aeolian sediments evolution controlled by fluvial processes climate change and human activities since lgm in the qaidam basin qinghai tibetan plateau abstract aeolian sediments are widely distributed in the eastern qaidam basin qb the main habitats for human in the hyper arid basin during the holocene especially since 3 ka the evolution of aeolian sediments is an important factor for the environmental change and influence human activities and migration however many questions e g when the aeolian sediments start to accumulate what controls their initiation and how their evolution responds to climate change and human activities still need further studies in this study we present a detailed optically stimulated luminescence osl chronology for both aeolian and underlying fluvial sediments from the tiekui desert in the eastern qb to discuss aeolian and fluvial processes climatic changes desert evolution and human activities dating results show that 1 underlying fluvial sediments were formed during 23 9 12 1 ka and the erosion caused by the fluvial process may provide an explanation for the absence of aeolian sediments during and before this period 2 aeolian sediments accumulated from ca 9 8 ka to modern times with loess development from 9 8 ka to 1 6 ka and 1 4 0 7 ka and dune sand accumulation at 1 6 1 4 ka and 0 7 0 ka through the comparison with the local and global palaeoclimatic records we suggest that desert evolution in this region was sensitive to climatic changes induced by the asian summer monsoon detailed local historical records of the past 2000 years suggest that desert evolution was also influenced by human activities

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

thermoluminescence dating of loess and palaeosols from the lantian section shaanxi province china abstract ten samples of loess and palaeosol collected from the upper part of lantian section shaanxi have been dated using the fine grain 4 11 m tl technique palaeodose values were determined by the regeneration method readhead 1982 the tl ages obtained ranged from 2 4 104 years for the upper malan loess l1 to 1 5 105 years for the upper part of loess l2 of the lishi loess fine grain tl dating does not seem to be suitable for the samples older than 150 ka the uncertainty of the tl age estimate especially for the palaeosol sample may be primarily an effect of disequilibrium of the 238u decay chain and of water content variations since deposition of sediments

river terrace systems in north west europe an archive of environmental change uplift and early human occupation abstract staircases of large scale aggradational river terraces are a notable feature of many valleys in the temperate lattitudes particularly in areas beyond the reach of the erosive activities of pleistocene ice sheets it is now recognized that the cyclic fluctuations of climate during the quaternary have driven the generation of terraces through the direct and indirect influence of both temperature and precipitation on fluviatile activity where fossiliferous deposits are preserved within terrace sequences it is often possible to date these and to correlate them with the oceanic record thus providing an important framework for the evidence of environmental change on land middle and late pleistocene terraces in different areas can commonly be seen to have formed in synchrony with glacial interglacial cycles or with longer periodicity megacycles climatic forcing alone is insufficient to cause terraces to form however uplift is also necessary so that terrace sequences can provide a useful record of crustal movement in northwest europe where some of the best known studies of river terrace sequences have been carried out the fluviatile deposits are also an important repository for palaeolithic artefacts from which a record of early human occupation can be reconstructed

uniform postglacial slip rate along the central 600 km of the kunlun fault tibet from 26al 10be and 14c dating of riser offsets and climatic origin of the regional morphology late pleistocene holocene sinistral slip rates on several segments of the kunlun fault in northeastern tibet have been determined these determinations are based on the measured displacement of alluvial surfaces whose surface ages were determined by cosmogenic 2 6 al and 1 0 be dating of quartz pebbles and by 1 4 c dating of charcoal in the west at three sites along the xidatan dongdatan segment of the fault near 94 e terrace riser offsets ranging from 24 to 110 m with cosmogenic ages ranging from 1800 to 8200 yr yield a mean left lateral slip rate of 11 7 1 5 mm yr 1 field observations indicate minimum offsets of 9 12 m this offset when combined with the long term slip rate indicates that great earthquakes m 8 rupture this segment of the fault with a recurrence interval of 800 1000 yr at two sites along the dongxi anyemaqin segment of the fault near 99 e terrace riser offsets ranging from 57 to 400 m with 1 4 c ages ranging from 5400 to 37 000 yr bp yield a minimum slip rate of 10 mm yr 1 at one site the 1937 january 7 m 7 5 and the penultimate earthquakes produced 4 m of left slip and 0 4 m of reverse slip the maximum recurrence interval of earthquakes with such characteristic slip is thus 400 yr farther east near 100 5 e along the maqen segment of the fault the 180 m offset of a lateral moraine emplaced between the last glacial maximum 20 ka and 11 100 yr bp yields a mean slip rate of 12 5 2 5 mm yr 1 the slip rates are constant within uncertainty throughout the 600 km of the kunlun fault that we studied the average slip rate is 11 5 2 0 mm yr 1 extrapolating this rate to the reminder of the fault we conclude that most 80 per cent of the 300 morphological offsets measured in the field or on spot satellite images post date the last glacial maximum most of the terraces we studied were deposited during the humid period of the early holocene optimum 9 5 ka the formation of younger terraces reflects late holocene climate change

quaternary glacial history of the kanas valley chinese altai nw china constrained by electron spin resonance and optically stimulated luminescence datings abstract the chinese altai is located on the northern edge of central asia rich geological records of quaternary glaciations are preserved in this area however the glacial history in the chinese altai has hardly been investigated this study aims to rebuild the regional glacial history in the kanas valley of the chinese altai we present 14 electron spin resonance esr ages and 3 optically stimulated luminescence osl ages from glacial landforms by integrating with ages from previous studies five major glacial advances are identified during marine oxygen isotope stages mis 6 5 4 3 and 2 with ages of 167 0 16 0 123 0 18 0 ka 97 0 19 0 78 0 7 0 ka 76 0 16 0 73 1 6 6 ka 52 1 7 8 34 4 4 2 ka and 28 0 3 3 16 1 1 5 ka respectively the glacial advance during mis 5 is the local last glacial maximum and glaciers became successively more restricted from mis 5 to mis 2 in addition the extensive mis 3 glacial advance in the chinese altai contrasts with the absence of mis 3 glacial advance in the mongolia altai these glacial patterns reflect that precipitation brought by the westerlies might play a primary role on driving glacial advances during the last glacial in the chinese altai this glacial chronology is in reasonable agreement with existing glacial chronologies from other parts of the altai tian shan and pamir indicating similar climate controls on the patterns of quaternary glaciation across central asia highlands

late quaternary glacial history of the karlik range easternmost tian shan derived from 10be surface exposure and optically stimulated luminescence datings abstract the karlik range located in the easternmost part of the tian shan is a key area in reconstructing paleoclimate in central asia but few studies have been conducted to constrain the timing and extent of quaternary glaciations in its highlands we investigated the late quaternary glacial history in the turgan valley on the northern slopes of the karlik range using cosmogenic 10be surface exposure and optically stimulated luminescence osl dating techniques four major glacial events were dated to 0 79 0 59 ka little ice age lia 15 8 1 6 ka lateglacial 37 4 4 0 44 2 4 3 ka marine oxygen isotope stage mis 3 and 60 2 3 3 79 3 5 2 ka mis 4 or older with a pattern of continuously restricted glaciations after mis 4 this glacial chronology is consistent with the studies from other parts of the tian shan the overall pattern of glaciations across the tian shan suggests that change in precipitation brought by the westerlies was the primary factor influencing the timing and extent of glacial advances during the last glaciation however lower temperature of the karlik range affected by the siberian high may counteract the effect of lower precipitation to drive a relatively extensive glacial advance in the easternmost tian shan

cenozoic cooling history and fluvial terrace development of the western domain of the eastern kunlun range northern tibet abstract the growth of the tibetan plateau resulted primarily from cenozoic india asia collision and continued convergence and thus the deformation timing and geomorphic evolution of northern tibet are critical to understanding the dynamics of orogenic plateau growth although previous studies have suggested that the altyn tagh shan and the eastern kunlun range of northern tibet have experienced differential faulting and exhumation history our knowledge of the temporal and spatial distribution of the growth of the northwestern tibetan plateau is still lacking in this study we integrate new geologic mapping low temperature themochronometry 18 apatite fission track ages and optically stimulated luminescence osl dating to provide constraints on the cenozoic cooling history of northwestern tibet and late quaternary fluvial terrace development we focus on where altyn tagh shan structures are juxtaposed against eastern kunlun range structures new fission track cooling ages from one traverse along the aksu river yielded three cooling age domains paleocene miocene and early pliocene with this new knowledge of 12 10 ma initiation of jianxiashan thrusting and exhumation we suggest a refined n s shortening rate of this thrust system of 2 0 2 4 mm yr and strain rates of 8 9 10 16 s 1 thermal history modeling suggests that the study area experienced two broad events including slow cooling through the aft paz since the early eocene and rapid cooling during the late miocene our osl dating results from the aksu drainage reflect two separate processes of aggradation and incision that occurred during the late pleistocene and holocene respectively which are interpreted to result from long term forcing of incision by a constant rate of tectonic uplift modulated by late quaternary climatic variations we interpret that this incision occurred at a rate of 1 mm yr which is faster than exhumation rates inferred from the aft data 0 3 0 5 mm yr these quaternary exhumation rates may reflect faster recent exhumation or uplift associated with the proximal altyn tagh fault in accordance with previous studies we present a refined cenozoic tectonic model for the evolution history of northern tibet the deformation pattern of northern tibet results from clockwise rotation of preexisting weaknesses and transpressional deformation along the kunlun fault and the haiyuan fault

