quaternary tectonic response to intensified glacial erosion in an orogenic wedge active orogens are thought to behave as internally deforming critical taper wedges that are in rough long term equilibrium with tectonic influx and erosional outflux spatial and temporal variations in climate are therefore hypothesized to have a significant influence on denudation topography and deformation of orogens thereby affecting wedge taper however the impact of the most severe transition in northern hemisphere climate during the cenozoic era the onset of glaciation has hitherto not been empirically documented here we analyse the spatial patterns of denudation and deformation and their temporal variations in the heavily glaciated st elias orogen in southern alaska low temperature thermochronometry thermokinematic modelling and offshore seismic reflection and borehole data suggest that the global scale intensification of glaciation in the middle pleistocene epoch enhanced glacier growth and caused ice streams to advance to the edge of the continental shelf this led to focused denudation across the subaerial reaches of the orogen and burial of the actively deforming wedge toe by the eroded sediment we propose that this climatically driven mass redistribution forced a structural reorganization of the orogen to maintain critical taper our empirical results thus support decades of numerical model predictions of orogenesis and provide compelling field evidence for the significant impact of climate change on tectonics intense glaciation during the middle pleistocene epoch led to focused denudation and mass redistribution within the st elias orogen in southern alaska and resulted in structural reorganization of the orogen the tectonic response of this orogen to climate change is consistent with predictions of numerical models

comparison of smectite and illite rich gouge frictional properties application to the updip limit of the seismogenic zone along subduction megathrusts along plate boundary subduction thrusts the transformation of smectite to illite within fault gouge at temperatures of 150 c is one of the key mineralogical changes thought to control the updip limit of seismicity if correct this hypothesis requires illite rich gouges to exhibit frictionally unstable velocity weakening behavior here we report on laboratory experiments designed to investigate the frictional behavior of natural and synthetic clay rich gouges we sheared 5 mm thick layers of commercially obtained pure ca smectite a suite of smectite quartz mixtures and natural illite shale grain size ranging from 2 to 500 m in the double direct shear geometry to shear strains of 7 30 at room humidity and temperature xrd analyses show that the illite shale contains dominantly clay minerals and quartz within the clay sized fraction 40 mpa our data specifically the velocity strengthening behavior of illite shale under a wide range of conditions do not support the hypothesis that the smectite illite transition is responsible for the seismic aseismic transition in subduction zones we suggest that other depth and temperature dependent processes such as cementation consolidation and slip localization with increased shearing may play an important role in changing the frictional properties of subduction zone faults and that these processes in addition to clay mineralogy should be the focus of future investigation

the influence of climate on the tectonic evolution of mountain belts simple physical arguments analogue experiments and numerical experiments all suggest that the internal dynamics of actively deforming collisional mountain ranges are influenced by climate however obtaining definitive field evidence of a significant impact of climate on mountain building has proved challenging spatial correlations between intense precipitation or glaciation and zones of rapid rock uplift have indeed been documented in numerous mountain ranges and are consistent with model predictions more compelling evidence such as tectonic changes in response to rather than just coincident with climate change has however rarely been documented triggered by a climate driven increase in erosion rate friction dominated mountain ranges are expected to show a number of simultaneous responses a decrease in the width of the range a temporary increase in sediment yield a persistent increase in the rate of rock uplift and a reduction in the subsidence rate of surrounding basins the most convincing field evidence for such a coordinated response of a mountain range to climate change comes from the european alps and the st elias range of alaska field studies and experimental research during the past two decades have provided considerable evidence for a significant influence of climate on tectonics recent advances suggest that model predictions can guide future fieldwork aimed at substantiating this view

unravelling the development of a spheroidally weathered diorite gabbro santa margarita ecological reserve peninsular ranges southern california usa abstract within santa margarita ecological reserve smer southern california an 108 ma diorite gabbro pluton has weathered spheroidally resulting in the formation of concentric rindlets i e a rindlet zone around an unaltered ellipsoidal core of the parent rock to our knowledge little is known about how spheroidal weathering is produced in mediterranean climates like that characteristic of portions of the peninsular ranges hence we undertook a detailed study aimed at determining the textural and chemical changes associated with the spheroidal weathering of the diorite gabbro pluton the parental spheroidally weathered corestone is characterized by a hypidomorphic granular texture and consists primarily of plagioclase amphibole and biotite along with minor amounts of pyroxene and quartz within the corestone sericite and uncommonly calcite and chlorite replace plagioclase the latter mineral also infrequently replaces portions of amphibole and biotite such alteration products are derived from sub solidus deuteric alteration of the pluton xrd clay mineral analysis of the 13 rindlets indicates the presence of mostly kaolinite and vermiculite and a far lesser volume of green smectite thin section study of rindlet samples suggests that vermiculite is derived from the weathering of biotite the most extensively altered mineral in the rindlet zone such alteration is paralleled by statistically significant losses of k mass across the rindlet zone in addition statistically significant losses of ca and na mass across the rindlet zone likely reflect conversion of sericite to kaolinite in contrast the absence of statistically significant losses of mg fe and mn over most of the rindlet zone implies that fluids were mostly oxidizing and that any mg leached from amphibole was likely fixed within smectite while leached fe and mn precipitated out as oxides or oxyhydroxides though calcite was present in the corestone its absence in the rindlets indicates that fluids were sufficiently acidic to dissolve and remove it previous studies have shown that spheroidal weathering occurs when volume expansion produced by a positive v of reaction builds up internal elastic strain energy in the rock for example this type of reaction occurs when iron oxidizes within biotite resulting in an expansion of d 001 from 10 a to 10 5 a or when biotite is transformed into vermiculite leading to an expansion of d 001 from 10 a to 14 a data presented here suggest that the conversion of biotite to vermiculite and the resulting positive v produced the spheroidal fracturing of the corestone at smer hence these and other data discussed in this paper suggest that the weathering of biotite is the primary driving force in the formation of spheroidally weathered corestone in the mediterranean climate of the peninsular ranges

the importance of overpressure timing and permeability evolution in fine grained sediments undergoing shear abstract we summarise new experimental data which clarify the hydrological behaviour of clayey sediments undergoing shear and which emphasise the importance of the relative timing of deformation and overpressure fluid flow in fine grained materials subjected to shear is strongly dependent on the previous stress history of the material underconsolidated sediments such as those that retain high porosities through retarded dewatering and consequent excess pore fluid pressure generation deform by bulk volume loss which reduces permeability the deformation fabrics are pervasive in style weakly developed and without a significant influence on hydrological properties in contrast sediment that has been consolidated and then subjected to excess pore fluid pressure deforms dilatively along discrete brittle shear zones which markedly affect the permeability moreover below a certain threshold of effective stress these localised zones prompt a markedly non linear increase in hydraulic conductivity a laboratory demonstration and quantification of the concept of fracture permeability

snow accumulation rate on qomolangma mount everest himalaya synchroneity with sites across the tibetan plateau on 50 100 year timescales annual layer thickness data spanning ad 1534 2001 from an ice core from east rongbuk col on qomolangma mount everest himalaya yield an age depth profile that deviates systematically from a constant accumulation rate analytical model the profile clearly shows that the mean accumulation rate has changed every 50 100 years a numerical model was developed to determine the magnitude of these multi decadal scale rates the model was used to obtain a time series of annual accumulation the mean annual accumulation rate decreased from 0 8m ice equivalent in the 1500s to 0 3m in the mid 1800s from 1880 to 1970 the rate increased however it has decreased since 1970 comparison with six other records from the himalaya and the tibetan plateau shows that the changes in accumulation in east rongbuk col are broadly consistent with a regional pattern over much of the plateau this suggests that there may be an overarching mechanism controlling precipitation and mass balance over this area however a record from dasuopu only 125 km northwest of qomolangma and 700 m higher than east rongbuk col shows a maximum in accumulation during the 1800s a time during which the east rongbuk col and tibetan plateau ice core and tree ring records show a minimum this asynchroneity may be due to altitudinal or seasonal differences in monsoon versus westerly moisture sources or complex mountain meteorology

association between atmospheric circulation patterns and firn ice core records from the inilchek glacierized area central tien shan asia 1 glacioclimatological research in the central tien shan was performed in the summers of 1998 and 1999 on the south inilchek glacier at 5100 5460 m a 14 36 m firn ice core and snow samples were collected and used for stratigraphic isotopic and chemical analyses the firn ice core and snow records were related to snow pit measurements at an event scale and to meteorological data and synoptic indices of atmospheric circulation at annual and seasonal scales linear relationships between the seasonal air temperature and seasonal isotopic composition in accumulated precipitation were established changes in the 18o air temperature relationship in major ion concentration and in the ratios between chemical species were used to identify different sources of moisture and investigate changes in atmospheric circulation patterns precipitation over the central tien shan is characterized by the lowest ionic content among the tien shan glaciers and indicates its mainly marine origin in seasons of minimum precipitation autumn and winter water vapor was derived from the arid and semiarid regions in central eurasia and contributed annual maximal solute content to snow accumulation in tien shan the lowest content of major ions was observed in spring and summer layers which represent maximum seasonal accumulation when moisture originates over the atlantic ocean and mediterranean and black seas

fault zone architecture of the san jacinto fault zone in horse canyon southern california a model for focused post seismic fluid flow and heat transfer in the shallow crust abstract we report results of a new study of the architecture of the san jacinto fault zone in horse canyon california where stream incision has exposed a nearly continuous outcrop of the fault zone at 0 4 km depth the fault zone at this location consists of a fault core transition zone damage zone and tonalitic wall rocks we collected and analyzed samples for their bulk and grain density geochemical data clay mineralogy and textural and modal mineralogy progressive deformation within the fault zone is characterized by mode i cracking subsequent shearing of already fractured rock and cataclastic flow grain comminution advances towards the strongly indurated cataclasite fault core damage progression towards the core is accompanied by a decrease in bulk and grain density and an increase in porosity and dilational volumetric strain palygorskite and mixed layer illite smectite clay minerals are present in the damage and transition zones and are the result of hydrolysis reactions the estimated percentage of illite in illite smectite increases towards the fault core where the illite smectite to illite conversion is complete suggesting elevated temperatures that may have reached 150 c chemical alteration and elemental mass changes are observed throughout the fault zone and are most pronounced in the fault core we conclude that the observed chemical and mineralogical changes can only be produced by the interaction of fractured wall rocks and chemically active fluids that are mobilized through the fault zone by thermo pressurization during and after seismic events based on the high element mobility and absence of illite smectite in the fault core we expect that the greatest water rock ratios occur within the fault core these results indicate that hot pore fluids circulate upwards through the fractured fault core and into the surrounding damage zone though difficult to constrain we speculate that the site studied during this investigation may represent the top of a narrow ephemeral hydrothermal circulation cell that dissipates heat generated from rupture events at deeper levels 4 km

