piggyback basin development above a thin skinned thrust belt with two detachment levels as a function of interactions between tectonic and superficial mass transfer the case of the subandean zone bolivia abstract the subandean fold and thrust belt of bolivia is characterised by two major detachment levels and large piggyback basins sand box and numerical models have been used to study sedimentation and erosion control on thrust belt evolution and to study the retroactive effects of tectonics on piggyback development in thin skinned thrust belts with two detachment levels analogue models show that surface processes play a dominant role in controlling wedge evolutions erosion promotes fault reactivation and tectonic delamination passive roof duplex while sedimentation promotes forward shifting of the frontal thrust and consequently piggyback basin development numerical models were used to understand the development of the subandean fold and thrust belt of bolivia numerical experiments show that the simultaneity of basement tilting and high sedimentation rates promotes the formation of a stable tectonic wedge outer and inner faults are alternately active during the beginning of deformation a kinematic evolution that favours the development of piggyback basins between the step by step history of the thrust belt predicts that each change in tectonic location is recorded with large unconformities in basins but these unconformities are not well preserved from progressive erosion in the final geometry

kinematic models of fluvial terraces over active detachment folds constraints on the growth mechanism of the kashi atushi fold system chinese tian shan during detachment folding the relationship between differential uplift and shortening depends on the mechanism of fold growth such as limb rotation or hinge migration and may vary over the lifetime of a fold thus neither long term shortening rates nor the present fold geometry unambiguously constrain the kinematics of fold growth where rivers cut through growing anticlines flights of abandoned fluvial terraces act as passive kinematic markers as shortening progresses the terraces become deformed and thereby preserve critical information about the kinematics and evolution of active fold growth to constrain recent fold growth across three detachment folds in the kashi atushi fold system in the sw tian shan china we surveyed flights of deformed terraces and compared them with geometric models of successively emplaced horizontal unconformities terraces across pregrowth strata deformed by hinge migration limb rotation and a combination of the two migration of angular hinges and curved hinge zones were also compared each kinematic model predicts both a distinct geometry for the deformed terraces and contrasting angular relationships between the terraces and the pregrowth strata notably limb rotation and migration of curved hinge zones result in progressively rotated terraces that cut across pregrowth strata whereas all limb lengthening models result in parallelism between pregrowth strata and terrace straths across much of the fold the kashi atushi terraces show clear evidence of abandoned axial surfaces concentrated deformation near the core of the folds and progressive tilting with age when compared to the model predictions the folds are likely growing by a combination of limb rotation in the tight cores of the folds and hinge zone migration of pregrowth strata across the flanks of the folds

grain size dependent concentration of cosmogenic 10be and erosion dynamics in a landslide dominated himalayan watershed for documenting recent or late quaternary erosion rates at the scale of a small watershed or even an entire mountain range the use of in situ terrestrial cosmogenic nuclides tcn such as 10be in river sediments has become widespread over the last decade in mountainous settings however landslides may induce a two fold complication in the cosmogenic nuclide budget first they may episodically deliver large amounts of sediment with low tcn concentrations to the river channel second they may generate a grain size concentration dependence in these sediments however studies that have explored grain size dependence in landslide dominated areas have reached differing conclusions and the underlying mechanisms remain poorly understood the present study focuses on the khudi khola river basin a small drainage basin in the central himalayas the area is characterized by steep slopes heavy rainfall and high sediment production rates importantly the watershed contains a large area of active landsliding in situ 10be was analyzed in sediments of grain sizes ranging from 75 m to 4 cm collected from five locations upstream downstream and in the small tributaries which drain the landslides in all sampling locations including those situated upstream of the landslides the finest grains 75 250 m are two to four times more concentrated in 10be than the largest clasts 4 7 mm we developed a numerical slope model which includes a low level of background soil erosion and episodic denudation from large mass wasting events we then introduced a coarsening of average grain size with soil depth to the model our simulation shows that the data available for this valley are compatible with a scenario in which landslides deliver coarse grains to the channel that are less concentrated in tcn and have deeper provenance best fit estimates of the model parameters suggest recurrence times of 3000 to 9000 years for a major landslide on the same slope and mean long term landslide denudation rates of 1 7 to 4 7 mm yr 1 a negative correlation between tcn concentration and grain size is also observed directly upstream and 5 km downstream of the landsliding area suggesting that nearly all of the sediment carried by the river is derived from ancient landslides while almost no sediment is supplied by erosion of soil mantled slopes despite these complications apparent denudation rates directly derived from the tcn concentrations and from previously published data in the region are all on the same order of magnitude around 2 mm yr 1 however a factor of three variability remains between the different studies depending on the location the year of sampling and the analyzed grain size fraction thus although tcn derived average denudation rates provide a useful first order estimate even in fast eroding terrains dominated by landslides caution should be applied when using quantitative results in such settings

residual shear strength of unsaturated soils via suction controlled ring shear testing abstract results from a comprehensive series of suction controlled ring shear tests conducted on statically compacted specimens of silty clayey sand and silty sand are presented the experiments were accomplished in a newly developed servo suction controlled ring shear apparatus suitable for testing unsaturated soils under large deformations and suction controlled conditions via the axis translation technique the present work focuses primarily on two crucial aspects of compacted unsaturated soil behavior namely the behavior of silty clayey sand under suction controlled ring shear testing and the effects of pre shearing and suction histories on unsaturated residual shear strength of compacted silty sand test results corroborate the important role played by matric suction on residual shear strength properties of unsaturated soils for the range of net normal stresses and suction states investigated the increase in residual shear strength with increasing suction was confirmed to be a linear trend for silty sand but significantly nonlinear for silty clayey sand results from multi stage ring shear tests confirmed that the residual shear strength of unsaturated soils is virtually independent of the pre shearing and suction histories experienced by the soil

detachment folding in the southwestern tian shan tarim foreland china shortening estimates and rates abstract geologic observations of the chinese tian shan foreland reveal active contractional deformation along the entire margin to quantify the amount of shortening and understand the structural style we mapped the stratigraphy and structure of four folds expressed at the western end of the foreland north of kashi in this region upper tertiary through quaternary sediments are conformable but an abrupt transition from parallel to unconformable bedding in the uppermost strata suggests a transition from pre fold strata to strata deposited on a growing fold the folds have very steep 60 90 limbs and are box like to isoclinal suggestive of detachment folding total north south shortening across the center of the region is 9 km of which 5 7 km occurred in the kashi atushi fold system shortening estimates determined with excess area methods for individual folds decrease from a maximum of 6 8 km in the northwest to a minimum of 0 7 km in the southeast timing derived from a paleomagnetic study shows that the transition to syn folding strata occurred 1 2 ma in the middle of the study area resulting in an average shortening rate for the kashi atushi fold system of 5 mm yr if folding was coeval the shortening rate is high compared with foreland deformation east of the study area suggesting that the regional stresses or response of the foreland stratigraphy are unique to the kashi atushi fold system kinematics

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

active thrusting and folding along the northern tien shan and late cenozoic rotation of the tarim relative to dzungaria and kazakhstan we have studied geometries and rates of late cenozoic thrust faulting and folding along the northern piedmont of the tien shan mountain belt west of urumqi where the m 8 3 manas earthquake occurred on december 23 1906 the northern range of the tien shan rising above 5000 m overthrusts a flexural foredeep filled with up to 11 000 m of sediment of the dzungarian basement our fieldwork reveals that the active thrust reaches the surface 30 km north of the range front within a 200 km long zone of neogene quaternary anticlines fault scarps are clearest across inset terraces within narrow valleys incised through the anticlines by large rivers flowing down from the range in all the valleys the scarps offset vertically the highest terrace surface by the same amount 10 2 0 7 m inferring an early holocene age 10 2 kyr for this terrace which is continuous with the largest recent fans of the piedmont yields a rate of vertical throw of 1 0 0 3mm yr on the main active thrust at the surface a quantitative morphological analysis of the degradation of terrace edges that are offset by the thrust corroborates such a rate and yields a mass diffusivity of 5 5 2 5 m 2 kyr a rather fresh surface scarp 0 8 0 15 m high that is unlikely to result from shallow earthquakes with 6 m 7 in the last 230 years is visible at the extremities of the main fold zone we associate this scarp with the 1906 manas earthquake and infer that a structure comprising a deep basement ramp under the range gently dipping flats in the foreland and shallow ramps responsible for the formation of the active fault propagation anticlines could have been activated by that earthquake if so the return period of a 1906 type event would be 850 380 years the small size of the scarp for an earthquake of this magnitude suggests that a large fraction of the slip at depth 2 3 is taken up by incremental folding near the surface comparable earthquakes might activate flat detachments and ramp anticlines at a distance from the front of other rising quaternary ranges such as the san gabriel mountains in california or the mont blanc aar massifs in the alps we estimate the finite cenozoic shortening of the folded dzungarian sediments to be of the order of 30 km and the cenozoic shortening rate to have been 3 1 5 mm yr assuming comparable shortening along the tarim piedmont and minor additional active thrusting within the mountain belt we infer the rate of shortening across the tien shan to be at least 6 3 mm yr at the longitude of manas 85 5 e a total shortening of 125 30 km is estimated from crustal thickening assuming local airy isostatic equilibrium under the same assumption serial n s sections imply that cenozoic shortening across the belt increases westwards to 203 50 km at the longitude of kashgar 76 e as reflected by the westward increase of the width of the belt this strain gradient implies a clockwise rotation of tarim relative to dzungaria and kazakhstan of 7 2 5 around a pole located near the eastern extremity of the tien shan west of hami 96 e 43 5 n comparable to that revealed by paleomagnetism between tarim and dzungaria 8 6 8 7 a 6 mm yr rate of shortening at the longitude of manas would imply a rate of rotation of 0 45 m y and would be consistent with a shortening rate of 12 mm yr north of kashgar taking such values to be representative of late cenozoic rates would place the onset of reactivation of the tien shan by the india asia collision in the early to middle miocene 16 22 9 m y in accord with the existence of particularly thick late neogene and quaternary deposits such reactivation would thus have started much later than the collision roughly at the time of the great mid miocene changes in tectonic regimes denudation and sedimentation rates observed in southeast asia the himalayas and the bay of bengal and of the correlative rapid change in seawater sr isotopic ratio 20 to 15 ma like these other changes the rise of the tien shan might be a distant consequence of the end of indochina s escape

