hypocentre determination offshore of eastern taiwan using the maximum intersection method summary the maximum intersection maxi method which derives from the master station method msm determines within a 3 d velocity model the absolute hypocentral location based on observed arrival times first the spatial node that better satisfies the arrival time differences computed at all station pairs plus or minus an error tolerance value in seconds is defined as the preliminary hypocentral solution pred second because pred depends neither on the estimate of origin time nor on the residual root mean square rms residual outliers are objectively detected and cleaned out from the original data set without any iterative process or weighting third a statistical minimization residual rms is conducted in a small domain around the pred node which results in a unique final solution the maxi method is applied to the determination of earthquake hypocentres with the proper station correction terms in the southernmost extremity of the ryukyu subduction zone where several dense seismic clusters occur near the seismogenic plate interface the location of earthquakes recorded at both the taiwanese and japanese networks is obtained for about a thousand events between 1992 and 1997 the process uses a detailed 3 d velocity model based on multiple geophysical data sources obtained in the junction area between subduction and collision east of taiwan the earthquake clustering and the significant drop in residual statistics 1 20 0 80 and 0 35 s for taiwanese catalogue msm and maxim solutions respectively indicate the accuracy of the method which can be used to routinely determine absolute hypocentre location based on observed arrival times

climate change during the early paleogene in the bogota basin colombia inferred from paleosol carbon isotope stratigraphy major oxides and environmental magnetism abstract paleosols in the bogota basin colombia record an increase in chemical weathering across the paleocene eocene p e transition rock magnetic properties and major element geochemistry exhibit an abrupt change in an interval identified as including the p e boundary as established by previously published biostratigraphy and a u pb date on volcanic zircons 56 2 1 6 ma during the stratigraphic interval that contains the p e transition magnetic susceptibility increases significantly with an order of magnitude higher concentration of magnetite maghemite and hematite the preponderance of pure stoichiometric magnetite in the paleosols of this interval indicates that the increase in magnetic susceptibility is due to changes in the rate of pedogenesis rather than an increase in the erosion of nearby volcanic rocks which would contribute titanomagnetite pedogenic structures preserved within the paleosols a lack of iron oxides as cement friability of the sandstones and previously published thermochronologic data are not consistent with burial diagenesis as an explanation for the origin of the magnetic mineral assemblage these enhanced pedogenesis and related chemical weathering is also confirmed by increases in the concentration of fe 2 o 3 and al 2 o 3 and loss on ignition values an increase in mean precipitation across this interval is inferred by the lack of carbonate nodules and a decrease in sio 2 in paleosols thus we hypothesize that there was an intensification of chemical weathering during the interval that contains the p e transition

magnitude scales for very local earthquakes application for deception island volcano antarctica abstract different magnitude scales are calculated for a set of volcano tectonic earthquakes recorded in deception island volcano antarctica the data set includes earthquakes recorded during an intense seismic series that occurred in january february 1999 with hypocentral distances that range between 0 5 and 15 km this data set is enlarged to include some regional earthquakes with hypocentral distances up to 200 km the local magnitude scale m l fixed at a hypocentral distance of 17 km is used as the reference for the other magnitude scales studied in the present work m l is determined on a standard wood anderson simulated trace assuming a gain of 2080 maximum peak to peak amplitudes are measured on the vertical components of a short period sensor the m w scale is calculated in the vertical component both for p and s waves the attenuation correction of the ground motion displacement spectra is introduced using data from coda waves studied in the area the comparison between m l values and m w estimations indicates severe discrepancies between both values a magnitude duration scale is calibrated from the comparison between coda durations of the recorded events and their assigned local magnitude scales in order to investigate the causes of the discrepancy between the m l and m w values we analyze two possible error sources a wrong coda q value or the effects of the near surface attenuation that initially are not taken into account in the correction of the ground displacement spectra the analysis reveals that the main cause of this discrepancy is the effect of the near surface attenuation the near surface attenuation is also the cause of the determination of an anomalous spectral decay slope after the corner frequency and the determination of this corner frequency value this near surface attenuation represented by is estimated over the data set obtaining an average value of 0 025 with this value the m w scale is recalculated using an automatic algorithm the new m w values are more consistent with the m l values obtaining a relationship of m w 0 78 m l 0 02

rock magnetism iron oxide mineralogy and geochemistry of quaternary red earth in central china and their paleopedogenic implication abstract this paper presents a detailed investigation on the rock magnetism iron oxide mineralogy and geochemistry of a quaternary red earth qre in central china the magnetic profile of qre showed a characteristic vertical variation pattern the uniform red clay urc section 0 2 2 m of the profile had a higher magnetic susceptibility while vermiculated red clay vrc section 2 6 m had a very low 8 m 3 kg 1 rock magnetism and differential xrd analysis revealed that magnetite maghemite and hematite were the main magnetic carriers in the urc section the major elements fe 2 o 3 and al 2 o 3 of qre increased with depth while the sio 2 content decreased with depth indicating a leaching of the mobile elements and an enrichment of the immobile elements in comparison with the urc the vrc has a greater depletion in the content of na mg k and mg indicating a stronger weathering intensity the dithionite citrate bicarbonate dcb extracted iron fed the ratio of fed to total iron oxide fe fet and the weathering indices of qre confirmed that the vrc had experienced a stronger pedogenesis than the urc strong pedogenesis in the vrc resulted in a transformation of the highly magnetic maghemite to the weakly magnetic hematite which was responsible for the weak magnetism and hard magnetic behavior of the vrc our studies suggest that the vrc had experienced a hot climate with a dry season following one that was warm and moister magnetic reduction of the vrc section resulting from the transformation of highly magnetic maghemite to weakly magnetic hematite appeared to be an important paleopedogenic process in the qre we concluded that the magnetic parameters hard isothermal remanent magnetization hirm and sirm of qre can be used for the analysis of paleopedogenic processes

mineral magnetic studies of the vermiculated red soils in southeast china and their paleoclimatic significance abstract vermiculated red soil the main pedostratigraphical unit of the red soil sequences widespread in subtropical and tropical china has experienced a higher degree of pedogenesis than loess paleosols and the underlying red clays in the loess plateau of northern china previous studies suggested that magnetic properties of the vermiculated units of the red soils are significantly degraded compared to those of the non vermiculated counterparts the mechanism for this magnetic decrease however has not been well determined in order to resolve this problem this study has investigated two red soil sequences of different origin in southeast china by integrating environmental and mineral magnetic research the results show that the magnetic depletion in the vermiculated units was probably caused by both dissolution of magnetic minerals in the white veins and transformation of highly magnetic maghemite to weakly magnetic hematite it appears that stronger pedogenesis favors the transformation of more maghemite to hematite and magnetic properties associated with the relative concentration of maghemite to hematite can be used as climate indicator in the vermiculated red soils the variation trends of the magnetic parameters of the vermiculated red soils prior to 0 85 0 9 ma suggest a strengthening of the east asian summer monsoon the reverse trend of these parameters after 0 85 0 9 ma may correlate with a significant strengthening of the east asian winter monsoon since 0 85 ma

magnetic susceptibility of soil an evaluation of conflicting theories using a national data set magnetic susceptibility values for topsoils across england arc combined with data for soil type geochemistry and concentrations of magnetotactic bacteria in order to evaluate different theories for explaining soil magnetism strongly magnetic soils in unpolluted areas are found over weakly magnetic substrates and are dominated by ultrafine superparamagnetic grains magnetotactic bacteria are present in insufficient concentrations to account for strongly magnetic soils and crop burning is discounted as a major factor a small number of samples show high values associated with either airborne magnetic particulates from pollution or residual primary ferrimagnetic minerals from igneous substrates the results are used to construct a new mechanism for the formation of secondary ferrimagnetic minerals that links abiological weathering and biological fermentation processes the fundamental driving force in the mechanism is fe supply which may be linked to climate observed causative associations between climate and the magnetic susceptibility of loess palaeosol sequences are supported by the findings