a sequence stratigraphic interpretation of a mudstone dominated succession the lower jurassic cleveland ironstone formation uk microfacies analysis using optical and backscattered electron imagery has been undertaken on 37 samples from the cleveland ironstone formation staithes yorkshire uk four lithofacies were encountered clay rich mudstones silt rich mudstones sand rich mudstones and concretionary carbonates two types berthierine siderite rich ironstones and apatite rich concretionary horizons successive units were found to stack systematically into upward coarsening units on a small 0 1 1 0 m scale upward coarsening and upward fining packages were also found on a larger 1 0 3 0 m scale the small scale upward coarsening units are interpreted to be parasequences while the large scale upward fining and upward coarsening packages are interpreted to be retrogradational and progradational parasequence sets respectively the ironstones occur at the level where the stacking patterns change from being overall progradational to retrogradational while the apatite rich concretionary units occur at the level where the stacking patterns change from being retrogradational to progradational the concretionary carbonates are interpreted to have formed close to at major stratal surfaces the ironstones are interpreted to be either the correlative equivalent of sequence boundaries or part all of the forced regressive system tract while the apatite rich units are interpreted to have precipitated close to at maximum flooding surfaces condensed sections and or major transgressive surfaces

chronology for terraces of the nalinggele river in the north qinghai tibet plateau and implications for salt lake resource formation in the qaidam basin abstract the nalinggele river located in the northern qinghai tibetan plateau is the largest river originating from the northern slope of the eastern kunlun mountains and flowing into the enclosed qaidam basin controversy exists whether the formation of its terraces reflects the history of the plateau uplift or climate changes or both the salt lakes in the enclosed qaidam basin fed by this river bear an unusual world class enrichment of lithium and boron elements which are critical resources for regional economy the concentration of lithium is one of the highest found in brine resource in the world and sourced from the upstream water of the river the chronology of the river terraces is essential to understand the plateau uplift history the regional climate change the evolution of the terminal salt lakes and the process of enrichment of the valuable elements however the age constraint for the terraces of the rivers in the east kunlun mountains is still limited and debated and no dating work has been reported yet for terraces of the nalinggele river five terraces were identified in this river in this study the terraces were dated using quartz optically stimulated luminescence osl dating the results indicate that the osl ages 7 5 ka 9 9 ka 11 3 ka and 13 1 ka of the four terraces t1 t2 t3 and t4 are consistent with geomorphic relationship and that they formed since 13 1 ka and were probably triggered by climatic change rather than by the plateau uplift the sediment of t5 is too coarse to collect osl samples and not dated based on our dating we confirm the previous view that the lithium concentration in the terminal salt lakes should have initiated since 15 13 ka we further propose that the formation of salt lakes and the enrichment of their resources in the qaidam basin should have occurred mainly in interglacial periods e g the holocene a warm and humid period not as previously thought to be in the glacial periods a dry and cold period and that during the glacial periods the basin was mainly under wind erosion

inhibition of dissolution within shallow water carbonate sediments impacts of terrigenous sediment input on syn depositional carbonate diagenesis the early diagenetic chemical dissolution of skeletal carbonates has previously been documented as taking place within bioturbated shallow water tropical carbonate sediments the diagenetic reactions operating within carbonate sediments that fall under the influence of iron rich terrigenous sediment input are less clearly understood such inputs should modify carbonate diagenetic reactions both by minimizing bacterial sulphate reduction in favour of bacterial iron reduction and by the reaction of any pore water sulphide with iron oxides thereby minimizing sulphide oxidation and associated acidity to test this hypothesis sediment cores were taken from sites within discovery bay north jamaica which exhibit varying levels of fe rich bauxite sediment contamination at non impacted sites sediments are dominated by caco3 up to 99 by weight pore waters from the upper few centimetres of cores show evidence for active sulphate reduction reduced so4 cl ratios and minor caco3 dissolution increased ca2 cl ratios petrographic observations of carbonate grains specifically halimeda and amphiroa show clear morphological evidence for dissolution throughout the sediment column in contrast at bauxite impacted sites the sediment is composed of up to 15 non carbonate and contains up to 6000 g g 1 fe pore waters show no evidence for sulphate reduction but marked levels of fe ii suggesting that bacterial fe iii reduction is active carbonate grains show little evidence for dissolution often exhibiting pristine surface morphologies samples from the deeper sections of these cores which pre date bauxite influence commonly exhibit morphological evidence for dissolution implying that this was a significant process prior to bauxite input previous studies have suggested that dissolution driven by sulphate reduction and sulphide oxidation can account for the loss of as much as 50 of primary carbonate production in localized platform environments the finding that chemical dissolution is minor in a terrigenous impacted carbonate environment therefore has significant implications for carbonate budgets and cycling and the preservation of carbonate grains in such sediment systems

late quaternary deposition and incision sequences of the golmud river and their environmental implications abstract golmud river is a large river that originates from the kunlun mountains and drains into the qaidam basin on northern tibetan plateau well developed fluvial terraces in the river valley record complex history of tectonic movements and climate changes in this area the current study investigated fluvial terraces in three cross sections along the river xiaogangou nachitai and sanchahe the ages of the terraces were constrained using optically stimulated luminescence osl and radiocarbon dating methods the results characterize two stages of fluvial landform evolution since the late quaternary the sanchahe deposition stage 82 16 ka and the golmud incision stage 16 ka until now during the deposition stage tectonic movements were relatively stable which drove the deposition meanwhile the enhanced glaciations and precipitation during the last glacial promoted the aggradations in the river valley as well during the incision stage four substages at 16 13 ka 13 11 ka 11 5 ka and 5 ka till now are identified these substages correspond to the incision of the four terraces the incision was mainly driven by the tectonic uplift after the last glacial maximum

climate forcing of fluvial system development an evolution of ideas starting from traditional ideas on the climatic steering of fluvial system dynamics it appears that there are different kinds of climatic influences on system dynamics they vary from direct climatic forcing like peak precipitation to indirect like permafrost and partial forcing like vegetation vegetation or its absence and not directly climate is considered as the main cause of fluvial incision or deposition during temperate or cold periods however other external factors than climate and non climatic factors such as local basin characteristics like subsoil lithology and relief express their effects on the fluvial systems by their role in the energy balance of the river catchment finally internal factors in fluvial system evolution like thresholds and response time should not be neglected

evolution of the northeast german basin inferences from a 3d structural model and subsidence analysis abstract a 3d structural model of the northeast german basin was evaluated with special emphasis on its evolution as an intracontinental depression the study includes investigations on subsidence history and structural setting of the basin thickness evolution and calculated tectonic subsidence volumes of permian to quaternary sediments in the northeast german basin indicate that the subsidence history was related to five stages of basin evolution which differ in their subsidence mechanisms for the initial rift phase in the late carboniferous to early permian a dominant thermal event and subordinate horizontal stresses were indicated by thickness variation evolution and by structural evidence the main part of basin subsidence occurred in a nw se oriented basin in the subsequent phase of thermal relaxation with maximum subsidence from early permian rotliegend to middle triassic muschelkalk from middle triassic the thermal subsidence pattern was superposed by further tectonic events in the middle triassic regional extension led to a reconfiguration of the southern part of the basin where new nne ssw trending troughs rheinsberg and gifhorn troughs developed in the jurassic the northwestern part of the basin was uplifted while in the south the keuper subsiding areas continued to sink and nw se trending depressions related to salt margins became important differentiation continued into cretaceous times when regional compression caused uplift of the southeastern part of the basin and basin margins a final subsidence phase occurred in the cenozoic this was accompanied by intensive salt movement recent basin configuration reflects the superposition of structural elements resulting from different evolution stages the main structural characteristics of the basin are 1 a vertical tectonic zonation in a pre zechstein succession which lacks significant internal structures and a strongly deformed post zechstein succession which was decoupled due to the thick zechstein salt and 2 a marked asymmetry of the basin with a shallow northern slope and a steep bounding fault at the southern margin elbe fault system the northwestern part of the basin shows the structural properties of an intracratonic sag basin with persisting subsidence and with minor salt mobilisation in contrast initial structures in the southeastern part are strongly overprinted by younger tectonic events including middle triassic to jurassic extension late cretaceous inversion and late to post cretaceous salt movements tectonic elements that deform the whole sedimentary succession are restricted to the basin s southern eastern and northeastern margins where salt thickness decreases combined volumetric and backstripping investigations show that 2 3 of the total subsidence was induced by the sediment load and 1 3 was caused by tectonics the tectonic subsidence history varies laterally across the basin while tectonic subsidence curves in the northwestern part of the basin show fast subsidence during the permian and early triassic decreasing exponentially with time subsidence curves in the southeastern part indicate repeated tectonic activity however the tectonic subsidence volume created during permian to late triassic is significantly higher than the tectonic subsidence during younger phases of basin history

cenozoic environmental evolution of the qaidam basin and its implications for the uplift of the tibetan plateau and the drying of central asia abstract a complete cenozoic pollen sequence of the qaidam basin has been constructed with absolute age control the cenozoic environmental evolution of the qaidam basin and its implications for the uplift of the tibetan plateau and the drying of central asia during the cenozoic era is discussed based on the interpretation of the pollen sequence the commencement of eolian deposition in central china and the change of climatic distribution pattern of china the results suggest that in the qaidam basin relatively dry climates prevailed in the eocene oligocene and pliocene pleistocene these dry periods resulted from the effects of a subtropical high pressure zone and the uplift of the surrounding mountains and the tibetan plateau respectively about a 600 km northward drift of western china has probably occurred during the late cenozoic resulting in the eocene oligocene arid climate belt twisting about six degrees of latitude the tibetan plateau reached probably 1500 m elevation by the latest miocene 8 5 ma not as high as it was thought previously the cenozoic environmental evolution of northwest china does not support the idea that the retreat of the paratethys sea played an important role in the late cenozoic drying of central asia at least not in northwest china