volume loss model for trace element enrichments in mylonites mylonites from three widely separated localities along the fries ductile deformation zone in the blue ridge province show substantial enrichments in trace and minor elements tio sub 2 p sub 2 o sub 5 zr y and v and depletions in rb and sr relative to the protolith two end member hypotheses can explain the enrichments one involves partitioning to and from an infiltrating fluid and assumes that all the elements were mobile the second hypothesis assumes the high field strength cations were largely immobile and that their enrichment is due to large volume losses in the mylonites modeling indicates that ti is immobile for fluid rock ratios as high as 10 sup 4 and petrographic and modal data support a volume loss mechanism volume loss was accommodated by loss of sio sub 2 and alkalies during feldspar dissolution calculated fluid rock volume ratios required to produce the observed sio sub 2 losses assuming ti mobility range from 70 to 600 variable enrichments in p zr y and v are attributed to selective mobility of these elements during fluid infiltration

fracture surface energy of the punchbowl fault san andreas system the energetics of earthquake rupture slip weakening and rupture surface formation are poorly understood by measuring the energy associated with fracture damage along the punchbowl fault in the devil s punchbowl los angeles county park part of the san andreas system chester et al show that the fracture surface energy for rupture along a mature fault of this type accounts for only a small fraction of the energy released during large earthquakes as determined by seismologists this suggests that mechanisms such as melt lubrication and thermal pressurization are responsible for slip weakening fracture energy is a form of latent heat required to create an earthquake rupture surface and is related to parameters governing rupture propagation and processes of slip weakening1 2 3 fracture energy has been estimated from seismological and experimental rock deformation data4 5 6 7 8 yet its magnitude mechanisms of rupture surface formation and processes leading to slip weakening are not well defined8 9 10 here we quantify structural observations of the punchbowl fault a large displacement exhumed fault11 12 in the san andreas fault system and show that the energy required to create the fracture surface area in the fault is about 300 times greater than seismological estimates would predict for a single large earthquake if fracture energy is attributed entirely to the production of fracture surfaces then all of the fracture surface area in the punchbowl fault could have been produced by earthquake displacements totalling 1 km but this would only account for a small fraction of the total energy budget and therefore additional processes probably contributed to slip weakening during earthquake rupture

1300 years of climatic history for western central asia inferred from tree rings more than 200 000 ring width measurements from 384 trees were obtained for 20 individual sites ranging from the lower to upper local timber lines in the northwest karakorum of pakistan and the southern tien shan of kirghizia samples were obtained predominantly from juniper species juniperus and were analysed to reconstruct regional climatic variation patterns in western central asia since ad 618 site distri bution represents diverse ecological conditions e g combinations of temperature and moisture stress within the karakorum and tien shan mountains permitting both intra montane and inter montane comparisons of chronologies three different types of chronologies ree ecting interannual decadal and centennial scale ring width variations were calculated a statistic skeleton plotting technique was used to identify ring width pointer years interannual a 101 year kernel e lter was used to identify decadal scale variations and for a subset of long lived trees the mean ring width of the entire single series was used to identify centennial trends after extracting and calibrating each of these three distinct wavelengths in ring width variation the results were combined into a comprehensive reconstruction ree ecting primarily temperature e uctuations in western central asia since ad 618 the nature and the temporally changing strength of the climatic signals of this reconstruction are discussed in detail a maximum latewood density record of pinus tienschanica from central tien shan was used as a predictor series to calibrate and validate tree ring width variation in so doing we link our results to the circumpolar maximum latewood density network briffa et al 1998a 1998b schweingruber and briffa 1996

tectonic geomorphology the hills came tumbling down large earthquakes can build mountains but they can also trigger landslides that wear landscapes away an analysis from the 2008 wenchuan earthquake shows that landslides destroyed more topography than was created by uplift

geologic and geochemical study of the picacho gold mine california gold in a low angle normal fault environment the picacho gold deposit located in southeasternmost california is a low grade gold deposit in a nearly flat lying denudational fault of regional extent and probable oligocene age the deposit is hosted by intensely fractured and faulted mesozoic leucogranite and by chloritic augen gneiss and schist and is overlain unconformably and in fault contact by unmineralized late oligocene quechan volcanic rocks the deposit is structurally characterized by normal and normal oblique faults of low to high dip at shallow depths in the mine merging downward with a synchronous low dipping ore stage extensional fault system the chocolate mountains gatuna fault of probable oligocene age in deeper portions of the deposit the fault system was infiltrated during much of its active life by hot dilute highly exchanged meteoric water having temperatures of 170 210 c salinity 2 wt nacl equivalent and calculated 18ofluid between 2 6 and 5 2 this main stage fluid precipitated quartz pyrite and specular hematite accompanied by silicification and sericitization auriferous ore stage pyrite was precipitated late in the fault evolution probably by mixing of reducing ore fluid with relatively oxidized main stage fluid during regional oligocene extension on the chocolate mountains gatuna fault the picacho deposit is characterized by a gold arsenic antimony geochemical signature consistent with bisulfide complexing of gold in reducing fluid in contrast with typical denudation fault hosted base metal rich deposits associated with high salinity fluids elsewhere in the southwestern united states the deposit is overprinted by miocene normal faults having a wide range of dips these postore faults are associated with red earthy hematite precipitation pyrite oxidation and supergene enrichment of gold

spatial and temporal variability of snow accumulation using ground penetrating radar and ice cores on a svalbard glacier a 50 mhz ground penetrating radar was used to detect horizontal layers in the snowpack along a longitudinal profile on nordenskjoldbreen a svalbard glacier the profile passed two shallow and one deep ice core sites two internal radar reflection layers were dated using parameters measured in the deep core radar travel times were converted to water equivalent yielding snow accumulation rates along the profile for three time periods 1986 99 1963 99 and 1963 86 the results show 40 60 spatial variability in snow accumulation over short distances along the profile the average annual accumulation rate for 1986 99 was found to be about 12 higher than for the period 1963 86 which indicates increased accumulation in the late 1980s and 1990s

orogeny and orography the effects of erosion on the structure of mountain belts a numerical model of the coupled processes of tectonic deformation and surface erosion in convergent orogens is developed to investigate the nature of the interaction between these processes crustal deformation is calculated by a two dimensional finite element model of deformation in response to subduction and accretion of continental crust erosion operates on the uplifted surface of this model through fluvial incision which is taken to be proportional to stream power the relative importance of the tectonic and erosion processes is given by a dimensionless erosion number relating convergence velocity rock erodibility and precipitation rate this number determines the time required for a system to reach steady state and the final topographic shape and size of a mountain belt fundamental characteristics of the model orogens include asymmetric topography with shallower slopes facing the subducting plate and an asymmetric pattern of exhumation with the deepest levels of exhumation opposite to subduction these characteristics are modified when the regional climate exhibits a dominant wind direction and orographically enhanced precipitation on one side of the mountain belt the two possible cases are dominant wind in the direction of motion of the subducting plate and dominant wind direction in the opposite direction of the subducting plate velocity models of the former case predict a broad zone of exhumation with maximum exhumation in the orogen interior models of the latter case predict a focused zone of exhumation at the margin of the orogen and at high erosion number a reversal in the topographic asymmetry natural examples of these two cases are presented the southern alps of new zealand exhibits the climate and exhumation asymmetry characteristic of wind in the direction opposite to motion of the subducting plate the asymmetry of topography suggests that erosion is not efficient enough to have reversed the topographic asymmetry the contrasting example of dominant wind in the direction of subduction motion is provided by the olympic mountains of washington state in this case exhumation of deep levels of the cascadia accretionary wedge shows a broad domal pattern consistent with the observed orographic precipitation

coseismic horizontal shortening associated with the 2008 wenchuan earthquake along the baishahe segment from high resolution satellite images abstract many coseismic deformation data from the wenchuan earthquake of 12 may 2008 have been published however most of the data record strike slip and vertical offsets and there is little information on the horizontal shortening components to determine the amount of horizontal shortening we suggest a new method of measuring the differences in the positions of geometrical markers observed in satellite images before and after the earthquake we found two roads that run nearly parallel to the earthquake rupture but on opposite sides and we examined the spacing between them before and after the earthquake we were able to measure horizontal shortenings that average 6 6 1 84 m with a maximum of 11 0 m and a minimum of 1 1 m as an alternative method we used a gps rtk field survey system to measure the spacing of the two roads after the earthquake and then measured the difference between that and the spacing determined from satellite images before the earthquake this method gave horizontal shortenings that average 7 1 1 3 m with a maximum of 9 85 m and a minimum of 3 8 m the shortenings measured using either of these two methods are larger than those directly measured in the field in the immediate vicinity of the fault which suggests that the coseismic horizontal shortening is distributed over a wider area that extends some distance away from the brittle fault scarp itself finally the results support a low angle fault model for the wenchuan earthquake and they provide useful insights into the seismotectonics of eastern tibet especially the building of the longmenshan range

cataclastic rocks of the san gabriel fault an expression of deformation at deeper crustal levels in the san andreas fault zone the san gabriel fault a deeply eroded late oligocene to middle pliocene precursor to the san andreas was chosen for petrologic study to provide information regarding intrafault material representative of deeper crustal levels cataclastic rocks exposed along the present trace of the san andreas in this area are exclusively a variety of fault gouge that is essentially a rock flour with a quartz feldspar biotite chlorite amphibole epidote and fe ti oxide mineralogy representing the milled down equivalent of the original rock anderson and osborne 1979 anderson et al 1980 likewise fault gouge and associated breccia are common along the san gabriel fault but only where the zone of cataclasis is several tens of meters wide at several localities the zone is extremely narrow several centimeters and the cataclastic rock type is cataclasite a dark aphanitic and highly comminuted and indurated rock the cataclastic rocks along the san gabriel fault exhibit more comminution than that observed for gouge along the san andreas the average grain diameter for the san andreas gouge ranges from 0 01 to 0 06 mm for the san gabriel cataclastic rocks it ranges from 0 0001 to 0 007 mm whereas the san andreas gouge remains particulate to the smallest grain size the ultra fine grain matrix of the san gabriel cataclasite is composed of a mosaic of equidimensional interlocking grains the cataclastic rocks along the san gabriel fault also show more mineralogiec changes compared to gouge from the san andreas fault at the expense of biotite amphibole and feldspar there is some growth of new albite chlorite sericite laumontite analcime mordenite and calcite the highest grade of metamorphism is laumontite chlorite zone zeolite facies mineral assemblages and constrained uplift rates allow temperature and depth estimates of 200 30 c and 2 5 km thus suggesting an approximate geothermal gradient of 50 c km such elevated temperatures imply a moderate to high stress regime for the san andreas which is consistent with experimental rock failure studies moreover these results suggest that the previously observed lack of heat flow coaxial with the fault zone may be the result of dissipation rather than low stress much of the mineralogy of the cataclastic rocks is still relict from the earlier igneous or metamorphic history of the protolith porphyroclasts even in the most deformed rocks consist of relict plagioclase oligoclase to andesine alkali feldspar quartz biotite amphibole epidote allanite and fe ti oxides ilmenite and magnetite we have found no significant development of any clay minerals illite kaolinite or montmorillonite for many sites the compositions of these minerals directly correspond to the mineral compositions in rock types on one or both sides of the fault whole rock major and trace element chemistry coupled with mineral compositions show that mixing within the zone of cataclasis is not uniform and that originally micaceous foliated or physically more heterogeneous rock units may contribute a disproportionally large amount to the resultant intrafault material as previously found for the gouge along the san andreas chemical mobility is not a major factor in the formation of cataclastic rocks of the san gabriel fault we see only minor changes for si and alkalies however there is a marked mobility of li which is a probable result of the alteration and formation of new mica minerals the gouge of the san andreas and san gabriel faults probably formed by cataclastic flow there is some indication presently not well constrained that the fine grained matrix of the cataclasite of from the san gabriel fault formed in response to superplastic flow