duration dependence of magnetic susceptibility enhancement in the chinese loess palaeosols of the past 620 ky abstract past climate has been interpreted from the loess palaeosol record found in china there is no argument that the palaeosols are more strongly weathered than the underlying less well weathered loess and that these changes have been governed by glacial interglacial climate fluctuations however the duration of pedogenesis may have also contributed to the development of palaeosol properties previous studies have not attempted to separate these two factors which both affect the intensity of soil formation and have assumed that the degree of soil development and pedogenic magnetic susceptibility enhancement depended solely on the climate conditions we show that the magnetic susceptibility enhancement of palaeosols of the lower malan and upper lishi formations s 1 s 5 correlated to the interglacials of the past 620 ky depends partly on the duration of pedogenesis this suggests that pedogenic magnetic susceptibility enhancement of palaeosols should not be used for such direct palaeoclimate reconstructions as determining the amount of rainfall or the temperature of the soil forming intervals however used in combination with other proxies other magnetic properties fe d fe d fe t color indices the depth of decalcification particle size magnetic properties of palaeosols and loess layers can provide valuable insight into climatic conditions of soil forming episodes it follows that multiproxy evidence provides better insight into climate dynamics than the interpretation of a single proxy

sensitivity and response of beryllium 10 in marine sediments to rapid production changes geomagnetic events a box model study the response and the sensitivity of the marine beryllium 10 flux to abrupt production changes e g caused by a geomagnetic event are investigated by using a simple box model the effect of mixing processes in the water column on the 10be flux is simulated and the influence of bioturbation on the sedimentary record is studied while the effect of the oceanic residence time is found to be small bioturbation can drastically change the shape and the amplitude of the modeled 10be peak the simulations indicate that 10be production peaks persisting for more than 1500 years are recorded well in deep sea sediments if bioturbation induced integration times are small tbio 1000 years while sediment cores with tbio 1000 years are found to be not well suited for stratigraphic purposes the results further show that the sedimentary 10be peak lags initial signal this time lag is almost independent of the event duration for tbio 1000 years ranging between about 400 and 600 years therefore the model results support the idea that marine 10be peaks corresponding to geomagnetic events can be used as a global time marker to match marine terrestrial and ice core chronologies on the millennial and if the time lag of 500 100 years is considered the submillennial timescale

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

a 4000 year lacustrine record of environmental change in the southern maya lowlands peten guatemala a 4000 yr sediment core record from lake salpeten guatemala provides evidence for maya induced forest clearance and consequent soil erosion between 1700 cal yr b c and 850 cal yr a d radiocarbon ages of wood seeds and charcoal support an age depth model with average errors of 110 cal yr relatively low carbonate 18o values between 1300 and 400 cal yr b c coincide with pollen evidence for forest loss consistent with increased surface and groundwater flow to the lake minimum 18o values between 400 cal yr b c and 150 cal yr a d suggest a high lake level as do 14c dated aquatic gastropods as much as 7 5 m above the present lake stage high lake levels resulted from reduced evaporation to precipitation ratios increased hydrologic input caused by anthropogenic deforestation or both the preclassic abandonment 150 a d and early classic late classic boundary 550 a d are marked by relatively high 18o values indicating reduced lake levels oxygen isotope composition increased further coincident with the terminal classic maya demographic decline between 800 and 900 a d this period of high 18o may have been caused by the greater aridity that has been documented in northern yucatan lakes or by decreased hydrologic input to the lake as a consequence of forest recovery reduced soil erosion after 850 cal yr a d coincided with the terminal classic maya demographic decline and permitted forest recovery and resumption of organic sedimentation

review of recent developments in mineral magnetism of the chinese loess mineral magnetism of the chinese loess has been investigated for more than 20 years although there is a consensus that the neoformation of fine grained maghemite particles in the superparamagnetic sp and single domain sd grain size regions accounts for the magnetic enhancement in the chinese paleosols quantitative retrieval of paleoclimatic signals in terms of rock magnetic proxies is still a subject of debate the ambiguities arise from the inherent complexities of magnetic proxies as well as the multiple factors that control the pedogenic processes therefore a better description of the magnetic assemblage including its mineralogy grain size distribution and stoichiometry of two distinct origins pedogenic and eolian can help us better understand mechanisms behind variations in magnetic proxies at different timescales in order to link them to the paleoclimatic processes this review focuses on recent developments in loess magnetism and carefully evaluates merits and limitations of rock magnetic proxies furthermore several currently unsolved problems are addressed

carbon isotopic ratios of wetland and terrace soil sequences in the maya lowlands of belize and guatemala abstract this article provides new data and synthesizes earlier findings on the carbon isotope ratios of the humin part of soil organic matter from a range of sites in the central maya lowlands changes down the soil profile in carbon isotope ratios can provide an important line of evidence for vegetation change and erosion over time especially in well dated aggrading profiles research thus far has provided substantial evidence for significant inputs from c4 vegetation in buried layers from the ancient maya periods in depositional soils but equivocal evidence from sloping soils we present new findings from soil profiles through ancient maya wetland fields upland karst wetlands ancient maya aguadas reservoirs and ancient maya terraces most of the profiles exhibited 13c enrichment greater than the 2 5 3 typical from bacterial fractionation seven of nine ancient maya wetland profiles showed 13c enrichment ranging from 4 25 to 8 56 in ancient maya dated sediments that also contained phytolith and pollen evidence of grass c4 species dominance upland karst sinks and ancient reservoirs produced more modest results for 13c enrichment these seasonal wetland profiles exhibited 13c enrichment ranging from 1 to 7 3 from the surface to ancient maya period sediments agricultural terraces produced mixed results with two terraces having substantial 13c enrichment of 5 34 and 5 66 and two producing only equivocal results of 1 88 and 3 03 from modern topsoils to maya classic period buried soils altogether these findings indicate that c4 plants made up c 25 of the vegetation at our sites in the maya classic period and only a few percent today these findings advance the small corpus of studies from ancient terraces karst sinks and ancient wetland fields by demonstrating substantial 13c and thus c4 plant enrichment in soil profile sections dated to ancient maya times these studies are also providing a new line of evidence about local and regional soil and ecological change in this region of widespread environmental change in the late holocene

modern sangamon and yarmouth soil development in loess of unglaciated southwestern illinois abstract the thebes section in unglaciated southwestern illinois contains a well preserved 500 kyr loess paleosol sequence with four loesses and three interglacial soils various magnetic mineralogical and elemental properties were analyzed and compared over the thickness of soil sola these proxies for soil development intensity have the following trend yarmouth geosol sangamon geosol modern soil quartz plagioclase zr sr and tio 2 na 2 o ratios were most sensitive to weathering frequency dependent magnetic susceptibility and anhysteretic remanent magnetization greatest in a horizons also correspond well with soil development intensity neoformed mixed layered kaolinite expandables suggestive of a warm humid climate were detected in the sangamon and yarmouth soil sola clay illuviation in soils was among the least sensitive indicators of soil development differences in properties among interglacial soils are interpreted to primarily reflect soil development duration with climatic effects being secondary assuming logarithmic decreases in weathering rates the observed weathering in the sangamon geosol is consistent with 50 kyr of interglacial weathering oxygen isotope stage 5 compared to 10 kyr for the modern soil oxygen isotope stage 1 we propose that the yarmouth geosol in the central midwest formed over 180 kyr of interglacial weathering including oxygen isotope stages 7 9 and 11

