palaeo moisture evolution in monsoonal central asia during the last 50 000 years abstract the late quaternary climate history of monsoonal central asia was inferred from 75 palaeoclimatic records which provide information about moisture conditions in the last 50 ka or part of this period wet conditions occurred during middle and late marine isotope stage 3 while the last glacial maximum lgm was characterized by dry climate conditions in the region a stepwise climate amelioration is suggested by the climate records following the lgm several climate signals of this period which were reported from high latitude ice core records are preserved in archives from monsoonal central asia as well during the early holocene high effective moisture was inferred from most records from the area dominated by the indian monsoon e g the tibetan plateau suggesting that holocene optimal climate conditions occurred there during this period in contrast areas which are dominated by the south east asian monsoon se monsoon and the westerlies in north western and north central china mongolia do not uniformly show an early holocene climate optimum for this area optimal conditions prevailed during the mid holocene these apparent contradictions can possibly be explained by the regional uplift and descent of air masses in the holocene during the early holocene strengthened insolation possibly caused an enhanced low level convergence over the tibetan plateau which led to the intensification of the summer monsoon the strong air uplift caused intensified precipitation and air divergence in the upper troposphere over the tibetan plateau the areas adjacent to the north therefore experienced an intensified descent of air masses and consequently increased aridity the majority of the palaeoclimatic records suggest reduced effective moisture since the late holocene in the region

paleomagnetic evidence for neogene rotational deformations in the aegean domain new paleomagnetic data are reported from the islands of skyros and lesbos in central aegea and the izmir foca region in western anatolia together with previous results obtained in northwestern greece and with results from northern aegea reported by others authors these data suggest that the lower miocene arc was almost rectilinear trending e w and that the curvature was acquired by opposed rotational deformations at each termination moreover the observed inclinations which are shallower than those expected on the basis of a geocentered dipole field suggest a large northward drift since middle miocene

timing and style of late pleistocene glaciation in the queer shan northern hengduan mountains in the eastern tibetan plateau glacial landforms and sediments provide evidence for the existence of two late pleistocene major glacial advances in the queer shan northern hengduan mountains in the eastern tibetan plateau in the current study optically stimulated luminescence and electron spin resonance dating results reveal that the two glacial advances occurred during marine isotope stage mis 3 and the last glacial maximum lgm in mis 2 respectively geomorphic evidence shows that the glacial advance during mis 3 was more extensive than that in mis 2 this glacial advance is synchronous with other glaciated areas in the himalaya and tibet but contrasts with global ice volumes that reached their maximum extent during the lgm glaciers in the queer shan are of the summer accumulation type and are mainly fed by precipitation from the south asian monsoon palaeoclimate proxies show that during mis 3 the south asian monsoon strengthened and extended further north into the tibetan plateau to supply more precipitation as snow at high altitudes this in turn led to positive glacier mass balances and caused glaciers to advance however during the lgm despite cooler temperature than in mis 3 the weakened south asian monsoon and the associated reduced precipitation were not as favourable for glacier expansion as in mis 3 copyright c 2010 john wiley sons ltd glacial landforms and sediments provide evidence for the existence of two late pleistocene major glacial advances in the queer shan northern hengduan mountains in the eastern tibetan plateau in the current study optically stimulated luminescence and electron spin resonance dating results reveal that the two glacial advances occurred during marine isotope stage mis 3 and the last glacial maximum lgm in mis 2 respectively geomorphic evidence shows that the glacial advance during mis 3 was more extensive than that in mis 2 this glacial advance is synchronous with other glaciated areas in the himalaya and tibet but contrasts with global ice volumes that reached their maximum extent during the lgm glaciers in the queer shan are of the summer accumulation type and are mainly fed by precipitation from the south asian monsoon palaeoclimate proxies show that during mis 3 the south asian monsoon strengthened and extended further north into the tibetan plateau to supply more precipitation as snow at high altitudes this in turn led to positive glacier mass balances and caused glaciers to advance however during the lgm despite cooler temperature than in mis 3 the weakened south asian monsoon and the associated reduced precipitation were not as favourable for glacier expansion as in mis 3 copyright c 2010 john wiley sons ltd

analyses of fault mechanisms and expansion of southwestern anatolia since the late miocene abstract neotectonic field studies and detailed analyses of neogene and quaternary fault mechanisms in southwestern anatolia enable us to recognize a succession of compressional and extensional events and to characterize the direction of corresponding regional stresses the three most important compressive phases occurred during the miocene and a much smaller one near the plio quaternary boundary the last one or two interrupted a widespread extension of much greater duration and amplitude the whole tectonic evolution resembles that of the aegean the large extension by normal faulting is consistent with a minimum stress along a nne ssw average direction it appears that this direction was n s during the pliocene and changed to ne sw sometime during the quaternary this dominant nne ssw extension which began during late miocene or earliest pliocene was related to the development of the southwestern anatolian graben system

