hydrological changes in western central asia kyrgyzstan during the holocene as inferred from a palaeolimnological study in lake son kul abstract the hydrology of western central asia is highly sensitive to climatic perturbations in order to understand its long term variability and to infer linkages between precipitation and atmospheric and oceanic systems we conducted a thorough sedimentary and geochemical study on a composite core retrieved in lake son kul central kyrgyzstan a multi proxy approach was conducted on lake sediments based on grain size analyses magnetic susceptibility total organic carbon toc total nitrogen tn and carbon and oxygen isotope analyses on bulk and biogenic materials ostracoda and molluscs shells at a resolution equivalent to ca 40 years aiming to characterise the sequence of palaeolimnological changes in son kul as indicated by 18 o record of bulk carbonates mainly consisting of aragonite the holocene hydrological balance was negative during most of time suggesting an excess of evaporation e over precipitation p limnological conditions fluctuated rapidly before 5000 cal yr bp indicating significant changes in regional hydrology and climate in particular the long term negative hydrological balance was impeded by several short stages with marked increase of precipitation lasting several decades to a few centuries e g 8300 8200 6900 6700 6300 6100 5500 5400 5300 5200 and 3100 3000 cal yr bp precipitation changes as inferred from 18 o data are also documented by increased minerogenic detritus and higher toc we propose that the seasonal pattern of precipitation varied transiently in western central asia during the holocene although evaporation changes may also account for the rapid changes observed in 18 o data when the annual water balance was less critical p e the excess of water might be ascribed to increased precipitation during cold seasons mainly because winter precipitation has more negative 18 o than its summer equivalent conversely when the annual water balance is negative p e the moisture was mainly delivered during the warm season as between 5000 and 2000 cal yr bp our results thus imply that moisture sources could have changed as well during the holocene moisture was delivered as today mainly during summer from the extended caspian aral basin and eastern mediterranean although arctic and even north atlantic seas might be important moisture sources when seasonal precipitation was dominated by winter precipitation we hypothesise that warming arctic and north atlantic seas were important for the north hemisphere circulation during the cold season

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

source radiation invariant property of local and near regional shear wave coda application to source scaling for the mw 5 9 wells nevada sequence 1 this study documents another unique property of local and regional shear wave coda that scattering in the earth s crust averages out source heterogeneities such as focal mechanism and directivity we consider two recent events which exhibited significant source directivity the first an mw 4 2 oakland hills california strike slip event on july 20 2007 resulted in uncharacteristically large amounts of damage in the montclair and south berkeley neighborhoods along strike and north west of the hypocenter but almost no damage to the south east the second event the mw 5 9 wells nevada dip slip event of february 21 2008 was well recorded by the earthscope transportable array usarray and determined to exhibit south west directivity we conclude with an example of corner frequency fc estimates from the wells sequence which showcase the coda s low variance and find that scaling is non self similar suggesting a change in dynamics between the mainshock and aftershocks

a new spectral ratio method using narrow band coda envelopes evidence for non self similarity in the hector mine sequence 1 the use of local and regional s wave coda is shown to provide stable amplitude ratios that better constrains source differences between event pairs we first compared amplitude ratio performance between local and near regional s and coda waves in the san francisco bay region for moderate sized events then applied the coda spectral ratio method to the 1999 hector mine mainshock and its larger aftershocks we find 1 average amplitude ratio standard deviations using coda are 0 05 to 0 12 roughly a factor of 3 smaller than direct s waves for 0 2 f 15 0 hz 2 coda spectral ratios for the mw 7 0 hector mine earthquake and its aftershocks show a clear departure from self similarity consistent with other studies using the same datasets and 3 event pairs green s function and target events can be separated by 25 km for coda amplitudes without any appreciable degradation in sharp contrast to direct waves

transient permeability and reseal hardening in fault zones evidence from dilation breccia textures t is well established that earthquake faulting can create permeability along a fault zone in high competence rocks by mismatch of the fault walls and by secondary fracture in a surrounding damage zone and that this permeability is created repeatedly during successive earthquake cycles less well proven is that such permeability is transient being episodically reduced by precipitation of cements in the fracture porosity the textures of carbonate dilation breccias formed at around 1 7 km depth on the dent fault zone nw england lend support to this economically important concept of transient fracture permeability the key observation is that many breccias reflect only a single episode of brecciation and reseal a generally applicable explanation of such single phase breccias is that they were resealed in the interval between major earthquakes that this reseal made the breccia stronger that the intact rock and that subsequent brecciation in the same rock volume was inhibited this reseal hardening model implies that transient permeability in fault zones may last no longer than the recurrence times of large earthquakes and that the permeability conduits will change position in the damage zone with time unless focused at a major fault jog or termination

extent and spatial distribution of pleistocene glaciations in eastern tibet as a contribution to the controversial discussion regarding the nature and extent of the pleistocene glaciation on the tibetan plateau additional observations and results were obtained during several chinese german joint expeditions in the investigation area of the eastern and central tibetan plateau it will be shown that the maximum extent of the last glaciation was limited to the glaciation of isolated mountain groups or smaller plateau glaciations these glaciations are characterized by glacial erosional features such as u shaped valleys in the inner mountain massifs and cirques in the higher summit areas accumulation forms such as terminal and lateral moraines less common than basal moraines are marked by granitic and basaltic erratics using two examples from the eastern margin of the tibetan plateau nianbaoyeze shan and northern chola shan the extent of pleistocene glaciations can be mapped by the distribution of terminal and lateral moraines and erratic granite boulders on the slopes of the surrounding schists two to three main pleistocene glaciations can be separated using weathering criteria paleosols and the overlying stratum on the moraines and associated terrace sequences overlying stratum consist of aeolian sandy silt or solifluction debris the younger moraines are found to be characterized by large erratics were therefore named big boulder moraine and can be found over the investigated area the ice free areas are characterized by pleistocene terraces along the main rivers loess deposits with sand and ice wedges at higher elevations e g the basin of zoige and paleosols in the basins below 3500 m a s l e g aba basin or garze basin the hypothesis of an extensive plateau glaciation could not be verified for this region a rising snowline equilibrium line altitudes elas is revealed in two cross sections during the last glacial maximum lgm at the eastern and northern margin of the tibetan plateau snowlines migrated from about 4000 m in the east minshan to 4300 m in the nianbaoyeze and to about 4700 m in the west bayan har shan a rise was also recorded from about 3800 m in the north central qilian shan up to a range of 4300 4950 m different exposures in the kunlun shan to approximately 5200 m in the tanggula shan in the center of the tibetan plateau the general increase of modern and lgm snowlines or elas towards the plateau corresponds with a decrease of precipitation from east to west and from north to south respectively precipitation was more pronounced at the eastern margin during glacial times than compared to present

