geostatistical integration of seismic velocity and resistivity data for probabilistic evaluation of rock quality this study applied a geostatistical approach to integrate various geophysical results for the probabilistic evaluation of rock quality designation rqd in regions between boreholes two of the geophysical survey results electrical resistivity and seismic velocity were transformed into a probabilistic distribution with the directly observed rqd values at the boreholes using an indicator value method the initial spatial distribution of rqd inferred from indicator kriging of observations from the boreholes was improved by support of the geophysical results based on the integration by a permanence ratio the integration was good enough to produce results that compensated for the defection of each exploration method also the probabilistic feature of the final product of the rqd distribution made it possible to assess a more quantitative rock quality evaluation and better decision making for safety design

mountain environment and early human adaptation in nw himalaya india a case study of siwalik hill range and leh valley abstract prehistoric sites are reported from the entire length and breadth of india most of these are surface sites and invite less attention and significance compared to the few sites that are buried the systematic excavation of prehistoric sites has contributed to the understanding of typo technological evolution in the backdrop of time and space however the early artifact bearing sites in himalaya beyond the indo gangetic plains although open air sites hold significance in terms of understanding the extent of human colonization in himalaya in relation to climate the sporadic evidence of early humans in the siwalik ranges of jammu and along the indus river in the leh valley undoubtedly confirm the advent of early humans to this geographical realm when most of the area had tectonically stabilized and the more or less present day landscape and ecology had developed in the region with ameliorated climate for early human settlement

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

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

optical chronology and climatic implication of glacial advances from the southern ladakh range nw himalaya india abstract morphological sedimentological and chronological evidence suggests the preservation of three glacial advances of decreasing magnitude in the puche valley near leh southern ladakh ranges the oldest moraine of puche glacier advance 1 pga 1 is optically dated to the early marine isotopic stage mis 2 31 5 3 3 ka that persisted until around the global last glacial maxima lgm 22 7 1 6 ka the pga 2 is optically dated to the post lgm 14 4 1 0 ka and perhaps was triggered by meltwater pulse 1a cooling the youngest pga 3 remains undated and could be of holocene age the optically stimulated luminescence osl ages suggest a greater role of westerlies in driving the glacier advances during the mis 2 in the southern ladakh ranges and are at variance with the previous suggestions that recommended monsoon driven glacier advances the osl ages compared to the previously obtained 10be surface exposure ages are younger by a magnitude the study explores probable causes for the variance in two chronologies and suggests employing multiple dating methods to minimize the uncertainty both in terms of age and climatic interpretation

thermal histories of co3 chondrites application of olivine diffusion modelling to parent body metamorphism abstract the petrologic sequence observed in the co3 chondrite group has been suggested to be the result of thermal metamorphism on a parent body we have developed a model to examine the possibility that chondrule and matrix olivines equilibrated in situ during parent body metamorphism the model considers fe mg interdiffusion between chondrule and matrix olivines zoning profiles comparable to those observed in chondrule olivines from partially equilibrated members of the series are reproduced successfully metamorphism of co3 chondrites on a parent body is therefore a viable model for the observed equilibration results indicate that peak metamorphic temperatures experienced by the co3 chondrites were around 500 c and that the range of peak temperatures between unequilibrated and equilibrated subtypes was relatively narrow around 100 c

validity of the radiocarbon dates beyond 35 000 years b p abstract if we take in account both the different kinds of material used for 14c dating and the old and new methods of sample preparation it is possible to estimate the reliability of the oldest of all the radiocarbon dates published it becomes clear that most of them should be considered as minimal ages and in particular those which were obtained by the isotopic enrichment method consequently all the radiocarbon ages attributed to the first interstadials of the early wurm may be considered as too young

experimental study of the effect of high temperature on primary wave velocity and microstructure of limestone to study the effect of high temperature on the microstructure and velocity of primary wave p wave propagation in rocks scanning electron microscope sem experiments mercury injection experiments and p wave velocity tests were conducted on limestone samples which had been heated at high temperature from 25 to 900 c and then the variations of p wave velocity and microstructure were analyzed consequently a p wave velocity based damage model was established to evaluate the damage level of limestone the experimental results showed that 1 the internal defects of limestone started to develop at 300 c and the range of 300 600 c was the main development stage 2 the porosity increased slowly with the rising of temperature below 200 c and rapidly increased above 300 c and 3 the p wave velocity grew a little below 100 c and decreased tardily in 100 300 c and then sharply decreased in 300 600 c the p wave velocity damage model also shows that damage of the samples occurred above 300 c this study suggests that 300 c should be the damage threshold temperature of limestone and in 300 600 c significant damage of limestone would occur

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

the kashiru pollen sequence burundi palaeoclimatic implications for the last 40 000 yr b p in tropical africa abstract a continuous pollen record from a central african highland site 3 28 s 29 34 e with 15 radio carbon dates spans at least the last 40 000 yr both modern and fossil pollen have been investigated a clear pattern of changes in vegetation and climate is suggested prior to 30 000 yr b p the occurrence of the montane conifer forest including the upper forest limit indicates climatic conditions colder and drier than now but more humid than in late glacial time between 30 000 and 15 000 yr b p grassland with afroalpine indicators expanded down to 2500 2000 m altitude as a result of dry and most probably cool climate the montane forest persisted in refuges although much reduced forest vegetation with the same floristic composition as today appeared after 13 250 200 yr b p suggesting more humid conditions the occurrence of a possible short term humid episode about 21 500 yr b p is correlated with some high lake level stages in east africa and with organic deposits in deep sea cores from the mediterranean and the atlantic ocean

the plio pleistocene geologic and climatic record of the kashmir valley india a review and new data abstract the kashmir valley located in the northwestern himalayas provides an intermontane valley fill comprising unconsolidated fluvio lacustrine sediments of more than a km thickness datable at 4 myr these sediments have been investigated for the last 7 years under an interdisciplinary multi agency project using a variety of proxy climatic data techniques and other analyses to decipher climatic change as a result of this study a variety of proxy climatic data from a long continental record is available now from northernmost south asia in this paper we briefly review the lithostratigraphic and chronologic framework of the sediment profile and proxy climatic data based on flora fauna stable isotopes pedology mineral magnetics and sedimentology lastly the climatic events are put in an absolute time frame for comparison with the global climatic trends the chronology is based on 14c thermoluminescence tl palaeomagnetic and fission track techniques

