sedimentary characteristics and origin of the late pleistocene ice complex on north east siberian arctic coastal lowlands and islands a review abstract the origin of late pleistocene ice rich fine grained permafrost sequences ice complex deposits in arctic and subarctic siberia has been in dispute for a long time corresponding permafrost sequences are frequently exposed along seacoasts and river banks in yedoma hills which are considered to be erosional remnants of late pleistocene accumulation plains detailed cryolithological sedimentological geochronological and stratigraphical results from 14 study sites along the laptev and east siberian seacoasts were summarized for the first time in order to compare and correlate the local datasets on a large regional scale the sediments of the ice complex are characterized by poorly sorted silt to fine sand buried cryosols toc contents of 1 2 4 8 wt and very high ground ice content 40 60 wt absolute a second large constituent of the ice complex are large syngenetic ice wedges resulting in a total ice content of the ice complex of up to 80 vol ice complex deposits were mostly formed during the middle weichselian interstadial and or during the late weichselian stadial periods a conceptual model of nival lithogenesis of ice complex deposits was developed that integrates various other formation hypotheses a combination of various local and regional paleogeographical geological and paleoclimate conditions controlled the formation of ice complex sequences during the late pleistocene in northern east siberia they are chronologically and stratigraphically but not genetically equivalent to eurasian and alaskan loess deposits

age determinations in the precambrian basement of the wadi araba area southwest jordan abstract the precambrian basement of jordan belongs to the northern margin of the arabian nubian shield age determinations by u pb isotopic analyses on sized and magnetic zircon fractions a monazite and an apatite sample and by rb sr isotopic studies on whole rocks and minerals of metasedimentary rocks granodiorites granites and dykes have elucidated the following events 1 a major regional high grade metamorphism accompanied by migmatization and synkinematic plutonism occurred at about 800 ma according to u pb zircon ages of metasediments and granites 2 during a postkinematic plutonic event between 615 and 600 ma extensive masses of granodioritic to granitic composition and dykes were emplaced the u pb data of zircons of the rocks yielded upper intercept ages with the concordia consistent with rb sr biotite ages the rb sr mineral ages of the older metasedimentary rocks document the resetting of the rb sr system due to the thermal pulse at this time 3 a younger plutonic event produced diorites and dykes at about 570 ma the plutonic events are related to the pan african orogenic phase the low initial87sr 86sr ratios of the plutonic rocks 0 7032 0 7046 correspond to values reported from equivalent rocks throughout the arabian nubian shield and suggest that no significant portions of ancient sialic crustal material contributed to the generation of the granitic to granodioritic magmas

depositional facies and environments in the permian umm irna formation dead sea area jordan abstract the permian umm irna formation in central jordan consists of a 60 m thick sequence of clastic sediments which can be divided into two fluvial sedimentary facies the lowermost facies 1 is characterized by the presence of five sandstone dominated fining upward sequences each sequence comprising an erosively based coarse to fine grained trough cross bedded sandstone overlain and laterally intertonguing with maroon siltstone and silty shale containing locally abundant carbonaceous plant material the overlying facies 2 also consists of up to five fining upward sequences each comprising an erosively based coarse grained pebbly sandstone grading up through fine grained sandstone and siltstone into silty shale the sandstones are tabular and laterally persistent internally complex units structured by erosively bounded trough cosets the thickness and grain size of the sandstones and the proportion of siltstone and silty shale is much greater than in facies 1 it also contains abundant ferruginous concretions glaebules deposition occurred on an unconfined braidplain sloping northwestwards away from an elevated provenance arabo nubian shield in the south and east the lowermost facies 1 is regarded as a distal environmental equivalent of the overlying facies 2 deposition was largely controlled by period c shifts of the active channel tract influenced by a gradual increase in the elevation of the source area thereby promoting basinwide progradation and vertical stacking of the two major facies components the ferruginous concretions glaebules in facies 2 are thought to have resulted from diagenetic processes in the vadose zone of a humid possibly tropical climate characterized by alternating wet and dry seasons and strong leaching the fluvial depositional system drained basinwards into a shallow water marine depository along the southern margin of the tethys ocean the ocean may have exerted a maritime influence on the climate of the alluvial plain

estimates of modern arc parallel strain rates in fore arcs deflections of slip vectors of interplate thrust earthquakes from expected directions are used to estimate arc parallel strain rates within the overriding plates at the world9s major convergent plate margins arc parallel extension strain rates between 10 8 yr and 10 7 yr and significant at 2 standard deviations are observed in the fore arcs of the aegean aleutian mariana sumatran southern kuriles new hebrides scotia and southern central american lat 8 to 12 n subduction zones and the himalayas northern chile lat 17 to 31 s and central america lat 11 to 18 n show arc parallel compression available geologic and geodetic estimates of fore arc slip and strain rates agree within a factor of two with slip vector estimates arc parallel strain in fore arcs is rapid enough to produce geologically significant effects such as unroofing of high grade metamorphic rocks and disruption of transported fore arc terranes fore arcs deform even where convergence is perpendicular to curved margins demonstrating that head on subduction can produce a three dimensional strain field

hydrogeochemistry of the thermal waters from the sciacca geothermal field sicily southern italy summary the sciacca basin southern sicily italy well known since the roman times for the importance of its thermo mineral waters is characterized by a large occurrence of thermal fluid discharges whose main thermal aquifer is located within the triassic carbonate rocks this reservoir represents the deepest formation cropping out in the area shallower and cooler thermal aquifers are located within the tertiary limestone and quaternary sand and gravel deposits in this work new geochemical and isotopic data of thermal waters and dissolved gases from springs and wells were investigated to assess the origin of thermal fluids and the structure of the hydrothermal system the main thermal aquifer at about 60 c and located at 43 m a s l is fed by an 18 o enriched 18 o 4 d 0 thermal marine end member affected by cooling and dilution 1 2 caused by mixing with inland originated meteoric waters 18 o 8 d 58 this meteoric recharge is likely related to the area of ficuzza and san genuardo mts located 12 and 23 km n of sciacca respectively at an altitude comprised between 900 and 1180 m a s l after this primary dilution the deep thermal aquifer emerging at the antiche terme selinuntine discharging site is not apparently affected by further dilution processes in the sciacca area where the sedimentary cover does not allow infiltration of local meteoric waters down to the triassic reservoir conversely the shallower thermal aquifers hosted within the tertiary quaternary sedimentary horizons are locally supplied by direct infiltration of meteoric water occurring at variable altitudes up to about 400 m a s l san calogero mt with the only exception of the molinelli thermal spring direct contribution from the deep thermal end member to thermal springs fed by the shallower aquifers can be considered negligible

particle size distribution of sediment transported by shallow flow abstract a small laboratory flume on a 0 035 m m 1 slope was used to examine particle selection in shallow flows initial experiments were carried out on smooth surfaces to measure travel rates of different sediment sizes grain size fractions were introduced by hand into 1 37 10 4 to 3 96 10 4 m2 s 1 flows and clear selective mobility occurred with slowest transport in the 63 90 m range following those experiments a sediment mixture was introduced a selectively from a vibrating overhead hopper into 1 39 10 4 to 8 16 10 4 m2 s 1 flows on roughened surfaces the highest discharge had sufficient energy to transport all particle sizes but 355 595 m were preferentially transported none of the lower discharges were competent to transport the full range of particles injected and 45 125 m grains were always preferentially transported sediment finer than the median bed grain diameter was entrapped in micro bed pockets the progressively coarsening of transported material in time observed for all flow conditions may be related to progressive filling of micro bed pockets by fines both transport and entrapment selectivity is strongly related to the ability of flow to transport the full range of grains present as well as to the relationship of the bed roughness to the particles transported

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

indian punch rifts tibet the strikes of late cenozoic normal faults in tibet fan systematically from a northwesterly to northeasterly direction from west to east they exhibit an axis of symmetry that bisects the himalayan arc and trends subparallel to india asia motion the two dimensional stress field inferred from the spatial pattern of normal fault orientations can be explained solely by collisional stresses localized along a southern part of the himalayan arc continued insertion of indian crust into tibet can explain the persistence of extension and may be increasing plateau crustal thickness and elevation coeval with rifting

the role of extension during brittle deformation within the nw indian himalaya 1 synorogenic extension has been recognized as an integral structural constituent of mountain belts and high elevation plateaus during their evolution in the himalaya both orogen parallel and orogen normal extension has been recognized however the underlying driving forces for extension and their timing are still a matter of debate here we present new fault kinematic data based on systematic measurements of hundreds of outcrop scale brittle fault planes in the nw indian himalaya this new data set as well as field observations including crosscutting relationships mineral fibers on fault planes and correlations with deformation structures in lake sediments allows us to distinguish different deformation styles the overall strain pattern derived from our data reflects the large regional contractional deformation pattern very well but also reveals significant extensional deformation in a region which is dominated by shortening in total we were able to identify six deformation styles most of which are temporally and spatially linked representing protracted shortening our observations also furnish the basis for a detailed overview of the younger deformation history in the nw himalaya which has been characterized by extension overprinting previously generated structures related to shortening the four dominant deformation styles are 1 shortening parallel to the regional convergence direction 2 arc normal extension 3 arc parallel extension and finally 4 e w extension this is the first data set where a succession of both arc normal and e w extension has been documented in the himalaya importantly our observations help differentiate e w extension triggered by processes within the tibetan plateau from arc parallel and arc normal extension originating from the curvature of the himalayan orogen

