evolution of the indian summer monsoon and terrestrial vegetation in the bengal region during the past 18 ka the indian summer monsoon ism is a major global climatic phenomenon long term precipitation proxy records of the ism however are often fragmented and discontinuous impeding an estimation of the magnitude of precipitation variability from the last glacial to the present to improve our understanding of past ism variability we provide a continuous reconstructed record of precipitation and continental vegetation changes from the lower ganges brahmaputra meghna catchment and the indo burman ranges over the last 18 000 years 18 ka the records derive from a marine sediment core from the northern bay of bengal nbob and are complemented by numerical model results of spatial moisture transport and precipitation distribution over the bengal region the isotopic composition of terrestrial plant waxes dd and d13c of n alkanes are compared to results from an isotope enabled general atmospheric circulation model isocam for selected time slices pre industrial mid holocene and heinrich stadial 1 comparison of proxy and model results indicate that past changes in the dd of precipitation and plant waxes were mainly driven by the amount effect and strongly influenced by ism rainfall maximum precipitation is detected for the early holocene climatic optimum ehco 10 5 6 ka bp whereas minimum precipitation occurred during the heinrich stadial 1 hs1 16 9 15 4 ka bp the isocam model results support the hypothesis of a constant moisture source i e the nbob throughout the study period relative to the pre industrial period the model reconstructions show 20 more rain during the mid holocene 6 ka bp and 20 less rain during the heinrich stadial 1 hs1 respectively a shift from c4 plant dominated ecosystems during the glacial to subsequent c3 c4 mixed ones during the interglacial took place vegetation changes were predominantly driven by precipitation variability as evidenced by the significant correlation between the dd and d13c alkane records when compared to other records across the ism domain precipitation and vegetation changes inferred from our records and the numerical model results provide evidence for a coherent regional variability of the ism from the last glacial to the present

itrf2008 plate motion model 1 the itrf2008 velocity field is demonstrated to be of higher quality and more precise than past itrf solutions we estimated an absolute tectonic plate motion model made up of 14 major plates using velocities of 206 sites of high geodetic quality far from plate boundaries deformation zones and glacial isostatic adjustment gia regions derived from and consistent with itrf2008 the precision of the estimated model is evaluated to be at the level of 0 3 mm a wrms no gia corrections were applied to site velocities prior to estimating plate rotation poles as our selected sites are outside the fennoscandia regions where the gia models we tested are performing reasonably well and far from gia areas where the models would degrade the fit antarctica and north america our selected velocity field has small origin rate bias components following the three axis x y z respectively 0 41 0 54 0 22 0 64 and 0 41 0 60 95 per cent confidence limits comparing our model to nnr nuvel 1a and the newly available nnr morvel56 we found better agreement with nnr morvel56 than with nnr nuvel 1a for all plates except for australia where we observe an average residual rotation rate of 4 mm a using our selection of sites we found large global x rotation rates between the two models 0 016 ma and between our model and nnr morvel56 of 0 023 ma equivalent to 2 5 mm a at the earth surface

the source and paleoclimatic implication of hydrogen isotopic composition of n alkanes in sediments from the yixian formation western liaoning province ne china abstract hydrogen isotopic composition of n alkanes was measured in sediments from an excavated profile of the early cretaceous yixian formation in liaoning province ne china aiming to assess the significance of the d value of n alkanes in ancient lacustrine sediments as the indicator for determining the source inputs of organic matters and paleoclimatic conditions the d values of n alkanes are in the range of 250 to 85 and display an obvious three stage variation pattern through the profile which is consistent with the distribution of the dominated n alkanes and the profile of their 13 c values the d and 13 c values of n alkanes suggest that short chain n alkanes are primarily derived from photosynthetic bacteria and algae n c 29 and n c 31 are mainly originated from terrestrial higher plants n c 28 and n c 30 may be derived from the same precursor but via the different biological mechanism of hydrogen isotopic fractionation while the source inputs of medium chain n alkanes are more complicated with n c 23 being derived from some specific algae or biosynthesized by various aquatic organisms the paleoclimatic conditions are reconstructed via two approaches the reconstructed hydrogen isotopic values of lake water and meteoric water expressed as d lw and d mw respectively were at the intervals of 51 8 to 17 0 and 118 1 to 43 5 respectively indicating a general climate transition from semi arid to arid the calculated d lw mw values vary from 37 0 to 89 1 and display a similar but a significant large scale variation trend with the d c 23 long 28 8 to 85 0 long represents long chain n alkanes and d mid long 15 4 to 43 4 mid represents medium chain n alkanes values the discrepancy may be attributed to the source input overlap for n alkanes and the uncertainties of e water lipid values the coupling of d c 23 long d mid long and d lw mw values with the paleoclimatic evidence indicates that the d values of n alkanes could be more sensitive to the change of paleoclimatic conditions

reconstructing lake evaporation history and the isotopic composition of precipitation by a coupled δ18o δ2h biomarker approach summary over the past decades 18 o and 2 h analyses of lacustrine sediments became an invaluable tool in paleohydrology and paleolimnology for reconstructing the isotopic composition of past lake water and precipitation however based on 18 o or 2 h records alone it can be challenging to distinguish between changes of the precipitation signal and changes caused by evaporation here we propose a coupled 18 o 2 h biomarker approach that provides the possibility to disentangle between these two factors the isotopic composition of long chain n alkanes n c 25 n c 27 n c 29 n c 31 were analyzed in order to establish a 16 ka late glacial and holocene 2 h record for the sediment archive of lake panch pokhari in high himalaya nepal the 2 h n alkane record generally corroborates a previously established 18 o sugar record reporting on high values characterizing the deglaciation and the older and the younger dryas and low values characterizing the bolling and the allerod periods since the investigated n alkane and sugar biomarkers are considered to be primarily of aquatic origin they were used to reconstruct the isotopic composition of lake water the reconstructed deuterium excess of lake water ranges from 57 to 85 and is shown to serve as proxy for the evaporation history of lake panch pokhari lake desiccation during the deglaciation the older dryas and the younger dryas is affirmed by a multi proxy approach using the hydrogen index hi and the carbon to nitrogen ratio c n as additional proxies for lake sediment organic matter mineralization furthermore the coupled 18 o and 2 h approach allows disentangling the lake water isotopic enrichment from variations of the isotopic composition of precipitation the reconstructed 16 ka 18 o precipitation record of lake panch pokhari is well in agreement with the 18 o records of chinese speleothems and presumably reflects the indian summer monsoon variability

denali fault slip rates and holocene late pleistocene kinematics of central alaska the denali fault is the principal intracontinental strike slip fault accommodating deformation of interior alaska associated with the yakutat plate convergence we obtained the first quantitative late pleistocene holocene slip rates on the denali fault system from dating offset geomorphic features analysis of cosmogenic 10be concentrations in boulders n 27 and sediment n 13 collected at seven sites offset 25 170 m by the denali and totschunda faults gives average ages that range from 2 4 0 3 ka to 17 0 1 8 ka these offsets and ages yield late pleistocene holocene average slip rates of 9 4 1 6 12 1 1 7 and 8 4 2 2 mm yr 1 along the western central and eastern denali fault respectively and 6 0 1 2 mm yr 1 along the totschunda fault our results suggest a westward decrease in the mean pleistocene holocene slip rate this westward decrease likely results from partitioning of slip from the denali fault system to thrust faults to the north and west

environmental influences over the last 16 ka on compound specific δ13c variations of leaf wax n alkanes in the hani peat deposit from northeast china compound specific carbon isotope ratios 13c of leaf wax n alkanes c21 c33 odd carbon numbered n alkanes were measured in the hani peat sequence from northeast china these data were compared with lipid biomarker compositions to assess changes in local vegetation and paleoclimate for the last 16 ka the 13c values of n alkanes range between 36 6 and 30 7 showing that the compounds originate from c3 plants much larger variations 5 4 in the n alkane 13c values than those of atmospheric co2 during the last 16 ka 0 5 indicate that the isotopic values were affected by environmental factors in addition to the postglacial 13c variations in the atmospheric reservoir the stratigraphic records of 13c reveal decoupled fluctuations among the individual n alkanes particularly between 15 5 and 11 4 ka synchronous excursions in the 13c offsets among individual n alkanes 13c and lipid biomarker paleoplant proxies paq and c23 c31 and c27 c31 from 14 9 to 13 2 ka and 12 7 to 11 6 ka suggest that vegetational changes are the most likely causes for the decoupled 13c variations parallel fluctuations of the 13c values of terrestrial higher plant derived c29 and c31n alkanes and the n alkane average chain length acl from 11 to 6 ka indicate that the 13c variations responded to net evaporation changes negative shifts in the n alkane 13c values coinciding with the acl decreases at 10 5 9 3 ka and 8 1 ka indicate the short term onset and fluctuations of the summer monsoon strength in eastern china during the early holocene

extensional deformation along the late precambrian cambrian baltoscandian passive margin the sarektjakka nappe swedish caledonides the structural evolution of a part of the late precambrian baltoscandian passive margin just before the inception of seafloor spreading is described recording the change from deformation by faulting to dominantly magmatic extension of the crust the allochthon of the scandinavian caledonides contains the imbricated passive margin of continental baltica overlain by various exotic terranes the sarektjakka nappe in the seve nappe complex which contains the outer parts of baltica s passive margin consists of sedimentary rocks occurring as screens between vendian 573 74 ma diabase dykes these dykes constitute 70 80 of the nappe and locally form sheeted dyke complexes the sarektjakka nappe largely escaped penetrative caledonian deformation and preserves igneous metamorphic and structural elements that are linked to the evolution of a pre caledonian rift to a passive continental margin extensional deformation before dyke emplacement is recorded by normal faults pull apart structures and folds unconformities dykes affected by brittle deformation and fluidization of sediments during dyke emplacement indicate close relations between the deposition of sediments extensional deformation and dyke emplacement the sarektjakka nappe is compared with other parts of the baltica s passive margin and its tectonic evolution is discussed

n alkane parameters from a deep sea sediment transect off southwest africa reflect continental vegetation and climate conditions abstract an isobathic transect of marine surface sediments from 1 n to 28 s off southwest africa was used to further evaluate the potential of the chain length distribution and carbon stable isotope composition of higher plant n alkanes as proxies for continental vegetation and climate conditions we found a strong increase in the n c 29 33 weighted mean average 13 c values from 33 near the equator to around 26 further south additionally c 25 35 n alkanes reveal a southward trend of increasing average chain length from 30 0 to 30 5 the data reflect the changing contribution of plants employing different photosynthetic pathways c 3 and c 4 and or being differently influenced by the environmental conditions of their habitat the c 4 plant proportions calculated from the data ca 20 for rivers draining the rainforest to ca 70 at higher latitude correspond to the c 4 plant abundance in continental catchment areas postulated by considering prevailing wind systems and river outflows furthermore the c 4 plant contribution to the sediments correlates with the mean annual precipitation and aridity at selected continental locations in the postulated catchment areas suggesting that the c 4 plant fraction in marine sediments can be used to assess these environmental parameters

deformation during terrane accretion in the saint elias orogen alaska the saint elias orogen of southern alaska and adjacent canada is a complex belt of mountains formed by collision and accretion of the yakutat terrane into the transition zone from transform faulting to subduction in the northeast pacific the orogen is an active analog for tectonic processes that formed much of the north american cordillera and is also an important site to study 1 the relationships between climate and tectonics and 2 structures that generate large to great magnitude earthquakes the yakutat terrane is a fragment of the north american plate margin that is partly subducted beneath and partly accreted to the continental margin of southern alaska interaction between the yakutat terrane and the north american and pacific plates causes significant differences in the style of deformation within the terrane deformation in the eastern part of the terrane is caused by strike slip faulting along the fairweather transform fault and by reverse faulting beneath the coastal mountains but there is little deformation immediately offshore the central part of the orogen is marked by thrusting of the yakutat terrane beneath the north american plate along the chugach saint elias fault and development of a wide thin skinned fold and thrust belt strike slip faulting in this segment may be localized in the hanging wall of the chugach saint elias fault or dissipated by thrust faulting beneath a north northeast trending belt of active deformation that cuts obliquely across the eastern end of the fold and thrust belt superimposed folds with complex shapes and plunging hinge lines accommodate horizontal shortening and extension in the western part of the orogen where the sedimentary cover of the yakutat terrane is accreted into the upper plate of the aleutian subduction zone these three structural segments are separated by transverse tectonic boundaries that cut across the yakutat terrane and also coincide with the courses of piedmont glaciers that flow from the topographic backbone of the saint elias mountains onto the coastal plain the malaspina fault pamplona structural zone separates the eastern and central parts of the orogen and is marked by reverse faulting and folding onshore most of this boundary is buried beneath the western or agassiz lobe of the malaspina piedmont glacier the boundary between the central fold and thrust belt and western zone of superimposed folding lies beneath the middle and lower course of the bering piedmont glacier

lower temperature as the main cause of c4 plant declines during the glacial periods on the chinese loess plateau abstract the distribution of c3 and c4 plants changed in regionally contrasting ways during the last glacial period c4 plant expansion in low latitude africa and america coincided with c4 plant decreases in mesoamerica and the us great plains this c4 plant expansion has been attributed to lower pco2 and increased aridity and the decline in c4 plants is believed to have been caused by increased winter precipitation and lower temperatures however it is still difficult to generalize whether pco2 temperature or aridity was mainly responsible for c3 vs c4 vegetation changes during glacial periods paleoclimate conditions on the chinese loess plateau clp offer opportunities to further evaluate the role of temperature in the c3 vs c4 competition detailed climate records have shown that the clp region was drier and colder during glacial periods with aridity favoring c4 expansion and lower temperatures favoring c3 expansion here we present two high resolution compound specific carbon isotope records of n alkanes from the clp as vegetation biomarkers to estimate the relative abundance of c4 plants during the last two glacial interglacial transitions more negative 13c values during the glacial periods from two clp sites clearly show that in contrast with low latitude sites c4 plants declined this decrease in c4 abundance was caused by lower temperature despite the lower pco2 and increased aridity on the clp during glacial time

