the landslide hazard in the himalayas geological control and human action abstract mountains are high energy environments characterised by instability and variability much of this instability is the result of a variety of landsliding processes mudflows rockfalls and debris slides avalanches being especially important this landsliding constitutes a major hazard in the himalayas early work has suggested that certain rock types are more predisposed to failure than others it also seems possible that specific types of failure are related to certain rock types and properties this analysis suggests that these relationships can be employed in a hazard assessment phyllite rocks are the most susceptible to landsliding followed by shales schists poorly cemented sandstones gneiss granites and quartzite this order is also appropriate for slope failures within weathered material although weathered gneiss appears to be more susceptible to rill and gully erosion clearly rock type exerts a major influence on landsliding but assessing the role of rock type in comparison to the effect of human activity is difficult human activity is often influenced by the nature of slopes including the type and depth of material on the slopes as these are affected by rock type it is difficult to differentiate the contributing factors because of this it would be dangerous to assume that landsliding in the himalayas can be completely explained and predicted by the nature of the rock type

slope deposits in the upper nalon river basin nw spain an approach to a quantitative comparison the upper nalon river basin cantabrian mountains nw spain exhibits a variety of slope processes and deposits including landslides rockfall and soil creep geomorphic maps were used to quantitatively ascertain the relationships between these deposits and topographic characteristics of exposure gradient and altitude at the nodes of a square grid with 250 m spacing n 926 a correspondence analysis allows the analysis of qualitative variables lithology and origin of deposit and quantitative variables altitude with a class interval of 200 m and gradient in 10 classes the results suggest that lithology is the main conditioning factor of the differences and similarities between deposits

syn thinning pluton emplacement during mesozoic extension in eastern mongolia 1 this paper documents relationships between deformation and magmatic activity that occurred in the central part of eastern mongolia during late mesozoic continental scale nw se extension two coarse grained biotite bearing syn tectonic intrusions are described the nartyn granite that extends over an area greater than 30 by 10 km was emplaced within low grade metasediments and shows a weak pervasive magmatic fabric reworked by solid state deformation along its margins the northwestern roof of the granite is marked by a normal shear zone the choyr shear zone characterized by top to the nw motions the shear zone is overlain by the choyr basin which is filled with unmetamorphosed continental sedimentary rocks of early cretaceous ages from structural and geochronological data we propose that the nartyn massif was emplaced as a flat laccolith type intrusion at ca 136 130 ma during crustal thinning the altanshiree granite located 140 km east of the nartyn granite is a syn kinematic pluton of similar age 134 128 ma also emplaced during crustal thinning in the nartyn and altanshiree areas extension implies pervasive crustal thinning combined with limited exhumation these areas are different from classical metamorphic core complexes where strong strain localization along detachments induces exhumation of hot middle to lower crust results also suggest that early cretaceous syn extensional intrusions are an important feature of the tectonic history of eastern mongolia

origin and causes of the mammoth steppe a story of cloud cover woolly mammal tooth pits buckles and inside out beringia to account for the vastness of the northern arid steppes during glacial episodes i propose the proximate key variable was simply frequent clear skies this hitherto under emphasized point is the hub which best explains many questions low maritime cloud cover best accounts for today s tundra and in a related way the cloudy polar front accounts for the whole of the taiga even during glacial maxima the proximity of the sea to the bering isthmus created intermittent maritime cloud cover this regional cloud cover produced an ecological interruption or buckle of the arid steppe belt while this beringian mesic buckle did not serve as an intercontinental ecological barrier to most steppe adapted species it does seem to have limited the distributions of woolly rhinos camels american kiangs short faced bears badgers and some others at the beginning of the holocene this narrow refugium seems to have been a source of some mesic adapted species which colonized westward into the now tundra vegetation of northern asia and eastward into northern north america this holocene expansion from a limited and regional pleistocene refugium created our present misconceptions about beringia the mid strait mesic ecological conditions were the exception to the more extensive arid adapted communities of the mammoth steppe 2000 published by elsevier science ltd all rights reserved

estimation of deformation temperatures flow stresses and strain rates from an intra continental shear zone the main boundary thrust nw himalaya uttarakhand india abstract this work generates thermal and tectonic data from the mylonitized rocks of the main boundary thrust mbt south and north to this major thrust the siwalik range and the lesser himalaya respectively have been receiving a renewed interest amongst the petroleum geoscientists understanding temperature flow stress and strain rates related to a major thrust is crucial in thermal mechanical modelling of the terrains adjacent to it strongly sheared proterozoic chandpur phyllites and abundant syntectonic quartz veins occur along the mbt zone one of the major foreland verging thrusts in the himalayan orogen near the sahenshahi temple at dehradun uttarakhand state india microstructure analyses show intense ductile top to s shear in terms of s c fabric and xrd analyses indicate presence of clays e g illite and clinochlore these clays not only bear the signatures of the intense fluid activity but also enhance the fault movement by reducing the mechanical strength of the fault zone rocks thermometry based on qualitative quartz grain boundary mobility 300 550 c and quantitative laser raman spectroscopy for carbonaceous materials 340 370 c reveal the maximum estimates of the deformation temperature and metamorphic temperature respectively the higher temperature microstructures can be found in lower temperature domains under the presence of fluids hence the quartz thermometry estimates a broader temperature range than the raman thermometry previous works report that the phyllites present at the base of a thrust sheet experiences deformation at

