present and former equilibrium line altitudes in the taiwanese high mountain range abstract previously reported values of former equilibrium line altitudes ela for taiwan are based on sparse field data or extrapolations from japan or china this paper presents new calculations based on recently obtained geological data hebenstreit r bose m 2003 geomorphological evidence for a late pleistocene glaciation in the high mountains of taiwan dated with age estimates by optically stimulated luminescence osl zeitschrift fur geomorphologie n f suppl bd 130 31 49 hebenstreit r murray a s bose m this vol late pleistocene and early holocene glaciations in taiwanese mountains quaternary international from three taiwanese mountain massifs nanhuta shan hsueh shan and yushan using established calculation methods benn d i lehmkuhl f 2000 mass balance and equilibrium line altitudes of glaciers in high mountain environments quaternary international 65 66 15 29 porter s c 2001 snowline depression in the tropics during the last glaciation quaternary science reviews 20 10 1067 1091 the relationship of annual precipitation and summer jja temperature ohmura a kasser p funk m 1992 climate at the equilibrium line of glaciers journal of glaciology 38 130 397 411 obtained from a 30 year meteorological database is used to estimate the present theoretical virtual equilibrium line altitude ela t at about 4000 m over the southern and 3900 m over the northern part of taiwan the ela was 3350 3500 m during late glacial to early holocene time 11 8 ka including a minimum post glacial mountain uplift rate of 5 mm a lundberg n dorsey r j 1990 rapid quaternary emergence uplift and denudation of the coastal range eastern taiwan geology 18 7 638 641 lin c h 1998 tectonic implications of an aseismic belt beneath the eastern central range of taiwan crustal subduction and exhumation journal of the geological society of china 41 3 441 460 in the calculation the ela depression ela was 400 550 m during this period data from lgm or earlier are still rare but glacial landforms and deposits indicate the ela position at 2775 3195 m and the ela of 705 1125 m

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

characteristics of late quaternary monsoonal glaciation on the tibetan plateau and in east asia abstract glaciers fed by monsoonal precipitation are mainly located on the tibetan plateau and easternmost asia these are characterized by simultaneous accumulation and ablation in summer season the southeast part of the tibetan plateau experiences monsoonal precipitation in excess of 1000 mm yr resulting in maritime temperate glaciers in contrast precipitation in the middle and northwest part of the tibet plateau decreases from 1000 to 200 mm yr resulting in the formation of continental cold glaciers during the last glacial the regions of heavy monsoonal precipitation were restricted to the southeast corner of the plateau the westerly weak precipitation zone shifted southward and occupied the major northwest part of the plateau where the extreme continental type glaciers greatly expanded in the eastern margin of asia including taiwan central japan hokkaido and probably mount changbai maritime type glaciers were more extensive because of higher monsoonal precipitation especially heavy snowfall in northwest japan owing to the rich moisture content of the winter monsoon over the japan sea the millennial scale monsoon intensity and glacial cycle in the tibetan plateau are strongly affected by the precession cycle and the orbit inclination cycle which dominate the solar irradiance variation in low latitudes as the high radiation and strong monsoon caused the warmer and wetter climate during 40 30 ka the low radiation produced a weak monsoon and large depression of temperature and precipitation around 21 ka this climatic pattern differs from that in the high latitudes where the eccentricity cycle is prominent the temperature during the last glacial maximum lgm was 6 9 c lower than today on the tibetan plateau and the equilibrium line altitude was depressed by about 1000 m in the southeast part and in the east south and west margins of the plateau where precipitation was high the equilibrium line depression was 500 300 m in the inner and especially the west part of the plateau this variation in equilibrium lines might be caused by the combined effect of the decrease in precipitation the expansion of extreme continental glaciers and the active uplift of glaciated mountains the estimation of a glaciated area of about 350 000 km2 in the tibetan plateau and roughly 500 000 km2 in high asia based on observations of prominent features of lgm glacier extension may be the direct evidence that shows there was no quaternary unified ice sheet developed in the tibetan plateau