humid glacials arid interglacials critical thoughts on pedogenesis and paleoclimate based on multi proxy analyses of the loess paleosol sequence crvenka northern serbia abstract loess paleosol sequences lps provide unique terrestrial archives for past environmental and climate changes the loess units are generally interpreted to reflect more arid conditions whereas paleosols are thought to document more humid conditions this paradigm may however deserve to be challenged in some regions because it does not take into account past changes in dust accumulation rates here we present a multi proxy sedimentological and geochemical characterization of the lps crvenka serbia spanning the last 140 ka commonly used analyses such as magnetic susceptibility organic carbon content grain size and weathering indices allow the quantification of the intensity of pedogenesis however loess accumulation rates were much higher during glacials than during interglacials so that it is not trivial to infer past rates of pedogenesis and related paleoclimate conditions novel proxies based for example on lipid biomarkers and their isotopic composition are not so directly affected by changes in loess accumulation rates and might provide interesting new insights long chain plant derived n alkanes in the lps crvenka suggest a minor but non negligible contribution of deciduous trees and shrubs c27 and c29 during mis 1 2 4 and 6 whereas grasses and herbs c31 and c33 dominate the alkane input during mis 3 and 5 this is in agreement with the notion that parts of southeast europe served as refugia for deciduous trees during glacials on the other hand edaphic conditions on the drought prone loess plateaus seem to have been more arid during mis 3 and 5 compound specific d analyses on the alkanes show only little changes on glacial interglacial timescale when compared with the isotopic enrichment of the mediterranean sea during the last glacial this likely indicates a complex combination of reduced temperatures increased rainfall reduced evapotranspiration and more advection of north atlantic moisture although disentangling these factors is difficult interpretation in terms of humid glacials and more arid interglacials seems to be supported also by other novel lipid biomarkers so called gdgts glycerol dialkyl glycerol tetraethers

asynchronous evolution of the isotopic composition and amount of precipitation in north china during the holocene revealed by a record of compound specific carbon and hydrogen isotopes of long chain n alkanes from an alpine lake both the timing of the maximum east asian summer monsoon easm intensity in monsoonal china and the environmental significance of the chinese stalagmite oxygen isotopic record delta o 18 have been debated here we present a ca 120 year resolution compound specific carbon delta c 13 and hydrogen sd isotopes of terrestrial long chain n alkanes extracted from a well dated sediment core from an alpine lake in north china our delta c 13 data together with previously reported pollen data from a parallel core demonstrate a humid mid holocene from ca 8 5 ka bp assuming that the climatic humidity of north china is an indicator of the easm intensity then the maximum easm intensity occurred in the mid holocene our sd data reveal a similar long term trend to the delta o 18 record from nearby lianhua cave indicating that the synchronous sd and delta o 18 records faithfully record the sd and delta o 18 of precipitation respectively the most negative sd and delta o 18 values occur in t he early mid holocene from ca 11 5 ka bp this contrast in the timing of isotopic variations demonstrates a complex relationship between the isotopic composition of precipitation and precipitation amount or easm intensity further comparisons indicate a possible linkage between the precipitation amount in north china and the west east thermal gradient in the equatorial pacific in addition the temperature of the moisture source area may play an important role in determining the isotopic composition of precipitation in monsoonal china c 2016 elsevier b v all rights reserved

constraining the area of rapid and deep seated exhumation at the st elias syntaxis southeast alaska with detrital zircon fission track analysis the chugach st elias orogen southeast alaska southwest yukon formed in response to the ongoing yakutat microplate subduction collision with the north american plate due to heavy glaciation the region is a prime location to study active convergent orogenesis and climate tectonic interactions this study focuses on the long term distribution of deformation in the st elias syntaxis area where dextral motion along the plate bounding fairweather fault transitions into convergence we present 2718 new zircon fission track single grain ages from 26 glaciofluvial outwash samples the grain ages range from 293 ma to 0 2 ma and each sample contains two to five age populations with peaks between 267 64 ma and 1 2 0 7 ma 1 the rocks of the yakutat microplate are dominated by latest cretaceous and eocene fission track ages while the rocks of the north american plate in the syntaxis region reveal two exhumation phases at 5 1 ma and 2 7 ma the spatial pattern of 5 ma cooling ages shows that the area of rapid and deep exhumation at the st elias syntaxis is more extensive than previously known and confined to the south by the fairweather fault to the west by the seward glacier catchment and to the east possibly by the inferred connector fault the area seems to be 4800 km2 large and may extend farther to the north the new zircon fission track data further suggest a transpressional plate boundary since 30 ma and the onset of plate collision 15 12 ma

hydrogen isotopic compositions along a precipitation gradient of chinese loess plateau critical roles of precipitation evaporation and vegetation change as controls for leaf wax δd abstract the hydrogen isotopic compositions d of long chain plant leaf waxes can reflect changes of continental hydrology and thus have been increasingly utilized for paleoclimate reconstruction one of the unresolved major issues is whether variations of leaf wax d dwax signals along a precipitation gradient reflect changes of precipitation d precipitation amount and or evapo transpiration this ambiguity limits our interpretation of dwax in geological records as well as the quantitative reconstruction of paleohydrological variability here we systematically investigated d of soil water and waxes extracted from soil and plant leaves in the chinese loess plateau clp and its surrounding areas along a precipitation gradient with mean annual precipitation map varying from 140 mm to 676 mm the results showed that while the variation of modeled precipitation d has no significant correlation with map soil water d soil dwax and individual plant dwax exhibit negative correlations with map in relatively arid areas the d values of soil water and plant leaf waxes are significantly more positive due to much lower precipitation relative to evapo transpiration suggesting that effective precipitation p e ratio has played a crucial role in the d enrichment of soil and plant leaf waxes in this region while parallel decreasing trends in dwax are found along the increase of precipitation gradient among dominant plants including artemisia spp aster hispidus stipa bungeana and cleistogenes squarrosa in the region with similar slopes the large d offsets between plant groups suggest that plant type is an important factor in controlling plant hydrogen isotope fractionations our results indicate that dwax preserved in paleosols can be used to infer past conditions of water availability in arid and semi arid inland regions but with a mechanism that is different from the influence of amount effect in humid areas moreover vegetation changes should be constrained by independent paleobotanical data before monsoon related paleohydrology in the clp and its surrounding areas can be quantitatively reconstructed using the plant wax d proxy

hydrogen isotope ratios of lacustrine sedimentary n alkanes as proxies of tropical african hydrology insights from a calibration transect across cameroon abstract hydrogen isotope values d of sedimentary aquatic and terrestrial lipid biomarkers originating from algae bacteria and leaf wax have been used to record isotopic properties of ancient source water i e precipitation and or lake water in several mid and high latitude lacustrine environments in the tropics however where both processes associated with isotope fractionation in the hydrologic system and vegetation strongly differ from those at higher latitudes calibration studies for this proxy are not yet available to close this gap of knowledge we sampled surface sediments from 11 lakes in cameroon to identify those hydro climatological processes and physiological factors that determine the hydrogen isotopic composition of aquatic and terrestrial lipid biomarkers here we present a robust framework for the application of compound specific hydrogen isotopes in tropical africa our results show that the d values of the aquatic lipid biomarker n c17 alkane were not correlated with the d values of lake water carbon isotope measurements indicate that the n c17 alkane was derived from multiple source organisms that used different hydrogen pools for biosynthesis we demonstrate that the d values of the n c29 alkane were correlated with the d values of surface water i e river water and groundwater which on large spatial scales reflect the isotopic composition of mean annual precipitation such a relationship has been observed at higher latitudes supporting the robustness of the leaf wax lipid d proxy on a hemispheric spatial scale in contrast the d values of the n c31 alkane did not show such a relationship but instead were correlated with the evaporative lake water d values this result suggests distinct water sources for both leaf wax lipids most likely originating from two different groups of plants these new findings have important implications for the interpretation of long chain n alkane d records from ancient lake sediments in particular a robust interpretation of palaeohydrological data requires knowledge of the vegetation in the catchment area as different plants may utilise different water sources our results also suggest that the combination of carbon and hydrogen isotopes does help to differentiate between the metabolic pathway and or growth form of organisms and therefore the source of hydrogen used during lipid biosynthesis

the active tectonics of the eastern himalayan syntaxis and surrounding regions source parameters of 53 moderate sized earthquakes obtained from the joint inversion of regional and teleseismic distance long period body waves provide the data set for an analysis of the style of deformation and kinematics in the region of the eastern himalayan syntaxis focal mechanisms of eastern himalayan events show oblique thrust consistent with the n ne directed movement of the indian plate as it underthrusts a boundary that strikes at an oblique angle to the direction of convergence earthquakes near the sagaing fault show strike slip mechanisms with right lateral slip earthquakes on its northern splays however indicate predominant thrusting evidence that the dextral motion on the sagaing fault which accommodates a portion of the lateral motion between india and southeast asia terminates in a zone of thrust faulting at the eastern himalayan syntaxis remaining motion between india and southeast asia is accommodated in a zone of distributed shear in east burma and yunnan manifested by strike slip and oblique normal faulting east west extension crustal thinning and clockwise rotation of crustal blocks we determined strain rates throughout the region with a moment tensor summation using 25 years modern and 85 years modern and historic of earthquake data we matched the observed strains with a fifth order polynomial function and from this we determined both the velocity field and rotations with respect to a specified region velocities calculated relative to south china stationary show that the entire area extending from 20 n 36 n within deforming asia yunnan western sichuan and east tibet constitutes a distributed dextral shear zone with clockwise rotations up to 1 7 m y maximum in the region of the eastern syntaxis proper integrated strains across this zone relative to south china stationary show 38 mm yr 12mm yr of north directed motion at the himalaya remaining plate motion relative to south china fixed must be taken up by the underthrusting of india beneath the lesser himalaya strike slip motion on the sagaing fault and intraplate ne directed shortening within ne india as well as ne directed shortening within the eastern syntaxis proper 10 mm yr 2 mm yr of relative right lateral motion between india and southeast asia is absorbed in the region between the sagaing and red river faults 94 e 100 e it is the clockwise vorticity relative to south china associated with the deformation in yunnan east tibet and western sichuan that provides the relative north directed motion of 38 12 mm yr at the himalaya not all of the deformation is accommodated in right lateral shear between india and south china and between east tibet and south china velocity gradients exist that are parallel to the trend of the shear zone relative to a point within western sichuan 32 n 100 e the velocity field shows that the yunnan crust is moving s se at rates of 8 10 mm yr relative to south china there is no eastward expulsion of crustal material beyond the eastern margin of the tibetan plateau

hydrogen isotope ratios of leaf wax n alkanes in loess and floodplain deposits in northern china since the last glacial maximum and their paleoclimatic significance abstract the hydrogen isotopic composition of leaf wax n alkanes d n alkane is increasingly used as a proxy for estimating d of past precipitation d p however aridity can also affect sedimentary d n alkane complicating the interpretation of paleo d n alkane records in order to evaluate the effects of the complex interactions and balance between precipitation hydrogen isotope composition and aridity on sedimentary d n alkane records we present two d n alkane records from the north china plain and the western chinese loess plateau across a steep east west climatic gradient in the east asian summer monsoon area since the last glacial maximum the estimated d p changes based on a present day relationship between d p and rainfall amounts can explain much of the d n alkane variations in the north china plain but do not explain the large variations of d n alkane in the western chinese loess plateau comparison of d n alkane records with observed d n alkane values in modern plants and published pollen data indicates that changes in vegetation play a minor role in the variations of d n alkane instead d n alkane values are coincident with aridity both temporally and spatially i e the higher d n alkane values the drier climate and vice versa aridity effects are more evident in the western chinese loess plateau than in the north china plain therefore on glacial interglacial scale sedimentary d n alkane records from the north china plain mostly reflect changes in d p values whereas those from the western chinese loess plateau largely reflect the effects of aridity mainly due to a greater evapotranspirational deuterium enrichment caused by a drier climate in the western chinese loess plateau than in the north china plain further calibrations from modern sediments are required to better define the quantitative relationship between the d n alkane and climate in northern china

holocene changes in biome size and tropical cyclone activity around the northern south china sea abstract the south china sea scs characterized by a large continental shelf is located at the edge of the asian monsoon domain in this study two marine sediment cores from the northern scs nscs continental slope were investigated to construct composite vegetation and precipitation isotopic composition records based on the 13c and d values of plant wax n alkanes throughout the holocene last 11 200 years i e 11 2 ka the composite 13cwax record indicates an overall predominance of c3 vegetation over the last 11 2 ka before 8 ka bp higher 13cwax values are attributed to preferential wax input from grassland and wetland biomes on the exposed continental shelf after the inundation of the shelf by eustatic sea level rise until ca 8 ka bp grassland and wetland biomes suffered a major size reduction and arboreal vegetation became better represented in the 13cwax record the composite temperature corrected dwax t record suggests that moisture source variability drove precipitation isotopic composition changes during the holocene lower dwax t values before 8 3 ka bp are interpreted as a larger moisture contribution by pacific ocean tropical cyclones whereas higher dwax t values after 8 5 ka bp are interpreted as a larger moisture contribution from the indian ocean summer monsoon higher incidence of tropical cyclones in the nscs during the early holocene was related to a temporary westward shift of the western pacific warm pool and enhanced insolation over the northern hemisphere both external and internal forcing mechanisms regulated moisture source changes in east asia during the holocene