ice age megafauna in arctic alaska extinction invasion survival abstract radical restructuring of the terrestrial large mammal fauna living in arctic alaska occurred between 14 000 and 10 000 years ago at the end of the last ice age steppe bison horse and woolly mammoth became extinct moose and humans invaded while muskox and caribou persisted the ice age megafauna was more diverse in species and possibly contained 6 more individual animals than live in the region today megafaunal biomass during the last ice age may have been 30 greater than present horse was the dominant species in terms of number of individuals lions short faced bears wolves and possibly grizzly bears comprised the predator scavenger guild the youngest mammoth so far discovered lived ca 13 800 years ago while horses and bison persisted on the north slope until at least 12 500 years ago during the younger dryas cold interval the first people arrived on the north slope ca 13 500 years ago bone isotope measurements and foot loading characteristics suggest megafaunal niches were segregated along a moisture gradient with the surviving species muskox and caribou utilizing the warmer and moister portions of the vegetation mosaic as the ice age ended the moisture gradient shifted and eliminated habitats utilized by the dryland grazing species bison horse mammoth the proximate cause for this change was regional paludification the spread of organic soil horizons and peat end pleistocene extinctions in arctic alaska represent local not global extinctions since the megafaunal species lost there persisted to later times elsewhere hunting seems unlikely as the cause of these extinctions but it cannot be ruled out as the final blow to megafaunal populations that were already functionally extinct by the time humans arrived in the region

mantle dynamics uplift of the tibetan plateau and the indian monsoon convective removal of lower lithosphere beneath the tibetan plateau can account for a rapid increase in the mean elevation of the tibetan plateau of 1000 m or more in a few million years such uplift seems to be required by abrupt tectonic and environmental changes in asia and the indian ocean in late cenozoic time the composition of basaltic volcanism in northern tibet which apparently began at about 13 ma implies melting of lithosphere not asthenosphere the most plausible mechanism for rapid heat transfer to the midlithosphere is by convective removal of deeper lithosphere and its replacement by hotter asthenosphere the initiation of normal faulting in tibet at about 8 3 ma suggests that the plateau underwent an appreciable increase in elevation at that time an increase due solely to the isostatic response to crustal thickening caused by india s penetration into eurasia should have been slow and could not have triggered normal faulting another process such as removal of relatively cold dense lower lithosphere must have caused a supplemental uplift of the surface folding and faulting of the indo australian plate south of india the most prominent oceanic intraplate deformation on earth began between about 7 5 and 8 ma and indicates an increased north south compressional stress within the indo australian plate a tibetan uplift of only 1000 m if the result of removal of lower lithosphere should have increased the compressional stress that the plateau applies to india and that resists india s northward movement from an amount too small to fold oceanic lithosphere to one sufficient to do so the climate of the equatorial indian ocean and southern asia changed at about 6 9 ma monsoonal winds apparently strengthened northern pakistan became more arid but weathering of rock in the eastern himalaya apparently increased because of its high altitude and lateral extent the tibetan plateau provides a heat source at midlatitudes that should oppose classical symmetric hadley circulation between the equator and temperate latitudes and that should help to drive an essentially opposite circulation characteristic of summer monsoons for the simple case of axisymmetric heating no dependence on longitude of an atmosphere without dissipation theoretical analyses by hou lindzen and plumb show that an axisymmetric heat source displaced from the equator can drive a much stronger meridianal monsoonlike circulation than such a source centered on the equator but only if heating exceeds a threshold whose level increases with the latitude of the heat source because heating of the atmosphere over tibet should increase monotonically with elevation of the plateau a modest uplift 1000 2500 m of tibet already of substantial extent and height might have been sufficient to exceed a threshold necessary for a strong monsoon the virtual simultaneity of these phenomena suggests that uplift was rapid approximately 1000 m to 2500 m in a few million years moreover nearly simultaneously with the late miocene strengthening of the monsoon the calcite compensation depth in the oceans dropped plants using the relatively efficient c4 pathway for photosynthesis evolved rapidly and atmospheric co2 seems to have decreased suggesting causal relationships and positive feedbacks among these phenomena both a supplemental uplift of the himalaya the southern edge of tibet and a strengthened monsoon may have accelerated erosion and weathering of silicate rock in the himalaya that in turn enhanced extraction of co2 from the atmosphere thus these correlations offer some support for links between plateau uplift a downdrawing of co2 from the atmosphere and global climate change as proposed by raymo ruddiman and froehlich mantle dynamics beneath mountain belts not only may profoundly affect tectonic processes near and far from the belts but might also play an important role in altering regional and global climates

new insights into the weichselian environment and climate of the east siberian arctic derived from fossil insects plants and mammals multidisciplinary study of a key section on the laptev sea coast bykovsky peninsula east lena delta in 1998 2001 provides the most complete record of middle and late weichselian environments in the east siberian arctic the 40 m high mamontovy khayata cliff is a typical ice complex section built of icy silts with a network of large syngenetic polygonal ice wedges and is richly fossiliferous in combination with pollen plant macrofossil and mammal fossils a sequence of ca 70 insect samples provides a new interpretation of the environment and climate of the area between ca 50 and 12 ka the large number of radiocarbon dates from the section together with an extensive 14c database on mammal bones allows chronological correlation of the various proxies the bykovsky record shows how climate change and the last glacial maximum in particular affected terrestrial organisms such as insects and large grazing mammals both during the presumed karginsky interstadial mis 3 and the sartanian glacial mis 2 the vegetation remained a mosaic arctic grassland with relatively high diversity of grasses and herbs and dominance of xeric habitats the tundra steppe type this biome was supported by a constantly very continental climate caused by low sea level and enormous extension of shelf land variations within the broad pattern were caused mainly by fluctuations in summer temperature related to global trends but overprinted by the effect of continentality no major changes in humidity were observed nor were advances of modern type forest or forest tundra recorded suggesting a major revision of the karginsky interstadial paradigm the changing subtypes of the tundra steppe environment were persistently favourable for mammalian grazers which inhabited the shelf lowlands throughout the studied period mammal population numbers were lowered during the lgm especially toward its end and then flourished in a short but impressive peak in the latest weichselian just before the collapse of the tundra steppe biome throughout mis 3 and mis 2 the climate remained very favourable for the aggradation of permafrost no events of regional permafrost degradation were observed in the continuous bykovsky sequence until the very end of the pleistocene

