intersections between wind regimes topography and sediment supply perspectives from aeolian landforms in central asia abstract the widespread aeolian deposits of the central asian steppes and piedmonts offer potential to better understand the dynamics of the major eurasian climate subsystems over quaternary timescales however current assumptions linking climate processes with aeolian activity remain poorly substantiated and potentially problematic emerging datasets suggest that loess accumulation rates and the timing of peak dust flux along the tien shan piedmont are highly variable between sites the degree to which desert dunes reflect wind regimes and therefore provide records of climate circulation is unknown and the presumed genetic link between the region s desert dunes and piedmont loess deposits remains hypothetical these uncertainties raise questions as to the nature of the relationship between aeolian flux deposition and palaeo climate here we investigate the relationship between wind regimes and the distribution morphology and timing of two aeolian landform types dunes and loess in the topographically diverse ili basin of southeast kazakhstan and western china we establish late holocene ages for three dune sites and one loess profile and infer that the location and morphology of these landforms can be used to test their genetic link with recent wind regimes we assess the morphologic characteristics of linear dunes at four sites using a semi automated mapping approach and analyse the variability in dune orientations with respect to sand shifting wind trajectories identified from meteorological reanalysis data for each site the most frequently occurring wind direction appears to be responsible for sediment supply while the strongest winds drive dune orientation wind orientations are strongly influenced by topography back trajectories incorporating dust transport and deposition potential to the loess site suggest both westerly and northerly delivery of fine grained material to the piedmont and that the most common source areas lie in regions where surface sediment contains a mixture of coarse and fine grained material to facilitate entrainment into suspension

rock magnetism in loess from the middle tian shan implications for paleoenvironmental interpretations of magnetic properties of loess deposits in central asia 1 considerable attention has recently been paid to the magnetic properties of loess deposits in central asia however paleoenvironmental interpretations of magnetic properties of loess deposits in south tajikistan the ili basin and the tarim basin remain controversial current meteorological observations demonstrate that the mean annual precipitation in the junggar basin exceeds that in the tarim basin and falls below that in the ili basin and south tajikistan this study of rock magnetism in loess from the junggar basin improves our understanding of the complicated relationships between magnetic properties climate and source materials for loess deposits of central asia this study involved multiparameter investigations of rock magnetism in a 71 m loess section in the dongwan area on the northern slope of the middle tian shan in the junggar basin variations in concentration of coarse eolian ferrimagnetic minerals appear to provide the main control over the magnetic properties of loess in this area the contribution of ultrafine pedogenically produced magnetic grains to the magnetic susceptibility is minimal furthermore long term increasing trends in the and the saturation isothermal remanent magnetization sirm were found in the dongwan loess section these trends may be linked with intensified aridification of central asia in the mid pleistocene this study suggests that reduced precipitation of westerly moisture from tajikistan into the tarim basin might play a critical role in the paleoenvironmental interpretations of magnetic properties in the loess deposits of central asia

late pleistocene fire in the ili basin central asia and its potential links to paleoclimate change and human activities abstract evidence of late pleistocene fire activity in central asia is important for understanding the underlying processes and controls of fire here two microcharcoal records from two separate loess sections covering the last 70 thousand years kyr in the ili basin are reported the results show that total microcharcoal concentrations are similar in both records and are correlated with insolation indicating consistent basin wide fire trends related to moisture changes driven by insolation in addition two anomalous fire events were identified at 45 35 ka and 6 0 ka we argue that these events are possibly related to ancient human activities rather than to pure natural factors such as sedimentation wind taphonomic change or climate change

changes in sand content of loess deposits along a north south transect of the chinese loess plateau and the implications for desert variations geological records have shown that the deserts east of the helan mountains in northern china were covered by grass during the holocene optimum whereas during marine oxygen isotope stages 2 and 4 distribution of the deserts was almost the same as at present the wide advance retreat cycles of the deserts may have exerted an important control on grain size changes in the loess of the loess plateau by altering the distance between the source and the accumulation zone of the loess this challenges the widely accepted model that winter monsoon winds were the sole factor responsible for spatial and temporal changes in loess texture to observe spatial changes in sedimentological characteristics of loess during the last glacial interglacial cycle the texture of loess was measured along a north south transect of the loess plateau this transect consists of nine loess sections starting at yulin in the transitional region between the loess plateau and the mu us desert and ending at weinan in the southernmost part of the loess plateau southward changes in sand 63 m content along the transect suggest that variations in desert extent have indeed played a significant role in loess grain size distributions particularly in the northern part of the loess plateau it is proposed that sand content 63 m of loess in the loess desert transitional zone may be used as a proxy indicator for proximity to the desert margin

pleistocene chemical weathering history of asian arid and semi arid regions recorded in loess deposits of china and tajikistan quaternary loess soil sequences in china and tajikistan are valuable archives of the chemical weathering history for arid and semiarid regions of asia the development of new proxies independent of grain size are vital to reconstruct the long term chemical weathering history of eolian deposits in this study we analyze major elemental and rb sr and ba concentrations of decarbonated residue from representative loess and soil units along a north south transect on the chinese loess plateau and compare these concentrations among different grain size fractions results show that most of the elemental abundances and ratios vary considerably among different grain size fractions for both loess and paleosols indicating transport driven compositional differentiation of minerals during subaerial transport however cao na2o mgo tio2 ratios show little variation among different size fractions for the loess soil transect loess soil sequences at lingtai northern china and chashmanigar southern tajikistan for the past 1 50 1 77 ma show lower cao na2o mgo tio2 ratios in soil units than in adjacent loess horizons in good agreement with greater weathering intensity in soils than in loess units the cao na2o mgo tio2 ratio of the decarbonated residue is therefore a reliable proxy for chemical weathering of loess deposits that is independent of grain size the cao na2o mgo tio2 ratios of the lingtai and chashmanigar sections display a relatively regular oscillation within a narrow range in the early pleistocene and a rapid increase in average values and in variance from 0 85 0 6 ma to the present indicating lowered chemical weathering intensity in both the dust source regions and the depositional areas this event may be causally related to the expansion of northern hemisphere ice and or the regional tectonic uplift of high mountains in asia since the mid pleistocene

loess deposits from the tajik depression central asia magnetic properties and paleoclimate abstract continuous accumulation of dust during the quaternary has formed widespread loess deposits in southern tajikistan the magnetic susceptibility variations of these aeolian sediments have recorded the paleoclimatic fluctuations in a similar direct and complete way to the well studied sediments from the central loess plateau in china 11 susceptibility measurements were carried out in situ at intervals of 10 cm along seven partly overlapping sections in the loess paleosol sequence of karamaidan ca 100 km east of dushanbe nearly 250 oriented samples were taken for rock magnetic investigations careful field observation revealed a total actual loess thickness of ca 100 m for a composite profile with thirteen intervening pedocomplexes pc standard demagnetization techniques yielded a characteristic component of natural remanent magnetization nrm which was used to obtain a well defined magnetostratigraphy the section covers a total timespan of approximately 1 m y including the brunhes and the youngest part of the matuyama polarity chron the susceptibility variations correlate excellently with those of the chinese loess record at xifeng 22 although minor differences in the relative amplitude of the susceptibility signal occur close correlation with the astronomically tuned oxygen isotope record 26 enables refined dating of the loess sequence at karamaidan and demonstrates the global significance of the recorded paleoclimatic variations especially with respect to paleoprecipitation on land during the quaternary

thermoluminescence dating of the orkutsay loess section in tashkent region uzbekistan central asia abstract the chronology of loess in central asia was investigated by means of thermoluminescence dating tl in the 1970s when age estimates ranging from 20 ka to over 800 ka were taken as providing an absolute chronology this has caused major misinterpretation of central asian loess stratigraphy and palaeoclimatic reconstruction we present a new tl study of a loess section at orkutsay in the tashkent region uzbekistan nine samples spreading over a large stratigraphic interval yield apparent tl ages ranging from 20 ka to 134 ka we interpret our tl results with reference to recent tl dating studies of loess from other regions we consider most of our tl age estimates obtained by the regeneration method to be underestimated a single tl date of 92 8 ka obtained by the total bleach method for loess just below the first pedocomplex pc 1 of the last interglacial is also significantly younger than expected we attribute the underestimation to sensitivity change induced by the laboratory optical bleach and instability of the tl signal we conclude that the current tl techniques as employed in this study cannot provide a reliable absolute chronology for the sequence below pc 1 and cannot provide even a relative chronology for the loess below pc2 for the orkutsay section the dating limit is around 130 ka the results of this study suggest that the previous central asian loess chronology based on early tl studies is not valid

eddies and the annular modes of climate variability the dominant modes of month to month varia tion in the troposphere are realistically simulated in a gen eral circulation model whose lower boundary is prescribed with realistic topography and seasonally varying climato logical sea surface temperatures in both hemispheres these internal modes describe a nearly zonally symmetric north south shifting of the zonal jets as anomalous westerlies vac illate between high 50 60 a nd low 30 40 latitudes the eddy structures evolve with the jets and the corre sponding eddy momentum forcings support the shifts in jet position stationary synoptic wave variations mainly ac count for the total eddy forcings in the northern south ern hemisphere pronounced eddy variations occur over the north atlantic sector