on the suitability of baked clay for archaeomagnetic studies as deduced from detailed rock magnetic studies summary extensive rock magnetic investigations have been carried out on baked clays from four kilns two from bulgaria and two from switzerland found in archaeological sites of different age knowledge of the magnetic characteristics of the grains responsible for the archaeomagnetic signal enables us to determine which baked clays have the stablest magnetization and why this is so this is important in directional studies but even more so in painstaking palaeointensity studies that require a very careful evaluation of the suitability of the burnt clay material the proposed rock magnetic experiments enable the identification of the carriers responsible for the remanence and an adequate interpretation of the experimental results connected with the palaeointensity evaluation the experimental methods employed are illustrated with the particular results obtained from each of the four kilns studied the preliminary elucidation of the magnetic mineralogy of the archaeological samples helps first by obtaining a more reliable palaeointensity result and secondly by explaining some of the discrepancies in the palaeodirectional results examples of successful and failed palaeointensity experiments are given in relation to the magnetic properties previously established for each oven the burnt clay materials in this present study satisfy the essential condition of carrying a thermoremanence in spite of that it is shown that there are many factors that can produce undesirable magnetic properties and thus restrict the suitability of these materials for archaeomagnetic analysis the most important factors influencing the magnetic behaviour during magneto diagnostic experiments are the degree of heating in antiquity the initial composition of the unbaked material and the burial conditions the large difference in heating temperatures within a particular archaeological feature is a major cause of variation in magnetic behaviour amongst individual specimens and so preventing a successful pre selection of specimens for palaeointensity experiments nevertheless the study has shown a very good coincidence between the determined rock magnetic characteristics and the success rate in palaeointensity evaluation

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

a new method in mineral magnetism for the separation of weak antiferromagnetic signal from a strong ferrimagnetic background 1 this paper describes a new magnetic method for determining the contribution of weakly magnetic hematite against a strongly magnetic e g magnetite background the method involves measurements of mfr a residual or final remanence after hysteretic demagnetization of saturated isothermal remanent magnetization in terms of sensitivity and precision our proposed method is superior to the currently popular approach known as the hirm method compared to the latter mfr has no error amplification caused by subtraction of terms the method utilizes the available software for hysteretic demagnetization function on an automated vibrating sample magnetometer vsm this in turn automatically decreases some of the disturbing effects of the strong magnetic background e g magnetic viscosity initially non zero offset of hirm for partially oxidized magnetite etc

direct estimates of pedogenic magnetite as a tool to reconstruct past climates from buried soils 1 variations in magnetic properties of buried soils can be used to reconstruct past climatic conditions during paleosol formation most methods however are based on comparisons between the magnetically enriched upper soil horizons and the magnetically unaltered parent material in thin loess paleosol sequences such a comparison can be problematic because all horizons soil and underlying loess may be affected to varying degrees by pedogenesis we propose two direct estimates of pedogenic magnetite based on the analysis of anhysteretic remanent magnetization ratios carm isothermal remanent magnetization and coercivity distributions these estimates are independent of any information regarding the parent material and are possible if pedogenic minerals have similar magnetic properties throughout the study region this condition seems to be met throughout the midwestern united states and a few loessic soils elsewhere the remanence carrying part of pedogenic magnetite is composed of single domain particles with consistent well constrained magnetic properties these particles are extremely well dispersed in the soil matrix as indicated by the absence of noticeable magnetostatic interaction effects our analyses of over 70 modern loessic soil profiles demonstrate that the abundance of pedogenic magnetite correlates well with modern climate and that the method is suited for reconstruction of past climates from paleosols

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

magnetic enhancement is linked to and precedes hematite formation in aerobic soil 1 soil formation usually increases magnetic susceptibility most often by increasing the concentrations of magnetite and maghemite which are two ferrimagnetic iron oxides here we provide evidence that magnetic enhancement in aerobic soils not affected by detrital magnetic inputs or thermal transformation of other iron oxides is mostly due to the formation of maghemite which is later transformed into hematite the iron oxide that gives red color to soil we show that the maghemite hematite ratio is influenced by the particular environment and the degree of soil development so it constitutes an effective tool for paleoenvironmental and planetary studies

an outline of neotectonic structures and morphotectonics of the western and central pannonian basin abstract neotectonic deformation in the western and central part of the pannonian basin was investigated by means of surface and subsurface structural analyses and geomorphologic observations the applied methodology includes the study of outcrops industrial seismic profiles digital elevation models topographic maps and borehole data observations suggest that most of the neotectonic structures in the pannonian basin are related to the inverse reactivation of earlier faults formed mainly during the miocene syn and post rift phases typical structures are folds blind reverse faults and transpressional strike slip faults although normal or oblique normal faults are also present these structures significantly controlled the evolution of landforms and the drainage pattern by inducing surface upwarping and river deflections our analyses do not support the postulated tectonic origin of some landforms particularly that of the radial valley system in the western pannonian basin the most important neotectonic strike slip faults are trending to east northeast and have dextral to sinistral kinematics in the south western and central eastern part of the studied area respectively the suggested along strike change of kinematics within the same shear zones is in agreement with the fan shaped recent stress trajectories and with the present day motion of crustal blocks derived from gps data

pedosediments of karstic sinkholes in the eolianites of ne yucatan a record of late quaternary soil development geomorphic processes and landscape stability abstract the pedogenetic and geomorphic processes controlling soil development in tropical karstic landscapes are still poorly understood we have discovered and studied thick pedosediments in karst pockets developed in late pleistocene lithified calcareous dunes eolianites in the ne coast of the yucatan peninsula the morphological geochemical and mineralogical characteristics of the pocket fills were interpreted as a record of pedogenesis and geomorphic dynamics that shaped the soil mantle during the holocene sand fraction mineralogy and the zr ti ratio indicated a mixed origin of the soil parent material volcanic and granitic metamorphic components redeposited in the lithoral and coastal environments were identified within the soil matrix primary minerals were transformed by weathering and caused desilicification accumulation of clay hydroxy interlayered vermiculite and kaolinite and dithionite citrate bicarbonate extractable iron oxides fed reworked pedofeatures indicative of clay illuviation and redoximorphic processes were observed this set of processes points to a continuous phase of humid pedogenesis several thousand years long in the early middle holocene however the development of thick recalcified pedosediments in the pockets contrasting with the thin background rendzinas requires active soil redeposition during a late phase of geomorphic activity the available accelerator mass spectrometry ams radiocarbon date indicates that the switch of the erosion sedimentation processes could be related to ancient maya land use impact

mineralogic and climatic interpretations of the luochuan loess section china based on diffuse reflectance spectrophotometry we examined the top 135 m that is the entire pleistocene of the classic luochuan section on the chinese loess plateau with a diffuse reflectance spectrophotometer from the near ultraviolet through the visible and into the near infrared from the reflectance data we calculated sample brightness which with some caveats is a reasonable proxy for magnetic susceptibility mineralogic changes were identified by factor analyzing the first derivative of the percent reflectance data and examining samples with high factor scores two factors which explain about 96 of the cumulative variance are distinguished by the relative proportion of hematite and goethite the minerals that are responsible for the color changes in the loess sequence both hematite and goethite are present in both loess and paleosol but goethite dominates in loess whereas hematite dominates in paleosol the goethite factor exhibits an inverse correlation with magnetic susceptibility the hematite factor exhibits a weak positive correlation with susceptibility paleoclimatic interpretations are drawn from comparison of susceptibility to the concentration of spectrally identified hematite based on this comparison paleosols in the early pleistocene wucheng formation are characterized by conditions that are drier than today a dry summer monsoon whereas later pleistocene paleosols are characterized by a wet summer monsoon

magnetic minerals in calcic luvisols chromic developed in a warm mediterranean region of spain origin and paleoenvironmental significance abstract soil formation under aerobic conditions usually enhances magnetic signals mainly through neoformation of sub micron magnetite and or maghemite in order to better understand the nature and magnitude of the enhancement in this work we characterized the iron fe oxides and magnetic properties of two calcic luvisols chromic developed on calcareous orthoquartzites in a spanish region with a warm mediterranean climate weathering of the fe bearing minerals in the parent material mostly fe rich smectite had resulted in the neoformation of hematite and maghemite rather than goethite thus causing a substantial increase in magnetic susceptibility saturation magnetization m s and other magnetic signals the absolute frequency dependent magnetic susceptibility fd which is a typical proxy for the concentration of sub micron superparamagnetic pedogenic maghemite was strongly correlated with the concentration of hematite hm the estimated percent frequency dependent magnetic susceptibility fd was 15 7 this and various other magnetic indicators indicate that the grain size distribution gsd of the pedogenic maghemite is narrower around the superparamagnetic single domain threshold than is that of maghemite in soils and paleosols developed under other temperate climates e g the chinese loesss plateau where fd fd ratio fd the hematite goethite ratio and several indicators of the degree of weathering provides a better tool for paleoclimatic reconstructions than does the current use of alone

