early human occupation of a maritime desert barrow island north west australia abstract archaeological deposits from boodie cave on barrow island northwest australia reveal some of the oldest evidence for aboriginal occupation of australia as well as illustrating the early use of marine resources by modern peoples outside of africa barrow island is a large 202 km 2 limestone continental island located on the north west shelf of australia optimally located to sample past use of both the pleistocene coastline and extensive arid coastal plains an interdisciplinary team forming the barrow island archaeology project biap has addressed questions focusing on the antiquity of occupation of coastal deserts by hunter gatherers the use and distribution of marine resources from the coast to the interior and the productivity of the marine zone with changing sea levels boodie cave is the largest of 20 stratified deposits identified on barrow island with 20 m 3 of cultural deposits excavated between 2013 and 2015 in this first major synthesis we focus on the dating and sedimentology of boodie cave to establish the framework for ongoing analysis of cultural materials we present new data on these cultural assemblages including charcoal faunal remains and lithics integrated with micromorphology sedimentary history and dating by four independent laboratories first occupation occurs between 51 1 and 46 2 ka overlapping with the earliest dates for occupation of australia marine resources are incorporated into dietary assemblages by 42 5 ka and continue to be transported to the cave through all periods of occupation despite fluctuating sea levels and dramatic extensions of the coastal plain the changing quantities of marine fauna through time reflect the varying distance of the cave from the contemporaneous shoreline the dietary breadth of both arid zone terrestrial fauna and marine species increases after the last glacial maximum and significantly so by the mid holocene the cave is abandoned by 6 8 ka when the island becomes increasingly distant from the mainland coast

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

late holocene asian monsoon variations recorded in lake rara sediment western nepal the himalayas are a key location for understanding centennial to millennial scale variations in the asian monsoon yet few studies of the late holocene have been conducted in this sensitive area direct evidence for shifts in monsoonal wind strength is often limited to marine proxy records while terrestrial reconstructions e g lake levels and spleothems focus on precipitation here we present the first evidence of terrestrial summer monsoon wind strength changes from lake rara western nepal based on mn ti ratios a proxy for lake stratification these data indicate a link between the arabian sea and the himalayas suggesting that centennial to millennial scale changes in wind strength occurred synchronously distinct similarity is also observed between lake rara and the southern part of china which may support previous suggestions that the southern part of china is influenced by indian summer monsoon copyright 2012 john wiley sons ltd

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

middle to late holocene environmental changes in the depositional system of the tropical brackish bolgoda lake coastal southwest sri lanka abstract the tropical bolgoda lake is one of the largest lagoonal estuaries in sri lanka organic constituents in this lake were investigated using 28 surface sediments three cores from the lake and four short cores from mangrove mud elemental and molecular compositions of sediments and living organic matter om were determined using cns elemental analysis and gas chromatography mass spectrometry respectively chronology of events was determined using accelerated mass spectrometry ams 14 c data for bulk oms woods and mollusk shells the history of bolgoda lake can be divided into two major chrono stratigraphic divisions namely a lower sedimentary succession from ca 7 0 cal ky b p to 2 5 cal ky b p and an upper sedimentary succession from ca 2 5 cal ky b p to the recent according to the sapropelic depositional system concentrations of the mangrove biomarker taraxone increased significantly at ca 7 0 cal ky b p the lower part of the sediment sequence had moderate productivity and was mainly deposited under marine terrestrial influence in oxygen poor anoxic conditions during mid holocene sea level highstands a drastic increase in total organic carbon toc content reaching 29 was found in one of the bolgoda cores this increase occurred because of sea level regression at about 2 5 cal ky b p this change was probably caused by development of a beach rock sandbar and the estuary system changed to a semi closed lake due to the sea level regression as a result aquatic vascular plants predominate in this depositional system after ca 2 5 cal ky b p toc content decreased slightly but relatively high toc contents were maintained in the muddy sediments in moderately sized and shallow 1 2 m tropical estuaries lagoons such as bolgoda lake drastic changes in toc contents may be the most sensitive indicator of sea level variations increase in higher plant om with higher n c 29 n c all and n c 37 n c all alkane ratios also suggest a climatic transition from wetter to somewhat drier after the middle holocene accumulations of pyrogenic polycyclic aromatic hydrocarbons pahs in the modern sediments record anthropogenic activity after european settlement in the 15th century

