lake went through an interval 36 000 28 000 ybp of very low amplitude psv followed by the mono lake excursion 28 000 27 000 ybp and four subsequent recurrences 27 000 12 500 ybp of the excursion waveform with relatively diminished amplitudes lower than the excursion amplitude but higher than psv amplitudes at mono lake since 12 500 ybp this pattern clearly suggests that the mono lake excursion is related to typical psv it also suggests that the core dynamo process responsible for psv is capable of near impulse onset persistence over a time scale of 15 000 years and quasi periodic behavior that is non wave length dispersive in time

electromagnetic ray trace tomography electromagnetic em tomography can be used to estimate the distribution of electrical rock properties between boreholes for typical oil field well spacings and reservoir electrical characteristics crosswell em measurements are sensitive primarily to the electrical conductivity not the permittivity ray tracing methods normally associated with undamped propagating waves can also be applied to the rapidly attenuated diffusive em waves encountered in the petroleum reservoir environment thermal noise considerations place an upper limit of approximately 20 skin depths on the separation between wells

bayesian method for hydrogeological site characterization using borehole and geophysical survey data theory and application to the lawrence livermore national laboratory superfund site a stochastic bayesian approach for combining well logs and geophysical surveys for enhancing subsurface characterization is presented the main challenge we face is in creating the bridge to link between ambiguously related geophysical surveys and well data the second challenge is imposed by the disparity between the scale of the geophysical survey and the scale of the well logs our approach is intended to integrate and transform the well log data to a form where it can be updated by the geophysical survey and this tends to be a convoluted process our approach starts with generating images of the lithology conditional to well logs each lithology image is then used as the basis for generating a series of shaliness images conditional to well log data shaliness images are converted to resistivity images using a site specific petrophysical model relating between shaliness resistivity and lithology to create the necessary interface with the cross well resistivity survey the lithology and resistivity images are then updated using cross well electromagnetic resistivity surveys we explored the limits of the approach through synthetic surveys of different resolutions and error levels employing the relationships between the geophysical and hydrological attributes which are weak nonlinear or both the synthetic surveys closely mimic the conditions at the llnl superfund site we show that the proposed stochastic bayesian approach improves hydrogeological site characterization even when using low resolution resistivity surveys

estimation of the spatial distribution of fluid permeability from surface and tomographic gpr data and core with a 2 d example from the ferron sandstone utah reservoir analogs provide detailed information that is applicable to fluid transport simulations but that cannot be obtained directly from reservoirs because of inaccessibility the ferron sandstone of east central utah is an analog for fluviodeltaic reservoirs its excellent outcrop exposures are ideal for detailed study ground penetrating radar gpr data were collected in and between two cored boreholes and are used to build a 2 d fluid permeability model in four steps first an anisotropic gpr propagation velocity model is obtained from traveltime tomography between two boreholes and between each borehole and the earth s surface second the geometry of the sedimentological features is imaged by prestack kirchhoff depth migration of constant offset gpr data acquired along a line between the two holes at the earth s surface third a background permeability is assigned to each layer by interpolating the geometrical average of the measured permeabilities in each sedimentological element finally the

climatic variations and geomorphology of the indus river valley between nimo and batalik ladakh nw trans himalayas during late quaternary abstract the indus river valley is tectonically unstable exhibiting complex topography landscape relief and varied sedimentation the major geomorphic landforms are alluvial fans debris cones fluvio lacustrine deposits scree and talus cones in the present work a transect between nimo and batalik along the river was studied to consider the geomorphological landform evolution during the quaternary based on the distribution of the sediments along the valley mass movements catastrophic land sliding and tectonic activity transported material from steep slopes to valley bottoms which were responsible for forming lakes preserved as thick piles of fine sediment while the outburst floods redistributed sediment down valley three phases of lake formation are recorded in the 136 km stretch 35 000 26 000 bp lamayuru palaeolake 17 000 13 000 bp rizong palaeolake occupying 35 km of the valley length and 14 000 5000 bp khalsi saspol palaeolake 55 km in length and having the highest lake levels the lake formation is attributed to deglaciation after the last glacial maximum lgm and holocene warming tectonic activity seismites are concentrated only at 10 and 6 ka

acquisition and processing of wide aperture ground penetrating radar data a 40 channel wide aperture ground penetrating radar gpr data set was recorded in a complicated fluvial aeolian environment in eastern canada the data were collected in the multichannel format usually associated with seismic reflection surveys and were input directly into a standard seismic processing sequence filtering static corrections common midpoint gathering velocity analysis normal and dip moveout corrections stacking and depth migration the results show significant improvements over single channel recordings in noise reduction and depth of penetration by stacking and in spatial positioning and reduction of diffraction artifacts by migration these characteristics increase the potential for reliable interpretation of structural and stratigraphic details thus without having to develop any new software gpr data processing technology is brought to the same level of capability flexibility and accessibility that is current in seismic exploration

palaeoclimatic reconstruction by using the varvite sediments of bharatpur upper lahaul valley nw himalaya india a 6 m thick varvite profile exposed at bharatpur 77 27 e 32 48 n altitude 4692 m in the nw himalaya was investigated to understand the past climatic signatures during the late quaternary period the radiocarbon chronology brackets the varvite sedimentation between 24 3 and 7 2 ka bp and the sedimentary sequence is bounded by river born gravel at the top and glacial outwash at the bottom the proxies used were lithology chronology ams radiocarbon dating geochemical analysis loss on ignition loi and mineral magnetism other parameters e g chemical index of alteration cia chemical index of weathering ciw al2o3 sio2 fe2o3 cao mgo and al na ratio were also used based on the combined data set six phases of warm and cold climatic conditions are reconstructed the mean cia ciw and al na ratios reveal that the sediments were incorporated from sedimentary rocks by moderate silicate chemical weathering process based on the available chronology the basal most glacial outwash event can be estimated as ca 24 3 ka bp and the laminated section shows continuity of sedimentation from the late quaternary to holocene the period between ca 24 3 and 22 6 ka can be regarded as an arid phase from ca 22 6 20 5 ka bp a slight increase in monsoonal precipitation is observed followed by decreased precipitation from ca 20 5 to 18 ka bp the period from ca 18 to 15 7 reveals warm and humid climatic conditions we suggest that a cold event from ca 15 7 to 11 5 may correspond to the younger dryas yd which in turn is followed by a phase of maximum moisture of the holocene climate optimum hco ca 11 5 7 2 ka bp in the study area the increased cia during deglaciation and hco suggest high chemical weathering whereas the lgm last glacial maximum and yd are represented by the low cia the observed climatic phases events are in agreement with the records from other parts of the himalaya

soil carbon isotope evidence for holocene habitat change in the kenya rift valley in eastern africa the altitude of the boundary between montane forest and lowland savanna grassland changed substantially in response to climate change during the later holocene but this is not clearly reflected in regional pollen records the carbon 13 to carbon 12 ratios of tropical grasses are higher than those of most other plants and this difference is preserved in soil organic carbon stable isotope ratios soil organic matter 13 c 12 c ratios in profiles along an altitude transect in the central rift valley of kenya suggest that the forest savanna boundary advanced more than 300 meters in altitude this could have implications for understanding the effects of climate change on the configuration of floral zones prehistoric hunter gatherer land use patterns and the timing of the advent of neolithic food production