paleoenvironmental and archaeological investigations at qinghai lake western china geomorphic and chronometric evidence of lake level history abstract qinghai lake located on the northeastern qinghai tibet plateau qing zang gaoyuan is china s largest extant closed basin lake its position relative to major asian climate systems makes it sensitive to global climate change the lake has been the subject of numerous paleoenvironmental investigations including dating of shoreline features around the lake basin here we report new age estimates of shoreline features geomorphic exposures and archaeological sites that contribute to the development of a lake level history for qinghai lake and a landscape model of the qinghai lake basin lake highstands above 3230 m 36 m above the modern lake level appear to date to late mis 5 70 110 ka the lake has had much more modest highstands since then no evidence of mis 3 lake stands higher than modern were found and early holocene highstands are no more than 12 m above modern if the age of highstands greater than 3230 m is confirmed through future work then the qinghai lake basin hydrologic balance prior to 70 ka was dramatically different than after that time including during the holocene a simple hydrologic balance model provides insights into the combination of precipitation evaporation and runoff generation needed to sustain the lake at 3260 m the highest shoreline observed a range of factors may explain the difference primarily the relative strength of the east asian monsoon the basin was apparently subject to extensive alluviation during mis 3 interrupted by widespread erosion and development of cryogenic features before and during the last glacial maximum lgm loess that presently drapes much of the lower basin landscape began to be deposited after the lgm 16 18 ka the landscape model outlined here has implications for archaeological visibility of early human occupation of the qinghai tibet plateau

holocene lake stages and thermokarst dynamics in a discontinuous permafrost affected region north eastern tibetan plateau abstract sediments of a thermokarst system on the north eastern tibetan plateau were studied to infer changes in the lacustrine depositional environment related to climatic changes since the early holocene the thermokarst pond with a length of 360 m is situated in a 14 5 6 km tectonically unaffected intermontane basin which is underlain by discontinuous permafrost a lake sediment core and bankside lacustrine onshore deposits were analysed additionally fossil lake sediments were investigated which document a former lake level high stand the sediments are mainly composed of marls with variable amounts of silt carbonate micrite and organic matter on the basis of sedimentological grain size data geochemical xrf mineralogical xrd and micropaleontological data ostracods and chironomide assemblages a reconstruction of a paleolake environment was achieved lacustrine sediments with endogenic carbonate precipitation suggest a lacustrine environment since at least 19 0 cal ka bp however because of relocation and reworking processes in the lake the sediments did not provide distinct information about the ultimate formation of the lake the high amount of endogenic carbonate suggests prolonged still water conditions at about 9 3 cal ka bp ostracod shells and chironomid head capsules in fossil lake sediments indicate at least one former lake level high stand which were developed between the early and middle holocene from the late holocene the area was possibly characterized by a lake level decline documented by a hiatus between lacustrine sediments and a reworked loess or loess like horizon after the lake level decline and the following warming period the area was affected by thermally induced subsidence and a re flooding of the basin because of thawing permafrost

stable isotopes of lake and fluid inclusion brines dabusun lake qaidam basin western china hydrology and paleoclimatology in arid environments the qaidam basin underlain by salt is the largest 120 000 km2 on the qinghai tibet plateau western china numerous shallow to ephemeral saline lakes and dry saline pans are present on the qarhan salt plain dabusun lake the largest about 200 km2 contains high salinity na mg cl brines whereas it precipitates halite it is fringed by a potash salt flat the dominant inflow to dabusun lake the golmud river contains dilute na hco 3 rich meteoric waters dabusun lake brines fall on an evaporation trend given by d 3 3 18o 43 both d and 18o values increase with salinity which in turn varies considerably with flooding and evaporation the isotope compositions of the fluid inclusion brines from modern halite formed along the lake s edge are intermediate to those of dabusun lake brines and those from the salt flat shallow sediments beneath qarhan consist of interbedded salts and mud a short core section 1 3 1 7 m depth from the northern edge of dabusun lake was found to contain three dissolution surfaces and three mud partings the 18o values for fluid inclusions in 22 primary halite samples from this section show a record of episodic flooding lower 18o values followed by evaporation gradual increase in 18o values primary fluid inclusions in halite crystallized initially at the surface provide a geochemical record of surface brines their major element compositions varied through time more concentrated fluids indicate more arid conditions in the basin whereas wetter conditions prevailed during intervals of non salt deposition when laminated muds accumulated the isotope compositions together with the activity of h2o of fluid inclusions in primary halite were used to determine isotope variations in regional precipitation and hence paleoclimatic changes on the qinghai tibet plateau during the past 50 000 years

