magnetostratigraphical dating of loess deposits in china the age of chinese loess deposits has long been disputed biostratigraphical and earlier magnetostratigraphical investigations placed the entire loess formation within the pleistocene the new palaeomagnetic measurements reported here on a bore hole section near lochuan shaanxi province suggest a clearly defined magnetic polarity zonation which extends below the olduvai subchron a late pliocene age of 2 4 myr is assigned to the oldest loess sediments measured the intensity variations of natural remanent magnetization nrm and low field magnetic susceptibility are indicative of climatic changes during loess deposition

soil development of three chernozem like profiles from north bulgaria revealed by magnetic studies abstract a detailed magnetic study of three soil profiles of calcic chernozem luvic phaeozem and orthic luvisol described in the soil atlas of bulgaria was carried out in order to reveal the potential of magnetic methods for characterization of soil forming processes and properties of pedogenic iron oxides thermomagnetic analysis of susceptibility and sem edx observations revealed that the main pedogenic mineral in all three soils is fine grained superparamagnetic to single domain maghemite thermal stability of this pedogenic phase up to temperatures of 500 c is revealed by the partial thermomagnetic analyses of susceptibility depth variations of magnetic parameters and ratios point to the presence of stable single domain to pseudo single domain grains in humic horizons the quantity of which decreases sharply towards lower soil horizons these magnetic grain size changes are best expressed in orthic luvisol and reflect intensified processes of translocation of substances downward

signature of magnetic enhancement in a loessic soil in nebraska united states of america our study of a loessic soil profile from east central nebraska shows that the a horizons of the modern soil are characterized by higher concentrations of fine grained b0 1 am magnetic minerals this pedogenic magnetic component leads to higher values of concentration dependent parameters such as magnetic susceptibility v isothermal remanent magnetization irm and anhysteretic remanent magnetization arm combined with increases in frequency dependent susceptibility vfd and arm irm ratios hysteresis properties are relatively insensitive towards the presence of this pedogenic magnetic component the magnetic properties of the soil profile are dominated by ferrimagnetic magnetite or maghemite analyses of bsoftq irm sirm and bhardq irm hirm however do show that approximately 80 90 of the remanence carrying magnetic component exists in the form of hematite or goethite and that the magnetically enhanced horizons are enriched in both ferri and antiferromagnetic minerals the pedogenic magnetic component is most likely caused by the conversion of paramagnetic iron bearing minerals to ferriand antiferromagnetic minerals soil compaction lessivage or decalcification cannot explain the observed magnetic soil properties magnetic analyses of loess paleosol sequences from the midwestern united states may yield valuable information about regional variability of paleoclimate based on the fine grained nature of the pedogenic magnetic component we expect grain size dependent proxies arm arm irm vfd to yield better paleoclimatic information than low field magnetic susceptibility used in previous analyses d 2004 elsevier b v all rights reserved

the late pleistocene palaeoclimatic record of north atlantic deep sea sediments revealed by mineral magnetic measurements eight cores of north atlantic deep sea sediment are correlated using simple rapid and non destructive measurements of magnetic susceptibility and isothermal remanence this stratigraphy is demonstrably related to late pleistocene palaeoclimatic variations by comparison with the oxygen isotope and microfossil records of these cores fluctuations in the concentration dependent magnetic properties of the cores largely reflect their lithological composition consisting of climatically modulated cycles of marl glacial horizons and nannofossil chalk interglacial horizons high magnetic concentration characterises glacial horizons which correspond to periods when carbonate productivity was severely restricted and ice rafted detrital inputs were prolific coincident with the migration south of the north atlantic polar front to within 3 of latitude north of the coring site in contrast interglacial horizons are characterised by low magnetic concentration and high carbonate content of the sediment consequent on the retreat of the polar front and the re establishment of coccolith floras in its wake during these periods ratios formed between individual magnetic parameters are independent of magnetic concentration and are thus free of any climatic influences wrought by carbonate oscillations in this study however such ratios exhibit a definite response to palaeoclimatic variations attributable to differences in the composition and grain size of the magnetic mineral assemblage of glacial vis a vis interglacial horizons of the cores these differences in mineral magnetic composition are substantially confirmed by mossbauer effect studies of selected samples representing peak glacial and interglacial horizons of one core such glacial interglacial contrasts in the concentration mineralogy and grain size of the magnetic assemblage most probably result from variations in the source and flux density of detritral inputs induced by changes in climate x ray diffraction studies of the same core indicate that variations in the mineralogy of the detrital fraction of the sediment are consistent with those of the magnetic assemblage together these data point to the conclusion that a subsidiary low latitude possibly aeolian detrital flux supplements high latitude ice rafted input in glacial horizons of the cores the low latitude flux however is also identifiable in interglacial horizons independent evidence suggests that this low latitude aeolian flux may be derived from the sahel region of north africa and transported to the coring site by harmattan winds associated with saharan dust outbreaks

partly pedogenic origin of magnetic variations in chinese loess quaternary sequences of interbedded aeolian silts loess and buried soils palaeosols potentially provide one of the best terrestrial records of past climates1 5 magnetic susceptibility variations in loess and palaeosol sequences from china are strongly correlated with climate induced fluctuations of oxygen isotope ratios in deep sea sediments2 4 6 8 as an explanation of this correlation it has been suggested that the recorded variations in magnetic susceptibility depend primarily on the degree of dilution by non magnetic bulk loess constituents of a uniform magnetic assemblage derived from remote but unknown sources6 8 it has also been suggested that such a model involving changes in the accumulation rate of loess superimposed on a constant flux of magnetic particles provides a relative geological timescale through the control of loess deposition by astronomically modulated climate fluctuations7 here we report a preliminary test of this model using rock magnetic properties especially sensitive to variations in magnetic grain size our results show that palaeosols are characterized by much finer magnetic grain size assemblages than are the intervening loess units this suggests that a simple model based on constant magnetic influx and dilution by variable amounts of non magnetic loess is inadequate our magnetic measurements establish the close comparability of the fine grained magnetic minerals in the palaeosol samples to those in contemporary soils and thus point to a partially pedogenic origin for the magnetic mineral assemblages in the palaeosols

paleoclimatic forcing of magnetic susceptibility variations in alaskan loess during the late quaternary visual matches and statistical tests suggest correlations between marine isotope curves retrodictive solar insolation at lat 65 n and magnetic susceptibility profiles through late quaternary age alaskan loess sections the susceptibility changes largely appear to reflect variability in magnetite content due to climatically controlled changes in wind intensity and competence magnetic susceptibility profiles through massive loess can provide stratigraphic context for intercalated paleosols and tephras a prominent paleosol correlated with marine isotope stage 5 occurs several metres above the old crow ash in loess sections indicating that this important tephra is older than suggested by thermoluminescence dates and may have been deposited ca 215 25 ka

separation of local signals from the regional paleomonsoon record of the chinese loess plateau a rock magnetic approach we propose a method based on thermal unblocking of low temperature saturation remanent magnetization for a quantitative estimation of the superparamagnetic cullity 1972 fraction size d 30 nm of magnetite produced by pedogenesis in the chinese loess plateau liu 1988 we applied this method to the proxy climatic records of the last 130 ka from two sites 250 km apart but separated by the mountain range liupan shan xifeng to the east 35 7 n 107 6 e and baicaoyuan to the west 36 2 n 105 0 e currently have humid and arid microclimates respectively as expected the superparamagnetic fraction increases during known warm temperature intervals at each site furthermore the more humid site clearly has higher overall superparamagnetic fractions during most of the last 130 ka however during the period 5 to 10 ka ago the relative humidity at both sites was the same within experimental errors bulk grain size evidence confirms the magnetic data and we suggest that the present easterly summer monsoon in china came from a more southerly direction during this time to flow parallel to liupan shan resulting in very similar summer humidity at xifeng and baicaoyuan

