style and timing of glaciation in the lahul himalaya northern india a framework for reconstructing late quaternary palaeoclimatic change in the western himalayas

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

the old alluvium of singapore and the extinct drainage system to the south china sea in both sand quarry faces and boreholes the old alluvium of singapore is a matrix supported pebbly sand with minor beds of better sorted sands and clays the beds can be grouped into four textural classes pebbles coarse sand with fine pebbles medium to coarse sand clay and silt each with characteristic sedimentary structures the deposit appears to be the proximal facies of an ancient braided river alluvium of possible pleistocene age this widespread but scattered alluvium is found both on land and offshore on the sunda shelf in southeast asia it is believed to have been deposited during low sea levels in singapore the mineralogy of the grains forming the old alluvium suggests a mixed provenance of granitic and low grade metamorphic origin the volume and freshness of the deposited material indicate an environment of considerable relief seasonal rainfall and extremely active erosional processes conditions considerably different from the current ones the old alluvium was probably deposited by seasonal rivers which experienced periodic large floods such regional conditions could have prevailed over much of southeast asia at the time of deposition of the old alluvium

timing of late quaternary glaciations in the himalayas of northern pakistan optically stimulated luminescence dating of late quaternary glaciogenic sediments was undertaken in critical areas of the himalayas of northern pakistan in order to examine the timing of glaciation the dates demonstrate that several glaciations occurred during the last glacial cycle in swat the grabral 2 stade and the kalam i stade were dated at ca 77 ka and ca 38 ka respectively the error on the former date is large and it is conceivable that the moraines may have formed during the early part of oxygen isotope stage 3 rather than during oxygen isotope stage 4 the kalam i stade however clearly represents a glaciation during oxygen isotope stage 3 the oldest moraines and those at the lowest altitude in the indus valley at shatial have an age of ca 60 ka these also relate to a major glacial advance during oxygen isotope stage 3 a younger series of moraines the jalipur tillite and glaciofluvial sands at liachar in the indus valley and moraines at rampur tarshing have ages of ca 27 ka ca 21 23 ka and ca 15 ka respectively these dates show that glaciers also occupied parts of the indus valley during oxygen isotope stage 2 these dates and the morphostratigraphy show that glaciation in the pakistani himalaya was more extensive during the early part of the last glacial cycle and that the local last glacial maximum in pakistan was asynchronous with the maximum extent of northern hemisphere ice sheets copyright 2000 john wiley sons ltd

the changing geomorphology of the humid tropics abstract it is debatable whether tropical geomorphology is intrinsically different from the geomorphology of other places the traditional geomorphology of the humid tropics had certain expectations with regard to landforms and processes a number of case studies over the last three decades however using new concepts and field and laboratory techniques have changed such expectations this paper primarily examines the research themes of the last ten years or so identifies the major trends and attempts to predict areas where interest is expected to concentrate in near future the following topics among the current research trends are highlighted geochemical erosion movement on tropical slopes rivers in the tropics tropical landforms hydrology and sedimentation in the rainforest denudation efficiency in the humid tropics the quaternary evolution and changes and the applied side of tropical geomorphology clearly the landforms and geomorphological processes in the tropics are dependent only partially on climate but to greater extent on neotectonism lithology episodic and catastrophic events such as tropical cyclones and above all on anthropogenic alterations of the landscape a wide variety of landforms and processes are found in the humid tropics and generalisations are extremely difficult in the next century geomorphological studies in the tropics are likely to develop along certain lines environmental investigations will form a major component along with the study of postulated sea level rise current major research trends will undoubtedly continue but increasingly through a multidisciplinary and multipeople approach large scale investigations involving pantropic correlation of past events such as synchronised large floods will grow use of new research tools such as satellite imagery various dating facilities etc will become common and expected it seems likely that the arrival of so much information will modify mainstream geomorphological and sedimentological theories or will provide these with a tropical version

earthquakes produce carbon dioxide in crustal faults abstract fourier transform infrared ftir microanalysis of pseudotachylytes i e friction induced melts produced by seismic slip from the nojima fault japan reveals that earthquakes almost instantaneously expel 99 wt of the wall rock co 2 content carbon is exsolved because it is supersaturated in the friction melts by extrapolation to a crustal scale fault rupture large events such as the m7 2 kobe earthquake 1995 may yield a total production of 1 8 to 3 4 10 3 tons co 2 within a few seconds this extraordinary release of co 2 can cause a flash fluid pressure increase in the fault plane and therefore enhance earthquake slip or trigger aftershocks it may also explain the anomalous discharge of carbon monitored in nearby fault springs after large earthquakes because carbon saturation in silicate melts is pressure dependent ftir can be used as a new tool to constrain the maximum depth of pseudotachylyte formation in exhumed faults