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

time dependent cracking and brittle creep in crustal rocks a review abstract rock fracture under upper crustal conditions is driven not only by applied stresses but also by time dependent chemically activated subcritical cracking processes these subcritical processes are of great importance for the understanding of the mechanical behaviour of rocks over geological timescales a macroscopic manifestation of time dependency in the brittle field is the observation that rocks can deform and fail at constant applied stresses a phenomenon known as brittle creep here we review the available experimental evidence for brittle creep in crustal rocks and the various models developed to explain the observations laboratory experiments have shown that brittle creep occurs in all major rock types and that creep strain rates are extremely sensitive to the environmental conditions differential stress confining pressure temperature and pore fluid composition even small changes in any of these parameters produce order of magnitude changes in creep strain rates and times to failure three main classes of brittle creep model have been proposed to explain these observations phenomenological statistical and micromechanical statistical and micromechanical models explain qualitatively how the increasing influence of microcrack interactions and or the increasing accumulated damage produces the observed evolution of macroscopic deformation during brittle creep however no current model can predict quantitatively all of the observed features of brittle creep experimental data are limited by the timescale over which experiments are realistically feasible clearly an extension of the range of available laboratory data to lower strain rates and the development of new modelling approaches are needed to further improve our current understanding of time dependent brittle deformation in rocks

a late pleistocene holocene lacustrine record from lake manas zunggar northern xinjiang western china information on the late quaternary palaeoclimate in the zunggar desert northern xinjiang is deduced from the study of three 5 m long cores taken from lake manas analyses including the mineralogical composition of bulk sediments stable isotope contents of carbonates organic matter pollen and diatoms were performed to help reconstruct the environmental evolution of the area the chronology is provided by 9 ams 14c dates done on carbonates or organic matter the record suggests a late pleistocene humid episode radiocarbon dated at 37 000 32 000 yr b p this episode is followed by a period of extreme aridity attributed to the last glacial maximum the early mid holocene record indicates conditions generally wetter than today as previously established for western china however our results show that the holocene period is rather complex after a minor wet warm pulse estimated to be around 12 000 yr b p the most important environmental change is recorded at 10 000 yr b p it led to the establishment of a steppic vegetation cover in the catchment and of a permanent lake which lasted 4000 years fluvial sedimentation took place between about 6000 and 4500 yr b p and it coincided with a decrease in moisture availability for vegetation growth a second lacustrine episode is recorded from about 4500 to 2500 yr b p although the pollen record and a sudden influx in detrital organic matter suggest a short term dry event around 3800 3500 yr b p the last 2500 years show climate unstability and the step wise establishment of hypersaline conditions in lake manas the major post glacial environmental changes appear to be roughly in phase with those observed in tibet

late quaternary climate precipitation δ18o and indian monsoon variations over the tibetan plateau the himalaya tibet orogen contains one of the largest modern topographic and climate gradients on earth proxy data from the region provide a basis for understanding tibetan plateau paleo climate and paleo elevation reconstructions paleo climate model comparisons to proxy data compliment sparsely located data and can improve climate reconstructions this study investigates temporal changes in precipitation temperature and precipitation o18 op18 over the himalaya tibet from the last glacial maximum lgm to present we conduct a series of atmospheric general circulation model gcm echam5 wiso experiments at discrete time slices including a pre industrial pi pre 1850 ad mid holocene mh 6 ka bp and lgm 21 ka bp simulations model predictions are compared with existing proxy records model results show muted climate changes across the plateau during the mh and larger changes occurring during the lgm during the lgm surface temperatures are 2 0 4 0 c lower across the himalaya and tibet and 5 0 c lower at the northwest and northeast edge of the tibetan plateau lgm mean annual precipitation is 200 600 mm yr lower over on the tibetan plateau model and proxy data comparison shows a good agreement for the lgm but large differences for the mh large differences are also present between mh proxy studies near each other the precipitation weighted annual mean 18op lapse rate at the himalaya is about 0 4 km0 4 km larger during the mh and 0 2 km0 2 km smaller during the lgm than during the pi finally rainfall associated with the continental indian monsoon between 70 e 110 e and 10 n 30 n is about 44 less in the lgm than during pi times the lgm monsoon period is about one month shorter than in pi times taken together these results document significant spatial and temporal changes in temperature precipitation and 18op over the last 21 ka these changes are large enough to impact interpretations of proxy data and the intensity of the indian monsoon

chronology of relict lake deposits in the spiti river nw trans himalaya implications to late pleistocene holocene climate tectonic perturbations abstract the spiti river that drains through the arid trans himalayan region is studied here the relict deposits exposed along the river provide an opportunity to understand the interaction between the phases of intense monsoon and surface processes occurring in the cold and semi arid to arid trans himalayan region based on geomorphological observation the valley is broadly divided into the upper and lower spiti valley the braided channel and the relict fluvio lacustrine deposits rising from the present riverbed characterize the upper valley the deposits in the lower valley occur on the uplifted bedrock strath and where the channel characteristics are mainly of meandering nature conspicuous is the occurrence of significantly thick lacustrine units within the relict sedimentary sequences of spiti throughout the valley the broad sedimentary architecture suggests the formation of these palaeolakes due landslide driven river damming the optically stimulated luminescence osl dating of quartz derived from the bounding units of the lacustrine deposits suggests that the upper valley preserves the phase of deposition around 14 6 ka and in the lower valley around 50 30 ka the review of published palaeoclimatic palaeolake chronology of spiti valley indicates that the lakes were probably formed during the wetter conditions related to marine isotope stage iii and ii the increased precipitation during these phases induced excessive landsliding and formation of dammed lakes along the spiti river the older lacustrine phase being preserved on the uplifted bedrock strath in the lower valley indicates late pleistocene tectonic activity along the kaurick chango normal fault

palaeoclimatic significance of magnetic properties from late quaternary lacustrine sediments at pithoragarh kumaun lesser himalaya india abstract mineral magnetic studies were carried out on lacustrine deposits from pithoragarh palaeolake kumaun lesser himalaya india these deposits have already provided valuable information for the reconstruction of palaeoclimatic changes and tectonic uplift in the himalayan region according to radiocarbon chronology the lake existed from 35 to 10 kyr bp using magnetic data radiocarbon ages and lithology the top of the well studied 13 m thick wadda section can be correlated to the basal part of the 4 7 m thick riyasi section fuzzy c means cluster analysis using only magnetic parameters enables a subdivision of the riyasi section into five magnetic zones based on three clusters these clusters are related to the relative contribution of the various magnetic constituents i e coarse hem c and ultrafine hem f grained hematite both showing relatively soft magnetic behaviour for the lowermost three zones existing pollen data from the wadda section helps to establish the climatic implications of the magnetic clusters and zones the model is as follows during humid periods magnetic mineralogy is mainly controlled by hem f formed in situ whereas during colder and more arid conditions detrital input of hem c and also hem f from the catchment area predominates climatic interpretation for the upper part of the section is attempted on the basis of the magnetic data but has to be confirmed by further pollen studies