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

phytoliths stable carbon isotopes and micromorphology of a buried alluvial soil in southern mexico a polychronous record of environmental change during middle holocene abstract the reconstruction of the maya lowlands vegetational history and its paleoecological implications during the middle late holocene was carried out using phytolith analysis and organic matter stable isotopic ratios three sections located in a terrace of the usumacinta river were studied tierra blanca i tierra blanca ii and el pochote they consisted of a series of alluvial sediments alternating with paleosols that contained artifacts belonging to the formative classic and postclassic periods according to the mesoamerican chronology our results showed that the middle holocene paleosols had well developed vertic features with 16 13c values which evidence seasonal semiarid conditions however phytolith content recorded a predominance of c3 plants and paleosol micromorphology showed a set of features related to an alternation of humid and drier conditions therefore stable isotope composition reflects the integral signal of the last period of soil formation phytoliths and soil micromorphology correspond to a more extensive record that represents the successive stages of pedogenetic and environmental changes

late quaternary climatic changes revealed by luminescence dating mineral magnetism and diffuse reflectance spectroscopy of river terrace palaeosols a new form of geoproxy data for the southern african interior lyons j r tooth s duller g 2014 late quaternary climatic changes revealed by luminescence dating mineral magnetism and diffuse reflectance spectroscopy of river terrace palaeosols a new form of geoproxy data for the southern african interior quaternary science reviews 95 43 59

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

a quantitative model of magnetic enhancement in loessic soils we present a quantitative model for the climatic dependence of magnetic enhancement in loessic soils the model is based on the widely accepted hypothesis that ultrafine magnetite precipitates during alternating wetting and drying cycles in the soil micropores the rate at which this occurs depends on the frequency of drying wetting cycles and on the average moisture of the soil both parameters are estimated using a statistical model for the soil water balance that depends on frequency and intensity of rainfall events and on water loss by evapotranspiration monthly climatic tables are used to calculate the average soil moisture and the rate of pedogenic magnetite production which is proportional to a new parameter called magnetite enhancement proxy mep our model is tested by comparing mep calculated for known present day climates with the magnetic enhancement of modern soils the magnetic enhancement factor defined as the ratio between a given magnetic enhancement parameter and mep is expected to be a site independent constant we show that magnetic enhancement differences between soils from the chinese loess plateau and from midwestern u s are explained by our model which yields similar magnetic enhancement factors for the two regions our model is also successful in predicting the mean annual rainfall threshold above which magnetic enhancement declines in a given type of climate

the magnetic properties of loess and paleosol samples from the chinese loess plateau spanning the last 22 million years abstract magnetic measurements susceptibility isothermal and anhysteretic remanence and quotients derived from these are presented for a suite of loess and paleosol samples from sites on the chinese loess plateau the three sites xifeng dongwan and qinan qa i together span most of the last 22 million years the results provide the first multi parameter magnetic measurements from pre pleistocene loess paleosol sequences that began accumulation in the early miocene mass specific measurements have been corrected for carbonate concentrations which peak in the loess layers and range up to 57 all the magnetic properties recorded indicate variability on both orbital and supra orbital timescales the changing magnetic properties allow the record to be divided into a sequence of eight sample groups that broadly parallel the main supra orbital changes in magnetic susceptibility the pre pleistocene parts of the record include intervals mainly late miocene and pliocene during which loess as well as paleosol layers are characterized by high values for properties such as frequency dependent susceptibility fd usually associated with strong weathering most of the miocene record prior to 8 5 ma with the exception of a brief interval from ca 14 4 to 15 9 ma shows reduced values for indicators of pedogenic ferrimagnetic concentrations in both the loess and paleosol layers as well as a low amplitude of variability between loess and paleosol values the palaeoenvironmental implications of this part of the sequence are unclear since they hinge on the type of model of pedogenic magnetic mineral formation adopted high field remanence measurements indicate that the coercivity of the antiferromagnetic minerals represented declined progressively throughout the whole period in both the loess and the paleosol samples though there is no unambiguous evidence for long term diagenetic alteration of the magnetic properties on timescales beyond the orbital ones that drive the loess paleosol alternations the present results suggest caution in applying existing climofunctions based on magnetic susceptibility to deposits spanning the whole of the last 22 ma

sediment magnetic signature of land use and drought as recorded in lake sediment from south central minnesota usa abstract sediment magnetic properties of a short core from sharkey lake mn record the effects of euroamerican settlement and climate change over the last 150 yr the onset of european style farming led to increased erosion reflected in high values of concentration dependent parameters such as magnetic susceptibility isothermal remanent magnetization irm and anhysteretic remanent magnetization arm these high values are only partially due to increased supply of terrigenous material to the lake and recent sediment contains an additional component of authigenic fine single domain magnetite most likely magnetosomes from magnetotactic bacteria high organic productivity in the lake during the 1920s to 1940s drought increased this authigenic component resulting in highly magnetic fine grained sediment a comparison with older holocene sediment from the same lake shows that over time most of the fine magnetic signal is lost after deposition leading to decreases in magnetization and a bimodal grain size distribution of ultrafine superparamagnetic grains and coarser multidomain particles evident from measurements of arm irm ratios hysteresis measurements and low temperature analyses the effects of dissolution and the superposition of climate and land use signals complicate the use of recent sediments as modern analogs for sediment magnetic analyses

use of soils and palaeosols on volcanic materials to establish the duration of soil formation at different chronological scales abstract in this paper we present an overview of the mexican volcanic palaeosol sequences as a valuable tool to establish the duration of soil formation at different chronological scales we have selected four study cases which cover time intervals from decennial centennial to millennial pedogenesis the first case corresponds to the soils in el chichon volcano where the short interval between the eruptions gives the opportunity to study the soil formation in periods less than 500 years in this interval the transformation from regosol to andosol is observable in el nevado de toluca pedogenesis of longer duration 4000 to 6000 y characterizes a vitric andosol stage in this area the transformation of andosol to luvisol is also shown in periods longer than 10 000 years the third study case corresponds to the tlaxcala palaeosol sequence where pedogenesis in intervals from 10 000 to 100 000 years is observable in this case no andosols are present and a complete set of luvisols showing different properties is found this differentiation is not only related to the duration of the pedogenesis but also to the climatic conditions which lead to changes in specific properties clay content weathering of the primary minerals fed content in this way these soils are valuable for palaeoenvironmental reconstruction the fourth case is related to faster pedogenesis in the volcanic regions of mexico where highly developed luvisols are found formed in intervals less than 15 000 y in this case the influence of a pre weathered volcanic material as a source of clay allows the rapid transformation

recent surface temperature trends in the interior of east antarctica from borehole firn temperature measurements and geophysical inverse methods 1 we use measured firn temperatures down to depths of 80 to 90 m at four locations in the interior of dronning maud land east antarctica to derive surface temperature histories spanning the past few decades using two different inverse methods we find that the mean surface temperatures near the ice divide the highest elevation ridge of east antarctic ice sheet have increased approximately 1 to 1 5 k within the past 50 years although the onset and rate of this warming vary by site histories at two locations nus07 5 78 65 s 35 64 e and nus07 7 82 07 s 54 89 e suggest that the majority of this warming took place in the past one or two decades slight cooling to no change was indicated at one location nus08 5 82 63 s 17 87 e off the divide near the recovery lakes region in the most recent decade inversion results indicate both cooler and warmer periods at different sites due to high interannual variability and relatively high resolution of the inverted surface temperature histories the overall results of our analysis fit a pattern of recent climate trends emerging from several sources of the antarctic temperature reconstructions there is a contrast in surface temperature trends possibly related to altitude in this part of east antarctica

