provenance and tectonic setting of the paleoproterozoic metasedimentary rocks from the liaohe group jiao liao ji belt north china craton insights from detrital zircon u pb geochronology whole rock sm nd isotopes and geochemistry abstract geochronological geochemical and isotopic studies were carried out on the paleoproterozoic metasedimentary rocks from the jiao liao ji belt north china craton to constrain their provenance and tectonic setting as well as to evaluate the effects of weathering and sedimentary processes on the source rock signature u pb isotopic dating using the la icp ms method on zircons from the paleoproterozoic metasedimentary rocks reveals that the depositional age can be constrained in the period between 1 98 and 1 9 ga geochemical data reveal low intermediate degrees of weathering of the source compositionally immature and poorly sorted detailed analysis of detrital zircon u pb geochronology whole rock sm nd isotope and geochemistry show that these metasedimentary rocks are derived from a mixed provenance the predominant derivation is from metavolcanic rocks of the liaohe group and paleoproterozoic gneissic granitoids there is also an input of archean continental crust the metasedimentary rocks were probably deposited in a back arc basin within an arc system thus supporting the paleoproterozoic arc continent collision model as already proposed by some authors

quantifying groundwater surface water interactions in a proglacial valley cordillera blanca peru a myriad of downstream communities and industries rely on streams fed by both groundwater discharge and glacier meltwater draining the cordillera blanca northern peruvian andes which contains the highest density of glaciers in the tropics during the dry season approximately half the discharge in the region s proglacial streams comes from groundwater however because of the remote and difficult access to the region there are few field methods that are effective at the reach scale to identify the spatial distribution of groundwater discharge an energy balance model rhodamine wt dye tracing and high definition kite borne imagery were used to determine gross and net groundwater inputs to a 4 km reach of the quilcay river in huascaran national park peru the hflux computer programme http hydrology syr edu hflux html was used to simulate the quilcay river s energy balance using stream temperature observations meteorological measurements and kite borne areal photography inference from the model indicates 29 of stream discharge at the reach outlet was contributed by groundwater discharge over the study section rhodamine wt dye tracing results coupled with the energy balance show that approximately 49 of stream water is exchanged no net gain with the subsurface as gross gains and losses the results suggest that gross gains from groundwater are largest in a moraine subreach but because of large gross losses net gains are larger in the meadow subreaches these insights into pathways of groundwater surface water interaction can be applied to improve hydrological modelling in proglacial catchments throughout south america copyright 2016 john wiley sons ltd

structural tests of diapir hypotheses in archean crust of ontario detailed structural maps of two granitoid complexes in the wabigoon subprovince are used to test three diapir hypotheses advanced in earlier papers the gneiss masses of and individual domes within the complexes fail the test for solid state diapirism the gneiss domes also fail the test for tensile bending caused by hypothetical magmatic diapirs in the subsurface an oval pluton located near the best exposed gneiss dome proves to be a synformal sheet rather than a funnel shaped magmatic diapir this pluton could be a syenite diorite phacolith emplaced into a concordant zone of dilation during the late upright folding of the gneiss mass about horizontal axes earlier tight folds were probably recumbent and south verging and like the gneissosity generated in a ductile shear regime with subhorizontal glide planes these observations have important implications for archean tectonics especially the relative horizontal displacement of large greenstone masses potentially allochthonous greenstone belts

flow and fabric development during the diapiric rise of magma scaled isothermal experiments of the internal circulation induced by viscous drag at a diapir country rock interface are compared with published theoretical studies of flow induced finite deformation inside a rising sphere and new numerical results are presented for the incremental strain pattern developed in spherical diapirs the results predict a time dependent deformation history within rising diapirs that produces finite strains characterized by strong oblate flattening strains at the margin and strong vertical prolate strains in the center with an intervening zone of low plane strain finite strains are discussed in terms of the different sub fabrics expected to form in granitoids after considering the history of rheology and temperature distribution in rising magma strong rheological and temperature gradients are predicted for the margins of internally circulating diapirs that can lead to the formation of strong penetrative foliations at the margin and magmatic or even isotropic fabrics in the i

transtensional origin of multi order cross folds in a high grade gneiss complex southwestern grenville province formation during post peak gravitational collapse the well mapped western part of the ottawa river gneiss complex orgc new name a large metamorphic core complex hosts a system of gently plunging cross folds of outcrop to regional scale situated in the ductile detachment zone between the lower grade cover and high grade core of the complex the cross folds are buckle structures that deform the attenuated gneissic layering plunge parallel to the regional elongation lineation range from upright to recumbent and exhibit distinctive hinge parallel elongation lineations all features of extension dominated ductile transtension our l s fabric data are consistent both with kinematic modelling that predicts progressive constrictional strain in the hinge zones of transtensional folds and with dynamic modelling that predicts rotation of flattened fold limbs into moderately dipping attitudes on the basis of petrologic data we show that cross folding postdated the peak ottawan metamorphism and took place during retrogression and exhumation of the thrust sheet stack the cross folds form an inclined system that is principally developed in retrograde melt weakened amphibolite facies rocks with the transtensional origin implying that exhumation and retrogression of the high grade core of the complex took place in an oblique extensional setting a transtensional origin for the cross folds removes the need to appeal to orogen parallel regional shortening an implausible requirement of previous interpretations and is compatible with data indicating that much of the visible fabric and structure of amphibolite facies domains of the orgc developed during post peak exhumation retrogression and gravitational collapse of the thrust sheet stack

the deformation and tectonic evolution of the huahui basin northeast china during the cretaceous early cenozoic abstract the cretaceous huahui basin lies along the dunhua mishan fault dun mi fault which is one of the northern branches of tan lu fault in northeastern china the study of the formation and the tectonic movements that took place in the basin can provide very important information for deciphering the tectonic evolution of northeastern china during cretaceous early cenozoic the field analysis of fault slip data collected from different units in the basin demonstrates changes in the paleo stress state that reveals a three stage tectonic movement during the cretaceous early cenozoic the earliest tectonic movement was nw se extension which was responsible for the formation of the basin and sedimentary infilling during the early cretaceous dating of the andesite in the fill indicates it began during about 119 17 0 80 ma the extensional structures formed in the latest early cretaceous imply that this tectonic movement lasted until the beginning of the late cretaceous the second stage began during the late cretaceous when the tectonic stress state changed and was dominated by nw se compression and ne sw extension which caused the inversion of the extensional basin this compression folded the early cretaceous deposits and reactivated pre existing faults and uplifted pre existing granite in the basin the strata and the unconformity in the basin shows that this compressive phase probably took place during the late cretaceous and ended in the early paleogene by a compressional regime with ne sw compression and nw se extension that constitutes the third stage the tectonic stress fields documented in the huahui basin provide insight into the influences of plate tectonics on the crustal evolution of northeastern china during the cretaceous to early cenozoic these results show that the development of huahui basin was controlled by the northwestward subduction of the paleo pacific plate during the cretaceous and later by the far field effects of india asia collision in the paleogene

controls on back arc basin formation the relationship between subduction and back arc spreading has been well known since the early days of plate tectonics however the reasons why back arc basins are associated with some subduction systems but not all has remained elusive we examine the kinematic controls on subduction and back arc basins for both the present day and cenozoic to differentiate between the major competing hypotheses for back arc basin formation and to explain their temporal and spatial distribution our new data set of subduction and back arc basin parameters uses a new set of paleo oceanic age grids muller et al 2005 associated with a moving atlantic indian ocean hot spot reference frame o neill et al 2005 the plate model includes detailed reconstructed spreading histories of back arc basins based on marine geophysical and satellite gravity data our combined rotation and oceanic paleo age model provides the age distribution of subducting lithosphere through space and time convergence rates and the absolute motion of the downgoing and overriding plates we find that back arc basins develop when the age of subducting normal oceanic lithosphere is greater than 55 million years additionally we establish an age dip relationship showing that the intermediate dip angle of the subducting slab is always greater than 30 with back arc spreading our results suggest that back arc basin formation is always preceded by an absolute motion of the overriding plate away from the subduction hinge thereby creating accommodation space between the overriding and subducting plates once back arc extension is established it continues regardless of overriding plate motion indicating back arc spreading is not a simple consequence of overriding plate behaviour the landward migration of the overriding plate as a precursor to back arc extension may indicate that extension on the overriding plate is influenced by the oceanward lateral flow of the mantle however once back arc extension is established rollback of the subduction hinge appears to be the primary force responsible for the continued creation of accommodation space our analysis indicates the driving mechanism for back arc extension is a combination of surface kinematics properties of the downgoing slab the effect of lateral mantle flow on the slab and mantle wedge dynamics