ironstones and green marine clays in the dongjeom formation early ordovician of korea abstract in the sino korean north china block the occurrence of ironstone is reported for the first time from the lower ordovician dongjeom formation korea the dongjeom formation comprises much quartzose sediment deposited on the extensive carbonate platform and is composed of three coarsening upward sequences ironstone beds are distributed on the tops of the lower two sequences suggesting that they mark approximately maximum flooding events during the relative lowstand of sea level when the dongjeom formation was deposited extensive weathering in the source areas coupled with higher order sea level rises resulted in the formation of the dongjeom ironstones the dongjeom ironstones include much green marine clays ironstones of the lowest sequence are characterized by glaucony facies and those of the middle sequence by chamosite facies chemical compositions of dongjeom glauconies reveal that they were originally nascent to slightly evolved 3 to 5 k 2 o wt and that they were affected by illitization after burial their immature compositions suggest that glauconies were formed in about 10 3 to 10 4 years or less on the seafloor the substrates for glauconitization are interpreted as detrital mineral grains regressions after glauconitization introduced iron oxides to the green grains eventually forming the iron oxide rich band under the most oxidizing conditions the distribution of glauconies in limited horizons suggests that the dongjeom glauconies are autochthonous in origin chamosites have granular shapes and are mixed with quartzose sand grains suggestive of reworking during storms the dongjeom chamosites were transformed from the precursor berthierines the occurrence of glauconies in correlative horizons in korea and north china may indicate that glauconitization in the host sediments which were deposited in far northern gondwana occurred under the influence of a coeval transgressive event

quaternary and active faulting observed on the 1985 academia sinica royal society geotraverse of tibet active and recent faulting along the main north south road in tibet is dominated by normal faulting occurring on northerly trending planes and by strike slip faulting both of which reflect an east west extension of the plateau normal faulting is prevalent in the southern half of the plateau but we saw no evidence for any major graben in the northern half strike slip faulting on roughly easterly trending structures is m ore prevalent in the northern half but conjugate faulting with right lateral slip on northwesterly trending planes and left lateral slip on northeasterly trending planes is common in the southern half in two areas we also observed components of thrust faulting apparently in association with young strikeslip faulting our most important results are bounds on the rates of slip on the two main strands of the kunlun strike slip fault system which trends east w est through the kunlun range ground moraine containing boulders of pyroxenite is separated by 30 km from the nearest outcrop of such rock implying that amount of displacement in the last 1 5 to 3 m a therefore the average rate of slip during the quaternary period has been between 10 and 20 mm a with a likely value of 13 mm a abundant fresh tension cracks and mole tracks imply continued slip on the main strand the xidatan tuosuohu maqu fault and the likely occurrence of a major earthquake in the last few hundred years consistent offsets of gullies and dry stream channels of about 10 m may reflect slip of that amount during such an earthquake and possible multiple offsets at one site suggest that slip may occur by large displacements of 10 m during infrequent great earthquakes along the other strand the kunlun pass fault offsets of roughly 50 to 150 m of apparently post glacial valleys and of one glacier and its terminal moraine suggest a holocene rate of slip between 5 and 20 mm a and most likely about 10 mm a on this fault these rapid rates of displacement imply that tibet is being extruded rapidly eastward at a rate com parable to the rate at which india is penetrating into eurasia and therefore that at present a substantial fraction of this penetration is being absorbed by the eastward extrusion of tibet

stream response to quaternary tectonic and climatic change evidence from the upper weihe river central china abstract seven terraces of upper weihe river in the longxi basin on the north flank of the qinling mountains are capped with a succession of loess units and paleosols that correlate with the standard marine isotope chronology based on fieldwork and terrace ages which were determined using loess paleosol stratigraphy paleomagnetic optical stimulated luminescence osl and radiocarbon dating the results show that the fluvial fills were deposited during marine oxygen isotope stages miss 22 20 18 16 12 6 4 and 2 respectively whereas terracing occurred during glacial interglacial transitions this in turn points to eccentricity related climatic changes that may have driven recurrent incision and aggradation processes and significantly influenced the formation of staircase terraces of weihe river through the direct and indirect influence of both temperature and precipitation on fluviatile activity on the basis of terrace ages and its heights incision rates were enhanced from 865 to 412 ka 0 27 m ka decreased from 412 to 128 ka 0 09 m ka and increased from 128 ka to present 0 32 m ka

spatial and temporal variations in early diagenetic organic matter oxidation pathways in lower jurassic mudstones of eastern england abstract the lower liassic succession of the east midlands platform eastern england comprises shallow marine mudstones and oolitic ironstones in these sediments temporal and spatial variations in the relative importance of early diagenetic anaerobic organic matter oxidation pathways are recorded the ironstones are stratigraphically condensed and were deposited upon the market weighton swell mws a topographic high in the basin in shallow water and high energy conditions at times of low relative sea level at times of higher sea level stratigraphically condensed mudstones were deposited upon the mws away from the mws stratigraphically expanded mudstones were deposited throughout the lower liassic the ironstones contain berthierine ooids and pore filling cement and siderite pore filling cement with rare pyrite replacing berthierine and siderite mudstones deposited away from the mws contain pyrite as the sole early diagenetic iron mineral contrastingly mudstones deposited upon the mws contain both early diagenetic pyrite and mn rich siderite the presence of berthierine and siderite in the ironstones indicates that sulphide was absent from early diagenetic pore waters and that fe iii reduction dominated anaerobic organic matter oxidation in contrast in mudstones deposited away from the mws the presence of pyrite indicates that sulphate reduction was a predominant pathway for anaerobic organic matter oxidation in mudstones deposited upon the mws the presence of both pyrite and mn rich siderite suggests that both sulphate reduction and fe iii reduction were important during early diagenesis it is proposed that this spatial and temporal variation in relative importance of early diagenetic anaerobic organic matter oxidation reactions was a result of variation in physical sedimentary parameters sediment accumulation rate and energy of environment at times of low net sediment accumulation rates in shallow water high energy environments suboxic diagenesis fe iii and mn iv reduction dominated giving rise to the characteristic berthierine siderite ironstone assemblage at times of higher sedimentation accumulation rates in deeper lower energy environments sulphate reduction dominated leading to pyrite formation at intermediate conditions fe iii mn iv and sulphate reduction were all important leading to precipitation of both pyrite and mn rich siderite

osl chronology and palaeoclimatic implications of aeolian sediments in the eastern qaidam basin of the northeastern qinghai tibetan plateau abstract aeolian sediments are widely distributed in the hyper arid qaidam basin and are good palaeoclimatic records due to limited age control aeolian processes and their relevance to palaeoclimatic change are poorly understood in this study we present 28 optically stimulated luminescence osl ages for both loess 14 samples and aeolian sand 14 samples from 8 profiles in eastern qaidam basin eqb in order to provide a detailed chronology for understanding the timing of aeolian processes and associated environmental conditions we reconstructed the history of aeolian activity in the eqb since deglaciation by combining osl chronologies lithologic stratigraphy and grain size analysis the results indicate that 1 aeolian sand underlying the loess accumulated at ca 12 4 11 5 ka and 10 8 ka but not during the last glacial maximum 2 loess accumulation started at 10 ka and lasted to 0 45 ka at least while most of the loess was deposited during 8 4 5 ka 3 palaeoclimates in the eqb are inferred to be arid during 12 4 11 5 ka relatively humid during 10 8 ka humid during 8 4 5 ka and relatively arid during 4 5 0 45 ka and 4 evolution of aeolian sediments were mainly controlled by effective moisture and also affected by local topography

glacial effects limiting mountain height the height of mountain ranges reflects the balance between tectonic rock uplift crustal strength and surface denudation tectonic deformation and surface denudation are interdependent however and feedback mechanisms in particular the potential link to climate are subjects of intense debate spatial variations in fluvial denudation rate caused by precipitation gradients are known to provide first order controls on mountain range width crustal deformation rates and rock uplift moreover limits to crustal strength are thought to constrain the maximum elevation of large continental plateaus such as those in tibet and the central andes there are indications that the general height of mountain ranges is also directly influenced by the extent of glaciation through an efficient denudation mechanism known as the glacial buzzsaw here we use a global analysis of topography and show that variations in maximum mountain height correlate closely with climate controlled gradients in snowline altitude for many high mountain ranges across orogenic ages and tectonic styles with the aid of a numerical model we further demonstrate how a combination of erosional destruction of topography above the snowline by glacier sliding and commensurate isostatic landscape uplift caused by erosional unloading can explain observations of maximum mountain height by driving elevations towards an altitude window just below the snowline the model thereby self consistently produces the hypsometric signature of the glacial buzzsaw and suggests that differences in the height of mountain ranges mainly reflect variations in local climate rather than tectonic forces

alluvial sequence in the north piedmont of the chinese tian shan over the past 550 kyr and its relationship to climate change abstract a new division of middle and late pleistocene alluvial sequence in the north piedmont of the chinese tian shan based on geomorphologic stratigraphic and chronologic criteria provides a framework for examining their relationship to climate change during glacial interglacial transitions over the past 550 kyr at least four major alluviation episodes occurred within the piedmont along the major river valleys in this region each episode of alluvial fan deposition morphologically correlates with a major river terrace these correlations create a regionally applicable framework for subdivision of the quaternary alluvial sequence in the study area where seven stepped river terraces are defined our new chronology of this fluvial sequence suggests that following intervals of aggradation three highest river terraces and equivalent alluvial fans were abandoned at 530 ka 300 ka and 10 ka respectively paleosols at the base of the loess sequences that directly overlie the older terraces and fans suggest that episodes of aggradation occurred late in the glacial cycles the subsequent incision that caused abandonment stabilization of these terraces and fans occurred near to glacial interglacial transitions a relatively high degree of synchrony in major river incision events across the piedmont despite disruption by several discrete structure zones with asychronous tectonic activities supports the dominant control exerted by climatic conditions on alluvial deposition and terrace creation during the quaternary across the north piedmont of the chinese tian shan