variation of soil magnetism across the russian steppe its significance for use of soil magnetism as a palaeorainfall proxy abstract modern soils across the chinese loess plateau exhibit strong but disputed correlation between their pedogenic magnetic content and annual rainfall a soil magnetism rainfall transfer function could provide a quantitative proxy of quaternary rainfall for this region however some argue that magnetic dilution through spatially varying fluxes of weakly magnetic dust controls the soil magnetic properties here we test the soil magnetism rainfall couple by examining 22 russian steppe soils free of present dust accumulation across a climatic transect from the semi arid caspian region to the more humid caucasus the soils display systematic increases in topsoil ferrimagnetic concentrations with the exception of climate and its co variant vegetation soil forming factors are essentially constant across this stable area hence the soil magnetic variations dominantly reflect climate and from statistical analysis principally rainfall further the russian steppe magnetic rainfall relationship matches that observed for the chinese loess plateau these independent data thus substantiate the soil magnetism rainfall climofunction and by inference eliminate dust dilution as a significant magnetic factor

re arrangement of atmospheric circulation at about 2 6 ma over northern china evidence from grain size records of loess palaeosol and red clay sequences abstract recent studies have shown that the red clay sequence underlying the quaternary loess of the chinese loess plateau is wind blown in origin continuous atmospheric dust deposition in the past 7 0 ma has been documented to address the wind system that transported the tertiary red clay two north south transects were studied in the chinese loess plateau one of the transects was designed to study spatial changes in grain size of the last glacial interglacial loess records and the other to observe particle changes of the tertiary red clay underlying the quaternary loess the loess transect consists of nine sections and the red clay transect of four sections analyses of closely spaced samples show that there is a strong southward decrease in grain size of both loess and palaeosol horizons of the late pleistocene which is consistent with the idea that the aeolian materials of the quaternary in the loess plateau are transported by the northerly winter monsoonal winds grain size distribution of the red clay sequences however does not show such a change from north to south along the red clay transect the particle size distribution is almost identical in the four sections suggesting that the winter monsoonal winds might have played a less important role in transporting the red clay material it is suggested that the red clay may have been transported by the westerlies from the dust source regions of northwestern china onto the loess plateau a remarkable re arrangement of atmospheric patterns at about 2 6 ma therefore has been recorded by the red clay loess shift it is speculated that this re arrangement of atmospheric patterns may have been caused by the onset of glaciation in the northern hemisphere

source parameters of the 1980 mammoth lakes california earthquake sequence from the more than 1500 mammoth lakes earthquakes recorded on three component digital seismographs spudich et al 1981 150 were used in an analysis of the locations mechanism and source parameters a composite fault plane solution of nine earthquakes 3 9 m 5 1 defines a right lateral strike slip mechanism on a steeply dipping nearly east west plane striking s75 e or left lateral strike slip on a nearly north south plane striking n10 e vertical cross sections of well located aftershocks indicate possibly three east west planes that coincide with the locations of the four largest earthquakes with ml 6 0 using the spectral analysis of s waves brune 1970 source parameters for 67 earthquakes were determined forty eight had magnitudes greater than or equal to 3 0 seismic moments ranged from 9 20 1018 dyn cm to 2 33 1024 dyn cm earthquakes with seismic moment greater than about 1 0 1021 dyn cm had nearly constant stress drops 50 bars earthquakes with seismic moment less than about 1 0 1021 dyn cm had stress drops that apparently decrease as seismic moment decreases

waveform inversion for point source moment tensor retrieval with variable hypocentral depth and structural model summary in the inversion scheme of high frequency seismograms recorded by a local network we have developed the unconstrained moment tensor description to study weak events which are believed to reflect small scale complexities of the tectonic structure in order to allow the source mechanism to change with time each moment tensor component has its own time history in the inversion the measure of the similarity between the synthetic seismograms and the observed records is obtained by minimizing the norm l2 of their difference the initial synthetic seismograms are constructed by summing a set of time dependent functions named base functions these base functions are computed by normal mode summation for a discrete set of source depths and for two structural models considered to represent acceptable extremes for the region under study in the course of the inversion using a linear interpolation new base functions are computed for intermediate values of the starting depths and structures thereafter new synthetic seismograms are computed and compared with the observed records until the convergence is reached within some pre assigned threshold for the norm l2 the method has been tested by treating as observed records synthetic seismograms both displacement and velocity generated for instantaneous and finite duration sources the observed records have been computed for two structures one belonging to the structural range within which the base functions were computed the other lying outside this range random noise has been superimposed on the records when inverting synthetic records computed for a structure contained within the range of interpolation for the base functions the full moment tensor is retrieved satisfactorily provided that the noise level does not exceed about 20 per cent for records computed for a structure lying outside this range a spurious volumetric part of the moment tensor appears however if the volumetric part of the moment tensor is removed the source time function can be reconstructed satisfactorily and the source mechanism can be determined from the deviatoric part of the moment tensor the procedure has been applied to vertical component seismograms recorded in the friuli ne italy area for the ml 2 9 event of 1987 december 27 the retrieved source mechanism is in agreement with the distribution of the few first arrival polarities available and the source time function indicates a possible multiple rupture process

high resolution hematite goethite records from chinese loess sequences for the last glacial interglacial cycle rapid climatic response of the east asian monsoon to the tropical pacific 1 in order to study the variability of dry versus humid conditions resulting from the east asian monsoon eam we analyzed hematite and goethite from two high resolution chinese loess sections by diffuse reflectance spectroscopy the hematite and goethite concentrations are higher in interglacial paleosols than in glacial loess sediments whereas the hematite goethite hm gt ratios are lower in paleosols than in loess such changes are consistent with higher precipitation and temperature and increased pedogenesis during interglaciation and lower precipitation and temperature and decreased pedogenesis during glaciation the hm gt ratio can be employed as a tool to assess short term variations in humidity and aridity of the eam the hm gt ratios of the last glacial loess displays millennial scale abrupt climate oscillations revealing a pattern of significantly reduced and enhanced summer monsoon moisture our results indicate that the eam responded to tropical pacific climate by millennial scale changes in precipitation during the last glaciation

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

rock magnetic and geochemical proxies for iron mineral diagenesis in a tropical lake lago verde los tuxtlas east central mexico magnetic and non magnetic mineral analyses were conducted on a lacustrine sequence from lago verde in the tropical coast along the gulf of mexico that covers the last 2000 years the site witnessed the transformation of the environment since the early olmec societies until forest clearance in the last century through these analyses we investigated the processes that affected the magnetic mineralogy in order to construct a model of past environmental changes and compare this model with the archeological record and inferred climatic changes in the northern hemisphere of tropical america volcanic activity has played a major influence on sediment magnetic properties as a purveyor of ti magnetites ti maghemites and as a factor of instability in the environment anoxic reductive conditions are evident in most of lago verde s sedimentary record direct observations of magnetic minerals and ratios of geochemical fe ti and ferrimagnetic f and paramagnetic p susceptibility data are used as parameters for magnetite dissolution p fe f and precipitation f ti of magnetic minerals intense volcanic activity and anoxia are recorded before a d 20 leading to the formation of framboidal pyrite increased erosion higher evaporation rates lower lake levels anoxia and reductive diagenesis in non sulphidic conditions are inferred for laminated sediments between a d 20 850 this deposit matches the period of historical crisis and multiyear droughts that contributed to the collapse of the maya civilization dissolution of magnetite a high organic content and framboidal pyrite point to anoxic sulphidic conditions and higher lake levels after a d 850 higher lake levels in lago verde broadly coincide with the increased precipitation documented during the medieval warm period a d 950 1350 in the northern tropical and subtropical regions of the american continent for the little ice age a d 1400 1800 the relatively moist conditions inferred are in concordance with the glacial advances recorded in central mexico higher erosion rates reflect destruction of the rainforest over the last 40 years