40ar 39ar age constraints on cretaceous fossil bearing formations near the china north korea border abstract abundant mesozoic terrestrial plant fish and invertebrate fossils have been discovered from the lishugou formation and the underlying xiaolin formation in the eastern liaoning province of ne china since the 1970s these discoveries have great potential for substantially increasing our knowledge on the evolution of paleoecosystems and paleoenvironments in east asia however previous geological and geochronological studies for these fossil bearing formations are rare because the fossil outcrops are near the border between china and north korea here we present robust 40ar 39ar ages of 99 9 0 4 ma for one sample from the lishugou formation and 109 1 0 2 ma and 122 4 0 2 ma for two samples from the upper and lower parts of the xiaolin formation from dandong city liaoning china our new age data indicate that the lishugou and xiaolin formations were deposited contemporaneously with the jiufotang formation from the classic jehol outcrops in western liaoning therefore our results provide an accurate age calibration for the fossils discovered from the liaodong peninsula and suggest that the hypothesis of the jehol migration should be reappraised

rock glaciers and mountain hydrology a review abstract in mountainous regions climate change threatens cryospheric water resources and understanding all components of the hydrological cycle is necessary for effective water resource management rock glaciers are climatically more resilient than glaciers and contain potentially hydrologically valuable ice volumes and yet have received less attention even though rock glacier hydrological importance may increase under future climate warming in synthesising data from a range of global studies we provide the first comprehensive evaluation of the hydrological role played by rock glaciers we evaluate hydrological significance over a range of temporal and spatial scales alongside the complex multiple hydrological processes with which rock glaciers can interact diurnally seasonally annually decadally and both at local and regional extents we report that although no global extent complete inventory for rock glaciers exists currently recent research efforts have greatly elaborated spatial coverage using these research papers we synthesise information on rock glacier spatial distribution morphometric characteristics surface and subsurface features ice storage and hydrological flow dynamics water chemistry and future resilience from which we provide the first comprehensive evaluation of their hydrological contribution we identify and discuss long intermediate and short term timescales for rock glacier storage allowing a more balanced assessment of the contrasting perspectives regarding the relative significance of rock glacier derived hydrological contributions compared to other water sources we show that further empirical observations are required to gain a deeper hydrological understanding of rock glaciers in terms of i their genesis and geomorphological dynamics ii total ice water volume iii water discharge and iv water quality lastly we hypothesise that at decadal and longer timescales under future climate warming degradation of ice within rock glaciers may represent an increasing hydrological contribution to downstream regions and thus increased hydrological significance while rock glacier water stores persist

structure of the castillo granite southwest spain variscan deformation of a late cadomian pluton a geometrical reconstruction of the 500 ma old castillo granite pluton sw iberia is completed on the basis of structural and geophysical rock magnetism techniques the pluton is intrusive into latest proterozoic earliest cambrian metasediments and conforms a tabular intrusion 6 km in diameter and 1 7 km thick that was emplaced at a depth of 10 km its magnetic fabric reveals that the strike of moderately to steeply dipping magmatic flow planes forms a high angle to the regional tectonic trends magnetic foliations and associated moderately to gently plunging magnetic lineations represent magmatic flow planes and directions the internal anisotropy of the granite together with the structure shown by the country rocks attest the lateral propagation of the pluton and its latter inflation the pluton s root zone would correspond to a likely thin subvertical feeder structure initiated near the orientation of regional 1 at the time of emplacement during the variscan orogeny the pluton was tilted and underwent localized brittle ductile strain in relation to shear zone deformation in the footwall of a major ductile thrust tilting permits the observation and study of a vertical profile of the intrusion localized deformation caused superposition of tectonic zonations on the magmatic ones a reactivation of the basal contact of the pluton and dismemberment from its root this and other granitoid plutons of similar age emplaced at a similar depth constrained the creation of crustal mechanical heterogeneity and anisotropy this controlled the site of pluton emplacement the nucleation of a major ductile thrust and localization of deformation and tectonic displacements along the pluton margins during later orogenic reactivation

challenges and recommendations in mapping of glacier parameters from space results of the 2008 global land ice measurements from space glims workshop boulder colorado usa on 16 18 june 2008 the us national snow and ice data center held a glims workshop in boulder co usa focusing on formulating procedures and best practices for operational glacier mapping using satellite imagery despite the progress made in recent years there still remain many cases where automatic delineation of glacier boundaries in satellite imagery is difficult error prone or time consuming this workshop identified six themes for consideration by focus groups 1 mapping clean ice and lakes 2 mapping ice divides 3 mapping debris covered glaciers 4 assessing changes in glacier area and elevation through comparisons with older data 5 digital elevation model dem generation from satellite stereo pairs and 6 accuracy and error analysis talks presented examples and work in progress for each of these topics and focus groups worked on compiling a summary of available algorithms and procedures to address and avoid identified hurdles special emphasis was given to establishing standard protocols for glacier delineation and analysis creating illustrated tutorials and providing source code for available methods this paper summarizes the major results of the 2008 glims workshop with an emphasis on definitions methods and recommendations for satellite data processing while the list of proposed methods and recommendations is not comprehensive and is still a work in progress our goal here is to provide a starting point for the glims regional centers as well as for the wider glaciological community in terms of documentation on possible pitfalls along with potential solutions

tectonic evolution of the bindura shamva greenstone belt northern zimbabwe progressive deformation around diapiric batholiths abstract the bindura shamva greenstone belt northern zimbabwe and adjacent batholiths are regarded as one of the type areas for granite greenstone tectonics structural observations and three dimensional strain analyses have been used to propose a model for the tectonic evolution of this late archaean greenstone belt the data indicate that pluton emplacement triggered the deformation of the greenstone sequences and that the deformation history is single phase progressive rather than polyphase they do not however lead to an unambiguous interpretation of the emplacement mechanism structural features are best explained by a combination of pluton diapirism and ballooning plutonism criteria used as evidence for pluton related deformation include the pattern of foliation and stretching lineation trajectories the variation in strain type and strain intensity fold types sense of shear at the batholith greenstone interface metamorphic zoning and timing of porphyroblast growth specific structural and strain patterns within cleavage triple points interdomal synclinoria saddle culminations and batholith margins demonstrate interference between strain fields developed around each batholith

glacier recession and water resources in peru s cordillera blanca the tropical glaciers of the cordillera blanca peru are rapidly retreating resulting in complex impacts on the hydrology of the upper rio santa watershed the effect of this retreat on water resources is evaluated by analyzing historical and recent time series of daily discharge at nine measurement points using the mann kendall nonparametric statistical test the significance of trends in three hydrograph parameters was studied results are interpreted using synthetic time series generated from a hydrologic model that calculates hydrographs based on glacier retreat sequences the results suggest that seven of the nine study watersheds have probably crossed a critical transition point and now exhibit decreasing dry season discharge our results suggest also that once the glaciers completely melt annual discharge will be lower than present by 2 30 depending on the watershed the retreat influence on discharge will be more pronounced during the dry season than at other periods of the year at la balsa which measures discharge from the upper rio santa the glacier retreat could lead to a decrease in dry season average discharge of 30

the impact of glaciers on the runoff and the reconstruction of mass balance history from hydrological data in the tropical cordillera blanca peru a 41 years series of runoff and precipitation data from the peruvian cordillera blanca demonstrates the high hygric seasonality in this tropical high mountain range in this area glaciers have a crucial impact on runoff which is of essential importance for the highly populated and cultivated valley of the callejon de huaylas particularly during the dry season whereas the mid latitudes glacier runoff amplifies the seasonal variation of runoff the effect of glaciers in the low latitudes is a smoothing one it decreases clearly with the decreasing degree of glaciation in addition particular circumstances of this tropical environment allow the reconstruction of a glacier mass balance history from the hydrological data for the second half of the 20th century it shows a high synchronicity with the global trend of periods with glacier mass loss and gain comparison with length variations of three individual glaciers indicate a rather fast reaction of these glaciers to changes in mass balance although the mass balance variations show some differences among the individual catchment basins the over all trend is uniform a general positive correlation of mass balance variations with soi is obvious but not regular

the origin and microstructures of metamorphic felsic dykes emplaced during brittle ductile extension southeast sinai structural petrographic and chemical analyses of a set of northeast trending quartzofeld spathic dykes in wadi kid area southeastern sinai show that they are the product of anatexis of pelitic rocks metamorphic p t data indicate that anatexis could have occurred only 2 km below the present erosion level the partial melts intruded into overlying rocks during regional metamorphism along a set of northeast oriented extensional fractures thereby recrystallizing and in some cases obtaining tectonite fabrics the fractures were formed perpendicular to the regional mineral lineation and show that the area was within the deeper parts of the brittle ductile transition zone the original depth of the presently exposed crustal level corresponds well with the theoretical and experimentally derived depths of the brittle ductile transition zone in high heat flow regimes the emplacement of a granitoid pluton or gneiss dome possibly of dioritic composition could be responsible for both melting and tensile fracturing of the overlying rocks

improved estimates of glacier change rates at nevado coropuna ice cap peru accurate quantification of rates of glacier mass loss is critical for managing water resources and for assessing hazards at ice clad volcanoes especially in arid regions like southern peru in these regions glacier and snow melt are crucial dry season water resources in order to verify previously reported rates of ice area decline at nevado coropuna in peru which are anomalously rapid for tropical glaciers we measured changes in ice cap area using 259 landsat images acquired from 1980 to 2014 we find that coropuna ice cap is presently the most extensive ice mass in the tropics with an area of 44 1 km 2 and has been shrinking at an average area loss rate of 0 409 km 2 a 1 0 71 a 1 since 1980 our estimated rate of change is considerably lower than previous studies 1 4 km 2 a 1 or 2 43 a 1 but is consistent with other tropical regions such as the cordillera blanca located 850 km to the nw 0 68 a 1 thus if glacier recession continues at its present rate our results suggest that coropuna ice cap will likely continue to contribute to water supply for agricultural and domestic uses until 2120 which is nearly 100 years longer than previously predicted

analysis of fault slip inversions do they constrain stress or strain rate fault slip data commonly are used to infer the orientations and relative magnitudes of either the principal stresses or the principal strain rates which are not necessarily parallel or equal at the local scale of an individual fault the shear plane and slip direction define the orientations of the local principal strain rate axes but not in general the local principal stress axes at a large scale the orientations of p and t axes maxima for sets of fault slip data do not provide accurate inversion solutions for either strain rate or stress the quantitative inversion of such fault slip data however provides direct constraints on the orientations and relative magnitudes of the global principal strain rates to interpret the inversion solution as constraining the global principal stresses requires that 1 the fault slip pattern must have a characteristic symmetry no lower than orthorhombic 2 the material must be mechanically isotropic and 3 there must be a linear constitutive relationship between the global stress and the global strain rate isotropic linear elastic constitutive equations are appropriate to describe the local deformation surrounding an individual slip discontinuity fault slip inversions however constrain the characteristics of a large scale cataclastic flow which is described by constitutive equations that are probably but to an unknown degree anisotropic and nonlinear such material behavior would not strictly satisfy the requirements for the stress interpretation thus at the present state of knowledge fault slip inversion solutions are most reliably interpreted as constraining the principal strain rates