the last glaciation of earth size and volume of ice sheets abstract the volume and size of the late glacial ice sheets in the northern hemisphere has been estimated based on geomorphic and chronostratigraphic data limited glacial extents during the late glacial maximum characterized both arctic canada and northern eurasia in contrast to the presence of the large laurentide scandinavian and devensian ice sheets to the south glacial maxima were not synchronous throughout the northern hemisphere for example the novaya zemlya ice sheet reached its maximum extent ca 39 000 bp approximately 20 000 years earlier than the maximum extent of the contiguous scandinavian ice sheet western and central siberia and the chukhui peninsula were marked by limited glaciation during the last glacial maximum although pre sartanian events were more extensive mountain glaciation in northeast asia was similarly restricted during the last glacial maximum spatial and dynamic characteristics of the last glaciation developed in response to climatic factors the establishment and strength of high pressure systems over siberia limited precipitation and glacier formation throughout northeastern eurasia

fission track and 40ar39ar evidence for episodic denudation of the gangotri granites in the garhwal higher himalaya india abstract in order to document quantitatively the cooling and denudation history of the higher himalayan granites bordering the tethyan sedimentary zone fission track ft apatite and 40 ar 39 ar mica ages have been determined on the gangotri leucogranites and biotite granites in the garhwal region of india gangotri is the source area of the ganges river and lies in the midst of the highest himalayan peaks in india a total of 15 apatite ages from a vertical profile 2580 4370 m on the gangotri granites yields ft ages in the range of 1 5 0 6 to 2 4 0 5 ma indicating that the rock column with a relief of 1800 m cooled through 130 10 c within only 1 million years during the late pliocene an average denudation rate of 2 mm yr is estimated for the past 2 4 million years from the gangotri granites we also report a muscovite 40 ar 39 ar age of 17 9 0 1 ma and a biotite age of 18 0 0 1 ma these reflect cooling of the rocks through 300 350 c probably related to an early miocene pulse of denudation caused by a basement cover detachment the martoli normal fault above the leucogranites time temperature pathways indicate that the cooling of the rocks in the late pliocene quaternary was five to six times the magnitude of cooling between 18 and 2 ma indicating a distinct pulse of rapid denudation in the late pliocene quaternary we interpret these young apatite ages and fast denudation as a geomorphic response increased erosion and cooling of the rocks to a major pulse of tectonic uplift in the higher himalaya shortly before 2 4 ma the effect of climatic cooling on this denudation is considered secondary to the role of tectonic forcing and indeed produced a positive feedback to the primary cause although our study is confined to the garhwal region it is probable that other granitic bodies of the higher himalaya bordering the tethyan sedimentary rocks and forming the loftiest summits in the himalaya have also experienced episodic denudation one major pulse in the early miocene which was mainly tectonic denudation and another in the late pliocene quaternary which was mainly erosional the latter is well recorded by apatite ft data and is consistent with the hypothesis that rapid uplift and denudation of the himalayan rocks may have influenced the initiation of the ice ages in the northern hemisphere

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

eemian and late glacial holocene palaeoenvironmental records from permafrost sequences at the dmitry laptev strait ne siberia russia abstract terrestrial permafrost sections from the southern and northern coasts of dmitry laptev strait have preserved records of landscape transition from glacial to interglacial periods they allow geomorphologic and environmental changes to be traced from pre eemian time to the eemian and from the late glacial to the holocene the transition from one period to another induced extensive thawing of permafrost thermokarst evolving thermokarst depressions transformed formerly frozen ground into taberal unfrozen deposits with accumulating overlying lacustrine deposits lacustrine horizons rich in palaeontological remains retain evidence of changes in environmental conditions the pollen records reflect changes from grass sedge dominated vegetation during the early eemian to shrub dominated spectra during the middle eemian thermal optimum followed by late eemian grass sedge dominated tundra vegetation abundant larix pollen have been found in middle eemian deposits from the south coast of the dmitry laptev strait oyogos yar but are absent in similar deposits from the north coast bol shoy lyakhovsky island likely indicating that the northern tree line was located near the oyogos yar region during the eemian thermal optimum grass sedge dominated tundra vegetation occurred during the late glacial holocene transition which was replaced by shrub tundra during the early holocene rich fossil ostracod records from eemian and late glacial holocene lacustrine deposits could be correlated with the eemian thermal optimum and the late glacial allerod warm period for both periods the stable oxygen isotope data from the fossil ostracods suggest an approximate mean summer water temperature range between about 10 and 19 c in the palaeo lakes

transtensional deformation in the central himalaya and its role in accommodating growth of the himalayan orogen 1 field mapping structural analysis and geochronologic data from northwestern nepal reveal major normal right slip motion along a previously unrecognized west northwest striking system of shear zones that we term the gurla mandhata humla fault system gmh the gmh obliquely cuts across the greater himalayan crystalline sequence and into the lesser himalayan imbricate thrust belt via two right step over structures the average slip direction on the gmh parallels the strike of the himalayan orogen motion along this fault system has resulted in an apparent left separation of the south tibet detachment main central thrust zone and lesser himalayan imbricate thrust belt along a north striking segment of the fault system we estimate a minimum of 21 km of net slip on the southern branch of the gmh by restoring the trace of the main central thrust zone parallel to the average slip direction on the fault taking into account slip estimates from the northern branch of the gmh yields a minimum net slip estimate of 24 4 to 32 4 km for the gmh the 232th 208pb ion microprobe monazite ages from leucogranite bodies indicate that motion on the gmh occurred after 15 ma its initiation immediately followed crustal thickening between the main central thrust zone and indus yalu suture zone motion on the gmh is contemporaneous with arc normal contraction in the southernmost himalayan orogen these observations can be explained by a model that involves foreland propagating structural systems facilitating arc normal contraction in the foreland and arc parallel extension in the hinterland that work together to maintain the arcuate shape of the himalayan orogen

grain size properties and organic carbon stock of yedoma ice complex permafrost from the kolyma lowland northeastern siberia the organic carbon stock in permafrost is of increasing interest in environmental research because during the late quaternary a large pool of organic carbon accumulated in the sedimentary deposits of arctic permafrost because of its potential to degrade and release organic carbon the organic matter inventory of yedoma ice complex deposits is relevant to current concerns about the effects of global warming in this context it is essential to improve the understanding of preserved carbon quantities and characteristics the paper aims to clarify the yedoma ice complex origin and to develop an approach for volumetric organic matter quantification therefore we analyzed the grain size and the organic matter characteristics of the deposits exposed at the stratigraphic key site duvanny yar lower kolyma river northeast siberia a distinct bimodal grain size distribution confirms a polygenetic origin of the frozen sediments from a flood plain environment the total organic carbon content averages 1 5 1 4 wt while the volumetric organic carbon content averages 14 8 kg m however large scale extrapolations for yedoma ice complex deposits in general are not reasonable yet because of their rather unclear spatial distribution we conclude that yedoma ice complex formation at duvanny yar was dominated by water related alluvial fluvial lacustrine as well as aeolian processes the total organic carbon content of the studied deposits is low if compared to other profiles but it is still a significant pool

ice complex permafrost of mis5 age in the dmitry laptev strait coastal region east siberian arctic ice complex deposits locally known as the buchchagy ice complex are exposed at both coasts of the east siberian dmitry laptev strait and preserved below the yedoma ice complex that formed during mis3 and mis2 marine isotope stage and lateglacial holocene thermokarst deposits mis1 radioisotope disequilibria 230th u of peaty horizons date the buchchagy ice complex deposition to 126 16 13 kyr and 117 19 14 kyr until 98 5 kyr and 89 5 kyr the deposit is characterised by poorlysorted medium to coarse silts with cryogenic structures of horizontal ice bands lens like and lenslike reticulated segregation ice two peaty horizons within the buchchagy ice complex and syngenetic ice wedges 2e4 m wide up to 10 m high are striking the isotopic composition d18o dd of buchchagy ice wedge ice indicates winter conditions colder than during the mis3 interstadial and warmer than during mis2 stadial and similar atmospheric winter moisture sources as during the mis2 stadial buchchagy ice complex pollen spectra reveal tundra steppe vegetation and harsher summer conditions than during the mis3 interstadial and rather similar vegetation as during the mis2 stadial short term climatic variability during mis5 is reflected in the record even though the regional chronostratigraphic relationship of the buchchagy ice complex to the last interglacial remains unclear because numerical dating is widely lacking the present study indicates permafrost ice complex formation during mis5 sensu lato and its preservation afterwards palaeoenvironmental insights into past climate and the periglacial landscape dynamics of arctic lowlands in eastern siberia are deduced from the record

cryostratigraphy of late pleistocene syngenetic permafrost yedoma in northern alaska itkillik river exposure abstract extremely ice rich syngenetic permafrost or yedoma developed extensively under the cold climate of the pleistocene in unglaciated regions of eurasia and north america in alaska yedoma occurs in the arctic foothills the northern part of the seward peninsula and in interior alaska a remarkable 33 m high exposure along the lower itkillik river in northern alaska opened an opportunity to study the unmodified yedoma including stratigraphy particle size distribution soil carbon contents morphology and quantity of segregated wedge and thermokarst cave ice the exposed permafrost sequence comprised seven cryostratigraphic units which formed over a period from 48 000 to 5 000 14c yr bp including 1 active layer 2 intermediate layer of the upper permafrost 3 4 two yedoma silt units with different thicknesses of syngenetic ice wedges 5 buried peat layer 6 buried intermediate layer beneath the peat and 7 silt layer with short ice wedges this exposure is comparable to the well known mus khaya and duvanny yar yedoma exposures in russia based on our field observations literature sources and interpretation of satellite images and aerial photography we have developed a preliminary map of yedoma distribution in alaska