an integrated rock magnetic and geochemical approach to loess paleosol sequences from bohemia and moravia czech republic implications for the upper pleistocene paleoenvironment in central europe abstract two central european loess paleosol sequences mis 6 2 from central bohemia zem chy and southern moravia dobsice situated in the important climatic transition zone between the oceanic atlantic and continental climate regimes were investigated for rock magnetism geochemistry grain size and micromorphology in both sites the magnetic profile shows good agreement with the standard model of magnetic enhancement in paleosols as established in the chinese loess the magnetic signal is dominated by the presence of fine grained magnetite and maghemite formed in situ and controlled by the intensity of soil formation magnetic proxies corresponded to proxies of chemical weathering and leaching intensity such as the chemical index of alteration cia the cation exchange capacity cec and the rb sr ratio correlation coefficient r 0 6 0 93 during the whole lower weichselian mis 5d 5a and in general also during the pleniglacial mis 4 2 nevertheless for the eemian period mis 5e this relationship was not always valid either due to weak magnetic enhancement at dobsice or even weak depletion of the magnetic minerals with soil formation at zem chy the presented data demonstrate that magnetic signals can be overprinted more easily than chemical proxies during later diagenetic events and are hence not in all cases reliable for deciphering paleoclimate changes during all periods of the studied time interval rock magnetic geochemical and micromorphological results suggest drier conditions in southern moravia compared to central bohemia during the weichselian glacial probably due to the more continental climate in southern moravia

archaic settlement in el tebernal veracruz first insights into paleoenvironmental conditions and resource exploitation abstract we present first results about an archaic 9000 4000 bp site el tebernal in the eastern part of mexico at el tebernal a set of lithic artifacts was found associated with a paleosol lower paleosol and buried by an upper paleosol and a modern soil the artifacts are made from local limestone and chert selected paleosol properties were evaluated total organic carbon grain size distribution carbon stable isotope composition magnetic susceptibility and micromorphology that provide information about paleoenvironmental conditions the lower paleosol is composed of the following horizons 3e 3eb 3be 3btg1 3btg2 3c while the upper paleosol only has a 2a horizon the lower paleosol is very well developed with in situ clay coatings moderate weathering of primary minerals and a matrix free of carbonates although the alluvium in the lowermost part of the profile contains a mixture of limestone and volcanic materials the entire sequence is covered by the modern soil mantle which is formed by an a horizon radiocarbon ages determined on soil organic matter from the 3btg1 and 2a horizons were 5580 to 5320 cal bp and 2350 to 2320 cal bp respectively we interpret the age of 3btg1 as close to the final stage of soil formation because the organic matter content in this horizon is illuviated pedogenesis likely began sometime prior to the reported age in the early holocene the paleosol properties indicate a long period of landscape stability n 10 3 10 4 years under humid and temperate conditions it is probable that volcanic events from pico de orizaba located several kilometers from el tebernal affected this stability one of the last eruptions produced a block and ash flow of dacitic composition dated at 4100 bp that contributed to the end of pedogenesis the upper paleosol 2a horizon as well as the modern soil contain ceramics from the post classic period ad 900 1521 the profile is cut by a channel and infilled by a dark material that dates to 1140 to 970 cal bp ad 810 980 in consequence the area has been strongly affected by human occupations during the holocene we suggest these ceramic societies caused erosion and activation of geomorphic processes

high resolution hydrothermal structure of hansbreen spitsbergen mapped by ground penetrating radar detailed ground penetrating radar gpr surveys at 50 and 200 mhz on hansbreen a polythermal glacier in southern svalbard are presented and interpreted comparison of the variations in character of the radar reflections with borehole thermometry and water levels in moulins suggests that gpr can be used to study the hydrothermal properties of the glacier the high resolution of the gpr data shows that the hydrothermal structure of the glacier is highly variable both along the centre line and on transverse profiles water contents for many places and depths within the glacier were calculated by estimating radar wave velocities to point reflectors we find typical water contents of 1 2 for the temperate ice but wetter ice associated with surface crevassing and moulins typically 4 water content there is evidence that wet ice sometimes overlays drier ice the hydrothermal structure is thus shown to be very complex temperature gradients in the cold ice indicate freezing rates of temperate ice below cold ice of 0 1 0 5 m a while isolated point reflectors within the cold ice indicate large water filled bodies that are probably related to the regular drainage structure of the glacier

paleorainfall reconstructions from pedogenic magnetic susceptibility variations in the chinese loess and paleosols the rock magnetic properties of the chinese loess and paleosols constitute a unique and sensitive record of east asian paleoclimate through the quaternary period systematic variations in the concentration and grain size of the magnetic minerals in these sediments have produced systematic variations in the magnetic susceptibility signal which can be easily and rapidly measured at many sites across the loess plateau variations in many other rock magnetic properties can be used to identify the key shifts in ferrimagnetic grain size but magnetic susceptibility alone is sufficiently sensitive to record stadial and interstadial climate stages as well as glaciations and interglaciations past changes in rainfall and monsoon activity for this region are reconstructed from the susceptibility variations the susceptibility record is calibrated using the modern relationship between rainfall and pedogenic susceptibility on the loess plateau our rainfall reconstructions identify enhanced summer monsoonal activity in the chinese loess plateau region in the early holocene and the last interglaciation in the presently semiarid western area of the plateau annual precipitation in interglacial times was up to 80 higher than at present in the more humid southern and eastern areas values were up to 20 higher than today s levels during the last glaciation precipitation decreased across the entire plateau typically by 25 the relationship between pedogenic susceptibility climate and weathering age was examined over the northern hemisphere temperate zone and the observed positive correlation between rainfall and susceptibility indicates that climate rather than soil age is the predominant factor that controls pedogenic susceptibility enhancement in loess soils

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

mineral magnetic properties of an alluvial paleosol sequence in the maya lowlands late pleistocene holocene paleoclimatic implications abstract in the maya lowlands region along the usumacinta river late pleistocene holocene profiles exhibit sedimentary characteristics and soil formation processes as a result of environmental conditions and human environmental interactions here we report a comprehensive environmental magnetic investigation on paleosols and sediments at the tierra blanca archaeological site which shows clear evidences of human occupation the pedogenetical magnetic properties were characterized by rock magnetism studies to determine the composition concentration and domain size distribution of magnetic minerals the late pleistocene paleosols were formed under the influence of a humid climate as shown by the presence of recent fine hematite formation directly related to reduction oxidation processes during gleysol development the transition from early to middle holocene was obtained from a paleovertisol dated as 2 34 2 3 ka which showed a marked heterogeneity in its magnetic parameters due to continuous argilloturbation processes the environmental conditions retrieved indicate the presence of a drought period around 5 5 ka the upper two paleosols were less developed and seems to be strongly affected by human activities during the maya classic period dated between 1 14 and 0 97 ka these soils were formed under more humid conditions and yielded a magnetic mineralogy hematite magnetite maghemite due to incipient weathering and anthropic disturbance

bed properties and hydrological conditions underneath mccall glacier alaska usa during three summer field seasons 2003 2005 and 2006 we carried out radio echo sound ing measurements with a 5 mhz central frequency ice penetrating radar on mccall glacier arctic alaska usa along the central flowline and 17 cross profiles two way travel time was after migration converted to ice thickness which in combination with a recent digital elevation model of the surface of the glaciated area resulted in a detailed map of the bed topography this reveals a complex basal topography in the confluence area of the different glacial cirques the pattern of subglacial water flow following the hydraulic potential gradient was calculated for the whole glacier area and shows a confluence of subglacial water downstream from the confluence of the glacier cirques from the ice thickness map the total ice volume was estimated as slightly less than 0 5 km 3 bed reflection power brp was determined for the glacier after correction for ice thickness dependence results reveal a clear relationship between the brp pattern and basal sliding anomalies along the central flowline

paleoclimatic significance of the mineral magnetic record of the chinese loess and paleosols the origins of the magnetic susceptibility variations of the chinese loess and paleosols are explored by scanning and transmission electron microscopy of magnetic extracts and by magnetic modeling of magnetic hysteresis data to provide quantified estimates of the major magnetic components microscopy identifies several distinct size and shape characteristics in the magnetic carriers lithogenic magnetites intact and abraded dominate the coarse grained magnetic fraction the smallest of the coarse grains is 2 i m the remaining magnetic materal is ultrafine in size with two types of magnetite particles present type a particles strongly resemble soil magnetites produced by inorganic precipitation type b particles which occur rarely are probably bacterial in origin quantitative modeling of these magnetic assemblages shows that over 90 of the susceptibility variations is accounted for by the superparamagnetic magnetite component compared to the loess units the paleosols are richer in magnetite particularly of superparamagnetic size and have a threefold higher ratio of magnetite to hematite we identify pedogenic formation of magnetite as the major contributor to the loess magnetic record matching this record against other paleoclimatic records we find an extremely high correlation with the standard 18o record the chinese loess sequences record a very high resolution magnetic stratigraphy directly related to changing climate