evolution of chaka salt lake in nw china in response to climatic change during the latest pleistocene holocene abstract the late pleistocene and holocene hydrologic balance of chaka salt lake in the eastern qaidam basin of nw china was studied based on the analysis of lithostratigraphy mineralogy total organic carbon and total nitrogen from a 9 0 m long sediment core an age depth model for the lake sediments is based on eight accelerator mass spectrometry ams 14 c measurements of organic matter and a 1700 year radiocarbon reservoir correction the pitzer model was used to calculate the sequence of minerals precipitated as a function of salinity assuming that the initial lake water was recharged from adjacent rivers and springs lake salinity values were derived from a good match between the calculated and observed mineral sequences our multi proxy based hydrologic reconstruction of chaka lake indicates that it was a clastic dominated freshwater lake between 17 2 and 11 4 cal ka bp which may have resulted from the input of glacial water into the lake at that time during the lateglacial and holocene a warm climatic regime predominated between 13 9 and 12 7 cal ka bp and then a cold climatic regime prevailed between 12 7 and 11 4 cal ka bp these warm and cold periods correlate with the bolling allerod and younger dryas events in the region beginning at 11 4 cal ka bp a saline or hypersaline lake developed which may have resulted from increased summer insolation and temperatures these conditions persisted throughout the holocene modeling indicates that lake salinity fluctuated between 66 and 223 ppt from 11 4 to 7 2 cal ka bp and then increased to 223 322 ppt between 7 2 and 6 0 cal ka bp when most regions of china recorded high moisture availability i e the so called mid holocene climatic optimum lake salinity decreased to 66 223 ppt during a short time period between 6 0 and 5 3 cal ka bp possibly caused by reduced evaporation subsequently salinity values rapidly increased to 223 322 ppt between 5 3 and 5 2 cal ka bp and a hypersaline lake with a salinity higher than 324 ppt similar to modern chaka salt lake became established around 5 2 cal ka bp this establishment may have been related to the weakening of asian monsoon regional comparisons of paleoclimatic records indicate that large temporal and spatial variations exist in the occurrence and intensity of drought over western china since the lateglacial

first paleomagnetic results from mio pliocene series of the hellenic sedimentary arc abstract paleomagnetic measurements have been conducted on the mio pliocene series along the external sedimentary hellenic arc in order to detect the presence or absence of rotational deformations in different sections of the arc in the central eastern part of the arc crete and rhodes paleomagnetic directions are very closely aligned along the north south direction showing that this portion of the arc has not undergone significant rotation since at least 7 m y for crete and 4 m y for rhodes in the western and northwestern parts results from south peloponnesos zakinthos kephallinia and corfu indicate that this section of the arc has undergone a clockwise rotation detailed analysis of the data from the three ionian islands shows that their rotation began about 5 m y b p and has proceeded since then at roughly 5 m y giving a total amplitude of about 26 it is suggested that the beginning of this rotation is related to the lower pliocene compressive phase which most probably initiated the tectonic activity of the present day ionian margin

timing and style of late quaternary glaciation in northeastern tibet glacial successions in the anyemaqen and nianbaoyeze mountains of northeastern tibet are reassessed and new glacial chronologies are presented for these regions cosmogenic radionuclide and optically stimulated luminescence dating indicates that two glacial advances occurred in marine isotope stage mis 3 and mis 2 in the anyemaqen mountains a third advance occurred in the early holocene we suggest that glaciation was synchronous in the anyemaqen and nianbaoyeze mountains as well as in other glaciated areas of tibet and the himalaya that are influenced by the asian monsoon the maximum extent of glaciation occurred early in the last glacial cycle mis 3 during a time of increased insolation when the monsoon intensified and supplied abundant precipitation as snow at high altitude to feed high altitude glaciers this suggests that precipitation as snow is fundamental in controlling glaciation in these regions however the occurrence of glacial advances during the insolation minimum of mis 2 suggests that despite reduced precipitation at this time the annual temperatures were cold enough to maintain positive glacier mass balances the numerically defined chronologies for the anyemaqen and nianbaoyeze mountains presented here provide a framework for comparing glacial advances in other parts of high asia

loess sedimentation in tibet provenance processes and link with quaternary glaciations abstract well preserved loess deposits are found on the foothills of mountains along the middle reaches of the yarlung zangbo river in southern tibet optically stimulated luminescence osl dating is used to determine loess ages by applying the single aliquot regeneration technique geochemical mineralogical and granulometric measurements were carried out to allow a comparison between loess from tibet and the chinese loess plateau our results demonstrate that i the loess deposits have a basal age of 13 11 ka suggesting they accumulated after the last deglaciation ii loess in southern tibet has a glacial origin resulting from eolian sorting of glaciofluvial outwash deposits from braided river channels or alluvial fans by local near surface winds and iii the present loess in the interior of tibet has accumulated since the last deglaciation when increased monsoonal circulation provided an increased vegetation cover that was sufficient for trapping eolian silt the lack of full glacial loess is either due to minimal vegetation cover or possibly due to the erosion of loess as glaciofluvial outwash during the beginning of each interglacial such processes would have been repeated during each glacial interglacial cycle of the quaternary

deformational behaviour of continental lithosphere deduced from block rotations across the north anatolian fault zone in turkey abstract theoretical considerations of lithosphere deformation across transform plate boundaries predict an expression in terms of 3istributed deformation the magnitude of rotation is expected to diminish away from the fault zone in a way which depends on the length of the fault the amount of displacement and the ductility of the lithosphere palaeomagnetic studies across the north anatolian transform fault zone which separates the eurasian plate and anatolian block in northern turkey show that clockwise rotations predicted from the sense of dextral motion are indeed present and have attained finite rotations of up to 270 during the 5 ma history of neotectonic deformation such rotations are however confined to narrow 10 km wide zones between system bounding faults and appear to have resulted from rotation in ball bearing fashion of equidimensional blocks a few kilometres in size outside of this zone only anticlockwise rotations are observed these are unrelated to deformation across the fault zone and record regional anticlockwise rotation of turkey which is complementing clockwise rotation of greece and accompanying neogene opening of the aegean sea the observed behaviour of continental lithosphere satisfies no plausible value of power law behaviour we therefore conclude that relative motion across this transform boundary occurs as a discrete zone of intense deformation within a brittle layer comprising the seismogenic upper crust this is presumed to be detached from a continuum deformation response to shearing in the lower crust and mantle beneath

