long term fluvial archives in the fen wei graben central china and their bearing on the tectonic history of the india asia collision system during the quaternary abstract staircases of large scale river terraces are striking features of the landscape in the fen wei graben adjacent to the qinling orogenic belts central china field investigations indicate that all five river terraces are composed of a basal channel gravel and an overlying thick loess palaeosol succession as chinese loess stratigraphy has been well studied it favours age determination of these terraces and their correlation with the marine oxygen isotope stages our research indicates that the ages of the five terraces are approximately 2 6 1 2 0 9 0 65 and 0 15 ma respectively the formation of these river terraces within the fen wei graben has been attributed to nw se crustal extension associated with left lateral displacement between the north and south china blocks in response to the northward movement of india towards asia since cenozoic time thus the stepped terraces in the fen wei graben reflects elements of the india asia collision systems in which terraces define episodes of accelerated northward movement of india towards asia during the quaternary

magnetostratigraphical dating of loess deposits in china the age of chinese loess deposits has long been disputed biostratigraphical and earlier magnetostratigraphical investigations placed the entire loess formation within the pleistocene the new palaeomagnetic measurements reported here on a bore hole section near lochuan shaanxi province suggest a clearly defined magnetic polarity zonation which extends below the olduvai subchron a late pliocene age of 2 4 myr is assigned to the oldest loess sediments measured the intensity variations of natural remanent magnetization nrm and low field magnetic susceptibility are indicative of climatic changes during loess deposition

rheological differences between archaean and younger crust can determine rates of quaternary vertical motions revealed by fluvial geomorphology surface uplift is widely observed in subaerial regions of continental crust that are distant from plate boundaries often revealed by river terrace staircases with altitude ranges of several hundred metres which typically span the quaternary this characteristic geomorphology has been explained by forcing of flow in the weak lower crustal layer by surface processes non steady state erosion and cyclical loading by ice sheets and sea level fluctuations this study tests this interpretation by showing that analogous river terrace staircases are absent in archaean crust which lacks the weak lower crustal layer found elsewhere

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

evolution of the alluvial fans of the luo river in the weihe basin central china controlled by faulting and climate change a reevaluation of the paleogeographical setting of dali man site abstract the luo river is located in the southern part of the chinese loess plateau and the northern part of the weihe basin in central china in the basin it flows proximal to the site of the luyang wetland core which is an important archive of climate change over the past 1 myr in this region in this paper the contribution of the luo river to the sedimentary record is analyzed by reconstructing the evolution of this river during the middle to late pleistocene it is argued that an alluvial fan of the luo river has contributed to the sedimentary archive until approximately 200 240 ka from this moment onwards the fan became incised and terraces began to form the formation of a new alluvial fan further downstream led to the disconnection of the luo river from the luyang wetland core site we propose that this series of events was caused by the displacement of an intra basinal fault and the resultant faulting forced folding which caused increased relative subsidence and thus increased sedimentation rates at the core site therefore a complete sediment record in the luyang wetland was preserved despite the disconnection from the luo river the chronology of the fans and terraces was established using existing age control u series esr osl pirir 290 and magnetic susceptibility correlation and through correlation of the loess paleosol cover to marine isotope stages based on sedimentological characteristics of the fluvial sequence we suggest that incision of the luo river occurred in two steps small incisions took place at transitions to interglacials and the main incision phases occur at the transition from an interglacial to glacial climate due to the incision basal parts of the oldest luo river alluvial fan are exposed and it is in one of these exposures that the famous dali man skull was retrieved this study shows that the dali man did not live on a river terrace as previously thought but on an aggrading alluvial fan during wet glacial conditions

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

evolution of thermokarst in east siberian ice rich permafrost a case study thermokarst lakes and basins are major components of ice rich permafrost landscapes in east siberian coastal lowlands and are regarded as indicators of regional climatic changes we investigate the temporal and spatial dynamics of a 7 5 km2 partly drained thermokarst basin alas using field investigations remote sensing geographic information systems gis and sediment analyses the evolution of the thermokarst basin proceeded in two phases the first phase started at the pleistocene holocene transition 13 to 12 ka bp with the initiation of a primary thermokarst lake on the ice complex surface the lake expanded and persisted throughout the early holocene before it drained abruptly about 5 7 ka bp thereby creating a 20 m deep alas with residual lakes the second phase 5 7 ka bp to present is characterized by alternating stages of lower and higher thermokarst intensity within the alas that were mainly controlled by local hydrological and relief conditions and accompanied by permafrost aggradation and degradation it included diverse concurrent processes like lake expansion and stepwise drainage polygonal ice wedge growth and the formation of drainage channels and a pingo which occurred in different parts of the alas this more dynamic thermokarst evolution resulted in a complex modern thermokarst landscape however on the regional scale the changes during the second evolutionary phase after drainage of the initial thermokarst lakes were less intense than the early holocene extensive thermokarst development in east siberian coastal lowlands as a result of a significant regional change to warmer and wetter climate conditions

magnetostratigraphic age and monsoonal evolution recorded by the thickest quaternary loess deposit of the lanzhou region western chinese loess plateau abstract the loess paleosol sequences of the chinese loess plateau clp are major paleoclimatic archives which document the evolution of the east asian monsoon eam and changes in the northern hemisphere ice sheets during the quaternary glacial interglacial cycles however the mechanisms regulating the trend of eam variations on a tectonic scale are unclear the loess deposits of the western clp which have a close relationship with tectonics and climate are much better suited to exploring these mechanisms than those of the central clp however studies of long term eam evolution from the western clp have been hindered by the lack of long accurately dated sequences with high sediment accumulation rates here we address this problem via high resolution magnetostratigraphic magnetic susceptibility and grain size analyses of a 416 2 m long drill core located at xijin village near lanzhou paleomagnetic dating indicates that the basal age of the xijin loess is 2 2 ma the and grain size records reveal that the east asian summer monsoon easm and east asian winter monsoon eawm strengthened synchronously at 1 24 ma subsequently during interglacial periods the easm began to penetrate and then dominate in the lanzhou region this was followed by two stepwise uptrends commencing at 0 87 and 0 62 ma which resulted in an increasingly moist interglacial climate in the region we suggest that the uplift of the tibetan plateau was largely responsible for these three stepwise enhancements of the easm overall however the long term trend of strengthening in eawm in the area may have been primarily caused by long term global cooling from the late pliocene onwards