middle to late wisconsinan climate and ecological changes in northern alaska evidences from the itkillik river yedoma abstract continuous paleoenvironmental records covering the period prior to the last glacial maximum in northeastern beringia are sparse this study presents a multi proxy analysis of a 35 m high yedoma exposure located on the right bank of the itkillik river in alaska the exposure accumulated over 39 thousand years kyr during the middle wisconsinan interstadial and the late wisconsinan glacial advance we identified five stratigraphic units based on pollen carbon and ice content and isotopic composition 18o of the sediments middle wisconsinan climate in northern alaska promoted peat accumulation prior to 33 6 cal kyr bp calibrated kyr before present reconstructed july air temperatures were 1 2 c lower than current at 34 8 cal kyr bp consistent with the timing of the interstadial climatic optimum in interior alaska and yukon colder by up to 4 c and drier conditions characterize the transition from interstadial to glacial conditions between 33 6 and 29 8 cal kyr bp late wisconsinan 29 8 17 9 cal kyr bp july air temperatures were 2 3 c lower than today with grassland vegetation dominated by poaceae artemisia and forbs in contrast to the modern cyperaceae dominance moister and warmer environmental conditions after 17 9 cal kyr bp correspond to the late glacial to early holocene interval

isotopic analyses and hydrochemistry of the thermal springs along the eastern side of the jordan dead sea wadi araba rift valley abstract the isotopic composition of the present precipitation as well as the groundwaters of jordan is found to lie between the eastern mediterranean and the meteoric water lines whereas the isotopic compositions of precipitation and groundwater from north and central jordan plot between both lines those of southern jordan cluster closer to the meteoric water line the deep sandstone aquifer complex in central jordan receives water from the overlying tertiary upper cretaceous units as well as from the sandstones of southern jordan both contributions mix in the eastern part of central jordan flow from there in a westerly direction and discharge on the slopes above the dead sea at the interface of fresh groundwater and dead sea water mixing between the latter two waters takes place under a normal geothermal gradient the water is then discharged as thermal water with an isotopic composition following the equation d 3 97 18 o 16 9

late quaternary ice sheet history of northern eurasia the maximum limits of the eurasian ice sheets during four glaciations have been reconstructed 1 the late saalian 140 ka 2 the early weichselian 100 80 ka 3 the middle weichselian 60 50 ka and 4 the late weichselian 25 15 ka the reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in russia and siberia and with marine seismic and sediment core data the barents kara ice sheet got progressively smaller during each glaciation whereas the dimensions of the scandinavian ice sheet increased during the last ice age the barents kara ice sheet attained its maximum size as early as 90 80 000 years ago when the ice front reached far onto the continent a regrowth of the ice sheets occurred during the early middle weichselian culminating about 60 50 000 years ago during the late weichselian the barents kara ice sheet did not reach the mainland east of the kanin peninsula with the exception of the nw fringe of taimyr a numerical ice sheet model forced by global sea level and solar changes was run through the full weichselian glacial cycle the modeling results are roughly compatible with the geological record of ice growth but the model underpredicts the glaciations in the eurasian arctic during the early and middle weichselian one reason for this is that the climate in the eurasian arctic was not as dry then as during the late weichselian glacial maximum

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

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 periglacial climate and environment in northern eurasia during the last glaciation this paper summarizes the results of studies of the late weichselian periglacial environments carried out in key areas of northern eurasia by several queen teams european science foundation esf programme quaternary environment of the eurasian north the palaeoglaciological boundary conditions are defined by geological data on timing and extent of the last glaciation obtained in the course of the eu funded project eurasian ice sheets these data prove beyond any doubt that with the exception of the northwestern fringe of the taymyr peninsula the rest of the eurasian mainland and severnaya zemlya were not affected by the barents kara sea ice sheet during the last glacial maximum lgm inversed modelling based on these results shows that a progressive cooling which started around 30 ka bp caused ice growth in scandinavia and the northwestern areas of the barents kara sea shelf due to a maritime climate with relatively high precipitation along the western flank of the developing ice sheets in the rest of the eurasian arctic extremely low precipitation rates less than 50 mm yr 1 did not allow ice sheet growth in spite of the very cold temperatures palaeoclimatic and palaeoenvironmental conditions for the time prior to during and after the lgm have been reconstructed for the non glaciated areas around the lgm ice sheet with the use of faunal and vegetation records permafrost eolian sediments alluvial deposits and other evidences the changing environment from interstadial conditions around 30 ka bp to a much colder and drier environment at the culmination of the lgm at 20 15 ka bp and the beginning of warming around 15 ka bp have been elaborated from the field data which fits well with the modelling results

the deep permafrost carbon pool of the yedoma region in siberia and alaska estimates for circumpolar permafrost organic carbon oc storage suggest that this pool contains twice the amount of current atmospheric carbon the yedoma region sequestered substantial quantities of oc and is unique because its deep oc was incorporated into permafrost during ice age conditions rapid inclusion of labile organic matter into permafrost halted decomposition and resulted in a deep long term sink we show that the deep frozen oc in the yedoma region consists of two distinct major sub reservoirs yedoma deposits late pleistocene ice and organic rich silty sediments and deposits formed in thaw lake basins generalized as thermokarst deposits we quantified the oc pool based on field data and extrapolation using geospatial datasets to 83 61 57 gt for yedoma deposits and to 128 99 96 gt for thermokarst deposits the total yedoma region 211 160 153 gt is a substantial amount of thaw vulnerable oc that must be accounted for in global models

permafrost carbon stock and decomposability of a globally significant carbon pool 1 the magnitude of future co2 induced climate warming is difficult to predict because of uncertainties in the role of ecosystems and oceans as co2 sources and sinks siberia has extensive areas 1 106 km2 of deep up to 90 m deposits of organic rich frozen loess wind blown silt that accumulated during the pleistocene but have not been considered in most global carbon c inventories similar deposits occur less extensively in alaska recent warming at high latitudes causes this permafrost permanently frozen ground to thaw raising questions about the fate of c in thawing permafrost here we show that siberian loess permafrost contains a large organic c pool 450 gt more than half the quantity in the current atmosphere that decomposes quickly when thawed and could act as a positive feedback to climate warming

seismotectonics of the himalayan collision zone geometry of the underthrusting indian plate beneath the himalaya fault plane solutions and well determined focal depths of medium sized earthquakes topography and landsat imagery in conjunction with seismicity maps cross sections and available geological information are used to investigate the present tectonics of the himalayan continental collision zone most of the accurately located epicenters of events along the himalayan arc 78 e 95 e that occurred between 1961 and 1981 are concentrated in a narrow zone about 50 km wide lying between the northerly dipping main boundary mbt and main central mct thrusts most of these events are located just south of the mct though the epicenters of the events are in general well located their depths as determined by teleseismic travel time data are very unreliable events with accurately determined depths obtained from identification of surface reflected phases define a simple planar zone from about 10 km and 20 km depth with an apparent dip of about 15 this result is all the more remarkable considering that the events used were located along about an 1800 km length of the himalyan arc except for one all available focal mechanisms of events within this zone indicate shallow 30 north dipping thrusts this shallow north dipping zone apparently defines a part of the detachment that separates the underthrusting indian plate from the lesser himalayan crustal block the spatial extent and the geometry of this interplate thrust zone strongly indicate that the mbt and nearby subsidiary surface and blind thrusts rather than the mct are currently the most active structures of the himalayan arc we suggest that the great himalayan earthquakes m 8 occur along the same detachment surface as defined by the thrust type medium sized events events located to the south of the mbt and beneath the ganges foredeep show normal faulting with t axes perpendicular to the himalayan trend the above results suggest that the indian continental plate is underthrusting the himalayan crustal blocks in a relatively coherent and simple geometry and that this geometry is not much different from that observed along oceanic subduction zones the november 19 1980 earthquake that occurred near the mct near 88 5 e shows a predominantly strike slip focal mechanism one of the nodal planes of this mechanism is transverse to the himalayan structural grain and moreover this plane has a trend similar to that of the recently mapped yadong gulu rift in the tethyan himalaya and in southern tibet just northeast of the earthquake we interpret this predominantly left lateral strike slip mechanism to indicate a possible genetic relationship between transverse structural features in the underthrusting indian plate the kishangang basement fault and the upper himalayan blocks and tibet

characterisation and palaeoclimate of a loess like permafrost palaeosol sequence in ne siberia abstract we studied a 15 m high loess like permafrost palaeosol sequence the tumara palaeosol sequence tps which developed on a middle pleistocene fluvio glacial terrace of the tumara river various analytical methods were applied to characterise the tps similar to typical loess palaeosol sequences e g in china europe etc pedogenetic clay formation mineral weathering and smaller grain sizes are interpreted as representing warmer and more favourable climatic conditions interglacials or interstadials soil organic matter som however reveals an unfamiliar inverse pattern high organic carbon contents c org 1 characterise the dark grey glacial palaeosols whereas lower contents c org 0 5 are found in the brown interglacial stadial palaeosols this can be explained with permafrost and water logging having inhibited som mineralisation during cold periods d l ratios of aspartic acid and lysine proved to be useful proxies for both som aging and palaeotemperature with amino acid racemization being enhanced in interglacial stadial palaeosols on the basis of the geochemical and grain size results further palaeoclimatically relevant proxies describing the palaoewind strength u ratio the mineral weathering chemical index of alteration rb k and the changing mineral input signal ba ti zr ti al were applied to the tps in combination with numeric dating results radiocarbon and luminescence and in the context of other northern hemispheric records the simple warm cold stratigraphy as derived from the palaeoenvironment climate proxies suggests that the tps represents the last 240 000 years