geochemical characterization using geophysical data and markov chain monte carlo methods a case study at the south oyster bacterial transport site in virginia 1 the study demonstrates the use of ground penetrating radar gpr tomographic data for estimating sediment geochemical parameters using data collected at the department of energy south oyster bacterial transport site in virginia by exploiting the site specific mutual dependence of gpr attenuation and extractable fe ii and fe iii concentrations on lithofacies we develop a statistical model in which lithofacies and fe ii and fe iii concentrations at each pixel between the boreholes are considered as random variables the unknown variables are estimated by conditioning to the colocated gpr data and the lithofacies measurements along boreholes using a markov chain monte carlo method cross validation results show that the geophysical data constrained by lithofacies have the potential for providing high resolution multidimensional information on extractable fe ii and fe iii concentrations at the south oyster site

water and sediment geochemistry of major kumaun himalayan lakes india four major himalayan lakes in kumaun region in india namely nainital bhimtal sattal and naukuchiatal have been studied to understand water and sediment geochemistry the lakes are characterised by varying degrees of natural and human influences the nainital is intensively used and is a major tourist destination whereas the other three lakes have attracted much attention lately the lakes have a tectonic origin and are characterised by dolomites limestones shales and silicate rocks the water chemistry is dominated by ca mg and hco3 an indication of a carbonate lithology source for the water composition about 55 80 of na and only 30 40 of ca in the lakes are derived from silicate lithology the nainital lake is also characterised by a high chemical index of alteration which is reflected in its high carbonate and the clay mineral content of the sediments model calculations show that 33 and 67 of nitrate in sattal lake is contributed by agriculture and cultural effects respectively the 87sr 86sr ratios in the lakes are very high 0 72 with samples from sattal lake being extremely radiogenic 0 82 similar to many himalayan rivers the 1 sr 87sr 86sr in sediments show two major sources for sr silicates and carbonates the contributions of sr from carbonate and silicate lithology is estimated to be 25 and 60 respectively in bhimtal lake

mapping permeability in heterogeneous aquifers using hydrologic and seismic data a new method is presented for identification of the permeability distribution in near surface aquifers in addition to using the usual sparsely sampled pressure and permeability data the method incorporates densely sampled seismic data as obtained from a reflection or tomography survey along with empirical relationships between seismic and hydraulic properties the procedure is to first estimate by hydrologic inversion a pressure field then the velocity permeability pressure relationship is used to map the inverted pressure and measured seismic data to multivalued estimates of the permeability of those the most probable value based on the hydrologic inversion is selected in synthetic case studies the tremendous increase in coverage offered by the seismic data leads to dramatically better results in terms of both accuracy and resolution an appealing feature is the use of relatively easy to acquire pressure data a second is the incorporation of geophysical data which can sample an entire aquifer remotely without the need for an expensive and invasive drilling program

new species of silurian acanthodians from the mackenzie mountains canada two new acanthodian taxa are described the ischnacanthid xylacanthus kenstewarti is based on large dentigerous jaws and granulacanthus joenelsoni is based on isolated spines the isolated remain

tectonic footprints and landscape evaluation along kulur river valley kumaun lesser himalaya india abstract tectonic reactivation along the major boundary thrusts and subsidiary thrust faults in the himalaya during the quaternary period has resulted in the rejuvenation of the landforms considering the role of neotectonic activity in the hazardous kumaun region we aim to study the neotectonically formed landscape along the kulur river valley a non glacier fed tributary of the saryu river in the zone of the berinag thrust bt the field evidences encompassing a variety of geomorphic indicators e g unpaired fluvial terraces palaeo river channels alluvial fans active and stabilized landslides lineaments waterfalls alignment of springs deeply dissected hills straight meandering course of rivers streams v shaped valleys triangular fault facets and water logged river ponding along with integrated values of eight morphometric parameters and stream steepness index ks indices characterize the modification of landscape in the kulur river valley the computed morphometric parameters in the kulur river drainage and its tributaries show that the basin has been tilted and uplifted forming v shaped valleys along with deformed and disequilibrium longitudinal profile thereof suggesting it to be controlled by lithology and tectonics based on the response of active tectonics in form of geomorphic features and quantitative measurements of river channels the entire basin has been divided into three segments in which the northern and southern segments are active compared to the middle sector a possible nne ssw trending lineament fault running parallel to the kulur river has been observed in the upper catchment and is characterized by fluvial terraces river ponding and deflection and offsetting of drainage with rectangular pattern etc this may have given rise to the widening and straightening of river courses which provide the favorable room for river ponding resulting in deposition of about 2 m thick lacustrine mud deposit

dip moveout by fourier transform the conventional normal moveout nmo and common midpoint cmp stacking process enhances reflections having a particular moveout velocity while attenuating events such as multiple reflections having different moveout velocities unfortunately this process also acts as a dip filter applied to the cmp stack in other words nmo and stacking enhances reflections having a particular slope in the cmp stack while attenuating reflections having different slopes nmo and stacking like any dip filter degrades lateral resolution fortunately this dip filtering action can be suppressed by applying in addition to nmo a prestack process known variously as devilish prestack partial migration and dip moveout as the latter term implies this process is a dip dependent moveout correction that enables reflections from both horizontal and dipping reflectors to be stacked with the same nmo velocity stated another way nmo velocities estimated from dip moveout corrected seismograms are independent of the dips o

a δ 13 c record of late quaternary climate change from tropical peats in southern india stable isotope ratios of carbon in soils or lake sediments1 3 and of oxygen and hydrogen in peats4 5 have been found to reflect past moisture variations and hence to provide valuable palaeoclimate records previous applications of the technique to peat have been restricted to temperate regions largely because tropical climate variations are less pronounced making them harder to resolve here we present a 13c record spanning the past 20 kyr from peats in the nilgiri hills southern india because the site is at high altitude 2 000 m above sea level it is possible to resolve a clear climate signal we observe the key climate shifts that are already known to have occurred during the last glacial maximum 18 kyr ago and the subsequent deglaciation in addition we observe an arid phase from 6 to 3 5 kyr ago and a short wet phase about 600 years ago the latter appears to correspond to the mediaeval warm period which previously was believed to be confined to europe and north america6 7 our results therefore suggest that this event may have extended over the entire northern hemisphere

numerical estimation of effective permeability in sand shale formations a numerical approach is used to estimate effective permeability in sand shale formations under steady state uniform flow conditions permeability is modeled as a binary second order stationary random function taking on two possible values kss and ksh in sandstone and shale respectively this model is realistic since experience with sandstone reservoirs has shown that randomly dispersed low permeability shales are the single dominant heterogeneity affecting flow behavior the cases of both spatially correlated and uncorrelated permeabilities are considered for the case of spatially correlated permeability an autocovariance model was fitted to data from the assakao fluvial sandstone which outcrops in the tassili region of the central sahara the turning bands method was used to simulate the spatially correlated permeabilities of blocks discretizing the flow field effective permeability was found to depend on the shale volume fraction the spatial covariance structure and the dimensionality of the flow system existing analytical methods for estimating effective permeability in a two phase medium are found to be inaccurate when compared to numerical results or unapplicable to stratified environments in addition to providing a check of analytical work the numerical approach is found to be a useful tool for exploring the effects of reservoir heterogeneity on flow behavior in a qualitative sense

vegetation and climate during the last 30 000 years in ladakh abstract pollen analysis was carried out from a 23 m core dating from about 30 000 to 9000 yr b p from the alpine tsokar lake about 4572 m above sea level in ladakh trans himalayan region this study reveals the continuation of the alpine steppe with four periods of expansion of juniperus communities during 28 000 30 000 yr b p 21 000 18 375 yr b p slightly before 15 800 yr b p and at 10 000 yr b p these phases of juniperus expansion were interpreted as events of amelioration of climate within the alpine steppe during the later part of the last weichselian glaciation in the alpine trans himalayan region