loess paleosol formation on the russian plain abstract the east european loess province is the largest one not only in the northern hemisphere but also on the earth the chronostratigraphic scheme for this province was worked out on the basis of data obtained by different research methods accumulation of loess like deposits began at the end of the pliocene in the post akchagilian time deposition of silt material and loess formation began in the second half of the eopleistocene during this period up to the holocene about 1 ma 6 interglacial soil complexes can be identified according to paleomagnetic data the brunhes matuyama boundary occurs within the don loess which corresponds to maximum don glaciation of eastern europe the composition of the loess paleosol complex of the middle pleistocene is much more complicated there are 3 interglacial soil horizons overlain by the middle pleistocene moraine of the dnieper glaciation a well developed interstadial soil horizon bryansk soil can be distinguished within the late pleistocene formation 32 26 ka bp the structure of the loess paleosol complex varies over different regions of the east european loess province these differences can be shown on a new type of map that of loess paleosol chronocomplexes

palaeopedology and magnetic susceptibility of a loess palaeosol sequence in southwest germany abstract a loess palaeosol sequence that formed during the last and the penultimate glacial interglacial cycle was studied by pedological geochemical and rock magnetic methods particular emphasis was placed on magnetic susceptibility in order to derive a climatic signal problems of separating the influence of palaeo relief hydrological influence and climate complicate the interpretation but the results show that minimal levels of soil formation cause a distinct enhancement of the magnetic properties higher magnetic susceptibility signals characterise the more oxidized parts of the palaeosols alternatively hydromorphic processes operating on the ferrimagnetic minerals cause a decrease in magnetic susceptibility reflecting both past climate and changes in the palaeoenvironment extremely low susceptibility values characterise the reduced greyish zones of the interglacial bt horizons additional complications are introduced because magnetic susceptibility may change along the horizons of one soil profile eluvial horizons tend to have lower concentrations of ferrimagnetic minerals than the loess parent material whereas the corresponding illuvial horizons show an increase it is considered that palaeoclimatic interpretation based solely on magnetic susceptibility must be treated with great caution

a magnetic investigation of a late quaternary loess palaeosol record in siberia summary a late quaternary loess palaeosol sequence at kurtak in the yenisey river valley southern siberia has been studied magnetically the 34 m section 340 samples exhibits variations in magnetic susceptibility which can be correlated with oxygen isotope stages 1 7 a detailed sampling of stage 5 a further 209 samples permits the identification of substages 5a e the susceptibility variations themselves are in the opposite sense to that found in the classic sections of the chinese loess plateau but are in agreement with the wind intensity model which has been put forward to explain similar findings in loess sequences in alaska published results for the susceptibility of magnetite imply volume fractions of 0 2 per cent in glacial stages 2 and 4 dropping to 0 05 per cent in stages 1 3 and 5 these fluctuations match the aeolian flux variations observed in core v21 146 from the north pacific even though the warmer intervals are characterized by lower susceptibilities the observed frequency dependence of susceptibility indicates that new magnetic material is produced as a result of pedogenesis during interglacial and interstadial times

a late quaternary magnetic record of tunisian loess and its climatic significance magnetic measurements for a 10 m loess palaeosol sequence from the matmata plateau in southern tunisia show significant down profile variations in concentrations of pedogenic ferrimagnetic minerals the sequence appears to correlate with regional and global records of climate change over the past 70 kyr there is strong evidence from comparisons of mineral magnetic properties in modern soils and palaeosols that the sequence holds a proxy record of winter precipitation

magnetic susceptibility and mineral zonations controlled by provenance in loess along the illinois and central mississippi river valleys abstract magnetic susceptibility ms patterns have proven useful for regional stratigraphic correlations of zones within thick oxidized peoria and roxana silts along the illinois and central mississippi river valleys for more than 350 km variations in ms of c horizon loess are controlled by silt sized magnetite content and are interpreted to reflect changes in sediment provenance due to fluctuations of the superior and lake michigan glacier lobes and the diversion of the mississippi river to its present course grain size distributions and scanning electron microscopic observations indicate that stratigraphic changes in ms are not significantly influenced by eolian sorting or diagenetic dissolution respectively three compositional zones lower middle and upper are delineated within peoria silt which usually can be traced in the field by ms the occurrence of clay beds interstadial soils and or subtle color changes these zones can be correlated with but are generally of more practical use than previously studied dolomite zones mckay 1977 or clay mineral zones frye et al 1968 however mineralogical analyses can help to substantiate zone boundaries when in question ms and compositional zones may indirectly record a climatic signal primarily through the effect that global cooling has had on ice lobe fluctuations in the upper mississippi drainage basin

magnetic mineralogy of soils across the russian steppe climatic dependence of pedogenic magnetite formation formation of ferrimagnets in well drained buffered unpolluted soils appears to be related to climate and especially rainfall if robust this magnetism rainfall couple can be used to estimate past rainfall from buried soils particularly the multiple soils of the quaternary loess soil sequences of central asia however dispute exists regarding the role of climate vs dust flux for the magnetic properties of modern loessic soils here we examine the mineralogical basis of the magnetism rainfall link for a climate transect across the loess mantled russian steppe where critically dust accumulation is minimal at the present day magnetic and independent mineralogical analyses identify in situ formation of ferrimagnets in these grassland soils increased ferrimagnetic concentrations are associated with higher annual rainfall xrd and electron microscopy show the soil formed ferrimagnets are ultrafine grained 50 nm and pure ferrimagnetic contributions to ma ssbauer spectra range from 17 in the parent loess to 42 for a subsoil sample from the highest rainfall area total iron content varies little but the systematic magnetic increases are accompanied by decreased fe2 content reflecting increased silicate weathering for this region parent materials are loessial deposits topography is rolling to flat and duration of soil formation effectively constant the variations in soil magnetic properties thus predominantly reflect climate and its co variant organic activity statistical analysis identifies strongest relationships between rainfall and magnetic susceptibility and anhysteretic remanence this magnetic response correlates with that of the modern soils across the chinese loess plateau such correlation suggests that the rainfall component of the climate system not dust flux is a key influence on soil magnetic properties in both these regions

rock magnetism and pedogenetic processes in luvisol profiles examples from central russia and central mexico abstract despite a vast literature concerning magnetic properties of loess sequences we still do not fully understand how magnetic components and properties are related to particular soil forming processes that can vary with each type of genetic horizon in order to establish the role of lithogenic factors in the link between magnetic properties and soil forming processes we carried out a study of two complete profiles of buried interglacial luvisols one formed in loess in russia alexandrovsky quarry and the other in volcaniclastics in mexico barranca tlalpan in both profiles soil genetic horizons have contrasting differences of their magnetic properties in the alexandrovsky profile the magnetic susceptibility is enhanced in the paleosol compared to parent material in the barranca tlalpan sequence enhancement is absent in the soil profile increase of fine grained magnetic components in the soil is attributed to neoformed minerals however this process cannot compensate for the loss of lithogenic magnetic minerals in any of the genetic horizons and the resulting trend is depletion in the whole soil profile the pedogenic environment of eluvial horizons in both luvisols is destructive to all magnetic components both primary and secondary higher concentrations of antiferromagnetic components hematite and goethite found in e horizons are related to redoximorphic processes