timing of glaciation during the last glacial cycle evaluating the concept of a global last glacial maximum lgm abstract it has long been known that mountain glaciers and continental ice sheets around the globe reached their respective maximum extent at different times during the last glacial cycle often well before the global last glacial maximum lgm c 23 19 ka which is formally defined by peaks in global sea level and marine oxygen isotope records however there is increasing evidence from around the world that it was not only mountain glaciers which were asynchronous with the global lgm but also some regions of the large continental glaciers the barents kara ice sheet in northern eurasia together with a majority of ice masses throughout asia and australasia reached their maximum early in the last glacial cycle a few thousand years before the global lgm period the east antarctic ice sheet also reached its maximum extent several millennia before the global lgm in numerous mountainous regions at high mid and low latitudes across the world glaciers reached their maximum extent before marine isotope stage mis 2 in mis 5 4 and 3 this is in contrast to most sectors of the laurentide ice sheet the cordilleran ice sheet the se sector of the fennoscandinavian ice sheet and the alpine ice sheet in central europe which appear to have reached their maximum close to the global lgm in mis 2 the diachronous maximum extents of both mountain glaciers and continental ice sheets during the last glacial cycle means that the term and acronym last glacial maximum lgm has limited chronostratigraphical meaning when correlating glacial deposits and landforms

timing of glacier expansion during the last glacial in the inner tien shan kyrgyz republic by osl dating abstract optically stimulated luminescence osl dating was applied to glacial sediments and adjacent loess from moraines in the teskey ala too and at bashy ranges in the inner tien shan kyrgyz republic kyrgyzstan two large glacier expansions during the last glacial were observed in the two study areas teskey terskey stages i and ii moraines were dated to marine isotope stage mis 4 early mis 3 and mis 2 and at bashy stage ii in the at bashy range dated to late mis 3 mis 2 the timing of the two expansions during the last glacial coincided with global cold periods and with advances of the major northern hemisphere ice sheets however the fact that the greater expansion occurred in mis 4 early mis 3 in the teskey ala too range suggests that climate during mis 4 early mis 3 was more humid than during mis 2 it is possible that the strengthened siberian high during mis 2 restricted the impact of the westerlies and this reduced precipitation in the study area

lateral moraines of glacier de tsidjiore nouve form development and implications the relationship between supraglacial lateral moraines and lateral dump moraines at arolla switzerland is discussed a detailed study of the lateral moraines of glacier de tsidjiore nouve reveals their complex form as superimposed and nested ridges and the current mode of development possibly related to the passage of a kinematic wave sedimentological analysis indicates that much of the constituent debris is of supraglacial origin it is transported either directly from the base of slopes flanking the pigne d arolla ice fall or via englacial septa comprising marginal sediment incorporated in the accumulation zone a calculation of the volume of debris in the lateral moraines suggests that glacier de tsidjiore nouve has recently been more active in transporting and depositing supraglacial debris than in glacial erosion sensu stricto

a framework for late quaternary lake level fluctuations in lake karakul eastern pamir focusing on lake glacier landform interaction abstract this paper presents a framework for late quaternary lake level fluctuation in the closed basin lake lake karakul eastern pamir on the basis of the stereoscopic observation of remote sensing data field mapping and relative dating the palaeoshorelines approximately 60 in number observed around the lake karakul can be classified into four groups h shorelines m shorelines l shorelines and ll shorelines in the descending order of height the highest level of each of the above palaeoshoreline groups is 205 m 85 m 35 m and 10 m above the present lake level 3915 m asl from the glacial landform developments and related valley fill sedimentation patterns around the threshold of the present basin closure the lake level fluctuation defined by these palaeoshoreline groups was found to be a consequence of the water balance change within the closed basin with respect to the timing of the palaeolake highstands the relationship between lacustrine terraces and terminal moraines suggests the synchroneity of the highest stand of each palaeolake with the corresponding maximum glacier advance the tentative chronology of the lake level fluctuation was established from the synthesis of the style of geomorphic development and related glaciation relative dating on moraine gravels and the correlations to established glacial histories in and around the pamir the periods of the palaeolake highstands indicated by h m l and ll shorelines seem to be correlated with the antepenultimate glacial mis 8 penultimate glacial mis 6 early last glacial mis 4 and the late last glacial mis 2 periods respectively based on this chronology each of the 60 palaeoshorelines are expected to show stable lake surfaces during lake regressive stages toward the terminations from the glacial maxima of mis 8 6 4 and 2 given that the distinct landforms of each palaeoshoreline group were formed in association with the predominant stagnation or small re transgression of the palaeolake the short term cooling and or wetter episodes which turned positive lake hydrologic balances from negative ones were superimposed on the major palaeoclimate changes during the glacial termination periods

from hydroplastic to brittle deformation controls on fluid flow in fold and thrust belts insights from the lower pedraforca thrust sheet se pyrenees abstract we present a multidisciplinary study to decipher the controls of deformation on fluid flow regime in fold and thrust belts using the lower pedraforca thrust sheet in the se pyrenees as an example we integrate field based and petrographic observations and geochemical and geochronological data to differentiate seven types of fractures eight types of calcite cement cc1 to cc8 and two sets of stylolites during the deformation stretching the studied thrust sheet during syn sedimentary hydroplastic normal faulting affecting poorly consolidated upper cretaceous and eocene syn orogenic sediments calcite cement did not precipitate during burial bed parallel stylolites formed and cc1 and cc2 precipitated from formation waters in a closed palaeohydrological system during the layer parallel shortening cc3 precipitated from formation waters 5 4 vsmow with 87sr 86sr ratios of 0 707922 and at 70 c cc4 precipitated from formation waters recording different burial conditions as the up to 4 dispersion in 18o of this cement suggests contrarily during folding and thrusting cc5 to cc7 precipitated in an open palaeohydrological system cc6 precipitated from formation waters 5 vsmow with 87sr 86sr ratios of 0 707817 and at 75 c these fluids carried hydrocarbons and probably interacted with upper triassic evaporites an 87sr 86sr ratio of 0 708230 for cc5 indicates that formation waters also interacted with clays within continental deposits during this period stylolites formed in relation to faulting and previous hydroplastic normal faults reactivated as reverse and strike slip faults allowing fluid flow cc7 precipitated after cc6 also from fluids in isotopic disequilibrium with their adjacent host rock the fluid system continued open during the oligocene when cc8 precipitated in normal faults affecting syn orogenic conglomerates deposited during the reactivation of the lower pedraforca thrust sheet the influence of deformation on fluid flow observed in the lower pedraforca thrust sheet is similar to that observed in other fractured areas worldwide

