the geology of the rengali province implications for the tectonic development of northern orissa india abstract the rengali province in northern orissa india is a distinct lithological structural and metamorphic belt bound by major shear zones between the singhbhum province and the northern eastern ghats belt and the ne part of the bhandara province the rengali province comprises an amphibolite facies sequence of intercalated basement gneiss and meta volcanosedimentary lithologies deformation is characterised by a variation in strain from relatively low for much of the central and ne part of the belt to a strongly deformed zone south of the intra province riamal shear zone geochronological constraints suggest dextral displacement along the bounding kerajang and barakot shear zones occurred prior to ca 980 ma and d 2 within the eastern ghats belt and post the meso neoproterozoic metamorphism within the sausar and gangpur groups which may have once represented a single contiguous belt deformation associated with the dextral displacement of the singhbhum province relative to the bhandara province resolved the rengali province as a distinct and comparatively high strain belt which accommodated large scale dextral shearing at amphibolite facies conditions progressive shearing and later reactivation associated with late retrogression was confined to the southern margin of the rengali province along the kerajang fault zone the latest brittle reactivation along the kerajang fault zone deforms the ib river and talchir permo triassic coal sequences

evidence for proterozoic collision from airborne magnetic and gravity studies in southern granulite terrain india and signatures of recent tectonic activity in the palghat gap abstract the composite airborne total intensity map of the southern granulite terrain sgt at an average elevation of 7000 2100 m shows bands of bipolar regional magnetic anomalies parallel to the structural trends suggesting the distribution of mafic ultramafic rocks that are controlled by regional structures shear zones and thrusts in this region the spectrum and the apparent susceptibility map computed from the observed airborne magnetic anomalies provide bands of high susceptibility zones in the upper crust associated with known shear zones thrusts such as transition zone moyar bhavani and palghat cauvery shear zones mbsz and pcsz the quantitative modelling of magnetic anomalies across transition zone mbsz and pcsz suggest the presence of mafic rocks of susceptibility 1 5 4 0 10 3 cgs units in upper crust from 8 10 km extending up to about 21 22 km which may represent the level of curie point geotherm as indicated by high upper mantle heat flow in this section two sets of paired gravity anomalies in sgt and their modelling with seismic constraints suggest gravity highs and lows to be caused by high density mafic rocks along transition zone and cauvery shear zone csz in the upper crust at depth of 6 8 km and crustal thickening of 45 46 km south of them respectively high susceptibility and high density rocks 2 8 g cm3 along these shear zones supported by high velocity high conductivity and tectonic settings suggest lower crustal mafic ultramafic granulite rocks thrusted along them these signatures with lower crustal rocks of metamorphic ages of 2 6 2 5 ga north of pcsz and neoproterozoic period 0 6 0 5 ga south of it suggest that the sgt represents mosaic of accreted crust due to compression and thrusting these observations along with n verging thrusts and dipping reflectors from dharwar craton to sgt suggest two stages of n s directed compression i between dharwar craton and northern block of sgt during 2 6 2 5 ga with transition zone and moyar shear towards the west as thrust and ii between northern and southern blocks of sgt with csz as collision zone and pcsz as thrust during neoproterozoic period 0 6 0 5 ga the latter event may even represent just a compressive phase without any collision related to pan african event the proposed sutures in both these cases separate gravity highs and lows of paired gravity anomalies towards north and south respectively the magnetic anomalies and causative sources related to moyar shear mbsz and pcsz join with those due to transition zone mettur and gangavalli shears in their eastern parts respectively to form an arcuate shaped diffused collision zone during 2 6 2 5 ga most of the proterozoic collision zones are highlands plateaus but the csz also known as the palghat gap represents a low lying strip of 80 100 km width which however appears to be related to recent tectonic activities as indicated by high upper mantle heat flow and thin crust in this section it is supported by low density low velocity and high conductive layer under csz and seismic activity in this region as observed in case of passive rift valleys they may be caused by asthenospheric upwarping along pre existing faults thrusts mbsz and pcsz due to plate tectonic forces after the collision of indian and eurasian plates since miocene time

accelerator mass spectrometer ages for the younger dryas event in atlantic canada abstract in atlantic canada bulk sediment dates for the onset of a late glacial cooling widely regarded as the younger dryas event are highly variable ranging from 14 300 270 to 10 800 100 yr b p we present the first accelerator mass spectrometer ams 14c dates from atlantic canada at or close to the boundaries of this event from six sites in new brunswick and nova scotia the mean of five dates places the onset of this cooling at ca 10 770 yr b p the inclusion of a sixth perhaps anomalously old date changes the mean to 10 880 yr b p the termination averages three dates ca 10 000 yr b p these dates place the timing of the younger dryas event in atlantic canada closer in line with the traditional chronozone boundaries of 11 000 and 10 000 yr b p in northwest europe

estimating groundwater exchange with lakes 1 the stable isotope mass balance method groundwater inflow and outflow contributions to the hydrologic budget of lakes can be determined using a stable isotope 18o 16o mass balance method the stable isotope method provides a way of integrating the spatial and temporal complexities of the flow field around a lake thereby offering an appealing alternative to the traditional time and labor intensive methods using seepage meters and an extensive piezometer network in this paper the method is applied to a lake in northern wisconsin demonstrating that it can be successfully applied to lakes in the upper midwest where thousands of similar lakes exist inflow and outflow rates calculated for the wisconsin lake using the isotope mass balance method are 29 and 54 cm yr respectively which compare well to estimates derived independently using a three dimensional groundwater flow and solute transport model of 20 and 50 cm yr such a favorable comparison lends confidence to the use of the stable isotope method to estimate groundwater exchange with lakes in addition utilization of stable isotopes in studies of groundwater lake systems lends insight into mixing processes occurring in the unsaturated zone and in the aquifer surrounding the lake and verifies assumed flow paths based on head measurements in piezometers

widespread evidence of 1500 yr climate variability in north america during the past 14 000 yr there is debate concerning the spatial extent and magnitude of the recently identified 1500 yr climate oscillation existing evidence is largely restricted to the north atlantic and adjacent landmasses the spatial extent magnitude and effects of these climate variations within the terrestrial environment during the holocene have not been established we show that millennial scale climate variability caused changes in vegetation communities across all of north america with a periodicity of 1650 500 yr during the past 14 000 calendar years cal yr times of major transitions identified in pollen records occurred at 600 1650 2850 4030 6700 8100 10 190 12 900 and 13 800 cal yr b p consistent with ice and marine records we suggest that north atlantic millennial scale climate variability is associated with rearrangements of the atmospheric circulation with far reaching influences on the climate

gravity field structure and tectonics of the eastern ghats abstract the eastern ghats are a prominent topographic feature on the indian peninsula stretching from the southern tip of the peninsula to near bhubaneswar 20 n 86 e along the east coast the belt is characterised by occurrences of high grade metamorphic rocks such as pyroxene granulites sillimanite gneisses charnockites and gabbro anorthosite masses the gravity field over the eastern ghats is appreciably positive as compared to the surrounding low grade gneissic terrain analysis of the gravity field along the coastal and southern granulite terrain comprising the eastern ghats shows that a large number of gravity highs are associated with charnockites of basic and intermediate nature as well as gabbro anorthosite masses the lows appear to be associated with acid charnockites syenite masses or granitic intrusives the boundary between the eastern ghats terrain and the adjoining dharwar bastar cratons appears to be a faulted one the crust underneath the eastern ghats is inferred to be of a higher density than that of the dharwar bastar cratons to its west the gravity field over the eastern ghats is compared to that of similar terrains in other parts of the world it is inferred that the eastern ghats are characterised by a crust of higher than normal density

characterizing shallow aquifers using tritium and 14c periodic sampling based on tritium half life abstract thirteen water production wells in glacial sediments in and around waterloo ontario canada were sampled for major ions 3h 13c 14c and 18o in 1976 and again in 1988 to gauge the movement of bomb spike tritium and 14c through the waterloo aquifer and also to assess the reliability of a hydrogeochemical interpretation of the dynamic character of an aquifer based only on single sampling episode the suite of samples collected in 1976 was not able to indicate how fast the tritium spike was moving or even if each well screen was intercepting the front end or tail end of the bomb spike peak corresponding to infiltration of mid 1960s precipitation the second sampling event portrayed movement which qualitatively at least gave information relating to the more permeable zones of the aquifer and direction of water movement water from all but one of the 13 wells sampled in 1988 registered a drop in tritium relative to the 1976 sampling a well is deemed to be intercepting the front end of the peak of the bomb spike if its 1988 tritium activity 2 tu analytical uncertainty is greater than one half that of the tritium activity of well water measured in 1976 8 tu uncertainty only one well and two shallow piezometers met this criterion ten wells had tu1988 tu1976 ratios which could be interpreted as either greater than or less than 0 5 if the analytical uncertainties of both analyses in this ratio are rigorously applied screens of two wells intercept the tail end of the spike because both their uncertainty adjusted tu1988 tu1976 ratios range from 0 29 to 0 41 carbon 14 activity for individual wells varied by no more than 6 per cent modern carbon pmc between 1976 and 1988 bomb spike 14c is not so easily detected as tritium in passage through aquifers because the thermonuclear input of 14c into the atmosphere was much less intense relative to pre bomb background levels than that for tritium also incongruent dissolution of dolomite coupled with differing dissolution kinetics between dolomite and calcite precipitates 14c bearing calcite in the saturated zone although the chemistry of an aquifer can be reasonably characterized by a single sampling episode the recharge rate and groundwater flow paths are best delineated from a geochemical perspective by multiple samplings in which a persistent chemical and or isotopic tracer is sought out and repeatedly analyzed in the waterloo aquifer these are tritium and cl the sameness of 14c activity in waters sampled 12 a apart makes this a poor candidate to use in this scheme

crustal structure and tectonics of the northern part of the southern granulite terrane india deep seismic reflection studies investigating the exposed archean lower continental crust of the southern granulite terrane india yield important constraints on the nature and evolution of the deep crust including the formation and exhumation of granulites seismic reflection images along the kuppam bhavani profile reveal a band of reflections that dip southward from 10 5 to 15 0 s two way time twt across a distance of 50 km the bottom of these reflections beneath the dharwar craton is interpreted as the moho further south another reflection band dipping northward is observed these bands of reflectivity constitute a divergent reflection fabric that converges at the moho boundary observed at the mettur shear zone reflection fabrics that intersect at a steep angle are interpreted as a collisional signature due to the convergence of crustal blocks which we infer resulted in crustal thickening and the formation of granulites anomalous gravity and magnetic signatures are also observed across the mettur shear zone the gravity model derived from the bouguer gravity data corroborates seismic results the tectonic regime and seismic reflection profiles are combined in a 3 d representation that illustrates our evidence for paleo subduction at a collision zone the structural dissimilarities and geophysical anomalies suggest that the mettur shear zone is a suture between the dharwar craton in the north and another crustal block in the south this study contributes significantly to our understanding of the operation of archean plate tectonics here inferred to involve collision and subduction furthermore it provides an important link between the gondwanaland and global granulite evolution occurring throughout the late archean