dynamic rupture on a material interface with spontaneous generation of plastic strain in the bulk abstract we discuss 2d simulations of in plane ruptures on a fault between different solids in a model that includes dynamic generation of plastic strain off the fault the fault is governed by a regularized friction with a gradual response to abrupt changes of normal stress while plastic strain in the bulk is governed by a coulomb yielding criterion the occurrence of off fault damage stabilizes the slip velocity on the fault stable self sustaining ruptures propagate on the material interface as narrow unidirectional pulses in the direction of slip on the more compliant side of the fault plastic strain is generated only on the stiffer side of the fault the tensional quadrant in the direction of rupture propagation in a strip of approximately constant width that is correlated with the slip velocity on the fault simulations for various values of confining normal stress material contrast and cohesion in the bulk suggest that significant generation of off fault damage is limited to conditions that correspond to the top few kilometers of the crust the results are compatible with field observations of shallow asymmetric damage patterns in the structure of several large faults

identifying a reference frame for calculating mass change during weathering a review and case study utilizing the c program assessing element immobility and critical ratio methodology abstract the first step in calculating mass changes that occur during the transformation of plutonic rock to saprock involves the determination of a reference frame i e an immobile element whose mass was conserved during the alteration process procedures for identifying the statistical properties of immobile elements have been available since 1990 but have not generally been applied we therefore developed the c program assessing element immobility aei that allows for rapid assessment of those elements possessing the statistical properties of immobility aei utilizes algorithms that test for equal distributions and unchanging means of ratios subcompositional independence and subcompositional invariance following discussion of the general mathematical and statistical procedures implemented in aei we utilize it in a case study involving three sites in an 30 m thick section of regolith zr i is located near the base of the regolith while zr ii and zr iii are located at depths of 20 m and 5 m respectively from each site previous workers chemically analyzed a number of samples from saprock and adjacent unweathered corestones in addition xrd work showed that from zr i to zr ii to zr iii biotite was altered to vermiculite vermiculite kaolinite and vermiculite mixed layer biotite vermiculite kaolinite respectively at zr iii the most dominant clay mineral is kaolinite aei performs a series of tests to assess whether or not a given set of elements possess the statistical properties for immobility it identified the following elements as a potential reference frame al na fe mg ti and p at zr i si al fe mn mg ti and p at zr ii and mg and mn at zr iii however critical ratio methodology indicated that the precision as measured by the smallest 95 confidence interval is greatest for al2o3corestone al2o3saprock and na2ocorestone na2osaprock at zr i for sio2corestone sio2saprock at zr ii and for mgocorestone mgosaprock at zr iii mass balance results using al2o3 and na2o at zr i were nearly identical and as a result only the results derived from al2o3 are reported here using al2o3 sio2 and mgo as reference frame elements for zr i zr ii and zr iii respectively revealed the following statistically significant losses of k mass 14 9 8 at zr i 28 11 9 at zr ii and 33 8 7 at zr iii in addition at zr iii the statistically significant loss of 36 13 11 p mass is attributed to the dissolution of apatite and the small nominal loss of 6 5 5 ca mass may reflect incongruent leaching of plagioclase and or apatite in contrast the small additions of 5 5 4 al 5 2 2 fe and 4 2 2 ti mass at zr iii are likely the result of the translocation of kaolinite and kaolinitized biotite particles into the crack system by downward percolating fluids and the exchange and adsorption of al fe and ti ions onto the illuviated clay lining as it evolved over time overall the interplay between eluviation and illuviation at zr iii translates into a statistically significant 5 3 3 increase in bulk mass

glacial melt under a porous debris layer in this paper we undertake a quantitative analysis of the dynamic process by which ice underneath a dry porous debris layer melts we show that the incorporation of debris layer airflow into a theoretical model of glacial melting can capture the empirically observed features of the so called ostrem curve a plot of the melt rate as a function of debris depth specifically we show that the turning point in the ostrem curve can be caused by two distinct mechanisms the increase in the proportion of ice that is debris covered and or a reduction in the evaporative heat flux as the debris layer thickens this second effect causes an increased melt rate because the reduction in latent energy used for evaporation increases the amount of energy available for melting our model provides an explicit prediction for the melt rate and the temperature distribution within the debris layer and provides insight into the relative importance of the two effects responsible for the maximum in the ostrem curve we use the data of nicholson and benn 2006 to show that our model is consistent with existing empirical measurements

effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments with implications for provenance studies the bulk chemical compositions mineralogy and mineral proportions of sands and muds of the mallacoota basin in southeastern australia reflect the composition of weathering profiles mantling source rocks rather than bedrock muds contain abundant clay minerals that are virtually absent from the source rocks but abundant in the weathering profiles sands are strongly enriched in quartz relative to source rocks even in the headwaters of the fluvial system demonstrating that feldspar destruction occurs by in situ chemical weathering within profiles and before detritus enters the fluvial system k feldspar is proportionally more abundant in fluvial sands than in source rocks because plagioclase is more rapidly destroyed than either quartz or k feldspar in weathering profiles subsequent erosion and sorting produce sands enriched in quartz with high k feldspar plagioclase ratios relative to source rocks the composition of plagioclase incorporated into the fluvial sands is also controlled by chemical weat

on steady states in mountain belts the dynamic system of tectonics and erosion contains important feedback mechanisms such that orogenic systems tend toward a steady state this concept is often invoked but the nature of the steady state is commonly not specified we identify four types of steady state that characterize the orogenic system and illustrate these cases by using numerical model results and natural examples these types are 1 flux steady state 2 topographic steady state 3 thermal steady state and 4 exhumational steady state they refer to the erosional flux the topography the subsurface temperature field and the spatial pattern of cooling ages respectively models suggest that the topography will reach a steady mean form at the scale of an orogenic belt but perfect topographic steady state is unlikely to be achieved at shorter length scales thermal steady state is a precondition for exhumational steady state and in the case of temperature dependent deformation topographic steady state exhumational steady state is characterized by reset age zones spatially nested according to closure temperature as illustrated in natural systems from new zealand the cascadia accretionary margin and taiwan

principal fault zone width and permeability of the active neodani fault nobi fault system southwest japan the internal structure and permeability of the neodani fault which was last activated at the time of the 1891 nobi earthquake m8 0 were examined through field survey and experiments a new exposure of the fault at a road construction site reveals a highly localized feature of the past fault deformation within a narrow fault core zone the fault of the area consists of three zone units towards the fault core a protolith rocks b 15 to 30 m of fault breccia and c 200 mm green to black fault gouge within the fault breccia zone cataclastic foliation oblique to the fault has developed in a fine grained 2 m wide zone adjacent to the fault foliation is defined by subparallel alignment of intact lozenge shaped clasts or by elongated aggregates of fine grained chert fragments the mean angle of 20 between the foliation and the fault plane suggests that the foliated breccia accommodated a shear strain of 5 assuming simple shear for the rotation of the cataclastic foliation previous trench surveys have revealed that the fault has undergone at least 70 m of fault displacement within the last 20 000 years in this locality the observed fault geometry suggests that past fault displacements have been localized into the 200 mm wide gouge zone gas permeability analysis of the gouges gives low values of the order of 10 20 m2 water permeability as low as 10 20 m2 is therefore expected for the fault gouge zone which is two orders of magnitude lower than the critical permeability suggested for a fault to cause thermal pressurization during a fault slip

elevation change of fedchenko glacier pamir mountains from gnss field measurements and tandem x elevation models with a focus on the upper glacier fedchenko glacier experienced a large thickness loss since the first scientific investigations in 1928 as the largest glacier in the pamir mountains this glacier plays an important role for the regional glacier mass budget we use a series of global navigation satellite systems observations from 2009 to 2016 and tandem x elevation models from 2011 to 2016 to investigate recent elevation changes accounting for radar wave penetration minimizes biases in elevation that can otherwise reach up to 6 m in dry snow on fedchenko glacier with mean values of 3 4 m in the high accumulation regions the seasonal elevation changes reach up to 5 m the glacier surface elevation decreased along its entire length over multi year periods thinning rates increased between 2000 and 2016 by a factor of 1 8 compared with 1928 2000 resulting in peak values of 1 5 m a 1 even the highest accumulation basins above 5000 m elevation have been affected by glacier thinning with change rates between 0 2 and 0 4 m a 1 from 2009 to 2016 the estimated glacier wide mass balance rates are 0 27 0 05 m w e a 1 for 2000 to 2011 and 0 51 0 04 m w e a 1 between 2011 and 2016

snow accumulation variability at altitude of 7010 m a s l in muztag ata mountain in pamir plateau during 1958 2002 summary precipitation over high mountain is significant for glacier development and river runoff in arid tarim basin in the northwest china however a coherent perspective of precipitation variability at high altitude in tarim basin has not been presented until now here a 41 m ice core at altitude of 7010 m a s l was drilled and gotten to determine annual snow accumulation rates at muztag ata mountain in the headwater of tarim river in pamir plateau during summer 2003 using strong seasonally variation of oxygen isotope and radioactivity reference layers the core was dated reliably back to 1958 and resulted in a 45 year record between 1958 and 2002 the mean annual snow accumulation was about 605 mm water equivalent which is almost 10 times than precipitation in piedmont with elevation below 3000 m a s l the snow accumulation is characterized by high values in 1960s and early 1970s followed by a drop in the middle 1970s and a recent decreasing trend further analysis suggests the upstream zonal flow variation as the major mechanism linking the regional snow accumulation fluctuation to macroscale circulation conditions during the high snow accumulation years the westerly winds between 30 and 50 n from the mediterranean sea to pamir plateau are weakened the decreased upstream westerly winds generate anomalous cyclonic flows in the pamir plateau which results in an enhanced advection of moisture from the tropics to the vicinity of muztag ata mountain and is thus consistent with enhanced snow accumulation at the core site during the low snow accumulation years the above processes are reversed on the basis of this high altitude snow accumulation and temperature a linear regression model is established to simulate annual mass balance in muztag ata region results reveal that snow accumulation conditions largely determine the annual mass balance which has stronger impaction on tarim river runoff

