etude petro structurale des chevauchements ductiles himalayens sur la transversale de l everest makalu nepal oriental tectonic and microtectonic data in eastern nepal indicate that the major observed thrusting 100 km on the main central thrust mct postdates the barrovian metamorphism of the high himalaya gneisses this result at variance with the famous reverse metamorphism model better explains the abnormal metamorphic superpositions in the himalayas and accounts for the lack of high pressure assemblages under the thick allochtonous high himalaya tibetan slab pressure and temperature estimates by microprobe analysis on plagioclase biotite garnet kyanite sillimanite and cordierite assemblages are presented for samples collected along the mct shear zone and across the gneiss slab in the everest makalu area since there is very little difference in pressure at the front of the slab kathmandu klippe and its root these estimates support the existence of important late metamorphic thrusting the decrease of pressure towards the top of the gneiss pile combined with a small temperature increase explains the k

soil development rates in the transantarctic mountains soil chronosequences were identified at three sites 78 85 s within the transantarctic mountains for determining rates of soil development in cold desert ecosystems more than 175 soils were sampled in xerous and ultraxerous environments on moraines containing sandstone and dolerite and ranging from late holocene ca 6 ka to pre late quaternary ca 250 ka in age based on five linear and nonlinear models highly significant correlations p 0 01 exist between drift age and the following surface boulder weathering features and soil properties percentage of boulders containing desert varnish spalling and pitting depths of staining visible salts ghosts pseudomorphs and coherence in soils electroconductivity in the zone of salt enrichment and total profile salts in the absence of leaching soluble salts readily accumulate in cold desert soils a morphogenetic sequence of soluble salts is presented that relates field observations with laboratory data soil color is highly correlated p 0 01 with dithionite extractable fe within a site the proportion of clasts 15 mm on the surface of the desert pavement increases with time due likely to deflation of fines by strong winds therefore the dominant processes in these cold desert soils are salinization rubification reddening due to oxidation of iron bearing minerals and desert pavement formation

evolution of soil pores and their characteristics in a siliceous and calcareous proglacial area soil chronosequences in alpine areas have often been applied to trace physical mineralogical and chemical soil properties over time how the soil pore system of undisturbed soils evolves however has not yet been clarified we therefore investigated two soil chronosequences in the swiss alps spanning a time period from a few decades up to the early holocene late pleistocene one soil sequence developed on siliceous parent material in the sustenpass proglacial area of the stein glacier with soils aged from 30a to 10 ka while the second developed on calcaric parent material in the klausenpass with soils aged from 110a to 14 ka proglacial area of the griess glacier we hypothesised that the overall pore size of the topsoil and consequently the relative proportion of macropores decrease with increasing soil age the pore size characteristics were determined by using x ray computed tomography independent of the parent material calcareous vs siliceous macroporosity decreased with time the greatest changes seemed to occur between the little ice age lia and about 3 4 kyr of soil evolution vegetation composition and the functional richness of the plant community exert an influence on soils that developed on siliceous parent material by giving rise to more small pores besides pore sizes pore characteristics also changed with time in general the tortuous structure of the soils became more complex with time the evolution of the pore characteristics such as tortuosity number and length of pore networks seem also to be related to biologic factors such as root properties plant species and soil organic matter composition it remains however unanswered how these time dependent biologic factors interact with and influence in detail the pore network this aspect certainly merits investigation in greater detail in the future

overturned marble layers evidence for upward extrusion of the backbone range of taiwan abstract the backbone range is part of the taiwan mountain belt which was formed due to the oblique collision between the luzon arc and the eurasian passive continental margin from plio pleistocene to the present stable isotope compositional profiles of thin marble layers from this mountain range show that marble layers from rock sections with an inverted metamorphic zonation were all overturned after the peak metamorphism and that marble layers from rock sections with a normal metamorphic zonation were not overturned exhumation folding seems to be the responsible process an upward extrusion exhumation model is therefore postulated as the probable mechanism for the mountain building process this model can well explain the fanning orientation of rock cleavage s dipping in a regional scale as well as the metamorphic characteristics across the mountain range the model also shows that the recorded stretching lineation is secondary in nature meaning the exact direction of rock movement during the initial exhumation stage in response to the oblique collision cannot be deduced

morphological characteristics of the basque continental shelf bay of biscay northern spain their implications for integrated coastal zone management this contribution integrates and analyzes data from high resolution multibeam seismic profiles bathymetric lidar and surficial sediment data for the geomorphological seascapes characterisation and process description of the basque inner and middle continental shelf northern spain from the data obtained the basque shelf is characterised by a heterogeneous seafloor where on a small spatial scale different morphologies and sedimentary processes can be observed tectonic activity and sea level changes together with present processes of sediment supply and climatic conditions have a critical influence on the present configuration of the continental shelf and the distribution of seafloor types on the basis of all of the datasets seafloor classification bedform analysis long term sea level change induced seafloor features and anthropogenic features over the seafloor are described as a result three distinct zones have been identified for the basque shelf related to the main geomorphological features and seascapes as summarised below i a western part with a northwestern orientation which coincides with the prevailing wave direction this zone is characterised by a predominantly rocky substrate except within the mouth of the nervion estuary where sandy sediments appear to infill a paleo channel ii a central part which is oriented towards the northeast and receives less wave energy within this zone a sedimentary seabed is predominant sorted bedforms are well developed and can be detected in water depths in excess of 90 m iii an eastern zone which is characterised by sedimentary seafloor and shore terraces here a flat rocky seafloor is covered by a thin layer of sediments throughout the study area the bathymetry and sedimentary features of the shoreface and inner shelf are controlled mainly by climatic conditions coastal dynamics and the underlying geological framework the integration of these data sets together with their interpretation is a valuable source of information for integrated coastal zone management iczm and constitutes a useful tool for implementing various european directives

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

contrasting p t paths in the eastern himalaya nepal inverted isograds in a paired metamorphic mountain belt petrology and phase equilibria of rocks from two profiles in eastern d f matrix assemblages are overprinted by decompression reaction textures and in zones f and g progress into the sillimanite field nepal from the lesser himalayan sequences across the main central thrust zone and into the greater himalayan sequences the two terranes were brought into juxtaposition during formation of sillimanite biotite gedrite foliation seams s3 formed at reveal a paired metamorphic mountain belt pmmb composed of two thrust bound metamorphic terranes of contrasting metamorphic conditions of 674 33 c and 5 7 1 1 kbar the contrasting average geothermal gradients and p t paths of these two metastyle at the higher structural level the greater himalayan sequences experienced high t moderate p metamorphism with an anmorphic terranes suggest they make up a pmmb the upperplate position of the greater himalayan sequences produced an ticlockwise p t path low p inclusion assemblages of quartz hercynitic spinel sillimanite have been overgrown by peak anticlockwise p t path with the high average geothermal gradient being possibly due to high radiogenic element content in this terrane metamorphic garnet cordierite sillimanite assemblages that equilibrated at 837 59 c and 6 7 1 0 kbar matrix in contrast the lower plate lesser himalayan sequences were deeply buried metamorphosed in a clockwise p t path and display minerals are overprinted by numerous metamorphic reaction textures that document isobaric cooling and re equilibrated samples preserve inverted isograds as a result of progressive ductile overthrusting of the hot greater himalayan sequences during prograde metamorphism evidence of cooling to 600 45 c at 5 7 1 1 kbar below the main central thrust the lesser himalayan sequences are a continuous though inverted barrovian sequence of high p moderate t metamorphic rocks metamorphic zones upwards from the

soil carbon accretion along an age chronosequence formed by the retreat of the skaftafellsjokull glacier se iceland abstract climate warming has led to glacial retreat worldwide where surfaces exposed to the atmosphere are subjected to weathering vegetation colonization and new soil formation on young soils developing along the recessional path left by the skaftafellsjokull glacier se iceland we investigated the accretion of soil organic carbon soc and nitrogen n representing an age chronosequence of 120 years in total 54 sampling sites were distributed along three moraines deposited in 1890 1945 and 2003 for comparison soil samples were collected from nearby birch woodlands betula pubescens ehrh representing soils in a mature ecosystem likely to establish on the moraines in the future results show that the average soc and n concentrations increase with time and at faster rates over the latter part of the chronosequence period investigated 1945 1890 after 120 yrs the soil contains 1 1 kg c m 2 in the surface layer 0 10 cm which is still about one third of the 3 2 kg c m 2 in soil under the birch woodlands the n stock estimated at 0 06 kg n m 2 after 120 yrs is almost one fourth of that under the woodlands the data suggest that landscape affects vegetation establishment and in turn both landscape and vegetation affect soil development thus concentrations of soc n and noncrystalline oxalate extractable al and fe are higher within depressions in the proglacial landscape the comparison of soc stock in the moraine soils with that under the birch forest shows that the young proglacial soils still have a large potential to accrete soc within the developing pedosphere with the observed accrual rate of 9 1 g c m 2 yr 1 in the top at 10 cm it may take the moraine soils an additional period of 220 yrs to accrue soc stocks comparable with those under the birch forest given the fact that all icelandic glaciers are receding assessing soc accretion in new soil formation may be important to off setting the greenhouse gas emissions

video transects reveal that tidal sand waves affect the spatial distribution of benthic organisms and sand ripples the sandy seabed of shallow coastal shelf seas displays morphological patterns of various dimensions the seabed also harbors a rich ecosystem increasing pressure from human induced disturbances necessitates further study on drivers of benthic community distributions over morphological patterns moreover a greater understanding of the sand ripple distribution over tidal sand waves may improve morphological model predictions here we analyzed the biotic abundance and ripple morphology in sand wave troughs and crests using video transects we found that both the epibenthos and endobenthos are significantly more abundant in sand wave troughs where ripples are less abundant and more irregularly shaped finally we show that camera systems are relatively quick and effective tools to study biotic spatial patterns in relation to seabed morphology

rates of weathering and chemical depletion in soils across a chronosequence of lake michigan sand dunes abstract accumulation of soil organic matter and depletion of base cations and trace metals were measured in surface soils i e o horizon and upper 15 cm of mineral soil across a 4150 year soil chronosequence of dune capped beach ridges bordering northern lake michigan within 400 years of beach ridge formation coniferous forest develops soil c and n accumulate to steady state levels of 40 and 1 3 mg ha 1 respectively and the ph of the upper mineral soil decreases from 8 5 to 4 3 as carbonate minerals dissolve after substantial proportions of ca and mg have been removed an incipient spodic horizon can be observed the upper surface of which progressively deepens with increasing soil age analysis of soil strain of the upper mineral soil showed gradual dilation reaching 121 after several centuries of soil development after accounting for soil dilation quantities of ca mg p zn mn fe and v in the upper 15 cm of mineral soil decreased exponentially to low asymptotic levels representing quantities contained in weathering resistant minerals mass balance modeling indicated weathering and elemental losses in the order of decreasing decay constant as ca mg mn zn p v fe al k na ti this sequence is consistent with weathering of carbonates then ferromagnesian minerals then feldspars p levels are tightly coupled with ca losses in soils older than 200 years suggesting that ca rather than fe or al stabilizes p high concentrations of heavy metals in the organic horizon relative to the upper mineral soil indicate atmospheric inputs of industrial pollutants