recovery lakes east antarctica radar assessment of sub glacial water extent 1 a fast flowing tributary of recovery ice stream penetrates more than 500 km into the interior of east antarctica recent satellite based studies found surface features in the onset area of this tributary that indicate a significant subglacial hydraulic system including four large smooth basins the typical surface expression of large subglacial lakes as well as eleven smaller areas over which ice sheet surface elevations rapidly changed by discharge filling of subglacial water here we present the first ice penetrating radar evidence of subglacial conditions in this area we identified a distinct ice water interface only over a limited area within the boundaries of the investigated large smooth basins previously hypothesized to be water filled lakes the radar characteristics in some areas are similar to those of a drained lake indicating that parts of the bed are wet but not a typical lake we also find evidence for discrete water bodies outside of the lake boundaries the lines of evidence indicate that the northern most two recovery lakes have recently drained

magnetic stratigraphy of chinese loess as a record of natural fires magnetic susceptibility records of paleosols and loess show high correlation with oxygen isotope stratigraphy of ocean sediments kukla 1987 providing a global paleoclimatic record different models have been put forth to explain the nature and cause of susceptibility variations but consensus has not yet been achieved our low temperature studies reveal a secondary magnetite component in paleosols that is characterized by a higher verwey transition 115k than that for the magnetite 100 k in unaltered loess the same shift in the verwey transition can be achieved by heating and cooling loess samples this is consistent with a new hypothesis that the magnetic signal from paleosols may be produced by natural fires in the past natural fire intensity is sensitive to the amount of annual precipitation so that increased fire induced susceptibilities should reflect an increase in the humidity of regional climate

tectonic implications of the gps velocity field in the northern adriatic region 1 continuous and episodic gps observations between 1991 and 2004 show that adria moves independently of both stable eurasia and nubia adria moves nne at 3 4 5 mm yr increasing from n to s relative to eurasia and may be fragmenting along the gargano dubrovnik seismic zone the observed 2 3 mm yr of n s adria eurasia convergence is taken up by contraction across a narrow 70 km zone in the eastern alps and concomitant extrusion of the alpine north pannonian unit the adria central dinarides boundary is a broader collisional zone with intense 1 1 5 mm yr shortening near shore and 2 mm yr spread across the dinarides the remaining 1 2 mm yr motion e of the alps and ne of the dinarides is absorbed by the inverted contracting pannonian basin leaving no significant deformation above 0 5 mm yr in the western and northern carpathians and european platform

theory and application of the day plot mrs ms versus hcr hc 2 application to data for rocks sediments and soils 1 new theoretical curves relating the hysteresis parameters mrs ms and hcr hc for single domain sd superparamagnetic sp pseudo single domain psd and multidomain md grains and their mixtures are applied to published data for natural materials the day plot of mrs ms versus hcr hc has been used to crudely classify samples into box like sd psd and md or sometimes incorrectly md sp regions with arbitrary boundaries new type curves for md psd sd md and sd sp grains and mixtures permit more subtle and precise modeling the predicted md trend and its junction with the psd trend are observed in two data sets for magnetite spherules from carbonate rocks and for temperature varying hysteresis results spanning the verwey transition the latter data are the basis of a suggested new method for pinpointing the psd md threshold size selected data for pottery clays soils and paleosols generally follow sd md type curves and indicate intermediate size psd magnetite with narrow to broad size distributions a lake sediment section with known grain size progression tracks in the predicted sense along the sd md trend selected data for glaciomarine and pelagic sediments are also generally compatible with sd md trends examples of remagnetized carbonate rocks submarine basaltic glasses and glassy rims of pillow basalts all follow predicted sp sd or sp psd mixing curves with a large range in volume fraction of sp grains 0 75 but a narrow range of sp particle sizes 10 2 nm larger sp grains spanning the range to sd size 25 30 nm are absent for unknown reasons oceanic dolerites gabbros and serpentinized peridotites in some cases fall in a novel region of the day plot parallel to but below magnetite sd md mixing curves

late holocene climate reconstructions for the russian steppe based on mineralogical and magnetic properties of buried palaeosols abstract insights into past climate changes and corresponding evolution of soils and the environment can be gained by multidisciplinary studies of palaeosols here we focus on palaeosols buried beneath archaeological monuments specifically funerary mounds kurgans in the russian steppe the kurgans were constructed and each of the palaeosols buried over a range of different timesteps from the mid holocene to 600 years before present yr bp integrated magnetic mineralogical and pedological data were used to obtain estimates of past climate especially precipitation changes through both time and space a soil magnetism based climofunction derived previously from modern steppe soils and modern climate was applied to each set of palaeosols to obtain quantitative reconstructions of annual precipitation for the time at which the soils were buried independent soil property data clay mineralogy salt content iron mineralogy from mossbauer analysis and optical and electron microscopy were also obtained in order to test and substantiate the magnetic inferences the data obtained indicate that the climate of the lower volga steppe area has varied from the mid holocene onwards precipitation minima occurred at 5000 3800 and 1600 yr bp with intervals of enhanced precipitation at 1900 yr bp and 600 yr bp these rainfall variations appear to occur synchronously with changes in middle eastern precipitation and lake levels suggesting they are controlled by index changes in the north atlantic oscillation

magnetostratigraphy of the qiliting section se china and its implication for geochronology of the red soil sequences in southern china summary the red soil sequences in southern and southeastern china provide important terrestrial archives of palaeoclimate and palaeoenvironment and are important sources of palaeolithic settlements and therefore early human occupation here we present detailed palaeomagnetic investigation coupled with mineral magnetic and petrographic analyses of a red soil sequence at qiliting southeastern china the sediments contain both strongly magnetic minerals such as maghemite and magnetite and weakly magnetic minerals such as haematite and possibly goethite maghemite and haematite were identified as the main carriers of the natural remnant magnetisations only haematite dominates the characteristic remnant magnetisations palaeomagnetic findings suggest that the qiliting sedimentary sequence recorded the early brunhes chron and the late matuyama chron including the jaramillo subchron our finding coupled with previously published magnetostratigraphy establishes that the red soil sequences in southern china began to accumulate no later than the jaramillo age i e 1 0 ma it is further suggested that the capabilities of recording magnetic polarity stratigraphy in chinese red soil sequences are variable between areas because of different climate regimes

focal mechanisms in anisotropic media summary focal mechanisms of seismic sources in anisotropic media are more complicated than in isotropic media planar shear faulting produces pure double couple dc mechanism in isotropy but generally non double couple non dc mechanism in anisotropy the non dc mechanism can comprise both the isotropic iso and compensated linear vector dipole clvd components the amount of the iso and clvd components depends on strength and symmetry of anisotropy and on the orientation of faulting shear faulting in anisotropy generates a pure dc mechanism provided that faulting is situated in symmetry planes of orthorhombic or of higher anisotropy symmetries the fault plane solution i e the orientation of the fault normal and the slip direction can be retrieved from the seismic moment tensor and from elastic parameters describing anisotropy at the source numerical modelling shows that shear faulting in anisotropic rocks present in the earth crust the earth mantle or in the subduction zones can produce mostly mechanisms with the clvd up to 30 per cent and with the iso up to 15 per cent the fault plane solutions calculated under the assumption of isotropy typically deviate from the true solutions by an angle of 5 to 10

