mineral assemblage anomalies in the slip zone of the 1999 taiwan chi chi earthquake ultrafine particles preserved only in the latest slip zone we determined mineral assemblages of samples from the taiwan chelungpu fault and from milling and heating experiments by using x ray diffraction and scanning and transmission electron microscopy the fault system contains three dominant fault zones the shallowest of which slipped during the 1999 chi chi earthquake the quartz and clay mineral contents of the primary slip zone were low and it contained partly amorphous ultrafine particles several tens of nanometers up to 30 weight percent of materials in that zone could not be fit to standard diffraction patterns whereas nearly 100 weight percent of those in surrounding samples could be the unfitted component could be attributed to the observed ultrafine particles produced by comminution during the earthquake because weak diffraction intensities are caused from mineral lattice distortion granulation and amorphous coatings such particles are a potential proxy for identifying the slip zone of the most recent earthquake along a fault

a record of holocene climate change in the guanzhong basin china based on optical dating of a loess palaeosol sequence optical dating was used to obtain a chronology for a loess palaeosol sequence in the guanzhong basin on the loess plateau in china the sedimentary sequence recorded two dry episodes 3 7 2 4 ka and 1 2 0 8 ka ago in the holocene as shown by the presence of two layers of loess within the holocene deposits these two arid events are consistent with records of global climate change in the holocene and also coincident with major historic events in china this finding suggests that loess paleosol sequences in china can record global climate changes and implies that rapid climate change affected the progress of human civilization in addition changes in the sedimentation rate through the section suggest that agricultural expansion may have accelerated the rate of dust accumulation

production of nanoparticles during experimental deformation of smectite and implications for seismic slip abstract nanoparticles and amorphous materials are common constituents of the shallow sections of active faults understanding the conditions at which nanoparticles are produced and their effects on friction can further improve our understanding of fault mechanics and earthquake energy budgets here we present the results of 59 rotary shear experiments conducted at room humidity conditions on gouge consisting of mixtures of smectite ca montmorillonite and quartz experiments with 60 50 25 0 wt ca montmorillonite were performed to investigate the influence of variable clay content on nanoparticle production and their influence on frictional processes all experiments were performed at a normal stress of 5 mpa slip rate of 0 0003 v 1 5 ms 1 and at a displacement of 3 m to monitor the development of fabric and the mineralogical changes during the experiments we investigated the deformed gouges using scanning and transmission electron microscopy combined with x ray powder diffraction quantitative phase analysis this integrated analytical approach reveals that at all slip rates and compositions the nanoparticles grain size of 10 50 nm are partly amorphous and result from cataclasis wear and mechanical solid state amorphization of smectite the maximum production of amorphous nanoparticle occurs in the intermediate slip rate range 0 0003 v 0 1 ms 1 at the highest frictional work and is associated to diffuse deformation and slip strengthening behavior instead the lowest production of amorphous nanoparticles occurs at co seismic slip rates v 1 3 ms 1 at the highest frictional power and is associated with strain and heat localization and slip weakening behavior our findings suggest that independently of the amount of smectite nanoparticles they produce fault weakening only when typical co seismic slip rates 0 1 ms 1 are achieved this implies that estimates of the fracture surface energy dissipated during earthquakes in natural faults might be extremely difficult to constrain

field to nano scale evidence for weakening mechanisms along the fault of the 2016 amatrice and norcia earthquakes italy abstract in august and october 2016 two normal fault earthquakes m w 6 0 and m w 6 5 respectively struck the amatrice norcia area in the central apennines italy the mainshocks nucleated at depths of 7 9 km with the co seismic slip propagating upward along the mt gorzano fault mgf and mt vettore fault system mvfs to recognize possible weakening mechanisms along the carbonate hosted seismogenic faults that generated the amatrice norcia earthquakes the fresh co seismic fault exposure i e nastrino exposed along the mt vettoretto fault was sampled and analyzed this exposed fault belongs to the mvfs and was exhumed from 2 3 km depth over the fresh fault surface phyllosilicates concentrated and localized along mm to m thick layers and truncated clasts and fluid like structures were found at the nano scale instead of their common platy lamellar crystallographic texture the analyzed phyllosilicates consist of welded nm thick nanospherules and nanotubes similar to phyllosilicates deformed in rotary shear apparatus at seismic velocities or altered under high hydrothermal temperatures 250 c moreover the attitude of the mt vettoretto fault and its kinematics inferred from exposed slickenlines are consistent with the co seismic fault and slip vectors obtained from the focal mechanisms computed for the 2016 mainshocks all these pieces of evidence suggest that the mt vettoretto fault slipped seismically during past earthquakes and that co seismic slip was assisted and facilitated at depths of w 6 0 amatrice and m w 6 5 norcia earthquakes the microstructures found along the mt vettoretto fault which is certainly a seismogenic fault provide a realistic synoptic picture of co seismic processes and weakening mechanisms that may occur in carbonate hosted seismogenic faults