the santa rosa event 40ar 39ar and paleomagnetic results from the valles rhyolite near jaramillo creek jemez mountains new mexico the jaramillo event was originally defined by doell and dalrymple in 1966 on the basis of k ar ages from sanidine in the normally transitionally and reversely magnetized rhyolite domes named cerro del abrigo cerro santa rosa i and cerro santa rosa ii respectively that erupted following collapse of the archetypal valles caldera new mexico we have collected new paleomagnetic data from the three domes and new 40 ar 39 ar laser fusion and furnace incremental heating experiments on sanidine crystals from the cerro santa rosa i rhyolite step wise alternating field and thermal demagnetization techniques applied to 52 samples from seven sites indicate that the original paleomagnetic results of doell and dalrymple science 152 1966 1060 1061 are valid cerro del abrigo is normally magnetized whereas the santa rosa i dome is transitional with an inclination of 363 toward the east and the santa rosa ii dome is of reversed polarity twenty five laser fusion experiments on sanidine crystals from the the cerro santa rosa i dome together with the saddle shaped spectrum obtained by incrementally heating the sanidine in a furnace reveal that this rhyolite contained a small but significant component of excess argon prior to eruption our preferred age of 936 8 ka 2c for the santa rosa i rhyolite is based on the concordant laser fusion isochron and incremental heating plateau ages this age is significantly older than was inferred on the basis of earlier laser fusion 40 ar 39 ar results that suggested a trapped component characterized by a 40 ar 36 ar ratio lower than the atmospheric value of 295 5 our new age distinguishes the santa rosa i dome by 65 kyr from the termination of the jaramillo normal subchron 1001 10 ka and by 37 kyr from basaltic lavas at haleakala and tahiti which record the kamikatsura event 899 6 ka moreover this determination is a factor of three more precise than the best previous estimate for a proposed geomagnetic event in this time period the cerro santa rosa i rhyolite dome once intimately linked with the end of the jaramillo event and the acceptance of plate tectonic theory now defines a highly resolved feature the santa rosa event in a terrestrial geomagnetic reversal time scale that is consistent with the global record of magnetic field intensity from marine sediments fl 2002 elsevier science b v all rights reserved

alluvial terrace systems in zhangjiajie of northwest hunan china implications for climatic change tectonic uplift and geomorphic evolution abstract this paper reports the latest details from two comprehensive investigations of alluvial terrace sequences in zhangjiajie northwest hunan province china seven alluvial terrace units along the maoxi river and four terrace sequences along the suoxi river record significant regional geomorphic history rates of regional quaternary uplift and climate change are reconstructed using topographic and stratigraphic evidence from terrace and adjacent cave deposits along with electron spin resonance esr and thermo luminescence tl dating controls between 928 ka and 689 ka the time averaged uplift rate or incision rate was 0 16 m ka the rate decreased to 0 05 m ka between 689 ka and 347 ka and then increased slightly to 0 11 0 14 m ka after 347 ka the inferred incision rate increased roughly from 0 21 0 32 m ka to 0 51 m ka from the late pleistocene to present the seven alluvial phases t7 t1 and their associated chronology are consistent with climatic variations at regional and or global scales suggesting that these terraces represent climate driven pauses imprinted atop the record of long term tectonically induced incision by rivers insights from these alluvial terrace staircases and cave features indicate that the spectacular sandstone peak forest landscape of the study area has emerged since the middle period of the middle pleistocene

stacked 2 6 ma grain size record from the chinese loess based on five sections and correlation with the deep sea δ18o record 1 this study aims to establish a stacked climate record of the quaternary period from the chinese loess sequence and to address the forcing mechanisms for the regional climate history of the loess plateau by correlating the stacked record with a composite 18o record in deep sea sediments a total of 18 352 samples were obtained from five loess sections located at baoji lingtai jingchuan puxian and pingliang in the southern and middle loess plateau these yielded high resolution grain size records between section correlation of these shows that although small depositional hiatuses are present in places within a single section most parts of the sections display near continuous dust deposition throughout the quaternary the grain size records were tuned simultaneously to the theoretical variations in obliquity and precession of the earth s orbit the grain size records plotted on their orbital timescales were then averaged to form a stacked loess grain size time series termed the chiloparts record this resolves most of the orbital timescale paleoclimate events buried in the loess soil sequences of the southern and middle loess plateau and can be used as a regional archive of the pleistocene climate history in the loess plateau comparison of the chiloparts record with a composite marine 18o record shows that for the past 1 8 ma the loess paleosol record can be correlated almost cycle by cycle with the marine record several discrepancies in the climatic events between the two records have also been identified implying that regional forcing mechanisms may have played a part in the climatic evolution of the chinese loess plateau

