structure and evolution of the 22 february 1993 toga coare squall line organization mechanisms inferred from numerical simulation abstract mechanisms responsible for meso and convective scale organization within a large tropical squall line that occurred on 22 february 1993 during the tropical ocean global atmosphere coupled ocean atmosphere response experiment are investigated using a three dimensional numerical cloud model the squall line occurred in an environment typical of fast moving tropical squall lines characterized by moderate convective available potential energy and moderate to strong vertical shear beneath a low level jet with weak reverse vertical shear above a well simulated aspect of the observed squall line is the evolution of a portion of its leading convective zone from a quasi linear to a three dimensional bow shaped structure over a 2 h period this transition is accompanied by the development of both a prominent mesoscale vortex along the northern edge of the 40 60 km long bow shaped feature and elongated bands of weaker reflectivity situated rearward and oriented transverse to the leading edge within enha

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

sinkhole formation mechanisms and geostatistical based prediction analysis in a mantled karst terrain abstract efforts to evaluate sinkhole formation and quantify the controlling factors are hindered by the lack of historical observations or coarse resolution datasets in many areas we applied recent advances in gis based sinkhole mapping and spatial statistics to comprehensively investigate the factors controlling sinkhole formation in the mantled karst setting of dougherty county georgia sinkholes form at varying spatial and temporal scales within the test site a three stage methodology was conducted firstly 275 sinkholes that formed or were enlarged between 1999 and 2011 were detected by comparing the results of sinkhole inventories derived from two dems acquired in 1999 and 2011 additionally a lidar dem 1 m resolution was used to gather a spatially detailed sinkhole inventory of 3412 sinkholes the sinkhole inventory data was converted into sinkhole density maps for subsequent analyses ordinary least squares ols and geographically weighted regression gwr spatial statistical models were applied to quantify the impact of controlling factors on sinkhole density controlling factors included geologic hydrologic anthropogenic hydrogeologic and geomorphologic variables for the two sinkhole inventory datasets analyzed overburden thickness aquifer fluctuations and proximity to fractures streams and wetlands were the most influential controlling factors on sinkhole formation gwr p values

characterization of hematite α fe2o3 goethite α feooh greigite fe3s4 and pyrrhotite fe7s8 using first order reversal curve diagrams 1 first order reversal curve forc diagrams have become a standard tool in rock magnetism yet magnetite is the only magnetic mineral that is well characterized using forc diagrams we present forc diagrams for predominantly single domain sd synthetic aluminous hematite a fe2 xalxo3 and goethite a feal ooh and natural greigite fe3s4 and pyrrhotite fe7s8 to constrain interpretation of forc diagrams from natural samples hematite and goethite have low spontaneous magnetizations and negligible magnetic interactions while greigite and pyrrhotite have higher spontaneous magnetizations and can have strong magnetic interactions the coercivity of hematite systematically increases with al content only for samples produced using the same synthesis method but it is variable for samples produced with different methods even for similar al content this precludes use of magnetic coercivity alone to quantify the al content of natural hematites goethite has much higher coercivity than hematite for all measured samples sd and superparamagnetic sp behavior is common in natural greigite samples with peak coercivities ranging from

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

sinkhole swarms from initiation to stabilisation based on in situ high resolution 3 d observations abstract we study in this paper the evolution of sinkhole fields along the dead sea coastal plains from initiation to stabilisation the prevailing hypothesis attributes their formation to the dissolution of a buried halite layer by groundwater but fails to explain their evolution in some places and their stability in others based on thirteen years of high resolution laser scanning and field surveys we trace a complete evolutionary cycle of sinkholes and show that the prevailing theory explains only the first out of a four stage cycle we show that following the formation stage an acceleration phase begins when the sinkholes interact with the drainage system a deepening and spatial localisation phase ensues then some parts of the field cease to expand leading to a fourth stage of stabilisation we further show that during their embryonic stage sinkhole development is limited due to a lack of connectivity between the surface and subsurface hydrological processes but as this connectivity evolves the development rate increases up to three orders of magnitude moreover observations show a high correlation with hydrological seasonality the most active field demonstrated a development rate of 13 540 m 3 month during the wet season in contrast to a rate of 1010 m 3 month during the dry season these measurements and observations allow us to propose a new theoretical model for sinkhole swarm development from initiation to stabilisation with linkage to seasonality and hydrology

the influence of loess cave development upon landslides and geomorphologic evolution a case study from the northwest loess plateau china abstract loess caves landslides collapses bank erosion and soil erosion which are independently and interactively shaping the modern loess landscape are widely distributed across the chinese loess plateau the study area is located in a small watershed in huining county gansu province which is one of the areas with the strongest development of loess caves across the loess plateau this area is an ideal site for studying geological hazards and geomorphic evolution on the loess plateau seventeen landslides and 176 loess caves with a density of 887 units km2 were investigated with a uav unmanned aerial vehicle and mapped by gis geographic information system using high resolution uav images and topographic data we carried out an interpretation of loess caves bank erosion and landslides studied the spatial distribution and developmental patterns of loess caves landform morphology and the relationship between loess caves and landslides based on gis spatial analysis mathematical statistics and field surveys and analyzed the influence of loess microtopography on slope landforms finally six typical evolutionary models of soil erosion loess cave development landslide occurrence barrier dam formation are preliminarily proposed the primary slope stage early cave stage accelerated cave stage cave connecting stage landslide creeping stage and landslide dam forming stage this study is a useful exploration and an attempt to reveal the influence of loess cave development on slope stability and disaster chain effects

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

subsidence rings and fracture pattern around dolines in carbonate platforms implications for evolution and petrophysical properties of collapse structures abstract this work focuses on the study of collapse dolines which are the most expressive collapse structures in carbonate rocks and their relations with preexisting and syn collapse fractures the study area has two fracture sets that were formed before folding early n s e w and late ne sw nw se striking sets which concentrate most of the dissolution in the region and allow the formation of the dolines we define subsidence rings as the circular and ellipsoidal concentric zones around collapse structures which are subjected to subsidence due to major collapses and represent locations where new fractures are formed in these subsidence rings the downfaulted topography plunges towards the doline center and reaches more than 10 m in relation to unaffected areas away from dolines the topographic data indicate that the mean radius of the combined rings is twice the radius of the collapse which corresponds to the closed depression due to failure and downfall of blocks the subsidence process enlarges links preexisting fractures and forms a new set of semicircular concentric opening mode fractures here named collapse fractures increases in the apertures and densities of these fractures occur towards the dolines which increases fracture porosity around collapse structures fractures are reactivated as normal faults close to the main collapse at the doline edge this increase in fracture intensity could represent an indicator of permo porous quality improvement in these areas further this fracturing increases structural instability raising the risk of accidents in areas built on soluble carbonate rocks since the affected area may be much larger than previously predicted subsidence rings around collapse dolines could merge with other rings from neighboring collapse structures and potentially increase porosity and permeability as well as linking areas in carbonate reservoirs

