magnetic susceptibility of soils in different slope positions in saskatchewan canada abstract the magnetic susceptibility of soils varies with the slope position due to some factors such as texture and drainage class this study attempts to link to soil profile characteristics soil horizon type organic and inorganic c sand and oxalate feo and dithionite fed extractable iron measured on soil cores collected from the three uncultivated soil catenas in saskatchewan the parent material at all sites consisted of medium textured hummocky glacial till the waitville catena gray luvisol was developed under trees the weyburn catena dark brown chernozem under grass and the oxbow catena black chernozem had trees on the lower slope and grass in the center of the depression and on the upper and middle slopes in all the three catenas a downslope decrease in was correlated with increasing feo fed ratios and decreasing sand content lower slope gleyed profiles in the two chernozemic catenas had high feo fed ratios and low the impact of gleying was most evident in the solum and tended to increase in the c horizons of these profiles the of the sand and silt fractions was positively correlated with that of the bulk soil whereas the of the clay fraction did not vary with the of the bulk soil stable sand sized magnetite grains are believed to be rare in these soils

middle miocene southern ocean cooling and antarctic cryosphere expansion magnesium calcium data from southern ocean planktonic foraminifera demonstrate that high latitude similar to55degreess southwest pacific sea surface temperatures ssts cooled 6degrees to 7degreesc during the middle miocene climate transition 14 2 to 13 8 million years ago stepwise surface cooling is paced by eccentricity forcing and precedes antarctic cryosphere expansion by similar to60 thousand years suggesting the involvement of additional feedbacks during this interval of inferred low atmospheric partial pressure of co2 pco 2 comparing ssts and global carbon cycling proxies challenges the notion that episodic pco2 drawdown drove this major cenozoic climate transition sst salinity and ice volume trends suggest instead that orbitally paced ocean circulation changes altered meridional heat vapor transport triggering ice growth and global cooling

soil aggregate stability within morphologically diverse areas abstract knowledge of spatial distribution of soil aggregate stability as an indicator of soil degradation vulnerability and its possible prediction are required for many scientific and practical environmental studies the goal of our study was to provide a model for predicting soil aggregate stability within morphologically diverse areas where soil properties have been affected by soil material redistribution due to erosion the study was performed on a study site 6 ha area in the loess region of southern moravia czech republic haplic chernozem which is an original dominant soil unit has been transformed into different soil units eroded phases of chernozem regosol colluvial chernozem and colluvial soil 36 sampling spots were selected in order to represent diverse soils the following soil properties were measured oxidable organic carbon content cox caco3 content phh2o phkcl soil particle density s bulk density d porosity p actual field soil water content field content of iron and manganese in ammonium oxalate extract feo and mno and dithionite citrate extract fed and mnd and mass specific magnetic susceptibility lf and hf the aggregate stability was assessed using various tests to study different disruption mechanisms terrain attributes were derived from a digital elevation model in general the lowest soil aggregate stability was observed on steep slopes which were highly impacted by soil erosion the highest aggregate stability was measured on soils sampled at relatively flat upper parts which were less influenced by erosion processes higher stability was also obtained on toe slopes where the sedimentation of previously eroded soil material occurred the simple correlations revealed that characteristics resulting from the tests studying aggregate slaking due to the compression of the entrapped air water stable aggregate index and coefficient of vulnerability from fast wetting test were positively impacted by the cox p feo mno fed mnd lf and hf values and negatively by the d value the soil aggregate stability was also negatively influenced by the plan and total terrain curvatures i e larger aggregate stability was measured at concave parts in comparison with that at convex parts almost no statistically significant relationships were found in the case of the tests evaluating either aggregate disintegration caused by the micro cracking due to the different swelling or by the physico chemical dispersion due to the osmotic stress or the mechanical aggregate breakdown the multiple linear regressions resulted in the model for estimating the wsa index using the cox content total terrain curvature and actual field soil water content field in this model the cox content positively and the total terrain curvature and field value negatively influenced the value of the wsa index since cox was positively related with iron content and thus also with the magnetic susceptibility the alternative model was proposed for less costly and time consuming wsa estimation the wsa index may be predicted by combining the mass specific magnetic susceptibility lf and hf total terrain curvature and actual field soil water content field

age and stratigraphic context of pliopithecus and associated fauna from miocene sedimentary strata at damiao inner mongolia china since the discovery of mammalian fossils in central inner mongolia in the beginning of the 20th century this area has produced a rich and diverse record of miocene faunas nevertheless the stratigraphy has remained poorly constrained owing to scattered faunal horizons and lack of continuous vertical exposures consequently most age estimates of these miocene sites are based on paleontological evidence alone with very few sites having been dated independently our field investigations in damiao in siziwang qi inner mongolia have yielded more than 30 new fossiliferous localities from three horizons including a pliopithecid fauna this study presents the litho bio and magnetostratigraphy of the damiao area and provides age estimates for the three fossil bearing horizons the sedimentary sequence is interpreted as the remains of a fluvial system comprising channels subaerially exposed floodplains and floodbasin environments the two local stratigraphic sections measured and sampled for paleomagnetic analysis coincide with species rich vertebrate fossil localities the paleomagnetic results and faunal evidence suggest a correlation of lowermost fossil horizon dm16 producing relatively rich small mammal assemblage to the early miocene chron c6ar or c6an 1r roughly in 20 21 ma age range the pliopithecid locality level dm01 represents latest middle miocene and has an age estimate of about 12 1 ma while the youngest localities dm02 with cervoids and abundant and diverse small mammal fauna represents the earliest late miocene with an age estimate of about 11 6 ma our magnetostratigraphic results confirm that the damiao strata constitute one of the best sequences in inner mongolia with early middle and late miocene mammalian faunas in stratigraphic superposition the results also provide constraints on the paleoenvironmental evolution and bioevents of the area the occurrence of pliopithecid primates in the middle miocene of inner mongolia suggests humid habitats and challenges the scenarios suggesting arid and highly seasonal conditions for central asia since early miocene the presence of pliopithecids may also bear witness to locally humid environments and greater habitat heterogeneity than previously known in central inner mongolia

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

magnetic mineral assemblages in soils and paleosols as the basis for paleoprecipitation proxies a review of magnetic methods and challenges abstract magnetic iron oxide minerals principally magnetite maghemite hematite and goethite are formed in well drained soils in response to a suite of physical chemical and biological factors despite a wide range of complexity in the pedogenic processes that lead to magnetic mineral formation dissolution and transformation there are well documented empirical relationships between various magnetic mineral assemblages in soils with environmental and climatic conditions recently there has been an increase in the number of quantitative magnetic paleoprecipitation proxies that have been developed and there is great potential for magnetic methods to be used in the geologic record to develop reconstructions of past climates magnetic paleoprecipitation proxies have been widely utilized in quaternary or younger loess paleosol systems however they have yet to be utilized in the pre quaternary fossil record future studies of magnetic mineralogy of soils and paleosols should aim to explore non loessic modern soils and pre quaternary paleosols with more focus on understanding the interaction between magnetic mineral assemblages and soil moisture applications of existing and novel magnetic paleoprecipitation proxies in the fossil record should prove to be a valuable resource for paleoclimatologists

frequency dependence of magnetic susceptibility as a proxy for fine grained iron minerals and aggregate stability of south chilean volcanic ash soils aggregate stability as is an important property controlling erodibility of volcanic ash soils and is known to be strongly affected by fine grained iron fe and aluminum al minerals assuming that frequency dependence of magnetic susceptibility ms is related to the amount of fine grained fe minerals and considering that formation of fine grained fe and al minerals is closely coupled in volcanic ash soils we hypothesized that the measurement of ms can be used to evaluate as of these soils to verify this we investigated volcanic ash soils along a 120 km transect in southern chile reaching from the andean southern volcanic zone svz to the pacific coastal range stability of 1 cm macroaggregates from topsoil 0 5 cm and subsoil 20 25 cm was determined by wet sieving combining long term water immersion and subsequent ultrasonic treatment ms was measured at 465 and 4650 khz to calculate its frequency dependence we found an increasing amount of organic matter fine grained fe and al minerals and clay and decreasing bulk density with increasing distance from the svz indicating progressing soil development along the transect likewise as increased with increasing distance from the svz and was found to be controlled primarily by soil organic matter and fine grained fe and al minerals while ms itself showed only slight variation its frequency dependence continuously increased with increasing distance from the svz indicating an increasing fraction of fine grained ferrimagnetic particles accordingly frequency dependence of ms was found to be linearly related to the amount of fine grained fe minerals as quantified by dithionite extraction and moreover due to the close linear relationship between fine grained fe and al phases it revealed to be suitable for estimating the total amount of both fine grained fe and al minerals analysis of underlying material 60 65 cm indicated that the increase in frequency dependence of ms with increasing distance from the svz was caused by fine grained ferrimagnetic particles of pedogenic and lithogenic origin although overall organic matter content turned out to be more closely related to the stability of the investigated aggregates we conclude that frequency dependence of ms can be used as an easily obtainable proxy for assessing the contribution of fine grained fe and al minerals to as

miocene pollen record of kc 1 core in the qaidam basin ne tibetan plateau and implications for evolution of the east asian monsoon abstract thick cenozoic deposits in the qaidam basin provide great potential for understanding the tectonic history paleoclimatic changes and evolution of the east asian monsoon this study examines the pollen record from the kc 1 core for the interval covering the later early to late miocene 18 5 ma thermophilic taxa percentages are high between 18 and 14 ma and decrease after this time a pattern which fits well with the middle miocene climatic optimum mmco between 18 and 14 ma and global climatic cooling after 14 ma during the same period xerophytic taxa percentages gradually increase and those of the conifers gradually decrease suggesting an aridification process in the qaidam region driven by the gradual strengthening of the east asian winter monsoon eawm and weakening of the east asian summer monsoon easm the global climate cooling process appears to have driven the climatic development of the qaidam basin region throughout the miocene but the uplift of the tibetan plateau also contributed

land use change and erosional history in a lake catchment system on the canadian prairies abstract the introduction of agriculture in the late 1800s and early 1900s brought about many changes in the natural prairie landscape of western canada the objective of this research project is to evaluate landscape response to land use change by relating observed changes in the sedimentary record of a lake drainage basin to documented land use change that has occurred since the onset of settlement a 52 cm lake sediment core was sectioned into 1 cm layers the sediment was separated into allogenic and authigenic fractions using a wet chemical extraction technique close interval 210pb dating enabled the calculation of sediment and elemental influx rates prior to european settlement erosion rates were low