molecular and isotopic stratigraphy in an ombrotrophic mire for paleoclimate reconstruction a 40 cm deep sphagnum dominated peat monolith from bolton fell moss in northern england was systematically investigated by lipid molecular stratigraphy and compound specific 13c and d analysis using gas chromatography gc gc mass spectrometry gc ms gc combustion isotope ratio ms gc c irms and gc thermal conversion irms gc tc irms techniques 210pb dating showed the monolith accumulated during the last ca 220 yr a period encompassing the second part of little ice age while the distributions of lipids including n alkan 1 ols n alkan 2 ones wax esters sterols n alkanoic acids alkandioic acids and hydroxy acids display relatively minor changes with depth the cooler climate event was recorded in the concentrations of n alkanes and organic carbon cpi values of n alkanes and n alkanoic acids and the ratio of 5 n alkylresorcinols sterols superimposed on the fossil fuel effect the relatively cooler climate event was also recorded by 13c values of individual hydrocarbons especially the c23n alkane a major compound in certain sphagnum spp the d values of the c29 and c33n alkanes correlated mainly with plant composition and were relatively insensitive to climatic change in contrast the c23n alkane displayed variation that correlated strongly with recorded temperature for the period represented by the monolith agreeing with previously reported deuterium records in tree ring cellulose spanning the same period in scotland germany and the usa with more negative values occurring during the second part of little ice age these biomarker characteristics including the compound specific 13c and d records provide a new set of proxies of climatic change potentially independent of preserved macrofossils which will be of value in deeper sections of the bog where the documentary records of climate are unavailable and humification is well advanced

a 15 ka lake water δd record from genggahai lake northeastern tibetan plateau and its paleoclimatic significance abstract the mid chain and long chain n alkanes in sediments of genggahai lake on the northeastern tibetan plateau have been assigned as being predominantly from aquatic plants thus at the lake compound specific hydrogen isotopic data for mid and long chain n alkanes d n alkanes are indicators of the variation in lake water d d lw genggahai d lw is determined by the local meteoric water d d mw and by lake surface evaporation as evidenced by modern observational data and the broad correlation between genggahai d lw and average lake water depth during the past 15 ka with more negative d lw values corresponding to greater average water depth as demonstrated by the mid and long chain d n alkanes data the most negative interval of genggahai d lw was during the early holocene an overall trend towards more positive values from the early to the late holocene clearly indicates the long term evolutionary history of local d mw which could be related to the intensity of the indian summer monsoon ism via the rainfall amount effect therefore the record of d lw at genggahai during the past 15 ka which resembles that of stalagmite 18 o records from the core ism region apparently reflects the long term evolution of ism intensity furthermore several short term positive excursions in genggahai d lw values during the late holocene reflect enhanced lake surface evaporation via an isotopic enrichment mechanism that apparently resulted from periods of weakened ism intensity our results highlight the fact that unambiguous source determination of n alkanes is vital for determining the paleoclimatic significance of lacustrine d n alkanes data

palaeoclimate records in compound specific δd values of a lipid biomarker in ombrotrophic peat compound specific d values recorded by means of gas chromatography thermal conversion isotope ratio mass spectrometry gc tc irms of the biomarker n alkane n tricosane n c23 representative of the dominant sphagnum species in a 40 cm peat profile from bolton fell moss cumbria uk correlate with vegetation changes in the past 200 years age depth model based on 210pb dating the bog vegetation is sensitive to climate change correlating with the global scale cooler period of the later 19th and early 20th centuries the correlation with meteorological records suggests compound specific d values of lipid biomarkers have potential for use as a new climate proxy

an 40ar 39ar thermochronology of the ofoten troms region implications for terrane amalgamation and extensional collapse of the northern scandinavian caledonides fifteen 40ar 39ar cooling ages are reported for metamorphic hornblende and muscovite from far traveled terranes constituting the ofoten nappe stack of northern norway eight cooling ages on hornblende range from 425 to 394 ma and seven muscovite ages from the same or nearby outcrops as the hornblendes range from 400 to 373 ma these data are compared with 40ar 39ar ages from over a large part of the northern caledonides to evaluate regional mineral cooling patterns results indicate that 1 scandian silurian devonian metamorphism was predominant 2 most of the nappes investigated contain some vestige of pre scandian tectonism and or metamorphism 3 hornblende and muscovite cooling ages are progressively younger to the west and south which suggests a hinged to the east mineral cooling pattern and 4 a late out of sequence thrust is the only disruption of this cooling pattern synmetamorphic amalgamation of the nappes resulted from scandian a type subduction the hinged to the east mineral cooling pattern implies isostatic adjustment and exhumation of the footwall of a west dipping crustal scale extensional fault located somewhere west of the present norwegian coast during late synorogenic gravitational collapse the late out of sequence fault formed contemporaneously with uplift in the hinterland implying a kinematic and temporal connection with east directed contractional faulting in the foreland

coordinated hydrological regimes in the indo pacific region during the past two millennia instrumental data suggest that major shifts in tropical pacific atmospheric dynamics and hydrology have occurred within the past century potentially in response to anthropogenic warming to better understand these trends we use the hydrogen isotopic ratios of terrestrial higher plant leaf waxes delta d wax in marine sediments from southwest sulawesi indonesia to compile a detailed reconstruction of central indo pacific warm pool ipwp hydrologic variability spanning most of the last two millennia our paleodata are highly correlated with a monsoon reconstruction from southeast asia indicating that intervals of strong east asian summer monsoon easm activity are associated with a weaker indonesian monsoon im furthermore the centennial scale oscillations in our data follow known changes in northern hemisphere climate e g the little ice age and medieval warm period implying a dynamic link between northern hemisphere temperatures and ipwp hydrology the inverse relationship between the easm and im suggests that migrations of the intertropical convergence zone and associated changes in monsoon strength caused synoptic hydrologic shifts in the ipwp throughout most of the past two millennia

the variations of stable carbon isotope ratio of land plant derived n alkanes in deep sea sediments from the bering sea and the north pacific ocean during the last 250 000 years two piston cores one located far from the continents the north pacific ocean es core and another located comparatively closer to the continents the bering sea bow 8a core were investigated to reconstruct environmental changes on source land areas the results show significant contribution of terrestrial organic matter to sediments in both cores the d 13 c values of n c27 n c29 and n c31 alkanes in sediments from the north pacific es core show significant glacial to interglacial variation whereas those from the bering sea core do not variations of d 13 c values of land plant n alkanes are related to the environmental or vegetational changes in the source land areas environmental changes especially aridity rainfall and pco2 during glacial interglacial transitional periods can affect vegetation and therefore c3 c4 plant ratios resulting in d 13 c changes in the preserved land plant biomarkers maximum values of d 13 c as well as maximum average chain length values of long chain n alkanes in the es core occur mostly at the interglacial to glacial transition zones reflecting a time lag related to incorporation of living organic matter into soil and transportation into ocean basins via wind and or ability of c4 plants to adapt for a longer period before being replaced by c3 plants when subjected to gradual climatic changes irregular variations with no clear glacial to interglacial trends in the bow 8a core may result from complex mixture of aerosols from westerly winds and riverine organic matter from the bering sea catchments in addition terrestrial organic matter entering the bering sea could originate from multiple pathways including eolian riverine and ice rafted debris and possibly be disturbed by turbidity and other local currents which can induce resuspension and re sedimentation causing an obliterated time relation in the bering sea biomarker records d 2005 elsevier b v all rights reserved

hydrogen isotope ratios of recent lacustrine sedimentary n alkanes record modern climate variability abstract hydrogen isotope ratios were measured on n alkanes n c12 to n c31 extracted from recent lake surface sediments along a n s european transect to test if modern climate variability is recorded in these biomarkers d values of the n alkanes are compared to d values of meteoric water from the iaea gnip database spanning a range from 119 in northern sweden to 41 in southern italy to lake water d values and to mean annual temperatures varying between 2 0 c in the north and 13 7 c in the south d values of the short chained n alkanes n c12 to n c20 excluding algal derived n c17 and n c19 are higher in the north and lower in the south the isotopic fractionation e for hydrogen between meteoric water and the short chained n alkanes is increasing from n to s by more than 100 and is significantly correlated to mean annual temperature for n c16 and n c18 this suggests that these n alkanes may originate from a different source in the northern lakes possibly due to petroleum contamination or are synthesized using a different biochemical pathway the n c17 and n c19 alkanes of algal origin the n c21 and n c23 alkanes originating from water plants and the long chain n alkanes n c25 n c27 n c29 and n c31 of terrestrial origin clearly correlate with d values of meteoric water lake water and mean annual temperature indicating that they excellently record the d value of meteoric water the mean hydrogen isotope fractionation ec17 w of 157 sd 13 between n c17 and meteoric water is fairly constant over the wide range of different climates and lake environments suggesting only minor influence of environmental factors on this biochemical fractionation this suggests that d values of n c17 are suitable to reconstruct the isotopic composition of source water the mean fractionation between the long chain n alkanes and water is 128 sd 12 the mean difference of 31 between both e values is likely due to evaporative enrichment of deuterium in the leaf water if this is the only influence on the enrichment the difference between the d values of terrestrial and aquatic compounds might be suitable to reconstruct terrestrial evapotranspiration of the lake environment

seismic hazard in western canada from gps strain rates versus earthquake catalog 1 probabilistic seismic hazard analyses psha are commonly based on frequency magnitude statistics from 50 100 yearlong earthquake catalogs assuming that these statistics are representative of the longer term frequency of large earthquakes we test an alternative psha approach in continental western canada including adjacent areas of northwestern u s a using regional strain rates derived from 179 global positioning system gps horizontal velocities gps strain rates are converted to earthquake statistics seismic moment rates and ground shaking probabilities in seismic source zones using a logic tree method for uncertainty propagation median gps based moment rates and shaking estimates agree well with those derived from earthquake catalogs in only two zones puget sound and mid vancouver island in most other zones median gps based moment rates are 6 150 times larger than those derived from earthquake catalogs shaking estimates 2 5 times larger although the gps based and catalog estimates commonly agree within their 67 uncertainties this discrepancy may represent an under sampling of long term moment rates and shaking by earthquake catalogs in some zones however a systematic under sampling is unlikely over our entire study area although not demonstrated with a high confidence level long term regional aseismic deformation may account for a significant part of the gps catalog discrepancy and in some areas represent as much as 90 of the total deformation budget in order to integrate gps strain rates in psha models seismic versus aseismic partitioning of long term deformation needs to be quantified and understood in terms of the underlying mechanical processes

changes in the hydrological cycle in tropical east africa during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm at ca 55 8 ma is one of the most studied instances of past greenhouse gas induced global warming as such it provides a rich opportunity to examine the impact of such global change on local climates the effects of increased continental and sea surface temperatures on local precipitation and humidity during the petm remain poorly constrained and studies reveal complex regional differences whilst some localities appear to experience a net increase in humidity others exhibit the opposite crucially there are few records of hydrological change from tropical regions recent onshore drilling expeditions in tanzania have yielded expanded sedimentary sections deposited in a marine environment that span much of the late cretaceous and paleogene and show exceptionally good preservation of both calcareous microfossils and organic matter the petm interval has previously been constrained by both biostratigraphy and carbon isotopic records and spans ca 7 m of section lipid distributions including various terrestrial marine and bacterial biomarkers and their hydrogen isotopic compositions as well as mineralogy were used to examine east african vegetation and hydrological responses to the global change occurring at the petm although total organic carbon contents decrease the concentrations of both higher plant n alkanes n alkanoic acids and soil bacterial glycerol dialkyl glycerol tetraethers biomarkers increase dramatically at the onset of the petm negative carbon isotope excursion cie suggesting an increased discharge of fluvial sedimentary organic matter similarly mineralogical indicators of terrestrial input including ti al and si al ratios quartz contents and notably the proportion of kaolinite also increase at the onset of the cie however higher plant leaf wax n alkanes c27 c29 and c31 become more deuterium enriched throughout the same interval suggesting a more arid and or hotter rather than a more humid environment this evidence collectively suggests an east african early petm climate characterised by overall hot and arid conditions punctuated by intense perhaps seasonal precipitation events these data match observations from other locations at mid latitudes suggesting that the humid climate often suggested for the petm was not globally widespread

spatial patterns of soil n alkaneδd values on the tibetan plateau implications for monsoon boundaries and paleoelevation reconstructions 1 between 2010 and 2011 this project collected and analyzed forty nine superficial soil samples for wax derivedn alkane d values dwax along a south to north transect of the tibetan plateau from the southern plateau and nepalese himalayas passing through the nam co basin to qilian mountains twenty two paired river water samples were also collected from northeastern tibet during this period and analyzed for d drw the drw and dwaxvalues become progressively more negative northward from 27 5 n and reach a minimum at 30 6 n nam co basin north of the nam co basin to 35 n isotope values increase due to increasing contributions from the year round westerlies and recycled moisture from the plateau relatively high and constant dwax and drw values prevail in areas north of 35 n in northeastern tibet results show that these dwaxvalues vary considerably with location and relate closely to the influences of the summer monsoon and circulation changes these changes track the spatial variability of isotopes from modern river water and precipitation at large spatial scales paleoelevation reconstructions should take into account the impact of mixing between continental and monsoon derived moisture on the relationships with elevation and dwax and linear isotopic lapse rates for central northeastern tibet based on extended and more sensitive relative to 18o dwax and drw values we infer that in the past the westerlies reached further south to the north piedmont of the nyainqentanglha range and that indian summer monsoon moisture pushes across the tanggula mountains and approaches the kunlun mountains