age constraints on the late quaternary evolution of qinghai lake tibetan plateau dating and geomorphology of shoreline features in the qinghai lake basin of northwestern china suggest that contrary to previous interpretations the lake likely did not reach levels 66 140 m above modern within the past 90 000 yr maximum highstands of 20 66 m above modern probably date to marine isotope stage mis 5 mis 3 highstands are undated and uncertain but may have been at or below post glacial highs the lake probably reached 3202 3206 m 8 12 m during the early holocene but stayed below 3202 m after 8 4 ka this shoreline history implies significantly different hydrologic balances in the qinghai lake basin before 90 ka and after 45 ka possibly the result of a more expansive asian monsoon in mis 5

palaeolatitudes from dsdp leg 73 sediment cores implications for the apparent polar wander path for africa during the late mesozoic and cenozoic summary palaeolatitudes estimated from dsdp sediments provide important constraints on the apparent polar wander path apwp of africa during the cenozoic a revised apwp is suggested based on new information about palaeomagnetic poles from the african continent and predicted palaeolatitudes are compared with those determined from leg 73 sediments other published paths are discussed

late quaternary highstands at lake chilwa malawi frequency timing and possible forcing mechanisms in the last 44 ka the extensive shoreline deposits of lake chilwa southern malawi a shallow water body today covering 600 km2 of a basin of 7500 km2 are investigated for their record of late quaternary highstands osl dating applied to 36 samples from five sediment cores from the northern and western marginal sand ridges reveal a highstand record spanning 44 ka using two different grouping methods highstand phases are identified at 43 7 33 3 ka 26 2 21 0 ka and 17 9 12 0 ka total error method or 38 4 35 5 ka 24 3 22 3 ka 16 2 15 1 ka and 13 5 12 7 ka finite mixture model age components with two further discrete events recorded at 11 01 0 76 ka and 8 52 0 56 ka highstands are comparable to the timing of wet phases from other basins in east and southern africa demonstrating wet conditions in the region before the lgm which was dry and a wet lateglacial which commenced earlier in the southern compared to northern hemisphere in east africa we find no evidence that wet phases are insolation driven but analysis of the dataset and gcm modelling experiments suggest that heinrich events may be associated with enhanced monsoon activity in east africa in both timing and as a possible causal mechanism

late pleistocene lake and glaciation evolution on the northeastern qinghai tibetan plateau a review late pleistocene paleoclimatic history on northeastern qinghai tibetan plateau qtp has been reconstructed mainly from lake sediments however data regarding dry wet climate changes reported in this region are still not clear and controversial based on shoreline features and highstand lacustrine sediments around lakes on the qtp high lake level histories in this paper were summarized and compared with paleoclimatic records from lake sediments ice core and glaciation evolution surrounding mountains on the ne qtp during late pleistocene the results indicate that periods of high lake level occurred at mis 5 mis 3 and early middle holocene and most likely corresponding to warm and wet climate periods while periods of low lake level existed in intervening intervals corresponding to cold and dry climate periods which most likely coincide with glacial advances surrounding high mountains with an exception no wide glacial advance in study area was found during mis 3 possibly suggesting that effective moisture is lower than that in the other region of ne qtp in this period

temperature variability and vertical vegetation belt shifts during the last 50 000 yr in the qilian mountains ne margin of the tibetan plateau china abstract a 13 94 m long sediment core collected from a medium sized lake in the qilian mountains ne tibetan plateau china was analysed palynologically at 81 horizons the interpretation of indicator taxa yielded various vertical shifts of the vegetation belts these palaeovegetation results have been checked with lake surface pollen spectra from 8 lakes representing different altitudinal vegetation belts our main findings are the following a short period of the late marine isotope stage 3 around 46 000 yr ago was characterized by interglacial temperature conditions with a tree line above its present day altitude during the lgm the vicinity of the lake was not covered by ice but by sparse alpine vegetation and alpine deserts indicating that the climate was colder by 4 7 c than today markedly higher temperatures were inferred from higher arboreal pollen frequencies between 13 000 and 7 000 yr ago with a holocene temperature optimum and a maximal picea betula mixed forest expansion between 9 000 and 7000 yr ago when temperatures exceeded the present day conditions by at least 1 2 c alpine steppes and meadows and sub alpine shrub vegetation dominated around the lake since the middle holocene suggesting that vegetation and climate conditions were exceptionally stable in comparison to previous periods