constitutive mass balance relations between chemical composition volume density porosity and strain in metasomatic hydrochemical systems results on weathering and pedogenesis relations characterizing the chemical physical and mechanical changes resulting from metasomatic hydrochemical processes are developed using mass balance models which formally link chemical composition to bulk density mineral density volumetric properties porosity and amount of deformation strain rigorous analysis of aqueous solute transport effects is then made possible in a variety of porous media flow environments including chemical weathering pedogenesis soil formation diagenesis ore deposition and enrichment and metamorphism application of these linear constitutive relations to chemical weathering profiles shows that immobile and locally mobile chemical elements with masses conserved on the scale of soil profiles can be accurately identified from analysis of appropriate data arrays and then used as natural geochemical tracers to infer the nature and extent of hydrochemical weathering processes and volume changes during pedogenesis assumptions commonly made in the past about the supposed immobility of certain elements e g ti and zr become unnecessary quantitative differentiation between the effects of residual and supergene fractionation is then easily made these methods are applied to ni rich laterites developed by weathering of ultramafic rocks showing that during ordinary residual enrichment ni is concentrated by as much as 4 protolith peridotite concentrations this occurs simply by silicate mineral dissolution and removal of chemical elements other than ni e g mg with a corresponding reduction in saprolite density and increase in bulk porosity without significant deformation in contrast laterites with mineable concentrations of ni which are similarly undeformed such as the nickel mountain mine in riddle oregon have experienced in addition to residual enrichment strong supergene enrichment by fractionation of ore elements between a leached zone from which ni is extracted and a complementary enriched zone positioned farther along the direction of ground water flow soil forming processes in podzol chronosequences developed on sandy beach terraces of the mendocino coast of california involved soil column collapse of 60 percent by dissolution of silicate minerals in the albic horizon of al and fe leaching and 70 percent dilation expansion in the overlying organic rich layer by root growth the amount of erosion based upon paleosurface reconstructions using the excess mass of fe al pb ga and cu in the zone of supergene enrichment spodic horizon below the ground water table indicates that subsurface erosion by dissolutional collapse is three times that of surficial erosion finally using published chemical data for ti zr and cr on major bauxite deposits in australia where erosion rates are thought to be low we infer that there may have been major amounts of dissolutional collapse to explain the upwards increase of detrital zircon and rutile in weathering profiles

fracturing and hydrothermal alteration in normal fault zones large normal fault zones are characterized by intense fracturing and hydrothermal alteration displacement is localized in a slip zone of cataclasite breccia and phyllonite surrounding corrugated and striated fault surfaces slip zone rock grades into fractured but less comminuted and hydrothermally altered rock in the transition zone which in turn grades abruptly into the wall rock fracturing and fluid flow is episodic because permeability generated during earthquakes is destroyed by hydrothermal processes during the time between earthquakes

episodic growth of the chocolate mountains anticlinorium recorded by the neogene bear canyon conglomerate southeastern california u s a abstract between indian pass and picacho state recreation area southeastern california the neogene bear canyon conglomerate crops out in and around the chocolate mountains anticlinorium and can be subdivided into three unconformity bounded sequences that are designated from oldest to youngest i ii and iii each of these sequences is composed of interstratified debris flow channelized stream flow and sheet flood deposits debris flow deposits are poorly sorted inversely graded pebble to boulder paraconglomerates with subangular clast populations large clasts extruding into overlying layers are a characteristic of such beds in contrast sheet flood and channelized stream flow deposits are well sorted orthoconglomerates with subrounded to rounded clasts the bear canyon conglomerate unconformably overlies a lower miocene volcanic and epiclastic unit metasedimentary and metavolcanic rocks of the jurassic winterhaven formation a probable jurassic orthogneiss and the upper cretaceous to paleogene orocopia schist geochemical paleocurrent and clast count data suggest that alluvial material in the bear canyon conglomerate was derived from local exposures underlain by one or more of these units and then was funneled into an approximately north south trending structural depression in the axial trace of the chocolate mountains anticlinorium though the exact timing of deposition of the three sequences in the bear canyon conglomerate is difficult to constrain stratigraphic and published geochronological data when viewed in the context of regional tectonic patterns suggest that sequence i probably was deposited after 17 ma and before 9 45 ma in contrast sequence ii was deposited after sequence i and then was folded either sometime prior to or after 9 45 ma sequence iii is interstratified with the 9 45 ma basalts of black mountain and was folded prior to deposition of flat lying quaternary alluvial sediments the east west trending copper basin reverse fault cuts sequence iii in addition key components of a conjugate set of northwest and northeast trending dextral and sinistral slip faults respectively transect the copper basin fault the axis of the chocolate mountains anticlinorium and the 9 45 ma basalts of black mountain however neither the copper basin nor the conjugate faults disrupt flat lying quaternary alluvial sediments episodic growth of the east west trending chocolate mountains anticlinorium during deposition of the neogene bear canyon conglomerate and subsequent formation of the east west trending copper basin fault and the conjugate set of dextral and sinistral faults all record transient north south shortening within the margin of the north american plate these transient periods of north south shortening followed extensional deformation of lower miocene continental arc volcanic rocks and are strain compatible with the 12 10 ma to 6 ma development of the eastern california shear zone numerous other examples of late cenozoic east west trending folds and reverse faults are reported in the literature to have formed during development of this 100 110 km wide zone of dextral shear we therefore conclude that the geology and development of the chocolate mountains anticlinorium between indian pass and picacho state recreation area reflect changing continental margin strain patterns as the boundary between the farallon and north american plates was transformed from a paleogene convergent margin to a wholly neogene transform setting

extensional reactivation of the chocolate mountains subduction thrust in the gavilan hills of southeastern california the ne vergent chocolate mountains fault of south eastern california has been interpreted as either a subduction thrust responsible for burial and prograde metamorphism of the ensimatic orocopia schist or as a normal fault involved in the exhumation of the schist our detailed structural analysis in the gavilan hills area provides new evidence to confirm the latter view a zone of deformation is present at the top of the orocopia schist in which lineations are parallel to those in the upper plate of the chocolate mountains fault but oblique to ones at relatively deep levels in the schist both the orocopia schist and upper plate contain several generations of shear zones that show a transition from crystalloblastic through mylonitic to cataclastic textures these structures formed during retrograde metamorphism and are considered to record the exhumation of the orocopia schist during early tertiary time as a result of subduction return flow the gatuna fault which places low grade supracrustal metasediments of the winterhaven formation above the gneisses of the upper plate also seems to have been active at this time final unroofing of the orocopia schist occurred during early to middle miocene regional extension and may have involved a second phase of movement on the gatuna fault formation of the chocolate mountains fault during exhumation indicates that its top to the ne sense of movement provides no constraint on the polarity of the orocopia schist subduction zone this weakens the case for a previous model involving sw dipping subduction while providing support for the view that the orocopia schist is a correlative of the franciscan complex

rapid post seismic landslide evacuation boosted by dynamic river width how rivers evacuate large landslide deposits is crucial for predicting post seismic hazards a 2d hydro sedimentary model demonstrates that a narrowing river channel increases sediment transport which reduces export time by orders of magnitude

warming and wetting climate during last century revealed by an ice core in northwest tibetan plateau glaciers on the tibetan plateau tp exist in different states of extension and retreat responding to the westerly winds and indian monsoon however few studies to date have focused on climate change in the westerlies dominated northwest tp here we report an ice core climate record during the last century retrieved from the kuokuosele kksl glacier in the westerlies dominated eastern pamir northwest tp the ice core has dated based on annual layer counting using ice core delta o 18 seasonal cycles constrained by both the beta beta activity peak and cs 137 concentration peak in 1962 63 reconstruction of delta o 18 and annual accumulation from the ice core and comparison with observed temperature and precipitation at nearby meteorological stations as well as cru climate research unit data confirm their climatic and regional significance both ice core delta o 18 and accumulation increased during the last century thus pointing to a warming and wetting trend in the westerlies dominated northwest tp

pulverized fault rocks and damage asymmetry along the arima takatsuki tectonic line japan abstract we present field and laboratory data on pulverized rocks at the hakusui kyo outcrop of the arima takatsuki tectonic line attl which is a dextral strike slip fault with 17 km displacement juxtaposing granite to the south against rhyolite to the north the majority of slip at the surface is localized to a clay rich gouge fault core 8 10 cm in width surrounded by a coarsening outwards fault breccias up to 3 m wide fault damage is highly asymmetric with respect to the slipping zone the granite south of the fault has a pulverized damage zone up to 200 m wide while the rhyolite to the north has only about 3 m wide non pulverized fault breccia the degree of pulverization in the granite decreases approximately logarithmically with normal distance from the slip zone the highly fractured pulverized rocks exhibit several distinct textural characteristics in thin section grains appear to be highly comminuted but the original grain shapes and margins are recognizable microfractures tend to be tensile in no preferred orientation grain fragments display little to no rotation and lack evidence of in situ shear consequently at macroscale the rocks appear to preserve original granitic textures despite being highly fractured and friable the observed pulverization and rock damage asymmetry are most consistent with generation mechanism involving ruptures on a bimaterial interface with statistically preferred propagation direction leading to damage primarily on the side with higher seismic velocity at depth this is supported by laboratory measurements of p wave ultrasonic velocities on intact samples which indicate that the granites have consistently higher velocity than the rhyolite with increasing confining pressure

a spatially resolved estimate of high mountain asia glacier mass balances from 2000 to 2016 glacier mass balances in high mountain asia are uncertain satellite stereo imagery allows a spatially resolved estimate for about 92 of the glacierized area and yields a region wide average of about 16 gt yr 1 for 2000 to 2016

chemical and physical characteristics of pulverized tejon lookout granite adjacent to the san andreas and garlock faults implications for earthquake physics we present new detailed analyses of samples of pulverized tejon lookout granite collected from sections adjacent to the san andreas and garlock faults in southern california the tejon lookout granite is pulverized in all exposures within about 100 m from both faults chemical analyses indicate no or little weathering in the collected samples although xrd analysis shows the presence of smectite illite and minor kaolinite in the clay size fraction weathering products may dominate in the less than 1 micron fraction the average grain size in all samples of pulverized tejon lookout granite ranges between 26 and 208 microns silt to fine sand with the particle size distribution in part a function of proximity to the primary slip zone the san andreas fault samples that we studied are generally finer grained than those collected from adjacent to the garlock fault the particle size distribution for each studied sample from both faults follows a pseudo power law with a continuously changing exponent which suggests that pulverization is not simply a consequence of direct shear the average particle size that we determined for our samples is considerably coarser than reported in previous investigations which we attribute to possible measurement errors in the prior work our data and observations suggest that dynamic fracturing in the wall rock of the san andreas and garlock faults only accounts for about 1 or less of the earthquake energy budget