groundwater recharge connectivity between a hills and plains area of western taiwan using water isotopes and electrical conductivity water isotopes d 18o as well as electrical conductivity were employed to clarify hydrological relationships among precipitation stream water and groundwater in the douliou hills dlh of taiwan they are also used to evaluate the importance of groundwater recharge sources in the proximal fan of choshuichi alluvial plain csap which is connected to the eastern extreme of the dlh results indicate that the most important source of groundwater in the dlh comes from summer precipitation in most cases the summer precipitation recharges stream water via base flow based on 18o and ec values groundwater in the proximal fan of the csap can be divided into groundwater from 5 wells nearby the dlh near dhl group and groundwater from 6 wells nearby the choshui stream near cs group semi quantitative results calculated by ternary end member mixing analysis emma for 18o and electrical conductivity values indicate that for the near dlh group precipitation in the csap contributes 40 50 of water to the proximal fan groundwater while dlh groundwater donates 20 55 and choshui stream water 0 29 precipitation in the csap is the most important recharge source dlh groundwater s contribution is more notable in deep groundwater and choshui stream water s contribution decreases with distance from the choshui stream for the near cs group anthropogenic pollution adds ions to the groundwater restricting the effectiveness of the ternary emma approach this study provides new insights into groundwater recharge in the csap it should be applicable to future studies of hill and plains water connectivity in other regions

response of interior north america to abrupt climate oscillations in the north atlantic region during the last deglaciation several broad scale climatic oscillations during the last deglaciation are well documented in regions around the north atlantic ocean this paper reviews empirical evidence for these deglacial climatic oscillations from non coastal north america and discusses implications for testing climatic simulations and for understanding the cause and transmittal mechanisms paleoclimatic interpretation of oxygen isotope records from several small sites in the eastern great lakes region indicates a classic deglacial climatic sequence that is comparable with records from europe and greenland the climatic events as interpreted from crawford lake oxygen isotopes include the bolling allerod boa warming at 12 700 14c bp a warm boa at 12 500 10 920 14c bp an intra allerod cold period shortly before 11 000 14c bp a cold younger dryas yd climate reversal at 10 920 10 000 14c bp the holocene warming at 10 000 14c bp a brief preboreal oscillation pb at 9650 14c bp and an early holocene cold event at 7500 14c bp 8200 cal bp some of these events were also evident from changes in upland and aquatic vegetation and sediment lithology the pronounced yd climatic reversal has been documented from pollen records along the ecotones at this time and from glacier readvances in the great lakes region along the rocky mountains from alberta to colorado the yd event is indicated by alpine glacier advance and or shift in timberline vegetation in minnesota and upper new york early holocene climatic instability is also suggested by oxygen isotope records and or varve thickness the regional variations in evidence for the yd and other events in north america suggest that climatic oscillations may have different expressions in paleo records depending on geographic location and characteristics of a particular site the extent and magnitude of these climatic oscillations across north america suggest that these oscillations are an expression of climatic change that was probably widespread rather than locally induced by a nearby glacier the location of these sites implies that climatic signals were likely carried over the northern hemisphere through the atmosphere as indicated by general circulation models we hypothesize that the lack of evidence for a cold yd in interior north america west of the great lakes region and east of the rocky mountains was caused by the trapping of cold arctic air mass north of the laurentide ice sheet and by uninterrupted northward expansion of warm caribbean air this strongly contrasted climate also produced non analogous biological assemblages

vegetation et fluctuations climatiques postglaciaires sur la cote septentrionale gaspesienne quebec the postglacial ca 13 000 bp vegetational and climatic history is reconstructed from the pollen analytical study of the sediments of two lakes located in coastal northern gaspe peninsula j arrive lake altitude 56 m was submerged by the goldthwait sea until about 11 400 bp euloge lake 83 m in altitude and less than 1 km from the shore escaped the marine invasion before 10 400 bp the vegetation very scarce at first evolved to a herb tundra that lasted for over a millenium a cold climatic oscillation correlative with the younger dryas is identified at both sites between 10 700 and 10 400 bp during this herb tundra phase after 10 400 bp dwarf birch and willows colonized the sites leading to a shrub tundra the afforestation of the area began only around 9300 bp with the late arrival of spruce and aspen this phase was interrupted at 8650 bp by the upsurge of green alder in response to another cold oscillation since 7250 bp the present forested landscape finally developed in three steps characterized by i a high diversity of forest species until 2500 bp ii a loss of diversity until 1000 bp that favoured spruce and balsam fir and iii an increase of heliophilous trees shrubs and herbs these reconstructions contribute to the late glacial palaeogeography of eastern north america through the unravelling of conditions close to the retreating ice

geophysics of proposed proterozoic sutures in canada abstract sutures have been identified or proposed at several sites in the canadian shield although many authors have suggested that some form of primitive plate tectonic processes have played a major role in the formation of the archean crust of the superior structural province proterozoic sutures resembling phanerozoic examples have been proposed only within the younger churchill and grenville provinces and at or near the boundaries between the older superior and slave provinces and the younger provinces gravity magnetic seismic and paleomagnetic data related to three proposed sutures in the latter category have been interpreted and generally support the view that the shield comprises a mosaic of once separated but now joined cratonic blocks the sutures vary in complexity from wide zones containing distinctive rocks formed at ancient accreting and consuming plate margins to cryptic sutures marked only by abrupt changes in metamorphism and zones of cataclasis paired negative and positive gravity anomalies associated with these sutures have been interpreted in terms of juxtaposed crustal blocks of different density and thickness magnetic anomaly patterns change abruptly at structural province boundaries available seismic results support the concept of thickened crust in the younger province as derived from gravity modelling most authors prefer interpretation of proterozoic pole positions in terms of one plate models but in some cases the interpretation of paleomagnetic data is equivocal and two plate models have been proposed

precise radiocarbon dating of late glacial cooling in mid latitude south america abstract variability of atmospheric 14c content often complicates radiocarbon based chronologies however specific features such as periods of constant 14c age or steep changes in radiocarbon ages can be useful stratigraphic markers the younger dryas event in the northern hemisphere is one of those periods showing conspicuous 14c wiggles although the origin of those variations is not fully understood we can make practical use of them and determine i whether the younger dryas was global in extent if so ii were the initial cooling and the final warming synchronous worldwide and iii what are the implications of these similarities differences here we report high resolution ams 14c chronologies from the mid latitudes of south america that pinpoint a cool episode between 11 400 and 10 20014c yr b p the onset of the final cool episode of the late glacial in the southern mid latitudes i e the huelmo mascardi cold reversal preceded the onset of the younger dryas cold event by 550 calendar years both events ended during a radiocarbon age plateau at 10 20014c yr b p thus the huelmo mascardi cold reversal encompasses the younger dryas as well as a couple of short term cool warm oscillations that immediately preceded its onset in the north atlantic region

climatic changes in areas adjacent to the north atlantic during the last glacial interglacial transition 14 9 ka bp a contribution to igcp 253 this paper presents a summary of the evidence for climatic changes during the last glacial interglacial transition 14 9 ka bp in land areas adjacent to the north atlantic it is a synthesis of the results of the 12 regional summaries compiled by contributors to the north atlantic seaboard programme of igcp 253 that are published separately in this issue of journal of quaternary science eighteen palaeotemperature curves are compared and arranged in three transects one from southern europe to spitsbergen a second from ireland to poland and the third from southern new england to the labrador baffin shelf area ten maps are presented that summarise the synoptic climatic conditions of the region in 500 year time periods the purpose of the exercise is to examine the extent to which any emerging patterns support the ruddiman and mclntyre model of large scale shifts in the position of the oceanic polar front during the last glacial interglacial transition some broad agreement emerges although the influence of oceanic changes is diminished in areas that lay in close proximity to the laurentide and fennoscandian ice sheets attention is drawn to limitations in the compilations and to the potential for improved models in the future

climatic and limnological changes associated with the younger dryas in atlantic canada pollen diatom and chironomid fossils from the sediments of a core from brier island bog lake nova scotia were studied in an attempt to relate changes in microfossil composition to a climatic cooling in atlantic canada correlative with the european younger dryas ca 10 to 11 ka our paleolimnological data were then compared to similar types of data from splan pond new brunswick to determine if there were any significant differences between a coastal and a more inland site nonarboreal pollen was dominant throughout the brier island core and the interval 10 0 11 0 ka did not show the typical decline in picea and increases in tundra like vegetation characteristic of many sites in atlantic canada however the limnological indicators did undergo marked changes in taxon composition the chironomid assemblage was initially dominated by shallow water warm adapted chironomid taxa followed by abundant sergentia a cold stenotherm during 10 11 ka sergentia disappeared in the post younger dryas interval and the warm adapted genera resumed dominance chironomid inferred paleotemperature reconstructions revealed that at both brier island bog lake and splan pond summer surface water temperatures dropped abruptly to between 13 and 17 c during the 10 11 ka interval suggesting that a cooler climate was present in atlantic canada correlative with the european younger dryas diatom assemblage changes during the same period corroborate the occurrence of limnological fluctuations

sub surface structure of a craton mobile belt interface evidence from geological and gravity studies across the rengali province eastern ghats belt boundary eastern india abstract bouguer gravity anomalies characteristically vary from negative to positive values across craton mobile belt boundaries in precambrian shields this transition is also documented in eastern india where proterozoic granulites of the eastern ghats belt egb form part of a mobile belt to the south of the late archaean amphibolite facies rengali province the northern margin of the egb with the rengali province is a sub vertical cambro ordovician strike slip shear zone on which the talchir gondwana sedimentary basin was deposited during late palaeozoic extension this extension also led to partial uplift of the lower crust below the terrane boundary closely coordinated geological and gravity studies were conducted through the basin across the craton mobile belt contact modeling of the bouguer anomaly using 2 d and 3 d compact inversion schemes along with 2 d forward modeling indicates significant differences in the density configurations of the uppermost crusts of the egb and the rengali province as indicated by the surface geology however both inverse and forward models consistently predict that below 7 km density configurations across the contact are similar and have low upper crustal values suggesting that typically cratonic crust lies below both terranes since it is highly unlikely that lower crust can remain unaffected during granulite facies metamorphism it is inferred that the present sub surface egb crust could not have experienced the high grade event rather the egb rocks were probably overthrust onto the craton significantly after granulite metamorphism the top of the thrust sheet may have been eroded prior to or post dating the overthrusting leaving the present egb granulites stranded on low density cratonic crust below