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

the quaternary glacial history of the lahul himalaya northern india this paper presents the first glacial chronology for the lahul himalaya northern india the oldest glaciation the chandra glacial stage is represented by glacially eroded benches at altitudes greater than 4300 m above sea level this glaciation was probably of a broad valley type the second glaciation the batal glacial stage is represented by highly weathered and dissected lateral moraines which are present along the chandra valley and some of its tributaries this was an extensive valley glaciation the third major glaciation the kulti glacial stage is represented by well preserved moraines in the main tributary valleys of the chandra valley this represents a less extensive valley glaciation two minor glacial advances the sonapani i and ii are represented by small sharp crested moraines which are within a few hundred metres or few kilometres of the present day glaciers the change in style and extent of glaciation is attributed to an increase in aridity throughout the quaternary due either to global climatic change or uplift of the pir panjal mountains to the south of lahul which restricted the northward penetration of the south asian summer monsoon 1996 john wiley sons ltd

response of glacial landscapes to spatial variations in rock uplift rate 1 the response of glaciated landscapes to rapid rock uplift driven by tectonic convergence is an important often neglected aspect of proposed interactions between plate tectonic processes and climate change rivers typically respond to more rapid rock uplift in part through increasing channel gradients in contrast the glacial buzzsaw hypothesis suggests that glaciers can erode as quickly as the fastest rock uplift rates 6 10 mm yr without any increase in mean elevations however it has not been established how this is achieved we examined moving window maps swath and longitudinal profiles hillslope relief and hypsometry for glacierized and formerly glacierized basins in areas of spatially variable rock uplift rate in the southern alps new zealand and around nanga parbat pakistan to determine whether glaciers have a specific response to rapid rock uplift the response of these glaciated landscapes to rapid rock uplift 6 10 mm yr comprises 1 modest steepening of the longitudinal profiles in smaller glaciated basins 2 maintenance of shallow downvalley slopes in larger glaciated basins 30 km2 southern alps 100 km2 nanga parbat 3 development of tall headwalls and 4 steepening of the basin as a whole dominated by hillslope lengthening around nanga parbat headwalls several kilometers high constitute 50 of the basin relief at rapid rock uplift rates although glaciers can incise the valley floor swiftly they cannot prevent headwalls from reaching exceptional heights the associated increase in mean distance between cirque heads i e a decrease in drainage density causes regional mean elevation to rise with increasing rock uplift rate however this is much less than the changes in elevation expected in unglaciated ranges

seismic imaging crustal stress and gps data analyses implications for the generation of the 2008 wenchuan earthquake m7 9 china abstract seismic imaging together with global positioning system gps and crustal stress data analyses show that the mw7 9 2008 wenchuan earthquake occurred within a distinct area of high crustal stress 17 5 mpa and high poisson s ratio 7 10 anomalies centered on the longmen shan shan means mountain in chinese tectonic fault belt low p wave and s wave velocities in the southwest sw segment contrast with high velocity anomalies in the central portion cp and northeast ne segment within the uppermost 15 km depths along the tectonic fault belt though a presumably ductile zone with low velocity anomalies separates the cp and ne segment the rupture initiated near the southwestern end of the cp at a zone of high poisson s ratio which extends down into the lower crust these low velocity and high anomalies immediately below the source hypocenter together with the high crustal stress indicate the presence of high pressure fluids from the lower crust which might have reduced the mechanical strength of the fractured rock matrix and triggered the earthquake our study suggests that the structural heterogeneity and high crustal stress played an important role in the nucleation of the wenchuan earthquake and its rupture process

outgoing long wave radiation variability from ir satellite data prior to major earthquakes abstract our analysis of the continuous outgoing long wave earth radiation olr indicates anomalous variations prior to a number of medium to large earthquakes the most recent analysis of olr is from the m9 0 sumatra andaman islands mega trust event we compared the reference fields for december 2001 to 2004 and found olr anomalous values 80 w m 2 2 within the epicentral area on dec 21 2004 5 days before the event we used the noaa ir daily one degree and monthly two and half degree gridded data to differentiate between the global and seasonal variability and the transient local anomalies the cause of such anomalies is not fully understood one possible explanation is the existence of thermal outgoing radiation as a result of near ground air ionization and latent heat change due to change of air humidity and temperature this phenomenon is hypothesized to be part of a relationship between tectonic stresses electrochemical and thermodynamic processes in the atmosphere and increasing mid ir flux all part of a family of electromagnetic em phenomena related to earthquake activity the time scale of the observed variations is a few weeks before the onset of the seismic event in comparison with several years of data the observed time series preceding the earthquake had unusually high olr the olr anomaly corresponds to a large area of ground coverage and coincides with the main epicentral zone the significance of these observations is explored using data from most recent east asian earthquake swarm of december 2004 and three other earthquakes

surface deformation related to the 2008 wenchuan earthquake and mountain building of the longmen shan eastern tibetan plateau abstract the 12 may 2008 ms 8 0 wenchuan earthquake china was one of largest continental thrusting events worldwide based on interpretations of post earthquake high resolution remote sensing images and field surveys we investigated the geometry geomorphology and kinematics of co seismic surface ruptures as well as seismic and geologic hazards along the longmen shan fold and thrust belt our results indicate that the wenchuan earthquake occurred along the ne sw trending yingxiu beichuan and guanxian anxian faults in the longmen shan fold and thrust belt the main surface rupture zones along the yingxiu beichuan and guanxian anxian fault zones are approximately 235 and 72 km in length respectively these sub parallel ruptures may merge at depth the yingxiu donghekou surface rupture zone can be divided into four segments separated by discontinuities that appear as step overs or bends in map view surface deformation is characterized by oblique reverse faulting with a maximum vertical displacement of approximately 10 m in areas around beichuan county earthquake related disasters e g landslides are linearly distributed along the surface rupture zones and associated river valleys the wenchuan earthquake provides new insights into the nature of mountain building within the longmen shan eastern tibetan plateau the total crustal shortening accommodated by this great earthquake was as much as 8 5 m with a maximum vertical uplift of approximately 10 m the present results suggest that ongoing mountain building of the longmen shan is driven mainly by crustal shortening and uplift related to repeated large seismic events such as the 2008 wenchuan earthquake furthermore rapid erosion within the longmen shan fold and thrust belt occurs along deep valleys and rupture zones following the occurrence of large scale landslides triggered by earthquakes consequently we suggest that crustal shortening related to repeated great seismic events together with isostatic rebound induced by rapid erosion related unloading is a key component of the geodynamics that drive ongoing mountain building on the eastern tibetan plateau