particle size and energetics of gouge from earthquake rupture zones surprisingly considering the forces that we see at the surface not all the energy involved in an earthquake is transformed into ground motion much of it is consumed by frictional heating and rock pulverization an analysis of pulverized rock or gouge collected from the san andreas fault in california and from a rupture zone at 2 km depth in a south african gold mine contradicts the commonly held view that gouge surface energy is a negligible component of earthquake energy balance the analysis reveals unexpected diminutive particles in gouge samples indicating that pulverization not frictional heating is the major consumer of earthquake energy at depth this might explain the heat flow anomaly seen in the san andreas fault system and perhaps some other long standing puzzles in earthquake energetics grain size reduction and gouge formation are found to be ubiquitous in brittle faults at all scales1 2 3 4 and most slip along mature faults is observed to have been localized within gouge zones5 6 this fine grain gouge is thought to control earthquake instability3 6 7 8 and thus understanding its properties is central to an understanding of the earthquake process7 9 here we show that gouge from the san andreas fault california with 160 km slip and the rupture zone of a recent earthquake in a south african mine with only 0 4 m slip display similar characteristics in that ultrafine grains approach the nanometre scale gouge surface areas approach 80 m2 g 1 and grain size distribution is non fractal these observations challenge the common perception that gouge texture is fractal10 11 and that gouge surface energy is a negligible contributor to the earthquake energy budget3 9 12 we propose that the observed fine grain gouge is not related to quasi static cumulative slip but is instead formed by dynamic rock pulverization during the propagation of a single earthquake

the 1200 year composite ice core record of aleutian low intensification future changes in north pacific wintertime climate will be largely determined by the response of the aleutian low alow pressure system to anthropogenic forcing although the alow has intensified over the twentieth century global climate model projections of future alow variability are equivocal in order to evaluate decadal to centennial alow forcing mechanisms and provide context for the modern intensification here we combine a new denali ice core alaska sea salt sodium record with the mount logan ice core yukon sodium record to develop a composite 1200 year record of alow variability the composite record indicates that the recent secular alow intensification began circa 1741 and is unprecedented in magnitude and duration over the past millennium north pacific ice core snow accumulation and stable isotope records are consistent with this interpretation the alow intensification is associated with warming tropical pacific sea surface temperatures consistent with dynamic theory and instrumental correlations

residual regolith derived from the biotite controlled weathering of cretaceous tonalite quartz diorite peninsular ranges southern california usa a case study abstract though k feldspar free tonalite and quartz diorite are common plutonic rocks in exhumed continental margin magmatic arc rocks around the globe how they weather has not been extensively studied we therefore undertook an investigation aimed at understanding how an approximately 6 m thick section of residual regolith saprock and overlying alfisol developed from cretaceous k feldspar free tonalite and quartz diorite at santa margarita ecological reserve southern california usa we analyzed three samples of soil 10 of saprock and 10 of corestone for their major trace and rare earth element compositions thin sections of each major textural group also were studied and point counted common xrd techniques were used to determine clay mineralogy three samples of soil and five of saprock were analyzed for their ph within the saprock an extensive network of cracks was likely produced by the volumetric expansion that accompanied the conversion of biotite to vermiculite migrating near neutral fluids responsible for this conversion resulted in a loss of k mass and affected several trace elements that are commonly found in biotite but with the exception of an interval between 177 and 270 cm left most other major trace and rare earth elements ree little affected within the 177 to 270 cm interval at a depth of 208 cm relative to the immobile framework incongruent leaching of plagioclase by acidic solutions resulted in the losses of si al ca na pb sr and ga mass in contrast more neutral solutions added heavy ree hree and y mass at 177 to 237 cm depths while acidic solutions removed ree and y mass at 270 cm depth in the soil acidic solutions attacked plagioclase biotite and apatite leaching and removing relative to the immobile framework ca na mg k and p mass in addition the dissolution of apatite resulted in depletions in hree and y mass none of the elemental mass removed from the soil accumulated in the directly underlying saprock and must have been removed from the near vertical plane of sampling within the saprock the above changes are mostly the result of near neutral ph water rock interactions occurring within a warm and dry holocene climate identified changes in elemental mass other than those associated with the conversion of biotite to vermiculite are localized and are likely the result of the paths taken by fluids with differing ph moving through the complex network of cracks any model purporting to describe the evolution of residual regolith must explain such natural complexities

microfracture analysis of fault growth and wear processes punchbowl fault san andreas system california abstract fabric and timing relations of mode i microfractures are used to test current hypotheses for the origin of damage along large displacement faults by the processes of fault growth and wear oriented samples 0 075 m to 1 km from the punchbowl fault surface i e ultracataclasite layer document an increase in development of preferred orientation and increase in density of microfractures towards the ultracataclasite layer defining a zone of fault related microfracture damage about 100 m thick a distinct microfracture set that is perpendicular to the slip direction of the fault is present throughout the damage zone this implies that the average orientation of the maximum principal compressive stress within the damage zone was nearly normal to the fault surface two additional microfracture sets are present one oriented at low angles to the fault within meters of the ultracataclasite layer and another low angle set that occurs in the outermost damage zone the preferred orientations and timing relations are most consistent with local damage accumulation from stress cycling associated with slip on a geometrically irregular relatively weak fault surface low angle microfractures nearest the ultracataclasite layer also may record wear associated with the passage of earthquake ruptures and those in the outermost damage zone may be consistent with andersonian fault formation and subsequent fault weakening

application of high resolution dem data to detect rock damage from geomorphic signals along the central san jacinto fault abstract we analyze geomorphic properties extracted from lidar and srtm shuttle radar topography mission data to test whether the damage zone along the central san jacinto fault sjf zone can be resolved with remotely sensed data in a quantitative fashion the sjf is one of the most active faults in southern california with well expressed geomorphology and a fast slip rate as seen in the geology and by gps we use arcmap and the taudem toolbox to compare several morphometric parameters including drainage density dd on both sides of the fault using a 1 km and a 5 km buffer for the lidar and srtm data respectively we also analyze the spatial patterns of dd near the fault using two different definitions of spatial dd the high resolution of the lidar data allows us to focus on a single fault eliminating the effects of parallel nearby faults from the lidar data we find that the highest dd values occur in areas between two fault strands followed generally by rocks on the northeast side of the fault with the lowest dd values occurring on the southwest side of the fault the srtm data shows a band of high dd values centered on the main fault trace with 1 km width our results indicate that there is a strong correlation between drainage density and proximity to the fault with zones of structural complexity along the fault displaying the highest dd we interpret this to largely be an effect of degree of rock damage as these are areas that are expected to be more damaged and field observations support this contention if we are correct then it appears that the northeast side of the sjf is generally more damaged south of the trifurcation area there is evidence that the signal is reversed on the larger scale with more damage on the southwest side of the fault inferred from the srtm data possibly caused by extension between the coyote creek and clark faults the implications of the observed asymmetry could be geological evidence for rupture propagation direction because a preferred propagation direction is predicted to produce asymmetric damage structure that would be recorded in the volume of rock surrounding a fault

on the origin of mixed layered clay minerals from the san andreas fault at 2 5 3 km vertical depth safod drillhole at parkfield california a detailed mineralogical study is presented of the matrix of mudrocks sampled from spot coring at three key locations along the san andreas fault observatory at depth safod drill hole the characteristics of authigenic illite smectite i s and chlorite smectite c s mixed layer mineral clays indicate a deep diagenetic origin a randomly ordered i s mineral with ca 20 25 smectite layers is one of the dominant authigenic clay species across the san andreas fault zone sampled at 3 066 and 3 436 m measured depths md whereas an authigenic illite with ca 2 5 smectite layers is the dominant phase beneath the fault sampled at 3 992 m md the most smectite rich mixed layered assemblage with the highest water content occurs in the actively deforming creep zone at ca 3 300 3 353 m true vertical depth of ca 2 7 km with i s 70 30 and c s 50 50 the matrix of all mudrock sam ples show extensive quartz and feldspar both plagioclase and k feldspar dissolution associated with the crystalli zation of pore filling clay minerals however the effect of rock deformation in the matrix appears only minor with weak flattening fabrics defined largely by kinked and fractured mica grains adopting available kinetic models for the crystallization of i s in burial sedimentary envi ronments and the current borehole depths and thermal structure the conditions and timing of i s growth can be evaluated assuming a typical k concentration of 100 200 ppm for sedimentary brines a present day geothermal gradient of 35c km and a borehole temperature of ca 112c for the sampled depths most of the i s minerals can be predicted to have formed over the last 4 11 ma and are probably still in equilibrium with circulating fluids the exception to this simple burial pattern is the occurrence of the mixed layered phases with higher smectite content than predicted by the burial model these minerals which characterize the actively creeping section of the fault and local thin film clay coating on polished brittle slip surfaces can be explained by the influence of either cooler fluids circulating along this segment of the fault or the flow of k depleted brines

mechanics of grain size reduction in fault zones 1 recent observations of nanometer scale particles in the cores of exhumed fault zones raise questions about how such small particles are formed and how they survive especially if significant shear heating is produced during an earthquake commercial crushing and grinding operations encounter a grind limit near 1 mm below which particles deform plastically rather than fracturing a fragmentation model and low temperature plasticity mechanics indicate that it is not possible to produce under compressive loading and short timescale significantly smaller particles at any strain rate however shock loading and subcritical crack growth can produce nanometer scale fragments in compression under tensile loading the fragment size is determined by a competition between the nucleation of cracks and stress relaxation in their neighborhoods therefore higher tensile strain rates produce smaller fragments the ultimate limit is determined by the availability of elastic strain energy which does not place a significant constraint on the minimum grain size grain growth kinetics suggests that survivability of grains is very temperature sensitive a 10 nm quartz fragment will double its size in 0 1 s at 1000c in 20 s at 800c in 14 h at 600c and in 10 years at 400c the observation of grains smaller than 10 nm places meaningful constraints on the dynamic fields and permeability of the fault zone during a large earthquake microstructural analysis of the grains and rock damage may be used to infer whether fragmentation occurred under macroscopic tension or compression

spatial variability in microscopic deformation and composition of the punchbowl fault southern california implications for mechanisms fluid rock interaction and fault morphology abstract we examine the distribution and nature of microstructures geochemistry and mineralogy along two traverses across the punchbowl fault southern california to determine the morphology and deformation mechanisms of the fault zone in schistose rocks the punchbowl fault is an exhumed fault that has two main strands of slip localization and has a total of 44 km of right slip protolith in the study area consists of the pelona schist which is primarily a quartz albite muscovite actinolite schist with thin to medium banding and rare metabasalts the traverses are 1 3 km apart and were conducted at a site with a single fault strand and a site where both principal strands of the fault are exposed the fault zone thickness is a function of the type of measurement that is used to define it for the single strand site analysis of the distribution of microfractures shows that the fault zone consists of a roughly 40 m thick damaged zone adjacent to the fault core the damaged zone is marked by an increase in veins thin cataclasite bands inter and intragranular fracturing and alteration relative to the country rock brittle grain size reduction occurs in a zone 10 m thick as measured from the fault core which consists of a continuous 10 cm thick very fine grained cataclasite that experienced repeated alteration vein injection and grain size reduction whole rock geochemical analyses of the fault related rocks suggest that the geochemically defined fault zone is less than 10 m thick volume loss at the site with one fault strand appears to have been small the dominant alteration reactions associated with the fault core are the hydration of hornblende and actinolite accompanied by the alteration of muscovite to produce a quartz chlorite albite epidote ultracataclasite the composition of the fault core is variable and locally influenced by one of the adjacent protoliths the examination of the two fault strand sites shows that two damaged zone fault core structures are present the region between the two strands experienced a greater degree of deformation than the protolith but the total deformation is much less than immediately adjacent to the fault cores the total thickness of the damaged zone around the two strands is less than 200 m the fault core enveloped by a damaged zone morphology as well as the textures of the fault core rocks are similar to rocks associated with the north branch san gabriel fault which formed in crystalline rocks with a total displacement of 22 km fault thickness is less in the pelona schist than in the crystalline rocks perhaps owing to more efficient strain localization in the schists thus the faults of the san andreas system may be thinner in regions where schists or franciscan rocks are the protolith but the main fault core may be a constant feature of the fault zone transformation induced weakening is less important in this part of the punchbowl fault since the protolith has a large amount of mica the structure of the fault zone with two principal slip surfaces is marked by both chemical changes and microstructures and indicates that some parts of the san andreas fault system may consist of multiple slip surfaces each with a damaged zone that together may create a fault zone 100 m thick and in which slip is localized to zones meters to decimeters thick

