pennsylvanian early triassic stratigraphy in the alborz mountains iran new fieldwork was carried out in the central and eastern alborz addressing the sedimentary succession from the pennsylvanian to the early triassic a regional synthesis is proposed based on sedimentary analysis and a wide collection of new palaeontological data the moscovian qezelqaleh formation deposited in a mixed coastal marine and alluvial setting is present in a restricted area of the eastern alborz transgressing on the lower carboniferous mobarak and dozdehband formations the late gzhelian early sakmarian dorud group is instead distributed over most of the studied area being absent only in a narrow belt to the se the dorud group is typically tripartite with a terrigenous unit in the lower part toyeh formation a carbonate intermediate part emarat and ghosnavi formations the former particularly rich in fusulinids and a terrigenous upper unit shah zeid formation which however seems to be confined to the central alborz a major gap in sedimentation occurred before the deposition of the overlying ruteh limestone a thick package of packstone wackestone interpreted as a carbonate ramp of middle permian age wordian capitanian the ruteh limestone is absent in the eastern part of the range and everywhere ends with an emersion surface that may be karstified or covered by a lateritic soil the late permian transgression was directed southwards in the central alborz where marine facies nesen formation are more common time equivalent alluvial fans with marsh intercalations and lateritic soils qeshlaq formation are present in the east towards the end of the permian most of the alborz emerged the marine facies being restricted to a small area on the caspian side of the central alborz there the permo triassic boundary interval is somewhat similar to the abadeh shahreza belt in central iran and contains oolites flat microbialites and domal stromatolites forming the base of the elikah formation the p t boundary is established on the basis of conodonts small foraminifera and stable isotope data the development of the lower and middle part of the elikah formation still early triassic in age contains vermicular bioturbated mudstone wackestone and anachronostic facies like gastropod oolites and flat pebble conglomerates three major factors control the sedimentary evolution the succession is in phase with global sea level curve in the moscovian and from the middle permian upwards it is out of phase around the carboniferous permian boundary when the dorud group was deposited during a global lowstand of sealevel when the global deglaciation started in the sakmarian sedimentation stopped in the alborz and the area emerged therefore there is a consistent geodynamic control from the middle permian upwards passive margin conditions control the sedimentary evolution of the basin which had its depocentre s to the north climate also had a significant role as the alborz drifted quickly northwards with other central iran blocks towards the turan active margin it passed from a southern latitude through the aridity belt in the middle permian across the equatorial humid belt in the late permian and reached the northern arid tropical belt in the triassic

quantification of magnetic coercivity components by the analysis of acquisition curves of isothermal remanent magnetisation abstract a new method of analysing isothermal remanent magnetisation irm acquisition curves based on cumulative log gaussian analysis robertson and france phys earth planet inter 82 1994 223 234 is proposed it is based on the curve fitting of the irm acquisition curve versus the logarithm of the applied field with i the acquisition curve on a linear scale ii the acquisition curve expressed as a gradient and iii the acquisition curve on a probability scale even when a sample is not saturated its magnetic properties can be defined although with less certainty the number of magnetic components required for an optimal fit to a measured irm acquisition curve is evaluated statistically the method discriminates on the basis of different mineral coercivity therefore additional rock magnetic tests are still required to separate minerals with similar coercivities

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

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

environmental magnetic study of a xeralf chronosequence in northwestern spain indications for pedogenesis article i nfo magnetic enhancement of a and b horizons during soil development is a common phenomenon to better understand the exact mechanism for the magnetic enhancement especially the mineral transformation pathways systematic rock magnetic studies were conducted on a xeralf chronosequence in northwestern spain a positive correlation was found between the average grain size and the concentration of pedogenic maghemite particles with the exception of some a horizons in which multiple factors seem to influence the nature and concentration of neoformed ferrimagnets it is argued that the interaction between the positively charged iron oxides and the anionic ligands present in the solution of these acidic soils plays an important role in this respect the time trends of the average grain size of pedogenic ferrimagnets and the strong correlation between the concentrations of hematite and maghemite in the magnetically enhanced horizons a and b are consistent with the hypothesis of a gradual formation of maghemite later converted into hematite via a precursor most likely ferrihydrite therefore this study provides strong evidence for the dynamic evolution of magnetic minerals upon pedogenesis