outcrops as guides to subsurface natural fractures example from the nikanassin formation tight gas sandstone grande cache alberta foothills canada abstract outcrop studies are essential for understanding subsurface fractures because some key attributes such as length and height distribution cannot be measured using wellbores discrepancies between outcrop and subsurface fracture attributes arise because loading paths due to burial exhumation and thermal paths differ consequently even where rock type and structural setting are close matches differences may exist in mechanical properties and fracture growth here we investigate petrologic criteria and disseminated arrays of quartz filled microfractures as tools for comparing and contrasting fractures in outcrop with those as sampled by core for tight gas sandstones fracture cements are key diagnostic criteria for proving correspondence between outcrop and core we offer guidelines on selecting suitable outcrop analogs that differ markedly from current practice our illustration uses outcrops and core samples of late jurassic to early cretaceous nikanassin formation a tight gas sandstone but aspects of the outcrop vetting procedure can be applied to other rock types in some core and outcrops nikanassin formation fractures contain quartz and ankerite cement assemblages crack seal and rind textures and aperture size distributions that show that the outcrop and subsurface localities we examined share the same fracture stratigraphy and similar diagenesis these outcrops can thus be used to measure attributes including those that are unlikely to be captured in core such as fracture height and length distributions relative and absolute fracture intensity with structural position and degree of fill by synkinematic cement in our example absolute fracture intensity and distribution of postkinematic carbonate cements are site specific and differ between outcrop and core but in ways that can be quantified

source characteristics of seismicity associated with underground wastewater disposal a case study from the 2008 dallas fort worth earthquake sequence oil and natural gas production from shale formations using hydraulic fracturing or hydrofracking techniques has grown rapidly since 2008 and represents a vital and growing domestic energy resource the waste fluids from increased production called brine are typically injected into deep underground disposal wells to avoid discharge into streams and other sensitive drinking water supplies the environmental protection agency estimates that approximately 400 million gallons of brine are currently disposed of on a daily basis in more than 28 000 wells in the united states and the volume of injection continues to grow dramatically this process has recently been implicated as the source of some potentially induced seismicity in gas producing states such as oklahoma texas arkansas and ohio

late holocene climatic and environmental changes in arid central asia abstract late holocene climate and environmental changes in arid central asia were analyzed using various paleoclimate archives such as ice cores tree rings lake sediments historical documents glacial fluctuations and archeological data over the last 2000 years arid central asia witnessed three humid periods from ad 0 410 650 890 and 1500 1820s dry periods occurred in 420 660 and in 900 1510s concerning temperature the most striking features are the existence of the medieval warm period mwp and the little ice age lia the mwp was recorded in the 9 12th centuries and was accompanied by an anomalously dry climate whereas the lia extended from the 15 18th centuries and was accompanied by pluvial conditions temperature and precipitation show significantly negative correlations on annual decadal and centennial timescales temperature was generally above average when dry climate conditions predominated on decadal to centennial timescales during the last 1000 years the coldest decades of the last millennium the period 1630 1650s matched with an anomalously wet episode the combination of paleoclimatic evidence clearly suggests that the combination of cold and wet climate condition during the lia was responsible for the strong glacial advances in several mountain systems of central asia

record of glacier variations during the last glacial in the turkestan range of the pamir alay kyrgyz republic moraines in five valleys of the turkestan range of the pamir alay kyrgyz republic were analyzed based on their geographical position and elevation morphology and ecological characteristics the moraines represent four glacial advances turkestan stage i during the last glacial stage ii during the late holocene stage iii during the little ice age ad 1400 1900 and stage iv during the 20th century in turkestan stage i the glaciers expanded to about 5 10 km from their present termini during marine isotope stage mis 2 radiocarbon ages for several soil layers buried in a lateral moraine of the asan usin glacier frontal area indicate that glaciers shrank or stagnated between at least 48 and 42 kyr bp during the warm climate of mid mis 3 these findings suggest that the glacier expansion in mid mis 3 was relatively small compared to the glacier expansion of mis 2 during the last glacial

asynchronous maximum advances of mountain and continental glaciers the last maximum glacier advance in many mountain ranges appears to have predated the last maximum advance of the wisconsinan continental ice sheets 20 000 years b p published evidence from widely spaced localities in north and south america europe asia and hawai i suggests that some mountain glaciers extended farther during one or more stades early in the last glaciation roughly 115 000 30 000 years b p than at its end when low global temperature and high precipitation presumably were most favorable for the growth of glaciers variations in the timing of glacier advances in different mountain ranges suggest that alpine glaciers are dependent on regional climate as well as global conditions their study might provide sensitive tests for theories of global climate change glacial deposits are often used as time markers in neotectonic and geomorphic studies and their ages sometimes are inferred from distant measurements or from proxy histories of global climate change undated geomorphic features such as moraines sharply incised streams and river terraces which commonly have been associated with the last maximum glacier advance 20 000 years b p or last deglaciation 13 000 years b p may actually be older by a factor of 2 to 4 or more conversely deposits assigned to the maximum advances of the penultimate global glaciation 130 000 years b p may actually date from early in the most recent glacial cycle and be younger by a comparable factor rates of faulting or folding estimated from displacements or deformation and the assumed ages of such geomorphic features might be too great or too small by corresponding factors