fossil organic matter characteristics in permafrost deposits of the northeast siberian arctic 1 permafrost deposits constitute a large organic carbon pool highly vulnerable to degradation and potential carbon release due to global warming permafrost sections along coastal and river bank exposures in ne siberia were studied for organic matter om characteristics and ice content om stored in quaternary permafrost grew accumulated froze partly decomposed and refroze under different periglacial environments reflected in specific biogeochemical and cryolithological features om in permafrost is represented by twigs leaves peat grass roots and plant detritus the vertical distribution of total organic carbon toc in exposures varies from 0 1 wt of the dry sediment in fluvial deposits to 45 wt in holocene peats variations in om parameters are related to changes in vegetation bioproductivity pedogenic processes decomposition and sedimentation rates during past climate variations high toc high c n and low 13c reflect less decomposed om accumulated under wet anaerobic soil conditions characteristic of interglacial and interstadial periods glacial and stadial periods are characterized by less variable low toc low c n and high 13c values indicating stable environments with reduced bioproductivity and stronger om decomposition under dryer aerobic soil conditions based on toc data and updated information on bulk densities we estimate average organic carbon inventories for ten different stratigraphic units in northeast siberia ranging from 7 2 kg c m 3 for early weichselian fluvial deposits to 33 2 kg c m 3 for middle weichselian ice complex deposits to 74 7 kg c m 3 for holocene peaty deposits the resulting landscape average is likely about 25 lower than previously published permafrost carbon inventories

characteristics of cryogenic soils along a latitudinal transect in arctic alaska the morphological chemical and physical properties of arctic tundra soils were examined along a 200 km latitudinal gradient in northern alaska which includes two major physiographic provinces the arctic coastal plain and the arctic foothills annual air temperature and precipitation increase along the gradient from north to south soils on the arctic coastal plain support wet nonacidic tundra vegetation and have high carbonate contents soil on the arctic foothills support moist nonacidic tundra in the northern part and moist acidic tundra in the southern part most arctic tundra soils are characterized by medium texture poor drainage and high organic matter content from north to south along the transect the base saturation of the active layer decreases and exchangeable aluminum increases from north to south most soils have strongly developed cryogenic features including warped and broken horizons ice lenses thin platy structure and organic matter frost churned into the ice rich upper permafrost horizons

ductile extrusion of the higher himalayan crystalline in bhutan evidence from quartz microfabrics quartz textures measured from deformed quartz tectonites within the lesser himalaya and higher himalaya crystalline of bhutan show similar patterns orientation and distribution of the quartz crystallographic axes were used to confirm the regional shear sense the asymmetry of c axis and a axis patterns consistently indicates top to the south shearing the obliquity of the texture and the inferred finite strain plane strain to moderately constrictional suggest the strain regime had a combination of rotational and irrotational strain path in most of the samples from the bhutan himalaya the inferred deformation mechanisms suggest moderate to high temperature conditions of deformation that produced the observed crystallographic preferred orientation much higher temperature of deformation is indicated in the quartz veins from a leucogranite the observed ductile deformation is pervasively developed in the rocks throughout the investigated area the intensity of deformation increases only slightly in the vicinity of the main central thrust simultaneous southward shearing within a large part of the higher himalaya crystalline near and above the main central thrust and normal faulting across the south tibetan detachment is explained by the tectonically induced extrusion of a ductily deforming wedge the process of extrusive flow suggested here can be approximated quantitatively by channel flow models that have been used to describe subduction zone processes channel flow accounts for some observed phenomena in the himalayan orogen such as inverted metamorphic sequences near the main central thrust not related to an inversion of isotherms and the syntectonic emplacement of leucogranites into the extruding wedge locally leading to an inversion of isotherms due to heat advection

paleoenvironmental and paleoclimatic records from permafrost deposits in the arctic region of northern siberia ice complexes extremely ice rich permafrost deposits with large ice wedges are widely distributed in the arctic region of northeast siberia they present excellent archives for the reconstruction of late quaternary paleoenvironmental conditions in nonglaciated areas in 1998 1999 and 2000 russian and german scientists worked together on the bykovsky peninsula southeast of the lena delta in order to investigate the ice complex and its associated sediments intensive cryolithological and sedimentological studies radiocarbon age determinations paleobotanical studies micropaleontological investigations studies of mammal and insect fossils and stable isotope analyses of ground ice were performed radiocarbon data have been obtained from the entire exposed sequence coveringapproximately the last 60 000 years the results indicate that compared with modern time the investig ated ice complex sequence was formed duringtwo cooler and more arid stages of the late pleistocene with relatively uniform environmental conditions separated by a stage with environmental variations and more intensive soil formation caused by climate amelioration the late pleistocene environmental changes were not as strong as those occurring during the pleistocene holocene transition where a sharp break is evident r 2002 elsevier science ltd and inqua all rights reserved

soil organic carbon pools in the northern circumpolar permafrost region of all soils in the northern permafrost region is approximately 18 782 10 3 km 2 o r approximately 16 of the global soil area in the northern permafrost region organic soils peatlands and cryoturbated permafrost affected mineral soils have the highest mean soil organic carbon contents 32 2 69 6 kg m 2 here we report a new estimate of the carbon pools in soils of the northern permafrost region including deeper layers and pools not accounted for in previous analyses carbon pools were estimated to be 191 29 pg for the 0 30 cm depth 495 80 pg for the 0 100 cm depth and 1024 00 pg for the 0 300 cm depth our estimate for the first meter of soil alone is about double that reported for this region in previous analyses carbon pools in layers deeper than 300 cm were estimated to be 407 pg in yedoma deposits and 241 pg in deltaic deposits in total the northern permafrost region contains approximately 1672 pg of organic carbon of which approximately 1466 pg or 88 occurs in perennially frozen soils and deposits this 1672 pg of organic carbon would account for approximately 50 of the estimated global belowground organic carbon pool

sedimentation of the late miocene bahe formation and its implications for stable environments adjacent to qinling mountains in shaanxi china abstract an important key site along the bahe river in the lantian area shaanxi province northern china exposes a conformable sedimentary sequence that records the transition from early late miocene fluvial sediments into late miocene and pliocene aeolian red clay and finally into pleistocene loess although the red clay and pleistocene loess in northern china have been intensively studied over the years the bahe formation beneath the red clay in the lantian area has been less well studied here we present the preliminary results of a detailed lithostratigraphical investigation of the bahe formation on the northern slopes of the bailuyuan plateau and discuss the style of sedimentation during its deposition the bahe formation in the lantian area is composed of fluvial and lacustrine deposits laid down in the weihe graben during the late miocene six main facies assemblages have been distinguished 1 massive or crudely bedded conglomerates 2 cross stratified conglomerate and sandstone deposits 3 minor sandstone deposits 4 fine grained deposits 5 gritty mudstone and sandstone deposits and 6 marl deposits these assemblages represent the deposits of active channels crevasse splays sheet floods and floodplains with paleosols and lakes thick and laterally pervasive units of fine grained sediments formed as suspension fall out on the floodplain indicating low energy conditions and a relatively gentle surface gradient in the area are by far the most common sedimentary component channel related sandstones and conglomerates indicate that the rivers had a low sinuosity and were braided to anastomosing types the bahe fluvial system operated for several million years in a tectonically inactive setting in a vegetated area under a relatively arid climate this environmental interpretation is consistent with that derived from the interpretation of the vertebrate fossil fauna recovered from the sediments

pseudotachylyte generated in the semi brittle and brittle regimes bench canyon shear zone central sierra nevada pseudotachylyte cuts cretaceous plutonic and volcanic rocks in the bench canyon shear zone central sierra nevada california as documented by optical and scanning electron microscopy the pseudotachylyte displays evidence for a friction melt origin including vesicles amygdules crystallites flow fabrics and embayed crystal fragments based on fault related rock association vein morphology and inferred crustal level of generation two distinct types of pseudotachylyte are documented in the shear zone pseudotachylyte associated with cataclasite was generated at shallow crustal levels 1 10 km via unstable velocity weakening abrasive wear friction pseudotachylyte associated and interlayered with mylonite was generated at deeper crustal levels 10 15 km most likely via stable velocity strengthening adhesive wear friction this pseudotachylyte underwent ductile deformation in the solid state interlayered pseudotachylyte and mylonite records cyclic aseismic seismic slip at a transitional crustal level between the semi brittle field of quartzofeldspathic rocks and the base of the seismogenic zone the cyclicity is attributed to strain rate fluctuation effected by strain resistant phacoids pore fluid pressure variation ductile instabilities or downward fault propagation the mode of deformation within the shear zone progressed from i production of mylonite during amphibolite to greenschist facies conditions to ii generation of pseudotachylyte by intermittent seismic faulting within a background of aseismic shear in the upper realm of the semi brittle field 300 400 c to iii generation of pseudotachylyte through seismic events in the brittle 300 c during uplift exhumation and cooling some of the latter may have been generated at shallow enough crustal levels 4 km to allow vesicle formation the exhumation of a crustal level exposing such an assemblage provides a rare opportunity to study the enigmatic nature of the transitional change from semi brittle flow to seismogenic rupturing