palaeomagnetic estimates of crustal shortening in the himalayan thrusts and zangbo suture this article reports new palaeomagnetic results from precisely dated late palaeocene limestones from the former northern margin of the indian subcontinent now in tibet between the major himalayan thrusts and the india tibet suture zone convergence in the suture and intracontinental thrusting can be estimated separately and are respectively found to be of the order of 550 km 650 km and 400 km 400 km comparison with kinematic models derived from magnetic anomalies constrains the age of the collision at about 50 myr

observations of sand waves megaripples and hummocks in the dutch coastal area and their relation to currents and combined flow conditions 1 this paper aims to investigate the distribution and stability of large scale bed forms in response to storm and fair weather conditions in a shallow marine environment multibeam and side scan sonar data off the dutch coast median grain size 0 25 0 35 mm were collected to monitor sand waves 100 800 m and superimposed megaripples 1 40 m through multiple storm and fair weather events box cores were used to observe the vertical bed structure and grain size in the dutch coastal area two dimensional 2 d megaripples x 1 15 m are the dominant bed forms in current dominated 0 4 m s tidal flow regimes with oscillatory flows 0 4 m s undulating bed topography of mound like 3 d bed forms 20 40 m is observed immediately after storms these bed forms are covered by smaller 3 d megaripples which are related to sets of low angle converging laminae in box cores interpreted as hummocky cross stratification hcs the sand waves form compound bed forms of sets of 2 d and 3 d megaripples the morphology of the sand waves is a function of the general wind wave climate of the marine environmental setting with flat topped 3 d sand waves occurring in shallow wave dominated settings and 2 d sand waves occurring in the tide dominated environment farther offshore copyright 2005 by the american geophysical union

chemical mineralogical and morphological characterization of three podzols developed on glacial deposits in northern europe the chemistry mineralogy and micromorphology of three soil profiles formed on genetically different quaternary deposits have been studied in relation to the podzolization process the soil materials showed quite uniform geochemical composition both within and between the study sites independent of great geographical distance and there is accumulation of sesquioxides in the bs horizons at all three sites mineralogical distributions derived from calculated normative compositions x ray diffraction analysis and thin section point counting show similar depth related trends the clay fractions at all three sites are dominated by a vermiculitic phase which contains variable degrees of polymeric hydroxy al in the interlayer space in most b horizons

early stage development of selected soil properties along the proglacial moraines of skaftafellsjokull glacier se iceland abstract soil development was studied along a chronosequence in 2010 in a proglacial environment in se iceland we investigated morphological physical chemical and mineralogical changes in the soil representing over 120 year period in total 54 sampling sites were distributed along three moraines deposited in 1890 1945 and 2003 for comparison samples were collected from a nearby downy birch betula pubescens ehrh forest representing soils in a mature ecosystem likely to establish on the moraines in the future after 120 years since deglaciation and formation of ac horizon sequence bulk density decreased from 1 36 g cm 3 to 1 07 g cm 3 concentrations of soil organic carbon soc and total nitrogen n increased with time from being zero up to 1 77 of soc and 0 10 of n soil ph h2o declined rapidly and was the only soil property that attained a steady state compared to that under the birch forest the concentration of oxalate extractable al and fe increased over time although at a slower rate of change compared to that for other soil properties freshly exposed moraines contained a considerable amount of the extractable elements indicating a relative abundance of poorly crystalline al and fe phases in the subglacial moraines the data support the conclusion that after 120 years of soil formation proglacial soils are still young and may yet need one or two centuries to develop properties typical of well drained volcanic soils

deformation of leucogranites of the crystalline main central sheet in southern tibet china abstract towards the top of the main central sheet in southern tibet china leucogranites intrude metamorphic rocks related to rocks of the main central thrust in the himalayas our study shows that the leucogranites suffered a northward shear deformation the significance of this event is discussed in terms of gravity driven decollement of the 10 000 m thick tethyan sedimentary pile over its crystalline basement

how far did india drift during the late cretaceous placenticeras kaffrarium etheridge 1904 ammonoidea used as a measuring tape abstract india once a member of the lost supercontinent gondwana broke away from it and made a solitary northward excursion and finally collided with asia during its long voyage india remained isolated for 100 ma and is expected to be characterized by stunning endemic biodiversity but this is not recognized by the terrestrial faunal and floral content and their distribution patterns paint no simple scenario for example the inter trappean vertebrate faunas of india which lived during india in exile do not show any made in india assemblages but rather betray a mixed biota having both gondwanan and laurasian affinities these differential distribution patterns of fauna and flora and their affinities with those of other areas prompted many workers to envisage an array of suggestions regarding the time of india s final separation from gondwana the time of northward drifting and different palaeopositions during its long journey but closer examination of the nature of the vertebrate fossil records reveals that the so called elusive endemicity of indian fauna during its sojourn is in fact a product of taxonomic artefact the majority of the faunas have been described on the basis of poor fossil data and comparisons for biogeographic correlations are made at higher taxonomic levels which perhaps masked india s faunal distinctiveness yet the biological processes that constrain biogeographical distribution operate at the species level in this paper we present our own data to reconstruct the palaeoposition of india in the late cretaceous and to estimate the time of its northward migration the present study is based on a newly recorded ammonite species placenticeras kaffrarium etheridge from the coniacian horizons in bagh central india the species abounds in bagh and represents a complete population structure it resembles significantly the populations described from the coeval horizons of madagascar and zululand south africa p kaffrarium has a stunning display of intraspecific variability represented by at least seven distinct morphotypes reported from zululand and madagascar the indian population significantly matches the latter two populations variant by variant and remarkably also for the sexual dimorphs within each variant geographic range is a biological property of a species and ammonite species have differential distribution patterns depending on the length of larval longevity oceanic circulation patterns and favourable environments placenticeras was a nektobenthic genus living in the shallowest depths of epicontinental seas and could not cross a narrow strait wider than a few hundred kilometers palaeogeographic distribution patterns of all placenticeratid species during the late cretaceous support this view and show the wandering nature of the genus over time however they always exhibit a latitudinally limited distribution and are restricted mainly to the subtropics north and south of the equator thus it appears that the p kaffrarium population of zululand madagascar and bagh constitute a homogenous single breeding population implying geographical proximity of these areas connected by exclusively shallow seas till the coniacian other fossil records of ammonites and geophysical data also support this view shortly after this india started its northward drift by the late maastrichtian india was completely isolated by a wide oceanic gap from the rest of the gondwana fragments and the northern part of india crossed the equator this is evident from strong endemicity of ammonite species assemblages of the northwest and southern indian subcontinent which constitute the most diverse communities known

the distribution of macrozoobenthos in the southern north sea in relation to meso scale bedforms this study investigates the distribution of macrozoobenthos in relation to meso scale bedforms in the southern north sea three sites on the dutch continental shelf were sampled that are representative of large areas of the north sea and show diverse morphological settings these sites are i part of a shoreface connected ridge ii the lower part of a concave shoreface and iii a sandwave area within these sites two or three different morphological units were distinguished sampling was undertaken in two seasons for two consecutive years the species composition was analysed for differences in benthic assemblage within sites based on the meso scale morphology and between sites and seasons in addition the benthic assemblage was correlated to water depth median grain size d50 and sorting d60 d10 results show that significant differences in the benthic assemblage can be found related to meso scale bedforms but macro scale morphological setting and seasonal effects are more important 2006 elsevier ltd all rights reserved

petrogenetic and tectonic significance of young leucogranites from the northwestern himalaya pakistan in the himalaya of northwestern pakistan small discordant bodies of leucogranite intrude metamorphosed basement of the indian crust as the first step in assessing the tectonic significance of these granites we have used the shrimp ion microprobe to obtain u pb dates on zircon zircons of igneous appearance are scarce in the leucogranites and with one exception are associated with xenocrystic components which occur as discrete grains and as cores rimmed by young zircon zircons of igneous appearance are high in u 5000 to 40 000 ppm low in th u 0 01 to 0 05 and frequently colored a distinct blue xenocrystic components give a range of proterozoic ages consistent with ages previously reported for indian crust in sharp contrast zircons of igneous appearance yield clusters of concordant tertiary ages two leucogranite dikes from southern localities yield rather old emplacement ages of about 35 ma swat and about 50 ma naran together with previously determined 40ar 39ar and fission track cooling ages these ages document immediate and rapid metamorphism and denudation following eocene collision three leucogranite dikes from northern localities within the nanga parbat haramosh massif are very young having emplacement ages of about 2 3 ma 5 ma and 7 ma the formation and emplacement of these leucogranites during the rapid late tertiary denudation of the nanga parbat region suggests to us that decompression melting may be a viable mechanism for leucogranite genesis

magnetostratigraphy of syntectonic growth strata and implications for the late cenozoic deformation in the baicheng depression southern tian shan abstract the collision between india and eurasia in the cenozoic has caused a series of intracontinental deformation in the foreland basins of tian shan but there are debates about the timing of tectonic deformation and the relationship between tectonic uplift and sediment accumulation in the foreland basins based on the magnetostratigraphy of growth strata in the baicheng depression southern tian shan we suggest that an episode of crustal shortening in the late cenozoic evidenced by syntectonic growth strata in the kelasu yiqikelike structural belt kysb initiated at 5 3 ma since then the sedimentation rate accelerated abruptly and coarse molasse deposits accumulated combined with the results of growth strata on both flanks of tian shan and the fact that the xiyu formation on the southern limb of the kasangtuokai anticline was involved into the growth strata we conclude that the period from 7 5 ma to the early pleistocene was one of the important episodes of intracontinental deformation in the foreland basins of tian shan as a response to the cenozoic collision between india and eurasia

initial soil development and carbon accumulation on moraines of the rapidly retreating werenskiold glacier sw spitsbergen svalbard archipelago article i nfo the rapid retreat of the werenskiold glacier the svalbard archipelago high arctic is leading to an extensive broadening of the proglacial zone covered with recent moraine till on older glacigenic deposits or directly on bedrock schists to study the type and intensity of initial soil development under a harsh periglacial climate a chronosequence of six soils was established between the glacier front and its terminal moraine on 1 to about 80 year old moraines although the surface layer over the entire area of study is frost active the patterned features are not well developed the succession of vegetation mainly saxifraga sp and lichens starts 5 6 years after deglaciation successively covering up to 30 of the soil surface then stagnating present day soil forming processes within the uppermost soil layer comprise initial weathering of primary minerals chlorites and amphiboles carbonate dissolution and base cation leaching associated with ph lowering accumulation of organic matter and nitrogen and an increase in pedogenically derived fe soil development measures are time related and in general fit a logarithmic model the intensity of transformation including organic carbon and nitrogen accumulation started at high rates comparable to those reported in low arctic and alpine environments however in the fourth fifth decade after deglaciation it reached a quasi steady state low annual precipitation is probably a crucial factor that controls plant succession and leaching of carbonates thus limiting mineral weathering organic matter accumulation and soil development on the werenskiold moraines