molecular isotopic stratigraphy of long chain n alkanes in lake baikal holocene and glacial age sediments the molecular distribution and the carbon isotopic composition d 13 c of n alkanes extracted from a lake baikal core spanning the last 20 kyr of sediment accumulation have been investigated a terrestrial origin has been inferred for the odd carbon numbered long chain c27 n alkanes on the basis of the observed high cpi27 33 values range 8 7 10 8 typical of n alkanes derived from leaf waxes of higher plants a shift in the abundance of n c27 alkane relative to n c31 homologue is observed across the late pleistocene glacial holocene interglacial climate change perhaps indicative of the climate induced vegetational change previously deduced from palynological analyses compound specific isotope analyses indicate remarkably uniform d 13 c values in the range of 31 0 to 33 5 for the leaf wax c27 c33 nalkanes in the entire cored sequence such an isotopic compositional range is characteristic for n alkanes biosynthesized by plants utilizing the c3 photosynthetic pathway our data suggest that the observed 13 c enrichment in the bulk organic matter in the glacial age sediments relative to d 13 c values of total organic carbon in the holocene section is therefore unlikely to be attributed to an expansion of c4 type vegetation in the baikal watershed during the late pleistocene glacial interval 2000 elsevier science ltd all rights reserved

d h variation in terrestrial lipids from santa barbara basin over the past 1400 years a preliminary assessment of paleoclimatic relevance we analyzed d h ratios of common terrestrial leaf wax lipids in a 1400 year sediment core from the santa barbara basin sbb to test whether they accurately record terrestrial climate in southern california the d h ratios of long chain n alkanes vary substantially with depth but are poorly correlated with other terrestrial climate proxies interference from fossil hydrocarbons may be at least partly responsible long chain n alkanoic acids exhibit nearly constant downcore d h ratio values this constancy in the face of known climatic shifts presumably reflects a substantial residence time for leaf wax compounds in terrestrial soil and or on the basin flanks alternatively the isotopic composition of meteoric waters in southern california may not covary with climate particularly aridity however the d values of n c22 and n c24 fatty acids commonly attributed to terrestrial aquatic sources are partially correlated with southern california winter palmer drought severity index a tree ring based climatic proxy r 2 0 25 p 0 01 on multi centennial scales with an inferred ca 215 year time lag the improved correlation of these biomarkers can be explained by the fact that they are not stored in terrestrial soil nor are subject to interference from fossil hydrocarbons our study indicates that the sbb is unlikely to preserve high resolution leaf wax d h records that can serve as quantitative paleoclimate proxies though some qualitative information may be retained more generally the sources of lipids in marginal marine basins need to be carefully evaluated prior to attempting paleoclimate reconstruction based on the leaf wax d h proxy

soil n alkane δd vs altitude gradients along mount gongga china the altitude effect on the isotopic composition of precipitation and its application to paleoelevation reconstruction using authigenic or pedogenic minerals have been intensively studied however there are still no studies on variations in biomarker d along altitude transects to investigate its potential as a paleoelevation indicator although it has been observed that d of higher plant lipid may record changes in precipitation d dp here we present d values of higher plant derived c27 c29 and c31n alkanes from surface soil along the eastern slope of mount gongga china with great changes in physical variables and vegetation over a range from 1000 to 4000 m above sea level the weighted mean d values of these n alkanes dwax show significant linear correlations with predicted dp values r2 0 76 with an apparent isotopic enrichment ewax p of 137 9 indicating that soil dwax values track overall dp variation along the entire altitudinal transect leaf dwax is also highly correlated with mountain altitude by a significant quadratic relationship r2 0 80 evapotranspiration is found declining with altitude potentially lowering dwax values at higher elevations however this evapotranspiration effect is believed to be largely compensated by the opposing effect of vegetation changes resulting in less varied ewax p values over the slope transect this study therefore confirms the potential of using leaf dwax to infer paleoelevations and more generally to infer the d of precipitation

present day geodynamics of the northern north american cordillera abstract diffuse continental deformation results from interactions at plate boundaries buoyancy forces generated by gradients in gravitational potential energy and loads applied to the base of the lithosphere using finite element models we calculate a deviatoric stress field associated with buoyancy forces and then perform an iterative inversion to calculate deviatoric stress fields associated with boundary forces in the northern north american cordillera our results reveal the presence of two distinct geodynamic domains in the outboard domain approximately equal magnitudes of boundary and buoyancy forces can account for the observed deformation along the aleutian megathrust in contrast large boundary forces related to subduction of the pacific and yakutat slabs dominate the force balance in south central alaska and combine with relatively small buoyancy forces to reproduce the observed kinematic indicators in the inboard domain encompassed by interior and northern alaska and western canada boundary and buoyancy forces alone cannot reproduce the observed deformation therefore we infer that deviatoric stresses due to basal tractions from a deeper mantle convection cell contribute to surface deformation in the inboard domain low effective lithospheric viscosity in south central alaska and the balancing effect of an independent geodynamic system driven by basal tractions in northern alaska combine to confine the anomalously large yakutat related boundary deviatoric stresses to south central alaska deviatoric stresses associated with flat slab subduction of the yakutat microplate are a factor of two greater than boundary force estimates for the andean and indian eurasian convergent margins where buoyancy and boundary forces are roughly equal in magnitude and dominate the force balance

large scale hydrological change drove the late miocene c4 plant expansion in the himalayan foreland and arabian peninsula carbon isotope changes in paleosols from siwalik pakistan and marine sediments from the bengal fan indicate a major c 4 plant expansion in the himalayan foreland during the late miocene however the timing and mechanisms behind the c 4 plant expansion remain enigmatic here we present high resolution 60 k y biomarker and compound specific isotope data spanning the past 11 m y from ocean drilling program site 722 in the arabian sea an 5 6 increase in leaf wax 13 c values indicates a marked rise of c 4 plants from 10 to 5 5 ma with accelerated expansion from 7 9 to 5 5 ma a concurrent 50 rise in leaf wax d values is attributed to a combined effect of changes in precipitation amount and evaporation indicating that source regions for the plant waxes became progressively drier from 10 to 5 5 ma in contrast to earlier reports our isotope records biomarker abundances alkenone u k 37 and globigerina bulloides abundance data do not suggest enhanced summer monsoon circulation during this time interval rather our results suggest that large scale hydrological changes drove the late miocene expansion of c 4 plants in the himalayan foreland and arabian peninsula

a new zealand record of sea level rise and environmental change during the paleocene eocene thermal maximum abstract the global warming associated with the paleocene eocene thermal maximum petm ca 55 5 myr ago is the most dramatic identified short term temperature increase of the cenozoic one direct consequence of a warming world is a rise in sea level due primarily to the thermal expansion of water as oceans warmed the kumara 2 core south island new zealand spans the paleocene eocene transition and provides a rare southern hemisphere continental margin record of the petm lithology palynology and compound specific stable isotope compositions of higher plant leaf wax n alkanes reveal a 4 85 m petm and a carbon isotope excursion cie of ca 4 5 larger than the 2 5 to 3 5 cies generally recorded by deep sea foraminifera there is a shift from a terrestrial to a marine potentially anoxic sedimentary depositional environment at the base of the petm interpreted as being the result of a local sea level rise coincident with the onset of the cie is the appearance of pollen associated with thermophilic conditions and the development of nypa mangrove swamps moreover there is a reorganisation of the angiosperm pollen assemblage during the petm and an initial increase in fern spores and decrease in gymnosperms crucially all of these changes occur below the horizon characterised by the most negative 13c values suggesting that 1 the recorded negative excursion of 4 5 may indeed reflect the shift in atmospheric co2 isotopic composition and 2 that the large input of 13c depleted carbon into the ocean atmosphere system was not geologically instantaneous with at least some of the added carbon lagging warming sea level rise and vegetation change furthermore compound specific hydrogen isotope analyses show a large degree of variability both directly before and during the cie suggesting that the petm in new zealand was characterised by complex and transient changes in the hydrological regime similar to those reported in north america the arctic and eastern africa thus the new petm record from kumara 2 reveals local climatic and biotic responses driven by a combination of global warming and the consequential change in local depositional environment induced by sea level rise

the biogeochemistry of ellesmere lake u k i source correlation of leaf wax inputs to the sedimentary lipid record abstract analyses of the free lipid distributions from ellesmere lake sediments taken from two depths and comparison with leaf wax lipid distributions from six deciduous tree species around the lake were made in order to assess lipid sources close correlations of aliphatic lipid distributions in the carbon number range c 20 c 50 were seen c 28 and c 29 sterols were observed in both sediment and leaf waxes but c 27 sterols were only present in the sediments and were thus assigned a nonleaf wax source unsaturated steroidal ketones were observed both in the sediment and in certain leaf waxes and were assigned specific sources alkan 2 ones were not present in the leaf waxes but were present in the sediment samples with an almost identical distribution to the sediment n alkanes indicating a microbially mediated source c 20 c 30 n aldehydes which have not previously been widely reported in free lipid distributions of freshwater lacustrine sediments were prominent in the surface sediment and in the leaf waxes examined

investigating the long term palaeoclimatic controls on the δd and δ18o of precipitation during the holocene in the indian and east asian monsoonal regions abstract this paper aims to achieve an improved understanding of the long term change trends of precipitation d and 18 o values d p and 18 o p in the asian monsoonal region and their relationship with the corresponding humidity trends during the holocene to do this we first review the observed modern spatial pattern of summer precipitation distribution in the east asian summer monsoon easm region under different easm intensities and the relationship between modern observed 18 o p values and corresponding precipitation amounts on monthly and inter annual timescales in the easm and indian summer monsoon ism regions second we compare holocene lacustrine and marine compound specific hydrogen isotopic records of n alkanes n alkanoic acid d n lacustrine authigenic carbonate and cave stalagmite oxygen isotopic records 18 o c and 18 o s from the asian monsoonal region all of which are closely related to d p and 18 o p variations the results demonstrate that in both the ism and easm regions all of these isotopic records exhibit roughly similar long term characteristics i e they were all more negative during the early holocene and early mid holocene ca 11 6 ka b p b p means before present present 1950 ad and then became more positive towards the late holocene third we compare representative paleo humidity records from the asian monsoonal region the results confirm that in the ism region a humid interval occurred in the early holocene and early mid holocene ca 11 6 ka b p and subsequently the climate became more arid towards the late holocene this indicates an enhanced ism during the early holocene and early mid holocene ca 11 6 ka b p and an ism of decreasing intensity towards the late holocene on a holocene orbital scale both 18 o p and d p appear to be controlled by an amount effect in the ism region consistent with the region s inter annual modern 18 o p data this evidence indicates that both 18 o p and d p paleo records are significantly related to paleo humidity in the ism region in contrast holocene humidity variations in the easm region exhibit clear spatial differences a humid mid holocene interval ca 8 3 ka b p occurred in southern and northern china but an arid interval from ca 7 3 ka b p occurred in central china in the middle reaches of the yangtze river based on precipitation distribution patterns under different easm intensities in the easm region over the past few decades we conclude that easm intensity was enhanced during the mid holocene ca 8 3 ka b p relative to the ism intensity the response of easm intensity to summer insolation was relatively slow in the easm region the relationship between climate and 18 o p and d p is more complex consistent with analyses of regional inter annual modern 18 o p data this evidence demonstrates that both 18 o p and d p paleo records cannot be used directly as paleo humidity i e precipitation amount or easm intensity indicators in the easm region further comparison and analyses demonstrate that the coupled variations in west east equatorial pacific temperature gradients and the west pacific subtropical high wpsh played an important role in determining easm intensity during the holocene

centennial scale climate variability during the past 2000 years on the central tibetan plateau it is currently suggested that climate change on the northeastern tibetan plateau tp was influenced alternately by the monsoon and the westerlies however the mechanisms driving holocene climate

troposphere mapping functions for gps and very long baseline interferometry from european centre for medium range weather forecasts operational analysis data 1 in the analyses of geodetic very long baseline interferometry vlbi and gps data the analytic form used for mapping of the atmosphere delay from zenith to the line of site is most often a three parameter continued fraction in 1 sin elevation using the 40 years reanalysis era 40 data of the european centre for medium range weather forecasts for the year 2001 the b and c coefficients of the continued fraction form for the hydrostatic mapping functions have been redetermined unlike previous mapping functions based on data from numerical weather models isobaric mapping functions niell 2000 and vienna mapping functions vmf boehm and schuh 2004 the new c coefficients are dependent on the day of the year and unlike the niell mapping functions niell 1996 they are no longer symmetric with respect to the equator apart from the opposite phase for the two hemispheres compared to vmf this causes an effect on the vlbi or gps station heights that is constant and as large as 2 mm at the equator and that varies seasonally between 4 mm and 0 mm at the poles the updated vmf based on these new coefficients and called vmf1 hereinafter yields slightly better baseline length repeatabilities for vlbi data the hydrostatic and wet mapping functions are applied in various combinations with different kinds of a priori zenith delays in the analyses of all vlbi international vlbi service for geodesy and astrometry ivs r1 and ivs r4 24 hour sessions of 2002 and 2003 the investigations concentrate on baseline length repeatabilities as well as on absolute changes of station heights

assessing paleohydrologic controls on the hydrogen isotope compositions of leaf wax n alkanes in chinese peat deposits abstract the high concentrations of lipid biomarkers in peat and the close relation between peatland development and hydrological conditions merit further assessment of the paleohydrological proxy potential of the 2h 1h ratio of leaf wax n alkanes 2halk in peat deposits in the context of the dynamics of the east asian summer monsoon detailed investigation of modern processes is an important way to improve our understanding of the controls on 2halk records from chinese peat deposits this review first synthesizes the results of investigations of modern processes in the dajiuhu peatland of central china complemented by results from other peatlands and nearby non peatland sites to evaluate how the 2h 1h ratio changes from source water to leaf water and then to lipids in leaf waxes and ultimately to peat deposits the results reveal that the precipitation 2h values and the peatland plant types are the two major factors that control the 2halk signals preserved in peat at dajiuhu comparison of results from holocene 2halk sequences from other chinese peat deposits illustrates how peat 2halk values respond to paleoclimate changes on centennial to millennial timescales throughout the east asian summer monsoon region finally proposed incubations of peat forming plants in controlled chambers that could assess the response of plant 2halk values to environmental stresses are described as an example responses of the compound specific biomarker 2h and 13c values of sphagnum the dominant plant in the dajiuhu peatland could provide important information on the symbiotic relation between sphagnum and microbes it is expected that experiments such as these that combine the carbon and hydrogen isotope compositions of multiple lipids will yield important new insights into the responses of peatland ecosystems to climate changes