dating fluvial sediments by optically stimulated luminescence selection of equivalent doses for age calculation fluvial sediments are not an ideal material for optical dating because of insufficient or and uneven exposure to daylight prior to burial the equivalent doses for a sample obtained using the single aliquot regenerative dose method usually show a large scatter which may be attributed to many factors here we developed a technique to evaluate the contributions from each factor using this technique relatively well bleached aliquots were identified and the average of their equivalent doses was taken for age calculation

river system reformed by the eastern kunlun fault implications from geomorphological features in the eastern kunlun mountains northern tibetan plateau abstract the eastern kunlun fault is a famous sinistral strike slip fault and the eastern kunlun mountains is one of the most outstanding landmarks on the tibetan plateau comprehensive geomorphic analyses in this study constrain the activation of the eastern kunlun fault and the uplift process of the eastern kunlun mountains the three largest rivers flowing into the qaidam basin the nalenggele river the golmud river and the xiangride river all run across the mechanically strong granitoid belt and precambrian basement in the eastern kunlun mountains and reach the soft mesozoic and cenozoic hoh xil basin meanwhile the drainage patterns and longitudinal profiles of these three rivers are significantly reformed by the eastern kunlun fault the horizontal throws caused by the eastern kunlun fault inferred from drainage pattern 110 km for the golmud river and 90 km for the xiangride river are consistent with the previous estimated strike slip displacement of the eastern kunlun fault horizontal segments occur on river longitudinal profiles induced by the rapid strike slip movement of the eastern kunlun fault all the above evidences imply that the river system of the eastern kunlun mountains was built before the initiation of the eastern kunlun fault meanwhile the distribution of normalized steepness indices ksn shows that rapid rock uplift occurred between the eastern kunlun fault and the northern front of the eastern kunlun mountains

long lasting epeirogenic uplift from mantle plumes and the origin of the southern african plateau 1 we investigate under what conditions the present day long wavelength anomalous elevation 500 m of the southern african plateau can be attributed to mesozoic plume events the anomalous long wavelength topography of the southern african plateau cannot be easily explained by recent heating of the upper mantle as opposed to other areas of the african superswell and geomorphological studies provide few hard constraints on the timing of the uplift a mesozoic origin for the plateau uplift is attractive in that southern africa experienced several large magmatic events in the mesozoic we formulate numerical and scaling models to investigate if plume material ponded beneath cratonic lithosphere in the mesozoic could produce 500 m of present day elevation we find that starting plume heads are ineffective at producing much long lasting uplift because the material spreads into a thin layer tens of km thick the ponded plume material also suppresses secondary convection by having a stable boundary at its base over time heat continues to flow out of the top of the lithosphere and a net imbalance of heat flow in the lithosphere develops resulting in subsidence even after the plume material has cooled to the temperature of the mantle adiabat secondary convection supplies less heat to the lithosphere than is lost upward by conduction the cratonic lithosphere returns to its original thermal structure on a timescale of less than 200 m y even two mantle starting plume heads one at the time of karoo volcanism ca 183 ma and the other at the time of kimberlite eruption ca 80 90 ma in our models cannot produce much 200 m of the present day anomalous elevation however significant uplift can be generated by plume tails provided they linger beneath the lithosphere for 25 30 m y and if the uplift effects of mesozoic plume heads and tails are considered together then it is possible to account for 500 m of present day elevation consequently a mesozoic plume model for plateau uplift in southern africa appears to be a viable model if plume tails delivered heat to the southern african lithosphere over a period of 25 m y or more

a review of glacial sequences of the kunlun pass northern tibetan plateau abstract in the kunlun pass area of northern tibet glacial landforms and sediments provide evidence for three major quaternary glaciations esr and tl dating suggest that they date to 600 700 ka wangkun glaciation 260 ka yakou glaciation and 61 13 ka yuzhufeng glaciation the last glacial each glaciation is less extensive than its predecessor the wangkun glaciation is the largest quaternary glaciation the extent of the glaciers during the wangkun glaciation was 3 5 times larger than that of the present glaciers during the last glacial glaciers advanced several times the moraines near the modern glaciers are probably the products of neoglaciation and little ice age

holocene climate change inferred from stratigraphy and osl chronology of aeolian sediments in the qaidam basin northeastern qinghai tibetan plateau abstract paleoclimatic reconstruction based on aeolian sediments in the eastern qaidam basin qb has been hindered by the limited chronological data here we present 61 optically stimulated luminescence osl ages on the basis of these osl ages and the lithologic stratigraphy we propose the effective moisture index emi for aeolian sediments to reconstruct the effective moisture change based on the emi from twelve sections the effective moisture change moisture sources and relevant mechanisms for paleoclimatic change in the eastern qb are discussed the results indicate that 1 aeolian deposition started at least before 12 4 0 7 ka during the deglaciation the paleosols developed at the early and mid holocene and aeolian sand and loess accumulated at mid and late holocene 2 effective moisture history was hyper arid at 12 8 11 6 ka humid and variable at 11 6 8 3 ka moderately humid and stable at 8 3 3 5 ka and increasingly arid at 3 5 0 ka 3 the effective moisture change was mainly controlled by the asian summer monsoon asm which mainly followed the change of northern hemispheric summer insolation and the westerlies strengthened and increased the aridity in the qb when the asm shrank

holocene incisions and flood activities of the keriya river nw margin of the tibetan plateau abstract fluvial terraces are common in the tectonically active western kunlun mountains wklm region northwestern margin of the tibetan plateau and incision of rivers since 5 ka was attributed to the accelerated uplift of the wklm however it is difficult to evaluate their tectonic or climatic origin without detailed chronology in this study optically stimulated luminescence osl dating was applied to fluvial flood and aeolian sediments on five lowest fluvial terraces 49 m in total along the keriya river and the 21 osl ages from 11 samples revealed the incision processes since the mid holocene especially the fast incision 3 5 0 ka 10 9 mm a during the late holocene this was supported by the climatic background i e increased precipitation from the westerlies and meltwater from frequent glacial advance retreat events as a response to the climatic changes large scale floods were frequent as well e g at 3 5 2 6 0 87 and 0 25 ka which were crucial for the fast incisions on the filling gravels additionally the flood also caused the river s further extension into the taklamakan desert and controlled the evolution of oases in the desert including ancient cities and cultures consequently we suggest that climatic change was important for the incision and formation of cut in fill terraces along the keriya river during the holocene and influences from other factors including surface uplift should not be ignored but were difficult to be evaluated

a 900 k y record of strath terrace formation during glacial interglacial transitions in northwest china the timing of the development of strath terraces with respect to climatic variability remains equivocal previous studies attribute strath terrace formation to glacial or interglacial climates or to variations in sediment and water fluxes that cause lateral erosion followed by vertical incision a chronology of strath terrace formation spanning similar to900 k y has been generated on the basis of loess paleosol couplets and paleomagnetic thermoluminescence and radiocarbon dating of strath terraces in the qilian shan of northeastern tibet repetitive stratigraphic and geomorphic patterns on each terrace indicate that they formed during glacial interglacial transitions long term bedrock incision rates and inferred rock uplift rates appear steady and unrelated to strath formation over the past 900 k y

extension and magmatism in the oslo rift southeast norway no sign of a mantle plume the late carboniferous permian 300 240 ma oslo graben in southeast norway is a classical continental magmatic rift about 8 12 km of mafic magma was produced during a period of 40 60 my the mantle derived rock volume is 3 105 km3 with an average melt production rate of 0 005 km3y 1 initial subsidence and the onset of magmatism preceded graben formation by 5 10 my upper crust extension inferred from dykes and faults is 10 whereas the total crust appears to have been thinned by up to 30 the mantle upwelled with a velocity 2 mmy 1 and suffered conductive heat loss adiabatic melting models therefore do not apply a melting model that takes into account syn rift conductive cooling depth variable stretching and mantle composition suggests that the lithospheric solidus must have been reduced relative to anhydrous peridotite and that mantle thinning should be greater than crustal stretching the lithospheric affinity of primitive rocks the initial subsidence the absence of a hot spot track and the low magma production rate indicate that oslo graben magmatism was not associated with a mantle plume we conclude that the oslo graben was more wet than hot and that extension and magmatism were caused by passive necking of the lithosphere

tectonic subsidence history and thermal evolution of the orange basin the orange basin offshore southwest africa appears to represent a classical example of continental rifting and break up associated with large scale transient volcanism the presence of lower crustal bodies of high seismic velocities indicates that large volumes of igneous crust formed as a consequence of lithospheric extension we present results of a combined approach using subsidence analysis and basin history inversion models our results show that a classical uniform stretching model does not account for the observed tectonic subsidence moreover we find that the thermal and subsidence implications of underplating need to be considered another departure from the uniform stretching model is renewed sub crustal thinning and linked to that uplift in the cenozoic that is necessary to reproduce the observed phases of erosion and the present day depth of the basin the dimension of these events has been examined and quantified in terms of tectonic uplift and sub crustal thinning based on these forward models we predict the heat flow evolution not only for the available real wells but also for virtual wells over the entire study area finally the hydrocarbon potential and the temperature evolution is presented and shown in combination with inferred maturation of the sediments for depth intervals which comprise potential source rocks 2009 elsevier ltd all rights reserved

an introduction to the geological significance of sediment transport and accumulation on the amazon continental shelf in order to understand the formative processes and resulting stratigraphy on the amazon shelf and adjacent shoreline of amapa geological investigations were undertaken as part of a multidisciplinary amazon shelf sediment study amasseds the design of the study provided results of a multifaceted nature integrated with observations in other disciplines focused on sedimentary processes representative of fluctuating conditions on several time scales and broadly distributed on the shelf including regions not investigated in the past on short time scales most muddy sediment is transported northwest of the river mouth from there it moves seaward as fluid mud to cause rapid accumulation of foreset beds and moves northwestward to prograde the northernmost amapa shoreline and to supply sediment to the guianas fluid muds cover the shelf as far northward as 3 5 n and allow strong tides to propagate to shore where tidal currents cause most of the amapa shoreline to undergo erosion today averaged over decades and centuries about half of the amazon sediment discharge accumulates on the adjacent shelf and another significant fraction one sixth leads to accretion of the northernmost amapa shoreline and northwestward bypassing of sediment the remaining sediment is hypothesized to be trapped in deltaplain deposits of the lower amazon river system the foreset region and shoreline represent the two common loci of sediment accumulation that alternate their predominance on time scales of millennia and lead to a two stage progradation of coastal plain and subaqueous deltaic deposits this muddy regressive sedimentation during high sea level is replaced by formation of erosional sand layers during low sea level and transgressive conditions future research in the study area should address important considerations that were delineated by the present study including mechanisms of shoreline accretion the holocene history recorded in topset and coastal plain strata the role in local sedimentation played by the large shoal extending from cabo norte and the entrapment of amazon sediment by the delta plain