geochemical behaviour of ni cr cu zn and pb in an andosol cambisol climosequence on basaltic rocks in the french massif central abstract the objective of this study is to identify parameters influencing trace elements te vertical distributions in an andosol andic cambisol climosequence in order to understand processes involved in the current distribution of trace elements from basaltic rocks to associated soils six pedons developed on tertiary massive basaltic formations located at similar position in the hill slopes submitted to the same wet mountainous climate but under various microclimatic conditions altitude and annual rainfall were considered the six studied soils are andic and rich in organo metallic complexes two different and quantitative methods were used to compare the geochemical distributions of major and trace elements both being calculated with ti as invariant element isovolumetric mass balance and enrichment factors anthropogenic pedogenetic microclimatic inherited factors were discriminated anthropogenic influences are pointed out for k in two pedons and for pb in all studied sites distributions of other te are affected by discontinuities between underlying rocks and soil horizons zinc and cu distributions are controlled by organic matter whereas cr and ni distributions are influenced by pedogenetic processes results emphasize the relative trace element immobilization in andic soils under temperate climate

mineralogy micromorphology and chemical analysis of andosols on the island of sao miguel azores abstract a study concerning soil genesis was conducted on surface and buried volcanic soils of sao miguel island azores of eight soil profiles three were selected for detailed study of pedogenesis a series of techniques which include chemical micromorphological xrd and dxrd analysis micropicking on impregnated soil blocks tem eds and ir spectroscopy analyses were used the soils showed an incipient to moderate degree of weathering as typically occurs in many young volcanic districts four different stages of soil development were clearly identified the first stage of soil development was characterised by dominance of primary minerals and some allophane and ferrihydrite formation with an feo fed ratio of about 0 86 lom soil the second stage of soil development was indicated by halloysite and ferrihydrite formation in the lower horizons along with an feo fed ratio of about 0 62 san surface soil the third stage of soil development was characterized by halloysite and ferrihydrite formation in the lower horizon but also by clay illuviation and stronger pumice weathering and an feo fed ratio of about 0 51 san buried soil the fourth stage of soil development concerned the lix soils buried soils older than 5000 years bp which had a much higher content in hydrated halloysite and considerable amounts of goethite and hematite these soils exhibit the most expressed weathering features and an feo fed ratio of about 0 25 the presence of young surface soils and well developed buried soils can be explained by i the longer pedogenesis of buried soils or possibly by ii the presence of a climate more seasonal than that of the present day

occurrence and origin of soils with andic properties in calabria southern italy abstract andic like soils along with andosols have previously been reported in non volcanic ecosystems of the coastal and mountainous areas of the calabria region southern italy but little is known about their properties soil formation processes and volcanic source areas chemical mineralogical microscopic sub microscopic and magnetic analyses were carried out on 8 soils which were selected from the major calabrian geological sectors in order to assess relationships between parent material and bedrock soil chemical properties revealed an occurrence of andic or vitric properties in the studied soils as a whole and the optical microscopy enabled to identify volcanic glass micro pumices and soil isotropic matrix clearly indicating volcanic inputs three groups of soils identified on the basis of the degree of andic properties showed rather homogeneous also in terms of chemical properties clay mineralogy and land use as well as with regard to micromorphology and magnetic susceptibility part of the intra group similarities was a consequence of similar distances between sites and volcanic source area as suggested by the correlations found between ferrihydrite content andic i e of ammonium oxalate extractable al 0 5 fe and phosphate retention and magnetic properties vs distances from several sicilian districts the elemental composition obtained by sem eds analyses of soil glass fragments supported these findings and related the origin of most of the studied soils to the high potassium calc alkaline magmatism of the southernmost eolian islands mainly lipari and vulcano except for soils from the marine terraces of northern calabria pra and the aspromonte massif del which were both linked albeit uncertainly to campanian volcanism soil magnetic properties were significantly 0 79 correlated to the andic properties so confirming the high performance of magnetic susceptibility as low cost proxy for the identification of volcanic constituents