reappraisal of paleomagnetic data from gargano south italy vandenberg j 1983 reappraisal of paleomagnetic data from gargano south italy in e mcclelland brown and j vandenberg editors palaeomagnetism of orogenic belts tectonophysics 98 29 41 the platform limestones of apulia italy outcropping in the gargano peninsula have been restudied paleomagnetic research has been carried out on upper cretaceous lower cretaceous and jurassic rocks despite the low intensities of the nrm 10 100 pa m all samples 268 could be cleaned by stepwise a f and or thermal demagnetization treatments nrm directions could be determined accurately and reproducibly for 85 of the samples using a sct cryogenic magnetometer and double precision measuring procedures nrm of the jurassic limestone is carried by secondary haematite and the results are therefore rejected from further consideration the upper and lower cretaceous limestones have an nrm carried by magnetite minor bedding tilt corrections improve the grouping of the site mean results the upper cretaceous scaglia limestone turonian senonian reveals a characteristic mean direction of decl 327 7 incl 38 2o a ss 4 3 21 sites while the lower cretaceous maiolica limestone neocomian aptian albian reveals a characteristic mean direction of decl 303 1 o incl 35 1 as s 8 7o 8 sites the cretaceous results show a post aptian albian counterclockwise rotation of about 25 which is expressed by the smeared distribution of the late cretaceous site mean results and a post senonian i e tertiary counterclockwise rotation of the same amount with respect to the pole these results are in excellent agreement with contemporaneous paleomagnetic results from other peri adriatic regions a tertiary counterclockwise rotation of all the stable adriatic block is strongly supported by the new results

late pleistocene paleoclimatic history documented by an oxygen isotope record from carbonate sediments in qarhan salt lake ne qinghai tibetan plateau late pleistocene paleoclimatic variability on the northeastern qinghai tibetan plateau ne qtp was reconstructed using a chronology based on ams 14 c and 230 th dating results and a stable oxygen isotopic record these are derived from lake carbonates in a 102 m long qarhan sediment core isl1a collected from the eastern qaidam basin previous research indicates that the d 18 o values of lacustrine carbonates are mainly controlled by the isotopic composition of lake water which in turn is a function of regional p e balance and the proportion of precipitation that is monsoon derived on the ne qtp modern isotopic observations indicate that the d 18 o values of lake carbonates in hyper arid qaidam basin are more positive during the warm and wet period due to strong evaporation and continental effect in this basin the positive d 18 o values in the arid region indicate drier climatic conditions based on this interpretation and

late cenozoic climate changes in china s western interior a review of research on lake qinghai and comparison with other records abstract we review late cenozoic climate and environment changes in the western interior of china with an emphasis on lacustrine records from lake qinghai widespread deposition of red clay in the marginal basins of the tibetan plateau indicates that the asian monsoon system was initially established by 8 ma when the plateau reached a threshold altitude subsequent strengthening of the winter monsoon along with the establishment of the northern hemisphere ice sheets reflects a long term trend of global cooling the few cores from the tibetan plateau that reach back a million years suggest that they record the mid pleistocene transition from glacial cycles dominated by 41 ka cycles to those dominated by 100 ka cycles during terminations i and ii strengthening of the summer monsoon in china s interior was delayed compared with sea level and insolation records and it did not reach the western tibetan plateau and the tarim basin lacustrine carbonate 18 o records reveal no climatic anomaly during mis3 so that high terraces interpreted as evidence for extremely high lake levels during mis3 remain an enigma following the last glacial maximum lsm several lines of evidence from lake qinghai and elsewhere point to an initial warming of regional climate about 14 500 cal yr bp which was followed by a brief cold reversal possibly corresponding to the younger dryas event in the north atlantic region maximum warming occurred about 10 000 cal yr bp accompanied by increased monsoon precipitation in the eastern tibetan plateau superimposed on this general pattern are small amplitude centennial scale oscillations during the holocene warmer than present climate conditions terminated about 4000 cal yr bp progressive lowering of the water level in lake qinghai during the last half century is mainly a result of negative precipitation evaporation balance within the context of global warming

late holocene vegetation and climate oscillations in the qaidam basin of the northeastern tibetan plateau abstract pollen evidence from sediment cores at hurleg and toson lakes in the qaidam basin was obtained to examine vegetation and climatic change in the northeastern qinghai tibetan plateau the chronologies were controlled by 210pb and 137cs analysis and ams 14c dating pollen assemblages from both lakes are dominated by chenopodiaceae 40 artemisia 30 35 and poaceae 20 25 with continued occurrence but low abundance of nitraria ephedra and cyperaceae artemisia chenopodiaceae a c pollen ratios from two lakes show coherent large oscillations at centennial timescale during the last 1000 yr a c ratios were high around ad 1170 1270 1450 1700 and 1920 suggesting that the vegetation was more steppe like under a relatively moist climate than that during the intervening periods wet dry climate shifts at the two lakes 2800 m asl are in opposite phases to precipitation changes derived from tree ring records in the surrounding mountains 3700 m asl and to pollen and snow accumulation records from dunde ice core 5300 m asl showing that a dry climate in the basin corresponds with a wet interval in the mountains especially around ad 1600 this contrasting pattern implies that topography might have played an important role in mediating moisture changes at regional scale in this topographically complex region