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

palaeoclimatic changes in the qinghai lake area during the last 18 000 years abstract multi proxy analysis of a sediment core from qinghai lake including pollen carbonate toc tn and 13 c of organic matter was used to document regional climatic changes during the last 18 000 years climate was very cold and dry before 16 9 cal kyr bp the warm and wet period which began at about 14 1 cal kyr bp culminated at 6 5 cal kyr bp and came to its end at about 4 5 cal kyr bp after that the climate gradually became colder and drier during the transitional period from the late glacial to the holocene the climate fluctuated frequently the short term climatic oscillations including the bolling allerod younger dryas and the cooling event at ca 8 2 cal kyr bp appear to be recorded in the qinghai lake sedimentary record the climatic evolution in the qinghai lake area during the past 18 000 years indicates that solar insolation changes on the ten thousand year scale are the likely driving force of the east asia monsoon

abnormal rb sr ratio in lacustrine sediments of qaidam basin ne qinghai tibetan plateau a significant role of aeolian dust input abstract the rb sr ratio is an important indicator of weathering intensity in both lacustrine and loess sediments because of the inertness of the rb element and the activity of the sr element during the weathering process generally the environmental interpretation of rb sr ratio proxy in lacustrine sediments is contrary to that in the loess paleosol sequence it shows a negative correlation between the rb sr ratio and chemical weathering intensity in lacustrine sediments but shows a positive pattern in the loess paleosol sequence however in this study we investigated the rb sr ratio of a lacustrine core isl1a from qarhan salt lake qsl in eastern qaidam basin qb and found the rb sr ratio indicated a positive correlation with regional precipitation this pattern is similar to that of the loess paleosol sequence rather than the lacustrine sediments according to grain size statistics and the comparison of rb sr ratio with other proxies halite and calcite contents grain size and f values of grain size discriminant function we preliminarily proposed that the abundant input of aeolian materials transported by the strong northwest wind cause these unexpected rb sr ratio fluctuations in the isl1a core the comparison between background rb and sr elemental data of relevant regions and these of the core indicated the aeolian origin of rb sr ratio in the lacustrine sediments and the rb and sr elemental composition probably represents the geochemical characteristics of the dust source area the sr nd isotopic composition indicates that the erosive paleo lake strata in western qb could be the origin of aeolian materials in lacustrine sediments in the qsl as well as the loess deposits in dulan county qinghai lake basin and xining basin the regional correlation between proxies of the isl1a core and other aeolian records also supports the aeolian origin of detrital input in the core finally we propose that the origin of the detrital input must be distinguished before the rb sr ratio is applied as a weathering intensity proxy in lacustrine sediments especially in arid basins

senonian basin inversion and rejuvenation of rifting in africa and arabia synthesis and implications to plate scale tectonics abstract the late paleozoic to tertiary stratigraphic record of much of the african plate reflects the effects of continental rifting and passive margin development several short lived but widespread and tectonically important compressional or wrench dominated events occurred however during the permian to recent evolution of africa we focus here on the best documented of these events which occurred during the late santonian at that time older sedimentary basins mostly ene wsw trending were folded and inverted including some basins along the tethyan margin from morocco to the syrian arc and the intraplate benue southern chad basins and the lugh mandera basin in oman ophiolites were obducted following the santonian tectonism an extensive phase of rifting occurred in central and north africa and northern arabia spanning from campanian to maastrichtian or paleocene times rejuvenation or acceleration of subsidence occurred in several basins located along the tethyan margin along the atlantic and indian ocean margins as well as within the intraplate domain rifting was sometimes accompanied by magmatic activity especially in offshore northern libya and along the indian ocean margin compressional deformations rejuvenated or developed by latest maastrichtian times along the tethyan margin and locally within the intraplate domain one of the most remarkable attributes of the santonian tectonic event which we consider representative of the major trans african stress field changes is the rapidity with which the change was reflected stratigraphically across north and central africa and its short duration the cause of the santonian compressional event is directly linked to the change in poles of rotation for the opening of the atlantic at 83 85 ma the end of the cretaceous normal magnetic quiet zone this was also synchronous with the obduction of ophiolites along the northeast margin of arabia oman the onset of separation between india and madagascar with formation of the mascarene oceanic basin and the development of the european alpine chain we interpret these phenomena as causally related aspects of a global tectonic event the santonian compressional event as well as the campanian maastrichtian rifting event and the end cretaceous compressional event illustrate the critical connection between intraplate tectonic histories and processes occurring at sometimes very distant plate boundaries

rates of fluvial bedrock incision within an actively uplifting orogen central karakoram mountains northern pakistan abstract terrestrial cosmogenic nuclide tcn 10 be surface exposure ages for strath terraces along the braldu river in the central karakoram mountains range from 0 8 to 11 ka this indicates that strath terrace formation began to occur rapidly upon deglaciation of the braldu valley at 11 ka fluvial incision rates for the braldu river based on the tcn ages for strath terraces range from 2 to 29 mm a the fluvial incision rates for the central gorged section of the braldu river are an order of magnitude greater than those for the upper and lower reaches this difference is reflected in the modern stream gradient and valley morphology the higher incision rates in the gorged central reach of the braldu river likely reflect differential uplift above the main karakoram thrust that has resulted in the presence of a knickpoint and more rapid fluvial incision the postglacial fluvial incision rate 2 3 mm a for the upper and lower reaches are of the same order of magnitude as the exhumation rates estimated from previously published thermochronological data for the baltoro granite in the upper catchment region and for the adjacent himalayan regions

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

late quaternary river terrace sequences in the eastern kunlun range northern tibet a combined record of climatic change and surface uplift the kunlun range a reactivated orogenic belt constitutes the northern margin of the tibetan plateau the extreme relief and major landforms of the kunlun range are a product of late cenozoic tectonics and erosion however well developed late quaternary terraces that occur along the northern slope of the kunlun range probably resulted from climatic change rather than surface uplift the terrace sequences formed in thick quaternary valley fills and have total incision depths of 50 60 m optically stimulated luminescence dating was employed to place time controls on the valley fills and associated terraces dating results suggest that periods of significant aggradation were synchronous between different rivers and correspond to the last glacial stage the abrupt change from aggradation to incision occurred between 21 9 2 7 and 16 2 2 ka coincident with the last glacial interglacial transition additional terraces developed during the late glacial period and early to middle holocene based on a broader set of chronological data in northern tibet at least four regional incision periods can be recognized chronological data terrace elevation profiles and climate proxy records suggest that these terracing periods were triggered by cool and or wet climatic conditions a geometric survey of the riverbed longitudinal profile suggests that surface uplift serves as a potential dynamic forcing for long term incision a model is proposed for terrace formation as a response to climatic perturbation in an uplifted mountain range

thermomechanical structure of european continental lithosphere constraints from rheological profiles and eet estimates summary the eet equivalent elastic thickness of the lithosphere is a measure of the integrated lithospheric strength it is directly related to the mechanical thickness and rheology of the crustal and mantle lithosphere we present a comparison of eet estimates and strength profiles based on the extrapolation of rock mechanics data for different parts of the european and eurasian continental lithosphere we discuss the temporal and spatial variations in the mechanical thickness and strength inferred from data for precambrian segments of europe s lithosphere variscan europe and the alpine collision belt this analysis demonstrates important spatial and temporal variations in lithospheric rigidity for orogenic belts and sedimentary basins in eastern and western europe and asian parts of eurasia the eet estimates based on synthetic rheological profiles constrained by newly available geophysical data are consistent with the estimates of eet derived from flexural studies of sedimentary basins forelands and orogenic belts these rheological profiles suggest weakening of the major parts of the european and eurasian continental lithosphere by decoupling of the crustal and upper mantle parts a comparison with the seismicity depth distribution for some selected sites suggests that the intra plate seismicity is essentially restricted to the upper crustal parts of europe s lithosphere providing additional support to the notion of the decoupled lithosphere the presence of intra plate stress fields can explain a significant part of the observed variations in eet estimates within individual thermotectonic age groups a comparison of wavelengths of crustal and lithospheric folding with observations shows these wavelengths to be consistent with estimates of eet inferred from the rheological response of basins and orogens at more moderate levels of intra plate stress