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

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

aeolian dust dynamics in central asia during the pleistocene driven by the long term migration seasonality and permanency of the asiatic polar front loess paleosol sequences preserve detailed archives of climate change reflecting the dynamics of aeolian dust sedimentation and the paleodust content of the atmosphere the detailed investigation of particle size distributions psds of windblown sediments is an increasingly used approach to assess the paleorecord of aeolian dust dynamics the central asian loess belt offers the potential to reconstruct pleistocene atmospheric circulation patterns along an adjacent west east transect within interior eurasia through granulometric studies in this study we present the aeolian dust record of the loess sequence at remisowka se kazakhstan which reflects a detailed signal of glacial interglacial climate and atmospheric dynamics in central asia on the basis of radiocarbon and amino acid geochronologic data long term semicontinuous trends in the aeolian dust record of the last glacial cycle are observed and interpreted to reveal their paleoclimate signal in consideration of the modern synoptical atmospheric circulation patterns and aeolian dust transport in central asia it is likely that the observed trends reflect the long term migration seasonal duration and permanency of the polar front during the late pleistocene previously published models which focused on the reciprocal glacial interglacial influence of the zonal westerlies and the asiatic high on the aeolian dust transport in central asia were overly simplified and should be modified to include the major influence of the asiatic polar front as the polar front activity is intimately connected with the development and position of the interhemispherically active high level planetary frontal zone hpfz the presented data give insight to long term aeolian dust dynamics and climate variability of interior eurasia which are linked with interhemispheric climates

quantitative estimates of pedogenic ferromagnetic mineral formation in chinese loess and palaeoclimatic implications abstract the quasi continuously deposited loess sediments of the central chinese loess plateau constitute one of the most complete and long lasting records of quaternary palaeoclimate on land much of this record has been uncovered by measurement and interpretation of the magnetic properties of the loess the polarity of natural remanent magnetization has provided absolute age dates by correlation with the geomagnetic polarity time scale magnetic low field susceptibility has been used to reconstruct the cyclic changes of pleistocene palaeoclimates although the origin of the signal is still poorly understood from comparison with the 10 be concentration throughout the sequence we are able to determine the contributions to susceptibility from inherited and authigenic sources for the last 130 ky since the production of authigenic magnetite is directly related to regional precipitation annual palaeoprecipitation rates can be calculated palaeoprecipitation rates similar to present day rates are derived for oxygen isotope stage 5 including the last interglacial in contrast cold periods corresponding to oxygen isotope stages 2 and 4 experienced negligible precipitation the beginning and end of the time interval represented by oxygen isotope stage 3 however was characterized by short episodes when precipitation exceeded the holocene average

automated delineation of karst sinkholes from lidar derived digital elevation models abstract sinkhole mapping is critical for understanding hydrological processes and mitigating geological hazards in karst landscapes current methods for identifying sinkholes are primarily based on visual interpretation of low resolution topographic maps and aerial photographs with subsequent field verification which is labor intensive and time consuming the increasing availability of high resolution lidar derived digital elevation data allows for an entirely new level of detailed delineation and analyses of small scale geomorphologic features and landscape structures at fine scales in this paper we present a localized contour tree method for automated extraction of sinkholes in karst landscapes one significant advantage of our automated approach for sinkhole extraction is that it may reduce inconsistencies and alleviate repeatability concerns associated with visual interpretation methods in addition the proposed method has contributed to improving the sinkhole inventory in several ways 1 detection of non inventoried sinkholes 2 identification of previously inventoried sinkholes that have been filled 3 delineation of sinkhole boundaries and 4 characterization of sinkhole morphometric properties we applied the method to fillmore county in southeastern minnesota usa and identified three times as many sinkholes as the existing database for the same area the results suggest that previous visual interpretation method might significantly underestimate the number of potential sinkholes in the region our method holds great potential for creating and updating sinkhole inventory databases at a regional scale in a timely manner

simulation experiment on sinkhole formation caused by soils disintegration and the advance forecasting of sinkhole risk sinkholes are a common geological hazard around the world however it is difficult to carry out the associated indoor simulation experiments because of the complicated factors involved our previous research showed that sinkholes in the aerated zone caused by soil disintegration exhibit accurate critical conditions therefore the kind of sinkhole formation is simulated in the paper before the simulate experiment the critical value of the disintegration of clay samples is tested which helps to control the simulation conditions with a designed simulation apparatus soil disintegration was conducted 70 times from october 23 2017 to june 1 2018 and a sinkhole formed this experiment results indicate two developmental laws of sinkholes forming in the aerated zone one is the forming process which has three stages soil void formation soil void expansion and roof collapse second is that the two conditions water content is less than the critical value and contact between water and soil causing the sinkhole formation at the forming two conditions are clear and can easily be monitored by the associated factors in the field where sinkholes have occurred or are about to occur according to the principle another simulation experiment was carried out as a result an advanced prediction of a sinkhole is achieved in the aerated zone

the different climatic response of pedogenic hematite and ferrimagnetic minerals evidence from particle sized modern soils over the chinese loess plateau abstract in recent years increasing interest in loess studies has focused on qualitative and quantitative paleoclimatic reconstruction using the imperfect antiferromagnetic mineral hematite however the linkage between the hematite formation and climatic variables remains controversial here we present the results of a comprehensive investigation of the magnetic properties and statistical analysis of a suite of clay and silt fractions of modern soil samples from 179 sites across the chinese loess plateau clp and adjacent regions our objective was to clarify the relationships between modern climatic variables and pedogenic hematite as well as pedogenic ferrimagnetic minerals first order reversal curve measurements were also conducted on representative particle sized subsamples from a n s transect to understand the differences in magnetic mineralogy between the two fractions our results show that pipette extraction separates the fine grained superparamagnetic sp and most of the single domain sd magnetic grains into the clay fraction and that the remaining silt fraction displays the magnetic properties of coarse pseudo single domain psd or a mixture of multidomain md psd and a few sd particles only the pedogenic clay fraction shows a strong correlation with climatic variables the application of redundancy analysis helps to distinguish the climate variables controlling the formation of ferrimagnetic minerals and hematite during pedogenesis on the clp pedogenic ferrimagnetic minerals are sensitive to mean annual precipitation while pedogenic hematite formation is preferentially dependent on mean annual temperature the confirmation of the temperature dependent nature of hematite on the clp provides a new possibility for quantitatively reconstructing the paleotemperature history of chinese loess paleosol sequences

critical altitudinal shift from detrital to pedogenic origin of the magnetic properties of surface soils in the western pamir plateau tajikistan

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

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

the influence of urbanization of sinkhole development in central pennsylvania the karsted limestone valleys of central pennsylvania contain two populations of sinkholes solution sinkholes occur in the champlainian limestone units along the margins of the valleys solution sinkholes are permanent parts of the landscape and although a nuisance to construction do not present other problems the second population is the suffosional or soil piping sinkholes these occur on all carbonate rock units including the beekmantown and gatesburg dolomites that comprise the two principal carbonate aquifers in the valley suffosional sinkholes are the principal land use hazard suffosional sinkholes are transient phonomena they occur naturally but are exacerbated by runoff modifications that accompany urbanization suffosional sinkholes are typically 1 5 2 5 m in diameter depending on soil thickness and soil type the vertical transport of soil to form the void space and soil arch that are the precursors to sinkhole collapse is through solutionally widened fractures and cross joints and less often through large vertical openings in the bedrock the limited solution development on the dolomite bedrock combined with soil thickness seldom greater than 2 m limits the size of the sinkholes all aspects of suffosional sinkhole development are shallow processes transport piping void and arch formation and subsequent collapse take place usually less than 10 m below the land surface factors exacerbating sinkhole development include pavement street and roof runoff which accelerates soil transport such seemingly minor activities as replacing high grass and brush with mowed grass is observed to accelerate sinkhole development dewatering of the aquifer is not a major factor in this region

