the progressive evolution of a continental climate in southeast central european lowlands during the middle pleistocene recorded in loess paleosol sequences 1 abstract little is known about the long term quaternary climate evolution of central and south east europe because suitable terrestrial paleoenvironmental records are scarce we present a multiproxy record of loess paleosol sequences in the middle and lower danube basins over the past 700 k y in these lowlands the continentality of interglacial climate progressively increased during the middle pleistocene corresponding trends are seen in other climate prox ies in the same region and in the lowlands of the northern black sea but not or less clearly in climate archives from outside these lowlands we conclude that a small scale increase in paleoelevation of central european mountain ranges the alps carpathians and dinarides during the middle pleistocene might be the cause of the progressive increase in climate conti nentality of southeast european lowlands

the loess and loess like deposits along the sides of the western mediterranean sea genetic and palaeoclimatic significance abstract the loess and loess like deposits on the northern and southern sides of the western mediterranean generally dating to the upper pleistocene are derived from aeolian mobilization of dust from local sources and from their sedimentation where trapped in a dense steppe environment these aeolian deposits however differ from each other as regards the nature of the source material the sedimentary processes and the post depositional weathering loess deposits are more frequent on the north side of the mediterranean where deposited in attenuated periglacial conditions than in north africa where they accumulated in peridesert areas during pluvial periods

contemporary crustal deformation in east asia constrained by global positioning system measurements global positioning system gps measurements collected since the early 90 s allow us to derive geodetic velocities at 16 permanent stations in east asia and 68 campaign mode sites in north china the resulting velocity field shows the following 1 contrary to the early inferences that the shanxi rift has accommodated significant right slip motion our results suggest that the rift system at least in its northern part in north china is under ese wnw extension at a rate of 4 2 mm yr the velocity field also suggests that an ese wnw trending left lateral shear zone deforming at a rate of 2 1 mm yr may exist along the north rim of north china at the latitude of 40 n separating actively extending north china in the south from relatively stable mongolia in the north 2 central and east china move at a rate of 8 11 mm yr east southeast with respect to siberia implying that the overall east southeastward motion is the dominant mode of deformation in east china 3 the india plate moves at a rate of 6 1 mm yr slower than the nuvel 1a model prediction relative to the eurasia plate 4 significant eastward motion 20 2 mm yr with respect to siberia occurs in southeastern tibet about half of this eastward motion 11 mm yr is absorbed by structures along the eastern boundary of the tibetan plateau

surface deformation and lower crustal flow in eastern tibet field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern tibetan plateau since about 4 million years ago instead central eastern tibet has been nearly stationary relative to southeastern china southeastern tibet has rotated clockwise without major crustal shortening and the crust along portions of the eastern plateau margin has been extended modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle this model also predicts east west extension on the high plateau without convective removal of tibetan lithosphere and without eastward movement of the crust east of the plateau

motion of the pacific plate relative to eurasia and its potential relation to cenozoic extension along the eastern margin of eurasia extension along the eastern margin of eurasia has been regarded commonly as a far field effect of the india eurasia collision however some aspects of the timing and location of this extension make a link between the collision and extension difficult we suggest that some extensional features commonly interpreted as effects of the collision may be related more simply to changes in plate convergence rates along the eastern plate boundary of eurasia an analysis of the motion of the pacific plate relative to eurasia suggests that the rate of pacific eurasia convergence varied significantly during the tertiary period from a late cretaceous convergence rate of 120 140 mm yr the rate declined substantially during early tertiary time and reached a minimum in eocene time of 30 40 mm yr in oligocene to earliest miocene time the average convergence rate increased moderately to 70 95 mm yr then decreased again to 65 70 mm yr during early to middle miocene time from late miocene to the present the rate of convergence increased to an average of 100 110 mm yr the paleocene through middle miocene episode of relatively slow convergence correlates with a period of widespread extension along the eastern margin of eurasia decreased convergence may have been related to a net reduction in horizontal compressional stress transmitted between the pacific and eurasian plates which resulted in widespread extension adjacent to the margin of eurasia