precipitation variability over northwest himalaya from 4 0 to 1 9 ka bp with likely impact on civilization in the foreland areas abstract we present a stalagmite based high resolution climatic record between 4 0 and 1 9 ka bp from dharamjali cave in pithoragarh kumaun himalaya an area which is influenced primarily by the indian summer monsoon ism and supplemented by the indian winter monsoon iwm the chronology of the 41 5 cm long dh 1 stalagmite was constructed using a stalage model on six 230th u dates however some samples have higher 232th concentrations leading to an increase in the final age uncertainties hence the chronology supports only the possible climatic boundaries however the significance of this work lies in its being one of the rare studies of speleothems to reconstruct high resolution climatic changes in the nw india for the upper holocene the 18o values ranging between 5 3 and 10 show a large variation compared to the areas dominated by a single monsoon and this can be ascribed to the two sources of moisture e g ism and iwm in the study area during the upper holocene the sample consists of aragonite except for two sections of calcite growth from 0 7 3 cm and 8 5 13 5 cm from the top the climatic reconstruction within the age uncertainties indicates strengthened precipitation from 4 0 ka bp with a sharp drop 2 in 18o values peaking at 3 7 ka bp a gradual decline in precipitation is observed from 3 7 to 3 0 ka bp with possible droughts centered at 3 4 3 2 and 3 0 ka bp subsequently climatic amelioration took place between 3 0 and 2 9 ka bp showing fluctuating trend in 18o values with comparatively more rainfall possibly generated by the iwm in the form of thunderstorms and hailstorms from 2 9 to 2 7 ka bp precipitation declined from 2 7 to 2 4 ka bp with a decadal scale major drought event strongest in the present data set at 2 5 2 4 ka bp whereas an abrupt drop in stalagmite 18o values from 2 4 to 2 3 ka bp points to increased precipitation intensity thereafter the precipitation gradually decreased until ca 2 1 ka bp with one of the driest events at 2 1 ka bp a century scale increasing trend in the precipitation intensity is observed from 2 1 to 2 0 ka bp following which the precipitation again declined accordingly five sudden drought events are documented centering at 3 4 3 2 3 0 2 5 2 4 and 2 1 ka bp a gradual reduction in precipitation from 3 7 to 3 0 ka bp coincides with reduction and deurbanisation and step wise disintegration of the harappan civilization along the indus ghaggar sarasvati valleys in the foreland areas of northwestern india

palaeoclimatic conditions in the upper pleistocene and holocene bhimtal naukuchiatal lake basin in south central kumaun north india abstract a 52 m thick upper pleistocene and holocene terrestrial succession in the bhimtal naukuchiatal basin south central kumaun himalaya india was studied using chronological palaeontological palynological and 13c measurements the section recorded evidence for climatic changes at least two phases of arid climate and one phase of humid climate were recognised preliminary palaeomagnetic studies revealed a reversal of polarity presumably correlatable with the mono lake excursion prior to this no reversal event in the upper pleistocene holocene terrestrial sediments of indian subcontinent is known a fossiliferous horizon discovered in the lower part of the section consisted of sorex and mus this is the only report of a late pleistocene micromammalian assemblage in the kumaun himalaya

glacial to interglacial contrasts in the northern indian ocean differences between the 18o 16o ratios of planktonic foraminifera deposited during the last glacial maximum about 18 000 yr ago and those deposited during the holocene show that in the indian ocean the south west monsoon was weaker than today but that the north east monsoon was stronger the upwelling observed in modern conditions along the southern coast of arabia had disappeared because of the low speed of the southwestern winds during glacial summers the reduction in rainfall and runoff over the continent caused a reduction of the salinity gradient in the bay of bengal and along the western coast of india increased precipitation fell on the sea south of 10 n while strong evaporation over the northernmost arabian sea produced an enhanced salinity gradient in that area

isotope evidence for pleistocene climatic changes in kashmir india stable carbon isotope ratios of organic carbon from palaeosols in loess and oxygen isotope ratios of pedogenic and lacustrine carbonates reveal significant pleistocene climatic changes in the kashmir basin the extreme 13c values of 16 and 25 reported here indicate a shift from arid to sub humid conditions the 18o values of pedogenic carbonates is 2 higher than that of the underlying lacustrine carbonates suggesting that they were deposited in different climatic conditions

palaeovegetation and climate oscillation of western odisha india a pollen data based synthesis for the mid late holocene abstract the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period here we present fossil pollen data and examine their climatic interpretation based on a 200 cm deep trenched sedimentary profile from mahanadi river side located near the barpahar hillock of bargarh district odisha which is influenced by the south west and north east monsoon the 5840 y chronology of the sediment core is based on three 14c dates on soil samples during 5840 4380 bp dense tropical mixed deciduous forest consisting of madhuca syzygium and acacia flourished in the region along with rhizophora under a warm and humid climate governed by high monsoonal activity this phase of climate is associated with the holocene climatic optimum which falls within the temporal range of 8000 5000 bp subsequently an increase in humidity was discerned between 4380 and 3230 bp as evident by increase in forest elements under warm and relatively humid climate in response to an increased monsoon the climate during 3230 1860 bp was mild and in general less humid than today this climate event was inevitably influenced by a notable global cold event 4200 years ago which is synchronous with the collapse of the world s first human empire in mesopotamia after this event there was a return of more humid climate from 1860 to 1300 bp marked by high values of potamogeton myriophyllum nymphoides and fungal and trilete fern spores this is further supported by the presence of rhizophora and sonneratia indicating high precipitation under the influence of coastal habitation a striking signal of the little ice age lia was observed since 1300 bp when the climate became relatively dry as recognized in a sudden decline in major arboreals along with high frequency of occurrence of dry herbs this changing pattern of humidity was also reflected in the proportions of marshy aquatic taxa as well as ruderal taxa which is a result of human impact the study will be helpful to display the palaeovegetation and climate in the region between bengal and the ganga plain

analysis of vegetation and climate change during late pleistocene from ziro valley arunachal pradesh eastern himalaya region abstract vegetation and climate during later part of late pleistocene have been reconstructed from ziro valley arunachal pradesh eastern himalaya based on pollen data along with carbon isotope and magnetic susceptibility data the study reveals that the area and the vicinity is occupied by mixed broad leaved conifer forest and pine grass savanah at variable densities at least since 66 000yr bp the phases of expansions and declines of oaks with decline and increase of pines and grasses probably occurred under increase warm moist and decrease cool dry of s w monsoon precipitation respectively the increasing trend of s w monsoon and temperature is recorded during 44 000 to 34 000 cal yr bp synchronizing with the peat development and which peaked at around 35 000 cal yr bp this may link to the interstadial phase during the last major glacial cycle in the himalayan region it is also reflected in the decline of 13c value indicating dominance of c 3 type of vegetation the increased values of fd and lower values lf magnetic susceptibility recorded during the phase of the peat deposit further advocate s higher monsoon intensity impact of expansion of glacier felt with peak lgm around 20 000 cal yr bp is perceived tree line had moved to lower altitudes due to increased aridity and low temperature during this time existence of savannah type of vegetation is also evident by the increase of c4 taxa decreased fd and increased lf susceptibility also indicate reduced s w monsoon intensity