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

an assessment and comparison of 230th and ams 14c ages for lacustrine sediments from qarhan salt lake area in arid western china the age framework of qarhan salt lake in arid western china is still controversial due in part to 1 age discrepancy between conventional 14c and 230th dating results and 2 no ams 14c ages of organic carbon from drilling cores in qarhan salt lake were reported until now in order to discuss these chronological problems upper 54 50 m lacustrine sediments from a drilling core isl1a recovered from qarhan salt lake were dated based on 230th and ams 14c dating techniques results show that 1 ams 14c ages of total organic carbon toc from 4 65 to 30 29 m are almost in stratigraphic order and consistent with 230th ages of halite in the corresponding layers 2 ams 14c ages of toc from 30 29 to 54 50 m are younger with increasing depth this phenomenon was also found in shell bar in the study area suggesting that ams 14c ages from upper 30 29 m are more reliable while those from lower 24 21 m in isl1a may be underestimated 3 230th ages of halite from lower 24 m lacustrine sediments are obviously older than ams 14c ages of toc in the corresponding layers which results into different age framework of salt lake sediments in qarhan salt lake 4 if extrapolating these reliable ams 14c ages in isl1a similar age framework with 230th ages in this core confirms that 230th ages are much close to the true ages of these sediments which suggests that the forming timing of the bottom salt layer is 50 ka

luminescence dated aeolian deposits of late quaternary age in the southern tibetan plateau and their implications for landscape history abstract aeolian deposits are widely distributed in the interior of the tibetan plateau and their chronology is poorly known it is not yet clear whether they accumulated only after the last deglaciation or over a longer time we applied quartz osl dating to aeolian samples from the lhasa area with osl ages ranging from 2 9 0 2 to at least 118 11 ka the probability density frequency pdf distribution of 24 ages reveals age clusters at about 3 8 16 21 33 and 79 83 ka indicating enhanced sediment accumulation then the results show that aeolian deposition occurred throughout most of the last 100 ka this implies that 1 an ice sheet covering the whole tibetan plateau during the last glacial maximum lgm could not have existed and 2 erosion during the last deglaciation was not as strong as previously proposed such that not all pre holocene loess was removed the age distribution shown in the pdf indicates that aeolian accumulation is episodic sand formation events revealed by age clusters at 3 8 and 16 21 ka imply roughly synchronous environmental responses to corresponding global scale arid events

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

cosmogenic 10be and 26al exposure dating of nam co lake terraces since mis 5 southern tibetan plateau abstract lake paleo shorelines can be used to reconstruct lake level fluctuations which serve as sensitive indicators of climate change the tibetan plateau tp contains the highest areal proportion of lakes in china and dramatic past lake level changes have led to the formation of numerous relict shorelines here we present 24 10be and 26al exposure ages for five of seven lake terraces situated north of nam co on the southern tp the ages of four high stands marked by terraces t7 t6 t5 and t4 are 81 5 9 0 ka 33 6 1 9 ka 19 9 1 9 ka and 15 2 0 4 ka the topographically highest terrace t7 correlates with periods of enhanced indian summer monsoon ism and supports an mis 5 maximum lake expansion on the tp as opposed to mis 3 ages of two lower terraces t5 and t4 possibly correspond to melt water pulse mwp events we also evaluate different possible sources of uncertainty from geologic processes on 10be exposure ages of lake terraces subaerial erosion following terrace exposure has the most significant influence on 10be exposure ages on ancient high terraces for example 80 ka while inherited 10be from prior exposure and partial shielding by shallow water beach or talus are the most important geological source error of 10be exposure ages for relatively low and young terraces for example

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

revision of the timing magnitude and distribution of neogene rotations in the western aegean region to evaluate the dimension and the timing of the clockwise rotating domain and the nature of the structures that accommodate the rotating domain in the western aegean region paleomagnetic analyses were carried out in northern western and southwestern greece the results show that the rotating domain covers an area including the external albanides western mainland greece including evia and probably at least partly the peloponnesos smaller clockwise rotations on the order of 30 408 were reported previously from the chalkidiki peninsula and the islands of skyros and limnos previously two phases of approximately 258 of rotation were suggested the last one during the plio pleistocene our analysis shows that the western aegean domain rotated approximately 408 clockwise between 15 13 and 8 ma followed by an additional 108 after 4 ma the rotating domain is accommodated in the north by deformation associated with the scutari pec fault zone and in the west by the ionian thrust and the hellenic subduction zone to the south no rocks older than 10 ma are available so no conclusive data are obtained to the east of the rotating domain extensional detachment systems of the cyclades and rhodope areas were active during the rotation phase and may explain at least part of the differences in finite amounts of rotation between nonrotation or counterclockwise rotations observed in northern and eastern greece and the large clockwise rotations in western greece d 2004 elsevier b v all rights reserved

how cold was the little ice age a proxy based reconstruction from finland applying modern analogues of fossil midge assemblages climate dynamics during the past ca 700 years in southern finland were reconstructed using fossil midge diptera nematocera assemblages aiming to estimate quantitatively the temperature change that has occurred from the little ice age to the present midge stratigraphies of two sediment cores from eastern and southern finland were chosen to be examined for temperature inferences utilizing the modern analogue technique the new midge based temperature inference model had a coefficient of determination of 0 901 and a prediction error of 0 498 c showing improvement over the previous finnish models the combined curve of the inferred temperatures derived from both of the cores showed a decrease towards ca 1700 ad when temperatures were approximately 1 c cooler than the past 700 years average and almost 2 c colder than present the temperatures began to increase in southern finland from 1800 ad and in eastern finland from 1900 ad onwards the highest temperatures were reached at the top of the core representing the present climate warming although there was slight overestimation in the recent inferred values the reconstructed trends were in close correspondence with the previous proxy based historical and measured data that suggests that the reconstruction was realistic and reliable