high resolution 14c dating of a 25 000 year lake sediment record from equatorial east africa abstract we dated a continuous 22 m long sediment sequence from lake challa mt kilimanjaro area kenya tanzania to produce a solid chronological framework for multi proxy reconstructions of climate and environmental change in equatorial east africa over the past 25 000 years the age model is based on a total of 168 ams 14 c dates on bulk organic matter combined with a 210 pb chronology for recent sediments and corrected for a variable old carbon age offset this offset was estimated by i pairing bulk organic 14 c dates with either 210 pb derived time markers or 14 c dates on grass charcoal and ii wiggle matching high density series of bulk organic 14 c dates variation in the old carbon age offset through time is relatively modest ranging from 450 yr during glacial and late glacial time to 200 yr during the early and mid holocene and increasing again to 250 yr today the screened and corrected 14 c dates were calibrated sequentially statistically constrained by their stratigraphical order as a result their constrained calendar age distributions are much narrower and the calibrated dates more precise than if each 14 c date had been calibrated on its own the smooth spline age depth model has 95 age uncertainty ranges of 50 230 yr during the holocene and 250 550 yr in the glacial section of the record the 13 c values of paired bulk organic and grass charcoal samples and additional 14 c dating on selected turbidite horizons indicates that the old carbon age offset in lake challa is caused by a variable contribution of old terrestrial organic matter eroded from soils and controlled mainly by changes in vegetation cover within the crater basin

holocene indian ocean sea level antarctic melting history and past tsunami deposits inferred using sea level reconstructions from the sri lankan southeastern indian and maldivian coasts abstract holocene sea level change in the northern indian ocean was studied using geochemical and geophysical approaches molluscs were sub sampled for radiocarbon dating from sediment cores retrieved from a south sri lankan coastal lagoon they were then combined with previously published sediment core radiocarbon ages from the same lagoon we observe a 20 fold reduction in sedimentation rates at around 4 ka attributed to a decrease in the rate of sea level rise previously reported radiocarbon ages based on total organic matter in the lagoon show remarkable agreement with our new dates suggesting stable and homogeneous sedimentation during the last 8 ka comparison of down core age trends of both data sets reveal that sediments are older than coeval molluscs except for the horizons adjacent to the paleo tsunami layers indicating fresh and younger sediments are provided during tsunami events which could become a new proxy for identifying paleo tsunamis compilation of previously reported sea level indicators from sri lanka southeastern india and the maldives together with predicted sea level obtained from a glacio hydro isostatic adjustment model gia suggest that 3 4 m of global sea level equivalent ice sheet melting occurred during the mid holocene due to the retreat of the antarctic and or greenland ice sheets previous works suggests late holocene ca 4 ka climate anomalies in both the low and high latitudes we suggest the low latitude climate anomaly transmitted via atmosphere to the high latitude during the late holocene seems to have induced changes in polar ice sheets

on the structure and origin of major glaciation cycles 1 linear responses to milankovitch forcing time series of ocean properties provide a measure of global ice volume and monitor key features of the wind driven and density driven circulations over the past 400 000 years cycles with periods near 23 000 41 000 and 100 000 years dominate this climatic narrative when the narrative is examined in a geographic array of time series the phase of each climatic oscillation is seen to progress through the system in essentially the same geographic sequence in all three cycles we argue that the 23 000 and 41 000 year cycles of glaciation are continuous linear responses to orbitally driven changes in the arctic radiation budget and we use the phase progression in each climatic cycle to identify the main pathways along which the initial local responses to radiation are propagated by the atmosphere and ocean early in this progression deep waters of the southern ocean appear to act as a carbon trap to stimulate new observations and modeling efforts we offer a process model that gives a synoptic view of climate at the four end member states needed to describe the system s evolution and we propose a dynamic system model that explains the phase progression along causal pathways by specifying inertial constants in a chain of four subsystems solutions to problems involving systems of such complexity are not born full grown like athena from the head of zeus rather they evolve slowly in stages each of which requires a pause to examine data at great lengths in order to guarantee a sure footing and to properly choose the next step victor p starr