annual rainfall and nitrogen isotope correlation in macropod collagen application as a palaeoprecipitation indicator abstract collagen has been extracted and analysed for 15 n from modern kangaroos macropods macropus eugenii m antilopinus m fuliginosus m rufus m robustus in western australia and south australia comparison of nitrogen isotope ratios with annual rainfall for the respective areas produced a good negative correlation for macropods but not for other marsupials this may be related to metabolic adaptations in macropods to compete against water loss hence the correlation between 15 n and annual rainfall may be species specific nitrogen isotope analyses on collagenic material extracted from fossil macropods macropus spp have been determined from two late pleistocene deposits in south australia corroboration with spore pollen and sedimentological data confirm that 15 n of collagenic material can be used as a proxy for palaeoprecipitation levels in australia this has great potential for understanding palaeoclimatic changes especially drought periods in australia during the pleistocene

the younger dryas cold interval as viewed from central greenland abstract greenland ice core records provide an exceptionally clear picture of many aspects of abrupt climate changes and particularly of those associated with the younger dryas event as reviewed here well preserved annual layers can be counted confidently with only 1 errors for the age of the end of the younger dryas 11 500 years before present ice flow corrections allow reconstruction of snow accumulation rates over tens of thousands of years with little additional uncertainty glaciochemical and particulate data record atmospheric loading changes with little uncertainty introduced by changes in snow accumulation confident paleothermometry is provided by site specific calibrations using ice isotopic ratios borehole temperatures and gas isotopic ratios near simultaneous changes in ice core paleoclimatic indicators of local regional and more widespread climate conditions demonstrate that much of the earth experienced abrupt climate changes synchronous with greenland within thirty years or less post younger dryas changes have not duplicated the size extent and rapidity of these paleoclimatic changes

basin formation in the high himalaya by arc parallel extension and tectonic damming zhada basin southwestern tibet 1 the late miocene pleistocene zhada basin in southwestern tibet provides a record of subsidence and basin formation within an active collisional thrust belt the 800 m thick basin fill is undeformed and was deposited along an angular unconformity on top of tethyan strata that were previously shortened in the himalayan fold thrust belt modal sandstone petrographic data conglomerate clast count data and detrital zircon u pb age spectra indicate a transition from detritus dominated by a distal northern source to a local southern source this transition was accompanied by a change in paleocurrent directions from uniformly northwestward to basin centric at the same time the depositional environment in the zhada basin changed from a large braided river to a closed basin lake sedimentation in the zhada basin was synchronous with displacement on the qusum and gurla mandhata detachment faults which root beneath the basin and exhume midcrustal rocks along the northwestern and southeastern flanks of the basin respectively these observations indicate that accommodation for zhada basin fill was produced by a combination of tectonic subsidence and damming as midcrustal rocks were evacuated from beneath the zhada basin in response to arc parallel slip on crustal scale detachment faults

cretaceous tertiary structural evolution of the north central lhasa terrane tibet 1 in the north central lhasa terrane of tibet two distinct structural levels of an east west striking thrust system are exposed along the north trending late cenozoic xiagangjiang rift upper paleozoic strata deformed by the south directed langgadong la thrust and cretaceous strata involved in variably north and south directed thrusting characterize these lower and upper structural levels respectively these two structural levels are separated by the tagua ri passive roof thrust balanced cross section restoration suggests that the thrust system accommodated 103 km 53 shortening the 40ar 39ar results together with an interpretation of synthrust deposition of upper cretaceous strata suggest that the majority of shortening occurred during the late cretaceous paleocene cretaceous strata lie unconformable on permian rocks volcanic tuffs directly above the unconformity yield u pb zircon ages of 131 ma upper cretaceous strata record a change from shallow marine to nonmarine deposition indicating uplift above sea level during this time the overall south directed vergence of the thrust belt is consistent with substantial crustal thickening in central tibet by large scale northward underthrusting of lhasa terrane basement beneath the qiantang terrane prior to the indo asian collision the documented decoupling of contractional deformation at shallow crustal levels appears to be a regional characteristic of tibet from at least the bangong suture in the north to the tethyan himalaya to the south this style of deformation explains the absence of basement exposures and major denudation in this region despite substantial crustal shortening

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

the late pleistocene environment of the eastern west beringia based on the principal section at the main river chukotka chukotka is a key region for understanding both quaternary environmental history and transcontinental migrations of flora and fauna during the pleistocene as it lies at the far eastern edge of asia bordering the bering sea the now submerged land bridge is the least understood region of beringia yet the most critical to understanding migrations between the old and new worlds the insect fauna of the main river ledovy obryv ice bluff section which is late pleistocene in age mis 3 2 is markedly different from coeval faunas of areas further to the west as it is characterized by very few thermophilous steppe elements from the fauna we reconstruct a steppe tundra environment and relatively cold conditions the reconstructed environment was moister than that of typical steppe tundra described from further west the data from this locality if typical of the chukotka peninsula as a whole may indicate that a barrier associated with the environments of the land bridge restricted trans beringian migrations particularly the more thermophilous and xeric adapted elements of the beringian biota supporting the hypothesis of a cool but moist land bridge filter inferred from evidence from several other studies