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

age and provenance of the target materials for tektites and possible impactites as inferred from sm nd and rb sr systematics sm nd and rb sr analyses of tektites and other impactites can be used to place constraints on the age and provenance of target materials which were impact melted to form these objects tektites have large negative e nd 0 values and are uniform within each tektite group while the e sr 0 are large positive values and show considerable variation within each group chemical trace element and isotopic compositions of tektites are consistent with production by melting of sediments derived from old terrestrial continental crust each tektite group is characterized by a uniform nd model age t chur nd interpreted as the time of formation of the crustal segment which weathered to form the parent sediment for the tektites 1 1 15 ae for australasian tektites 2 1 91 ae for ivory coast tektites 3 0 9 ae for moldavites 4 0 65 ae for north american tektites and 5 0 9 ae for high si irghizites sr model ages t ur sr are variable within each group reflecting rb sr fractionation and in the favorable limit of very high rb sr ratios approach the time of sedimentation of the parent material which melted to form the tektites australasian tektites are derived from 0 25 ae sediments moldavites from 0 0 ae sediments ivory coast tektites from 0 95 ae sediments possible parent sediments of other tektite groups have poorly constrained ages our data on moldavites and ivory coast tektites are consistent with derivation from the ries and bosumtwi craters respectively irghizites are isotopically distinct from australasian tektites and are probably not related sanidine spherules from a cretaceous tertiary boundary clay have initial e nd 2 e sr 5 and are not derived from old continental crust or meteoritic feldspar they may represent a mixture of basaltic oceanic crust and sediments implying an oceanic impact these isotopic results are also consistent with a volcanic origin for the spherules

source of a freshwater influx at the last glacial maximum in the indian ocean an alternative interpretation recent analysis of a sediment core in the eastern arabian sea revealed a negative pulse of about 1 in the 18o value of the planktonic foraminifera around the last glacial maximum lgm this pulse has been attributed to i increased runoff into the bay of bengal from the east flowing south indian rivers due to enhancement of the northeast winter monsoon and ii an increase in arabian sea surface temperature caused by the weakening of the southwest monsoon at the lgm we show that the speculation on which the latter hypothesis is based is not supported by observational data and cannot fully account for the observed magnitude of the spike with a view to assessing the validity of the first mechanism we have modelled the mixed layer of the bay of bengal as a well mixed box the model calculations show that to account for the pulse requires a change of about 10 in either the annual rate of river input or its isotopic composition for the northeast monsoon to account for the pulse it would mean that the rainfall should have increased by a factor of five to ten during the lgm no evidence for such an increase is indicated in the available palaeoclimatic data we explain the freshwater spike by invoking increased discharge of glacial meltwater from the tibetan plateau into the bay of bengal we show that the proxy climate data from the indo tibetan region that has become available recently provides substantial evidence for the occurrence of a warming event around the lgm which supports our mechanism

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

temperature influence on the physical and mechanical properties of a porous rock san julian s calcarenite this work has been funded by the universidad de alicante under the projects uausti11 11 vigrob 212 and gre09 40 and by the generalitat valenciana under the project gv 2011 044

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

a genetic model of thrust bounded intermontane basin using scaled sandbox analogue models an example from the karewa basin kashmir himalayas india the himalayan mountain system has many depressions of regional dimensions which are found oriented mostly e w to ne sw mainly to the north of the main boundary fault mbf the karewa basin in the kashmir himalaya has sediments belonging to late neogene to quaternary formations which represent an almost 1 300 m thick succession of sand mud and gravels exposed in the river valleys and the plateau margins of the entire kashmir valley sandbox analogue experiments show a great variety of wedge shapes showing significant changes in the taper angles due to the change in basal friction between two pop ups or depressions pop down of significant dimensions develop along the strike of the growing wedge in order to maintain the critical angle these depressions initially receive material from the hinterland and later on from the foreland end of the wedge the depressions have developed due to the change in the surface slope of the wedge and receive the eroded material only from the adjacent upheaved portions of the wedge on continuation of the experiments in cases where the wedge is highly unstable these depressions are coupled with the wedge along with their sand fills the depositional history of the karewa sediments indicates a sequential evolutionary pattern of the basin and thus represents a natural analogue of the sandbox experiments

late quaternary geomorphic evolution of the lower narmada valley western india implications for neotectonic activity along the narmada son fault geomorphic data combined with stratigraphic studies provide significant information to constrain timing and amount of fault movement the lower narmada valley lies astride the narmada son fault nsf an important ene wsw trending tectonic element responsible for the current intraplate seismicity being experienced in the central part of the indian plate varying nature and degree of tectonic movements along the nsf during late pleistocene and holocene have produced four geomorphic surfaces in the lower narmada valley the alluvial plain s1 ravine surface s2 a gravelly fan surface s3 and the valley fill terrace surface s4 two major phases of tectonic movements in a compressive stress regime are recorded along the nsf slow synsedimentary subsidence of the basin during late pleistocene due to differential movement followed by inversion of the basin during the holocene marked by differential uplift along the nsf the study suggests that the inversion of the basin is in response to the significant increase in the intensity of compressive stresses in the indian plate mainly during the early holocene the present incisive drainage and recent seismic activity indicate that the compressive stresses continue to accumulate along the nsf due to continued northward movement of the indian plate