formation rates of smectites derived from two holocene chronosequences in the swiss alps the formation rate of smectitic components in alpine soils is derived from two chronosequences in the swiss alps covering a time span of 11 500 years the soils developed on granitic parent material the lithologies between the two chronosequences investigation areas however showed some distinct differences with respect to the main mineralogy and to a lower extent to the chemistry the chronofunctions of smectitic phase formation g kgclay year were fitted to data using an exponential formation model extensive mineral weathering resulted in significant losses of chlorite and mica and the corresponding formation of smectite and regularly and irregularly interstratified mica smectite this formation is especially pronounced in the early stages of soil formation our investigations reveal that the greatest changes in soil clay mineralogy of alpine soils on granitic or gneiss host material occur within the first 1000 3000 years of soil development at both investigation sites the annual formation rates are in a similar order of magnitude with 0 1 g kg year or even higher at the start of soil formation and with values 0 01 g kg year after about 7000 years the pedogenetic smectites from the e or bs horizons included several populations with various interlayer charges this heterogeneity seems to be related to the nature of their precursors

soil formation rates on silicate parent material in alpine environments different approaches different results abstract high mountain soils develop in particularly sensitive environments consequently deciphering and predicting what drives the rates of soil formation in such environments are a major challenge in terms of soil production or formation from chemical weathering the predominating perception for high mountain soils and cold environments is often that the chemical weathering portion of soil development is temperature inhibited often to the point of non occurrence several concepts exist to determine long term rates of soil formation and development we present three different approaches 1 quantification of soil formation from minimally eroded soils of known age using chronosequences known surface age and soil thickness sast 2 determination of soil residence times srt and production rates through chemical weathering using un stable isotopes e g 230 th 234 u activity ratios and 3 a steady state approach using cosmogenic isotopes e g 10 be for each method data from different climate zones and particularly from high mountains alpine environment are compared the sast and steady state approach give quite similar results for alpine environments european alps and the wind river range rocky mountains usa using the srt approach soil formation rates in mountain areas but having a temperate climate do not differ greatly from the sast and steady state approaches independent of the chosen approach the results seem moderately comparable soil formation rates in high mountain areas alpine climate range from very low to extremely high values and show a clear decreasing tendency with time very young soils have up to 3 4 orders of magnitude higher rates of development than old soils 10 5 to 10 6 yr this apparently is a result of kinetic limits on weathering in regions having young surfaces and supply limits to weathering on old surfaces due to the requirement for chemical weathering to occur soil production rates cannot be infinitely high consequently a speed limit must exist in the literature this limit has been set at about 320 to 450 t km 2 a our results from the sast approach show however that in alpine areas soil formation easily reaches rates of up to 800 2000 t km 2 a these data are consistent with previous studies in mountain regions demonstrating that particularly young soils intensively weather even under continuous seasonal snowpack and thus that the concept of temperature controlled soil development soil forming intervals in alpine regions must be reconsidered

seismic and aseismic weakening effects in transtension field and microstructural observations on the mechanics and architecture of a large fault zone in se tibet

formation of patterned ground and fine scale soil development within two late holocene glacial chronosequences jotunheimen norway abstract chronosequences of 250 to 130 years were established on two late holocene glacier forelands in the jotunheimen region of southern norway patterned features occurring within chronologically established time units were studied young patterned features forming 10 20 years after deglaciation are frost active vegetation cover is minimal within the young patterned features consisting of bryophytes organic crusts soil development within patterned ground is also minimal absent because frost action retards horizonization with time and distance from the glaciated ice margin frost activity declines within the patterned features suggesting that a thin active periglacial zone exists near the ice margin initially frost activity decreases at the borders of the features with the centers stabilizing later in time this results in fine scale soil heterogeneity and variations of soil development fine scale pedogenic development is first encountered at the borders of patterned ground that has developed on terrain exposed since the 1930s yet soil development is predominantly absent at the centers of patterned ground with time and distance from the ice margin frost activity declines and allows patterned features to homogenize from border to center positions in regard to soil characteristics across the chronosequences soils within patterned features pedogenically follow previous soil chronosequence studies evolving from usda classifications of entisols into inceptisols frost disturbance within patterned ground however produces a lag effect that results in longer periods of time for pedogenesis to occur and thinner soils than that of the surrounding terrain

palaeomagnetic data about southern tibet xizang i the cretaceous formations of the lhasa block summary a palaeomagnetic study of middle to late cretaceous redbeds from linzhou basin lhasa block north of the yarlung zangbo suture zone gives a stable palaeomagnetic direction of magnetization with a positive fold test six sites 57 samples d 333 i 38 k 78 95 8 pole 64 n 348 e we discuss the problem of a possible remagnetization but consider that this direction of magnetization gives a good approximation for the palaeolatitude of the lhasa block during middle to late cretaceous time results from more recent tibetan formations are also presented late cretaceous to palaeocene sediments and volcanics give a lower palaeolatitude of 10 n and but more recent andesites have emplaced about 30 n close to the present day latitude an interpretation is proposed whereby the lhasa block which was a part of asia in the early cretaceous has undergone first a southward motion accompanied by an anticlockwise rotation and then after the palaeocene a northward motion under the constraint of the colliding india

fast but spatially scattered smectite formation in the proglacial area morteratsch an evaluation using gis proglacial areas in the alps usually cover a time span of deglaciation of about 150 years time since the end of the little ice age in the 1850s in these proglacial areas soils have started to develop due to the continuous retreat of the morteratsch glacier swiss alps the corresponding proglacial area offers a continuous time sequence from 0 to 150 year old surfaces furthermore an optimal digital dataset about the development of vegetation and soils is available for this area the soils have been developing on glacial till having a granitoidic character we investigated the clay mineral assemblage at 35 sites within the glacier forefield smectite can be used as a proxy for weathering intensity in these environments in the proglacial area the smectite concentration in the topsoil steadily increased with time of weathering however this development displayed a strongly scattered trend the complex interplay of biological physical and chemical processes in pedogenesis and clay mineral evolution limits our ability to predict and interpret landscape dynamics we consequently tried to analyse the role of topographic and vegetation modifications on the smectite content sites not or only slightly prone to erosion flattening slope ridge steepening slope ridge or flat morphology promoted the formation of smectite in addition the texture of the soil material influenced soil moisture and hence the degree of weathering and the development of vegetation although vegetation is not a fully independent factor because it is interrelated to the surrounding environmental conditions it seemed to exert its influence on weathering and consequently the formation of smectite green alder stands and grass heath where moister soils develop that have a finer texture or where more organic acids are produced were correlated with a higher smectite content humus forms serve as a proxy for the soil biota and soil organic matter composition at sites having a eumoder and a higher soil organic matter content the smectite concentration was elevated at these sites the production of chelating compounds or organic acids in the soil is believed to promote the development of smectites via an intermediate stage of hydroxy interlayered minerals and the subsequent removal of the hydroxide polymers in this work we have demonstrated that the topographic signature and the effect of vegetation on the formation of smectite and consequent weathering are pervasive our results will serve as a basis for further spatio temporal modelling

vegetation influence on soil formation rate in a proglacial chronosequence lys glacier nw italian alps abstract climate change has huge impacts on alpine ecosystems one of the most visible effects in the alps is glacier retreat since the end of the little ice age lia which caused the exposure of previously glaciated surfaces these surfaces are open air laboratories verifying theories regarding ecosystem and soil development in order to increase our knowledge on the effects of time and vegetation primary succession on soil development in proglacial areas we sampled soils and surveyed plant communities on stable points in the proglacial area of the lys glacier in the italian north western alps valle d aosta region the sampling points were located on dated sites based on literature and or historical photographs glacial till is attacked by weathering processes immediately after deposition and stabilization with a consequent loss of soluble compounds decrease of ph and primary mineral weathering the speed of these processes was largely increased after the establishment of a continuous vegetation cover thanks to the organic matter accumulation caused by litter input and root decomposition below the soil surface on sialic glacial tills below timberline and under a quasi climax larch rhododendron forest fast and steady decrease in ph values increase in organic matter content and horizon differentiation were observed in particular genetic eluvial horizons formed in approximately 60 years while diagnostic albic horizons were developed after ca 90 years pointing to an early start of the podzolization processes cheluviations of fe and secondarily al were analytically verified however illuviations of fe al and organic matter in incipient b horizons were not sufficient to obtain diagnostic spodic horizons on lia materials under grazed grassland below timberline and alpine prairie above timberline acidification and weathering were slightly slower and no redistribution with the depths of fe and al oxi hydroxides was observed a cambic bw horizon developed on the oldest lia moraines therefore it seemed that this fast onset of the podzolization process in comparison to other proglacial chronosequences in the alps was mainly driven by vegetation properties rather than by specific climatic conditions

metamorphic reactions related to decompression and synkinematic intrusion of leucogranite high himalayan crystallines bhutan the high himalayan crystallines hhc of bhutan were penetratively deformed intruded by leucogranite and metamorphosed during the collision of the indian and asian plates metamorphic reaction textures in the hhc show that it experienced decompression while maintaining a laterally heterogeneous and locally inverted internal temperature range of c 600 750c this thermal structure was produced by thrusting hot migmatitic rocks over lower grade rocks within the hhc and by the advection of heat from the intrusion of leucogranite dykes and sills during decompression a variable velocity field within the hhc during exhumation and extrusion between india and tibet caused the inversion of top to the south sense of shear present throughout most of the hhc to top down to the north shear near its top

the four plutonic belts of the transhimalaya himalaya a chemical mineralogical isotopic and chronological synthesis along a tibet nepal section

north south extension within the convergent himalayan region recent work by burg et al 1984 indicates the presence of east west striking gently north dipping normal faults in the higher himalayas and southern tibet that formed during postcollisional convergence of india and tibet these faults extend for at least 800 km along strike we interpret these normal faults as probable late miocene extensional features with perhaps several tens of kilometres of down to the north displacement a simple elastic model suggests that these normal faults may have formed during gravitational collapse of the miocene topographic front between india and tibet in this interpretation gravitational collapse occurred by southward motion relative to india and tibet of a wedge of crustal rocks bounded above by gently north dipping normal faults and below by thrust faults that probably dip north north south extension produced in this way is probably confined to upper crustal levels only and does not reflect regional extension of the entire lithosphere

manaslu leucogranite a collision signature of the himalaya a model for its genesis and emplacement the manaslu pluton is one of 10 leucogranites that formed in the overthrusted higher himalaya after the indo eurasian collision field and analytical data indicate that the underlying migmatites of the tibetan slab may be where the leucogranitic melts were generated the himalayan crustal thrusting of a hot slab over a rather cold volcano sedimentary pile le fort 1975a provides the necessary release of fluids these fluids cross the main central thrust mct induce the partial anatexis of the overheated tibetan slab and produce a leucogranitic magma the emplacement of the magma at first is located along the main disharmonic plane above the mct between the infrastructure and the superstructure there it generates a convective hydrothermal system extending very far laterally according to the stratification of permeabilities progressive emplacement of the granite proceeds as the convected fluids including the fluids released by the saturated magma dissolve the mainly calcareous host rocks of tibetan sedimentaries a frozen image of this caving out progression is given by the extensive network of granitic dikes outside the pluton the two quite independant fluid cycles of the generation and of the emplacement were triggered or guided by the tectonics due to collision this two fold model dominated by fluid activity may be of importance for other leucogranites and granites