how long lived is ultrahigh temperature uht metamorphism constraints from zircon and monazite geochronology in the eastern ghats orogenic belt india abstract along the coast of peninsular india the eastern ghats expose a deep crustal section through a composite proterozoic orogenic belt to quantify the late mesoproterozoic early neoproterozoic pressure p temperature t time t evolution of the eastern ghats province new shrimp u pb zircon and monazite age data from multiple localities are reported and integrated with the results of phase equilibria modelling samples of residual granulite migmatite and enderbite yield a spread of weighted mean 207pb 206pb zircon and monazite ages between ca 970 and ca 930 ma based on ranges of spot ages from several samples the late prograde to peak ultrahigh temperature uht metamorphism counter clockwise evolution ccw to t 950 c at p 8 kbar and initial cooling is interpreted to have occurred between ca 1130 and ca 970 ma regionally extensive enderbite and charnockite magmas were emplaced into the hot suprasolidus crust around the time of peak metamorphism for the residual granulites and migmatites the retrograde p t t path is characterized by close to isobaric cooling to the variable but elevated solidi for different samples weighted mean ages between ca 970 and ca 930 ma in several samples are interpreted to record the timing of crystallization of melt trapped by the percolation threshold in each of these samples two additional weighted mean ages of ca 980 ma from korhonen f j saw a k clark c brown m bhattacharya s 2011 new constraints on uht metamorphism in the eastern ghats province through the application of phase equilibria modelling and in situ geochronology gondwana research 20 764 781 extend this range back in time by 10 my the variability in the calculated weighted mean ages across the region is interpreted to be due mainly to differences in the temperature of the elevated solidus from sample to sample suggesting a slow cooling rate of 1 c my during the retrograde stage of this long lived uht metamorphism these results demonstrate that the eastern ghats province sustained uht conditions t 900 c for 50 my and perhaps for as long as 200 ma from ca 1130 to 930 ma during a single ccw tectono metamorphic event

crustal and lithospheric scale structures of the precambrian superior grenville margin abstract the lithosphere beneath the margin of the archean superior and proterozoic grenville provinces was investigated with a northwest southeast oriented 650 km long profile of 40 magnetotelluric stations dominant geoelectric strike azimuths of n45 e and n85 e were defined for the crust and the lithospheric mantle respectively a 2 d isotropic resistivity model derived using the crustal strike images resistive laurentian margin rocks dipping southeast to the base of the crust bounded to the northwest by the grenville front and to the southeast by the central metasedimentary belt boundary zone the observation is in contrast to conductive mid to lower crust elsewhere in the region a 2 d isotropic resistivity model determined using the lithospheric mantle strike azimuth reveals an extremely resistive region in the upper 100 km of the mantle lithosphere of the northern grenville province the geometry of this body which includes a well defined base and southeast dip suggests that it is superior lithosphere a sub vertical conductor located approximately 50 km along strike from the mesozoic kirkland lake and cobalt kimberlite fields is interpreted to be due to re fertilization of an older mantle scar the resistivity model includes a horizontal conductor at 160 km depth beneath the southern superior province that is possibly the resistivity signature of the lithospheric asthenospheric boundary

geophysical signatures of uranium mineralization and its subsurface validation at beldih purulia district west bengal india a case study the beldih open cast mine of the south purulia shear zone in eastern india is well known for apatite deposits associated with nb rare earth element uranium mineralization within steeply dipping altered ferruginous kaolinite and quartz magnetite apatite rocks with e w strikes at the contact of altered mafic ultramafic and granite quartzite rocks a detailed geophysical study using gravity magnetic and gradient resistivity profiling surveys has been carried out over 1 km2 area surrounding the beldih mine to investigate further the dip depth lateral extension and associated geophysical signatures of the uranium mineralization in the environs of south purulia shear zone the high to low transition zone on the northern part and high to low anomaly patches on the southeastern and southwestern parts of the bouguer reducedto pole magnetic and trend surface separated residual gravity magnetic anomaly maps indicate the possibility of highly altered zone s on the northern southeastern and southwestern parts of the beldih mine the gradient resistivity survey on either side of the mine has also revealed the correlation of low resistivity anomalies with low gravity and moderately high magnetic anomalies in particular the anomalies and modeled subsurface features along profile p6 perfectly match with subsurface geology and uranium mineralization at depth two dimensional and three dimensional residual gravity models along p6 depict the presence of highly altered vertical sheet of low density material up to a depth of 200 m the drilling results along the same profile confirm the continuation of uranium mineralization zone for the low density material this not only validates the findings of the gravity model but also establishes the geophysical signatures for uranium mineralization as low gravity moderate tohigh magnetic and low resistivity values in this region this study enhances the scope of further integrated geophysical investigations along the south purulia shear zone to delineate suitable target areas for uranium exploration

identification of sources and causes of leakage on a zoned earth dam in northern taiwan hydrological and isotopic evidence abstract seepage through an earth dam body must be regulated as a well planned process if it is not properly managed the abnormal seepage may cause dam failure this study employed stable isotopic and statistical methods to identify the source and cause of an abnormal leakage on the zoned earth dam of the xin shan reservoir located in northern taiwan water samples from the dam area over a 2 a period were collected and analyzed for their stable o and h isotope compositions in addition a 4 a period of hydrological data including rainfall reservoir level well level seepage of filter drainage and leakage were statistically analyzed with a stepwise multiple regression approach both the stable isotopic and hydrological results indicate that the abnormal leakage on the dam shell comes from the filter drainage in the dam the reason for abnormal leakage is due to unexpected and significant precipitation sourced water flowing into the dam s body the dam filter fails to drain out the incoming water sufficiently thus generating the abnormal seepage in addition the defect in the dam filter may also cause the drainage filter to drain off reservoir seepage inadequately therefore it is suggested that checking the filter function and preventing excessive precipitation sourced water from flowing into the dam are the two top priorities for the follow up remedial strategy of the dam

nature of the crust below the southern granulite terrain sgt of peninsular india across the bavali shear zone based on analysis of gravity data abstract the bavali shear zone is a major proterozoic structure in the southern granulite terrain sgt of peninsular india a detailed gravity survey has been carried out in order to delineate the crustal structure and tectonics of the shear zone and adjacent areas the bouguer anomaly map of the region shows a number of features i an e w gravity gradient zone with an average gradient of 3 0 mgal km in the west and 0 4 mgal km in the east across the shear ii a broad gravity low with a relief of 20 mgal in the wynad plateau se of the shear iii a series of gravity lows in the southern part of the shear between kannur and vayittiri iv a broad gravity high of 30 40 mgal encircling the charnockite province in the nw part of the shear and v a sharp localised gravity high closure of 40 50 mgal towards coast at nileswaram spatially filtered gravity anomaly maps clearly exhibit contrasting gravity signatures on either side of the shear zone with relatively higher gravity values within the northern block crustal thickness estimates in general vary from 36 to 41 km with a thinning of 2 to 3 km towards the north below the shear zone using two dimensional crustal models determined from gravity anomaly profiles across the bavali shear zone it is interpreted that the shear zone extends downward close to a plane separating blocks of different crustal densities the shear zone dips steeply towards the south and its downward extension meets with a slight moho rise suggesting that the bavali shear zone is a crustal scale structure eastwards below the wynad plateau however the shear zone becomes less prominent suggesting local variations in its geometry the models also point out the presence of a thick high density body 2 98 g cc in the lower part of the crust below the northern charnockite province which narrows towards the wynad plateau region in the east the presence of such a high density body could be due to factors such as evolution together with the protoliths of overlying charnockitic rocks a dense lower crustal residual fraction during anorthosite genesis or emplacement during pan african later anorogenic events the models also indicate that the wynad plateau region is characterised by a relatively homogeneous crust

environmental significance and hydrochemical processes at a cold alpine basin in the qilian mountains isotope geochemistry of precipitation river water well water and spring water in the babao river basin china during different seasons showed that regional runoff was dominated by precipitation in summer and autumn and by underground water in winter and spring the 18o and d values of precipitation and spring water displayed a clear altitude effect water from the main stream and tributaries displayed a converse altitude effect in the summer wet season the isotopic composition of the various water sources was not well correlated with elevation during the winter dry season the spatial distribution of the stable isotope signals of river water demonstrated the influence of rainfall inputs evaporation and variable flow an end member mixing model used for hydrograph separation indicated that in the summer wet season the babao river water was recharged by precipitation 71 9 spring water 11 7 and well water 16 4 whereas the winter dry season recharge was sourced from spring water 28 2 and well water 71 8

regional and residual gravity anomaly separation using singular spectrum based frequency filtering methods a case study of shallow subsurface modeling from nagpur india we present here the application of a single and multichannel singular spectrum analysis ssa based data filtering algorithm for regional and residual gravity field separation initially the single channel ssa method was tested on synthetic gravity profile data generated using gravity and magnetics modelling system gm sys a gravity modeling software for a sedimentary basin structure corrupted with gaussian white noise and compared with the convnetional fast fourier transform fft based wave number non data adaptive and discrete wavelet transform semi data adaptive filtering approaches the comparative results show that the residual filtering of gravity data using the ssa method produces less minimal artifacts compared to fft based wave number filtering and wavelet filtering methods following the synthetic examples we further employed multichannel ssa based frequency filtering on 2d gridded gravity data from umred nagpur district maharashtra india to separate the residual anomaly for modelling the shallow subsurface structures the modelled depth sections of two mutually perpendicular profiles suggest the presence of alluvium lameta kamthi and barakar formations with varying thicknesses the formations identified from the models show a clear match with the local geology and nearby borehole information we suggest that the single and multichannel ssa based frequency filtering are robust approaches for separating regional and residual components from gravity anomalies

structural evolution across the eastern ghats mobile belt bastar craton boundary india hot over cold thrusting in an ancient collision zone along the western margin of the eastern ghats mobile belt egmb ultrahigh temperature granulites are thrust westward over hornblende granites and sedimentary rocks of the bastar craton multiply deformed migmatitic gneisses and porphyritic charnockite of the egmb unit preserve thrust related shear fabrics s3m in the cratonic foreland undeformed granites show a progressive decrease in grain size and increase in penetrative foliation to the east evolving into orthogneiss near the mylonitized contact zone with charnockite foreland fabrics with a consistent top to the west shear sense are conformable with s3m in charnockite and correlate with s3b in polydeformed orthogneisses of cratonic windows s3b in the windows parallels s3m in overlying egmb migmatitic gneisses while s3m accompanied granulite metamorphism in the egmb s3b temperature estimates vary from t 700 c in the windows to t 550 c in the west decreasing temperature and later fabric formation in the west are explained by an evolving thermal profile in the cold craton which is caused by thrusting against hot lower crustal egmb rocks based on lithologic structural and metamorphic variations across the contact and resemblances between the egmb and rayner complex the craton mobile belt boundary is considered a result of indo antarctic collision leading to the formation of an ancient supercontinent

contrasting pressure temperature deformation history across a vestigial craton mobile belt boundary the western margin of the eastern ghats belt at deobhog india at deobhog migmatitic gneisses and granulites of the eastern ghats belt are juxtaposed against a cratonic ensemble of banded augen gneiss amphibolite and calcsilicate gneiss intruded by late hornblende granite and dolerite in the migmatitic gneiss unit early isoclinal folds syn d1m and d2m are reoriented along n s trending and e dipping shear planes s3m with s1m s3m intersection lineations having steep to moderate plunges the near peak p t condition was syn d3m 900 c 9 5 kbar as inferred from syn d3m grt opx bearing leucosomes in mafic granulites and from thermobarometry on grt corona opx cpx pl qtz assemblages the p t values are consistent with the occurrence of opx spr crd assemblages in spatially associated high mg al pelites a subsequent period of cooling followed by isothermal decompression 800 850 c c 7 kbar is documented by the formation of coronal garnet and its decomposition to opx pl symplectites in mafic granulites hydrous fluid infiltration accompanying the retrograde changes is manifested in biotite replacing opx in some lithologies the cratonic banded gneiss granite unit also documents two phases of isoclinal folding d1b d2b with the l2b lineation girdle different from the lineation spread in the migmatitic gneiss unit calcsilicate gneiss hbl pl cpx scap cal and amphibolite hbl pl grt cpx within banded gneisses record syn d2b peak metamorphic conditions c 700 c 6 5 kbar followed by cooling to c 500 c manifested in the stabilization of coronal clinozoisite epidote the d3b shear deformation post dates granite and dolerite intrusions and is characterized by top to the west movement along n s trending e dipping shear planes deformation mechanisms of quartz and feldspar in granites and banded gneisses and amphibole plagioclase thermometry within shear bands in dolerites document an inverted syn d3b thermal gradient with temperature increasing from 350 to 550 c in the west to 700 c near the contact with the migmatitic gneiss unit the thermal gradient is reflected in the stabilization of chlorite after hornblende in s3b shears to the west and post d2b neosome segregation along d3b folds and shears to the east the contrasting lithologies early structures and peak metamorphic conditions in the two units indicate unconnected pre d3p t deformation histories the shared d3 deformation in the two units the syn d3 inverted thermal gradient preserved in the footwall cratonic rocks and the complementary cooling and hydration of the hanging wall granulites across the contact are attributed to westward thrusting of hot eastern ghats granulites on cool cratonic crust it is suggested that the eastern ghats migmatitic gneiss unit is not a reworked part of the craton but a para autochthonous allochthonous unit emplaced on and amalgamated to the craton