sedimentology geochemistry and osl dating of the alluvial succession in the northern gujarat alluvial plain western india a record to evaluate the sensitivity of a semiarid fluvial system to the climatic and tectonic forcing since the late marine isotopic stage 3 abstract the alluvial successions in the northern gujarat alluvial plain western india have been investigated for reconstructing the climatic fluctuations during the last 40 ka alluvial architecture and geochemical proxies indicate prevalence of a strengthened indian summer monsoon ism with fluctuations between the late marine isotopic stage 3 mis 3 37 ka to the early mis 2 27 ka a gradual onset of aridity declining ism after 27 ka with peak aridity at 22 ka is observed a gradual strengthening of ism at around 18 and 12 ka followed by a short reversal in ism intensity between 12 and 11 ka is attributed to the younger dryas yd cooling event the aeolian sand sheet dated to 6 and 3 5 ka represents the onset of regional aridity following this a short lived humid phase was observed after 2 ka which includes the medieval warm period mwp the study suggests that the variability in the ism to the latitudinal migration of the inter tropical convergence zone was caused by insolation driven cooling and warming events in the north atlantic the incision of the valley fill alluvium occurred in two distinct phases the older incision phase occurred after 11 ka and before 6 ka whereas the younger incision phase that led to the development of present day topography is bracketed between 3 5 ka and before 1 ka the older incision phase is ascribed to the early to mid holocene enhanced ism climatically driven whereas the younger incision seems to be modulated by the activation of basement faults tectonically driven

increasing magmatic oxidation state from paleocene to miocene in the eastern gangdese belt tibet implication for collision related porphyry cu mo au mineralization in the gangdese belt of southern tibet paleocene eocene magmas record the final stage of neo tethyan subduction and are associated with few economic porphyry deposits in contrast magmas formed during later stages of the india asia collision in the oligo miocene are associated with several large porphyry cu mo au deposits especially in the eastern part of the belt 89 e 93 e in a previous study we showed that these oligocene miocene magmas were more hydrous than the earlier paleocene eocene magmas in this study we show that the later magmas were also more oxidized paleocene eocene rocks from the eastern gangdese belt are characterized by low zircon ce4 ce3 ratios mostly 50 32 3 141 9 average 74 3 30 1 n 33 and higher f o2 values fmq 0 8 2 9 average 1 8 0 8 n 6 estimated from magnetite ilmenite pairs estimates of magmatic oxidation state from amphibole compositions also show an increase from fmq 1 2 to 2 1 average 1 6 0 2 n 40 in the paleocene eocene to 2 0 to 2 8 average 2 5 0 2 n 58 in the miocene sparse whole rock fe3 fe2 ratios show the same general trend the amphibole results are systematically shifted to higher fmq compared to data from magnetite ilmenite pairs but their trend is internally consistent the higher oxidation states and water contents of miocene igneous rocks from the eastern gangdese belt may explain their unique association with large porphyry deposits in tibet because it has been shown from other studies that the potential for hydrous calc alkaline magmas to transport au is maximized near fmq 1 0 and cu at higher f o2 fmq 1 0 in comparison the somewhat less oxidized and less hydrous paleocene eocene magmas would have been less fertile for the formation of such deposits we suggest that these differences reflect the tectonomagmatic evolution of the cenozoic gangdese collisional orogen from early collision related magmatism in the paleocene eocene to late collisional magmatism in the miocene asthenospheric upwelling following slab breakoff in the miocene caused interaction between mantle derived magmas and previously subduction modified tibetan lithosphere the resultant evolved magmas had high oxidation states and water contents which are favorable properties for the subsequent formation of magmatic hydrothermal porphyry cu mo au deposits

near ir spectral evidence for the presence of iron poor orthopyroxenes on the surfaces of six m type asteroids abstract the first verifiable near infrared absorption features in the 0 9 m spectral region are reported for asteroids 16 psyche 69 hesperia 110 lydia 125 liberatrix 201 penelope and 216 kleopatra these weak features 1 3 are attributed to orthopyroxenes present on the surfaces of these asteroids 16 psyche and 125 liberatrix have full rotational coverage while 69 hesperia 110 lydia 201 penelope and 216 kleopatra have 75 rotational coverage qualitative 2 m absorption features are present but are very weak 1 absorption band positions suggest relatively low abundances of calcium and iron in the pyroxenes this indicates relatively reducing redox conditions for these asteroids their parent bodies and the nebular regions in which they formed four potential interpretations for these asteroids include 1 they are exposed metallic cores or core fragments of differentiated parent bodies with residual orthopyroxene mantle material 2 they are the result of a smelting like reaction that converts olivine to pyroxene and metallic iron in the presence of carbon at high temperatures 3 they are analogs to the primitive metal rich bencubbinite meteorites or 4 they represent metallic surfaces which have accumulated silicate debris from external sources of the two original interpretations for the m asteroids the enstatite chondrite interpretation chapman and salisbury 1973 icarus 19 507 522 gaffey and mccord 1979 mineralogical and petrological characterizations of asteroids in gehrels t ed asteroids univ of arizona press tucson pp 688 723 can be eliminated for these asteroids because the pyroxene in enstatite chondrites is iron free and does not exhibit such absorption features the iron meteorite interpretation remains valid but with modification for m asteroids 16 psyche and 216 kleopatra these spectral results combined with previous determinations of high radar albedos indicate that these bodies are most probably exposed core fragments of differentiated bodies m asteroids 69 hesperia 110 lydia 125 liberatrix and 201 penelope exhibit similar spectral features consistent with exposed core fragments but radar observations would be needed to confirm a high metal abundance observations of m asteroids 136 austria and 325 heidelberga suggest the absence of absorption features in the 0 4 to 2 5 m region within the scatter of the data verification of the presence or absence of features across the surfaces of these two asteroids requires full rotational coverage the interpretations for these featureless m asteroids are not well constrained but remain consistent with the iron meteorite and enstatite chondrite interpretations

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

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

graphite magnetite aggregates in ordinary chondritic meteorites aggregates consisting largely of submicrometre graphite and magnetite crystals have been identified in 14 unequilibrated and regolith breccia ordinary chondrites like other primitive components they formed before the meteorites accreted chondrite clasts rich in graphite magnetite occur in three regolith breccias and are a new kind of unequilibrated ordinary chondrite they were probably the source of graphite magnetite aggregates in regolith breccias