late pleistocene mis 3 2 palaeoenvironments as recorded by sediments palaeosols and ground squirrel nests at duvanny yar kolyma lowland northeast siberia abstract a detailed study of the duvanny yar section in the kolyma lowland yakutia provides the most extensive knowledge to date about late pleistocene soil formation processes and environments in the north east siberian arctic late quaternary palaeoenvironmental changes were reconstructed using paleopedological data and a range of palaeoecological bio indicators palynomorphs plant macrofossils and insects the frozen sediments representing marine isotope stage 3 mis 3 which encompasses the karginsky interstadial include profiles of four palaeosols of different ages the oldest palaeosol is early karginskian and three overlying soil horizons represent a late karginskian pedocomplex palaeopedological data indicate a change of from synlithogenic soil formation processes to epigenic ones during these intervals the intervening periods of synlithogenic pedogenesis were accompanied by active accumulation of eolian deposits the earlier karginskian period of pedogenesis occurred in the absence of eolian sedimentation and when summer conditions were warm the wide spectrum of peaty and peaty gley soils observed in the late karginskian deposits developed under conditions of progressive cooling the structure and content of fossil rodent burrows dated to approximately 30 000 yr bp from frozen late pleistocene deposits at duvanny yar indicate an arid and severe climate a depth of active layer of 60 80 cm and a wide distribution of disturbed habitats with pioneer and steppe vegetation

role of oblique convergence in the active deformation of the himalayas and southern tibet plateau noting similarities with subduction along curved oceanic trenches and using a simple block model we show that radial vergence evident in earthquake slip vectors along the himalayan deformation front east west extension on north trending normal faults in the himalayas and southern tibet and right lateral strike slip on the karakorum jiali fault zone can all result from basal shear caused by the indian plate sliding obliquely beneath tibet along a gently dipping arcuate plate boundary within the framework of this mechanism the normal faults in the himalayas and southern tibet are not proxies for the uplift history of tibet the distribution and style of the faults in the himalayas and southern tibet suggest that the basal drag from the underthrusting indian lithosphere extends northward beneath most of southern tibet

eohimalayan fold and thrust belt implications for the geodynamic evolution of the nw himalaya india 1 in the himalayas the eocene deformation phase is called the eohimalayan event by means of a forward and backward balanced cross section along a classical traverse through the tethyan himalaya we constrain eohimalayan sw vergent folding and sw directed thrusting in a belt above a basal thrust at 10 km depth this thrust is located at the structural position of the southern tibetan detachment system with a ne directed normal sense displacement suggesting miocene reactivation of a major eocene contractional fault stepwise palinspastic restoration demonstrates that this eocene contractional fault has been subsequently openly folded due to southwestward propagation of the himalayan thrust system

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

the origin of thermal waters from the eastern flank of the dead sea rift valley western jordan thermal waters emerging along the eastern flank of the northernmost part of the dead sea rift valley close to the yarmuk river are dilute ca so4 hco3 and na cl water types with measured temperatures of 35 60 c and estimated teperatures according to silica solubility of 60 110 c they are fed only by present day recharged meteoric waters wadi hasa al himma and north shuna thermal baths and by meteoric waters contaminated with saline waters el ma in thermal bath although they have been known for a long time there is still dispute about their origins and the source of heat on the basis of new chemical and isotopic analyses the saline waters could represent residual pockets of groundwater in equilibrium with those filling the dead sea depression before the last retreat of lake lisan at 17 15 kyr bp or with the ancient seawaters of the sedom lagoon in the early pleistocene in both cases unaffected by significant evaporation processes but chemically and isotopically modified by water rock interaction

late miocene topographic inversion in southwest tibet based on integrated paleoelevation reconstructions and structural history article investigations of the deformation history of the himalayan orogen support interpretations of rapid and striking changes in the landscape of the tibetan himalaya and high himalaya we examine this issue by integrating oxygen isotope based paleoelevation reconstructions of the zada basin in southwestern tibet with information on the structural evolution of the high and tibetan himalaya between 79 e and 84 30 e 18 opsw values were calculated from 18 occ values from pristine fluvial miocene gastropod shells analyses comparing the most negative 18 osw and reconstructed 18 opsw values to 18 osw versus elevation relationships based on both thermodynamic models and an empirical data set suggest a decrease in the mean watershed elevation of 1 to 1 5 km since the late miocene geologic mapping and structural data from crustal scale fault systems in the zada region and regions to its east indicate a phase of arc normal shortening and vertical thickening since the middle miocene followed by ongoing arc parallel extension and vertical thinning these results suggest that regions in this part of the orogen transitioned from undergoing arc normal shortening to arc parallel extension in the late miocene and that arc parallel extensional structures root deeply within the himalayan thrust wedge when combined with data on the distribution age and provenance of sedimentary basins our geologic mapping structural data and paleoelevation results suggest that this transition from shortening to extension was accompanied by a topographic inversion from mountains to basins in b4 m y these observations can be explained by a foreland propagating fault system that accommodates outward radial expansion of the himalayan orogen

patterns and rates of riverbank erosion involving ice rich permafrost yedoma in northern alaska abstract yedoma a suite of syngenetically frozen silty ice and organic rich deposits with large ice wedges that accumulated during the late pleistocene is vulnerable to thermal degradation and erosion because of the extremely high ice contents this degradation can result in significant surface subsidence and retreat of coastal bluffs and riverbanks with large consequences to landscape evolution infrastructure damage and water quality we used remote sensing and field observations to assess patterns and rates of riverbank erosion at a 35 m high active yedoma bluff along the itkillik river in northern alaska the total volumetric ground ice content including wedge segregated and pore ice was estimated to be 86 the process of riverbank erosion and stabilization include three main stages typical of the areas with ice rich permafrost 1 thermal erosion combined with thermal denudation 2 thermal denudation and 3 slope stabilization active riverbank erosion at the main study site started in july 1995 when the itkillik river changed its channel the total retreat of the riverbank during 1995 2010 within different segments of the bluff varied from 180 to 280 m the average retreat rate for the most actively eroded part of the riverbank was almost 19 m y from august 2007 to august 2011 the total retreat varied from 10 to almost 100 m the average retreat rate for the whole 680 m long bluff was 11 m y for the most actively eroded central part of the bluff 150 m long it was 20 m y ranging from 16 to 24 m y more than 180 000 m3 of ground ice and organic rich frozen soil or almost 70 000 metric tons t of soil solids including 880 t of organic carbon were transported to the river from the retreating bank annually this study reports the highest long term rates of riverbank erosion ever observed in permafrost regions of eurasia and north america

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

strontium isotopic chemical and sedimentological evidence for the evolution of lake lisan and the dead sea precise strontium isotope ratios combined with chemical analyses and sedimentological information are used to monitor the water sources and the evolution of the dead sea and its late pleistocene precursor lake lisan 70 18 kyr b p the materials analyzed include bulk aragonite water leached soluble salts and residual aragonite and gypsum from the lisan formation in the perazim valley near the sw shore of the dead sea the residual aragonite and the associated soluble salts display systematic fluctuations in 17sr86sr ratios between 0 70803 and 0 70806 and from 0 70805 to 0 70807 respectively in individual soluble salt residual aragonite pairs the soluble salt displays a higher 87sr86sr ratio gypsum samples yield 17sr86sr ratios similar to the soluble salts from adjacent layers in the section this shows that in individual samples the source of sr in aragonite was distinct from that in soluble salts and the gypsum the sterility of the lisan sediments their strictly nonbioturbated fine lamination and their high content of chloride salts indicate that lake lisan was a saline or even hypersaline water body in the absence of alternative sources of hco3 and s042 the abundance of primary aragonite and gypsum in the lisan column reflects an import of very large volumes of freshwater into the otherwise saline lake resulting in a density stratification of this water body the history of the upper water layer and that of the lower brine is reflected in the chemical and strontium isotope composition of the aragonite and in that of the associated soluble salts and in the gypsum samples respectively whereas the bicarbonate and much of the ca2 required for aragonite crystallization were supplied by the freshwater the complementary ca2 and sr 2 were added by the lower brine the upper water layer of lake lisan acted as a so42 capacitor during the lake s rise periods it was removed therefrom as prominent gypsum beds upon climatic induced drier period mixing or even complete overturn of the lake the evolution of lake lisan took place between two distinct modes the first was characterized by an extensive supply of freshwater and resulted in a rise of the lake s level a density layered structure and precipitation of aragonite the second mode was marked by a diminishing freshwater input resulting in mixing or complete overturn of its water and precipitation of gypsum these two modes reflect the climatic evolution of the region in the late pleistocene which fluctuated between drier and wetter periods the transition to the holocene is accompanied by the dry up of lake lisan and its contraction to the present dead sea

deformation of leucogranites of the crystalline main central sheet in southern tibet china abstract towards the top of the main central sheet in southern tibet china leucogranites intrude metamorphic rocks related to rocks of the main central thrust in the himalayas our study shows that the leucogranites suffered a northward shear deformation the significance of this event is discussed in terms of gravity driven decollement of the 10 000 m thick tethyan sedimentary pile over its crystalline basement