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

magnetic and chemical parameters of andic soils and their relation to selected pedogenesis factors in the case of andic soils developed on volcanic rocks permanently humid conditions are essential for andosolisation processes although volcanic rocks are usually rich in highly magnetic iron oxides knowledge about these minerals in andic soils with respect to the soil development is missing the aim of this contribution is to investigate the relationship between magnetic and basic chemical properties of soils developed on volcanic basement and parameters related to the pedogenesis factors the studied sites are located on basaltic lava flows in the eastern part of the french massif central investigated pedons with alu andic sil andic and vitric properties were pedologically described and analysed by a set of magnetic and soil chemical methods magnetic parameters include low field volume specific and mass specific magnetic susceptibility frequency dependent magnetic susceptibility remanent properties including s ratio and coercivities chemical parameters included the phh2o soil organic matter total cation exchange capacity base saturation and content of fe and al extracted in dithionite citrate acid ammonium oxalate and pyrophosphate solutions micro morphology of andosols and parent material was observed by scanning electron microscopy completed with energy dispersive spectrometry the pedogenesis factors are represented by parent rock age annual precipitation and soil thickness our findings suggest that 1 precipitation is the most important pedogenesis factor with a strong relationship to the relative magnetic grain size concentration of ferrimagnetic minerals aluminium dissolved in pyrophosphate and acid ammonium oxalate and content of organic matter 2 parent material age shows a well pronounced relationship with magnetic grain size parameters represented by the frequency dependent susceptibility and ratio of saturation remanent to saturation induced magnetisation mrs ms selective dissolution parameters and phh2o 3 thickness of soil profile shows a link to mrs ms phh2o and content of organic matter

characterisation of soils by mineral magnetic measurements processes of iron mineral authigenesis diagenesis and dissolution in interaction with primary inputs of iron minerals act to produce vertical differentiation of soil magnetic properties thus magnetic iron oxides in common with other iron forms may both respond to and reflect soil forming processes investigation of the degree of detectable and persistent magnetic differentiation within different soil materials can provide insights into the nature and direction of distinct sets of soil processes evidence of clear association between magnetic variation and discrete types of soil environment also has applied significance in several areas of environmental study for example the observed magnetic variation can be used to discriminate between individual soils and soil horizons for the purposes of soil surveying sediment tagging and tracing and empirical modelling of source sediment linkages this paper reports the use of mineral magnetic techniques to characterise the iron oxide assemblages within soils of varying type and provenance the effect of different pedogenic regimes have been investigated through measurement of a range of magnetic parameters including magnetic susceptibility frequency dependent susceptibility and anhysteretic and saturation remanences contrary to current pedological thought but in accord with other magnetically based studies e g mullins the presence of magnetite maghemite typically of superparamagnetic single domain grain size within soils has been found to be an extremely widespread phenomenon its contemporary neoformation within the soil environment is inferred however the input of artificially generated ferrimagnetic material is indicated for one of the magnetically enhanced soils examined here and the possibility of extraneous sources of magnetite in topsoils should be considered before pedogenic processes of magnetic enhancement are inferred from the data presented discrimination of industrially derived magnetic particles appears possible on the basis of their very low levels of frequency dependent susceptibility fd low anhysteretic remanence arm and dissociation from the finer clay sized not the formation but the active dissolution of ferrimagnetic minerals is indicated for soils affected by the processes of gleying and podsolisation eluvial horizons of podsolised profiles demonstrate almost total loss of detectable magnetic content variations in the form of the iron reprecipitated in the underlying illuvial layers may reflect differences in the pedological characteristics of these horizons within gleyed waterlogged soils processes of magnetite dissolution appear to be grain size specific preferential reduction of those grains of ultrafine superparamagnetic and fine single domain magnetic grain size is indicated where soil forms a major contributor to catchment sediment loads this has significance in the area of source sediment modelling soil derived from permanently wet or highly leached catchment areas is unlikely to contribute to peaks in the magnetic content of deposited sediments further only those erosional processes that operate at a faster rate than those of magnetic depletion will have the capacity to produce peaks in sediment ferrimagnetic concentrations such as have been observed within the historical magnetic record

how abundant is pedogenic magnetite abundance and grain size estimates for loessic soils based on rock magnetic analyses 1 the upper soil horizons of many modern and ancient soils are enriched in fine grained pedogenic ferrimagnetic minerals we use three grain size and concentration dependent proxies anhysteretic remanent magnetization isothermal remanent magnetization ratios coercivity spectra derived from alternating field demagnetization of saturation isothermal remanent magnetization and hysteresis properties to quantify the abundance and grain size of the pedogenic magnetic component our analyses of modern loessic soils from the midwestern united states show that relatively small additions 2 10 vol of the total ferrimagnetic component of fine grained coarse superparamagnetic to fine pseudosingle domain magnetite or maghemite are sufficient to explain the changes in concentration and grain size dependent properties observed in the upper soil horizons furthermore the pedogenic components of all studied sites display a narrow range of magnetic properties which argues for a common origin of these particles over a wide range of climatic conditions