a review of coastal palaeoclimate and relative sea level reconstructions using δ13c and c n ratios in organic material holocene reconstructions of relative sea level rsl and environmental change in the coastal zone have become progressively more numerous since the importance of assessing possible future sea level rises has become apparent traditionally this has been achieved using a combination of biological and physical indicators e g pollen diatoms foraminifera grain size etc in some circumstances microfossils can be rare or absent from holocene sediments and in these cases carbon isotope ratios 13c and organic carbon to total nitrogen ratios c n can be used because they have the potential to provide information as to the origin of organic material preserved in coastal environments the distinction in 13c and c n of the various sources of carbon to estuarine sediments has led to its wide use as a tracer of carbon pathways and storage in estuaries more recently these techniques have been applied to holocene sediments to decipher changes in palaeocoastal environments and thus position relative to sea level and or palaeoriver discharge which have direct relevance to palaeoclimate this paper reviews the studies that have utilised this technique and explores examples from a wide range of coastal environments saltmarshes estuaries lagoons isolation basins and fjords it also discusses the potential alteration of geochemical signatures as a result of decompositional processes organic matter decomposition has been shown to change sediment 13c and c n values and thus an understanding of the processes involved is necessary in order to have confidence in the palaeoenvironmental interpretation of holocene 13c and c n decompositional shifts in c n and particularly 13c can occur over a relatively short time period however it is the direction of change in 13c and c n rather than absolute values that is key for interpreting changes in relative sea level and thus such changes are commonly preserved

high times on the tibetan plateau paleoelevation of the thakkhola graben nepal east west extension in the tibetan plateau is generally assumed to have resulted from gravitational collapse following thickening and uplift on the basis of this assumption several studies have dated east west extensional structures to determine when the plateau attained its current high elevation however independent estimates of elevation are needed to determine whether extension occurred before during or after the plateau achieved its current elevation because the isotopic composition of meteoric water decreases with increasing elevation significant change in local elevation throughout the thakkhola graben depositional history should be recorded by change in 18 o values of fluvial and lacustrine carbonates the 18 o values of 16 to 23 of thakkhola graben carbonates reflect meteoric water values similar to modern values and suggest that the southern tibetan plateau attained its current elevation prior to eastwest extension initiation of thakkhola graben extension is constrained between 10 and 11 ma based on magnetostratigraphy of the older tetang formation the 13 c values of soil carbonates suggest an age younger than 8 ma for the base of the thakkhola formation

the tibetan plateau as amplifier of orbital scale variability of the east asian monsoon 1 asian monsoon climate variability at geological time scales is modulated by both the earth s orbital changes and tectonic uplift of the tibetan plateau tp here using bandpass filtered versions of previously published high resolution geological records from chinese loess we show that the orbital scale variability of the east asian summer monsoon easm has increased dramatically since the late pliocene climate model simulations indicate that the increase in the variability of the northern easm at both precession and tilt periods may be at least partially attributed to the uplift of the tp

monsoons and the dynamics of deserts the existence of subtropical deserts such as the sahara has often been attributed to the annual mean zonal mean hadley circulation which shows strong descent in the subtropics however the zonal mean hadley circulation shows considerable evolution over the course of the year with very strong subtropical descent during winter but practically no zonal mean subtropical descent during summer when rainfall over the eastern sahara and the mediterranean is least charney 1975 proposed a biosphere albedo feedback mechanism whereby local anthropogenic effects related to over grazing could affect the radiative balance enhancing summertime diabatic descent and leading to desertification of the subtropics in general the present study which uses an idealized model suggests a monsoon desert mechanism for desertification whereby remote diabatic heating in the asian monsoon region can induce a rossby wave pattern to the west integral with the rossby wave solution is a warm thermal structure that interacts with air on the southern flank of the mid latitude westerlies causing it to descend this adiabatic descent is localized over the eastern sahara and mediterranean and over the kyzylkum desert to the south east of the aral sea by the mountains of north africa and south west asia trajectories indicate that the monsoon desert mechanism does not represent a simple walker type overturning cell instead the descending air is seen to be mainly of mid latitude origin it is speculated that the monsoon forced adiabatic descent may result in clear air and therefore a local diabatic enhancement which effectively doubles the strength of descent with this mechanism desertification can be forced by remote changes in monsoon strength rather than by local effects this conclusion is supported by the observed dramatic strengthening of descent over the mediterranean and east sahara during the onset of the asian monsoon and on the longer timescale by relating prehistoric lake levels to milankovitch monsoon forcing the latter may help to explain the perceived discrepancies between the palaeoclimate of the eastern sahara and the strength of a tropic wide monsoon the monsoon desert mechanism may not be confined to the asian monsoon alone and the existence of other monsoon climate regions over the globe may in a similar way explain the observed summertime strengthening of the oceanic sub tropical anticyclones and the existence of western continental deserts and mediterranean type climate regions