magnetostratigraphy and magnetic susceptibility of the las carreras loess paleosol sequence in valle de tafi tucuman nw argentina abstract stratigraphic studies on loess deposits in the intramontane basin of valle de tafi 27 s 66 w revealed up to 31 intercalated paleosols in order to clarify the chronostratigraphic position of the sediments we performed paleomagnetic investigations in the 50 m thick las carreras section the characteristic remanent magnetization chrm obtained after alternating field af demagnetization gives clear evidence of the matuyama brunhes boundary mbb at a profile depth of 26 7 m and of the jaramillo subchron at depths from 38 7 to 44 9 m we assign a minimum age of 1 15 ma to the onset of loess sedimentation which calls for a complete reassessment of the antiquity of loess in the region thus the las carreras sequence which is probably continuous and complete represents one of the longest quaternary terrestrial paleoclimatic records reported from the southern hemisphere the magnetic susceptibility signal follows the behavior known for argentinian eolian sediments though with certain restrictions and an overall weak correlation with pedostratigraphy this behavior is opposite to the pattern reported from the chinese loess plateau clp and seems to be influenced strongly by changing source materials contributing to the susceptibility signal in valle de tafi

fluvial processes and paleopedogenesis in the teotihuacan valley mexico responses to late quaternary environmental changes a paleosol sequence in the teotihuacan valley was studied in order to reconstruct landscape evolution during the late pleistocene holocene in a cut belonging to a river gully san pablo the sequence is constituted by 4 pedostratigraphic units labeled as sp1 sp4 separated by volcanogenic alluvial colluvial sediments sp4 at the base of the sequence has a prismatic structure clay cutans and vertic features sp3 shows abundant signs of zooturbation krotovinas and clay cutans both paleosols are interpreted to have formed in stable humid forest landscapes during marine isotope stage 3 mis3 however towards the end of mis3 these conditions alternated with the periods of contrasting seasonal climate the overlying sp2 unit is a pedocomplex demonstrating 2 petrocalcic horizons combined with redoximorphic features the pedocomplex merges laterally with gradually stratified gleyic channel deposits gravels in the base to fine sand and silt in the top the age of the lower caliche is 24 000 bp and thus sp2 formed during mis2 including the last glacial maximum lgm the environmental conditions during lgm are mostly dry with stages of high humidity evidenced by gleyic processes and fluvial activity at the end of the pleistocene the landscape becomes highly unstable and pedogenesis is replaced by sedimentation new paleochannels cut through the previously formed paleosols these channels are infilled by poorly sorted sediments with no gradation the configuration of all paleochannels is nne ssw nearly at 90 to the modern san pablo river flow geomorphic stability during the early and middle holocene allowed the development of sp1 in a dry environment the a horizon of this paleosol has been dated at 2900 bp it is well developed with strong vertic features this paleosol is thought to have formed the soil cover when the classic period teotihuacan culture flourished in the valley between the first and third centuries ad soils above sp1 are poorly developed and erosion deposition processes predominate over pedogenesis recent landscape instability is due to human activities that intensified erosion processes during the classic and especially the postclassic and colonial periods

spatial mapping of multi year superimposed ice on the glacier kongsvegen svalbard ground penetrating radar gpr and satellite ers 2 synthetic aperture radar sar are used to map the thickness and extent of the superimposed ice si zone on the surge type glacier kongsvegen svalbard gpr imagery shows sub horizontal si layers lying unconformably above a discrete boundary below this boundary the ice has a gpr signature similar to that of ice further down glacier in the ablation zone this boundary is posited to represent the closing of crevasses that were created during the last surge of kongsvegen in 1948 open crevasses would have interrupted the formation of sheet layers of si due to efficient vertical drainage of the snowpack aerial photographs suggest that the crevasses closed sometime in the period 1956 66 a classified sar image from 2003 is used to delineate the extent of the si zone the si extent in the sar image agrees well with the si zone mapped by gpr using the si spatial depth distribution we estimate the mean annual accumulation of superimposed ice to be 0 16 0 06 m w e a 1 locally up to 0 43 m a 1 w e this corresponds to 15 33 of the local winter balance and 5 10 of the total winter balance measured since 1987

using magnetic susceptibility to facilitate more rapid reproducible and precise delineation of hydric soils in the midwestern usa abstract standard field indicators currently used for hydric soil delineations usda nrcs 1998 field indicators of hydric soils in the united states version 4 0 in g w hurt et al ed united states department of agriculture nrcs fort worth tx are useful but in some cases they can be subjective difficult to recognize or time consuming to assess magnetic susceptibility ms measurements acquired rapidly in the field with a portable meter have great potential to help soil scientists delineate and map areas of hydric soils more precisely and objectively at five sites in illinois from 5 to 15 ha in area with contrasting soil types and glacial histories the ms values of surface soils were measured along transects and afterwards mapped and contoured the ms values were found to be consistently higher in well drained soils and lower in hydric soils reflecting anaerobic deterioration of both detrital magnetite and soil formed ferrimagnetics at each site volumetric ms values were statistically compared to field indicators to determine a critical ms value for hydric soil delineation such critical values range between 22 10 5 and 33 10 5 si in silty loessal or alluvial soils in illinois but are as high as 61 10 5 si at a site with fine sandy soil a higher magnetite content and slower dissolution rate in sandy soils may explain the difference among sites with silty parent material the lowest critical value 22 10 5 si occurs in soil with low ph 4 5 5 5 since acidic conditions are less favorable to ferrimagnetic mineral neoformation and enhance magnetite dissolution because of their sensitivity to parent material properties and soil ph critical ms values must be determined on a site specific basis the ms of studied soil samples 0 5 cm depth is mainly controlled by neoformed ultrafine ferrimagnetics and detrital magnetite concentrations with a minor contribution from anthropogenic fly ash neoformed ferrimagnetics are present in all samples but based on high fd 5 to 10 are most prevalent in high ph mollisols of northeastern illinois scanning electron microscope images display significantly more detrital magnetite alteration in hydric soils substantiating that reductive dissolution of magnetite aided by microorganisms is a primary cause for lower ms fly ash comprises 8 50 of the 5 m strongly magnetic particles and typically accounts for 5 15 of the total ms signal the proportion of fly ash in 5 m strongly magnetic fractions is greater in hydric soils because of lower natural magnetite contents possibly combined with historical topsoil accumulation in lower landscapes magnetic fly ash particles are also more altered in low ms soils implying that significant magnetite dissolution can occur in less than 150 years

magnetic enhancement paths in loess sediments from tajikistan china and hungary saturation magnetization and saturation remanence of 139 loess and paleosol samples from tajikistan china and hungary increase linearly with low field susceptibility in all sections investigated thus magnetic enhancement is caused by increasing quantities of ferrimagnetic minerals the observed variations of high field susceptibility h are attributed to variations in the amount of clay minerals as h is linearly correlated with the 2 m grain size mineral fraction the magnetic enhancement process is compared with a theoretical mixing model based on two magnetic mineral assemblages with different but invariable coercivities the two component model provides a good approximation to the data from hungary and the magnetically enhanced paleosol samples in tajikistan and china discrepancies between model calculation and data arise in the behaviour of the loess samples in tajikistan here a three component model improves the agreement between data and mixing calculation the magnetic enhancement in the loess in tajikistan and china is different from the one in the paleosols and the link between paleoclimate and susceptibility is not as straightforward as in the hungarian loess paleosol sequence

quantitative estimates of palaeoprecipitation at xifeng in the loess plateau of china abstract using10be recent studies heller et al 1993 beer et al 1993 have tried to reconstruct palaeoclimatic records by separating the secondary pedogenic and primary aeolian detrital contributions to the magnetic susceptibility of chinese loess here we use a technique which monitors the temperature dependence of magnetic remanence to estimate the magnetisation and relative contribution of the superparamagnetic sp single domain sd and multidomain md ferrimagnetic components in the xifeng loess section on the assumption that the sp ferrimagnetic component is dominantly of pedogenic origin the magnetisation of this component has also been determined for samples taken from the topmost palaeosol s0 at six sites over the loess plateau and directly correlated with present day precipitation at these sites this correlation is then used to estimate quantitatively palaeoprecipitation for the topmost 16 m of the xifeng section which covers about the last 140 000 years the data indicate a considerably reduced precipitation during the glacial loess forming periods and a significantly higher level of precipitation than today during the last interglacial period