early diagenetic alteration of lateritic particle coatings in amazon continental shelf sediment abstract intense chemical weathering in the tropical amazon river basin strips crustal material of alkali and alkaline earth metals leaving a residue composed predominantly of oxyhydroxides of fe hydroxides of al and cation poor clays this lateritic residue often coats soil particles within the marine environment lateritic particle coatings on sand undergo or have the capacity to undergo rapid reaction and mineralogical alteration 1 at least 20 of fe in coatings can be readily liberated during short term incubation in anoxic sediment 2 coatings change color from red white to green yellow during burial implying fe3 fe2 3 average mg cation content of coatings increases net addition from 1 85 near the amazon s mouth to 4 76 120 km from the mouth or with burial 4 a narrowing of the measured range and a slight increase of si al occurs near mouth to offshore 5 mg fe al layer silicates are probably forming by transformation of kaolinite or other cation stripped material of similar composition in coatings mg uptake by lateritic particle coating reactions assuming comparable involvement of all particle sizes could account for up to 67 of the mg discharged in solution by the amazon river evidence for mg fe al layer silicate formation supports the hypothesis that ancient ironstone minerals formed in some cases by direct alteration of lateritic material

reconstruction of the 30 40 ka bp enhanced indian monsoon climate based on geological records from the tibetan plateau abstract multi proxy records from ice caps lakes and pollen records from the tibetan plateau are used to reconstruct the palaeoclimate during the period 30 40 ka bp lake geomorphological and lacustrine sedimentological studies show that numerous high lake level stands and or freshwater lakes occurred in large areas of western china at this time including over the tibetan plateau where the area contains mostly shallow water and saline hypersaline water lakes under extremely dry conditions of today pollen based reconstruction of tibetan vegetation shows systematic differences from the present alpine steppe forests were shifted ca 400 km further north and the alpine conifer forest extended ca 400 800 km beyond their present western limits variations in 18 o curves from ice cores from the plateau suggest that the temperature was 2 4 c higher and precipitation was 40 to over 100 higher than today all of the evidence consistently suggests the existence of an exceedingly strong summer monsoon climate over the plateau the vigorous evaporation of the tropical ocean surface would also play an important role in promoting the penetration of moisture rich southwest monsoon over the tibetan plateau these climate patterns with strong summer monsoon circulation during the period 30 40 ka bp reflect the 20 ka earth orbital precessional cycle when the tibetan plateau region received greater solar radiation which thus enlarged the thermodynamical contrast between the plateau and the mid south portion of the indian ocean

patterns of landscape evolution on the central and northern tibetan plateau investigated using in situ produced 10be concentrations from river sediments abstract quantifying long term erosion rates across the tibetan plateau and its bordering mountains is of critical importance to an understanding of the interaction between climate tectonic movement and landscape evolution we present a new dataset of basin wide erosion rates from the central and northern tibetan plateau derived using in situ produced 10 be concentrations of river sediments basin wide erosion rates from the central plateau range from 10 1 0 9 to 36 8 3 2 mm kyr slightly higher than published local erosion rates measured from bedrock surfaces these values indicate that long term downwearing of plateau surfaces proceeds at low rates and that the landscape is demonstrably stable in the central plateau in contrast basin wide erosion rates from the kunlun shan on the northern tibetan plateau range from 19 9 1 7 to 163 2 15 9 mm kyr although the erosion rates of many of these basins are much higher than the rates from the central plateau they are lower than published basin wide erosion rates from other mountains fringing the tibetan plateau probably because the basins in the kunlun shan include both areas of low relief plateau surface and high relief mountain catchments and may also result from retarded fluvial sediment transport in an arid climate significantly higher basin wide erosion rates derived from the tibetan plateau margin compared to the central plateau reflect a relatively stable plateau surface that is being dissected at its margins by active fluvial erosion

formation of volcanic rifted margins are temperature anomalies required 1 a major controversy for understanding volcanic margin formation is whether a thermal anomaly in the mantle is required to generate the characteristic thick igneous crust we use a fluid dynamical model of mantle flow that includes feedback from melting on the physical properties of the mantle to study the temporal evolution of volcanic margins during continental breakup we test how weak the mantle must be to induce small scale convection and thus enhance melt production during breakup we find that the mantle reference viscosity required to generate a breakup instability is sufficiently low that an unrealistic time dependence develops in the subsequent oceanic spreading system the viscosity increase associated with dehydration melting can stabilize the system but only at the expense of eliminating the breakup instability an exhaustible reservoir of hot mantle resolves this inconsistency melt productivity increases through a deepening of the mantle solidus while a concurrent increase in buoyancy and a decrease in viscosity in the melting region promote an initial transient phase of small scale convection

landscape and climate on the northern tibetan plateau during the late quaternary abstract palaeoclimate reconstruction on the northern tibetan plateau resulted in a large spectrum of different and partly divergent interpretations for the climate evolution during the late glacial and the holocene in some cases this is caused by incomplete understanding of the geomorphological processes influencing the different proxies used to overcome these limitations and to enhance the understanding of the complex process interactions in a sensitive and highly dynamical environment a detailed analysis of different members of the sedimentary system at lake heihai on the northern tibetan plateau was conducted lake level variations during the late pleistocene were influenced by sediment supply to an alluvial fan this sediment surplus resulted in the temporary blocking of the outflow of lake heihai high sediment supply presumably occurred during or shortly after large glaciations in the kunlun shan the spatial distribution of aeolian sediments revealed a strong relationship to possible source areas this resulted in a spatially heterogeneous distribution of the aeolian sediments furthermore topographic effects have an important influence on the preservation of the sediments aeolian sediments deposited in sheltered positions might not be comparable with other archives with a similar grain size nevertheless deposition of loess during the mid holocene indicates a shift to wetter climate conditions on the northern tibetan plateau this might be caused by the intrusion of the east asian summer monsoon into the area during the late holocene the asian summer monsoon retreated and aeolian sediments were reactivated

late quaternary systematic stream offsets caused by repeated large seismic events along the kunlun fault northern tibet abstract the kunlun fault is one of the largest strike slip faults in northern tibet china in this paper we focus upon the kusai lake kunlun pass segment of the fault to understand the geomorphic development of offset streams caused by repeated large seismic events based on tectono geomorphic analysis of high resolution satellite remote sensing images combined with field studies the results indicate that systematic left lateral stream offsets appear at various scales across the fault zone lateral offsets of small gullies caused by the 2001 m w 7 8 kunlun earthquake vary typically from 3 m to 6 m meanwhile streams with cumulative offsets of 10 m 25 30 m 50 70 m 250 300 m and 750 1400 m have resulted from repeated large seismic events during the late quaternary an average slip rate of 10 1 mm year has been estimated from the lateral stream offsets and 14 c ages of alluvial fan surfaces incised by the streams a three dimensional model showing tectono geomorphic features along a left lateral strike slip fault is also presented the kusai lake kunlun pass segment provides an opportunity to understand the relationship between geomorphic features produced by individual large seismic events and long term geomorphic development caused by repeated large seismic events along a major strike slip fault

geomorphology how tibet might keep its edge the stability of the margins of the himalayan tibetan mountain belt constitutes a puzzle repeated damming of major tibetan rivers by glaciers so controlling river erosion is a possible explanation much attention has focused on how and when the tibetan plateau formed but far less research has been done on the controls on river incision into the plateau itself oliver korup and david montgomery address this issue which also relates to the question of why the tibetan plateau is still there at all despite hosting one of the deepest gorges on earth the plateau edge is extremely well defined and according to widely accepted stream power theory should be heavily dissected by one of asia s most powerful rivers the yarlung tsangp or yarlung zangbo korup and montgomery propose that the southeastern edge of the plateau was preserved in part by the presence of glaciers that were large enough during the holocene to stall aggressive river downcutting along the plateau margin

the influence of large landslides on river incision in a transient landscape eastern margin of the tibetan plateau sichuan china deep landscape dissection by the dadu and yalong rivers on the eastern margin of the tibetan plateau has produced high relief narrow river gorges and threshold hillslopes that frequently experience large landslides large landslides inundate river valleys and overwhelm channels with large volumes 10 5 m 3 of coarse material commonly forming stable landslide dams that trigger extensive and prolonged aggradation upstream these observations suggest that strong feedbacks among hillslope processes channel morphology and incision rate are prevalent throughout this landscape and are likely characteristic of transient landscapes experiencing large increases in local relief in general landslide effects are a by product of rapid incision initiated by regional uplift however over timescales relevant to landscape evolution 10 4 yr large landslides can also act as a primary control on channel morphology and longitudinal river profiles inhibiting incision and further preventing the complete adjustment of rivers to regional tectonic climatic and lithologic forcing we explore a probabilistic numerical model to provide a quantitative framework for evaluating how landslides influence bedrock river incision and landscape evolution the time average number of landslide dams along a river course and thus the magnitude of the landslide influence is set by two fundamental timescales the time it takes to erode landslide deposits and erase individual dams and the recurrence interval of large landslides that lead to stable dams stable gradually eroding landslide dams create mixed bedrock alluvial channels with spatial and temporal variations in incision ultimately slowing long term rates of river incision thereby reducing the total amount of incision occurring over a given length of river a stronger landslide effect implies that a higher percentage of channel length is buried by landslide related sediment leading to reduced river incision efficiency the longer it takes a river channel to incise into a landslide dam and remove all landslide related sediment the more control these events have on the evolution of the river profile and landscape evolution this can be the result of slow erosion of stable dams or a higher frequency of large events