neotectonics in the eastern north anatolian fault region turkey advocates crustal extension mapping from sar ers imagery and digital elevation model abstract this paper concerns the neotectonics of the eastern part of the anatolian block bounded respectively to the north and the east by the north anatolian naf and the east anatolian faults eaf meeting at karliova the study is based on imagery of synthetic aperture radar sar scenes acquired by the european remote sensing ers satellite and on views of a digital elevation model dem complemented with fault analysis in the field we show that extensional tectonics associated with transcurrent displacements prevail in the karliova triangle and beyond new local releasing bends or pull apart basins and push up structures along the naf have been demonstrated more importantly anatolia is composed of blocks less than 50 km in width that are tilted and move relative to each other they are compatible with a detachment within the crust of anatolia we argue that an escape wedge has migrated through time from west to east with successive jumps to form the present day karliova triangle at each stage the escape wedge was easterly bounded by a ne sw striking fault zone similar to the eaf in each escape wedge clockwise block rotations predate strike slip tectonics along the n110 e striking naf this is the case for instance for the erzincan basin where the first movements were parallel to the sw striking ovacik fault an early equivalent of the eaf and turned later to the west the detached crustal blocks moved southwestward then westward and extended at the same time in order to occupy the increasing surface within the successive escape wedges this is not the behaviour of simple lateral extrusion of the anatolian lithospheric block induced by forces applied at its boundaries by the adjacent plates but rather that of detached crustal blocks submitted to extension as a consequence of backward retreat of the hellenic slab and buoyancy forces arising from crustal thickness differences

the multiple vortex nature of tropical cyclogenesis abstract this study explores the extent to which potential vorticity pv generation and superposition were relevant on a variety of scales during the genesis of tropical storm allison allison formed close to shore and the combination of continuous doppler radar satellite aircraft and surface observations allows for the examination of tropical cyclogenesis in great detail preceding allison s genesis pv superposition on the large scale created an environment where decreased vertical shear and increased instability surface fluxes and low level cyclonic vorticity coexisted this presented a favorable environment for meso scale pv production by widespread convection and led to the formation of surface based meso scale vortices termed convective burst vortices cbvs the cbvs seemed to form in association with intense bursts of convection and rotated around each other within the meso circulation field one cbv eventually superposed with a mesoscale convective vortex mcv resulting in a mor

electrically active convection in tropical easterly waves and implications for tropical cyclogenesis in the atlantic and east pacific abstractin this study the authors investigated the characteristics of tropical easterly wave convection and the possible implications of convective structure on tropical cyclogenesis and intensification over the atlantic ocean and the east pacific ocean easterly waves were partitioned into northerly southerly trough and ridge phases based on the 700 hpa meridional wind from the national centers for environmental prediction national center for atmospheric research reanalysis dataset waves were subsequently divided according to whether they did or did not develop tropical cyclones i e developing and nondeveloping respectively and developing waves were further subdivided according to development location finally composites as a function of wave phase and category were created using data from the tropical rainfall measuring mission trmm microwave imager precipitation radar pr and lightning imaging sensor as well as infrared ir brightness temperature data from the nasa global merged ir br