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

chemical zoning and homogenization of olivines in ordinary chondrites and implications for thermal histories of chondrules we studied the extent and degree of homogenization of chemical zoning of olivines in type 3 ordinary chondrites in order to obtain some constraints on cooling histories of chondrites based on mg fe and cao zoning olivines in type 3 chondrites are classified into four types a single chondrule usually contains olivines with the same type of zoning microporphyritic olivines show all four zoning types barred olivines usually show almost homogenized chemical zoning we have calculated cooling rates or burial depths needed to homogenize the chemical zoning by solving the diffusion equation using the zoning profiles as an initial condition mg fe zoning of olivine may be altered during initial cooling whereas cao zoning is hardly changed barred olivines may be homogenized during initial cooling because their size is relatively small to simulated microporphyritic olivine chondrules cooling from just below the liquidus at moderately high rates is preferable to cooling from above the liquidus at low rates for postaccumulation metamorphism of type 3 chondrites in order to keep mg fe zoning unaltered the maximum metamorphic temperature must be less than about 400 c if we assume cooling rates based on fe ni data calculated cooling rates for both fa and cao homogenization are consistent with those by fe ni data for type 4 chondrites a hot ejecta blanket several tens of meters thick on the surface of a parent body is sufficient to homogenize mg fe zoning if the temperature of the blanket is 600 700 c burial depths for petrologic types of ordinary chondrites in a parent body heated by 26al are broadly consistent with those previously proposed

reconstruction of last glacial to early holocene monsoon variability from relict lake sediments of the higher central himalaya uttrakhand india abstract proglacial lake sediments at goting in the higher central himalaya were analyzed to reconstruct the summer monsoon variability during the last glacial to early holocene sedimentary structures high resolution mineral magnetic and geochemical data suggest that the lacustrine environment experienced fluctuating monsoonal conditions optically stimulated luminescence osl dating indicates that the lake sedimentation occurred before 25 ka and continued after 13 ka during this period goting basin witnessed moderate to strengthened monsoon conditions around 25 ka 23 5 ka 22 5 ka 22 ka 18 ka 17 ka 16 5 ka and after14 5 13 ka the last glacial phase ended with the deposition of outwash gravel dated at 11 ka indicating glacial retreat and the onset of holocene condition additionally centennial scale fluctuations between 16 5 ka and 12 7 ka in the magnetic and geochemical data are seen a close correspondence at the millennial scale between our data and that of continental and marine records from the indian sub continent suggests that goting basin responded to periods of strengthened monsoon during the last glacial to early holocene we attribute the millennial scale monsoon variability to climatic instability in higher northern latitudes however centennial scale abrupt changes are attributed to the result of albedo changes on the himalaya and tibetan plateau

drainage conformation and transient response of river system in thrust segmentation of northwest himachal himalaya india abstract in the northwest himalayan region the ongoing out of sequence deformation caused emergence of back thrust bt around 43ka which attributed the growth of anticlines parallel to the strike of major thrusts this spatial and temporal geomorphic deformation is accompanied by coexisting river incision in the axial zone of anticlines and base level fall along with upstream migration of knickpoints in the longitudinal river course we used the stream power incision model spim which relates the normalized steepness index ksn and concavity index ref with the slope s of longitudinal river profile as a power law function of upstream area a and estimated these parameters for beas soan and sutlej rivers to decipher the spatial distribution of deformation pattern using srtm dem and based on strike parallel variations of the ksn we identified segmented nature of the nw himalayan thrusts further the dynamics of river basins and transience along the tributaries and main stem rivers has been analyzed by chi analysis which is attributed to geometric disequilibrium of the rivers the results of ksn and analysis together suggests that the crustal shortening of nw himalaya is caused by segmental reactivation of the thrusts further investigating the change in steepness along longitudinal course aids in understanding the differential uplifts patterns in actively deforming segments of major nw himalayan thrusts

panigarh cave stalagmite evidence of climate change in the indian central himalaya since ad 1256 monsoon breaks and winter southern jet depressions abstract variations in petrography stable isotopes reflectance and luminescence along the central growth axis of a 14 5 cm stalagmite from panigarh cave indicate cooler and slightly wetter conditions in the himalayan foothills of northern india during the little ice age lia which lasted from ad 1489 1889 based on deposition of calcite and ad 1450 1820 based on rapid changes in 18o values conditions were warmer and drier during the preceding medieval climate anomaly mca and also in the post lia periods as evidenced by deposition of aragonite a review of currently existing stalagmite and other proxy data from south and east asia reveals a broad spatial pattern in precipitation over south and east asia during the lia with northern areas showing generally increased precipitation and southern areas reduced precipitation during the mca and after the lia the records suggest this pattern was reversed weaker ism during the lia brought drought conditions to the core ism area but triggered more monsoon breaks that brought higher precipitation to the himalayas at the same time the weaker ism may also have pushed more depressions along the path of the southern winter jet which brought more winter precipitation to the himalayas and therefore a lia wetter in our study area

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

morphological analysis of olivine grains annealed in an iron nickel matrix experimental constraints on the origin of pallasites and on the thermal history of their parent bodies two types of pallasites can be distinguished on the basis of the grain shape of olivine rounded or angular it has been suggested that these two types of textures resulted from different degrees of annealing at high temperature in the parent body in order to characterize the kinetics of rounding of olivine grains in an fe ni matrix we carried out a series of annealing experiments using a mixture of olivine and fe ni powder we were able to reproduce at a miniature scale the range of textures in pallasites the rate of rounding was rapid enough to be observed and measured at the scale of a few micrometers to 20 m even though the experiments were performed below the solidus of the fe ni metal for instance grains 14 m in diameter became nearly spherical within 7 days at 1400 oc for the morphological analysis of olivine grains we used two independent techniques the critical diameter method and the gaussian diffusion resample method a new technique specially developed for our study both techniques indicate that the rounding time scale is proportional to the cube of the grain size and that morphological adjustments in our experiments occurred by volume diffusion in the olivine lattice not by surface diffusion along the olivine metal boundaries we used our experimental data to estimate the time scales required for the development of olivine metal textures in natural pallasites we determined that small scale rounding of olivine grains in a solid metal matrix can be produced within relatively short time intervals 100 years to produce rounded olivine grains 0 1 mm in radius at 1300 1400oc