facies architecture and high resolution sequence stratigraphy of an upper cretaceous platform margin succession southern central pyrenees spain abstract excellent exposures of upper cretaceous santonian carbonate platforms on the northern flank of sant corneli anticline southern central pyrenees provide detailed information of facies architecture in both depositional strike and dip directions basic accretional units are differentiated by facies contrast across mappable surfaces these surfaces do not show clear evidence of subaerial erosion and are correlated basinward with bedding planes across which there are subtle changes in skeletal composition two types of basic accretional units have been identified based on bedding patterns internal facies architecture and skeletal composition 1 rudist buildups consist of a rudist and coral belt at the platform margin passing landward into a slender hippuritid lithosome locally overlain by a bioclastic blanket that passes basinward into bioclastic apron like clinobeds and into fine grained packstone wackestone 2 calcarenite wedges consist of yellow brown benthic foraminifer rich grainstones to grain dominated packstones with scattered rudist shells and small coral colonies passing basinward into mud dominated packstones to wackestones with variable siliciclastic content quartz sand to silt and clay rudist buildups and calcarenite wedges alternate although not rhythmically these changes in platform skeletal composition reflect changes in the dominant type of carbonate producing biota independently of the changes in accommodation both types of basic accretional units rudist buildups and calcarenite wedges form simple sequences and parasequences according to internal lithofacies arrangement and inferred sea level cyclicity cycles or paracycles high frequency sea level cyclicity fits in the milankovitch frequency band long term changes in accommodation governing aggradation progradation and backstepping of basic sequences and parasequences reflect tectonic influence rather than long term changes in eustatic sea level

pleistocene paleoenvironmental changes in the high mountain ranges of central china and adjacent regions abstract during several joint chinese german expeditions the quaternary landscape and paleoclimatic evolution of the mountain ranges and grabens surrounding the loess plateau of central china was studied the results are compared with proxy data from the interior loess plateau to help reconstruct atmospheric circulation during late pleistocene times middle to late pleistocene alluvial terraces and fans capped with loess units and paleosols show that aggradational episodes correlate with periods of glaciation and increased loess accumulation in turn degradation correlates with interglacials or interstadials and increased soil formation this implies that climate is the primary control on quaternary paleohydrology and alluvial sedimentation and erosion the high mountains which barely reached the last glacial ela were only glaciated during the most favourable climatic period of glaciation the glaciation the glacial and alluvial forms point to a cool early to maximum glacial period with increased precipitation and to a maximum to final period with cold dry conditions during the last glaciation the maximum advance of the small glaciers took place towards the end of a relatively humid and cold period between ca 32 and 23 ka the following dry cold stage between ca 23 and 13 ka was rather unfavourable for glacial advance proxy data from the loess plateau supports the view that glaciations were more or less dominated by cold dry winter monsoon climate whereas during the interglacial interstadials a warmer and more humid climate prevailed implying a strengthening of the summer monsoon influence the results prove variations of the monsoon that in turn modulates paleohydrology periglacial dynamics glacier advances dust flux and soil formation

timing and style of late quaternary glaciation in the eastern hindu kush chitral northern pakistan a review and revision of the glacial chronology based on new optically stimulated luminescence dating abstract glacial landforms and sediments provide evidence for two late quaternary major glaciations in the eastern hindu kush new optically stimulated luminescence osl dating was undertaken to define the timing of these glaciations and associated sediment deposition the drosh glacial was defined by osl dating to have occurred during marine isotopic stage 3 producing an extensive valley glaciation that extended to an altitude of 1300 m above sea level asl in the main valley with an equilibrium line altitude ela depression of 1200 m the pret glacial produced a valley glaciation that extended to an altitude of 1670 m asl in the main valley with an ela depression of 1000 m the new osl dating suggests that this glacial stage probably represents several glacial advances that occurred during the latter part of the last glacial moraines representing two minor glacial advances the shandur and barum glacial stages were also recognized near the contemporary glaciers these probably formed during the middle late holocene and little ice age respectively this study and comparisons with adjacent regions suggest that there was limited glaciation during the global last glacial maximum lgm in the hindu kush deglaciation in the mountain ranges of the himalayas and the consequent meltwater discharge into the adjacent seas was negligible immediately after the global lgm and it was therefore of minor importance as a forcing factor for global climate change during the end of the last glacial cycle however our studies show that glaciation and particularly deglaciation is important in controlling the deposition of thick valley fills and the landscape evolution of the high mountain environments

constraints on bed scale fracture chronology with a fem mechanical model of folding the case of split mountain utah usa abstract a technique is presented for improving the structural analysis of natural fractures development in large scale fold structures a 3d restoration of a fold provides the external displacement loading conditions to solve by the finite element method the forward mechanical problem of an idealized rock material with a stress strain relationship based on the activation of pervasive fracture sets in this elasto plasticity constitutive law any activated fracture set contributes to the total plastic strain by either an opening or a sliding mode of rock failure inherited versus syn folding fracture sets development can be studied using this mechanical model the workflow of this methodology was applied to the weber sandstone formation deformed by forced folding at split mountain anticline utah for which the different fracture sets were created and developed successively during the sevier and the syn folding laramide orogenic phases the field observations at the top stratigraphic surface of the weber sandstone lead to classify the fracture sets into a pre fold wnw ese fracture set and a ne sw fracture set post dating the former the development and relative chronology of the fracture sets are discussed based on the geomechanical modeling results starting with a 3d restoration of the split mountain anticline three fold fracture development models were generated alternately assuming that the wnw ese fracture set is either present or absent prior to folding process depending on the initial fracture configuration the calculated fracture patterns are markedly different showing that assuming a wnw ese joint set to predate the fold best correlates with field observations this study is a first step addressing the complex problem of identification of fold related fracturing events using an elementary concept of rock mechanics when tight to complementary field observations including petrography diagenesis and burial history the approach can be used to better constrain fractured reservoir characterization

middle and late pleistocene glaciations in the southwestern pamir and their effects on topography abstract glacial chronologies provide insight into the evolution of paleo landscapes paleoclimate topography and the erosion processes that shape mountain ranges in the pamir of central asia glacial morphologies and deposits indicate extensive past glaciations whose timing and extent remain poorly constrained geomorphic data and 15 new 10be exposure ages from moraine boulders and roches moutonnees in the southwestern pamir document multiple pleistocene glacial stages the oldest exposure ages 113 10 ka underestimate the age of the earliest preserved glacial advance and imply that the modern relief of the southwestern pamir peaks at 5000 6000 m a s l valleys at 2000 3000 m a s l already existed in the late middle pleistocene younger exposure ages 40 80 ka 30 ka complement the existing central asian glacial chronology and reflect successively less extensive late pleistocene glaciations the topography of the pamir and the glacial chronologies suggest that in the middle pleistocene an ice cap or ice field occupied the eastern pamir high altitude plateau whereas westward flowing valley glaciers incised the southwestern pamir since the late pleistocene deglaciation the rivers of the southwestern pamir adjusted to the glacially shaped landscape localized rapid fluvial incision and drainage network reorganization reflect the transient nature of the deglaciated landscape