the quaternary glacial history of nanga parbat abstract during one or more times throughout the quaternary an extensive glacier system occupied the valleys of the nanga parbat massif glacial landforms in the astor valley provide evidence for two separate glacial advances with ice advancing more than 15 km down valley from the present ice fronts elsewhere in the massif geomorphic and sedimentological evidence provide evidence for a less extensive glaciation where glaciers advanced no more than 12 km beyond their present positions intense erosion and mass movement has destroyed any depositional evidence for earlier pleistocene glaciations however truncated spurs hanging valleys steep valley sides and over deepened trunk valleys provide evidence of an earlier more extensive glaciation small moraines near the snouts of the present glaciers provide evidence for at least three limited glacial advances that post date the extensive valley glacier system on the basis of geomorphology sedimentology and relative weathering characteristics glacial landforms are correlated across the nanga parbat massif furthermore the age of the maximum extent of valley glaciation is tentatively assigned to early in the last glacial cycle with two late pleistocene readvances or periods of stagnation followed by three periods of limited glacial advance during the holocene

push moraines and glacier contact fans in marine and terrestrial environments the local climatic regime and the mass balance state are important determinants of the dynamics of terrestrial and marine glacier fronts which in turn determine the sediments and landforms produced at the glacier front many modern glaciers undergoing overall retreat in areas of maritime climate produce winter push moraines during a late winter readvance followed by a summer retreat whilst in more continental regions no significant winter readvance occurs and annual push moraines are absent the frontal dynamics which lead to these changes are analysed and the form structure sequence and field relations of both terrestrial and marine push moraines are described from iceland spitsbergen and baffin island long term changes in mass balance leading to major glacier advances or readvances also generate large push moraines in terrestrial environments push moraine formation is accompanied by uplift rejuvenation and down cutting of outwash systems whose sediments become closely associated with glaciotectonic structures which permit pre syn and post tectonic sequences to be identified the development of ice marginal fan moraine complexes is modelled as a function of the relative magnitude of two parameters the velocity of ice movement and the calving rate a high ice velocity just exceeded by the calving rate gives closely spaced push moraines and confluent ice marginal fans a high velocity far exceeded by the calving rate produces closely spaced moraines but separate ice marginal fans a low ice velocity in combination with a high calving rate results in well separated and feebly developed push moraines while a low ice velocity and a low calving rate produces feeble push moraines and coalescent fans

quaternary landscape evolution in the eastern hindu kush pakistan abstract the eastern hindu kush in northern pakistan is among the most dynamically active tectonic and geomorphic areas in the world during the quaternary valley fill sediments of great thickness have been deposited by glacial fluvial eolian and mass movement processes fluvial incision eroded these sediments and formed terraces their development was controlled by tectonic and climatic factors and therefore they record information about the quaternary landscape evolution and glaciations investigations included the mapping of landforms especially the terraces and sedimentological analyses on valley fill deposits this resulted in a classification with six main types of terraces morainic glaciofluvial fluvial lacustrine mass movement debris and fan terraces tectonic terraces were not recognized but tectonically influenced sediments have been found near the shyok suture zone this classification corresponds with results from the nearby karakoram two major late pleistocene glaciations are recognized during marine isotopic stage 3 mis 3 drosh glacial stage and in the mis 2 early holocene pret glacial stage moraines from the neoglacial shandur glacial stages i and ii and the little ice age barum glacial stage i are located near the contemporary glaciers during deglaciations huge terraces were formed the upper terrace or broz fan formation and the middle terrace or ayun fan formation between the drosh and pret glacial stages and the lower terrace or urghuch fan formation after the pret glacial stage the chronology presented in this paper shows that there was only limited glaciation in the eastern hindu kush during the global last glacial maximum lgm

timing of late quaternary glaciations south of mount everest in the khumbu himal nepal moraines south of mount everest in the khumbu himal were dated using optically stimulated luminescence clustering of ages and morphostratigraphy allowed three advances to be dated 1 the periche glacial stage ca 18 25 ka 2 the chhukung glacial stage ca 10 ka and 3 the lobuche stage ca 1 2 ka the periche stage is coincident with oxygen isotope stage 2 the chhukung stage represents a late glacial or early holocene glacial advance and the lobuche stage is a late holocene glacial advance that predates the little ice age