high altitude accumulation and preserved climate information in the western pamir observations from the fedchenko glacier accumulation basin the accumulation region of fedchenko glacier represents an extensive snow reservoir in the pamir mountains feeding the longest glacier in central asia observed elevation changes indicate a continuous ice loss in the ablation region of fedchenko glacier since 1928 while the mass balance of the accumulation region is largely unknown in this study we show that accumulation varies considerably in the main accumulation basin with accumulation rates up to 2400 mm w e a 1 in the west decreasing to 1 in the center although the elevation difference is

smectite and fluid budget at nankai odp sites derived from cation exchange capacity abstract pore fluid chlorinity lower than seawater is often observed in accretionary wedges and one of the possible causes of pore water freshening is the smectite to illite reaction this reaction occurs during diagenesis in the 80 150 c temperature range low chlorinity anomalies observed at the toe of accretionary wedges have thus been interpreted as evidence for lateral fluid migration from inner parts of the wedge and the seismogenic zone however temperature conditions in nankai trough are locally high enough for the smectite to illite transition to occur in situ cation exchange capacity is here used as a proxy for smectite content in the sediment and the amount of interlayer water released during the smectite to illite reaction represents in average 12 water molecules per cation charge water and chloride budget calculations show that there is enough smectite to explain the chlorinity anomalies by in situ reactions the shape of the pore fluid chlorinity profiles can be explained if compaction is also taken into account in the model lateral flow is not needed this argument based solely on chloride concentration does not imply that lateral flow is absent however previous estimations of lateral fluid fluxes and of the duration of transient flow events along the decollement should be reconsidered

seismic cycles earthquakes landslides and sediment fluxes linking tectonics to surface processes using a reduced complexity model in tectonically active mountain ranges landslides triggered by earthquakes mobilise large volumes of sediment that affect river dynamics this sediment delivery can cause downstream changes in river geometry and transport capacity that affect the river efficiency to export this sediment out of the epicentre area the subsequent propagation of landslide deposits in the fluvial network has implications for the management of hazards downstream and for the long term evolution of topography over multiple seismic cycles a full understanding of the processes and time scales associated with the removal of landslide sediment by rivers following earthquakes however is still lacking here we propose a nested numerical approach to investigate the processes controlling the post seismic sediment evacuation at the mountain range scale informed by results from a reach scale model first we explore the river morphodynamic response to a landslide cascade at the reach scale using a 2d modelling approach the results are then used to describe empirically the evacuation of a landslide volume which avoids using a computationally extensive model in catchments which may have thousands of co seismic landslides second we propose a reduced complexity model to quantify evacuation times of earthquake triggered landslide clusters at the scale of a mountain range examining the hypothetical case of a mw 7 9 earthquake and its aftershocks occurring on the alpine fault new zealand our approach combines an empirical description of co seismic landslide clusters with the sediment export processes involved during the post seismic phase our results show that the inter seismic capacity of the mountain range to evacuate co seismic sediment is critical to assess the sediment budget of large earthquakes over one to several seismic cycles we show that sediment evacuation is controlled by two timescales 1 the transfer time of material from hillslopes to channels and 2 the evacuation time of the landslide deposits once it has reached the fluvial network in turn post seismic sediment evacuation can either be connectivity limited when sediment delivery along hillslopes is the main limiting process or transport limited when the transport by rivers is the limiting process despite high values of runoff we suggest that the southern alps of new zealand are likely to be in connectivity limited conditions for connection velocities 2 m yr 1 are sufficient to allow most of co seismic sediments to be mobilised and potentially exported out of the range within less than one seismic cycle because of the poorly constrained rate of sediment transfer along hillslopes our results potentially raise the issue of co seismic sediment accumulation within mountain ranges over several seismic cycles and of the imbalance between tectonic inputs and sediment export we therefore call for renewed observational efforts to better describe and quantify the physical processes responsible for the redistribution and mobilization of sediment from landslide scars and deposits

prolonged seismically induced erosion and the mass balance of a large earthquake large earthquakes deform the earth s surface and drive topographic growth in the frontal zones of mountain belts they also induce widespread mass wasting reducing relief the sum of these two opposing effects is unknown using a time series of landslide maps and suspended sediment transport data we show that the mw7 6 chi chi earthquake in taiwan was followed by a period of enhanced mass wasting and fluvial sediment evacuation peaking at more than five times the background rate and returning progressively to pre earthquake levels in about six years therefore it is now possible to calculate the mass balance and topographic effect of the earthquake the choshui river has removed sediment representing more than 30 of the added rock mass from the epicentral area this has resulted in a reduction of surface uplift by up to 0 25 m or 35 of local elevation change and a reduction of the area where the chi chi earthquake has built topography for other large earthquakes erosion may evolve in similar predictable ways reducing the efficiency of mountain building in fold and thrust belts and the topographic expression of seismogenic faults prolonging the risk of triggered processes and impeding economic regeneration of epicentral areas

characterization of pulverized granitoids in a shallow core along the san andreas fault littlerock ca summary we present results on the composition structure and particle size distribution psd of pulverized and damaged granitic rocks in a 42 m deep core adjacent to the san andreas fault near littlerock ca the cored section is composed of pulverized granites and granodiorites and is cut by numerous mesoscopic secondary shears the analysis employs xrd xrf thin sections and semi automated particle size analyser methods including a novel calibration method the mean particle size for the majority of samples falls between 50 and 470 m the psds can be fitted by a power law with d values ranging between 2 5 and 3 1 as well as by a superposition of two gaussians fracture surface energy calculations based on the observed particle distributions provide very low values indicating that the part of the total earthquake energy budget expended for breaking or shattering rocks is small shear deformation is likely to dominate near secondary faults the most pronounced fault related alteration occurs along the secondary shears and is a function of both composition and depth the alteration to clay appears to be the result of fluid rock interaction and brittle deformation under low temperature conditions rather than of surface related weathering the particle size reduction noted in the core reflects multiple mechanisms of comminution the zones of pulverization that lack significant weathering likely result from repeating episodes of dynamic dilation and contraction

distributed ice thickness and volume of all glaciers around the globe 1 a new physically based approach for calculating glacier ice thickness distribution and volume is presented and applied to all glaciers and ice caps worldwide combining glacier outlines of the globally complete randolph glacier inventory with terrain elevation models shuttle radar topography mission advanced spaceborne thermal emission and reflection radiometer we use a simple dynamic model to obtain spatially distributed thickness of individual glaciers by inverting their surface topography results are validated against a comprehensive set of thickness observations for 300 glaciers from most glacierized regions of the world for all mountain glaciers and ice caps outside of the antarctic and greenland ice sheets we find a total ice volume of 170 103 21 103 km3 or 0 43 0 06 m of potential sea level rise

a nonsteady state firn densification model for the percolation zone of a glacier 1 a simple steady status firm densification model is modified to account for short term time variations of accumulation rate and surface temperature the temporal surface elevation and mass changes at two sites in the percolation zone of an ice sheet in response to various climate histories are determined it is shown that a straight forward translation of observed short term ice sheet surface elevation variations into mass changes may be completely misleading particularly for the percolation zone of the ice sheet where temperature driven variations of melting refreezing rates have a strong impact on near surface density in the lower percolation zone the mass change associated with a temperature anomaly in respect to the mean climate may for example amount to as little as 10 percent of the observed simultaneous surface elevation change moreover significant surface elevation change may occur even in periods of constant surface climate and consequently unchanged mass balance as a delayed response to previous changes of the local surface climate forcing the model with cyclic temperature variations mimicking fluctuations of west greenland instrumental temperature records during the past hundred years shows that surface elevation may increase by as much as 1 m in 5 years in periods with no mass change at all in the lower percolation zone temperature induced density changes rather than fluctuations of accumulation rate are the dominant cause of short term surface elevation changes in contrast to the situation in the higher percolation zone where short term surface elevation change is dominated by fluctuations of accumulation rate

an unusual occurrence of probable pleistocene corestone within a cretaceous dioritic enclave peninsular ranges california abstract we here document an unusual occurrence of probable pleistocene corestone within an 5 m by 5 m dioritic enclave contained within a cretaceous tonalitic pluton santa margarita ecological reserve sw california the enclave lies within 3 5 km of the seismically active 1 5 2 ma elsinore fault zone and may have been subjected to 70 90 ground shaking events since 22 000 18 000 years ago the studied corestone is elliptical with major axis measuring 55 cm and minor axis 26 cm in length it is surrounded by a discontinuous 7 cm thick rind that breaks apart under slightly greater finger pressure than does the surrounding saprolite in order to assess changes in the physical and chemical properties of the corestone rind and saprolite we collected along an 66 5 cm long traverse 4 samples from the corestone 1 from the rind and 5 from the saprolite for bulk and grain density porosity and major and trace element analyses textural and clay mineral data along with the redistribution of elemental mass indicate that the weathering of biotite and to much lesser degrees apatite and the an rich cores of plagioclase played critical roles in the production of saprolite especially in a narrow 20 cm wide zone adjacent to the rind of the corestone within this zone bulk densities reach their minimum values while porosities and positive volume strains reach their maximums in addition the maximum loss of k fe mn and ca mass occurred just inside this region and is paralleled by the highest cia values and highest additions of si and rb mass in contrast the masses of na and sr are progressively increased and decreased respectively along the entire sampling traverse while the loss of mg ti and p mass is episodic with the greatest losses occurring within the narrow zone adjacent to the rind and at the end of the traverse the above observations indicate that the conversion of biotite to expandable mixed layered clay minerals aided by the alteration of the an rich cores of plagioclase produced sufficient stress on grain boundaries that a weakening or loss of intercrystalline cohesion occurred however unlike the well documented isovolumetric development of saprolite in other areas at the study site saprolitization was accompanied by a volume expansion we speculate that repeated ground shaking in response to earthquakes generated in the nearby elsinore fault zone may be responsible for this difference important byproducts of ground shaking would include additional weakening or loss of intercrystalline cohesion and the production and enhancement of new and older fluid pathways respectively the fact that the most intensely altered material at the study site lies adjacent to the boundary between the rind and saprolite suggests that this interface acted to guide fluid flow around the corestone and rind and into the adjacent saprolite where elemental mass was redistributed down various paths leading to the underlying water table most of the leached elemental mass was removed from the area of the sampling traverse but small increases in si rb and na mass suggest redistribution of these elements from elevated areas outside the area sampled during this study the result of the above complex set of processes is a variably porous and chemically altered saprolitic enclave that is still undergoing modification as it adjusts to the vicissitudes of the paralithic environment and continuing ground shaking during earthquakes generated along the elsinore fault