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

mesoproterozoic ophiolitic melange from the se periphery of the indian plate u pb zircon ages and tectonic implications abstract the kanigiri melange within the proterozoic nellore khammam schist belt in southern peninsular india includes ophiolitic fragments that represent the remnants of an oceanic plate the ophiolitic units were accreted along a ne trending suture that juxtaposes the proterozoic eastern ghats granulite belt eggb against the archean nellore schist belt of the dharwar craton the ophiolite components in the kanigiri melange include plagiogranites and gabbros which show mutually intrusive relations indicating their coeval nature we report laser ablation icp ms age data and ree geochemistry of zircons from the gabbro and granite the zircons from both gabbro and granite show high ree contents prominent hree enrichment and a conspicuous negative eu anomaly suggesting a common melt source zircon ree abundances and normalized patterns show little intersample and intrasample variations u pb dating of the zircons reveals prominent mesoproterozoic ages for the plagiogranite with the ca 1 33 ga age of the kanigiri ophiolitic melange offering important clues for arc continent collision during the final stages of amalgamation of the columbia derived fragments within the neoproterozoic supercontinent assembly

effects of water sediment interaction and irrigation practices on iodine enrichment in shallow groundwater abstract high iodine concentrations in groundwater have caused serious health problems to the local residents in the datong basin northern china to determine the impact of water sediment interaction and irrigation practices on iodine mobilization in aquifers isotope 2 h 18 o and 87 sr 86 sr and hydrogeochemical studies were conducted the results show that groundwater iodine concentrations vary from 14 4 to 2180 g l and high iodine groundwater 150 g l mainly occurs in the central area of the datong basin sediment iodine content is between 87 sr 86 sr values and groundwater chemistry suggest that aluminosilicate hydrolysis is the dominant process controlling hydrochemical evolution along groundwater flowpath and the degradation of toc iodine rich sediment mediated by microbes potentially triggers the iodine release from the sediment into groundwater in the discharge area the vertical stratification of groundwater 18 o and 2 h isotope reflects the occurrence of a vertical mixing process driven by periodic surface irrigation the vertical mixing could change the redox potential of shallow groundwater from sub reducing to oxidizing condition thereby affecting the iodine mobilization in shallow groundwater it is postulated that the extra introduction of organic matter and o 2 no 3 so 4 could accelerate the microbial activity due to the supplement of high ranking electron acceptors and promote the iodine release from the sediment into shallow groundwater

exceptionally steep north south gradients in lake temperatures during the last deglaciation during the transition from the last glacial to the present interglacial climate late glacial period high summer insolation1 combined with the presence of the laurentide ice sheet is thought to have promoted the development of strong summer thermal gradients in north america south of the ice margin2 here we use palaeoecological methods to obtain quantitative evidence for the existence of these gradients our palaeoclimate reconstructions are based on water temperatures inferred from fossil assemblages of aquatic midge larvae in five lakes along a 240 km transect extending from central new brunswick canada to southeastern maine usa we show that the temperature gradient shifted during the killarney oscillation ko and younger dryas yd cooling events and that water temperature differences of 9 and 11 c existed over distances of 55 and 240 km respectively during parts of the late glacial period these gradients are much stronger than the current north south trends of lake summer surface water temperatures for these five lakes and for lakes across the northern tree line the rapid motion of such steep temperature gradients may have affected the progressive development of aquatic and terrestrial ecosystems in the region

a water isotope approach to assessing moisture recycling in the island based precipitation of taiwan a case study in the western pacific 1 this study employs a dual isotope and three end member linear mixing model to semiquantitatively assess vapor contributions of advection transpiration and evaporation to precipitation and to compare the extent of moisture recycling including transpiration and evaporation among areas of various topographic types in taiwan an island located in the western pacific the three topographic types examined are the mountainous regions foothill regions as represented by two reservoir stations and coastal plains results indicate that the moisture fractions from advection and evapotranspiration in mountain precipitations are about 63 and 37 respectively and those in precipitation of plain and foothill regions are about 69 and 31 respectively moreover transpiration accounts for most of the recycling moisture while evaporation offers minor contribution since the transpiration fraction of recycling moisture is higher in forest mountain area than in plain foothill region topographic type is the major factor affecting the extent of transpiration nevertheless the two reservoirs examined in this study do not offer significant contribution of recycling moisture to local precipitation in addition to topographic type temperature and rainfall may be two other factors controlling the extent of transpiration transpiration would be promoted in greater rainfall regions but reduced in higher temperature areas additionally about 25 of precipitation in plain foothill region is of relocated moisture from evapotranspiration induced from forest mountains it should be noted that this isotope based approach has its limitations and should be applied with caution

archean granitoids at the contact of eastern ghat granulite belt and singhbhum orissa craton in bhuban rengali sector orissa india abstract the small granite plutons occurring at the contact of the singhbhum orissa iron ore craton ioc to the north and the eastern ghat granulite belt eggb to the south in eastern indian shield are characterised by the presence of enclaves of the granulites of eggb and the greenschist facies rocks of ioc these granites also bear the imprints of later cataclastic deformation which is present at the contact of the ioc and the eggb in situ pb pb zircon dating of these granites gives minimum age of their formation 2 80 ga a whole rock three point rb sr isochron age of this rock is found to be 2 90 ga therefore the true age of formation of these granites will be around 2 90 2 80 ga these granitic rocks also contain xenocrystic zircon components of 3 50 ga and show a later metasomatic or metamorphic effect 2 48 ga obtained from the analyses on overgrowths developed on 2 80 ga old zircon cores the presence of granulitic enclaves within these contact zone granite indicates that the granulite facies metamorphism of the eggb is 2 80 ga or still older in age the cataclastic deformations observed at the contact zone of the two adjacent cratons is definitely younger than 2 80 ga and possibly related to 2 48 ga event observed from the overgrowths as 2 80 ga granite plutons of small dimensions are also observed at the western margin of the ioc it can be concluded that a geologic event occurred 2 80 ga over the ioc when small granite bodies evolved at the marginal part of this craton after its stabilisation at 3 09 ga

tectonic inheritance of the indian shield new insights from its elastic thickness structure abstract a new evaluation of the elastic thickness te structure of the indian shield derived from isotropic fan wavelet methodology documents spatial variations of lithospheric deformation in different tectonic provinces correlated with episodic tectono thermal events the te variations corroborated by shear velocity crustal thickness and seismogenic thickness reveal the heterogeneous rheology of the indian lithosphere the thinned attenuated lithosphere beneath peninsular india is considered to be the reason for its mechanically weak strength

first report of sapphirine bearing rocks from the palghat cauvery shear zone system southern india abstract silica deficient mg al granulites from paramati within the palghat cauvery shear system contain sapphirine in association with corundum spinel and sillimanite gedrite which occurs commonly in this locality coexists with cordierite corundum and sillimanite mineral assemblages and reaction textures indicate peak metamorphism at ultrahigh temperature conditions this new locality provides evidence for extreme crustal metamorphism along the archean proterozoic collision boundary in southern india

stable isotopic characteristic of taiwan s precipitation a case study of western pacific monsoon region abstract the stable oxygen and hydrogen isotopic features of precipitation in taiwan an island located at the western pacific monsoon area are presented from nearly 3 500 samples collected during the past decade for 20 stations results demonstrate that moisture sources from diverse air masses with different isotopic signals are the main parameter in controlling the precipitation s isotope characteristics the air mass from polar continental pc region contributes the precipitation with high deuterium excess values up to 23 and relatively enriched isotope compositions e g 3 2 for 18o during the winter with prevailing northeasterly monsoon by contrast air masses from equatorial maritime em and tropical maritime tm supply the precipitation with low deuterium excess values as low as about 7 and more depleted isotope values e g 8 9 and 6 0 for 18o of tm and em respectively during the summer with prevailing southwesterly monsoon thus seasonal differences in terms of 18o d and deuterium excess values are primarily influenced by the interactions among various precipitation sources while these various air masses travel through taiwan secondary evaporation effects further modify the isotope characteristics of the inland precipitation such as raindrop evaporation reduces the deuterium excess of winter precipitation and moisture recycling increases the deuterium excess of summer precipitation the semi quantitative estimations in terms of evaluation for changes in the deuterium excess suggest that the raindrop evaporation fractions for winter precipitation range 7 to 15 and the proportions of recycling moisture in summer precipitation are less than 5 additionally the isotopic altitude gradient in terms of 18o for summer precipitation is 0 22 100 m greater than 0 17 100 m of winter precipitation the greater isotopic gradient in summer can be attributed to a higher temperature vs altitude gradient relative to winter the observed spatial and seasonal stable isotopic characteristics in taiwan s precipitation not only contribute valuable information for regional monsoon research crossing the continent ocean interface of east asia but also can serve as very useful database for local water resources management

late quaternary records of vegetation and fire in southeastern north carolina from jones lake and singletary lake abstract we conducted fossil pollen charcoal and geochemical analyses of sediment cores from jones lake and singletary lake spanning the last 50 000 cal yr b p to examine the linkages between climate vegetation and fire activity on the atlantic coastal plain and particularly emphasize changes since the last glacial maximum application of the modern analog technique mat to fossil pollen data allowed for quantitative estimates of holocene climate but pleistocene assemblages had no modern analogues preempting their use for quantitative reconstructions the mat data indicate markedly lower mean annual precipitation and temperatures during the late pleistocene relative to the holocene increased charcoal accumulation during interstadials indicates increased fire activity during these warm intervals geochemical data 13c 15n c n and pollen concentrations indicate a sparsely vegetated pleistocene landscape that produced few fires followed by an increase in biomass and fire activity around the lakes during the holocene transition a quercus spp maximum in the early holocene is associated with low charcoal abundances while increased dominance of pinus spp during the middle holocene is associated with dramatic increases in charcoal it is unclear if the quercus pinus transition was the result of changing fire regimes or if the fire regime changed in response to vegetation the regional asynchronicity of the quercus pinus transition may indicate another forcing mechanism besides climate change such as prehistoric human activity is responsible for the ecological change macroscopic charcoal and c n ratios reach unprecedented values during the late holocene possibly as a result of deforestation by both prehistoric native americans and later immigrant populations