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

late miocene and pliocene large land mammals and climatic changes in eurasia the fossil teeth of land mammals offer a powerful tool to map the regional details of past climate change in the terrestrial realm we use meanplant eaterhypsodonty molarcrownheight oflateneogenemammallocalitiestomaplatemioceneandpliocenepalaeoprecipitation on the eurasian continent and with higher temporal resolution in europe the results show that the mid latitude drying in eurasia affected thecentral parts ofthecontinentfirst and thatthedrying of western europeafter about7 8maseemstohavecoincidedroughlyintimewith a return to more humid conditions in eastern asia with a return to a drier east and more humid west in the pliocene within europe the hypsodonty based palaeoprecipitation maps suggest that the sequence from mn 9 to mn 12 ca 11 1 6 8 ma was dominated by an east west continental marine humidity gradient which gradually intensified and with a shift of dryer conditions eastwards in mn 12 ca 7 5ma thiswaspartlyoverlainfrommn13onwardsbyanorth southorientedgradient whichpersistedatleasttotheendofthepliocene the maps for both the earliest late miocene mn 9 ca 11 1 9 7 ma and the earliest pliocene mn 14 ca 4 9 4 2 ma show very low regional differentiation possibly suggesting perturbed phases in the evolution of the mammal communities analysis of hypsodonty and dietary structure of the mammalian plant eater community in europe during the entire interval shows that the miocene pliocene boundary was marked by a strong decrease in mesodont species and mixed feeders and an increase in brachydont species and omnivores in this view the shift in the latest miocene from east west to partly north south polarised hypsodonty patterns corresponds mainly to an increase in hypsodont species and grazers it seems probable that the east west gradient was primarily driven by precipitation while the north south gradient would also have been strongly influenced by temperature related effects of humidity

the miocene climatic optimum evidence from ectothermic vertebrates of central europe abstract data sets of central european temporal distributions of thermophilic ectothermic vertebrates channidae varanidae chamaeleonidae cordylidae tomistomidae alligatoridae giant turtles and of north alpine foreland basin nafb distributions of ectothermic vertebrates adapted to dryer habitats albanerpeton inexpectatum salamandra sansaniensis bufo cf viridis chamaeleo caroliquarti gekkonidae varanus hofmanni bransateryx sp are analysed two main migration events of thermophilic ectotherms at 20 ma and 18 ma in the lower miocene are discerned they indicate the beginning of the miocene climatic optimum in central europe 42 45 n palaeolatitude with a lower limit of the mean annual temperature mat of 17 4 c derived from the minimal mat of their extant relatives furthermore additional palaeobotanical data and records of bauxite point to a mat of 22 c this warm and humid optimum peaked at 18 16 5 ma ottnangian karpatian and is confirmed by the coexistence of all investigated thermophilic taxa the following period early badenian is characterised by probably unchanged temperatures but a seasonality in precipitation with dry periods up to six months two major seasonal phases between 16 3 and 15 7 ma earliest early badenian and between 14 7 and 14 5 ma early middle badenian transition are indicated by an immigration of dry adapted taxa from the surrounding karst plateau to the nafb it is presumed that the tectonical reorganisation of the central paratethys realm had considerable influence on this regional humidity pattern the warm period ended abruptly between 14 0 and 13 5 ma middle late badenian transition with major regional extinction events of most of the thermophilic groups in central europe and a drop of the mat of probably more than 7 c to temperatures around 14 8 15 7 c this drop can be attributed predominantly to a decrease of more than 11 c of the minimum cold months temperature this temperature decrease marked the beginning of a climatic zonation of the european continent and is also evidenced by a progressively southward disappearance of the crocodile diplocynodon from 38 45 n palaeolatitude to 30 37 n during the middle and earliest late miocene the results correlate well with palaeobotanical data from the mid latitudes of europe and north america and the deep sea temperature curve generated from oxygen isotope ratios

particle size and analytical considerations in the mineral magnetic interpretation of soil loss from cultivated landscapes abstract prior research has highlighted the potential for using soil magnetism as a rapid estimator of total cumulative soil loss on cultivated land in this study the influences of particle size choice of magnetic measurement and initial conditions on a proposed model linking surface soil magnetism and soil loss are described and evaluated output model curves are generated for several parameter sets corresponding to different model assumptions and physical scenarios output is also compared to a new high resolution surfacial magnetism data set from a cultivated site gilbert farm in northwestern alabama usa to further evaluate the model magnetic susceptibility values at gilbert farm range from 150 to 220 10 8 m 3 kg 1 in a control soil profile the original model output ranges from 180 to 192 10 8 m 3 kg 1 and many magnetism values in the cultivated area fall outside this range introduction of a particle size sorting correction factor decreases the range of output values and results in even greater numbers of out of range observations however there is evidence suggesting that particle size distributions in the upper soil at this site are not strongly affected by differences in water erosion mechanism lower tillage depths cause magnetic susceptibility values to come in range but may be unrealistic and create a twin value problem for complex magnetic profiles use of the remanence sirm volume susceptibility lf ratio profile with values ranging from 35 to 120 ma m 1 10 5 si instead of magnetic susceptibility as used in the original model was found to eliminate out of range and twin value anomalous magnetism values were identifiable and treatable on the high resolution magnetism maps but other types of natural spatial variation remain at issue

simple equations to represent the volume area depth relations of shallow wetlands in small topographic depressions abstract small topographic depressions have important functions in hydrology and ecology because they store water in the form of shallow lakes wetlands or ephemeral ponds the relations between the area a the volume v and the depth h of water in depressions are important for evaluating water and dissolved mass balances of the system the a h and v h relations are usually determined from fine resolution elevation maps based on detailed survey data simple equations are presented in this paper which can be used to 1 interpolate a h and v h data points obtained by a detailed survey 2 approximate unknown a h and v h relations of a depression from a minimal set of field data without a time consuming elevation survey and 3 serve as a geometric model of depressions in simulation studies the equations are simple power functions having two constants the first constant s is related to the size of the depression and the second constant p is related to the geometry of the depression the power functions adequately represent a h and v h relations of all 27 wetlands and ephemeral ponds examined in this paper which are situated in the northern prairie region of north america assuming that the power functions are applicable for other similar topographic depressions an observer only needs to measure a and h twice to determine the two constants in the equation the equations will be useful in field studies requiring approximate a h and v h relations and in theoretical and modeling studies

using magnetic susceptibility to assess soil degradation in the eastern rif morocco 25 pag 4 tabl 7 fig the definitive version is available at http www3 interscience wiley com journal 2388 home

palynological evidence for miocene climate change in the forecarpathian basin central paratethys nw bulgaria abstract we reconstruct quantitatively the middle to upper miocene climate evolution in the southern forecarpathian basin central paratethys area northwest bulgaria by applying the coexistence approach to 101 well dated palynofloras isolated from three cores the climatic evolution is compared with changes in vegetation and palaeogeography the middle miocene was a period of a subtropical warm temperate humid climate with mean annual temperature mat between 16 and 18 c and mean annual precipitation map between 1100 and 1300 mm thereby during the entire middle miocene a trend of slightly decreasing temperatures is observed and only small climate fluctuations occur which are presumably related to palaeogeographic reorganisations the vegetation shows a corresponding trend with a decrease in abundance of palaeotropic and thermophilous elements the upper miocene is characterised by more diverse climatic conditions probably depending on palaeogeographic and global climatic transformations the beginning of this period is marked by a slight cooling and a significant drying of the climate with mat 13 3 17 c and map 652 759 mm after that fluctuations of all palaeoclimate parameters occur displaying cycles of humid dryer and warmer cooler conditions which are again well reflected in the vegetation our study provides a first quantitative model of the middle upper miocene palaeoclimate evolution in southeastern europe and is characterised by a relatively high precision and resolution with respect to the climate data and stratigraphy

how old is the asian monsoon system palaeobotanical records from china the recent discovery of monsoon records in early miocene raised a question of the time when the east asian monsoon system initiated a distinguishing feature of the modern monsoon system is its geographic distribution which disturbs the zonal pattern indigenous to the planetary climate system and the appearance of the monsoonal climate pattern in the geological records should signify the onset of the monsoon system here we present the results of a compilation of palaeobotanical and lithological data from 125 sites over china that has revealed two completely different patterns of climate zones the palaeogene pattern with a broad belt of aridity stretched across china from west to east and the neogene pattern with the arid zone restricted to northwest of china which has persisted until today the reorganization of the climate system around the oligocene miocene boundary provides evidence for the establishment of the modern east asian monsoon since then the neogene has witnessed significant variations of the monsoon system including enhancement of aridity and monsoon intensity at about 15 13 my around 8 my and 3 my the new data do not support the onset of the asian monsoon system around 8 my rather the new data led to a hypothesis that the transition to the monsoon climate system in east asia occurred in the latest oligocene