quantifying grain size distribution of pedogenic magnetic particles in chinese loess and its significance for pedogenesis quaternary glacial interglacial cycles have been imprinted on the chinese loess paleosol sequences through pedogenesis in order to accurately decode the paleoclimatic signals carried by these pedogenic particles it is essential to quantify the pedogenically produced magnetic particles in terms of mineralogy as well as grain size distribution gsd to date the gsd has not been accurately determined because of the dearth of available means for analyzing extremely fine grained nanometer scale pedogenic magnetic particles using low temperature techniques we systematically investigated the temperature dependency of fd defined as 1hz 10hz where 1hz and 10hz are ac magnetic susceptibility measured at 1 and 10 hz respectively from two characteristic loess profiles one located at the western chinese loess plateau and the other in the central plateau on the basis of neel theory for a shape anisotropy dominant grain and experimental analysis at low temperatures a quantitative gsd for pedogenic particles in chinese loess paleosols was constructed we found that the dominant magnetic grain size lies just above the superparamagnetic single domain threshold 20 25 nm and that the gsd is almost independent of the degree of pedogenesis this observation agrees well with other constraints from previous studies this new gsd model improves our understanding of the pedogenic processes in chinese loess enabling further explicit linkage of environmental magnetism to paleoclimate changes

environmental magnetism principles and applications 1 in environmental magnetism rock and mineral magnetic techniques are used to investigate the formation transportation deposition and postdepositional alterations of magnetic minerals under the influences of a wide range of environmental processes all materials respond in some way to an applied magnetic field and iron bearing minerals are sensitive to a range of environmental processes which makes magnetic measurements extremely useful for detecting signals associated with environmental processes environmental magnetism has grown considerably since the mid 1970s and now contributes to research in the geosciences and in branches of physics chemistry and biology and environmental science including research on climate change pollution iron biomineralization and depositional and diagenetic processes in sediments to name a few applications magnetic parameters are used to routinely scan sediments but interpretation is often difficult and requires understanding of the underlying physics and chemistry thorough examination of magnetic properties and of the environmental processes that give rise to the measured magnetic signal is needed to avoid ambiguities complexities and limitations to interpretations in this review we evaluate environmental magnetic parameters based on theory and empirical results we describe how ambiguities can be resolved by use of combined techniques and demonstrate the power of environmental magnetism in enabling quantitative environmental interpretations we also review recent developments that demonstrate the mutual benefit of environmental magnetism from close collaborations with biology chemistry and physics finally we discuss directions in which environmental magnetism is likely to develop in the future

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

the hidden nature of parent material in soils of italian mountain ecosystems abstract soils with andic features are known to be very important as regards both ecosystem fertility and susceptibility to land degradation in recent years there has been an increasing number of finds of these soils in non volcanic mountain ecosystems nvme in different parts of the world under different environmental settings in italian nvme there has been extensive investigation proving that these soils have a much wider distribution than previously thought but despite these important findings very little is known about their genesis or properties against this background our investigation aims to question the nature of parent material in andic soils in italian nvme we consider this question fundamental for proper understanding of such soils we address the question of the parent material by highlighting similarities dissimilarities between soils and their underlying bedrocks and ascertaining whether soils developed as a result of in situ weathering or because of eolian inputs the study was conducted on 41 soil profiles distributed throughout italian nvme performing an integrated analysis of i grain size distribution gsd by laser granulometry ii end member modelling of obtained gsd iii soil bedrock differences in magnetic susceptibility and iv soil bedrock differences based on the geochemistry of 38 elements the final results from these investigations show that the investigated soils are mainly derived from eolian sediments and that weathering of the underlying bedrock plays a minor role two main types of eolian parent materials seem to coexist in different proportions according to the soil type eolian sediments with a similar composition of the underlying bedrock termed autochthonous loess and eolian sediments of volcanic type pyroclasts autochthonous loess represents the main component of the parent material in the following studied soils aluandic andosols cambisols phaeozems and podzol 67 63 44 and 73 respectively all these soils exhibit low to moderate andic features volcanic type eolian sediments constitute about 90 of the parent material in most andic soils that are silandic andosols but occur in different proportions in most of the investigated soils the nature of soil parent materials surprisingly follows a clear trend with latitude with autochthonous loess characterizing most parent materials in northern italy whilst volcanic sediments form most parent materials in the south in accordance with their latitude other soils exhibit an intermediate behaviour