using oxygen hydrogen and tritium isotopes to assess pond water s contribution to groundwater and local precipitation in the pediment tableland areas of northwestern taiwan summary environmental isotopes including stable hydrogen and oxygen and radioactive tritium isotopes are employed to assess groundwater sources in the taoyuan chungli tableland tct northwestern taiwan we evaluate the contribution to groundwater resources of copious ponds distributed throughout the tct results indicate that both precipitation and pond water are the end sources of proximal shallow groundwater p sgw in the tct recharge of p sgw to deep groundwater in the proximal fan region p dgw is obvious because values of p dgw are similar to those of p sgw and no barrier restricts p sgw entering p dgw however the infiltration of precipitation or pond water to shallow groundwater in the mid and distal fan regions md sgw is restricted somewhere because of impermeable confining layers overlying the md sgw in addition apart from the upstream recharge of the p sgw md sgw overlying the deep groundwater in the mid distal fan regions md dgw contributes to md dgw through barrier layer leakage between md sgw and md dgw overall values indicate that pond sourced moisture accounts for about 6 of precipitation in the studied tableland this contribution fraction is larger than that in the western plains or reservoir catchments of taiwan the calculations also indicate that precipitation and pond water respectively contribute 51 and 49 to p sgw among the 49 contribution from pond water to p sgw 46 is from direct infiltration and the remaining 3 is via the evaporation precipitation process the fractional results clearly indicate that pond water is a vital source of both local precipitation and groundwater

archean proterozoic evolution of indian charnockites isotopic and geochemical evidence from granulites of the eastern ghats belt pyroxene granulites and charnockites are associated with metasedimentary khondalite garnet sillimanite gneiss and migmatites in the eastern ghats mobile belt various stages of in situ granulitization similar to those observed in southern india and sri lanka are present geochemically the granulite suite around visakhapatnam is bimodal with acid and mafic variants there is an increase in the concentration and fractionation of the rare earth elements ree from pyroxene granulites to charnockites and six sm nd models ages t dm range from 2 86 to 2 35 ga with 2 1 ga for a younger granite the charnockites a pyroxene granulite and granite define a pb pb isochron age of 1176 pm 201 ma u pb ages of zircons and monazites from a charnockite near phulbani orissa yield near concordant data with ages of 985 pm 5 ma and 965 pm 7 ma respectively the new isotopic data and the available ages from the northeastern part of the eastern ghats in orissa suggest a major charnockite formati

using hydrogen oxygen and tritium isotopes to identify the hydrological factors contributing to landslides in a mountainous area central taiwan over a 1 year period 343 samples including precipitation creek pond and groundwater were collected from june 2003 to may 2004 analyses were performed for stable oxygen and hydrogen isotope compositions selected samples were also analyzed for tritium the goal was to identify possible hydrologic factors contributing to a severe landslide in the li shan area central taiwan the isotope characteristics indicate that groundwater from fu shou shan farm located up slope from the landslide area is a major source for slope groundwater in addition to precipitation the groundwater is mainly recharged by pond water at fu shou shan farm according to the calculation of a two end member equation with 18o the contribution of farm groundwater to slope groundwater is significantly higher than that of precipitation up to a factor of five the estimated drainage efficiency of the existing system is only 23 draining off the slope groundwater in the up slope region to decrease farm groundwater flow into the slope area is a feasible strategy to effectively reduce the risk of landslide

characterization of the groundwater response to rainfall on a hillslope with fractured bedrock by creep deformation and its implication for the generation of deep seated landslides on mt wanitsuka kyushu island abstract in this study the hydrogeological response of a hillslope affected by gravitational deformation was analyzed based on the data obtained for two observation boreholes a 10 m borehole representing a relatively superficial section of the hillslope dominated by soil and old landslide deposits and a 40 m borehole representing the bedrock aquifer for this analysis the precipitation events in the area groundwater levels of the two boreholes electrical conductivity and isotopic concentration oxygen and hydrogen of the groundwater in the boreholes and rainfall samples were measured derived from the rainfall data the antecedent precipitation index api with a 6 h half life offers a good correlation with the peaks in the groundwater levels in the bedrock aquifer the characteristics of the groundwater response suggest the existence of a single structure in the bedrock that controls the response of the hillslope the structure serves as a conduit which rapidly drives the rainfall water recharge into the bedrock evidently this process is unrelated to the superficial section represented by the observations in the 10 m borehole the structure is associated with an area of high hydraulic conductivity in the bedrock caused by the gravitational deformation in the hillslope the strong control of this structure in the hillslope s hydrogeological response makes it responsible for the hillslope s stability during high precipitation events this information is highly relevant to areas featuring the generation of several deep seated landslides under heavy rain conditions

abrupt changes in marine conditions sunneshine fiord eastern baffin island nwt during the last deglacial transition younger dryas and h 0 events

assessing groundwater sources and their association with reservoir water using stable hydrogen and oxygen isotopes a case study of the taipei basin northern taiwan the purpose of this isotopic study is to identify groundwater sources in taipei basin tpb and their association with water of the feitsui reservoir ftr northern taiwan to this end water samples including precipitation catchment surface water tpb groundwater ftr water and catchment surface water of ftr were analyzed for stable hydrogen and oxygen isotope compositions 2h and 18o isotopic results support previous reports that dahan stream and xindian stream waters are the major recharge sources of tpb groundwater these recharge regions are located along the southern border of the tpb further isotopic evidence finds that water from the southern hills catchment area of the tpb also recharges tpb groundwater and most importantly indicates that tpb groundwater is highly related to ftr water however for caution s sake future comprehensive study is needed to confirm hydrological connectivity between the ftr water and tpb groundwater

the dynamic relationship between ground water and the columbia river using deuterium and oxygen 18 as tracers abstract deuterium and oxygen 18 were used as natural tracers to investigate the hydraulic relationship between the columbia river and the blue lake gravel aquifer near portland oregon a time series of stable isotope data collected from surface and ground waters during a march 1990 aquifer test confirms that the river and aquifer are hydraulically connected calculations based on simple mixing show that the river contributed 40 50 of the yield of three wells after 5 6 days of pumping data collected during august 1990 show that the river contributed 65 80 of the yield of one well after 22 days of pumping and indicate that the contribution of the river was still increasing

stable isotopic and geochemical identification of groundwater evolution and recharge sources in the arid shule river basin of northwestern china stable isotopic dvsmow and 18ovsmow and geochemical signatures were employed to constrain the geochemical evolution and sources of groundwater recharge in the arid shule river basin northwestern china where extensive groundwater extraction occurs for agricultural and domestic supply springs in the mountain front of the qilian mountains the yumen tashi groundwater ytg and the guazhou groundwater gzg were ca hco3 ca mg hco3 so4 and na mg so4 cl type waters respectively total dissolved solids tds and major ion mg2 na ca2 k so42 cl and no3 concentrations of groundwater gradually increase from the mountain front to the lower reaches of the guazhou basin geochemical evolution in groundwater was possibly due to a combination of mineral dissolution mixing processes and evapotranspiration along groundwater flow paths the isotopic and geochemical variations in melt water springs river water ytg and gzg together with the end member mixing analysis emma indicate that the springs in the mountain front mainly originate from precipitation the infiltration of melt water and river in the upper reaches the lateral groundwater from the mountain front and river water in the middle reaches are probably effective recharge sources for the ytg while contribution of precipitation to ytg is extremely limited the gzg is mainly recharged by lateral groundwater flow from the yumen tashi basin and irrigation return flow the general characteristics of groundwater in the shule river basin have been initially identified and the results should facilitate integrated management of groundwater and surface water resources in the study area copyright 2015 john wiley sons ltd

cooling in the gulf of st lawrence and estuary region at 9 7 to 7 2 14c ka 11 2 8 0 cal ka palynological response to the pbo and 8 2 cal ka cold events laurentide ice sheet air mass circulation and enhanced freshwater runoff abstract an examination of post younger dryas yd pollen stratigraphies in the gulf of st lawrence and st lawrence estuary region reveals features in the pollen records that represent breaks in the normal vegetation succession widespread vegetation suppression and a delay in migration of plant taxa between 9 7 and 7 2 14 c ka 11 2 and 8 0 cal ka the domination of alnus crispa at sites bordering the st lawrence estuary gulf region in gaspesie and northern new brunswick within this timeframe represents a diversion from the typical vegetation progression from picea and or populus or picea betula to pinus and or betula and signifies a shift to a cooler drier climate coinciding with the a crispa expansion and domination in that region was the contraction of picea populations in other areas in southwestern new brunswick and eastern and southeastern nova scotia picea was replaced by the first appearance of tree birch b papyrifera whereas in western and southwestern newfoundland picea gave way to a resurgence of shrub birch betula glandulosa the picea contraction and immediate resurgence of betula represents cooling and is reliably dated at 9720 110 14 c bp 10 800 11 240 cal bp in southwest newfoundland this first post yd episode of widespread cooling is correlated with the north atlantic preboreal oscillation pbo centered around 9650 14 c bp 10 900 11 180 cal bp in the adjacent great lakes region sites exposed to winds from the gulf of st lawrence in eastern new brunswick prince edward island and northern nova scotia show a lingering persistence of picea and delay in arrival of pinus to 8 0 and 7 7 14 c ka 9 0 and 8 4 cal ka yet pinus was dominant as early as 9 4 14 c ka 10 6 cal ka in southwestern new brunswick at the same time tundra vegetation persisted at high elevations in western and southwestern newfoundland only to be replaced by upslope migration of shrub birch heath by 8 14 c ka prolonged broad scale cooling to 8 14 c ka and to as late as 7 7 14 c ka extended up to 200 km inland in areas exposed to the st lawrence estuary and gulf region and was in response to strong cold dry anticyclonic winds coming off the retreating laurentide ice sheet in combination with enhanced freshwater runoff through the gulf of st lawrence the end of the period of prolonged cooling and onset of regional warming coincided with the diversion of western canada runoff and agassiz ojibway drainage to hudson bay and reduced effect or final break up of the laurentide ice sheet several sites document a subsequent cold shift that interrupted regional warming at 7650 to 7200 14 c bp 8400 to 8000 cal bp and which is variously represented by the suppression of pinus and resurgence of picea sometimes with a crispa quebec maritime region or by an abrupt decrease of picea and resurgence of betula western newfoundland this second post yd cool interval is equated with the 8200 cal bp cold event registered in the greenland ice isotopic record