recent developments in centrifuge modelling of tectonic processes equipment model construction techniques and rheology of model materials abstract the experimental tectonics laboratory at queen s university is equipped with a large capacity centrifuge that is capable of subjecting tectonic models measuring 127 76 mm in plan and up to 51 mm in depth to accelerations as high as 20 000 g this high capacity greatly extends the range of potential model materials and permits the use of relatively stiff and or brittle substances a number of new techniques of model construction have been devised that permit internal and surface strain patterns and kinematic evolution to be monitored in detail one particularly useful technique which will find application in non centrifuged experiments as well allows the preparation of highly uniform anisotropic multilayers composed of alternating layers of plasticine and silicone putty with individual layer thicknesses as low as 20 m and with controllable ratio between thicknesses of the relatively competent and incompetent units examples of models constructed using these new techniques are illustrated one particular type of the commonly used model material silicone putty has been subjected to a series of rheological test the results indicate that at strain rates in the range 10 6 10 3 s 1 applicable to the centrifuge experiments the silicone putty exhibits power law rheology with n 7 2 at higher strain rates the material appears to tend towards linear behaviour available rheological data and dimensional analysis using standard scaling laws and appropriate model ratios suggest that the microlaminated plasticine silicone putty multilayer is a suitable analogue in centrifuged experiments for interbedded sequences of indurate limestone and incompetent shale the excellent degree of dynamic similitude attained is demonstrated by the realistic form of fold and fault structures developed in models constructed of this material

global distributions of glacier properties a stochastic scaling paradigm many problems in global climate and earth systems science require knowledge of regional or global scale distributions of glacier properties which includes mass balance ice velocity flux thickness volume and surface area among others with roughly 160 000 glaciers worldwide obtaining information on the global probability distributions of most ice properties is expensive and often infeasible only surface area distributions are relatively easy to measure either by direct observation or remote sensing while other properties are difficult to observe this work shows that scaling relationships from the continuum dynamics of ice can link the distribution of surface areas to the global and regional distributions of any other continuum property some data inventories already exist for constructing reasonable distributions of glacier sizes and this analysis presents theoretical arguments based on glacier network topologies similar in concept to river networks to suggest a power law times an exponential distribution of surface areas in agreement with the data therefore by using existing data or the theoretical distributions of surface areas specific distributions for other glacier properties in any region of the world can be constructed as an example predictions up to a scaling constant are made for the distribution of glacier volumes characteristic thicknesses characteristic velocities and characteristic response times in the alps

an inventory and estimate of water stored in firn fields glaciers debris covered glaciers and rock glaciers in the aconcagua river basin chile abstract an inventory of firn fields glaciers debris covered glaciers and rock glaciers was conducted in the aconcagua river basin of the semiarid andes of central chile a total of 916 landforms were identified of which rock glaciers were the most abundant 669 and occupied the most total area glaciers and debris covered glaciers were less numerous but were about five times larger in comparison the total area occupied by glaciers and debris covered glaciers was roughly equivalent to the total area of rock glaciers debris covered glaciers and rock glaciers were subcategorized into six ice content classes based on interpretation of surface morphology with high resolution satellite imagery over 50 of rock glaciers fell within a transitional stage 85 of debris covered glaciers were either fully covered or buried most landforms occupied elevations between 3500 and 4500 m glaciers and firn occurred at higher elevations compared to rock glaciers and debris covered glaciers rock glaciers had a greater frequency in the northern part of the study area where arid climate conditions exist firn and glaciers were oriented south debris covered glaciers west and rock glaciers southwest an analysis of water contribution of each landform in the upper andes of the aconcagua river basin was conducted using formulas that associate the size of the landforms to estimates of water stored minimum and maximum water storage was calculated based on a range of debris to ice content ratios for debris covered glaciers and rock glaciers in the aconcagua river basin rock glaciers accounted for 48 to 64 of the water stored within the landforms analyzed glaciers accounted for 15 to 25 debris covered glaciers were estimated at 15 to 19 firn fields contained only about 5 to 8 of the water stored expansion of agriculture prolonged drought and removal of ice rich landforms for mining have put additional pressure on already scarce water resources to develop long term sustainable solutions the importance of the water stored in rock glaciers or other alpine permafrost landforms such as talus slopes must be weighed against the economic value of mineral resources

diapirism during regional compression the structural pattern in the chibougamau region of the archean abitibi belt quebec the major fold pattern of the chibougamau region in the archean abitibi belt quebec is the result of two fold phases the principal f1 synclines first formed as subsiding fault troughs and were shortened in ns direction and molded around volcanic centers that had been consolidated by large synvolcanic plutons they have a general easterly direction but curve locally to the ne or se n trending f1 folds are locally present in the anticlinoria and are thought to have been produced by the upwelling of basement gneiss and or synvolcanic plutons the f2 folds have rather regular easterly trends their axial plane schistosity s2 is the predominant planar fabric element basin margin faults were transformed into east trending thrust faults during the f1 and f2 folding

glacier recession on cerro charquini 16 s bolivia since the maximum of the little ice age 17th century cerro charquini bolivia cordillera real 5392 m a s l was selected as a site to reconstruct glacier recession since the maximum of the little ice age lia in the central andes five glaciers located on differently exposed slopes present comprehensive and well preserved morainic systems attributed to former centuries the moraines were dated by lichenometry and show a consistent organization on the different slopes the past geometry of the glaciers was reconstructed using ground topography and aerophotogrammetry lichenometric dating shows that the lia maximum occurred in the second half of the 17th century after which the glaciers have receded nearly continuously over the last decades of the 20th century 1983 97 recession rates increased by a factor of four on the northern and western slopes glaciers receded more than on the southern and eastern slopes by 78 and 65 of their lia maximum area respectively the mean equilibrium line altitude ela rose by about 160 m between the lia maximum and 1997 recession rates were analysed in terms of climatic signal suggesting that glacier recession since the lia maximum was mainly due to a change in precipitation and that the 19th century may have been drier for the 20th century a temperature rise of about 0 68c appears to be the main cause of glacier recession recent climatic conditions from 1983 to 1997 correspond to a mass deficit of about 1 36 m w e a 1 if such conditions persist the small glaciers below 5300 m a s l in the cordillera real should disappear completely in the near future

small glaciers disappearing in the tropical andes a case study in bolivia glaciar chacaltaya 16 o s glaciar chacaltaya is an easily accessible glacier located close to la paz bolivia since 1991 information has been collected about the evolution of this glacier since the little ice age with a focus on the last six decades the data considered in this study are monthly mass balance measurements yearly mappings of the surface topography and a map of the glacier bed given by ground penetrating radar survey a drastic shrinkage of ice has been observed since the early 1980s with a mean deficit about 1 m a 1 w e from 1992 to 1998 the glacier lost 40 of its average thickness and two thirds of its total volume and the surface area was reduced by 40 with a mean estimated equilibrium line altitude lying above its upper reach the glacier has been continuously exposed to a dominant ablation on the whole surface area if the recent climatic conditions continue a complete extinction of this glacier in the next 15 years can be expected glaciar chacaltaya is representative of the glaciers of the bolivian eastern cordilleras 80 of which are small glaciers 0 5 km2 a probable extinction of these glaciers in the near future could seriously affect the hydrological regime and the water resources of the high elevation basins

influence of the subducting plate velocity on the geometry of the slab and migration of the subduction hinge abstract geological observations indicate that along two active continental margins east asia and mediterranean major phases of overriding plate extension resulting from subduction hinge retreat occurred synchronously with a reduction in subducting plate velocity in this paper results of fluid dynamical experiments are presented to test the influence of the velocity of the subducting plate on the hinge migration velocity and on the geometry of the slab results show that hinge retreat decreases with increasing subducting plate velocity in addition phases of hinge retreat alternate with phases of hinge advance for relatively high subducting plate velocities due to interaction of the slab with the bottom of the box simulating the upper lower mantle discontinuity such slab kinematics could explain the episodic behaviour of back arc opening observed in convergent settings the geometry of the slab and the kinematics of subduction are significantly affected by the velocity of the subducting plate three subduction modes with accompanying slab geometry can be recognized a relatively low subducting plate velocity is accompanied by relatively fast hinge retreat with backward sinking of the slab and a backward draping slab geometry with increasing subducting plate velocity hinge migration is relatively small resulting in subvertical sinking of the slab and a folded slab piling geometry for a very high velocity the hinge migrates forward resulting in forward oriented subduction vectors and a forward draping slab geometry

the problem of strain marker centers and the fry method abstract the fry method and its variants will underestimate finite strain when applied to strain markers deformed heterogeneously at marker scale despite homogeneous behavior at a population scale this difference results from the post deformation centers not coinciding with the original pre deformation centers the amount of error may rapidly approach 50 for small strains in ideal cases but is likely to be in the range of 20 30

cretaceous deformation history of the middle tan lu fault zone in shandong province eastern china abstract based on field analysis of fault slip data from different rock units of the cretaceous basins along the middle part of the tan lu fault zone shandong province eastern china we document polyphase tectonic stress fields and address the changes in sense of motion of the tan lu fault zone during the cretaceous the cretaceous deformation history of the tan lu fault zone can be divided into four main stages the first stage during the earliest cretaceous was dominated by n s extension responsible for the formation of the jiaolai basin we interpret this extension to be related to dextral strike slip pull apart opening guided by the tan lu fault zone the second stage during the middle early cretaceous was overwhelmingly rift dominated and characterized by widespread silicic to intermediate volcanism normal faulting and basin subsidence it was at this stage that the tan lu parallel yi shu rift was initiated by e w to wnw ese extension the tectonic regime then changed during the late early cretaceous to nw se oriented transpression causing inversion of the early cretaceous rift basin and sinistral slip along the tan lu fault zone during the late cretaceous dextral activation of the tan lu fault zone resulted in pull apart opening of the zhucheng basin which was subsequently deformed by ne sw compression this deformation chronology of the tan lu fault zone and the associated cretaceous basins allow us to constrain the regional kinematic models as related to subduction along the eastern margin of asia or related to collision in the tibet region