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

spatial and temporal analysis of water chemistry records 1958 2000 in the huanghe yellow river basin 1 the chemistry of major dissolved ions ca2 mg2 na k hco3 so42 cl and dissolved silica sio2 in the river water of the huanghe yellow river china was studied from historical records at 100 stations in the drainage basin for the period 1958 2000 not all the parameters were continuously monitored during the entire period this river system 750 000 km2 presents an exceptional temporal and spatial water chemistry variability compared to other major rivers the total dissolved solid tds concentration of the huanghe varied over 2 to 3 orders of magnitude throughout the basin with a median tds concentration of 452 mg l which is about 4 times the world spatial median value wsm in particular the concentrations of na k so42 and cl were 10 20 times higher than in other major world rivers similar to the changjiang yangtze river and many other himalayan rivers the tds at a given station is seasonally variable and inversely related to river runoff with a variation factor less than 2 0 despite a water dilution of fourfold to fivefold in the summer flood season in addition to chemical weathering of sedimentary rocks evaporation and fractional crystallization were found to be the major natural process controlling the major element chemistry of the huanghe owing to the abundance of loess and clastic rocks under arid and semiarid climates a persistent increasing trend from year to year has been observed in the concentrations of tds and all the salts except for hco3 at all main channel stations except for the uppermost lanzhou the rate of increase in the tds concentration was the highest in the middle reaches 10 52 mg l yr 1 at toudaoguai and remained to be unusually high in the lower reaches 5 5 mg l yr 1 at stations luokou and lijin the increasing trend coincided with a significant decrease in water discharge at most of the main channel stations in the past 40 years and is attributed to increasing regulations of reservoirs and intensive water withdrawal for irrigation and diversions as well as many other anthropogenic processes despite the increasing trend in tds concentrations the seaward tds flux to the sea by the huanghe has decreased dramatically from more than 20 109 kg yr in the 1960s to less than 10 109 kg yr at present due to the sharp decrease in water discharge sometimes completely dried up in the lower reaches of the river the significant decreases in sea ward fluxes of water and dissolved salts are expected to have profound physical ecological and socio economic impacts on the lower reaches of the river the coastal areas and the bohai sea

the environmental effects of the uplift of the qinghai xizang plateau the intense upheaval of the qinghai xizang plateau took place 2 ma bp the terraces of the yellow river in the lanzhou region and its upper sections provide a record of the uplift of the plateau the interaction of glaciation cycles resulting from climatic changes and pulsating tectonic upheavals are both involved in the record of environmental change across the plateau three tectonic climatic events which are termed respectively the qinghai xizang movement the huanghe yellow river movement and the gonghe movement occurred 2 1 5 1 0 and 0 15 ma bp the upheaval of the qinghai xizang plateau was the trigger mechanism of the asian monsoon the loess plateau was formed in the monsoon triangle of east asia human origins and human evolution may have been stimulated by the uplift of the qinghai xizang plateau

rapid fluvial incision and headward erosion by the yellow river along the jinshaan gorge during the past 1 2 ma as a result of tectonic extension abstract in north china the ordos block located northeast of the tibetan plateau is regarded as a stable craton surrounded by the yinchuan graben to the west the hetao graben to the north and the fenwei graben to the southeast the major tectonic structure around this block in the cenozoic reflects intensive extension as a response to the eastward extrusion of the tibetan plateau intermittent downcutting by the yellow river starting from the planation surface level on the ordos block and penetrating the bedrock resulted in the formation of the jinshaan gorge a series of well preserved fluvial terraces was identified along this gorge providing new insight into the far field effect of the eastward extrusion of the tibetan plateau magnetostratigraphic records from the planation surface and uppermost terrace suggest that this gorge has been entrenched over its total length in the period from 3 7 to 1 2 ma a preliminary explanation is proposed here for the morphological evolution of the yellow river in the jinshaan gorge on the basis of terrace correlation between seventeen geomorphic sections multiwave headward erosion initiated by the yellow river along this gorge has been reconstructed this process may be attributed to the lowering of the base level the fenwei graben this graben has been formed during the cenozoic as the tibetan plateau extruded eastwards resulting in accelerated ground subsidence a combined approach of magnetostratigraphy pedostratigraphy and optically stimulated luminescence osl was adopted to establish a new geochronology for terraces in the gorge at 1 2 ma 1 1 ma 787 ka 412 ka 245 ka 128 ka 29 ka and 11 ka these ages provide an excellent framework for calculating the extension within the fenwei graben the average incision rate appears to be enhanced significantly since 412 ka indicating a rapid extension within the fenwei graben during this time

magnetostratigraphic dating of river terraces rapid and intermittent incision by the yellow river of the northeastern margin of the tibetan plateau during the quaternary up to 23 paleosols have been identified in loess sequences that overlie fluviatile sediments on seven terraces of huang he the yellow river and daxia he in the linxia basin at the northeastern margin of the tibetan plateau the magnetostratigraphic record in the oldest sequence appears to be fairly complete and spans the entire quaternary it includes evidence for the jaramillo and olduvai normal polarity subchrons within the matuyama chron as well as the cobb mountain and stage 54 formerly gilsa events age constraints within the brunhes are provided by 14c and thermoluminescence optical stimulated luminescence dating the magnetostratigraphic chronology of the quaternary sediments indicates that terraces were formed at about 1 66 1 4 1 1 0 6 0 12 0 055 and 0 01 ma the terraces may represent climatically induced pauses in long term tectonically induced incision by the rivers on the basis of terrace heights and ages incision rates were highest from 1 66 to 1 4 ma 1 m kyr decreased from 1 4 to 0 12 ma 0 1 m kyr and increased from 0 12 ma to present 0 75 m kyr if river incision is attributed solely to uplift of the tibetan plateau then this uplift appears to have been rapid as well as intermittent following the first evidence of the existence of huang he in this area at about 1 75 ma however the effects of uplift cannot be fully separated from incision caused by changes in climate copyright 1997 by the american geophysical union