the groundwater recharge regime of some slightly metamorphosed neoproterozoic sedimentary rocks an application of natural environmental tracers isotope data of precipitation and groundwater in parts of the voltaian basin in northern ghana were used to explain the groundwater recharge regime in the area groundwater recharge is an important parameter in the development of a decision support system for the management and efficient utilization of groundwater resources in the area it is therefore important to establish the processes and sources of groundwater recharge 18o and 2h data for local precipitation suggest enrichment relative to the global meteoric water line gmwl and indicate that precipitation takes place at a relative humidity less than 100 the groundwater data plot on an evaporation line with a slope of 5 suggesting a high degree of evaporative enrichment of the precipitation in the process of vertical infiltration and percolation through the unsaturated zone into the saturated zone this finding is consistent with the observation of high evapotranspiration rates in the area and ties in with the fact that significant clay fraction in the unsaturated zone limits vertical percolation and thus exposes the percolating rainwater to the effects of high temperatures and low humidities resulting in high evapotranspiration rates groundwater recharge estimates from the chloride mass balance cmb method suggest recharge in the range of 1 8 32 of the annual average precipitation in the form of rainfall the highest rates are associated with areas where open wells encourage significant amount of groundwater recharge from precipitation in the area in the northern parts of the study area groundwater recharge is lower than 12 the recharge so computed through the application of the cmb methodology takes on a spatial distribution akin to the converse of the spatial pattern of both 18o and 2h in the area as such the locations of the highest recharge are associated with the most depleted values of the two isotopes this observation is consistent with the assertion that low vertical hydraulic conductivities slow down vertical percolation of precipitation down to the groundwater water the percolating precipitation water thus gets enriched in the heavier isotopes through high evapotranspiration rates at the same time the amount of water that finally reaches the water table is considerably reduced copyright 2013 john wiley sons ltd

multiple tectonothermal events in the granulite blocks of southern india revealed from epma dating implications on the history of supercontinents abstract we report age data on zircon monazite uraninite and huttonite from a suite of 29 samples covering four major granulite blocks in southern india using an electron microprobe technique the rocks analysed in this study cover all of the major lithounits in these terrains and include garnet bearing and garnet free charnockites garnet biotite gneisses khondalites calc silicate rocks and a suite of orthogneisses biotite gneiss biotite hornblende gneiss two pink metagranites representing the magmatic phase were also analysed zircons from the madras block yield well defined isochrons at 2 5 2 6 ga core to rim analyses of single zircon grains show age zoning with 2 6 2 9 ga igneous cores mantled by 2 4 2 5 ga rims detrital zircons show age up to ca 3 2 ga monazites in this block have cores and rims with 2 5 2 3 ga a suite of 19 samples from the madurai block brings out the multiple tectonothermal events in this terrain zircons from an orthogneiss yield well defined isochrons at 1 7 0 1 ga 0 82 0 05 ga and 0 58 0 04 ga from core inner rim and rim portions respectively zircon grains in other rocks preserve either core or secondary growth ages at 0 8 1 0 ga zircons in a pink metagranite from this block show sharply defined isochrons of 0 68 0 03 ga for the core and 0 57 0 01 ga for the secondary portion a late pan african overprint is observed throughout this block with zircon rims monazite uraninite and huttonite yielding age values in the range of 0 45 0 60 ga zircons from both the trivandrum and nagercoil blocks show a major tectonothermal event at 0 55 ga with faint indications of previous tectonothermal events during 0 8 1 0 and 1 7 2 0 ga monazite data from both the trivandrum and nagercoil blocks are essentially similar to those from the madurai block except for presence of relic monazite in the former our study confirms the notion that the palghat cauvery shear zone marks the major terrain boundary between an archean craton in the north and proterozoic terrains in the south it also strengthens the view of paleoproterozoic accretion and pan african reworking of blocks south of this shear zone the ages of production accretion and reworking in the terrains of southern india yield important information for the histories of columbia 1 8 1 5 ga rodinia 1 1 1 0 ga and gondwana 0 6 0 5 ga supercontinents the southern indian terrains formed part of a worldwide network of orogenic belts that is centered around 1 8 ga and outlines the configuration of columbia accretion of terrains in the madurai block to archean rocks north of the palghat cauvery shear zone at this time is consistent with the ages suggested to be the oldest metamorphic event in the eastern ghats orogen of eastern india and the rayner belt of coastal east antarctica our data confirm earlier evidence that all of southernmost india underwent resetting of isotopic systems during the final accretion of gondwana at the time of the pan african orogeny 0 5 ga the possibility that the trivandrum and nagercoil terrains accreted to the madurai block after 0 7 ga suggests that this pan african zone may also have involved accretion and closure of ocean basins if that happened then this zone may be the long sought suture between east and west gondwana

the proterozoic mount isa fault zone northeastern australia is it really a ca 1 9 ga terrane bounding suture abstract in marked contrast to palaeoproterozoic laurentia the location of sutures and boundaries of discrete crustal fragments amalgamated during palaeoproterozoic formation of the north australian craton remain highly speculative interpretations of suture locations have relied heavily on the analysis of regional geophysical datasets because of sparse exposure of rocks of the appropriate age the mount isa fault zone has been interpreted as one such palaeoproterozoic terrane bounding suture furthermore the coincidence of this fault zone with major shale hosted massive sulphide pb zn ag orebodies has led to speculations that trans lithospheric faults may be an important ingredient for the development of this deposit type this study has integrated geophysical and geochemical data to test the statute of the mount isa fault as a terrane bounding suture forward modelling of gravity data shows that basement rocks on either side of the mount isa fault have similar densities these interpretations are consistent with geochemical observations and sm nd data that suggest that basement lithologies on either side of the mount isa fault are geochemically and isotopically indistinguishable from each other and that the mount isa fault is unlikely to represent a suture zone that separates different palaeoproterozoic terranes our data indicate that the crustal blocks on both sides of the mount isa fault zone must have been in within close proximity of each other since the palaeoproterozoic and that the western fold belt was part of the ancestral north australian craton well before the 1 89 1 87 ga barramundi orogeny it appears that deep crustal variations in density may be related to the boundary between a shallowly west dipping high density mafic to ultramafic plate and low density basement rocks this interpretation in turn impacts on crustal scale models for the development of shale hosted massive sulphide pb zn mineralisation which do not require trans lithospheric faults to tap deep seated metal reservoirs and or mantle plumbing systems the approach applied herein demonstrates the value of multi disciplinary investigations to the critical assessment of long lived proterozoic fault systems which in the absence of methodical analysis are commonly assumed to represent terrane bounding sutures

a plausible model for evolution of schist belts and granite plutons of dharwar craton india and madagascar during 3 0 2 5 ga insight from gravity modeling constrained in part from seismic studies abstract gravity modeling of an e w profile across dharwar craton india and madagascar integrated with the results of deep seismic sounding dss across the dharwar craton suggest a thick crust of 40 42 km under the eastern part of eastern dharwar craton edc the western dharwar craton wdc and the central part of the madagascar towards east of these blocks the crustal thickness is reduced to 36 38 km along the eastern ghat fold belt egfb shear zone between the edc and the wdc and the east coast of madagascar respectively these zones of thin crust are also characterized by high density lower crustal rocks associated with thrusts the seismic section across dharwar craton shows domal shaped reflectors in the lower crust and upper mantle under the wdc which may be related to asthenopheric upwelling during an extension phase the occurrences of large schist belts with volcano sedimentary sequences of marine origin of late archean period 3 0 2 7 ga as rift basins in the wdc and madagascar also suggest an extensional phase in this region during that period it is followed by a convergence between the wdc and the edc giving rise to collision related shear and thrust zones between the wdc and the edc associated with high density lower crustal rocks the seismic section shows upwarped reflectors in the upper crust which may be related to this convergence eastward dipping reflectors under wdc and edc and west verging thrusts suggest convergence from the west to the east which resulted in easterly subduction giving rise to subduction related k granite plutons of the edc of 2 6 2 5 ga in this regard the closepet granite in the edc which extends almost parallel to the shear zone between the wdc and edc and shows an i type calk alkaline composition may represent relict of an island arc and the linear schist belts with bimodal volcanics of the edc east of it might have developed as back arc rift basins subsequent collision between india and antarctica along the egfb during middle proterozoic indicated by eastward dipping reflectors in the crust and the upper mantle and west verging thrust gave rise to contemporary high grade rocks of the egfb 1 6 1 0 ga and associated mafic and felsic intrusives of this belt the part of adjoining cuddapah basin contemporary to the egfb towards the west consisting of marine shelf type of sediments which are highly disturbed and thickest at its contact with the egfb may represent a peripheral foreland basin gravity modeling provides thickest crust of 42 km in the southern part of the wdc and does not support sharp increase in crustal thickness of 50 60 km with high velocity upper mantle as suggested from receiver function analysis it may represent some foreign material of high density trapped in this section such as part of oceanic crust during convergence and subduction that is referred to above it is supported from eastward dipping reflectors in lower crust and upper mantle in adjoining region

lithospheric flexure and gravity anomalies at proterozoic plate boundaries in the canadian shield abstract proposed proterozoic sutures in the canadian shield show paired positive and negative gravity anomalies previous interpretations ascribe the negative anomaly to an increase in crustal thickness of the older province towards the suture and the positive to increased density and thickness of the younger province here the asymmetrical negative anomaly is interpreted to be the result of flexure of the older lithosphere as it is thrust under the younger more buoyant plate the absence of any visual correlation between topography and observed gravity over suture zones suggests the presence of subsurface loads which are thought to be the primary sources for the related positive gravity anomalies two dimensional modelling of suture anomalies has resulted in the following estimates for elastic plate thicknesses in the canadian shield 60 km for the slave plate and 75 120 125 km for the cape smith labrador and grenville areas of the superior province flexural rigidities at sutures increase with the age of the lithosphere when loaded supporting previous results obtained in oceans and mountain ranges

structural setting of the neoarchean terrains in the commonwealth bay area 143 145 e terre adelie craton east antarctica lithological and structural maps from the east commonwealth bay unit ecb terre adelie and georges v land antarctica are presented with a summary of the main structural and metamorphic data obtained in the area the ecb unit is structured during the late archean lower proterozoic at 2 4 2 5 ga with i granulite metamorphism at 9 6 kbar and 850 50 c of lower mid crust and amphibolite metamorphism p 5 kbar t 750 c of the upper crustal levels ii the lower crustal granulites are uplifted and suffered local partial melting and then retrogression into the amphibolite facies at 550 50 c 5 kbar granulites are extruded in the core of a crustal scale anticlinal fold granulites being retrogressed only on the rims of the anticline crustal scale folding along with other structural features results from intense ne sw shortening that prevailed during the late archean orogenic cycle strike slip and extensive motions are only minor in that process iii top to the east thrusting and nappe piling has at least locally occurred under lower amphibolite to greenschist facies conditions finally it seems that iv the paleoproterozoic 1 7 ga structural imprint may have only affected the rims of the archean units the tectonic context observed in the 1 7 ga cape hunter phyllites features mainly e w shortening component and vertical extrusion the eastern mertz and western port martin parts of the archean block were reactivated by localized dextral shearing