miocene to holocene exhumation of metamorphic crustal wedges in the nw himalaya evidence for tectonic extrusion coupled to fluvial erosion the himalayan crystalline core zone exposed along the sutlej valley india is composed of two high grade metamorphic gneiss sheets that were successively underthrusted and tectonically extruded as a consequence of the foreland directed propagation of crustal deformation in the indian plate margin the high himalayan crystalline sequence hhcs is composed of amphibolite facies to migmatitic paragneisses metamorphosed at temperatures up to 750 c at 30 km depth between eocene and early miocene during early miocene combined thrusting along the main central thrust mct and extension along the sangla detachment induced the rapid exhumation and cooling of the hhcs whereas exhumation was mainly controlled by erosion since middle miocene the lesser himalayan crystalline sequence lhcs is composed of amphibolite facies para and orthogneisses metamorphosed at temperatures up to 700 c during underthrusting down to 30 km depth beneath the mct the lhcs cooled very rapidly since late miocene as a consequence of exhumation controlled by thrusting along the munsiari thrust and extension in the mct hanging wall this renewed phase of tectonic extrusion at the himalayan front is still active as indicated by the present day regional seismicity and by hydrothermal circulation linked to elevated near surface geothermal gradients in the lhcs as recently evidenced in the himalayan syntaxes active exhumation of deep crustal rocks along the sutlej valley is spatially correlated with the high erosional potential of this major trans himalayan river this correlation supports the emerging view of a positive feedback during continental collision between crustal scale tectono thermal reworking and efficient erosion along major river systems

holocene thermokarst dynamics in central yakutia a multi core and robust grain size endmember modeling approach abstract differentiating thermokarst basin sediments with respect to the involved processes and environmental conditions is an important tool to understand permafrost landscape dynamics and scenarios and future trajectories in a warming arctic and subarctic thermokarst basin deposits have complex sedimentary structures due to the variability of yedoma source sediments reworking during the late glacial to holocene climate changes and different stages of thermokarst history here we reconstruct the dynamic growth of thermokarst lakes and basins and related changes of depositional conditions preserved in sediment sequences using a combination of biogeochemical data and robust grain size endmember analysis remma this multi proxy approach is used on 10 sediment cores each 300 400 cm deep from two key thermokarst sites to distinguish four time slices that describe the holocene thermokarst lake basin evolution in central yakutia cy biogeochemical proxies and remma reveal fine grained sedimentation with rather high lake levels and or reducing conditions and coarse grained sedimentation with rather shallow lake levels and or oxidizing i e terrestrial conditions in relation to distal and proximal depositional and post sedimentary conditions statistical analysis suggests that the biogeochemical parameters are almost independent of thermokarst deposit sedimentology thus the biogeochemical parameters are considered as signals of secondary post sedimentary reworking the remma results are clearly reflecting grain size variations and depositional conditions this indicates small scale varying depositional environments frequently changing lake levels and predominantly lateral expansion at the edges of rapidly growing small thermokarst lakes and basins these small bodies finally coalesced forming the large thermokarst basins we see today in cy considering previous paleoenvironmental reconstructions in siberia we show the initiation of thaw and subsidence during the late glacial to holocene transition between about 11 and 9 cal kyrs bp intensive and extensive thermokarst activity for the holocene thermal maximum htm at about 7 to 5 cal kyrs bp severely fluctuating water levels and further lateral basin growth between 3 5 cal kyrs bp and 1 5 cal kyrs bp and the cessation of thermokarst activity and extensive frost induced processes i e permafrost aggradation after about 1 5 cal kyrs bp however gradual permafrost warming over recent decades in addition to human impacts has led to renewed high rates of subsidence and abrupt rapid cy thermokarst processes

extent and chronology of glaciations abstract the goal of the inqua commission on glaciation work group 5 extent and chronology of glaciations was to assemble glacial chronologies from around the world to better understand ice sheet volumes and extents at various times and to compile a gis supported database for past ice sheet extents the project involved the contribution of over 200 scientists working in more than 80 countries and territories throughout the world the resulting compilation represents the most complete survey of evidence of glaciation ever attempted the results are published in the form of three volumes europe north america and south america asia africa australia antarctica quaternary glaciations extent and chronology part i europe 2003a quaternary glaciations extent and chronology part ii north america 2003b quaternary glaciations extent and chronology part iii south america 2003c each of which contain a series of maps in digital format accompanied by an explanatory text which includes discussion of the type and quality of data used

deep yedoma permafrost a synthesis of depositional characteristics and carbon vulnerability abstract permafrost is a distinct feature of the terrestrial arctic and is vulnerable to climate warming permafrost degrades in different ways including deepening of a seasonally unfrozen surface and localized but rapid development of deep thaw features pleistocene ice rich permafrost with syngenetic ice wedges termed yedoma deposits are widespread in siberia alaska and yukon canada and may be especially prone to rapid thaw processes freeze locked organic matter in such deposits can be re mobilized on short time scales and contribute to a carbon cycle climate feedback here we synthesize the characteristics and vulnerability of yedoma deposits by synthesizing studies on the yedoma origin and the associated organic carbon pool we suggest that yedoma deposits accumulated under periglacial weathering transport and deposition dynamics in non glaciated regions during the late pleistocene until the beginning of late glacial warming the deposits formed due to a combination of aeolian colluvial nival and alluvial deposition and simultaneous ground ice accumulation we found up to 130 gigatons organic carbon in yedoma parts of which are well preserved and available for fast decomposition after thaw based on incubation experiments up to 10 of the yedoma carbon is considered especially decomposable and may be released upon thaw the substantial amount of ground ice in yedoma makes it highly vulnerable to disturbances such as thermokarst and thermo erosion processes mobilization of permafrost carbon is expected to increase under future climate warming our synthesis results underline the need of accounting for yedoma carbon stocks in next generation earth system models for a more complete representation of the permafrost carbon feedback

reevaluation of the lake sediment chronology in the dead sea basin israel based on new 230th u dates the dead sea is surrounded by chemical and detrital sediments that were deposited in its larger precursor lakes lake samra and lake lisan the sedimentary history of these lakes was recon structed by means of 230th234u ages of 30 samples mostly of argonite laminae from 8 columnar sections up to 110 km apart the general validity of the ages was demonstrated by subjecting them to tests of internal isotopic consistency agreement with stratigraphic order and concordance with 14c ages in the south only the part of the samra formation older than 170 000 yr is exposed while the aragonite detritus rhythmites found in the central and northern region are generally younger than 120 000 yr the lisan formation started accumulating about 63 000 yr b p with the clay and aragonite beds in the south central area reflecting a rise in water level to at least 280 m the upper part of the lisan formation the aragonite rich white cliff member started accumulating about 36 000 yr b p the lake probably reached its highest level sometime after this based on the ages of lisan sediments preserved in the southernmost reaches of the basin

fluvial incision and tectonic uplift across the himalayas of central nepal the pattern of fluvial incision across the himalayas of central nepal is estimated from the distribution of holocene and pleistocene terraces and from the geometry of modern channels along major rivers draining across the range the terraces provide good constraints on incision rates across the himalayan frontal folds sub himalaya or siwaliks hills where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces farther north and upstream in the lesser himalaya prominent fill terraces were deposited probably during the late pleistocene and were subsequently incised the amount of bedrock incision beneath the fill deposits is generally small suggesting a slow rate of fluvial incision in the lesser himalaya the terrace record is lost in the high range where the rivers are cutting steep gorges to complement the terrace study fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate this approach allows quantification of the effect of variations in channel slope width and discharge on the incision rate of a river the determination of incision rates requires an additional lithological calibration the two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared in the sub himalaya river incision is rapid with values up to 10 15 mm yr it does not exceed a few millimeters per year in the lesser himalaya and rises abruptly at the front of the high range to reach values of 4 8 mm yr within a 50 km wide zone that coincides with the position of the highest himalayan peaks sediment yield derived from the measurement of suspended load in himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range the observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat ramp flat geometry of the main himalayan thrust fault the morphology of the range reflects a dynamic equilibrium between present day tectonics and surface processes the sharp relief together with the high uplift rates in the higher himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the tibetan plateau driven by late cenozoic climate change or late miocene reactivation of the main central thrust

depth resolved physicochemical characteristics of active layer and permafrost soils in an arctic polygonal tundra region author s wu y ulrich c kneafsey t lopez r chou c geller j mcknight k dafflon b soom f peterson j hubbard s abstract 2018 the authors permafrost physicochemical parameters play a key role in controlling the response of permafrost carbon to climate change we studied the physicochemical parameters of permafrost in an arctic tundra region to evaluate 1 how soil parameters vary with depth and whether and how they are interrelated 2 whether and how permafrost soil differs from its overlaying active layer and 3 whether soil property depth relationships are different across geomorphic features e g low flat and high centered polygons we also explored the possible biogeochemical processes that led to these soil characteristics and how they may affect biogeochemical reactions upon permafrost thaw we observed 1 consistent relationships between soil property and depth and between major parameters 2 large contrasts of key soil parameters between active layer and permafrost indicative of potentially different response of the permafrost carbon to warming when compared to the active layer and 3 a correlation between soil hydraulic conductivity and topographic features that impacts soil hydrologic processes our analysis suggests that the permafrost has a marine derived chemical signature that differs from the active layer and shapes the physicochemical fingerprints of the different geomorphic features specifically we revealed the unique signatures of the high center polygons indicative of possible microbial activity at depth g1 m our study suggested consistent key soil parameter depth correlations while demonstrating complex lateral and vertical variabilities these results are valuable for identifying approaches to upscale point based measurements and for improving model parameterization to predict permafrost carbon behavior and feedback under future climate