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

neotectonics and glacial deformation in the karakoram mountains and nanga parbat himalaya abstract the karakoram mountains and the nanga parbat himalaya are one of the most rapidly rising mountain areas in the world with uplift rates in the order of 2 mm yr large scale regional warping is the most likely form of uplift with the greatest rates around the nanga parbat haramosh massif only two active faults have been recognised in the pakistan karakoram the rakhiot and the misgar valley fault the rakhiot fault zone is a neotectonic expression of the rapid uplift centred around the nanga parbat syntaxis deformation structures in quaternary and recent sediments in the rakhiot area are not produced solely by neotectonic processes but also by processes in the glacial depostional environment and slope related processes structures present vary from neotectonic shear zones folds thrusts and high angled faults glacially produced folds thrusts shears and joints and debris slides bounded by discrete shear zones the distinction between these structures is vital in making valid neotectonic models for high active mountain belts

historical geomorphology and pedology of the gandak megafan middle gangetic plains india the gandak megafan of eastern uttar pradesh and northwestern bihar lies in the middle gangetic plains the gandak river has shifted about 80 km to the east due to tilting in the last 5000 years this has created a soil chronoassociation similar to the chronosequences found on some flights of river terraces this chronoassociation has five members qgd1 5 they are distinguished on the basis of profile development clay mineralogy and calcium carbonate content chlorite transforms to vermiculite on a large scale from qgd1 to qgd3 and decreases drastically in member qgd4 kaolinite and interstratified kaolinite smectite are abundant in the older members of the chronoassociation the youngest soils qgd1 500 b p while qgd3 soils like those on the older gandak plain and old rapti plains date back to 2500 b p qgd4 soils like those on the oldest gandak plain are dated as 5000 years b p whilst the oldest qgd5 soils as on the old ghaghra plain and ganga ghaghra interfluve date back to 10000 b p these soils which include pedogenic calcite and a saline epipedon indicate a dry climatic spell during the period 9000 11000 b p faults developed on the megafan are not related to the basement structures

a note on the extent of glaciation throughout the himalaya during the global last glacial maximum abstract quantitative chronologies for the impressive glacial successions that occur throughout the himalaya have until recently been almost totally lacking within the last decade two new techniques have promised to remedy this situation these techniques optically stimulated luminescence and cosmogenic nuclide surface exposure dating enable the age of many glacial features to be determined and have allowed us to study the extent and timing of himalayan glaciation in the late quaternary new data show that the local last glacial maximum lgm occurred during the early part of the last glacial cycle in most areas during marine isotope stage 3 mis 3 mis 3 was a time of increased insolation when the south asian summer monsoon strengthened and penetrated further north into the himalaya the concomitant increased precipitation occurring as snow at high altitudes produced positive glacier mass balances thereby allowing glaciers to advance on the other hand during the global lgm 18 24 ka himalayan glaciation was very restricted in extent generally extending

progress in the application of gas geochemistry to geothermal tectonic and magmatic studies gas geochemistry and their associated isotope systematics are developing into powerful tools to understand geological environmental processes and affirm source origins of geo fluids in addition to the traditional noble gas indicators such as he and ar other major and trace gases including co2 n2 h2 ch4 co ne kr and xe abundances and isotopes have shown considerable application in many fields of the earth and environmental sciences for example key constraints on geochemical processes including the degassing history of the solid earth to form the atmosphere and oceans the origin and migration characteristics of natural gas the scale of climate variability the p t characteristics of both subaerial and deep water geothermal reservoirs and the dynamics of the earthquake cycle are only a few areas where gas geochemistry has been successfully exploited following the frontiers in gas geochemistry special issue in this journal 2013 this volume will reflect this diversity in scope and application of gas geochemistry focusing on geothermal tectonic and magmatic studies amenable to the gas geochemistry approach

gas geochemistry and seismotectonics a review abstract publications on soil and spring gases have been examined regarding their relationships with both tectonic and seismic activities the main sources behaviours and uses of species detected in soils and springs are displayed and their mode of sampling and analysing briefly described the main patterns of degassing in soils are described and we outline the wide range of geochemical signatures as the result of both permeability and mineralogical contrasts because thermomineral waters have been in contact with great volumes of crustal rocks at various depths spring gases might be more representative of the local environment than soil gases moreover gas signature comparisons show that spring gases are much more enriched with deep gases and slightly contaminated by atmospheric gases therefore they can be considered as better samples for identifying precursors of earthquakes environmental perturbations are examined and it is shown from divergent cases that pressure temperature soil moisture or earth tides may generate very high perturbations of the degassing process such effects demonstrate that no systematic correction law can be proposed and that removing external contributions from gas concentrations must be performed case by case this demonstrates therefore the need for the simultaneous measurement of external parameters during gas monitoring a qualitative examination of about 150 claimed precursors proposed in the literature has been reviewed as noted by previous authors anomalies appear at distances sometimes much greater than typical source dimensions and occur in the field of strain higher than 10 9 most of them being in the field of strain higher than 10 8 taking into account the very high heterogeneity of such a set of data we can suggest that amplitudes of gas anomalies are independent of both magnitudes and epicentral distances of related earthquakes suggesting local conditions to control amplitudes on the contrary precursory time and duration of anomalies seem to increase both with magnitudes and epicentral distances abundant evidence demonstrates the major role of crustal fluids in the earthquake cycle many works have outlined the fact that crustal instabilities can appear as the result of low stress strain perturbations during loading it has been suggested that motion of fluids may occur at various scales from microcrack fluid transfer up to changes of hydraulic levels of water tables the study of subsequent anomalies is expected to supply a tool for earthquake prediction following previous authors we outline the need for further methodological improvements including the setting up of multiparameter station networks and the simultaneous recording of the main external parameters atmospheric pressure water and air temperature soil moisture for signal processing