magnetism of chinese loess deposits summary the age of chinese loess deposits has long been disputed biostratigraphical and earlier magnetostratigraphical investigations placed the entire loess formation within the pleistocene and ascertained a maximum loess age of about 1 2 myr a new collection of nearly 500 samples from a natural outcrop and a borehole section near lochuan lat 35 8 n long 109 2 e shaanxi province has been dated by magnetic stratigraphy thermal cleaning of the natural remanent magnetization nrm removes a strong secondary component of viscous origin along the present geomagnetic field which resides largely in magnetite the characteristic nrm component is due to haematite which is thought to be of chemical origin rhythmical intensity variations of nrm and initial susceptibility depend on the loess lithology and may reflect climatic changes during loess deposition the palaeomagnetic results are consistent between the two sections and yield a clearly defined magnetic polarity zonation the brunhes matuyama boundary and the jaramillo subchron have been positively identified in both outcrops at exactly the same stratigraphic level the olduvai subchron has been found in the borehole section which records the entire loess sequence most probably the formation of chinese loess began shortly after the matuyama gauss polarity transition therefore a late pliocene age of about 2 4 myr is assigned to the oldest loess sediments measured

spatial and altitudinal variations in the magnetic properties of eolian deposits in the northern tibetan plateau and its adjacent regions implications for delineating the climatic boundary abstract delineating the climatic boundary i e of precipitation and temperature in the northern tibetan plateau and along its margins is important for understanding the dynamics of global atmospheric circulation and the processes of dust production in central asia to date however meteorological data are scarce for this vast region which limits our understanding of regional climatic patterns and past climatic changes in eurasia in the present study we use a synthesis of both new and published rock magnetic data from the late pliocene the last glacial interglacial cycle and modern eolian sediments to identify the climatic boundary in the northern tibetan plateau and its adjacent areas the results demonstrate that eolian deposits under different environmental scenarios exhibit a clear contrast in the type and grain size distribution of magnetic minerals with the transition from humid to arid climatic regimes a gradual shift from magnetic minerals of predominantly pedogenic origin to predominantly detrital origin can be observed in the surface soils the spatial and altitudinal variations in the magnetic properties of surface soils reveal a distinct boundary of pedogenic intensity in the eastern qilian mountains the western pamir plateau and the northern tianshan mountains the inferred variations in pedogenic intensity combined with analysis of the available meteorological data demonstrate that the pedogenic boundary represents a critical climatic boundary between sub humid to semi arid and arid regions in the northern tibetan plateau and the adjacent regions stronger pedogenesis occurs in surface soils at higher altitudes on the windward side of the major mountains of the northern tibetan plateau supporting the conclusion that precipitation rather than temperature exerts the dominant effect on the magnetic enhancement of surface soils in addition a comparison of several late pliocene pleistocene and last glacial interglacial loess red clay sequences suggests that the modern spatial pattern of the climatic gradients in the northeastern tibetan plateau and the adjacent regions has been maintained since at least the late pliocene or early pleistocene moreover the results demonstrate that during the warm and humid interglacial periods a steepened rainfall gradient occurred in the northern tibetan plateau and its adjacent regions in the future detailed rock magnetic investigations of eolian deposits or surface soils could provide new insights into the dynamics of atmospheric circulation and the natural boundary conditions for paleoclimate modeling in the northern tibetan plateau

scale free distribution of dead sea sinkholes observations and modeling there are currently more than 5500 sinkholes along the dead sea in israel these were formed due to the dissolution of subsurface salt layers as a result of the replacement of hypersaline groundwater by fresh brackish groundwater this process has been associated with a sharp decline in the dead sea water level currently more than one meter per year resulting in a lower water table that has allowed the intrusion of fresher brackish water we studied the distribution of the sinkhole sizes and found that it is scale free with a power law exponent close to 2 we constructed a stochastic cellular automata model to understand the observed scale free behavior and the growth of the sinkhole area in time the model consists of a lower salt layer and an upper soil layer in which cavities that develop in the lower layer lead to collapses in the upper layer the model reproduces the observed power law distribution without involving the threshold behavior commonly associated with criticality

a numerical study of a squall line over the taiwan strait during tamex iop 2 abstract a two dimensional numerical cloud model was used to investigate a squall line that occurred over the taiwan strait on 16 may 1987 during tamex taiwan area mesoscale experiment this squall line illustrated multicellular behavior as revealed by many doppler analyses the simulated squall line produced 13 new cells successively in a 6 h simulation thus maintaining itself in a long lasting state the simulation result recaptured many of the interesting features also observed the air in the front to rear inflow was ingested into the squall line system primarily from the low levels in front of the system and accelerated upward and backward over a surface pool of cold air in the system relative frame beneath this front to rear flow a rear to front current developed between 2 and 4 km in altitude it descended into the cold pool near the surface part of this descending air moved forward toward the gust front region and part of it moved backward the relative pressure maximum coincided with the co

multidisciplinary approach for paleoenvironmental reconstruction in loess paleosol studies of the darai kalon section southern tajikistan the available data on the loess paleosol formation in south tajikistan illustrate the completeness of climatostratigraphic records however studies with a multidisciplinary approach have not been practically used for paleoenvironmental reconstructions this study partially corrects the lack of data on paleolandscape evolution in the loess area of pamir and tien shan piedmonts darai kalon serves as a key section embracing the upper part of the matuyama chron and the entire brunhes chron high resolution magnetic susceptibility record shows that during the brunhes epoch the climate cycles reflected by the central asian loess paleosol succession can be correlated to the deep sea oxygen isotope curve the combination of pedological and palynological material is particularly useful for mutual interpretation lithological and mineralogical data essentially extend our understanding of pedogenetic and paleoclimatic dynamics the tendency of soil and paleoenvironmental evolution recorded in the darai kalon section can be associated with subtropical semi humid forest and forest steppe landscapes the variation of paleoclimatic parameters and paleovegetation type are characteristic of the contemporary vertical zone of cinnamon soils

mineral magnetic properties of surface soils and sands across four north african transects and links to climatic gradients 1 in light of their earlier success in characterizing and differentiating soils sediments and atmospheric particulates magnetic measurements were carried out on samples of north african surface soils and sands the main aims were to document spatial variations in magnetic properties explore their possible links to climatic gradients and their likely basis and thereby help to differentiate potential sources for sahara sahel derived dusts samples were collected along four broadly north to south orientated transects located in egypt niger mali and benin and southern togo these transects cover major climatic gradients ranging from hyper arid to tropical across the rainfall range spanned by the niger and mali transects 800 mm yr there are significant north to south gradients in magnetic mineral concentrations this is seen most clearly in the concentrations of the finest ferrimagnetic minerals magnetite maghemite which are strongly represented in the clay fraction concentrations of the imperfect antiferromagnetic minerals predominantly haematite also increase with increasing rainfall by analogy with studies spanning a similar rainfall gradient in areas of more uniform lithology we suggest that the most likely cause for these trends is increased chemical weathering linked to the progressively wetter climate across the sahara sahel transition within the set of samples from egypt rainfall 100 to 5 mm yr there is a marked gradient in the coercivity of remanence in the antiferromagnetic minerals present with coercivity increasing southwards paralleling the trend toward increasing aridity given the strong spatial discrimination demonstrated especially in the niger and mali transects these potentially climate linked gradients hold out the promise of discriminating between dust source regions