history of the great kanto earthquakes inferred from the ages of holocene marine terraces revealed by a comprehensive drilling survey abstract we measured the emergence ages of four marine terraces in the chikura lowland which lies to the southeast of the boso peninsula in eastern japan to reevaluate the history of the great earthquake occurrences along the sagami trough over the past 10 000 years the dates of the marine terraces are measured via radiocarbon dating of shell fossils obtained from the marine deposits the sampling method employed in this study collects core samples using a dense and systematic drilling survey which increased the reliability when correlating shell fossils with marine terraces in addition radiocarbon dating was performed with accelerator mass spectrometry which produces more highly accurate measurements than those measured in previous studies moreover we explored the surface profiles of the terraces with detailed digital elevation model dem data obtained using lidar the maximum emergence ages of the marine terraces were dated at 6300 cal ybp 3000 cal ybp and 2200 cal ybp from the top terrace excepting the lowest terrace which was estimated at ad1703 in addition another previously unrecognized terrace was detected between the highest and the second terrace in both the dating and the geomorphological analyses and was dated at 5800 cal ybp the newly obtained ages are nearly a thousand of years younger than previously estimated ages consequently the intervals of the great earthquakes that occurred along the sagami trough are estimated to be much shorter and more varied than those of previous estimations this result revises the data used in the current assessment of the probabilities of earthquakes along the sagami trough which could devastate the tokyo metropolitan area furthermore it demonstrates that the current approach could be a powerful tool to increase the accuracy of assessments of the other areas with depositional marine terraces

sea level at the last glacial maximum evidence from northwestern australia to constrain ice volumes for oxygen isotope stage 2 new sea level information from the bonaparte gulf in northwestern australia is used to constrain the magnitude and rates of change of ice volumes during the last glacial maximum lgm the region is tectonically stable and far from the former ice covered regions the glacio hydro isostatic adjustment of the coast is therefore relatively small and the corrections for this evect are not sensitive to details of the rebound model microfossil analysis and ams radiocarbon dating of 11 gravity cores taken across the shelf and bonaparte gulf demonstrate that 1 the lgm sea levels were locally at 125 4 m 2 the lgm terminated abruptly at 19 000 cal yr bp with a rapid rise in sea level of about 15 m over the next 500 years and 3 the onset of the minimum sea levels occurred before 22 000 cal yr bp when corrected for the glacio hydro isostatic evects the increase of lgm ice volumes over the present day ice volume is 52 5 106 km3 the termination of the lgm is marked by a rapid ice discharge of 5 2 106 km3 2001 elsevier science b v all rights reserved

the murray springs clovis site pleistocene extinction and the question of extraterrestrial impact some of the evidence for the recent hypothesis of an extraterrestrial impact that caused late pleistocene megafaunal extinctions firestone et al 2007 proc natl acad sci usa 104 16016 16021 was based upon samples collected at murray springs a clovis archaeological site in southeastern arizona here we describe sampling and analyses of magnetic separates from within above and below the lower younger dryas boundary lydb black mat at murray springs as well as radiation measurements from the lydb at murray springs and two other well stratified clovis sites the main magnetic fraction at murray springs is maghemite magnetic microspherules have terrestrial origins but also occur as cosmic dust particles we failed to find iridium or radiation anomalies the evidence for massive biomass burning at murray springs is addressed and found to be lacking we could not substantiate some of the claims by firestone and others but our findings do not preclude a terminal pleistocene cosmic event

reappraisal of sea level lowstand during the last glacial maximum observed in the bonaparte gulf sediments northwestern australia abstract during the last glacial maximum lgm ice volume reached a relative maximum and global temperature was lower than today understanding continental ice volume change requires accurate reconstruction of relative sea level but tectonic uplift and isostatic adjustment effects complicate many records using marine sediment cores from the bonaparte gulf in northwestern australia a so called far field tectonically stable site yokoyama et al 2000 reported that the lgm terminated abruptly at 19 ka with a rapid sea level rise 19 ka event their sea level reconstruction determined the age of the lgm termination but the timing of its inception remained less well constrained partly because the number of radiocarbon analyses was insufficient to clarify lgm duration here we return to the bonaparte gulf and present a new relative sea level that better constrains lgm duration with high resolution radiocarbon dating of a recently recovered marine sediment core water depth 120 m length 583 cm radiocarbon dating of 23 molluscs and 26 bulk organic matter samples together with total organic carbon total nitrogen and stable carbon isotopes provide a record of paleoenvironmental variability in response to sea level change our results indicate that the lgm sea level minimum occurred at 20 8 cal ka bp and the lgm duration was shorter than previously reported