rivers and loess the significance of long river transportation in the complex event sequence approach to loess deposit formation abstract rivers are essential for loess deposit formation river systems which relate directly to loess deposit formation include the danube and the rhine the mississippi and the missouri the thames and the medway the indus ganges and brahmaputra the dnepr don and volga the clutha mataura and rakaia new zealand rivers the yellow river rivers in south america siberian rivers flowing north the odra and the wisla between the mountains and the ice the syr darya and amu darya into the desert the contention is that rivers are not just important in major loess deposit formation they are mandatory necessary imperative obligatory essential indispensable requisite for a complete and satisfactory study of a loess deposit we need to know how the material is produced how it is transported and distributed across the landscape how intermediate deposits are formed how transportation provides the defining properties i e open structure collapsibility draping across the landscape and what may happen post deposition e g chernozemisation fragipan formation increased collapsibility etc if rivers are essential then it would appear that the british loess is probably alpine material delivered by the proto rhine and the polish loess is not derived from the ice sheet to the north but from the mountains to the south the lack of loess in canada is explained by the absence of suitable rivers the loess in russia and neighbouring countries can be classified as jefferson et al jefferson i f evstatiev d karastenev d mavlyanova n g smalley i j 2003b the engineering geology of loess and loess like deposits a commentary on the russian literature engineering geology 68 333 351 suggested on the basis of associated rivers a new deposit of glacial loess is recognised associated with the dnepr don and volga rivers the uswr loess the smalley leach smalley i j leach j a 1978 the origin and distribution of the loess in the danube basin and associated regions of east central europe a review sedimentary geology 21 1 26 available from www geo edu ro sgr mod downloads pdf smalley sedgeo 1978 pdf vision of the loess in the danube basin and east central europe is probably misconceived they assigned a great significance to glacial action and put loess in a northern band it appears that this proposed glacial influence is minimal and that the danube loess is essentially mountain loess derived from the alps the carpathians the sudeten mountains and other high regions the danube system is a classic example of a river controlling loess distribution

weathering and clay mineral formation in two holocene soils and in buried paleosols in tadjikistan towards a quaternary paleoclimatic record in central asia abstract the upper part of the karamaydan section tadjikistan shows the most detailed loess paleosol sequence yet known for the brunhes chron and the central and lower parts of the chashmanigar section provide similar detail for most of the matuyama chron to enable paleoclimates to be deduced the primary and secondary minerals in the silt and clay fractions must be determined separately to evaluate the type and intensity of mineral weathering and clay mineral formation to distinguish between inherited and pedogenetically formed clay minerals the original petrographic homogeneity of the parent material from which a soil developed must be established the main sources of pedogenic clay minerals are phyllosilicates in the silt fractions illites and vermiculites are the dominant pedogenetically formed clay minerals in the b or bt horizons of the holocene climaphytomorphic soils and in all paleosols s and pedocomplexes pk in karamaydan and chashmanigar except s xvii in which large amounts of smectites were formed there is little difference in the type and amount of pedogenic clay mineral formation between the holocene soils and the paleosols in the brunhes epoch at karamaydan as well as during most of the matuyama epoch at chashmanigar these results indicate that the climates of the interglacials represented by the b or bt horizons of the buried paleosols of young mid and old pleistocene age were similar to that of the holocene

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

a 6 ma chemical weathering history the grain size dependence of chemical weathering intensity and its implications for provenance change of the chinese loess red clay deposit abstract major element chemical analyses of the baishui loess red clay sequence 35 24 10 n 106 54 43 e gansu province china reveal that the chemical weathering intensities inferred from cia chemical index of alteration values have progressively weakened and increased in amplitude with decreasing age the general trend of the cia can be correlated well with the oxygen isotope variations of the deep sea sediments analyses of multiple size fractions

a complex double couple source mechanism for the ms 7 2 1929 grand banks earthquake abstract the m s 7 2 grand banks earthquake of 1929 was one of the largest and the most fatal earthquakes to have occurred in canada with most of the death and destruction having been caused by a tsunami and submarine landslide associated with the earthquake it has been suggested hasegawa and kanamori 1987 that a single force landslide mechanism was more consistent with the data than was a double couple source and that therefore the event was not an earthquake however that particular study considered only four double couple solutions and left many unanswered questions in particular with respect to the source time function and sediment volume involved here a larger number of seismograms are used to examine the full range of double couple solutions to determine more definitively the nature of the event waveform modeling using both forward and inverse methods indicates that this event was an earthquake with a complex source mechanism the first and largest subevent was a strike slip double couple event occurring on a northwest striking plane two later subevents were probably strike slip double couples on northeast striking planes but other mechanisms cannot be completely ruled out the first subevent has a well constrained focal depth of 20 2 km the second and third subevents also appear to have occurred at 20 km but are constrained only to within 5 km these depths provide further evidence that the event was not a landslide the sum of the subevent moments corresponds to an m w of 7 2 0 3 which is in close agreement with the m w of 7 1 0 1 obtained by the cmt method using long period data these m w 9s are also consistent with the m s of 7 2 0 3 and m b of 7 1 0 2 calculated directly from the seismograms modeling of the seafloor displacement for this mechanism indicates that the tsunami was generated by the landslide and not directly by the earthquake

zonal jet structure and the leading mode of variability an observational analysis of the northern hemisphere circulation during winter reveals that the leading mode of variability depends on longitude in particular the first eof of the zonal mean circulation differs over the atlantic and pacific sectors these results provide motivation for a series of model runs where a simple gcm is used to investigate the effects of the zonal jet structure on the leading mode of variability in the northern hemisphere model results indicate that the leading mode of variability depends on the distance between the eddy driven and subtropical jets when the jets are well separated the leading mode of variability describes latitudinal shifting of the eddy driven jet however when the two jets are nearly collocated pulsing of the combined jet dominates the variability this change coincides with a weakening of the positive feedback between the eddies and zonal flow anomalies these results provide a possible explanation for the reduced amplitude of the northern annular mode in the pacific sector relative to that in the atlantic sector during northern hemisphere winter

reevaluation of late pleistocene loess profiles at remizovka kazakhstan indicates the significance of topography in evaluating terrestrial paleoclimate records we report on a loess paleosol sequence lps near remizovka located in the northern tian shan piedmont of southeastern kazakhstan this site represents a key record for late pleistocene climatic fluctuations at the intersection of major northern hemisphere climate subsystems this paper develops a synthesized dataset of previous conflicting studies at remizovka by characterizing their paleo topographic context which had remained previously overlooked digital elevation models satellite images and archival photography characterize recent topographic developments two well developed pedocomplexes which we investigate in detail and date by luminescence mark the paleotopography during marine oxygen isotope stage mis 5 peak dust accumulation rates here occurred during the middle mis 5 and mis 4 early mis 3 these are partially comparable with records from neighboring regions but not in phase with global ice volume records this discrepancy may be related to a distinct regional environmental response to larger scale climatic drivers and local topographic influences on dust deposition patterns our findings confirm the potential of the lps remizovka to provide high resolution paleoclimate data for the late pleistocene the three dimensional stratigraphic reconstruction reinforces the caution required to correctly interpret loess formation processes prior to their interpretation as paleoclimate archives and provides guidelines for a more suitable approach

geochemical composition of tajikistan loess and its provenance implications the tajikistan tj loess has great significance for the study of quaternary climate changes and dust source in central asia in this paper we investigate the geochemical composition and provenance of loess our results show that the major elements in order from high to low average content are sio2 al2o3 cao fe2o3 mgo k2o na2o tio2 p2o5 mno fe ti p and mn contents in loess are similar to those in the ucc as is the case with si al and mg contents in paleosols ca is distinctly enriched in loess and si al and k are depleted na is depleted in both loess and paleosols and p is depleted only in paleosols in contrast to the ucc paleosols show enrichments in all trace elements except for ba sr and zr but in loess some trace elements e g ba co ni and zr show depletion the cia value of tj loess is lower than that of kashmir loess the latter being influenced by differences in the sorting and tectonic environment there are no great changes about provenance during the formation of tj loess and the deposit areas have a shorter distance to the provenance geochemical data and atmospheric circulations demonstrate that the tj loess was mainly transported by the near surface northerly or northwesterly winds but there may be an additional and local source making a certain contribution to the formation of loess deposits in the south of tianshan

alluvial plains formation in response to 100 ka glacial interglacial cycles since the middle pleistocene in the southern tian shan nw china abstract the tenet of the milankovitch theory is that northern hemisphere solar insolation controlled by earth s orbital is responsible for cyclic climate variations eccentricity in this context is responsible for cyclic variability of 100 ka and may drive periodicity in climate change during the middle and late pleistocene although abundant evidence exists for 100 ka cyclic climatic fluctuations driving glacial interglacial cycles our knowledge about the record of cyclic climatic changes preserved in terrestrial landscapes remains limited especially over multi millennial several glacial interglacial timescales the intermontane yanqi basin in the southeastern tian shan central asia preserves at least seven generations of alluvial surfaces spanning multiple glacial cycles and yields insights into the record of climatic fluctuations that lead to aggradation and incision of river systems we complement existing chronologic data with two new cosmogenic 10be depth profiles and four surface exposure ages of alluvial surface abandonment in the south tian shan piedmont within the yanqi basin new surface exposure dating reveals the successive abandonment of these surfaces with a 100 ka cyclicity between 5 1 0 9 and 550 ka and indicates that there were multiple aggradation incision cycles the superimposed 100 ka cycles of aggradation incision are best explained by eccentricity driven climate change within these cycles sediment is produced during glaciations by glacial and periglacial erosion however due to the dry and cold conditions of the glacial periods in central asia there is little discharge available to transport and evacuate the sediment from the valleys to the piedmont later during the glacial to interglacial transition higher precipitation and high discharge due to glacial melt water resulted in higher transport capacity of the river beyond a threshold to evacuate sediment subsequent rapid incision occurs after the upstream sediment reservoir is depleted and its timing corresponds to the glacial to interglacial transition period in our study area compared with the aggradation and incision of the northern piedmont of the tian shan governed by the westerlies the sedimentary systems of the south tian shan piedmont within the yanqi basin are mainly controlled by eccentricity driven glacial interglacial cycles