mechanics of fold and thrust belts and accretionary wedges cohesive coulomb theory a critically tapered fold and thrust belt or submarine accretionary wedge is one that is on the verge of coulomb failure everywhere including its base where frictional sliding along a decollement is assumed to be occurring cohesion within a wedge can add significantly to the overall strength near the toe the effect of this is to decrease the near toe taper leading to a critical topographic profile that is concave upward if the decollement is planar we obtain an approximate self consistent solution for the state of stress within a thin skinned cohesive critical coulomb wedge and determine the relationship between the wedge taper and its strength and basal friction the theory is then applied to the presently deforming fold and thrust belt of western taiwan fitting of theoretical critical wedge shapes to topographic profiles and measurements of the step up angles of thrust faults from the basal decollement are used to constrain the taiwan wedge strength parameters an attractive assertion fully consistent with all the observations is that the mechanics of fold and thrust belts and accretionary wedges is governed by normal frictional and fracture strengths of rocks measured in the laboratory in particular if byerlee s law b 0 85 is adopted as the coefficient of sliding friction on the base we find a coefficient of internal friction 0 9 1 0 in the wedge and a wedge cohesion so 5 20 mpa other solutions having strengths and ambient stresses up to 4 times lower than this can also however satisfy the data

hydromechanical triggering of landslides from progressive local failures to mass release 1 water infiltrating during intense rainfall on steep slopes gradually weakens the wet soil mass inducing localized failures that may initiate a cascade of load redistributions and successive failures propagating across a hillslope the challenge of linking the progressive nature of local events culminating in an abrupt landslide is addressed by a new hydromechanical triggering model that links key hydrologic processes with threshold based mechanical interactions a hillslope is represented as assembly of soil columns interconnected by frictional and tensile mechanical bonds represented as virtual bundles of fibers increasing water load exerted on mechanical bonds causes gradual failure of fibers until restraining forces are exceeded following failure at the soil bedrock interface the load on a column is redistributed to its neighbors via intact mechanical primarily tensile bonds which in turn may also fail and transmit the load downslope as compressive stresses when soil internal compressive strength is exceeded a load bearing column may liquefy and initiate a landslide release that could propagate downslope or retrogressively upslope the model reproduces observed power law frequency magnitude relationships of landslides with exponents ranging between 1 0 and 2 2 in agreement with landslide inventory data we applied a criticality measure defined by ramos 2011 to evaluate the specific influences of slope angle soil texture and root reinforcement on attainment of hillslope criticality in which a small local failure may trigger release of a large soil mass the model provides new insights on the conditions giving rise to an abrupt transition from a seemingly stable hillslope to a catastrophic landslide

the neogene xiyu formation a diachronous prograding gravel wedge at front of the tianshan climatic and tectonic implications the tarim and junggar basins in central asia are capped by a thick pile of conglomerates called the xiyu formation that are commonly linked to a change in climate and or accelerated uplift near the plio pleistocene boundary in order to better understand their origin and significance we carried out a combined structural and magnetostratigraphic study in the quilitage syncline southern tianshan where the base of the xiyu conglomerates is observed at both sides of the syncline a balanced cross section shows that even at a local scale the base of the xiyu conglomerates cannot be regarded as a single continuous stratigraphic layer on the southern flank of the quilitage syncline we collected 172 samples collected for magnetostratigraphic dating identify 17 polarity chrons that date the new section from 5 2 to 1 7 ma and constrain the base of the xiyu conglomerate here at 1 7 ma this is 4 2 ma younger than the age of the xiyu previously found on the northern limb of the same syncline together with other magnetostratigraphic studies carried out around the tianshan our study unambiguously demonstrates that the onset of deposition of the xiyu conglomerates is diachronous and that the conglomerates are systematically younger toward the basin consequently the xiyu formation should not be considered as a chronostratigraphic marker related to any particular tectonic or climatic event but is instead a prograding gravel wedge that has prograded over the underthrusting forelands a synthesis of chronologic and structural results yields progradation rates over the last 10 ma on the order of 2 0 mm yr and 3 9 mm yr south and north of the tianshan mountains respectively these rates are comparable to the shortening rate across the tianshan range suggesting that underthrusting is the main factor governing the progradation rate of the xiyu formation

kinematics of fault related folding derived from a sandbox experiment we analyze the kinematics of fault tip folding at the front of a fold and thrust wedge using a sandbox experiment the analog model consists of sand layers intercalated with low friction glass bead layers deposited in a glass sided experimental device and with a total thickness h 4 8 cm a computerized mobile backstop induces progressive horizontal shortening of the sand layers and therefore thrust fault propagation active deformation at the tip of the forward propagating basal decollement is monitored along the cross section with a high resolution ccd camera and the displacement field between pairs of images is measured from the optical flow technique in the early stage when cumulative shortening is less than about h 10 slip along the decollement tapers gradually to zero and the displacement gradient is absorbed by distributed deformation of the overlying medium in this stage of detachment tip folding horizontal displacements decrease linearly with distance toward the foreland vertical displacements reflect a nearly symmetrical mode of folding with displacements varying linearly between relatively well defined axial surfaces when the cumulative slip on the decollement exceeds about h 10 deformation tends to localize on a few discrete shear bands at the front of the system until shortening exceeds h 8 and deformation gets fully localized on a single emergent frontal ramp the fault geometry subsequently evolves to a sigmoid shape and the hanging wall deforms by simple shear as it overthrusts the flat ramp system as long as strain localization is not fully established the sand layers experience a combination of thickening and horizontal shortening which induces gradual limb rotation the observed kinematics can be reduced to simple analytical expressions that can be used to restore fault tip folds relate finite deformation to incremental folding and derive shortening rates from deformed geomorphic markers or growth strata

weathering of the oporto granite geotechnical and physical properties abstract this paper characterizes the weathering products of the two mica oporto granite in terms of its mineralogical chemical geotechnical and physical properties this information is used to identify a physical property that can be used as an index of the degree of weathering and to estimate other properties in outcrop the oporto granite is always weathered and weathering profiles frequently exceed 20 m within these profiles granitic saprolites are composed of quartz feldspars and some mica with kaolinite and gibbsite as final weathering products the average percentage of secondary minerals determined by bulk x ray diffraction xrd is low in both weathered rock 2 4 and saprolite 8 7 geotechnically the saprolites exhibit no or low plasticity plasticity index pi 12 the skeleton character of the saprolites is reflected in the significant proportion of fines 29 5

a method for evaluating the stability of an unsaturated slope in natural terrain during rainfall abstract the stability of an unsaturated slope in natural terrain was evaluated based on the variation in the suction stress in the soil layer induced by rainfall a field monitoring site where landslides have occurred in the past was selected as the study area to apply the concept of slope stability analysis considering the suction stress in unsaturated soil the soil water characteristic curve swcc and the suction stress characteristic curve sscc of the unsaturated soil obtained from the study area were estimated using the van genuchten 1980 model and the lu and likos 2006 model respectively the phenomenon of ground saturation induced by the infiltration of rainfall into unsaturated soil is similar to the wetting path of the swcc the curve fit parameters estimated from the swcc wetting path were therefore used to determine the matric suction and suction stress in the unsaturated soil the amount of rainfall and the volumetric water content of the soil were measured using a rain gauge and time domain reflectometer tdr sensors respectively at the monitoring site an infinite slope was chosen as representative of the slope of the natural terrain in the study area because the slope length is very long but the depth of the soil layer over the rock is very shallow the stability of this unsaturated slope in natural terrain was evaluated based on the safety factor of an infinite slope considering the suction stress in the unsaturated soil layer the safety factor of the slope suddenly decreased during and just after a rainfall and then recovered notably the safety factor of this natural slope exhibited continuous fluctuations because of changes in the suction stress caused by the evaporation and infiltration of water in the unsaturated soil layer the variation in the suction stress in unsaturated soil induced by rainfall can be estimated from the results of laboratory tests performed to estimate the wetting process based on the swcc and sscc in combination with field monitoring data collected by sensors to measure the volumetric water content or matric suction in the soil therefore the infinite slope stability of a slope in natural terrain can be evaluated in real time by estimating the suction stress in the unsaturated soil due to rainfall when the volumetric water content or matric suction in the soil is being monitored in the field

quantification of three dimensional folding using fluvial terraces a case study from the mushi anticline northern margin of the chinese pamir fold deformation in three dimensions involves shortening uplift and lateral growth fluvial terraces represent strain markers that have been widely applied to constrain a fold s shortening and uplift for the lateral growth however the utility of fluvial terraces has been commonly ignored situated along northern margin of chinese pamir the mushi anticline preserves along its northern flank flights of passively deformed fluvial terraces that can be used to constrain three dimensional folding history especially lateral growth the mushi anticline is a geometrically simple fault tip fold with a total shortening of 740 110 m and rock uplift of 1300 m geologic and geomorphic mapping and dgps surveys reveal that terrace surfaces perpendicular to the fold s strike display increased rotation with age implying the fold grows by progressive limb rotation we use a pure shear fault tip fold model to estimate a uniform shortening rate of 1 5 1 3 0 5 mm a and a rock uplift rate of 2 3 2 1 0 8 mm a parallel to the fold s strike longitudinal profiles of terrace surfaces also display age dependent increases in slopes we present a new model to distinguish lateral growth mechanisms lateral lengthening and or rotation above a fixed tip this model indicates that eastward lengthening of the mushi anticline ceased by at least 134 ka and its lateral growth has been dominated by rotation our study confirms that terrace deformation along a fold s strike not only can constrain the lateral lengthening rate but can serve to quantify the magnitude and rate of lateral rotation attributes that are commonly difficult to define when relying on other geomorphic criteria

water and sediment yield from a small catchment in the hilly granitic region south china abstract shenchong experimental basin is located in subtropical deqing county in the hilly region of south china it has a catchment area of 0 73 km2 and is underlain by granitic rocks with a weathering mantle of about 30 m water and sediment yield were monitored at the basin outlet and at a location about 230 m upstream such that the section between the two stations coincides with the concentration of large gullies these gullies produce most of the sediment yield of the basin and the pattern of sediment discharge mirrors that of rainfall however gullies contribute comparatively little runoff to the basin outflow other surface types including bare slopes bare rills and the valley floor together yield considerable runoff because of their large areal coverage

late quaternary slip rates across the central tien shan kyrgyzstan central asia 1 slip rates across active faults and folds show that late quaternary faulting is distributed across the central tien shan not concentrated at its margins nearly every intermontane basin contains neogene and quaternary syntectonic strata deformed by holocene north south shortening on thrust or reverse faults in a region that spans two thirds of the north south width of the central tien shan slip rates on eight faults in five basins range from 0 1 to 3 mm yr fault slip rates are derived from faulted and folded river terraces and from trenches radiocarbon optically stimulated luminescence and thermoluminescence ages limit ages of terraces and aid in their regional correlation monte carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95 confidence limits faults in basins appear to merge at relatively shallow depths with crustal scale ramps that underlie mountain ranges composed of pre cenozoic rocks the sum and overall pattern of late quaternary rates of shortening are similar to current rates of north south shortening measured using global positioning system geodesy this similarity suggests that deformation is concentrated along major fault zones near range basin margins such faults separated by rigid blocks accommodate most of the shortening in the upper crust index terms 8107 tectonophysics continental neotectonics 9320 information related to geographic region asia 8010 structural geology fractures and faults