a comparison of different magnetic methods for determining the relative grain size of magnetite in natural materials some results from lake sediments abstract a new rapid method for identifying relative grain size variations in magnetic involves the parameter anhysteretic susceptibility arm i e specific arm obtained in a 1 oe steady field which is particularly sensitive to the single domain sd and small pseudo single domain psd grains of the finer magnetite fraction a second parameter low field susceptibility is relatively more sensitive to the coarser magnetite fraction larger psd and smaller multidomain md grains we can then obtain a measure of the ratio of coarse to fine grain magnetite for large numbers of samples by plotting arversus a simple idealized model based on sized magnetite samples is proposed to explain the use of the armversus plot for detecting relative grain size changes in the magnetic content of natural materials the sediments of three lakes that contain magnetite or a similar magnetic carrier and have a wide range of values of arm and are used to test the model the model is used to interpret the magnetic variations observed and the interpretations are supported by high field hysteresis measurements of the same sediments the combination of the high field hysteresis method of day et al 1 and the arm vs method is a powerful technique allowing the rapid identification of both the relative grain size and domain state for large numbers of samples containing magnetite the armvs method should be used as an intial means of identifying distinct groups of samples the high field hysteresis method should then be applied to a few representative samples from each group to confirm the initial interpretation

lake catchment based studies of erosion and denudation in the merevale catchment warwickshire u k sediment yields estimated from contemporary stream monitoring of suspended sediment in the merevale forested catchment north warwickshire were compared with the sediment yield record obtained from analysis of lake sediment in the downstream reservoir total sediment volume and mass for nine periods since 1861 were calculated by extrapolation of synchronous levels in 54 cores identified from magnetic susceptibility and other magnetic measurements and by using 210pb and 137cs analysis to provide an absolute sediment chronology sediment yield estimated from the two methods show comparable but low 50 200 kg ha 1 yr 1 levels of sediment loss while suggesting that lake sediments can be a useful means for extending the period over which contemporary monitoring exists the study stresses the need for detailed historical records of land use and climate against which long term sediment yield records can be evaluated

mapping units based on spatial uncertainty of magnetic susceptibility and clay content abstract this study aimed to use spatial uncertainty of magnetic susceptibility ms and clay content to improve soil mapping units in an experimental area of 870 ha a regular sampling grid containing 371 points was set in which ms and clay content were assessed at a depth range of 0 0 25 m using a digital elevation model and field observations a 4440 m transect was established on the study area from hilltop to the foothill toward the gentlest slope standard deviation maps based on 200 realizations of the sequential gaussian simulation measured spatial estimate uncertainties to limit transition zones along the transect uncertainty isolines representative of the transition between soil mapping units were selected both attributes presented peaks of uncertainties near the change of mapping units previously known uncertainty zones previously delineated ranged from 45 to 210 m and from 60 to 170 m for ms and clay content respectively however after extrapolating the uncertainties to the side of the transect amplitude changes of the uncertainty zones were observed especially in the transition regions between landscape shape and geology delineation of mapping units which incorporated the uncertainties of ms and clay content was similar however due to lower cost and promptness ms becomes the most feasible alternative knowing spatial uncertainties enables readjusting limits in maps of soil mapping units and may support identification of most favorable regions for determining modal pedon representative of each unit

rapid cenozoic glaciation of antarctica induced by declining atmospheric co2 the sudden widespread glaciation of antarctica and the associated shift towards colder temperatures at the eocene oligocene boundary 34 million years ago refs 1 4 is one of the most fundamental reorganizations of global climate known in the geologic record the glaciation of antarctica has hitherto been thought to result from the tectonic opening of southern ocean gateways which enabled the formation of the antarctic circumpolar current and the subsequent thermal isolation of the antarctic continent5 here we simulate the glacial inception and early growth of the east antarctic ice sheet using a general circulation model with coupled components for atmosphere ocean ice sheet and sediment and which incorporates palaeogeography greenhouse gas changing orbital parameters and varying ocean heat transport in our model declining cenozoic co2 first leads to the formation of small highly dynamic ice caps on high antarctic plateaux at a later time a co2 threshold is crossed initiating ice sheet height mass balance feedbacks that cause the ice caps to expand rapidly with large orbital variations eventually coalescing into a continental scale east antarctic ice sheet according to our simulation the opening of southern ocean gateways plays a secondary role in this transition relative to co2 concentration

origin signature and palaeoclimatic influence of the antarctic circumpolar current the antarctic circumpolar current acc is today the strongest current in the world s ocean with a significant influence on global climate its assumed history and influence on palaeoclimate while almost certainly equally profound are here called into question in this paper we review 30 years of accumulated data interpretation and speculation about the acc deriving mainly from dsdp and odp drilling in the southern ocean for most of this time a conventional view of acc development signature and influence has held sway among palaeoceanographers and marine geologists in this view the acc began at about 34 ma close to the eocene oligocene boundary the time of onset of significant antarctic glaciation and the time of creation of a deep water gap tasmanian seaway between australia and antarctica as the south tasman rise separated from north victoria land this is the smoking gun of synchroneity the southern ocean sediment record shows a latest eocene development and subsequent geographic expansion of a siliceous biofacies its northern limit taken to indicate the palaeoposition of the acc axis in addition the acc was considered to have caused antarctic glaciation by isolating the continent within a cold water annulus reducing north south heat transport a different and later date for antarctic south american opening drake passage was proposed but the timing of acc onset there was disputed and the simple story survived recent developments however call it into question modern physical oceanography shows that all or most of present day acc transport is confined to narrow jets within deep reaching circumpolar fronts and numerical modelling has suggested that a steady reduction in greenhouse gas concentration through the cenozoic could cause antarctic glaciation with or without a contribution from ocean circulation change the rapidity of antarctic glacial onset at the eocene oligocene boundary and coeval creation of a deep water gap south of tasmania both survive but in light of the new information the presence of a siliceous biofacies cannot be claimed as evidence of the existence of a continuous deep reaching oceanic front and therefore of an acc and the possibility arises that cool and cold sea surface temperatures were effects of antarctic glaciation rather than evidence of a major contributor to its cause in considering future work we emphasise the importance of additional information from ancillary fields better definition of the necessary and sufficient properties of oceanic fronts additional determinations of cenozoic atmospheric pco2 and further developments in models of antarctic glaciation but also suggest the way forward in marine geology our knowledge of the development and palaeoclimatic significance of the acc will be best served by grainsize studies of bottom current strength at selected locations and geochemical or mineralogical studies of clays and ird as a way of examining provenance and therefore surface and bottom current directions and the existence of interocean connections

the middle miocene climatic transition east antarctic ice sheet development deep ocean circulation and global carbon cycling abstract the middle miocene represents a major change in state in cenozoic climatic evolution following the climax of neogene warmth in the late early miocene at 16 ma the early stage of this climatic transition from 16 to 14 8 ma was marked by major short term variations in global climates east antarctic ice sheet eais volume sea level and deep ocean circulation in the later stage from 14 8 to 12 9 ma climatic developments included major growth of the eais and associated antarctic cooling a distinct increase in the meridional temperature gradient large fluctuations in sea level followed by a global sea level fall and important changes in deep water circulation including increased production of southern component water east antarctic ice sheet growth and polar cooling also had large effects on global carbon cycling and on the terrestrial biosphere including aridification of mid latitude continental regions increased stability of the eais after 14 8 ma represents a crucial step in the establishment of late neogene global climate systems what controlled these changes in polar climates and the east antarctic ice sheet deep ocean circulation changes probably played a major role in the evolution and variation in polar climates as they have throughout the cenozoic oxygen and carbon isotopic evidence for warm saline deep water production in the eastern tethyan northern indian ocean indicates that meridional heat transport to the antarctic inhibited cenozoic polar cooling and eais growth during the early middle miocene from 16 to 14 8 ma inferred competition between warm low latitude sources derived from the eastern tethyan northern indian ocean and a cold high latitude source southern component water from 16 to 14 8 ma may have been associated with instability in the antarctic climate and cryosphere reduction of warm saline deep water flow to the southern ocean at 14 8 ma may have decreased meridional heat transport to the antarctic cooling the region and leading to increased production of southern component water these middle miocene climatic and cryospheric changes in the antarctic had profound effects on marine and terrestrial climates as the meridional surface temperature gradient increased boundaries between climatic zones strengthened leading to increased aridification of mid latitude continental regions in australia africa and north and south america enhancing the development of grasslands and stimulating the evolution of grazing mammals

the evolution of miocene climates in north china preliminary results of quantitative reconstructions from plant fossil records the miocene climate evolution in north china is preliminarily discussed by means of comparisons in seven climate parameters quantitatively reconstructed by the coexistence approach on 34 selected macro and microfloras over north china the miocene temperatures show no great difference in the western and eastern part of north china temperature fluctuations particularly in mean annual temperature are found within floras from several sites the fluctuation pattern from a climate optimum in the mid miocene to cooling decline in the late miocene is generally consistent with the global trend of miocene temperature change the reconstructed precipitation from all the sites studied shows much wetter conditions in north china during the miocene than at present which corroborates the results from paleoprecipitation proxy of fossil mammals like the situation in paleo temperature the miocene precipitation from north china shows no distinct difference between the western and eastern regions it is suggested that north china particularly in the western part was by no means under an arid or semi arid environment during the miocene north china is an ideal region for study of the impact of the east asian monsoon system however the pattern of precipitation change derived from the monsoon index msh and mean annual precipitation map shows contradictory results therefore there appears no definite conclusion on when the east asian summer monsoon intensified possible reasons for inconsistency in temperature and precipitation changes are discussed directions of future work to improve the resolution of climate evolution are also pointed out c 2010 elsevier b v all rights reserved