the freezing level in the tropical andes peru an indicator for present and future glacier extents along with air temperatures the freezing level height flh has risen over the last decades the mass balance of tropical glaciers in peru is highly sensitive to a rise in the flh mainly due to a decrease in accumulation and increase of energy for ablation caused by reduced albedo knowledge of future changes in the flh is thus crucial to estimating changes in glacier extents since in situ data are scarce at altitudes where glaciers exist above 4800 m above sea level asl reliable flh estimates must be derived from multiple data types here we assessed the flhs and their spatiotemporal variability as well as the related snow rain transition in the two largest glacier covered regions in peru by combining data from two climate reanalysis products tropical rainfall measuring mission trmm precipitation radar bright band data micro rain radar data and meteorological ground station measurements the mean annual flh lies at 4900 and 5010 m asl for the cordillera blanca and vilcanota respectively during the wet season the flh in the cordillera vilcanota lies 150 m higher compared to the cordillera blanca which is in line with the higher glacier terminus elevations coupled model intercomparison project version 5 cmip5 climate model projections reveal that by the end of the 21st century the flh will rise by 230 m 190 m for representative concentration pathway rcp 2 6 and 850 m 390 m for rcp8 5 even under the most optimistic scenario glaciers may continue shrinking considerably assuming a close relation between flh and glacier extents under the most pessimistic scenario glaciers may only remain at the highest summits above approximately 5800 m asl

late jurassic early cretaceous continental convergence and intracontinental orogenesis in east asia a synthesis of the yanshan revolution abstract the basic tectonic framework of continental east asia was produced by a series of nearly contemporaneous orogenic events in the late middle jurassic to early cretaceous commonly the late mesozoic orogenic processes were characterized by continent continent collision large scale thrusting strike slip faulting and intense crustal shortening crustal thickening regional anatexis and metamorphism followed by large scale lithospheric extension rifting and magmatism to better understand the geological processes this paper reviews and synthesizes existing multi disciplinary geologic data related to sedimentation tectonics magmatism metamorphism and geochemistry and proposes a two stage tectono thermal evolutionary history of east asia during the late middle jurassic to early cretaceous ca 170 120 ma in the first stage three orogenic belts along the continental margins were formed coevally at ca 170 135 ma i e the north mongol okhotsk orogen the east paleo pacific coastal orogen and the west bangong nujiang orogen tectonism related to the coastal orogen caused extensive intracontinental folding and thrusting that resulted in a depositional hiatus in the late jurassic as well as crustal anatexis that generated syn kinematic granites adakites and migmatites the lithosphere of the east asian continent was thickened reaching a maximum during the latest jurassic or the earliest cretaceous in the second stage ca 135 120 ma delamination of the thickened lithosphere resulted in a remarkable 120 km lithospheric thinning and the development of mantle derived magmatism mineralization metamorphic core complexes and rift basins the middle jurassic early cretaceous subduction of oceanic plates paleo pacific meso tethys and mongol okhotsk and continent continent collision e g lhasa and qiangtang along the east asian continental margins produced broad coastal and intracontinental orogens these significant tectonic activities marked by widespread intracontinental orogeny and continental reconstruction are commonly termed the yanshan revolution movement in the chinese literature

the western central asian orogenic belt a window to accretionary orogenesis and continental growth abstract the architecture of accretionary orogens is a key to understand continental growth here we present an overview of the orogenic components and their amalgamation in the western central asian orogenic belt caob the caob records the convergence and interactions among various types of orogenic components including the japan type mariana type and alaska aleutian type arc systems as well as the active marginal sequences of the siberia craton which incorporated wide accretionary complexes and accreted arcs and terranes during construction of the caob the kazakhstan arc chain was characterized by multiple subduction whereas the northern fringe of the tarim craton remained mostly as a passive margin the multiple convergence and accretions among these various orogenic components generated huge orogenic collages in the late paleozoic and even in the early triassic involving parallel amalgamation circum microcontinent amalgamation and oroclinal bending the preservation of trapped basins played a significant role in orogenesis with some parts of the oceanic plate being subducted and others behaving as rigid units the orogenesis in the caob was long lived lasting for more than 800 m y involving multiple subduction and long continuous accretion and featuring the complexity of accretionary orogenesis and continent growth

glacier change in western north america influences on hydrology geomorphic hazards and water quality the glaciers of western canada and the conterminous united states have dominantly retreated since the end of the little ice age lia in the nineteenth century although average rates of retreat varied from strong in the first half of the twentieth century with glaciers stabilizing or even advancing until 1980 and then resuming consistent recession this retreat has been accompanied by statistically detectable declines in late summer streamflow from glacier fed catchments over much of the study area although there is some geographical variation over recent decades glaciers in northwest bc and southwest yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat and glacier fed streams in that region have experienced increasing flows in many valleys glacier retreat has produced geomorphic hazards including outburst floods from moraine dammed lakes mass failures from oversteepened valley walls and debris flows generated on moraines in addition to these hydrologic and geomorphic changes evidence is presented that glacier retreat will result in higher stream temperatures possibly transient increases in suspended sediment fluxes and concentrations and changes in water chemistry with climate projected to continue warming over the twenty first century current trends in hydrology geomorphology and water quality should continue with a range of implications for water resources availability and management and hydroecology particularly for cool and cold water species such as salmonids copyright 2008 john wiley sons ltd

importance of longwave emissions from adjacent terrain on patterns of tropical glacier melt and recession tropical glaciers constitute an important source of water for downstream populations however our understanding of glacial melt processes is still limited one observed process that has not yet been quantified for tropical glaciers is the enhanced melt caused by the longwave emission transfer here we use high resolution surface temperatures obtained from the thermal infrared imagery of the cuchillacocha glacier in the cordillera blanca peru in june 2014 to calculate a margin longwave flux this longwave flux reaching the glacier margin from the adjacent exposed rock varies between 81 and 120 w m 2 daily this flux is incorporated into a physically based melt model to assess the net radiation budget at the modeled glacier margin the simulation results show an increase in the energy available for melt by an average of 106 w m 2 during the day when compared with the simulation where the lw margin flux is not accounted for this value represents an increase in ablation of 1 7 m at the glacier margin for the duration of the dry season this study suggests that including the quantification of the glacier margin longwave flux in physically based melt models results in an improved assessment of tropical glacier energy budget and meltwater generation

pattern and kinematic polarity of late mesozoic extension in continental ne asia perspectives from metamorphic core complexes 1 late mesozoic extension in ne asia resulted in the development of a large extensional province metamorphic core complexes mccs are the major features in this province and have 40ar 39ar ages of 130 110 ma for the mylonites and u pb zircon ages of 150 110 ma for the integral granitic intrusions based on this and previous studies this paper summarizes major characteristics of these mccs and recognizes a regional kinematic shear sense most mccs in the transbaikalia region sino mongolia border tract and the northwest central portion of the north china craton ncc show a top to the southeast se shear whereas those in the eastern and southern ncc locally underwent top to the northwest nw shear the three largest basins songliao huabei and ordos in north china are located in the transitional zone between domains of opposing shear sense we interpret the extension in the transbaikalia sino mongolia tract and northwestern part of the ncc to reflect late orogenic collapse of thickened crust following middle late jurassic collision along the okhotsk suture the southeastward extension is probably controlled by crustal scale top to the se tangential shear the transition from contraction to extension is marked by detachment faults that nucleated as extensional crenulation cleavage ecc i e c in sub horizontal ductile shear zones late in orogenic crustal thickening the combined effect of gravitational loading and thermal uplifting is considered to be the origin of the late or post orogenic collapse the top to the nw extension in the ne of the ncc might reflect antithetic sub extensional zones or mesozoic back arc extension as a far field effect of cretaceous pacific plate subduction

assembling north china craton within the columbia supercontinent the role of double sided subduction abstract an evaluation of recent s wave receiver functions s wave velocities and two versions of p wave tomographic images along various transects in the north china craton provides some clues on the subduction collision history of the different crustal blocks and their final amalgamation within the paleoproterozoic columbia supercontinent interpretation of a n s seismic section of the craton suggests thick slab debris sinking to various depths in the mantle the w e seismic corridors show the preservation of a thick 200 km lithospheric root tectosphere beneath the ordos block and its variable and extensive erosion towards the yanliao block eastern block this zone is characterized by layers with marked velocity contrast and suggests repeated stacking of the remnants of underplated and accreted paleoproterozoic oceanic lithosphere the present day lithosphere asthenosphere boundary beneath this region probably marks the erosional plane along which decratonization occurred through subduction erosion from the east and thermal and material erosion by upwelling asthenosphere from below resulting in the partial destruction of the tectosphere and its thinning towards the east within the asthenosphere below the yanliao block younger and thinner slabs predominate in the absence of any prominent thick high velocity layers these younger slabs define a westward polarity and constitute a mega scale duplex formed by underplating through phanerozoic subduction process particularly the pacific plate subduction from the east the lithologic associations within the inner mongolia suture zone dividing the yinshan block to the north and ordos block to the south correspond to an accreted ocean plate stratigraphic sequence with the tonalite trondhjemite granodiorite ttg gneisses charnockites and calc alkaline granites representing a continental arc built up through subduction from the north the seismic transects bring out a contrasting polarity in the subduction regime with an oblique east to southward subduction of the yinshan block and a westward subduction of the yanliao block here i propose a double sided subduction history for the ncc similar to the ongoing subduction process in the western pacific such double sided subduction is considered to promote rapid amalgamation of continental fragments within supercontinents and the subduction polarities and mantle dynamics of ncc are therefore considered to be critical in evaluating the final assembly of the paleoproterozoic supercontinent columbia