crustal rheology and faulting at strike slip plate boundaries 1 an analytic model this paper investigates how rheologic stratification within the crust affects the formation and long term evolution of fault systems at a strike slip plate boundary we present an analytic model of deformation at a strike slip plate margin within a two layer viscoelastic crust with fixed shear modulus but varying viscosity in each layer faulting is represented by static elastic dislocations of fixed shallow depth extent imposed at a high critical stress threshold for fracture of a new fault and a lower one for sliding on a preexisting fault to drive crustal deformation we impose basal velocity boundary conditions at the moho representing a narrow zone of high shear in the mantle in this study we restrict attention to deformation at the surface where simple analytic solutions exist for velocities and stresses our results suggest that when a primarily elastic brittle upper crust is underlain by a low viscosity lower crust the deformation zone in the upper crust widens in time at steady state the surface width of the deformation zone may be significantly greater than the prescribed narrow mantle shear zone the long term width of the deformation zone increases with the viscosity contrast within the crust and with the thickness of the low viscosity lower crust widening of the deformation zone is accompanied by the fracture of new faults in the upper crust leading to the formation of a system of parallel strike slip faults surrounding the plate boundary for fixed plate velocity and fracture criteria we find that the width of the brittle fault network within the total distributed deformation zone is primarily governed by strength properties of the upper crust and by the viscosity contrast within the crust

magnitude of late quaternary left lateral displacements along the north edge of tibet images taken by the earth observation satellite spot of the quaternary morphology at 18 sites on the 2000 kilometer long altyn tagh fault at the north edge of tibet demonstrate that it is outstandingly active long term left lateral strike slip offsets of stream channels alluvial terrace edges and glacial moraines along the fault cluster between 100 and 400 meters the high elevation of the sites mostly above 4000 meters in the periglacial zone suggests that most offsets resulted from slip on the fault since the beginning of the holocene these data imply that slip rates are 2 to 3 centimeters per year along much of the fault length and support the hypothesis that the continuing penetration of india into asia forces tibet rapidly toward the east

stratigraphy and spatial and temporal paleoclimatic trends in southeastern eastern european loess paleosol sequences abstract the loess paleosol sections batajnica stari slankamen serbia mircea voda romania and stary kaydaky ukraine are presently located in areas of different types of steppe and are highly sensitive for recording climatic changes a stratigraphy for these three southeastern eastern european sections is presented based on pedostratigraphy and correlation of recently obtained susceptibility records with susceptibility data of other sections of the area koriten mostistea vyazivok of the chinese loess plateau and with the benthic 18o record of odp 677 six pedocomplexes were studied at the serbian and romanian sections and five at the ukrainian section the oldest are related to marine isotope stage mis 17 batajnica stari slankamen and mircea voda and mis 13 15 stary kaydaky some points concerning the existing loess chronostratigraphies of bulgaria ukraine and china are discussed comparative study of the profiles allows the tracing of paleoclimatic and paleoenvironmental changes in southeastern eastern europe in time and space reconstruction of paleoprecipitation based on susceptibility rainfall relationships and calculations of sedimentation rates are evaluated

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

on the dynamics of extensional basin geological and geophysical data from the north china bohai basin and basin and range province were examined and compared they are similar to each other in many respects surficial geological structures are characterized by a series of half grabens with their one flank constituted by normal fault those extensional structures usually extend to a depth of 6 8 km therefore the stress condition in the upper 8 km can be written as sigma 2 sigma x sigma y where x y denote the directions of maximum compression and maximum tension on the horizontal plane while z signifies the vertical direction

silt 2 62 μm 9 4φ the particles in finer grained detrital sediments are usually composed of quartz they fall into two size grades sand 2 mm 62 m and silt 62 m 2 m these size gradings conceal important geological processes since there are geological controls on both the quartz sand and silt populations sand nature is largely controlled by geochemical reactions for example in cooling granite from which it is eventually released by weathering action the quartz is among the last part of the rock system to solidify and the eutectic like reaction which occurs ensures that the quartz exists as small crystalline units each suffering considerable cooling and recrystallisation stresses silt is broken quartz and has traditionally been considered to lack a specific geological control the situation is confused by the large range of materials that fall into the size category but there do seem to be distinguishable modes and possibly comminution limits within the 60 m span the controls operating in this size range are probably the critical concentration of moss defects in the quartz particles moss postulated the formation of specific crystal defects in the quartz formed in granites these affect sand formation and it is possible that they also control the mode size of silt particles within the silt range there may be several usefully definable populations as moss proposed for sand the quaternary appears to be a silt rich period due to tectonic and glacial activity but silt production is apparent throughout the sedimentary record very long term silt producing processes are required to produce silt in nature on a large scale very energetic processes are required many processes that are believed to generate silt particles have been listed however large scale production is essentially due to glacial grinding or to intense weathering processes in high cold tectonically active mountain regions the region of high asia of crustal overlap is a major generator of silt particles these form the productive alluvial soils of north india most of the nation of bangladesh the loess deposits along the syr darya and amu darya rivers in central asia and the great loess deposits of north china some claims have been made for silt production in hot deserts large amounts of very fine aerosolic dust are produced but in terms of loess sized particles this is a small scale process and leads to modest disputed deposits the loess deposits around the sahara usually have smaller mode sizes e g nigeria or larger mode sizes e g libya tunisia than the true chinese mode at 25 m this paper aims to introduce the distinguishing properties of sand and silt discuss in detail the possible processes of silt formation in relation to the evidence of what is produced describe the major silt populations and conclude on the most likely formation process es in particular three silt ranges are discussed in relation to the r size diagram c 2 5 m d1 20 30 m and d2 60 m these can represent canadian quickclay qq chinese loess and the ideal loughborough loess ll and north african loess nal it is intended that this paper will put into context the diverse work in the area and in so doing shed light on what is an often overlooked subject