use of mineral magnetic measurements to investigate soil erosion and sediment delivery in a small agricultural catchment in limestone terrain abstract understanding sediment delivery at the hillslope scale requires information on the spatial distributions and magnitudes of erosion and deposition empirical models such as the rusle may be useful for predicting erosion but are poorly suited for quantifying deposition cesium 137 cs 137 is useful for quantifying both erosion and deposition but is costly to inventory over a large area and directly gauges soil redistribution only for recent decades the use of rapidly acquired magnetic measurements represents a relatively new potential means of mapping and measuring soil redistribution in this study variations in surface magnetism are analyzed to determine patterns of erosion and sedimentation in a small agricultural catchment in northwestern alabama usa magnetic indicators of erosion are combined with published soil morphology cs 137 and short term suspended sediment data from this former experimental watershed to evaluate long term sediment delivery all magnetic parameters measured could be related to soil erosion although their patterns in space are not identical magnetic evidence suggests approximately 30 cm of soil loss on the steepest mid slope portions of the catchment distributing soil loss across space according to magnetic patterns gives average long term values lower than a prior estimate based on cs 137 data long term sediment delivery calculated using soil morphology to determine depositional volume ranges up to 45 depending on the magnetic parameter used to index soil loss and assumptions regarding deposit geometry these results suggest the need for continued refinement of magnetic techniques for purposes of erosion model validation and general sediment tracing applications

the use of magnetic susceptibility to measure long term soil redistribution abstract several studies have documented the severity of recent soil erosion on the canadian prairies where cultivation started about a century ago little quantitative information is available on erosion before 1960 this study attempts to quantify post and pre 1960 soil erosion in a small cultivated basin near saskatoon saskatchewan canada by measuring 137cs and magnetic susceptibility distribution with depth soil cores were collected along six transects three across closed depressions and three across the drainage channel in the cultivated field and one transect across an uncultivated depression the cores were sliced into 3 cm layers and the soil analyzed for 137cs and organic and inorganic c high variability in with depth in eroding areas as indicated by 137cs made it impossible to use to quantify past soil losses in these locations however these eroding upper and middle slope positions have a much higher than lower slope areas where soil deposition occurs and where the variability in with depth could be used to estimate soil deposition estimating soil deposition from the vs depth profiles was more successful in the closed depressions than in the drainage channel where the profiles may reflect the variable source areas of the materials rather than the pedological conditions the data indicated that soil deposition since 1960 has been about 30 to 50 of that prior to 1960 this suggests that soil deposition rates and by implication soil erosion rates have been relatively steady since cultivation of these soils started although there are clear indications that the spatial pattern of deposition has varied

significant mid latitude aridity in the middle miocene of east asia abstract the east asian climate history during the neogene is a complicated and contentious issue in particular because of its bearing on the development of the east asian monsoon and tibetan uplift chronology here we present a paleoprecipitation analysis based on mean molar tooth height hypsodonty of large herbivorous mammals to investigate the spatial pattern of climate zonation in east asia during the middle miocene we show a generally humid and uniform situation before the late middle miocene replaced by a mid latitude arid belt from the late middle miocene into the earlier part of the late miocene these findings are concordant with the global phenomena of the middle miocene climate optimum and the subsequent cooling and suggest that the predominant climate in east asia for most of the miocene was planetary rather than monsoonal our results support a late initiation of the east asian summer monsoon coincidentally with the beginning of eolian red clay deposition in the later late miocene at 7 8 ma

recent sediment flux and erosional processes in a welsh upland lake catchment based on magnetic susceptibility measurements abstract single sample magnetic susceptibility measurements are used to correlate synchronous levels in 16 cores of dated 210 pb 137 cs recent sediment taken from the deep and oligotrophic llyn peris n wales in order to provide a basis for calculating total sediment and chemical influx through time results show that sediment influx has steadily increased since c 1750 a d to reach peak levels in the period 1966 1976 a d equivalent to a rise in erosion in the catchment from c 5 t km 2 yr 1 to c 42 t km 2 yr 1 comparison of down core susceptibility fluctuations with sediment pollen and organic pigment data indicates that maximum susceptibility values relate to periods of channel erosion and minimum susceptibility values relate to periods of slate debris inwash from spoil tips in the catchment a study of historical records reveals that pre twentieth century peak levels of erosion were due to the effects of extractive industries while twentieth century erosion has been caused by overgrazing increased trampling pressure and heavy construction works in the catchment

listric versus planar normal fault geometry an example from the eisenstadt sopron basin e austria in a gravel pit at the eastern margin of the eisenstadt sopron basin a satellite of vienna basin austria neogene sediments are exposed in the hanging wall of a major normal fault the anticlinal structure and associated conjugated secondary normal faults were previously interpreted as a rollover anticline above a listric normal fault the spatial orientation and distribution of sedimentary horizons and crosscutting faults were mapped in detail on a laser scan of the outcrop wall subsequently in order to assess the 3d distribution and geometry of this fault system a series of parallel ground penetrating radar gpr profiles were recorded behind the outcrop wall both outcrop and gpr data were compiled in a 3d structural model providing the basis for a kinematic reconstruction of the fault plane using balanced cross section techniques however the kinematic reconstruction results in a geologically meaningless normal fault cutting down and up section additionally no evidence for a weak layer serving as ductile detachment horizon i e salt or clay horizon can be identified in stratigraphic profiles instead the observed deflection of stratigraphic horizons may be caused by a displacement gradient along a planar master fault with a maximum displacement in the fault centre decreasing towards the fault tips accordingly the observed deflection of markers in the hanging wall and in a nearby location in the footwall of the normal fault is interpreted as large scale fault drag along a planar fault that records a displacement gradient instead of a rollover anticline related to a listric fault

dating quaternary fault scarps formed in alluvium using morphologic parameters abstract ages of fault scarps as well as those other types of transport limited slopes can be estimated by comparing their morphology with the morphology of scarps of known age age estimates are derived by fitting the scarp profiles to synthetic profiles generated using a diffusion equation or alternatively by classification using a linear discriminant function the usefulness of morphology derived age estimates depends on the relative importance of non age related morphologic variation data from more than 200 scarp profiles demonstrate that morphologic variation not related to scarp age can introduce significant uncertainties into morphology derived age estimates

mapping the architecture of glaciofluvial sediments with three dimensional georadar three dimensional 3 d ground penetrating radar georadar mapping offers new opportunities for determining the geometries and facies of surficial sedimentary units to investigate the potential of this high resolution technique and at the same time study the architecture of quaternary glaciofluvial deposits georadar data have been collected on a dense grid established across a sequence of braided river gravels and sands in northeastern switzerland results of this survey are striking 3 d images that provide many more details and much more reliable information on the heterogeneities of the shallow underground than are afforded by conventional georadar profile data continuous subhorizontal and oblique reflections can be traced throughout vertical sections and horizontal slices of the georadar data block to a depth of approx 15 m clearly defined are the dominant flow direction of the ancient braided river system the boundaries between different sedimentary facies and the level of the ground water table trough fill sediments and subhorizontal channel deposits observed on 7 m high quarry walls can be followed confidently in the subsurface the orientation shape and size of the troughs and the strike and dip of the cross bedding are all well resolved

addressing the effects of sampling on ecometric based paleoenvironmental reconstructions abstract ecometric analysis involves the examination of quantifiable functional traits across the taxa in a biotic community well documented relationships between certain functional traits and environmental gradients in the present provide the empirical framework for a large body of research that uses ecometrics to reconstruct environments in the fossil record in current applications of the technique the taxa present in a fossil assemblage are summarized using the mean value of an environmentally informative trait this study explores some of the quantitative pitfalls inherent to this approach through analysis of dental crown height a trait that is widely used to infer paleo precipitation of late pleistocene ungulate assemblages from the lake victoria basin in western kenya we illustrate how ecometric means vary as a function of sample size sampling artifacts have the potential to bias ecometric means and the environmental inferences derived from them whenever there is a non random distribution of traits across the species abundance distribution e g if abundant taxa have different traits than rare taxa this sampling issue also means that the degree of analytical precision implied by quantitative paleoenvironmental reconstructions e g annual precipitation at time x was 500 mm yr derived from ecometrics may be unwarranted we recommend that analytical approaches be modified to circumvent these problems and explore three potential solutions 1 specimen based rarefaction 2 coverage based rarefaction and 3 weighting ecometric means by taxonomic abundances of these only the latter is robust to variation in sampling effort because abundance data are not always available and are potentially unreliable we outline alternative approaches that could be implemented to contend with sample bias

active fault kinematics and crustal stresses along the ionian margin of southeastern sicily since the late cretaceous onset of plate convergence between africa and europe the malta escarpment has been converted from a mesozoic passive margin into a mega hinge fault system with an additional sinistral strike slip component the modern tectonic stress regime with nw se directed maximum horizontal stresses has been established since late messinian times since the pleistocene sinistral strike slip deformation and contemporaneous normal faulting along the malta escarpment have induced the opening of oblique trending onshore grabens at the eastern margin of the hyblean plateau in this study we focus on the kinematics the controlling state of stress and the temporal variation of the neotectonic to active strike slip and normal fault structures the stress tensor calculations reveals that the widespread map scaled to meso scaled normal fault structures are governed by the long term extensional state of stress during the quaternary this long term stress tensor is predominantly controlled by gravitational induced stresses due to vertical load 1 sv and lateral extension due to the topographic gradient of the malta escarpment 3 sh ne sw in this case the average tectonic stresses 2 sh nw se transmitted by the regional to plate tectonic stress field are significantly smaller than the gravitational induced stresses in contrast the clear localization of conjugate sets of meso scaled strike slip fault structures and shear zones without accompanying normal fault structures give strong indications for episodic seismotectonic strike slip faulting under critical stress conditions in this state tectonically induced maximum horizontal stresses are successively increased by ongoing plate convergence from low level stress magnitudes 1 sv 2 sh nw se up to critical stress magnitudes 1 sh nw se 2 sv which are significantly larger than gravitational stresses at the critical state seismotectonic stress release occurs by active strike slip faulting as recently indicated in mid crustal levels by the moderate 1990 augusta earthquake and re establishes the long term extensional state of stress because the strike slip faults and shear zones in the study area were formed as surface ruptures they additionally give indications of episodic large earthquakes in this region with magnitudes greater than 6 0 as reported by several large earthquakes devastating e and se sicily in historical times