drainage evolution of the heihe river in western hexi corridor china derived from sedimentary and magnetostratigraphic results abstract the uplifting of the tibetan plateau has significantly changed the environment in surrounding areas by delivering abundant water and sediment the heihe river draining the qilian shan in the ne tibetan plateau acts as a dominant sediment routing system from the uplifted ne tibetan plateau to the hexi corridor as well as the badain jaran desert reconstructing the evolution of the heihe river could provide evidence for the birth of the badain jaran desert and enhance the understanding of sedimentary basin fill and the relationship between tectonism drainage evolution and environmental changes with this aim two parallel cores dwj and xkjd with depths of 140 and 68 2 m respectively were drilled in the floodplain of the heihe river the facies analysis of the sedimentary sequences from the drilling cores showed that the sedimentary environment changed from the lake system to a delta system and finally to a fluvial system at the depths of 133 3 and 68 m respectively the magnetostratigraphic results revealed ages of approximately 1 75 and 1 12 ma for the dwj and xkjd cores respectively and an age of approximately 1 1 ma for the transition from delta to fluvial environment in both the cores the change of the sedimentary environment at approximately 1 1 ma was caused by the formation of the integrated heihe river the integrated heihe river may have developed via mechanisms such as river capture and river diversion due to the uplifting of the north qilian shan and the longshou shan the present study suggested that the formation of large inland rivers such as the heihe river and the shiyang river in nw china played an important role in the evolution of the deserts and the loess plateau

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

active faulting mountain growth and erosion at the margins of the tibetan plateau constrained by in situ produced cosmogenic nuclides abstract the india asia collision zone is a key area for understanding continental plateau formation and mountain building two fundamental questions in this context are how the northeastward motion of india is partitioned between strike slip and thrust faults and how mountain building is counteracted by erosion cosmogenic nuclides allow us to address these questions because they provide age constraints on tectonically offset landforms and constraints on erosion rates after considerable debate on whether or not major strike slip faults move at high rates of up to 20 30 mm yr and absorb most of the continental deformation it now appears that the three largest faults altyn tagh haiyuan kunlun have millennial slip rates of no more than 8 13 mm yr consistent with rates of elastic strain accumulation determined by geodetic methods furthermore a significant portion of the lateral slip on these faults is transferred to thrust faults within the collision zone both observations indicate that the eastward tectonic escape of material along these faults is less important than often assumed with respect to mountain building and erosion cosmogenic nuclide studies show that thrust faults at the northeastern and eastern margins of tibet qilian shan longmen shan have vertical slip rates of 0 3 to 2 mm yr while catchment wide erosion rates vary from 0 02 to 1 0 mm yr with high relief areas eroding significantly faster than the plateau interior and growing mountains in the foreland the deeply incised regions have apparently reached an erosional steady state in which rock uplift is balanced by erosion river terraces at active mountain fronts document repeated changes between sediment deposition and fluvial incision during the quaternary incision and terrace formation occurred predominantly at glacial interglacial transitions but also during interglacial periods hence flights of terraces at the fault bounded mountain fronts record the interplay between sustained rock uplift and a temporally variable climate

cyclic quaternary alluviation and terracing in a nonglaciated drainage basin on the north flank of the qinling shan central china abstract pleistocene alluvial terraces of the nonglaciated ba river drainage basin on the north flank of the qinling shan are capped by a succession of loess units and paleosols that correlate with the standard marine isotope chronology and are used to date the subjacent alluvial gravels alluvial fills were deposited during isotope stages 2 6 8 12 and 16 whereas terracing occurred during interglacial stages 1 5 7 11 and 15 the apparent absence of terraces dating to stage 14 and stage 4 may be due to the lesser intensity of these glaciations compared to that of stage 2 although disruption of the alluvial regime by local tectonism is a likely alternative for the lack of a stage 4 terrace a stage 10 terrace was not positively identified from available exposures its possible absence could be related to post stage 12 uplift aggradational episodes correlate with glaciations and loess deposition whereas degradational episodes correlate with interglaciations or interstades and soil formation implying that climate is the primary control on quaternary paleohydrology this in turn points to variations in the earth s orbital geometry as the major factor that modulates both climate and ultimately the fluvial system in the qinling shan in this region glaciations were dominated by a cold dry winter monsoon climate whereas during interstades and interglaciations a warmer and wetter climate prevailed implying strengthening of the summer monsoon both the loess paleosol and the alluvial records are consistent with climate model simulations spanning the last 18 000 yr that show a change from cold dry conditions during the last glacial maximum to a climate warmer and wetter than present during the first half of the holocene

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

age and palaeoclimatic significance of the loess of lanzhou north china extending in a broad arc that abuts the sandy non gobi deserts the loess plateau of northern china1 3 is one of the most massive accumulations of loess in the world the loess sequence is typically characterized by an alternation of silty or sandy loess with more clay rich palaeosols these alternations in conjunction with their enclosed faunas and distinctive mineralogies have been interpreted as reflecting pleistocene glacial interglacial cycles3 8 because it holds implications for the climatic and anthropological history of china9 10 the definition of a reliable chronological framework for loess deposition is of great interest recent palaeomagnetic studies4 5 have indicated that loess deposition in shaanxi province commenced 2 4 myr ago to assess the synchrony of loess accumulation across the loess plateau we have dated a 330 m thick loess sequence near lanzhou gansu province the magnetostrati graphical results reported here indicate that the base of this loess succession dates from 1 3 my r ago this young age in comparison to the shaanxi sequence is attributed to uplift along the northern fringe of the tibetan plateau11 that precluded early pleistocene loess preservation in this mountainous region palaeosols in the basal loess occur on average once every 25 kyr suggesting that climates conducive to soil forming events may have been modulated by orbital precession in the early pleistocene