dislocation model for aseismic crustal deformation at hollister california geodetic observations at many active plate margins reveal relatively steady aseismic motion during the time between major earthquakes we model the aseismic motion by the relative motion between several blocks that suffer frictional resistance in the upper crust frictional drag is represented by uniform dislocation on a fault surface we assume that friction occurs only on the upper brittle zone of each block boundary and that frictionless sliding occurs below this zone using a bayesian inversion procedure we invert geodetic data to determine the parameters of the block and dislocation model parameters to be estimated include the two horizontal components of velocity for each block and the dislocation rate dip angle slip angle and width of each rectangular fault patch for hollister we assume five blocks and nine rectangular fault patches rates of length change on 92 lines observed by trilateration make up the data triangulation leveling very long baseline interferometry satellite ranging and global positioning system data can also be easily included in our model our inversion procedure uses prior estimates of all block and fault parameters based on geological and seismological data the block parameters are estimated from geological observations of fault displacement rates while the widths of the fault patches are estimated from earthquake hypocentral depths we choose prior estimates of the dislocation rate to match observed creep rates the estimated block motion is well resolved by the geodetic data and agrees well with the geological estimates this suggests that the block motion is steady on time scales from 10 years to 1 m y the net motion across the san andreas calaveras fault system is 38 3 mm yr oriented s38 e thus some additional displacement possibly offshore is needed to match the rate of 56 mm yr predicted by plate tectonic models the depth of the transition from frictional to free sliding varies considerably from 0 4 km on the southern calaveras to 11 km on the central san andreas fault two segments of the san andreas north of 36 50 and south of 36 40 have the greatest potential for moderate to large earthquakes

present day crustal deformation in china constrained by global positioning system measurements global positioning system gps measurements in china indicate that crustal shortening accommodates most of india s penetration into eurasia deformation within the tibetan plateau and its margins the himalaya the altyn tagh and the qilian shan absorbs more than 90 of the relative motion between the indian and eurasian plates internal shortening of the tibetan plateau itself accounts for more than one third of the total convergence however the tibetan plateau south of the kunlun and ganzi mani faults is moving eastward relative to both india and eurasia this movement is accommodated through rotation of material around the eastern syntaxis the north china and south china blocks east of the tibetan plateau move coherently east southeastward at rates of 2 to 8 millimeters per year and 6 to 11 millimeters per year respectively with respect to the stable eurasia

present day kinematics of the eastern california shear zone from a geodetically constrained block model we use global positioning system gps data from 1993 2000 to determine horizontal velocities of 65 stations in eastern california and western nevada between 35 and 37 n we relate the geodetic velocities to fault slip rates using a block model that enforces path integral constraints over geologic and geodetic time scales and that includes the effects of elastic strain accumulation on faults locked to a depth of 15 km the velocity of the sierra nevada block with respect to nevada is 11 1 0 3 mm yr with slip partitioned across the death valley 2 8 0 5 mm yr panamint valley 2 5 0 8 mm yr and airport lake owens valley 5 3 0 7 4 6 0 5 mm yr faults the western mojave block rotates at 2 1 0 8 my clockwise with 3 7 0 7 mm yr of left lateral motion across the western garlock fault we infer 11 2 mm yr of right lateral motion across the mojave region of the eastern california shear zone