loess depositional dynamics and paleoclimatic changes in the yili basin central asia over the past 250 ka abstract widely distributed loess deposits within the tianshan mountains are important archives for studying late quaternary climate in this central asian region however insufficient age control for these regional loess records especially over glacial interglacial cycles severely limits our understanding of loess depositional dynamics and accurate interpretation of paleoclimate conditions across central asia in this study we applied k feldspar optical dating and magnetic susceptibility grain size distribution caco3 and color to loess paleosol sections in the yili basin of the tianshan mountains to constrain loess depositional dynamics identify timing of loess paleosol formation and clarify the role of paleoclimate influence in this region since the late middle pleistocene our results demonstrate that loess deposition started as early as 350 ka in the yili basin following river down cutting associated with glacial interglacial transitions and exposure of riverbed sediments enhanced dust emission from flood plains played an important role in loess deposition very rapid loess deposition as high as 60 120 g cm 2 ka 1 on river terraces occurred during the last interglacial when loess accumulation at different locations of the site had remarkably different rates ranging from 10 to 100 g cm 2 ka 1 this heterogeneous behavior indicates that not only climatic changes influenced yili basin loess deposition and preservation but by complex interaction of local geomorphology wind velocity and changes of materials in dust origins depositional hiatuses frequently occurred during the past 250 ka likely induced by strong erosion resulting from increased wind strength and dry cold climate with poor vegetation cover in the region magnetic susceptibility grain size distribution caco3 and color analyses of the loess paleosol sequences showed that paleosols formed around 288 ka 230 191 ka 120 106 ka 92 89 ka and 84 71 ka hence a generally moist climate characterized the yili basin before marine isotope stages mis 9 mis 7 mis 5d mis 5b and the mis 5 mis 4 transition respectively this study suggests a climate pattern of moist interglacial and dry glacial periods in the tianshan mountains whereas substages of interglacials had cold moist and warm dry climate characteristics

source regions and formation of the loess sediments on the high mountain regions of northwestern china loess on the high mountains of northwestern china is largely controlled by the topographic features distributed mainly on the northern slopes of the tianshan and kunlun mountains as well as in the ili valley between the northern and central tianshan ranges loess distributed in different regions has different ages with the oldest early pleistocene loess occurring in the ili valley geochemical mineralogical and granulometric analyses demonstrate that the loess in the three different regions has different provenance the loess on the northern tianshan and kunlun mountains is mainly derived from the junggar and taklimakan deserts respectively whereas the loess in the ili valley is derived mainly from the sary ishikotrau desert located in the republic of kazakhstan however these deserts serve mostly as holding areas for the silts rather than original source regions the production of the silt sized particles is mainly associated with glacial abrasion and tectonic induced rock denudation thus the loess in the studied regions can be described as mountainous loess rather than simply glacial loess or desert loess it is unlikely that the mechanisms of loess formation are the same in different regions given their dependence on specific geomorphological conditions and associated processes

moisture dynamics in central asia for the last 15 kyr new evidence from yili valley xinjiang nw china based on high resolution palynological investigations and ams 14 c dating the continuous lacustrine sediments contained in yili valley xinjiang provide an opportunity to reconstruct the effective moisture changes for the last 15 kyr in central asia the relatively warm and humid climate of the bolling allerod 15 12 9 cal kyr bp is a generalization but it seems to show some fluctuations the time of the younger dryas yd interrupted the increasing trend of effective moisture in the study region the climate was cold and relatively dry in the early yd period 12 9 12 0 cal kyr bp whereas the desert vegetation community appeared around 11 8 cal kyr bp almost the driest time since the 15 cal kyr br a sharp increase in effective moisture marked the beginning of the holocene in the yili valley the early holocene 10 6 7 6 cal kyr bp was the wettest time with a developed temperate steppe a dry climate with desert vegetation arose in the early mid holocene 7 6 6 5 cal kyr bp spanning 1100 years a second humid phase emerged between 6 5 and 5 2 cal kyr bp whose vegetation community was represented by temperate steppe moisture was reduced again and the climate became drier between 5 2 and 3 3 cal kyr bp when vegetation was dominated by desert steppe in the yili valley regional comparisons indicate that the moisture changes in yili valley were mainly influenced by the north atlantic ocean ssts through the westerlies the mean position of the siberian high pressure cell probably made a great contribution to the drought between 7 6 and 6 5 cal kyr bp the climate changes were generally consistent between the westerly dominant central asia and asian monsoon regions since the last deglaciation possibly forced by summer insolation conditions in the northern hemisphere c 2011 elsevier ltd all rights reserved

grain size dependent geochemical characteristics of middle and upper pleistocene loess sequences from the junggar basin implications for the provenance of chinese eolian deposits abstract thick loess paleosol sequences are widely distributed in the arid inland basins of northwestern china the geochemical composition of these sediments provides important constraints on the provenance of chinese eolian deposits however grain size dependent geochemical characteristics of early middle pleistocene loess deposits from these arid inland basins have not been investigated the paucity of such studies hinders a full understanding of provenance changes of loess deposits from the chinese loess plateau clp in the present study we performed a detailed major trace and rare earth element analysis of multiple grain size fractions of middle pleistocene loess deposits from the dongwan section dw in the junggar basin we found that the major trace and rare earth element concentrations of the dw loess are grain size dependent with higher concentrations in the fine fraction in addition the 75 m from the dw section changed significantly at 0 5 ma which may have arisen from intensified physical erosion or increased wind speeds in the northern tianshan area

comparison of particle size characteristics of the tertiary red clay and pleistocene loess in the chinese loess plateau implications for origin and sources of the red clay the origin of the tertiary red clay underlying the pleistocene loess in the chinese loess plateau remains controversial although several lines of evidence have suggested a wind blown origin this study examines the particle size parameters of the late miocene and pliocene red clay by comparing it with those of the late pleistocene loess the particle size distribution of a total of 15 339 loess and 6394 red clay samples taken from 12 loess sections along a north south transect and two red clay sequences at lingtai and jingchuan was systematically analysed the median grain size skewness and kurtosis of the late pleistocene loess all show a systematic southward change and are principally influenced by distance from source region the spatial and temporal differentiation of dust deposits is expressed in a skewness kurtosis median grain size ternary diagram from which the distance to the source region can be inferred the particle size characteristics of the tertiary red clay sediments are very similar to those of the palaeosols within the late pleistocene loess deposits suggesting an aeolian origin for the red clay based on the comparison of red clay and loess in the ternary diagrams it is inferred that the source sink distance was greater in the neogene than in the last and penultimate interglacials and that the dust source region in north western china underwent a progressive expansion during the period from at least 7ae0 ma to the present

luminescence dating of the zeketai loess section in the ili basin northwestern china methodological considerations abstract loess deposits in xinjiang northwestern china are ideal archives for past environmental changes in the westerlies dominated central asia among previous luminescence dating studies of loess in xinjiang few have attempted to systematically investigate the methodological aspects in this study we report results of a multiple procedure luminescence dating of the zeketai loess section in the ili basin central xinjiang optically stimulated luminescence osl and post infrared infrared stimulated luminescence pirir signals were used for quartz and polymineral grains of different sizes the pirir ages obtained with two protocols agree well with each other and constrain the loess deposition between 50 ka and 88 ka the osl ages of fine grained quartz are in stratigraphic order and range from 37 ka to 61 ka but are 30 younger than the pirir295 ages of both fine and medium grained polyminerals although the causes of the discrepancy between the ages derived from different luminescence dating protocols are still to be understood we stress that the quartz osl ages of loess in this region are likely to be underestimated especially for samples older than 40 ka the polymineral or potassium feldspar pirir signal is recommended for dating loess in the ili basin at least as an internal check

enigma of earthquakes at ridge transform fault plate boundaries distribution of non double couple parameter of harvard cmt solutions the distribution of the non double couple parameter of shallow earthquakes reported in the harvard cmt catalogue shows systematic characteristics depending on the epicentral locations and types of fault mechanisms the authors suggest that they can be explained by the presence of subevents with different double couple mechanisms in a single rupture sequence the earthquakes at the ridge transform fault plate boundaries show a particularly interesting pattern it is suggested that two types of faulting expected in the area i e normal faults at ridges and strike slip faults at transform faults tend to occur almost simultaneously although this hypothesis needs to be delineated by careful analyses using bodywave waveforms