engineering and geological characteristics of granite weathering profiles in south china granite weathering profiles are widely distributed in south china their engineering and geological characteristics are major geotechnical subjects that are important in the design and construction of civil engineering projects this paper presents a summary of the weathering characteristics and zoning of granite weathering profiles in south china and discusses their engineering and geological properties a five grade scheme has been adopted in the zoning of a granite weathering profile studies have shown that the completely weathered granites cwg in south china have the following characteristics low moisture content low to medium plasticity w l 22 5 39 0 i p 6 5 11 8 medium void ratio 0 36 1 29 weak shrinkage and medium compressibility a 1 2 0 24 0 8 mpa 1 and high shear strength phi 20 30degrees c 20 40 kpa the cwgs are usually at a low or high plastic state and most of them are over consolidated soils a majority of the physical and mechanical properties have good statistical correlations with the degree of weathering the data presented in the paper are important in geotechnical engineering projects such as slope stability evaluation in china c 2002 elsevier science ltd all rights reserved

a geologically constrained monte carlo approach to modeling exposure ages from profiles of cosmogenic nuclides an example from lees ferry arizona we present a user friendly and versatile monte carlo simulator for modeling profiles of in situ terrestrial cosmogenic nuclides tcns our program available online at http geochronology earthsciences dal ca downloads models html permits the incorporation of site specific geologic knowledge to calculate most probable values for exposure age erosion rate and inherited nuclide concentration while providing a rigorous treatment of their uncertainties the simulator is demonstrated with 10be data from a fluvial terrace at lees ferry arizona interpreted constraints on erosion based on local soil properties and terrace morphology yield a most probable exposure age and inheritance of 83 9 14 1 19 1 ka and 9 49 2 52 1 21 104 atoms g 1 respectively 2 without the ability to apply some constraint to either erosion rate or age shallow depth profiles of any cosmogenic nuclide except for nuclides produced via thermal and epithermal neutron capture e g 36cl cannot be optimized to resolve either parameter contrasting simulations of 10be data from both sand and pebble sized clasts within the same deposit indicate grain size can significantly affect the ability to model ages with tcn depth profiles and when possible sand not pebbles should be used for depth profile exposure dating

soil erosion processes and sediment sorting associated with transport mechanisms on steep slopes summary sediment size distribution greatly affects sediment transport and deposition a better understanding of sediment sorting will improve understanding of erosion and sedimentation processes which in turn will improve erosion modeling to address this issue a total of 12 rainfall simulation experiments were conducted in a 1 m by 5 m box with varying steep slopes 10 15 20 and 25 and the simulated rainfall lasted for 1 h at a rate of 90 mm h 1 for each simulated event runoff and sediment were sampled at 3 min intervals which were performed to study in detail the temporal change in size distribution of the eroded materials these data were used to interpret the real time sequence of transport mechanisms acting in response to the simulated rainfall total soil loss is the sum of suspended saltating and contact loads the proportion of sediment r 2 0 452 p n 120 suspension saltation transports the finer than 0 054 mm size sediment was the most important erosion mechanism during interrill erosion processes however after rill development on hillslopes bed load transport by rolling of medium to large sized sediment particles coarser than 0 152 mm became an increasingly important transport mechanism and it were also enhanced by increased slope overall the study supports a strong relationship between the sediment transport of contact rolling load and stream power the partition of soil loss into these more meaningful components appears to be essential both for initial data interpretation and for subsequent use of such data for soil loss prediction

comparison of soil physicochemical properties and mineralogical compositions between noncollapsible soils and collapsed gullies abstract this study aimed to compare soil physicochemical properties and mineralogical compositions including the cohesive force and internal friction angle using direct shear tests with designed water contents and temperatures between noncollapsible soil and collapsed gullies two pedons were collected from longmen town anxi county fujian province with severely collapsed gullies that developed from granitic rocks and another two pedons were collected from metamorphic regions gande town without soil erosion the samples were subjected to x ray diffraction xrd analysis and their soil physicochemical properties were compared noncollapsible soils had superior physicochemical characteristics e g these soils contained higher amounts of cations especially total iron oxides fet furthermore noncollapsible soils were able to resist shearing due to their greater cohesive force and the internal friction angle did not differ considerably from that of the collapsed soils kaolinite illite hydroxy interlayered vermiculite hiv and gibbsite were the dominant clay minerals in the noncollapsible soils however in the collapsed soils kaolinite accounted for 85 of the total clay mineral composition the cohesive force and internal friction angle were significantly correlated with sesquioxides of all non collapsible and collapsed pedons such as fed free fe oxides 0 762 0 637 and total iron fet 0 783 0 708 as well as magnetic susceptibility 0 650 0 740 p

estimation of slip rates in the southern tien shan using cosmic ray exposure dates of abandoned alluvial fans cosmic ray exposure dates based on in situ produced 10 be in combination with measured heights of fault scarps that cut three abandoned fans imply a slip rate of less than 2 mm yr on the bounding thrust fault along a segment of the southern flank of the tien shan of central asia this rate somewhat lower than those for the segment farther west and for the northern margin of the belt implies that the distribution of shortening across the tien shan must change markedly along the belt the date of abandonment of the smallest of the three fans is consistent with fan formation since the last glacial maximum but the other two fans appear to have been formed and abandoned prior to that time these and other results suggest that advances and retreats of alpine glaciers may not be synchronized with continental ice sheets and that not all prominent geomorphological features in arid asian regions have formed since the last glacial maximum in this study we have assessed the relationship between cosmogenic nuclide content of individual clasts and the time since their deposition on a surface cosmogenic nuclide accumulation represents the integrated total surface exposure of rocks in source regions during transport and since deposition postdepositional processes erosion burial bioturbation and cryoturbation all of which decrease the quantity of cosmogenic nuclides produced in a rock in a given time and hence the apparent exposure age also cause significant scatter among apparent ages of samples from the surfaces very low 10 be concentrations in material from active streambeds and at depth below one of the fan surfaces indicate that exposure prior to deposition onto fan surfaces was minimal

10be derived himalayan denudation rates and sediment budgets in the ganga basin abstract the himalayas represent the archetype of mountain building due to active continental collision and are considered in many studies as the locus of intense interactions between climate denudation and tectonics estimates of modern denudation rates across the entire range remain however relatively sparse in this study in situ produced cosmogenic 10 be concentrations were measured in detritic quartz in order to determine basin scale denudation rates for the central part of the himalayan range river sand was sampled over several years in the main trans himalayan rivers from the himalayan front to the ganga outlet in bangladesh the calculated 10 be denudation rates of the trans himalayan river basins range from 0 5 to 2 4 mm yr 1 average 1 3 mm yr 1 and vary by up to a factor of 3 between sampling years these denudation rates strongly contrast with the 0 007 mm yr 1 denudation rate of southern tributary basins draining the indian craton this work also shows that in the ganga basin no systematic evolution of average 10 be concentrations is observed during floodplain transfer implying that distal samples can be used to estimate the integrated denudation rate of the whole central himalayan range samples from the ganga in bangladesh display remarkably low variability in 10 be concentration implying an average himalayan denudation rate of 1 0 1 1 mm yr 1 however within the floodplain several samples suggest a recent perturbation of sediment transport dynamics with a recent increase in the relative sediment contribution from southern tributaries the himalayan sediment flux deduced from the 10 be denudation rate of the range is 610 230 mt yr 1 this flux is consistent within uncertainty with sediment fluxes derived from sediment gauging the similarity of the two flux estimates suggests that himalayan erosion fluxes have remained stable over the last centuries even if the large uncertainties associated with each method hamper more precise assessments

effects of fractal dimension and water content on the shear strength of red soil in the hilly granitic region of southern china abstract deep residual soil formed by the long term weathering of large granite under the impact of high temperature and abundant rainfall in southern china is prone to instability and deformation which has caused a large number of collapsing gullies in this study five different soil grading ratios and five water contents were employed to systematically investigate the effects of the soil fractal dimension and water content on the red soil shear strength the soil fractal dimension increased with soil fine particle content clay and silt the soil saturated hydraulic conductivity ks decreased with the soil fractal dimension whereas the soil air entry value and residual water content r showed a positive relationship with the fractal dimension shearing tests showed that the soil shear strength increased with normal stress but decreased with the soil water content this reduction in the soil shear strength caused by the increasing water content was more notable for the soil with a lower fractal dimension analyses of the main effect tests showed that the water content presented greater effects on the soil cohesion and friction angle than the soil fractal dimension a stepwise regression analysis showed that a linear relationship occurred between soil matric suction and soil cohesion average r 0 981 and p 004 or friction angle average r 0 951 and p 016 for the same matric suction the soil cohesion and friction angles decreased with the soil fractal dimension and the relationship between the soil fractal dimension with the soil cohesion r 0 951 and p 013 and friction angles r 0 922 and p 026 could be described by logarithmic functions soil fractal dimensions influenced both the soil hydraulic properties and shear strength parameters and the overall effects of fine particles loss would decrease the shear strength of gully red soil

quaternary climate change and the formation of river terraces across growing anticlines on the north flank of the tien shan china nested stream terraces warped upward over actively growing anticlines along the north flank of the tien shan in western china appear to record alternating phases of valley widening and incision differences of relative heights between remnants of four separate strath terraces along one river and between two such terraces along another reach 100 to 120 m over the crests of the anticlines we infer that this spacing is due to alternating stages of valley widening and rapid incision associated with climate changes with a periodicity of 100 kyr the crests of the anticlines appear to emerge from the aggrading flanks of the anticlines at an average rate of about 1 mm a the maximum heights of 25 and 35 10 m for the lowest terraces above their projected initial profiles imply ages of roughly 25 kyr and 35 kyr 10 kyr hence they suggest that flood plains which were abandoned to form the terraces developed adjacent to active stream beds during the last glacial period when climates were relatively