a mid european decadal isotope climate record from 15 500 to 5000 years b p oxygen isotope ratios of precipitation delta18op inferred from deep lake ostracods from the ammersee southern germany provide a climate record with decadal resolution the record in detail shows many of the rapid climate shifts seen in central greenland ice cores between 15 000 and 5000 years before the present b p negative excursions in the estimated delta18op from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the north atlantic deviating millennial scale trends however indicate that climate gradients between europe and greenland changed systematically reflecting a gradual rearrangement of north atlantic circulation during deglaciation

the ustic isohumisol chernozem distributed over the chinese loess plateau modern soil or palaeosol abstract the ustic isohumisol chernozem widely distributed over the chinese loess plateau is classified as a modern soil by agricultural pedologists and as a palaeosol by geoscientists high resolution investigations into this soil including field observations element analysis optically simulated luminescence dating and measurements of magnetic susceptibility and particle size distribution were carried out over the plateau uplands the results show that the formation of physico chemical properties and development of the soil profiles has kept pace with the land surface growth because of incessant dust accumulation during the holocene the continuously intensified weathering of accumulated dust from 11 500 a b p had resulted in an increased chemical differentiation through time during the early holocene the development of the ustic isohumisol occurred over the uplands between 8500 and 3100 a b p when the chemical differentiation reached its maximum because of increased precipitation and ample soil moisture in response to the mid holocene climatic optimum the soil formation had sustained for ca 5400 years and ceased at 3100 a b p a major pedogenic regression occurred from 3100 a b p because of climatic aridity and intensified dust accumulation over the loess plateau the newly accumulated loess and topsoil has the ustic isohumisol buried at a depth of ca 50 80 cm in general the pedogenic regression has been intensified by incorporation of the reworked components by increased runoff and erosion redeposition large scale land reclamation extended to the uplands at ca 2170 a b p an agricultural landscape of dry farming has formed since ca 1500 a b p thereafter the present topsoil has accumulated and has been affected by the intensified cultivation and addition of barnyard manure in history the solubles are retained in the topsoil because of dry climate and scant soil moisture

a regional aridity phase and its possible cultural impact during the holocene megathermal in the guanzhong basin china evidence of climatic variations and the impact of past farming was identified in a holocene loess profile near xi an in the guanzhong basin china detailed studies of the profile indicate that crop cultivation began at 7000 yr bp in the neolithic and carried on to present in the area disturbance of the profile by cultivation has not masked evidence of changes in aeolian dust deposition and bio pedogenic processes caused by climatic variations increased dust deposition indicates that a remarkable aridity phase occurred from 6000 to 5000 yr bp during the holocene megathermal 8500 3000 yr bp the aridity and intensified aeolian dust deposition interrupted the formation of the brown soil developing under a warm humid subtropical climate during the megathermal the palaeosol s0 normally associated with the megathermal period is thus separated into two distinct soils namely s01 and s02 this variability in megathermal climate may have been widespread across northwestern china it is also possible that t

slickenside kinematic indicators abstract a new classification of slickenside kinematic indicators is presented based on 61 criteria these slickensides have been subdivided into eleven major groups v or crescentic markings steps fractures trains of inclined planar structures trailed material asymmetric elevations deformed elements mineralogical crystallographic orientations asymmetric plan view features asymmetric cavities and asymmetric folds this classification constitutes a useful tool for geologists interested in the determination of the shear sense in fault surfaces bearing slickensides examples of application of this classification to natural fault surfaces at different scales are presented

holocene environmental change inferred from the loess palaeosol sequences adjacent to the floodplain of the yellow river china abstract chinese loess deposits are generally considered to be the product of dust storms and dust falls from the central asia arid zones that were transported across china by the northwesterly continental monsoon in contrast the zhengzhou loess found southeast of the loess plateau adjacent to the floodplain of the yellow river records a different eolian regime and dust source the zhengzhou loess was investigated by field observations measurements of magnetic susceptibility particle size distribution loss on ignition caco3 and chemical contents both field observations and the laboratory results indicate that during the last glacial the zhengzhou loess was supplied by two different eolian regimes and dust sources one was from the fresh flood deposits of the yellow river driven by the northeast winds from the low lying floodplain and the other was from the dust storms and dust falls that traveled across the loess plateau driven by the northwesterly continental monsoon from the central asian arid lands the early holocene 11 500 8500 a bp was a transition during the change in eolian regime and dust source because of the weakened northwesterly monsoon along with the global climatic amelioration following the retreat of the northwesterly monsoon from the onset of the mid holocene climatic optimum at 8500 a bp dust supply from the drifting sand zone on the yellow river floodplain became dominant because of the intensified strength of the northeast winds from the bohai sea from 3100 a bp onwards climatic aridity and extensive human disturbance have resulted in intensive eolian processes causing the incursion of the drifting sand into the zhengzhou loess zone these results show that loess accumulation is more complex than traditionally assumed the origin of loess deposits elsewhere outside the loess plateau may be related to dust sources derived from alluvial sediments of major river systems