relevant magnetic and soil parameters as potential indicators of soil conservation status of mediterranean agroecosystems summary the main sources of magnetic minerals in soils unaffected by anthropogenic pollution are iron oxides and hydroxides derived from parent materials through soil formation processes soil magnetic minerals can be used as indicators of environmental factors including soil forming processes degree of pedogenesis weathering processes and biological activities in this study measurements of magnetic susceptibility are used to detect the presence and the concentration of soil magnetic minerals in topsoil and bulk samples in a small cultivated field which forms a hydrological unit that can be considered to be representative of the rainfed agroecosystems of mediterranean mountain environments additionalmagneticstudiessuchasisothermalremanentmagnetization irm anhysteretic remanent magnetization arm and thermomagnetic measurements are used to identify and characterize the magnetic mineralogy of soil minerals the objectives were to analyse the spatial variability of the magnetic parameters to assess whether topographic factors soil redistribution processes and soil properties such as soil texture organic matter and carbonate contents analysed in this study are related to the spatial distribution pattern of magnetic properties the medians of mass specific magnetic susceptibility at low frequency lf w ere 36 0 and 31 1 10 8 m 3 kg 1 in bulk and topsoil samples respectively high correlation coefficients were found between the lf in topsoil and bulk core samples r 0 951 p 0 01 inaddition volumetricmagneticsusceptibilitywasmeasuredinsituinthefield is andvalues varied from 13 3 to 64 0 10 5 si high correlation coefficients were found between lf in topsoil measured in the laboratory and volumetric magnetic susceptibility field measurements r 0 894 p 0 01 the results obtained from magnetic studies such as irm arm and thermomagnetic measurements show the presence of magnetite which is the predominant magnetic carrier and hematite the predominance of superparamagnetic minerals in upper soil layers suggests enrichment in pedogenic minerals the finer soil particles the organic matter content and the magnetic susceptibility values are statistically correlated and their spatial variability is related to similar physical processes runoff redistributes soil components including magnetic minerals and exports fine particles out the field this research contributed tofurtherknowledgeontheapplicationofsoilmagneticpropertiestoderiveusefulinformation on soil processes in mediterranean cultivated soils

paleomagnetism and tectonics of the southern tarim basin northwestern china we report late carboniferous permian and early tertiary paleomagnetic data from the southern tarim basin prefolding magnetizations were isolated in each case the late carboniferous permian and early tertiary poles lie at 64 6 n 166 5 e a95 6 3 and 58 1 n 202 0 e a95 12 7 respectively the late jurassic to early tertiary j3 e1 paleolatitudes of tarim and several basins throughout central asia are similar yet significantly 10 to 20 shallower than those predicted by the eurasian apparent polar wander path resolving this discrepancy remains a major problem in asian paleomagnetism discordance of the late paleozoic poles from tarim and siberia suggest that tarim has rotated about 30 counterclockwise with respect to siberia since the permian where paleomagnetic samples of both late carboniferous to early triassic c3 t1 and j3 e1 ages were collected from the same area of tarim a great circle passes through the means of the poles and the sampling locality this suggests that 1 only a difference in inclination and not declination distinguishes the two data sets and 2 vertical axis block rotations of the c3 e1 strata occurred after e1 although based on data of lesser quality the mean early to middle jurassic j1 2 pole from tarim differs significantly from the eurasian reference pole requiring radical tectonic solutions to resolve them the tarim j1 2 pole is indistinguishable from both the mean j3 e1 and c3 t1 poles the similarity of all the poles and the analogous tectonic setting of present day central asia to that of the late paleozoic in eastern north america raises the question whether all the data from tarim are overprinted