mechanisms of loess sized quartz silt production and their relative effectiveness laboratory simulations the production of loess sized quartz silt is frequently ascribed to glacial grinding mechanisms in this study a series of laboratory simulations was set up the purpose of which was to demonstrate that a range of geomorphic mechanisms are capable of producing silt under laboratory conditions the geomorphic mechanisms investigated were aeolian abrasion fluvial comminution glacial grinding salt weathering and frost weathering the results confirmed that under laboratory conditions all of these mechanisms were capable of producing silt the relative effectiveness of these mechanisms at producing silt under laboratory conditions was then calculated in order to provide a starting point for a consideration of their potential effectiveness within the natural environment these results indicate that fluvial and aeolian activity are highly effective at producing quartz silt over short time periods in a dust storm of four days duration 287 g of silt could potentially be produced from every kilogram of sand entrained while fluvial comminution in a turbulent fluvial environment could potentially produce 900 g of silt from every kilogram of sand entrained within 32 h over longer periods of time the glacial grinding and weathering mechanisms represent more continuous and hence more effective silt producing mechanisms although it is realised that the relative importance of each silt producing mechanism will differ spatially and temporally due to differences in climate relief geology and geomorphic history the findings from this work do have implications for the genesis of loess deposits they demonstrate that glacial and cold weathering processes are not solely responsible for fine particle formation and that efficient silt producing mechanisms can operate within a variety of environments under suitable conditions weathering together with episodic contributions from aeolian and fluvial mechanisms could be responsible for a considerable proportion of global quartz silt production

ice complex formation in arctic east siberia during the mis3 interstadial abstract a continuous 15 m long sequence of ice complex permafrost yedoma exposed in a thermo cirque at the southern coast of bol shoy lyakhovsky island new siberian archipelago dmitry laptev strait was studied to reconstruct past landscape and environmental dynamics the sequence accumulated during the marine isotope stage 3 mis3 interstadial between 49 and 29 ka bp in an ice wedge polygon the frozen deposits were cryolithologically described and sampled on a vertical bluff between two ice wedges according to sedimentological and geochronological data the section is subdivided into three units which correlate with environmental conditions of the early middle and late mis3 period palynological data support this stratification the stable isotope signature of texture ice in the polygon structure reflects fractionation due to local freeze thaw processes while the signature of an approximately 5 m wide and more than 17 m high ice wedge fits very well into the regional stable water isotope record regional climate dynamics during the mis3 interstadial and local landscape conditions of the polygonal patterned ground controlled the ice complex formation the sequence presented here completes previously published mis3 permafrost records in northeast siberia late quaternary stadial interstadial climate variability in arctic west beringia is preserved at millennial resolution in the ice complex a mis3 climate optimum was revealed between 48 and 38 ka bp from the ice complex on bol shoy lyakhovsky island

extensional development of gabo valley southern tibet abstract gabo valley a n s trending extensional valley in southern tibet forms part of a chain of similar valleys that extends roughly northward from the himalayas for 150 km within the chain each of the valleys are laterally offset from one another and are connected by ne trending transfer faults with probable left slip displacement gabo valley itself is marked by numerous active fault scarps the morphology of the valley and the distribution of faults and alluvial fans indicate the valley was formed by two fault blocks that rotated in opposite directions a northern block on the east side and beneath the valley rotated down to the west and a southern block on the west side and under the valley rotated down to the east a smooth transition zone appears to connect the two fault blocks beneath the central part of the valley the most active faults which are presumably the faults with the greatest displacement and that accommodate much of the block rotation occur at the ends of the valley and merge with the ne trending transfer faults

fault analysis and paleostress evolution in large strain regions methodological and geological discussion of the southeastern himalayan fold and thrust belt in pakistan abstract we document the structure and kinematics of the southeastern part of the fold and thrust belt of the pakistani himalaya field analysis documents the importance of strike slip faulting associated with folding accordingly a transpression regime is inferred to be responsible for variable amounts of shortening from fault block to fault block the analysis of fault populations that affect the mesozoic to early miocene sediments allows distinguishing two paleostress tensor directions a dominant nw se compression and a minor e w compression are compatible with buckling around the n s axis of the near by hazara kashmir syntaxis from the lack of both systematic overprinting relationships and spatial trend the two tensors were obtained at different locations we conclude that in each location any of these two shortening directions can dominate the distribution of the paleostress tensors substantiates a transpressional regime due to far field himalayan compression and a lateral escape component of the allochthonous fold and thrust belt away from the growing hazara kashmir anticline

pedogenetic interpretations of particle size distribution curves for an alpine environment abstract the qilian mountains are generally capped by a productive silty soil layer wherever the environment allows as holocene loess is prevalent across the qilian mountains we assume that at least some of these fine sediments are derived from loess deposition and that soils across the region may be genetically linked to test these hypotheses nine pedons in different landscapes within a typical alpine watershed of the qilian mountains were sampled we also collected fine earth samples from glacier surfaces and crevices of glacial debris in the moraine zone the particle size distribution psd is used as a proxy for identifying aeolian fractions in soils the psd curves of all of the fine earth fractions examined are polymodal although three modal sizes of roughly 16 m 35 m and 80 m are found in almost all sediments in varying proportions these modal sizes have been identified as three sources of aeolian sediments in different transport systems the composition and thickness of loess sediments are related to local site conditions and may be related to the paleoenvironmental history of the site clastic debris and vegetation cover serve as dust traps during different stages of soil formation in this alpine environment and soils grow upward with accumulating loess sediment our study demonstrates that psd curves can be used to determine the origins and especially aeolian origins of soils furthermore this study provides insight into the pedology ecology and paleoenvironmental history of loess affected ecosystems in alpine areas of the qinghai tibetan plateau

salinization and dilution history of ground water discharging into the sea of galilee the dead sea transform israel abstract the mechanism governing salinization of ground water discharging into the sea of galilee in israel has been the subject of debate for several decades because the lake provides 25 of the water consumed annually in israel correct identification of the salt sources is essential for the establishment of suitable water management strategies for the lake and the ground water in the surrounding aquifers existing salinization models were evaluated in light of available and newly acquired data including general chemistry and o h c and cl isotopes based on the chemical and isotopic observations the proposed salt source is an ancient intensively evaporated brine 21 to 33 fold seawater which percolated through the valley formations from a lake which had formed in the rift valley following seawater intrusion during the late miocene low na cl and high br cl values support the extensive evaporation whereas high ca cl and low mg cl values indicate the impact of dolomitization of the carbonate host rock on the residual solution based on radiocarbon and other isotope data the dilution of the original brine occurred in two stages the first took place 30 000 a ago by slightly evaporated fresh to brackish lake water to form the sea of galilee brine the second dilution phase is associated with the current hydrological regime as the sea of galilee brine migrates upward along the rift faults and mixes with the actively circulating fresh ground water to form the saline springs the spatially variable chemical and isotopic features of the saline springs suggest not only differential dilution by fresh meteoric water but also differential percolation timing of the original brine into the tectonically disconnected blocks registering different evaporation stages in the original brine consequently various operations to reduce the brine contribution to the lake may be differentially effective in the various areas

age of initiation of collision between india and asia a review of stratigraphic data abstract the collision of india with asia is perhaps the most profound tectonic event to have occurred in past 100 ma it is responsible for the uplift of the himalayas and tibetan plateau and has been argued to have been responsible for geological geochemical and climatological consequences of global extent yet the age of initiation of this collision remains poorly constrained the literature is replete with estimates that range from the late cretaceous 65 ma to latest eocene

fault systems and paleo stress tensors in the indus suture zone nw pakistan abstract analysis of fault striations measured in the kohistan part of the indus suture zone nw himalaya pakistan has been carried out to document dynamic evolution during the brittle stage of the collision of india and asia processing of the data with a direct inversion method identified four stress fields which were chronologically ordered from field evidence as sse nnw compression e w compression radial extension and ssw nne compression the last corresponds to the present day stress field defined from seismic activity the earlier stress fields are related to times during the miocene when convergence related stresses were disturbed by the formation of the nearby nanga parbat and indus syntaxes

an end member algorithm for deciphering modern detrital processes from lake sediments of lake donggi cona ne tibetan plateau china abstract deciphering significant sedimentological processes from a set of sediment samples is an important step in reconstructing environmental changes one approach going beyond classical methods is the unmixing of grain size distributions this paper presents a flexible end member modelling algorithm that is based on eigenspace analysis and considers inherent uncertainties it has been applied to the detrital grain size components of lacustrine surface sediment samples of lake donggi cona qinghai province china it allows up to five grain size end members to be characterised and quantified in an optimal model an end member with a major mode in the clay domain accounts for 34 of variance within the grain size data set it may represent sedimentation of suspension load from linear and laminar runoff during heavy precipitation events in summer three end members in the fine sand to medium silt domains make up 60 of lacustrine sedimentation they may represent local to remote aeolian processes that peak in wintertime a multimodal end member explaining the remaining 6 of variance may represent further fluvial and littoral dynamics or random fluctuations and measurement errors several model runs of different scaling and numbers of end members provided a suitable way to determine uncertainties inherent to the model a comparison of 12 different model runs and their respective uncertainties yielded a distinct model of robust end members the clay and medium silt end members are robust features of detrital sedimentation within lake donggi cona they alone explain 54 4 of total variance in the data however no spatial pattern or relation to water depth is found for any of the grain size end members thus when past detrital sedimentation at lake donggi cona is reconstructed a special focus should be on the robust features attributed to aeolian and suspension related sedimentation processes as well as on effective sediment mixing processes impeding a distinct correlation between grain size and spatial attributes further applications of the end member modelling algorithm to other depositional environments are encouraged to demonstrate its universal applicability