permian triassic boundary interval in the middle east iran and n oman progressive environmental change from detailed carbonate carbon isotope marine curve and sedimentary evolution abstract the end permian negative 13c excursion is well known but its cause and chronology are still in question in an attempt to decipher the timing and reasons for this strong decrease we established high resolution sedimentological biostratigraphical and carbonate carbon isotopic studies in four sections in iran abadeh shareeza zal and djulfa and two in oman wadi sahtan the position of the sections on two different margins of the neotethys has allowed us to distinguish between local and global signals this high resolution chemostratigraphy tested for isochrony on the basis of an updated high resolution conodont and ammonoid biostratigraphy allows the discrimination of nine successive isotopic events ie 0 8 for the permian triassic boundary interval ptbi the negative excursion of the ptbi has been separated into four distinct parts a first drop ie 0 occurs in the late wuchiapingian with an amplitude of around 1 3 a second decrease begins ie 1 2 at the base of the dzhulfites ammonoid beds changhsingian and continues gradually until the extinction event top jolfensis conodont interval without important second order variations its amplitude varies between 1 5 and 2 8 and its duration has been estimated around 2 2 ma revealing a non catastrophic phenomenon the lower meishanensis praeparvus conodont zone records stationary to slightly increasing values ie 3 the interval of the curve after the extinction event between the upper meishanensis praeparvus zone and the base of the i isarcica zone records numerous second order variations ie 4 7 its amplitude is of 1 2 3 1 these second order variations are correlatable in iran but with some uncertainty with oman poor correlation of these small peaks with others published sections might be due to a higher sensitivity to local perturbations and a lower buffer capacity of the whole ocean we assume that the processes leading to the extinction event also caused the isotopic decrease before the extinction level with a maximal amplitude of only 2 8 this allows consideration of some possible mechanisms that were rejected as unrealistic to cause a 4 6 excursion

pleistocene environmental dynamics recorded in the loess of the middle and lower danube basin abstract the substantial loess deposits of the middle and lower danube basin in southeastern europe represent one of the thickest and most comprehensive terrestrial palaeoenvironmental records on the continent yet are also the least well understood environmental conditions over the last million years have resulted in relatively continuous deposits uninterrupted by glaciation and tundra conditions which nevertheless reflect oscillations between relatively warm humid interglacial and cold dry glacial intervals this relative environmental stability may have proven important for hominins migrating into and through the region the loess stratigraphy comprises distinct loess paleosol sequences reflecting glacial interglacial phases which can be quantified for intensity using environmental magnetism and geochemistry these phases are emphasised by variations in vegetation and malacofauna which respond to climatic change the loess deposits demonstrate broadly similar sedimentological characteristics across the basin danubian loess deposits initiated in response to the tectonic formation of the pannonian basin retreat of the large palaeolakes and increased sediment supply from the danube the period from 1 ma 500 ka mis 27 13 was characterised by alternating loess deposition and pedogenesis during glacial and interglacial periods respectively in response to relatively humid forested conditions this period represents the opening of the danube corridor and provides the backdrop for initial hominin arrival into europe after 500 ka and particularly after mis 9 loess accumulation rates increased in response to relatively more steppic arid environments mis 9 and 13 15 were the most humid phases of the last 600 ky the mis 5 interglacial period was the warmest and relatively most humid period preceding the holocene and was followed by substantially increased loess accumulation during mis 4 which may be linked to north atlantic circulation the complexity of the mis 3 interstadial paleosol suggests that conditions were not uniformly warm and wet during this time mis 3 corresponds with the first arrival of anatomically modern humans to europe the last glacial maximum and younger dryas of mis 2 were characterised by substantially increased loess accumulation indicating cold steppe environments most likely influenced by the north atlantic although conditions were sufficiently mild that the region acted as a refugium for thermophilic biota as may also have been the case for most of the pleistocene glacial cycles the holocene soil represents relatively wamer and more humid conditions corresponding to the current interglacial