bedrock benches and boulder bars floods in the burdekin gorge of australia the burdekin gorge of northeastern australia lies within the seasonal tropics and is characterized by high discharge variability slackwater sediments and paleostage indicators in the gorge record seven large floods that have occurred during the past 1 200 yrs these floods range in magnitude from 11 000 to 30 000 m 3 s 1 and are characterized by large downstream variations in hydraulics the floods generate high values of velocity boundary shear stress and stream power per unit area downstream fluctuations in these variables help to explain the location of boulder bars high flood levees small scale erosional features in the bedrock and the formation of inner channels boulder bars and flood levees form where shear stress and stream power decrease due to channel widening small scale erosional features such as potholes and troughs are best developed at sites of channel constriction and associated increases in shear stress and stream power the development of the inner channel appears to be controlled by complex interactions between bedrock lithology and structure and by flow hydraulics all of the channel features are related to the hydraulics of large floods which therefore are the dominant controls on many aspects of channel morphology in this bedrock gorge

nature and timing of quaternary glaciation in the himalayan tibetan orogen abstract much effort has been made in recent years to define the timing and extent of quaternary glaciation throughout the himalayan tibetan orogen these studies are challenging because of the logistical and political inaccessibility of the region and the inherent problems associated with the application of numerical dating techniques nevertheless the studies are providing abundant evidence for significant glacial advances throughout the last several glacial cycles and are beginning to accurately define the extent and timing of glaciation in selected regions studies are showing that himalayan tibetan glaciers in arid regions during the last glacial cycle reached their maximum extent early in the cycle and that global last glacial maximum glacier advances were significantly less extensive however along the more monsoonal influenced greater himalaya there is increasing evidence to suggest that glaciation was more extensive later in the last glacial cycle but this has yet to be fully assessed in addition the new studies are showing that throughout most himalayan tibetan regions significant glacier advances occurred during the lateglacial and early holocene with minor advances in some regions during the mid holocene the still relatively poor chronological control in the himalayan tibetan orogen however makes it difficult to construct correlations across the region and with regions elsewhere in the world this in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation across the himalayan tibetan orogen and to quantify paleoclimate change in this high altitude subtropical region the lateglacial and holocene glacial records however are particularly well preserved in several himalayan tibetan regions glacial successions such as these have the greatest potential to be examined in detail using newly developing numerical dating and geomorphic and sedimentologic methods to derive high resolution terrestrial records of glaciation that will help in paleoclimatic reconstruction for high altitude subtropical regions

holocene floodplain lake sediments in the amazon 14c dating and palaeoecological use abstract the holocene biostratigraphic record of amazon lowland rain forests is fragmentary and is based on restricted number of cores the majority representing sedimentation in a floodplain environment these biostratigraphic data have often been interpreted as demonstrating climatic oscillation between wetter and drier conditions and the subsequent vegetation changes here we survey and 14c date a further six western amazon floodplain lakes and examine their fluvially controlled sedimentation processes the lakes which are of the cutoff type are located along the rivers manu tambopata and amazon solimoes in the peruvian amazon lowlands all the lakes cored are under the influence of current overbank sedimentation of the parent suspension rich whitewater rivers and receive an annual fill of allochthonous inorganic suspension during the flood most of the cores collected were rich in minerogenic sediments gyttja clay loss on ignition we think that the observed bias towards older 14c ages documented in the gyttja clays is caused by the high proportion of old fine particulate organic matter being recirculated and resedimented within the suspension load the strong fluvial control of lake sedimentation and the unreliability of the 14c dates from the amazon suspension rich floodplains call for caution in palaeoecological interpretation furthermore owing to the low number of within lake replicate cores in the amazon holocene stratigraphy analyses we consider the postulated holocene climatic oscillation schemes to be tentative only

shifting of the kosi river northern india the kosi river shifts laterally over the himalaya foreland plain by continual minor cutoffs and bank cutting and by episodic major shifts across watersheds by moving into and then out of preexisting adjacent less actively aggrading streams migration is unidirectional because after a channel is filled to instability floodwater will drain preferentially into a new adjacent low rather than across it to the next watershed or back to the last abandoned channel major shifts seem stochastic and autocyclic they do not correlate with the many severe quakes and floods that undoubtedly helped prime the system for shifts

anastomosing river deposits sedimentation rates and basin subsidence magdalena river northwestern colombia south america situated in a tectonically active foreland basin the magdalena river consists of vertically accreting levee confined channels and adjacent extensive wetlands which are interpreted as an anastomosing river sedimentary system equivalent rates of basin filling and subsidence average 3 8 mm yr 1 based on 18 14c dates from five bore holes drilled to depths of 55 m and sediment transport budgets from 35 years of measurement located in a savanna tropical climate anastomosing river deposits of the magdalena are remarkably similar to the anastomosing deposits of the upper columbia river in a temperate cold climate in western canada suggesting that climate is not a controlling factor of anastomosis the geometry of anastomosing channel fills in the magdalena consists of stratigraphically non uniform low sinuous narrow stringers of sand up to 30 m thick by 600 m wide a width depth ratio of 20 thin 1 2 m off channel crevasse splay sand sheets extend laterally up to 10 km distance when buried both sand deposits become encased by lacustrine or marsh mud to form stratigraphic traps while there are few modern anastomosing river systems as compared to braiding and meandering there may be a disproportionately large number of ancient anastomosed fluvial rock sequences due to the rapid rate of vertical accretion such a different depositional style and geometry of sand bodies have considerable significance in the interpretation of some ancient fluvial rock sequences because it provides an alternative to the meandered and braided river deposition models