ductile extrusion of the higher himalayan crystalline in bhutan evidence from quartz microfabrics quartz textures measured from deformed quartz tectonites within the lesser himalaya and higher himalaya crystalline of bhutan show similar patterns orientation and distribution of the quartz crystallographic axes were used to confirm the regional shear sense the asymmetry of c axis and a axis patterns consistently indicates top to the south shearing the obliquity of the texture and the inferred finite strain plane strain to moderately constrictional suggest the strain regime had a combination of rotational and irrotational strain path in most of the samples from the bhutan himalaya the inferred deformation mechanisms suggest moderate to high temperature conditions of deformation that produced the observed crystallographic preferred orientation much higher temperature of deformation is indicated in the quartz veins from a leucogranite the observed ductile deformation is pervasively developed in the rocks throughout the investigated area the intensity of deformation increases only slightly in the vicinity of the main central thrust simultaneous southward shearing within a large part of the higher himalaya crystalline near and above the main central thrust and normal faulting across the south tibetan detachment is explained by the tectonically induced extrusion of a ductily deforming wedge the process of extrusive flow suggested here can be approximated quantitatively by channel flow models that have been used to describe subduction zone processes channel flow accounts for some observed phenomena in the himalayan orogen such as inverted metamorphic sequences near the main central thrust not related to an inversion of isotherms and the syntectonic emplacement of leucogranites into the extruding wedge locally leading to an inversion of isotherms due to heat advection

mid proterozoic pb pb ages for some himalayan base metal deposits and comparison to deposits in rajasthan nw india abstract lead isotope ratios from three base metal deposits rangpo gorubathan in the eastern lesser himalaya and bageswar in the lesser himalaya of kumaun have been studied the first two deposits generally stratiform and stratabound occur within pelitic psammopelitic wacke type metasediments which are locally carbonaceous the bageswar deposit is hosted by silicified dolomitic carbonate rocks the pb isotope ratios appear to be homogenous in two and heterogenous in one of the deposits model pb pb ages obtained for the rangpo and gorubathan deposits are 1800 ma and for the bageswar deposit 1550 1700 ma dispersion in isotopic ratios reflect the geochemical heterogeneity particularly with respect to larger variation in the composition of pb isotope ratios in the bageswar deposit may be explained by the participation of pb from heterogenous sources pb isotope characteristics of the himalayan deposits are compared with those of a number of base metal deposits in the delhi aravalli belt in rajasthan nw india ore lead from the deposits of both the himalaya and of rajasthan are enriched in 206pb and 207pb however lead in all cases plots on the evolution lines corresponding to sources with higher u pb ratios but the sources of lead in the himalayan deposits had a lower th u ratio the geologic observations as well as the pb isotope compositions are consistent with a sedimentary diagenetic origin of the himalayan base metal deposits

cooling history of the nw himalaya pakistan fission track and 40ar 39ar cooling ages indicate that the late tertiary cooling history of the himalayan ranges of northern pakistan is largely a function of uplift and erosion interpretation of cooling ages which range from under 0 5 ma to over 80 ma suggests that during the late tertiary long term uplift rates at least doubled from under 0 2 mm yr to in some cases well over 0 5 mm yr uplift rates show strong and systematic regional variations as well which reflect the greater uplift of eastern and northern regions the association of very rapid uplift and erosion with the nanga parbat haramosh massif can be explained by a locally vigorous collision of india with eurasia near a promontory of indian crust the resultant rapid uplift of the nanga parbat haramosh massif reactivated the main mantle thrust melange zone with a reversed sense of motion discontinuities in the coolingage distribution along the main mantle thrust in the southern swat hazara region may be the result of the thermal effects of overthrusting

understanding coastal morphodynamic patterns from depth averaged sediment concentration this review highlights the important role of the depth averaged sediment concentration dasc to understand the formation of a number of coastal morphodynamic features that have an alongshore rhythmic pattern beach cusps surf zone transverse and crescentic bars and shoreface connected sand ridges we present a formulation and methodology based on the knowledge of the dasc which equals the sediment load divided by the water depth that has been successfully used to understand the characteristics of these features these sand bodies relevant for coastal engineering and other disciplines are located in different parts of the coastal zone and are characterized by different spatial and temporal scales but the same technique can be used to understand them since the sand bodies occur in the presence of depth averaged currents the sediment transport approximately equals a sediment load times the current moreover it is assumed that waves essentially mobilize the sediment and the current increases this mobilization and advects the sediment in such conditions knowing the spatial distribution of the dasc and the depth averaged currents induced by the forcing waves wind and pressure gradients over the patterns allows inferring the convergence divergence of sediment transport deposition erosion occurs where the current flows from areas of high to low low to high values of dasc the formulation and methodology are especially useful to understand the positive feedback mechanisms between flow and morphology leading to the formation of those morphological features but the physical mechanisms for their migration their finite amplitude behavior and their decay can also be explored

changes of soil phosphorus speciation along a 120 year soil chronosequence in the hailuogou glacier retreat area gongga mountain sw china abstract the hailuogou glacier gongga mountain sw china has been retreating in response to global warming a soil chronosequence hailuogou chronosequence has developed in the retreat area and a primary plant succession has developed on it to investigate the changes of soil phosphorus p fractions along the young soil chronosequence in the cold and humid climate soil samples were collected at seven sites of different ages 0 to 120 years in all soil samples concentrations of total p and of different p fractions bioavailable p al fe bound p p bound by al and fe oxides or hydroxides ca bound p and residual p were determined using a sequential extraction technique organic p was determined using the high temperature ignition method for the youngest 0 years 12 years soils p forms were dominated by residual p and topsoil forms of ca bound p al fe bound p organic p microbial biomass p and bioavailable p were less than 1 86 from 30 to 120 years for the topsoil concentrations of ca bound p and organic p gradually increased the concentration of bioavailable p in surface soil also showed a trend of increase with percentages of 5 11 5 to total soil p the concentration of residual p decreased the concentration of fe al bound p contributed less than 5 to total soil p at all sites ca bound p and organic p were the dominant p fractions at the older sites ages 80 and 120 years soil p bioavailability and solubility were influenced by the changes of ph and concentrations of fe and al oxide and hydroxide the variations of vegetation and microbial activity are also considered as the impact factors of soil p forms in the later stage of soil development 80 120 years plenty of soil p was transformed into biomass p pool 299 3 kg ha 1

isotopic characteristics of precipitation groundwater and stream water in an alpine region in southwest china the hydrological cycle has been enhanced under the warmer climatic conditions on the southeastern edge of the tibetan plateau china to investigate the complex hydrological system in the study area 18o and 2h were measured on waters in a mountainous region huangbengliu watershed the stream water tends to be isotopically more depleted in 18o and 2h than precipitation and groundwater but more enriched than meltwater a clear seasonality with higher isotopic values of stream water in summer and lower values in winter is evident coinciding with the timing of the peak discharge the correlation between 18o and 2h in stream water shows that the isotopic signature of precipitation is well preserved in stream flow and the evaporation during the stream flow is only minor the isotopic composition of stream water shows a decreasing trend from upstream to downstream which results from tributary water inputs with heavy isotope depleted water according to an isotopic mass balance model the fraction of meltwater inputs over the total stream flow ranged from 25 5 to 61 8 the study demonstrates that the ice snow melting and tributary inputs are the prevailing mechanisms regulating stream isotope hydrology in alpine regions on the edge of the tibetan plateau

thrust tectonics and the deep structure of the pakistan himalaya the systematic restoration of thrust systems provides a powerful constraint on the deep structure of orogenic belts a balanced cross section through the imbricated upper crust of the indian plate in the footwall to the main mantle thrust of the western himalaya restores to a minimum width of 730 km the implicit shortening being in excess of 470 km this requires the himalaya and southern tibetan region to be underlain by a wedge of indian crust however a full appraisal of gross crustal structure awaits deep seismic control

a revised identification of the oldest sea floor spreading anomalies between australia and antarctica we propose that magnetic anomalies south of australia and along the conjugate margin of antarctica that were originally identified as anomalies 19 to 22 may be anomalies 20 to 34 the original anomaly identification has two troublesome aspects 1 it does not account for an extra anomaly between anomalies 20 and 21 and 2 it provides no explanation for the rough topography comprising the diamantina zone with our revised identification there is no extra anomaly and the diamantina zone is attributed to a period of very slow spreading 4 5mm yr half rate between 90 and 43 m y the ages bounding the interval of slow spreading 90 and 43 m y correspond to times of global plate reorganizations our revised identification opens up the possibility that part of the magnetic quiet zone south of australia formed during the cretaceous long normal polarity interval breakup of australia and antarctica probably occurred sometime between 110 and 90 m y b p the breakup unconformity identified by falvey in the otway basin may correspond to a eustastic sea level change

the tectonic history of kohistan and its implications for himalayan structure the tectonic history of kohistan northern pakistan involves two collisional events cleavage and folding developed at 90 100 ma along the northern suture between the kohistan island arc and the asian plate at the same time there was major folding and shearing of the lower part of the kohistan arc approximately 100 km south of the suture this deformation was followed by ocean subduction south of the kohistan arc generating the kohistan calc alkaline batholith with subsequent ocean closure during the eocene and obduction of the kohistan arc together with the adjacent part of the asian plate over the indian continental crust the construction of balanced cross sections through the imbricated upper part of the indian continental crust in the footwall to this southern suture indicates a minimum displacement of 470 km requiring the western himalayan hinterland to be underlain by a large wedge of indian middle to lower crust there is some shortening of the overriding kohistan and asian plates by thrusts and shear zones but it is insufficient to satisfy the palaeomagnetic data there must be major crustal shortening involving thrusts in the hindu kush and pamirs north of kohistan the post eocene thrust direction which for most of pakistan is towards 160 is almost perpendicular to that immediately to the east in the himalayan belt generating complex refolded thrust patterns in the hazara syntaxis and large scale folding and rapid uplift with associated brittle faulting and seismic activity adjacent to the nanga parbat syntaxis these different thrust trends indicate that major thrust movement as well as the folds and deformation fabrics cannot always be related to plate movement vectors but are modified by or develop from complex rotations during place collision or from the gravitational spreading of a thickened crust a regional approach is required to recognize and correctly attribute the various components in thrust displacements

variation in soil chemical properties along toposequences in an arid region of the levant abstract detailed characterization of soils and their variation along different topography positions has not been investigated in depth for mediterranean arid regions there is a need to accurately understand the variation and the spatial distribution of soil properties within dry region of the levant such understanding is required to optimize the use and management of scarce land and water resources the objective of this study was to examine the effect of hillslope characteristics on the variation of selected soil chemical properties in an arid mediterranean climate at each of five selected transects four sites were chosen to represent four different topographic positions summit shoulder backslope and toeslope a soil profile was examined at each site and a representative sample from each horizon was withdrawn for chemical analyses the analyses indicated that generally the carbonate contents of the surface horizons decreased from higher to lower positions of the toposequence the carbonate content increased with depth for profiles occupying the lower positions this suggests more intense leaching within soil at lower positions the effect of steepness and curvature on controlling the variation of soil properties was obvious at the summit and shoulder positions leaching process seems to hinder the effect of steepness and curvature for soils at lower positions lower positions receive runoff water and organic matter from upper positions which complicate the relationship between landform shape and organic matter content continuous tillage resulted in lower organic matter contents for soils at lower positions higher ph values were reported for soils down along the transect due to the movement of soil material from upper hillslope positions electrical conductivity exchangeable calcium and potassium contents decreased downslope due to higher moisture accumulation however no obvious relationship was found between the variation of ph or ec in one hand and the variation of steepness and curvature on the other potassium content was variable due to its greater mobility the analyses indicated that variation in the soil cec is governed by two factors the leaching pattern which is controlled by hillslope position and the accumulation of eolian carbonates at the soil surface the distribution of iron oxides and types of clay minerals indicated more weathering in a descending direction and with soil depth which is attributed to higher availability of soil moisture along the same direction these relationships suggested systematic variation of chemical properties along toposequences in this arid environment