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

westerlies asia and monsoonal asia spatiotemporal differences in climate change and possible mechanisms on decadal to sub orbital timescales abstract the westerlies dominated climatic regime wdcr in the present interglacial period was proposed because precipitation moisture variations between arid central asia and mid latitude monsoonal asia are out of phase or anti phased on different timescales during the holocene in this study we first review the development of the theoretical framework of the wdcr and then outline the boundary of its core area from the caspian sea in the west to the western hexi corridor in the east with the northern and southern limits coinciding with the domain of arid central asia next we present a synthesis of multiple lines of evidence for the occurrence of the wdcr on multi millennial sub orbital herein to decadal timescales during the holocene finally we examine the possible physical mechanisms responsible for the wdcr we find that external factors insolation changes induced by orbital factors generated the wdcr on a sub orbital timescale whereas a circum global teleconnection silk road pattern was the most significant factor responsible for the wdcr on centennial and decadal timescales the study provides a comprehensive summary of the development of our knowledge of the wdcr over the past several decades together with a tentative theoretical framework for understanding climatic and environmental changes within its region of influence in addition it forms a scientific basis for environmental management and ecological restoration in this arid region in the context of global warming

mineral magnetic properties of loess paleosol couplets of the central loess plateau of china over the last 1 2 myr 1 we have conducted a multiparameter investigation of 15 loess paleosol couplets s0 l1 to s14 l15 from the jiaodao section in the central loess plateau of china using environmental magnetic approaches coupled with soil science techniques the magnetic parameters display systematic variations that seem to be closely related to paleoclimate variations and intensity of pedogenesis high temperature susceptibility curves of paleosols show a generally decreasing trend in reversibility from the base of the lishi formation to the holocene black loam possibly indicating a decrease in weathering intensity this may reflect a long term increase in aridity and or a general long term cooling trend of the interior of the asian continent from 1 2 ma to the present several samples display wasp waisted hysteresis loops these are most pronounced in moderately enhanced paleosols less pronounced in the practically unaltered loess and subdued in the well developed paleosols but wasp waistedness reappears in the most developed paleosols this wasp waistedness sequence suggests that the composition concentration and grain size of magnetic minerals all contribute to the hysteresis behavior of samples from the studied loess paleosol sequence but each factor has a different effect at different stages of pedogenesis

the influence of particle size variations on the magnetic properties of sediments from the north eastern irish sea this paper considers the magnetic properties of a range of recent and contemporary sediments from the north eastern part of the irish sea principal component ordinations of the results show a close link between magnetic property variations and particle size the magnetic properties of a subset of samples particles sized by a combination of sieving and pipette analysis confirm that variations in ferrimagnetic magnetite grain size parallel those in particle size despite the fact that the magnetic grains in the fine grades have diameters 1 2 orders of magnitude smaller than those of the particle size fraction in which they occur this is best explained by postulating that the fine magnetic grains occur in the clay fraction but are present in declining concentrations in the coarser grades up to 4o as an artefact of the pipette method most samples have a biomodal distribution of magnetic minerals with a coarse mode associated with heavy minerals in the sands or coarse silts and a fine mode in the clays magnetic susceptibility x and saturation isothermal remanent magnetization sirm largely pick out the coarse mode where present anhysteretic remanent magnetization arm largely picks out the fine mode the results open up the possibility of normalizing samples from these environments for particle size and more specifically clay content by means of arm or arm x values the most likely source for the uniform and almost exclusive stable single domain magnetite which dominates the magnetic properties of the clays is thought to be bacterial magnetosomes the measurements as a whole do not appear to hold much promise for discriminating sediment source types

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

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

dynamical influence of microphysics in tropical squall lines a numerical study abstract based on environmental conditions of the 22 and 23 june squall lines during the convection profonde tropicale in 1981 copt81 experiment in west africa a series of numerical simulations are performed with a two dimensional nonhydrostatic cloud model to examine the dynamical effect of microphysics in tropical squall lines the role of ice phase microphysics strongly depends on ambient conditions for the environment of strong convective instability the ice phase is important regarding the system scale structure but is not important to the convective scale dynamics on the other hand the ice influence is crucial to the squall line convective system if the environment has a weak convective instability and is almost saturated at low levels

distribution and morphology of sinkholes triggered by flooding following tropical storm alberto at albany georgia usa abstract flooding of the flint river in july 1994 triggered the collapse of at least 312 sinkholes in the karstic dougherty plain at albany georgia we examined the distribution and morphology of these new sinkholes to evaluate the mode of formation to characterize early stages of the evolution of sinkhole form and to estimate the lowering of the surface associated with the development of new sinkholes eighty eight percent of sinkholes occur inside the limits of flooding especially in areas of sandy overburden and they often follow joint controlled linear trends sinkhole dimensions are log normally distributed with median values of circumference 5 7 m length 1 8 m width 1 6 m and depth 0 7 m asymmetry l w 1 2 cross sectional forms range from narrow cylinders to large bowls with many sinkholes having undercut sides flooding triggered the formation of sinkholes by saturating and liquefying overburden which caused soil arches to collapse and flow into cavities in bedrock the prevalence of sinkholes near the periphery of flooding suggests that drainage and loss of buoyant support as flood waters subsided may also have contributed to failure a volume ratio index is used to quantify the three dimensional geometric form of sinkholes initially small cylindrical shafts open over a bedrock joint followed by progressive slumping that leads to widening and increases in volume to a final bowl form estimates of the aggregate volume of overburden transported underground in flooded areas range from 7 990 to 11 130 m3 averaged over flooded areas this accounts for 0 26 to 0 37 mm km2 lowering of the surface based on a 500 year recurrence interval for the flood event values for lowering of the surface range from 0 52 to 0 74 mm per 1 000 years these values are an order of magnitude less than estimates of carbonate dissolution and suggest that transport of overburden underground is limited by triggering events

the loess record in southern tajikistan and correlation with chinese loess in the present study the chashmanigar loess soil sequence in southern tajikistan is studied this loess section has a paleomagnetic basal age of about 1 77 myr magnetic susceptibility color reflectance and grain size were systematically measured for closely spaced samples from the section paleosols consistently have a finer grain size distribution higher magnetic susceptibility redder color reflectance and lower dust sedimentation rate than loess horizons suggesting a colder drier and dustier environment during glacial periods than in interglacial periods the grain size record was tuned to variations in obliquity and precession of the earth s orbit the resulting magnetic susceptibility grain size and color reflectance time series all show well expressed astronomical periodicities during the pleistocene the mid pleistocene climate transition characterized by a shift of dominant climatic periods from 41 kyr to 100 kyr at about 1 0 0 8 myr is clearly documented in these proxy records comparison of the chashmanigar loess record with the lingtai loess section in china and the odp site 677 n 18 o record shows that during the entire pleistocene the climate cycles recorded by the central asian loess can be well correlated to the chinese loess and deep sea oxygen isotope records it is suggested that alternations of loess and soil horizons both in central asia and china could be basically forced by global ice volume variations although different wind systems have controlled the pleistocene loess transport and sedimentation in the two areas 2002 elsevier science b v all rights reserved

the origin typology spatial distribution and detrimental effects of the sinkholes developed in the alluvial evaporite karst of the ebro river valley downstream of zaragoza city ne spain three types of sinkhole have been mapped in a 50 km2 stretch of the ebro river valley downstream of zaragoza large collapse sinkholes large shallow subsidence depressions and small cover collapse sinkholes the sinkholes relate to the karstification of evaporitic bedrock that wedges out abruptly downstream giving way to a shale substratum twenty three collapse sinkholes up to 50 m in diameter by 6 m deep and commonly hosting saline ponds have been identified in the floodplain they have been attributed to the upward stoping of dissolutional cavities formed within the evaporitic bedrock by rising groundwater flows twenty four large shallow subsidence depressions were mapped in the floodplain these may reach 850 m in length and were formed by structurally controlled interstratal karstification of soluble beds halite or glauberite and gypsum by rising groundwater flow and the progressive settlement of the overlying bedrock and overburden sediments a total of 447 small cover collapse or dropout sinkholes have been recognized in a perched alluvial level along the southern margin of the valley these sinkholes result from the upward propagation of voids through the alluvial mantle caused by the downward migration of detrital sediments into dissolutional voids the majority of these sinkholes commonly 1 5 2 m in diameter are induced by human activities over the karstic bedrock there is a significant increase in sinkhole density downstream this is interpreted as being a result of the evaporitic bedrock wedging out and the convergence of the groundwater flow lines in the karstic aquifer the collapse sinkholes in this area locally with a probability of occurrence higher than 140 sinkholes km2 year cause substantial damage to the linear infrastructures buildings and agriculture and they might eventually cause the loss of human lives copyright 2006 john wiley sons ltd