miocene climate in europe patterns and evolution to improve our understanding of long term climate changes during the neogene in eurasia the international research network neclime neogene climate evolution in eurasia was established in the year 2000 in this first synthesis results of neclime activities focussing on the miocene of europe as one key area are combined to present a summary of the climate evolution in time and space more than 300 miocene fossil floras have been compiled and quantitatively analysed in terms of several climatic parameters during the last few years in this volume alone about 75 new data sets are available to synthesize the results of this volume quantitative climate maps for europe are generated on palaeogeographic maps for langhian and early tortonian for the first time characteristic climate patterns appear for each time interval and can be related to both global climate change and alpine tectonics generally the climate maps combine and support the individual results discussed in this volume for the individual regions

middle miocene to earliest pliocene sedimentological and geochemical records of climate change in the western qaidam basin on the ne tibetan plateau global cooling tibetan plateau uplift and the retreat of the para tethys sea have long been thought to be the key controls of the cenozoic climate change in the asian inland however due to the scarcity of long term palaeoclimate records it is not entirely clear which of these factors plays the major role here we present new sedimentological and geochemical proxy records toc carbonate so42 and cl from a 1040 m late cenozoic sedimentary sequence ca 17 to 5 0 ma from the western part of the qaidam basin the largest inland basin on the ne tibetan plateau geochemical records reveal an evident two stage change from ca 17 ma to 11 1 ma phase i the proxies show an upward decrease of carbonate content and toc concentration and a persistent increase in the concentration of the soluble anions so42 and cl even though superimposed high frequency fluctuations are evident from ca 11 1 ma to 5 0 ma phase ii the average concentrations of so42 and cl are higher than those from phase i and a sharp decrease in the carbonate content occurred the sedimentological and geochemical proxy records demonstrate that the qaidam basin has experienced increased aridity since ca 11 1 ma we suggest that the miocene global cooling exerted a significant influence on the drying of the qaidam basin by decreasing evaporation rates and water vapour concentrations in the atmosphere the mio pliocene episodic and persistent uplift of the ne tibetan plateau exerted an important influence superimposed upon this driving force while during ca 11 1 to 8 ma the rapid uplift of the altun shan might have played a key role in climate change of the qaidam basin c 2013 elsevier b v all rights reserved

cenozoic expansion of grasslands and climatic cooling abstract mountains ocean currents forests and swamps have played an important role in regulating global climate for hundreds of millions of years but the truly novel event of the cenozoic was the evolution and expansion of grasslands with their uniquely coevolved grasses and grazers neogene expansion of the climatic and geographic range of grasslands at the expense of woodlands is now revealed by recent studies of paleosols fossils and their stable isotopic compositions grasslands and their soils can be considered sinks for atmospheric co2 ch4 and water vapor and their cenozoic evolution a contribution to long term global climatic cooling grassland soils are richer in organic matter than are woodland and desert soils of comparable climates and when eroded their crumb clods form sediment unusually rich in organic matter grasslands also promote export of bicarbonate and nutrient cations to lakes and to the oceans where they stimulate productivity and c burial this increased productivity and

application of ground penetrating radar to investigation of near surface fault properties in the san francisco bay region abstract in many geologic environments ground penetrating radar gpr provides high resolution images of near surface earth structure gpr data collection is nondestructive and very economical the scale of features detected by gpr lies between those imaged by high resolution seismic reflection surveys and those exposed in trenches and is therefore potentially complementary to traditional techniques for fault location and mapping sixty two gpr profiles were collected at 12 sites in the san francisco bay region results show that gpr data correlate with large scale features in existing trench observations can be used to locate faults where they are buried or where their positions are not well known and can identify previously unknown fault segments the best data acquired were on a profile across the san andreas fault traversing pleistocene terrace deposits south of olema in marin county this profile shows a complicated multi branched fault system from the ground surface down to about 40 m the maximum depth for which data were recorded

repeated palaeoseismic activity of the ventas de zafarraya fault s spain and its relation with the 1884 andalusian earthquake one of the most destructive historical earthquakes m 6 7 in spain occurred in 1884 along the normal ventas de zafarraya fault located in the central betic cordilleras palaeoseismic and radiocarbon data presented in this study are the first to constrain the timing of the pre 1884 fault history in the last 10 ka these data yield a recurrence interval of between 2 and 3 ka for major earthquakes under the assumption of uniform return periods along the normal fault the holocene slip rate is estimated to be in the order of 0 35 0 05 mm year which is significantly higher than the mean slip rate of 0 17 0 03 mm year since the tortonian several of the most important deformations and secondary features such as landslides and liquefaction are related to strong ground motion and document the holocene activity of the ventas de zafarraya fault

the neogene of eurasia spatial gradients and temporal trends the second synthesis of neclime article i nfo this volume represents the second synthesis of the international open research network neclime neogene climate evolution in eurasia that was established in 2000 to study climate change in eurasia during the neogene and its impact on ecosystems the main objectives of neclime research are 1 proxy data based quantitative reconstructions of neogene climate in eurasia by means of standardised techniques 2 the modelling of atmospheric and oceanic circulation and of biomes using neogene boundary conditions and 3 the analysis of the interaction between palaeogeography vegetation and climate presently 94 scientists from 34 countries are neclime members contributing with their published data to a collective data base integrating proxies from various sources such as palaeobotany vertebrate palaeontology and geology the following core topics are addressed in the volume precipitation patterns and landscape opening the asian monsoon systems the potential of past climates for the evaluation of future climate change scenarios as well as short term change and variability of climate highlights of the single contributions are summarised in a proxy data section and in a modelling section respectively it is shown that the integrative approach presented in this volume brings about a much better and much more detailed understanding of neogene climate dynamics in eurasia than previously achieved even though neogene climate changes may have regional aspects differing considerably from each other and from the general global trend the results from the various proxy and modelling studies consistently show that later neogene cooling implicated more pronounced latitudinal and longitudinal gradients on the other hand the issue reveals a number of problems and questions resulting from the contrary nature of palaeozoological and palaeobotanical palaeoclimate proxies and modelling results mainly at a more regional level the models can not yet explain the relatively warm high latitudes during the neogene and we still do not sufficiently understand the role of the various boundary conditions such as co2 palaeogeography and palaeovegetation in the observed neogene climate change and its regional differentiation these apparent uncertainties underline the importance of the study of palaeo scenarios in order to enhance the reliability of future climate projections

comparing mineral magnetic properties of sediments in two reservoirs in strongly and mildly eroded regions on the guizhou plateau southwest china a tool for inferring differences in sediment sources and soil erosion shibanqiao reservoir 0 24 km 2 and xiaohe reservoir 0 28 km 2 have catchments of 6 00 km 2 and 22 69 km 2 respectively they essentially represent strongly eroded shibanqiao and mildly eroded xiaohe regions in guizhou plateau southwestern china sediment cores were retrieved from the two reservoirs and soils were also sampled from their catchments mineral magnetic measurements were performed on the sediments and soils and the particle size analysis of selected sediment cores and soil profiles were also made sirm versus chi if was used to compare sediment and soil samples in addition correlations between percentages of different particle size fractions and magnetic parameters ratios of sediment samples were also checked these results revealed differences in sediment sources and soil erosion in these two representative catchments the sediments in shibanqiao reservoir are derived from both the topsoil and subsoil when erosion is relatively weak it is limited to the topsoil and preferentially transports the relatively finer magnetic grains into the reservoir which may imply rain splash and or sheet erosion in this relatively steep catchment stronger erosional forces are capable of not only moving relatively coarser ferrimagnetic grains from the topsoil but also incising the subsoil and moving anti ferromagnetic minerals into the reservoir which seems to hint at not only sheet wash but also rill and gully erosion as there are no stable streams nor channel networks developed in this mountainous catchment contributions from river bank erosion to sediment yield are almost negligible the sediments in xiaohe reservoir which has a lower relief are predominately derived from topsoil erosion here erosion is concentrated to the topsoil and preferentially transports the relatively fine magnetic grains into the reservoir when erosional forces are weak however even when erosional forces increase in this relatively flat catchment erosion is still restricted to the topsoil thus relatively coarser ferrimagnetic grains from the topsoil are transported to the reservoir but the subsoil remains undisturbed and there are no significant changes in the proportion of anti ferromagnetic minerals in the sediments consequently only sheet washing occurs even when erosion is intensifying in this hilly plain catchment in general the more effective erosion in the shibanqiao catchment is probably due to its steeper topography than xiaohe catchment although higher and more seasonal rainfalls and lower percentages of woodlands may also contribute to the differences in susceptibility to erosional forces c 2011 elsevier b v all rights reserved less

magnetostratigraphy and paleoclimatic interpretation of a continuous 7 2 ma late cenozoic eolian sediments from the chinese loess plateau an almost 300m thick eolian sequence of late cenozoic sediments which includes 162 5m of quaternary loess paleosols and 126m of late tertiary eolian red clay from the central part of the chinese loess plateau was investigated to determine the magnetostratigraphy the results show that eolian dust accumulation and by inference the related east asia paleomonsoon had begun by 7 2ma as paleomonsoon are largely controlled by the tibetan plateau this implies that the plateau had reached some critical elevation by 7 2ma the section also documents a rapid increase in eolian dust accumulation in the late cenozoic at 3 2ma that is probably due to the influence of global ice volume on the east asian monsoon

chronological sequence and subdivision of chinese neogene mammalian faunas six land mammal ages are recognized for the neogene of east asia the ages are based upon updated large and small mammal faunas and replace or redefine the land mammal stages erected by li et al 1984 comparisons and correlations are made to faunas in europe northern and southern asia and north america in addition methods of utilizing mammalian faunal data to define and recognize geochronologic ages are discussed