magnetic analyses of soils from the wind river range wyoming constrain rates and pathways of magnetic enhancement for soils from semiarid climates in order to constrain the rate of magnetic enhancement in soils we investigated modern soils from five fluvial terraces in the eastern wind river range wyoming profiles up to 1 2 m deep were sampled in 5 cm intervals from hand dug pits or natural riverbank exposures soils formed in fluvial terraces correlated to the sacajawea ridge 730 610 ka bp bull lake 130 100 ka bp and pinedale age 20 ka bp glacial advances one soil profile formed in holocene age sediment abundance mineralogy and grain size of magnetic minerals were estimated through magnetic measurements magnetic enhancement of the a horizon as well as an increase in fine grained magnetic minerals occurred mostly in bull lake profiles but was absent from the older profile such low rates of magnetic enhancement may limit the temporal resolution of paleosol based paleoclimate reconstructions in semiarid regions even where high sedimentation rates result in multiple paleosols a loss of ferrimagnetic and an increase in antiferromagnetic minerals occurred with age our findings suggest either the conversion of ferrimagnetic minerals to weakly magnetic hematite with progressing soil age or the presence of ferrimagnetic minerals as an intermediate product of pedogenesis absolute and relative hematite abundance increase with age making both useful proxies for soil age and the dating of regional glacial deposits all coercivity proxies are consistent with each other which suggests that observed changes in hirm and s ratio are representative of real changes in hematite abundance rather than shifts in coercivity distributions even though the modified l ratio varies widely

climatic interpretation of the luochuan and lingtai loess sections china based on changing iron oxide mineralogy and magnetic susceptibility abstract hematite and goethite estimated from diffuse reflectance spectra and magnetic susceptibility ms have been determined from both the luochuan and lingtai loess sections of the loess plateau of central china changing concentrations of these iron oxides and ms were used to determine paleoclimatic change based on a model that relates pedogenic production of hematite and magnetite to precipitation we propose two precipitation phases on the loess plateau during the last 2 6 ma from the wucheng red clay boundary up to paleosol s5 mis 13 precipitation on the loess plateau was moderate probably not frequently exceeding 450 mm yr and highly seasonal from s5 to the present precipitation during interglacial times has gradually increased to the present levels of 600 650 mm yr for the localities examined throughout the pleistocene spanning both glacial and interglacial conditions hematite to goethite ratios display a consistent decrease this decrease suggests that precipitation on the loess plateau has been getting less seasonal and or has been occurring during times when temperature was lower in addition to these long term changes it also appears that iron oxide records from the loess plateau exhibit 400 500 ka cycles from the wucheng red clay boundary to s5 these 400 500 ka cycles may be analogous to similar length cycles recorded in 13 c marine records in the south china sea and may be linked through weathering and silica production as a result of the asian monsoon

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

an 85 ka record of climate change in lowland central america drill cores obtained from lake peten itza peten guatemala contain a 85 kyr record of terrestrial climate from lowland central america that was used to reconstruct hydrologic changes in the northern neotropics during the last glaciation sediments are composed of alternating clay and gypsum reflecting relatively wet and dry climate conditions respectively from 85 to 48 ka sediments were dominated by carbonate clay indicating moist conditions during marine isotope stages mis 5a 4 and early 3 the first gypsum layer was deposited at 48 ka signifying a shift toward drier hydrologic conditions and the onset of wet dry oscillations during the latter part of mis 3 peten climate varied between wetter conditions during interstadials and drier states during stadials the pattern of clay gypsum wet dry oscillations during the latter part of mis 3 48 23 ka closely resembles the temperature records from greenland ice cores and north atlantic marine sediment cores and precipitation proxies from the cariaco basin the most arid periods coincided with heinrich events when cold sea surface temperatures prevailed in the north atlantic meridional overturning circulation was reduced and the intertropical convergence zone itcz was displaced southward a thick clay unit was deposited from 23 to 18 ka suggesting deposition in a deep lake and pollen accumulated during the same period indicates vegetation consisted of a temperate pine oak forest this finding contradicts previous inferences that climate was arid during the last glacial maximum lgm chronozone 21 2 ka at 18 ka peten climate switched from moist to arid conditions and remained dry from 18 to 14 7 ka during the early deglaciation moister conditions prevailed during the warmer bolling allerod 14 7 12 8 ka with the exception of a brief return to dry conditions at 13 8 ka that coincides with the older dryas and meltwater pulse 1a the onset of the younger dryas at 12 8 ka marked the return of gypsum and hence dry conditions the lake continued to precipitate gypsum until 10 3 ka when rainfall increased markedly in the early holocene

present crustal movement and strain distribution in central europe inferred from gps measurements in 1992 an international collaboration was initiated to study the present day geodynamics of central europe the primary tool of this research is the global positioning system gps therefore the central european gps geodynamic reference network was established in 1994 the network extends from the south in the eurasian african plate boundary zone to the east european pre cambrian platform in the northeast during the first phase of the project four gps campaigns were organized between 1994 and 1997 analysis of gps data provided rms repeatabilities around 2 mm in the horizontal and 5 6 mm in the vertical component for each campaign the velocities of gps sites situated on the eurasian plate were compared with those predicted by the nnr nuvel 1a plate velocity model the intraplate velocity field shows that the northern part of central europe seems generally stable with velocities under 2 mm yr however the southern sites close to the plate boundary zone show higher values and abrupt changes of velocities indicating the existence of narrow deformation zones the primary feature revealed by the strain calculation in the alpine pannonian dinaric system is the dominant north south contraction resulting from the collision of the african and eurasian plates transmitted by the adriatic microplate however the direction of contraction in the alpine pannonian dinaric junction zone changes from nw se at the northeastern boundary of the adriatic microplate to ne sw toward the bohemian massif the magnitudes of these strain rates are similar 8 0 5 3 ppb yr and 8 6 2 5 ppb yr respectively over 200 350 km subnetworks we observe e w oriented 93 13 right lateral shear 12 5 ppb yr between the alpine north pannonian unit and the southernmost sites in the dinarides and southern alps along with left lateral shear 97 7 10 2 ppb yr relative to the stable bohemian massif in the north both the strain field and the intraplate velocities presented show that the alpine north pannonian unit is presently crushed out to the east with 2 mm yr velocity on average along two main fault zones as a consequence of the compression caused by the adria alpine collision

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

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

magnetic parameters reflecting pedogenesis in pleistocene loess deposits of argentina abstract quaternary loess sequences of argentina with interbedded loess and buried soils palaeosols provide terrestrial records of past climates and environmental conditions study of rock magnetic parameters measured over a large area of the pampean loess seems to indicate that the existing magnetoclimatological models cannot adequately account for the complexities of the pampean loess the chinese loess has been considered as typical where magnetic properties are largely controlled by pedogenesis on the other hand the siberian loess is an alternative magnetoclimatological model in which palaeosols appear as magnetic lows and the intercalated loess as magnetic highs argentine loess is apparently closer to the siberian model however considering the data obtained in argentina the situation seems to be more complicated the higest magnetic values sirm and susceptibiliy values in silty and sandy loess indicate a more efficient entrainment of dense iron oxides particles during stormy dry glacial intervals the parent material shows the highest susceptibility values 100 10 8 m3 kg while the waterlogged horizons show the lowest ones below 20 10 8 m3 kg pedogenesis resulting in the development of bc and b soil horizons of palaeosols in the parent loess produced decreases in susceptibility values and increases in the f factor this phenomenon occurs at some degree of humidity in which the process of gleying caused the total depletion of both susceptibility and frequency factor the magnentic data allows consideration of the relevance of major cycles arid humid separated by discontinuities as the main factor favoring one particular behavior of the magnetic parameters the b horizons of palaeosols developed during an arid cycle will not show a notable difference in the magnetic records from the parent material in contrast during humid climate condition the pristine loess can be progresively obliterated by pedogensis through to the extreme situation of gleying