satellite observation of ch4 and co anomalies associated with the wenchuan ms 8 0 and lushan ms 7 0 earthquakes in china abstract spatial and temporal variations of total column of ch 4 and co totch 4 and totco associated with the 12 may 2008 wenchuan and 20 april 2013 lushan earthquakes in western sichuan china were investigated using satellite data from aqua airs in order to understand the lithospheric and atmospheric interactions during the seismic activity the wenchuan m s 8 0 and lushan m s 7 0 earthquakes occurred in the longmenshan fault zone it was observed that large amounts of gases emitted from the earth s crust into the atmosphere before during and after the earthquakes the anomalies of totch 4 and totco occurred along the fault zone and the peak values were found at the intersection areas where the crust stress approached the maximum furthermore temporal anomalies of totch 4 and totco occurred during and after the wenchuan earthquake but 3 months before the lushan earthquake the anomalies related to the lushan earthquake could be partially attributed to the wenchuan earthquake because of the seismotectonic changes and fractures in the crust produced by the wenchuan earthquake

a comparison of clast fabric and shape in late precambrian and modern glacigenic sediments abstract northeastern svalbard contains a well preserved glacigenic sequence of vendian late precambrian age in which terrestrial lacustrine intertidal and marine glacial facies are represented diamictite facies are of two main types massive and weakly to strongly bedded diamictite field appearance and relationships with other facies however provide insufficient information to allow a clear interpretation of the precise mode of glacial deposition by combining this information with data concerning the fabric of clasts in modern glacigenic sediments where the mode of glacial deposition is better known a wider understanding of the processes of glacial deposition in vendian time is obtained several diamictite samples were interpreted to be of lodgement tillite facies and material o water laid and glacigenic sediment flow origin was also recorded clast shape analyses indicate that most glacial debris was transported at least for a time at the glacier bed little angular supraglacial debris was present implying that the ice mass was of ice cap or ice sheet dimensions with few subaerial rock exposures clast shape in the late precambrian deposits was not useful in distinguishing between the variety of lithofacies derived from basally transported glacial material too few systematic studies of clast striation in modern glacigenic sediments are yet available for this criterion to be helpful in distinguishing between tillite facies lithofacies analysis together with clast fabric and shape studies provide useful and complementary lines of evidence concerning the ode of deposition of ancient diamictite sequences an understanding of the depositional processes and patterns of modern glacial sedimentation provides a fundamental framework for such studies

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

long continental records of climate an introduction abstract the symposium on long continental records presented new information on past climates on land it seems that throughout the last 2 5 million years the climate in the middle latitudes changed in the same complex fashion as during the better known late pleistocene and holocene times over 40 interglacial glacial shifts took place during this interval out of those 40 10 12 glacials were markedly stronger and or longer lasting than the others the apparently abrupt shifts from interglacials to glacials were probably gradual oscillatory coolings interrupted by warming episodes in that respect the detailed anatomy of the past climate changes does not differ substantially from the climate oscillations documented by instrumental weather records in the last two centuries the pronounced expansions of dry and cold steppes on land were accompanied by corresponding increases of the ice volume indicated by the oxygen isotope ratio the two exceptions occurred around 1 4 ma ago and 1 6 ma ago the reason for this discrepancy is not known by far the most expressed change of land environments occurred at about 2 4 ma ago

tropical snowline changes at the last glacial maximum a global assessment snowline reconstructions from the tropics and subtropics 33 s 33 n at the last glacial maximum lgm have been extracted from a new database which provides information on glacier equilibrium line altitudes elas for over 350 glacier valley localities during the late quaternary about 60 of the intra regional variability observed change in ela ela between the lgm and today is related to headwall altitude reflecting the influence of basin morphometry e g catchment size glacier slope on the response to climate change glacier valley aspect which influences the local patterns of radiation and precipitation also causes intra regional variability in ela although this influence varies greatly between regions overall reconstructed elas are smallest in the himalayas relatively small in the southern central andes and east africa and largest in the northern andes mexico and papua new guinea estimates of the temperature change implied by the range of ela within any one region calculated using the cru 10 modern climate database are consistent with high altitude temperature changes projected from reconstructions of temperature changes at lower altitude sites based in vegetation and geochemical data in the 21 ka tropics data set farrera et al 1999 climate dynamics 15 823 856

glacial geomorphology and recent glacial recession of the harmukh range nw himalaya abstract a comprehensive description of the glaciation and glacial geomorphology of the harmukh range northwest himalaya is reported first time in this study the geomorphic system of the range is dominated by glaciation and provides an excellent opportunity to assess the glacial fluctuations from the late quaternary to the present using a time series of the satellite data from 1992 to 2018 the glacier area snout and equilibrium line altitude ela changes of the existing glaciers in the harmukh range were estimated the glacier cover has receded from 7 47 0 58 km2 in 1992 to 6 24 0 62 km2 in 2018 a deglaciation of 16 46 0 24 the glaciers showed an upward shift in ela from 47 m to 80 m during the last two and a half decade the observations revealed that other than the climatic factors the ela change and glacier recessions are influenced by the glacier size mean altitude and the aspect of the glaciers further the high resolution google earth images supplemented by field observations were used for mapping various glacial geomorphic landforms the nature of glacial grooves overdeepenings the height of the lateral moraine deposits and trimlines indicated appreciable thickness of the former glaciers the pattern of the glaciated valleys revealed that the area has predominantly experienced alpine type of glaciation with most of the glaciers centred on the harmukh peak based on the shape and the number of lateral moraine ridges present it is suggested that the area has witnessed three major glacial advances by tracing the outer limits of the glacial valleys moraine boulders and ice scoured terrain it was estimated that the glaciers in the range covered 629 km2 during the glacial maxima the presence of numerous rock glaciers and debris free cirque glaciers on the north eastern slopes of the range indicated a strong climatic and topographical control on the pattern situation and extent of glaciers however there is a need for detailed field based mapping of the glacial geomorphology and geochronological study in order to better understand the nature and extent of paleo glaciation the observed glacier recession and the past climatic variations in this hitherto understudied glaciated region of the kashmir himalaya