paleomagnetic constraints on the late cretaceous and cenozoic tectonics of southeastern asia abstract many features of the cenozoic tectonic history of central and southeastern asia can be understood as direct consequences of the thrust and penetration of india into asia recent indentation experiments with plasticine tapponnier et al 7 have extended this idea and have led to the prediction of a pattern of large rotations and displacements of continental blocks that can be tested by paleomagnetism the available cretaceous and cenozoic paleomagnetic data from this part of the world have been reviewed and a new apwp for eurasia has been constructed for reference the negligible rotation of south china and large clockwise rotation of indochina are consistent with the model i e with an history of large scale left lateral strike slip motion along the altyn tagh and red river faults data from malaya and borneo can be reconciled with the model although in a less straightforward fashion the large counter clockwise rotation of south tibet implies that it rotated in sympathy with india during the collision and suggests that future indentation experiments should include this feature finally a middle cretaceous reconstruction of the south margin of asia is proposed one interesting result is the restored continuity of geological features in tibet and indochina with active subduction of oceanic indian plate crust taking place to the south at subtropical latitudes

india asia convergence driven by the subduction of the greater indian continent the most spectacular example of plate convergence on earth was the motion of the indian plate towards eurasia and the subsequent collision density estimates of the greater indian continent after its upper crust is scraped off at the himalayan front suggest that this continental plate is readily subductable potentially explaining why the convergence did not halt on collision the most spectacular example of a plate convergence event on earth is the motion of the indian plate towards eurasia at speeds in excess of 18 cm yr 1 ref 1 and the subsequent collision continental buoyancy usually stalls subduction shortly after collision as is seen in most sections of the alpine himalayan chain however in the indian section of this chain plate velocities were merely reduced by a factor of about three when the indian continental margin impinged on the eurasian trench about 50 million years ago plate convergence accompanied by eurasian indentation persisted throughout the cenozoic era1 2 3 suggesting that the driving forces of convergence did not vanish on continental collision here we estimate the density of the greater indian continent after its upper crust is scraped off at the himalayan front and find that the continental plate is readily subductable using numerical models we show that subduction of such a dense continent reduces convergence by a factor similar to that observed in addition an imbalance between ridge push and slab pull can develop and cause trench advance and indentation we conclude that the subduction of the dense indian continental slab provides a significant driving force for the current india asia convergence and explains the documented evolution of plate velocities following continental collision

geological interpretation of dekorp 2 s a deep seismic reflection profile across the saxothuringian and possible implications for the late variscan structural evolution of central europe abstract a 250 km long deep seismic section the first of its kind in west germany s dekorp project is interpreted in terms of late variscan collisional tectonics the structural model used is based on the intracontinental thrust tectonics concept of modern collision orogens the crustal profile across the saxothuringian zone seems to indicate north facing ramps antiformal stacks and culminations within the crystalline basement of the internal mid european variscides that have been only partially overprinted by permo mesozoic crustal stretching

hotspot tracks and the early rifting of the atlantic abstract many hotspot tracks appear to become the locus of later rifting as though the heat of the hotspot weakens the lithosphere and tens of millions of years later the continents are split along these weakened lines examples are the west coast of greenland east coast of labrador madeira hotspot the south coast of mexico north coast of honduras guyana hotspot and the south coast of west africa north coast of brazil st helena hotspot a modern day analog of a possible future rift is the snake river plain where the north american continent is being pre weakened by the yellowstone hotspot track this conclusion is based on reconstructions of the motions of the continents over hotspots for the past 200 million years the relative motions of the plates are determined from magnetic anomaly isochrons in the oceans and the motion of one plate is chosen ad hoc to best fit the motions of the plates over the hotspots however once the motion of this one plate is chosen the motions of all the other plates are prescribed by the relative motion constraints in addition to the correlation between the predicted tracks and sites of later continental breakup exposed continental shields correlate with the tracks their exposure may be the result of hotspot induced uplift which has led to erosion of their former platform sediment cover

magmatism and metamorphism in the ladakh himalayas the indus tsangpo suture zone abstract ladakh india provides a complete geological section through the northwestern part of the himalayas from kashmir to tibet within this section the magmatic metamorphic and geotectonic evolution of the northern himalayan orogeny has been studied using petrographic geochemical and isotope analytical techniques the beginning of the himalayan cycle was marked by large basaltic extrusions panjal trap of permian to lower triassic age at the northern margin of the gondwana continent indian shield these continental type tholeiitic basalts were followed by a more alkaline volcanism within the triassic to jurassic lamayuru unit of the gondwana continental margin lower jurassic to cretaceous oceanic crust and sediments ophiolitic melange s s accompany the triassic to cretaceous flysch deposits within the indus tsangpo suture zone the major structural divide between the indian shield high himalaya and the tibetan platform so far no relic of paleozoic oceanic crust has been found subduction of the tethyan oceanic crust during upper jurassic and cretaceous time produced an island arc represented by tholeiitic and calc alkaline volcanic rock series dras volcanics and related intrusives accompanied by volcaniclastic flysch deposits towards the tibetan continental margin subsequent to the subduction of oceanic crust large volumes of calc alkaline plutons trans himalayan or kangdese plutons intruded the tibetan continental margin over a distance of 2000 km and partly the dras island arc in the ladakh region the collision of the indian shield and tibetan platform started during the middle to upper eocene and caused large scale still active intracrustal thrusting as well as the piling up of the himalayan nappes the tectonically highest of these nappes is built up of oceanic crust and huge slices of peridotitic oceanic mantle spongtang klippe in the high himalayas the tectonic activity was accompanied and outlasted by a barrovian type metamorphism that affected triassic sediments of the kashmir nun kun synclinorium up to kyanite staurolite grade and the deeper seated units up to sillimanite grade cooling ages of micas are around 20 m y muscovite and 13 m y biotite towards the indus tsangpo suture zone metamorphism decreases with no obvious discontinuity through greenschist prehnite pumpellyite to zeolite grade remnants of possibly an eo himalayan blueschist metamorphism have been found within thrust zones accompanying ophiolitic melange in the suture zone

shortening budgets and the role of continental subduction during the india asia collision abstract the india asia collision provides a remarkable example of diffused deformation because the zone of compressive strain extends far into the hinterland of the himalaya molnar and tapponnier s science 189 1975 419 concept of india as a rigid indenter responsible for the diffused deformation has been widely accepted perhaps uncritically this review gives a reappraisal of landmark papers by dewey et al philos trans r soc london a 327 1988 379 eclogae geol helv 82 1989 717 which discussed the shortening budget in se asia and the evidence for the amount and the rate of the convergence between india and asia taking place after the initial collision of these continents at roughly 55 50 ma evidence for the total convergence comes from magnetic anomaly palaeomagnetic and volumetric balancing studies the results are consistent in showing about 1800 2100 km convergence between india and asia in the western sector 2475 km in the central and 2750 2800 km in the eastern sector the rate of convergence between india and asia over the period since initial collision is roughly 5 cm year however the possible long term rate of convergence within the himalaya is considerably less i e 1 5 2 0 cm year a fraction of the total convergence this shortfall can be made up by adding to the rate for the himalaya alone the convergence rates in other parts of the diffused zone of compressive strain i e tibet tien shan altai this works well for the post oligocene but not for the earlier post collisional history when the areal extent of thrust fold tectonics was much more limited possibly the apparent shortening deficit before the miocene was made up by strike slip faulting but with the notable exception of the red river fault evidence for widespread pre miocene strike slip faults is not convincing summation of the amount of shortening in thrust fold regimes in the himalaya and its hinterland falls short of that required by the total convergence figures quoted above the deficit arises firstly because of the likelihood that pre collisional crustal shortening of uncertain areal extent in tibet reduces tibet s contribution 40 according to dewey et al philos trans r soc london a 327 1988 379 eclogae geol helv 82 1989 717 to the shortening budget for the cenezoic revised shortening budgets are presented on the assumption that most of the lhasa block southern tibet was already thickened prior to collision this thickening is difficult to quantify secondly balanced cross sections from various parts of the himalaya give 60 70 shortening that is only about 500 km roughly half of the shortening proposed by dewey et al the conclusion of le pichon et al tectonics 11 1992 1085 that only indian mid upper crust is involved in the himalayan thrust sheets is supported but it needs to be reassessed in the light of the recognition of eocene oligocene thickening in the himalaya this early crustal thickening antedates the sequence of thrusts which started with the main central thrust and therefore the shortening estimates based on balanced cross sections probably underestimate the total shortening in the himalaya the prospect of substantial underthrusting of india beneath tibet minimizes the amount of horizontal shortening of tibetan lithosphere during the cenozoic the conclusion is that either the total convergence deduced from geophysical and volumetric work is too large or the deficit must be made up by shortening mechanisms other than thrust fold regimes i e strike slip faulting which serves to move rocks out of the way of india

contemporary glacigenic inputs to the dust cycle the importance of glacigenic dust in the earth s system during glacial periods is widely acknowledged under contemporary conditions the world s largest dust sources are in low lying hot arid regions and this is where most aeolian research is focused however the processes of dust production and emissions are still operating in cold climate regions particularly in proglacial areas this paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle it focuses on how elements in the glacial and aeolian geomorphic sub systems interact to determine the magnitude frequency and timing of aeolian dust emissions and on feedback mechanisms between the systems where they have been measured dust emission intensity and deposition rates in glacierised catchments are very high in some cases far exceeding those in lower latitudes however few studies span long time scales the impact of future glacier retreat on the balance between sediment supply availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered this balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths which promote dust emissions and patterns and rates of soil development and vegetation succession on recently deglaciated terrain which protect sediments from deflation retreat of the antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non glacigenic sources in the southern hemisphere copyright 2012 john wiley sons ltd

unroofing history of a suture zone in the himalaya of pakistan by means of fission track annealing ages abstract the uplift history of the swat valley and hazara region of northwestern pakistan has been established using 22 fission track dates on apatite zircon and sphene a major fault the main mantle thrust mmt strikes east west across the swat valley separates regions of markedly differing fission track age regimesm and may be a suture zone separating an extinct island arc terrane on the north from the indian plate to the south fission track ages ranging from about 55 to 58 m y for sphene 18 to 53 m y for zircon and 9 to 17 m y for apatite were obtained from the region north of the mmt to the south the fission track age ranges are 20 to 25 m y for sphene 17 to 26 m y for zircon and 16 to 23 m y for apatite disparate zircon and sphene ages on each side of the mmt imply different cooling histories for each side of the fault prior to 15 m y similar apatite ages on both sides of the fault imply similar cooling histories during the past 15 m y this may indicate that faulting ceased by 15 m y mean uplift rates have been derived from the fission track data using mainly the mineral pair method uplift rates in the region north of the mmt increased from 0 07 to 0 20 mm yr during the period 55 to 15 m y south of the fault uplift rates averaged in excess of 0 70 mm yr for the period 25 to 15 m y during the past 15 m y uplift across the mmt in the swat valley showsno discontinuities ranging from 0 16 mm yr in the south to 0 39 mm yr in the north a plausible interpretation for the fission track uplift data has the mmt verging to the south with overthrusting taking place at a depth between 3 5 and 6 0 km juxtaposing two terranes that were originally separated by a substantial but unknown distance in this model regional uplift followed cessation of faulting just prior to 15 m y