cenozoic ostracoda and palaeoenvironments of the northeastern tarim basin western china abstract the paleogene rocks of the northeastern tarim basin in western china are composed mainly of reddish gypsum bearing coarse grained sediments and fossils are rare within these clastic facies however since the onset of the himalayan orogeny in the miocene continuous uplift of the tianshan mountains resulted in the rapid subsidence and appearance of a shallow lake environment as a result of this ostracods are widespread in the late cenozoic rocks of the tarim basin the brackish water ostracod cyprideis thrived from the mid to late miocene gypsum bearing sand and mud sediments were also deposited widely in the shallow brackish water lake environments this situation is similar to that of the qaidam basin which lies to the south of the altun mountains from the pliocene onwards the rates of subsidence and sedimentation increased the resulting regression of the lake led to disappearance of ostracods from a large part of the basin to the north of the kuqa depression the tianshan mountains underwent continuous uplift during the late himalayan orogeny as a result the quaternary lake deposits have a much greater extent than those of the pliocene and extend even further southward than those of the miocene consequently the brackish water ostracod cyprideis became dominant again during the quaternary from the end of the early pleistocene to present in this area an abundant and high diversity fauna of fresh to brackish water ostracods appeared alongside abundant cyprideis this situation is similar to that of the southern qaidam basin to the north of kunlun mountains the quaternary assemblages mainly consist of cyprideis torosa candoniella lactea candona neglecta candona arcina cypridopsis vidua limnocythere inopinata cypris subglobosa ilyocypris gibba ilyocypris biplicata eucypris inflata candoniella albicans darwinula sp and stenocypris sp under the extremely arid climate in the tarim basin freshwater originated mainly from snow melt this suggests that the tianshan mountains to the north were uplifted rapidly to above the snow line during the last million years the evolution of the ostracod assemblages indicates that the late himalayan orogeny not only controlled the deposition of biota assemblages but also took an important role in the hydrocarbon accumulation and migration

geological features and landslide mechanisms of an unstable coastal slope petacciato italy abstract on the basis of geological and geomorphological surveys landslide phenomena are analysed on a slope along a stretch of the adriatic coast near petacciato molise italy locally a blue clay sequence of pleistocene outcrops stratified with silty sandy layers bedding dips 3 8 ne and the slope has a similar attitude this sequence evolves upwards to sands and conglomerates with thickness of up to 40 m on which the built up area is located several episodes of landslide reactivation occurred in the past century involving the zone between the built up area and the sea along a coastal slope of over 2000 m long and 200 m high important roads and railway lines have been heavily damaged as well as the town itself the typology of the movement is a rotational translational slide the displacement reaches tens of centimetres at each reactivation episode along the entire coastal slope extending well beyond the shore line detailed studies already exists but different mechanism failures have been proposed to explain the landslide phenomena in this study a new failure mechanism is proposed sudden spreading of terzaghi k peck r b 1948 soil mechanics in engineering practice wiley and sons new york and analytical approaches have been adopted to evaluate the slope stability based on the geotechnical and monitoring data and the geometrical and geological features of the slope

a note of caution on the use of boulders for exposure dating of depositional surfaces abstract exposure dating of boulders has been widely applied to determine the age of depositional surfaces under the assumption that the pre depositional nuclide component in most boulders is negligible here we present a case study on fluvial terraces at the active mountain front of the eastern andes where this assumption is clearly invalid because sandstone boulders n 13 from terraces at two sites contain a highly variable inherited 10be component and have apparent 10be ages that exceed the age of the respective surface by up to 90 ka likewise boulders from active stream channels n 5 contain a substantial inherited 10be component equivalent to 5 48 ka of exposure the age of the fluvial terraces is well determined by two approaches that allow to correct for the pre depositional nuclide component 10be dating of amalgamated pebbles and 10be depth profiles on sand samples at site 1 three terraces have 10be ages of 3 5 ka t2 11 13 ka t3 and 16 20 ka t4 which are consistent with the terrace stratigraphy the age of terrace t3 is confirmed by a calibrated 14 c age of 12 61 0 20 ka bp obtained from a wood sample at site 2 terrace t3 has a 10be age of 13 16 ka the average inherited 10be concentration of sand grains determined from depth profiles and stream sediments is small and equivalent to 1 3 ka of exposure in contrast the mean inheritance of pebbles and boulders is higher and equivalent to exposure times of 10 ka and 30 ka respectively these differences in the pre depositional nuclide component are related to the different provenance and transport history of sand pebbles and boulders the sand is derived from rapidly eroding miocene sediments exposed near the mountain front whereas the pebbles and boulders originate from triassic sandstones in the internal part of the fold and thrust belt on their way to the mountain front boulders and pebbles were temporarily stored and irradiated in alluvial fans that are currently reworked as sediment deposition in intramontane basins and their subsequent excavation is common in the andes and other fold and thrust belts the presence of pre depositional nuclide components should be evaluated when applying exposure dating at active mountain fronts

mesozoic and cenozoic tectonic history of the central chinese tian shan reactivated tectonic structures and active deformation 1 the present day topography of the tian shan range is considered to result from crustal shortening related to the ongoing india asia collision that started in the early tertiary in this study we report evidence for several episodes of localized tectonic activity which occurred prior to that major orogenic event apatite fission track analysis and u th he dating on apatite and zircon indicate that inherited paleozoic structures were reactivated in the late paleozoic early mesozoic during a cimmerian orogenic episode and also in the late cretaceous paleogene around 65 60 ma these reactivations could have resulted from the accretion of the kohistan dras arc or lithospheric extension in the siberia mongolia zone activity resumed in the late mesozoic prior to the major tertiary orogenic phase finally the ongoing deformation which again reactivates inherited tectonic structures tends to propagate inside the endoreic basins that were preserved in the range leading to their progressive closure this study demonstrates the importance of inherited structures in localizing the first increments of the deformation before it propagates into yet undeformed areas

present day crustal deformation in china constrained by global positioning system measurements global positioning system gps measurements in china indicate that crustal shortening accommodates most of india s penetration into eurasia deformation within the tibetan plateau and its margins the himalaya the altyn tagh and the qilian shan absorbs more than 90 of the relative motion between the indian and eurasian plates internal shortening of the tibetan plateau itself accounts for more than one third of the total convergence however the tibetan plateau south of the kunlun and ganzi mani faults is moving eastward relative to both india and eurasia this movement is accommodated through rotation of material around the eastern syntaxis the north china and south china blocks east of the tibetan plateau move coherently east southeastward at rates of 2 to 8 millimeters per year and 6 to 11 millimeters per year respectively with respect to the stable eurasia

cosmogenic dating of fluvial terraces fremont river utah absolute dating of river terraces can yield long term incision rates clarify the role of climate in setting times of aggradation and incision and establish the rates of pedogenic processes while surface exposure dating using cosmogenic 10be and 26al would seem to be an ideal dating method the surfaces are composed of individual clasts each with its own complex history of exposure and burial the stochastic nature of burial depth and hence in nuclide production in these clasts during exhumation and fluvial transport and during post depositional stirring results in great variability in clast nuclide concentrations we present a method for dealing with the problem of pre depositional inheritance of cosmogenic nuclides we generate samples by amalgamating many individual clasts in order to average over their widely different exposure histories depth profiles of such amalgamated samples allow us to constrain the mean inheritance to test for the possible importance of stirring and to estimate the age of the surface working with samples from terraces of the fremont river we demonstrate that samples amalgamated from 30 clasts represent well the mean concentration depth profiles show the expected shifted exponential concentration profile that we attribute to the sum of uniform mean inheritance and depth dependent post depositional nuclide production that the depth dependent parts of the profiles are exponential argues against significant post depositional displacement of clasts within the deposit our technique yields 10be age estimates of 60 9 102 16 and 151 24 ka for the three highest terraces corresponding to isotope stages 4 5d and 6 respectively the mean inheritance is similar from terrace to terrace and would correspond to an error of 30 40 ka if not taken into account the inheritance likely reflects primarily the mean exhumation rates in the headwaters of order 30 m ma

holocene hydrological changes inferred from alluvial stream entrenchment in north tian shan northwestern china abstract we analyze the possible contribution of climate change or tectonics on fluvial incision from the study of a case example along the northern flank of tian shan the rivers that exit the high range fed large alluvial fans by the end of the last glacial period they have since deeply entrenched the piedmont by as much as 300 m we have surveyed several terraces that were cut and abandoned during river entrenchment providing information on intermediate positions of the riverbed during downcutting they suggest a gradual decline in river slope during a major phase of incision throughout the holocene tectonic uplift affects only a zone about 5 km wide corresponding to a growing anticline and is shown to account for about 10 of total incision incision was therefore most probably driven by climate change from observed fluvial incision we estimate the water discharge in excess of that needed to carry the sediments supplied by hillslope erosion in the headwaters we used a model based on a transpor

irregular earthquake cycle along the southern tianshan front aksu area china 1 a long deformation record 16 5 ka showing nonsteady earthquake recurrence is established for the aksu thrust tianshan china on the basis of cosmogenic 10be dating of faulted surfaces topographic leveling across the aksu fault scarp indicates up to 10 m uplift across a moraine abandoned 16 5 ka and similar uplift of 6 m across two inset surfaces yielding ages of 12 5 and 5 ka successively smaller uplifts of terraces younger than 5 ka indicate that three or more major earthquakes occurred during this period these data show that the aksu thrust fault was quiet for at least 7500 years and active in the last 5000 years and probably in the interval 16 5 12 5 ka the seismic cycle along the aksu thrust fault over the last 16 500 years was thus strongly irregular showing long quiescence and clustering which is a challenge for paleoseismology and hazard assessment this irregularity also makes it more difficult to estimate long term shortening rates nevertheless we are able to constrain a minimum total shortening rate 7 mm yr across the southern tianshan front for the last 12 500 years that is about a third of the total geodetic rate for the western tianshan 20 mm yr

quantifying the morphology of flow patterns in landslide affected and unaffected soils summary in mountainous regions landslides are a common natural phenomenon they are often triggered by a combination of steep relief and long lasting rainfalls therefore hydrological conditions in the soil are crucial for their initiation because direct measurements of water flow are difficult and model predictions uncertain we used a dye to visualise flow patterns directly we combined dye tracer experiments with field observations root density and rock fragment content and measurements of soil properties bulk density soil water retention curve and saturated hydraulic conductivity we quantified the morphology of flow patterns by image indices and mutual information that measures the overall dependency between variables and compared two shallow landslides of different ages with a landslide unaffected hillslope our results showed that flow patterns on the landslides were more fragmented and contained larger stained objects than on the landslide unaffected site we relate these findings to a larger stone content and a stronger macropore soil matrix interaction moreover we detected a fissure network on the younger landslide that probably affects its hydrological behaviour field observations soil hydraulic properties and dye tracer studies describe different hydrological aspects of the studied sites and complement the information provided by the morphological image indices