40ar 39ar and paleomagnetic constraints on the evolution of volcan de santa maria guatemala 40 ar 39 ar dating of 15 lava flows indicates that volcan de santa maria grew episodically to 8 km 3 in size at an average rate of 0 12 km 3 ka between 103 and 35 ka the composite cone grew in four phases including two periods of intense activity at ca 72 ka and ca 35 ka during which 1 5 km 3 and 3 km 3 of basaltic to andesitic magmas were erupted there is no evidence of further volcanism after ca 35 ka until the great dacitic eruption in 1902 the average eruptive rate is 0 16 km 3 ka if products of the 1902 eruption and subsequent santiaguito dome are included whereas the mono lake excursion is not clearly recorded at volcan de santa maria as had been inferred from earlier studies virtual geomagnetic poles vgps of the 35 ka cone forming lavas exhibit high amplitude paleosecular variation that may correspond in time to the mono lake excursion two older packages of lava flows are each associated with a distinctive cluster of vgps which supports the 40 ar 39 ar age model and the conclusion that cone building was episodic during the final 60 of cone growth lavas evolved from basaltic to andesitic 51 57 sio 2 with time but with a regression to slightly less evolved compositions during the onset of the final cone building phase despite the relatively small volume of santa maria cone growth processes and geochemical evolution through time mirror observations at other currently active volcanoes along the central american volcanic arc and may prove useful as an analogy in assessing long term hazards posed by other predominantly basaltic andesitic composite volcanoes

ground penetrating radar investigation of a lake bonneville deita provo level brigham city utah field experiments carried out in the brigham sand and gravel company pit near brigham city utah show an impressive similarity between observed gravelly deltaic foreset facies in highwall exposures and inclined reflections detected by ground penetrating radar gpr beneath the pit floor the radar indicates additional inclined strata more than 30 m deep in a test to compare different antenna frequencies 50 100 and 200 mhz using a 400 v transmitter 50 mhz antennas are capable of detecting gravel facies in excess of 30 m whereas signal loss for the 100 and 200 mhz antennas occurs below 23 and 17 m respectively though providing higher resolution

quaternary fluvio lacustrine deposits of the lamayuru basin ladakh himalaya preliminary multidisciplinary investigations preliminary multidisciplinary investigations were carried out in a 105 m thick late pleistocene terrestrial sequence in the lamayuru basin ladakh himalaya palaeomagnetic studies reveal a reversal of polarity at about 35 ka bp this is the only report of this reversal event in the late pleistocene terrestrial sequences of the indian subcontinent the valley fill sequence is the product of an interplay of lacustrine with fluvio deltaic to colluvial processes four fossiliferous horizons have yielded ostracods and gastropods indicating shallow freshwater conditions the lamayuru lake was created by tectonically induced instabil ity about 35 40 ka bp an event that may be represented widely throughout the himalaya

the mono lake excursion recorded in phonolitic lavas from tenerife canary islands paleomagnetic analyses and coupled k ar and ar ar dating abstract we present a coupled paleomagnetic dating investigation conducted on three different lava flows from the island of tenerife canary islands spain erupted during the mono lake excursion mle paleomagnetic analyses consist in zero field demagnetizations af and or thermal and of thellier and thellier experiments using the picrit 03 set of criteria to select reliable intensity determinations one of the flows is characterized by a direction largely deviated from the one expected from an axial geocentric dipole gad field its paleointensity value is very low 7 8 t the two other sites are characterized by inclinations slightly shallower than the gad value and by low intensity values about 12 and 21 t present value 38 t the three k ar ages combined with two 40 ar 39 ar ages range from 32 0 to 33 2 ka and they are not statistically distinguishable from one another it therefore appears that these lavas have recorded the mle the only excursion in this time interval confirming its brief duration shorter than the minimum age uncertainties available the mean age is younger but within the uncertainties consistent with the age of the 10 be peak and of the marine intensity low when reported in the most recent ice age model these new results are the first ones with radiometric dating produced from the northern hemisphere combined with existing cosmogenic marine and volcanic paleomagnetic data these results are discussed in terms of dating and geometry of the earth magnetic field during the excursion

late quaternary holocene landscape evolution of a monsoon influenced high himalayan valley gori ganga nanda devi ne garhwal the garhwal himalaya provides an excellent natural laboratory in which to examine landscape evolution in a monsoon influenced high mountain environment geomorphic and sedimentological analysis and 10be cosmogenic radionuclide crn surface exposure dating of moraines fans and river and strath terraces in the gori ganga valley of nanda devi ne garhwal indicate that fans and river terraces developed rapidly by debris flow and flood processes during periods of deglaciation these phases of high sediment transfer occurred at 1 2 4 5 and 7 8 ka fan incision rates subsequent to major times of resedimentation after each glacial advance are between 19 and 57 mm year this contrasts with bedrock incision rates based on mid holocene strath terraces of 5 mm year these rates indicate that despite episodes of rapid denudation and resedimentation linked to glacial activity in this region the background rates of denudation are similar to those for other regions of the himalaya averaging several millimeters per year furthermore these data show the importance of climatic controls on landscape evolution and suggest a strong monsoonal control on the dynamics of earth surface processes in this region

a hydrogeophysical model for relations between electrical and hydraulic properties of aquifers abstract factors influencing relations between electrical and hydraulic properties of aquifers and aquifer materials are discussed both direct and inverse relations are shown to be possible and to exist a general hydrogeophysical model is outlined for aquifer scale relations which are shown to depend primarily on two factors the character of the material level relationship and the mutual relation between the direction of groundwater flow aquifer layering and hydrogeophysical conditions in the aquifer

a stochastic approach to the characterization of lithofacies from surface seismic and well data heterogeneity of natural geologic formations strongly influences groundwater flow and contaminant migration this study presents a formal stochastic approach for the integration of surface seismic data and well data into the identification of the spatial arrangement location geometry and interconnectedness of lithofacies and incorporating this information in the estimation of the log permeability probability density function pdf to achieve this goal normal move out nmo corrections are applied to the seismic reflection data to estimate interval seismic velocities calibration curves constructed from the well logs transform these velocity estimates into a lithology indicator prior probability field from the well data and the indicator prior probability field the indicator covariance function and its associated confidence limits are computed neighboring lithology logs and the indicator covariance function are then combined to update the indicator probability field the conditional log permeability pdf is finally computed by weighting the log permeability distribution of each lithology with respect to its indicator probability field the effectiveness of the proposed procedure is shown to depend on the quality of the seismic data and the degree of correlation between seismic and hydrogeologic soil properties a synthetic case study is performed which shows that the surface seismic and well data complement each other with optimal results achieved when both types of data are incorporated into a joint identification procedure

palaeoclimatic response to quaternary gravels a case study from kumaun himalaya india study of quaternary intramontane bhimtal palaeolake deposits and the gaula piedmont fan deposits representing sediment source to sink scenario respectively have revealed that gravelly sequences have directly responded to climatic turnovers creating contrasting lithofacies associations humid climatic conditions favoured thickly developed river generated clast supported gravelly deposits composed of clasts derived from a distant source these deposits show intense lateral and vertical changes in lithofacies constitution in contrast arid phases are represented by extensive debris flows composed of clasts derived from adjacent mountain slopes gravelly deposits systematically interbedded in the stratigraphic records have potential for palaeoclimatic studies that is sometimes ignored

hydrostratigraphic interpretation using indicator geostatistics in this paper we describe an approach that uses indicator geostatistics to interpret qualitative borehole logs and compute experimental variograms for complex alluvial sediments borehole descriptions are first transformed into binary indicator values based on inferred relative permeability from the borehole descriptions the resulting indicator data can then be used to compute variograms and construct three dimensional variogram models the ranges of computed indicator variograms for a groundwater contamination site in santa clara valley california are very sensitive to the orientation of the search plane these variograms are consistent with known stratigraphie features and describe the spatial structure of deposits from different depositional environments indicator kriging weighs all the available data on the basis of a three dimensional anisotropic variogram model and provides an estimate of uncertainty in the hydrostratigraphic correlation kriged indicator values represent probabilities that sediments at a specific location fall into one of two indicator categories the location of the 0 5 indicator contour is approximately the boundary between high and low permeability sediments that might be constructed in a geologic cross section