palaeomagnetism of the loess palaeosol sequence in viatovo ne bulgaria in the danube basin abstract the results of a palaeomagnetic investigation of a 27 m thick loess palaeosol sequence in viatovo ne bulgaria are presented in this paper the sequence consists of topsoil s 0 seven loess horizons l 1 l 7 and six interbedded palaeosols s 1 s 6 overlying a red clay terra rossa complex magnetic viscosity experiments irm acquisition ams analysis and nrm stepwise alternating and thermal demagnetisation experiments of pilot samples were implemented for precise determination of the characteristic remanence and construction of a reliable magnetostratigraphical scheme analysis of irm acquisition curves using the expectation maximization algorithm of heslop et al heslop d dekkers m kruiver p van oorschot h 2002 analysis of isothermal remanent magnetization acquisition curves using the expectation maximization algorithm geophys j int 148 58 64 suggests that the best fitting is obtained by three coercivity components component 1 corresponds to sd maghemite magnetite while component 2 is probably related to the presence of oxidised detrital magnetites the third component shows varying coercivities depending on the degree of pedogenic alteration of the samples and probably reflects the presence of detrital magnetite grains oxidised at different degree the relevance of the viatovo section as a key representative sequence for the loess cover in the danube basin is confirmed by the presence of geomagnetic polarity changes in the lower part of the sequence the youngest one recorded in the seventh loess unit l 7 can be identified as corresponding to the matuyama brunhes palaeomagnetic polarity transition two normal magnetozones were found in the red clay complex probably corresponding to the jaramillo and olduvai subchronozones of the matuyama chron

bedrock versus superficial deposits in the swiss jura mountains what is the legitimate soil parent material soils are generally considered to be the result of in situ weathered products of geological substrata nevertheless the earth s surface is mainly composed of superficial deposits made of sediments reworked during periods of climate instability glaciation aridification flooding etc but to what extent do these deposits influence present day soil development and or lessen the contribution of the geological substratum in the swiss jura mountains characterization and distribution of superficial deposits along a toposequence are used in order to decipher the polygenic sources of soil parent materials and question the importance of lithodependence in soil development the in situ weathering material and the allochtonous deposits are discriminated through analysis of mineralogical composition grain size distribution of the soil mineral fraction and multivariate statistical treatment as expected calcite is dominant in the autochonous mineral phase leading to high ph values in deep soil layers however the mineralogical composition of the surficial deposits is made of local mineral components mixed with allochtonous aeolian deposits this exogenous material is dominated by quartz and phyllosilicates and is reflected by low ph values in soil surficial horizons the grain size distribution curves of the insoluble residue from bedrocks are unimodal and dominated by fine loam and clays in contrast surficial deposits display polymodal curves demonstrating the contribution of various aeolian episodes and or sources analysis of the surface texture of quartz sand grains shows glacial marks intersected by aeolian shock marks indicating the posteriority of wind transportation loess material originates from alpine moraines of the swiss plateau and is mixed with deposits originating from more proximal jura moraines diluting the alpine signature consequently the soil development does not follow the expected and conventional decalcification process but is directly influenced by the origin of the primary sediments even when present only in small amounts and their evolution copyright 2012 john wiley sons ltd

the cenozoic tectonic evolution of the great north china two types of rifting and crustal necking in the great north china and their tectonic implications abstract the great north china underwent widespread continental rifting during cenozoic time that caused extension and necking of the crust in this area and formed four major rift systems in this paper we provide geological and geophysical evidence that rifting and extension in the western part of the great north china differs from that in its eastern part in age and nature the space time relationships show that the origins of the western rift group of the great north china are probably related to the tibet plateau tectonics whereas those of the eastern rift group are related to the subduction events in the western margin of the pacific plate furthermore the quaternary tectonic regime in the eastern part of the great north china differs from the neogene tectonic pattern and shows relations with western rifts we speculate that during the quaternary the processes that caused rifting in the west have spread further east and now affect the eastern part of the great north china