examination of surface exposure ages of antarctic moraines using in situ produced 10be and 26al concentrations of 10be t12 1 5 106 y and 26a1 t12 0 72 106 y have been determined by accelerator mass spectrometry ams in a suite of quartz samples taken from sandstone boulders in several moraines in arena valley a dry valley adjacent to the taylor glacier in the quatermain mountains southern victoria land east antarctica these isotopes are produced in surficial quartz by cosmic ray spallation of o and si the concentrations in these samples ranged from 6 1 105 to 3 0 107 at g 1 for 10be and from 9 4 106 to 1 2 108 at g 1 for 26a1 depending upon the extent of exposure at the surface analyses of 10be in several samples from a single moraine at altitudes ranging from 1300 to 1650 m permitted an estimation of the air attenuation pathlength of cosmic ray neutrons the value of 142 96 41 g cm 2 is consistent with other published values production rates of 17 6 4 at g 1 y 1 for 10be and 113 54 16 at g 1 y 1 for 26a1 at 1300 m and 87 s and a 26al 10be production ratio of 6 5 1 3 1 3 were calculated from the data these values correspond to sea level production rates at high geomagnetic latitude of 6 4 at g 1 y 1 and 41 7 at g 1 y 1 for 10be and 26a1 respectively consistent with determinations based on 11 ky glacially polished surfaces in the sierra nevada in california these production rates imply exposure ages for the various moraines ranging from 50 ky to 2 5 my in accordance with other geological evidence the 10be and 26al ages of these rocks compare favorably with those found using a similar dating method based on in situ production of 3he examination of the 3he concentrations in conjunction with the present data set yields an estimate of 3he production of 230 8540 at g 1 y 1 corresponding to 85 31 15 at g 1 y 1 at sea level this is lower than previously reported values of 240 60 at g 1 y 1 and 190 at g 1 y 1 scaled to sea level and high geomagnetic latitude based respectively on volcanic flows less than 2000 years old at low latitude and samples collected from 14 400 year old volcanic flows this discrepancy is likely due to diffusive losses which may become significant up to 50 for surface exposure ages on the order of 2 0 my nevertheless the general correlations among the three isotopes suggest that 3he does not suffer gross losses through diffusion

quaternary evolution of a large alluvial fan in a periglacial setting crau plain se france constrained by terrestrial cosmogenic nuclide 10be abstract located in the foreland of the western alps the crau plain was the outlet of the durance river in the pleistocene in order to constrain its geodynamic evolution in terms of chronology and denudation rates the two main quaternary deposits of this plain have been studied based on cosmogenic nuclide 10 be concentration measurements along depth profiles the abandonment of the miramas and luquier alluvial surfaces occurred at the beginning of glacial periods wurm isotopic stage 4 and riss isotopic stage 6 respectively discrepancy in denudation rates under similar geomorphological and lithological conditions suggests different denudation processes during glacial and interglacial periods the denudation rate has been estimated at about 25 mm ka 1 for the interglacial period and about 60 mm ka 1 for the glacial period the abandonment of the crau plain as the outlet of the durance river occurred sometime between 75 and 35 ka

benggang erosion the influencing factors abstract in the tropical and southern subtropic granite areas of south china a special kind of small scale erosional landform is widely distributed called benggang by the local people many natural factors are responsible for the development of benggang such as lithology precipitation relief vegetation etc which are discussed in detail in this paper study shows that the development of benggangs is the outcome of a joint operation of natural factors and human activities lithology especially the characteristics of the granite weathering mantle provides material in which benggangs can develop while intense rainstorms in a tropical monsoon climate act as a powerful force to cause benggang erosion the slope characteristics such as steepness and exposure control the spatial difference of the distribution of benggangs the development of benggangs results from the reverse succession of vegetation induced by human activities in this region and the density of benggangs is closely related to forest cover and unit timber growing stock

application of lp icp ms to benthic foraminifers abstract a laser microprobe coupled with an inductively coupled plasma mass spectrometer lp icp ms was used to determine mg mn sr and ba contents of benthic foraminifers in the solid state calcite shells of cibicides wuellerstorfi oridorsalis umbonatus pyrgo spp and aragonite tests of hoeglundina elegans which were taken from the surface sediments of the northwestern north atlantic ocean were ablated by a laser beam multiple measurements were achieved on single tests since the diameters of ablation pits 20 50 m are significantly smaller than those of the shells 250 m mg ca mn ca and ba ca of the ablated materials are significantly affected by fe mn oxide coatings and extraneous ba bearing phases and sr ca is not noticeably influenced by those contaminants there is no substantial variation of sr ca within and between shells of a foraminiferal species on the contrary sr ca is species dependent sr ca of pyrgo spp is three times as high as that of h elegans and nearly twice as high as those of c wuellerstorfi and o umbonatus

excess area and depth to detachment a plot of the excess area in cross section vs the depth to a reference level for several stratigraphic horizons in a compressional fold produces a curve that gives the depth to detachment the curve is a straight line for detachment folds the slope of the line is the displacement on the lower detachment and the depth intercept where excess area zero is the depth to detachment for a fault bend fold the result is a line that abruptly changes slope at the position corresponding to the upper detachment the difference in slope between the two parts of the line is the displacement on the upper detachment added layer parallel shear produces a curve on the graph tested on detachment folds from the jura mountains the method accurately predicts the depth to detachment he tip top field anticline in the wyoming thrust belt is found to be interpretable as either a detachment anticline with a basal detachment close to the top of the basement or as a fault bend fold with a basal detachment at the base of the triassic the excess area diagram is useful for testing a cross section for balance determining the structural style detachment anticline vs fault bend fold and for examining alternatives in the construction of cross sections

shear strength and dilative characteristics of an unsaturated compacted completely decomposed granite soil shear strength and dilative characteristics of a re compacted completely decomposed granite cdg soil are studied by performing a series of single stage consolidated drained direct shear tests under different matric suctions and net normal stresses the axis translation technique is applied to control the pore water and pore air pressures a soil water retention curve swrc is obtained for the cdg soil from the equilibrium water content corresponding to each applied matric suction value for zero net normal stress using a modified direct shear apparatus shear strength increases with matric suction and net normal stress and the failure envelope is observed to be linear the apparent angle of internal friction and cohesion intercept increase with matric suction a greater dilation angle is found at higher suctions with lower net normal stresses while lower or zero dilation angles are observed under higher net normal stresses with lower suctions also at a saturated condition experimental shear strength

using 10be and 26al to determine sediment generation rates and identify sediment source areas in an arid region drainage basin we measured 10 be and 26 al in 64 sediment and bedrock samples collected throughout the arid 187 km 2 yuma wash drainage basin southwestern arizona from the measurements we determine long term time integrated rates of upland sediment generation 81f 5gm 2 year 1 and bedrock equivalent lowering 30f 2mm a 1 consistent with other estimates for regions of similar climate lithology and topography in a small f 8k m 2 upland sub basin differences in nuclide concentrations between bedrock outcrops and hillslope colluvium suggest weathering of bedrock beneath a colluvial cover is a more significant source of sediment 4010 4 kg year 1 than weathering of exposed bedrock surfaces 1010 4 kg year 1 mixing models constructed from nuclide concentrations of sediment reservoirs identify important sediment source areas hillslope colluvium is the dominant sediment source to the upper reaches of the sub basin channel channel cutting of alluvial terraces is the dominant source in the lower reaches similarities in nuclide concentrations of various sediment reservoirs indicate short sediment storage times 10 3 years nuclide concentrations measured in channel sediment from tributaries of yuma wash and in samples collected along the length of the wash were used to construct mixing models and determine sediment sources to the main stem channel we find an exponential decrease in the channel nuclide concentrations with distance downstream suggesting that as much as 40 of sediment discharged from yuma wash has been recycled from storage within basin fill alluvium sediment generation and denudation rates determined from the main stem are greater 25 than rates determined from upland sub basins suggesting that currently sediment may be exported from the basin more quickly than it is being generated in the uplands independence of nuclide concentration and sediment grain size indicates that channels transport sediment in discrete pulses before rapidly depositing poorly sorted material suggesting that differences in transport times for different size materials are minimal d 2002 elsevier science b v all rights reserved

production of cosmogenic radionuclides at great depth a multi element approach abstract for the last two decades in situ produced cosmogenic nuclides are increasingly applied in earth sciences to quantify surface processes in parallel significant reduction of the analytical uncertainties linked to advances in accelerator mass spectrometry ams allows more precise measurements however among all the published works on cosmogenic nuclides only few studies are dedicated to a better understanding of their production systematic or to a better constrain of the physical parameters involved in their production thus an approach to investigate in situ produced cosmogenic nuclides 10 be 26 al and 36 cl along a single 11 meter long core drilled from the surface and composed of carbonates and quartzose conglomerates has been launched these measurements have been used to quantify muon induced productions based on natural samples for each studied nuclide contrary to the current most oftenly used calculation of muon induced production parameters which are based on irradiation experiments at discrete energies productions based on natural samples are considering the entire energy range of particles reaching the ground surface the evolution of 36 cl concentrations with depth needs to agree with those parameters deduced from 10 be and 26 al data this is optimized when considering a fast muon induced 36 cl production contribution and a spallation production rate at sea level high latitude slhl of 42 0 2 0 atoms 36 cl g ca 1 a 1 1 sigma uncertainty

major temporal variations in shortening rate absorbed along a large active fold of the southeastern tianshan piedmont china the investigation of deformation rates on a mountain piedmont can provide key information for improving our understanding of the overall dynamics of a mountain range here we estimate the shortening rate absorbed by a quaternary emergent detachment fold on the southeastern piedmont of the tianshan china our work is primarily based on new 10be cosmogenic exposure dating of deformed alluvial surfaces the method we have developed combines depth profiling with sampling of surface cobbles thereby allowing exposure time erosion rate and inheritance to be simultaneously constrained the exposure ages of the uppermost uplifted alluvial surfaces are around 140 17 ka140 17 ka 130 9 ka130 9 ka and 47 9 ka47 9 ka from west to east a terrace lying below the 140 ka surface is dated at 65 5 ka65 5 ka the ages of the uplifted and folded alluvial surfaces were then combined with estimates of shortening obtained using two distinct methods 1 the excess area method where sedimentation rates extracted from magnetostratigraphic studies are used to determine the amount of sedimentation after the abandonment of the river and 2 a folding model derived from sandbox experiments the late pleistocene shortening rates are shown to be between 0 4 0 1 mm yr0 4 0 1 mm yr and 0 8 0 5 mm yr0 8 0 5 mm yr on the western part of the fold and 2 1 0 4 mm yr2 1 0 4 mm yr along its central part the central part of the frontal yakeng anticline therefore accommodates up to 25 of the total shortening currently absorbed across the whole eastern tianshan range 8 mm yr however this situation seems to have prevailed for only the last 150 ka as the shortening rate absorbed by this nascent fold was previously ten times slower while the initiation of folding of the yakeng anticline can be traced back to 5 5 ma ago the basinward migration of the active deformation front onto the yakeng fold is a relatively recent phenomenon and appears to be diachronous from west to east probably in relation to the tectonic activity of the folds in the hinterland