recent fluctuations in the extent of the firn area of austfonna svalbard inferred from gpr in spring during 2004 07 we conducted ground penetrating radar gpr measurements on the austfonna ice cap svalbard with the original aim of mapping the thickness and distribution of winter snow here we further exploit the information content of the data and derive a multi year sequence of glacier facies distribution that provides valuable spatial information about the total surface mass balance smb of the ice cap beyond the usually evaluated winter balance we find that following an initial decrease in the extent of the firn area 2003 04 the firn line lowered within two subsequent years by 40 100m elevation in the north and west and 150 230 m in the south and east of the ice cap corresponding to a lateral expansion of the firn area along the profiles by up to 7 3 and 13 3 km respectively the growth of the firn area is in line with stake measurements from etonbreen that indicate a trend towards less negative smb over the corresponding period

monitoring glacier changes using multitemporal multipolarization sar images this paper presents a processing chain for the change detection of arctic glaciers from multitemporal multipolarization synthetic aperture radar sar images we produce terrain corrected multilook complex covariance data by including the effects of topography on both geolocation and sar radiometry as well as azimuth slope variations on polarization signature an unsupervised contextual non gaussian clustering algorithm is employed for the segmentation of each terrain corrected polarimetric sar image and subsequently labeled with the aid of ground truth data into glacier facies we demonstrate the consistency of the segmentation algorithm by characterizing the expected random error level for different sar acquisition conditions this allows us to determine whether an observed variation is statistically significant and therefore can be used for the postclassification change detection of arctic glaciers subsequently the average classified images of succeeding years are compared and changes are identified as the detected differences in the location of boundaries between glacier facies in the current analysis a series of dual polarization c band envisat asar images over the kongsvegen glacier svalbard is used for demonstration

time dependence of magnetic susceptibility of soil chronosequences on the california coast abstract as the age of the soils in a chronosequence on the california coast increases the difference between the magnetic susceptibility of eluvial and illuvial horizons increases and the residual susceptibility after extraction with citrate bicarbonate dithionite cbd decreases enhanced susceptibility results from the conversion of nonferrimagnetic minerals to secondary ferrimagnetic forms most likely maghemite and the preferential accumulation of inherited and pedogenic magnetic minerals little enhancement occurs for pedons younger than 40 000 yr by 124 000 yr most of the magnetic susceptibility can be attributed to forms soluble in cbd magnetic susceptibility appears to vary systematically over time for three chronosequences from areas with mean annual precipitation ranging from 650 to 1500 mm yr 1 magnetic susceptibility enhancement may be a useful parameter for estimating soil age in certain climates

a conceptual model for the enhancement of magnetic susceptibility in soils abstract mineral magnetic properties of soils can be strongly influenced by soil forming factors understanding how climate influences magnetic transformations in soils may offer insight into paleoclimate and the pedologic history of landscapes based on our experience with soils in california and hawaii we have developed a conceptual model of the pathways that can lead to enhancement of the magnetic susceptibility in soils we base our model on three sources of iron in soils magnetite maghemite and other iron bearing minerals we find that preferential accumulation transformation diagenesis lessivage neoformation authigenesis and solubilization are the main processes that convert the primary lithogenic minerals inherited from soil parent material to the secondary pedogenic minerals found in the solum biosynthesis is included in the model but does not appear to be an important process in aerobic soil environments our model shows that a major process in the enhancement of eluvial and illuvial horizons is neoformation of secondary magnetite and maghemite resulting from precipitation of iron from the soil solution the processes and products in the model are independent of whether the parent material is transported alluvium or loess or residuum for the soils that we have studied the rates of susceptibility enhancement are shown to be dependent on climate and parent material

properties of magnetic mineralogy of alaskan loess evidence for pedogenesis abstract the in situ pedogenic enhancement of ferrimagnetic content provides the well established patterns of magnetic susceptibility variation within mid to low latitude loess deposits such as those of china and central europe however this pattern of high magnetic susceptibility in palaeosols and lower values in unweathered loess is not replicated in the higher latitude loess deposits of alaska and siberia in these localities the relationship is inverted with high values in loess and low values in palaeosols this inverse relationship has been explained by the idea that magnetic susceptibility is reflecting the magnitude of an aeolian ferrimagnetic component of consistent mineralogy the grain size of which is related to average wind velocity however the results of the magnetic study presented in this paper suggest that there are differences in magnetic properties between alaskan loess and palaeosols not only in magnetic grain size and concentration but also in magnetic mineralogy this complicates the simple hypothesis of a wind velocity signal by introducing an additional factor into the climatic signal in contrast to the enhancement of susceptibility observed in palaeosols of the loess plateau china we suggest that the low magnetic susceptibility values in the alaskan palaeosol units are a reflection at least in part of the alteration of the ferrimagnetic content by post depositional processes associated with waterlogging i e gleying of the soils

svalbard glacier elevation changes and contribution to sea level rise 1 we compare satellite altimetry from the ice cloud and land elevation satellite icesat 2003 2007 to older topographic maps and digital elevation models 1965 1990 to calculate long term elevation changes of glaciers on the svalbard archipelago results indicate significant thinning at most glacier fronts with either slight thinning or thickening in the accumulation areas except for glaciers that surged which show thickening in the ablation area and thinning in the accumulation areas the most negative geodetic balances occur in the south and on glaciers that have surged while the least negative balances occur in the northeast and on glaciers in the quiescent phase of a surge cycle geodetic balances are related to latitude and to the dynamical behavior of the glacier the average volume change rate over the past 40 years for svalbard excluding austfonna and kvitoya is estimated to be 9 71 0 55 km3 yr 1 or 0 36 0 02 m yr 1 w equivalent for an annual contribution to global sea level rise of 0 026 mm yr 1 sea level equivalent

pedogenic and lithogenic contributions to the magnetic susceptibility record of the chinese loess palaeosol sequence summary we have studied the magnetic properties of 69 loess and palaeosol samples from the loess plateau in china our methodology involves the combination of differential dissolution of secondary iron oxides and oxyhydroxides using citrate bicarbonatedithionite cbd with measurements of magnetic parameters because most of these parameters are additive we can use pre and post cbd values to determine the mineral magnetic properties of the cbd soluble material we can also calculatc the partitioning of iron atnong various phases approximately two thirds of the total iron in our samples exists as paramagnetic iron in silicate minerals antiferromagnetic material haematite constitutes almost all of the remainder however the magnetic susceptibility record of the loess palaeosol sequence arises primarily lrom a small amount of iron in ferrimagnetic phases this iron consists of a cbd resistant component which rcpresents multidomain grains inherited from the parent material of the loess and a cbd soluble component which represents grains near the superparamagnetic single domain boundary the first component appears in nearly uniform amounts throughout the loess column and is the dominant ferrimagnetic phase in the magnetically less enhanced loess accumulation of the second component in the palaeosols gives rise to the magnetic susceptibility enhancement of the loess column the magnetic properties of the cbd soluble component indicate that it formed as a result of in sitir pedogenesis which confirms our earlier conclusion that the palaeoclimate record of the loess palaeosol sequence at the sites that we have sampled is primarily a record of pedogenesis

surface wave attenuation by vegetation with the stem root and canopy abstract to experimentally study the performance of the stem root and canopy on wave attenuation by vegetation a total of 112 laboratory experiments were conducted with seven vegetation models four vegetation densities five wave heights and four water depths wave period was assumed constant limiting the understanding of wave attenuation phenomena by vegetation frictional energy losses from sidewall and bottom were measured and removed by comparing with non vegetated tests experimental results show that wave attenuation by vegetation with stems roots and canopies varied with wave conditions due to vertically non uniform physical vegetation properties the root significantly impacted wave dissipation when the relative root height was greater than 0 167 higher wave attenuation occurred when the still water level was located at the canopy geometrical centroid the transmission coefficients of vegetation of the stem root and canopy ranged from 0 21 to 0 83 an empirical formula for predicting transmission coefficients of vegetation with stems roots and canopies was obtained based on experimental data the wave energy dissipated by vegetation was estimated in terms of drag coefficients calculated by analytical models of dalrymple et al 1984 and kobayashi et al 1993 a semi empirical analytical equation was proposed on the basis of experimental data for predicting wave attenuation by vegetation of the stem root and canopy