heavy metal release by peat erosion in the peak district southern pennines uk upper north grain ung is a heavily eroding blanket peat catchment in the peak district southern pennines uk concentrations of lead in the near surface peat layer at ung are in excess of 1000 mg kg 1 for peatland environments these lead concentrations are some of the highest globally high concentrations of industrially derived atmospherically transported magnetic spherules are also stored in the near surface peat layer samples of suspended sediment taken during a storm event that occurred on 1 november 2002 at ung and of the potential catchment sources for suspended sediments were analysed for lead content and the environmental magnetic properties of anhysteretic remanent magnetization arm and saturation isothermal remanent magnetization sirm at the beginning of the storm event there is a peak in both suspended sediment and associated lead concentration sirm arm values for suspended sediment samples throughout the storm reveal that the initial lead flush is associated with a specific sediment source namely that of organic sediment eroded from the upper peat layer using the magnetic fingerprinting approach to discrimination of sediment sources this study reveals that erosion of the upper peat layer at ung is releasing high concentrations of industrially derived lead and by inference other toxic heavy metals associated with industrial particulates into the fluvial systems of the southern pennines climate change scenarios for the uk involving higher summer temperatures and stormier winters may result in an increased flux both of sediment associated and dissolved heavy metals from eroding peatland catchments in the southern pennines adversely affecting the quality of sediment and water entering reservoirs of the region copyright 2005 john wiley sons ltd

reappraisal of miocene eolian deposition in tianshui basin china based on an investigation of stratigraphy and provenance eolian deposition in china is intimately related to asian desertification the fine grained sediments in the cenozoic basins along the northeastern tibetan plateau are increasingly reported as eolian deposits due to their loess like characteristics thus extending the onset time of asian desertification from the late miocene to the early miocene however the basin scale stratigraphic correlation and geographic origin of these fine grained sediments remain poorly investigated limiting any interpretation of the transportation and paleoclimatic conditions responsible for their emplacement this study combines analyses of detrital zircon u pb geochronology and heavy mineral assemblages to present the first comprehensive stratigraphic and provenance study of miocene sediments in the tianshui basin in northeastern tibet comparison of results from 64 sand sized and silt sized samples from various sedimentary beds across the basin reveals that the main stratigraphic packages can be correlated basin wide confirming that the silt sized sediments were a natural part of the basin fill statistical visualizations of the large data set from northern and western china clearly shows that the west qinling mountains are the main source of the tianshui basin silts contribution estimates corroborate this conclusion and eliminate the likelihood of substantial contributions from other mountains and drylands moreover the significant differences between the tianshui basin silts and the chinese loess plateau red clay are reflected by their heavy mineral compositions and euhedral zircon u pb ages these provenance analyses strongly contradict the previous assumption of desert origin for the tianshui basin silts moreover the northward transport of the tianshui basin silts conflicts with the prevailing dust pathway driven by the asian westerlies and winter monsoons which do not support the eolian interpretation for their formation consequently we suggest that the miocene tianshui basin silts cannot be used as an indicator of extensive desertification in contrast with the suggestions of previous studies this proposal undermines the corresponding hypothesis of an early miocene onset of asian interior desertification and further raises questions about the validity of prevalent paleoclimatic interpretations drawn from fine grained basin sediments

vertebrate paleontology biostratigraphy geochronology and paleoenvironment of qaidam basin in northern tibetan plateau abstract qaidam basin is the largest terrestrial basin of the tibetan plateau and has the most continuous sedimentary record in the cenozoic although constituting the first known fossil vertebrates of the tibetan plateau and discovered in early scientific expeditions in the 1930s mammalian fossils from qaidam basin have not played a significant role in studying the basin stratigraphy our explorations in the qaidam basin during the past 8 years have resulted in the first well documented collection of fossil vertebrates from there in addition to being the best organisms for terrestrial biostratigraphy in the cenozoic the new fossil vertebrates offer a unique window into the ancient biotas that chronicle the late cenozoic uplift of the plateau and associated environmental changes here we establish for the first time a faunal sequence of early oligocene to early pliocene age four mammalian faunas are recognized olongbuluk mammal fauna middle miocene tuosu mammal fauna early late miocene shengou mammal fauna early late miocene and huaitoutala mammal fauna early pliocene all four mammal faunas can be directly or indirectly tied to a paleomagnetic section in the olongbuluk huaitoutala area permitting robust calibration of the chronology of these faunas at least four fish faunas are also found lulehe fish fauna late early to early late oligocene shengou fish fauna early late miocene eboliang fish fauna late late miocene to early pliocene and yahu fish fauna early pliocene the fish faunas represent the only records of their respective times in the tibetan plateau and thus by themselves cannot be used for age determination however these fish faunas are either integrated into paleomagnetic sections or directly tied to mammal faunas of known ages permitting independent assessment of their chronology zoogeographically qaidam mammal faunas show increasing endemism through time presumably related to topographic barriers formed by the growth and uplift of the tibetan plateau and to climatic changes triggered by the same tectonic process fishes that were trapped in internally drained basins developed pachyostotic morphologies caused by hypersaline environments which are associated with the increasing aridity of the tibetan plateau since early pliocene

tracing movements of topsoil by magnetic measurements two case studies an array of magnetic measurements is used to trace the occurrence of magnetically enhanced topsoil in two different environmental settings the first is a cultivated slope section where the results confirm that movements of topsoil have occurred but that identification of specific erosional processes is problematic the second is a lake catchment system where measurements on soils and sediments allow a partial reconstruction of soil movements from different sources over the last 200 y the study highlights both the need to analyse the magnetic mineralogies of different particle size fractions and the difficulties that may be encountered in trying to discriminate between topsoil and subsoil material on the basis of demagnetization parameters alone

tracer techniques in aeolian research approaches applications and challenges abstract aeolian processes the entrainment transport and deposition of sediments by wind impacts climate biogeochemical cycles food security environmental quality and human health considering the multitude of interactions between aeolian processes and all the major components of the earth system there is a growing interest in the scientific community to quantify the wind related sediment movement process and redistribution rates at different spatial and temporal scales however this quantification is rather challenging due to the complexities of physical mechanisms involved in aeolian processes and the inherent fundamental differences from the rather well studied processes controlling fluvial erosion traditional techniques such as erosion plots and surveying methods for monitoring wind erosion are capable of quantifying sediment movement on small scales but they have a number of limitations in terms of the representativeness of the data obtained spatial and temporal resolution and the patterns over extended areas and the costs involved the demand for alternative methods of soil loss and sediment redistribution assessment in order to complement and enhance the existing methods has directed attention to use tracing approaches for monitoring rates and spatial patterns of sediment redistribution at various scales a comprehensive synthesis of available information from different scientific disciplines on aeolian tracer techniques their applications and limitations are important in understanding the role of aeolian processes and their interactions with the earths systems in changing climate and management scenarios the objective of this paper is to provide a scientific review of the current tracer approaches in aeolian studies including fallout radionuclides rare earth elements sediment finger printing and soil magnetism as well as giving an introduction of the potential tracers that are in development

iron geochemistry of loess and red clay deposits in the chinese loess plateau and implications for long term asian monsoon evolution in the last 7 0 ma abstract recently some groups of authors have demonstrated that the tertiary red clay deposits underlying the pleistocene loess paleosol sequence in the chinese loess plateau are wind blown in origin thus extending the eolian record in the plateau from 2 6 ma back to about 7 0 ma and providing a good opportunity to reconstruct long term monsoon changes as magnetic susceptibility the widely used paleomonsoon proxy of loess deposits is problematic in reconstructing the monsoon history recorded in the red clay the development of other proxies is urgently needed in this study we analyzed the ratios of citrate bicarbonate dithionite cbd extractable fe2o3 to total fe2o3 concentrations in four loess sections along a north south transect of the loess plateau and in the lingtai loess red clay sequence of 305 m thick the fe2o3 ratio in the loess sections clearly shows higher values in soil units than in loess horizons and a southward increase in this ratio is also remarkable along the transect these are in good agreement with the temporal spatial variations in the east asia summer monsoon intensity identified by other monsoon proxies and soil development observations the fe2o3 ratio thus attests to being a good proxy indicator of the summer monsoon evolution the lingtai fe2o3 ratio record shows high values over three time intervals 4 8 4 1 ma 3 4 2 6 ma and during the interglacial periods of the past 0 8 ma the increase in summer monsoon intensity over the three intervals also coincides with the well developed soil characteristics it is therefore concluded that the east asia summer monsoon has experienced a non linear evolution since the late miocene the occurrence of a monsoon prime at about 4 8 4 1 ma implies that the tibetan plateau one of the most important boundary conditions in maintaining the monsoon circulation must have been uplifted to a critical height at that time

miocene vegetation and climatic changes reconstructed from a sporopollen record of the tianshui basin ne tibetan plateau abstract the miocene vegetation and climate history of western china remains unclear however widely distributed miocene sediments of the tianshui basin in the ne tibetan plateau provide a great potential for deciphering the miocene vegetation and climate history of this region this paper presents first sporopollen record from these sediments covering the period from 17 1 to 6 1 ma sporopollen data reveal that temperate warm temperate broad leaved forest of quercus ulmus and betula dominated the tianshui region between 17 1 and 14 7 ma which was replaced by forest or forest steppe of ulmus artemisia and betula between 14 7 and 11 7 ma after a return to a broad leaved forest of betula and quercus during 11 7 8 5 ma the forest decreased rapidly and was replaced mostly by steppe vegetation mainly composed of artemisia chenopodiaceae and poaceae after 8 5 ma we interpret the observed vegetation changes as a result of global climate change which is characterized by global cooling development of arctic ice sheets and permanent el nino state after the middle miocene climatic optimum the rapid development of steppe at about 8 5 ma suggested a permanent drying of the asian interior at this time coinciding with the onset of the well known hipparion red clay deposition in north china