frictional melting of clayey gouge during seismic fault slip experimental observation and implications clayey gouges are common in fault slip zones at shallow depths thus the fault zone processes and frictional behaviors of the gouges are critical to understanding seismic slip at these depths we conducted rotary shear tests on clayey gouge 41 wt clay minerals at a seismic slip rate of 1 3 m s here we report that the gouge was melted at 5 mpa of normal stress and room humidity conditions the initial local melting was followed by melt layer formation clay minerals e g smectite and illite and plagioclase were melted and quenched to glass with numerous vesicles both flash heating and bulk temperature increases appear to be responsible for the melting this observation of clayey gouge melting is comparable to that of natural faults e g chelungpu fault taiwan due to heterogeneous fault zone properties e g permeability frictional melting may be one of the important processes in clayey slip zones at shallow depths

patterns of mineral transformations in clay gouge with examples from low angle normal fault rocks in the western usa abstract neoformed minerals in shallow fault rocks are increasingly recognized as key to the behavior of faults in the elasto frictional regime but neither the conditions nor the processes which wall rock is transformed into clay minerals are well understood yet understanding of these mineral transformations is required to predict the mechanical and seismogenic behavior of faults we therefore present a systematic study of clay gouge mineralogy from 30 outcrops of 17 low angle normal faults lanf s in the american cordillera to demonstrate the range and type of clay transformations in natural fault gouges the sampled faults juxtapose a wide and representative range of wall rock types including sedimentary metamorphic and igneous rocks under shallow crustal conditions clay mineral transformations were observed in all but one of 28 faults one fault contains only mechanically derived clay rich gouge which formed entirely by cataclasis clay mineral transformations observed in gouges show four general patterns 1 growth of authigenic 1m d illite either by transformation of fragmental 2m 1 illite or muscovite or growth after the dissolution of k feldspar illitization of fragmental illite smectite is observed in lanf gouges but is less common than reported from faults with sedimentary wall rocks 2 retrograde diagenesis of an early mechanically derived chlorite rich gouge to authigenic chlorite smectite and saponite mg rich tri octahedral smectite 3 reaction of mechanically derived chlorite rich gouges with mg rich fluids at low temperatures 50 150 c to produce localized lenses of one of two assemblages sepiolite saponite talc lizardite or palygorskite chlorite quartz and 4 growth of authigenic di octahedral smectite from alteration of acidic volcanic wall rocks these transformation groups are consistent with patterns observed in fault rocks elsewhere the main controls for the type of neoformed clay in gouge appear to be wall rock chemistry and fluid chemistry and temperatures in the range of 60 180 c

an early holocene erosion phase on the loess tablelands in the southern loess plateau of china abstract a holocene loess profile to the west of xi an china was studied multi disciplinarily to investigate the relationships between soil erosion and monsoonal climatic change the proxy data obtained from this aeolian loess and palaeosol sequence indicate large scale variations of climate in the southern loess plateau since the last glaciation a rainwash bed indicative of a wetter climate excessive runoff and erosion on the loess tablelands was identified relating to the early holocene before the onset of the climatic optimum this is synchronous with the early holocene physiographic erosional stage identified in the valleys in north china it means that severe erosion took place when the region was undergoing climatic amelioration during the early holocene the evidence presented in this paper shows that the erosion occurred as a regional response to a monsoonal climatic shift in the southern loess plateau during the last glaciation prior to the erosion phase the land surface on the tablelands had been largely stable except for the rapid accumulation of aeolian dust and the resultant increase in its elevation relatively slow dust accumulation and intensive bio pedogenesis responding to the holocene climatic optimum followed the erosion phase the loess tablelands were most vulnerable to erosion during the large scale monsoonal climatic shift from dry cold glacial to humid warm post glacial conditions in the southern loess plateau