continuous profiles of electromagnetic wave velocity and water content in glaciers an example from bench glacier alaska usa we conducted two dimensional continuous multi offset georadar surveys on bench glacier south central alaska usa to measure the distribution of englacial water we acquired data with a multichannel 25 mhz radar system using transmitter receiver offsets ranging from 5 to 150 m we towed the radar system at 5 10 km h 1 with a snow machine with transmitter receiver positions established by geodetic grade kinematic differentially corrected gps nominal 0 5 m trace spacing for radar velocity analyses we employed reflection tomography in the pre stack depth migrated domain to attain an estimated 2 velocity uncertainty when averaged over three to five wavelengths we estimated water content from the velocity structure using the complex refractive index method equation and use a three phase model ice water air that accounts for compression of air bubbles as a function of depth our analysis produced laterally continuous profiles of glacier water content over several kilometers these profiles show a laterally variable stratified velocity structure with a low water content 0 0 5 shallow layer 20 30 m underlain by high water content 1 2 5 ice

structure of hood lake syenite an undeformed archean pluton in the western superior province southern canadian shield abstract the hood lake syenite is a late archean pluton that has escaped significant tectonic deformation the intrusive contact dips inward in most localities which provides some constraint of its three dimensional geometry the pluton has a concordant planar fabric of perthite megacrysts and could have grown by mature diapirism mushrooming as well as by in situ ballooning only magmatic diapirism seems to be capable of explaining the heart like map pattern of the pluton and its location at the junction of two vertical zones of weakness a regional fault and a ductile shear zone

emplacement kinematics of a granite diapir the chindamora batholith zimbabwe the geometric features of a large 50 40 km granitic batholith and its surrounding greenstone belt envelope are described the batholith is made up of several intrusive components and an intrusion sequence based on contact relations and xenoliths has been established the igneous rocks show a local foliation s fabric and preferred orientation of minerals the intensity of this fabric accords with the finite strain determined from xenolith shape analysis when the strain variations are analysed in detail it appears that the batholith was built up by a succession of magmatic pulses each of which led to a stretching of the previously consolidated igneous material so called balloon tectonics evidence is presented that xenolith deformation commences only when the surrounding igneous material has crystallized and a method is suggested whereby the position of the surface separating crystal supported phase plastic behaviour from melt supported phase liquid behaviour at different stages in the plutonic history can be determined ductile shear zones are present and their geometry accords well with the shape changes necessary to allow the outer parts of the pluton to stretch

the physical basis of glacier volume area scaling ice volumes are known for only a few of the roughly 160 000 glaciers worldwide but are important components of many climate and sea level studies which require water flux estimates a scaling analysis of the mass and momentum conservation equations shows that glacier volumes can be related by a power law to more easily observed glacier surface areas the relationship requires four closure choices for the scaling behavior of glacier widths slopes side drag and mass balance reasonable closures predict a volume area scaling exponent which is consistent with observations giving a physical and practical basis for estimating ice volumes glacier volume is insensitive to perturbations in the mass balance scaling but changes in average accumulation area ratios reflect significant changes in the scaling of both mass balance and ice volume

on granitoid emplacement and related structures a review granitoid magmas are emplaced at the upper crust under a complex interaction of gravitational processes and horizontal tectonics natural intrusive bodies show a wide variety of structural patterns that must be strongly related with their dynamic history of ascent and emplacement comparisons of natural structural patterns with experimental and numerical models are necessary to interpret in a coherent fashion the emplacement mechanism involved from natural experimental numerical and theoretical considerations one can reach important conclusions on the problem of ascent and final emplacement of granitoid magmas in the earth s crust the present paper reviews the principal emplacement mechanisms referred to in the literature that is doming diapirism ballooning stoping cauldron subsidence and dike propagation dike propagation is the most effektive process in magma transport from deep zones in the crust and upper mantle extensional fractures for dike propagation and magma ascent can be developed at depth in the crust according to the modern dike propagation theory in orogenic domains magmas reach the upper crust through narrow channels or dikes and are accumulated in a final reservoir in the form of a discordant supracrustal pluton or a ballooning pluton if during emplacement any regional deformation acts simultaneously

emplacement of synkinematic plutons in the variscan odenwald germany controlled by transtensional tectonics in the odenwald area sw germany an intermediate level of variscan magmatic arc is exposed between 360 and 335 ma the neunkirchen intrusive complex intruded into an active ne sw trending zone of ductile divergent strike shear after the thermal peak of metamorphism but before the emplacement of the magmatic rocks shear zones developed in the wall rocks the microfabrics of these zones infer plastic deformation of feldspar hornblende and quartz and an increasing degree of postkinematic annealing towards the intrusive complex during emplacement and solidification the magmatic rocks experienced bulk strain the intrusive complex locally crosscut the shear zones of the wall rocks but show magmatic and also mylonitic foliations which parallel these zones a change from plastic to brittle behavior of feldspar and amphibole and a varying degree of postkinematic annealing of quartz suggest that in the intrusive complex strike shear continued during cooling in wall rocks and plutonic rocks kinematic indicators imply sinistral displacement in the wall rocks adjacent to the intrusive complex strike shear was combined with normal displacement this suggests that a component of horizontal extension which was associated with strike shear transtension facilitated ascend and emplacement of the magma transtension occurred at the same time when the schwarzwald vosges area in the south of the odenwald was subjected to nw se compression transtension was probably initiated by lateral escape of crustal fragments during overall convergent plate movements transtension is also supposed to be associated with significant uplift of metamorphic rocks

impact of spatial spectral and radiometric properties of multispectral imagers on glacier surface classification abstract using multispectral remote sensing glacier surfaces can be classified into a range of zones the properties of these classes are used for a range of glaciological applications including mass balance measurements glacial hydrology and melt modelling however it is not immediately evident that multispectral data should be optimal for imaging glaciers and ice caps thus this investigation takes an inverse perspective taking into account spectral and radiometric properties in situ spectral reflectance data were used to simulate glacier surface response for a suite of multispectral sensors sensor simulated data were classified and compared in addition airborne multispectral imagery was classified for a range of spatial resolutions and intercompared in three different ways in these analyses the most important property which determined the suitability of a multispectral imager for glacier surface classification was its radiometric range i e gain settings low resolution imagery 250 m pixels is too coarse to represent the true complexity present on a glacier while medium resolution imagery 60 m 30 m or 20 m accurately represented the results derived from high resolution airborne imagery of those studied here the satellite imagers currently in use that are most suitable for glacier surface classification are landsat tm etm and aster each with particular gain settings both sentinel 2 and the oli on landsat 8 are also expected to be similarly qualified landsat mss is also found to be radiometrically well suited for glacier surface classification but its lower spatial resolution makes it a secondary selection

late mesozoic compressional to extensional tectonics in the yiwulushan massif ne china and its bearing on the evolution of the yinshan yanshan orogenic belt part i structural analyses and geochronological constraints abstract with a cratonic nucleus the north china craton ncc experienced a complex tectonic evolution with multiphase compressional and extensional events during mesozoic times along the northern part of the ncc the yinshan yanshan fold and thrust belt was a typical intraplate orogen jurassic and cretaceous continental sedimentation magmatism widespread intraplate characterize the yinshan yanshan orogenic belt the geodynamic significance of these tectonic events is still in dispute in the western part of the liaoning province the yiwulushan massif crops out at the eastern end of the yinshan yanshan orogenic belt the yiwulushan massif presents an elliptical domal shape with a ne sw striking long axis the structural evolution of this massif brings new insights for the understanding of the mesozoic plutonic tectonic history of the ncc a multidisciplinary study involving structural geology geochronology anisotropy of magnetic susceptibility ams and gravity modeling have been carried out the presentation of the new results splits into two parts part i this paper deals with field and laboratory structural observations and presents the main geochronological results the ams gravity modeling data will be provided in a companion paper part ii the early compressional deformation d1 corresponds to a late jurassic to early cretaceous southward thrusting the subsequent deformation is related to the early cretaceous exhumation of the yiwulushan massif a detailed structural analysis allows us to distinguish several deformation events d2 d3 and d4 the cretaceous extensional structures such as syntectonic plutons bounded by ductile normal faults metamorphic core complexes and half graben basins are recognized in many places in east asia these new data from the yiwulushan massif constitute a link between transbaikalia mongolia north china and south china indicating that nw se extensional mesozoic tectonics occurred throughout the entire region

tropical glacier meltwater contribution to stream discharge a case study in the cordillera blanca peru original abstract discharge measurements climate observations and hydrochemical samples gathered monthly 1998 99 in the yanamarey and uruashraju glacier fed catchments of the cordillera blanca peru permit an analysis of the glacier meltwater contribution to stream flow these glacier catchments feed the rio santa which discharges into the pacific ocean based on a water balance computation glacier melt contributes an estimated 35 of the average discharge from the catchments for comparison a volumetric end member mixing model of oxygen isotopes shows glacier melt contributes 30 45 to the total annual discharge based on stream geochemistry discharge from the yanamarey glacier catchment provides 30 of the annual volume discharged from the querococha watershed which is 10 glacierized by analogy the larger rio santa watershed also 10 glacierized receives at least 12 of its annual discharge from melting glacier ice tributary watersheds to the rio santa with larger fractions of glacier cover have less variable runoff and enhanced discharge demonstrating that the glaciers effectively buffer stream discharge seasonally with continued glacier melting stream flow will likely become more variable and there will be less dry season runoff

salt stocks as natural analogues of archaean gneiss diapirs the internal structures of salt stocks in the hannover region northwestern germany are natural analogues of structures in major archaean gneiss diapirs of western ontario a major lithological interface within rather than at the stratigraphic top of the zechstein evaporites corresponds to the transitional contact between leucocratic gneiss and mantling rocks the cuspate geometry of the end region of supracrustal synclines greenstone belts a feature commonly cited in favour of cross folding can be readily explained by analogy with comparable evaporite structures

strain patterns of crescentic granitoid plutons in the archean greenstone terrain of ontario abstract granitoid plutons of crescentic outcrop pattern in the archean terrain of northwestern ontario are dominated by constrictive strains that are interpreted to be due to intrusion rather than regional deformation the strain patterns of antiformal plutons are characterized by subvertical lineations in contrast the strain patterns of synformat plutons are characterized by subhorizontal lineations presumably only the last flow increments were recorded by the deformed mineral aggregates employed as strain gauges and occurred when the granitoid magma was largely crystalline simple kinematic models are capable of explaining many but not all elements of the natural strain patterns