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

petrogenesis of acapulcoites and lodranites a shock melting model abstract acapulcoites are modeled as having formed by shock melting cr like carbonaceous chondrite precursors the degree of melting of some acapulcoites was low enough to allow the preservation of 3 6 vol relict chondrules shock effects in acapulcoites include veins of metallic fe ni and troilite polycrystalline kamacite fine grained metal troilite assemblages metallic cu and irregularly shaped troilite grains within metallic fe ni while at elevated temperatures acapulcoites experienced appreciable reduction because graphite is present in some acapulcoites and lodranites it seems likely that carbon was the principal reducing agent reduction is responsible for the low contents of olivine fa 4 14 mol and low ca pyroxene fs 3 13 mol in the acapulcoites the observation that in more than two thirds of the acapulcoites the fa value is lower than the fs value in contrast to the case for equilibrated ordinary chondrites the low feo mno ratios in acapulcoite olivine 16 18 compared to 32 38 in equilibrated h chondrites the relatively high modal orthopyroxene olivine ratios e g 1 7 in monument draw compared to 0 74 in h chondrites and reverse zoning in some mafic silicate grains lodranites formed in a similar manner to acapulcoites but suffered more extensive heating loss of plagioclase and loss of an fe ni s melt acapulcoites and lodranites experienced moderate post shock annealing presumably resulting from burial beneath material of low thermal diffusivity the annealing process repaired damaged olivine crystal lattices lending acapulcoites and lodranites the appearance of unshocked i e shock stage s1 rocks any high pressure phases that may have formed during initial shock reverted to their low pressure polymorphs during annealing some samples were subsequently shocked again several acapulcoites reached shock stage s2 levels alh 84190 reached s3 and the lodranite mac 88177 reached s5

lake evolution during the past 30 000 years in china and its implications for environmental change abstract taking china as a whole lake expansion occurred 500 b c 0 a d 650 950 a d and 1250 1650 a d over the past 3000 yr the expansions were mainly due to climatic fluctuations and correspond to frequent flood reports three regional characteristics of lake development have been recognized 1 fluctuations of near coastal lakes and those in other regions as well were out of phase during 500 b c 500 a d which possibly resulted from out of phase fluctuations of climate and sea level on 10 to 100 yr time scale 2 as the lower yellow river channel migrated southward the lakes in the south of the north china plain formed and reached their largest sizes much later than those in the north 3 for the lakes in the middle and lower yangtze river valley the higher a lake basin lies above a neighboring river and the further the lake is from the river s mouth in general the younger the lake is through land reclamation the ancient chinese have changed most of the lakes greatly however human activities were also constrained in certain ways by the natural changes of the lakes reclamation usually was banned and farmland was abandoned to repair reservoirs while lakes were expanding

mineral magnetic record of environment in late pleistocene and holocene sediments lake manas xinjiang china a study of magnetic parameters was carried out on a late pleistocene and holocene sedimentary sequence 5 m from lake manas northern xinjiang china that has already been ana lysed for bulk sediment mineralogy stables isotopes from carbon ates and biogenic material magnetic minerals confirm major changes in palaeoenvironmental and palaeohydrological conditions that were deduced from other methods they also provide complementary information on changes in the lake system during the early and middle holocene the most important mineral mag netic change results from the authigenic formation of ferrimagnetic greigite fe3s 4 during the lacustrine episodes dated from 8 7 kyr b p to 5 5 kyr b p 380 335 cm and from 4 5 kyr b p to 3 5 kyr b p 320 285 cm respectively our data also indicate an abrupt break in sedimentary conditions which coincides with a short term retmxtowards dry climatic conditions around 3 5 kyr b p which was only suggested from other proxy data

seismically induced soft sediment deformation structures seismites around sumdo in the lower spiti valley tethys himalaya abstract soft sediment deformation structures were observed in 120 m thick fluvio lacustrine sediments exposed in the sumdo area in the lower spiti valley tethys himalaya himachal pradesh india these structures vary in their morphology and pattern and occur at eight stratigraphic levels s1 s8 spaced at irregular intervals the deformation structures include over steepened stratification diapiric flame like intrusions of clayey material or complex type recumbent folding of flame like nature pseudonodules large scale soft sediment folding faulting small scale associated with folding and sand dykes these structures are restricted to single stratigraphic layers separated by undeformed beds and can be correlated over a large distance the deformation of the soft sediments is attributed to the combined effects of fluidization liquefaction and shear stress and can be related to past seismic activity in the area recently on 19 january 1975 a major earthquake kinnaur earthquake of magnitude 6 8 caused extensive damage including ground rupturing in the sumdo kaurik area this earthquake has been related to the activation of the kaurik chango fault the deformed layers seismites reported here lie adjacent to this fault zone and can be related with episodic seismicity along this fault it is evident from this study that the kaurik chango fault has been re activated a number of times and that the area suffered at least nine major earthquakes with a magnitude of more than 6 during late pleistocene holocene time including the 1975 kinnaur earthquake

transmission electron microscopy of l group chondrites 2 experimentally annealed kyushu abstract kyushu shock facies d samples were annealed for approximately 90 hours at 800 c 900 c and 1000 c to provide a basis for interpreting natural effects in shock facies e with increasing temperature dislocation distributions in olivine progressively recover giving curved shapes loops and arrays cracks become healed and small voids are trapped on healed cracks and regular dislocation arrays subgrain boundaries plagioclase crystallizes from maskelynite at 900 c and 1000 c with small grain sizes comparable to those in facies e material orthopyroxene shows recovered substructures while diopside retains shock induced twinning in conjunction with other experimental data the results indicate annealing of facies e material for 10 3 s at 1000 1050 c consistent with published estimates of initial cooling rates from ar diffusion radiometric studies the fine structures are distinguishable from those due to slower cooling and analogies can be drawn with primary cooling effects in ordinary chondrites

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

chemical zoning of olivine in several pallasites chemical zoning profiles of olivines in the esquel imilac and yamato 8451 pallasites were measured by using an electron probe microanalyzer in order to study their cooling histories pallasite olivines are considered to be compositionally uniform but show faint zoning for fe mg cao al2o3 cr2o3 and mno within a few hundred micrometers from the rim the cao al2o3 and cr2o3 contents of olivines in pallasites decrease gradually toward the rim the fe mg zoning and the mno enrichment in olivine rims of pallasite olivines may reflect a redox process on the basis of diffusion calculations to estimate the cooling rate by using chemical zoning of pallasite olivine the formation process of chemical zoning was discussed similar cooling rates obtained for the fe mg cao and mno profiles of an olivine imply that these zoning patterns formed during the same event

lacustrine sedimentation in a semiarid alpine setting an example from ladakh northwestern himalaya abstract the lamayuru lacustrine strata in ladakh typify many of the carbonate rich pleistocene alpine lakes found in the semiarid environment of the northern himalaya created by a 200 m thick landslide the lake was in existence by at least 35 000 yr ago and may have persisted until 500 1000 yr ago represented in the center by thin turbidites and laminated muds the lacustrine sedimentation along the lake margins and low relief deltas characteristically displays a marked contrast between 1 clastic lenses representing rapid sporadic matrix poor debris flows and periglacial inputs from the alpine slopes and 2 abundant diverse shallow water biologically dominated carbonate strata among which organism rich chalky beds and oncolithic and encrusted stem rich strata predominate resemblances of the lamayuru lacustrine strata and their setting to those of former lakes throughout areas north of the greater himalayan crest suggest that the alpine semi arid environment would favor diversified spacially restricted carbonate sedimentation punctuated by occasional clastic influxes such a depositional regime contrasts strongly with that found immediately south of the himalayan crest where more humid conditions promote a more continuous clastic influx into intramontane lakes