erosion control in south china abstract severe soil erosion is common in south china where torrential rainfall erodes the deeply weathered and denuded granitic hills locally developed control measures have been applied successfully to reduce erosion including the benching of steep slopes the construction of check dams and reforestation of particular importance is the treatment of large gullies locally called broken hills these have led to the disintegration of hillslopes and the deposition of colluvium and fines on the agricultural land gully treatment includes the stabilization of the headwalls the containment of sediments in the gully floor zone and the reclamation of flatland below the gully mouth re vegetation of the slopes is essential and the planting of economic crops provides incentive to the farmers to preserve the vegetation cover

geological and physical factors affecting the friction angle of compacted sands this study evaluated the effects of physical characteristics and geologic factors on the shear strength of compacted sands from wisconsin that are used as granular backfill for mechanically stabilized earth walls and reinforced soil slopes physical properties and shear strength were determined for 30 compacted sands collected from a broad range of geological deposits relationships between strength deformation behavior geologic origin and physical properties were used to categorize the sands into four friction angle groups sands with the lowest friction angle are derived from weathering of underlying sandstones and tend to be medium fine well rounded and poorly graded sands sands with the highest friction angle are from recent glacial activity and tend to be coarser grained well graded and or angular sands a multivariate regression model was developed that can be used to predict friction angle of compacted sands from comparable geological origins based on effective particle size d10

assessing the sources of sediment transported in gully systems using a fingerprinting approach an example from south east china abstract eroded sediment is an important feature of permanent gully s development however obtaining the specific characteristics of the sediment transport in the gully can be difficult thus a composite fingerprinting technique incorporating uncertainty analysis has been employed to investigate the mean relative contribution of sediment sources in permanent gullies in this study 31 tracers were measured at 62 different sampling sites from three layers of a gully wall surface layer sl sandy soil layer ssl and semi weathering rock layer swl and 36 sediment samples from the slumping deposit and alluvial fan of the gullies the sediment source tracing procedure was therefore used to assess the relative contribution of each source the mean relative contribution from the sl to the sediment of the slumping deposit is higher in the active gully g1 and is relatively lower in the potentially stable g2 and stable gullies g3 thus there was no obvious gully bank retreat in g2 and g3 in different places of the g1 alluvial fan the mean relative contribution of the sl ssl and swl ranged from 9 11 36 43 and 46 55 respectively however the sediment contribution of the sl increased in g2 and g3 due to the changes in the erosion type the mean relative contributions of the sl were 33 5 g2 and 30 3 g3 these findings have important implications for the establishment of a scientific basis for permanent gully sediment transport management and control policies

effects of hydromechanical loading history and antecedent soil mechanical damage on shallow landslide triggering evidence suggests that the sudden triggering of rainfall induced shallow landslides is preceded by accumulation of local internal failures in the soil mantle before their abrupt coalescence into a landslide failure plane the mechanical status of a hillslope at any given time reflects competition between local damage accumulated during antecedent rainfall events and rates of mechanical healing e g rebonding of microcracks and root regrowth this dynamic interplay between damage accumulation and healing rates determines the initial mechanical state for landslide modeling we evaluated the roles of these dynamic processes on landslide characteristics and patterns using a hydromechanical landslide triggering model for a sequence of rainfall scenarios the progressive nature of soil failure was represented by the fiber bundle model formalism that considers threshold strength of mechanical bonds linking adjacent soil columns and bedrock the antecedent damage induced by prior rainfall events was expressed by the fraction of broken fibers that gradually regain strength or mechanically heal at rates specific to soil and roots results indicate that antecedent damage accelerates landslide initiation relative to pristine undamaged hillslopes the volumes of first triggered landslides increase with increasing antecedent damage however for heavily damaged hillslopes landslide volumes tend to decrease elapsed time between rainfall events allows mechanical healing that reduces the effects of antecedent damage this study proposed a quantitative framework for systematically incorporating hydromechanical loading history and information on precursor events e g such as recorded by acoustic emissions into shallow landslide hazard assessment

making unsaturated soil mechanics accessible for engineers preliminary hydraulic mechanical characterisation and stability assessment the paper presents an accessible approach for preliminary hydraulic and mechanical characterisation of unsaturated soils and stability analysis of geo structures under unsaturated conditions the approach is accessible in the sense that the laboratory investigation and geotechnical analyses can be completed in a relatively short time and at a reasonable cost the overall philosophy behind this approach is that laboratory testing should not be eliminated but kept to a minimum and that any simplification introduced should be conservative the paper illustrates that shear strength can be characterised conservatively by performing constant water content tests with no facilities to control monitor suction and that water retention behaviour can be predicted successfully by performing a single water retention measurement the paper also demonstrates that stability analyses can be carried out within the classical framework of limit analysis we show that a preliminary analysis of the influence of infiltrating rainwater on suction can be carried out using a simple and conservative method that makes use of solutions available in saturated geotechnical textbooks such an approach may be used to assess when it is worthwhile or necessary to conduct further time consuming and costly unsaturated experimental testing field monitoring and numerical analyses when considering the stability of geostructures

monitoring of gully erosion on the loess plateau of china using a global positioning system abstract with the development of a technique global positioning system gps has become progressively less expensive lighter and easier to use the accuracy of gps has been improved and it appears applicable to the continuously monitoring morphology changes on the earth surface with small and slow change the objective of this study is to use gps to measure the morphology of gullies in a small catchment near suide shaanxi province china there are three main gully types in the study area bank gullies floor gullies and hill slope gullies and this study mainly focuses on the hill slope gullies the hill slope gullies in the study area are mainly discontinuous and are developing rapidly the gully density in the study area is very large the retreat rate of hill slope gullies is 0 16 2 02 m year 1 the relationships between the upslope drainage area a and the critical slope gradient s for hill slope gullies is s 0 1839a 0 2385 the values of as2 range from 41 to 814 m2 for the hill slope gully headcuts and most of them fell into the range of 100 300 m2 both of these relationships are suggested as indexes for estimating the location of gully headcuts

pliocene pleistocene initiation style and sequencing of deformation in the central tien shan in response to the indo asian collision deformation of the tien shan initiated at 25 ma along the northwestern margin of the tarim basin 300 km north the kyrgyz range began deforming 15 ma later although multiple intervening structures across the tien shan are currently active the sequencing of initial deformation across the orogen s entire width remains poorly known to determine whether deformation migrated sequentially northward or developed less predictably we documented deformation patterns within the naryn basin in south central kyrgyzstan detailed mapping and a published balanced cross section across the naryn basin suggest that deep seated relatively steeply dipping thrust faults have disrupted the basin during late cenozoic deformation dating of deformed fluvial terraces with ages between 10 and 250 ka constrains the rate of deformation across relatively young structures in the tien shan interior based on geodetic surveys of dated terraces local rates of relative rock uplift span from 0 3 to 3 5 mm yr folding rates and patterns are temporally persistent at a given site moreover they mimic modern geodetic rates measured from interferometric synthetic aperture radar extrapolating these rates into the past suggests that structures within the interior of the naryn basin formed in the last 1 myr whereas the ranges surrounding the basin initiated at least 1 4 myr earlier hence within the naryn basin itself deformation has migrated from margins to interior similarly these new chronologies indicate that at least some deformation in the interior of the tien shan initiated millions of years later than along either orogenic margin 2014 american geophysical union all rights reserved

denudation rates determined from the accumulation of in situ produced 10be in the luquillo experimental forest puerto rico we present a simple method for estimation of long term mean denudation rates using in situ produced cosmogenic 10be in fluvial sediments procedures are discussed to account for the effects of soil bioturbation mass wasting and attenuation of cosmic rays by biomass and by local topography our analyses of 10be in quartz from bedrock outcrops soils mass wasting sites and riverine sediment from the icacos river basin in the luquillo experimental forest puerto rico are used to characterize denudation for major landform elements in that basin the 10be concentration of a discharge weighted average of size classes of river sediment corresponds to a long term average denudation of 43 m ma 1 consistent with mass balance results

modeling the shortening history of a fault tip fold using structural and geomorphic records of deformation 1 we present a methodology to derive the growth history of a fault tip fold above a basal detachment our approach is based on modeling the stratigraphic and geomorphic records of deformation as well as the finite structure of the fold constrained from seismic profiles we parameterize the spatial deformation pattern using a simple formulation of the displacement field derived from sandbox experiments assuming a stationary spatial pattern of deformation we simulate the gradual warping and uplift of stratigraphic and geomorphic markers which provides an estimate of the cumulative amounts of shortening they have recorded this approach allows modeling of isolated terraces or growth strata we apply this method to the study of two fault tip folds in the tien shan the yakeng and anjihai anticlines documenting their deformation history over the past 6 7 myr we show that the modern shortening rates can be estimated from the width of the fold topography provided that the sedimentation rate is known yielding respective rates of 2 15 and 1 12 mm yr across yakeng and anjihai consistent with the deformation recorded by fluvial and alluvial terraces this study demonstrates that the shortening rates across both folds accelerated significantly since the onset of folding it also illustrates the usefulness of a simple geometric folding model and highlights the importance of considering local interactions between tectonic deformation sedimentation and erosion

mechanisms of active folding of the landscape southern tian shan china 1 we explore the kinematic mechanisms of active large scale folding based on analysis of two adjacent major anticlines in tian shan central asia that share an acceleration of shortening rate leading to topographic emergence and folded geomorphic surfaces their folding mechanisms are fundamentally different yakeng anticline is a gentle pure shear detachment fold with 1200 m of shortening and a well constrained history of growth beginning at 5 5 ma with an order of magnitude increase in shortening rate from 0 16 to 1 2 1 6 mm yr at 0 16 0 21 ma the shape of the deformed topographic surface and of subsurface horizons deposited during deformation is a linearly proportional image at reduced amplitude of the deeper structure which shows that instantaneous uplift rates have been pointwise linearly proportional to the current finite fold amplitude in contrast quilitak anticline is a complex fault bend fold with uplift rates proportional to the sine of the fault dip showing discontinuities in uplift rate across active axial surfaces the 10 to 20 km wide anticline is topographically emergent only in a central 5 to 7 km wide mountainous uplift the abrupt southern edge of which is marked by 600 to 700 m high triangular facets that result from active folding of a pediment across an active axial surface the giant facets are shown to form by kink band migration and record postemergence deformation since an order of magnitude acceleration in shortening rate from 0 6 to 4 5 mm yr apparently contemporaneous with yakeng sections logged across the active 115 m wide hinge zone show that recent strata provide a bed by bed record of fold scarp growth which is quantitatively deciphered by fitting bed shapes to a finite width kink band migration model