the last glacial maximum to holocene environment changes in the southern okinawa trough presented here are the oxygen and carbon isotope records of two epipelagic planktonic foraminiferal species globigerinoides sacculifer and neogloboquadrina dutertrei from a sediment core which was collected from the southern okinawa trough these isotope records provide an opportunity to understand the paleoceanographic evolution of the okinawa trough since the last deglaciation the younger dryas cooling event in the okinawa trough is reported for the first time in this paper these data also record meltwater spikes during the younger dryas interval and the entry of the kuroshio current into the okinawa trough the oxygen isotope sequence also records the warm and or humid climate conditions around east asia at about 5 6 ka and the evolution of the kuroshio current during the late holocene

climate and geomorphology in the uppermost geomorphic belts of the central mountain range taiwan abstract the central mountain range of taiwan is in its lower parts exposed to strong denudation by mass movements caused by extreme rainfalls and active tectonics even though the uppermost regions of the mountains are also influenced by earthquakes and typhoon rains present geomorphic activity is low investigations based on field work and air photo study in nanhuta shan 3742 m and yushan 3952 m and the analysis of climate data indicate the presence of a periglacial belt with a lower limit at 3600 3700 m the upper limit of the periglacial belt in taiwan is not met ground temperature measurements in nanhuta shan show that freeze thaw activity at 3560 m during the winter is restricted to the top few centimetres of the ground and the maximum frost depth is 25 cm the only indicator landforms within the periglacial belt are smooth slopes the high relief energy and a lack of fine material account for the absence of other periglacial landforms relict solifluction terraces debris cones and slope failures found between 3400 and 3600 m in nanhuta shan are strong evidence for a period of increased slope activity during the holocene which in two cases were dated by osl to approx 3 ka at least one solifluction unit developed during a cooler phase between 3 ka and today

supply and removal of sediment in a landslide dominated mountain belt central range taiwan abstract a strong coupling between hillslope and valley systems is often inferred for mountain landscapes dominated by bedrock landsliding we reveal the nature of this link using data sets on landsliding and sediment transport from two montane catchments draining the eastern central range of taiwan here the magnitude frequency distribution of landslides can be modeled by a robust power law but this scale invariance is not mirrored in the sediment discharge at the mountain front instead downstream sediment loads reflect a complex response to both sediment supply and ambient hydraulic conditions the rivers do not transport significant amounts of sediment unless it is provided by hillslope mass wasting in the catchment removal of landslide debris is a function of the transport capacity of the stream at the site of entry thus there is a dual supply and transport control on sediment loads in bedrock floored streams over a monitoring period of 25 yr the bulk of the sediment leaving the mountain bel

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

heinrich event imprints in the okinawa trough evidence from oxygen isotope and planktonic foraminifera planktonic foraminiferal faunas oxygen isotope and modern analog technique sea surface temperature records were obtained in piston core dgks9603 28degrees08 869 n 127degrees16 238 e water depth 1100 in collected from the middle okinawa trough during the last glaciation four cold events were identified and correlate heinrich events he h2 5 of the last 45 ka during the last deglaciation core dgks9603 has begun to be influenced by the kuroshio since about 16 cal ka bp three weakenings of this warm current occurred at about 2 8 5 3 11 4 and 15 5 cal ka bp respectively among the three fluctuations the oldest one is synchronous with he1 and could be a response to the strong cooling observed in the north atlantic ocean the fluctuation occurring at about 11 4 cal ka ago corresponds to the younger dryas within the age error bars our observations provide new evidence that the hes documented from greenland and the northern north atlantic had a global climatic impact changes in the intensity of the east asian monsoon could be the main mechanism responsible for the paleoccanographic variations observed in the okinawa trough c 2001 elsevier science b v all rights reserved

p wave seismic velocity and vp vs ratio beneath the italian peninsula from local earthquake tomography abstract we investigate the p wave velocity structure and the vp vs ratio beneath the italian peninsula down to 100 and 60 km depth respectively by seismic travel time tomography we invert data provided by the international seismological centre isc 1997 2005 making use of some alternative strategies for the travel time approach in a well constrained and worldwide adopted code simulps resolution for the different layers is discussed and sensitivity analyses are performed through test inversions to explore the resolution characteristics of the model at different spatial scales the resulting tomographic images provide a detailed sketch of the p wave anomalies clearly showing among the other features the shape of the ivrea body in the western alps the upwelling of the oceanic crust in the ligurian sea and the slab under the calabrian arc they are less informative for the vp vs ratio nevertheless some features are very interesting and deserve further investigation like the anomalous decrease of the vp vs ratio under the ligurian sea or the variations of the vp vs ratio calculated in the first 10 km depth of the apenninic region with respect to the lower values of the alpine region at the same depth the tomographic cross sections reveal a continuous superposition of two kinds of crusts transitional over adriatic all along the peninsula but do not show any slab intended as a clear vertical downgoing high velocity material in either the northern or central apennines