a heinrich like event h 0 dc 0 source s for detrital carbonate in the north atlantic during the younger dryas chronozone in the north atlantic we define h 0 as a heinrich like event which occurred during the younger dryas chron on the se baffin shelf prior to 11 ka surface water productivity was reasonably high as measured by the numbers of diatom and planktic foraminifera per gram but an abrupt increase in detrital carbonate dc 0 event from approximately 15 up to 50 carbonate by weight occurred at 11 14c ka and continued to circa 10 ka these deposits 2 6 m thick are dominated by detrital calcite and silt and clay sized sediments during this event dc 0 h 0 ice extended onto the inner shelf but did not reach the shelf break and probably originated from a center over labrador ungava as a consequence the pattern of ice rafted debris and sediment provenance shown by h o in the north atlantic is different from that during h 1 14 5 ka or h 2 20 ka when the ice sheet extended along the axis of hudson strait and may have reached the shelf break for example there is no concrete evidence for dc o is cores on the floor of the labrador sea due east of hudson strait hu75 55 56 but h o has been noted in cores off newfoundland and west of ireland a coeval carbonate event to dc 0 but this one dominated by dolomite occurs in hu82 su5 on the west side of davis strait with a source either from northern baffin bay or cumberland sound although other sources for north atlantic detrital carbonate cannot be totally excluded our evidence suggests that h 0 represents the expression of glaciological instability of the laurentide ice sheet within the general region of hudson strait and probably to the north cumberland sound and northernmost baffin bay there is one younger dc event dated circa 8 4 ka present in sediments along the labrador margin and in hudson strait which represents the final collapse of the ice sheet within hudson strait and hudson bay

holocene vegetation dynamics of anticosti island quebec and consequences of remoteness on ecological succession abstract the postglacial vegetation history of anticosti island in the gulf of st lawrence quebec was reconstructed from pollen analysis of three sites providing the first paleoecological data for the island the earliest plant communities 8550 7770 14c yr b p 9500 8500 cal yr b p were characterized by a high representation of green alder alnus crispa indicating an open environment with sparse spruce picea between 7770 and 3700 14c yr b p 8500 4000 cal yr b p the island was colonized by mixed deciduous and coniferous forests dominated by paper birch betula papyrifera and spruce a major increase in the abundance of balsam fir abies balsamea occurred ca 3700 14c yr b p 4000 cal yr b p indicating development of the closed fir spruce forests as they exist today the island s remoteness from continental seed plant sources influenced plant colonization afforestation and ecological succession the gulf of st lawrence slowed plant migration and tree species had to spread from the gaspe peninsula repeated drops in fir pollen percentages during the last 4 000 years may reflect the activity of defoliating insects

facies characteristics of talchir formation jharia basin india implications for initiation of gondwana sedimentation abstract a long phase of nondeposition that prevailed in peninsular india since the late proterozoic came into an end with the onset of gondwana sedimentation the talchir formation the lowest unit of gondwana supergroup deserves special attention for understanding the late paleozoic geological history in this part of the globe signatures of three major events have been identified in the talchir formation in different gondwana basins of india 1 intracratonic rifting 2 permo carboniferous glaciation and 3 marine incursion but a unique model to explain the specific relation between these events is yet to be formulated the present study reveals that the talchir succession of jharia basin of eastern india bears certain evidences which may lead to a possible solution to this problem the lower part of the succession is represented by a glacigenic conglomerate which underwent brecciation possibly due to hydraulic fracturing during deglaciation facies analysis leads to the conclusion that a thick fan deposit presumably produced through resedimentation of preexisting unconsolidated glacial sediments represents the rest of the talchir succession the presence of fragments of brecciated conglomerate within this fan deposit confirms a significant break in the sedimentation history three fining upward cycles can be identified within the proximal part of the fan succession the lower and the middle cycles bear the signature of emplacement of subaqueous high density flows and variations in facies pattern developed through progressive flow transformation the upper cycle however is represented by sheet flood and stream flow deposits products of dominantly suspension fall out over a vast area with periodic influx of coarser material constitute the distal fan deposit the fan succession is unconformably overlain by a fluvial succession which in turn interfingers with the fluviolacustrine deposits of the younger barakar formation derived from the opposite side of the basin this indicates asymmetric pattern of basin filling as expected in a continental extensional setting the overall character of this succession indicates that 1 emplacement of the intracratonic rift system was a post glaciation event 2 initial phase of deposition was dominated by resedimentation of the preexisting glacial debris and 3 marine incursion probably followed deglaciation and persisted for a short time until isostatic equilibrium was attained before the rift system came into existence

two cases of continental collisions and related tectonics during the proterozoic period in india insights from gravity modelling constrained by seismic and magnetotelluric studies abstract the aravalli delhi mobile belt admb in nw india includes the proterozoic aravalli and delhi rifts and fold belts a seismic profile and gravity modelling across the admb shows several dipping reflections and suggests a thick crust 45 46 km and a high density 3 04 g cm 3 dome shaped body in the lower crust this high density body in the lower crust may represent underplated lower crust caused by extension during evolution of the proterozoic rifts part of the gravity high observed over the admb is attributed to the upthrust blocks of high density lower crustal granulite rocks the gravity low along the eastern margin of the admb is modelled as being due to a westerly dipping 45 low density body in the crust in accordance with seismic reflectors which may represent remanents of the subducted crustal rocks the hindoli group of rocks above this body is characterized by high conductivity indicating a high fluid content and a fractured nature which may be related to the collisional tectonism of this region a sharp gravity high along the western margin of the admb is attributed to the basic rocks of an ophiolite melange the gravity low and high west of the admb are attributed to plutonic activity and bimodal calc alkaline volcanics in linear basins and are related to arc and back arc rift magmatism respectively the admb therefore represents a proterozoic collision zone between the bundelkhand craton towards the east and the rajasthan craton towards the west with a plausible subduction towards the west along the eastern margin of the admb the thrusting is mainly confined to the obducted block towards the west although some thrusting is inferred even in the subducted block the central indian suture cis is located at the southern margin of the satpura mobile belt smb in central india and separates high grade metasediments and granulite towards the north from low grade proterozoic volcanogenic successions towards the south a seismic profile and gravity modelling across the cis show a thick crust with a thicker crust north of the cis compared to the south and a contact in the lower crust whose projection on the surface coincides with the cis the cis at the surface coincides with a low density 2 65 g cm 3 and conductive body that is interpreted to be fluid filled and fractured in nature the high density 2 81 g cm 3 body modelled in the upper crust north of the cis coinciding approximately with a highly conductive body and dome shaped seismic reflectors may represent an upthrust block from the lower crust as high density granulite rocks are exposed in this region short wavelength gravity highs and lows south of the cis represent exposed metavolcanics and granite intrusions which represent tholeiitic series rocks to calc alkaline series rocks associated with island arcs and back arc magmatism therefore the large wavelength gravity low south of the cis is modelled as a low density body below the moho which conforms with seismic reflectors and may represent crustal rocks subducted towards the south thrusting in this case is indicated in the subducted block towards the north of the cis the bipolar gravity anomaly across the cis therefore indicates a collision zone between the bundelkhand craton towards the north and bhandara deccan cratons towards the south

exposed cross sections through the continental crust implications for crustal structure petrology and evolution abstract the continental crust is exposed in cross section at numerous sites on the earth s surface these exposures which appear to have formed by obduction along great faults during continental collision may be recognized by exposures of deep crustal rocks exhibiting asymmetric patterns of metamorphic grade and age across the faults and by distinctive bouguer anomaly patterns reflecting dipping basement structure and an anomalously deep mantle from an examination of five complexes which meet these criteria it is concluded that the most prominent layering in the crust is not compositional but metamorphic the lower crust consists of granulite facies rocks of mafic to intermediate composition while the intermediate and shallow levels consist predominantly of amphibolite facies gneisses and greenschist facies supracrustal rocks respectively post metamorphic granitic intrusions are common at intermediate to shallow levels position of discontinuities in refraction velocity where present commonly correspond to changes in composition or metamorphic grade with depth the continental crust is characterized by lateral and vertical heterogeneities of varying scale which are the apparent cause of the complex seismic reflections recorded by cocorp field observations coupled with geochemical data indicate a complex evolution of the lower crust which can include anatexis multiple deformation polymetamorphism and reworking of older crustal material the complexity of the crust is thus the result of continuous evolution by recycling and metamorphism through time in a variety of tectonic environments

tectonic model for the evolution of the limpopo belt abstract constraints on which any model for the tectonic evolution of the limpopo belt must be based include the following data crustal thickening to at least 65 km between 2700 and 2650 ma ago was responsible for the formation of the granulite terrane exposed in the limpopo belt today this crustal thickening probably resulted from the thrusting of the kaapvaal craton over the zimbabwe craton along the south dipping triangle tuli sabi shear zone other northwardverging thrusts related to this event occur in the kaapvaal craton south of the limpopo belt in the central and southern marginal zones and the kaapvaal craton this shortening is directed to the southwest while in the northern marginal zone it was directed to the north northwest peak metamorphism was superimposed on the thickened crust and then nearly isothermal decompression of several kbars occurred throughout the belt during this decompression rocks moved upward and spread outward onto the adjacent cratons from the zone of thickened crust along several inward directed shear zones creating a regional pop up high grade rocks were thrust over low grade rocks on the cratons producing along the terrane boundary retrograde metamorphism in the limpopo belt and prograde metamorphism on the cratons

sedimentologic and palynologic records of the last deglaciation and holocene from ballston lake new york continuous pollen and sediment records from two 8 5 m long cores document late pleistocene and holocene sedimentation and vegetation change in the ballston lake basin eastern new york state pebbles at the base of both cores and the geomorphology of the watershed reflect the presence of the mohawk river in the basin prior to 12 900 70 cal yr b p ballston lake formed at the onset of the younger dryas yd by an avulsion of the mohawk river the transition from clay to gyttja with low magnetic susceptibility ms low bulk density and high organic carbon indicates rapid warming and increased lake productivity beginning 11 020 cal yr b p ms measurements reveal that the influx of magnetic particles associated with pre holocene clastic sedimentation ceased after 10 780 cal yr b p the pollen record is subdivided into six zones bl1 12 920 to 11 020 cal yr b p is dominated by boreal forest pollen bl2 11 020 to 10 780 cal yr b p by pine pinus forest pollen bl3 10 780 to 5290 cal yr b p by hemlock tsuga and mixed hardwood pollen bl4 5290 to 2680 cal yr b p by mixed hardwood pollen bl5a 2680 cal yr b p to 1030 cal yr b p by conifer and mixed hardwood pollen and bl5b 1030 cal b p to present by increasing ragweed ambrosia pollen a 62 decrease in spruce picea pollen in 320 cal years during bl1 reflects rapid warming at the end of the yd holocene pollen zones record more subtle climatic shifts than occurred at the end of the yd one of the largest changes in the holocene pollen spectra began 5300 cal yr b p and is characterized by a marked decline in hemlock pollen this has been noted in other pollen records from the region and may record preferential selection of hemlock by a pathogen or parasites