paleosols beneath a lava flow in the southern basin of mexico the effect of heat on the paleopedological record abstract volcanic activity affects past and present landscapes here we present a case study related to the heat impact of the xitle lava flow on the former soil cover the eruption occurred 1670 years b p in south mexico city the evaluated properties include those related to the soil memory used as tools of paleoenvironmental interpretation in volcanic paleosols macro and micromorphology color grain size distribution magnetic susceptibility and carbon and nitrogen contents changes of these properties by the heat influence are relevant for an adequate paleoenvironmental reconstruction two sites and three soil profiles are selected to show soil modifications by the volcanic activity the two sites represent the following 1 slightly transformed paleosol buried by the lava flow but separated from it by a 10 cm thick volcanic ash layer site cuicuilco enah 2 moderately and strongly transformed paleosols two profiles inside the copilco archeological zone one of the copilco profiles represents a buried paleosol with a very thin 3 cm ash layer on top at the contact with the lava the second profile is the most affected by the lava flow as it is directly beneath the lava all studied paleosols are sandy have a low amount of organic matter narrow c n ratios and very high values of magnetic susceptibility the strongest modifications are observed in the upper horizons which are in contact with the lava however the presence of the ash layer minimizes the heat effect despite the observed modifications it is possible to establish three cycles of soil formation in the paleolandscape the first and the oldest related to the development of a luvisol type soil indicates a longer time of landscape stability during the second cycle a pedosediment with a high concentration of artifacts was formed the last and the youngest cycle includes the ab and the aeb horizons present only in copilco they form by an andosol type pedogenesis which reflects a shorter time of soil development the presence of the aeb horizon is interpreted as the result of the degradation of the ab horizon either due to the heat effect of the lava or to cultivation and irrigation practiced by the pre hispanic communities

magnetoclimatology teleconnection between the siberian loess record and north atlantic heinrich events new environmental magnetic data from loess and paleosol successions in outcrops in the upper reaches of the ob river drainage southern siberia track the major climatic variations over the last glacial interglacial cycle profiles of magnetic susceptibility and alternating deposition of loess and soil formation events correspond to oxygen isotope stages 1 5 the magnetic susceptibility data in association with the stratigraphic succession confirm that the wind vigor magnetoclimatological model is a viable alternative to the classic pedogenic model interpretation of magnetic susceptibility data from loess paleosol successions must therefore consider eolian dynamics available source materials and transport directions in addition to pedogenic processes rapid magnetic fluctuations are also observed these are identified for the first time in siberian records as the signature of the abrupt cold pulses responsible for the heinrich layers in north atlantic marine sediments the data thus form a component of climatic teleconnections across the northern hemisphere allowing correlations to be made among 1 siberian magnetic susceptibility stratigraphy 2 data recorded from other loess paleosol successions in china european russia europe and north america 3 north atlantic ice rafted detritus and 4 sea surface temperatures derived from molecular stratigraphy of marine sediments off the northwest coast of africa

anisotropic radio wave scattering from englacial water regimes mýrdalsjokull iceland colinear polarized 5 mhz radar profiling data were obtained on m rdalsjokull a temperate glacier in iceland radar transects and therefore polarization planes were aligned approximately parallel transverse and oblique to the ice flow direction echoes from the shallower half to two thirds of the ice were 10 20db stronger on the oblique and longitudinal transects than those on the transverse transects anisotropy as a function of depth is clearly seen at the sites where the transects cross strong scattering on longitudinal transects apparently caused extinction of a radar reflecting layer that was continuously profiled on the transverse transects a radio wave scattering model shows that scattering from a longitudinal water filled conduit parallel to the glacier surface can explain the observed azimuthal variations of the echo we conclude that low frequency mhz radio waves can help to characterize englacial water regimes

spatial and temporal reconstructions of changes in the asian palaeomonsoon a new mineral magnetic approach abstract a new quantitative approach is proposed for estimating palaeoprecipitation across the chinese loess plateau at present there is a strong rainfall gradient across the plateau from 300 mm yr in the near desert conditions in the northwest to over 750 mm yr in the southeast just 700 km distant we find that the concentration of ferrimagnetic iron oxide minerals in nine modern soil types represented by 37 individual soil profiles is strongly correlated with this contemporary rainfall gradient the ferrimagnetic concentration rises along this gradient from 0 01 in the northwest to over 0 2 in the southeast the nine modern soil types have been used in the construction of a rainfall vs magnetic susceptibility least squares regression climofunction past variations of loess soil iron oxide content are easily established through magnetic susceptibility measurements and so can be used to reconstruct the rainfall of former interglacial and glacial periods the physical and pedological basis of the rainfall vs susceptibility relationship is discussed and potential limitations of our rainfall reconstruction method are explored our palaeoclimate reconstructions indicate dramatic changes in rainfall due to variations in the structure of the asian monsoon the rainfall variations are about four times greater than has been suggested for this region by atmospheric general circulation modelling our data indicate increased rainfall throughout central china both in interglacial periods and in the early holocene the increases in monsoonal rain were particularly pronounced at our westernmost sites adjacent to the northeastern edge of the tibetan plateau in contrast for glacial periods a reduction in rainfall is found across the whole loess area with the greatest decreases in the southeast

bed reflectivity beneath inactive ice streams in west antarctica radio echo sounding res techniques are used to examine spatial changes inbed reflectivityacrossrelictice streams inwest antarctica measurementsfrom adjacent interstream ridgesare usedto correctthe measuredpower returned fromthebed for attenuation and losses due to geometric spreading scattering and absorption res measurements near boreholes drilled on ice stream c isc indicate high coefficients of bed reflectivity r40 1 in locations where the bed wasthawed and boreholes connected to thebasalwatersystem andlow reflectivitycoefficients r50 02 atlocationsthat were frozen and not connected intermediate values of bed reflectivity were measured at locations where the connection to the basal water systemwas weak measurements across four relictmargins show thatbedreflectivity usuallyjumpsfromlow tohighvaluesseveral kilometers inside the outermost buried crevasses we interpret this to be a transition from frozento thawedbasal conditions anddiscuss implications of these observations

records of magnetic properties in quaternary loess and its paleoclimatic significance a brief review due to the successive deposition quaternary loess paleosol sequences potentially provide one of the best terrestrial records of paleoclimatic changes magnetostratigraphy and paleoclimate are two major aspects of magnetic investigation in northern china and other regions of the world the classic loess sections across the chinese loess plateau indicate that wind blown loess deposition began close to the base of matuyama 2 6 ma however progress has also been made in extending the record below the loess into the red clay and the aeolian record can now be carried back beyond 7 ma the surprising similarity between the initial susceptibility is curve obtained from numerous loess paleosol sequences and the oxygen isotope fluctuation from the deep sea sediments provides impressive evidence of the global significance of the magnetic record as a useful proxy in paleoclimatic studies magnetic susceptibility ms has been extensively used to reconstruct the paleoclimate however the actual mechanism of ms enhancement of paleosols remains controversial the important questions why does is fluctuate in loess sections and what are the causes of the is enhancement in paleosols have been matters of debate in the last 10 years currently the viewpoint that pedogenesis plays an important role in the ms enhancement of paleosols has been generally accepted pedogenic magnetite is an important contributor to the ms enhancement is is not only simply controlled by the abundance of strong magnetic minerals but also by their grain size distributions the increment of superparamagnetic sp grains o0 1mm which is induced by pedogenesis could enhance the is of paleosols the formation of sp minerals has been debated as either biotic or abiotic it is now possible to propose a quantitative model for the reconstruction of paleoclimate according to the paleoprecipitation deduced from proxy indicators such as is fluctuation grain size stable isotope composition caco3 content rb sr and ratio of citrate bicarbonatedithionite extractable fe2o3 to total fe2o3 fed fet r 2002 elsevier science ltd and inqua all rights reserved