microtectonic and geochemical characterization of thrusting in a foreland basin example of the south pyrenean orogenic wedge spain abstract in orogenic systems thrust faults play a major role in stacking different tectonic units and may act as conduits for the expulsion of large amounts of fluid of different origins metamorphic diagenetic meteoric this study focuses on the monte perdido thrust unit emplaced in the paleogene jaca thrust sheet top basin in the sw central pyrenees we aim to decipher the mechanisms and p t conditions of deformation in fault zones and characterize the related fluid involvement through combined microstructural geochemical and microthermometry analyses two thrust faults cutting platform limestones marls and siliciclastic turbidites of the lower part of the basin fill paleocene lower eocene have been studied the fault zones are characterized by metre thick shear zones with highly deformed foliated clay rich sediments foliation is underlined by preferentially oriented phyllosilicates several generations of shear and extension calcite quartz and chlorite bearing veins attest to fluid rock interactions during a multi stage deformation microstructural observations and stable isotope analyses on calcite from veins and host sediments suggest that deformation was aseismic and dominated by diffusive mass transfer from pressure solution sites along cleavage and stylolites to the precipitation sites in veins with mineralizing fluids in equilibrium with the host sediments our results suggest an essentially closed hydrologic system and imply the absence of significant fluid flow along the studied fault zones microthermometric study on fluid inclusions present in calcite and quartz veins and calcite quartz oxygen isotopic fractionation determined for the first generation shear veins allow a geothermal gradient of 34 c km to be estimated analytical results demonstrate an evolution of the fault zones in three stages the first stage was related to the emplacement of the monte perdido thrust unit during the middle eocene at a temperature of 208 c and a burial depth of 5 7 km the second stage corresponds to a fault reactivation at a temperature of 240 c and a burial depth of 6 5 km the latter deformation may have been related to folding of the monte perdido thrust unit during the emplacement of the underlying gavarnie thrust unit during the late eocene early oligocene with deeper burial resulting from aggradation of the thrust sheet top basin fill the last event corresponds to the formation of a dilatant vein system likely related to the exhumation of the massif

loess deposits in the northern kyrgyz tien shan implications for the paleoclimate reconstruction during the late quaternary article i nfo loess deposits on the northern slopes of the kyrgyz tien shan were examined their particle size characteristics show silt size dominancy n80 with minor contribution from sand 12 and clay 7 the loess was dated using optically stimulated luminescence osl and radiocarbon methods to define the timing of deposition the osl ages of fine and coarse quartz fractions were consistent with each other within 2 uncertainty level ex ceptseveralsamplesdepositedduringmis2 basedontheoslages fourmajorloessdepositionalperiodsarerec ognized in thenorthern kyrgyz tienshan during the late quaternary the holocene mis2 mis3 and mis4 the rate of dust accumulation in the northern tien shan during mis 2 was greater than that during mis 3 or mis 4 this implies that cold dry conditions varied significantly during the late quaternary in the study area the accumulation patterns of the kyrgyz loess deposits in the northern tien shan are closely related to climate fluc tuations during the late quaternary influenced by changes in the mid latitude westerlies asian summer mon soons and siberian high pressure shp systems during which there was no significant cessation of deposition 2013 elsevier b v all rights reserved

information from folds a review abstract folds are spectacular geological structures that are seen in layered rock on many different scales to mark 30 years of the journal of structural geology we review the information that can be gained from studies of folds in theory experiment and nature we first review theoretical considerations and modeling from classical approaches to current developments the subject is dominated by single layer fold theory with the assumption of perfect layer parallel shortening but we also review multilayer fold theory and modeling and folding of layers that are oblique to principal stresses and strains this work demonstrates that viscosity ratio degree of non linearity of the flow law anisotropy and the thickness and spacing distribution of layers of different competence are all important in determining the nature and strength of the folding instability theory and modeling provide the basis for obtaining rheological information from natural folds through analysis of wavelength thickness ratios of single layer folds and fold shapes they also provide a basis for estimating the bulk strain from folded layers information about folding mechanisms can be obtained by analysis of cleavage and fabric patterns in folded rocks and the history of deformation can be revealed by understanding how asymmetry can develop in folds by how folds develop in shear zones and how folds develop in more complex three dimensional deformations

multi scale fracture network characterisation on carbonate platforms abstract characterisation of fracture networks at different scales is challenging and important to many fields of geoscience especially when access to multiple resolution datasets is limited here we develop an integrated analysis of fracture networks on carbonate platforms using three scales of observation small outcrop intermediate airborne lidar and large 3d seismic statistical analyses and ternary diagrams of geometrical and topological data from cariatiz south east spain and pernambuco east brazil are used to understand the relationships and distribution of fracture networks between multi scale datasets a variety of fracture types at each scale of observation reveal how complex fracture networks are on carbonate platforms our results demonstrate that fracture network properties behave differently depending on the fracture size and that transitional scale gaps between datasets constrain fracture characterisation airborne lidar maps show that intermediate sized fractures appear to have a better controlled orientation and a lower connectivity than smaller fractures from the same area in cariatiz fracture branch length distributions fit a negative exponential or log normal distribution for massive non stratabound units this work is important as it demonstrates that the use of outcrop data is a good approach to understand fracture complexity of carbonate platforms understanding sub seismic fracture networks is therefore critical in quantifying fluid flow and permeability in carbonate reservoirs

conditions during syntectonic vein formation in the footwall of the absaroka thrust fault idaho wyoming utah fold and thrust belt abstract the twin creek limestone in the footwall of the absaroka thrust sheet contains three sets of bed normal syntectonic calcite veins vein formation occurred during cretaceous motion along the absaroka thrust fault as indicated by 1 crosscutting relationships among these vein sets 2 a previously dated solution cleavage and 3 calcite twin analysis fluid inclusions in the veins and overburden estimates constrain inclusion entrapment temperatures to be between 175 c and 328 c results from stable oxygen isotopes indicate that the host and vein fluid compositions were in near isotopic equilibrium applying both reasonable geothermal gradients and constraints on overburden temperature yields fluid pressures during vein precipitation that are near hydrostatic all data taken together suggest both that vein formation within the twin creek formation occurred in a relatively closed system and that the veins filled near hydrostatic fluid pressure because the veins fill precursory cracks vein filling might not reflect the maximum fluid pressure that existed during the complete vein forming process