high resolution heat flow density in the lower congo basin 1 heat flow density hfd has been derived in the lower congo basin from 293 conventional probe measurements 424 oil exploration data and about 1 000 000 bottom simulating reflector bsr values each set of data provides independent estimates of temperature gradients associated with specific uncertainties and geographic distributions but a statistical comparison in overlapping domains shows a relatively good consistency in situ conductivity has been measured in conventional surveys and estimated from rock composition and porosity in oil exploration boreholes in the deep offshore measurements and estimates are consistently low and increase significantly toward the shelf domain thermal conductivity does not change significantly in the interval between the water bottom and the bsr and can be estimated from the surface measurements to provide an inference of hfd the combined sets of hfd in the lower congo basin cover the overall domain of the continental margin and a part of the oceanic domain high resolution imaging of the bsr by three dimensional 3 d seismic studies provides in addition good quality nominal resolution of 500 m in the deep offshore at short length scales on the order of kilometers large variations of hfd from 30 to 140 mwm 2 exist above salt diapirs and canyons related to heat refraction on the other hand no small scale effect related to fluid flow has been detected although active venting is known at larger length scale hfd in the deep offshore is different on both sides of the congo submarine channel 54 8 mwm 2 to the north and 48 12 mwm 2 to the south which are also characterized by different basin tectonic styles at the margin scale hfd is significantly different in the oceanic domain 42 3 mwm 2 the deep continental offshore 52 10 mwm 2 and the continental shelf 65 15 mwm 2 a progressive reduction of the radiogenic heat contribution in the extended continental crust is the more likely the cause of these differences mantle heat flow below the continental margin is consequently high compared to that expected 15 mwm 2 for old shields such as congo

the great west african tertiary coastal uplift fact or fiction a perspective from the angolan divergent margin 1 we explore exhumation in the coastal kwanza basin by combining analyses of tertiary hiatuses and apatite fission tracks planktonic biozones show five major hiatuses in the oligo miocene and plio pleistocene between gaps oligo miocene strata accumulated under marine conditions a marine setting refutes the idea of a massively raised coastal plateau in the mid tertiary marine conditions continued until 5 ma fission track data suggest three thermal events 150 ma during rifting and volcanism 100 70 ma during shortening and volcanism and 20 10 ma during exhumation tertiary uplift was spatially highly variable for the kwanza basin we infer that tertiary uplift on the west african margin is indeed a fact but that estimates of uplift timing and size are unreliable when extrapolated to adjoining areas massive uplift 2000 4000 m of the precambrian craton had little structural effect in the outer basin instead minor uplifts on the shelf drove late tertiary deformation on the slope

thermoluminescence dating of sediments abstract the potential for using the thermoluminescence behaviour of sediments for dating them was first recognized by soviet scientists g v morozov and v n shelkoplyas and for over a decade their tl dates obtained from a variety of sediments have appeared in the soviet literature since 1977 tl sediment dates have been published by six additional groups using a variety of methods in this review we describe the principles of tl dating the various methods used and contrast tl dating of sediments with the now well accepted tl dating of pottery we conclude that while tl dating has the potential to solve many sedimentary problems more fundamental research needs to be carried out before such dates should be accepted a set of criteria for acceptable dates is proposed

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago

drainage geomorphic evolution in response to paleoclimatic changes since 12 8 ka in the eastern kunlun mountains ne qinghai tibetan plateau abstract investigation of the geomorphologic evolution of drainage basins can provide insight into the response of mountain basin systems to paleoclimate fluctuations this study investigates the evolution of geomorphic units and their connectivity from upstream piedmont to downstream salt lake since the late quaternary in the golmud river catchment of the eastern kunlun mountains klm the study aims to elucidate the debate over linkages between 1 landform evolution and paleoclimatic change and 2 dynamic geomorphic processes and lake evolution in the lower basin based on geomorphic and sedimentological observations and an optically stimulated luminescence osl chronology we show three main phases of geomorphic processes 1 upstream piedmont alluvial fans and an alluvial delta fan at the salt lake margin have surface sediment osl ages of 12 8 11 4 ka suggesting a valley aggradation stage in which mass periglacial detritus were eroded and redeposited in the drainage basin 2 incision terraces in alluvial valley fills provide ages between 11 4 and 8 8 8 1 6 2 and 4 9 3 9 ka incision is ascribed to the reduction in supply of detritus owing to glacial recession and enhanced precipitation in the early to middle holocene and 3 widely distributed swamp sediments in the distal delta fan date to 3 2 1 8 ka suggesting a wetter stage within the late holocene climatic deterioration loess indicative of aridity was deposited intermittently during the middle to late holocene we reconstructed a wetness index based on wetness scores of drainage geomorphic units which is consistent with published moisture proxies this association implies that 1 landform processes in klm responded well to precipitation fluctuations in indian summer monsoon ism dominant regions indicating their climatic forcing and 2 precipitation variations in the eastern klm have been mainly controlled by ism intensity since 12 8 ka linking the geomorphologic evolution of mountain basin systems to downstream arid basin evolution shows that the periods of fluvial terrace incision early to middle holocene were probably important sources of lake salt mineral enrichment the landscape evolution patterns of mountain basin systems in the eastern klm offer a model for assessing the linkages between geomorphic processes paleoclimatic changes and lake evolution in other arid regions

tibetan plateau river incision inhibited by glacial stabilization of the tsangpo gorge much attention has focused on how and when the tibetan plateau formed but far less research has been done on the controls on river incision into the plateau itself oliver korup and david montgomery address this issue which also relates to the question of why the tibetan plateau is still there at all despite hosting one of the deepest gorges on earth the plateau edge is extremely well defined and according to widely accepted stream power theory should be heavily dissected by one of asia s most powerful rivers the yarlung tsangp or yarlung zangbo korup and montgomery propose that the southeastern edge of the plateau was preserved in part by the presence of glaciers that were large enough during the holocene to stall aggressive river downcutting along the plateau margin a considerable amount of research has focused on how and when the tibetan plateau formed in the wake of tectonic convergence between india and asia1 although far less enquiry has addressed the controls on river incision into the plateau itself2 widely accepted theory3 predicts that steep fluvial knick points river reaches with very steep gradients in the eastern himalayan syntaxis at the southeastern plateau margin should erode rapidly4 driving a wave of incision back into the plateau preservation of the plateau edge thus presents something of a conundrum that may be resolved by invoking either differential rock uplift matching erosional decay5 6 7 or other mechanisms for retarding bedrock river incision8 9 in this region where high stream power excludes the potential for aridity as a simple limit to dissection of the plateau10 here we report morphologic evidence showing that quaternary depression of the regional equilibrium line altitude where long term glacier mass gain equals mass loss was sufficient to repeatedly form moraine dams on major rivers such damming substantially impeded river incision into the southeastern edge of the tibetan plateau through the coupled effects of upstream impoundment and interglacial aggradation such glacial stabilization of the resulting highly focused river incision centred on the tsangpo gorge could further contribute to initiating and accentuating a locus of rapid exhumation known as tectonic anaeurysm6

climatic limits on landscape development in the northwestern himalaya the interaction between tectonism and erosion produces rugged landscapes in actively deforming regions in the northwestern himalaya the form of the landscape was found to be largely independent of exhumation rates but regional trends in mean and modal elevations hypsometry frequency distribution of altitude and slope distributions were correlated with the extent of glaciation these observations imply that in mountain belts that intersect the snowline glacial and periglacial processes place an upper limit on altitude relief and the development of topography irrespective of the rate of tectonic processes operating

late quaternary landscape evolution in the kunlun mountains and qaidam basin northern tibet a framework for examining the links between glaciation lake level changes and alluvial fan formation abstract the qaidam basin in northern tibet is one of the largest hyper arid intermontane basins on earth alluvial fans pediment surfaces shorelines and a thick succession of sediments within the basin coupled with moraines and associated landforms in the adjacent high mountain catchments of the kunlun mountains record a complex history of late quaternary paleoenvironmental change and landscape evolution the region provides an ideal natural laboratory to examine the interaction between tectonics and climate within a continent continent collision zone and to quantify rates of landscape evolution as controlled by climate and the associated glacial and hydrological changes in hyper arid and adjacent high altitude environments geomorphic mapping analysis of landforms and sediments and terrestrial cosmogenic radionuclide surface exposure and optically stimulated luminescence dating serve to define the timing of formation of late quaternary landforms along the southern and northwestern margins of the qaidam basin and in the burhan budai shan of the kunlun mountains adjacent to the basin on the south these dates provide a framework that suggests links between climatic amelioration deglaciation lake desiccation and alluvial fan evolution at least three glacial advances are defined in the burham budai shan of the kunlun mountains on the northern side of this range these occurred in the penultimate glacial cycle or early in the last glacial cycle during the last glacial maximum lgm lateglacial and during the holocene on the south side of the range advances occurred during the penultimate glacial cycle mis 3 and possibly the lgm lateglacial or holocene several distinct phases of alluvial fan sedimentation are likewise defined alluvial fans formed on the southern side of the kunlun mountains prior to 200 ka ice contact alluvial fans formed during the penultimate glacial and during mis 3 extensive incised alluvial fans that form the main valley fills north of the burham budai and extend into the qaidam basin are dated to 30 ka these ages suggest that there was a period of alluvial fan aggradation and valley filling that persisted until desiccation of the large lakes in the qaidam basin post 30 ka led to base level lowering and active incision of streams into the valley fills the continued lateglacial and holocene desiccation likely led to further degradation of the valley fills ice wedge casts in the qaidam basin date to 15 ka indicating significant lateglacial climatic amelioration while holocene loess deposits north of the burham bdudai suggest that aridity has increased in the region since the early holocene from these observations we infer that the major landscape changes within high glaciated mountains and their adjacent hyper arid intermontane basins such as the kunlun mountains and qaidam basin occur rapidly over millennial timescales during periods of climatic instability