regional earthquakes in northern tibetan plateau implications for lithospheric strength in tibet 1 a total of 400 regional earthquakes were located in northern tibetan plateau from data recorded by indepth iv and pku eastern kunlun arrays from may 2007 to june 2009 the distribution of these earthquakes is compatible with a continuously deforming tibetan lithosphere most earthquakes occur at a depth range of 0 15 km but no event is deeper than 30 km this observation strongly supports the existence of a hot and weak lower crust beneath the northern tibet the crustal seismogenic zone appears slightly thicker beneath the northern tibet than in the southern plateau possibly reflecting a difference in the rheological dry vs wet structure of the crust the absence of lower crustal and uppermost mantle earthquakes in northern tibet is consistent with a localized asthenospheric upwelling under the qiangtang and songpan ganze terranes finally the lack of mantle earthquakes should be fully addressed in any models of subduction in northern tibet

a geomorphic evaluation of the landslides around dehradun and mussoorie uttar pradesh india the mussoorie hills of northern india are characterized by a rugged topography with hill ranges rising steeply from about 600 m above mean sea level to over 2300 m and deep cut valleys the area comprises the proterozoic cambrian rocks of the krol belt which have been thrust over the neogene sedimentary rocks siwalik group along the main boundary thrust various geomorphological parameters have been assessed in conjunction with the geological and anthropogenic aspects to evaluate the occurrence of the different types of landslides in the area the evidence of neotectonism was provided by the various geomorphic criteria seventy five landslides were identified by remote sensing these were studied in the context of geological aspects such as lithology proximity to active faults and lineament density geomorphological aspects such as landform slope lateral erosion by streams drainage texture spring sapping elevation difference between adjacent valleys altitude and relief and anthropogenic factors including landuse land cover and distances from roads the important causes were found to be lithology proximity to the active faults main boundary thrust and sairku fault slope angle and aspect lateral erosion by stream undercutting and deforestation due to human interference the triggering factors include rainfall and seismicity the preventive measures to be adopted to stabilise the slopes have also been described

middle to late miocene extremely rapid exhumation and thermal reequilibration in the kung co rift southern tibet 1 the kung co rift is an approximately nnw striking wsw dipping normal fault exposed in southern tibet and is part of an extensive network of active approximately ns striking normal faults exposed across the tibetan plateau detailed new and published u th he zircon and apatite thermochronometric data from the footwall of the early miocene kung co granite provide constraints on the middle miocene to present day exhumation history of the footwall to the kung co fault inverse modeling of thermochronometric data yield age patterns that are interpreted as indicating 1 initiation of normal fault slip at 12 13 ma and rapid exhumation of the footwall between 13 and 10 ma 2 acceleration of normal fault slip at rates of 21 9 6 9 mm yr at 10 ma 3 rapid thermal reequilibration between 10 and 9 ma and 4 slow exhumation and or quiescence from 9 ma to the present day hanging glacial valleys in the footwall and fault scarps that cut late quaternary till and moraine deposits indicate that fault slip continues today middle to late miocene initiation of extension across the kung co rift is broadly the same as the documented initiation of ew extension across the south central tibetan plateau eastward flow of middle or lower crust from beneath tibet accommodated by northward underthrusting of indian crust beneath tibet provides a plausible explanation for the onset of ew extension across the tibetan plateau

isotopic characteristics of the gurla mandhata metamorphic core complex implications for the architecture of the himalayan orogen isotopic data from the gurla mandhata metamorphic core complex provide insight on the character of rocks exposed within it and permit possible correlations of these rocks to those exposed in the himalayan thrust belt whole rock sr and nd isotopic analyses show that rock units in the metamorphic core have isotopic signatures that correlate to those of greater and lesser himalayan rocks exposed in the foreland these data are the first to document lesser himalayan rocks north of the higher himalayan physiographic zone when combined with previously published structural reconstructions of the himalayan orogen these data reveal a crustal architecture that requires significant uplift of lesser himalayan rocks in the hinterland with respect to their position in the foreland a greater amount of underthrusting of the lesser himalayan rocks and more shortening in the hinterland within the tethyan himalaya physiographic zone than currently estimated

variations in bone collagen δ13c and δ15n values of fauna from northwest europe over the last 40 000 years we report here a signal in the temporal variation of stable isotopes in protein from surviving animal bone in northwest europe over the past glacial cycle there is a change in the average 13c values of fauna in the holocene and there is also a significant reduction in 15n values of herbivore bone collagen towards the end of the last glaciation with a subsequent recovery soon after the start of the holocene this change is observed for several species and is restricted to those regions most affected by the glacial advance comparison with ice core data shows that there is a strong correlation between the average 13c values of three herbivore species and ice core co2 concentration the data presented here show how readily available faunal bone collagen 13c and 15n measurements provide a record of past climate and environmental change on a regional to continental scale

static stress interactions in extensional earthquake sequences an example from the south lunggar rift tibet 1 an extensional earthquake sequence occurred in 2004 8 across a graben in the south lunggar rift on the tibetan plateau we use insar data to determine the location fault geometry and slip distribution of these earthquakes and to test whether the sequence is compatible with static stress triggering the mw 6 2 and 6 3 earthquakes in 2004 and 2005 both ruptured west dipping faults on the east side of a graben in 2008 a mw 6 7 earthquake ruptured a pair of east dipping fault segments on the other side of the graben offset from the earlier ruptures we compute first order dislocation models of stress change and demonstrate that the order and spatial configuration of this sequence of events is compatible with triggering by static stress transfer a continuation of the sequence would be most likely to occur on the northern extension of the 2008 rupture although variable slip rate along the rift may mean that the sequence has run its course the insar data for the 2008 earthquake also reveal slip on a fault that cuts the graben at a highly oblique angle we suggest that this is a release fault accommodating differential throw in the hanging wall and associate the deformation with a mw 6 0 aftershock activity on such a release fault has not been directly imaged before the zhongba sequence is one of several examples of recent clustered normal fault earthquakes on the plateau and may be an example of phase locking of similar faults