environmental magnetism past present and future environmental magnetism involves the application of rock and mineral magnetic techniques to situations in which the transport deposition or transformation of magnetic grains is influenced by environmental processes in the atmosphere hydrosphere and lithosphere the first explicit description of environmental magnetism as a distinct field was in 1980 since that time environmental magnetism has become a broad field that is finding application in an ever increasing array of scientific disciplines in this review of the present state of environmental magnetic studies we divide the field into three broad but arbitrary categories the first involves the use of mineral magnetic assemblages in the geological record to study physical processes in depositional environments this category includes the correlation of sediment cores using magnetic susceptibility measurements studies of geomagnetic field behavior the analysis of depositional and postdepositional mechanical processes that affect sediments and the examination of magnetic parameters that might represent proxies for paleoclimatic variation the second category encompasses studies of the processes responsible for variations in the magnetic minerals brought into a sedimentary environment these provenance investigations include studies of changes in catchment derived sediment in lakes fluctuations in contributions from terrigenous aeolian and glaciogenic components in deep sea sediments and the origin of atmospheric particulates the final category addresses in situ changes and transformations of magnetic minerals in sedimentary environments including pedogenesis authigenetic diagenetic formation of ferrimagnetic phases dissolution of magnetic minerals due to reductive diagenesis and contributions of biomagnetism to sedimentary magnetism because environmental magnetism can address problems in so many disciplines and because many of these problems may be inaccessible to other techniques it is likely that the scope of environmental magnetism will continue to expand rapidly environmental magnetism is capable of providing important data for studies of global environmental change climatic processes and the impact of humans on the environment all of which are major research initiatives in the international scientific community these factors suggest that environmental magnetism has a bright and diverse future

a preliminary magnetic study of soil samples from west central minnesota abstract various rock magnetic techniques were applied to characterize magnetically the samples of a soil profile taken from west central minnesota there is a marked change in magnetic properties as a function of depth in the core x ray analysis and curie temperature measurements carried out on the magnetic fractions indicate that magnetite is the dominant iron oxide in both the top soil and the subsoil the intensity of anhysteretic remanent magnetization arm decreases sharply as the depth increases in contrast the stability of arm was found to be higher for the subsoil the surface soil sample was capable of acquiring a significant amount of viscous remanent magnetization vrm the vrm acquisition coefficient s a of the subsoil s a 3 18 10 6 emu g 1 3 18 10 6 a m 2 kg 1 was about ten times weaker than that of the top soil sample s a 3 868 10 7emu g 1 3 868 10 7 a m 2 kg 1 the magnetic domain state indicator the ratio of coercivity of remanence to coercive force h cr h c was 1 5 and 3 85 for the top soil and subsoil respectively it appears that the observed variations in magnetic properties down the present soil core is due only to a difference in grain size we conclude that the magnetic grains in surface soil samples were more single domain sd like whereas the magnetite grains in the subsoil samples were more likely in pseudo single domain psd or small multidomain md range the observed lower stability for the surface soil samples is attributed to the presence of superparamagnetic grains whose presence was confirmed by transmission electron micrographs

volcanic soils of france abstract in france andic soils mainly occur in the massif central andic and other volcanic soils 5000 km 2 and on the vosges and the morvan hercynian massifs in the massif central silandosols on recent pyroclastics are distinguished from aluandosols on older mio pliocene lavas after a brief introduction to the parent materials soil characterisation survey genesis properties and land use are reviewed in two periods from 1960 to 1979 and from 1980 to 2000 soil distribution is related schematically to topo climatic sequences comparing recent pyroclastics to older volcanic lavas an udic or perudic soil moisture regime is the primary factor in andosol genesis in france silandosols occur only on recent pyroclastics and aluandosols on old lavas after reworking by glacial erosion from a mantle of loose and pre weathered materials the anthropic impacts include accelerated erosion and changes in carbon content

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

what do the hirm and s ratio really measure in environmental magnetism the hard isothermal remanent magnetization hirm and the s ratio are widely used in environmental magnetism to quantify the absolute and relative concentrations respectively of antiferromagnetic minerals hematite and goethite in mineral mixtures we demonstrate that synthetic al substituted hematite and goethite exhibit a wide range of coercivities which significantly influences the hirm and s ratio these parameters are therefore not necessarily straightforward indicators of the absolute and relative concentrations of hematite goethite to circumvent this problem we propose a new parameter the l ratio which is the ratio of two remanences after alternating field af demagnetization of an irm imparted in a 1 t field with a peak af of 100 mt and 300 mt irmaf 300mt irmaf 100mt these parameters are easily measured using modern vibrating sample or alternating gradient magnetometers changes in hirm only reflect changes in the absolute concentration of hematite and or goethite if the l ratio is relatively constant conversely l ratio fluctuations indicate variable coercivities that possibly reflect changes in the source of hematite goethite corresponding hirm and s ratio variations should be interpreted with caution in such cases the l ratio can be determined using equivalent terms depending on available instrumentation and measurement protocols for example the hirm is equivalent to irmaf 300mt likewise 0 5 sirm irm 100mt where irm 100mt represents the remanent magnetization obtained by first saturating the sample in a high field and then applying a back field of 100 mt is equivalent to irmaf 100mt the hirm 0 5 sirm irm 100mt ratio is therefore a suitable substitute for the l ratio when measurements are made with a long core magnetometer the newly proposed l ratio is straightforward to measure on a wide range of instruments and can provide significant new insights and reduce ambiguities associated with interpretation of two widely used parameters in environmental magnetism the hirm and s ratio