dating of erosion surface and terraces in the eastern qilian shan northwest china the actively deformed foreland of eastern qilian shan mountains contains well preserved geomorphic features such as erosion surfaces river terraces and tectonically uplifted alluvial fans providing suitable archives for research on regional tectonic activities and palaeoclimatic changes these geomorphic surfaces are well dated by using a combination of magnetostratigraphy electron spin resonance thermoluminescence infra red stimulated luminescence radiocarbon dating and correlation with the well established loess palaeosol sequences of china our results show that the erosion surface formed about 1 4 ma ago and the age of river terraces is 1 24 ma 820 860 ka 780 ka 420 440 ka 230 250 ka 140 ka 60 ka and 10 ka respectively valley incision rates of e 0 09 0 25 m ka 1 have been identified the repetitive stratigraphic and geomorphic pattern of these terraces indicates the fluvial sedimentation incision cycles are tightly associated with the 100 ka glacial interglacial climatic cycles copyright c 2006 john wiley sons ltd

late quaternary downcutting rates of the qianyou river from u th speleothem dates qinling mountains china abstract dating deposits in caves formed by rivers may yield insight into rates and processes of bedrock incision three cave passages at different levels have developed in the walls of the qianyou river valley in the qinling mountains south of the city of xian china twelve speleothem samples near the position of palaeowater tables in three cave passages are dated by the 230th dating method the results show that the river cut down at the rate of 0 23 0 02 mm yr from 358 000 38 000 to 247 000 28 000 yr ago 0 19 0 03 mm yr from 247 000 28 000 to 118 000 19 000 yr ago and 0 51 0 08 mm yr from 118 000 19 000 yr ago until today these fall very close to the glacial interglacial transition following marine oxygen isotope stages 10 8 and 6 respectively the increase in downcutting rates during the interglacial period is consistent with warm wet weather increasing rates of erosion this may lead us toward an underlying mechanism for modulating incision that is not in a direct response to the presence of headwater glaciers

hydrochemistry and controlling mechanism of lakes in permafrost regions along the qinghai tibet engineering corridor china abstract lakes are the main water resource for migrating animals and herdsmen in permafrost regions along the qinghai tibet engineering corridor qtec and play a crucial role in regulating the balance between regional surface water and groundwater hydrochemical properties also affect the soil environment ecological conditions and hydrological cycle in this study 127 water samples were collected from lakes to analyze hydrochemistry characteristics the results are discussed in the context of relationships between water chemistry and local conditions including climate topography and geology the results showed that 43 3 of lakes are fresh 19 7 are brackish 18 9 are saline 17 3 are brine and only 0 8 are bitter the dominant cation is na followed by mg2 ca2 and k the dominant anion is cl followed by so42 and hco3 in the northern section of study region whereas ca2 na and hco3 are the dominant ions in the lakes of the southern section the higher concentrations of carbonate in the southern lakes reflect contributions from groundwater discharge in contrast the higher concentrations of sodium chloride and sulfate in the northern section indicate that they are dominated by the interaction of evaporates additionally cation exchange precipitation and dissolution have also modified the distribution of hydrochemical compositions thermokarst processes in particular have induced changes in the hydrochemistry of lake waters in the permafrost regions of the qtec in that the ion concentrations are closely related to ground ice content in the context of persistent climatic warming and steadily increasing anthropogenic activities the salinity of lakes along the qtec is likely to increase in the future

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

influence of climate change on saline lakes of the tibet plateau 1973 2010 abstract levels and surface areas of saline lakes are indicators of climate change and climate variability the surface extents of 93 saline lakes with areas larger than 20 km2 excluding dry saline lakes on the tibet plateau were delineated from landsat images obtained in 1973 1977 1989 1992 1999 2001 and 2008 2010 based on remote sensing spatial analysis techniques and gis the dynamic changes of the saline lake surface areas from 1973 to 2010 were analyzed the total surface area of these saline lakes increased especially since around 2000 and the total surface area increased by 47 during 1973 1977 to 2008 2010 during 1973 1977 to 1989 1992 saline lakes with decreased areas were mainly distributed in the northern and middle parts of the tibet plateau whereas those in other places tended to expand since around 2000 nearly all the saline lakes expanded mean annual temperature mean annual maximum temperature mean annual minimum temperature annual precipitation and evaporation on the tibet plateau were analyzed over the past four decades the climate has become warmer and wetter rising temperature and dropping evaporation are two dominant factors responsible for saline lake expansion the salinity of many saline lakes decreased during this climate warming new analyses included factors responsible for the changes i e tectonics climate lake basin shape glaciers catchments open or closed systems and human activities

climatic and tectonic controls on strath terraces along the upper weihe river in central china abstract the weihe river in central china is the largest tributary of the yellow river and contains a well developed strath terrace system a new chronology for the past 1 11 ma for a spectacular flight of strath terraces along the upper weihe river near longxi is defined based on field investigations of loess paleosol sequences and magnetostratigraphy all the strath terraces are strikingly similar having several meters of paleosols that have developed directly on top of fluvial deposits located on the terrace treads this suggests that the abandonment of each strath terrace by river incision occurred during the transition from glacial to interglacial climates the average fluvial incision rates during 1 11 0 71 ma and since 0 13 ma are 0 35 and 0 32 m ka respectively these incision rates are considerably higher than the average incision rate of 0 16 m km for the intervening period between 0 71 and 0 13 ma over all our results suggest that cyclic quaternary climate change has been the main driving factor for strath terrace formation with enhanced episodic uplift