architecture kinematics and exhumation of a convergent orogenic wedge a thermochronological investigation of tectonic climatic interactions within the central st elias orogen alaska abstract the kinematics and architecture of orogenic systems along the leading edges of accreting terranes may be heavily influenced by climate but little research has been devoted to the long term effects of glacial erosion on orogenesis here we use low temperature apatite and zircon u th he and fission track thermochronometry along with subsidiary structural relationships and seismicity to develop a new architectural model of the st elias orogen in southern alaska which is one of the best examples of a glaciated orogenic wedge worldwide these data illustrate that the orogen consists of a deformational backstop on the leeward flank and a rapidly deforming and eroding thin skinned fold and thrust belt on the windward flank a structure beneath the bagley ice field separates these distinct deformational domains which we propose is a backthrust that makes the orogen doubly vergent thermochronometry within the orogenic wedge suggests that denudation and deformation are strongly influenced by glacial erosion long term exhumation at rates of up to 4 mm yr is concentrated within a narrow zone along the windward flank where glacier equilibrium lines intersect the orogenic wedge the onset of enhanced glaciation also coincided with a marked acceleration in exhumation across the orogenic wedge accelerated backthrust motion and a major shift in deformation away from the north american yakutat terrane suture chugach st elias fault we propose that accelerated glacial erosion forced the redistribution of strain along the backthrust and an en echelon array of forethrusts that lie beneath the zone of heaviest glaciation which in turn are systematically truncated by the backthrust this focusing of deformation matches predictions from analytical models of orogenic wedges and implies a high degree of coupling between climate and tectonics in this glacially dominated orogen

a computer model of sheath nappes formed during crustal shear in the western gneiss region central norwegian caledonides abstract the eastern western gneiss region of central norway is part of the deepest exposed norwegian caledonides where basement gneisses and an overlying thrust nappe sequence have been folded into large fold nappes structural analysis of a fold nappe within the central part of the district the grovudal area suggests that it has a strongly sheath like form and that other fold nappes of the western gneiss region may also have sheath like forms the structural history within the grovudal area is dominated by intense east directed subhorizontal shear in an overthrust sense followed by asymmetric refolding with an easterly vergence a computer generated kinematic model was developed to test whether the regional interference patterns could be explained by sheath fold development during this type of deformation the computer model shows that the major regional interference patterns could have been formed by such a kinematic history but does not rule out other possibile histories the proposed kinematic history is however compatible with the regional tectonic history of the main caledonian nappe pile suggesting that the complex nappe interference patterns typical of the region were formed in a kinematically simple but intense ductile deformation associated with caledonian continental imbrication

hydrogen isotopic compositions of long chain leaf wax n alkanes in lake qinghai sediments record palaeohydrological variations during the past 12 ka abstract lake qinghai the largest saltwater lake in china is located on the northeastern qinghai tibetan plateau the lake sediments record the climatic variation and response to global climate change on the plateau numerous studies of the lake have been conducted but various opinions remain regarding the palaeoclimatic conditions for the lake since the last glacial maximum especially the palaeohydrological conditions for the northeastern plateau in the early holocene here we discuss the hydrogen isotopic composition d of long chain leaf wax n alkanes for studying the hydrological changes in the lake since the holocene the results show that on the northeastern qinghai tibetan plateau c 31 d values were quite negative avg 202 4 in the early holocene 8 12 ka indicating a strong monsoon and greater precipitation during that period during 8 4 ka c 31 d values gradually became more positive indicating that the monsoon gradually weakened and precipitation gradually decreased the c 31 d values were more positive in the late holocene with a mean value of 186 3 showing that the regional monsoon weakened and the amount of precipitation was low in addition c 31 d values indicated large amounts of precipitation in the early holocene but the c 29 d values during the same period were significantly more positive than c 31 due to a large contribution from aquatic plants therefore the water level of the lake was low in this period which could be related to strong evaporation of the lake water because of the high temperature in the early holocene our study clarifies the changes in the monsoon and precipitation in the northeastern qinghai tibetan plateau and it provides a new estimate of the water level variation in lake qinghai in the early holocene

structural expressions and tectonic implications of general noncoaxial flow in the midcrust of a collisional orogen the northern scandinavian caledonides mapping and strain analysis in the northern scandinavian caledonides indicate that one way in which contemporaneous upper crustal extension and deeper thrusting within collisional orogens may be linked in a kinematically compatible manner is through the ductile flow of rocks in the midcrust of these mountain belts in the ofoten efjorden region of north norway amphibolite facies metamorphism and strong penetrative strain occurred at deep levels of the caledonian nappe stack as it was thrust eastward onto the western margin of baltica kinematic analysis of deformation in the lower portion of the caledonian nappe stack indicates that the rock mass underwent heterogeneous noncoaxial flow with components of foreland directed simple shear and subvertically shortened pure shear general noncoaxial flow simultaneous simple shear pure shear can accomplish foreland directed tectonic transport subvertical thinning and transport parallel elongation at deep levels of a nappe stack this pattern of flow is significant technically for two reasons first it suggests spreading of the caledonian allochthon during thrust emplacement and second it can form a kinematic link between normal faulting at shallower structural levels and thrusting at the base of the nappes by analogy with the caledonides general noncoaxial flow of midcrustal rocks may represent an important process in other collisional and contractional orogens particularly in those that have undergone upper crustal extension while thrusting continued in the foreland

high relief topography of the nima basin in central tibetan plateau during the mid cenozoic time abstract there remains inconsistence of uplift history of the tibetan plateau here we estimated paleoelevation of mid cenozoic nima basin located in central tibet using multi proxies they included meteoric water and vegetation isotope proxies based on hydrogen and carbon isotopic compositions d and 13c respectively of terrestrial plant wax lipid of n alkanes and temperature proxy derived from microbial membrane lipid of branched glycerol dialkyl glycerol tetraethers brgdgts lipid analysis on sedimentary rocks in the nima basin yielded 222 12 and 30 0 0 7 for d and 13c of n c29 alkane respectively and brgdgt derived mean annual air temperature maat of 21 5 3 1 c for the paleo basin using the sea level meteoric water 18o and miocene siwalik paleovegetation 13c as low elevation references values of d and 13c of n c29 alkane in this study suggested paleoelevations of 4546 m and 2800 m respectively whereas by using a subtropical sea surface temperature as a reference brgdgt derived maats suggested a paleoelevation of 893 m we believed that the three estimates reflect a high relief topography in the study basin during the mid cenozoic representing elevations of orographic barrier of southerly oceanic moisture basin catchment and basin lake level respectively this scenario implies a low elevation of the basin relative to the lhasa terrane located to the south during the mid cenozoic hence challenging the classical crustal thickening models assuming a simple crustal thickening uplift relationship

compound specific d h ratios and molecular distributions of higher plant leaf waxes as novel paleoenvironmental indicators in the chinese loess plateau abstract we measured d h ratios of individual long chain leaf wax n alkanes isolated from a loess profile spanning the last 130 ka from xifeng china the d values show large variation 140 to 200 for the past 130 ka and are highly correlated with changes in magnetic susceptibility ms an accepted proxy for past monsoon circulation in the chinese loess plateau peaks in high d values 140 to 160 coincide with low ms values for loess sections formed under relatively dry conditions marine isotope stages miss 2 and 4 whereas peaks in low d values 190 to 200 coincide with high ms values for paleosol sections formed under relatively wet conditions miss 1 3 and 5 we attribute the isotopic variations to the combined effects of varying aridity which controls the soil and leaf water evaporation and temperature and monsoon intensity which alter the d h ratios of precipitation we also discovered a strong negative correlation between the molecular distributions ratios of c31 c29 and c31 c27 n alkanes and the d values of n alkanes based on studies of modern plants and the xifeng loess sequence the complex relationship between ms and monsoon circulation has been difficult to understand mechanistically however the climatic controls on the d h ratios of individual long chain n alkanes and c31 c29 n alkane ratios can be readily demonstrated and calibrated from modern plants and surface soils therefore these new molecular and isotopic proxies have potential as quantitative proxies for paleoenvironmental reconstruction in the chinese loess plateau

empirical relationship between leaf wax n alkane δd and altitude in the wuyi shennongjia and tianshan mountains china implications for paleoaltimetry article i nfo estimating past elevation not only provides evidence for vertical movements of the earth s lithosphere but also increases our understanding of interactions between tectonics relief and climate in geological history development of biomarker hydrogen isotope based paleoaltimetry techniques that can be applied to a wide range of sample types is therefore of continuing importance here we present leaf wax derived n alkane d dwax values along three soil altitudinal transects at different latitudes in the wuyi shennongjia and tianshan mountains in china to investigate dwax gradients and the apparent fractionation between leaf wax and precipitation ewax p we findthatsoil dwax trackaltitudinal variationsof precipitation d along the three transects that span variable environment conditions and vertical vegetation spectra an empirical dwax altitude relation is therefore established in which the average dwax lapse rate of 2 27 0 38 100 m is suitable for predicting relative paleoelevation change relative uplift the application of this empirical gradient is restricted to phases in the mountain uplift stage whenthe atmospheric circulation had not distinctly changed and to when the climate was notarid anempirical dwax latitude altitudeformulaisalsocalculated dwax 3 483lat 0 0227alt 261 5 which gives the preliminary spatial distribution pattern of dwax in modern china meanvalue of ewax p intheextreme humid wuyimountainsisquite negative 154 compared to the humid shennongjia 129 and the arid but with abundant summer precipitation tianshan mountains 130 which suggests aridity or water availability in the growing season is the primary factor controlling soil sediment ewax p along the tianshan transects values of ewax p are speculated to be constant with altitude while along the wuyi and shennongjia transects ewax p are also constant at the low mid altitudes but become slightly more negative at high altitudes which could be attributed to overestimates of precipitation d or the vegetation shift to grass conifer additionally a reversal of altitude effect in the vertical variation of dwax was found in the alpine zone of the tianshan mountains which might be caused by atmospheric circulation change with altitude this implies that the paleo circulation pattern and its changes should alsobe evaluated whenstable isotope based paleoaltimetry is applied

deformation rates estimated from earthquakes in the northern cordillera of canada and eastern alaska 1 we estimate deformation rates from earthquake catalog statistics to investigate current strain distribution resulting from the collision of the yakutat block with north america the collision is accommodated over a broad region of alaska and nw canada in a variety of tectonic regimes our estimates have significant uncertainties but the results are generally in agreement with other deformation rate estimates gps and geological data and provide useful first order constraints on local long term tectonic deformation and seismic hazard we estimate that 50 75 of relative plate motion is taken up by earthquakes on the yakutat north america boundaries with lateral crustal extrusion other far field strain and possibly aseismic creep accommodating the remainder we calculate dextral strike slip of 4 5 10 2 mm a on the denali fault system in alaska remarkably similar to late pleistocene holocene rates from geomorphic offsets right lateral motion essentially bypasses the denali fault in easternmost alaska and westernmost yukon passing instead along the totschunda and duke river fault systems right lateral transpression of 5 10 mm a suggests that the alaskan fore arc does not have fully block like behavior between the denali and tintina kaltag faults in alaska 10 20 mm a of dextral shear is accommodated by several ne trending bookshelf faults significant seismic deformation in cases higher than expected from gps data is indicated in the ne cordillera where preexisting faults have a strong control on the pattern and mechanisms of current deformation

lipid geochemistry of sediments from upton broad a small productive lake major lipid classes isolated from 3 sections of the sediment profile of upton broad a shallow lake formed about 500 yr ago were correlated with input and with changes attributable to early diagenesis surficial sediment contains lipids characteristics of the known recent algal and microbial input preservation of chlorophyll pigments and absence of appropriate markers suggest that diagenesis is minimal older deposits from the eutrophic phase of the lake s history contain higher levels of bacterial lipids and diagenetic products the earliest sediment contains lipids characteristic of terrigenous input subjected to more extensive diagenesis than the younger sediment recognition of early diagenesis in anoxic sediment suggests that distributions of the shorter chain homologous free n alkanes alkanols and alkanoic acids result from microbial synthesis using material initially deposited at the sediment surface rather than partial preservation of the lipids of primary source organisms

estimating the hydrogen isotopic composition of past precipitation using leaf waxes from western africa abstract the hydrogen isotopic composition of plant leaf wax n alkanes d wax is a novel proxy for estimating d of past precipitation d p however vegetation life form and relative humidity exert secondary effects on d wax preventing quantitative estimates of past d p here we present an approach for removing the effect of vegetation type and relative humidity from d wax and thus for directly estimating past d p we test this approach on modern day late holocene 0 3 ka sediments from a transect of 9 marine cores spanning 21 n 23 s off the western coast of africa we estimate vegetation type c 3 tree versus c 4 grass using 13 c of leaf wax n alkanes and correct d wax for vegetation type with previously derived apparent fractionation factors for each vegetation type late holocene vegetation corrected d wax d vc displays a good fit with modern day d p suggesting that the effects of vegetation type and relative humidity have both been removed and thus that d vc is a good estimate of d p we find that the magnitude of the effect of c 3 tree c 4 grass changes on d wax is small compared to d p changes we go on to estimate d vc for the mid holocene 6 8 ka the last glacial maximum lgm 19 23 ka and heinrich stadial 1 hs1 16 18 5 ka in terms of past hydrological changes our leaf wax based estimates of d p mostly reflect changes in wet season intensity which is complementary to estimates of wet season length based on leaf wax 13 c