horizontal cleavage in southeastern sinai the case for a coaxial strain history abstract a horizontal cleavage and associated lineation are developed in a low pressure igneous related metamorphic terrain in southestern sinai the cleavage is axial planar to recumbent folds which are never large and varies from a smooth slaty cleavage to a discrete crenulation cleavage structural evidence on the macro meso and microscales suggests that cleavage and lineation were formed during irrotational extension and not by simple shear estimates of strain using the march method indicate 50 70 vertical shortening this structural evidence when combined with metamorphic and age data strongly suggests that the cleavage was formed by the forceful emplacement of a pluton at depth

diagnosing the imbalance of glaciar santa rosa cordillera raura peru for glaciar santa rosa in the cordillera raura peru the extent and volume are determined for 1980 and 1961 from topographic mapping and for two undated earlier stages lme and max from moraines the regime of the glacier in terms of ice flow and mass balance is evaluated for the 1977 83 period more than half of the water discharge from the glacier is not renewed by precipitation but supplied by the ice thinning the rate of surface lowering of 2 m a 1 liquid water equivalent corresponds to an energy amount for melting of 22 w m 2 sensitivity analyses of glaciar yanamarey in the nearby cordillera blanca show that such a decrease of energy available for melting could be produced by a cloudiness increase of one tenth an air temperature decrease of more than 2 c a decrease in specific humidity of 1 g kg 1 or some combination of heat budget processes such changes in the atmospheric environment would be required to stabilize the glacier at its recent volume as another indication of the recent imbalance the maximum volume flux is found about 100 m below the equilibrium line altitude under continuation of recent climatic conditions the glacier may disappear within a few decades these inferences corroborate a recent assessment for the neighboring cordillera blanca

deformation of the archean quetico shebandowan subprovince boundary in the canadian shield near kashabowie northern ontario the southern boundary of the quetico metasedimentary subprovince of the superior province of the canadian shield near kashabowie ontario is a vertical east west feature affected by dextral transpression that had a north northwest south southeast compressional component a synmetamorphic locally d1 microfabric and magnetic susceptibility fabric with an east directed extension lineation is kinematically compatible with this pattern it shows the same bedding cleavage relationship and the same direction of structural facing on d1 in both the quetico metasediments and the shebandowan greenstone subprovince on the south side of the quetico subprovince in the low grade rocks of the study area there is a single phase of penetrative deformation giving a nearly vertical schistosity at a consistent angle anticlockwise with respect to the now nearly vertical east west striking strata the absence of penetrative polyphase deformations may be due to the near parallelism of the subprovince boundary with the s

post rift geodynamics of the songliao basin ne china origin and significance of t11 coniacian unconformity abstract the t11 unconformity lies between the qingshankou and yaojia formations in the post rifting sequence of the cretaceous songliao basin ne china it is intimately associated with petroleum reservoirs and considered to be a disconformity forming in the tectonic quiet stage we present the interpretations from new seismic surveys and cored sections of the cretaceous continental scientific drilling borehole ccsd sk 1 in order to resolve the nature and origin of t11 unconformity the t11 is often a low angle unconformity with underlying qingshankou formation having been deformed and eroded prior to deposition of the yaojia formation in the post rift evolution of the basin it marks an abrupt change from a deep lake to shallow lake or subaerial environment documented by reddening of the lacustrine mudstone extinction of the ostracod assemblages and a great increase of coarse detrital inputs the sharp change of depositional environment the truncation of gentle folds and the cluster of volcanic and paleoearthquake activities all happened simultaneously immediately before the development of t11 unconformity indicating a significant regional compressional uplift event in the basin the timing of the t11 unconformity formation is within the interval 88 86 2 ma correlations with coeval unconformities in other cretaceous sedimentary basins in eastern asia indicate that this compressional uplift coincided with an episode of global plate reorganization between the eurasian and paleo pacific plates that culminated at 88 87 ma during this short interval the northeast asian margin in eastern china south korea japan and russian far east experienced widespread violent volcanic and granite emplacement activity triggered by compression resulting from rapid and orthogonal slab subduction the post rift basin tectonic inversion occurred during t11 coniacian time thereafter the basin again evolved in an extension regime two subsidence phases in post rift history took place as the direct consequence of coniacian compression peak which defined the distribution of oil sources and reservoirs

measuring glacier surface temperatures with ground based thermal infrared imaging spatially distributed surface temperature is an important yet difficult to observe variable for physical glacier melt models we utilize ground based thermal infrared imagery to obtain spatially distributed surface temperature data for alpine glaciers the infrared images are used to investigate thermal microscale processes at the glacier surface such as the effect of surface cover type and the temperature gradient at the glacier margins on the glacier s temperature dynamics infrared images were collected at cuchillacocha glacier cordillera blanca peru on 23 25 june 2014 the infrared images were corrected based on ground truth points and local meteorological data for the control points the pearson s correlation coefficient between infrared and station temperatures was 0 95 the ground based infrared camera has the potential for greatly improving glacier energy budget studies and our research shows that it is critical to properly correct the thermal images to produce robust quantifiable data

some guidelines for the practical application of fry s method of strain analysis abstract a systematic analysis of patterns in artificial and natural point distributions is presented in order to demonstrate how the nature and degree of anticlustering of point distributions affect the character of fry diagrams derived from them ideally anticlustered artificial point distributions illustrate the nature of the dependence between the degree of anticlustering and the minimum number of points required in such a distribution if it is to reveal strain accurately by fry s method in addition these distributions provide straightforward results which aid in the interpretation of less ideally anticlustered natural point distributions the results from the artificial distributions may be used to estimate the minimum number of points required for strain determination in natural distributions of varying degrees of anticlustering as long as the anticlustering is sufficiently strong however application of the results from the artificial distributions to less strongly anticlustered natural point distributions shows not only that the existence of a vacancy field is an insufficient criterion for determining whether or not fry s method is appropriate for strain determination but also that the nature of the anticlustering in these natural distributions limits the effectiveness of enhancing strain definition by increasing the number of points composing the distribution

structural and stratigraphical constraints on the kinematics history of the southern tan lu fault zone during the mesozoic anhui province china abstract the tan lu fault zone tlfz extends in a nne ssw direction for more than 2000 km in eastern china it has been considered either as a major sinistral strike slip fault as a suture zone or as a normal fault we have conducted a structural analysis of the southern segment of this fault zone stlfz in the anhui province the ages triassic to palaeocene of the formations affected by the faults have been re appraised taking into account recent stratigraphical studies to better constraint the ages of the successive stages of the kinematics of the stlfz subsequently the kinematics of the faults is presented in terms of strain stress fields by inversion of the striated fault set data finally the data are discussed in the light of the results obtained by previous workers we propose the following history of the stlfz kinematics during the mesozoic at the time of collision a nne orientated tan lu margin probably connected two margins located north of the dabie and sulu collision belts during the middle late triassic the scb has been obliquely subducted below the ncb along this margin which has acted as a compressional transfer zone between the dabie and sulu continental subduction zones the stlfz has been initiated during the early jurassic and has acted as a sinistral transform fault during the jurassic following which the ncb scb collision stopped a nw trending extension related to metamorphic domes was active during the basal early cretaceous 135 130 ma it has been followed by a nw se compression and a ne sw tension during the middle late early cretaceous 127 to 105 ma possibly 95 ma at that time the tlfz was a sinistral transcurrent fault within the eastern part of the asian continent during the late cretaceous palaeocene the stlfz was a normal fault zone under a wnw ese tension

climatic warming glacier recession and runoff from alpine basins after the little ice age maximum records of discharge of rivers draining alpine basins with between 0 and 70 ice cover in the upper aare and rhone catchments switzerland for the period 1894 2006 have been examined together with climatic data for 1866 2006 with a view to assessing the effects on runoff from glacierized basins of climatic warming coupled with glacier recession following the little ice age maximum annual runoff from ice free basins reflects precipitation variations rising from minima between 1880 and 1910 to maxima between the late 1960s and early 1980s the more highly glacierized the basin the more runoff mimicked mean may september air temperature during two periods of warming runoff increased gradually from the 1900s rapidly in the 1940s before decreasing to the late 1970s rising runoff levels during the second warming period failed to exceed those attained during the first despite higher summer temperatures although temperatures continued to rise discharge from glacierized basins declined after reaching maxima in the late 1980s to early 1990s in the first warming period rising specific melt rates augmented by increasing precipitation opposed the impact of declining glacier area on runoff although melt continued to increase in the second period enhanced melting even in the exceptionally warm summer of 2003 appears to have been insufficient to offset reducing glacier surface area exposed to melt low or reducing levels of precipitation and increasing evaporation thus runoff from glacierized basins peaked in the late 1940s to early 1950s

recognition of pervasive prestrain in the total strain pattern of large folds abstract two methods are introduced for identifying states of pervasive prefold strain in the total strain field of large domes or basins the first method relies on the symmetry rule and is restricted to structures in which the planes of effective symmetry of the total strain field are non coincident with those of the fold form the second method seeks to demonstrate the existence of a strain induced anisotropy foliation or lineation prior to upright folding and utilizes narrow decollement zones within homogeneous rock units of domes or basins the methods are applied to large oval structures in two precambrian gneiss terranes of ontario