climatically controlled river terrace staircases a worldwide quaternary phenomenon a comparison of fluvial terrace sequences from around the world based on data collected as part of international geoscience programme igcp project no 449 has revealed significant patterns river terraces provide important records of uplift which is essential for their formation and of landscape evolution their cyclic formation however almost invariably seems to have been a response to climatic fluctuation sequences in the european core area of igcp 449 which has the longest and most extensive research history have been used as templates for worldwide comparison there is evidence for a global acceleration of uplift at the time of and perhaps in response to the mid pleistocene revolution when climatic fluctuation switched to 100 kyr milankovitch cycles terraces formed prior to this generally consist of wide aggradational sheets that probably each represent formation over several 41 kyr cycles subsequently river valleys became more steeply entrenched and terraces formed in response to the stronger 100 kyr climatic forcing in many cases at approximately one per cycle this paper uses the new data resource to explore differences between records in different climate zones between sequences with variable numbers of middle late pleistocene terraces and between systems in which the all important incision event has occurred in different parts of climatic cycles key records discussed include european examples from the rhine thames somme dniester dnieper don volga and aguas from asia the gediz turkey and orontes syria from north america the south platte and colorado from south africa the vaal and sundays from australia the shoalhaven and from south america the amazon paraguay and tributaries of the colorado and negro

a new osl chronology for dust accumulation in the last 130 000 yr for the chinese loess plateau abstract a sensitivity corrected multiple aliquot regenerative dose protocol has been developed for fine grained quartz osl dating of chinese loess its reliability has been assessed on the basis of the methodology and by dating reference samples of known age close to the transition from the last interglacial paleosol s 1 to the last glacial loess l 1 which corresponds to the marine oxygen isotope stage mis 5 4 transition on the basis of the fine grained quartz osl age estimates for 33 loess samples from the upper part of the luochuan profile a detailed chronostratigraphy of continuous dust accumulation in the past 130 ka has been proposed changes in the accumulation rate occurred during the last glacial period mis 4 to mis 2 unexpectedly high accumulation rates were found in the weakly developed l 1 2 s paleosol of the last interstadial mis 3 rather than in the classic l 1 1 and l 1 3 loess of the cold dry glacial condition mis 2 and 4 the osl ages show some disagreement with the previous numerical chronology for the loess paleosol sequence based on correlation of variations in grain size with sedimentation rate the latter method resulted in an almost constant accumulation rate from 72 to 12 ka

complex rifted continental margins explained by dynamical models of depth dependent lithospheric extension observations from a number of rifted margins e g south atlantic salt basin mid norwegian margin exmouth plateau reveal wide regions of extremely attenuated crust and depositional environments that indicate depth dependent lithospheric extension although the one dimensional thermal kinematic consequences of depth dependent extension are understood no comprehensive process based explanation for the complex style of these margins exists here we present self consistent numerical models of passive margin formation that explain the depth dependent extension the width of the margin its characteristic tripartite nature and why such margins are prone to deposition of evaporites under appropriate climatic conditions some features that are important to reproducing the observed characteristics include decoupling between upper and lower parts of the lithosphere during stretching contrasting wide and narrow extensional styles above and below the decoupling level and progressive focusing of crustal extension toward the rift axis

stratigraphic significance of ooidal ironstones from the cretaceous western interior seaway the peace river formation alberta canada and the castlegate sandstone utah u s a ooidal ironstones form prominent units and an appreciation of their sedimentological and stratigraphic significance is important for the interpretation of sedimentary successions ooidal ironstones from the albian paddy member of the peace river formation alberta canada and the campanian castlegate sandstone of the mesaverde group in colorado have been analyzed the ooidal ironstones are associated with a major sequence boundary and subsequent transgressive surface both are interpreted to have been deposited under conditions of low net sediment accumulation in well oxygenated bottom water conditions with episodic storm events reworking the sediments the paddy member ironstone is interpreted to have been deposited in an estuarine environment and the castlegate ironstone is interpreted to have been deposited in a shallow marine environment both ironstones are dominated by berthierine ooids and grain rimming and pore filling siderite with later ferroan dolomite and calcite in the castlegate ooidal ironstone petrographic geochemical and isotopic evidence coupled with thermodynamic considerations indicates that the ooidal ironstone mineralogy formed during suboxic diagenesis the conditions required for suboxic diagenesis were extensive sediment reworking and slow net sediment accumulation rates we propose that these conditions arose as a result of marine transgression during the initial relative sea level rise following the development of a sequence boundary ooidal ironstone formation ceased once sedimentation rates increased and transgression deepened water depths considerably these results illustrate the association between ooidal ironstones and major stratal surfaces in sedimentary successions and highlights the complexity that early diagenesis at such surfaces can take

quaternary geomorphological evolution of the kunlun pass area and uplift of the qinghai xizang tibet plateau abstract there is a set of late cenozoic sediments in the kunlun pass area tibetan plateau china paleomagnetic esr and tl dating suggest that they date from the late pliocene to the early pleistocene analyses of stratigraphy sedimentary characteristic and evolution of the fauna and flora indicate that from the pliocene to the early quaternary about 5 1 1 ma bp there was a relatively warm and humid environment and a paleolake occurred around the kunlun pass the elevation of the kunlun pass area was no more than 1500 m and only one low topographic divide existed between the qaidam basin and the kunlun pass basin the geomorphic pattern in the kunlun pass area was influenced by the kunlun yellow river tectonic movement 1 1 0 6 ma bp the wangkun glaciation 0 7 0 5 ma is the maximum quaternary glaciation in the pass and in other areas of the plateau during the glaciation the area of the glaciers was 3 5 times larger than that of the present glacier in the pass area there was no xidatan valley that time the extreme geomorphic changes in the kunlun pass area reflect an abrupt uplift of the tibet plateau during the early and middle pleistocene this uplift of the plateau has significance on both the plateau itself and the surrounding area

late pleistocene evolution of salt lakes in the qaidam basin qinghai province china abstract the qaidam basin is a tectonically controlled depression at 2700 m altitude on the northern margin of the qinghai xizang tibet plateau rimmed by the high aljun qilian ranges to the north and kunlun peaks to the south rising above 5000 m the basin floor experiences hyper arid conditions with evaporation precipitation ratios exceeding 100 1 periglacial and glacial conditions prevail on montane peaks with permafrost above 3800 m on the basin floor small waterbodies lie on extensive halite salt flats on the largest the qarhan salt flat 5800 km2 in extent the small lakes dabuxun and taijinier represent contracted remnants of a once expansive water body throughout neogene time a succession of clastic sediments indicates lake depo centre migration from nw to se towards late pliocene evaporitic conditions developed with formation of gypsum halite celestite mirabilite and bloedite continued deformation through pleistocene time has developed a series of nw se trending domes and troughs this setting has continued to exert a controlling influence on basin and brine evolution with progressive development through sulfate to chloride brines as dry conditions intensified in late pleistocene expanded lake conditions qarhan mega lake corresponding to near the 2800 m contour indicate the existence of past climates much more humid than those of today a drilling program has defined the lateral and vertical extent of evaporitic halite deposits freshwater clastics and shell deposits which predate the halite phase indicate humid lacustral conditions until after 40 000 30 000 yr b p desiccation from about 25 000 yr until about 9000 yr b p resulted in deposition of halite to 60 m thick with thin parting muds representing brief returns to more humid environments high lake shorelines with aragonitic ooids surrounding the dry playa kunteyi and high level ostracod rich beach and near shore deposits on xiao qaidam attest to the presence of expanded late pleistocene lacustral conditions on lakes other than qarhan preceding the final evaporite stage clastic sediments associated with the halite are dominated by loessial silts equivalent to the late pleistocene malan deposits of central china simultaneous halite and loess deposition reflect the dry conditions that developed in the qaidam basin during the latter part of the last glaciation and which have persisted ever since the final evolution of brines has resulted in development of extensive potassium rich brines and salts with the mineral carnallite providing the basis for a large potash extraction industry near golmud the hydrologic history documented by the analyses of lake sediments reflects the interaction of tectonic deformation and climatic change in the development of brines to the potash stage

evaluating the role of climate and tectonics during non steady incision of the yellow river evidence from a 1 24 ma terrace record near lanzhou china abstract the competing roles of bedrock uplift and climatic change in the formation of fluvial terraces remain uncertain most of recent studies have attributed terrace formation to climatic changes and held that even in tectonically active settings climate variations control cycles of terrace planation and abandonment based on field investigations of loess paleosol sequences magnetostratigraphy and optically stimulated luminescence osl dating we develop a new chronology for a spectacular flight of terraces along the yellow river near lanzhou china over past 1 24 ma all the terraces are strikingly similar in that they have several meters of paleosol developed directly above fluvial deposits on the terrace treads suggesting that the abandonment of each terrace due to river incision occurs during the transition from glacial to interglacial climates however the ages of terraces cluster in two relatively short time periods 1 24 0 86 ma and 0 13 ma present during the intervening time between 0 86 ma and 0 13 ma terraces either did not form or were not preserved we suggest that this record indicates that rock uplift rates varied through time and influenced terrace formation preservation thus our results demonstrate the utility of deep chronologic records from fluvial terraces for deconvolving the effects of tectonics and climate on fluvial incision

late pleistocene chronology of loess deposition near luochuan china abstract loess near luochuan was sampled for thermoluminescence tl dating simultaneously with magnetic susceptibility measurements to provide the first independent age estimates on a susceptibility record from the loess plateau of china tl age estimates on late pleistocene loess l1 are stratigraphically consistent with no statistical difference in tl ages by the total or partial bleach techniques or by measuring ultraviolet or green wavelengths in the tl analysis loess below the last interglacial soil s1 yielded disparate results and is in many localities in central and eastern china unsuitable for tl dating because of complications of tl saturation and uncertainties in estimating the environmental radiation tl age estimates on the l1 loess are consistent with previously reported tl ages for sites near beijing and xian as well as in general agreement with age models for loess deposition based on paleomagnetics and magnetic susceptibility the convergence of a variety of geochronologic indices indicate that the last major period of loess deposition in central china began 70 000 10 000 yr b p and terminated