comment on environmental setting micro morphologies and stable c o isotope composition of cold climate carbonate precipitates a review and evaluation of their potential as paleoclimatic proxies by denis lacelle quaternary science reviews 26 1670 1689

active detachment faulting above the peruvian flat slab the cordillera blanca detachment fault in the peruvian andes is to our knowledge the first active detachment to be documented above a modern flat slab crustal detachment has unroofed the ca 8 ma cordillera blanca batholith now the backbone of the highest mountain range in peru large magnitude slip along the fault was thermally enhanced by emplacement of the batholith the penultimate magmatic event prior to flattening of the nazca slab however extensional models based on arc magmatism and crustal thickening alone do not adequately explain the scale or structural asymmetry of a series of young deep seated west dipping normal faults across peru here we show that the onset of detachment faulting coincided with subduction of the aseismic nazca ridge and consequent flattening of the nazca slab we propose that slab buoyancy from ridge subduction triggered extensional collapse of the prethickened continental crust and that this buoyancy drove footwall uplift that exceeds basin subsidence the west dipping asymmetry of late cenozoic extensional faults in peru may be controlled by a preexisting crustal anisotropy older thrusts and or formation of riedel like shears kinematically linked to the flat nazca slab

musk ox ovibos moschatus of the mammoth steppe tracing palaeodietary and palaeoenvironmental changes over the last 50 000 years using carbon and nitrogen isotopic analysis abstract stable carbon and nitrogen isotope ratios have been used as markers for palaeoclimatic and palaeoecological reconstructions across various geographical and temporal ranges such studies are essential for understanding how a particular species responded to changing environmental conditions in the past especially changing vegetation which might have even generated conditions stressful enough to threaten the very survival of the species we present in this study a dataset of stable carbon and nitrogen isotope measurements 13 c and 15 n generated from 160 pleistocene and holocene musk ox ovibos moschatus specimens we used the dataset to evaluate the usefulness of these dietary indicators in tracing vegetation and climatic fluctuations in the holarctic region during the pleistocene and holocene our data show that musk ox stable isotopes largely followed changes in precipitation and that these variations were closely associated with events such as the cold and arid last glacial maximum lgm bolling allerod interstadial younger dryas stadial and the warmer and humid holocene regional differences in the isotopic composition of the musk ox populations are also noticeable altogether providing insights into how an adaptable generalist diet in the face of climate change might have helped this species survive the holocene megafaunal extinctions

a stable isotope study of fossil mammal remains from the paglicci cave southern italy n and c as palaeoenvironmental indicators a set of 102 tooth and bone samples of pleistocene age 32 600 13 300 yr bp belonging to the species cervus elaphus bos primigenius and equus caballus and coming from the paglicci cave southern italy was studied for the carbon 13c and nitrogen 15n isotopic composition of bone and dentine collage and for the carbon 13cc isotopic composition of tooth enamel carbonate the amount of collagen extracted from bone and tooth samples mg g was rather variable representing approximately only 0 5 15 of the collagen present in a fresh bone however the loss of an important fraction of the original collagen during diagenesis did not change the in vivo isotopic composition in general when the 13c of both collagen and carbonate and the 15n of collagen obtained from each level for the three species are compared wild ox shows the most increased values deer the most decreased values and horse shows intermediate results these differences are probably related to distinct diets or to differences in their physiological behaviour however the isotopic results suggest that the three species considered lived in an open environment with a diet based on c3 plants the stratigraphic sequence of light and heavy nitrogen isotope values between 19 000 and 15 000 may be related to shifts from arid to humid conditions while the overall trend shown by 13c toward lighter values may be related to a progressive development of a forest habitat

thermochronological constraints on the timing and magnitude of miocene and pliocene extension in the central wassuk range western nevada apatite fission track and u th he thermochronological data provide new constraints on the timing of faulting and exhumation of the wassuk range western nevada where east dipping normal faults have accommodated large magnitude ene wsw oriented extension extensional deformation has resulted in the exhumation of structurally coherent fault blocks that expose sections of preextensional mostly granitic upper crust in the grey hills and central wassuk range these fault blocks display westward tilts of 60 and expose preextensional paleodepths of up to 8 5 km based on the structural reconstruction of tilted preextensional tertiary andesite flows that unconformably overlie mesozoic basement rocks apatite fission track and u th he thermochronological data from the fault blocks constrain the onset of rapid footwall exhumation at 15 ma fission track modeling results indicate rapid fault block exhumation occurred between 15 and 12 ma which is in agreement with miocene volcanic rocks that bracket the tilting history in addition fission track and u th he data suggest reduced rates of cooling following major extension as well as renewed cooling related to active high angle faulting along the present day range front starting at 4 ma thermochronological data from structurally restored fault blocks indicate a preextensional miocene geothermal gradient of 27 5 c km the thermochronological constraints on the timing of extensional faulting and the eruptive history in the wassuk range imply a model for extension where crustal heating and volcanism precede the onset of rapid large magnitude extension and where synextensional magmatism is suppressed during the highest rates of extension