case study of an unusually heavy rain event over eastern taiwan during the mei yu season abstract a heavy rain event during the mei yu season was observed over eastern taiwan on 28 may 2001 under a potentially unstable environment with high cape and copious moisture this event with an unusually high daily rainfall maximum of 307 mm was observed in the ilan area over northeastern taiwan the retrogression of a mei yu front over the nearby ocean collocated with a short wave trough provided favorable large scale conditions for the production of localized heavy rainfall latent heating was suggested to be responsible for the retrogression and the development of the mei yu front over the nearby ocean to the east of taiwan in addition to the large scale forcings the local circulations and local topography modulated the rainfall distribution over the ilan area during the daytime hours the strengthened onshore wind component due to the intensified mei yu frontal circulation and orographic lifting provided enhanced rising motion over the windward slopes of the mountain to produce the significan

doline probability map using logistic regression and gis technology in the central ebro basin spain in the surroundings of zaragoza karstification processes are especially intense in covered karst areas where fluvial terraces lie directly on tertiary evaporites since the beginning of quaternary these processes have lead to the development of collapse and subsidence dolines with a wide range of sizes which have significant economic impacts to reduce economic impact and increase safety a regional analysis of this phenomenon is needed for spatial management therefore a probability map of dolines was developed using logistic regression and geographic information system gis techniques this paper covers the selection of input data manipulation of data using the gis technology and the use of logistic regression to generate a doline probability map the primary variable in the doline development in this area is geomorphology represented by the location of endorheic areas and different terrace levels secondary variables are the presence of irrigation and the water table gradient

orographic effects on a squall line system over taiwan abstract a north south oriented multicellular squall line during the taiwan area mesoscale experiment s tamex intensive observation period 2 was studied using dual doppler radar data as it moved over the island of taiwan over the open ocean it moved eastward at a constant speed 15 5 m s 1 as the squall line encountered taiwan island s complex mountainous areas the leading edge moved slower in the mountain ridge areas than over the valleys as a result its orientation became approximately parallel to the terrain contours in the upper levels the eastward movement of the squall line aloft was less affected by the terrain compared to the low levels as a result the westward tilt of the rising motion at the front became less significant part of the system relative rear to front flow entered the rising branch of the storm s circulation as a result of orographic lifting as illustrated by the trajectory analysis and was enhanced by latent heat release the system relative rear to front flow did

evaluating and comparing methods of sinkhole susceptibility mapping in the ebro valley evaporite karst ne spain abstract multiple sinkhole susceptibility models have been generated in three study areas of the ebro valley evaporite karst ne spain applying different methods nearest neighbour distance sinkhole density heuristic scoring system and probabilistic analysis for each sinkhole type separately cover collapse sinkholes cover and bedrock collapse sinkholes and cover and bedrock sagging sinkholes the quantitative and independent evaluation of the predictive capability of the models reveals that 1 the most reliable susceptibility models are those derived from the nearest neighbour distance and sinkhole density these models can be generated in a simple and rapid way from detailed geomorphological maps 2 the reliability of the nearest neighbour distance and density models is conditioned by the degree of clustering of the sinkholes consequently the karst areas in which sinkholes show a higher clustering are a priori more favourable for predicting new occurrences 3 the predictive capability of the best models obtained in this research is significantly higher 12 5 82 5 than that of the heuristic sinkhole susceptibility model incorporated into the general urban plan for the municipality of zaragoza although the probabilistic approach provides lower quality results than the methods based on sinkhole proximity and density it helps to identify the most significant factors and select the most effective mitigation strategies and may be applied to model susceptibility in different future scenarios

probabilistic sinkhole modelling for hazard assessment a method for quantitatively assessing sinkhole susceptibility spatial probability and hazard spatio temporal probability has been developed and independently tested in a 50 km2 sector of the ebro valley evaporite karst three genetic types of sinkholes have been mapped in the floodplain and a terrace surface 947 small cover collapse sinkholes type 1 terrace large collapse sinkholes type 2 floodplain and large subsidence depressions type 3 floodplain the type 1 sinkhole inventory includes two temporal populations 447 sinkholes formed before 24 november 2005 and 500 between that date and 2 november 2006 sinkhole susceptibility models have been elaborated analysing the statistical relationships between the sinkholes of the 2005 inventory and a set of potential conditioning factors the independent evaluation validation of the susceptibility models by means of several strategies random sequentially excluded and temporal has allowed us to select the most significant variables for each sinkhole type and assess quantitatively the quality of models which are reasonable for the three sinkhole types validation has also provided information on the contribution of specific variables and the effect of changing their accuracy to the prediction capability of models susceptibility models for type 3 sinkholes have been validated satisfactorily with the 2006 sinkhole inventory temporal validation the best susceptibility model has been transformed into a hazard map considering the frequency of sinkholes that occurred in each susceptibility class between 2005 and 2006 as well as their average size the susceptibility and hazard models obtained could be used as an objective basis for the application of mitigation measures either of preventive or corrective nature copyright 2008 john wiley sons ltd

inter profile correlation of the chinese loess paleosol sequences during marine oxygen isotope stage 5 and indications of pedogenesis abstract low field magnetic susceptibility has been widely used to determine the pedostratigraphy of the chinese loess paleosol sequences however uncertainties remain in correlating between the loess magnetic susceptibility and the marine oxygen isotope records because susceptibility variations are affected by both global and local paleoclimatic changes to provide a more sound paleoclimatic interpretation of magnetic susceptibility variations age models across marine oxygen isotope stage mis 5 for the jiuzhoutai jzt and yuanbao yb sections western chinese loess plateau were constructed through an integrated approach by linking the major pedostratigraphic boundaries of the loess profiles to the specmap oxygen isotope curve and by correlating relative magnetic paleointensity records with both the sint800 global paleointensity stack from marine sediments and 36cl records from the grip ice core results indicate good correlation of sirm60 mt a residual remanence of saturation isothermal remanent magnetization after a 60 mt alternating field demagnetization variations between these two sites which agree well with fluctuations in subtropical atlantic sea surface temperatures all cooling events recorded by ice core and atlantic marine sediments within mis5 have counterparts in sirm60 mt sirm60 mt is partially controlled by the degree of low temperature oxidation which is strongly temperature dependent however strong pedogenesis can decrease sirm60 mt due to further oxidation of partially oxidized magnetites above some critical points therefore we propose that sirm60 mt is best suited to record paleotemperature changes in loess profiles from the western chinese loess plateau where pedogenesis is the weakest furthermore by inter profile correlation between the yb and jzt sections we note that the seemingly uniform sub paleosol unit with a broad susceptibility peak previously assigned to mis5c between 34 4 and 37 4 m in the yb profile actually consists of two independent units lower part of s1l1 mis5b and s1s2 mis5c this indicates that susceptibility values can be strongly affected by local factors e g mainly precipitation therefore beside the simplistic traditional paleoclimatic interpretation of variations in loess susceptibility involving only cold dry and warm humid scenarios cold humid and warm dry scenarios should also be considered