geomorphological and sedimentological comparison of fluvial terraces and karst caves in zhangjiajie northwest hunan china an archive of sandstone landform development the zhangjiajie sandstone peak forest geopark zhangjiajie world geopark of northwest hunan china hosts a well preserved sequence of fluvial terraces and karst caves in this contribution a comparative study of fluvial terraces with karst caves along the middle lower suoxi river in zhangjiajie world geopark is presented to improve the understanding of the development of striking sandstone landscape in the upper suoxi river by integrating geomorphological sedimentological and geochronological techniques the possible correlation between fluvial terraces and karst caves as well as their climatic and tectonic implications is investigated the available electron spin resonance and thermo luminescence numerical ages coupled with morphostratigraphic analysis indicate that aggradation of fluvial terrace levels occurred at ca 347 34 ka t4 104 45 8 88 to 117 62 9 99 ka t3 60 95 5 18 ka t2 and holocene t1 followed by the stream incision fluvial terrace levels t4 to t1 correlate morphologically with the karst cave levels l1 to l4 yet the proposed chronology for the fluvial terrace levels is a bit later than the chronological data obtained from karst caves in northwest hunan where a unique sandstone peak forest landscape was extensively developed the fluvial terrace sequences as well as the cave systems are the important archives for studying the evolution of the sandstone landscape the beginning of the sandstone landscape development must be earlier than the aggradation of the fluvial terrace t4 allowing this unique landscape to occur in the middle pleistocene

differential impact of small scaled tectonic movements on fluvial morphology and sedimentology the huang shui catchment ne tibet plateau abstract the aim of this paper is to investigate the morphological implications of the interplay between tectonic movements at different rates timescales and spatial extent in a catchment of intermediate size the huang shui river a main tributary of the yellow river in the ne tibet plateau river incision started from a peneplain like surface that developed in post miocene pliocene times at the end of the tertiary a general tectonic uplift of the tibetan plateau initiated river incision this general uplift also caused local fragmentation of the huang shui catchment into blocks kilometers or maximally a few tens of kilometers of local extent that have subsided and or uplifted relative to one another fluvial deposition of 30 m in the subsiding blocks contrasts with erosion and formation of gorges in the uplifted blocks incision into the former peneplain was not continuous but a staircase of terraces developed under climatic influences terrace deposits are sometimes capped by interglacial soils or soil derived material apparently terrace incision occurred at the transition to the next cold period the different rates of uplift and subsidence of the individual blocks resulted in the simultaneous development of erosion and accumulation terraces of different sizes within the same catchment even within the same tectonic block this makes it impossible to connect the terraces of the different blocks except for the three youngest terraces representing the last 300 000 years thus illustrating the uniform tectonic history of the catchment since that time

an obliquity controlled early pleistocene river terrace record from western turkey investigation of the pleistocene sequence of the gediz river western turkey has revealed a record of early pleistocene river terraces eleven terraces spanning the interval from 1 67 to 1 245 million years ago mis 59 37 are preserved beneath basaltic lava flows the high number of terraces over this short time period reflects high frequency sedimentation incision cycles preserved due to the fortuitous combination of relatively high uplift rates 0 16 mm yr 1 and progressive southwards valley migration comparison of this record with odp967 from the eastern mediterranean basin suggests a link between the production of terraces and obliquity driven 41 000 year climate cycles in the early pleistocene

chinese loess and the paleomonsoon abstract this paper presents a general review of the recent research advances of the east asian paleomonsoon based mainly on studies of the loess soil sequences in the chinese loess plateau in the last 2 6 million years the paleomonsoonal history may be divided into about 166 events on a time scale of the earth s orbital variations during the last glacial period millenial scale oscillations of the monsoon system were prominent which can be fairly well correlated with the dansgaard oeschger cycles recognized in the greenland ice cores the monsoonal rainfall belt has experienced a wide repeated advance retreat change during the glacial interglacial cycles of the pleistocene both temporal and spatial changes of the monsoon system in the quaternary could have been linked closely to global ice volume variations

evidence for a new geomagnetic reversal from lava flows in idaho discussion of short polarity reversals in the brunhes and late matuyama polarity chrons k ar ages and paleomagnetic data for basalt samples from a new core hole site e at the idaho national engineering laboratory inel indicate that the age of the reversed polarity event recorded in snake river plain lavas is older than 465 50 ka 1000 years before present reported previously by champion et al 1981 nine basalt flows eight with normal polarity and one with reversed polarity were recognized in the site e core hole the flows above and below the reversed flow have ages of 491 80 ka and 580 93 ka respectively the inclination of the paleomagnetic field direction of the reversed flow at site e agrees with the inclination of reversed flows elsewhere at inel which have an age of 565 14 ka these reversed flows were previously thought to be correlative with the emperor event we suggest that this polarity event is an older event which we name the big lost reversed polarity subchronozone and subchron a review of data documenting short reversal records from volcanic and sedimentary rocks shows that there is evidence for eight polarity subchrons in the brunhes and two besides the jaramillo in the late matuyama these 10 short subchrons begin to indicate the many short events that cox 1968 hypothesized must exist if polarity interval lengths have a poisson distribution these events are true subchrons not excursions and may or may not have low associated paleointensities although low field strengths might explain why the reversal process aborts the mean sustained polarity interval length since late matuyama chron time is 90 000 years the similarity of this number with the 105 year period of the earth s orbital eccentricity suggests anew that linkage between geomagnetic paleoclimatic and possible underlying earth orbital parameters should be evaluated