increasing effective moisture during the holocene in the semiarid regions of the yili basin central asia evidence from loess sections abstract the evolution of holocene moisture in semiarid and arid regions of central asia is key to understanding changes in current and future water resources and has been a hotly debated topic in the past few decades central asian loess deposits have shown potential as records of past moisture changes particularly during the holocene here the variations in effective moisture during the holocene in the semiarid regions of the yili basin central asia are obtained from three loess sections reliable chronologies were constructed using 26 quartz optically stimulated luminescence osl ages the strengthening pedogenesis steady increases in magnetic susceptibility and continuous decreases in mean grain size in the three loess sections all suggest that effective moisture continuously increased throughout the holocene indicating a dry early holocene a moderately humid middle holocene and a wet late holocene rainfall carried by the asian summer monsoon and the westerlies contributes to the moisture changes in central asia however considering the dominance of evaporation over rainfall in controlling aridity humidity shifts in this region the continuous weakening of evaporation caused by a decrease in northern hemisphere summer insolation and associated atmospheric temperatures is primarily responsible for the wetting trend throughout the holocene in the semiarid regions of the yili basin

significance of non double couple components of deep and intermediate depth earthquakes implications from moment tensor inversions of long period seismic waves abstract analysis of long period seismic waves suggests that non double couple components in source moment tensors of intermediate depth and deep earthquakes are significant and appear to respond to the state of predominant strain release within slabs the strain regime is partially or fully induced by the sources themselves or by slab structures near the sources we observe consistency in the non double couple components from three different seismic wave inversions among 21 earthquakes studied 17 events have the same sign in the three non double couple components and the signs show a correlation with the state of strain release within the slabs the effects of unmodeled propagation structure and instability of the inversion procedure are unlikely to be responsible for the consistent non double couple components because the suites of seismic waves traverse different paths and the various inversion schemes have the different resolvabilities of the moment tensors

geochemistry and mineralogy of the late pleistocene loess palaeosol sequence in zlota near sandomierz poland implications for weathering sedimentary recycling and provenance abstract in order to determine the provenance of material the late pleistocene loess palaeosol sequence in zlota poland was analysed geochemically icp ms icp es and mineralogically qemscan investigating simultaneously the weathering signature and effect of sedimentary sorting a total number of 39 loess and soil samples were tested for the geochemical composition and 5 for the mineralogy the investigated samples compared to upper continental crust are enriched with elements such as si zr hf nb ta th u and rare earth elements especially the heavy rare earth elements related rather to felsic igneous rocks the enrichment of only two mafic elements ti and cr can be explained by heavy minerals admixture loess in zlota is strongly mixed and homogenized during transportation and or sedimentary recycling for each sample the uniform shape of the chondrite normalized rare earth elements patterns were found characterized by steep light rare elements lan smn 3 45 4 08 avg 3 81 constant negative eu anomalies eu eu 0 50 0 63 avg 0 56 and distinctly flat heavy rare earth elements gdn ybn 1 17 1 45 avg 1 28 the material is not significantly affected by chemical weathering and the post depositional modifications are not particularly important for the trace element composition both in loess and soils e g th u 3 1 4 65 avg 3 64 ce ce 0 96 1 09 avg 1 01 lan ybn 6 22 7 93 avg 6 94 the research reveals that relatively fresh felsic related parent material has been well mixed during transportation but post depositional alterations related only to the pedogenesis have not been intense enough to mask their chemical signature the investigated material has been probably originated in scandinavia likely norway but deflated directly from the glacial drift covering the terrain of poland

geochemical characteristics and environmental significance of talede loess paleosol sequences of ili basin in central asia the loess paleosol deposit in central asia is a sensitive indicator of the evolution of the quaternary paleoclimate in the westerlies providing insight into the quaternary climate history and its relationship with global climatic changes based on the geochemical analysis of elemental composition of densely sampled strata from talede loess paleosol sequence in the ili basin the results showed that sio2 had the highest major elements content followed by al2o3 the order of compositional abundance of major elements was generally as follows sio2 al2o3 cao fe2o3 mgo na2o k2o trace elements i e rb sr sc ni cu ga mo y pb th in the paleosol layers i e s0 sm s1 and the loess layer of l1 were enriched relative to underlain loess l2 horizons except for the contents of zr cs nd and la in paleosol layers all of geochemical proxies such as enrichment factor rb sr ratio eluvial coefficient ki and chemical weathering index display no obvious differentiation in the talede loess paleosol deposit the results indicate that the weak chemical weathering greater evaporation and low effective moisture in ili basin are to a degree weaker than those in the china loess plateau and the climate was warm dry during the interglacial period in addition the loess of ili area is rich in schistose minerals and implies that the loess may come from the deserts of central asia and it may be closely related to the widespread aridification of central asia

alluvial sequence in the north piedmont of the chinese tian shan over the past 550 kyr and its relationship to climate change abstract a new division of middle and late pleistocene alluvial sequence in the north piedmont of the chinese tian shan based on geomorphologic stratigraphic and chronologic criteria provides a framework for examining their relationship to climate change during glacial interglacial transitions over the past 550 kyr at least four major alluviation episodes occurred within the piedmont along the major river valleys in this region each episode of alluvial fan deposition morphologically correlates with a major river terrace these correlations create a regionally applicable framework for subdivision of the quaternary alluvial sequence in the study area where seven stepped river terraces are defined our new chronology of this fluvial sequence suggests that following intervals of aggradation three highest river terraces and equivalent alluvial fans were abandoned at 530 ka 300 ka and 10 ka respectively paleosols at the base of the loess sequences that directly overlie the older terraces and fans suggest that episodes of aggradation occurred late in the glacial cycles the subsequent incision that caused abandonment stabilization of these terraces and fans occurred near to glacial interglacial transitions a relatively high degree of synchrony in major river incision events across the piedmont despite disruption by several discrete structure zones with asychronous tectonic activities supports the dominant control exerted by climatic conditions on alluvial deposition and terrace creation during the quaternary across the north piedmont of the chinese tian shan

weathering and global denudation a negative correlation between sediment yield and weathering history as measured by the chemical alteration cia of the suspended sediment is observed for many of the world s major rivers and other regions of denudation the weathering history is a first order control on the sediment yield of such areas termed equilibrium denudation regions for other areas data scatter with either apparent increases or decreases of sediment yield for given cia values these areas are termed nonequilibrium denudation regions low sediment yields can be attributed to moderated erosion either natural or human induced and or the incorporation of unweathered glacial debris accelerated erosion resulting in high sediment yield is primarily human induced and results from cultivation and other land use each of these effects has a profound influence on global sediment discharge from the continents pre human suspended sediment discharge from the continents is estimated to be 12 6 times 10 15 g yr or about 0 6 the

mineral magnetic investigation of the talede loess palaeosol sequence since the last interglacial in the yili basin in the asian interior summary the loess palaeosol deposit in the asian interior is sensitive to the evolution of the westerlies thus providing a good opportunity to investigate regional palaeoenvironmental evolution and its relationship with global climatic changes multiparameter mineral magnetic investigations have been conducted on the talede section in the yili basin asian interior our study finds that 1 loess samples have higher concentration magnetic minerals than palaeosols though the magnetic mineral composition is similar ferrimagnetic magnetite antiferromagnetic hematite and lepidocrocite 2 large pseudo single domain psd and multidomain md like grains dominate both in loess and palaeosols however magnetic mineral grains in loess are much coarser than those in the palaeosols 3 palaeosols contain approx 30 per cent more amount of hematite than the loess samples the frequency dependent susceptibility of both loess and palaeosols is very low indicating the small amount of super paramagnetic grains and the higher fd per cent values of palaeosols also reveal that palaeosols have more amounts of ultrafine magnetic grains than loess the magnetic variations in part 1 and 2 can be well explained by the wind vigour model but the observed enrichment of hematite and ultrafine magnetic grains in palaeosols also reveals the first onset of pedogenic enhancement therefore the talede section could be seen as an end member of the classic chinese loess plateau clp magnetic enhancement model

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

size differentiated ree characteristics and environmental significance of aeolian sediments in the ili basin of xinjiang nw china abstract aeolian loess in the ili basin is an important geological archive for studying the changes in paleoclimate and sources of dust particles size differentiated rare earth elements ree may help to distinguish potential dust sources this study investigates the size differentiated ree characteristics from three sites including the zhaosu loess and the kekdala desert sediments from the ili basin and the chaona loess from the chinese loess plateau clp our results show that the patterns of variation of the ree characteristics in different size fractions can act as improved source tracers for aeolian sediments moreover the ree characteristics of the

deep and intermediate depth non double couple earthquakes interpretation of moment tensor inversions using various passbands of very broadband seismic data summary analysis of moment tensor inversions using various passbands of very broadband seismic data provides clear evidence that some non double couple moment tensors of intermediate depth and deep earthquakes result from the superposition of different double couple sources whose predominant principal axes are aligned with the predominant strain state within the subducting slabs the analyses are performed for three intermediate depth and deep earthquakes 1984 january 1 south of honshu 386 km 1985 april 23 luzon 181 km and 1987 may 7 northern sea of japan 417 km consistent non double couple moment tensors obtained using different sets of seismic waves in various low frequency bands suggest that these three significant non double couple components are not caused by unmodelled propagation errors of seismic waves in the inversion procedure because the various sets of seismic waves traverse very different ray paths for the south of honshu and the luzon events two major arrivals in the broadband p wave diplacement seismograms are observed with varying relative amplitudes or polarities from station to station the different double couple mechanisms which model the two phases combine to produce the significant non double couple moment tensors obtained at long periods the principal axes of the subevents closest in orientation to the predominant strain states within the slabs tend to be quite stable whereas the other two principal axes rotate between subevents this observation may explain the global nature of non double couple components in relation to the strain regime within the slab for the northern sea of japan event two major phases are observed in the p wave displacement waveforms but the variation in mechanism of two subevents that we model is not enough to explain the large non double couple component observed at long periods however since the non double couple component is exceptionally large compared with those for other deep earthquakes changes of focal mechanism with shorter delays than we can resolve appear to explain the overall radiation most simply