archaeomagnetic investigation and dating of neolithic archaeological site kovachevo from bulgaria abstract combined rock magnetic and archaeomagnetic investigation have been carried out on the neolithic site kovachevo from bulgaria the aim of the study is to provide an independent dating for the last usage of discovered oven related to the earlier stage of the site in comparison with the previously studied remains of ancient fire in the later layers studies on the magnetic mineralogy and stability of the iron oxide particles in the baked clay from the oven provided consistent and valuable data for evaluation of the suitability of the material for obtaining archaeomagnetic information as well as a basis for evaluation of the reliability of the obtained palaeointensity data careful and detailed sampling of the oven revealed the influence of magnetic refraction and wall tilting on the palaeodirection results the effect was minimized through averaging all the data for walls and floors of the oven archaeomagnetic dating was made utilizing the lanos method l approche bayesienne en chronometrie application a l archeomagnetisme in barrandon j n guibert p michel v eds datation xxie rencontres internationales d archeologie et d histoire d antibes editions apdca antibes pp 113 139 bayesian inference of calibration curves application to archaeomagnetism in buck c e millard a r eds tools for chronology crossing disciplinary boundaries springer verlag london 2003 pp 43 82 and gives the period 5712 5571 b c as the most probable time of the last usage of the studied oven this result is in agreement with the archaeological evidence and 14c data

holocene loess accumulation and soil development at the western edge of the chinese loess plateau implications for magnetic proxies of palaeorainfall a high resolution holocene sequence of loess palaeosols and incipient soils at the western edge of the chinese loess plateau dated usingoptically stimulated luminescence techniques is used to identify the respective influence of dust accumulation rate time and climate on soil magnetic properties dust deposition and soil formation have both been quasi continuous through the holocene at this site the soils are thus accretionary in nature the degree of soil development as indicated both by geochemical and magnetic properties which correlate strongly varied through the holocene compared with the less weathered loess units each palaeosol is enriched in nitrogen and organic carbon depleted of carbonate due to leaching and displays higher values of pedogenic magnetic susceptibility frequency dependent susceptibility remanences and magnetisation magnetic grain size indicators show that the pedogenic ferrimagnets are ultrafine of single domain and superparamagnetic dimensions sediment accumulation rates were lowest from b12 to 2 5 ka providing ample time 100 s of years for weathering and soil formation to proceed yet pedogenesis through this interval was relatively weak conversely soil development was stronger during later intervals when loess accumulation rates were higher and soil forming intervals were correspondingly shorter in terms of jenny s 1941 soil forming equation accumulation rate and thus time sediment source parent material and topography show no systematic variation between the loess and the palaeosols therefore climate seems to be the key soil forming factor which has controlled the geochemical and magnetic properties of these holocene palaeosols r 2002 elsevier science ltd all rights reserved

source properties of the 29 january 2011 ml 4 5 oroszlany hungary mainshock and its aftershocks abstract in the most seismically active region of hungary an earthquake of m l 4 5 occurred near the town of oroszlany on 29 january 2011 the mainshock was followed by more than 200 aftershocks this event is the first earthquake in the country above m l 4 that was recorded on a significant number of three component digital seismic stations according to the inversion of arrival times the hypocenter of the mainshock was at a depth of about 5 km near oroszlany with horizontal errors of about 1 5 km the aftershocks were confined to a small region next to the mainshock for the main event we obtained an average moment magnitude of m w 4 2 p and s wave source radii of r p 970 and r s 972 m and static stress drops of p 6 67 10 5 and s 17 60 10 5 pa from the analysis of p and s wave displacement spectra respectively the retrieved spectral source parameters for the investigated events agree well with the results of earlier research we have also shown that our local waveform inversion method applied in this study is suitable to estimate the earthquake source mechanism for low magnitude events using local waveforms exclusively the moment tensor computed for the mainshock from local waveform data shows a strike slip mechanism with a north south striking and an east west striking nodal plane agreeing well with regional moment tensor solutions of other agencies the source mechanisms of four aftershocks with m l 2 were also successfully estimated three of them had strike slip mechanism very similar to that of the mainshock whereas the fourth one was a thrust faulting event with some strike slip component the subhorizontal p axis struck about northeast southwest for both the mainshock and all the analyzed aftershocks coinciding with the general trend of the compressional stress field in the epicentral region

a 14 000 year environmental change history revealed by mineral magnetic data from white lake new jersey usa abstract the increasing use of magnetic parameters as a proxy for environmental change necessitates the understanding of processes that link magnetic properties of sediments especially organic rich lake sediments and environmental change to explore the magnetic mineral paleoenvironment link we have recovered a 14 000 yr mineral magnetic record from white lake a hardwater lake containing organic rich sediments in northwestern new jersey usa pre 14 ka 1 ka 1000 cal yr bp sediments are dominated by clays and the magnetic variations of the clays recorded the deglaciation process the initial development of the lake and the stabilization of the watershed the rapid increase in organic matter and carbonate around 14 ka likely marks the bolling warming event the marl sediments were deposited from 14 to 11 ka and displayed a continued decline in magnetic mineral concentration which indicates increasing marl precipitation in the lake and stabilization of the watershed by vegetation growth the holocene gyttja dominated sediments generally have weak magnetizations however yellowish marl layers in the holocene sediments display strong magnetizations the strong magnetization of marl layers at 1 3 3 0 4 4 and 6 1 ka probably resulted from oxidation of the precipitated marl sediments near to shore which were then eroded transported and redeposited during periods of low lake levels this study demonstrates that multiple magnetic parameters can provide a more detailed and robust interpretation of environmental change than lithologic data alone

a multi methodological approach to reconstruct the configuration of a travertine fissure ridge system the case of the cukor quarry suttő gerecse hills hungary abstract travertines are continental carbonates that precipitate from spring waters mainly due to co2 degassing they are widely quarried as building stone which has led to numerous often abandoned travertine quarry outcrops these and other outcrops however merely represent the surface expressions of the complex architecture of travertine bodies and their deep rooted feeding systems integration of field observations and geochemical analyses with crucial subsurface geophysical data is required in order to fully understand travertine systems and their relationship to the local geological framework such a multi methodological approach is illustrated here for the case of the abandoned cukor quarry radio magnetotelluric rmt and electrical resistivity tomography ert surveys provide unique insights into local tectonics geobody architecture and the topography preceding travertine deposition altogether the lens shaped isolated domal geobody with spring proximal lithofacies and subvertical bedding in addition to the contrasting geochemistry and age with surrounding travertine enabled the unequivocal reconstruction of the dismantled cukor fissure ridge this study illustrates the high potential of this multi methodological approach on poorly exposed strongly weathered quarried and tectonically deformed travertine bodies and provides information on the complex feeding system beneath travertine deposits their reconstruction can be interpreted in light of the neo tectonic expression of regional uplift helps to complete the regional tectonic history and provides insights into older landscapes that lack preservation or would no longer be immediately recognized at the surface

environmental magnetism of brackish water sediments from lake tougou ike on the japan sea coast abstract we made rock magnetic measurements of core sediments from a brackish water lake on the japan sea coast lake tougou ike in tottori prefecture the core samples mostly consist of non glacial varved sediments and massive clay and silt including volcanic ash layers we measured low field magnetic susceptibility anhysteretic remanent magnetization arm and isothermal remanent magnetization irm of discrete samples at about 10 cm interval these magnetic concentration parameters show clear correlation with lithology of the sediments in particular sandy parts of the non glacial varves are suggested to contain greater amounts of coarse grained magnetite several horizons within the non glacial varves are characterized with significantly high values of coercivity parameters corresponding with intercalations of thin mud layers thermal demagnetization experiments of three component irms and measurements of hysteresis parameters indicate presence of hematite at these horizons factor analysis of the magnetic parameters combined with mineral magnetic data revealed a characteristic component contributed by the magnetic concentration parameters and the feldspar content which is interpreted as representing detrital input of volcaniclastic materials it is suggested that coercivity parameters would be particularly useful for detecting detrital inputs and estimation of their origin