gas geochemistry applied to earthquake prediction an overview terrestrial gases in groundwater and soil air have been extensively studied in recent years in seismically active areas especially in ussr china japan and united states in search of premonitory changes that might be useful for earthquake prediction concentrations of radon helium hydrogen mercury carbon dioxide and several other volatiles have been found generally to be anomalously high along active faults suggesting that the faults may be paths of least resistance for the terrestrial gases generated or stored in the earth to escape to the atmosphere temporal gas concentration changes with durations of a few hours to many months have been observed before many large earthquakes at a relatively small number of favorably situated stations at epicentral distances of up to several hundreds of kilometers these sensitive stations are generally located along active faults especially at intersections or bends of faults or some other structurally weak zones possibly because of tectonic strain concentration at such places however gas concentrations especially those measured at or near the ground surface may also be significantly affected by meteorological hydrological and other nontectonic changes in the environment the nontectonically induced variations must be carefully eliminated or recognized in the search of true earthquake related anomalies

patterns of development of lavaka madagascar s unusual gullies lavaka madagascar s abundant gullies show a complex pattern of development fourteen independent measures of size and shape in 93 lavaka were investigated by principal components analysis and discriminant function analysis typical lavaka start either as wounds and raw patches on mid hillside that develop step like head scarps or as toe slopes collapsed by seepage slumping or undercutting they become deep raw vertical sided teardrop to heart shaped gashes that may be deepest and broadest uphill as the walls retreat slump and become overgrown lavaka become longer broader gentler and partly filled concavities they can grow to reach from the valley floor to the hill crest or even beyond the crest before healing over unless excessive erosion creates tors and inselbergs they heal over and end up as unremarkable hillside reentrants and side valleys

geomorphology of the gran sabana guayana shield southeastern venezuela abstract the forms of the gran sabana have been developed mainly on rocks of the gently folded precambrian roraima group a sequence of quartzites and siliceous conglomerates with intercalated jasper chert arkose siltstone and shale locally intruded by diabase dikes and sills two planation surfaces are preserved on the gran sabana the auyan tepui 2000 2900 m elevation and the wonken 900 1200 m surfaces with a speculative mesozoic initial age they are still extending table mountains dominate the landscape they comprise pediments foothills precipitous scarps hundreds of meters high a rim and a flattish summit the table mountain topography is controlled by joint systems water percolates along joints and bedding planes dissolves the siliceous cement the quartzite disaggregates and large blocks are isolated and collapse accumulating at the foot of the scarps and on top of the table mountain summits the percolating water forms large and intricate cave systems which frequently emerge in the scarp zone as high waterfalls these mark the lowest level of erosion of the table mountains karstic structures are prominent in the summit zone the evolution of the table mountain topography has been controlled by a combination of tectonic structural stratigraphic climatic and temporal factors

comparative uranium thorium and thermoluminescence dating of weathered quaternary alluvium in the tropics of northern australia abstract thermoluminescence tl age determinations of alluvial sediments in the tropics are evaluated by comparison with u th age determinations of pedogenic accumulations in the alluvium of the lower gilbert river a large fan delta in the wet dry tropics of northern queensland australia this study extends u th dating by applying it not only to calcretes but also to fe mn oxyhydroxide oxide accumulations while a direct correlation cannot be made between u th dates from secondary minerals and tl dates from the host sediments both sets of data show broad consistency in addition to providing a minima for acceptable tl ages u th dates are useful for determining the chronology of pedogenesis diagenesis they show that calcretes and ferricretes have formed under similar climatic conditions in the wet dry tropics of northern australia during the late pleistocene beneath about 5 12 m the gilbert fan delta consists of an extensive sand body older than 85 000 yr and probably about 120 000 yr in age representative of a period of major fluvial activity not repeated since this time above are muds and fine sandy muds that extend uninterrupted to the present surface except in the downstream fan where they are bisected by a thin unit of medium sand that tl dates at 40 000 50 000 yr b p a system of sandy distributary channels over the fan surface represents an early holocene fluvial phase probably more active than at present

a submerged late pleistocene delta and other features related to sea level changes in the malacca strait abstract bathymetry sea floor echo characteristics and shallow subbottom reflectors in the malacca strait and the slope of the mergui north sumatra basin of the southern andaman sea show a varied and locally complex character which we interpret as a pleistocene lowered sea level alluvial delta fan system sediment waves and elongate banks in the narrow and shoal southern part of the strait indicate strong bottom currents and a rugged subbottom topography demonstrates erosion during low sea level of the late quaternary shallow subbottom reflectors at the northwest approaches to the strait show progradation and cut and fill valleys and the presence of a compound late pleistocene delta of the confluent sumatran and malayan rivers the younger prograding layers are probably of mid wisconsin wurm age ca 40 20 10 3 yr b p and the deeper foresets may be early illinoian glacial stage riss ca 150 10 3 yr b p farther seaward a small fan progrades from the slope a short distance into the shallow northeastern part of the mergui north sumatra basin