incision rate of the yellow river in northeastern tibet constrained by 10be and 26al cosmogenic isotope dating of fluvial terraces implications for catchment evolution and plateau building unlike other large rivers flowing out of tibet the yellow river escapes from the plateau towards the ne crossing no less than five nw se striking actively growing ranges and intervening basins thick plio quaternary deposits and fluvial terraces testify to a phase of aggra dation and sediment infill up to the average surface elevation 3200 3250 m a s l of the gonghe guide and qinghai lake basins a set of seven main terraces across the gonghe basin suggests progressive down cutting of the yellow river carving the 500 m deep longyang gorge at the basin exit 10be and 26al concentrations in quartz of surface and sub surface samples of four terraces constrain the timing of incision by determining the burial age of the deposit and the exposure age of its surface modelling the depth dependence of the 10be concentration and the 26al 10be ratio allows us to constrain the onset of the ongoing phase of incision to 120 250 ka these ages suggest long term incision rates between 2 6 mm a together with the present morphology of the yellow river terraces across the gonghe basin and the longyang gorge our results imply rapid river catchment evolution and interaction between river dynamics tectonic and climate in northeastern tibet

pleistocene terraced fluvial succession northern slope of torino hill abstract a pleistocene terraced fluvial succession is found on the northern slope of the torino hill this succession consists of many relics of flat surfaces separated by scarps often associated with sandy and silty deposits perched from 30 to 400 m on the po plain terraced surfaces at high levels are more deformed dissected and mostly deprived of their original sediments lower ones are less deformed more continuous and preserved in the western sector of the area these surfaces form a declining terraced succession towards the plain in the eastern sector they form a terraced succession entrenched within the relief the succession is not linked either to the present hilly watercourses or to the po river now developed to the north of hilly relief because during the pleistocene the river flowed south of the torino hill on the contrary it is connected with modification by ancient northern piemonte plain watercourses this succession is the result of deformation of original plain sectors prior to the po river shifting north of the relief the comparison of chronological reference of fluvial morphological features and sediments with their altimetric distribution suggests a mean uplift of the torino hill of about 1 mm year the present morphology connected with this evolution favours landslide phenomena

post tectonic landscape evolution in ne iberia using staircase terraces combined effects of uplift and climate river incision into bedrock resulting from the combined effects of tectonic uplift and climate governs long term regional landscape evolution we determined spatial and temporal patterns of post orogenic stream incision from a sequence of well preserved staircase terraces developed over the last 1 ma in the central pyrenees and its southern foreland ebro basin ne spain extensive remnants of ten vertically separated terraces qt1 to qt10 from oldest to youngest were mapped along 170 km of the cinca river valley transverse to the pyrenean mountain belt multiple outcrops appear in the upper reach of the valley ainsa sector 50 km from headwaters as well as in the lower reach albalate sector 125 km from headwaters fluvial incision into bedrock was calculated using i differentially corrected gps measurements of the altitude of straths and ii numerical dating of alluvial sediments from the lower terraces qt5 to qt9 by optically stimulated luminescence previously reported by lewis et al 2009 and supplemented with new dates for the upper terraces qt1 qt2 and qt3 based on paleomagnetism and supported by soil development considering altitude differences and the elapsed time between successive well preserved terrace couples qt3 qt7 qt7 qt9 and qt9 active channel mean bedrock incision rates ranged from 0 76 to 0 38 m ka 1 at the upper reach of the valley ainsa section and from 0 61 to 0 20 m ka 1 at the lower reach albalate section river incision along the valley produced vertically separated near parallel longitudinal terrace profiles evidencing a rapid near uniform regional uplift as response to i the tectonic lithospheric thickening in ne iberia and ii the erosional download rebound related to the ebro basin exorheism moreover a subtle upstream divergence of strath profiles may have been a consequence of an increase in uplift rate toward the head of the valley additionally incision rates changed over time as indicate results from the lower reach albalate section the maximum rate was 1 48 m ka 1 between qt7 61 ka and qt8 47 ka and the minimum rate was 0 11 m ka 1 between qt3 401 ka and qt5 178 ka the highest incision rates were produced after the marine isotope stage 4 most likely in response to i an increased snowmelt discharge during the subsequent deglaciation related to the last maximum advance of glaciers in the southern pyrenees and ii a limited width of the valley after qt7 formation resulting from the deactivation of the westward river migration therefore incision rates over the last 1 ma in the cinca river valley were basically controlled by near uniform bedrock uplift in the context of climate variability the results reported in this study represent significant data on fluvial incision in ne iberia and provide an assessment of the regional post tectonic landscape evolution

slip rate gradients along the eastern kunlun fault 1 whether strike slip fault systems in eurasia accomplish eastward extrusion of tibetan crust and lithosphere depends largely on the kinematics of deformation at the fault tip here we present new slip rate determinations using millennial scale geomorphic markers from sites along the easternmost segment of the kunlun fault in north central tibet this fault system represents one of the major strike slip faults within the indo asian collision zone has been argued to exhibit uniform slip rates along much of its length and plays a central role in models for eastward extrusion of tibetan lithosphere displaced fluvial terrace risers along tributaries of the yellow river coupled with 14c ages of terrace material provide constraints on slip rates over late pleistocene to holocene time results indicate that slip rates decrease systematically along the eastern 150 km of the fault from 10 to 2 mm yr these data challenge the view that slip along the kunlun fault remains uniform along the entire length of the fault and instead reveal gradients in displacement similar to those expected at fault tips moreover slip along the fault appears to terminate within the thickened crust of the plateau and therefore any extrusion of tibetan lithosphere accomplished by slip along the kunlun fault must be absorbed by internal deformation of the plateau surrounding the fault tip