active tectonics of the st elias orogen alaska observed with gps measurements 1 we use data from campaign and continuous gps sites in southeast and south central alaska to constrain a regional tectonic block model for the st elias orogen active tectonic deformation in the orogen is dominated by the effects of the collision of the yakutat block with southern alaska our results indicate that 37 mm yr of convergence is accommodated along a relatively narrow belt of n nw dipping thrust faults in the eastern half of the orogen with the present day deformation front running through icy bay and beneath the malaspina glacier near the bering glacier the collisional thrust fault regime transitions into a broad northwest dipping decollement as the yakutat block basement begins to subduct beneath the counterclockwise rotating elias block the location of this transition aligns with the gulf of alaska shear zone implying that the pacific plate is fragmenting in response to the yakutat collision our model indicates that the bering glacier region is undergoing internal deformation and could correspond to the final stage of offscraping and accretion of sediments from the yakutat block prior to subduction predicted block motions at the western edge of the orogen suggest that the crust is laterally escaping along the aleutian fore arc

the eidsfjord shear zone lofoten vesteralen north norway an early devonian paleoseismogenic low angle normal fault abstract we report structural and 40ar 39ar isotopic information on the eidsfjord shear zone that document it to be a seismogenic tops west hinterland directed devonian ductile low angle 25 30 dip shallowing locally normal detachment fault anorthosite migmatitic gneiss in the detachment s upper plate mangerite in the lower plate and detachment mylonites are all cut by generations of abundant pseudotachylyte occurring over approximately 150 km2 the mean of four laser 40ar 39ar plateau ages for single crystals of recrystallized muscovite from mylonites defining the eidsfjord shear zone indicates an age of 403 6 1 1 ma 2 for deformation and recrystallization 40ar 39ar step heating analyses are reported for muscovite from mylonitized rocks of the fiskefjord shear zone a nearby tops east caledonian thrust that was reactivated as a tops west normal fault documenting cooling of the upper plate through the 350 c isotherm at 457 ma together with middle ordovician tectonothermal relics found farther west in lofoten tops down to the west normal slip movement on these extensional shear zones explains maintenance of high crustal levels throughout the siluro devonian scandian event potassium feldspar 40ar 39ar results document a pulse or multiple pulses of uplift and cooling between ca 235 ma and 185 ma consistent with formation of triassic jurassic rift basins flanking the lofoten ridge the eidsfjord detachment appears to mark the northern terminus of the early devonian detachment system traceable 800 km southward to the nordfjord sogn detachment and westward across the north atlantic to detachments of roughly the same age on the conjugate side of the orogen in east greenland the timing geometry kinematics and rheological development of eidsfjord detachment are grossly similar to the nordfjord sogn detachment but the former contrasts in that it presently lacks exposed deposits of devonian sedimentary rocks has smaller magnitudes of displacement a more prolonged exhumation history is severely chopped by later high angle normal faults related to rifting and final eocene continental separation and it has abundant pseudotachylite occurrences in the upper plate we interpret the eidsfjord detachment to be a rare example of an ancient eroded seismogenic low angle normal fault

ductile and brittle extension in the southern lofoten archipelago north norway implications for differences in tectonic style along an ancient collisional margin the lofoten archipelago north norway occupies the most inter nal position of the caledonian belt in northern scandinavia and rocks and structures exposed there are crucial to understanding processes of how the baltic basement and its cover allochthons responded to continental lithospheric subduc tion and subsequent continental separation relatively little is published about the structural and metamorphic development and especially the timing of these events consequently it is unknown how features exposed on these spatially isolated islands relate to those of the adjacent mainland rocks in lofoten were affected by caledonian regional metamorphism and structures record tops east contraction and later extension related to late to post caledonian basement exhumation tops west extension is preferentially developed in meter to km scale ductile shear zones containing west dipping extensional shear bands west verging rootless folds and asymmetric feldspar porphyroclasts west plunging sinistral oblique elongation lineations in the mylonitic foliation are interpreted to indicate the line of transport mesoscopic backfolds are locally developed within the tops west shear zones and further document west directed transport of structurally higher rocks the ductile extensional shear zones locally are cross cut by low angle tops west cataclastic normal faults reflecting progressive unroofing of the shear zones to shallower crustal levels during late and post caledonian extensional events northeast striking high angle brittle normal faults truncate all other fabrics and structures and juxtapose structurally deep undeformed precambrian basement with the caledonian nappe sequence 40 ar 39 ar data indicate that ductile extension in lofoten likely initiated soon after the caledo nian metamorphic peak at 430 ma and continued episodically until at least permian time rocks passed through the brittle ductile transition rapidly at 275 ma recent paleomagnetic data also point to later phases of brittle faulting in lofoten one in the jurassic cretaceous and one related to tertiary opening of the norwegian sea the magnitude and style of late to post caledonian exten sion and basement exhumation in lofoten differs markedly from the formation of phenomenal devonian basins and exposures of caledonian ultra high pressure assemblages in the western gneiss region wgr of southern norway differ ences in the styles of extension between northern and southern norway are interpreted to reflect inherited differences in crustal architecture that may have been enhanced during the caledonian orogeny

temperature and leaf wax δ2h records demonstrate seasonal and regional controls on asian monsoon proxies orbital scale precipitation isotope records can elucidate climate forcing mechanisms and provide benchmarks for climate model validation the ability to differentiate the influence of temperature seasonality and vapor transport history on precipitation isotope proxies is critical to both objectives we present a 300 k y leaf wax hydrogen isotope record from the south china sea with the effects of local condensation temperature removed 2 h wax t 2 h wax t reflects annually integrated precipitation 2 h in the pearl river catchment of southeast china depleted 2 h wax t lags minimum precession p min by 1 0 0 7 k y reflecting the influence of maximum summer insolation and minimum winter insolation with a minor influence of global ice volume which lags p min by 3 3 0 4 k y in contrast annually integrated cave 18 o minima in central china 1000 km north of our site lag p min by 2 7 0 3 k y in phase with ice volume minima this phase indicates that precipitation 18 o in central china is more strongly influenced by ice volume forcing at the precession band with a lesser influence of northern hemisphere insolation our new 2 h wax t data demonstrate that precipitation isotopes in asia have strong regional variability interpreting water isotope records within the context of regionally varying temperature seasonality and sensitivity to changing glacial boundary conditions is imperative to understanding asian hydroclimatic change

δd values of n alkanes in tibetan lake sediments and aquatic macrophytes a surface sediment study and application to a 16 ka record from lake koucha abstract a set of lake surface sediment samples and aquatic macrophytes from the eastern and central tibetan plateau and a sediment core from koucha lake northeastern tibetan plateau were analysed for hydrogen isotope signals of aliphatic lipid biomarkers the d values of n alkanes were correlated with those of meteoric water in the summer months and showed increasing pearson correlation coefficients with increasing n alkane chain length r 0 80 for n c 31 while in samples from the most humid regions southeastern tibetan plateau the apparent enrichment factors between meteoric water and lipids are close to those reported for other humid sites e 135 for mid chain and 125 for long chain n alkanes they become smaller e 118 to 41 mean value 86 at sites with a negative moisture balance northeastern and central tibetan plateau and qaidam basin this might be caused by enrichment in deuterium of the source water used for lipid synthesis as a result of lake water evaporation and soil and leaf water evapotranspiration in the core from lake koucha decreasing d values of all n alkanes between 15 and 10 cal ka bp give evidence for an intensification of the asian summer monsoon at ca 9 cal ka bp a ca 15 shift towards higher d values of mid chain n alkanes suggests enhanced evaporation of the lake water which outweighs higher precipitation amounts because of a temperature increase during the early holocene monsoonal maximum only a few surface sediment samples show a significant offset between d values of mid chain n alkanes and n c 31 d mid n c31 and no systematic dependence between this offset and environmental parameters such as mean annual precipitation was found in the core available data for most samples also do not show a significant offset only a slight increase 15 of d mid n c31 at ca 10 0 cal ka bp and a decrease 17 at ca 6 8 cal ka bp might indicate wetter and drier conditions respectively however interpretation of d mid n c31 throughout the record is difficult because of a lack of reliable data for n c 31 in key sections of the core so more records are necessary to further test the potential applicability of d mid n c31 as a proxy for palaeo hydrological conditions

paleoclimate significance of n alkane molecular distributions and δ2h values in surface peats across the monsoon region of china abstract leaf wax molecular distributions and isotopic values are generally considered paleohydrologic proxies here we evaluate the sensitivity of alkane chain length distributions and compound specific hydrogen isotopic compositions 2halk in surface peats to environmental parameters across the monsoon region of china the alkane average chain length acl carbon predominance index cpi and 2halk values show relatively large variations in multiple samples from a single site highlighting the complexity of the processes affecting these ratios at small spatial scales nonetheless the site averaged cpi values correlate significantly with the mean annual temperature r 0 57 p

effect of precipitation regime on δ d values of soil n alkanes from elevation gradients implications for the study of paleo elevation we measured dd values of long chain n alkanes isolated from 30 surface soil samples along two elevation transects on the tibetan plateau differing in precipitation regime and water source the east asian monsoon precipitation dominates the wetter regime on the eastern slope from 1230 to 4300 m of gongga shan on the eastern tibetan plateau precipitation from the polar westerlies dominates the drier region on the slope from 1900 to 5000 m in the west kunlun shan on the northwestern tibetan plateau the decrease in dd value with elevation in the wetter region greatly exceeded that in drier region by 1 9 0 1 100 m and 1 4 1 0 100 m respectively the apparent fractionation between leaf wax and precipitation ewax p values in the wetter region ca 164 were more negative than those in drier region ca 125 above 3200 m we also measured dd values in leaves of six common living trees values from 287 to 193 from gongga shan ranging from about 2900 4200 m the abundance weighted average values of the nalkanes ddwax show a strong reverse correlation with sample source elevation r 2 0 78 for soils from 2 0 85 for soils from west kunlun shan above 3200 m suggesting that n alkane ddwax faithfully records the precipitation dd and that the isotopic altitude effect of precipitation controls ddwax altitudinal gradients in the mountains the data show a fairly strong monotonic dependency of n alkane dd values on elevation for the eastern plateau but a complex relationship between n alkane dd values and elevation for the northwestern plateau the ddwax values at sites below 3200 m from the kunlun shan area exhibit an unexpected positive correlation with elevation the study confirms the potential for using sediment ddwax values to reconstruct paleo elevation in wetter regions but suggests caution in applying the approach to dry regions our results also show it is essential to consider the intricacy of the pattern of atmospheric circulation and water sources and their influence on the lapse rate of dd values with elevation

indentor corner tectonics in the yakutat st elias collision constrained by gps the yakutat st elias collision in se alaska and adjacent canada represents a prime example of present day tectonics associated with an indentor corner its eastern syntaxis is marked by high exhumation a sharp structural bend and strain concentration at the transition from shortening to oblique transpression here we present gps velocity and strain rate fields that cover the syntaxis including 11 new stations in the core of the st elias mountains these data are corrected for transient deformation glacial isostatic adjustment and postseismic and interseismic loading to produce residual velocities and strain rates representative of long term tectonics the main features of these velocity and strain rate fields are a peak in strain rates strain knot in the syntaxis at the junction between the main fault systems and a rapid rotation from convergence parallel to convergence normal orientations of the velocities and shortening axes around the syntaxis leading to shortening across the southern denali fault these features are consistent with the strain and tectonic patterns expected near an indentor corner at the transition from shortening to transpression with a combination of diffuse and localized deformation the gps velocities and strain rates show diffuse deformation around the syntaxis from pure convergence parallel shortening in the orogenic wedge to oblique extension that accommodates the strain rotation at the front of the syntaxis this indentor corner model also results in a near zero strike slip rate on the southern denali fault and shows no clear evidence for a throughgoing fault hypothesized to link the fairweather and totschunda faults

new insights into the appalachian orogen from geology and geochronology along the cape ray fault zone southwest newfoundland reverse oblique overthrusting of high grade port aux basques gneiss over the lower grade supracrustal windsor point group along the cape ray fault zone occurred during late silurian to early devonian time and is attributed to major oblique collision between gondwanan and laurentian continental blocks new u pb zircon 40 ar 39 ar and k ar data limit the timing of this orogenic event the megacrystic granitic phase of the cape ray igneous complex and the cape ray tonalite have been dated at 488 3 ma and 469 2 ma respectively a black rhyolite from the windsor point group yielded an ordovician age 453 5 4 ma a pretectonic gabbro sill within the windsor point group dated at 424 4 3 ma is cut by the windowglass hill granite dated at 424 2 ma synkinematic hornblende and biotite from the grand bay complex mylonites of the port aux basques gneiss have 40 ar 39 ar ages of 407 4 ma and 403 4 ma respectively which is indicative of a late silurian early devonian age for the amphibolite grade deformation these ages are compatible with a previously determined 415 ma monazite age interpreted as the time of peak metamorphism in the port aux basques gneiss and suggests rapid exhumation the east west flexure of the cape ray fault zone represents a tear fault accommodating differential shortening between the cape ray fault zone and the correlative fault system in central newfoundland mid devonian granites 386 3 384 2 ma intervene between the thrusting events and a younger sinistral transcurrent movement this deformation and magmatic history can be correlated throughout the northern appalachians along other major fault boundaries