terrain controls on depressional soil distribution in a hummocky morainal landscape in hummocky morainal landscapes soil distribution in well drained landscape positions tends to follow a consistent pattern soils in depressions however are more difficult to predict reliably this study had two objectives 1 to determine the parent material and landscape properties controlling the formation of the different depressional soils and 2 to use these controls to identify quantitative terrain based predictors of soil type in depressions only two terrain attributes specific dispersal area sda and elevation relative to open water bodies were required to distinguish three main soil groups gley recharge non gley recharge and discharge soils specific dispersal area is the downslope area draining flow from a given grid cell gley recharge soils occur primarily at points with sda of less than 2 m2 m 1 regardless of elevation within a given site because most of the runoff flowing to a point with very low sda values will pond or infiltrate vertically rather than flow downslope non gley recharge soils and discharge soils both occur at points with sda of greater than 2 m2 m 1 the majority of the non gley recharge soils occur above 5 m elevation relative to an open water body and the majority of the discharge soils occur below 5 m elevation relative to an open water body reflecting the importance of solute cycling in the development of discharge conditions buried and depositional soils could not be predicted from current terrain attributes because their profile characteristics were derived from the paleosurface

controlling factors for the spatial variability of soil magnetic susceptibility across england and wales abstract we review the nature and importance of soil factors implicated in the formation of secondary ferrimagnetic minerals in soils and palaeosols worldwide the findings are examined with respect to temperate regions through a comprehensive analysis of over 5000 samples of surface soil from england and wales taken from a 5 5 km grid over 30 soil and environmental attributes are considered for each sample as proxies for soil forming factors measurements of low field magnetic susceptibility mass specific and frequency dependent susceptibility mass specific and percentage on each sample provide estimates of the concentration and grain size of ferrimagnetic minerals maps of soil magnetism across england and wales show non random distributions and clusters one subset of data is clearly linked to contamination from atmospheric pollution and excluded from subsequent analyses the concentration of ferrimagnetic minerals in the non polluted set is broadly proportional to the concentration of minerals falling into the viscous superparamagnetic domain size range 15 25 nm this set shows clusters of high magnetic concentrations particularly over specific parent materials such as schists and slates mudstones and limestones bivariate analyses and linear multiple regression models show that the main controlling factors are parent material and drainage the latter represented by soil drainage classes and particle size together these two factors account for 30 of the magnetic variability in the complete dataset a second group of factors including climate mean annual rainfall relief slope and altitude and organisms land use organic carbon and ph have subordinate control climate as represented by mean annual temperature and also pedogenic time are deemed not relevant at these spatio temporal scales the findings are consistent with a largely abiotic system where the role of iron reducing bacteria appears minor at coarse spatial and temporal scales secondary ferrimagnetic mineral formation is controlled by the weathering capacity to supply fe to the surface soil at finer scales soluble fe precipitates as ferrihydrite before transformation in response to periodically anaerobic conditions into other minerals including nanoscale magnetite

pedostratigraphy and paleomagnetism of a 7 0 ma eolian loess red clay sequence at lingtai loess plateau north central china and the implications for paleomonsoon evolution abstract a 305 m thick loess red clay sequence was discovered recently at lingtai which is located in the middle part of the chinese loess plateau it consists of a complete pleistocene loess soil sequence with a thickness of about 175 m and 130 m of tertiary red clay deposits the red clay sequence at lingtai is the thickest one presently known in the loess plateau field observations show that the lingtai red clay contains over 110 couplets of pedogenic b horizons and horizontal carbonate nodule horizons and that it can be regarded as an extremely thick soil complex paleomagnetic studies of 680 samples suggest that the basal age of the lingtai loess red clay sequence is about 7 05 ma grain size analysis of samples taken at 3 3 cm intervals indicates that the red clay has the same sedimentological characteristics as those observed in the loess thus suggesting a wind blown origin of the tertiary red clay and continuous atmospheric dust deposition in the loess plateau during the last 7 05 ma the pedogenic characteristics of the paleosols within the pleistocene loess and the b horizons in the red clay suggest that the east asia summer monsoon in the latest miocene may have already been slightly stronger than that during the holocene this implies that at about 7 5 ma bp the tibetan plateau could have been uplifted to a critical height in maintaining the east asia summer monsoon system observations of the loess red clay sequence also suggest that the long term changes in the east asia summer monsoon strength have been nonlinear since the latest miocene

integrated geophysical techniques for subsurface imaging of active deformation across the himalayan frontal thrust in singhauli kala amb india abstract non invasive geophysical techniques employed across the himalayan frontal thrust hft at singhauli in the north western frontal himalaya to understand shallow subsurface geological structures and their nature in the context of active tectonics the combination of high resolution ground penetrating radar gpr electrical resistivity tomography ert and multi channel analysis of surface waves masw techniques with the different acquisition parameters found to be beneficial in gaining high resolution images of shallow subsurface geological structures the contact zone of resistivity obtained between 134 m suggests the juxtaposition of dissimilar lithological units explained as two faults dipping to the northwest related to the hft the average separation between fault 0 and fault i is 12m which in general agreement with the trench excavation survey the gpr radargram over a length of 45m show offset reflectors at a horizontal distance of 12 15m close to the active deformation zone the horizontal reflectors abruptly truncate across two northerly dipping planes the 2d vs section masw1 2 exhibited dipping attitude of the litho units with different velocity zones in the northeast direction which are also consistent with the local geological setting prominent liquefaction feature identified in the ert section specifically with the 1 and 1 5m electrode spacing show explicit expression of its existence due to contrasting resistivity ranging between 100 and 450 m a strong correlation has been established between the field based geological observations carried out earlier in this area through a trench excavation survey with the present work using geophysical techniques the integrated approach found to be highly beneficial in those areas where contrasting sub lithological units exist in terms of their physical properties this study argues for judicious use of the ert gpr and masw techniques to delineate shallow subsurface geology across various active faults in the himalayan terrain to comprehend the active deformation related to large magnitude paleoearthquakes and earthquake hazard assessment

geomorphology of active faulting and seismic hazard assessment new tools and future challenges by witold zuchiewicz and jerzy zasadni 2012 intended for this volume young tectonics of the outer western carpathians in the light of some morphometric indices in this paper we test the applicability of some morphometric indices commonly used in tectonic geomorphological studies to the area of the outer western carpathians representing an alpine fold and thrust belt this belt was shaped largely in miocene times and shows traces of pliocene quaternary tectonic activity consisting mainly in some remnant folding and faulting this is indicated by scarce examples of faulting within quaternary strata numerous cases of clast fracturing owing to palaeoearthquakes of relatively large magnitudes as well as warping and tilting of pleistocene and holocene strath terraces analysis of selected morphometric indices valley floor width valley height ratio riverbed gradients stream length gradient index basin elongation ratios and others conducted for the entire region and some chosen test areas in the westernmost part of the outer western ac c ep te d m an u sc r ip t accepted manuscript 24 carpathians proved their usefulness in detecting zones showing tendencies to young surface uplift however in the case of the stream length gradient index sl hack s index a word of caution should be added since the index is extremely sensitive to lithologic contrasts in the bedrock and its applicability to young tectonic analysis of fold and thrust belts appears to be strongly limited dr andrzej piotrowski apiot pgi gov pl szczecinie panstwowy instytut geologiczny szczecin poland and dr klaus reicherter rwth aachen university germany

visualization of tectonic structures in shallow depth high resolution ground penetrating radar gpr profiles ground penetrating radar gpr is applied to detect subsurface tectonic structures and to map the geometry of faulted blocks tectonic interpretations from a profile crossing the graben fault and a grid in a second order graben structure providing a 3d data set are correlated to the structural inventory of the outcrop folded layers of the roll over anticline are identified by continuous curved reflectors and an increasing dip towards the main graben fault faults are indicated by arrays of reflector terminations variations in the water and clay content caused by karstification and brecciation on fault planes are displayed by changing amplitudes of the detected signal the 3d visualization of the second order graben structure with a grid of gpr profiles illustrates the local stress pattern which coincides with structural observations in the outcrop and photo lineations

strong interannual variation of the indian summer monsoon in the late miocene the modern asian monsoon system exhibits strong interannual variation which has profound environmental and economical impacts it has been well documented that the mean asian monsoon state underwent significant changes in the late miocene 11 5 ma ago but how the interannual variability of the monsoon climate evolved during this period is still largely unknown in this study a long term simulation of the late miocene with a fully coupled atmosphere ocean general circulation model echam5 mpi om at t31l19 resolution is used to explore the interannual variation of the indian summer monsoon ism in the late miocene the regional climate model cosmo clm with a higher spatial resolution 1 1 is further employed to better characterize the spatial patterns of these variations our results show that although the mean ism circulation is weaker in the late miocene runs its interannual variation is as strong as or even stronger than at present and the dominant periods 2 6 2 7 years are shorter than at present 3 4 8 4 years it is noticed that while the extratropical influence on the ism variability is weaker than present a persistent el nino southern oscillation with stronger than present interannual variability is observed in our late miocene run this may have maintained a strong interannual variation of the ism with a shorter period in the late miocene our findings do not only improve our understanding of the asian monsoon evolution in the late miocene but also shed light on the future changes in the interannual variability of the ism

erosion under climate and human pressures an alpine lake sediment perspective we review the scientific efforts over the last decades to reconstruct erosion from continuous alpine lake sediment records we focused both on methodological issues showing the growing importance of non destructive high resolution approaches xrf core scanner as well as progresses in the understanding of processes leading to the creation of an erosion signal in lakes we distinguish continuous records from event records both provide complementary information but need to be studied with different approaches continuous regionally relevant records proved to be particularly pertinent to document regional erosion patterns throughout the holocene in particular applying the source to sink approach event based approaches demonstrated and took advantage of the strong non linearity of sediment transport in high altitude catchment areas this led to flood frequency and intensity reconstructions highlighting the influence of climate change upon flood dynamics in the mountain the combination of different record types both in terms of location high vs low elevation sedimentology high vs low terrigenous contribution and significance local vs regional is one of the main outputs of this paper it allows the establishment of comprehensive histories of nw french alps erosion but also and consequently soil dynamics and hydrological patterns throughout the holocene we also discuss the influence of glacier dynamics one of the major agents of erosion in the alps a major feature is the growing human influence upon erosion at a local scale since at least the middle of the bronze age 3500 cal bp however and according to the regional record from lake bourget only few periods of rising erosion at local scales generated a regional record that can be discriminated from wetter climatic periods among them the period between 200 bce and 400 ad appeared to be marked by a generalised rise in human triggered erosion at local scales in the northern french alps this review highlights the importance of modern high resolution and interdisciplinary studies of lake sediments in order to better understand the complex relationships between humans climate and the earth system in general we strongly argue that regional integration of data is now required to move a step further such an integration is easier with cost and time effective methods as well as after a better definition of approaches and their limits this should lead to a stronger collaboration between paleo data producers and modellers in the near future