rapid change from compression to extension in the north china craton during the early cretaceous evidence from the yunmengshan metamorphic core complex abstract the yunmengshan metamorphic core complex ymmcc is situated in the northern part of the eastern north china craton ncc the main structures in the ymmcc area include the arcuate sihetang shear zone shtsz and the ne striking shuiyu shear zone sysz we present structural and geochronological evidence to show that the shtsz was a top to the ssw thrusting zone formed between 140 and 137 ma the sysz is an extensional top to the se shear zone developed between 131 and 114 ma in association with intense magmatism and the development of the huairou rifted basin in the hanging wall ductile shearing on the sysz was followed by isostatic rebound from 114 ma to the end of the early cretaceous and then was replaced by brittle normal faulting the normal displacement on the sysz and subsequent isostatic rebound led to the formation of the ymmcc the mechanism of formation is consistent with a rolling hinge model of detachment faulting and core complex formation the structural evolution of the yunmengshan area in common with the whole eastern ncc thus records a rapid switch from a nne ssw shortening regime to a nw se extension one in the earliest cretaceous the intense nw se extension of the early cretaceous as recorded by the ymmcc was associated with peak lithospheric thinning in the eastern ncc we attribute the shortening to the final closure of the mongol okhotsk ocean between the siberian craton and the north china south mongol block and the extension to the back arc deformation related to the subduction of the izanagi plate in the pacific ocean we suggest that the yunmengshan area illustrates how back arc compression can be driven by the overriding plate motion while connection of the overriding plate to a larger continent favors subduction related back arc extension

diagnosing the imbalance of yanamarey glacier in the cordillera blanca of peru a detailed glaciological observation program was conducted on the yanamarey glacier in the cordillera blanca of peru including the monitoring of net balance and ice flow velocity during 1977 1988 and mappings of the surface topography in 1973 1982 and 1988 these observations are here evaluated to combine net balance surface lowering and ice flow into a consistent picture of the mode of operation of a tropical glacier on the scale of a decade the glacier extends between 5100 and 4500 m with a total area of 9 105 m2 and length of about 1 3 km maximum flow velocity is 17 4 m yr 1 and maximum volume flux 336 103 m3 yr 1 in the ablation area net balance is about 6 m yr 1 and surface lowering 3 m yr 1 about half of the mean annual water discharge from the glacier of 80 l s 1 is not renewed by precipitation but supplied by the ice thinning the rate of surface lowering of 1 5 m yr 1 liquid water equivalent translates to a glacier average departure heat supply for melting of 16 w m 2 sensitivity analyses indicate that this could be produced by a cloudiness increase of less than one tenth an air temperature decrease of 2 c an increment in specific humidity of less than 1 g kg 1 or some combination of heat budget processes such changes in the atmospheric environment would be required to stabilize the glacier at its recent volume as another indication of the recent imbalance the maximum volume flux is found some 100 m below the equilibrium line altitude under continuation of the recent climatic conditions the glacier may survive for more than half a century

a cleavage triple point and its meso scopic structures the mustio sink svecofennides of sw finland abstract a cleavage triple point ctp structure is analyzed located at the west side of the mustio gneiss dome in the svecofennides of southwest finland the presence of the ctp and the pattern of mesoscopic fold structures exclude the origin of the mustio dome by successive interference of fold phases the highly variable deformation structures are explained in a single phase deformation model by using the theoretical specific strain environments of a ctp these environments are 1 horizontal oblation on top of a dome 2 transition from horizontal to vertical oblation on the flanks of a dome and 3 vertical constriction in the center of the ctp it is shown that each strain environment is associated with specific development of foliation folds mesoscopic fold interference and strain intensity the theoretical strain environments are confirmed by strain analysis

emplacement of an archean gneiss dome northern ontario canada inflation inferred from magnetic fabrics 1 previous field structural studies of the ash bay gneiss dome revealed an upward convex foliation with an integral east west lineation defined by a quartzo felspathic matrix unfortunately the amphibolite facies gneisses lack traditional indicators of microfabric evolution such as kinematic indicators so that it is difficult to relate the foliation s orientation distribution to an emplacement mechanism for the dome fortunately anisotropy of magnetic susceptibility isolates a distinct microfabric because of the preferred orientation of high susceptibility accessory magnetite the magnetite subfabric developed late in the metamorphic crystallization history and its magnetic foliation and magnetic lineation are similarly oriented to the s l fabric of the quartz feldspar matrix however the magnetite foliation dips less steeply and forms a less convex domal surface than the field schistosity the metamorphic schistosity and the magnetite foliation thus isolate the domal deflection at different stages confirming the inflation and upward motion of the ash bay diapir during the closing stages of amphibolite facies metamorphism

decadal changes in glacier parameters in the cordillera blanca peru derived from remote sensing we present spatial patterns of glacier fluctuations from the cordillera blanca peru glacier area terminus elevations median elevations and hypsography at decadal timescales derived from 1970 aerial photography 2003 spot5 satellite data geographic information systems gis and statistical analyses we derived new glacier outlines from the 2003 spot images and ingested them in the global land and ice measurements from space glims glacier database we examined changes in glacier area on the eastern and western side of the cordillera in relation to topographic and climate variables temperature and precipitation results include 1 an estimated glacierized area of 569 6 21 km 2 in 2003 2 an overall loss in glacierized area of 22 4 from 1970 to 2003 3 an average rise in glacier terminus elevations by 113 m and an average rise in the median elevation of glaciers by 66 m showing a shift of ice to higher elevations especially on the eastern side of the cordillera and 4 an increase in the number of glaciers which indicates disintegration of ice bodies annual air temperature showed a significant upward trend in the last 30 years with larger temperature increases at lower elevations there was a slight but not significant decrease in precipitation our results are consistent with glacier retreat and warming trends noted in the last three decades in the tropics

timing of magmatism and deformation in the kamiskotia kidd creek area western abitibi subprovince canada abstract the kamiskotia kidd creek area comprises well preserved granitoid greenstone belt lithologies of the western most abitibi subprovince similar in composition and structural style to other late archean granitoid greenstone terranes e g kalgoorlie norseman western australia belingwe zimbabwe slave province canada it contains the kidd creek volcanogenic massive sulfide deposit and lesser deposits of the kamiskotia district and lode gold deposits associated with the destor porcupine fault zone near the prolific porcupine gold district the magmatic and tectonic history for the area is provided through detailed structural mapping and high precision u pb geochronology field observations support the following sequence of magmatic and structural events in the kamiskotia area 1 formation of older mafic and intermediate volcanic rocks followed by the emplacement of the kamiskotia gabbroic complex kgc and cogenetic massive sulfide bearing bimodal volcanic rocks kv also accompanied by coeval intrusion of granitoid a into the crystallizing kgc 2 regional bulk rotation about a sub horizontal axis of this stratigraphy to form a ne facing monocline 3 emplacement of three large granitoid intrusions imparting their respective contact strain aureoles on the stratigraphy 4 regional sub horizontal bulk north south shortening that formed a non penetrative east west flattening fabric with an element of 5 late dextral transpression that formed high strain zones related to western destor porcupine fault zone dpfz within less competent volcanic units and 6 emplacement of alkalic dikes associated with the late stages of transpressive deformation u pb ages help substantiate this chronology and aid in the correlation of kamiskotia lithologies across the southern abitibi subprovince zircon ages for the kgc and a kamiskotia rhyolite are 2707 2 ma and 2705 2 ma respectively these ages are coeval with the reid rhyolite with a zircon age of 2706 2 ma but are significantly younger than the kidd creek rhyolite and the prosser rhyolite with zircon ages of 2717 2 ma data refined by the addition of an abraded concordant analysis and 2716 6 3 ma respectively two of the granitoid intrusions have zircon ages of 2696 1 5 and 2694 4 ma the older granitoid intrusion has a titanite population with a 207 pb 206 pb minimum age of 2692 5 ma which may represent a protracted cooling history or a metamorphic event after the setting of the zircon u pb system two zircon fractions from the younger granitoid intrusion exhibit inheritance with 207 pb 206 pb minimum ages up to 2926 ma indicating the presence of significantly older crust in this region timing of north south compression and late transpression may be constrained by a u pb garnet titanite age on a late to post tectonic alkalic dike at 2687 3 ma

using atmospherically corrected landsat imagery to measure glacier area change in the cordillera blanca peru from 1987 to 2010 abstract the dynamic tropical glaciers of the peruvian cordillera blanca are rapidly changing and these changes are expected to affect water availability especially during the dry season in this study we quantify recent changes to these water reservoirs providing estimates of glacier area in the cordillera blanca and sub watersheds of the rio santa for the following years 1987 1996 2004 and 2010 we explore the effects of atmospheric and topographic corrections by comparing debris free glacier area estimates generated using raw scenes and corrected scenes our results suggest that these corrections can have a significant impact on debris free glacier area estimates when the same threshold is applied debris free glacier area estimates derived from uncorrected scenes are approximately 5 less than debris free glacier area estimates derived from atmospherically corrected scenes we determined that debris free glacier area estimates are most sensitive to the choice of threshold and topographic effects to map glacier area change we used high resolution satellite imagery to calibrate our selection of a single threshold for the normalized difference snow index ndsi this threshold value was applied to all ndsi images which were derived from four carefully selected and atmospherically corrected landsat thematic mapper tm scenes acquired at the end of the dry season in order to calculate total glacier area we manually mapped debris covered glaciers because automated methods were unsuccessful in this region as of august 2010 the cordillera blanca had a total glacier area of 482 km 2 which amounts to a 25 decrease since 1987 glaciers in the southern portions of the cordillera blanca which have lower median elevations on average lost a greater percentage of their area from 1987 to 2010 relative to their northern counterparts overall glacier area change in the cordillera blanca appears to be accelerating between 2004 and 2010 glaciers in the cordillera blanca lost area at a rate that was approximately 3 5 times the average rate of area loss from 1970 to 2003

mass balance of glaciar zongo bolivia between 1956 and 2006 using glaciological hydrological and geodetic methods the longest continuous glaciological mass balance time series in the intertropical zone of south america goes back to 1991 on glaciar zongo bolivia photogrammetric and hydrological data have been used to i check the specific net balance over long periods and ii extend the mass balance time series over the last 50 years these data reveal a bias in the glaciological mass balance which can be explained by the field measurement sampling network our study shows a large temporal variability of the surface mass balances in the ablation area and reveals strong relationships between independent surface mass balance data coming from selected ablation areas with numerous data it demonstrates the very large contribution 80 of low elevation ranges one third of the surface to the specific mass balance and consequently the importance of the reduction of the area of the tongue with these new results glaciar zongo offers the longest and most accurate mass balance series in any andean country the dataset shows that glaciar zongo experienced a relatively steady state over the period 1956 75 with even a slight mass gain over 1963 75 and a rapid and continuous decrease since then