development and validation of sinkhole susceptibility models in mantled karst settings a case study from the ebro valley evaporite karst ne spain abstract a preliminary sinkhole susceptibility analysis has been carried out in a stretch 50 km 2 in area of the ebro valley alluvial evaporite karst ne spain a spatial database consisting of a sinkhole layer and 27 thematic layers related to causal factors was constructed and implemented in a gis three types of sinkholes were differentiated on the basis of their markedly different morphometry and geomorphic distribution large subsidence depressions 24 large collapse sinkholes 23 and small cover collapse sinkholes 447 the susceptibility models were produced analysing the statistical relationships between the mapped sinkholes and a set of conditioning factors using the favourability functions approach the statistical analyses indicate that the best models are obtained with 6 conditioning factors out of the 27 available ones and that different factors and processes are involved in the generation of each type of sinkhole the validation of two models by means of a random split strategy shows that reasonably good predictions on the spatial distribution of future dolines may be produced with this approach around 75 of the sinkholes of the validation sample occur on the 10 of the pixels with the highest susceptibility and about 45 of the area can be considered as safe

multiple origins and interpretations of the magnetic susceptibility signal in chinese wind blown sediments abstract in most chinese loess paleosol sequences high magnetic susceptibility values are found in the soil horizons with low values in the loess layers the susceptibility signal has been widely used as a proxy climatic indicator however both the causes and mechanisms which control susceptibility still remain controversial our recent studies challenge some earlier interpretations of the magnetic susceptibility signal in chinese wind blown sediments first the prevailing hypothesis of pedogenic origin cannot totally account for the susceptibility variations in many sections second in some cases the principal carrier of the magnetization seems not to be the ultrafine pedogenic minerals rather coarse lithogenic magnetic minerals derived from local sources can also contribute significantly to the susceptibility signal finally not all the chinese soils have higher susceptibility values than that of loess or sand layers opposite relationships do exist it is concluded that the source and causes of susceptibility may be different from site to site or even at different times at a given site any single hypothesis cannot completely account for the susceptibility variations in the chinese loess plateau and its surrounding regions besides the previous explanations of carbonate leaching pedogenic processes and organic decomposition the contribution of source materials to magnetic susceptibility must also be taken into account

comparison of laser grain size analysis with pipette and sieve analysis a solution for the underestimation of the clay fraction classically the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method based on the stokes sedimentation rates for the fine fractions results from the two methods are compared with results from laser diffraction size analysis which is based on the forward scattering of monochromatic coherent light from a point of view of laboratory efficiency the laser sizing technique is far superior accuracy and reproducibility are shown by measurements on certified materials it appears that laser grain size measurements of certified materials correspond very well with the certificated measurements tests were also done on a set of randomly selected sediments of fluvial aeolian and lacustrine origin except for the 2 m clay fraction there is a coarsening of the mean diameter of one to two size classes 0 25 caused by the non sphericity of the particles the platy form of the clay particles induces considerable differences eight size classes between pipette and laser measurements the 2 m grain size defined by the pipette method corresponds with a grain size of 8 m defined by the laser particle sizer for the studied sediments using a higher grain size level for the clay fraction when laser analysis is applied enables workers in the geological and environmental field to compare classical pipette analysis with a laser sizing technique

moisture evolution in central asia since 26 ka insights from a kyrgyz loess section western tian shan abstract central asia ca is located in the hinterland of the eurasian continent and faces an extreme risk of continued aridification under the current global warming trend to predict future climate change in ca paleoclimate studies provide essential references however the mechanisms underlying climate changes in ca remain relatively poorly known here we investigate moisture variations in ca as recorded in a 6 m loess section in the western tian shan kyrgyzstan which has accumulated since 26 ka based on the radiometric ams 14c dating we reconstructed the evolution of the wind regime and moisture conditions in the western tian shan with a modified grain size index gsim and a new l proxy l while the frequency dependent magnetic susceptibility fd redness a and yellowness b did not provide reliable paleoclimatic indicators due to weak pedogenesis and other controlling factors the gsim records demonstrated a precipitation maximum in summer before 15 ka shifting to a maximum in spring after 15 ka probably associated with large scale modulation of the latitudinal climatic zones and atmospheric circulation in response to retreat of the northern hemisphere ice sheets based on the l records we place emphases on the important role of temperature modulated evaporation in moisture evolution across ca however this has only influenced moisture evolution in spring and summer with little effect on winter moisture conditions moreover the l records may also indicate that atmospheric humidity can partly affect the long term effective moisture variations

applying a weighted random forests method to extract karst sinkholes from lidar data summary detailed mapping of sinkholes provides critical information for mitigating sinkhole hazards and understanding groundwater and surface water interactions in karst terrains lidar light detection and ranging measures the earth s surface in high resolution and high density and has shown great potentials to drastically improve locating and delineating sinkholes however processing lidar data to extract sinkholes requires separating sinkholes from other depressions which can be laborious because of the sheer number of the depressions commonly generated from lidar data in this study we applied the random forests a machine learning method to automatically separate sinkholes from other depressions in a karst region in central kentucky the sinkhole extraction random forest was grown on a training dataset built from an area where lidar derived depressions were manually classified through a visual inspection and field verification process based on the geometry of depressions as well as natural and human factors related to sinkholes 11 parameters were selected as predictive variables to form the dataset because the training dataset was imbalanced with the majority of depressions being non sinkholes a weighted random forests method was used to improve the accuracy of predicting sinkholes the weighted random forest achieved an average accuracy of 89 95 for the training dataset demonstrating that the random forest can be an effective sinkhole classifier testing of the random forest in another area however resulted in moderate success with an average accuracy rate of 73 96 this study suggests that an automatic sinkhole extraction procedure like the random forest classifier can significantly reduce time and labor costs and makes its more tractable to map sinkholes using lidar data for large areas however the random forests method cannot totally replace manual procedures such as visual inspection and field verification

investigation of sinkholes spatial distribution using the weights of evidence method and gis in the vicinity of karapinar konya turkey abstract there are many sinkholes 182 in the vicinity of karapinar approximately 20 large sinkholes 10 m in diameter were formed within the obruk plateau between 1970 and 2012 the formation of sinkholes is the most important geological hazard in the study area because they can damage engineering structures settlements agricultural areas and eventually be a source of casualties to date no study has been conducted on the distribution of sinkholes in this region in this study the spatial distribution of the sinkholes and the factors controlling sinkhole development were studied through the use of geographical information systems using a sinkhole inventory and a spatial database containing information on the topography geology hydrogeology and land use initially 182 sinkholes were identified in the area by examining the digital elevation model produced for this study the sinkholes were verified in the field thirty two factor maps were produced to investigate their relationship with sinkholes using the weights of evidence method the sinkholes are mainly related to dissolution of the neogene age lacustrine insuyu formation consisting of limestone and clayey limestone sinkhole frequency increases in the vicinity of drainages 2000 3000 m and faults

holocene moisture evolution in arid central asia and its out of phase relationship with asian monsoon history we synthesize palaeoclimate records from the mid latitude arid asian region dominated today by the westerlies arid central asia aca to evaluate spatial and temporal patterns of moisture changes during the holocene sediment records from i i takes with reliable chronologies and robust proxies were selected to reconstruct moisture histories based on a five class ordinal wetness index with assigned scores from the driest to wettest periods at individual sites for 200 year time slices the proxies used in these records include pollen and diatom assemblages sediment lithology lake levels and geochemistry mainly isotope data the results of our synthesis show that aca as a whole experienced synchronous and coherent moisture changes during the holocene namely a dry early holocene a wetter less dry early to mid holocene and a moderately wet late holocene during the early holocene most of the lakes experienced very low water levels and even dried out before ca 8 ka 1 ka 1000cal a bp hence the effective moisture history in aca is out of phase with that in monsoonal asia as documented by numerous palaeoclimate records in monsoonal asia a strong summer monsoon and humid climate characterized the early holocene and a weakened summer monsoon and drier climate prevailed during the late holocene which were mainly controlled by changes in low latitude summer insolation in contrast we propose that the pattern of holocene effective moisture evolution in the westerly dominated aca was mainly determined by north atlantic sea surface temperatures ssts and high latitude air temperatures that affect the availability amount and transport of water vapor also topography of the tibetan plateau and adjacent asian highlands could have contributed to the intensification of dry climate in aca during the early holocene as a result of strengthening the subsidence of dry air masses associated with stronger uplift motion on the plateau by intense heating under a stronger summer insolation summer insolation might have played a key role in directly controlling moisture conditions in aca but only after the northern hemisphere ice sheets had disappeared in the mid and late holocene c 2007 elsevier ltd all rights reserved