wasp waisted hysteresis loops mineral magnetic characteristics and discrimination of components in mixed magnetic systems rock magnetic studies of complex systems that contain mixtures of magnetic minerals or mixed grain size distributions have demonstrated the need for a better method of distinguishing between different magnetic components in geological materials hysteresis loops that are constricted in the middle section but are wider above and below the middle section are commonly observed in mixed magnetic assemblages such wasp waisted hysteresis loops have been widely documented particularly with respect to rare earth permanent magnets basaltic lava flows remagnetized paleozoic carbonate rocks and an increasingly wide range of other rocks our modelling combined with a review of previous work indicates that there are several conditions that give rise to as well as magnetic properties that are characteristic of wasp waisted hysteresis loops first at least two magnetic components with strongly contrasting coercivities must coexist this condition can arise from either mixtures of grain sizes of a single magnetic mineral or a combination of magnetic minerals with contrasting cocrcivities or a combination of these two situations second materials that give rise to wasp waisted hysteresis loops will have relatively high ratios of the coercivity of remanence to coercive force b cr b c because b0 is controlled by the soft low coercivity component whereas bcris controlled by the hard high coercivity component third values of b cr b c 10 usually only occur for strongly wasp waisted loops when the low coercivity component comprises an overwhelmingly large fraction of the total volume of magnetic grains fourth a given mixture of superparamagnetic and single domain sd grains is more likely to give rise to wasp waisted hysteresis loops than an equivalent mixture of sd and multidomain grains fifth our results provide empirical confirmation that the total magnetization of a material is the sum of the weighted contributions of each component in the absence of significant magnetic interaction between particles thus to contribute significantly to wasp waisted behavior a mineral magnetic component must give rise to a significant portion of the total magnetization of the rock as a result minerals with weak magnetic moments such as hematite need to occur in large concentrations to cause wasp waistedness in materials that also contain ferrimagnetic minerals we outline a method for determining the magnetic components that can give rise to wasp waisted hysteresis loops this method is based on high and low temperature magnetic measurements that are used to identify the dominant remanence bearing mineral s and on mineral magnetic techniques that are used to discriminate between different magnetic domain states the method is illustrated with several examples from archaeological geological and synthetic materials

magnetic and geochemical characterization of andosols developed on basalts in the massif central france identification of andosols is primarily based upon the content of their colloidal constituents clay and metal humus complexes and on the determining of andic properties this needs time and cost consuming geochemical analyses our primary aim of this study is to describe the magnetic and geochemical properties of soils rich in iron oxides derived from strongly magnetic volcanic basement in this case andosols secondary aim is to explore links between magnetic and chemical parameters of andic soils with respect to genesis factors parent material age precipitation and thickness of the soil profile six pedons of andic properties developed on basaltic lavas were analyzed down to parent rock by a set of magnetic and geochemical methods magnetic data of soil and rock samples reflect the type concentration and particle size distribution of ferrimagnetic minerals geochemical data include soil reaction ph in h2o cation exchange capacity organic carbon and different forms of extractable iron and aluminum content our results suggest the following 1 magnetic measurements of low field mass specific magnetic susceptibility can be a reliable indicator for estimating andic properties and in combination with thermomagnetic curves may be suitable for discriminating between alu andic and sil andic subtypes 2 in the studied andosols strong relationships were found between a magnetic grain size parameters precipitation and exchangeable bases b concentration of ferrimagnetic particles and degree of crystallization of free iron and c parameters reflecting changes in magneto mineralogy and soil genesis parent material age soil depth