extension on the tibetan plateau recent normal faulting measured by insar and body wave seismology we use insar and body wave modelling to determine the faulting parameters for a series of five mw 5 9 7 1 normal faulting earthquakes that occurred during 2008 including the march 20 yutian earthquake mw 7 1 one of the largest normal faulting events to have occurred recently on the continents we also study three earlier normal faulting earthquakes that occurred in southern tibet between 1992 and 2005 coseismic deformation for each of these eight events is measured with ascending and descending interferograms from envisat ers and alos sar data elastic dislocation modelling of the line of sight insar displacements and body wave seismological modelling of p and sh waves are used to estimate fault parameters and are found to be in good agreement for all the events studied the use of insar to measure deformation allows a relatively precise determination of the fault location in addition to resolving the focal plane ambiguity only five of the eight events are associated with a clear surface topographic feature suggesting that an underestimation of the amount of extension would result from using the surface expressions of normal faulting alone the observations in all cases are consistent with slip on planar surfaces with dips in the range 40 50 that penetrates the uppermost crust to a depth of 10 15 km we find no evidence for active low angle dip less than 30 normal faulting the contribution of the normal faulting to overall extension estimated by summing seismic moments over earthquakes for the past 43 yr is 3 4 mm yr 1 or 15 20 per cent of the rates of extension measured across the plateau using gps 85 per cent of the moment release in normal faulting over the past 43 yr has occurred in regions whose surface height exceeds 5 km this observation adds weight to the suggestions that the widespread normal faulting on the plateau is the result of variations in the gravitational potential energy of the lithosphere

marked along strike variations in dip of normal faults the lokichar fault n kenya rift a possible cause for metamorphic core complexes abstract the lokichar fault is a major boundary fault in the northern kenya rift mapped from seismic reflection data the fault is a mixture of high 45 60 low 20 45 and very low 12 20 angle segments the areas of least displacement up to a maximum 10 km heave are the very low angle fault segments 12 20 the southern higher angle fault segment has a maximum estimated heave of about 20 km initiation of normal faults at a low angle cannot be easily explained by rock mechanics theory common explanations for such faults include 1 rotation of higher angle faults by the domino faulting model 2 rotation of large displacement faults by isostatic instability created by the faulting rolling hinge models and 3 reactivation of low angle pre existing fabrics the lokichar fault geometry is inconsistent with any of the above explanations the very low angle segments coincide with regions of intense igneous intrusive activity re orientation of the stress axes from the simple andersonian condition could permit normal faults to form at a lower angle this may happen around intrusive complexes or by setting up a basal shear stress between flowing and static crust if faults associated with metamorphic core complexes were associated with marked along strike changes in fault angle the resulting variations in footwall uplift could give rise to the antiformal metamorphic core complex geometry

regional differences in bone collagen δ13c and δ15n of pleistocene mammoths implications for paleoecology of the mammoth steppe in this study we present bone collagen 13c and 15n values from a large set of pleistocene woolly mammoths mammuthus primigenius from siberia alaska and yukon overall results for mammoth specimens from eastern beringia alaska and yukon significantly differ for both 13c and 15n values from those from western beringia northeastern siberia in agreement with palynological entomological and physiographic data from the same regions these isotopic differences strongly imply that the mammoth steppe the extensive ice free region spanning northern eurasia and northwestern north america was ecologically variable along its east west axis to a significant degree prior to the last glacial maximum lgm the high latitude portions of siberia and the russian far east appear to have been colder and more arid than central alaska and yukon which were ecologically more diverse during the lgm itself however isotopic signatures of mammoths from eastern beringia support the argument that this region also experienced an extremely cold and arid climate in terms of overall temporal trend beringia thus went from a condition prior to the lgm of greater ecological variability in the east to one of uniformly cold and dry conditions during the lgm

paleocene eocene record of ophiolite obduction and initial india asia collision south central tibet 1 uppermost cretaceous to eocene marine sedimentary sequences occur both to the south and north of the yarlung zangbo suture in south central tibet they consist of indian margin strata of the northern tethyan himalaya and asian margin strata of the gangdese forearc both assemblages are characterized by major changes in depositional environment and sedimentary provenance at 65 ma and an appearance of detrital chromium rich spinel of ophiolite affinity tio2 generally 0 1 wt during the paleocene ophiolitic melange exposed along the suture could have provided a source for detrital spinel the melange occurs in the hanging wall of a north dipping south directed mylonitic shear zone which includes a tectonic sliver of mafic schist amphibole from the schist yields 40ar 39ar ages of 63 ma which we attribute to cooling during slip along the shear zone and southward obduction of the melange melange obduction was coeval with the development of an angular unconformity within the gangdese forearc basin to the north between late maastrichtian time and 62 ma upper paleocene to middle eocene sandstones in the northern tethyan himalaya yield 200 120 ma u pb detrital zircon ages and 190 170 ma 40ar 39ar detrital mica ages these detrital grains were most likely sourced from regions north of the yarlung zangbo suture suggesting that onset of india asia collision in south central tibet is middle eocene or older in age collectively our results support previous suggestions that oceanic rocks were obducted onto the northern margin of india during latest cretaceous earliest tertiary time coeval changes in gangdese forearc sedimentation raise the possibility that this obduction event marks onset of tectonic interaction between india and asia at 65 ma alternatively in concert with the conventional view of eocene collision initiation the obducted oceanic rocks may be of intraoceanic origin while coeval changes in gangdese forearc sedimentation may be a consequence of an increase in the rate of ocean continent convergence following the demise of the intraoceanic subduction zone