diagenetic reddening of early eocene paleosols on king george island antarctica abstract the objective of this study was to determine if the early eocene paleosols on king george island maritime antarctica have acquired their reddish color during the paleopedogenesis by burial diagenesis and or by heating of a covering lava flow we used micromorphology diffuse reflectance spectroscopy x ray diffraction and mineral magnetic properties to identify the iron oxides in these paleosols these are weakly moderately developed paleosols formed on a basaltic tephra under a cool humid paleoclimate therefore prone to ferrihydrite and goethite rather than hematite formation however the iron oxide assembly was dominated by maghemite and hematite nevertheless the large grain size and high crystallinity of hematites suggested they are rather diagenetic than pedogenic the clustering content and distribution of hematites finely dispersed on the groundmass coating replacing primary minerals and as mottles and or nodules rather than their crystal size were responsible for the color differences these properties were likely the result of past pedogenesis processes forming originally ferrihydrite linked with paleodrainage conditions heating by the covering lava flow affected the magnetic properties of two profiles but without affecting their color taken together all these results suggest that the burial reddening took place by dehydration and transformation of ferrihydrite to hematite our findings highlight the importance of detailed mineralogical analysis to identify iron oxides present in reddish paleosols because identification based solely on morphology e g yellowish color gradual horizon transitions can lead to misinterpretation of paleoenvironmental conditions

changes of glacier facies on hornsund glaciers svalbard during the decade 2007 2017 abstract changes in glacier facies glacier zones such as firn or superimposed ice si are good indicators of glacier response to climate change they are especially important for fast warming svalbard where only a few glaciers are under glaciological mass balance monitoring this paper presents a first study of changes of glacier facies extent for three tidewater glaciers located in southern spitsbergen svalbard and it is based on both satellite remote sensing and terrestrial data analysis covering two time spans 2007 2017 for hansbreen and 2012 2017 for storbreen and hornbreen satellite remote sensing analysis include unsupervised classification of synthetic aperture radar sar data from both decommissioned envisat asar and modern satellite missions radarsat 2 sentinel 1 the results of the sar classification are compared to the information on glacier zones retrieved from terrestrial data i e shallow cores and visual interpretation of 800 mhz ground penetrating radar gpr profiles in addition a novel application of the internal reflection power irp coefficient as an objective method of distinguishing glacier zones based on gpr data is discussed changes in glacier facies areas over time are analysed as well as their correlation to hansbreen s mass balance the main finding of the study is that firn and si of hansbreen storbreen and hornbreen significantly decreased over the study period for example due to continuous negative mass balance between 2010 and 2017 the contribution of firn area to hansbreen s total area decreased ca 14 cumulative firn area loss during that time 45 whereas since 2012 si has not been distinguished as a vast area on this glacier in addition an east west gradient of firn area loss was observed as a result of differences in local climate conditions therefore for the common time span i e 2012 2017 hansbreen recorded a ca 12 loss of firn contribution to glacier area whereas hornbreen recorded ca 9 finally application of the irp coefficient as an objective method of glacier zones discrimination by gpr data gave very good results so the method is recommended for future analysis of glacier zones instead or as a support to popular visual interpretation of the gpr profiles

indications of pedogenesis in lower pleistocene tool bearing sediments in northern armenia and regional paleoclimatic reconstruction abstract indications of the early pleistocene paleopedogenesis were analyzed in multilevel sections of pedosediments at early acheulian sites within the lori plateau in northern armenia with the purpose of reconstructing the paleoclimatic conditions during the initial stage of early human occupation of this region at the study sites lithic tools typical of the acheulian technocomplex dating back to 1 4 1 9 ma were found the sections of studied pedosediments were shown to contain material from former paleosols that developed higher up the slope then were eroded and transported by colluvial processes presumably during catastrophic events and finally redeposided in an inverted order at the foot of the slope three evolutionary stages of lower pleistocene paleosols were identified which allow for paleoclimatic reconstruction of the initial stages of early human occupation of this region in the earliest chronointerval 1 9 1 77 ma vertic cambisols and colluvic regosols humic developed in the region in savanna like landscapes under sub tropical climatic conditions towards the end of this period 1 77 ma the climatic conditions remained sub tropical but became more humid with the development of stagnic cambisols and andosols with an abundance of redoximorphic features during the latest period studied between 1 77 and 1 4 1 5 ma the development of luvisols indicates a stronger leaching environment under a permanently humid climate with significant cooling early hominin communities had to adapt to the cooler environment to be able to continue their uninterrupted development into the middle pleistocene

mineral magnetic properties of a weathering sequence of soils derived from basalt in eastern china abstract the magnetic properties and magnetic mineralogy of a weathering sequence of soils developed on basalt parent material from eastern china were studied by rock magnetism x ray diffraction and soil chemical analyses to establish the connection between mineral magnetic properties and pedogenic development in a subtropical region the magnetic susceptibility of soils formed on basalt varied greatly and did not increase with the degree of pedogenic development the frequency dependent susceptibility fd values of soils ranged from 1 0 to 11 1 and increased with the pedogenic development highly significant linear relationship was found between the frequency dependent susceptibility and the fed content r2 0 683 and fed fet ratio r2 0 780 in soils indicating that pedogenic sp ferrimagnetic grains were associated with enrichment of the secondary iron oxide minerals in the weathering process of soil rock magnetism analysis showed that the major magnetic carriers in the weakly weathered soil profiles are magnetite and or maghemite and the highly developed soil profiles are generally enriched in magnetite maghemite grains of pedogenic origin and the magnetically hard haematite indicating that the magnetic component was transformed from a ferrimagnetic phase magnetite to antiferromagnetic phase hematite during pedogenic development results indicated that some of the magnetic parameters of soils in this case fd can be useful for pedogenic comparisons and age correlations in the weathering sequence of soil it is thus suggested that multiparameter rock magnetic investigations represent a more powerful approach for pedogenesis

mapping thermal and hydrological conditions beneath a polythermal glacier with radio echo sounding spatial patterns in residual bed reflection power brp r derived from ground based radio echo sounding were mapped and interpreted in terms of the thermal and hydrological conditions at the base of a high arctic polythermal glacier john evans glacier ellesmere island canada brp r is the residual from a statistical relationship between measured bed reflection power and ice thickness that describes the rate of dielectric loss with depth in the glacier we identified three types of thermal structure a positive brp r and an internal reflecting horizon occur over the glacier terminus the reflecting horizon is interpreted as the boundary between warm and cold ice and suggests the presence of a warm basal layer b positive brp r occurs without an internal reflector in the upper part of the ablation zone this suggests that ice is at the pressure melting point only at the bed c negative brp r without an internal reflector occurs in all other regions suggesting cold ice at the bed where brp r is positive its pattern is similar to the pattern of subglacial water flow predicted from the form of the subglacial hydraulic equipotential surface this suggests that hydrological conditions at the glacier bed are a major control on brp r probably because the dielectric contrast between ice and water is higher than that between ice and other subglacial materials

magnetic properties of modern soils and quaternary loessic paleosols paleoclimatic implications the magnetic properties of paleosols developed in quaternary sequences of loess have been used for stratigraphic definition correlation with other terrestrial and deep sea sequences and paleoclimatic paleorainfall reconstruction in some loess paleosol sequences including those of the chinese loess plateau tajikistan and the czech republic maxima in magnetic susceptibility values correspond with the paleosol horizons and minima with the least weathered loess layers in other loess soil sequences including those of siberia alaska and argentina the relationship is completely opposite with susceptibility minima associated with the most developed paleosols to account for these opposite relationships the respective roles of 1 magnetic enhancement and 2 magnetic depletion and or dilution in determining soil magnetic properties are investigated for a range of modern soil types most magnetic enhancement is seen in the upper horizons of well drained cambisols absence or loss of magnetic iron oxides is apparent in acid podsol profiles and waterlogged soils for the cambisol profiles significant correlation is found between susceptibility and organic carbon cation exchange capacity and clay content the mineralogy morphology and grain size of soil magnetic carriers extracted from three modern enhanced soils and a paleosol from the chinese loess plateau are also identified by independent petrographic means microscopy and x ray diffraction of magnetic extracts magnetite and maghemite of ultrafine grain size from 0 4 to 0 001 i m are the major contributors to the magnetically enhanced soils weathering can concentrate detrital magnetic grains especially in the fine silt size fractions of soils the magnetic data from the modern soils indicate that interpretation of paleosol magnetic properties must be done on a site specific basis taking into account the possibilities of pedogenic enhancement pedogenic dilution or depletion and allochthonous inputs of magnetic minerals excessively arid wet or acid soils are unable to form significant amounts of pedogenic ferrimagnets well drained intermittently wet dry soils with reasonable buffering capacity and a substrate source of fe show most magnetic enhancement for those soils which favour magnetic enhancement processes correlation has been found between the maximum value of the pedogenic susceptibility and the annual rainfall the almost unique pedogenic system in the chinese loess plateau where variation in soil forming factors other than climate is reduced to a global minimum allows use of the paleo susceptibility values as proxy paleorainfall values to identify the mechanism of any link between magnetic properties for example susceptibility and climate change the mineralogy and grain size of soil magnetic carriers requires detailed investigation given the prospect of 1 quantitative paleorainfall records from continental loess records 2 predictions of present and future climate change and 3 the value of paleoclimate data for testing of numerical climate models such magnetic investigations can contribute significantly to our understanding of past and future environmental change