land use change soil erosion and alluvial dynamic in the lower doubs valley over the 1st millenium ad neublans jura france abstract geochemical and particle size analyses surface scanning magnetic susceptibility microscopic charcoal counting and pollen analysis have been carried out on two cores from the lower doubs valley in order to reconstruct the land use history the interpretation of anthropogenic pollen indicators and micro charcoal deposits is discussed in relation to the lithological variation of sedimentary accumulation and evolution of the settlement the environmental changes which occurred during the 1st and the 6th century ad reflect the impact of human activities on the landscape in the immediate surroundings of the site multiproxy indicators indicate that soil erosion as a consequence of agricultural activities including fire practices a reactivation of hydrologic flow of the river recorded in the sedimentary sequences attests to a larger environmental perturbation between 1st 3rd and 7th 8th century ad

onset of asian desertification by 22 myr ago inferred from loess deposits in china the initial desertification in the asian interior is thought to be one of the most prominent climate changes in the northern hemisphere during the cenozoic era1 2 3 4 but the dating of this transition is uncertain partly because desert sediments are usually scattered discontinuous and difficult to date here we report nearly continuous aeolian deposits covering the interval from 22 to 6 2 million years ago on the basis of palaeomagnetic measurements and fossil evidence a total of 231 visually definable aeolian layers occur as brownish loesses interbedded with reddish soils this new evidence indicates that large source areas of aeolian dust and energetic winter monsoon winds to transport the material must have existed in the interior of asia by the early miocene epoch at least 14 million years earlier than previously thought3 5 regional tectonic changes and ongoing global cooling are probable causes of these changes in aridity and circulation in asia

artificial magnetic enhancement of stream bedload a hydrological application of superparamagnetism abstract laboratory heat treatment of natural rocks alters their mineralogy and produces a characteristic magnetization that can be used as a simple persistent tracer workers have shown that natural magnetic enhancements occur in soils on a wide range of bedrocks including limestones granites shales and sandstones the artificial magnetic enhancement tracing method may consequently be expected to be applicable to many localities in our study magnetite and hematite were grown in naturally paramagnetic mudstones and slates by rapid heating in air to 900 c and then quenching studies of magnetic remanence viscosity hysteresis and coercivity m ssbauer spectroscopy and the effect of temperature on magnetization have been used to determine the dominant processes affecting the magnetic mineralogy during heat treatment these are the growth of single domain magnetite followed by the formation of superparamagnetic magnetite probably by both the breakdown of the single domain magnetite and the growth of new crystals simultaneously with the formation of hematite the fine magnetite particles dominate most of the magnetic properties of the heat treated samples although hematite is produced in greater abundance the mineralogical changes of the magnetic grains are complex and depend on many interrelated variables however a very simple but effective heat treatment procedure has been developed that optimizes the enhancement of magnetic susceptibility and permits practical hydrological field experiments to be performed this work is concerned with stream bedload movement but the artificial magnetic enhancement method could also be useful in studying other sedimentological processes such as movement of sand waves and beach sands and the silting of harbours

middle miocene latitudinal climatic gradient in western europe evidence from pollen records abstract pollen analysis of sections spanning the middle miocene langhian and serravallian from southern spain to switzerland has been carried out with the aim of reconstructing the existing latitudinal environmental gradient floral assemblages indicate a tropical subtropical to warm temperate climate for the entire area during the middle miocene the presence in all pollen spectra of taxa with high temperature requirements demonstrates that the latitudinal gradient in temperature was relatively low the development of a diverse subarid flora in southern spain including neurada lygeum prosopis calligonum nitraria caesalpiniaceae etc points to a very dry climate with a marked seasonality these features clearly indicate that a very warm and dry climate i e a steppe environment was already present during the langhian in the northwestern mediterranean area on the other hand milder conditions are progressively inferred towards the north as subdesertic elements gradually disappeared and taxa with higher water requirements increased the latter dominates the pollen assemblages in the eastern central part of france and switzerland thus precipitations would have been evenly distributed throughout the year we interpret this gradient from subdesertic vegetation in the south to humidity adapted plant environments in the north as the result of a latitudinal gradient in precipitation

a rock magnetic record of pleistocene rainfall variations at the palaeolithic site of attirampakkam southeastern india abstract attirampakkam an open air stratified palaeolithic site in southeastern india is the focus of ongoing studies to investigate the nature of lower and middle palaeolithic occupation in relation to changing pleistocene environments the paucity of faunal or palaeobotanical remains at the site required the use of rock magnetic properties lf fd fd arm sirm arm sirm sirm lf arm lf arm fd s ratio hirm and hirm irm 300mt as proxies for deciphering the palaeoenvironments and palaeoclimates of the region rock magnetic data from stratified deposits within excavated trenches show that the bulk of the sedimentation was intermittent with no subaerial exposure of sediments for long periods and points to fluctuating wetter and drier climates associated with the acheulian to late middle palaeolithic levels there is a general trend towards a wetter climate from layer 5 upwards layer 7 offers evidence of bacterial magnetite arm lf 40 and arm fd 1000 suggesting the onset of micro anaerobic environments as a result of floods greigite is indicated in layer 5 sirm lf 30 10 3 a m 1 which indicates a reducing environment layer 2 represents an arid climate higher proportion of haematite and a coarser magnetic grain size layer 1a again is indicative of an arid climate presence of calcrete magnetically hard minerals and coarser magnetic grain size results indicate that the southeast coast of india experienced a mostly dry tropical climate during the pleistocene the detected occurrence of a few notably more arid intervals did not disrupt occupation of the site by successive groups of hominins

validation of temperature precipitation based aridity index paleoclimatic implications abstract water availability in the ecosystem is one of the most crucial environmental factors that determines global terrestrial biome distribution however aridity humidity conditions in the geologic past are difficult to quantify mainly owing to the lack of a proper parameter by using modern global climatic data we here examine five selected previously proposed aridity indices ais in which the climatic variables involved including both precipitation and temperature are simple and likely available in studies of paleoclimatology and paleoecology although with different degrees of uncertainty they were first evaluated along the modern climatic zones of eastern china with the main metric of thornthwaite humidity index hi and with the supplementary reference of soil moisture index smi and near ground atmospheric relative humidity rh then ais and the mean annual precipitation map were further statistically compared with hi smi and rh respectively based on 1189 monitored data sets from meteorological stations over the world the results show that the koppen aridity index aikoppen expressed as mean annual precipitation divided by mean annual temperature plus a constant of 33 is the most accurate and precise index among all selected indices supported by the highest correlation coefficient respectively to hi smi and rh three widely employed major indicators sensitive to hydrological dynamics in climatology and meteorology specifically aikoppen does well mirror corresponding hi along four representative transects from north america south america africa and australia which cover the typical arid and humid climates and span the main terrestrial biome types moreover our results also distinctly reveal that as also shown by many studies on modern climate precipitation alone is inadequate to measure the hydrological condition because both temperature and evapotranspiration are two other critical factors that strongly influence water balance in the ecosystem meanwhile evapotranspiration is mainly affected by temperature based on the validated aikoppen we briefly discuss the aridity humidity condition in china during the middle miocene the results demonstrate that moisture did decrease westward but it is also clear that western china in the middle miocene appears not to have been as dry as previously thought indicated by the aikoppen values representing a sub humid to humid climate

strengthened east asian summer monsoons during a period of high latitude warmth isotopic evidence from mio pliocene fossil mammals and soil carbonates from northern china the east asian monsoons have fluctuated in concert with high latitude warmth during the past several hundred thousand years with humid summer monsoon dominant climates characterizing warm intervals including interglacials and interstadials and arid winter monsoon dominant climates characterizing cool intervals including glacials and stadials of the states comprising the mid pleistocene to recent climatic regime interglacials are most similar in terms of high latitude ice volumes and temperatures to those extant during the late miocene and early pliocene thus an important question is whether mio pliocene climates in northern china were analogous to a hypothetical prolonged interglacial state with increased summer monsoon precipitation and expansion of forest and steppe environments at the expense of desert environments we utilize new and previously published carbon isotopic data from fossil teeth and soil carbonates to place constraints on paleovegetation distributions and to help infer the behavior of the monsoon system between 7 and 4 ma we find that plants using the c 4 photosynthetic pathway which today are largely grasses found in regions with warm season precipitation were present in northern china by late miocene time demonstrating that the c 4 expansion in china was not significantly delayed compared to the global c4 event during the late miocene early pliocene interval soil carbonate and tooth enamel 13 c data indicate 1 that nearly pure c 3 plant ecosystems existed in the southern chinese loess plateau clp and therefore ecosystems there were dominated by woody dicot herbaceous dicot or cool season grass vegetation or a combination of these and 2 that the clp was characterized by a pattern of northward increasing c 4 vegetation and aridity utilizing a broadened conceptual model for interpreting 13 c data and citing independent faunal floral and lithostratgraphic data we suggest that these patterns reflect northward expansion of forest and steppe ecosystems and relatively humid monsoon climates during the late miocene and early pliocene an important implication of this interpretation is that the forcing mechanism illuminated by the temporal correlation during the pleistocene between warm high latitudes and strong east asian summer monsoons is a robust feature of the eurasian tectonic climatic system that predates the plio pleistocene climatic reorganization