up in the refrigerator geomorphic response to periglacial environments in the upper mississippi river basin usa abstract james c knox was best known for his work on holocene and historical changes in fluvial systems but he also had a long standing interest in the effects of late pleistocene periglacial environments on landscape evolution in parts of the upper mississippi river basin that were just outside the laurentide ice sheet margin or as knox put it up in the refrigerator knox and others in the quaternary community of the midwestern u s often suggested that hillslope erosion was accelerated under periglacial conditions so that glacial periods have had a dominant effect on the landscape we see today this paper reviews the evidence and reasoning supporting that view in a study area of the upper mississippi basin bordered on three sides by ice margins of the last glaciation including the wisconsin driftless area and adjacent landscapes sparse but compelling paleoecological data and relict ice or sand wedge polygons provide clear evidence for a cold climate and widespread permafrost around the peak of the last glaciation in highly dissected relatively high relief parts of the study area the loess and soil stratigraphy on ridgetops and the colluvial mantles on steeper slopes are best explained by highly effective hillslope erosion including solifluction during and just after the last glacial maximum knox used the post depositional truncation of a loess unit to quantify contrasting late pleistocene and holocene sediment yields from a small driftless area watershed while the late pleistocene yield indicates accelerated erosion it is still lower than modern sediment yields in many tectonically active or semiarid landscapes and it may reflect deposition of highly erodible loess as well as effects of periglacial conditions the views of knox and other midwestern geomorphologists on landscape evolution through glacial interglacial cycles were highly influenced by the work of robert v ruhe ruhe proposed that an episode of widespread erosion during and just after the last glacial maximum can explain enigmatic aspects of quaternary stratigraphy and the soil landscape on the iowan erosion surface a very low relief landscape of the study area ruhe s key evidence is still valid though it needs to be separated from an implausible model of landscape evolution interpretation of the iowan erosion surface and other low relief landscapes just outside the ice margin also requires recognition of the profound effect of eolian processes on those landscapes under periglacial conditions many new insights on landscape evolution in the study area could result from wider application of cosmogenic nuclide based methods to assess glacial interglacial changes in basinwide rates of erosion and residence time of soils just as important a need exists for much more field based characterization of hillslope fluvial and eolian sediments for comparison with those of modern permafrost regions and past periglacial environments in europe

origin of regional rooted low angle normal faults a mechanical model and its tectonic implications rooted listric low angle normal faults 20 of regional extent have been recognized widely in the past few years in the north american cordillera and elsewhere the low angle geometry of these crustal scale normal faults conflicts with anderson s 1942 classic theory of faulting in that theory the orientations of principal stresses are assumed to be vertical and horizontal the predicted dip angle of normal faults is about 60 rather than 20 or less recent geological and geophysical studies in the mid tertiary extensional terrane of southeastern california and western arizona suggest that thick mylonitic gneisses in the lower plates of low angle detachment faults may represent unidirectionally sheared laminar flow in and below the midcrust directed ductile flow possibly related to the gravitational spreading of thickened lower crust may induce a shearing traction on the horizontal or subhorizontal base of the brittle upper crust thus the orientations of the principal stresses can no longer be vertical and horizontal at this interface a simple elastic model incorporates the effect of basal shearing due to gravitational spreading on stress distributions in an elastic upper crust this model shows that parallel belts of compression and extension can be produced if a shearing traction acting on the base of the elastic upper crust is considered in particular appropriate stress conditions for the formation of regional low angle normal faults 20 can be produced by the superposition of two stress fields a basal shear stress field induced by the basal shear traction and a contractional stress field in which the horizontal deviatoric stress is compressional and the vertical gradient of the horizontal normal stress component is constant this superposed stress field may represent a tectonic setting where a stress field with compressional deviatoric stress induced by plate subduction or convergence is superposed on a basal shear stress field induced by gravitational spreading of thickened lower crust these results may explain both puzzling parallel belts of extension and compression and the occurrence of major low angle normal faults in some orogenic systems

tectonostratigraphic subdivisions of the himalaya a view from the west 1 indian plate rocks in the central himalaya have traditionally been divided into orogen parallel fault bound tectonostratigraphic zones a straightforward westward extrapolation of these zones has proved problematic in part because of a lack of consensus on the existence or significance of major faults within the metamorphic zone of the indian plate in pakistan where more than 10 locations for the main central thrust mct have been proposed we address this ambiguity by systematically tracing established central himalayan tectonostratigraphy around the western himalayan syntaxis and across pakistan this exercise reveals the following stratigraphic and structural relationships 1 there is a westward decrease in neogene shortening across the himalayan fold and thrust belt such that there is no age equivalent thrust in pakistan with displacement and metamorphic juxtaposition equivalent to the central himalayan mct 2 shortening across the fold and thrust belt in western pakistan is concentrated in the unmetamorphosed foreland as opposed to the metamorphic zone in the central himalaya 3 lesser himalayan higher himalayan and tethyan rocks are in stratigraphic order within the metamorphic zone of pakistan which appears to be the metamorphic equivalent of kashmir tethyan stratigraphy 4 the combination of early paleozoic and late paleozoic tectonism in pakistan has locally eliminated upper proterozoic higher himalayan rock and lower to middle paleozoic tethyan rock from the metamorphic zone of pakistan 5 late cretaceous and or early paleocene proto himalayan deformation in the pakistan foreland telescoped and eroded stratigraphy prior to the main phase of himalayan orogeny 6 tectonostratigraphic zones are offset in eastern pakistan by the transverse jhelum balakot fault 7 there is no evidence within the indian plate of pakistan for a large scale normal fault system comparable to the south tibetan detachment system 8 stratigraphy as well as the age and tectonic setting of deformation and metamorphism must be taken into account when drawing tectonostratigraphic zones

3d ground penetrating radar imaging of ice complex deposits in northern east siberia abstractice complex deposits are characteristic ice rich formations in northern east siberia and represent an important part in the arctic carbon pool recently these late quaternary deposits are the objective of numerous investigations typically relying on outcrop and borehole data many of these studies can benefit from a 3d structural model of the subsurface for upscaling their observations or for constraining estimations of inventories such as the local carbon stock we have addressed this problem of structural imaging by 3d ground penetrating radar gpr which in permafrost studies has been primarily used for 2d profiling we have used a 3d kinematic gpr surveying strategy at a field site located in the new siberian archipelago on top of an ice complex after applying a 3d gpr processing sequence we were able to trace two horizons at depths below 20 m taking available borehole and outcrop data into account we have interpreted these two features as interfaces of major lithologic units and der

grain size distribution function of polymodal sediments in hydraulic and aeolian environments and numerical partitioning of the sedimentary components most continental sediments are polymodal composed of overlapping components of which the grain size generally obeys some type of natural distribution the grain size components and their function types can be determined from frequency and cumulative curve plots in order to define the function formula of the grain size distribution the function parameters can be estimated by fitting a defined function formula to the measured grain size data of the sample which simultaneously achieves numerical partitioning of the sedimentary components genetic analysis of grain size components of hydraulic and aeolian sediments demonstrates the following environmental implications fluvial sediment is composed of isolated saltation and suspension components the sediments in closed lake basins are dominated by a suspension silt clay component with a small proportion of saltation sand the fine sand component makes up the majority of desert sand overlapping with a small proportion of fine dust aeolian loess is composed of two overlapping components a short suspension time silt component and a long suspension time fine component aeolian material in the north pacific deep sea sediments is dominated by long suspension time fine dust the fine component in aeolian sediments shows a consistent grain size distribution and genetic connection from the desert sand loess of northern china to the north pacific ocean which is mainly transported by westerly winds and is dispersed in the atmosphere forming a background dust c 2002 elsevier science b v all rights reserved

late weichselian ice sheets in arctic and pacific siberia abstract interpretation of space images coupled with field data on glacial geomorphology and glacial geology of northern eurasia have provided compelling evidence for a continuous late weichselian ice sheet covering the entire arctic margin of the continent in addition to the scandinavian ice sheet three ice sheets of the same order the karan east siberian and beringian are identified within the major eurasian ice sheet also there is evidence and other considerations suggesting a former ice sheet in the sea of okhotsk ice spreading centers of the ice sheets were situated on the continental shelves off the siberian coasts thus we can term the ice sheets siberian so far the conventional stratigraphic approach to the problem of siberian glaciation has proven fruitless and yielded nothing but uncertainty while geomorphological studies have discovered a wealth of glacial landforms in arctic siberia it was these landforms and their spacing that made the existence of former siberian ice sheets evident the east siberian ice sheet rested on the shelves of the eastern laptev and east siberian seas and its flow was directed radially including up the yana and indigirka rivers the beringian ice sheet was grounded on the chukchi bering and beaufort sea shelves overriding the chukchi and seward peninsulas from the north and flowing through the bering strait it was continued by a thick floating ice shelf buttressed by the submarine aleutian commander ridge the okhotsk ice sheet was grounded on the okhotsk shelf specific gemorphic signatures of marine ice sheets the glacially cut corners have been identified on all promontories jutting out into the bering and okhotsk seas the beringian and okhotsk ice sheets are consistent with the results of deep sea drilling in the adjacent north pacific during leg 145 of d v joides resolution

the thermal springs of jordan the thermal springs alongside wadi araba dead sea and jordan valley jordan were investigated and sampled in a comprehensive field study of 2 weeks conventional physicochemical properties were measured in situ dissolved solids and isotopic composition were analyzed two main spring locations on the east side of the dead sea were mapped it became evident that the hottest springs are among the closest to prominent faults some springs are controlled by gas lift jordan s hot springs are described by means of a broad hydrochemical and physicochemical data set and several figures are presented based on their hydrochemistry the thermal springs are classified into four thermal provinces water genesis is discussed several geothermometers are applied to estimate reservoir temperatures observed discharge rate water temperature and isotopic composition are compared with data from the literature although discharge and water temperature are reported to be constant over the last decades groundwater overexploitation led to a shift of the isotopic composition what is documented for the first time in jordan thus the effect of groundwater mining on jordan s hot springs can be stated as a fact