sedimentation model for the quaternary intramontane bhimtal naukuchiatal lake deposits nainital india abstract the bhimtal naukuchiatal lake was created due to blocking of the valley by a huge debris flow along a narrow outlet at about 40 ka bp the lake basin was filled intermittently due to fluvio lacustrine and colluvial processes that deposited a thick sequence of interbedded mud and gravel in the basin fill sequence five major lithofacies most of them divisible into subfacies have been identified and assigned to specific depositional environments the coarsening upward cu mud silt cycles represent sedimentation in a lake setting the clasts and mud supported gravels consists of fining upward fu and cu sequences respectively indicating deposition by channel processes and debris flows having basin wide extent the pedogenic mottled clayey silt unit represents an important tectonic event when the lake was temporarily drained and sediments were sub aerially exposed fluctuating arid semiarid to humid climatic conditions and repeated tectonic activity may have governed the mode of sedimentation and ultimately the basin fill history

late quaternary climatic changes in the eastern kumaun himalaya india as deduced from multi proxy studies abstract an event of neotectonic activity on an ne sw trending subsidiary fault in the zone of e w running intracrustal boundary thrust south almora thrust in the champawat district of eastern kumaun himalaya resulted in creation of a lake at ca 21 5 bp the lake drained in the late holocene leaving behind a 5 0 m thick sedimentary sequence of mostly black and carbonaceous mud with a minor magnetic reversal between 20 5 and 19 7 ka bp at the base the profile studied by using multi proxies e g carbon isotopes pollen analysis palaeo and mineral magnetism and clay minerals has recorded globally well established abrupt climatic events in the last 20 000 years such as the lgm older dryas od younger dryas yd holocene warming 8 2 ka and 4 2 ka events most events estimated assuming a constant rate of sediment accumulation for similar lithologies may be related to the rapid changes in the local climate and albedo structure the itcz may have played a key role in controlling the behavior of the southwest monsoon from the lgm

sedimentation pattern in a trans himalayan quaternary lake at lamayuru ladakh india abstract located on the indo tsangpo suture zone lamayuru lake in western ladakh was created by neotectonic instability around 35 40 ka the valley fill sequence about 110 m thick reveals an interplay of lacustrine to fluvio deltaic to colluvial processes operating in response to changing climate and tectonic conditions based on integrated approach of sedimentology and palaeontological analysis we propose a sedimentation model for lamayuru lake with reference to changing climatic conditions and neotectonics the coarsening upward succession was divided into five lithofacies associations associations a e each association comprising one or more lithofacies represents a specific depositional environment and marks an independent episode of sedimentation a dominantly muddy sequence of facies association a a product of a lacustrine environment is followed by coarsening upward cycles association b composed of silt to sand that implies laterally shifting deltas thereafter thick sand and gravel deposits constituting fining upward fu unit cycles associations c and d represent deposition in a fluvial domain the upper part of association d composed of matrix supported gravel horizons was deposited as debris flows and marks the termination of sedimentation in the valley the clastic lithofacies facies associations a to d with plant fragments and charcoal presumably indicate warm humid climatic conditions in contrast association e comprising marl lithofacies occurring at four different levels is biogenic and indicates arid to semi arid climatic phases five main types of trace fossils including rhizoliths seem to be representatives of scoyenia ichnofacies and animal burrows indicating a thin population of soft bodied annelid and arthropod communities living under low energy condition nine fossiliferous horizons have yielded characteristic ostracods charophytes and gastropods indicating shallow low energy and cold water ecological conditions coarsening up lake succession extensive synsedimentary deformation tilting of lake beds and the entrenchment of the lamayuru drainage indicate basin evolution under an effective role of neotectonics in the area

climate and seismicity in the higher central himalaya during 20 10 ka evidence from the garbayang basin uttaranchal india abstract in the trans himalaya the trans himadri fault thf controlled the extent of past glaciers the rivers were impounded by glacial debris resulting in the formation of lakes that recorded regional climatic and seismic events one such lake formed at garbayang where the upper 28 m lacustrine succession spanned an age range of 20 10 ka magnetic susceptibility and sedimentological data suggest that the region experienced high amplitude low frequency millennial scale climate changes during the period 20 3 and 13 2 ka followed by low amplitude high frequency changes from 13 2 11 1 ka a sudden drop in magnetic susceptibility and elemental concentration of layers dated at 11 12 ka suggests cooling associated with the younger dryas occurrence of faulted strata seismites during 20 17 and 14 13 ka suggests recent activation of the thf this is noteworthy as the thf has been considered dormant since its last reactivation at 11 ma further the luminescence dates suggest that radiocarbon ages on organic carbon are grossly overestimated due to a hard water effect caused by the dominance of limestone in the lake catchment this implies that earlier radiocarbon based palaeoenvironmental reconstruction in the region will need revalidation

geophysical hydrological identification of field permeabilities through bayesian updating a new bayesian method is developed to identify the spatial distribution of permeabilities in addition to sparsely sampled permeability and pressure data this approach incorporates densely sampled seismic velocity data along with semiempirical relationships between seismic and hydraulic soil properties the procedure consists first of performing a hydrological inversion based solely on the permeability and pressure data in light of the available seismic data the velocity permeability pressure relationships are then used to update in a bayesian sense the image of the permeability field to investigate the usefulness of this approach synthetic case studies are performed these studies demonstrate that even when the seismic data are corrupted by a significant level of error a joint geophysical hydrological inversion can produce improved images of permeability moreover this paper derives rigorously the bounds on the error that can be tolerated in seismic velocities such that they are still useful for hydrological purposes

palaeoclimatic changes deduced from 13c 12c and c n ratios of karewa lake sediments india most long palaeoclimatic records based on isotope studies have come from deep sea cores however in order to obtain information on regional climatic variations it is essential to study continental deposits the chief limitation has been the lack of well preserved datable geological records with the exception of cave formations we report here values for the stable carbon isotope ratio 13c 12c and the elemental carbon to nitrogen c n ratio of the organic fraction of the palaeomagnetically and radiometrically dated pleistocene karewa lake sediments from kashmir india together the two ratios which are anticorrelated provide an excellent marker of the source of organic matter in the lake the karewa sediments indicate at least three major episodes of shallower than normal levels these episodes of shallow lake levels and hence a cold dry climatic regime are broadly correctable with deep sea records

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

geomorphic characteristics of landscape development and formation of lakes in the zone of munsiari thrust garhwal himalaya uttarakhand india abstract the present investigation is focused on imprint of tectonic perturbation along a major tributary known as the lastar gad gad river in southeast catchment of the mandakini river in garhwal himalaya based on morphotectonic studies across the watershed we recognized evidences of neotectonics along the jutogh munsiari thrust mt mct ii various geomorphic features e g ponding of streams and formation of lakes fluvio lacustrine deposits waterfalls stabilized and active landslide fans dissected hills paired and unpaired terraces fault scarps and offsetting of drainage pattern etc point to the active tectonics the field investigations are supported by computation of morphometric indices such as low values of valley floor width to valley height vf asymmetry factor af elongated and tilted river basin with narrow valley floor as well as higher bifurcation ratio rb and sinuosity parameters immature topography and landscape elongation and tilting of drainage basin and accelerated erosion all show that the basin is structurally controlled the uplift along the valley is further manifested by two significant indexes e g stream length sl and steepness index ks also the mud deposits lacustrine flats and swampy and soggy land within the valley suggest the existence of an ancient lake basin named as gethina palaeolake downstream of present day badanital lake the 14c ams radiocarbon chronology of the badanital lake core as well as gethina jagtoli palaeolake profiles indicate the formation of these lakes around 5 6 ka bp due to tectonic upheaval along the mt we assume that a huge landslide activity blocked the course of a small stream badani gad forming an ancient lake at gethina locality followed by deposition of a landslide fan on which was created the badanital subsequently the palaeolake basin was filled with sediments due to accelerated erosion from almost vertical hills in the catchment owing to this the gethina ancient lake was disappeared and the modern badanital lake shrank to its present state