asynchronous holocene climate optimum across mid latitude asia abstract the holocene climate optimum hco was an important interval in the development of human civilization and has been the focus of many paleoclimatic studies however there are significant regional differences in the timing of the hco due to the complex response of regional climates to insolation changes associated with internal feedbacks within the climate system here we present the results of a study of magnetic and geochemical properties of loess paleosol sequences from across mid latitude asia with the aim of assessing differences in the timing of the hco the hco generally occurred after 5 ka in tajikistan and xinjiang during 5 2 5 ka in the western chinese loess plateau clp and during 8 2 5 ka in the central clp this asynchroneity reflects differences in the response of regional climates to global climate change specifically the difference in timing between the central and western clp may have been related to shifts in the position of the east asian summer monsoon rain belt due to the changing longitudinal position of the western pacific subtropical high together with changes in the east west thermal gradient in the equatorial pacific i e shifts between la nina and el nino conditions

loess stratigraphy of central asia palaeoclimatic and palaeoenvironmental aspects abstract the loess palaeosol succession of central asia is comparable with that of the loess plateau in north china palaeomagnetic investigations and palaeontological studies in south tadjikistan suggest a date of 2 2 5 ma for the oldest loess indicating that dust storms became frequent in the region since 2 2 5 ma bp under the prevalently arid and semi arid environments of central asia aeolian processes had a gradually increasing influence on subaerial sedimentation during the pleistocene however atmospheric aeolian processes in central asia have mainly developed in accordance with pleistocene climatic cyclicity without extremely high intensification during the late pleistocene as implied by the previous tl dating results the identification of loess and palaeosol horizons with respective glaciations and interglacials is sometimes disputable nevertheless the available data in spite of limited evidence characterise well developed palaeosols of the middle and late pleistocene as warm and wet intervals associated with interglacials palynological studies of loess sections show that loess and palaeosol horizons have palynological spectra that are sometimes difficult to interpret interregional loess palaeosol correlation with glacial interglacial events as well as with oxygen isotope records should be supplied by multidisciplinary investigations

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

new insights into the palaeoclimatic interpretation of the temperature dependence of the magnetic susceptibility and magnetization of mid late pleistocene loess palaeosols in central asia and the chinese loess plateau the temperature dependence of magnetic susceptibility chi t curves and magnetization m t curves has been used as a routine rock magnetic tool to characterize the magnetic mineralogy and magnetic granulometry of chinese loess palaeosols however palaeoclimatic interpretation of these thermomagnetic analyses remains controversial in the present study total organic carbon toc thermomagnetic and low temperature magnetic experiments on mid late pleistocene loess palaeosols in central asia and the chinese loess plateau clp have been conducted we found that the m t cooling curves at room temperature were mostly lower than the corresponding heating curves whereas for the chi t analyses the cooling curves at room temperature were always much higher than the heating curves low temperature magnetic measurements demonstrated that a large amount of superparamagnetic ferrimagnetic particles were produced during the thermal treatment and resulted in the aforementioned differences this finding further indicated that the use of the m t curves to estimate the relative content of maghemite in the loess palaeosols from the clp was problematic in addition a positive correlation exists between the toc and the frequency dependent susceptibility chi fd in the clp suggesting that stronger pedogenesis would result in the simultaneous increase in the content of both maghemite and organic matter consequently the parameters delta chi 1 representing the relative content of pedogenic maghemite delta chi 2 inverted left perpendicular chi ph chi inverted right perpendicular delta chi 1 and chi ph related to the organic matter concentration which can be calculated from the chi t analyses can potentially be used as new indicators of pedogenesis and palaeoclimate in central asia and the clp

magnetic proxy climate results from the duanjiapo loess section southernmost extremity of the chinese loess plateau we report mineral magnetic results from a 7 5 m loess sequence 150 samples from the southernmost extremity of the chinese loess plateau which includes the last two glacial cycles in this area the loess sediments experienced particularly intense weathering processes the magnetic assemblage is dominated by a mixture of pseudo single domain psd and multidomain md magnetite with associated superparamagnetic sp grains of either magnetite or maghemite in the paleosols and weathered loess horizons all the rock magnetic parameters fluctuate in parallel with marine sediment 18o data over the last 150 kyr thus reflecting changing global paleoclimatic conditions this relationship is also supported by the evidence of milankovitch cycles in the magnetic susceptibility record paleorainfall estimates when compared with other studies from the chinese loess plateau underline the more humid character of this region during the last 130 kyr

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

pedosedimentary and climatic reconstruction of the last interglacial and early glacial loess paleosol sequence in south tadzhikistan abstract the thick loess paleosol sequences in tadzhikistan which indirectly record the environmental changes from the upper pliocene to the present day have been extensively described from a chronostratigraphical and archaeological point of view the genesis of the soil sedimentary complexes and their implications for palaeoenvironmental reconstruction in tadzhikistan however have been considered only relatively recently bronger a winter r derevjanko o aldag s 1993 loess paleosol sequences in tadjikistan as a palaeoclimatic record of the quaternary in central asia quaternary proceedings 4 69 81 lomov s p tursina t v zhou l p 1996 magnetic susceptibility of soils micromorphology and possible reconstructions of climate in soil micromorphology studies in soil diversity diagnostics dynamics 10th international working meeting on soil micromorphology moscow russia july 8 13 1996 p 145 the pedocomplex of last interglacial and early glacial age oxygen isotope stage 5 in the tagidjar and darai kalon sections near the town of khovaling is represented by three major stages of soil formation the soil characteristics have been micromorphologically analysed the distinction between primary and secondary carbonates is of major importance to understand the soil forming processes the relative distribution of needle fibre calcite nfc micritic infillings m hypocoatings chc coarse calcitic grains ccg and calcified root cells crc provides detailed insights into the environmental conditions prior during and following pedogenesis the abundance of coprolitic aggregates ca and pupal chambers gives a clear indication of the rate of biological activity which prevailed during the last two soil forming stages void pseudomorphs after gypsum crystals gypsum pseudomorphs are frequently observed beneath the cca horizons of the paleosols using the present day climate and soilscape as a reference base the obtained pedosedimentary events detected in the tadzhikistan sections provide a detailed palaeoenvironmental record indeed glacial and interglacial climates and soils respond to contemporaneous climatic schemes and soil forming processes which are still active in the region today the amount and the seasonal variability of precipitation mostly are at the origin of the variable soils formed during glacial and interglacial ages