implications of shortening in the himalayan fold thrust belt for uplift of the tibetan plateau 1 recent research in the himalayan fold thrust belt provides two new sets of observations that are crucial to understanding the evolution of the himalayan tibetan orogenic system first u pb zircon ages and sm nd isotopic studies demonstrate that 1 greater himalayan medium to high grade metasedimentary rocks are much younger than true indian cratonic basement and 2 these rocks were tectonically mobilized and consolidated with the northern margin of gondwana during early paleozoic orogenic activity these observations require that greater himalayan rocks be treated as supracrustal material in restorations of the himalayan fold thrust belt rather than as indian cratonic basement in turn this implies the existence of greater himalayan lower crust that is not exposed anywhere in the fold thrust belt second a regional compilation of shortening estimates along the himalayan arc from pakistan to sikkim reveals that 1 total minimum shortening in the fold thrust belt is up to 670 km 2 total shortening is greatest in western nepal and northern india near the apex of the himalayan salient and 3 the amount of himalayan shortening is equal to the present width of the tibetan plateau measured in an arc normal direction north of the indus yalu suture zone this information suggests that a slab of greater indian lower crust composed of both indian cratonic lower crust and greater himalayan lower crust with a north south length of 700 km may have been inserted beneath the tibetan crust during the cenozoic orogeny we present a modified version of the crustal underthrusting model for himalayan tibetan orogenesis that integrates surface geological data recent results of mantle tomographic studies and broadband seismic studies of the crust and upper mantle beneath the tibetan plateau previous studies have shown that incremental mesozoic and early cenozoic shortening had probably thickened tibetan crust to 45 55 km before the onset of the main cenozoic orogenic event thus the insertion of a slab of greater indian lower crust with maximum thickness of 20 km tapering northward could explain the cenozoic uplift of the tibetan plateau the need for tibetan crust to stretch laterally as the greater indian lower crust was inserted may explain the widespread east west extension in the southern half of the plateau our reconstruction of the himalayan fold thrust belt suggests that indian cratonic lower crust of presumed mafic composition and high strength should extend approximately halfway across the tibetan plateau to the banggong suture from there northward we predict that the tibetan plateau is underlain by more felsic and therefore weaker lower crust of greater himalayan affinity two slab break off events are predicted by the model the first involved neotethyan oceanic lithosphere that foundered 45 35 ma and the second consisted of greater indian lithosphere most likely composed of greater himalayan material that delaminated and foundered 20 10 ma asthenospheric upwelling associated with the break off events may explain patterns of cenozoic volcanism on the tibetan plateau although the model predicts a northward migrating topographic front due solely to insertion of greater indian lower crust the actual uplift history of the plateau was complicated by early middle tertiary shortening of tibetan crust

miocene initiation and acceleration of extension in the south lunggar rift western tibet evolution of an active detachment system from structural mapping and u th he thermochronology 1 ongoing extension in tibet may have begun in the middle to late miocene but there are few robust estimates of the rates timing or magnitude of neogene deformation within the tibetan plateau we present a comprehensive study of the seismically active south lunggar rift in southwestern tibet incorporating mapping u pb geochronology and zircon u th he thermochronology the south lunggar rift is the southern continuation of the north lunggar rift and comprises a 50 km n s central horst bound by two major normal faults the west dipping south lunggar detachment and the east dipping palung co fault the sld dips at the rangefront 20 w and exhumes a well developed mylonite zone in its footwall displaying fabrics indicative of normal sense shear the range is composed of felsic orthogneiss mafic amphibolite and leucogranite intrusions dated at 16 and 63 ma zircon u th he cooling ages are oligocene through late pliocene with the youngest ages observed in the footwall of the sld we tested 25 000 unique thermokinematic forward models in pecube against the structural and u th he data to fully bracket the allowable ranges in fault initiations accelerations and slip rates we find that normal faulting in the slr began in the middle miocene with horizontal extension rates of 1 mm a 1 and in the north accelerated at 8 ma to 2 5 3 0 mm a 1 as faulting commenced on the sld cumulative horizontal extension across the slr ranges from 10 km in the south to 19 21 km in the north

elevated stresses and creep rates beneath the brittle ductile transition caused by seismic faulting in the upper crust 1 large faults in the brittle upper continental crust are envisaged to terminate near the brittle ductile transition zone at a depth that is a complex function of material properties temperature stress and strain rate here we investigate the effect of coseismic displacement along a fault in the upper crust on the adjacent middle and lower crust using a two dimensional numerical model of faulting within an elastic frictional viscous rheology results demonstrate that a major displacement event can cause a dramatic increase in differential stress and creep strain rates in the crust near and below the lower termination of the fault a transient deflection of the brittle ductile transition zone and a zone of elevated strain rates down to the base of the crust the perturbation decays over timescales consistent with postseismic relaxation the stresses and strain rates predicted in such models are in accord with those inferred from microstructural damage analysis of exhumed metamorphic rocks indicating short term deformation at decaying stress and strain rates

environmental setting micro morphologies and stable c o isotope composition of cold climate carbonate precipitates a review and evaluation of their potential as paleoclimatic proxies abstract given the growing interest in carbonate deposits from polar regions as paleoclimatic proxies this review paper first provides a classification of the various types of cold climate carbonate precipitates followed by a summary of the 13 c and 18 o composition of the carbonate deposits and parent water from which the carbonates precipitated the cold climate carbonate precipitates were classified into three broad categories powders crusts and speleothem the carbonate powders include those that precipitated in relation to aufeis aggradation cryogenic aufeis calcite and in relation to the growth of various annual perennial ice formations in freezing caves cryptocrystalline calcite and calcite pearls the carbonate crusts can be further subdivided based on their lithic environment those that precipitated on the upper surface of bedrock clasts i e subglacially precipitated calcite and evaporative calcite crusts those that are located on the underside of clasts i e pedogenic carbonates and those that precipitated in rock outcrop fissures i e endostromatolites the cold climate carbonate precipitates have a highly variable isotopic composition with 18 o values ranging between 6 5 and 28 vsmow and 13 c values in the 10 20 vpdb range however each type of carbonate precipitates has a specific 13 c and 18 o range suggesting that their environmental setting and the mechanism by which they formed controls their 13 c and 18 o signature it was found that carbonate deposits that precipitated under equilibrium physico chemical conditions had a 13 c value that is in equilibrium with that of the parent water while its 18 o composition was more variable as it is in part controlled by the temperature of reaction and by the 18 o and calcite saturation state of the parent water by contrast the 18 o composition of biologically precipitated carbonate deposits endostromatolites reflect that of the parent water while its 13 c composition was enriched over that of the parent water due to bacterial methanogenesis in the case of kinetically precipitated carbonate deposits the 18 o and 13 c values are out of equilibrium relative to that of the parent water due to the faster rate of reaction