stable isotope and trace element time series from fedchenko glacier pamirs snow firn cores in summer 2005 two pilot snow firn cores were obtained at 5365 and 5206 m a s l on fedchenko glacier pamirs tajikistan the world s longest and deepest alpine glacier the well defined seasonal layering appearing in stable isotope and trace element distribution identified the physical links controlling the climate and aerosol concentration signals air temperature and humidity precipitation were the primary determinants of stable isotope ratios most precipitation over the pamirs originated in the atlantic in summer water vapor was re evaporated from semi arid regions in central eurasia the semi arid regions contribute to non soluble aerosol loading in snow accumulated on fedchenko glacier in the pamir core concentrations of rare earth elements major and other elements were less than those in the tien shan but greater than those in antarctica greenland the alps and the altai the content of heavy metals in the fedchenko cores is 2 14 times lower than in the altai glaciers loess from afghan tajik deposits is the predominant lithogenic material transported to the pamirs trace elements generally showed that aerosol concentration tended to increase on the windward slopes during dust storms but tended to decrease with altitude under clear conditions the trace element profile documented one of the most severe droughts in the 20th century

rupture mechanism and interface separation in foam rubber models of earthquakes a possible solution to the heat flow paradox and the paradox of large overthrusts abstract spontaneous stick slip along the interface between stressed foam rubber blocks is a simple analog of earthquake rupture and stick slip results from this model are used to elucidate the role of normal stress variations along the interface in the stick slip process observations indicate significant normal interface vibrations and separation during slip suggesting that dynamic changes in normal stress rather than a drop in the coefficient of friction may control stick slip as suggested for example by tolstoi oden and martins and brune and co workers observations of particle trajectories indicate that stick slip shear motion is associated with various degrees of fault separation for an asymmetric model the motion is consistent with slipping motion of the type suggested by schallamach and price for a symmetric model the motion is similar to that suggested by comninou and dundurs if interface waves of this type involving separation during slip occur in earthquakes they may be a solution to the heat flow paradox since a major part of the slip occurs during separation and during low normal stress thus frictional heat generation is reduced normal interface vibrations during stick slip may explain the high corner frequency of p wave spectra and the generally high levels of p wave spectra beyond the corner frequency schallamach comninou type waves are consistent with the partial stress drop abrupt locking self healing models of brune and heaton

climatic and atmospheric circulation pattern variability from ice core isotope geochemistry records altai tien shan and tibet several firn ice cores were recovered from the siberian altai belukha plateau central tien shan inilchek glacier and the tibetan plateau zuoqiupu glacier bomi from 1998 to 2003 the comparison analyses of stable isotope geochemistry records obtained from these firn ice cores identified the physical links controlling the climate related signals at the seasonal scale variability the core data related to physical stratigraphy meteorology and synoptic atmospheric dynamics were the basis for calibration validation and clustering of the relationships between the firn ice core isotope geochemistry and snow accumulation air temperature and precipitation origin the mean annual accumulation in water equivalent was 106 g cm 2 a 1 at inilchek glacier 69 g cm 2 a 1 at belukha and 196 gc m 2 a 1 at zuoqiupu the slopes in regression lines between the d 18 o ice core records and air temperature were found to be positive for the tien shan and altai glaciers and negative for southeastern tibet where heavy amounts of isotopically depleted precipitation occur during summer monsoons the technique of coupling synoptic climatology and meteorological data with d 18 o and d excess in firn core records was developed to determine climate related signals and to identify the origin of moisture in altai two thirds of accumulation from 1984 to 2001 was formed from oceanic precipitation and the rest of the precipitation was recycled over aral caspian sources in the tien shan 87 of snow accumulation forms by precipitation originating from the aral caspian closed basin the eastern mediterranean and black seas and 13 from the north atlantic

mass wasting triggered by the 2008 wenchuan earthquake is greater than orogenic growth shallow earthquakes lead to the uplift of mountain ranges but also trigger landslides that remove mass an analysis of the 2008 wenshuan earthquake suggests that more material was removed from the orogen by widespread landslides than was added by coseismic uplift

tectonic geomorphology of the serrania de san lucas central cordillera regional implications for active tectonics and drainage rearrangement in the northern andes abstract we explore the structural and geomorphological evidence for recent tectonic activity in the serrania de san lucas san lucas range slr the northern segment of the central cordillera in the colombian northern andes a morphostructural and geomorphological analysis was carried out in this isolated range using several topographic metrics like the local relief slope variability hypsometric integral swath profiles normalised concavity steepness ksn drainage basin shape index bs asymmetry factor af mountain front sinuosity smf and the ratio of valley floor width to valley floor height vf after remote sensing and geological analysis of the structural pattern we propose that the slr represents a horse tail termination of the palestina fault that seems to have reactivated in the miocene pliocene in a transpressive stress state during the andean orogeny based on this structural model and the geomorphic indices we divided the slr into two regional domains the simiti domain in the east and the palestina domain in the west the simiti domain is dominated by ne sw striking structures with a right lateral kinematic whereas the palestina domain is controlled by the n s right lateral palestina fault which is the predominant structure in the slr we demonstrate that recent tectonic activity and higher uplift rates have been preferably constrained to the simiti domain to the north of the simiti san blas faults along the ne sw striking faults in this area low smf and vf values suggest an active mountain front bounded by the reverse morales fault and quaternary uplift rates between 0 05 and 0 5 mm yr on the other hand the quaternary tectonic activity in the palestina domain was concentrated in the northern portion where climate has also played a significant role in controlling denudation rates and landscape evolution the variable uplift pattern between both domains has induced along strike changes in divide mobility and timing of drainage reorganisation within the slr discrete capture events forced a west southwest migration of the eastern side towards the western side of the slr the concentrated highest tectonic activity in the simiti domain progressively modified the topographic conditions and triggered the divide migration event our findings provide new and valuable information on the active tectonics and neogene to quaternary landscape evolution in this poorly studied area in the northern andes

stagnation and mass loss on a himalayan debris covered glacier processes patterns and rates the ablation areas of debris covered glaciers typically consist of a complex mosaic of surface features with contrasting processes and rates of mass loss this greatly complicates glacier response to climate change and increases the uncertainty of predictive models in this paper we present a series of high resolution dems and repeat lake bathymetric surveys on ngozumpa glacier nepal to study processes and patterns of mass loss on a himalayan debris covered glacier in unprecedented detail most mass loss occurs by melt below supraglacial debris and melt and calving of ice cliffs backwasting although ice cliffs cover only 5 of the area of the lower tongue they account for 40 of the ablation the surface debris layer is subject to frequent re distribution by slope processes resulting in large spatial and temporal differences in debris layer thickness enhancing or inhibiting local ablation rates and encouraging continuous topographic inversion a moraine dammed lake on the lower glacier tongue spillway lake underwent a period of rapid expansion from 2001 to 2009 but later experienced a reduction of area and volume as a result of lake level lowering and sediment redistribution rapid lake growth will likely resume in the near future and may eventually become up to 7 km long

the evolution of fedchenko glacier in the pamir tajikistan during the past eight decades fedchenko glacier is by far the largest glacier in the pamir tajikistan owing to early accurate mapping of the glacier it is possible to evaluate glacier changes over eight decades which is an exceptionally long time period for this remote mountain region during this time a total volume loss of 5 km3 was observed on the main trunk of the glacier while the total area changed by only 1 4 it is observed that the volume loss migrates from the lower parts of the glacier towards the upper ablation zone the comparatively small change in area is a result of the supraglacial debris cover on the glacier tongue which decouples the area loss from the volume loss to a considerable degree the observed velocities of the glacier do not reflect the volume changes up to now because the interannual variability is larger than possible long term changes so far the intra annual velocity distribution in the central ablation zone probably reflects the evolution of the basal drainage system based on ice thickness measurements and simple ice dynamic assumptions the total volume of fedchenko glacier is 123 4 8 km3

determining the age distribution of colle gnifetti monte rosa swiss alps by combining ice cores ground penetrating radar and a simple flow model ice cores from cold alpine glaciers may provide unique paleoclimate information fromnon polar latitudes we explore the three dimensional internal age distribution of the small cold glaciersaddle colle gnifetti monte rosa italy switzerland to compare the age depth relations from fourlocal deep ice cores tracking isochronous refection horizons detected by ground penetrating radar gpr among the core locations reveals consistent dating up to 80 yearsbp this approach is confned torecent ages duetothelackofclearrefectionsbelowthefrn icetransition weattempttoovercomethislimitation by including a two dimensional fow model adapted to the gpr derived surface accumulationand ice thickness distribution modeled and gpr isochrones are compared indicating agreement inshape but featuring a potential offset of 0 3 5m the modeled isochrones are interpolated to the corearray with ages assigned according to the ice core datings the resulting age distribution is consistentup to 110 yearsbp with age uncertainties increasing from 7 to 80 years in the lower half of the ice this combination of methods is novel for alpine sites and may be adapted for spatial extrapolation ofice properties other than age

phyllosilicate mineral assemblages of the safod pilot hole and comparison with an exhumed segment of the san andreas fault system 1 this paper establishes a reference phyllosilicate data set from the safod pilot hole for future safod drilling and presents an application of these data for studies of exhumed fault segments the chlorite assemblages in cuttings from two intervals of the safod pilot hole are separated into two populations based on x ray diffraction characteristics the first population is found in granite in both the deeper and shallower interval whereas the second population occurs only in clastic sedimentary rocks in the shallower interval the characteristics of the first population match those for protolith and cataclasite of the exhumed punchbowl fault whereas samples from intensely deformed ultracataclasite are most similar to the second this supports previous findings that the mineral assemblages in the ultracataclasite formed after the cessation of motion along the fault above a depth of 2 km and that mineral assemblages in these exhumed fault rocks have been overprinted by post faulting alteration

re analysis of seasonal mass balance at abramov glacier 1968 2014 abramov glacier located in the pamir alay kyrgyzstan is a reference glacier within the global terrestrial network for glaciers long term glaciological measurements exist from 1968 to 1998 and a mass balance monitoring programme was re established in 2011 in this study we re analyse existing mass balance data and use a spatially distributed mass balance model to provide continuous seasonal time series of glacier mass balance covering the period 1968 2014 the model is calibrated to seasonal mass balance surveys and then applied to the period with no measurements validation and recalibration is carried out using snowline observations derived from satellite imagery and after 2011 also from automatic terrestrial camera images we combine direct measurements remote observations and modelling the results are compared to geodetic glacier volume change over the past decade and to a ground penetrating radar survey in the accumulation zone resolving several layers of accumulation previously published geodetic mass budget estimates for abramov glacier suggest a close to zero mass balance for the past decade which contradicts our results we find a low plausibility for equilibrium conditions over the past 15 years instead we suggest that the glacier s sensitivity to increased summer air temperature is decisive for the substantial mass loss during the past decade