cosmogenic 10be as a tracer for hillslope and channel sediment dynamics in the clearwater river western washington state we use the 10be concentration in alluvial sand and gravel to document hillslope exposure history and trace the reduction in grain size of river alluvium in the clearwater river basin western washington state clearwater tributary basins wilson creek wc 6 km2 and east fork miller creek efmc 12 km2 were each sampled in headwater and downstream sites for 10be in alluvial sand 0 25 0 50 mm and gravel 22 6 90 mm grain size distributions were determined at each sampling site as well as at several locations along the main stem of the clearwater river channel and watershed geomorphology were quantified using long profile modeling and related morphometric analyses we found that the 10be concentrations differ significantly between the two grain size fractions at all four sampling locations at both headwater sites the gravel exhibits 25 lower 10be concentrations compared to the sand similarly the downstream site of lower wc exhibits 55 lower 10be concentration in the gravel compared to the sand in contrast the gravel from the downstream site on lower efmc exhibited 22 higher 10be concentration in the gravel compared to the sand the disparity in 10be concentration at the wc sites is best explained by shielding of the coarser grain size fraction and its delivery to the channel by deep seated landslide processes more intense landsliding in the downstream wc site is consistent with the increased disparity of 10be between the sand and gravel fractions at that site the inverse relationship between the sand and gravel 10be concentrations at the headwater efmc site is best explained by a sediment provenance mechanism where the hillslope weathering rate exceeds the down slope transport rate for this particular basin the inverse grain size dependency gravel sand observed in the downstream efmc site requires a more complex interplay between hillslope and channel processes including cobble weathering and grain size reduction during fluvial transport resulting in a dilution of the 10be signal in the sand fraction downstream these results underscore the importance of geomorphic consideration and the grain size sampled in the correct interpretation of basin average erosion rates

magnetostratigraphy of the yaha section tarim basin china 11 ma acceleration in erosion and uplift of the tian shan mountains we report a magnetostratigraphic and rock magnetic study of the yaha section located on the southern flank of the central tian shan mountains asia our results show a two fold increase in sedimentation rate as well as marked changes in rock magnetic characteristics ca 11 ma after 11 ma sedimentation rate remained remarkably constant until at least 5 2 ma these findings are consistent with sedimentary records from other sections surrounding the tian shan we conclude that uplift and erosion of the tian shan accelerated ca 11 ma long after the onset of the collision between india and asia and that the range rapidly evolved toward a steady state geometry via a balance between tectonic and erosion processes

cenozoic tectonic deformation and uplift of the south tian shan implications from magnetostratigraphy and balanced cross section restoration of the kuqa depression abstract the collision of india with eurasia has caused rejuvenated deformation and uplift of the remote tian shan intracontinental orogenic range and has led to deposition of thick cenozoic sediments in its flank depressions however our knowledge when and how the range was deformed and uplifted is still limited we carried out detailed tectonic investigations seismostratigraphic analysis and paleomagnetic dating of the thrust fold belt in the kuqa depression at the southern tian shan flank combined with re interpretation of other magnetostratigraphic results in the depression we determined ages of major stratigraphic boundaries and constructed and restored the balanced cross section across the depression the results show that the total cenozoic shortening along the cross section in the depression is 13 95 km significant shortening began at 36 ma accelerated since 13 ma and further increased two to three fold since 6 5 ma especially since 2 6 ma this shortening process caused the development of the kuqa thrust fold system associated with the variation of the sedimentation rate upward coarsening of sediments and a progressive development of growth strata we therefore argue that significant deformation and uplift of the south tian shan began at 36 ma becoming more evident since 13 ma and culminating since 6 5 ma reaching its peak after 2 6 ma

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

weathering profiles in granitoid rocks of the sila massif uplands calabria southern italy new insights into their formation processes and rates abstract in this paper we characterized several weathering profiles developed on granitoid rocks in the sila massif upland calabria southern italy integrating detailed macro and micromorphological observations with physico mechanical field tests and petrographic mineralogical and geochemical analyses we focused our attention on the main weathering and pedogenetic processes trying to understand apparent discrepancies between weathering grade classes based on field description and geomechanical properties and two common weathering indices such as the micropetrographic index ip and the chemical index of alteration cia our results showed that sericite on plagioclase and biotite chloritization that represent inherited features formed during late stage hydrothermal alteration of granitoid rocks may cause an overestimation of the real degree of weathering of primary mineral grains under meteoric conditions especially in lower weathering grade classes moreover the frequent identification of fe mn oxides and clay coatings of illuvial origin rather than or in addition to those formed in situ both at the macro and microscale may also explain an overestimation of the weathering degree with respect to field based classifications finally some apparent inconsistencies between field geomechanical responses and chemical weathering were interpreted as related to physical weathering processes cryoclastism and thermoclastism that lead to rock breakdown even when chemical weathering is not well developed hence our study showed that particular caution is needed for evaluating weathering grades because traditional field and geochemical petrographic tools may be biased by inherited hydrothermal alteration physical weathering and illuvial processes on the basis of chronological constraints to soil formation obtained from a 42 ka old volcanic input mixed to granite parent materials detected in the soil cover of the sila massif upland a first attempt to estimate soil formation rates was achieved for different depths of corresponding weathering profile zones soil formation rates ranged from 0 01 0 07 mm a 1 for a and bw horizons weathering class vi to 0 04 0 36 mm a 1 for the underlying saprolite c and cr layers class v by comparing these results with the corresponding erosion rates available in the literature for the study area that range from

weathering and pedogenesis in the sila grande massif calabria south italy from field scale to micromorphology abstract weathering and soil features in the upland landscapes developed on granitic terrains of the sila grande massif calabria south italy have been studied in this work the attempt to link field scale and micromorphological observations in order to better understand the main weathering processes and their controlling factors is revealed to be very powerful six soil profiles in the area around the cecita lake representative of different geomorphological units were characterised by field work optical microscopy and sem eds analysis a strong influence on weathering and pedogenesis by micro scale features of primary minerals and parent rock fabrics is shown key roles are played also by relief in the development and preservation or stripping of regolith soil mantles in relation to natural and man induced phenomena by time controlling rates and degree of development of the main weathering features by climate in terms of type and intensity of dominant processes

dating fluvial terraces with and profiles application to the wind river wyoming abstract fluvial strath terraces provide a record of river incision and the timing of climatic perturbations to the fluvial system dating depositional surfaces like terraces that are older than the range of 14 c however is difficult we employ a cosmogenic radionuclide crn profile technique that addresses a major problem of crn dating on such surfaces nuclide inheritance by measuring 10 be and 26 al profiles we constrain the exposure age and the mean crn inheritance for the deposit the crn profile also yields a self check on the assumptions underlying the method we report our attempts to date terraces along the wind river wy like many sequences of western north american fluvial terraces these are inferred to reflect oscillation between glacial and interglacial conditions in the headwaters previous dating of some of these terraces and the associated terraces and glacial deposits makes this a unique location to compare dating methods dates from five sites along the bull lake glacial correlative terrace wr 3 are 118 125 ka which agrees with dates on bull lake age moraines and independent age estimates on the terrace and is consistent with the model of terrace glacial relationship crn inheritance is significant and highly variable requiring it be considered despite the additional sampling complexity assuming all inheritance in wr 3 deposits arises during exhumation in the headwaters we obtain minimum mean rates of exhumation of 13 130 m my for the source rocks alternatively assuming the crns are inherited during clast transport the time of fluvial transport from source to terrace is 10 ka it increases downstream and is lower for sand than cobbles the crn ages for older terraces wr 7 300 ka and wr 15 510 ka are lower by 50 than previous estimates based on tephrochronology the most plausible explanation is eolian deflation of a once thicker loess cover on the terrace surfaces mean thicknesses of loess of 0 5 1 5 m are required to reconcile these concentrations of crn with the previous estimates of age difficulty in dating the older terraces emphasizes that geologic caution independent estimates of age and multiple sample sites should still be part of dating depositional surfaces with crns even when employing the inheritance correction technique

suction stress characteristics in granite red soils and their relationship with the collapsing gully in south china abstract the main goal of this research is to study the relationship between the soil suction stress and soil properties within four different soil profiles of collapsing gullies in the hilly granitic region of southern china large differences were found in the four soil layers between granite red soils which are manifested in terms of soil bulk density porosity particle composition clay minerals micromorphology organic matter cation exchange capacity permeability oxide and hydraulics properties the suction stress of the upper soils increases rapidly and almost linearly monotonously with the increase of matric suction whereas c layers increases rapidly first followed by a slow increase the suction stress of the lower soils is significantly smaller than the upper soils under the same matric suction these findings illustrate that the collapsing gully starts from the lower part of the granite red soil and finally caused the gravity collapse in the upper soils which is the main aspect that is different from the other types of soil erosion furthermore suction stress has a very significant correlation with soil properties with a positive correlation to the fine particle content iron and aluminum oxide and a negative correlation to coarse particles in addition suction stress can also be explained as being directly proportional to weathering degree our research provides a theoretical basis for the mass failures of the granite derived red soil in southern china

10be exposure dating of river terraces at the southern mountain front of the dzungarian alatau se kazakhstan reveals rate of thrust faulting over the past 400 ka abstract the mountain belts of the dzungarian alatau se kazakhstan and the tien shan are part of the actively deforming india asia collision zone but how the strain is partitioned on individual faults remains poorly known here we use terrace mapping topographic profiling and 10 be exposure dating to constrain the slip rate of the 160 km long usek thrust fault which defines the southern front of the dzungarian alatau in the eastern part of the fault where the usek river has formed five terraces t 1 t 5 the usek thrust fault has vertically displaced terrace t 4 by 132 10 m at two sites on t 4 exposure dating of boulders amalgamated quartz pebbles and sand from a depth profile yielded 10 be ages of 366 60 ka and 360 77 48 ka both calculated for an erosion rate of 0 5 mm ka combined with the vertical offset and a 45 70 dip of the usek fault these age constraints result in vertical and horizontal slip rates of 0 4 and 0 25 mm a respectively these rates are below the current resolution of gps measurements and highlight the importance of determining slip rates for individual faults by dating deformed landforms to resolve the pattern of strain distribution across intracontinental mountain belts

hinge migrated fold scarp model based on an analysis of bed geometry a study from the mingyaole anticline southern foreland of chinese tian shan 2015 american geophysical union all rights reserved fold scarps a type of geomorphic scarp formed by folding mechanisms of hinge migration or limb rotation serve to delineate both fault bend characteristics and folding histories which can in turn illuminate tectonic processes and seismic hazards associated with thrust systems because the subsurface geometry of folds is commonly difficult to determine existing fold scarp models which rely on both the fold type and its causative fault geometries remain uncertain with respect to the kinematic evolution of a given fold in this paper we develop a model to illustrate that irrespective of specific fold type and subsurface geometries fold scarp growth in the mechanism of hinge migration can be successfully reconstructed based on analyses of bed geometry this model reveals that the underlying bed dips and the ratio of hinge migration distance hinge width control the fold scarp shape and slope during initial growth ratio 1 the slope reaches a maximum which solely depends on underlying bed dips the scarp height however is independent of the hinge width and can be used to quantify folding magnitude application of our model to fold scarps in the mingyaole anticline in the southern foreland of chinese tian shan indicates that the modeled fold scarp geometry can roughly match with field observations the mingyaole shortening rate is estimated to be 5 0 mm a since 15ka such that this single fold has accommodated about half of the regional convergence during the holocene key points folding through curved hinges creates a distinctive fold scarp geometry scarp slope relies on ratio of hinge migration width but scarp height is not shortening rate of the mingyaole fold is estimated to be 5 0 mm a since 15 ka such that this single fold has accommodated about half of the regional convergence during the holocene