integrating geomorphological mapping trenching insar and gpr for the identification and characterization of sinkholes a review and application in the mantled evaporite karst of the ebro valley ne spain abstract this contribution illustrates the advantages of integrating conventional geomorphological methods with insar ground penetrating radar and trenching for sinkhole mapping and characterization in a mantled evaporite karst area where a significant proportion of the karstic depressions have been obliterated by artificial fills the main practical aim of the investigation was to elucidate whether buried sinkholes overlap the areas planned for the construction of buildings and services in order to apply a preventive planning strategy old aerial photographs and detailed topographic maps were the most useful sources of information for the identification of sinkholes and helped to obtain information on their chronology either a minimum age or bracketing dates the insar technique provided subsidence rate values ranging from 4 4 to 17 3 mm yr consistent with the spatial distribution of the mapped sinkholes this quantitative deformation data helped corroborating independently the existence of active buried sinkholes and improving the delineation of their limits the gpr profiles contributed to the precise location of sinkhole edges provided information on the geometry of buried sinkholes and deformation structures and helped to site trenches and to rule out the existence of sinkholes in particular areas the main input derived from the trenches includes 1 confirming or ruling out anomalies of the gpr profiles attributable to subsidence 2 precise location of the edge of some filled sinkholes 3 information on subsidence mechanisms recorded by various deformation structures and cumulative subsidence magnitude 4 calculating minimum long term subsidence rates using radiocarbon dates obtained from deformed sinkhole deposits 5 unequivocal evidence of active subsidence in areas assigned for the construction of buildings

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

sinkhole hazard assessment in minnesota using a decision tree model an understanding of what influences sinkhole formation and the ability to accurately predict sinkhole hazards is critical to environmental management efforts in the karst lands of southeastern minnesota based on the distribution of distances to the nearest sinkhole sinkhole density bedrock geology and depth to bedrock in southeastern minnesota and northwestern iowa a decision tree model has been developed to construct maps of sinkhole probability in minnesota the decision tree model was converted as cartographic models and implemented in arcgis to create a preliminary sinkhole probability map in goodhue wabasha olmsted fillmore and mower counties this model quantifies bedrock geology depth to bedrock sinkhole density and neighborhood effects in southeastern minnesota but excludes potential controlling factors such as structural control topographic settings human activities and land use the sinkhole probability map needs to be verified and updated as more sinkholes are mapped and more information about sinkhole formation is obtained

quantitative relationships between magnetic enhancement of modern soils and climatic variables over the chinese loess plateau environmental magnetism has been widely employed to reconstruct past climate changes on the chinese loess plateau clp and several climofunctions based on the magnetic properties of loess have been developed however systematic investigation of the quantitative relationship between topsoil magnetic enhancement and modern climate remains uncommon in this study we obtained surface soil samples from 257 sites over the clp and adjacent regions from this set we used 180 samples from sites unaffected by potential contamination to investigate the relationship between the commonly measured magnetic properties of magnetic susceptibility and magnetic remanence and modern climatic variables the spatial distribution of the results demonstrates a strong nw se gradient of the magnetic enhancement of surface soils the results of more detailed magnetic parameters indicate that pedogenic viscous superparamagnetic and stable single domain particles are mainly responsible for the magnetic enhancement of the soils in the studied region and that the magnetic grain size distribution of the ferrimagnetic components of pedogenic origin remains almost constant independent of pedogenic intensity the uniform mechanism of magnetic enhancement mainly linked with the concentration of the pedogenic components rather than with variations in magnetic grain size decreases the level of ambiguity in climate reconstructions based on magnetic measurements of chinese loess statistical analyses including correlation principal component analysis pca and multiple regression analysis suggest that annual rainfall rather than temperature exerts the dominant effect on soil magnetic enhancement finally we used the results to develop several transfer functions to reconstruct mean annual precipitation map transfer functions based on frequency dependent susceptibility fd and anhysteretic remanent magnetization arm provide the most reliable estimates of map this study significantly improves the understanding of the relationship between soil magnetic properties and climate

first order reversal curve forc diagrams for pseudo single domain magnetites at high temperature abstract the recently developed first order reversal curve forc technique for rapidly examining magnetic domain state has great potential for paleomagnetic and environmental magnetic investigations however there are still some gaps in the basic understanding of forc diagrams in particular the behavior of pseudo single domain psd grains and the contribution of magnetostatic interactions in this paper we address some of these problems we report the first forc diagrams measurements on narrowly sized and well characterized synthetic psd through multidomain md magnetite samples the forc diagrams evolve with grain size from single domain sd like to md like through the psd grain size range since each sample contains grains of essentially a single size individual psd grains evidently contain contributions from both sd like and md like magnetic moments in proportions that vary with grain size the evolving forc diagrams cannot be due to physical mixtures of sd and md grains of widely different sizes the forc diagrams were all asymmetric small psd samples have forc diagrams with a distinctive closed contour structure the distributions of the larger md grains display no peak and lie closer to the interaction field axis to assess the effect of magnetostatic interactions we measured forc diagrams between room temperature and the curie temperature on heating the forc distributions contract without changing shape until 500 c above this temperature the diagrams become more md like and in addition become more symmetric the temperature dependence of the interaction field parameter is proportional to that of the saturation magnetization in accordance with neel s interpretation of the preisach diagram the decrease in asymmetry with heating suggests that the origin of the asymmetry lies in magnetostatic interactions the magnetic hysteresis parameters as a function of temperature were determined from the forc curves as the grain size decreased the normalized coercive force was found to decrease more rapidly with temperature

analysis of the field dependence of remanent magnetization curves 1 a new method to calculate and analyze coercivity distributions of measured acquisition demagnetization curves of remanent magnetization is presented the acquisition demagnetization curves are linearized by rescaling both the field and the magnetization axes an appropriate filtering of the linearized curves efficiently removes measurement errors prior to evaluating the coercivity distributions the filtered coercivity distributions are modeled using a set of generalized probability density functions in order to estimate the contributions of different magnetic components an error estimation is calculated for these functions with analytical and numerical methods in order to evaluate whether the model is significantly different from the measured data three sediment samples from baldeggersee switzerland and three samples of urban atmospheric particulate matter pm have been analyzed using this method it is found that the coercivity distributions of some of the magnetic components show significant and consistent deviations from a logarithmic gaussian function large deviations are found also in the coercivity distributions of theoretical af demagnetization curves of single domain and multidomain particles constraints in the shape of model functions affect the identification and quantification of magnetic components from remanent magnetization curves and should be avoided as far as possible the generalized probability density function presented in this paper is suitable for appropriate modeling of gaussian and a large number of non gaussian coercivity distributions

the formation of loess deposits in the tashkent region and parts of central asia and problems with irrigation hydrocollapse and soil erosion abstract there are large problems of irrigation hydrocollapse and soil erosion associated with the loess deposits of central asia to get to grips with these we need a clear view of the nature and formation of the loess and in this region there are still disputes and disagreements and controversies important events in the loess deposit formation process can be identified and studied and relative significances assigned there are large loess deposits in the vicinity of tashkent in the north east of uzbekistan these were mapped and studied for many years by g a mavlyanov and associates they used a terminology which appears to be based on pavlov s nineteenth century usage and developed a polygenetic formation theory for loess deposits this was a formation theory very much associated with central asia and essentially favouring a proluvial mechanism a speculative look at the deposits near tashkent allows alternative terminologies and formation mechanisms to be considered in particular the widespread soviet antipathy to aeolian deposition can be examined the deposits associated with the chirchik river upstream of tashkent might be affected by the pavlov mechanisms but could be topped by aeolian deposits the collapse of loess when wetted is controlled by the nature of the ground and is a very significant interaction of soil and water in particular in central asia hydrocollapse and water erosion are closely related and are controlled by the complex nature of loess ground dust clouds in eastern uzbekistan are largely loess related but in the west dust material is raised from the drying aral sea bed this is often clay mineral agglomerate material and can carry dangerous pollutants