comparison between the hot spot and geomagnetic field reference frames hot spots are located on the earth s surface and are caused by hot plumes of upwelling mantle material they manifest themselves by volcanic activity which changes its location in response to the movement of the lithosphere over the mantle plume it has been suggested1 3 that hot spots are relatively stationary with respect to each other and also that they represent a frame of reference with which to measure the absolute movement of the lithospheric plates over the surface of the earth another frame of reference can be partially defined by the position of the mean magnetic dipole field of the earth as the dipolar field is believed to be closely related to the spin axis this frame of reference automatically gives information about the palaeolatitude and orientation of the lithospheric plates but since the position of the ancient dipole field of the earth does not give any information about palaeolongitude and since in many cases the definition of the field is relatively poor due to less than adequate rock collections during the time of interest hot spot reference frames have been favoured by many people we now report a comparison of the two frames of reference and show that over the past 200 myr there has been relative movement between the two frames of reference of about 20 and that this motion has not been constant with time

propagating rifts and continental breakup a simple quantitative model is proposed whereby continental breakup starts with a phase of continental rifting and continues with the propagation of rifts toward locked zones these zones are deformed in the rifting process while oceanic crust is generated in the wake of the rift tip the deformed zones will cause overlaps when a continental reassembly is attempted the model accounts for the shape and distribution of magnetic quiet zones at ocean continent boundaries and for the detailed geometry of some v shaped zones of oceanic magnetic anomalies the former provide an estimate of the scale at which the hypothesis of rigid plates fails and the latter are used to measure the velocity of rift propagation illustrations are provided for present rifting in the red sea and gulf of aden and for early rifting of the south atlantic and breakup of pangea

weathering and evolution of soils formed on granitic glacial deposits results from chronosequences of swiss alpine environments abstract two soil chronosequences of mountainous ecosystems in switzerland served as the basis to calculate the accumulation of soil organic matter transformation of pedogenic fe and al and net losses of the main elements ca mg k na fe al mn and si by means of mass balance calculations elemental losses due to deglaciation and exposure to the weathering environment were calculated these mass balance calculations indicate that extensive mineral weathering resulted in significant leaching losses of si major base cations and al particularly from the upper horizons the losses are especially pronounced in the early stages of soil formation in most cases the exponential decay model incorporating an asymptotic or logarithmic regression model seems to provide a good description of weathering the greatest changes in the soil chemistry of these alpine soils on granitic host material occurred within the first 3000 4000 years of soil development later the weathering rates decreased rapidly and the overall depletion of elements nearly reached an asymptote we also found that the mean ratio of al t fe d al d fe t of the fine earth of the a e and b horizons is closely linked to the duration of soil development a very rapid decrease of this ratio also occurred at the beginning of soil evolution in order to reach asymptotic values after about 3000 years consequently this ratio could be a good indicator of the age of alpine soils furthermore there is a close relationship between the mass of organic c or n in the whole profile and the soil age the older the soil the higher the corresponding mass per unit area the chronofunctions presented give a first attempt of the chemical soil evolution in the alps however only little data has been available up until now regarding alpine soils and this fact inhibits a more detailed observation of the changes that have occurred over a period of 2000 8000 years of soil formation under similar climatic conditions

two dimensional modeling of the p t t paths of regional metamorphism in simple overthrust terrains quantitative modeling of metamorphic p t t paths in thrust belts has so far been limited to one dimensional simplification we have developed a two dimensional time dependent finite element procedure capable of tracing and updating fault and strata boundaries during faulting for modeling thermal evolution of overthrust terrains we show that the two dimensionality of an overthrust and the speed and duration of thrusting have significant effects on the p t t paths of rocks in orogenic belts the results suggest that petrological studies of p t paths of rocks from different lateral positions in an orogenic belt along with two dimensional modeling procedure can put strong constraints on models of regional tectonic processes

late cretaceous emplacement of the indus suture zone ophiolitic melanges and an eocene oligocene magmatic arc on the northern edge of the indian plate we report three40ar 39ar dates on stratigraphically located samples of 82 6ma from a syenite cutting the indus suture zone ophiolitic melange and about 39 and about 45 ma from granodiorite intrusions north of the suture zone sedimentological observations indicate eocene to miocene deposition of coarse clastics by very large braided and meandering streams in a continental back arc setting these observations suggest that the ophiolitic melanges of the indus suture zone were emplaced in the late cretaceous shortly after a major change in plate motions in the indian ocean they further suggest that an andean type magmatic arc developed on the northern edge of the indian plate during the eocene and oligocene

structure and evolution of the himalaya tibet orogenic belt the 1981 french chinese expedition to tibet focused on the lhasa block extending earlier coverage 400 km north of the tsangpo suture the lhasa block stood between 10 and 15 n latitude over most of the upper cretaceous and eocene and if gondwanian in origin had detached from gondwana by early permian seismic profiles reveal a complex moho topography resulting both from multiple continental thrusting and large scale strike slip faulting subduction related granitoids representing mixtures of mantle and crustal components and anatectic granitoids have been analysed and dated this study emphasizes the role of smaller blocks in the accretion of the continental mosaic

new constraints on the tectonic evolution of the eastern indian ocean abstract from marine magnetic anomaly studies a fossil spreading ridge is identified beneath the nicobar fan in the northwestern wharton basin several north south trending transform faults offset this ridge left laterally east of the 86 e transform fault our findings show that this ridge which was part of the plate boundary between the indian and australian plates ceased its spreading shortly after formation of magnetic anomaly 20 45 6m y b p since the breakup of australia and antarctica probably occurred sometime between 110 and 90 m y b p we suggest that the indian australian and antarctic plates were moving relative to one another from about 90 to 45 m y b p a triple junction would have existed in the southeastern indian ocean during that period of time at anomaly 19 time 45m y b p the junction became inactive and australia and india became a single plate the northwest southeast trending southeast indian ridge was formed by connecting the india antarctica spreading center with the australia antarctica spreading center its activity has continued to the present time

rapid weathering processes of a 120 year old chronosequence in the hailuogou glacier foreland mt gongga sw china increasing numbers of young soil chronosequences have become exposed in global alpine areas as glaciers have retreated due to climate warming since the industrial revolution however knowledge on the initial stages of weathering at the decadal time scale is limited our aim is to reveal the weathering processes and influential factors in a 120 year old chronosequence on mt gongga in southwest china sixty nine soil samples and 17 water samples were collected from 6 sites with different exposure ages 0 30 40 52 80 and 120 years mineral compositions were determined using x ray diffractometry and four mineral pools i e 1 exchangeable cations 2 carbonates and apatite 3 biotite and hornblende and 4 refractory minerals were separated using a sequential extraction method the results reveal that the soil particle sizes of 2 mu m clay in the a horizons increased and the particle sizes of 20 2000 mu m sand decreased significantly with time the soil organic carbon accumulation rate was up to 14 g m 2 yr which is relatively high compared with other chronosequences of similar age the weathering can be generally divided into two stages the first stage was dominated by the weathering of carbonates and was present at sites with an exposure age of 52 years the second stage was characterized by the intense weathering of biotite hornblende and apatite and was present at the 80 and 120 year old sites where coniferous trees were the dominant plants the rapid weathering was a result of the interactions of the lithology rapid vegetation succession and climate in the hailuogou chronosequence fine silt was produced in large quantities by the strong glacial abrasion and freeze thaw cycles providing rich materials for the subsequent chemical and biogeochemical weathering the decarbonation and the rapid establishment of the conifer forest due to relatively high temperatures and precipitation promote mineral weathering by decreasing soil ph from 8 5 0 years to 4 8 120 years the high permeability of the soil horizons due to the high content of rock fragments and abundant precipitation allows water and organic acids to infiltrate and dissolve mineral soils above the impervious bedrock this study highlights the importance of carbonate weathering in alpine biogeochemical cycling during the initial stage of weathering in granitoid rock areas furthermore our results indicate that the weathering intensity increases with exposure age due to vegetation succession in the early stages of weathering c 2015 elsevier b v all rights reserved

rbsr dating of the kohistan arc batholith in the trans himalaya of north pakistan and tectonic implications the kohistan arc batholith in northern pakistan is situated between the indus suture and the northern suture it belongs to the trans himalayan belt which continues eastwards as the ladakh arc batholith in northwest india and the kangdese batholith in southern tibet in kohistan the island arc consists upward sequence of the chilas stratiform complex of norites noritic gabbros and chromite layered dunites which formed in the sub arc magma chamber plutons of tonalite and diorite one of which has a rbsr isochron age of 102 12 ma the chalt volcanics of basaltic tholeiites succeeded by andesites to rhyolites and the yasin group sediments which formed in overlying intra arc basins and which contain albian aptian faunas all these rocks were deformed by major fold structures which are correlated with the formation of the northern suture ne sw trending basic jutal nomal dykes north of gilgit cross cut all the above structures and have a39ar 40ar hornblende age of 75 ma thus the northern suture must have formed in the period 102 12 to 75 ma with the island arc attached to the eurasian plate further northward subduction of the tethyan plate gave rise to an andean type batholith two plutons of which have rbsr isochron ages of 54 4 ma and 40 6 ma the dir utror group of calc alkaline lavas and sediments with eocene fossils are remnants of the volcanic cover of the andean type batholith we suggest that late cretaceous blueschists formed during subduction under the active continental margin and that continental collision and formation of the indus suture was in the eocene the batholith was intruded by layered aplite pegmatite sheets at 34 14 ma and 29 8 ma rbsr ages in post collisional times the87sr 86sr initial ratios of all the dated rocks range between 0 7039 and 0 7052

zanskar shear zone northeast southwest extension within the higher himalayas ladakh india a complete geologic section through the northwestern himalayas is well exposed in ladakh india the collision between the indian shield and the tibetan platform caused large scale intracrustal thrusting and piling up of the himalayan nappes this compressional event was accompanied by prograde regional metamorphism the metamorphism ranges from low grade anchimetamorphism in the indus suture zone in the northeast to upper amphibolite grade in the higher himalaya tectonic unit in the southwest in the zanskar area a well exposed and morphologically prominent shear zone 2 25 to 6 75 km wide can be followed from the northwest to the southeast for at least 80 km in contrast to the main compressional tectonics this shear zone indicates an extensional event within the higher himalaya tectonic unit the zanskar shear zone involves granitic rocks leucogranites of miocene age and various metasediments and in general separates the late precambrian early cambrian sedimentary sequence phe formation from the underlying crystalline basement zanskar crystalline unit a normal sense of shear has been determined by using asymmetric macroscopic and microscopic structures such as pegmatite boudins feldspar augen and crystallographic fabrics the metamorphic isograds are very close within this shear zone as a result of shear deformation a gradual transition from upper amphibolite to lower greenschist facies occurs within 200 m movement in this zone occurred late in the metamorphic history under greenschist or lower metamorphic conditions the minimum horizontal extension and vertical displacement are on the order of 16 and 19 km respectively