the silurian to permian history of a metamorphic core complex in lofoten northern scandinavian caledonides 1 the lofoten archipelago exposes precambrian baltic basement and caledonian allochthonous sequences within a 1000 km long chain of gravity and magnetic highs and structural culminations along the extended british and norwegian continental shelf previous regional geophysical studies indicate that post caledonian extension and development of the northern norwegian shelf occurred during broadly defined carboniferous permian cretaceous jurassic and early tertiary events structures related to these events are known to young westward we report field structural and 40ar 39ar thermochronologic data from rocks exposed in lofoten that further define the history and style of post caledonian extension the islands of southwest lofoten also represent the most outboard exposures of caledonian basement in northern norway that presumably formed the middle to deep crustal core of the orogen metasedimentary rocks and penetratively deformed basement in lofoten record high grade silurian devonian metamorphism and top to the east hereinafter tops east thrusting followed by episodes of late devonian to early carboniferous tops west ductile extension which progressed into oblique left slip movements the structural style and timing of silurian contraction in this area are remarkably similar to that determined for the more forelandward areas on the mainland 120 km to the east supporting the inference that distal parts of the baltic continental margin that were once deeply subducted are presently exposed in lofoten the timings of post devonian structural events that affected rocks in lofoten are partially constrained by the ages of unconformities and strata known to be preserved in graben flanking the lofoten culmination the radiometric age and structural data presented in this study in combination with stratigraphic constraints suggest a westward progression through time of extensional deformation over a protracted interval of silurian to permian time the latest permian extension in lofoten is largely characterized by brittle structures that formed at conditions substantially less than 300 c compared to the exhumation history of the southern western gneiss region the depth of caledonian continental a type subduction and subsequent unroofing of lofoten are of lesser magnitude and the present erosional level remained in the middle crust for a much longer interval of time the permian 40ar 39ar mineral ages documented in this study are the youngest such ages yet identified in scandinavia these ages relate to episodes of deformation and cooling in response to extensional tectonic events that occurred roughly 100 m y after comparable effects identified on the caledonian mainland our preferred explanation for the carboniferous permian radiometric ages structural evolution and stratigraphic data for lofoten is that they all developed in the context of a long lived cordilleran style metamorphic core complex

δd values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record abstract the compound specific hydrogen isotope composition d of sedimentary n alkanes is increasingly used as a palaeoclimate proxy to explore the origin of the hydrogen isotope signal of n alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n alkane composition and d values of 31 plant biomass samples birch betula beech fagus oak quercus alder alnus hornbeam carpinus and myrtle myrtus as well as non stomata containing sphagnum cladonia and moss from 14 sites along a climatic gradient from northern finland to southern italy eleven of the sites were previously investigated for the n alkane d values in adjacent lake sediments and are compared to the leaf wax n alkane d values the distribution of terrestrial n alkanes in lake sediments was not found to be characteristic of the dominant vegetation around the lake evidently n alkane distributions within the same species at different sites were found to be variable these findings complicate the use of certain n alkane distributions in sediments as a palaeoenvironmental indicator d values of plant biomass n alkanes show a significant positive correlation with the precipitation d values biomass n alkane d values are in general less negative than the associated sedimentary n alkanes of terrestrial origin possibly due to the stronger evapotranspiration during the summer when sampling took place this suggests that n alkanes in leaves show seasonal variations and the sedimentary organic matter receives the lighter isotope signal of the autumn when most leaves are incorporated into the sediment the variability of the d values from non stomata containing plants is much higher than for broadleaf trees since stomata can regulate water loss through evapotranspiration the average chain length acl of n alkanes from deciduous tree leaves increases from north to south with increasing acl the hydrogen isotopic fractionation e between source water and n alkanes also increases our results prove that terrestrial n alkane d values record the d value of precipitation modified by the amount of isotope enrichment in the leaf water due to plant anatomy stomata vs no stomata and site specific meteorological conditions such as evapotranspiration relative humidity and soil moisture therefore terrestrial n alkanes in lake sediments can deliver information on changes in these parameters over geological timescales in lake sediments where aquatic n alkanes such as n c 17 record the lake water d value the isotopic difference between terrestrial and aquatic n alkanes could therefore be used to reconstruct changes in evapotranspiration

carbon and hydrogen isotope variation of plant biomarkers in a plant soil system stable carbon 13c and hydrogen d isotopic compositions of n alkanes anteiso alkanes n alkanoic acids n alkanols phytol and sterols in raw leaves of acer argutum and acer carpinifolium their fallen leaves mold and soils from a natural acer forest were measured in order to 1 understand isotopic variation of the plant biomarkers in a plant soil system and 2 evaluate which biomarker is the most effective recorder of soil vegetation long chain c24 n alkanes n alkanoic acids and n alkanols are gradually enriched in 13c up to 12 9 average of 4 3 and depleted in d up to 94 average of 55 from raw leaves to soils however anteiso alkanes phytol and sterols show little variation in both 13c 1 and d 2 from raw leaves to soils these isotope signatures in a plant soil system indicate that isoprenoid plant biomarkers such as sterols in soils faithfully preserve the isotopic compositions of dominant higher plants growing on the soils without a diagenetic effect upon the isotopic compositions in contrast long chain n alkyl molecules in soils undergo specific isotopic modification during biodegradation associated with early diagenesis and or a significant contribution from heterotrophic reworking

effect of lake evaporation on δd values of lacustrine n alkanes a comparison of nam co tibetan plateau and holzmaar germany compound specific hydrogen isotope ratio values of lacustrine n alkanes from two contrasting ecosystems the semiarid to arid nam co central tibet and the humid holzmaar germany were compared in order to assess whether or not these environmental conditions are recorded in the isotopic signatures of biomarkers increased evaporation of lake water at nam co is recorded by the n alkanes of aquatic origin hence isotopic enrichment results in a di erence between terrestrial and aquatic n alkanes in the opposite direction 68 from that known for humid climate conditions 30 predominating at holzmaar based on this isotopic di erence between terrestrial and aquatic n alkanes evaporation to inflow ratio e i values were estimated and suggest that the isotopic di erence is indicative of the general hydroclimatic characteristics of a lake system moreover the comparison with e i values calculated with actual stable water isotope data showed that the dd values of aquatic and terrestrial lacustrine n alkanes serve as a proxy for the relative isotopic di erences between lake and inflow waters and can be used to assess the proportion of water undergoing evaporation relative to the inflow and thus to reconstruct the lake water balance in the past 2008 published by elsevier ltd

compound specific δd values of long chain n alkanes derived from terrestrial higher plants are indicative of the δd of meteoric waters evidence from surface soils in eastern china the stable carbon and hydrogen isotope composition of higher plant derived long chain n alkanes 13cn alkanes and dn alkanes from 45 surface soil samples within well characterized vegetation zones from eastern china 18 n 50 n are reported the weighted average dn alkanes value for n c27 n c29 and n c31 in the samples and the annual average d of meteoric water recorded at 12 weather stations proximal to the sampling sites show similar spatial variations the d of n alkanes shows a gradual depletion in value with increasing latitude the results demonstrate that on a large spatial scale the d values of long chain n alkanes derived from higher plants have the potential to record the d of meteoric water although many other factors can also influence the isotope values there appears to be no apparent relationship between the d of the n alkanes extracted from the surface soil and the overlying vegetation type i e forest grassland or c3 c4 composition therefore palaeoenvironmental studies utilizing dn alkanes from higher plant derived material in geological samples have the potential to provide additional information with regard to the past hydrological cycle

transtensional origin of multi order cross folds in a high grade gneiss complex southwestern grenville province formation during post peak gravitational collapse the well mapped western part of the ottawa river gneiss complex orgc new name a large metamorphic core complex hosts a system of gently plunging cross folds of outcrop to regional scale situated in the ductile detachment zone between the lower grade cover and high grade core of the complex the cross folds are buckle structures that deform the attenuated gneissic layering plunge parallel to the regional elongation lineation range from upright to recumbent and exhibit distinctive hinge parallel elongation lineations all features of extension dominated ductile transtension our l s fabric data are consistent both with kinematic modelling that predicts progressive constrictional strain in the hinge zones of transtensional folds and with dynamic modelling that predicts rotation of flattened fold limbs into moderately dipping attitudes on the basis of petrologic data we show that cross folding postdated the peak ottawan metamorphism and took place during retrogression and exhumation of the thrust sheet stack the cross folds form an inclined system that is principally developed in retrograde melt weakened amphibolite facies rocks with the transtensional origin implying that exhumation and retrogression of the high grade core of the complex took place in an oblique extensional setting a transtensional origin for the cross folds removes the need to appeal to orogen parallel regional shortening an implausible requirement of previous interpretations and is compatible with data indicating that much of the visible fabric and structure of amphibolite facies domains of the orgc developed during post peak exhumation retrogression and gravitational collapse of the thrust sheet stack

distribution and stable isotopes of plant wax derived n alkanes in lacustrine fluvial and marine surface sediments along an eastern italian transect and their potential to reconstruct the hydrological cycle reconstructing terrestrial water budgets is of prime importance for understanding past climate and environment to shed more light on how plant wax derived n alkanes may be used for this purpose we investigated the distribution and stable isotopic compositions of hydrogen d and carbon 13c of plant wax derived n c29 and c31 alkanes in terrestrial coastal and offshore surface sediments in relation to hydrology along a nw se transect east of the italian apennines from the po river to the eastern gulf of taranto the plant wax average chain length increases southward and may relate to increasing temperature and or aridity the plant wax d of the terrestrial and coastal samples also increases southward and mainly reflects changes in the d of precipitation the 13c of plant waxes is primarily interpreted in terms of c3 vegetation changes rather than varying contributions by c4 plants the plant wax 13c d composition of the po river and apennine rivers differs considerably from that in southern italy and suggests a mainly southern source for plant waxes in marine sediments of the gulf of taranto this calibration provides a basis for the reconstruction of past changes in the italian water balance and n alkane source areas

current deformation in the northern canadian cordillera inferred from gps measurements 1 continuous and campaign style global positioning system gps measurements provide new constraints on the first order current deformation pattern of the northern cordillera of nw canada and eastern alaska the yakutat block is currently colliding with north america in the corner of the gulf of alaska our data infer that relative yakutat north america motion is accommodated across the eastern boundary by right lateral motion 40 mm a mainly on the fairweather fault and minor shortening 6 mm a to the north collision is taken up by shortening 31 mm a mainly on the chugach st elias fault system with westward extrusion and possible counterclockwise rotation of the yakutat block and alaskan fore arc facilitated by 23 mm a right lateral motion that is shared by several faults the seismicity pattern indicates that plate boundary deformation is far reaching producing strain throughout eastern alaska yukon and western northwest territories our gps data confirm the transfer of strain from the yakutat collision zone and enable the extent of plate boundary deformation to be mapped thereby defining the western edge of stable north america gps sites in sw yukon show motion of 3 10 mm a to the ne confirming that strain is transferred at least 400 km from the yakutat collision continued transfer north toward the mackenzie delta and ne to the mackenzie mountains indicated by current seismicity is not yet well resolved by the campaign gps data which are hampered by coseismic and postseismic effects of the 2002 mw 7 9 earthquake on the denali fault in eastern alaska

contemporary crustal deformation around the southeast borderland of the tibetan plateau 1 we derive a detailed horizontal velocity field for the southeast borderland of the tibetan plateau using gps data collected from the crustal motion observation network of china between 1998 and 2004 our results reveal a complex deformation field that indicates that the crust is fragmented into tectonic blocks of various sizes separated by strike slip and transtensional faults most notably the regional deformation includes 10 11 mm yr left slip across the xianshuihe fault 7 mm yr left slip across the anninghe zemuhe xiaojiang fault zone 2 mm yr right slip across a shear zone trending northwest near the southern segment of the lancang river fault and 3 mm yr left slip across the lijiang fault deformation along the southern segment of the red river fault appears not significant at present time the region south and west of the xianshuihexiaojiang fault system whose eastward motion is resisted by the stable south china block to the east turns from eastward to southward motion with respect to south china resulting in clockwise rotation of its internal subblocks active deformation is detected across two previously unknown deformation zones one is located 150 km northwest of and in parallel with the longmenshan fault with 4 6 mm yr right slip and another is continued south southwestward from the xiaojiang fault abutting the red river fault with 7 mm yr left slip while both of these zones are seismically active the exact locations of faults responsible for such deformation are yet to be mapped by field geology comparing our gps results with predictions of various models proposed for tibetan plateau deformation we find that the relatively small sizes of the inferred microblocks and their rotation pattern lend support to a model with a mechanically weak lower crust experiencing distributed deformation underlying a stronger highly fragmented upper crust

footwall involvement during arc continent collision ungava orogen northern canada geological evidence and theoretical models are presented to illustrate deformation paths followed by continental crust during underthrusting subduction and collision fieldwork in an early proterozoic collisional orogen indicates that a thrust belt and its autochthonous footwall basement are obliquely exposed in a crustal cross section with significant structural relief the collisional orogen records an evolution in the style and extent of involvement of the archaean footwall from 1 underthrusting without evidence of internal deformation 2 limited thrusting and ductile deformation of footwall rocks to 3 folding of the entire thrust belt and its footwall into cuspate lobate long wavelength structures the structural evolution occurred during hydration of basement rocks coeval with collision related metamorphism lithospheric strength profiles constrained by simple numerical heat conduction models suggest that the observed deformation path for the footwall crust was controlled by weakening due to heating of basement rocks and by changes in the relative strengths of different crustal layers the profiles predict a very weak lower crust and upper mantle at the time of footwall involved folding suggesting that the lower crust and upper mantle deformed by ductile flow concomitant with buckling of the stronger upper crust