controlling factors of gullying in the maracuja catchment southeastern brazil hundreds of gullies vocorocas of huge dimensions up to 400 500 m long 150 m wide and 50 m deep are very common in the small maracuja catchment in southeastern brazil these erosional features which occur with an uneven intensity throughout the area started due to bad soil management practices at the beginning of european settlement at the end of the 17th century and nowadays are still evolving but at a slower rate as surface soils are usually very resistant to erosion the outcrop of the more erodible basement saprolites seems to be an essential condition for their beginning an analysis of well known erosion controlling factors was performed aiming to explain the beginning and evolution of these gullies and to understand the reasons for their spatial distribution data shows that geology and mainly geomorphology are the main controlling factors since gullies tend to be concentrated in basement rock areas with lower relief domain 2 of maracuja catchment mainly at the fringes of broad and flat interfluves at the detailed scale 1 10 000 gullies are more common in amphitheatre like headwater hollows that frequently represent upper quaternary gullies paleogullies which demonstrate the recurrence of channel erosion so gullies occur in areas of thicker saprolites domain 2 in places with a natural concentration of surface and underground water hollows saprolites of the preserved non eroded hollows are usually pressurized confined aquifer due to a thick seal of quaternary clay layer in a similar configuration to the ones found in hollows of mass movement mudflow sites in southeastern brazil therefore the erosion of the resistant soils by human activities such as road cuts and trenches valos or their mobilization by mudflow movements seem to be likely mechanisms of gullying initiation afterwards gullies evolve by a combination of surface and underground processes such as wash and tunnel erosion and falls and slumps of gully walls copyright 2005 john wiley sons ltd

rill erosion processes on a steep colluvial deposit slope under heavy rainfall in flume experiments with artificial rain abstract understanding rill erosion processes is important in the prediction of soil erosion and the prevention of soil loss however limited information is available concerning the impacts of rainfall on rill erosion on steep slopes colluvial deposits with steep slopes make up the packed material underlying the collapsing walls in benggang which collapse due to hydraulic pressure and gravity they contain loose materials and large amounts of coarse particles the objectives of this study were to investigate the impacts of rainfall intensity and slope gradient on the rill erosion process rill development and rill flow dynamic mechanisms on the steep slopes of colluvial deposits the colluvial soils were subjected to simulated rainfall in a 5 m2 5 m by 1 m flume at heavy rainfall intensities 100 120 and 140 mm h 1 and on five steep slopes 20 25 30 35 and 40 rill erosion contributed significantly to colluvial slope erosion on average rills accounted for 61 of the soil loss and the effects of slope gradient were greater than those of the rainfall intensity after rill development rill density rill length width and depth all significantly increased correspondingly the soil loss rate sharply raised and irregularly fluctuated moreover the collapse of rill heads or sidewalls tended to increase the relative contribution to rill erosion and rill development the rill flow was characterized by transitional and subcritical flow regimes the rill flow velocity was the most sensitive hydraulic parameter and the unit stream power provided the optimal hydrodynamic parameter to characterize the dynamic mechanisms of rill erosion on colluvial deposits the collapse of rill heads or sidewalls could result in negative values for critical shear stress critical stream power and critical unit stream power of rill erosion which were 19 pa 5 3 n m 1 s 1 and 0 09 m s 1 respectively these results provide a better understanding of the mechanism of rill erosion on steep slopes

paleozoic accretion and cenozoic redeformation of the chinese tien shan range central asia the tien shan range in central asia contains two late paleozoic sutures the older southern suture marks the collision of a passive margin at the north of the tarim block and an active continental margin subduction under the latter was to the north the younger northern suture separates a northern carboniferous island arc from an active continental margin developed over a south dipping subduction zone the subduction direction under the island arc is unknown mesozoic elastics were deposited over the doubly sutured orogen rate and energy of sedimentation waned until deposition of oligocene conglomerates above a regional unconformity interpreted as marking the onset of deformation induced by the india asia collision molasse deposition accelerated in pliocene and quaternary time and deposition continues today as active thrusts generate relief paleozoic structures control the gross divergence of cenozoic thrusts across the orogen

soil slips on weathering limited slopes underlain by coarse grained granite or fine grained gneiss near seoul republic of korea abstract the chemical mineral physical and mechanical properties of two soil layers on soil slip scars in slopes underlain by coarse grained granite and fine grained granitic gneiss near seoul republic of korea were examined our aim is to study the effect of the mineral grain size of the bedrock on the soil layer structure and the return period of shallow soil slips because of the coarser slope materials in granite resulting from weathering the permeability is larger and the weathering front has a copious water supply also because of the smaller specific surface area of the minerals restricted leaching produces grus from the bedrock so that the rate of formation of soil and in particular the slip plane due to chemical weathering is faster since on granite slopes the leaching proceeds toward the surface the sliding plane is deeper with coarser soft grus resulting in the existence of a minimum c value in the soil layer on gneiss slopes by contrast leaching cannot proceed with decreasing soil depth and the sliding plane is deeper with finer soft grus just above hard grus and has similar c and values as the upper soft grus because the grain size of both soils is the same in the granite soil layers the sliding plane corresponds to the minimum shearing resistance whereas in the gneiss soil layers the shearing resistance increases gradually with soil depth and the sliding plane is formed when the weathering front is located deeper because of the faster soil formation rate and the shallower slip depth in granite slopes the return period of occurrence of soil slips should be shorter in granite slopes than in gneiss slopes

middle pleistocene glaciation in patagonia dated by cosmogenic nuclide measurements on outwash gravels the well preserved glacial record in argentine patagonia offers a 1 ma archive of terrestrial climate extremes in southern south america these glacial deposits remain largely undated beyond the range of radiocarbon dating at ca 40 ka dating old glacial deposits several 105 a by cosmogenic surface exposure methods is problematic because of the uncertainty in moraine degradation and boulder erosion rates here we show that cobbles on outwash terraces can reliably date old glacial deposits in the lago pueyrredon valley 47 5 s argentina favorable environmental conditions e g aridity and strong winds have enabled continuous surface exposure of cobbles and preservation of outwash terraces the data demonstrate that nuclide inheritance is negligible and we therefore use the oldest surface cobbles to date the deposit 10be concentrations in outwash cobbles reveal a major glacial advance at ca 260 ka concurrent with marine isotope stage 8 mis 8 and dust peaks in antarctic ice cores a 10be concentration depth profile in the outwash terrace supports the age and suggests a low terrace erosion rate of ca 0 5 mm ka 1 we compare these data to exposure ages obtained from associated moraines and find that surface boulders underestimate the age of the glaciation by 100 ka thus the oldest boulders in this area do not date closely moraine deposition the 10be concentration in moraine cobbles help to constrain moraine degradation rates these data together with constraints from measured 26al 10be ratios suggest that all moraine boulders were likely exhumed after original deposition we determine the local last glacial maximum lgm occurred at 27 25 ka consistent with the maximum lgm in other parts of patagonia

characteristics of weathering zones of granitic rocks in malaysia for geotechnical engineering design tropical climatic conditions cause severe weathering to rock masses resulting in thick weathering profiles consisting of different weathering zones with complex characteristics feasible geotechnical engineering design requires a detailed understanding of the characteristics of each weathering zone a typical weathering profile is usually characterized by field scale observation and geological study this paper presents the characteristics of weathering zones of various granitic rocks in the south of malaysia this region has a tropical climatic condition the study was carried out in four active quarries located in johor province malaysia and forty sections were investigated in the study areas a typical granitic weathering profile was characterized based on the geological and structural parameters i e joint characteristics corestone occurrence rock soil ratio mass homogeneity color of rock and discoloration at joints surfaces the profile includes common zones ranging from fresh to residual soil however two subzones are introduced based on corestone boulder occurrence in the highly weathered and completely weathered zones this study based on detailed field observations at the mentioned quarries followed by analysis presents an amalgamated picture of weathering zones in granitic profiles of a tropical region like malaysia moreover it is believed that the characterization of the typical weathering profile allows further classification of generally complex weathered rock masses for a specific geotechnical engineering design

cenozoic uplift exhumation and deformation in the north kuqa depression china as constrained by u th he thermochronometry placing spatial and temporal constraints on deformation uplift and exhumation using thermochronology methods can shed light on cenozoic orogenic evolution in the kuqa foreland new apatite u th he and previously published apatite fission track thermochronology are combined with vitrinite reflectance data and modeling to compile a low temperature multi stage thermal history of tectonic uplift thrust and exhumation a rapid uplift and exhumation event originated in south tianshan during the eocene 46 ma with systematic younging of mean apatite u th he ages from north to south from the margin towards the interior uplift and exhumation south edge of the biyoulebaoguzi anticline in the northern monocline belt at 36 ma with more than 3400 m of stratum denuded subsequently deformation and uplift south edge of the biyoulebaoguzi anticline in the northern monocline belt at 36 ma with more than 3400 m of stratum denuded subsequently deformation and uplift extended to the northern edge of kelasu yiqikelike at 10 ma and then at 6 ma the kanyaken anticline formed and uplifted resulting in 3000 3700 m of overburden erosion the data support sequential southward propagating deformation and uplift inferred exhumation in the north kuqa depression during the cenozoic probably as a result of the collision of india with asia far to the south of the tianshan

magnetostratigraphic data on neogene growth folding in the foreland basin of the southern tianshan mountains the tianshan range is one of the longest and highest mountain belts in central asia stretching east west for 2500 km uplift of this late paleozoic orogenic belt resulted from intracontinental deformation caused by the collision of the indian and eurasian plates during the cenozoic era to constrain the timing of cenozoic tectonic deformation of the tianshan range we analyzed the magnetostratigraphy of 3780 m thick neogene deposits from the kuqa foreland basin of southern tianshan the geometry measurements and magnetic fabric data show that syntectonic growth strata began to accumulate at 6 5 ma ago indicating that crustal shortening initiated in the latest miocene the increase in sedimentation rate and an abrupt change of the magnetic fabric parameters also occurred at 6 5 ma accompanied by onset of syntectonic growth strata the latest miocene crustal shortening is a signifi cant tectonic event in the foreland basin of the southern tianshan range in response to the india eurasia collision