a review of deformation pattern templates in foreland basin systems and fold and thrust belts implications for the state of stress in the frontal regions of thrust wedges aesthetically appealing thrust systems and related large scale anticlines in both active and fossil foreland fold and thrust belts and the economic potential associated with the m have captured the interest of structural geologists for many decades as a consequence a large amount of data on sub seismic deformation patterns from thrust related an ticlines is available in the literature we provide a review of deformation pattern templates from fi eld data in foreland fold and thrust belts and show that the most frequent tre nds of sub seismic syn orogenic deformation structures hosted in km scale thrust related folds frequently and pa radoxically indicate a syn th rusting strike slip stress fi eld con fi guration with a near vertical 2 and a sub horizontal 3 rather than a contractional one where the latter is expected to be the vertical principal axis of the stress ellipsoid this a pparent inconsistency between sub seismic syn orogenic deformation structures and stress fi eld orientation is here named the 2 paradox field data support a possible expla nation of the paradox provided by the major role played by i nherited early orogenic extensional deformation struc tures on thrust fault nucleation nucleation of major thru sts and their propagation is facilitated and driven by the positive inversion and linkage of the early orogenic sub s eismic extensional inheritance developed in the foreland basin this process eventually leads to the development of l argereversefaultzonesandcanoccurbothincontractional and strike slip stress fi eld con fi gurations

production characteristics of the fractured reservoirs of the la paz field maracaibo basin venezuela la paz oil field is one of the most famous well documented fractured reservoirs in the world since 1945 it has produced more than 830 million bbl of oil from both low porosity cretaceous limestones and underlying granitic basement the field is situated on a large inversion structure partially uplifted in the late eocene having the majority of the inversion occurring in the miocene pliocene fracture distributions initial rate and cumulative production distributions and trends in formation water chemistry all suggest that reservoir quality and reserves are controlled by natural fractures associated with miocene pliocene and younger strike slip faults and possibly by secondary microporosity related to the geometry of the earlier eocene block uplift production levels within the area of eocene uplift are anomalously high with one well producing 59 million bbl of oil typical wells in other parts of the field produce 1 million bbl of oil analysis of the distributions cited previously suggests that production has occurred from highly elliptical to linear drainage areas surrounding faults these restricted zones of fault related fractures allow for communication of hydrocarbons stored in the low porosity rock carbonate matrix to the wellbore in addition diagenetic microporosity may be an important component in matrix storage in the carbonates and may be due to local subaerial exposure during the eocene uplift this article shows that analysis of the natural fracture system with respect to the production characteristics in even old fields can give rise to new reservoir models leading to new infill locations within the field limits or additional exploration opportunities in the area

late holocene variation of the raigorodskogo glacier and climate change in the pamir alai central asia during the late holocene the raigorodskogo glacier in the pamir alai central asia expanded before 3215 after 1545 and at 310 cal years bp as dated by the 14c calibrated ages of wood samples from moraine deposits and terrace exposures the glacier expansions which were accompanied by increased melt water run off over the terrace surface were confined to the proglacial area the terrace deposits with intercalated buried soil layers provide evidence of two obvious warm periods when the glacier abruptly retreated during the late holocene shortly before 1545 cal years bp and again sometime before ca 500 cal years bp fallen juniperus turkestanica broken by moraine deposits suggests that the largest glacial expansion during the little ice age occurred 310 cal years bp the glacier expansion in the little ice age was on roughly the same scale as that which occurred in the cold period after 1545 cal years bp observational records of the glacier terminus and moraine positions indicate that recent glacier advances occurred in the years 1908 1911 sometime in 1911 1934 and in 1960 1977 these advances were small while the glacier recessions were larger in the 1900s with large recessions also sometime in 1911 1934 and in 1977 1998 the glacier recession rate of 27 m year in 1911 1934 was faster than the rates of 13 m year in 1977 1990 and 21 m year in 1990 1998 however the glacier recession rate has been accelerating recently particularly after 1990 this recession reflects recent climate warming in inland asia

late holocene glacier variations in the frontal and inner ranges of the tian shan central asia evidence for the timing and extent of late holocene glacial advances in the tian shan mountains central asia is based on lichenometric and radiocarbon dating of end moraines three phases of glacial advance occurred at 1700 2100 and 1100 1300 lichenometric l years ago and then during the little ice age 150 700 l years ago differences in the pattern of glacier variations between the northwestern frontal and inner areas of the tian shan are reflected in the equilibrium line altitude ela depression of 23 glaciers studied at nine selected sites the peripheral glaciers appear to have been significantly more extensive during late holocene advances than the glaciers of the inner areas this difference seems to be explained by regional differences in humidification in the northwestern periphery of the tian shan the cold periods of the late holocene were more humid than the warm period of the mid holocene whereas in the inner areas the pattern of climate changes was the opposite a warm and hu

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

the dallas fort worth earthquake sequence october 2008 through may 2009 this paper describes a sequence of small earthquakes m b 3 3 that occurred at the dallas fort worth airport texas between 30 october 2008 and 31 may 2009 analysis of records at regional station wmok identified more than 180 earthquakes in the sequence about 90 percent occurred in four clusters on 30 october 1 november 20 november 26 december and 15 17 may after the sequence began a six station temporary local network obtained high quality three component records for 11 earthquakes occurring between 20 november and 1 december analysis of these data demonstrated that all 11 earthquakes originated from a focus near 32 855 n 97 051 w with an estimated depth 4 4 km this location is less than 0 5 km from a well completed in august 2008 that extends to a depth of 4 2 km drilled to dispose of brines collected during flowback of hydraulic fracturing fluids associated with the production of natural gas brine disposal commenced at the well on 12 september 2008 seismograms and s p intervals for the earthquakes are similar though not identical and relative locations indicate they occurred along a north northeast south southwest trend with horizontal and vertical dimensions of 1 1 km and 0 2 km respectively this trend is approximately coincident with that of a mapped normal fault in the subsurface and consistent with the maximum horizontal in situ stress direction because of the absence of previous historical earthquakes the proximity of the brine disposal well and the similarity with other documented cases of induced seismicity it seems likely that fluid injection induced the 2008 2009 sequence