c and n stable isotope measurements on eurasian fossil mammals 40 000 to 10 000 years bp herbivore physiologies and palaeoenvironmental reconstruction abstract seventy seven specimens of fossil upper pleistocene early holocene woolly mammoth reindeer deer and bison from 17 different locations in eurasia have been measured for the nitrogen and carbon stable isotope composition of their collagen and for the carbon stable isotope composition of bioapatite the aim was 1 to check the existence of differences in n and c isotope ratios between and within different herbivore species mainly between mammoth and reindeer 2 to discuss these data in terms of animal physiology temporal and spatial distribution of animals and effects of climatic changes and 3 to obtain further information about the environmental changes that occurred in that area during the period considered a geographical variation from south west to north east in the 15n and or 13c values of collagen and bioapatite for all the herbivore species is apparent the most negative 13c values and the most positive 15n values being located in the north eastern area this was probably due to a different temperature and water stress on animals and plants and to a different plant availability the differences in 13c 12c and 15n 14n isotope ratios among species are mainly related to different food intake and different metabolic pathways it seems also that the diet of mammoths from north eastern siberia was higher in protein content compared with that of mammoths from the russian plain from this study it is clear that there was a rapid and important change in the amount of precipitation soon after the last glacial maximum the rainfall conditions around 40 000 and 30 000 years bp were probably similar to those existing around 10 000 years bp though lower than those existing after the glacial maximum

mass movement in the himalaya new insights and research directions abstract ongoing studies that relate tectonics to the processes at the surface of earth show that many more sources of information about agents of shallow denudation such as mass movement are required to comprehend the long term erosion that leads to deep denudation over geologic time mass movement in the himalaya is scale dependent from the massive extension of whole mountain ranges gravity tectonics through the sackung failure of single peaks to the smallest slope failures generally denudation of the himalayan orogen begins with slope failure onto glaciers and into river valleys and continues by glacial and fluvial transport the maximum size of stable slopes and mean angles of slope that are produced by these failures are complex and controlled by a variety of factors including mass strength of the rocks stress fields angles of internal friction controlled by rock type cohesion that includes the control of rock temperature bulk unit weight of rock and discontinuities the processes of mass movement in the himalaya have been described many times for the past two centuries recently developments in a variety of fields have been introduced to assess the character of mass movement geomorphometry remote sensing digital elevation models and geographic information system technology are revolutionizing the study of mass movement in the himalaya

normal faulting in central tibet since at least 13 5 myr ago tectonic models for the evolution of the tibetan plateau interpret observed east west thinning of the upper crust to be the result of either increased potential energy of elevated crust1 or geodynamic processes that may be unrelated to plateau formation2 3 4 5 6 a key piece of information needed to evaluate these models is the timing of deformation within the plateau the onset of normal faulting has been estimated to have commenced in southern tibet between about 14 myr ago7 and about 8 myr ago8 and in central tibet about 4 myr ago9 here however we report a minimum age of approximately 13 5 myr for the onset of graben formation in central tibet based on mineralization ages determined with rb sr and 40ar 39ar data that post date a major graben bounding normal fault these data along with evidence for prolonged activity of normal faulting in this and other tibetan grabens support models that relate normal faulting to processes occurring beneath the plateau thinning of the upper crust is most plausibly the result of potential energy increases resulting from spatially and temporally heterogeneous changes in thermal structure and density distribution within the crust and upper mantle beneath tibet this is supported by recent geophysical and geological data10 11 12 13 14 15 16 17 which indicate that spatial heterogeneity exists in both the tibetan crust and lithospheric mantle

nitrogen isotope analyses of reindeer rangifer tarandus 45 000 bp to 9 000 bp palaeoenvironmental reconstructions abstract pleistocene faunal 15 n variations are thought to reflect changes in climatic and environmental conditions researchers are still unclear however which climatic environmental parameter is the primary control on pleistocene faunal 15 n values through extensive nitrogen isotope analysis of late pleistocene reindeer rangifer tarandus collagen we investigated whether permafrost development during the late pleistocene coincided with changes in 15 n values after 45 ka bp reindeer 15 n declined with lowest 15 n values observed after the last glacial maximum lgm between 15 and 11 ka bp the decline in 15 n appears to be of a greater magnitude in more northern regions than in the south of france a pattern similar to that previously observed for horse on a global scale ecosystem 15 n is controlled by the relative openness of the nitrogen cycle which in turn is controlled by climate low soil and plant 15 n are observed in cold and or wet regions and high 15 n are seen in hot and or arid areas the regional pattern in reindeer 15 n decline mimics the pattern of climatic deterioration in europe culminating at the lgm with climate cooling being more intense in northern europe than in southern europe however the lowest reindeer 15 n values are observed after temperatures started to rise this may have been due to a lag in the response of the nitrogen cycle to increasing temperatures alternatively it may have been linked to the influence of permafrost degradation on soil and plant 15 n and thus faunal 15 n the renewed climatic cooling during the younger dryas did not see a fall in reindeer 15 n limited data does however suggest a post younger dryas depletion in reindeer 15 n values