danube loess stratigraphy towards a pan european loess stratigraphic model abstract the danube river drainage basin is the second largest river catchment in europe and contains a significant and extensive region of thick loess deposits that preserve a record of a wide variety of recent and past environments indeed the danube river and tributaries may themselves be responsible for the transportation of large volumes of silt that ultimately drive loess formation in the middle and lower reaches of this large catchment however this vast loess province lacks a unified stratigraphic scheme european loess research started in the late 17th century in the danube basin with the work of count luigi ferdinand marsigli since that time numerous investigations provided the basis for the pioneering stratigraphic framework proposed initially by kukla 1970 1977 in his correlations of loess with deep sea sediments loess palaeosol sequences in the middle and lower reaches of the danube river basin were a key part of this framework and contain some of the longest and most complete continental climate records in europe covering more than the last million years however the very size of the danube loess belt and the large number of countries it covers presents a major limiting factor in developing a unified approach that enables continental scale analysis of the deposits local loess palaeosol stratigraphic schemes have been defined separately in different countries and the difficulties in correlating such schemes which often change significantly with advances in age dating have limited the number of basin wide studies a unified basin wide stratigraphic model would greatly alleviate these difficulties and facilitate research into the wider significance of these loess records therefore we review the existing stratigraphic schemes and define a new danube basin wide loess stratigraphy based around a synthetic type section of the mosorin and stari slankamen sites in serbia we present a detailed comparison with the sedimentological and palaeoclimatic records preserved in sediments of the chinese loess plateau with the oxygen isotope records from deep sea sediments and with classic european pleistocene stratigraphic subdivisions the hierarchy of danubian stratigraphic units is determined by climatically controlled environmental shifts in a similar way to the chinese loess stratigraphic scheme a new unified danube loess stratigraphic model has a number of advantages including preventing confusion resulting from the use of multiple national schemes a more transparent basis and the potential to set pleistocene palaeoenvironmental changes recorded in the danube catchment area into a global context the use of a very simple labelling system based on the well established chinese loess scheme facilitates interpretation of palaeoenvironmental information reported from the danube basin loess sites in a wider more accessible context that can be readily correlated world wide this stratigraphic approach also provides for the first time an appropriate framework for the development of an integrated pan european and potentially pan eurasian loess stratigraphic scheme

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

early miocene european loess a new record of aridity in southern europe the intercalation of silty units and coarse grained units represented by conglomerates and breccia characterizes a lower miocene terrestrial sedimentary sequence in the north croatian basin a part of the southwestern pannonian basin system these sediments were previously interpreted as alluvial sediments where the silty units would reflect deposition on a floodplain however in this study we show new results that support a different interpretation of the genesis of the silty units the units which vary in thickness between 6 and 180 cm are mostly composed of structureless loose silt they are brownish yellow to yellowish brown in color and do not contain fossils scanning electron microscopy indicated that quartz grains show fracture faces conchoidal fractures v shaped percussion marks linear steps and conchoidal crushing features such microtextures together with the macroscopic characteristics of the silt units indicate that they were deposited by wind therefore this study reports the first occurrence of miocene loess outside of china silt sized particles were probably produced by salt weathering processes on salina type lake flats during long arid periods alluvial deposition was controlled by a more humid climate so the intercalation of eolian silty units with alluvial conglomerates and breccias reflects alternation of arid and more humid periods in the early miocene this agrees with regional paleoclimate studies that show cyclicity in the climate with a dry cycle and orbital scale climate variability controlling paleoenvironmental and sedimentary changes in the area during the early miocene

crustal deformation in great california earthquake cycles periodic crustal deformation associated with repeated strike slip earthquakes is computed for the following model a depth l h extending downward from the earth s surface at a transform boundary between uniform elastic lithospheric plates of thickness h is locked between earthquakes it slips an amount consistent with remote plate velocity vpl after each lapse of earthquake cycle time tcy lower portions of the fault zone at the boundary slip continuously so as to maintain constant resistive shear stress the plates are coupled at their base to a maxwellian viscoelastic asthenosphere through which steady deep seated mantle motions compatible with plate velocity are transmitted to the surface plates the coupling is described approximately through a generalized elsasser model we argue that the model gives a more realistic physical description of tectonic loading including the time dependence of deep slip and crustal stress buildup throughout the earthquake cycle than do simpler kinematic models in which loading is represented as imposed uniform dislocation slip on the fault below the locked zone parameters of the model are chosen to fit seismic and geologic constraints and the apparent time dependence of surface strain rates along presently locked traces of the 1857 and 1906 san andreas ruptures we fix vpl 35 mm yr tcy 160 years and l 9 11 km based on earthquake nucleation depths the geodetic data are then found to be described reasonably within the context of a model that is locally uniform along strike and symmetric about a single san andreas fault strand by lithosphere thickness h 20 30 km and elsasser relaxation time tr 10 16 years we therefore suggest that the asthenosphere appropriate to describe crustal deformation on the earthquake cycle time scale lies in the lower crust and perhaps crust mantle transition zone and has an effective viscosity between about 2 1018 and 1019 pa s depending on the thickness assigned to the asthenospheric layer predictions based on the chosen set of parameters are also consistent with data on variations of contemporary surface strain and displacement rates as a function of distance from the 1857 and 1906 rupture traces although the fit is degraded by asymmetry relative to the fault and by slip on adjacent fault strands