karst dissolution along fracture corridors in an anticline hinge jandaira formation brazil implications for reservoir quality abstract folded fractured and karstified structures have been recognized in several carbonate reservoirs however they are rarely fully identified from seismic or well data and have been poorly described the present study investigates the geological and structural controls that regional anticlines may exert on solution enlarged fracture corridors and epigenic karst concentrations in folded fractured carbonate units we performed regional mapping based on 106 2d seismic lines 51 well logs unmanned aerial vehicle uav imagery of four major outcrop sites i ii iii and iv and field investigations to parameterize fracture and karstic features density spacing length and aperture the study area is potiguar basin brazil where we identified the gentle ne trending apodi fold 10 km wide and 20 km long the fold formed along an inverted extensional fault during the latest miocene quaternary stress field and the envelope of the meandering trend of the apodi river coincides with the ne trending fold axis the fracture pattern in the fold hinge zone consists of two orthogonal syn folding fracture sets a ne sw striking hinge parallel set and an orthogonal nw se striking set these fractures and superposed karstification are mostly concentrated in the hinge zone along fracture corridors in an area 1 5 km wide and 20 km long we conclude that fracture corridors in anticline hinges are likely sites to have high fracture densities and wide apertures these corridors provide reservoir spaces that are favorable for the formation of karst cavities with significant increases in permeability and porosity along the fracture sets these features act as important fluid pathways and storage areas where matrix porosity is low the findings can be used for first order prediction in karstified carbonate reservoirs

last 1100 yr of precipitation variability in western central asia as revealed by tree ring data from the pamir alay we developed a 1108 yr chronology of tree ring widths based on 64 himalayan pencil juniper juniperus semiglobosa regel trees for the pamir alay mountains central asia dendroclimatological analysis demonstrates that precipitation has significant effects on tree growth in the semiarid mountainous area of northwestern tajikistan located on the edge of the great midlatitude karakum and kyzylkum deserts the highest level of linear correlation r 0 67 is observed between tree growth and seasonalised winter previous december february precipitation our studies also show that moisture precipitation palmer drought severity index from the previous june to the current september was the dominant climatic factor accounting for interannual variations in tree ring width suggesting that this should be considered in climate reconstruction using the transfer function method we reconstructed the region s drought history over the period ad 908 2015 the results of this moisture reconstruction showed that the most recent millennium was characterised by series of dry and wet stages the driest periods occurred before 1000 1200 1250 and at the end of the eighteenth century and beginning of the nineteenth century the wettest conditions existed in 1650 1700 and after 1990

earthquake magnitude scales the use and meaning of earthquake magnitude scales are examined common misunderstandings regarding local magnitude surface wave magnitude and body wave magnitude are discussed and clarified it is shown that no single magnitude will adequately describe the size of an earthquake and that different geographic regions pose different requirements inter relations between seismic moment and the various types of magnitude are examined magnitudes are recommended for equations or curves which specify the strong ground motion acceleration velocity displacement or response spectra as a function of distance from the earthquake source

two year survey of earthquakes and injection production wells in the eagle ford shale texas prior to the mw4 8 20 october 2011 earthquake abstract between november 2009 and september 2011 the earthscope usarray program deployed 25 temporary seismograph stations on a 70 km grid in south central texas between 27 n 31 n and 96 w 101 w this area includes the eagle ford shale for decades this geographic region has produced gas and oil from other strata using conventional methods but recent developments in hydrofracturing technology has allowed extensive development of natural gas resources from within the eagle ford our study surveys small magnitude seismic events and evaluates their correlation with fluid extraction and injection in the eagle ford identifying and locating 62 probable earthquakes including 58 not reported by the u s geological survey the 62 probable earthquakes occur singly or in clusters at 14 foci of these foci two were situated near wells injecting recently increased volumes of water eight were situated near wells extracting recently increased volumes of oil and or water and four were not situated near wells reporting significant injection extraction increases thus in this region while the majority of small earthquakes may be triggered induced by human activity they are more often associated with fluid extraction than with injection we also investigated the m w 4 8 20 october 2011 fashing earthquake the largest historically reported earthquake in south central texas that occurred two weeks after the removal of the temporary usarray stations a field study indicated that the highest intensity mmi vi region was about 10 km south of 2010 2011 foreshock activity and that there were no high volume injection wells within 20 km of the mmi v vi region or the foreshocks however the 20 october 2011 earthquake did coincide with a significant increase in oil water extraction volumes at wells within the mmi v vi region and this was also true for previous earthquakes felt at fashing in 1973 and 1983 in contrast our study found significant increases in injection prior to an mblg3 6 20 july 1991 earthquake near falls city texas thus the eagle ford geographic region with seismic activity associated both with extraction and injection appears to be more complex than the barnett shale of northeast texas where a similar survey found possible correlations only with fluid injection

soils as indicators of the pleistocene and holocene landscape evolution in the alay range kyrgystan abstract soils derived from quaternary glacial glaciofluvial and aeolian deposits in the alay range kyrgystan were studied to reconstruct the pleistocene and holocene landscape evolution geomorphologic studies radiocarbon dating of a horizons in palaeosols and iron fractionation were undertaken during the last glacial maximum lgm the abramov glacier in the alay range advanced down the koksu valley to an altitude of 2500 m asl about 50 km from the modern snout ela lowering about 600 m in addition several frontal moraine complexes could be identified at the valley bottom of the koksu river between 3100 m asl and the modern glacier snout at 3650 m asl the complexes can be assigned to the following glacier advances late glacial ela lowering 200 300 m early holocene to end of late glacial younger dryas ela lowering about 110 m neoglacial ela lowering about 50 m and little ice age ela lowering about 50 m similar glacier advances could be reconstructed according to the soil development on the lateral moraines near the abramov glacier at 3600 4000 m asl determination of pedogenic iron oxides corroborated the morphologic and radiocarbon results

fracture analysis of outcrop analogues to support modelling of the subseismic domain in carbonate reservoirs south central pyrenees the productivity of wells in fractured reservoirs depends in terms of rate and sustainability on the heterogeneity and variable connectivity of the open fracture network outcrop studies in cretaceous carbonates from the catalan pyrenees illuminate this issue and reveal the degree of uncertainty associated with the interpretation of fracture data from wells and seismic three examples are chosen to provide verifiable data parameters and concepts which can be applied to the workflow of fractured reservoir characterization we discuss fracture properties and distributions in the subseismic volume the coupled behaviour between litho mechanical properties in situ stress and fracturing and the permeability properties of fault damage zones the outcrops also highlight some of the difficulties involved in constructing static reservoir models and evaluating fracture interpretations derived from software based techniques such as surface curvature