structure and tectonics of the himalaya constraints and implications of geophysical data the himalayan range is a product of continental collision between india and eurasia and for several reasons it is a logical place to examine the physical causes and mechanisms of mountain building the exceptionally high mountains and the great length of the range alone single the himalaya out as a major structural feature the convergence rate between india and eurasia of about 50 mm yr 1 minster jordan 1978 requires rapid rates of slip and the occurrence of four major earthquakes with magnitudes in excess of 8 4 in the last 100 years attests to a high level of seismicity and a rapid rate of active deformation e g richter 1958 seeber armbruster 1981 the exposures of high grade metamorphic rocks in the greater himalaya may suggest large vertical transport of lower crustal rocks e g valdiya 1980a b and the occurrences of young postcollision granites imply recent large perturbations of the temperature structure of the range e g lefort 1981 moreover as sediments derived from the himalaya fill the broad ganga basin south of the range the mountain belt simul taneously seems to override the basin e g g d johnson et al 1979 n m johnson et al 1982 as such the processes occurring now and since the collision began in the early tertiary as well as the present structure of the himalayan belt are probably similar to those at different stages of collision and mountain building in other older orogenic belts such as the appalachians the scottish and scandinavian caledonides the alps and

soil development along primary succession sequences on moraines of hailuogou glacier gongga mountain sichuan china abstract soil properties related to soil development were measured in six profiles over approximately 180 years of soil development on recessional moraines of the hailuogou glacier sichuan of southwestern china it is hypothesized that soil development is strictly time dependent field and laboratory work indicate that as soil develops from initially coarse gravel outwash the properties undergo a progressive physical and chemical change such that there is a considerable profile differentiation between the youngest and the oldest soils the ph is also highly stratified it decreases with time from 8 5 to 4 2 in the upper mineral soil and increases with depth in all profiles accumulation of soil organic c and n increases with time but the rates of accumulation become slower with time within the investigated timespan soil c and n accumulated to a considerable level of 3 5 and 0 6 kg m2 respectively with mean annual rates of 28 g m2 for carbon and 3 5 g m2 for nitrogen the rapid accumulation of organic c and n accelerates the processes of soil formation but the content of organic c and n did not reach a steady state during the observed timespan the accumulation of soil organic matter results in increased acid production and in the chemical weathering of minerals that promote formation and translocation of the clay fraction and leaching of carbonate it is also directly responsible for development of soil properties such as cation exchange capacity cec and bulk density

soil development on moraines of mendenhall glacier southeast alaska 1 the moraines and soil morphology abstract soils on a sequence of well drained neoglacial moraines up to 240 years old plus an older soil were sampled to investigate soil development through the initial stages of podzolization pebbles and cobbles in the moraines are about 75 to 80 granitic rock computations based on minerals observed optically and on chemical analyses indicate that plagioclase and quartz are the predominant minerals in the fine earth the climate is perhumid leaching of the moraines may have begun before they were free of glacial ice but little organic matter accumulated under the initial vegetative cover of sparse dwarf fireweed 10 year site as alder thicket developed organic matter accumulated rapidly in oi oe and a horizons 38 year site as spruce trees began to replace alder organic matter was lost from the surface mineral soil to form an e horizon and an incipient bs horizon formed below it an oa horizon formed and the a horizon disappeared 70 and 90 year sites organic acid leaching continued to form a spodic bhs horizon in spruce forest 240 year site and a spodic bh horizon in spruce hemlock forest 240 year site hornblende has been etched slightly within 240 years apatite has been lost from e horizons and free fe presumeably in ferrihydrite has accumulated in b horizons the younger moraine soils both with and without incipient bs horizons are typic cryorthents and the 240 year old and older soils with spodic bhs and bh horizons are typic haplocryods they are expected to accumulate more organic matter and become andic humicryods which is the most common subgroup of soils in the area

between ice and ocean soil development along an age chronosequence formed by the retreating breiðamerkurjokull glacier se iceland as glaciers in iceland retreat they expose new surfaces for plant succession and soil formation in the foreland of brei amerkurjokull glacier we used a high time resolution chronosequence to study vegetation succession morphological physical and chemical changes in soils and the impact of avifauna on the vegetation and soils developing on the moraines in total 38 sampling sites were distributed along moraines deposited in 1890 1930 1945 1960 1982 1994 2004 and 2012 representing 8 age groups on moraines where the influence of seabirds was apparent soils were collected from bird hummocks one for each age group soil samples were also collected from nearby birch betula pubescens ehrh woodlands representing soils in a potentially future mature ecosystem the results show that mosses and grasses dominated and characterized the vegetation on the moraines with the exception of the two youngest moraines that were non or sparsely vegetated an ac horizon sequence slowly formed yet the a horizon remained thin 2 5 cm bulk density decreased with time since deglaciation from 1 2 g cm 3 down to 0 8 1 0 g cm 3 in the oldest moraines similarly soil ph h2o decreased with time reaching a steady state at the value of 6 after 67 yrs loi loss on ignition soc soil organic carbon and total n nitrogen concentrations along with ph naf increased over the time span investigated the increase in loi soc and n concentrations occurred slowly during the first few decades rates increased after 50 yrs since deglaciation but eolian input appeared to reduce the rates again in the 122 yr old moraine the highest soc and n concentrations were reached in the 82 yr old moraine 1 4 soc 0 07 n and the highest naf values of 9 3 after 67 yrs the lack of shrubs and dwarf shrubs indicated that the long distance from seed sources retarded vegetation succession within the brei amerkurjokull moraines which in turn affected the soil development on the moraines although perhaps to a lesser degree than expected the soil in the bird hummocks was characterized by dense root system and thick a or o horizons 14 cm generated by the dense growth of grasses and herbs accompanied by considerably much higher soc and n values 18 soc 1 1 n after 67 yrs when compared to the surrounding moraine soils additionally bulk density was much lower within the bird hummocks 0 26 0 75 g cm 3 and soil ph h2o was generally lower ranging between 5 2 and 6 2 depending on moraine age this study shows that the point centered input by avifauna into the terrestrial ecosystem is an important factor in locally enhancing vegetation growth and the rates of soil formation increasing the heterogeneity within the moraine soils

geometry of isograds in metamorphic terrains abstract a simple mathematical relation among the dip of isograd surface dip of isotherm surface temperature gradient t g pressure gradient p g and t gdp of reaction is given by 1 sin ga t p p g 1 t g cos cot p g is taken to be constant at 0 3 kb km four major theoretical models for shapes and orientations of isograds are formulated on the basis of the parameters t g and t p this offers a rational basis for studying the geometry of isograds normal reverse metamorphism and determination of temperature gradient two examples have been studied in the light of these models in one case the domed shape of the isograd is best explained by a downwardly directed t g in the other case reverse metamorphism is best explained as the result of a horizontal t g of 18 c km

synchrotron based p k edge xanes spectroscopy reveals rapid changes of phosphorus speciation in the topsoil of two glacier foreland chronosequences phosphorus p is a crucial element for life on earth and the bioavailability of p in terrestrial ecosystems which is dependent on the soil p stock and its speciation may limit ecosystem productivity and succession in our study for the first time a direct speciation of soil p in two glacier foreland chronosequences has been conducted using synchrotron based x ray absorption near edge structure xanes spectroscopy the chronosequences are located in the forefields of hailuogou glacier gongga shan china and damma glacier swiss alps the age since deglaciation of the investigated soils ranges from 0 to 120 years at hailuogou and from 15 to 700 years at damma differences in climate conditions cooler at damma in contrast to hailuogou precluding the establishment of forest in advanced ecosystem succession stages and in the chemical composition of the parent material result in different soil contents of total p and fe al oxyhydroxides which are much smaller at damma than at hailuogou nevertheless both chronosequences show similar trends of their topsoil p status with increasing soil age our study reveals a rapid change of topsoil p speciation in glacier retreat areas already during initial stages of pedogenesis initially dominating bedrock derived apatite p and al bound p is depleted fe bound p and particularly organically bound p is accumulated organic p strongly dominates in the topsoil of the mature soils outside the proglacial area of damma glacier age 700 3000 years and already 50 years after deglacation in the topsoil of the retreat area of hailuogou glacier a key factor for the change in topsoil p speciation is the establishment of vegetation resulting in soil organic matter som accumulation as well as accelerated soil acidification and apatite dissolution by organic acids which are produced by som degrading micro organisms mykorrhiza fungi and plant roots particularly the succession of grassland to forest seems to accelerate the transformation of topsoil p from apatite p into organic p the conceptual model developed by walker and syers 1976 to explain long term millennial changes of p speciation availability and turnover in soils and terrestrial ecosystems seems to be valid to describe short term changes of p speciation and p availability in proglacial topsoils already within a century of initial soil formation because the apatite depleted topsoil horizons in the young proglacial soils are shallow the change of topsoil p speciation should not seriously affect p availability and the p acquisition strategy of adult trees whose roots can easily access apatite containing c horizons in contrast p acquisition strategies of fungi micro organisms and plants confined to the topsoil probably change from apatite dissolution to mineralization of organic p already within 3000 years in a proglacial ecosystem succession from bare soil to grassland damma glacier chronosequence or even within 100 years in a proglacial ecosystem succession to forest hailuogou glacier chronosequence c 2013 elsevier ltd all rights reserved

bottom topography and roughness variations as triggering mechanisms to the formation of sorted bedforms 1 a new model is presented that addresses the occurrence of sorted bedforms on inner shelves of coastal seas these features consist of alternating bands of coarse and fine grains with small topographic undulations we show that inherent feedbacks between alongshore currents sea waves bottom topography and roughness variations result in the emergence of morphological patterns similar to the observed bed features we find that two modes are amplified which display different characteristics yielding a possible explanation to the diversity exhibited by sorted bedforms in the field the results illustrate that both roughness variations and bottom topography influence the generation of sorted bedforms

the tibetan side of the india eurasia collision results are reported from the 1980 joint french chinese field expedition in tibet the area covered was from the high himalaya in the south to the region of nagqu 250 km north of yangbajain ophiolites in the zangbo valley represent remnants of the crust of an ocean basin which lay adjacent to the gangdise granodiorite belt in the late mesozoic the ophiolites were thrust to the south onto the cretaceous melange and triassic flysch but the age of this event is unclear in the tertiary sediments of the indian margin and the xigaze basin were folded with steeply dipping cleavage which indicates some north south shortening of the crust however the tertiary volcanic sequence on the lhasa block and further north shows comparatively little folding and thrusting in the quaternary deformation of tibet was characterized by east west extension