a sixty thousand year paleomagnetic record from gulf of california sediments secular variation late quaternary excursions and geomagnetic implications a unique inclination record of geomagnetic secular variation for the past 60 000 years 60 ka has been obtained from continuously deposited sediments in the gulf of california recovered during deep sea drilling project dsdp leg 64 by hydraulic piston coring at site 480 the chronology of hole 480 was determined by 18o stratigraphy and varve counts indicating sedimentation rates approaching 1 m ka the paleomagnetic results of the upper 49 m show 1 the average inclination over this interval is identical to the geocentric axial dipole value at the sampling site 2 excursion directions occur between about 53 and 22 ka before present bp during this time the geomagnetic field was generally noisier than in the overlying and underlying sections with greater dispersion of the inclination 3 the laschamp excursion was apparently recorded at hole 480 between about 51 and 49 ka bp and the mono lake excursion between about 29 and 26 ka bp in addition a narrow 0 3 0 4 m zone near 23 ka bp has a very similar paleomagnetic signature as the excursion observed at summer lake oregon 1 and we suggest that the summer lake is distinct from and younger than the mono lake excursion by 3 5 ka and of considerably shorter duration lasting no more than a few hundred years 4 recurring inclination fluctuations were identified at site 480 characterized by end points with steep inclinations and shallow intermediate value s as compared with the geocentric axial dipole the inclination cycles are particularly apparent from 54 to 24 ka bp with a characteristic period of about 4 4 ka 5 the noisier inclination record between 54 and 24 ka bp might be related to the generally reduced dipole moment between about 20 and 50 ka and particularly low paleointensities for the laschamp and mono lake excursions

sharp decrease in summer monsoon strength 4000 3500 cal yr b p in the central higher himalaya of india based on pollen evidence from alpine peat age constrained pollen data and magnetic susceptibility of an alpine peat profile from the garhwal higher himalaya display a continuous record of climate and monsoon trends for the past 7800 yr about 7800 cal yr b p dominance of evergreen oak quercus semecarpifolia alder alnus and grasses in the pollen record reflect a cold wet climate with moderate monsoon precipitation from 7800 to 5000 cal yr b p vegetation was progressively dominated by conifers indicating ameliorated climate with a stronger monsoon a warm humid climate with highest monsoon intensity from 6000 4500 cal yr b p represents the mid holocene climatic optimum between 4000 and 3500 cal yr b p the abundance of conifers sharply decreased with the greatest increase in evergreen oak this trend suggests progressive cooling with a decrease in the monsoon to its minimum about 3500 cal yr b p two relatively minor cold dry events at ca 3000 and 2000 cal yr b p marked step wise strengthening of the monsoon until ca 1000 cal yr b p after a cold dry episode that culminated ca 800 cal yr b p the monsoon again strengthened and continued until today a sharp decrease in temperature and rainfall at 4000 3500 cal yr b p represents the weakest monsoon event of the holocene record this cold dry event correlates with proxy data from other localities of the indian subcontinent arabian sea and western tibet

contribution of diverse monsoon precipitation over central and northern india during mid to late holocene abstracts the indian summer monsoon ism precipitation pattern over indian subcontinent is looked through various high resolution speleothem oxygen 18o isotope records from mid to late holocene the six cave locations distributed from central to northern india describing regional climatic conditions due to stalagmite deposition are considered the stalagmite deposition reflects precipitation patterns by temporal variations of 18o values oxygen isotope values reflect cumulative precipitation that is basically interpreted by averaged latitudinal site of inter tropical convergence zone itcz under the paleoclimate modelling intercomparison project phase iii pmip3 simulation commonwealth scientific and industrial research organisation mk3l version 1 0 part 2 csiro mk3l 1 2 model output shows itcz movement from bay of bengal bob to arabian sea as during mid to late holocene which resulted due to solar insolation changes it reflects precipitation shift from bob to as as well as to core monsoon zone cmz to the western himalayas the past millennium epoch which consists little ice age lia and middle warm period mwp shows large variations in 850 hpa geopotential height leading to high anomalous precipitation variability all over india during ism the high fluctuation in 18o values during mid holocene over northern india led to drought conditions due to which indus valley civilization vanished the present study shows that the himalayas received higher precipitation during late holocene that is basically governed by western disturbances wd as well as ism present study summarizes that the mean annual precipitation cycle for entire epoch was roughly similar but spatial distribution of precipitation during various epoch was quite divergent from mid to late holocene the onset of ism was also similar but withdrawal was comparatively unalike wherever peaks of seasonal precipitation were alike over indian subcontinent region spatial distribution of precipitation were unlike

application of geophysical methods in describing spatial variability of saturated hydraulic conductivity in the zone of aeration abstract an attempt is made to apply surface geophysical methods for the determination of spatial variability of saturated hydraulic conductivities methods of vertical electrical sounding and dipole electromagnetic profiling were tested in an area of 100 100 m measurements were taken on a square grid 20 by 20 m the soil profile formed by coarse acid brown soil of relatively high permeability underlain by a weathered gneiss substratum is represented by four geoelectrical layers the saturated hydraulic conductivities of both individual soil layers and the integral soil medium were compared with the geophysical parameters they were estimated by a laboratory constant head permeameter and in the field by ponding infiltration measurements the hydraulic conductivities of the individual soil layers were statistically derived from the resistivities of the layers while the estimation of the conductivities of the integral soil medium generally needed some multivariate treatment of the geoelectrical data it was concluded that the geoelectrical methods may be effectively applied to determine the spatial variation pattern of both individual and integral saturated hydraulic conductivities in the field to estimate their relations to the deeper structural and tectonic phenomena and to differentiate soil layers according to their properties

multiproxy record of monsoon variability from the ganga plain during 400 1200 a d abstract understanding on the indian summer monsoon ism variability is chiefly based upon the marine proxies and a few continental records the ganga plain one of the most densely populated regions of the world marked by intensive cultivation of monsoon dependent crops and a rich cultural history is not yet well understood in the context of monsoon variability we present here a 400 1200 a d ams radiocarbon dated record of ropan chhapra tal in the central ganga plain using sedimentology environmental magnetism and stable isotope of oxygen for ism variability the environmental magnetic parameters lf arm sirm lf s ratio b 0 cr and hirm inferred antiferromagnetic mineralogy hematite and or goethite independent of grain size variation during 400 900 a d depicting climate variability within warm humid to warm arid conditions favouring stronger ism seasonality prevalence of ferrimagnetic mineralogy under less oxygenated conditions intermittently demonstrates an altered catchment regime or possibly in response to stronger winter monsoon the higher 18 o values around 500 580 and 740 a d indicate warm and arid conditions under weak ism the lower 18 o values around 480 540 and 700 a d and from 900 to 1200 a d occur during warm and humid conditions indicating maximum intensity of the ism increased silt content from 800 a d onwards is due to increased surface runoff in response to enhanced precipitation and the higher clay percentage around 500 580 and 740 indicates low energy ponding conditions under weak ism the well sorted nature of sediment indicates consistency of the lacustrine environments under fairly uniform energy and constant bottom water conditions under varied monsoonal intensity combinations of sediment textures and stable isotope indicate intense ism at 480 and 540 a d with flooding around 700 a d and a weak monsoon at 580 and 740 a d with drought at 500 a d during 900 1200 a d the multiproxy record suggests strong summer monsoon synchronous with medieval warm period mwp whereas after 1200 a d the weak monsoon phase coincides with the onset of the little ice age lia