stratigraphies and chronologies of late quaternary loess paleosol sequences in the core area of the central asian arid zone abstract the sporadic distribution of the quaternary loess in central asia makes it hard to establish a regional pedostratigraphy through visual tracing of marker strata the pedostratigraphic correlation presented here is thus completely based on the radiocarbon chronologies of the four studied sections the first noticeable feature is that poorly drained conditions predominated in the period between 48 000 and 30 000 14 c bp during which three entisols developed at 45 000 14 c bp 40 000 14 c bp and 35 000 14 c bp after a period of loess deposition between 30 000 and 18 000 14 c bp under poorly drained conditions an entisol at the westernmost site valikhanov south central kazakhstan developed between 18 000 and 10 000 14 c bp also under poorly drained conditions the time equivalent deposits at romantic and zeketai sections to the east do not exhibit any soil forming characteristics although poorly drained conditions are also imprinted in the time equivalent loess the holocene sequences in the central asian domain consist of an early holocene loess unit deposited between 10 000 and 5 000 14 c bp and a late holocene soil formed during the past 5000 years in comparison the climate was also wet between 48 000 and 20 000 14 c bp during which three mollisols developed under well drained conditions in the chinese loess plateau of the east asian domain the loess deposited between 23 000 and 10 000 14 c bp in the chinese loess plateau has neither observable marks of soil formation nor imprints of poorly drained conditions the holocene sequence in the east asian domain exhibits an out of phase relationship with that in the central asian domain consisting of an early holocene soil formed between 9000 and 4000 14 c bp and a late holocene loess unit deposited during the past 4000 years

holocene dust deposition in the ili basin and its implications for climate variations in westerlies dominated central asia abstract understanding holocene paleoclimate in arid central asia aca is helpful for predicting future climate however holocene climate patterns and their forcing mechanisms across aca are vigorously debated in the context of global climate change here we present a holocene loess profile sgx from the ili basin in the westerlies dominated central asia based on high resolution medium grained 38 63 m quartz optically stimulated luminescence osl dating and grain size and color measurements we reconstruct the holocene paleoclimate osl geochronology indicate that this sgx loess profile covers the last 11 5 ka and grain size analyses reveal that the sediments are sandy loess and the environmentally sensitive fractions are

on the geochemistry of the late quaternary loess deposits of dobrogea romania abstract ten samples of loess and palaeosols collected from the costinesti dobrogea romania loess deposit and covering a time span of about 690 90 ka were analyzed by x ray diffraction instrumental neutron activation analysis and x ray fluorescence in order to determine the origin as well as the climatic conditions during loess deposition the presence of illite and calcite suggests reduced weathering confirmed by climate proxies chemical index of alteration 54 6 64 0 chemical index of weathering 65 7 71 7 and rb sr 0 26 0 47 were lower than the neighboring hungarian loess but closer to the average loess the content of 28 trace elements including 10 ree confirmed an average rock composition close to the upper continental crust the elevated content of cr and ni indicated the presence of a certain amount of felsic rock material zr and hf whose content was more than twice that of the upper continental crust indicate significant sediment sorting the low values of climatic proxies as well as the absence of any statistical significant difference between loess and palaeosol material confirmed rather limited weathering during the formation of the south eastern dobrogea loess deposits

loess chronology of the middle and upper pleistocene in tadjikistan the loess paleosol sequences of central asia are continuous terrestrial records of the quaternary period and enable detailed comparison with paleoclimatic archives such as marine and ice core records in order to reconstruct regional and global paleoclimatic and paleoecological development during the past 130 000 years thermoluminescence tl and infrared stimulated luminescence irsl dating methods are applied to the extensively studied loess paleosol sequence of the section at darai kalon chashmanigar tadjikistan in order to determine a more accurate chronological framework and climatostratigraphic reconstruction for the last interglacial glacial cycle luminescence dating suggests that the loess above the first pedocomplex from the top pc1 accumulated during the last glacial period a high accumulation rate of up to 1 20 m per 1000 years was determined for the last glacial loess especially for the uppermost 5 8 m pc1 formed during the last interglacial period oxygen isotope stage 5 the loess between pc1 and pc2 is designated to be of penultimate glacial deposition age infrared stimulated luminescence and tl age estimates are in agreement to 80 000 years before present bp indicating a long distance transport of the aeolian dust prior to deposition the upper numerical age limit range is between 300 000 and 450 000 years however reliable dating of the loess older than 130 000 years is not possible due to age scatter between samples and an inadequate increase of paleodose with depth this high resolution dating study underlines the importance of the section at darai kalon and indicates that it is one of the most continuous loess paleosol records of the northern hemisphere the chronological results are particularly important for the reconstruction of the human evolution in central asia suggesting much older age estimates than previously obtained for most of the archeological key sites associated with pc5 and pc4 in tadjikistan

data dependent non double couple components of shallow earthquake source mechanisms effects of waveform inversion instability seismic moment tensors are routinely determined for global earthquakes using waveform inversions and the resulting double couple and non double couple characteristics are extensively used in tectonic analyses for shallow events several moment tensor components are intrinsically poorly resolved especially for surface wave inversions which can lead to artificial non double couple components or can obscure actual non double couple components in the source representations the relatively greater instability of surface wave inversions can cause differences between inversions based on only body waves and joint inversions of body and surface waves the harvard cmt catalog exhibits systematic variations in non double couple components with seismic moment which can be attributed to use of only body waves in inversions for small events and combined body and surface waves for large events systematic behavior of non double couple components with regional strain environment is significantly less dependent on seismic moment when solutions influenced by less stable surface waves are omitted

the loess sequence from remisowka northern boundary of the tien shan mountains kazakhstan part i luminescence dating abstract similar to the chinese loess the loess deposits surrounding the high mountain regions of central asia play an important role in understanding the climate and environmental change during the pleistocene in eurasia despite their thickness and widespread distribution the loess deposits in southeast kazakhstan have so far not been investigated in detail the remisowka loess palaeosol sequence is located in the vicinity of the north tien shan mountains at an altitude of 1070 m above sea level in the profile under study nine loess layers were distinguished intercalated by eight pedocomplexes and so indicating a similar cyclicity like the loess palaeosol sequences in central asia and china at the remisowka section 12 loess samples were taken to set up a more reliable chronological model for the section using a luminescence dating approach polymineral fine grains were investigated by infrared optically stimulated luminescence applying the multiple aliquot additive dose protocol preliminary fading experiments were carried out for one sample taken from the uppermost loess layer while the results of the uppermost layer are in agreement with geological age estimates and indicate a correlation to the late glacial age underestimation is very likely for the samples below the first weak palaeosol no significant age increase with depth was recognised the reason for this age underestimation is not yet fully understood but could be related to anomalous fading further methodological approaches are necessary as well as a combination of different chronometric techniques for improvement of the results

geochemical characterization of the late pleistocene loess palaeosol sequence in tyszowce sokal plateau ridge se poland abstract the late pleistocene loess palaeosol sequence in tyszowce sokal plateau ridge se poland has been analysed for major elements si na k mg ca fe mn al ti and p in order to determine its chemical composition stratigraphy and degree of chemical weathering for the investigation a total number of 85 loess and soil samples were tested the vertical differentiation of chemical composition is strongly correlated with the variability of pedo and lithostratigraphic units the loess palaeosol sequence in tyszowce is geochemically distinct from other loess presented in the worldwide literature the profile is generally enriched with silica while other chemical elements are relatively depleted the contents of the major elements except si are lower in relation to the global average loess gal composition weathering indices such as chemical index of alteration cia or k al molar ratio and a cn k diagram imply weak to moderate weathering of the source material

evidence of bias in estimations of earthquake size magnitudes of earthquakes determined using traditional methods show systematic deviations dependent on tectonic setting from accurate estimates of earthquake size magnitudes are overestimated for most of the continental earthquakes underestimated for mid oceanic ridges and differences of varying sign are obtained for subduction zones this is important in evaluating the seismic risk or consideration of effects such as the seismic versus aseismic strain release as seismic moments determined from magnitudes can be wrong by as much as a factor of four