total meltwater volume since the last glacial maximum and viscosity structure of earth s mantle inferred from relative sea level changes at barbados and bonaparte gulf and gia induced j2

summer monsoon variations over the last 1 2 ma from the weathering of loess soil sequences in china the loess soil sequence in northern china contains a near continuous record of quaternary paleoclimate magnetic susceptibility and grain size have so far been the only proxies available to address the long term changes of the east asian paleomonsoon extending back to more than one million years in this study the ratio of cbd citrate bicarbonate dithionite extractable free fe2o3 fed a measure of iron liberated by chemical weathering versus the total fe2o3 available fet was measured on samples at 10 cm intervals taken from two loess sections deposited over the last 1 2 ma variations of this index are highly consistent with other pedological indicators but in addition provide a quantitative measurement of the degree of pedogenesis in the loess plateau since chemical weathering in the region mainly depends upon summer precipitation and temperature weathering intensity primarily reflects changes in the east asian summer monsoon the new proxy has been used to document a series of summer monsoon changes of global significance which are not necessarily recorded by magnetic susceptibility

simulating the amplification of orbital forcing by ocean feedbacks in the last glaciation according to milankovitch theory the lower summer insolation at high latitudes about 115 000 years ago allowed winter snow to persist throughout summer leading to ice sheet build up and glaciation1 but attempts to simulate the last glaciation using global atmospheric models have failed to produce this outcome when forced by insolation changes only2 3 4 5 these results point towards the importance of feedback effects for example through changes in vegetation or the ocean circulation for the amplification of solar forcing6 7 8 9 here we present a fully coupled ocean atmosphere model of the last glaciation that produces a build up of perennial snow cover at known locations of ice sheets during this period we show that ocean feedbacks lead to a cooling of the high northern latitudes along with an increase in atmospheric moisture transport from the equator to the poles these changes agree with available geological data10 11 12 13 14 15 and together they lead to an increased delivery of snow to high northern latitudes the mechanism we present explains the onset of glaciation which would be amplified by changes in vegetation in response to weak orbital forcing

the influence of continental ice sheets on the climate of an ice age the climate influence of the land ice that existed 18 000 years before present 18k b p is investigated by use of a general circulation model of the atmosphere coupled with a static mixed layer ocean simulated climates are obtained from two versions of the model one with the land ice distribution of the present and the other with that of 18k b p in the northern hemisphere the tropospheric flow field is strongly influenced by the laurentide ice sheet and features a split flow straddling the ice sheet with a strong jet stream forming the southern branch the northern branch of the flow brings very cold air over the north atlantic ocean where thick sea ice is maintained the distribution of sea surface temperature sst difference between the two experiments in the northern hemisphere resembles the difference between the sst at 18k b p and at present as estimated by the climap project 1981 the 18k b p ice sheets have very little influence upon atmospheric temperature and sst in the southern hemisphere this is because the interhemispheric heat transport hardly changes as the loss of heat energy due to the reflection of solar radiation by continental ice sheets in the northern hemisphere is almost completely counterbalanced by the in situ reduction of upward terrestrial radiation hydrologic changes in the model climate are also found with statistically significant decreases in soil moisture occurring in a zone located to the south of the ice sheets in north america and eurasia these findings are consistent with some geological evidence of regionally drier climates from the last glacial maximum

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

pliocene uplift of the northern tibetan plateau neogene redbeds passing upward into upward coarsening conglomerate and debris flow deposits at the foot of the kunlun mountains record the change in paleoslope related to uplift of the surface of the northern tibetan plateau detailed magnetostratigraphy of a 4 5 km section near yecheng in the western kunlun mountains shows that the change from deposition on distal alluvial plains to proximal alluvial fans occurred during the gilbert reversed chron 4 5 3 5 ma the change in depositional facies was accompanied by an increase in sedimentation rate from an average 0 15 mm yr between the earliest oligocene and the earliest pliocene to 1 4 mm yr in the gauss normal chron 3 6 2 6 ma we interpret the change in depositional facies and increase in sedimentation rate as indicating that the main uplift of the northwestern tibetan plateau began ca 4 5 ma