multiproxy records of vegetation and monsoon variability from the lacustrine sediments of eastern ganga plain since 1350 a d abstract the lacustrine sediments of 90 cm thick profile of nikahari tal lake deoria district in the ganga plain were analyzed for multiproxy study using pollen analysis sedimentology and ams radiocarbon date to deduce short term climate and vegetational changes since about 1350 a d 600 bp the presence of arboreal and dominance of herbaceous vegetation along with aquatic elements and fresh water alga botryococcus from the basal part suggests the prior existence of lake and open grass land vegetation in the region however the scantiness of tree and shrubby taxa along with higher percentage of clay in the beginning indicates relatively warm and less humid climate than today the presence of cerealia with other culture pollen taxa indicates prevalence of agrarian practice in the region substantial increase in the tree taxa of holoptelea integrifolia madhuca indica acacia emblica officinalis syzygium cumini and myrtaceae along with the increase in shrubs marshy and aquatic elements suggest the expansion of forest grove within the grassland as a consequence of enhanced precipitation during 1420 1620 a d similar trends are observed by higher percentage of silt content owing to increased surface runoff in response to enhanced precipitation and high water budget under strong indian summer monsoon ism during above period a highly variable vegetation scenario existed during 1620 1900 a d as a consequence of fluctuating climatic conditions the variable percentages of silt and clay indicate the increase and decrease in the surface runoff so as the water column and energy in the lake in direct response to enhanced and weak ism respectively during 1620 1700 a d the arboreals became less diversified and a decline in the diversity of terrestrial herbs is also witnessed which is also corroborated by exceptionally high percentages of clay elucidating stagnant low energy ponding condition under weak ism during the little ice age lia during the time interval of 1700 1800 a d considerable improvement in the floristics has been noticed due to climate amelioration from 1800 a d onwards the increasing frequency trends of arboreal and aquatic taxa along with relatively increased silt content suggests moderately warm and humid climate the well sorted sediment explains the consistency in the water level and energy of the lake pollen analysis coupled with sediment grain parameters indicate intense ism from 1400 to 1600 a d and 1850 a d onwards and weak monsoon around 1600 1750 a d the signals of weak monsoon around 1650 1770 and 1850 a d are synchronous with the little ice age

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

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago

intermontane basin development in the past 4 myr in the north west himalaya the through the combined use of magnetic polarity stratigraphy with fission track dating of volcanic ashes a new chronology spanning 4 myr has been developed for the intermontane basin of kashmir in the northwestern himalaya

plio plistocene in sequence thrust propagation along the main central thrust zone kumaon garhwal himalaya india new thermochronological data abstract the kumaon and garhwal himalayas nw india have similar geologic tectonic topographic and precipitation pattern however low temperature thermochronological age pattern varies significantly along the strike as well as across the strike of major faults here we interpret the new set of thermochronological age data across the strike of major faults namely vaikrita thrust vt munsiari thrust mt berinag thrust bt and the baijnath nappe along pindari valley in the kumaon garhwal himalaya in the present work 18 new apatite fission track aft ages of samples collected along a north south transect have been reported ages in the hanging wall of vt which range from 2 1 0 2 to 4 2 0 7 ma have been found to be becoming younger linearly with distance from north to the vt this trend crosses the vt with significant jump in ages in the south of the vt ages are lying between 0 3 0 1 and 3 9 0 8 ma and show linear variation with distance from the vt to bt no significant jump in ages across the mt is observed and the linear trend of younging southward is continuing till the bt the break and displacement in age pattern with youngest ages close to thrusts possibly indicate progressive late thrust movement it reflects sequential uplift and cooling towards the south from the vt to bt which is consistent with an in sequence style of thrust propagation we compare our new data to the published thermochronological data from its adjacent traverses along the goriganga and dhauliganga valleys 25 km away from the present traverse towards east and west respectively in the kumaon garhwal himalaya in order to understand potential along strike variations in the kinematics our observations indicate a dynamic coupling between tectonic and surface processes in the garhwal kumaon himalaya and support that the geometry of crustal scale faults and their associated kinematics control exhumation pathways of rocks

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

depositional history and palaeoclimatic variations at the northeastern fringe of thar desert haryana plains india abstract the 400 m thick column of alluvial lacustrine and aeolian strata at the semi arid northeastern fringe of thar desert in haryana has vast potential to provide information on fluctuating climate since the middle pleistocene the sediment column has been deposited by himalayan fed rivers most of which subsequently disappeared due to climatic and tectonic reasons the distinctive lithologies with minor variations offer direct evidence to their depositional environments and indirect clues to the monsoonal climate of the region in this study broad palaeoclimatic variations since the terminal part of the last interstade have been inferred on the basis of sediment characters and luminescence dating of representative sections along the thar margin and in its ameliorated part the general field stratigraphy established for the upper part of late quaternary plains comprises a buried alluvial sequence of grey micaceous sand deposited by perennial rivers overlain by undifferentiated partially buried aeolian brown sands optically stimulated luminescence osl ages from the upper parts of alluvium indicate a gradual disorganization of the river system ca 28 20 ka the disorganization commencing at around 28 ka corresponds with the increasing aridity of the last glacial maximum lgm and shows the decreasing strength of the monsoon however the survival of river system until ca 20 ka even during the lgm aridity signifies that the monsoon had not completely disappeared in this region further weakening of monsoon is indicated by the deposition of aeolian sand over the alluvium the area witnessed a major phase of aeolian deposition ca 18 12 ka which extended up to the present day 600 mm isohyet the subsidiary phase appears to have prevailed in southern parts of haryana ca 9 7 ka younger aeolian activity has occurred since ca 3 2 ka near the thar front no record of aeolian deposition during lgm is identified in this area as in the core of the thar desert however the post lgm aeolian deposition in haryana is found to have begun earlier and continued longer than in the thar desert