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

evaluating the paleoclimatic significance of clay mineral records from a late pleistocene loess paleosol section of the ili basin central asia in this study we present clay mineral records from a late pleistocene loess paleosol sequence in the ili basin central asia and assess their significance for paleoclimatic reconstruction the results show that the clay minerals are mainly illite average 60 and chlorite 28 with minor kaolinite 9 and smectite 3 illite was of detrital origin with no obvious modification to its crystal structure increases in illite content in the loess are ascribed to wind intensity rather than pedogenesis high proportions of illite in the clay fraction and of muscovite in the bulk samples of the paleosol units may lead to an overestimation of the weathering intensity kaolinite was likely inherited from the sedimentary rocks while chlorite might have been inherited from both sedimentary and metamorphic rocks the paleoclimatic signals of kaolinite and chlorite were unclear due to reworking by both fluvial and eolian systems smectite was more likely formed by the transformation of biotite and illite and its variation in the loess sequence was also controlled by wind intensity this was largely due to aggregation and is unlikely to reflect moisture changes although the interpretation of paleoclimate evolution may contain some uncertainties clay mineralogy does provide the possibility of tracing dust provenance

heavy mineral assemblages and sedimentation rates of eastern central asian loess paleoenvironmental implications abstract central asian loess deposits record the evolution of aridification across the asian interior however paleoclimatic proxies are strongly influenced by the variation of the dust source and accumulation process in order to decipher the paleoenvironmental changes a sensitive paleoclimatic proxy with clear source and accumulation process will be needed in this study heavy mineral assemblages and sedimentation rates were investigated in a 30 kyr loess section in the ili basin xinjiang northwestern china during marine isotope stage mis 2 trends in dust sedimentation rate were similar to those of the chinese loess plateau clp in anti phase with northern hemisphere summer insolation nhsi at 65 n amphibole epidote ratios contents and mean grain size were low during cold phases such as the late last glacial maximum lgm and heinrich event h 1 their ratios were higher during adjacent warm periods this was attributed to aeolian sorting during transportation namely greater sorting between amphibole and epidote occurred in warmer phases and weaker sorting occurred in colder phases the amphibole epidote ratio could serve as a proxy for wind intensity and thus the siberian high sh intensity amphibole epidote ratio was a more appropriate proxy to record wind intensity than dust sedimentation rate which was also influenced by sediment availability a higher amphibole epidote ratio corresponded to a more negative east asian stalagmite 18o indicating an anti phase relationship between the sh and east asian summer monsoon easm during the mis 2

magnetic investigation of late quaternary loess deposition ili area china abstract a late quaternary loess section in ili river valley xinjiang northwest china has been studied magnetically samples from two sections exhibit variations in magnetic susceptibility which displays a positive relationship with pedogenesis intensity in s 0 and negative in s 1 and l 1 the detailed magnetic properties investigation reveals that concentration of initial magnetite and maghemite fm varies and may be dominated by wind intensity and source mineralogy furthermore this is the most important magnetic component influencing magnetic properties of loess paleosol sequences and controls magnetic properties of loess deposition in contrast concentration of pedogenic fm is low and has little influence on magnetic properties of loess however it is an ideal magnetic parameter to assess paleoclimate the magnetic minerals in s 1 soil units might be linked to reducing environments reflected by the enhancement of the coercive force of remanence

geochemical characterization of the luochuan loess paleosol sequence china and paleoclimatic implications abstract chemical major and trace element and isotopic sr nd analyses of the luochuan loess paleosol sequence in china were performed in order to examine the following problems 1 potential source heterogeneity 2 element behavior during pedogenesis 3 paleoclimatic implications and 4 the use of loess data to determine the average composition of the upper continental crust new results clearly indicate that rb sr u and ce abundances are severely depleted in paleosols relative to their parental loess the behavior of these elements is strongly controlled by the breakdown of primary minerals such as carbonate sr or by alteration processes in highly oxidizing environments ce and u the pattern of element variations through the upper section of the luochuan sequence mimics the magnetic susceptibility signal both in position and in intensity thus reinforcing the pedogenesic origin of the enhanced magnetic susceptibility in paleosols all loess samples display highly uniform ree patterns except for ce characterized by the upper continental crust ucc ratios la yb n 10 and eu eu 0 66 the paleosol ree patterns are similar to those of the loess with the same lree hree fractionation but they also show distinct and variable negative ce anomalies nd and sr isotopic compositions are rather uniform in both loess and paleosols and do not vary with stratigraphic position nd 10 5 to 9 2 87 sr 86 sr 0 715 to 0 719 the isotopic homogeneity in the luochuan sequence strongly suggests a uniform source region during the entire period of deposition since 800 ka ago to the present several conclusions may be drawn from the present study 1 1 no geochemical distinction can be made between loess layers l1 to l7 the sources and the dust storm trajectories must have been essendally the same for the last 800 ka 2 2 some elements e g ca rb sr u ce are strongly fractionated by pedogenesis between loess and paleosols ce mobility in soils is clearly demonstrated but the process responsible for this leaching is still poorly understood 3 3 systematic variations of element abundances and ratios between loess and paleosols can be used as chemical indicators for pedogenesic intensity and so for paleoclimatic change these chemical indicators serve a function similar to that of oxygen isotopes in deep sea sediments pelagic foraminifera or that of magnetic susceptibility in loess sequences they are different recorders of paleoclimatic change 4 4 the striking uniformity of ree patterns and la th ratios in the luochuan loess and paleosols as well as in loess worldwide is an excellent starting point for estimating the average composition of the upper continental crust

terrestrial mollusk records in the loess sequences from eastern central asia since the last deglaciation and their paleoenvironmental significance abstract a variety of proxies has been studied to document paleoclimatic changes in arid central asia aca however biological archives which can be directly related to climatic conditions are still scarce in this region here we report records of the total count fossils tcf of terrestrial mollusks organic carbon isotopes 13corg and loss on ignition loi since the last deglaciation in the talede and xrblk loess sections in xinjiang eastern central asia prior to the holocene the records show rare fossils with relatively low loi and more positive 13corg indicating low biomass organic carbon content under dry conditions which were unfavorable for the survival of snails in contrast tcf increased abruptly at the beginning of holocene coincident with a prominent increase in loi and a marked negative shift in 13corg furthermore tcf increased gradually to its maximum and 13corg became progressively negative with constant high loi from the early to late holocene the variations imply a trend towards wetter environment with optimal moisture precipitation relative humidity conditions occurring in the late holocene overall this holocene moisture evolution history could be attributed to the variations of westerlies strength modulated by the latitudinal temperature gradient and the insolation related evaporation should also be concerned

geochemical evidence for the origin of late quaternary loess in central alaska loess is extensive in central alaska but there are uncertainties about its source and the direction of paleo winds that deposited it both northerly and southerly winds have been inferred the most likely sources of loess are the tanana river south the nenana river southeast and the yukon river north late quaternary loess in central alaska has immobile trace element compositions cr sc th ta th sc th u eu eu gdn ybn that indicate derivation mostly from the tanana river however other ratios as sb zr hf lan ybn and quantitative modeling indicate that the yukon river was also a source during the last glacial period there may have been a longer residence time of the siberian and canadian high pressure cells along with a strengthened aleutian low pressure cell this would have generated regional scale northeasterly winds and explains derivation of loess from the yukon river however superim posed upon this synoptic scale circulation there may have been strong southerly katabatic winds from expanded glaciers on the northern flank of the alaska range these winds could have provided eolian silt from the tanana river yukon river and tanana river sediments are highly calcareous whereas fairbanks area loess is not this suggests that carbonate leaching in loess kept ahead of sedimentation and that late quaternary loess in central alaska was deposited relatively

correlation of loess paleosol sequences in east and central asia with se central europe towards a continental quaternary pedostratigraphy and paleoclimatic history abstract as recent small climatic fluctuations on a 102 103 year time scale can be correlated worldwide and represent a decline of mean annual temperature of only 1 c major climatic changes on at least a 105 year scale glacial interglacial cycles and probably a 104 year scale the approximate length of an interglacial must be of similar ages throughout the temperate climatic belt of the northern hemisphere this concept allows continental pedostratigraphical correlations detailed knowledge of the genesis of paleosols is needed to establish loess paleosol stratigraphies that can be used for paleoclimatic reconstruction most paleosols however are truncated and largely recalcified from overlying loess micromorphological studies allow primary and secondary carbonates to be distinguished and provide unequivocal evidence of clay illuviation this enables the recognition of typical loess weathered loess and the recognition of different genetic soil horizons such as cb bc ah bw and bt horizons for the brunhes epoch the sequence at karamaydan tadjikistan is more detailed than the corresponding section in luochuan china and even more than in se central europe except for the last glaciation the very good correlation with the deep sea oxygen isotope record which includes the development of an accurate astronomical time scale allows a detailed chronostratigraphical subdivision of the loess paleosol sequence in karamaydan which therefore should be regarded as a key sequence for reconstructing the climatic history of the brunhes epoch this implies that the loess paleosol sequences in se central europe are less complete than thought earlier pedocomplexes in karamaydan correspond with single paleosols in se central europe e g the f6 paleosol in stari slankamen correlates with pedocomplexes pk vi and v at karamaydan which were formed over a period of about 140 ka although pedogenesis was interrupted several times by loess deposition the f6 soil is therefore an example of a welded paleosol as are the f5 the f4 and the f2 paleosols in se central europe for most of the matuyama epoch the central and lower parts of the sequence at chashmanigar show more pronounced paleosols than the equivalent parts at luochuan in se central europe only at stari slankamen are three strongly developed though truncated paleosols f9 f11 above neogene sediments mineralogical investigations of the silt and clay subfractions show that there is little difference in the type and amount of pedogenic clay mineral formation between the holocene soils and the paleosols of the brunhes epoch at karamaydan and of the matuyama epoch at chashmanigar this suggests that the interglacial climates represented by the b or bt horizons of the buried paleosols of late middle and early pleistocene age were similar to that of the holocene

source analysis of a potential hydraulic fracturing induced earthquake near fox creek alberta an earthquake with a reported magnitude of 4 4 ml was detected on 13 june 2015 in western central alberta canada this event was the third felt earthquake this year near fox creek a shale gas exploration region our results from full moment tensor inversions of regional broadband data show a strong strike slip mechanism with near vertical fault plane solutions the decomposition of the moment tensor solution is overwhelmingly double couple while only a modest 20 contribution is attributed to compensated linear vector dipole the depth of this earthquake is 3 4 km near the base of the sedimentary layer and the moment magnitude m 3 9 of this event is considerably smaller than the initial reported ml value the hypocenter location depth and mechanism are favorable to a possible association between this earthquake and hydraulic fracturing operations within the duvernay shale

aeolian origin and palaeoclimatic implications of the red clay north china as evidenced by grain size distribution the red clay is an important deposit underlying the quaternary loess palaeosol sequence in the chinese loess plateau being regarded as an excellent record of palaeoclimate changes in the late tertiary several properties of the red clay have been measured previously in order to derive climatic information however the sedimentary processes involved and the origin of the materials remain controversial here we present results of grain size analyses of the red clay from four representative sites in the chinese loess plateau in particular their grain size distribution is compared with that of typical quaternary aeolian loess palaeosol as well as lacustrine and fluvial sediments it appears from the sedimentological evidence that the major part of the red clay is of aeolian origin it is rather similar in some of its properties to the quaternary loessic palaeosols the dust forming the red clay was transported by a wind system that was weaker than that involved in the accretion of the quaternary loess furthermore the red clay sediment has been modified by post depositional weathering copyright 2001 john wiley sons ltd

geochemistry of the xining xifeng and jixian sections loess plateau of china eolian dust provenance and paleosol evolution during the last 140 ka abstract loess and paleosol samples from three distant sections xining xifeng jixian of the chinese loess plateau were analyzed for chemical and nd sr isotopic compositions in order to obtain information about the paleoclimatic variation during the last 140 ka these three sections represent three different climatic conditions from arid in the west xining to more humid in the east jixian across the loess plateau isotopic analyses show that all the three sections display a restricted range of 143 nd 144 nd ratios or e nd 10 0 5 indicating the dominance of relatively young and uniform upper crustal sources for the eolian dust the loess and paleosol samples have typical upper crustal 87 sr 86 sr ratios 0 714 0 718 and their variation can partly be attributed to different carbonate silicate ratios in the samples ree data from the three sections are indistinguishable from each other they show typical upper crust patterns characterized by la yb n 10 and eu eu 0 65 the high degree of chemical and isotopic homogeneity suggests that the dust source region must have undergone multiple recycling and thorough sedimentary mixing processes various chemical indicators have been used to monitor the pedogenetic intensity in these sections although results for the jixian section agree reasonably well with the known climatic conditions on the loess plateau the other two sections yield results not in agreement with some well accepted proxies like magnetic susceptibility or grain size distribution some chemical proxy indicators established in our previous work on the luochuan section such as the systematic u depletion and negative ce anomalies in ree patterns in soils are not clearly recorded in the present case the discrepancy between different climatic proxies could be related to the effective soil water budget temperature as well as the rate of development of each proxy

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

controlling factors on heavy mineral assemblages in chinese loess and red clay abstract heavy mineral analysis is a sensitive technique in constraining provenance of sandstone but has rarely been applied to loess here we report a heavy mineral study of selected samples from the luochuan xifeng and caoxian loess red clay sections on the chinese loess plateau based on the novel qemscan quantitative evaluation of minerals by scanning electron microscopy technique we found that heavy mineral assemblages of loess deposited through the past 500 kyr are similar and unchanged by post depositional chemical dissolution in contrast in samples deposited from 900 ka to 3 ma the relative proportion of stable minerals tends to increase down section in addition the xifeng samples consistently display higher contents of unstable ferromagnesian minerals than the luochuan samples detailed analysis of surface textures displayed by different minerals by optical methods indicates that such a compositional difference can be ascribed to more effective diagenetic dissolution for the luochuan section explained by more extensive percolation of interstitial waters in wetter climatic conditions interestingly heavy mineral assemblages in the underlying upper miocene red clay from xifeng deposition age 7 ma are similar to those of recent loess deposited since 500 ka this similarity indicates that climate and or local preservation conditions hampered dissolution reactions thus helping to preserve an original provenance signal that remained largely unchanged throughout the considered time period our study demonstrates that climatically and time controlled diagenesis plays a key role in determining the composition of heavy mineral assemblages contained in loess deposited several hundreds of thousands years ago we also show that by using both qemscan and traditional optical techniques on the same samples we can obtain fundamental complementary information for a correct interpretation of the heavy mineral assemblage

distribution and composition of loess sediments in the ili basin central asia loess deposits in central asia provide an important record of regional climate and environmental change however in contrast to the intensively investigated loess deposits on the chinese loess plateau clp loess sediments in the ili basin of eastern central asia are poorly understood based on field investigation and existing literature this paper presents a preliminary study of the distribution strata and composition of the ili loess the distribution of the ili loess is clearly controlled by topographic and geomorphic conditions mainly in the river terraces low uplands and slopes of the tianshan mountains the thickness of the loess varies from several meters to over two hundred meters to characterize the ili loess composition the authors analyzed its grain size geochemistry x ray diffraction pattern and heavy mineral assemblage grain size analyses reveal that the ili loess consists predominantly of silt 4 63 mu m with a minor proportion of sand which is coarser than the loess of the clp and suggests a nearby provenance the bulk mineral components of the ili loess are dominated by quartz and feldspar with minor amounts of calcite chlorite mica dolomite and hornblende more than 20 types of heavy minerals were observed with major components of amphibole magnetite and epidote the major elements of the ili loess are characterized by high abundance of sio2 al2o3 and cao and minor amounts of fe2o3 mgo na2o and k2o compared to the clp loess the ili loess is relatively rich in na2o and displays higher na2o al2o3 ratios suggesting weak weathering the distribution patterns of rees indicate that both the ili loess and clp loess are of typical upper crustal composition with enrichment in lree negative eu anomalies and depletion of hree both the heavy mineral assemblage and geochemistry indicate that the local bedrock of the ili basin may have contributed only a little to the loess sediments c 2014 elsevier ltd and inqua all rights reserved

non double couple earthquakes 1 theory historically most quantitative seismological analyses have been based on the assumption that earth quakes are caused by shear faulting for which the equiv alent force system in an isotropic medium is a pair of force couples with no net torque a double couple or dc observations of increasing quality and coverage however now resolve departures from the dc model for many earthquakes and find some earthquakes especially in volcanic and geothermal areas that have strongly non dc mechanisms understanding non dc earth quakes is important both for studying the process of faulting in detail and for identifying nonshear faulting processes that apparently occur in some earthquakes this paper summarizes the theory of moment tensor expansions of equivalent force systems and analyzes many possible physical non dc earthquake processes contrary to long standing assumption sources within the earth can sometimes have net force and torque components described by first rank and asymmetric sec ond rank moment tensors which must be included in analyses of landslides and some volcanic phenomena non dc processes that lead to conventional symmetric second rank moment tensors include geometrically complex shear faulting tensile faulting shear faulting in an anisotropic medium shear faulting in a heteroge neous region e g near an interface and polymorphic phase transformations undoubtedly many non dc earthquake processes remain to be discovered progress will be facilitated by experimental studies that use wave amplitudes amplitude ratios and complete waveforms in addition to wave polarities and thus avoid arbitrary assumptions such as the absence of volume changes or the temporal similarity of different moment tensor com ponents

an implosive component to the source of the deep sea of okhotsk earthquake of 24 may 2013 evidence from radial modes and cmt inversion abstract we study the spectral amplitudes of the first two earth radial modes 0 s 0 and 1 s 0 excited by the sea of okhotsk earthquake of 24 may 2013 the largest deep event ever recorded in the search for an isotropic component to its source in contrast to the case of the 1994 bolivian earthquake we detect an implosive component m i 1 1 10 27 dyn cm equivalent to 3 of the full scalar moment but 14 of the lone deviatoric component exciting the earth s radial modes an independent moment tensor inversion using the standard globalcmt algorithm but after relaxing its zero trace constraint similarly yields an implosive isotropic component albeit with a larger amplitude while it fails to document one in the case of the 1994 bolivian deep earthquake an implosive component to the source is expected in the model of transformational faulting in which deep earthquake rupture nucleates and grows upon transformation of metastable olivine to ringwoodite in the cold subducting slab this interpretation is supported by quantitative estimates 0 9 4 m of the thickness of the transformed shear zone which scale favorably relative to earthquake fault length with the upper end of the range of laboratory results reported for ices germanates and silicates the resulting extent of the transformation in the metastable wedge is consistent with the local geometry of the deep slab as recently determined by rupture modeling and aftershock distribution our results are in contrast to those for the two runner up largest deep earthquakes the 1994 bolivian and 1970 colombian shocks for which a similar isotropic component could not be detected we attribute this difference to variability in the ratio of isotropic to deviatoric components which combined with the smaller size of the 1970 and 1994 events would make any putative implosive component fall below detection levels especially in the case of the 1970 colombian earthquake for which only analog narrow band records were available

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

source mechanism of two 1994 intermediate depth focus earthquakes in guerrero mexico abstract in may and december 1994 two medium size intermediate depth focus earthquakes occurred in guerrero mexico eastward of the rupture area of the great michoacan earthquake of september 19 1985 even though these are not major earthquakes 6 4 m w they were widely felt through central and southern mexico with minor damage at zihuatanejo and acapulco located along the pacific coast and mexico city both earthquakes separated by 100 km have similar focal depths and magnitudes however their focal mechanisms based upon the polarities of first arrivals show some differences the may earthquake shows a clear normal faulting mechanism 307 55 108 whereas the december earthquake mechanism solution suggests an initial thrust faulting 313 62 98 process although previous analysis including local and teleseismic stations reported a normal faulting for the december earthquake we find that modeling using the cmt focal mechanism solution fails to reproduce the first 5 sec of the observed p wave signal at the nearest broadband station 168 km and the s wave polarity at two strong ground motion local stations 32 53 km in fact the best fit for these stations is obtained using the thrust focal mechanism calculated from the first motion method seismic moment value and rupture duration time deduced from the teleseismic spectral analysis are 2 0 10 18 n m and 6 9 sec for the may event 2 8 10 18 n m and 7 1 sec for the december earthquake from the inferred seismic moment an average of 15 bars for both earthquakes is obtained inversion of teleseismic p wave data indicates a better fit using the cmt focal mechanism solution normal faulting than the first motion mechanism for both earthquakes although the adjustment9s differences are small for the may event for this earthquake the rupture consisted of two sources separated by 7 sec starting at a depth of 40 km and then propagating downdip reaching a depth of 60 km the december earthquake however released all its energy at a depth of 50 km in two main sources separated by 10 sec the non double couple components values are 0 004 and 0 01 for the may and december events respectively indicating that the december shock has a small contribution of non double couple radiation that could be the result of a changing mechanism this result agrees with the hypothesis that a slab subducting at a shallower angle our case is associated with the existence of random subfaults with different fault orientations from a tectonic point of view the complexity of the december earthquake could be the result of the observed complexity of the stress distribution around 101 w and the existence of compressional events beneath the normal faulting earthquakes near the coastline this feature permits the flexural stresses associated to the slab bending upward to become subhorizontal at the guerrero region we conclude that the may earthquake corresponds to a pure normal faulting whereas the december shock is a complex event with a variable fault geometry

magnetic granulometric and geochemical characterizations of loess sections in the eastern arid central asia implication for paleoenvironmental interpretations abstract loess deposits in the arid central asia aca contain sensitive messages concerning the evolution of the westerlies and the interior aridification of asia in this study we conducted a combined study of geophysical and geochemical characterization on loess sections in the eastern aca to discuss possible paleoclimate development since the late pleistocene era results show that the aca loess chiefly exhibited similar geophysical and geochemical compositions with loess deposits in other regions like the chinese loess plateau there are various accumulation rates that would have been responsible for the depositional difference within the aca loess profiles in addition there are three magnetic responses to the bulk grains and geochemical proxies in this study at the bottom segment of the section magnetic enhancement was associated with coarse grain sizes and water leaching magnetic enhancement responded to stronger pedogenesis and moderate paleo wind intensity in the uppermost parts moreover there is a transitional segment in the middle part of the section characterized by inordinately detrital inputs and weak pedogenic contributions thus it may be better to evaluate the magnetic climatology of the aca loess through different depositional stages furthermore this study generally reveals that the paleoclimate pattern in the aca was probably characterized by relatively low moisture during warm intervals and vice versa in the middle and bottom parts of the profiles but relatively enhanced moisture was indicated during the holocene period further studies are still necessary to obtain reliable proxies and chronology for a detailed paleoclimate interpretation of the aca loess

source fingerprinting loess deposits in central asia using elemental geochemistry with bayesian and glue models abstract the provenance of loess deposits in central asia is largely unexplored accordingly the goals of this research were to test and compare the performance of two different models generalized likelihood uncertainty estimation glue and a bayesian model for quantifying the uncertainty in source apportionment estimated for 46 target loess samples collected in the ili basin in eastern central asia model performance was evaluated using goodness of fit gof mean absolute fit maf and virtual mixtures vm in combination with root mean square error rmse and mean absolute error mae our dataset comprised 132 surficial samples collected from three potential sources comprising river alluvium n 29 sand dunes n 35 and topsoils n 68 all samples were analysed for elemental geochemistry six geochemical properties co er y ga dy and pb were selected in a composite fingerprint which classified 83 of the samples from the three source categories correctly based on both models source contributions to the loess samples were in the following order topsoils river alluvium sand dunes based on the gof and maf tests both models were accurate in predicting measured tracer concentrations in the loess samples the bayesian model was slightly more accurate mean rmse 1 6 mean mae 1 8 than the glue mean rmse 5 0 mean mae 4 7 model in predicting known source contributions overall our results provide confirmation that application of source fingerprinting with elemental geochemistry and uncertainty modelling techniques is useful for identifying the provenance of loess sediments in arid and desert environments

characteristics of well determined non double couple earthquakes in the harvard cmt catalog abstract this paper evaluates earthquakes in the harvard centroid moment tensor cmt catalog which possess well determined deviatoric non double couple mechanisms i e mechanisms with significantly large compensated linear vector dipole clvd components for a cmt m we measure the strength of the non double couple component with the statistic norm 2 6det m m 3 which is 0 0 for a pure double couple and 1 0 for a pure clvd for each cmt we measure whether norm is well determined by allowing individual elements of m to vary within their range of uncertainties as reported in the harvard catalog then determining the range of variation of norm as m varies the most well determined 11 of the catalog has a range for norm of 0 2 or less of these earthquakes about one quarter have predominantly clvd mechanisms with norm of 0 4 or greater these 283 mechanisms make up the principal data for this study these clvd earthquakes occur commonly in almost all tectonic environments along mid ocean ridges and transforms in shallow subduction zones within wadati benioff zones and in the interiors of plates in both oceanic and continental regions along ridge transforms the majority have horizontal t axes in shallow subduction zones the majority have horizontal p axes which are approximately perpendicular to the trench these observations are consistent with a schematic model which explains clvd mechanisms as the sum of two or more elementary double couple subevents with orientation fixed by the type and geometry of the plate boundary within ridge transforms subduction zones and wadati benioff zones where the plate motion lithospheric structure etc is sufficiently uniform about 75 of the clvd mechanisms conform to this model

mantle structure and seismotectonics of the sunda and banda arcs abstract we have examined the mantle structure and seismotectonic features of the sunda and banda arcs indonesia based on the p wave tomographic images focal mechanism solutions gravity anomaly and heat flow data on the basis of slab morphology and seismicity we can divide the arcs into three parts the western sunda eastern sunda and banda arc the slab like tomographic image penetrates to a depth of about 500 km below the western sunda arc where seismicity does not exceed a depth of 250 km in the eastern sunda arc where a seismic gap exists between 300 and 500 km depths the slab appears to be continuous and to penetrate into the lower mantle beneath the banda arc with seismicity down to a depth of about 650 km the slab dips gently and does not appear to penetrate into the lower mantle the positive gravity anomaly shows a systematic pattern namely the anomaly along the eastern sunda arc is larger than that in the western sunda and the banda arcs along the back arc side of the sunda and banda arcs the heat flow decreases from the west to the east seismic strain release from the shallow earthquakes calculated from the cmt solutions show the strain axes to be oblique to the structural trends the cmt solutions show that the eastern sunda arc is characterized by normal earthquakes along the trench and back arc thrusting earthquakes north of the volcanic line in the western sunda and the eastern sunda arcs earthquakes of the down dip extension type dominate the slab down to a depth of 200 km while down dip compression earthquakes occur below 500 km depth in the banda arc deep earthquakes show down dip extension to a depth of 500 km below this depth the state of stress is not clearly defined

abrupt climatic events recorded by the ili loess during the last glaciation in central asia evidence from grain size and minerals abstract the loess record of central asia provides an important archive of regional climate and environmental changes in contrast to the widely investigated loess deposits in the chinese loess plateau central asian loess paleosol sequences remain poorly understood here we present an aeolian loess section in the southern ili basin based on granularity and mineralogical analyses we reconstruct climatic changes during the last glaciation the results indicated that most of the abrupt climatic events such as dansgaard oeschger events and heinrich events were imprinted in this loess section although their amplitudes and ages showed some differences compared with the millennial oscillations recoded in loess and stalagmites in east asia the arid central asia responded more sensitively to the warming events than to the cooling events the shifting trajectory of westerlies across central asia played an important role in dust deposition during the stadials the north atlantic climatic signals may have been transmitted from central asia to the east asian monsoon regions via the westerlies

assessment of the dominant climatic factor affecting pedogenic development in eolian sequences during the holocene in arid central asia abstract eolian sediments are widely distributed and are one of the most important geological archives of past climatic changes for example the degree of pedogenic development of loess is widely used as an indicator of precipitation amount however in the case of arid lands characterized by drought conditions and where potential evaporation is much higher than precipitation it is unclear whether precipitation is the sole factor dominating pedogenic development or whether temperature is also an important factor affecting for pedogenic development in this study we compared variations in pedogenic development of sequences of holocene eolian sediments in arid basins and humid high mountains in northwest china to assess the role of precipitation and temperature in soil development the results indicate that the variation trend of pedogenic development was similar in both arid basins and high mountains with weak development in the early holocene and gradually increasing development into the late holocene in addition combining both temperature and moisture records reveals that the weakest soil development was in the early holocene when the climate was warm and dry and the strongest soil development was in the late holocene when the climate was warm and humid overall our results reveal that precipitation was the dominant climatic factor controlling changes in pedogenic development in the study area

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