palaeoclimatic and sedimentary history from magnetic susceptibility of loess in china the magnetostratigraphic age of the oldest loess sediments in the central chinese loess plateau investigated so far has recently been placed at ca 2 4 million years b p thus glaciations in central asia which are believed to provide the detritus for the formation of chinese loess commenced at the same time as the first ice rafted debris sank into the ocean basins of the northern hemisphere shackleton et al 1984 lithologic palaeontologic geochemical and especially rock magnetic variations throughout the loess column are indicative of palaeoclimatic fluctuations during loess deposition the variations of magnetic low field susceptibility in loess closely resemble those of the marine oxygen isotope record shackleton and opdyke 1976 and establish for the first time a continuous record of the pleistocene glacial and interglacial stages in a continental section spectral analysis of the rock magnetic time series indicates slow apparent sedimentation during interglacial periods which are characterized mainly by calcium dissolution and related compaction of the soils variable aeolic sediment influx as well as erosion and or polygenetic soil formation may also strongly influence the sedimentary history

the magnetic properties of particle sized samples from the luo chuan loess section evidence for pedogenesis abstract measurements of magnetic susceptibility and of laboratory remanences have been carried out on particle size fractions of loess and palaeosol samples from luo chuan china they show that the sub micron clay fraction of the palaeosol is greatly enriched in fine grained

two methods for firn area and mass balance monitoring of svalbard glaciers with sar satellite images this paper presents two methods for glacier monitoring on svalbard using synthetic aperture radar sar satellite images both methods were developed on glaciers in the kongsfjorden area the first method monitors the firn area extent and the firn line over time by thresholding and filtering the sar image manual detection of the threshold is preferable but using a constant threshold for all images also gives adequate results a retreat of the fire line position is visible especially on kongsvegen corresponding to consecutive years of negative mass balance the second method applies a k means classification to three clusters on the glacier surface the areal extent of the resulting class on the upper part of the glacier correlates remarkably well with the independently measured mass balance of kongsvegen having a correlation coefficient of around 0 89 for the various glaciers this is because the snow from the accumulation area influences the k means classification thus on glaciers where mass balance values are available new mass balance values can be predicted solely from sar images for glaciers where no mass balance is available the area change cannot be calibrated to absolute mass balance values but relative changes can be predicted

rock magnetic properties of recent soils from northeastern bulgaria summary in this paper basic rock magnetic studies of holocene loess soil samples from northeastern bulgaria are reported the sites are related to the danube river and located at different distances southwards thus representing various pedogenic conditions the study is primarily aimed at determining the main magnetic carrier and their physical characteristics grain size distribution magnetic enhancement etc oxyhydroxides maghemite and titanomagnetites of various oxidation degrees are assumed to be the main ferromagnetic minerals present our results suggest that the uppermost part of recent soil profiles is rich in stable near single domain sd particles while the illuvial horizons are characterized by a gradual decrease in grain sizes from highly viscous to a true superparamagnetic sp domain state the properties of samples from carbonate rich horizons of recent soils are basically controlled by detrital minerals while those from sites with more intensive pedogenesis and especially grey forest soils are influenced by strongly magnetic minerals formed in situ

pedostratigraphy and chronology of the late pleistocene for the extra glacial area in the central russian upland reference section aleksandrov quarry abstract new results on stratigraphy and chronology obtained on the basis of osl and 14c dating of paleosols sediments and cryogenic deformations in the aleksandrov quarry situated at the central russian upland are discussed due to the location of the site in a paleodepression the section presents various stages of soil formation cryogenesis and sedimentation starting from the mikulino interglacial to the middle last glacial time the studied sequence is well preserved and one of the most detailed soil sedimentary terrestrial archives within eastern europe it reflects climatic variations comprising the timespan from the marine isotopic stage mis 5e to mis 3 at the base of the paleodepression the pedogenetic stages are extraordinary detailed distinct paleosols are alternating with erosion accumulative stages forming the ryshkovo pedolitocomplex during the mikulino interglacial during the early valdai time two interstadial paleosols were developed and the middle valdai section comprises two main interstadial paleosols as well in general interstadial paleosols of the late valdai time are absent in the studied quarry for the first time the chronological boundaries of the mis 5e interglacial are recorded and thus the duration of soil formation could be determined from 12 to 15 thousand years furthermore stages of periglacial conditions during the early middle and late valdai time were dated the obtained ages form the base for a chronostratigraphic framework which was correlated with those of the loess paleosol archives of eastern central and western europe

soil magnetic susceptibility and its relationship with naturally occurring processes and soil attributes in pedosphere in a tropical environment abstract soil magnetic susceptibility has potential to be used as a pedoenvironmental indicator from which mineralogy pedogeochemical pedogeomorphological and pedogenic processes can be inferred it can be used in pedosphere studies as an auxiliary information for appropriate and sustainable soil use and management this research aimed to analyze how pedogenesis and geochemical processes affect the and some of its attributes as well as its potential use in discriminating soil great groups following the digital soil mapping approach the study area is located in sao paulo state brazil soil samples were collected for physical chemical analysis from 79 locations 0 20 cm depth at these sites magnetic susceptibility was measured with a portable field instrument and analyzed in terms of geology relief and soil class the results showed that geology strongly affects mainly in diabase derived soils followed by metamorphosed siltstone and siltstone in fluvial sediments the exhibits different behaviors due to different sediments deposited by the capivari river in less evolved soils such as cambisols lithology is a more important contributor to than pedogenesis in more evolved soils pedogenesis increases whereas argilluviation ferralitization reduces it the values did not decrease significantly or even increase downslope due to the presence of diabase on the lower parts differences in where observed between diabase bedrock located in different parts of the study area indicating more of an influence by geomorphic processes rather than lithology with respect to soil attributes positive correlations between and base saturation cation exchange capacity organic matter and iron and clay content were found whereas a negative correlation was found between and sand content the correlates with changes in lithology and soil class demonstrating its application as a potential tool for the discrimination of soil great groups and digital soil mapping

pleistocene climatic history of east and central asia based on paleopedological indicators in loess paleosol sequences a micromorphological comparison of the loess paleosol sequence of the karamaydan section central asia with the upper part of the luochuan section china clearly indicates that for the brunhes chron the sequence at karamaydan is more detailed than the corresponding section at luochuan single paleosols at luochuan correspond to pedocomplexes at karamaydan for example s 3 at luochuan corresponds to pk iii and s 4 to pk iv and both pks developed in a period longer than one interglacial about 104 years some pedocomplexes at luochuan are represented by more detailed successions at karamaydan for example the s 5 complex at luochuan corresponds to pedocomplexes v and vi the loess paleosol sequence at karamaydan should therefore be regarded as a key sequence for reconstructing the climatic history of the brunhes epoch correlation with the deep sea oxygen isotope record of bassinot et al which includes an accurate astronomical time scale allows a detailed chronostratigraphical subdivision of the loess paleosol sequence in karamaydan for the brunhes epoch the sequence in the central and lower parts of the chashmanigar section also in central asia shows much more pronounced paleosols than the equivalent sequence at luochuan although some ck or ckm horizons indicate the presence of hiatuses nevertheless for this part of the sequence it provides more paleoclimatic detail with cold dry stages represented by loess and warm humid stages interglacials by paleosols than even the deep sea cores

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