magnetic properties of loess grain size fractions from the section at paks hungary abstract the approximately 50 m thick loess palaeosol sequence at paks brickyard hungary was deposited largely during the brunhes normal polarity chron and its magnetic properties resemble those of similar sections in europe central asia and china in order to get information on the grain size dependence of some of the magnetic parameters two loess and two palaeosol samples were separated into a number of grain size fractions the separation method employs consecutive sedimentation and centrifugation steps performed on bulk samples suspended in water and diluted with calgon ten grain size fractions were obtained ranging from 50 m down to 10 nm several magnetic parameters of the different grain size fractions have been measured at room temperature low field susceptibility hysteresis parameters and at low temperature susceptibility and thermoremanent magnetisation they show a strong grain size dependence for the ferromagnetic minerals low temperature measurements allow discrimination of the paramagnetic vs the ferromagnetic signal and give information on the grain size distribution of the very fine ferromagnetic minerals and on the mineral types carrying the magnetic signal strong relationships between weathering processes destruction of paramagnetic minerals and possibly iron hydroxides and enhancement of the ferromagnetic signal are observed

inversion of gps measurements for a layer of negative dislocation distribution in north china 1 in north china most earthquakes occur at depths of 10 25 km and are considered to be the direct result of deformation or rupture of the brittle upper crustal layer to describe this mechanism a planar horizontal negative dislocation plane is used to represent the force of action of the lower crustal layer on an overlying brittle upper crust layer an area around beijing in north china has been chosen for applying this negative dislocation layer assumption a gps network capital circle gps network ccgn has been set up for monitoring crust deformations since 1992 in this paper observations from 1992 1995 and 1996 gps surveying campaigns were used to determine model parameters of a negative dislocation layer using a bayesian inversion procedure more than 95 of data residuals are found to be 2 mm yr indicating that the negative dislocation layer model can fit gps data well the inversion results show that the local tectonic movement is 2 1 mm yr in the north and 7 1 mm yr in the east and the high negative dislocation rates occur mainly in the south part of the north taihang mountain zone with a magnitude of 4 1 mm yr and the east part of the yan mountain zone with a magnitude of 3 1 mm yr by applying this negative dislocation layer model the continuous gps surveying data can be inverted to determine the negative dislocation rate distributions in the middle or upper seismogenic crust layer so as to predict the locations of potential earthquake sources

an early brunhes 0 78 ma age for the lower paleolithic tool bearing kozarnika cave sediments bulgaria abstract we present a new sedimentological profile and a magnetostratigraphy of the tool bearing kozarnika cave sediments from bulgaria modal analysis of cave infilling sedimentary texture indicates that the tool bearing layers contain a sizable fraction of sediment interpreted as loess we also find evidence for a relatively thick and well defined normal magnetic polarity in the upper middle part of the section interpreted as a record of the brunhes chron followed down section by reverse polarity directions interpreted as a record of the matuyama chron the lowermost levels with lower paleolithic tools layers 13a c lie in the early brunhes at a nominal maximum age of 0 75 ma while the brunhes matuyama boundary 0 78 ma falls in layer 13 lower immediately below this finding represents a conspicuous revision of previous age estimates for the same tool bearing layers

age of mammuthus trogontherii from kostolac serbia and the entry of megaherbivores into europe during the late matuyama climate revolution abstract at the drmno open pit coal mine near kostolac in serbia a nearly complete skeleton of mammuthus trogontherii nicknamed vika was discovered in a fluvial deposit overlain by a loess paleosol sequence where a second paleontological level named nosak with remains of m trogontherii was found we studied the magnetostratigraphy of the kostolac sedimentary sequence and found that the vika layer dates to 0 8 ma shortly before the brunhes matuyama boundary in addition according to our age model and previously reported optically stimulated luminescence and electron spin resonance dates the nosak fossils have an estimated age of 0 19 ma and lived during the earliest part of marine isotope stage 6 it appears therefore that at kostolac m trogontherii is preserved both at its earliest occurrence at 0 8 ma and close to its latest occurrence at 0 19 ma and may well have been present in between albeit not yet found we speculate that megaherbivores such as m trogontherii entered europe along a conjunct danube po river migration conduit connecting western asia levant with central southern europe where vast and exploitable ecosystems particularly suited for steppe or savanna adapted megaherbivores from asia and africa developed during the late early pleistocene climate revolution at around 0 8 ma