late quaternary glacial and climate history of the pamir mountains derived from cosmogenic 10be exposure ages moraines southwest of lake yashilkul pamir tajikistan were dated using 10be exposure ages of boulder surfaces we found evidence for 1 an extensive glaciation 60 000 yr ago 2 a less extensive glacial advance which deposited a characteristic hummocky moraine lobe with exposure ages ranging from 11 000 to 47 000 yr probably deposited at or before 47 000 yr ago and 3 lateral moraines with exposure ages of 40 000 yr 27 000 yr and 19 000 yr respectively increasing aridity in the pamir is most likely responsible for the progressively limited extent of the glaciers during the late pleistocene

asynchronous glaciation at nanga parbat northwestern himalaya mountains pakistan we present a new glacial chronology demonstrating asynchroneity between advances of himalayan glaciers and northern hemisphere ice sheet volumes glaciers at nanga parbat expanded during the early to middle holocene ca 9 0 5 5 ka no major advances at nanga parbat during the last global glacial stage of marine oxygen isotope stage 2 mis 2 between 24 and 11 ka were identified preliminary evidence also indicates advances between ca 60 and 30 ka these periods of high ice volume coincide with warm wet regional climates dominated by a strong southwest asian summer monsoon the general lack of deposits dating from mis 2 suggests that nanga parbat was too arid to support expanded ice during this period of low monsoon intensity advances during warm wet periods are possible for the high altitude summer accumulation glaciers typical of the himalayas and explain asynchronous behavior however the holocene advances at nanga parbat appear to have been forced by an abrupt drop in temperature ca 8 4 8 0 ka and an increase in winter precipitation ca 7 5 5 ka these results highlight the overall sensitivity of himalayan glaciation to orbital forcing of monsoon intensity and on millennial or shorter time scales to changes in north atlantic circulation

quaternary glaciation of tibet the geological evidence the question of the number and extent of pleistocene glaciations on the qinghai xizang tibet plateau remains contentious there has been considerable research activity in tibet by chinese scientists since the late 1950s and their principal findings including data on glacial and periglacial geomorphology sedimentology tectonics stratigraphy and lake history have been used to reconstruct ice margins and palaeosnowlines three and in places four distinct glaciations have been recognised the most extensive occurring in the later middle pleistocene valley and piedmont glacial systems with some mountain ice caps and a small ice sheet on the upper reaches of the huang he have been recognised but there is no evidence of a single tibetan ice sheet as the plateau and the himalaya karakoram underwent accelerating uplift through the quaternary there occurred progressive desiccation in the interior as the influx of indian ocean moisture was constrained equilibrium line elevations in the last glacial maximum were 4000 m in the south east and northeast plateau margins rising to 5500 m in the northwest interior the heat island provided by the plateau the progressive reduction in precipitation most marked during the glacials and the strong southeast to northwest precipitation gradients produced a glacier distribution pattern dominated by the trans tibetan mountain ranges tectonics and periglacial including aeolian processes have played an equal role with glaciation in generating the plateau s quaternary sedimentary succession

mechanical and fracture stratigraphy using examples from core studies this article shows that separate identification of mechanical stratigraphy and fracture stratigraphy leads to a clearer understanding of fracture patterns and more accurate prediction of fracture attributes away from the wellbore mechanical stratigraphy subdivides stratified rock into discrete mechanical units defined by properties such as tensile strength elastic stiffness brittleness and fracture mechanics properties fracture stratigraphy subdivides rock into fracture units according to extent intensity or some other observed fracture attribute mechanical stratigraphy is the by product of depositional composition and structure and chemical and mechanical changes superimposed on rock composition texture and interfaces after deposition fracture stratigraphy reflects a specific loading history and mechanical stratigraphy during failure because mechanical property changes reflect diagenesis and fractures evolve with loading history mechanical stratigraphy and fracture stratigraphy need not coincide in subsurface studies current mechanical stratigraphy is generally measurable but because of inherent limitations of sampling fracture stratigraphy is commonly incompletely known to accurately predict fractures in diagenetically and structurally complex settings we need to use evidence of loading and mechanical property history as well as current mechanical states

timing of multiple late quaternary glaciations in the hunza valley karakoram mountains northern pakistan defined by cosmogenic radionuclide dating of moraines moraines and associated landforms in the upper hunza valley karakoram mountains northern pakistan provide an excellent record of multiple glaciations during the late quaternary glaciers advanced at least eight times by using 10 be and 26 al surface exposure dating on moraine boulders and scoured bedrock we determined the timing of glaciation for four of these glacial advances ca 54 7 43 2 ka borit jheel glacial stage ca 25 7 21 8 ka ghulkin i glacial stage ca 18 4 15 3 ka ghulkin ii glacial stage and ca 10 8 9 0 ka batura glacial stage for two of the older advances the yunz and shanoz glacial stages our data set a limit of 60 ka although at present the uncertainties in dating make it impossible to describe unequivocally the climate processes controlling glaciations in the hunza valley the results suggest that precipitation changes related to oscillations in the southwest asian monsoonal system combine with cooling that is broadly associated with heinrich events to cause glacial advances in this region

evidence for temporally changing mechanical stratigraphy and effects on joint network architecture previous studies of jointing in sedimentary rocks have shown that joint network archi tecture is controlled by mechanical stratigraphy which is described by 1 the thickness and rigidity of stratigraphic units and 2 the nature of interfaces between beds using joint pattern to infer rigidity contrast between beds is complicated by the possibility that material properties of the beds may change between fracturing events observation of both an early bed contained joint set and a differently oriented late throughgoing joint set in the same beds of growth strata in the oliana anticline in the spanish pyrenees may reflect changing mechanical properties i e via diagenesis during the folding process using a schmidt hammer we assess the rigidity contrast between the individual units and show that the present day contrast is not great enough to terminate joints at interfaces this result is consistent with an interpretation that the late stage throughgoing joints formed in strata with conditions similar to those of the present day and that the early bed contained joints formed when the rigidity contrast between beds was significantly greater than that of the present day for example differential diagenesis rates between layers of differing grain size would produce temporally changing mechanical stratigraphy we propose that changes in mechanical stratigraphy may have previously been unrec ognized in other stratigraphic sections and that these changes affect joint network archi tecture and subsequent fluid flow pathways