quaternary glacial history of nw garhwal central himalayas a first account of the quaternary glacial history is presented for northwest garhwal central himalaya on the basis of sediments and landforms one glacial stage has been recognised this is called the bhagirathi glacial stage when extensive valley glaciers advanced down the bhagirathi valley to jhala 40 5 km from the snout of gangotri glacier the ela depression during this stage was ca 640 m the bhagirathi glacial stage is constrained by optically stimulated luminescence dates of ca 63 ka and 5 ka bp and this glaciation is considered equivalent to the last glaciation elsewhere in the world the maximum extent of ice occurred ca 63 ka bp this however does not correlate with the last glacial maximum for the northern hemisphere ice sheets 20 18 ka bp a series of sharp crested moraines are present between 1 to 3 km beyond the snouts of most of the present glaciers these moraines formed during the mid holocene 5 ka bp termed here the shivling glacial advance small moraines are inset into these and are dated at about 200 to 300 bp the bhujbas glacial advance ca 300 to 200 bp and considered equivalent to the little ice age in other parts of the world ela depressions of between 40 100 m and 20 60 m occurred during the shivling and bhujbas glacial advances respectively since the bhujbas glacial advance there has been progressive retreat of glaciers initially by downwasting and retreat and then by simple retreat this retreat has accelerated during the last few decades impressive paraglacial fans are associated with deglaciation representing very rapid resedimentation during and soon after ice retreat

gas emission from the qingzhu river after the 2008 wenchuan earthquake southwest china article i nfo article history accepted 12 october 2012 available online 23 october 2012 four gas and six water samples were collected from the qingzhu river in qingchuan county one of the re gions affected by the 2008 ms8 0 giant wenchuan earthquake gases were discharged soon after the earth quake but such emissions ceased in october 2008 the predominant gases are ch4 c o2 n 2 and o2 the n2 o2 and noble gases are of atmospheric origin in contrast the ch4 and co2 have typical biogenic signatures with high c1 c2 c3 13

fluctuations of raikot glacier during the past 70 years a case study from the nanga parbat massif northern pakistan the himalaya has some of the largest glacier concentrations outside the polar regions despite this long term measurements detecting the impact of global warming and changing precipitation patterns on glaciers are rare the nanga parbat massif in northern pakistan is an exception the cartographer and glaciologist r finsterwalder investigated glacier dynamics of this mountain massif in the 1930s and several other studies document changes since then the aim of this study is to detect and analyse the changes of raikot glacier over the past seven decades we use a multitemporal and multiscale approach based on repeat terrestrial images additional historical data and remotely sensed imagery corona aster landsat quickbird the multitemporal approach covers the period 1934 2007 while the analyses show a total glacier retreat of 200 m in 73 years this general trend was interrupted by a significant glacier advance between the 1950s and 1980s although down wasting processes can be inferred from an increase in debris covered area a general trend of reduced glacier thickness does not appear significant over the whole observation period

glacial advances in tibet during the younger dryas evidence from cosmogenic 10be 26al and 21ne was the abrupt climate cold reversal called the younger dryas yd a global climate excursion this study presents the first evidence for yd glacial advances on the tibetan plateau derived from 10be 26al and 21ne exposure ages of two erratics with a weighted mean age of about 11 600 years bp from a moraine at the eastern margin of the tibetan plateau this implies that the yd climate signal commonly thought to be initiated by decreased north atlantic deep water formation and transferred by ocean circulation was even recorded at the inner continental high altitude site of tibet implying atmospheric transport and thus a global character for this abrupt climatic change

three holocene and late pleistocene glacial stages inferred from moraines in the lingshi and thanza village areas bhutan abstract moraines formed by valley glaciers in lingshi area northwestern bhutan constitute three distinct stages with contrasts in the spatial distribution and size of moraines and surface features such as clasts soils and vegetation moraines in the thanza village area northern bhutan show three stages with similar characteristics to those in the lingshi area using morphostratigraphic criteria these three stages correlate with some glacial stages in the khumbu himal eastern nepal dates from moraines in the khumbu himal provide a tentative chronological sequence of these three stages valley glaciers in bhutan expanded during the following periods 1 the takaphu and raphsthreng stages are the little ice age and late holocene glacial advances 2 the jykhuje and tenchey stages represent the late glacial and or early holocene glacial advances and 3 the lingshi dzong and lunana stages are coincident with the last glacial period

co2 degassing over seismic areas the role of mechanochemical production at the study case of central apennines field observations coupled with experimental results show that co2 can be produced by mechanical energy applied to carbonate rocks becoming an unexpected additional gas source besides that degassed from the mantle or produced by thermometamorphism the evidence that a large amount of carbon dioxide associated with radiogenic type helium r ra as low as 0 01 0 08 is released through continental areas denotes the absence of a contribution from the mantle or from mantle derived fluids data collected during the seismic crisis which struck the central apennines in 1997 98 have shown an enhanced co2 flux not associated with the presence of mantle or thermometamorphic derived fluids on the other hand new experimental results highlight the possibility of producing co2 by mechanical energy that acts on the calcite crystalline lattice while the co2 released over the geothermal areas e g larderello geothermal field is obviously derived by mantlederived activities this is not the case of the huge amount of co2 released over the seismically active areas where the presence mantle derived products is ruled out we propose that mechanical energy e g released during seismic events microseismicity or creeping processes is a possible additional energy source able to produce co2 and thus could explain the presence of co2 degassing over tectonic areas where the influence of the mantle is low