soil c and n sequestration in organic and mineral layers of two coeval forest stands implanted on pyroclastic material mount vesuvius south italy tree species influence organic matter sequestration in forest soil we explored the pattern of soil organic carbon soc and soil organic nitrogen son sequestration in two 40 year old adjacent forest stands one with black pine pinus nigra arn and one with black locust robinia pseudoacacia l we compared the patterns of annual carbon c and nitrogen n sequestration in the organic and mineral soil layers of the two forests with literature data for 100 years old deciduous and coniferous forests from different climatic zones carbon and n inputs with aboveground litter fall were significantly higher in the black pine than in the black locust stand in the soil profile of the black pine stand the amount of soc was significantly higher and that of son significantly lower than in the black locust stand the average annual sequestration rates were 41 3 and 75 0 g c m 2 and 2 9 and 2 6 g n m 2 respectively in the black locust and the black pine stands in both forests most of soc and son were stored in the organic layers ol and of oh in the mineral soil layers the amount of soc was similar for the two stands whereas the amount of son was significantly higher in the black locust stand 23 7 vs 14 6 g n m 2 in all soil layers the concentrations of water soluble organic matter wsom were higher in the black locust stand compared to that with black pine manganese accumulated in the of oh layer of the black pine stand the results suggest different sequestration patterns with higher soc sequestration rates in the black pine stand and higher son sequestration rates in the black locust stand comparison with literature data suggests this to be a generality in c and n sequestration patterns for coniferous and deciduous forests

tectonic controls on the uplift of the nanga parbat massif pakistan himalayas cenozoic mountain belts like the himalayas contain regions that experienced rapid uplift in comparison with the areas around them1 whether this uplift occurred by buoyant rebound of previously thickened crust2 or during the crustal thickening process itself is uncertain3 4 here we show however that the 7 mm yr 1 recent uplift5 of the nanga parbat massif pakistan himalayas was accomplished during nw directed thrusting located along its western margin this 3 km wide liachar thrust zone operated from amphibolite facies to the present topographic surface and accommodates substantial crustal shortening the adjacent indus river valley itself cut by seismogenic faulting completely transects the massif showing that erosion keeps pace with geologically rapid thrust uplift6

metamorphism and tectonics of the himalaya metamorphism connected with the main growth and deformation stages of the himalaya ranges from mid cretaceous to the quaternary northward subduction gave rise in the early to mid cretaceous to an island are complex with greenschists amphibolites granulites and blueschists in the w kohistan ladakh and an andean type margin with greenschist amphibolite grade metamorphism in the e india and tibet ophiolitic nappes were thrust southwards over the indian continental margin in the palaeogene during the final stages of closure of the southern arm of tethys the indus zangbo suture bifurcates westwards and between the two sutures lies the kohistan ladakh island arc which was converted to an andean type arc in the palaeocene eocene the karakorum range underwent northward subduction at least during the late cretaceous to give rise to a complex and prominent calc alkaline batholith post collisional southward thrusting of crustal slabs over the indian continental margin took place in the early miocene with production of high grade metamorphism inverted isograds and crustal melt granites later southward thrusting in the pliocene to quaternary gave rise to localized low grade recrystallization against the thrusts

structural evolution and sequence of thrusting in the high himalayan tibetan tethys and indus suture zones of zanskar and ladakh western himalaya reply abstract the timing of motion on major thrusts in the western himalaya shows an extremely complex sequence that spans approximately 70 ma from the latest cretaceous throughout the tertiary three major phases of thrusting can be distinguished the earliest phase t1 is associated with emplacement of tethyan basin thrust sheets lamayuru sediments and spontang ophiolite south and south westwards onto the submerged northern passive margin of india 75 60 ma collision between india and asia occurred at 50 36 ma and was followed immediately by the major phase t2 of crustal shortening involving large scale south and south westward directed thrusting of the complete palaeozoic mesozoic and late tertiary tibetan tethys zone rocks preliminary balanced cross sections show a minimum shortening of 126 km of these rocks across the zanskar range the late collision phase t3 involved re thrusting of the previously stacked pile breaching or leap frog thrusting reversing the earlier stacking order in places and widespread steepening overturning and backthrusting along the whole northern margin of the tibetan tethys zone and throughout the indus suture zone

39 ar 40 ar dating of the trans himalayan calc alkaline magmatism of southern tibet the age of the trans himalayan calk alkaline magmatism has not been clearly established on the basis of geological control it is possible to infer a pre late cretaceous age for the plutonites at the southern edge of the batholith belt and a late cretaceous or younger age for the lava series on the top and or to the north of the plutons k ar radiometric data previously obtained by chinese groups agree with these geological ages the 39ar 40ar method has been used to analyse more accurately some of the rocks which have been sampled during the joint french chinese field work in southern tibet in the summer of 1980 the incremental degassing of argon gives generally more information about the thermal history of the sample using this method we now show that the earlier basic plutons of the southern edge of the trans himalayan belt have ages of 90 110 myr albian to cenomanian whereas the lavas of the upper unconformable series are clearly younger 60 myr palaeocene the ladakh and kohistan magmatic belts further west are probable equivalents of the trans himalaya north of the indus suture their precise ages are also poorly known orbitolinas of middle cretaceous aptian age have been found in the drosh yasin series which lie unconformably on dioritic plutons in the northern edge of the belt the few radiometric data that are available give ages in fairly good agreement with those we have obtained in the trans himalaya so we conclude that a subduction zone has been active during the cretaceous between india and asia the only outstanding question is whether this active margin was at that time close to india or to asia or somewhere in between

soil forming rates and processes on quaternary moraines near lago buenos aires argentina thirty four pedons on four moraine groups spanning the last 1 myr are used to investigate mechanisms and rates of soil development in santa cruz province argentina all soils are coarse loamy mesic typic haplocalcids or calcic haploxerolls occurring under short grass shrub steppe in a semi arid climate the dominant soil forming processes are the accumulation of organic matter carbonate and clay sized particles organic carbon accumulates rapidly in these soils but significantly higher amounts in the oldest two moraine groups are likely the result of slight differences in soil forming environment or grazing practices accumulation rates of carbonate and clay decrease with age suggesting either decreased influx in the earliest part of the record or attainment of equilibrium between influx and loss there are no changes in soil redness and preservation of weatherable minerals in the oldest soils indicates there is little chemical weathering in this environment measured dust input explains the accumulation of both clay and carbonate we present a carbonate cycling model that describes potential sources and calcium mobility in this environment calibration of rates of soil formation creates a powerful correlation tool for comparing other glacial deposits in argentina to the well dated moraines at lago buenos aires

high p t polymetamorphism dehydration melting and generation of migmatites and granites in the higher himalayan crystalline complex sikkim india the higher himalayan crystalline complex hhc in sikkim india consists of pelitic migmatites interlayered with calc silicate rocks and minor metabasites microstructural relationships between the mineral phases and deformational fabric elements and zoning characteristics of garnet indicate a prolonged and complex polymetamorphic history for the hhc the pelitic rocks in the upper part of the hhc contain the assemblage plagioclase quartz garnet k feldspar biotite sillimanite and are devoid of muscovite most of the mineral phases grew syn to post tectonically mineral growth coincided with development of a pervasive fabric s 2 during prograde metamorphism m 2 in the early stages of the collisional event some garnet grains display texturally distinct cores and rims which are separated by calcic plagioclase this texture suggests an earlier metamorphic episode m l m may represent pre himalayan metamorphism and decompression of the hhc later the collisional event led to renewed burial of the hhc and m 2 reactions m 2 is reflected by dehydration melting of muscovite and biotite to form granitic melts which either crystallized in situ to form leucosomes or migrated from their source regions to form larger granitic bodies geothermobarometric estimates for peak m 2 conditions indicate p 10 12 kbar t 800 850 c a subsequent metamorphic event m 3 occurred because of 5 kbar of decompression m 3 is recorded by the breakdown of porphyroblastic garnet in all hhc lithologies higher temperature and pressure estimates come from progressively higher structural levels of the complex the thermal gradient of 5 5 c km is anomalous and may be a consequence of thermal buffering during melting however the pressure gradient of 0 25 kbar km resembles a normal lithostatic gradient which suggests that the hhc in sikkim represents an inverted barrovian sequence this inverted zonation of the hhc is probably the result of large scale structural inversion and or tectonic juxtaposition because of ductile shearing

variations in weathering processes and rates with time in a chronosequence of soils from glen feshie scotland chemical and mineralogical characteristics have been determined for a chronosequence of six soil profiles ranging in age from 80 13 000 years bp developed on river terraces in the western cairngorms of scotland the c horizons are similar chemically and mineralogically and the soils have similar pedogenetic histories exchangeable ca and mg decrease with time and base saturation decreases exponentially from 24 6 in the ah horizon of the youngest profile to 2 8 in the comparable horizon of the 10 000 year old profile according to the chronofunction y 3 372 22 612 exp 0 0007365t long term weathering rates of base cations calculated from the loss of these cations relative to zr appear to decrease exponentially with time but this may be due to the method of calculation the magnitude of loss of base cations decreases in the sequence na k mg ca but when the relative mobilities of these elements are considered the loss is in the order mg na ca k this reflects the dissolution of chlorite and loss of mg and the more rapid weathering of plagioclase feldspar and loss of na and ca particularly in the coarse sand fraction than k feldspar the clay fractions although 2 of all horizons also show distinct patterns with age in that chlorite and mica are less abundant in older soils and vermiculite is more abundant the latter phase often having hydroxyaluminium polymers in the interlayer region the chemical and mineralogical trends in the soil sequence are closely associated and are induced by pedogenic weathering

predicting soil formation on the basis of transport limited chemical weathering abstract soil production is closely related to chemical weathering it has been shown that under the assumption that chemical weathering is limited by solute transport the process of soil production is predictable however solute transport in soil cannot be described by gaussian transport in this paper we propose an approach based on percolation theory describing non gaussian transport of solute to predict soil formation the net production of soil by considering both soil production from chemical weathering and removal of soil from erosion our prediction shows agreement with observed soil depths in the field theoretical soil formation rates are also compared with published rates predicted using soil age profile thickness sast method our formulation can be incorporated directly into landscape evolution models on a point to point basis as long as such models account for surface water routing associated with overland flow further our treatment can be scaled up to address complications associated with continental scale applications including those from climate change such as changes in vegetation or surface flow organization the ability to predict soil formation rates has implications for understanding earth s climate system on account of the relationship to chemical weathering of silicate minerals with the associated drawdown of atmospheric carbon but it is also important in geomorphology for understanding landscape evolution including for example the shapes of hillslopes and the net transport of sediments to sedimentary basins

topo oz insights into the various modes of intraplate deformation in the australian continent abstract as the fastest lowest flattest and amongst the most arid of continents australia preserves a unique geomorphic record of intraplate tectonic activity evidencing at least three distinct modes of surface deformation since its rapid northward drift commenced around 43 million years ago at long wavelengths several 1000s km systematic variations in the extent of neogene marine inundation imply the continent has tilted north down southwest up at intermediate wavelengths several 100s km several undulations of 100 200 m amplitude have developed on the 1 10 myr timescale at still shorter wavelengths several 10s km fault related motion has produced local relief at rates of up to 100 m myr over several million years the long wavelength north down tilting can be related to a dynamic topographic effect associated with australia s northward drift from the geoid low dynamic topography low now south of the continent to the geoid high dynamic topography low centred above the south east asian and melanesian subduction zones the short wavelength fault related deformation is attributed in time to plate wide increases in compressional stress levels as the result of distant plate boundary interactions and in space in part to variations in the thermal structure of the australian lithosphere at the intermediate wavelengths transient low amplitude undulations can be ascribed to either lithospheric buckling or the development of instabilities in the thermal boundary layer beneath the lithosphere in the latter case topographic asymmetries suggest the australian lithosphere is moving north with respect to the mantle beneath providing a unique attribution to the progressive alignment of seismic anisotropy and absolute plate motion observed near the base of the australian lithosphere