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

geomorphic altitudinal zonation of the high mountains of taiwan abstract the central range of taiwan has the characteristics of a high mountain area pleistocene glacial forms crests exceeding the timberline and debris slopes produced by frost weathering estimated denudation rates for taiwan have an average of 5 mm a and are presumed to be in equilibrium with the uplift rate these values are derived either from short term debris measurements in rivers or from fission track dating for a long term evaluation a 5 mm a denudation rate over long timescales seems reasonable but does not indicate whether this rate operated continuously throughout today it is apparent that mass movements and fluvial erosion triggered by typhoons are more intense at altitudes below 3000 m a s l and therefore the denudation rate in these altitudes is very likely higher than 5 mm a above 3000 m precipitation is lower mass movements are rare and above 3400 3500 m a s l frost weathering during winter produces debris slopes low fluvial activity in the seasonal to episodically occupied stream valleys does not significantly contribute to fluvial erosion only in very few places has backward erosion already reached the zone above 3000 m a s l and gravity related processes are active since glacial features are still preserved the denudation rate is considered to have been lower than 5 mm a since the last glacial cycle and denudation in the mountains is not in equilibrium from the top to the lower valleys

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

scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces abstract the decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains sloped surfaces and local rock formations that block them when a large part of the sky is blocked this correction is large and requires detailed model calculations this paper considers three geometries a rectangular obstruction a triangular obstruction and a sloped surface other geometries can be considered as a combination of these the results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides

correction of in situ cosmogenic nuclide production rates for geomagnetic field intensity variations during the past 800 000 years we present integrated relative production rates for cosmogenic nuclides in rock surfaces which take into account reported variations of the geomagnetic field intensity during the past 800 000 yr the calculations are based on the model simulating cosmic ray particle interactions with the earth s atmosphere given by masarik and beer simulation of particle fluxes and cosmogenic nuclide production in the earth s atmosphere j geophys res 104 d10 12099 12111 1999 corrections are nearly independent on altitude between sea level and at least 5000 m the correction factors are essentially identical for all stable and radioactive cosmogenic nuclides with half lives longer than a few hundred thousand years at the equator integrated production rates for exposure ages between 40 000 to 800 000 yr are 10 to 12 higher than the present day values whereas at latitudes 40 geomagnetic field intensity variations have hardly influenced in situ cosmogenic nuclide production correction factors for in situ 14c production rates differ from those of longer lived nuclides they are always smaller than 2 because the magnetic field intensity remained rather constant during the past 10 kyr when the major fraction of the 14c extant today was produced

rates of cooling and denudation of the early penglai orogeny taiwan as assessed by fission track constraints abstract as an attempt to define the timing of the peak temperature of the penglai orogeny and estimate the early cooling and denudation rates of the taiwan mountain belt fission track dating of zircon and apatite was conducted on several key metamorphic rock samples the zircon fission track ages for the metasandstone clasts collected from the central and northern parts of the coastal range were determined as 4 0 0 5 and 3 6 0 3 ma respectively both of the clasts were identified as from the ancient central range which was metamorphosed at temperatures high enough to cause a complete reset of the zircon fission track system during 1 2 ma they were exhumed and deposited in the coastal range basin due to the later penglai orogeny of taiwan obviously they have not further been annealed since their deposition in the coastal range the difference between the above fission track ages and the stratigraphical age of the host sedimentary formation represent the ancient cooling ages when they were exposed on the early central range these ancient cooling ages are comparable with the zircon fission track age of a present day outcrop of the tananao schist 1 8 0 2 ma this accordance implies that at ca 5 ma the northern and central parts of the central range achieved the peak temperature of the penglai orogeny and then they began to emerge above sea level accepting this scenario we calculate the rates of denudation and cooling of the central range to be ca 2 5 4 6 mm yr 1 and 120 c m y 1 respectively for the last 4 ma