late miocene quaternary rapid stepwise uplift of the ne tibetan plateau and its effects on climatic and environmental changes abstract the way in which the ne tibetan plateau uplifted and its impact on climatic change are crucial to understanding the evolution of the tibetan plateau and the development of the present geomorphology and climate of central and east asia this paper is not a comprehensive review of current thinking but instead synthesises our past decades of work together with a number of new findings the dating of late cenozoic basin sediments and the tectonic geomorphology of the ne tibetan plateau demonstrates that the rapid persistent rise of this plateau began 8 1 ma followed by stepwise accelerated rise at 3 6 ma 2 6 ma 1 8 1 7 ma 1 2 0 6 ma and 0 15 ma the yellow river basin developed at 1 7 ma and evolved to its present pattern through stepwise backward expansion toward its source area in response to the stepwise uplift of the plateau high resolution multi climatic proxy records from the basins and terrace sediments indicate a persistent stepwise accelerated enhancement of the east asian winter monsoon and drying of the asian interior coupled with the episodic tectonic uplift since 8 ma and later also with the global cooling since 3 2 ma suggesting a major role for tectonic forcing of the cooling

fluvial terrace formation in the eastern fenwei basin china during the past 1 2 ma as a combined archive of tectonics and climate change abstract the key to understanding the fluvial response to climate change and surface uplift is a thorough distinguishing between their roles in terrace formation previous studies have tended to attribute the fluvial behavior of deposit incision alternation to climate cyclicity a preliminary explanation is proposed here for terrace formation in the eastern part of the fenwei basin china the observed fluvial terrace sequence was developed by the yellow river deeply downcutting into the emei platform which was uplifted within the eastern fenwei basin and therefore it probably records the tectonic history of this platform on the basis of the magnetostratigraphy and optically stimulated luminescence osl dating a ca 1 2 ma chronology was established for this terrace sequence pedostratigraphic analysis of the loess deposits accumulated on each tread reveals that the terrace deposits are overlain immediately by a paleosol bed suggesting that the abandonment of these terraces due to fluvial incision occurred at the transitions from glacial to interglacial climates the glacial interglacial climate cycle probably has a temporal control on the fluvial behavior of deposit incision alternation even though the yellow river develops in the subsiding fenwei basin the terrace generation may be sporadic and in the form of unusual stacked pattern before the emei platform was uplifted within the eastern fenwei basin the terrace staircases however formed in synchrony with glacial interglacial climate cycles since this platform began to uplift in the late middle pleistocene this result indicates that uplift may be necessary in large terrace staircase genesis it can force the river system to downcut deeply enough during climatic transitions to separate terrace levels adequately favoring the generation and subsequent preservation of the terrace treads the terrace sequence of the yellow river in the eastern fenwei basin therefore can be considered as a combined archive of climate change and local tectonic activity

how and when did the yellow river develop its square bend the current course of the yellow river china involves an unusual 1500 km long angular bend around the ordos tectonic block although sedimentary evidence suggests that the river once followed a more direct path eastward into the bohai sea geologic evidence reveals that the yellow river formed in the eocene as an eastward draining river and developed its square bend around the ordos block in late miocene early pliocene time as a result of folding and uplift that are most probably related to the collision and penetration of india into eurasia as well as rifting around the ordos block the change in course of the yellow river predates flat lying pliocene pleistocene sediment deposits that unconformably overlie folded eocene miocene strata the yellow river provides a typical example of tectonic controls on the size morphology and longevity of rivers

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

micromorphology of the beiyuan loess paleosol sequence in gansu province china geomorphological and paleoenvironmental significance abstract the 35 5 m thick loess section at beiyuan in gansu province china provides the most detailed record on the loess plateau of the periodicities in earth orbital changes during and since the last interglacial it contains ten paleosols one of which is in the holocene loess four in the malan loess and five in the upper lishi loess and associated alluvium micromorphological study of the s1 paleosol series indicates that all of the component soils were subjected to moderate carbonate leaching and biological activity paleosols s1 c s1 d and s1 e developed in alluvium over a time interval equivalent to stage 5e of the deep sea core v28 238 alluvial deposition was episodic as evidenced by the separation of the paleosols since the development of s1 c the terrace has not been affected by floods and has received only wind blow dust additions the sbc index a ratio of the content of channels and excrements to the content of primary calcite grains appears to be a sensitive indicator of environmental change between the arid and sub humid environments represented by the loess and paleosols respectively the trends periodicities and amplitudes of environmental change revealed by the sbc ratio are in good agreement with those derived from other indices through the beiyuan section and with records from other parts of the world

quaternary paleolake development in the fen river basin north china abstract the taiyuan graben and the linfen graben are two fault controlled grabens in the fen river basin north china broad paleolakes periodically occupied the two grabens during the pleistocene this paper discusses how neotectonic activities and paleoclimate changes may have influenced the development of the paleolakes in the two grabens during the middle to late quaternary based on the lacustrine landforms and sediments the distribution of lake terraces and their correlation with loess paleosol series indicate that three paleolake regressions with vertical drops of about 40 60 m occurred in the two grabens at about 0 76 ma b p 0 55 ma b p and 0 13 ma b p analysis of the factors controlling paleolake development suggests that rapid tectonic uplift may be the main cause of the three paleolake regressions changes in the facies of the lacustrine sediment also suggest that when tectonic movements were relatively weak paleoclimate became the main factor causing 2 3 m fluctuations of the paleolake level

neogene and quaternary faulting in and along the qinling shan the structure of the qinling shan mountain range shaanxi china involves major east south east strike slip faults field observations made during two expeditions in 1983 and 1984 show that the faults are active and may have undergone several tens of kilometres of post eocene left lateral displacement the faults cut the morphology sharply and offset left laterally small channels their trace is marked by cataclastic to mylonitic non coaxial deformation zones at least 50 100 m wide the qinling faults allow the eastward extrusion of south china and may be considered the easternmost continuation of the altyn tagh fault system they link extensional tectonics in northeastern china to the himalayan collision