analysis of airborne magnetic and gravity anomalies of peninsular shield india integrated with seismic and magnetotelluric results and gravity anomalies of madagascar sri lanka and east antarctica abstract modelling of gravity and airborne magnetic data integrated with seismic studies suggest that the linear gravity and magnetic anomalies associated with moyar bhavani shear zone mbsz and palghat cauvery shear zone pcsz are caused by high density and high susceptibility rocks in upper crust which may represent mafic lower crustal rocks this along with thick crust 44 45 km under the southern granulite terrain sgt indicates collision of dharwar craton towards north and sgt towards south with n s directed compression during 2 6 2 5 ga this collision may be related to contemporary collision northwards between eastern madagascar western dharwar craton wdc and eastern dharwar craton edc arcuate shaped n and s verging thrusts mbsz mettur shear and pcsz gangavalli shear respectively across cauvery shear zone system csz in sgt also suggest that the wdc edc and sgt might have collided almost simultaneously during 2 6 2 5 ga due to nw se directed compressional forces with csz as central core complex in plate tectonics paradigm preserving rocks of oceanic affinity gravity anomalies of schist belts of wdc suggest marginal and intra arc basin setting the gravity highs of egfb along east coast of india and regional gravity low over east antarctica are attributed to thrusted high density lower crustal upper mantle rocks at a depth of 5 6 km along w verging thrust which is supported by high seismic velocity and crustal thickening respectively it may represent a collision zone at about 1 0 ga between india and east antarctica paired gravity anomalies in the central part of sri lanka related to high density intrusives under western margin of highland complex and crustal thickening 40 km along eastern margin of highland complex with several arc type magmatic rocks of about 1 0 ga in vijayan complex towards the east may represent collision between them with w verging thrust as in case of egfb the gravity high of sri lanka in the central part falls in line with that of egfb in case it is fitted in gulf of mannar and may represent the extension of this orogeny in sri lanka

delineation of lithostructural domains in northern orissa india from landsat thematic mapper imagery abstract image based reconnaissance geological mapping at 1 100 000 scale using landsat tm data has delineated a college of precambrian lithostructural domains within a 50 000 km 2 region which encompasses the northern portion of the archaean to proterozoic granulite grade eastern ghats tectonic province and the adjacent archaean mesoproterozoic singhbhum craton the domains identified in the present study display distinctive internal structures on satellite imagery most are bounded by clearly recognisable major shear zones and faults on imagery displacement directions may frequently be ascertained through local reorientation of planar structures adjacent to large strike slip shear zones and through juxtaposition of domains with different structuring the macroscopic megascopic structural overview provided by the landsat interpretation supported by preliminary field investigation suggests that the n s shortening e w fold thrust packages with associated ne and nw strike slip faulting is the dominant structural style in the northernmost part of the eastern ghats tectonic province followed by regional dextral transpression expressed in the form of major strike slip faults the largest of these structures kerajang fault which may be traced for over 250 km has demonstrable paleozoic mesozoic dextral motion associated with coal basin formation a precursor kerajang shear zone with dextral movement in excess of 100 km of indeterminate age may also have been instrumental in juxtaposing the singhbhum nucleus into its present position to the north of the eastern ghats tectonic province

wisconsinan late glacial environmental chage in new brunswick a regional synthesis a synthesis is presented of the history of deglaciation vegetation cover and climate in new brunswick canada during that part of the wisconsinan late glacial period 12 9 ka bp for which detailed records exist curves of inferred temperature variations in the region during this period are presented based upon qualitative interpretations of plant records and quantitative estimates based upon fossil chironomid assemblages

identification of groundwater sources of a local scale creep slope using environmental stable isotopes as tracers summary water plays an important role for slope stability and typically consists of local precipitation lp and original slope groundwater osgw high amount of the osgw leads the slope groundwater sgw easily to exceed the critical level that causes slope failure in a heavy raining event this study was to verify the source and significance of the osgw for a creep slope adjoining a hydropower plant northern taiwan by an environmental stable isotope approach isotope results indicate that the source of the osgw derived from leaking of the water transporting system of the power plant the leaking fraction in the sgw is as high as 70 80 high leaking component in the sgw indicates that the leaking water rather than local precipitation is the crucial factor for the mass movement of the creep slope since the mass movement poses a potential threat to the hydropower plant safety the most important measure for the remedial project is to perform a comprehensive check and repair the leak of the water transporting system

an event stratigraphy for the last termination in the north atlantic region based on the greenland ice core record a proposal by the intimate group it is suggested that the grip greenland ice core should constitute the stratotype for the last termination based on the oxygen isotope signal in that core a new event stratigraphy spanning the time interval from ca 22 0 to 11 5 k grip yr bp ca 19 0 10 0 k 14 c yr bp is proposed for the north atlantic region this covers the period from the last glacial maximum through termination 1 of the deep ocean record to the pleistocene holocene boundary and encompasses the last glacial late glacial of the traditional northwest european stratigraphy the isotopic record for this period is divided into two stadial episodes greenland stadials 1 gs 1 and 2 gs 2 and two interstadial events greenland interstadials 1 gi 1 and 2 gi 2 in addition gi 1 and gs 2 are further subdivided into shorter episodes the event stratigraphy is equally applicable to ice core marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon dated chronostratigraphy that has been used hitherto 1998 john wiley sons ltd

phanerozoic history of the mahanadi region india the mahanadi basin is a nw se stretching gondwana basin perpendicular to the east coast of india the metamorphic basement to the basin mainly comprises rocks of the eastern ghats mobile belt egmb which experienced a complex thermotectonic evolution involving several episodes of deformation and magmatism it can be inferred from 40ar 39ar ages on hornblende 845 ma and biotite 622 and 593 ma from basement rocks that the last high grade metamorphism in the western part of the egmb i e the western khondalite zone occurred during the late grenvillian with any pan african overprint only reaching anchimetamorphic conditions only pseudotachylite intrusions and their related thermal imprint with ages around 515 ma display a direct pan african signature fission track analyses on nine zircon 419 313 ma and 49 apatite 443 119 ma samples indicate a rift related formation of the mahanadi basin as an asymmetrical half graben in two stages during the permo carboniferous and the middle triassic moreover the gondwana breakup in eastern india is signified by dyke intrusions and the thermal overprint of thrusts and faults in the mahanadi region and the onset of ocean floor production in the mahanadi offshore basin at around 120 ma

kinematics of the gondwana basins of peninsular india abstract the gondwana successions 1 4 km thick of peninsular india accumulated in a number of discrete basins during permo triassic period the basins are typically bounded by faults that developed along precambrian lineaments during deposition as well as affected by intrabasinal faults indicating fault controlled synsedimentary subsidence the patterns of the intrabasinal faults and their relationships with the respective basin bounding faults represent both extensional and strike slip regimes field evidence suggests that preferential subsidence in locales of differently oriented discontinuities in the precambrian basement led to development of gondwana basins with varying but mutually compatible kinematics during a bulk motion grossly along the present day e w direction the kinematic disparity of the individual basins resulted due to different relative orientations of the basement discontinuities and is illustrated with the help of a simple sandbox model the regional e w motion was accommodated by strike slip motion on the transcontinental fault in the north

alkaline magmatism along the southeastern margin of the indian shield implications for regional geodynamics and constraints on craton eastern ghats belt suturing abstract deformed alkaline complexes at the contact between the eastern ghats belt egb and the archaean cratons in southeastern india mark the location of a collisional suture superimposing an earlier mesoproterozoic 1 5 1 3 ga rift this article offers a plausible geodynamic model explaining the alkaline magmatism and its relationship to regional crustal evolution the mesoproterozoic rift can be correlated to the breakup of the supercontinent columbia and may have opened an ocean between eastern india and east antarctica where the sedimentary sequences of the eastern ghats province egp were deposited between 1 4 and 1 2 ga inversion of the rift basin during the late mesoproterozoic 1 0 ga led to the collision of eastern india with east antarctica during rodinia assembly the collision formed the grenvillian egp rayner complex orogen where the egp sediments and the rocks of the rayner complex were deformed metamorphosed and migmatized at granulite facies condition the mesoproterozoic rifting and grenvillian basin closure may thus represent a wilson cycle related to the breakup of columbia and the assembly of rodinia the craton egb suture was subsequently modified significantly during pan african tectonism 0 5 0 6 ga when the egb granulites were thrust westward over the cratonic foreland along a number of amphibolite facies shear zones at the contact the shearing deformed and metamorphosed the cratonic margin and the alkaline complexes it hosts the thrust stacking in many places has the craton boundary and the alkaline rocks in the footwall and the egb granulites in the hanging wall the continuity of the pan african shear fabric across the craton granulite contact and the lack of grenvillian ages from the alkaline and other craton margin rocks in such regions give the apparent impression that the two crustal segments amalgamated during pan african tectonism and not during the earlier grenvillian collision geodynamic constraints however indicate that this was unlikely and the inconsistency arises because the present crustal geometry exposes only the eroded pan african thrust contact between the craton and the egb and not the original grenvillian suture which may be lying unexposed under the granulite thrust sheets

use of stable water isotopes to assess sources and influences of slope groundwater on slope failure this study employs stable oxygen and hydrogen isotopes as natural tracers to assess the headwater of a landslide next to a drainage divide and the importance of the slope s headwater in the study area the study is undertaken near wu she township in the mountains of central taiwan because a reservoir is located on the other side of the divide this study evaluates the relationship between the reservoir water and headwater of the landslide as well over a 1 year period water samples from september 2008 to september 2009 including local precipitation lp wu she reservoir s water wsrw slope groundwater sgw upper reach stream water ustw and down reach stream water dstw were analysed for deuterium d and oxygen 18o stable isotopes results indicate that wsrw is the predominant component in sgw approximately 70 of sgw originates from wsrw and 30 from lp based on a two end member mass balance mixing model for 18o the similar two end member mixing model is also employed to assess the contributions of ustw and sgw to dstw model results indicate that sgw is the major source of dstw with a contribution of about 67 accordingly about 47 of dstw sources from the wsrw in short owing to reservoir leakage wsrw contributes the greater part of both sgw and dstw plentiful wsrw in sgw threatens the stability of the slope in the divide area to avoid subsequent continuous slope failure necessary mitigation steps are required copyright 2011 john wiley sons ltd

superposed deformation and inherited structures in an ancient dilational step over zone post mortem of the rengali province india abstract in the eastern indian shield a dextral strike slip system juxtaposed the archaean singhbhum province against the proterozoic eastern ghats belt at 490 470 ma two wnw ese trending strands of the strike slip system enclose a multiply deformed d1 to d3 intervening domain called the rengali province with d3 representing dextral shearing in a granulite lens within the province an early fabric sgr was deformed by an amphibolite facies d1 d2 deformation continuum in the late archaean time forming cylindrical folds in the surrounding quartzofeldspathic gneisses quartzites and mica schists of the province superimposition of syn d3 shortening on d1 d2 folds generated complex non cylindrical geometries the granulites escaped d3 strain microstructures in the province bounding shear zones confirm that d3 deformation was associated with mylonitization dynamic recrystallization and greenschist facies metamorphism in the quartzites syn d3 folds can be correlated with rotation of d1 d2 structures through the shortening zone of bounding dextral shears since the province bounding shears form a step over zone the structural complexity within the rengali province arises from superposition of syn d3 shortening structures on initially asympathetically oriented inherited cylindrical d1 d2 folds hydrous fluid channeling causing greenschist facies metamorphism and quartz vein emplacement accompanied d3 as the step over zone was dilational in nature