mountain glaciation in japan and taiwan at the global last glacial maximum abstract montane glaciation in japan and taiwan was maximal in mis 3 4 and glacier extent at the global last glacial maximum lgm was much more limited data from four areas in japan and two in taiwan where the topographical and chronological positions of the terminal moraines are well determined and the chronology is controlled by radiocarbon ams and 10be cosmogenic dates are presented in this paper equilibrium line altitudes elas at global lgm are around 1500 m in the hidaka range hokkaido 2500 m in the northern japanese alps 2700 m in the central japanese alps 2800 m in the southern japanese alps in japan and 3300 m in northern taiwan and 3500 m in central taiwan the elas are mostly determined by maximum discharge accumulation ablation area ratio aar and glacier toe and headwall ratio thar methods the pattern of contours of elas indicates a strong influence of precipitation control on glacier development in this region the ela depression at global lgm in japan was 1100 1300 m except in the northernmost part of the northern japanese alps only 400 m where the present hypothetical ela is extraordinarily low because of abundant snowfall the ela depression at global lgm in taiwan is estimated at about 1100 1300 m without consideration of uplift

chinese loess record of monsoon climate during the last glacial interglacial cycle the thick loess paleosol succession of central china contains a detailed record of changes in east asian monsoon climate since the late miocene epoch the alternating loess paleosol stratigraphy closely resembles the marine oxygen isotope record implying that episodic dust deposition and pedogenesis are in phase with global ice volume fluctuations and controlled by variations in solar radiation reaching the land surface deposits equivalent to marine isotope stages mis 5 through 1 have been dated by 14c 10be luminescence and magnetic susceptibility and grain size models malan loess mis 4 2 decreases in thickness southeastward from 30 m in the western loess plateau to 5 m east of xi an downwind asian dust is found in japan the north pacific ocean and the greenland ice sheet where it has a chemical signature that points to a primary source in western china during glacial times the mean dust flux in the central loess plateau reached 0 35 mm year whereas in interglacial times it fell to 0 1 mm year times of high dust influx and reduced soil development coincided with strengthened winter monsoon conditions which are inferred from variations in loess grain size times of decreased dust accumulation and strong pedogenesis marked by high values of magnetic susceptibility represent times of strengthened summer monsoon conditions high frequency fluctuations in dust influx during deposition of the malan loess include peaks that likely correlate with north atlantic heinrich events the younger dryas oscillation is recorded in chinese eolian and organic deposits by a shift from cool humid late glacial conditions to cold and dry conditions followed by a return to milder humid climate at the beginning of the holocene warm moist climate associated with a strong summer monsoon characterized the first half of the holocene epoch when a widespread paleosol complex developed on the loess plateau increased dust deposition during the middle to late holocene marked a shift to cooler drier conditions

the application of spinel bearing metapelites to p t determinations an example from south india metasedimentary migmatites from the archean charnockitic terrain of south india contain the five phase equilibrium assemblage spinel cordierite garnet corundum sillimanite the assemblages is a result of anatexis which has generated a silica deficient anhydrous restite peak metamorphic conditions are defined by the intersection of two divariant reactions in the a12o3 sio2 feo mgo system at which the five phases coexist these reactions are univariant and their intersection invariant if the fe mg ratio of at least one femic phase is fixed

glacial retreat history of nanhuta shan north east taiwan from preserved glacial features the cosmic ray exposure perspective taiwan located at the junction of the pacific ocean the eurasian continent and the south china marginal sea is of particular interest for reconstructing paleoclimate periods in eastern asia this study reports the first cosmic ray exposure dating cre of glacial features in taiwan among the areas where glacial relicts have been described in taiwan the nanhuta shan range is probably the place where glacial landforms are best preserved we consequently focused on this area combining glacial geomorphology observations together with cre dating using in situ produced 10be of erratic boulders and ice sculpted surfaces when combined with the geomorphic characteristics of the sampled areas the obtained minimum cre ages suggest that the glacial retreat in the nanhuta shan commenced about 10 3 ka ago and retreat was complete by 7 1 ka ago this is consistent with the holocene warming trend deduced from other biological and physico chemical paleoclimatic records for the region estimates of local bedrock surface denudation rates either directly from in situ produced 10be measurements or from geomorphic considerations are employed to determine the preservation of such glacial features within the highly dynamic setting of taiwan