variations of slab dip and overriding plate tectonics during subduction insights from analogue modelling we present small scale laboratory models of oceanic subduction in which plates motion is imposed by lateral boundary conditions the oceanic plate moves trenchward at constant speed and subducts below a fixed overriding plate in this configuration the long term process of subduction is not steady state slab interaction with the upper mantle lower mantle boundary results in periods of slab flattening during which the dip of the slab diminishes followed by periods of slab steepening the overriding plate tectonic regime is influenced by the dynamics of subduction slab anchoring favouring trench perpendicular shortening when the slab is anchored slab flattening further favours shortening while slab steepening favours extension or smaller shortening rates non steady state long term subduction may explain part of the variability of slab geometries evidenced by statistical analyses of present day subduction zones experiments suggest that despite boundary conditions applied on the converging plates do not change tectonics pulses within the overriding plate may be caused by this non steady state behaviour

finite strain and deformation within the brianconnais castelvecchio cerisola nappe of the ligurian alps italy abstract the structural history of the castelvecchio cerisola brianconnais nappe ligurian alps italy was dominated by a southwestward overthrust shear that resulted in isoclinal folding and schistosity lineation fabric development within the nappe this deformation was due to the intracontinental shortening related to the collision of the european and adriatic plates during late cretaceous eocene times finite strain produced during the isoclinal folding and the schistosity lineation fabric development was determined from quartzites conglomerates and tuffs using fry s method strain type and intensities are strongly dependent on rock type other factors like the proximity to the major thrusts or the position in relation to the first phase recumbent folds seem to be of secondary importance the quartzites and conglomerates display a constrictional strain or else they approximate to plane strain while the pyroclastic rocks fall into the field of apparent flattening and are characterized by a higher intensity of deformation during nappe emplacement the deformation was not accommodated by simple shear alone the interpretation of strain patterns in the castelvecchio cerisola has led to a model in which longitudinal strain was superposed on layer parallel simple shear schistosity at a low angle to the major thrust faults incremental extension directions deduced from pressure shadows very frequent veins and stylolitic structures parallel to bedding support this hypothesis the data presented here emphasize that subvertical thinning associated with thrust shear and a small extension perpendicular to the emplacement direction occurred in the castelvecchio cerisola nappe

elevation change mass balance dynamics and surging of langjokull iceland from 1997 to 2007 in situ mass balance survey is a joint effort of the glaciology group institute of earth sciences university of iceland and the national power company landsvirkjun we thank philippe crochet and tomas johannesson from the icelandic meteorological office for providing the gridded climate data and for useful discussions about the climatology of langjokull the 2007 lidar data were collected by the uk natural environment research council airborne research and survey facility grant ipy 07 08 additional funding was provided by the united states national science foundation grant no dge 1038596 st catharine s st john s and trinity colleges and the university of cambridge b b roberts and scandinavian studies funds we thank cameron rye for initial help coding the mass balance model

evolution of the yiwulushan metamorphic core complex from distributed to localized deformation and its tectonic implications 1 the yiwulushan metamorphic core complex ysmcc is situated in the northern part of the eastern north china craton ncc that experienced significant lithospheric thinning in an extensional regime during the late mesozoic we present structural and geochronological evidence to show that the ysmcc underwent nne ssw extension in the late jurassic and wnw ese extension in the early cretaceous we show that the ysmcc started with a sub horizontal shear zone referred to as the yiwulushan detachment shear zone ydsz in the late jurassic between 157 and 147 ma with a top to the ssw shear sense the ydsz was subjected to limited doming probably toward the end of its formation the nne striking wnw dipping waziyu normal shear zone wzysz was formed along the western margin of the core complex during the early cretaceous and truncates the earlier ydsz the whole core complex underwent doming in a rolling hinge manner in the end of the latest early cretaceous thereafter the ysmcc was overprinted by brittle normal faults along its western margin in the late cretaceous development of the initially flat lying ydsz is associated with diffuse mid crustal flow whereas the formation of the rolling hinge type wzysz is characterized by localized deformation the late jurassic more diffuse deformation has a rather constant top to the ssw shearing and produced a variety of shear related structures such as recumbent isoclinal folds and transposition foliation the ysmcc evolution also demonstrates that the late mesozoic extension along the northern part of the eastern ncc started as early as the late jurassic rather than the previously proposed early cretaceous

an assessment of basin scale glaciological and hydrological sensitivities in the hindu kush himalaya glacier responses to future climate change will affect hydrology at sub basin scales the main goal of this study is to assess glaciological and hydrological sensitivities of sub basins throughout the hindu kush himalaya region we use a simple geometrical analysis based on a full glacier inventory and digital elevation model to estimate sub basin equilibrium line altitudes elas from assumptions of steady state accumulation area ratios the ela response to an increase in temperature is expressed as a function of mean annual precipitation derived from a range of high altitude studies changes in glacier contributions to streamflow in response to increased temperatures are examined for scenarios of both static and adjusted glacier geometries on average glacier contributions to streamflow increase by 50 for a 1 k warming based on a static geometry large decreases 60 on average occur in all basins when glacier geometries are instantaneously adjusted to reflect the new ela finally we provide estimates of sub basin glacier response times that suggest a majority of basins will experience declining glacier contributions by 2100

polyphase deformation and crustal evolution in the pipestone lake area of the archean wabigoon subprovince superior province canada archean supracrustal rocks in the western wabigoon subprovince superior province canadian shield have undergone four phases of deformation d1 d4 d1 confined to the oldest rocks includes a large refolded reclined isoclinal anticline f1 with moderately developed axial planar cleavage s1 rocks affected by d1 are overlain by a regional unconformity d2 includes post unconformity steeply plunging north northeast south southwest striking isoclinal folds f2 that are approximately coaxial with f1 but have contorted the f1 axial trace d3 is represented by east west striking steeply plunging folds at various scales f3 which occur mainly in rocks near the regional manitou stretch pipestone lake shear zone also interpreted to be a d3 structure d4 is represented by pervasive cleavage s4 locally penetrative but mainly spaced including crenulation cleavage fractures small faults and brittle ductile shears s4 is parallel to the margin of the jackfish lake pluton d1 d3 are ascribed to convergence of the wabigoon subprovince with adjacent subprovinces ending with formation of the manitou stretch pipestone lake shear zone as a presently steep thrust and oblique ramp structure d4 is the result of either diapiric emplacement of the jackfish lake pluton or marginal strain intensification due to the rigidity of the older ash bay dome during late north south compression previously available zircon u pb geochronology provides a maximum age for d1 of 2728 ma and an approximate age for d4 of 2698 ma the unconformity developed between d1 and d2 2725 2713 ma

episodicity of stress state in an overriding plate evidence from the yalu river fault zone east china abstract the ca 700 km long yalu river fault zone yrfz in east china adjacent to the pacific ocean underwent a polyphase evolution during the cretaceous when it controlled the development of rift basins interrupted by several shortening events the east china continent lies in an overriding plate with respect to the subducting paleo pacific plate during the cretaceous the yrfz is ideal for studying the episodicity of stress state in the overriding plate to constrain the polyphase evolution of the yrfz structural observations fault slip data measurements and la icp ms zircon u pb dating on cretaceous volcanic rocks and sandstones were undertaken in this study the first deformation d1 is characterized by sinistral strike slip shear in the earliest cretaceous the d2 event is featured by normal faulting deformation along the fault zone which led to development of rift basins during the rest of the early cretaceous sinistral faulting d3 developed again in the earliest late cretaceous followed by dextral normal faulting d4 and rift basin development during the rest of the late cretaceous and finally reverse dextral faulting d5 at the end of the cretaceous the fault slip data show that compressional directions during d1 d3 and d5 faulting events are n s n s and e w respectively extensional directions during d2 and d4 faulting events are nw se and n s the zircon u pb ages indicate that the early cretaceous basins d2 event controlled by the yrfz were active between 131 and 100 ma and the late cretaceous basins d4 event were active between 97 and 70 ma these u pb ages together with previous geochronological data show that the d1 and d3 episodes of compression each lasted 3 ma d2 extension lasted 31 ma and d4 extension 27 ma these data indicate an episodicity in the stress state with longer periods of extension and shorter periods of compression a slab driven model with relatively long periods of low velocity subduction alternating with shorter periods of high velocity subduction could account for the episodicity of stress state in the overriding plate from d1 to d5

toward hydro social modeling merging human variables and the social sciences with climate glacier runoff models santa river peru summary glacier shrinkage caused by climate change is likely to trigger diminished and less consistent stream flow in glacier fed watersheds worldwide to understand model and adapt to these climate glacier water changes it is vital to integrate the analysis of both water availability the domain of hydrologists and water use the focus for social scientists drawn from a case study of the santa river watershed below peru s glaciated cordillera blanca mountain range this paper provides a holistic hydro social framework that identifies five major human variables critical to hydrological modeling because these forces have profoundly influenced water use over the last 60 years 1 political agendas and economic development 2 governance laws and institutions 3 technology and engineering 4 land and resource use and 5 societal responses notable shifts in santa river water use including major expansions in hydroelectricity generation large scale irrigation projects and other land and resource use practices did not necessarily stem from changing glacier runoff or hydrologic shifts but rather from these human variables ultimately then water usage is not predictable based on water availability alone glacier runoff conforms to certain expected trends predicted by models of progressively reduced glacier storage however societal forces establish the legal economic political cultural and social drivers that actually shape water usage patterns via human modification of watershed dynamics this hydro social framework has widespread implications for hydrological modeling in glaciated watersheds from the andes and alps to the himalaya and tien shan as well as for the development of climate change adaptation plans