lake qinghai china closed basin like levels and the oxygen isotope record for ostracoda since the latest pleistocene abstract in 1985 a sino swiss limnogeological expedition to china s largest inland lake recovered seismic profiles and piston cores to help calibrate palaeoclimatic models of monsoon and insolation fluctuations over the northern tibet qinghai plateau since the last glacial maximum lake qinghai a perennial lake with an area of 4278 km2 1985 at 3194 m above sea level receives drainage from 30 000 km2 of catchment near the northwest corner of the plateau the 26 5 m deep terminal lake 1985 with brackish alkaline magnesium sulphate rich waters 14 g 1 1 tds has not overflowed since the last glacial but its levels have responded to climatic and hydrologic changes seismic reflection profiles for the sub bottom sediment structures revealed a complex topography with channels relict terraces tectonic tilting and deformation in deposits buried under a 4 6 m packet of mainly flat bedded sediments from which core samples were recovered the lowermost cored material 14 500 yr b p comprises mainly water lain loess deposited in a smaller flood plain lake of up a few metres depth under cold arid climatic conditions ams radiocarbon dating indicates average sedimentation rates for latest pleistocene and holocene deposits in central basin regions of 0 3 0 5 mm yr 1 the 18o values of fossil ostracod valves provide a record of changes in the isotopic chemistry of the lake waters that can be related to the precipitation evaporation budgets which have controlled the palaeo levels for lake qinghai the precipitation evaporation budget for the lake qinghai region is largely determined by the asian monsoon system the lake qinghai sediment record shows that there was no large influx of glacoer melt waters into the lake basin during the post glacial the regional climate remained arid until at least 12 500 yr b p when an incipient monsoon was possibly initiated river transported silts first reached the basin centre at 11 800 yr b p when the lake depth may have increased to 5 m possibly a monsoonal weakening for several centuries after 10 800 yr b p europe younger dryas caused a further period of aridity at 10 200 yr b p the basin began filling towards modern lake dimensions in response to a permanent strengthening of the asian monsoon substantial lake level rises probably characterised the periods 10 200 9800 9500 8500 8300 7200 yr b p and through perhaps a century at about 6800 yr b p decreasing levels probably characterised the intervening intervals short term lake level fluctuations through the mid holocene climatic optimum were minimal indicating a very stable climatic hydrologic regime an isotopic steady state for the lake waters since 3000 500 yr b p obscures the climatic hydrologic regime dependent 18o gradient but there is little stratigraphic evidence to suggest that the lake level has been significantly below its present level since that time three negative 18o excursions for the lake waters may correspond to known glacier advances on the plateau at 3000 2000 and 1500 yr b p during china s neoglacial

centennial blooming of anoxygenic phototrophic bacteria in qinghai lake linked to solar and monsoon activities during the last 18 000 years the productivity of anoxygenic phototrophic bacteria apb can be inferred in the sediments of qinghai lake from the changing abundance of bacteriophaeophytin a bph a using diffuse reflectance spectroscopy drs we identified bph a in qinghai lake sediments from the late glacial period through the holocene with a resolution of one sample every 30 50 years the bph a profile of qinghai lake demonstrates that in the last 18 000 years apb were only present between 4 2 and 14 ka bp a period of high rainfall and high summer solar insolation all the apb blooming events correspond to times of enhanced freshwater influx as revealed by percent redness an indicator of the input of iron oxide minerals our data suggest that solar insolation sets the stage for apb blooms which are then promoted by increased summer monsoon rainfall and nutrients resulting in the development of a chemocline in the lake the blooming of apb in qinghai lake appears as discrete centennial scale apb events likely linked to solar activities our results suggest the presence of solar induced century long intense summer monsoon episodes in the middle and early holocene and the late glacial period

exploration history and geology of the diamondiferous ultramafic saptarshi intrusions madhya pradesh india abstract the saptarshi field comprises a suite of at least eight known diamondiferous pipes and dykes within rio tinto s bunder project on the bundelkhand craton of madhya pradesh india the discovery made in 2004 followed regional scale area selection gravel sampling and subsequent ground geophysics soil geochemistry and prospecting the geology and petrography of the largest and most economically prospective pipe atri suggests that near the surface it forms a large vent comprised of two distinct lobes filled predominantly with primary pyroclastic rocks atri is composed of relict olivine phlogopite apatite minor spinel and ti oxides the rock is altered no primary olivine and little phlogopite remains instead much of the rock is now composed of serpentine chlorite carbonate other occurrences within the saptarshi field include small pipes and altered dykes atri is one example of the diverse assemblage of potassic rocks found on the indian subcontinent many parallels may be drawn with the nearby diamondiferous majhgawan pipe including mineral chemistry and petrography atri has many characteristics in common with olivine lamproite but many subtle deviations from type lamproite are observed we suggest that atri represents a local expression of potassic magmatism unique to the bundelkhand craton of india and is the product of partial melting of modally diverse veins in ancient metasomatized lithospheric mantle these rocks are not readily classified according to existing schemes devised for potassic rocks known from other petrological provinces a practical and workable scheme has not been devised that recognizes the unique characteristics of the diversity of lamproite like rocks the authors tentatively classify atri as a diamondiferous ultramafic intrusion with lamproitic affinities recognizing its obscured primary mineralogy its petrographic and textural characteristics and the important implications this classification has with respect to exploration the 1100 ma age of the saptarshi intrusions imply that they are part of a larger igneous province which includes the nearby majhgawan and hinota diamondiferous pipes this age temporally relates to the lamproites of western australia rio tinto completed an order of magnitude oom scoping study comprising large diameter and slim line delineation drilling and surface bulk sampling on the project in 2008