interpretation of drill core and georadar data of coarse gravel deposits abstract pollution in the shallow subsurface has led to an increasing need of understanding how to quantitatively characterize both the heterogeneity of gravel aquifers and the influence of heterogeneity on groundwater flow and solute transport models play an important role in decision making processes especially in the context of better characterizing and in forecasting the behavior of a given geological system the objective of the present paper is the derivation of a gradual lithofacies based interpretation of outcrop drill core and ground penetrating radar gpr or georadar data of different quality the presented method allows a probability estimation of drill core layer descriptions and radarfacies types representing defined sedimentary structure types the method includes a determination of initial structure type probabilities for grain size categories and combinations thereof described in drill core layer descriptions as well as a subsequent differentiation of these structure type probabilities in an iterative process considering additional information like main constituent quantity fraction and sorting of single grain size categories color chemical precipitation layer thickness and adjacent layer the radarfacies types are calibrated with drill cores located in the vicinity of georadar sections the calibration process consists of the assignment of the calculated structure type probabilities from the drill core layer descriptions to the corresponding radarfacies types considering the proportion in thickness between drill core layers and georadar structures the structure type probabilities can be given for points along boreholes and a grid with arbitrary mesh size along georadar sections the method is applied to field examples from the rhine wiese aquifer near basel in switzerland the resulting structure type probabilities can be used for conditioning stochastic simulations of geological models however the conditioned stochastic simulation of the rhine wiese aquifer is the topic of another paper the results show the importance of a detailed sedimentological analysis of outcrops and drill cores as well as its significance on the distinction of sedimentary structure types

palaeoclimatic conditions in the late pleistocene wadda lake eastern kumaun himalaya india abstract an episode of neotectonic activity on an east west trending fault in the zone of active intracrustal north almora thrust in the eastern kumaun himalaya resulted in the formation of a lake around 36 000 yr b p a 13 m continuous sequence made up largely of carbonaceous mud represents the lake that disappeared around 10 000 yr b p due to the revival of neotectonic activity on the basis of radiocarbon dating it appears that the rate of sedimentation varied from time to time during the existence of the lake palaeomagnetic studies show normal polarity except for a major deviation in the upper part of the section palynological investigations testify to the occurrence of three temperate humid and at least two well defined arid climatic phases which are correlated with previously documented late quaternary climatic changes as recorded in the himalaya as well as in tibet around 10 000 yr b p widespread deposition of a tectonically induced debris flow occurred in the lake basin at the terminal stage of the lake s life the two events ca 36 000 and 10 000 yr b p thus seem to represent two major neotectonic events in the kumaun lesser himalaya

estimation of field scale soil hydraulic and dielectric parameters through joint inversion of gpr and hydrological data 1 a method is described for the joint use of time lapse ground penetrating radar gpr travel times and hydrological data to estimate field scale soil hydraulic parameters we build upon previous work to take advantage of a wide range of cross borehole gpr data acquisition configurations and to accommodate uncertainty in the petrophysical function which relates soil porosity and water saturation to the effective dielectric constant we first test the inversion methodology using synthetic examples of water injection in the vadose zone realistic errors in the petrophysical function result in substantial errors in soil hydraulic parameter estimates but such errors are minimized through simultaneous estimation of petrophysical parameters in some cases the use of a simplified gpr simulator causes systematic errors in calculated travel times simultaneous estimation of a single correction parameter sufficiently reduces the impact of these errors we also apply the method to the u s department of energy doe hanford site in washington where time lapse gpr and neutron probe np data sets were collected during an infiltration experiment we find that inclusion of gpr data in the inversion procedure allows for improved predictions of water content compared to predictions made using np data alone these examples demonstrate that the complimentary information contained in geophysical and hydrological data can be successfully extracted in a joint inversion approach moreover since the generation of tomograms is not required the amount of gpr data required for analyses is relatively low and difficulties inherent to tomography methods are alleviated finally the approach provides a means to capture the properties and system state of heterogeneous soil both of which are crucial for assessing and predicting subsurface flow and contaminant transport

late pleistocene to early holocene lithic industries in the southern fringes of the himalaya the siwalik range especially in its western sector is known for numerous surface sites yielding large quantities of cobble tools these tools have for long been considered to belong to the lower palaeolithic but they are sometimes associated with other apparently more evolved tool types having a transversal trimmed cutting edge these types look like adzes axes and are made from large flakes split cobbles or flat cobbles moreover such assemblages composed of choppers along with these adze axe like tools occur on geological surfaces formed in the late pleistocene they are probably later than these deposits in age these assemblages compare well with the industries occurring further east in nepal or northern south east asia related to the hoabinhian industries it is suggested that they are linked through subsistence and technical behaviours to the particular environment of the sub himalayan belt and its eastern extension characterised by densely forested hilly landscapes generously irrigated by perennial streams besides this region was not severely disturbed during the last glacial maximum and could have been a refuge for many animal and vegetal species it has certainly favoured latitudinal circulation precisely circulation along the geomorphological features of human and animal populations despite the global climatic changes

hydrogeological characterization of the south oyster bacterial transport site using geophysical data a multidisciplinary research team has conducted a field scale bacterial transport study within an uncontaminated sandy pleistocene aquifer near oyster virginia the overall goal of the project was to evaluate the importance of heterogeneities in controlling the field scale transport of bacteria that are injected into the ground for remediation purposes geochemical hydrological geological and geophysical data were collected to characterize the site prior to conducting chemical and bacterial injection experiments in this paper we focus on results of a hydrogeological characterization effort using geophysical data collected across a range of spatial scales the geophysical data employed include surface ground penetrating radar radar cross hole tomography seismic cross hole tomography cone penetrometer and borehole electromagnetic flowmeter these data were used to interpret the subregional and local stratigraphy to provide high resolution hydraulic conductivity estimates and to provide information about the log conductivity spatial correlation function the information from geophysical data was used to guide and assist the field operations and to constrain the numerical bacterial transport model although more field work of this nature is necessary to validate the usefulness and cost effectiveness of including geophysical data in the characterization effort qualitative and quantitative comparisons between tomographically obtained flow and transport parameter estimates with hydraulic well bore and bromide breakthrough measurements suggest that geophysical data can provide valuable high resolution information this information traditionally only partially obtainable by performing extensive and intrusive well bore sampling may help to reduce the ambiguity associated with hydrogeological heterogeneity that is often encountered when interpreting field scale bacterial transport data

spatial correlation structure estimation using geophysical and hydrogeological data the large spatial variability of hydraulic properties in natural geologic systems over a wide range of scales and the difficulty of collecting representative and sufficient hydraulic property measurements using conventional sampling techniques render estimation of spatial correlation parameters difficult further compounding the estimation problem is the observation that the integral scale estimate is a function of the measurement support scale to mitigate these problems we investigate the use of tomographic geophysical data in combination with hydrogeological data in the spatial correlation estimation procedure two synthetic case studies were investigated where the scale of the geophysical measurements were varied relative to the scale of the hydrogeological properties the spatial correlation structure parameter estimation procedure was performed in the spectral domain where analysis of data having different support scales and spatial sampling windows was facilitated comparison of the spatial correlation structure parameters estimated from measured data with those of the synthetic aquifers revealed which type of data tomographic hydrogeological or a combination of both was most effective for recovering spatial correlation statistics under different sampling heterogeneity conditions these synthetic case studies suggest that collection of a few tomographic profiles and interpretation of these profiles together with limited well bore data can yield correlation structure information that is otherwise obtainable only from extensive hydrological sampling