tectonic block motion and glacial isostatic adjustment in southeast alaska and adjacent canada constrained by gps measurements 1 we use data from campaign and continuous gps sites in southeast alaska and the neighboring region of canada to constrain a regional tectonic block model that estimates block angular velocities and derives a self consistent set of fault slip rates from the block motions present day tectonics in southeast alaska is strongly influenced by the collision of the yakutat block our model predicts a velocity of 50 3 0 8 mm a toward n22 9 0 6 w for that block our results suggest that the eastern edge of the yakutat block is deforming along this edge the fairweather fault accommodates a large portion of the pacific north america relative plate motion through 42 9 0 9 mm a of dextral slip further south along the queen charlotte fault our model predicts an average of 43 9 0 6 mm a of dextral slip and a southward increasing amount of transpression strain from the yakutat collision is transferred far to the east of the strike slip system this strain transfer causes the region north of glacier bay to undergo a clockwise rotation south of glacier bay and inboard of the queen charlotte fault a smaller but clearly defined clockwise rotation is observed the heterogeneous block motion north and south of glacier bay may indicate the area is undergoing internal deformation and could explain regional patterns of diffuse seismicity the northern cordillera of canada displays a small northeasterly motion our block model suggests that the entire southeastern alaska northwestern canada margin is mobile

different altitude effect of leaf wax n alkane δd values in surface soils along two vapor transport pathways southeastern tibetan plateau abstract here we present 76 hydrogen isotope values for leaf wax derived n alkanes d wax being the abundance weighted average d values of c 29 and c 31 n alkanes in surface soils along two vapor transport pathway transects running across the southeastern tibetan plateau tp the first is the south himalayan sh transect with an altitude range of 1660 5050 m above sea level and representing the southern himalayan air mass and the second a combination of the zayu bomi zb altitude 1468 4800 m and bayi lhasa bl altitude 3050 4970 m transects together representing the brahmaputra yarlung zangbo river valley air mass d wax values and their relation to altitude did exhibit some variability nonetheless altitude was the predominant factor in determining soil d wax values with a lapse rate of 2 2 100 m r 2 0 78 n 76 based on overall soil d wax values despite changes in precipitation amount relative humidity rh and vegetation type furthermore our e wax rw values the isotopic fractionation between the d wax and d values of river water d rw remained approximately constant at 104 5 ranging between 99 and 110 confirming that the relation between altitude and isotopic hydrology river water and precipitation controls the n alkane d wax altitudinal gradients for all of the sample localities in the southern himalaya sh and the southern tp this endorses the efficacy of using d wax to reconstruct paleoelevation along the sh transect soil d wax values varied from 151 to 264 with an altitudinal lapse rate of 2 4 100 m r 2 0 84 n 32 this was due to the significant change in altitude over short distances along the zb transect soil d wax values varied from 174 to 263 with a lower lapse rate of 1 9 100 m r 2 0 68 n 29 the altitudinal lapse rate was 3 3 100 m above 3000 m r 2 0 63 n 19 and 1 35 100 m below 3000 m r 2 0 64 n 10 in the lower sub transect the latitudinal effect significantly counteracted the altitude effect along the bl transect soil d wax values varied from 205 to 244 with an altitudinal lapse rate of 1 4 100 m r 2 0 74 n 15 the lower lapse rate for soil d wax reflects a combination of local continental and altitudinal effects the differences we observed in soil d wax altitudinal lapse rates along the two vapor transport pathways imply that they are affected by subtle local environmental conditions moisture sources latitude and topography this should be considered fully during any reconstruction of paleoelevation

can sedimentary leaf waxes record d h ratios of continental precipitation field model and experimental assessments abstract d h ratios of leaf waxes d wax derived from terrestrial plants and preserved in lake sediments can provide important information on past continental hydrology ideally d wax can be used to reconstruct precipitation d h ratios d p which is a well established paleoclimate proxy however many other factors such as vegetation and relative humidity rh also affect d wax variation how the combination of these factors affects sedimentary d wax is unclear here we use a transect of 32 lake surface sediments across large gradients of precipitation relative humidity and vegetation composition in the southwestern united states to study the natural factors affecting sedimentary d wax d values of c 28 n alkanoic acids show significant correlation with d p values r 2 0 76 with an apparent isotopic enrichment of 99 8 indicating that sedimentary d wax values track overall d p variation along the entire transect leaf waxes produced by plants grown under controlled conditions rh 80 60 40 show a small increase in d h ratios as rh decreases consistent with prediction from the craig gordon model however the isotopic effect of rh on d wax along the natural transect is partially countered by the opposing influence of vegetation changes the correlation between d wax and d p values is significantly higher r 2 0 84 in the drier portions of the transect than in the wetter regions r 2 0 64 this study suggests that d h ratios of sedimentary leaf waxes can be used as a proxy for precipitation d variations with particularly high fidelity in dry regions although more studies in other regions will be important to further test this proxy

cross folds and back folds in the ofoten tysfjord area north norway and their significance for caledonian tectonics the outcrop pattern of caledonian allochthons in northern norway is controlled by two late fold sets cross folds f 3 which have axes at a high angle to the structural trend of the orogen and back folds f 4 which have axes parallel to the structural trend but verging in the opposite direction from that of nappe emplacement interference of cross folds and back folds produces ramsay type i dome and basin and type ii boomerang or canoe interference patterns on all scales the ofoten area contains the closure of a regionally extensive northeast trending back fold the ofoten synform within its core are klippen of the structurally highest nappes preserved in this portion of the caledonides at tysfjord 15 km south of ofoten some of the deepest structural levels within the orogen are exposed in the core of the tysfjord cross fold culmination the norwegian caledonides contain two strike parallel belts of gneiss domes underlain by precambrian basement rocks flanking an elongate structural basin to which the ofoten synform in part corresponds in ofoten tysfjord these domes and basins reflect a large scale cross fold back fold interference pattern structural characteristics of the cross folds and back folds indicate that they formed in response to layer parallel shortening implying that gneiss domes in these areas reflect interference of folds formed in crustal compression rather than diapirism because this dome and basin pattern is present along virtually the entire length of the norwegian caledonides we suggest that other gneiss domes in norway may have a similar origin the orientation of the cross folds in ofoten tysfjord suggests a component of sinistral shear affecting the orogen after the early silurian and before the late devonian paleomagnetic and structural data from other parts of the caledonides suggest large scale mid paleozoic post collisional lateral shear commonly with a sinistral sense although paleozoic strike slip faults have not been identified in the caledonides at this latitude we suggest that the cross folds may be an alternative expression of large scale sinistral shear

late caledonian extension in the ofoten area northern norway abstract structural observations along the base of the caledonian nappe pile in the ofoten region of northern norway demonstrate a complex interaction of compressional and extensional structures top to the west extensional structures are consistently superimposed on top to the east southeast compressional structures and control the basement cover relationships across the orogen extensional shear zones offsetting the basement cover contact appear to be restricted to the area east of the ofoten synform the eastern flank of the synform is an approximately 1 km wide w dipping shear zone with more than 30 km of dip slip offset the basement culimination roll over west of the synform is most likely controlled by the listric geometry of this shear zone at depth this major shear zone and other minor extensional shear zones within the rombak window have a ductile shear fabric with post kinematic recovery fabrics developed under middle to upper greenschist facies conditions suggesting that the footwall and hanging wall rocks were still at a mid crustal level some time after the extensional event the extensional shear zone flattens upsection and splays into a network of anastomosing detachment zones eastwards cutting both upsection and downsection in the direction of westward tectonic transport development of steeply dipping extensional basement faults and subhorizontal detachment faults in the cover have resulted in a complex basement cover relationship and reworking of the nappe stratigraphy established during the preceeding compressional event these relationships make restoration of the caledonian nappe pile to a pre orogenic configuration uncertain and shortening estimates difficult the recognition of the extensional event as a distinct post contractional tectonic event suggests a link with the devonian extensional collapse in southern norway a major difference between southern and northern norway however is the lack of brittle extensional features in the often area suggesting different amounts of extension and basement uplift in the two regions

assessment of the difference between mid and long chain compound specific δdn alkanes values in lacustrine sediments as a paleoclimatic indicator abstract previous studies have proposed that the difference between compound specific hydrogen isotopic composition of n alkanes d n alkanes of possible terrestrial origin and aquatic origin in lacustrine sediments is an indicator of hydroclimatic conditions for a lake environment e g terrestrial evapotranspiration of the lake drainage area or evaporation inflow ratio for the lake sachse d radke j gleixner g 2004 hydrogen isotope ratios of recent lacustrine sedimentary n alkanes record modern climate variability geochimica et cosmochimca acta 68 4877 4889 sachse d radke j gleixner g 2006 d values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record organic geochemistry 37 469 483 mugler i sachse d werner m xu b q wu g j yao t d gleixner g 2008 effect of lake evaporation on d values of lacustrine n alkanes a comparison of nam co tibetan plateau and holzmaar germany organic geochemistry 39 711 729 and this proposed indicator has been applied to a paleoclimatic study of koucha lake kcl on the northeastern tibetan plateau netp however the application was not very successful due to an apparent discrepancy between the reconstructed possible hydroclimatic variation based on the proposed indicator and precipitation amount variation based on pollen in the same lake aichner b herzschuh u wilkes h vieth a bohner j 2010a d values of n alkanes in tibetan lake sediments and aquatic macrophytes a surface sediment study and application to a 16 ka record from lake koucha organic geochemistry 41 779 790 we report new compound specific d n alkanes data for sediments since the last glacial from hurleg lake klk and genggahai lake ggh both also on the netp ca 300 km apart together d n alkanes data from the three lakes were analyzed to assess the difference between mid chain and long chain compound specific d n alkanes values in the sediments as a paleoclimatic indicator our results indicate that mid chain n c 23 and n c 25 and long chain n c 27 n c 29 and n c 31 n alkanes as compounds representative of aquatic and terrestrial origins respectively were valid only for klk correspondingly the use of differences between mid chain and long chain compound specific d n alkanes as a possible paleoclimatic indicator was feasible only for this lake hence our results emphasize the complex relationship between the chain length of lacustrine n alkanes and their actual origins and suggest that the correlation analysis of d n alkanes data for different chain length could be part of the possible evaluation method for the application of lacustrine compound specific d n alkanes data in paleoclimatic studies

a synthesis of hydrogen isotope variability and its hydrological significance at the qinghai tibetan plateau abstract hydrogen isotope ratios of sedimentary biomarkers are known to record the climatic variability in terrestrial and marine environments however there is still a lack of calibration studies that can quantitatively retrace the driving forces especially at the tibetan plateau here we elaborate the actual influence of environmental parameters such as temperature evapotranspiration salinity and biosynthetic fractionation on d values of n alkanes we measured hydrogen isotope values d of n alkanes in recent sediment and plant samples as well as d values of different water sources lake and inflow water precipitation as well as leaf root and soil water from six tibetan lakes along a 10 spanning longitudinal transect covering an aridity gradient as expected the deuterium record can be used to distinguish two water pools at the plateau i precipitation water which supplies water for the lake inflow and terrestrial plants and ii enriched lake water having a clear evaporative signal based on significant correlations of the source water and d values of n alkanes d of alkane n c 23 record the lake water isotope composition and track the evaporative enrichment of the lake system in contrast d of alkane n c 29 can be used to retrace the isotope composition of the inflow displaying the integrated rainfall signal in the vegetation period modified by soil and leaf water evaporation while temperature changes are less pronounced across the tibetan transect the isotopic difference between c 23 and c 29 could potentially be used as a proxy to reconstruct effective moisture precipitation minus evaporation areas with lower precipitation amounts and higher evaporation rates are characterized by higher d c 23 c 29 values this relationship is more pronounced in regions with mean annual precipitation below 350 mm even in contrasting environments the application of the d proxies is very promising combining other tibetan studies it is possible to present a comprehensive picture of the usage of compound specific hydrogen isotopes of n alkanes on the tibetan plateau

heterodynes dominate precipitation isotopes in the east asian monsoon region reflecting interaction of multiple climate factors abstract for the past decade east asian monsoon history has been interpreted in the context of an exceptionally well dated high resolution composite record of speleothem oxygen isotopes 18ocave from the yangtze river valley this record is characterized by a unique spectral response with variance concentrated predominantly within the precession band and an enigmatic lack of variance at the eccentricity and obliquity bands here we examine the spectral characteristics of all existing 250 kyr long terrestrial water isotope records in asia including a new water isotope record using leaf wax hydrogen isotope ratios from the chinese loess plateau there exist profound differences in spectral characteristics among all orbital scale asian water isotope records we demonstrate that these differences result from latitudinal gradients in the influence of the winter and summer monsoons both of which impact climate and water isotopes throughout east asia water isotope records therefore do not reflect precipitation during a single season or from a single circulation system rather water isotope records in east asia reflect the complex interplay of oceanic and continental moisture sources operating at multiple earth orbital periods these non linear interactions are reflected in water isotope spectra by the presence of heterodynes although complex we submit that water isotope records when paired with rapidly developing isotope enabled model simulations will have the potential to elucidate mechanisms causing seasonal precipitation variability and moisture source variability in east asia

seismicity of southwestern yukon canada and its relation to slip transfer between the fairweather and denali fault systems abstract several researchers have postulated the existence of a fault termed the connector fault that transfers slip from the fairweather to the denali fault systems in order to match the observed regional variations in fault slip and gps deformation earthquake locations seismic moment tensor information and gravity data presented in this study suggest that the connector fault is an active seismogenic structure that extends from the fairweather fault near hubbard glacier to the intersection of the duke river and totschunda fault systems seismicity and potential field data also suggest the existence of an east west trending cross structure between the totschunda and denali faults just north of 62 n that appears to be taking up compressional deformation similar to the duke river fault system to the south the intersection of this cross structure with the totschunda fault occurs near the termination of the 2002 denali fault mainshock rupture zone