cooling rates of porphyritic olivine chondrules in the semarkona ll3 00 ordinary chondrite a model for diffusional equilibration of olivine during fractional crystallization cooling rates of chondrules provide important constraints on the formation process of chondrite components at high temperatures although many dynamic crystallization experiments have been performed to obtain the cooling rate of chondrules these only provide a possible range of cooling rates rather than providing actual measured values from natural chondrules we have developed a new model to calculate chondrule cooling rates by using the fe mg chemical zoning profile of olivine considering diffusional modification of zoning profiles as crystals grow by fractional crystallization from a chondrule melt the model was successfully verified by reproducing the fe mg zoning profiles obtained in dynamic crystallization experiments on analogs for type ii chondrules in semarkona we applied the model to calculating cooling rates for olivine grains of type ii porphyritic olivine chondrules in the semarkona ll3 00 ordinary chondrite calculated cooling rates show a wide range from 0 7 c h to 2400 c h and are broadly consistent with those obtained by dynamic crystallization experiments 10 1000 c h variations in cooling rates in individual chondrules can be attributed to the fact that we modeled grains with different core fa compositions that are more fe rich either because of sectioning effects or because of delayed nucleation variations in cooling rates among chondrules suggest that each chondrule formed in different conditions for example in regions with varying gas density and assembled in the semarkona parent body after chondrule formation

late quaternary intensified monsoon phases control landscape evolution in the northwest himalaya the intensity of the asian summer monsoon circulation varies over decadal to millennial time scales and is reflected in changes in surface processes terrestrial environments and marine sedi ment records however the mechanisms of long lived 2 5 k y intensified monsoon phases the related changes in precipitation distribution and their effect on landscape evolution and sedimen tation rates are not yet well understood the arid high elevation sectors of the orogen correspond to a climatically sensitive zone that currently receives rain only during abnormal i e strength ened monsoon seasons analogous to present day rainfall anom alies enhanced precipitation during an intensified monsoon phase is expected to have penetrated far into these geomorphic threshold regions where hillslopes are close to the angle of failure we as sociate landslide triggering during intensified monsoon phases with enhanced precipitation discharge and sediment flux leading to an increase in pore water pressure lateral scouring of rivers and ov ersteepening of hillslopes eventually resulting in failure of slopes and exceptionally large mass movements here we use lacustrine deposits related to spatially and temporally clustered large land slides 0 5 km 3 in the sutlej valley region of the northwest him alaya to calculate sedimentation rates and to infer rainfall patterns during late pleistocene 29 24 ka and holocene 10 4 ka inten sified monsoon phases compared to present day sediment flux measurements a fivefold increase in sediment transport rates re corded by sediments in landslide dammed lakes characterized these episodes of high climatic variability these changes thus em phasize the pronounced imprint of millennial scale climate change on surface processes and landscape evolution

mid to late holocene climate response from the triloknath palaeolake lahaul himalaya based on multiproxy data abstract a 2 13 m thick palaeolake sequence deposited between the right lateral moraine and the valley wall of triloknath glacier has been studied at high resolution to understand the past climatic changes in lahaul himalaya the osl and ams 14c chronology suggests that the lake building activity was initiated post cooling phase since 6484 cal ybp the combination of sedimentological geochemical and environmental magnetic parameters helped to infer five first order climatic zones the influx of magnetic minerals along with a notable increase in antiferromagnetic mineralogy appearance of hematite and higher chemical index of alteration cia values during 5925 cal ybp to 5676 cal ybp suggests warm and wet conditions owing to enhanced indian summer monsoon ism precipitation corresponding to the mid holocene warming further reduction in the magnetic mineral concentration with few peaks of antiferromagnetic mineralogy and higher cia values suggests warmer episodes within an overall cold climate and the finer ferrimagnetic grain size suggests intermittent low energy and ponding conditions during 3904 cal ybp to 2365 cal ybp this was followed by fluctuating cold arid conditions in response to reduced ism precipitation during 2365 cal ybp and 1758 cal ybp further between 1758 cal ybp to the present episodic warming pedogenic enhancement and increased monsoon precipitation have been recorded a major warm episode medieval warm period as depicted from enhanced antiferromagnetic mineralogy and higher cia values has been recorded between 742 cal yrs bp and 593 cal ybp the sudden drop in the magnetic mineral concentration as well as the cia value around 300 cal ybp 1650 ce is likely because of colder conditions prevailing during the little ice age lia the study illustrates high sensitivity of the lake sediment sequence to witness the climatic episodes experienced in the glaciated regime of the triloknath glacier

controlled atmosphere thermal demagnetization and paleointensity analyses of extraterrestrial rocks we describe a system for conducting thermal demagnetization of extraterrestrial rocks in a controlled atmosphere appropriate for a wide range of oxygen fugacities within the stability domain of iron thermal demagnetization and thellier thellier paleointensity experiments on lunar basalt synthetic analogs show that the controlled atmosphere prevents oxidation of magnetic carriers when combined with multidomain paleointensity techniques this opens the possibility of highly accurate thermal demagnetization and paleointensity measurements on rocks from the moon and asteroids

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

intrinsic oxygen fugacity measurements on seven chondrites a pallasite and a tektite and the redox state of meteorite parent bodies abstract intrinsic oxygen fugacity fo2 measurements were made on five ordinary chondrites a carbonaceous chondrite an enstatite chondrite a pallasite and a tektite results are of the form of linear log f o 2 1 t plots except for the enstatite chondrite measured results agree well with calculated estimates by others the tektite produced fo2 values well below the range measured for terrestrial and lunar rocks the lowpressure atmospheric regime that is reported to follow large terrestrial explosions coupled with a very high temperature could produce glass with fo2 in the range measured the meteorite salta pallasite has low fo2 and lies close to hvittis e6 unlike the other samples results for salta do not parallel the iron wustite buffer but are close to the fayalite quartz iron buffer in slope minor reduction by graphite appears to have taken place during metamorphism of ordinary chondrites fo2 values of unequilibrated chondrites show large scatter during early heating suggesting that the constituent phases were exposed to a range of fo2 conditions the samples equilibrated with respect to fo2 in relatively short time on heating equilibration with respect to fo2 in ordinary chondrites takes place between grades 3 and 4 of metamorphism application of p t fo2 relations in the system c co co2 indicates that the ordinary chondrites were metamorphosed at pressures of 3 20 bars as it appears that they lay on the graphite surface a steep positive thermal gradient in a meteorite parent body lying at the graphite surface will produce thin reduced exterior an oxidized near surface layer and an interior that is increasingly reduced with depth a shallow thermal gradient will produce the reverse a body heated by accretion on the outside will have a reduced exterior and oxidized interior meteorites from the same parent body clearly are not required to have similar redox states