late quaternary geomorphic scenario due to changing depositional regimes in the tangtse valley trans himalaya nw india abstract records from the tangtse valley in the trans himalaya reveal depositional history since 48 ka with fluvial aggradation followed by incision lacustrine sediment fill and later incision varied sedimentary architecture with fluvial episodes intervened by lacustrine pulses flood events colluvial and glacial activity are preserved the valley is located west of the pangong tso bangong co one of the largest lakes in tibet which has served as a spillway flooding and damming the entire tangtse valley resulting in the formation of a lake today pangong tso consists of five basins separated by shallow sills and is fed by snow melt documentation based on 14 c and osl chronologies of the sediment sections throughout the valley reveals evidence of a sixth basin of pangong tso toward west occupying the present day tangtse valley between 9 6 5 1 ka this event coincides with periods of high lake levels in tibet china as well as intensified monsoon periods over the indian subcontinent a fluvial regime around 48 ka and 30 21 ka with comparatively arid conditions and dry phases interspersed by flooding is documented the valley has been incised to depths of 40 50 m in the upper part and to 130 m in the lower part the incision rate ranges from 0 3 to 1 2 mm yr 1 in the upper part and reaches as high as 10 8 mm yr 1 in the lower valley much of the incision took place between 22 and 9 6 ka although repeated sediment fill incision cycles in the valley from 30 22 ka 22 9 6 ka 9 6 5 1 ka 5 1 ka and even to present time were observed

ground penetrating radar for environmental applications abstract ground penetrating radar gpr is a near surface geophysical technique that can provide high resolution images of the dielectric properties of the top few tens of meters of the earth in applications in contaminant hydrology radar data can be used to detect the presence of liquid organic contaminants many of which have dielectric properties distinctly different from those of the other solid and fluid components in the subsurface the resolution approximately meter scale of the radar imaging method is such that it can also be used in the development of hydrogeologic models of the subsurface required to predict the fate and transport of contaminants gpr images are interpreted to obtain models of the large scale architecture of the subsurface and to assist in estimating hydrogeologic properties such as water content porosity and permeability its noninvasive capabilities make gpr an attractive alternative to the traditional methods used for subsurface characterization

microfossil evidence for changing salinity patterns in the bay of bengal over the last 20 000 years the monsson climate characterizing the northern indian ocean produces salinity gradients that are large compared with those in other open ocean areas these gradients are substantially independent of thermal and other ecologically important gradients this situation makes it possible not only to isolate the effect of salinity on sea bed distribution patterns of planktonic foraminifera but also to investigate past salinity changes along a north south transect of piston cores in the bay of bengal analysis of 152 surface sediment samples reveals that at least three factors other than salinity are important in controlling foraminiferal distribution sea bed dissolution surface productivity and surface temperature of these dissolution is the most important therefore in order to reconstruct past salinity patterns in the bay of bengal faunal indices need to be developed that isolate the effect of salinity we have developed two independent approaches the first uses ternary diagrams of the three dominant dissolution resistant species globoquadrina dutertrei globorotalia menardii pulleniatina obliquiloculata high values of g dutertrei are associated with low surface salinities the second approach uses dissolution buffered salinity transfer functions based on the total foraminiferal fauna in the 152 surface samples from the northern indian ocean applied to downcore samples these methods show the same basic historical pattern of salinity variation which is in turn consistent with independent inferences based on preliminary oxygen isotope data duplessy 1980 historical changes in the bay of bengal salinity are reconstructed along a north south transect of seven cores at 90 e the stratigraphy of the transect is controlled by oxygen isotope profiles that are similar to the generalized patterns observed in other areas over the past 20 000 yr salinity gradients are reconstructed for three time intervals 1 the last glacial maximum lgm 2 the mid termination mt and 3 the holocene during the lgm interval salinity was highger in the bay of bengal particularly in the north thus reducing the north south salinity gradient during the mt the middle of the transition from glacial to interglacial global climatic regimes northern bay of bengal surface salinity was considerably reduced while salinity to the south was generally similar to today thus the salinity gradient between 10 n and 15 n was considerably steeper than today in contrast the holocene gradient was approximately the same as the modern gradient with absolute values along the transect being slightly but uniformly higher these changes in the pattern of salinity are explained in terms of changes in the local patterns of precipitation and river run off during the lgm the salinity pattern probably results from decreased precipitation and decreased run off by the ganges brahmaputra river system during the mt decreased salinity in the northern bay of bengal is caused by increased precipitation and run off rather than by the influx of glacial meltwater the steeper mt salinity gradient in the central bay of bengal suggests increased eastward advection of equatorial surface waters by a southwest monsoon current somewhat more vigorous than today these patterns can be correlated with faunal evidence from the western arabian sea that suggest decreased upwelling during the lgm and increased upwelling during the mt this coupling of events may be associated with changes in the pattern or intensity of circulation during the southwest monsoon decreased intensity at the lgm 18 000 b p and increased intensity at the mt 10 500 to 12 500 b p

compressional velocity and porosity in sand clay mixtures laboratory measurements of porosity and compressional velocity were conducted on unconsolidated brine saturated clean ottawa sand pure kaolinite and their mixtures at various confining pressures a peak in p velocity versus clay content in unconsolidated sand clay mixtures at 40 percent clay by weight was found the peak in velocity is 20 30 percent higher than for either pure clay or clean sand a minimum in porosity versus clay content at 20 40 percent clay by weight is also observed such behavior is explained using a micro geometrical model for mixtures of sand and clay in which two classes of sediments are considered 1 sands and shaley sands in which clay is dispersed in the pore space of load bearing sand and thus reduces porosity and increases the elastic moduli of the pore filling material and 2 shales and sandy shales in which sand grains are dispersed in a clay matrix for these sediments the model reproduces the extrema in velocity and porosity and accounts for much of the scatter in

quaternary geology tectonics and distribution of palaeo and present fluvio glacio lacustrine deposits in ladakh nw indian himalaya a study based on field observations abstract the ladakh region of the northwestern indian himalaya is rich in quaternary deposits but it has not received much attention previous quaternary research in the region has focused on the glacial sequences and only some scattered data of the lacustrine deposits are available this article addresses the reconstruction of the palaeo lacustrine deposits and the present day lakes and their distribution in the ladakh region the region was under the influence of tectonic activity and cold climate during the late quaternary times tectonic activity at 50 000 years bp 35 000 years bp and 25 000 years bp has been recorded we report the presence of three major lakes in the region in the late quaternary these formed due to the damming of the indus river and its tributaries by debris avalanches initiated mainly by tectonic activity along the indus suture shyok suture and the karakoram fault these are the spituk leh palaeolake formed 50 000 years bp the lamayuru palaeolake dated to 35 000 years bp in the indus valley and the khalsar palaeolake 60 km in length in the shyok valley vast exposures of the palaeolake deposits ranging from 25 to 150 m in thickness are reported spituk section 25 m lamayuru section 110 m and khalsar 150 m and hundri 100 m and which have a wide lateral extent a glacial lake basin at bhaktpur city north of baralacha la is now completely filled the tsokar lake has been subdivided into smaller units now and the water level is lowering other lakes in the region e g pangong tso tso morari the twin kyun tso lakes are confined to the western side of the study area limited chemical weathering rapid erosion and cold climatic conditions in late quaternary times are suggested by the stable illite values in the lamayuru section four levels of palaeoseismic structures convolute structures sand dykes intraformational folds micro faulting are present in the khalsar section and at three levels in the tirit section at shyok nubra confluence palaeoseismic activity was also prevalent after 25 000 years bp as is evident from the three levels of palaeoseismic structures in the younger sediments