melt regimes stratigraphy flow dynamics and glaciochemistry of three glaciers in the alaska range we used ground penetrating radar gpr gps and glaciochemistry to evaluate melt regimes and ice depths important variables for mass balance and ice volume studies of upper yentna glacier upper kahiltna glacier and the mount hunter ice divide alaska we show the wet percolation and dry snow zones located below 2700ma s l at 2700 to 3900ma s l and above 3900ma s l respectively we successfully imaged glacier ice depths upwards of 480m using 40 100mhz gpr frequencies this depth is nearly double previous depth measurements reached using mid frequency gpr systems on temperate glaciers few holocene length climate records are available in alaska hence we also assess stratigraphy and flow dynamics at each study site as a potential ice core location ice layers in shallow firn cores and attenuated glaciochemical signals or lacking strata in gpr profiles collected on upper yentna glacier suggest that regions below 2800ma s l are inappropriate for paleoclimate studies because of chemical diffusion through melt flow complexities on kahiltna glacier preclude ice core climate studies minimal signs of melt or deformation and depth age model estimates suggesting 4815years of ice on the mount hunter ice divide 3912ma s l make it a suitable holocene age ice core location

implications for mechanical properties of brittle faults from observations of the punchbowl fault zone california field observations of the punchbowl fault zone an inactive trace of the san andreas are integrated with results from experimental deformation of naturally deformed punchbowl fault rocks for a qualitative description of the mechanical properties of the fault and additional information for conceptual models of crustal faulting the punchbowl fault zone consists of a single continuous gouge layer bounded by zones of extensively damaged host rock fault displacements were not only localized to the gouge layer but also to discrete shear surfaces within the gouge deformation in the exposure studied probably occurred at depths of 2 to 4 km and was dominated by cataclastic mechanisms textural data also suggest that significant amounts of pore fluids were present during faulting and that fluid assisted mechanisms such as dissolution diffusion and precipitation were operative the experimental data on specimens collected from the fault zone suggest that there is a gradual decrease in strength and elastic modulus and an increase in relative ductility and permeability toward the main gouge zone the gouge layer has fairly uniform mechanical properites and it has significantly lower strength elastic modulus and permeability than both the damaged and the undeformed host rock for the punchbowl fault and possibly other brittle faults the variations in loading of the gouge zone with time are primarily governed by the morphology of the fault and the mechanical properties of the damaged host rock in addition the damaged zone acts as the permeable unit of the fault zone and surrounding rock it appears that the gouge primarily governs whether displacements are localized and it therefore may have a significant influence on the mode of slip

hydrothermal alteration in an exhumed crustal fault zone testing geochemical mobility in the caleta coloso fault atacama fault system northern chile abstract crustal scale strike slip fault zones have complex and heterogeneous permeability structures playing an important role in fluid migration in the crust exhumed faults provide insights into the interplay among deformation mechanisms fluid rock interactions and bulk chemical redistributions we determined the whole rock geochemistry and mineral chemistry of the fault core of the caleta coloso fault in northern chile in order to constrain the physical and chemical conditions that lead to strong hydrothermal alteration the strike slip caleta coloso fault core has a multiple core architecture consisting of alternate low strain rocks protolith weakly deformed protolith and protocataclasites and high strain strands cataclasites and discrete band of ultracataclasite derived from a jurassic tonalite hydrothermal alteration associated with fault related fluid flow is characterized by a very low grade association consisting of chlorite epidote albite quartz and calcite chlorite thermometry indicates t values in the range of 284 to 352 c no variations in mineral composition or t values were observed among different cataclastic units mass balance and volume change calculations show significantly larger chemical mobility in the protocataclasites than in the cataclasite and ultracataclasite this suggests that fluid flow and chemical alteration are strongly controlled by deformation being protocataclasite relatively more permeable than cataclasite chlorite precipitation and grain reduction in cataclasite and ultracataclasite would reduce permeability acting as a barrier for fluid flow chemical mobility and volume changes in the coloso fault core suggest different effective fluid flow ratios during amalgamation of subsequent and subparallel deformation bands that finally control the fracture channeling allowing fault related fluid flow into each of them

determination of volume loss and element mobility patterns associated with the development of the copper basin fault picacho state recreation area se california usa abstract the fault zone architectural elements of the copper basin fault include a fault core inner damage zone and outer damage zone utilizing yb as a reference frame element significant elemental mass changes were documented across all three architectural zones with the greatest change in the fault core porosity and volumetric strain both increase toward the principal slip surface reaching a maximum in the inner damage zone and then dropping significantly in the fault core in the damage zone and unaffected wall rocks smectite is the most prominent clay species whereas illite dominates the fault core suggesting that temperatures may have reached 100 150 c or more during the production of the fault core a number of studies have interpreted similar mass changes and clay mineral reactions to indicate high water rock ratios such interpretations imply that during rupture permeability increased within the fault core allowing it to act as a pathway for hot chemically reactive fluids then during and after rupture co 2 and sio 2 rich fluids moved into the inner and outer damage zones where calcite and quartz precipitation healed the fractured and permeable rock

rock pulverization at high strain rate near the san andreas fault rocks near the san andreas fault are pervasively crushed at distances of up to 400 m from its core laboratory experiments and calculations suggest that the rocks were pulverized at high strain rates 150 s 1 associated with a supershear rupture a rupture propagating at a velocity equal to greater than that of seismic shear waves

provenance and earthquake signature of the last deglacial xinmocun lacustrine sediments at diexi east tibet abstract well preserved lacustrine sediments are found in some areas in east tibet this region is characterized by a windy and semi arid climate alpine valleys and frequent earthquakes measurements of rare earth elements observations from a scanning electron microscope and a high resolution record of grain size measurements allowed us to compare fine sediments from the xinmocun section in the diexi lake with loess from the chinese loess plateau and south china results indicate that fine grains of the xinmocun lacustrine sediments were transported by wind and trapped in the lake whereas the 16 m fraction was likely from local sources the grain size changes within the section repeatedly show abrupt coarsening and upward fining probably due to palaeoearthquake events large earthquakes in the study area often caused rockfalls and landslides exposing fine sediments that had accumulated on mountains slopes the fine grains were then retransported by wind to the diexi lake optically stimulated luminescence dating of the xinmocun section indicates continuous deposition from 18 65 to 10 63 ka these results indicate that palaeoearthquakes in the study area had a mean recurrence interval of 0 32 ka therefore we propose that lacustrine sediments in a tectonically active region have the potential to record a continuous history of palaeoearthquakes palaeoearthquakes probably produced numerous rockfalls and landslides in alpine valleys and provided significant sources of regional eolian dust

influence of a tectonically active mountain belt on its foreland basin evidence from detrital zircon dating of bedrocks and sediments from the eastern tibetan plateau and sichuan basin sw china abstract the tectonically active eastern tibetan plateau tp impacts the populous sichuan basin in the form of dust and exhumed detrital materials to better understand a detailed transport process of detrital material from the eastern tp to the sichuan basin eight samples were collected from the upper reaches of the min river in the eastern tp to the sichuan basin for zircon u pb chronological and grain size analysis the results are compared with those of previously studies zircon grains are comparatively coarse in three bedrock samples one fluvial sand sample and one dust sample but are distinctly fine in three lacustrine samples intriguingly the zircon grain size parameters from the fluvial sand and dust samples are similar to each other consistent with previous studies of this area the analysis of our u pb zircon ages indicates five major age populations at 180 350 ma 350 550 ma 700 1000 ma 1600 2000 ma and 2200 2600 ma which broadly correspond to five known granitoid magmatic events within the yangtze block the min river links lacustrine sediments from lixian fluvial sands from wenchuan leshan yibin and from the dadu river and the dayi conglomerate implying the dayi conglomerate was transported by fluvial rather than glacial processes the denuded detrital material mainly generated by seismic events in the eastern tp was transported by water flow into the western sichuan basin where two thick sedimentary depocenters developed and the relatively fine grains were then transported by wind to the northern sichuan basin thus the thick sediments in the western sichuan basin mainly transported by the min river probably exerted a major influence on dust deposition in the northern sichuan basin in contrast the jialing and dadu rivers made a minor contribution

a statistical framework for calculating and assessing compositional linear trends within fault zones a case study of the ne block of the clark segment san jacinto fault california usa utilizing chemical data derived from the various fault zone architectural components of the clark strand of the san jacinto fault southern california usa we apply for the first time non central principal component analysis to calculate a compositional linear trend within molar a cn k space in this procedure a cn k are calculated as the molar proportions of al2o3 a cao na2o cn and k2o k in the sum of molar al2o3 na2o cao and k2o cao is the molar cao after correction for apatite we then derive translational invariant chemical alteration intensity factors t for each architectural component through orthogonal projection of analyzed samples onto the compositional linear trend the chemical alteration intensity factor t determines the relative change in composition compared to the original state i e the composition of the altered wall rocks it is dependent on the degree of intensity to which the process or processes responsible for the change in composition of each architectural component has been active these processes include shearing fragmentation fluid flow and generation of frictional heat non central principal component analysis indicates that principal component 1 explains 99 7 of the spread of a cn k data about the calculated compositional linear trend i e the variance the significance level for the overall one way analysis of variance anova is 0 0001 such a result indicates that at least one significant difference across the group of means of t values is different at the 95 confidence level following completion of the overall one way anova the difference in means t test indicated that the mean of the t values for the fault core are different than the means obtained from the transition and damage zones in contrast at the 95 confidence level the means of the t values for the transition and damage zones are not statistically distinguishable the results of xrd work completed during this study revealed that the 2 m fraction is composed primarily of illite smectite with 15 illite in the damage zone of illite smectite with 30 illite in the transition zone and of discreet illite with very minor smectite in the fault core these changes parallel the increasing values of the chemical alteration intensity factors i e t based on the above results it is speculated that when fault zones are derived from tonalitic wall rocks at depths of 400 100 m the onset of the illite smectite to illite conversion will occur when t values exceed 0 20 0 12 the average chemical alteration intensity factor calculated for the transition zone under such conditions during repeated rupturing events frictional heat is produced and acidic fluids with elevated temperatures 125 c are flushed through the fault core over time the combination of shearing fragmentation and frictionally elevated temperatures eventually overcomes the kinetic barrier for the illite smectite to illite transition such settings and processes are unique to fault zones and as a result they represent an underappreciated setting for the development of illite from illite smectite the success of non central principal component analysis in this environment offers the first statistically rigorous methodology for establishing the existence of compositional linear trends in fault zones this method also derives quantifiable alteration intensity factors that could potentially be used to compare the intensity of alteration at different segments of a fault as well as offer a foundation to interpret the potential driving forces for said alteration and differences therein