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

asian monsoon oscillations in the northeastern qinghai tibet plateau since the late glacial as interpreted from visible reflectance of qinghai lake sediments abstract qinghai lake is a large saline lake on the qinghai tibetan plateau of central asia that is effected by both the indian and asian monsoons we used reflectance spectroscopy to characterize the sediments in a 795 cm long core taken from the southeastern part of the lake sediment redness which is related to iron oxide content seems to monitor paleoclimatic changes in the core iron oxides appear to be eroded from nearby red beds or loess deposits and are transported by fluvial means into the lake thus redness increases at times of increased precipitation that is as monsoon strength increases our redness monsoon proxy shows climate changes on several times scales on a millennial scale it records humid conditions during the early and mid holocene from about 4200 to 2300 yr bp low redness values suggest a two millennial long dry period which in the late holocene is followed by a more humid period on a centennial scale the redness proxy records not only the little ice age but also the medieval warm period the dark ages cool period and the roman warm period time series analysis of the redness record indicates a 200 yr frequency which corresponds to the de vries solar cycle suggesting that in addition to insolation changes resulting from orbital variations solar forcing also results from cyclic changes in the sun s luminosity

quaternary glaciation of the bailang river valley qilian shan abstract the qilian shan on the northeast margin of the qinghai tibetan plateau is weakly influenced by the asian monsoon until recently the quaternary glacial geology of this region has been poorly understood this paper describes a sequence of quaternary glacial deposits in the upper reaches of the bailang river using electron spin resonance esr thermoluminescence tl and radiocarbon dating tills loess buried soils and landforms were dated the oldest till was dated 463 ka bp by esr a younger till and its outwash terrace were dated to 135 and 130 ka bp the loess on this outwash terrace was dated to 141 7 11 4 ka bp at its base and 43 7 3 5 ka bp in its central part by tl dating a buried soil on a younger till was dated at 6920 78 ka bp using 14c the glacial landforms and these dating results show that glacial advances occurred during the little ice age the neoglacial mis 2 4 mis 6 and mis 12 glaciation during mis 12 implies that the qilian mountains were rising coevally with the qinghai tibetan plateau and were probably at a sufficient elevation for glaciation since at least 463 ka bp

tertiary geodynamical evolution of northwestern greece paleomagnetic results abstract paleomagnetic results have been obtained from 29 sites sampled in lower to upper oligocene flysch sections of the ionian zone in northwestern greece they indicate a clockwise rotation of about 45 of the entire region a comparison with previously published results relative to both younger and older formations shows that this rotation has occurred in two phases of comparable amplitude one during middle miocene and the other during pliocene and quaternary separated by a period of at least 7 ma during which no significant rotation has occurred no major rotation has occurred during the entire paleocene and eocene stages this large measured rotation implies a horizontal displacement of at least 100 km in epirus possible mechanisms involving a rotation of the nappe sheets rotation of the basement or a combination of the two are discussed the two phases of paleomagnetic rotation can be correlated with the tertiary and quaternary calc alkaline volcanic activity in the aegean sea a palinspastic reconstruction shows that the orientation of the major structures now striking n155 was almost east west in the middle miocene at the epoch of their formation

palaeomagnetic evidence from pelagic limestones for clockwise rotation of the ionian zone western greece abstract on the basis of a pilot study of all the major carbonate lithologies in the ionian zone of western greece the upper part of the upper senonian to upper eocene microbreccious limestones formation was selected as the most suitable facies for a detailed regional palaeomagnetic study the 51 sites sampled are situated on flanks of anticlines or monoclines which post date the acquisition of the characteristic remanent magnetization the regional folding occurred during post late eocene emplacement of nappe sheets which had undergone decollement on triassic evaporitic horizons the palaeomagnetic directions after correction for deviations of local fold axis orientation have a regional significance after this correction the mean palaeodeclination is about 35 e relative to the geographic pole with respect to the early tertiary african pole position these palaeodeclinations indicate an apparent 38 clockwise rotation of the nappe sheets the palaeoinclinations support a palaeogeographic model locating the carbonate sediments of the ionian zone on the northeastern margin of the adriatic promontory of the african plate the total rotation implied by the palaeodeclination data is possibly due to a combination of two different mechanisms 1 1 rotation of the nappe sheets during overthrust and emplacement during the main mid miocene compressional phase of deformation 2 2 rotation of the ionian zone basement and nappes associated with extension in the aegean basin during the last 13 m y

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

the aegean sea we summarize briefly the main features of a kinematic model of evolution of the aegean area since 13 ma the formation of the aegean sea by extensional tectonics is related to the subduction of the mediterranean floor below the hellenic arc we then make a quantitative estimate of vertical movements in the aegean area on the basis of geological data and demonstrate that the outer arc was built since the beginning of this episode of subduction by vertical uplift the easiest way to explain the uplift is by underplating finally we discuss briefly the dynamics of the subduction marginal sea formation processes in this continental collision framework

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

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr