geochemical characteristics of the eolian deposits in southern china and their implications for provenance and weathering intensity abstract the loess paleosol sequences in the middle lower reaches of the yantgze river are valuable geological records of quaternary environments that bear information about climate change for the subtropical zone of southern china type sections containing eolian deposits in this region mostly include the upper loess soil sequence referred to as xiashu loess formation the middle vermiculated red soil vrs and the underlying fluvial deposits or bedrock in this study xiashu loess paleosol formed in the xiashu loess and the vrs samples from xuancheng xc and jiujiang jj sections were analyzed for their elemental major and trace elements and isotopic sm nd geochemistry and compared with pleistocene loess and paleosol samples from the chinese loess plateau clp in northern china the results show an overall similarity in geochemical characteristics between the southern china loess and the average ucc indicating that the dust materials were derived from well mixed sedimentary protoliths which had undergone numerous upper crustal recycling processes in comparison with the loess of northern china the eolian deposits in southern china have higher tio2 zr hf and lower ba concentrations higher tio2 al2o3 u pb th pb and lower ba rb zr hf eu eu ce yb eu yb ratios and lower end 0 values with relatively greater range these features coincide with the complicated source rock compositions in the middle lower yangtze river which suggests local sources for the eolian deposits in this region the eolian deposits in southern china have experienced the intermediate k removal weathering stage ca sr na mg and k are the main mobile elements in the weathering process in comparison with the xiashu loess formation the vrs has greater depletion of na mg k and mn indicating a stronger weathering intensity or perhaps a longer period of weathering

polyphase deformation in a fore arc back arc basin salin subbasin myanmar burma the salin subbasin of myanmar part of the larger central basin is a fore arc back arc basin couplet situated between an oblique subduction zone to the west and a major right lateral strike slip fault to the east surface and subsurface expressions of folds and faults suggest that the basin experienced north northwest directed extensional deformation in the miocene followed by east northeast directed pliocene pleistocene transpressional deformation resulting in a variety of structural styles including thrust faults oblique reverse faults strike slip faults and normal faults fault propagation folds cored by west dipping thrust faults in the basin center are located above steps in the top of basement surface most likely fault controlled unconformities at the base of and within the pliocene pleistocene synorogenic section indicate that the thrust faults were active during the pliocene pleistocene the southeastern region contains broad north northwest trending uplifts and east northeast striking normal faults associated with thickened miocene synorogenic deposits pliocene pleistocene sedimentary rocks lie unconformably above the miocene section and are folded above the uplifts reflecting pliocene pleistocene compression in the southern part of the basin miocene sedimentary rocks thicken dramatically over the 20 n uplift and the yedwet uplift suggesting that the north northwest striking faults that bound them represent pliocene pleistocene inversion of miocene normal faults during the miocene the burma plate acted as a fore arc sliver coupled with the india plate subducting obliquely underneath it and moved northward relative to asia along the sagaing fault normal faulting and local basin formation took place at this time when the northern part of the burma plate collided with eastern asia in the pliocene transpressional deformation predominated creating thrust and reverse faults positive flower structures and inverted basins

factors of paleosol formation in a late cretaceous eolian sand sheet paleoenvironment marilia formation southeastern brazil abstract the marilia formation which crops out in southeastern brazil is interpreted as a late cretaceous eolian sand sheet area the sedimentary succession ca 110 m thick is characterized by alternating strata of eolian deposits and paleosols the paleosols constitute more than 66 of the thickness and are an important element in the interpretation of the paleoenvironmental controlling factors which affected the soil formation in this eolian sand sheet in this paper six paleosol profiles are described and assigned to two pedotypes itaja and apore the itaja pedotype is constituted of a sequence of five superimposed polygenetic profiles which show different phases of clay illuviation and carbonate precipitation and it has been classified as aridisol the apore pedotype overlies the itaja pedotype this pedotype shows an increase in leaching cia k ratios reddening and illuvial clay features in respect to itaja and has been classified as alfisol the analysis of the factors which controlled the soil formation revealed that both pedotypes formed on a stable landscape probably covered by a community of low stature plants in which the soils had sufficient time to develop very mature profiles the changes in soil forming processes were driven principally by variations in available soil moisture from precipitation using depth to carbonate functions from bk and cia k proxy from bt horizons of the itaja pedotype mean annual precipitation map estimates range from 240 to 1078 mm yr respectively these contrasting climatic conditions resulted in the superimposition of arid or semi arid with more humid climates and determined the considerable change in the pedogenic features with many horizons showing the interlacing of calcite and clay features in the apore pedotype cia k proxy from bt horizons estimates that averaged map was around 900 mm yr and the prevalent humid conditions can be attested by soil properties and abundance and depth of root traces our results show that the diversity in pedotypes is mainly attributed to differences in paleoclimatic conditions during maastrichtian time and that eolian sedimentation was restricted to periods of harsh arid conditions as in semi arid climates with map estimates around 240 mm yr the formation of soils with well developed calcic horizons was possible

assessing the utility of visible to shortwave infrared reflectance spectroscopy for analysis of soil weathering intensity and paleoclimate reconstruction abstract visible to shortwave infrared reflectance vswir spectroscopy is a fast and efficient approach for estimation of soil properties in order to test whether soil weathering intensity can be predicted using reflectance spectra in the vswir range 350 2500 nm and to examine the efficacy of this methodology to supplement or substitute for traditional mineralogical and geochemical techniques of paleoclimate reconstruction we investigated a quaternary soil sequence at shengli in the sichuan basin of southwestern china vswir absorption bands can be characterized by geometrical parameters including position p depth d width w asymmetry as and full width at half maximum f our results indicate that spectral features in the visible to near infrared vnir 350 1000 nm range can be interpreted in terms of the presence and or concentration of individual fe oxide phases spectrally detected water is mostly bound in clay minerals and this single dominant water source facilitates interpretation of shortwave infrared swir 1000 2500 nm parameters soil spectral parameters were compared with the fe oxide mineralogy major element composition and clay mineralogy of soil samples obtained from conventional laboratory analyses strong correlations are found between vnir parameters and fe oxide mineralogy with d 900 serving as the best proxy for total ferric iron concentration p 900 and d 700 d 500 exhibit similar variation trends and relationships to the hematite hematite goethite h h g ratio of soil samples confirming their value as monsoonal weathering intensity proxies lower values of p 900 and d 700 d 500 indicate warmer and seasonally drier pedoenvironments reflecting a stronger east asian summer monsoon the utility of some swir parameters for assessment of weathering intensity declines in inhomogeneous soils e g those having vermiform structure thus spectral evaluation of weathering intensity is most effective in soils that are relatively homogeneous for which weathering degree is highly correlated to as 2200 d 2200 d 1900 and as 1400 the utility of these spectral proxies depends mainly on the mineral composition of soils and the application type i e laboratory versus field studies the application of vswir in the field e g imaging spectroscopy or is shows promise for rapid in situ mapping of weathering intensity thus providing a convenient approach to paleoclimate reconstruction in remote and inaccessible regions

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

an 11 ma old red clay sequence on the eastern chinese loess plateau abstract older red clay deposits on the chinese loess plateau contain information of early paleomonsoon evolution and tectonic history of the ordos platform and the tibetan plateau a well conserved eolian red clay sequence was recently discovered at shilou on the eastern chinese loess plateau paleomagnetic measurements demonstrate that polarity zones recorded in the shilou red clay profile correspond well with polarity zones between c2an 1n and c5n 2n of the gpts and the basal age of the study profile is approximately 11 0 ma field observation grain size frequency distribution and quartz grain morphology suggest a wind blown origin for this sequence this indicates that the eastern loess plateau began to accumulate dust deposits at 11 ma ago implying earlier establishment of the east asian paleomonsoon probably owing to uplifting of the tibetan plateau and ongoing global cooling it also demonstrates that the eastern loess plateau belonging to the ordos platform was slowly uplifted and suffered from erosion in the early neogene and has no conserved eolian deposits older than 11 ma as in the western chinese loess plateau

an evaluation of geochemical weathering indices in loess paleosol studies abstract applying geochemical proxies as measure for the weathering intensity of paleosols and sediments such as loess the quaternary scientist is confronted with various element ratios that have been proposed in literature this paper gives an overview on the principle of geochemical weathering indices different types of indices are evaluated with respect to the suitability for loess paleosol sequences regarding the special characteristics of this type of sediments and paleosols case examples in this study are key sections in southeastern and eastern europe the loess paleosol sequences batajnica stari slankamen serbia mircea voda romania and stary kaydaky ukraine which represent archives of the late and mid pleistocene climate change of the region considering element behavior during weathering or diagenesis the chemical proxy of alteration cpa i e the molar ratio al2o3 al2o3 na2o 100 is proposed as the most appropriate index for silicate weathering the cpa was evaluated against commonly used weathering indices including the chemical index of alteration cia the chemical index of weathering ciw the plagioclase index of alteration pia the index b of kronberg and nesbitt and the ba sr and rb sr ratio depth profiles of sr type indices e g ba sr rb sr are likely to be influenced by the dynamics of secondary carbonate on the other hand common na type indices e g cia pia ciw may suffer from uncertainties in separating carbonate ca from silicate ca or from biases due to k fixation illitization the cpa is insensitive against such effects additionally using the cpa as with other na type indices provides the possibility to evaluate the homogeneity of the parent material regarding the relevant host minerals via the a cn k diagram

east asian summer monsoon intensity inferred from iron oxide mineralogy in the xiashu loess in southern china abstract the xiashu loess in comparison to the well studied loess sequences in the chinese loess plateau clp provides a good opportunity for studying east asian monsoon variations from a southern china perspective here we present a study of the iron oxide mineralogy of the xiashu loess using integrated geochemical and diffuse reflectance spectroscopy drs measurements as well as magnetic data our results show that the free iron oxide fe d to total iron fe t ratio fe d fe t hematite hm to goethite gt ratio hm gt and saturation isothermal remanent magnetization sirm to magnetic susceptibility ratio sirm all indicate particularly strong summer monsoons during the formation of paleosols ps5 and ps4 equivalent to marine isotope stage 13 and 11 respectively however magnetic susceptibility and fe d fe t are not consistently reliable indicators of summer monsoon intensity for the whole section our results indicate that a multi proxy approach can give a more reliable summer monsoon intensity reconstruction the summer monsoon shows a cooling trend and a declining of precipitation from 0 5 to 0 3 ma after which it becomes warmer and wetter towards the top of paleosol ps1 equivalent to mis 5 however ps1 was formed under a relatively cooler temperature and wetter soil conditions in comparison to ps5 and ps4 such supra orbital variations in the east asian summer monsoon superimposed on the effects of glacial interglacial cycles in southern china are also reflected in the 0 4 0 5 ma cycle of marine carbon isotopes in the global ocean possibly indicating a strong link between terrestrial weathering and the global carbon cycle

paleo pedological record of the rocourt pedosequence at veldwezelt hezerwater belgian pleistocene loess belt part 1 evolution of the parent material as the environment influences soil formation loess paleosols are important archives of former climatic conditions however this record is highly complex and all features need to be evaluated in order to obtain consistent information on soil formation this study revises the pedological record of the rocourt paleosol complex an important pedo stratigraphic marker for the eemian and early weichselian at an exceptionally well preserved in situ sequence veldwezelt hezerwater belgian loess belt contrasting hypotheses exist considering the evolution of the parent material after the deposition of the saalian loess and on the importance of aggrading aeolian deposition in this study soil morphological features and depth functions of x ray diffraction grain size distribution cec base saturation total fe al k na and ca content ph and electrical conductivity were established to reconstruct deposition dynamics weathering and carbonate content of the parent material texture analysis confirms the petrostratigraphic homogeneity of the parent material and suggests that it developed under a regime of fluctuating rates of primary dust deposition intermixed with periods of fluvial reworking of the dust strong weathering was identified in the lower stratigraphic unit supporting the general consensus that it formed during the eemian in saalian loess less information is present to confirm the origin of the upper less developed illuvial units which may have formed by welding or by pedogenesis in locally redistributed or aeolian material the overlying a horizons are clearly less weathered and evidence for early recalcification indicates that deposition of unweathered calcareous sediments gained importance during the formation of these horizons

soils as indicators of quaternary climatic change in mid latitude regions abstract soils result from changes to uppermost layers of the earth s crust occuring beneath stable land surfaces soil properties are determined by five factors or groups of factors climate organisms relief parent material and time quantitative climatic interpretation of soils depends upon mathematical relationships between individual soil properties and climatic factors i e climofunctions these are difficult to establish and often cannot be applied to diagenetically modified buried soils so most climatic interpretations of soils are qualitative or semi quantitative soil features formed by frost action are the most reliable climatic indicators most soils continue to develop over time however many soil dating techniques provide only a single date some time during the period of soil formation the beginning and end of a soil development period are best determined by reference to dated deposits over as large an area as possible but stratigraphical interpretation of soils is still impeded by imprecise definitions and procedures the soil chronosequences developed in the major loess deposits of europe and asia provide the best evidence for climatic change throughout the quaternary however only major glacial interglacial cycles are well expressed to obtain more detailed evidence of weaker interstadial cycles it is necessary to study chronosequences in mid latitude regions which were generally moister for much of the quaternary however these soils are less well preserved and present additional difficulties of interpretation because of greater variation in parent material relief and time as soil forming factors

chemical weathering of the loess deposits in the lower changjiang valley china and paleoclimatic implications abstract loess deposits xiashu loess are widely distributed in the lower changjiang valley east china and are considered to be of eolian origin with a similar provenance to the well documented loess of north central china the xiashu loess is characterized by strong dissolution of carbonate and considerable weathering of some silicate minerals especially plagioclase chemical mobility of ca sr na mg was observed in the xiashu loess sediments whilst most transition metals are relatively enriched chemical index of variation cia and element ratios of k na and k ca record several paleoclimate events in the lower changjiang valley during the mid late quaternary corresponding with isotopic records in deep sea sediments east china might be governed by stronger summer monsoons than north central china during interglacial periods of the mid late quaternary which may somewhat obscure the record of winter monsoons during glacial periods

accurate relative earthquake hypocenters reveal structure of the burma subduction zone the burma arc links the himalaya to the andaman sumatra trench and comprehension of the geological features in the region is vital to understand the active tectonic processes in the area subduction on the sumatra trench produced the devastating 2004 sumatra earthquake m w 9 0 but the mechanisms accommodating relative india sundaland motion in burma are still unknown previous seismological studies of the area use only earthquake catalog hypocenters so structural details of subducted material remain poorly understood here accurate relative hypocenters for 81 earthquakes are estimated using first arrivals picked from regional and teleseismic recordings depth determination is improved using measured travel time differences between p onsets and depth phases pp and sp the results clearly illustrate a slab 21 25 n dipping 25 at 40 80 km deep 40 at 80 120 km deep and 60 at 120 160 km deep and its strike follows the indo burman ranges at latitudes 25 n earthquakes become more shallow and a diffuse picture of hypocenters with an east west lateral discontinuity at depth is observed indicating lateral deformation of the slab previous studies suggest there is a transition at 90 km deep from shallower strike slip earthquakes to deeper thrust type events here accurate depth estimates combined with confirmation of two global centroid moment tensor solutions using body wave modeling shows that thrust and strike slip earthquakes both occur deeper than 100 km in the burma arc

plio pleistocene red clay deposits in the pannonian basin a review terrestrial red clays underlying quaternary loess deposits or filling fissures and recently existing caves in limestone are named tengelic red clay formation and kerecsend red clay formation middle pliocene to lower pleistocene they occur in three types in hungary 1 the oldest red clays are mainly in situ weathering crusts rich in kaolinite formed in warm humid subtropical or monsoon climate 2 the younger type is rich in smectite and goethite and 3 illite and chlorite dominant in the youngest part which formed under warm and dry climates in savannah steppe or forest steppe environments and is of wind blown origin representative samples were selected for study from a large number of profiles mineralogical some micromorphological and geochemical investigations of typical samples of red clays in hungary were performed this review focuses on the origin development and distribution in the pannonian basin

permanent upper plate deformation in western myanmar during the great 1762 earthquake implications for neotectonic behavior of the northern sunda megathrust the 1762 arakan earthquake resulted from rupture of the northern sunda megathrust and is one of those rare preinstrumental earthquakes for which early historical accounts document ground deformations in order to obtain more comprehensive and detailed measurements of coseismic uplift we conducted comprehensive field investigations and geochronological analyses of marine terraces on the two largest islands in western myanmar we confirm 3 4 m of coseismic coastal emergence along southwestern cheduba island diminishing northeastward to less than 1 m farther northeast uplift associated with the earthquake ranges from slightly more than 1 m to 5 6 m along the western coast of ramree island but is insignificant along the island s eastern coast this double hump pattern of uplift coincides with the long term anticlinal growth of these two islands thus we propose that the 1762 earthquake resulted from slip on splay faults under the islands in addition to rupture of the megathrust elastic modeling implies that fault slip during the 1762 earthquake ranges from about 9 to 16 m beneath the islands and corresponds to a magnitude of m w 8 5 if the rupture length of the megathrust is 500 km the island s uplift histories suggest recurrence intervals of such events of about 500 700 years additional detailed paleoseismological studies would add significant additional detail to the history of large earthquakes in this region

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

mineralogical and physico chemical properties of ferralic arenosols derived from unconsolidated plio pleistocenic deposits in the coastal plains of congo abstract the main characteristics of soils under commercial eucalyptus plantations on the atlantic coast of the congo were studied down to a depth of 5 m the objectives were to investigate the mineralogical assemblage and distinguish between current versus old pedogenetic processes and to find evidence of relations between minerals and cation retention in highly weathered sandy soil these soils developed from plio pleistocene sandy deposits were characterized by mineralogical uniformity over depth with quartz contents ranging from 850 to 930 g kg 1 a clay fraction dominated by kaolinite and a cation exchange capacity cec pedogenetic differentiations were weak in these soils because the elapsed time since deposition was too short to differentiate mineralogical horizons from weathered materials our study showed that beyond the properties that minerals confer to soil partially controlling the bioavailability of nutrients their mineralogical and chemical characteristics infer current and former pedogenetic processes in this highly weathered tropical soil

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

active tectonics and earthquake potential of the myanmar region this paper describes geomorphologic evidence for the principal neotectonic features of myanmar and its immediate surroundings we combine this evidence with published structural geodetic and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential three tectonic systems accommodate oblique collision of the indian plate with southeast asia and extrusion of asian territory around the eastern syntaxis of the himalayan mountain range subduction and collision associated with the sunda megathrust beneath and within the indoburman range and naga hills accommodate most of the shortening across the transpressional plate boundary the sagaing fault system is the predominant locus of dextral motion associated with the northward translation of india left lateral faults of the northern shan plateau northern laos thailand and southern china facilitate extrusion of rocks around the eastern syntaxis of the himalaya all of these systems have produced major earthquakes within recorded history and continue to present major seismic hazards in the region

teleseismic double difference relocation of earthquakes along the sumatra andaman subduction zone using a 3 d model 1 we have extended the double difference seismic tomography method to teleseismic distances with 3 d ray tracing conducted through nested regional global velocity models and applied the method to relocate seismicity from the sumatra andaman region before and after the great earthquakes of 2004 and 2005 we tested the algorithm s accuracy using both independent local data and an alternate relocation method and found good agreement between the results the use of depth phases differential times and a realistic 3 d velocity model improves the accuracy and precision of epicenters and focal depths systematically shifting them perpendicular to the trench and shallower respectively the relocations refine the location of the megathrust and other faults the patterns of aftershocks and their relation to slip during the two great earthquakes in addition the relocations reveal several discrete features not readily discernible in the scatter of teleseismic catalogs including an arcuate narrow band of earthquakes presumed to define the updip rupture limit in the 2005 event and a lineation at depth tracing the subduction of the investigator fracture zone when viewed in conjunction with tomography results the geometry and structural features of the subduction zone are revealed in unprecedented detail

present day crustal deformation around sagaing fault myanmar 1 global positioning system gps measurement campaigns in myanmar conducted in 1998 and 2000 allow quantifying the present day crustal deformation around the sagaing fault system in central myanmar both a regional network installed at four points within the country and a local 18 station network centered on the city of mandalay across the sagaing fault demonstrate that active deformation related to the northward motion of india is distributed across myanmar in a platelet that extends from the western edge of the shan plateau in the east to the andaman trench in the west in this platelet deformation is rather diffuse and distributed over distinct fault systems in the east the sagaing shan scarp fault system absorbs 10 mm yr this gps study combined with an on land geotectonic survey demonstrate that oblique slip of india along the rigid sundaland block is accommodated by a partitioned system characterized by distribution of deformation over a wide zone index terms 1206 geodesy and gravity crustal movements interplate 8155 1243 geodesy and gravity space geodetic surveys 8110 tectonophysics continental tectonics general 0905 8158 tectonophysics plate motions present and recent 3040 keywords tectonics gps fault southeast asia

abrupt changes in indian summer monsoon strength during the last deglaciation and early holocene based on stable isotope evidence from lake chenghai southwest china identifying variability and the mechanisms driving variability in the indian summer monsoon ism since the last deglaciation is critical for understanding past hydroclimatic change in this study we present an accelerator mass spectrometry radiocarbon dated record of delta o 18 variations in authigenic carbonates derived from lake chenghai in southwest china a region that receives moisture mainly from the indian ocean the delta o 18 values vary from 11 9 to 0 1 parts per thousand providing a detailed record of variations in ism precipitation delta o 18 values and lake hydrological balance the record shows that the ism generally strengthened in the post glacial between 15 6 and 8 8 cal ka bp but that three centennial to millennial scale drought events were superimposed on the long term trend drought events as indicated by substantial positive shifts in 8 18 0 value occurred from 15 6 0 2 to 14 4 0 2 12 5 0 2 to 11 7 0 2 and 10 1 0 1 to 10 0 0 1 cal ka bp corresponding to the heinrich 1 younger dryas and bond 7 cold events in the north atlantic region respectively the timings of these droughts are suggested to be related to meltwater discharge into the north atlantic the weakened atlantic meridional overturning circulation which leads in turn to the southward migration of the intertropical convergence zone and cooling in the tropical indian ocean

locked and loading megathrust linked to active subduction beneath the indo burman ranges it is unclear whether subduction is still active beneath the indo burman mountain range analyses of gps measurements from this region reveal a locked megathrust fault implying that subduction is active and could generate a large earthquake

stratigraphic and paleomagnetic evidence of mid pleistocene rapid deformation and uplift of the ne tibetan plateau abstract the ne tibetan plateau has become an important region for deciphering the cenozoic uplift of the plateau previous studies have verified that the quaternary uplift in this region had a multi stage character however geologists have not established which event constituted the main tectonic phase fortunately stratigraphic and paleomagnetic evidence from the jiuquan basin gansu province china now confirm that the laojunmiao movement represented as an angular unconformity occurred between 0 9 and 0 8 ma and an almost synchronous tectonic event has been well recorded within and around the plateau moreover many proxies indicate that the global climate changed more rapidly after 0 9 ma these proxies include eolian loess and vermiculated red soils caused by the asian monsoon the eolian sedimentation rate the stilostomella extinction changes in the global thermohaline circulation and the increased 13 c values recorded in the marine sediments based on the uplift driven climate change the mid pleistocene transition mpt could be the result of the laojunmiao movement certainly the laojunmiao movement and mpt had the significant impact on the quaternary earth we conclude that the laojunmiao movement was likely the main tectonic phase of the quaternary plateau uplift

hyposat an enhanced routine to locate seismic events a program package called hyposat has been under development that attempts to use the maximum information possible to estimate the hypocenter of a seismic source the standard input parameters can be used arrival times of first and later onsets with backazimuths and ray parameters or apparent velocities in addition travel time differences between different phases observed at the same station can be optionally used the observed standard deviations are used to weight all input parameters and the inversion is done with a generalized matrix inversion code

weathering trends and parent material characteristics of polygenetic oxisols from minas gerais brazil i mineralogy in geologically stable areas in the tropics climatic changes and geomorphic cycles give origin to polygenetic soils polygenesis involves new soil formation phases taking place on preweathered materials from previous phases resulting in soils with rather similar chemical and mineralogical properties polygenetic soils from minas gerais brazil were investigated with the purpose of distinguishing mineralogical aspects in relation to polygenesis the soil materials were studied by micromorphology and electron microscope and analyzed by xrd all soils are strongly weathered and even show weathered grains of ilmenite and quartz the soils show two phases of kaolinite formation pseudomorphs after mica and precipitation from solution and of accumulation of iron compounds desilication causes gibbsite formation from kaolinite occasionally even in the deep saprolite superposed processes can be due to progressively deeper weathering or to changes of the external environment

minimum magnitude of completeness in earthquake catalogs examples from alaska the western united states and japan we mapped the minimum magnitude of complete reporting m c for alaska the western united states and for the junec earthquake catalog of japan mc was estimated based on its departure from the linear frequency magnitude relation of the 250 closest earthquakes to grid nodes spaced 10 km apart in all catalogs studied mc was strongly heterogeneous in offshore areas the mc was typically one unit of magnitude higher than onshore on land also mc can vary by one order of magnitude over distance less than 50 km we recommend that seismicity studies that depend on complete sets of small earthquakes should be limited to areas with similar mc or the minimum magnitude for the analysis has to be raised to the highest com mon value of mc we believe that the data quality as reflected by the mc level should be used to define the spatial extent of seismicity studies where mc plays a role the method we use calculates the goodness of fit between a power law fit to the data and the observed frequency magnitude distribution as a function of a lower cutoff of the magnitude data mc is defined as the magnitude at which 90 of the data can be modeled by a power law fit mc in the 1990s is approximately 1 2 0 4 in most parts of california 1 8 0 4 in most of alaska aleutians and panhandle excluded and at a higher level in the junec catalog for japan various sources such as ex plosions and earthquake families beneath volcanoes can lead to distributions that cannot be fit well by power laws for the hokkaido region we demonstrate how neglecting the spatial variability of m c can lead to erroneous assumptions about deviations from self similarity of earthquake scaling

pleistocene paleoenvironmental changes in the high mountain ranges of central china and adjacent regions abstract during several joint chinese german expeditions the quaternary landscape and paleoclimatic evolution of the mountain ranges and grabens surrounding the loess plateau of central china was studied the results are compared with proxy data from the interior loess plateau to help reconstruct atmospheric circulation during late pleistocene times middle to late pleistocene alluvial terraces and fans capped with loess units and paleosols show that aggradational episodes correlate with periods of glaciation and increased loess accumulation in turn degradation correlates with interglacials or interstadials and increased soil formation this implies that climate is the primary control on quaternary paleohydrology and alluvial sedimentation and erosion the high mountains which barely reached the last glacial ela were only glaciated during the most favourable climatic period of glaciation the glaciation the glacial and alluvial forms point to a cool early to maximum glacial period with increased precipitation and to a maximum to final period with cold dry conditions during the last glaciation the maximum advance of the small glaciers took place towards the end of a relatively humid and cold period between ca 32 and 23 ka the following dry cold stage between ca 23 and 13 ka was rather unfavourable for glacial advance proxy data from the loess plateau supports the view that glaciations were more or less dominated by cold dry winter monsoon climate whereas during the interglacial interstadials a warmer and more humid climate prevailed implying a strengthening of the summer monsoon influence the results prove variations of the monsoon that in turn modulates paleohydrology periglacial dynamics glacier advances dust flux and soil formation

iron oxide mineralogy of terra rossa and its genetic implications abstract fe d fe d fe t hematite geothite ratios and al substitution in hematite and goethite were found to vary to a rather limited extent in 48 terra rossa samples from various locations around the world this seems to indicate a rather specific pedoenvironment in which terra rossa is formed it is suggested that this pedoenvironment is characterized by an association of mediterranean climate high internal drainage due to the karstic nature of a hard limestone and neutral ph conditions under those conditions relatively high amounts of fe are released fe d fe t ca 0 7 from autochthonous and or allochthonous primary fe sources followed by preferential formation of hematite over goethite both having a medium level of al substitution the close association between terra rossa and the underlying limestone must therefore be seen in the role the rock plays for the water and air regimes of the soil rather than in its material characteristics except for soil ph neither an fe content in the limestone insufficient to explain the fe content of the solum nor the addition of eolian or alluvial material can therefore be used as an argument against a genetic relationship between terra rossa and its underlying limestone

combined effects of eurasia sunda oblique convergence and east tibetan crustal flow on the active tectonics of burma it is widely accepted that deformation of the india sunda plate is the result of partitioned hyper oblique convergence presently sub meridian dextral strike slip faulting accommodates this india sunda motion in a buffer zone the burma platelet this wide dextral strike slip shear zone is complicated by the side effect of the tibet plateau collapse that can be described in term of crustal flow and gravity tectonics the loss of potential energy related to this plateau collapse affects most of the burmese platelet particularly in its northernmost part interaction of these two distinct geodynamic processes is recorded in the gps based regional strain field the analysis of seismic focal mechanism but also from direct geologic observations both onshore and offshore myanmar and bangladesh we propose the apparent e w shortening component of this so called partitioned hyper oblique subduction is only the effect of regional gravitational forces related to the tibet plateau collapse whereas the ns strike slip faulting accommodates the india sunda motion

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

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

genesis of subtropical soils with stony horizons in ne argentina autochthony and polygenesis abstract deep red soils combining characteristics of highly weathered materials together with a significant degree of clay illuviation and with stony horizons close to the saprolite are found in the province of misiones northeastern argentina two basic types of stony horizons have been found which with the fine grained material above are together considered autochthonous the first one is a ferruginous nodular horizon composed mainly of in situ goethitic nodules of gravel size resulting from weathering and glaebulization processes of basalt the second are siliceous horizons which are also in situ derived from pre existing quartz veins within the basalt in contrast different analytical evidences particularly the vertical and geographical variations in the som stable carbon isotope ratios and the mineralogical composition of fine and coarse fractions suggest that these red subtropical soils are polygenetic being the result of a two fold process linked to paleoecological fluctuations in the framework of these results different interpretations about the origin of these soils and their parent materials and particularly the tropical loess theory are discussed

tectonics and history of the andaman sea region abstract the andaman sea is an active backarc basin lying above and behind the sunda subduction zone where convergence between the overriding southeast asian plate and the subducting australian plate is highly oblique the effect of the oblique convergence has been formation of a sliver plate between the subduction zone and a complex right lateral fault system the late paleocene collision of greater india and asia with approximately normal convergence started clockwise rotation and bending of the northern and western sunda arc the initial sliver fault which probably started in the eocene extended through the outer arc ridge offshore from sumatra through the present region of the andaman sea into the sagaing fault with more oblique convergence due to the rotation the rate of strike slip motion increased and a series of extensional basins opened obliquely by the combination of backarc extension and the strike slip motion these basins in sequence are the mergui basin starting at 32 ma the conjoined alcock and sewell rises starting at 23 ma east basin separating the rises from the foot of the continental slope starting at 15 ma and finally at 4 ma the present plate edge was formed alcock and sewell rises were separated by formation of the central andaman basin and the faulting moved onshore from the mentawai fault to the sumatra fault system bisecting sumatra

structure and kinematics of the indo burmese wedge recent and fast growth of the outer wedge 1 the northern sunda subduction zone offshore burma and the associated indo burmese wedge mark the active eastern boundary of the burma platelet jammed between the india plate and the sunda plate the aim of this paper is to provide a structural and kinematics analysis of the indo burmese wedge based on seismic reflection geodetic and geological field data we found out that the indo burmese wedge is the place of diffuse strain partitioning right lateral shearing in the innermost part and e w shortening in the outermost part in the outer wedge thick skinned deformation overprints thin skinned deformation it can be explained by the required preservation of the critical taper after the fast westward propagation of the outer wedge above a very efficient clayey decollement layer the thick skinned deformation is here characterized by major right lateral strike slip faults the kaladan fault and the chittagong coastal fault and yet a typical internal deformation of the indo burmese wedge we suggest that the westward migration of internal right lateral shear deformation allows preservation of the strain partitioning ratios between internal n s trending right lateral shearing and external e w shortening some seismic lines show that the outer wedge deformation is not older than 2 ma its propagation could have been enhanced by the large amount of sediments filling up the sylhet flexural basin formed after the pliocene tectonic uplift of the shillong plateau

spatial variations of soil weathering processes in a tropical mountain environment the baturite massif and its piedmont ceara ne brazil abstract strong spatial variations in soil weathering processes were identified in the uplands and piedmont zones of the baturite massif ceara ne brazil a medium elevation tropical mountain characterized by a steep ecocline between humid climate of the summit zone and semi arid conditions of the erosional piedmont with the combined help of field surveys and laboratory analyses involving micromorphological observations as well as geochemical and mineralogical investigations this study demonstrates a close spatial correlation between soil weathering processes and present day water balance wbi variations i in the humid massif wbi 500 mm y 1 monosiallitization is exclusive in soil and upper saprolite horizons and leads to the neoformation of 1 1 clay minerals well crystallized kaolinite with minor amounts of gibbsite ii in the subhumid peripheral area of the massif 50 1 monosiallitization coexists with bisiallitization in the soil profiles producing a mixture of 1 1 kaolinite and 2 1 illite clay minerals along with lower weathering intensity iii in the semiarid piedmont 0 1 bisiallitization becomes the dominant weathering pathway conducive to grus formation and fersiallitic pedogenesis with the most vulnerable primary minerals weathered into high charge 2 1 clay minerals smectite and illite given that soils and weathering mantles are integrators of average bioclimatic conditions that prevail at timescales of 1 to 10 myr the distribution of soil weathering signatures in the study area is probably reflective of inevitable long term quaternary to neogene climatic fluctuations around median values close to the present ones paleoclimatic legacies inherited from the paleogene lateritization event are rare because of the denudation pulse occurring in the late tertiary and favoring soil stripping to the paleoweathering front on the erosional piedmont

lower to middle weichselian pedogenesis and palaeoclimate in central europe using combined micromorphology and geochemistry the loess paleosol sequence of alsheim mainz basin germany abstract lower to middle weichselian loess loess derivatives and buried soils of the loess paleosol sequence alsheim central europe were characterised by particle size distribution geochemical and micromorphological data high rates of sedimentation with alternating phases of relocation are the main cause for a much less differentiation into middle and upper weichselian loess paleosol units of the alsheim loess paleosol sequence compared to other loess paleosol sequences e g nussloch near heidelberg whereas the lower weichselian has distinct phases of pedogenesis resulting in ah bw and btw horizons to distinguish between different loess deposits locally and intraregional the degree of fineness is an easily applicable and suitable tool though inappropriate for interregional comparisons the chemical index of alteration cia is low 53 to gallet et al 1998 the highest weathering was detectable for btw horizons with cia values 70 a direct quantitative estimation of mean annual palaeotemperature and mean annual palaeoprecipitation can be provided by calculations based on geochemistry of soil horizons and sediments the present mean annual precipitation map in the mainz basin is 789 mm in contrast palaeoprecipitation data suggest a 150 mm higher amount for the last interglacial btw horizon a much lower amount of around 300 400 mm mapp periods of loess and sandy loess deposition and a mapp of micromorphology shows compacted granular structure and moderately to strongly developed pedality as characteristic properties for aquatic loess whereas channel microstructure with no pedality is typical for loess deposits spongy microstructure suggests a classification of the lower weichselian mosbach humus zones as chernozems the eemian paleosol btw horizon in als iii has only weak clay illuviation characteristic for drier regions in europe palaeoclimate and soil formation of the last glacial interglacial cycle calculated from geochemistry and micromorphological data are in good accordance with other proxy data in central europe this suggests that paleoclimate reconstruction based on palaeopedological analyses could be successfully implemented in europe such data may provide a useful alternative to other proxies for correlating european records

climatic and tectonic controls on chemical weathering in tropical southeast asia malay peninsula borneo and sumatra abstract clay mineralogy and major element geochemistry were investigated on 58 surface sediment samples collected in 27 rivers draining malay peninsula borneo and sumatra to assess the chemical weathering process and its controlling factors in tropical southeast asia the clay mineral assemblages show high kaolinite contents in malay peninsula average 80 sumatra 58 78 and south borneo 41 55 high illite contents in north borneo 47 77 and moderate smectite contents in sumatra 6 29 intensive chemical weathering is identified in all three investigated regions from both clay mineralogical and geochemical bulk and clay fraction results regardless of their various lithological and tectonic settings relatively the chemical weathering intensity increases gradually from north borneo to south borneo and further to malay peninsula and sumatra our results suggest that the east asian australian monsoon climatic condition with constant warm temperature and abundant precipitation throughout the year is the principal forcing factor on the chemical weathering and the tectonic activity including mountain uplift earthquakes and volcanic eruptions and their specific lithological characters is only a subordinate factor on the intensity of chemical weathering in tropical southeast asia

pedogenesis on the uplands of the diamantina plateau minas gerais brazil a chemical and micropedological study abstract little is known about the soil distribution on quartzitic uplands of brazil the diamantina plateau where deeply weathered oxisols latosols and shallow sandy soils occur side by side represents part of the higher and oldest planation on the quartzitic uplands of minas gerais state we studied representative soils from the diamantina plateau to help understand the pedogenesis and landscape evolution of this part of minas gerais we found evidence of a lithological and tectonic control on the distribution of soils in the landscape polygenetic oxisols acrustox occur at the top of the landscape at altitudes of 1300 m or more resting uncomformably on quartzitic saprocks xanthic types or mafic rocks rhodic types they change downslope to in situ quartzpsamments and haplorthods in the b horizon of the xanthic acrustox quartz grains smaller than 0 3 mm are surrounded by gibbsitic plasma forming subspherical microaggregates microaggregates in the bw horizon of all upland oxisols display inherited features of intense biological activity regardless of the parent material or texture the nutrient poor catena of xanthic acrustox ustic quartzpsamments oxyaquic haplorthods represents a sequence of increasing hydromorphic conditions downwards in which clay minerals are destroyed in low ph and ferrolysis in the poorly drained soils downslope low ph and eh induce the movement of reduced fe 2 and organic matter om bound al and fe both per descendum and through lateral flow downslope in the bottom micromorphological features and the chemistry of organic matter indicated that some bsh horizons represent buried a horizons subjected to post burial podzolization corroborating morphological field data this indicates the pertinence of the study of humic fractions in defining the bhs spodic horizons of brazilian spodosols

reconstructing neogene vegetation and climates to infer tectonic uplift in western yunnan china neogene climates and vegetation history of western yunnan are reconstructed on the basis of known fossil plants using the coexistence approach ca and leaf margin analysis lma four neogene leaf floras from tengchong jianchuan and eryuan in southwestern china are analyzed by the ca and the paleoclimatic data of one miocene carpoflora from longling and three pliocene palynofloras from longling yangyi and eryuan are used for comparison the miocene vegetation of the whole of west yunnan is subtropical evergreen broad leaved forest and a similar mean annual precipitation is inferred for tengchong longling and jianchuan however by the late pliocene a large difference in vegetation occurred between the two slopes of gaoligong mountain western yunnan the region of tengchong retained a subtropical evergreen broad leaved forest vegetation whereas in yangyi and eryuan a vertical vegetation zonation had developed which consists in ascending order of humid evergreen broad leaved needle and broad leaved mixed evergreen and coniferous forests distinctively the late pliocene vegetational patterns of west yunnan were already very similar to those of the present and the pliocene mean annual precipitation in tengchong was markedly higher than that of yangyi and eryuan considering that the overall vegetation of west yunnan and the precipitation at yangyi and eryuan have undergone no distinct change since the late pliocene we conclude that the hengduan mountains on the northern boundary of west yunnan must have arisen after the miocene and approached their highest elevation before the late pliocene furthermore the fact of the eastern portion of the tibetan plateau underwent a slight uplift after the late pliocene is also supported c 2010 elsevier b v all rights reserved

palaeoclimatic and site specific conditions in the early permian fossil forest of chemnitz sedimentological geochemical and palaeobotanical evidence abstract as significant indicators of deep time palaeoclimate a number of new palaeontological pedological and geochemical characteristics are provided for the chemnitz fossil lagerstatte to depict more precisely its environmental conditions for the first time several lines of evidence indicate that this fossil forest instantaneously preserved by volcanic deposits once received an annual precipitation of around 800 1100 mm but grew on a nearly unweathered palaeosol although the composition of this rich and diverse t0 assemblage suggests a hygrophilous dense and multi aged vegetation dominated by conservative lineages the habitat was affected by environmental disturbances and pronounced seasonality repeated changes in local moisture availability are suggested by geochemical proxies the co occurrence to intergrowth of calcic and ferric glaebules in the palaeosol and developmental traits of perennial vegetational elements specific substrate adaptation is reflected by different root systems and cyclic growth interruptions recorded in the stems branches and roots of long lived woody plants many differentially adapted terrestrial animals complete the more comprehensive reconstruction of a late sakmarian ecosystem and its climatic and preservational controls albeit spatially confined this diverse in situ record may contribute to understand wetland dryland dynamics of sub tropical northern hemisphere pangaea

remote reference magnetotellurics equipment and procedures during the past 3 years major advances in the magnetotelluric technique have improved the quality of magnetotelluric data to the point where random errors in the impedance tensor and tipper are generally smaller than the uncertainty in their interpretation the major factor in this improvement has been the introduction of the remote reference technique although the use of ultrasensitive magnetometers and minicomputers for in field data processing has also been important after a review of the remote reference technique this paper describes the equipment and procedures used for remote reference magnetotellurics by the authors magnetometers using d c superconducting quantum interference devices typically have a sensitivity of 10 14 t hz 1 2 a dynamic range of 10 7 in a 1 hz bandwidth and a slewing rate of 3 10 5 t s 1 at 10 khz the electric field measurements use conventional cu cuso 4 electrodes the remote magnetic reference signals are transmitted to the base station using fm analog telemetry the data are collected and processed by a minicomputer based on an lsi 11 microprocessor the essential results for example the apparent resistivities and the tipper components with their probable errors are available in the field practical details are given of the handling of superconducting devices low temperature cryostats and liquid helium in the field various spurious noise sources are mentioned and techniques for minimizing their effects are described

major changes in east asian climate in the mid pliocene triggered by the uplift of the tibetan plateau or global cooling since the mid pliocene east asian climates have experienced significant changes one view suggests that significant uplift of the tibetan plateau during this period could have been responsible for these dramatic changes in the strength of the east asian monsoon and for asian interior acidification while some other authors attribute these changes to the ongoing global cooling and rapid growth of the arctic ice sheet up to the present which factor dominates the major changes of east asian climate in the mid pliocene is still a contentious issue this study presents an analysis of several climate proxies including grain size cao na2o mgo tio2 ratio na ka ratio and dust accumulation rates of the xifeng red clay sequence in the eastern chinese loess plateau and the xihe pliocene loess soil sequence in west qinling they reveal that aridity in the continental interior and winter monsoon circulation both intensified whereas the east asian summer monsoon showed a weakening rather than intensifying trend since the mid pliocene these changes are also supported by the other multi proxy records from various regions in east asia previous numerical modeling studies have demonstrated that uplift of the tibetan plateau would have simultaneously enhanced continental scale summer and winter monsoon strength as well as central asian aridity the mid pliocene climate changes in east asia are therefore unlikely to be a response to plateau uplift on the contrary our recent modeling results give support to the view that ongoing cooling could have intensified both the aridity of the interior and the strength of the winter monsoon but weakened the summer monsoon in east asia c 2012 elsevier ltd all rights reserved

origin weathering and geochemical composition of loess in southwestern hungary abstract loess geochemistry generally reflects paleo weathering conditions and it can be used to determine the average composition of the upper continental crust ucc in this study major and trace element concentrations were analyzed on loess samples from southwestern hungary to determine the factors influencing their chemical compositions and to propose new average loess compositions all studied loess samples had nearly uniform chemical composition suggesting similar alteration history of these deposits chemical index of alteration values 58 69 suggested a weak to moderate degree of weathering in a felsic source area typical non steady state weathering conditions were shown on the al 2 o 3 cao na 2 o k 2 o patterns indicating active tectonism of the alpine carpathian system during the pleistocene whole rock element budgets were controlled by heavy minerals derived from a felsic magmatic or reworked sedimentary provenance geochemical parameters indicated that dust particles must have been recycled and well homogenized during fluvial and eolian transport processes

complex deformation pattern of the pamir hindu kush region inferred from multi scale double difference earthquake relocations abstract the wide range of focal depths and the corresponding fault plane mechanisms in the pamir hindu kush region are believed to reflect the ongoing deformation along the indian eurasian continental collision zone here we develop a multi scale double difference earthquake location algorithm to combine traveltime data recorded at local regional and teleseismic distances the 2906 relocated intermediate depth earthquakes of mw 4 5 we studied beneath the hindu kush show two groups of seismicity with a separation of ca 20 30 km these two groups exhibit thrust faults with different p axes and different locations reflecting the lateral geometry change of the seismic zone earthquakes beneath the pamir present a clear south dipping layer and unusual horizontal t axes there is a clear transition in direction of stress between the hindu kush and the pamir regions here we focus on the complex deformation pattern beneath the continental collision zone arising from a combination of compression tension shearing and necking states

palaeopedogenesis of red palaeosols in yunnan plateau southwestern china pedogenical geochemical and mineralogical evidences and palaeoenvironmental implication abstract red palaeosol as an important archive of ancient pedoenvironments effectively reflects the palaeoenvironmental change and tectonic uplift history of the plateau four red palaeosol profiles were collected at 2200 to 2400 m elevations from the yunnan plateau yp to investigate the pedogenic features chemical weathering process and mineral assemblages of soils pedological geochemical and mineralogical techniques were used to understand the palaeopedogenic palaeoenvironmental change and landscape evolution of the plateau pedologically the red palaeosols were characterized by the dark red color a hue of 5yr or redder strong acidity ph 50 g kg 1 and clay 50 contents the red palaeosols were enriched with fe 2 o 3 al 2 o 3 and tio 2 with very low contents of cao mgo na 2 o and k 2 o and slightly low contents of si 2 o and mno chemical weathering indices such as cia cia al 2 o 3 al 2 o 3 cao na 2 o k 2 o 100 sa sa sio 2 al 2 o 3 saf saf sio 2 al 2 o 3 fe 2 o 3 and a cn k diagram al 2 o 3 cao na 2 o k 2 o indicated that the red palaeosols had experienced strong chemical weathering processes scanning electron microscopy analyses revealed that quartz grains of the red palaeosols were characterized by a number of deep dissolution pits and cracks on their surfaces the clay minerals of the red palaeosols were composed of kaolinite gibbsite hematite and vermiculite in the order of abundance pedogenical geochemical and clay mineralogical evidences revealed that the red palaeosols were developed by palaeopedogenic processes under tropical climatic environments the presence of highly weathered soils at an altitude of 2200 2400 m indicated the influence of tectonic uplift on the soil vertical distribution it is estimated that the red palaeosols had uplifted about 1600 2000 m since their initial formation palaeopedogenesis of red palaeosols provides new insight into the palaeoclimatic and palaeoenvironmental reconstruct and tectonic movement of yp

magnetic properties of sediments of the red river effect of sorting on the source to sink pathway and its implications for environmental reconstruction we conducted a mineral magnetic study of river bank and subaqueous delta sediments from the red river in order to examine the role of sedimentary sorting on the variation of sedimentary magnetic properties from source to sink the magnetic mineralogy mainly consists of magnetite and hematite bulk sediment particle size variations have a strong influence on magnetic properties with the frequently used magnetic parameters fd arm arm and arm sirm exhibiting positive correlations with the 5 m water depth part of the subaqueous delta have lower and sirm values a finer ferrimagnetic grain size and higher proportions of hematite consistent with selective loss of coarse ferrimagnetic grains on the source to sink pathway we suggest that variations in magnetic properties in response to particle size compositions and therefore depositional environment changes should be carefully addressed when magnetic proxies such as arm sirm are used in the study of coastal and marine environmental changes e g sea level change in such cases the combined use of magnetic properties and geochemical indicators such as al ti ratio may provide better results for paleoenvironmental reconstruction

active faulting and tectonics of burma and surrounding regions this study of the active tectonics of burma and surrounding regions is based mostly on an interpretation of landsat imagery and on fault plane solutions for shallow and intermediate earthquakes fold axes in the indoburman ranges and an east dipping inclined zone of intermediate depth earthquakes suggest that a slab of oceanic lithosphere was recently subducted to the east under the indoburman ranges fault plane solutions of shallow earthquakes however do not show underthrusting at the present time instead p axes are oriented roughly north south parallel not perpendicular to the fold axes in the ranges p axes for fault plane solutions of intermediate shocks also trend north south parallel to the strike of the subducted slab and may indicate that the hanging slab is being dragged north by india through the surrounding asthenosphere the sagaing fault probably accommodates most of the right lateral slip of india past indochina but india s northward movement also causes internal deformation within burma thailand and yunnan differences between the tectonic fabric seen on the landsat images and the tectonic regime compatible with the fault plane solutions throughout the region imply major changes in the directions of relative motion in the orientations of strain and in the style of deformation in the late cenozoic presumably these changes reflect the transition from subduction to collision and strike slip motion as india penetrated into eurasia past burma large parts of burma and thailand may have rotated several tens of degrees clockwise in this process

accretionary tectonics of burma and the three dimensional geometry of the burma subduction zone the geometry of the burma wadati benioff zone wbz has been determined by fitting a trend surface parameterized with eight effective degrees of freedom to 184 well located hypocenters the dip of this surface which passes through the middle of the wbz varies from about 50 in the north near the eastern himalayan syntaxis to about 30 in the bay of bengal area the eastern edge of the indo burman ranges closely follows the map projection of the 60 km depth contour of the wbz the curvature of the indo burman ranges is controlled by the geometry of the interface between the more steeply dipping part of the indian plate and the leading edge of the overriding burma platelet shallow earthquakes beneath the indo burman ranges are primarily confined to the underthrusting indian plate their focal mechanisms indicate strike slip faulting and north south shortening parallel to the eastern margin of the indian plate

surface ruptures of the mw 6 8 march 2011 tarlay earthquake eastern myanmar abstract field observations indicate the m w 6 8 tarlay myanmar earthquake of 24 march 2011 resulted from the rupture of a short section of the left lateral nam ma fault we document coseismic left lateral offsets that range from approximately 10 cm to about 2 m along a 19 km long section of the fault based upon both field investigations and the interpretation of high resolution satellite imagery comparison of these early field and later remote measurements suggests that most of the paddy field offsets became obscured within a year or two our measurements indicate the magnitude of sinistral offset decreases gradually eastward from the epicentral area to the rupture terminus within the tarlay basin along the southern edge of a 2 3 km wide transtensional stepover our measurements confirm that the earthquake resulted from rupture of a structurally distinct segment of the nam ma fault bounded on the west by the fault s terminus and on the east by the tarlay basin stepover if the 215 km nam ma fault were to rupture entirely in a single event the magnitude of the resulting earthquake would likely be about m w 7 7 online material field observations and photos after the 2011 tarlay earthquake table of offset and maps with location and offset

climatic and tectonic controls on weathering in south china and indochina peninsula clay mineralogical and geochemical investigations from the pearl red and mekong drainage basins 1 results of clay mineralogy major element geochemistry and sr and nd isotopes in 93 argillaceous samples collected from drainage basins of the pearl red and mekong rivers reveal different degrees of chemical weathering in southeast asia despite similar climate conditions across these regions the kaolinite illite ratio illite chemistry index and illite crystallinity can be used as indicators of chemical weathering intensity these mineralogical proxies combined with the k2o na2o cao molar ratio chemical index of alteration cia and weathering trends observed from major element results indicate intensive silicate weathering in the pearl river basin moderate to intensive in the mekong river basin and moderate in the red river basin although a significant modification of epsilon nd 0 values in our riverine sediments during chemical weathering and transport is unlikely sr 87 sr 86 ratios are controlled by various states of chemical weathering of high sr minerals such as plagioclase rich in na and ca with a linear decrease trend from the pearl mekong to red river basins our results suggest that it is not the warm climate with heavy monsoon precipitation but tectonics playing the most significant role in controlling weathering and erosion processes in south china and indochina peninsula strong physical erosion caused by tectonic activities and river incision along the eastern margin of the tibetan plateau and along the red river fault system is responsible for high contents of primary minerals in the lowlands of red and mekong river basins

two seismic gaps on the sagaing fault myanmar derived from relocation of historical earthquakes since 1918 1 relocation of six m magnitude 7 0 earthquakes near the sagaing fault in myanmar since 1918 allows us to image earthquake history along the sagaing fault all the earthquakes were relocated on the sagaing fault by using the modified joint hypocenter determination method combining the relocated epicenters with information on foreshocks aftershocks seismic intensities and coseismic displacement we estimated the location of the fault plane that ruptured during each earthquake this analysis revealed two seismic gaps one between 19 2 n and 21 5 n in central myanmar and another south of 16 6 n in the andaman sea considering the length of the first seismic gap 260 km a future earthquake of up to m 7 9 is expected to occur in central myanmar because nay pyi taw the recently established capital of myanmar is located on the expected fault its large population is exposed to a significant earthquake hazard

present weathering rates in a humid tropical watershed nsimi south cameroon the study of biogeochemical and hydrological cycles in small experimental watersheds on silicate rocks common for the temperate zone has not yet been widely applied to the tropics especially humid areas this paper presents an updated database for a six year period for the small experimental watershed of the mengong brook in the humid tropics nsimi south cameroon this watershed is developed on precambrian granitoids north congo shield and consists of two convexo concave lateritic hills surrounding a large flat swamp covered by hydromorphic soils rich in upward organic matter mineralogical and geochemical investigations were carried out in the protolith the saprolite the hillside lateritic soils and the swamp hydromorphic soils biomass chemical analyses were done for the representative species of the swamp vegetation the groundwater was analysed from the parent rock saprolite weathering front to the upper fringe in the hillside and swamp system the chemistry of the wet atmospheric and throughfall deposits and the mengong waters was monitored in the nsimi watershed the carbon transfer occurs primarily in an organic form and essentially as colloids produced by the slow biodegradation of the swamp organic matter these organic colloids contribute significantly to the mobilization and transfer of fe al zr ti and th in the uppermost first meter of the swamp regolith when the organic colloid content is low i e in the hillside groundwater th and zr concentrations are extremely low 3 pmol l icp ms detection limits strongly insoluble secondary thorianite tho 2 and primary zircon zrsio 4 crystals control their mobilization respectively this finding thus justifies the potential use of both these elements as inert elements for isoelement mass balance calculations pertaining to the hillside regolith chloride can not be used as a conservative tracer of hydrological processes and chemical weathering in this watershed biogenic recycling significantly influences the low cl input fluxes sodium is a good tracer of chemical weathering in the watershed the sodium solute flux corrected from cyclic salt input was used to assess the chemical weathering rate even though low 2 8 mm kyr the chemical weathering rate predominates over the mechanical weathering rate 1 9 mm kyr compared to the rio icacos watershed the most studied tropical site the chemical weathering fluxes of silica and sodium in the mengong are 16 and 40 times lower respectively this is not only related to the protective role of the regolith thick in both cases but also to differences in the hydrological functioning this is to be taken into account in the calculations of the carbon cycle balance for large surfaces like that of the tropical forest ecosystems on a stable shield at the global level

mineralogy and chemistry of late pliocene early pleistocene paleosols on mount kenya weathering indices of relative age and paleoenvironmental reconstruction abstract iron and al extracts as weathering indices in paleosols have been used in many localities to determine relative age transformation of total chemical element concentrations to secondary forms translocation of organically complexed al and long standing inundation of soils with groundwater on mt kenya a succession of paleosols straddling the olduvai subchron are here analyzed to determine the degree to which fe al extracts assist paleoenvironmental reconstruction especially relative age determination genesis and translocation of alteration products and the effect of paleoclimatic deterioration with the advent of glaciation ca 2 0 ma and possibly before warmer humid climate from the onset of the plio pleistocene to the olduvai subchron thereafter reverting to a long episode of oscillating drier wetter ice age perturbations is written into the profile morphologies mineralogies and chemistries supporting earlier stratigraphic interpretations

morphological chemical and mineralogical properties of some manganese rich oxisols derived from dolomite in mpumalanga province south africa abstract we investigated the morphological chemical and mineralogical properties of unusual black oxisols rich in mn oxides derived from intense weathering of dolomite near graskop in mpumalanga province south africa soil mapping of a small catchment was carried out and seven horizons from two profiles were sampled for detailed analysis a consistent pattern was evident in which black lower subsurface horizons with weak nodule development grade upwards into redder or browner horizons containing abundant pisolitic occasionally magnetic nodules surface horizons are humus rich 3 c and acidic 50 60 acid saturation of effective cec subsurface horizons have low ecec 2 mm fraction only very weak lithiophorite peaks could be identified in x ray powder diffractograms of the nodular material aluminium in the form of gibbsite was slightly enriched in the nodules but not fe it is proposed that the nodules have formed via the reprecipitation of mn reductively dissolved from the fine earth fraction during periods of low redox potential we envisage that this has given rise to progressive sequestration of mn in hard nodules and removal of the black matrix colour unveiling the colours of iron oxides and humus the presence of al in lithiophorite a higher point of zero charge than for other mn oxides and redox inertia associated with the exceptionally large concentrations of mn ranging from about 10 to 18 mno2 in the whole soil including nodules are all thought to contribute to the accumulation and persistence of mn in these soils some trace metals showed marked enrichment in the nodules up to 800 500 and 1000 mg kg 1 of co cu and ni respectively

geochemical constraints on provenance of the mid pleistocene red earth sediments in subtropical china abstract the source of mid pleistocene red earth sediments in the middle to lower reaches of the yangtze changjiang river was investigated based on their geochemical characteristics the xuancheng and jiujiang red earth sediments have similar major and trace element distribution patterns compared to the loess and paleosol deposits of the chinese loess plateau the upper continental crust ucc and the post archean australian average shale paas the sediments display notable depletion of cao mgo na2o and accumulation of tio2 al2o3 and fe2o3 t the trace element distribution patterns of the red earth sediments are also different from those of loess and the paas but are similar to those of the loess deposits except for lower values of mobile trace elements sr ba and ni and higher values of zr and y the red earth samples have uniform la th ratios of 2 8 compatible with those of the ucc loess and paleosol they also have similar chondrite normalized ree patterns characterized by enriched lree and relatively flat hree profiles and consistent negative eu anomalies similar to those of the ucc the loess and paleosol and the yangtze deposits these results suggest that the red earth sediments have been subject to considerable mixing prior to deposition and strong subsequent chemical weathering the sediments have very uniform 143nd 144nd and 147sm 144nd ratios this points to well mixed and multi recycled sediments the 143nd 144nd and 87sr 86sr values of the red earth sediments match well with those of the deposits in the middle to lower reaches of the yangtze river but are different from those of the loess and paleosols this suggests that the red earth sediments are derived from the drainage basins of the middle to lower yangtze river and might have experienced more intense chemical weathering relative to the yangtze deposits as reflected by their higher rb sr ratios intense depletion of mobile elements and accumulation of immobile elements as well as their well developed net like structure

highly weathered mineralogy of select soils from southeastern u s coastal plain and piedmont landscapes abstract highly weathered clay mineralogical suites of southeastern u s soils which are exemplified in portions of upland well drained environments of the piedmont and atlantic and gulf coastal plain consist of kaolinite hydroxy interlayered vermiculite gibbsite iron oxides and to a lesser extent quartz halloysite and mica the development of these mineral assemblages is often coincident with ultisol formation in these landscapes by soil taxonomy these soils often have kandic horizons or are in subactive cec activity classes hydroxy interlayered vermiculite a mineral considered to be pedogenic and ubiquitous within these systems has been evaluated in past studies through depth distribution trends thermodynamics solubility and alluvial chronosequences to develop a more thorough understanding of mineral transformations and pedogenesis in these landscapes the average formula for hydroxy interlayered vermiculite developed from several regional studies m 0 28 si 3 46 al 0 54 al 1 38 fe 0 31 mg 0 31 al 1 31 oh 3 35 o 10 oh 2 suggests the 1 2 cell layer charge to be approximately 0 85 with approximately 67 of the charge offset by non exchangeable al hydroxy interlayers thermodynamic evaluations indicate a relatively more stable pedogenic environment for hydroxy interlayered vermiculite in near surface and eluvial environments dependent on the degree of hydroxy al interlayer infilling with a more stable environment for kaolinite in illuvial subsoils this corresponds with observations of mineral distribution with depth in representative soils of the region although other mechanisms and pathways which have been elucidated through several studies likely play a larger role quantification of mineral constituents in these systems faces challenges but satisfactory results can be obtained using a variety of techniques deconvolution of thermal dsc and tga output shows promise for quantifying discrete minerals that have overlapping temperatures of reactions chronosequence studies in the region have improved our understanding of the temporal state factor associated with the development of this mineralogy for example a study on the tallapoosa river of central alabama illustrated the presence of vermiculite and smectite and the relative absence of hydroxy interlayered vermiculite within the solum on holocene terraces but its presence on significantly older pleistocene terraces another study evaluated 29 pedons on seven alabama river terrace levels late pliocene to late holocene in central and south alabama and found clay mineralogy on the oldest terrace levels was similar to adjacent upland coastal plain landscapes the aggregate of findings indicate that given sufficient time in a leaching environment highly weathered mineralogical suites form in a variety of landscapes in this region

monsoonal climate evolution in southern china since 1 2 ma new constraints from fe oxide records in red earth sediments from the shengli section chengdu basin abstract southern china has experienced a dominantly monsoonal climate since the early quaternary owing to the influence of asian monsoons from several directions during that period pedogenic fe oxides hematite and goethite are regarded as sensitive indicators of monsoonal paleoclimates to obtain a better understanding of monsoonal climate changes in the subtropical zone of southern china samples from the shengli section chengdu basin were investigated using diffuse reflectance spectroscopy drs high resolution transmission microscopy hrtem x ray diffraction xrd x ray fluorescence xrf and inductively coupled plasma mass spectrometry icp ms tem results show that both hematite and goethite occur as fine particles with an irregular morphology most hematite grains have low crystallinity and nanoporous structure suggesting that they formed from a ferrihydrite precursor uniformity of trace element and ree distribution patterns eu and ce anomalies and la yb n ratios throughout the section suggests that the shengli deposits were probably well mixed in the source area prior to transport and deposition and that there has been little change in the source areas of primary materials since 1 2 ma the high chemical index of alteration cia of the red earth 79 88 reflects strong chemical weathering processes in southern china besides drs analyses of fe oxides show that most red earth samples at shengli contain more hematite than goethite which is opposite to typical loess paleosol profiles from northern china these results confirm that southern china generally experienced more intense weathering processes than northern china since 1 2 ma large fluctuations in major element oxide concentrations and clay mineral assemblages in the lower part of the section indicate climatic fluctuations between perennially humid and seasonally humid conditions in the mid pleistocene monsoonal climate evolution as proxied by the hematite hematite goethite hm hm gt ratio shows a long term but stepwise cooling and drying pattern in the chengdu basin with major transitions at 1 0 0 45 and 0 1 ma these transitions were probably triggered by episodes of tectonic uplift of the tibetan plateau and global climate change with consequent effects on the asian monsoons the transitions in our paleoclimate proxy records for southern china match well with shifts in the marine oxygen and carbon isotope records since the mid quaternary providing evidence of strong teleconnections between global and regional climates terrestrial weathering and the global carbon cycle