surface fault ruptures and slip distributions of the mw 6 6 11 april 2011 hamadoori fukushima prefecture northeast japan earthquake the 11 april 2011 hamadoori fukushima prefecture northeast japan earthquake occurred in a seismically active area one month after the 11 march 2011 off the pacific coast of tohoku earthquake the hamadoori earthquake resulted in a 14 km long down to the west normal slip rupture on the north northwest south southeast striking itozawa fault as well as a 16 km long down to the south normal slip rupture on the west northwest east southeast striking yunodake fault the slip along the itozawa fault increases abruptly from the southern end to the central part of the fault where the measured maximum displacement is close to 2 m the slip decreases gradually from the central section to the northwestern end of the fault the yunodake fault also has an asymmetric slip distribution with a peak of about 0 9 m near the northwestern section of the fault considering the direction of rupture propagation along the two faults it is apparent that the measured surface offset is asymmetric along the strike with the largest offsets observed nearer the end of the fault where the rupture began and showing a gradual decrease in the direction of rupture termination the surface observations of the slip distribution and the epicenter location are consistent with the general features of earthquake ruptures derived from slip inversion models on more than 60 of the rupture length of the hamadoori earthquake faults as well as on other historic normal fault earthquakes slip displacements are less than or equal to 30 of the maximum slip the moment magnitude m w of the earthquake estimated from ruptures length maximum and average displacements is between 6 5 and 6 8 in accordance with the seismologically determined value of 6 6 online material supplementary data of the surface slip distributions of the 11 april 2011 hamadoori earthquake along the itozawa and yunodake faults

a soil chronosequence in the semi arid environment of patagonia argentina abstract soil development with time was investigated on beach ridges with ages ranging from about 1380 to 6240 14c years bp at the eastern coast of central patagonia the main pedogenic processes are accumulation of organic matter and carbonate leaching and accumulation within the upper part of the soils soil formation is strongly influenced by incorporation of eolian sediments into the interstitial spaces between the gravel of which the beach ridges are composed different amounts of eolian material in the soils lead to differentiation into leptosols containing 10 fine earth in the upper 75 cm and regosols containing 10 fine earth soil depth functions and chronofunctions of organic carbon calcium carbonate ph ca zr mg zr k zr na zr fe zr mn zr and si al obtained from x ray fluorescence analysis were evaluated to establish soil chronofunctions mean values of the horizon data of 0 10 cm below the desert pavement were used which were weighted according to the horizon thicknesses the depth function of ph shows a decrease towards the surface indicating leaching of bases from the upper centimeters chronofunctions of ph show that within 6000 radiocarbon years of soil development ph drops from 7 0 to 6 6 in the leptosols and from 8 1 to 7 5 in the regosols the higher ph of the regosols is due to input of additional bases from the eolian sediments chronofunctions of ca zr and k zr indicate progressive leaching of ca and k in the regosols showing close relationships to time r2 0 972 and 0 995 na leaching as indicated by decreasing na zr ratios shows a strong correlation to time only in the leptosols r2 0 999 both leptosols and regosols show close relationships to time for fe zr r2 0 817 and 0 824 mn zr r2 0 940 and 0 803 and si al 0 971 and 0 977 indicating enrichment of fe and mn and leaching of si leaching of mobile elements takes place on a higher level in the regosols than in the leptosols from the beginning of soil formation hence a significant part of the eolian sediments must have been incorporated into the beach ridges very soon after their formation

holocene colluviation and its implications for tracing human induced soil erosion and redeposition on the piedmont loess lands of the qinling mountains northern china abstract colluvial components incorporated in loess soil sequences have preserved evidence of soil erosion and redeposition in the middle reaches of the yellow river drainage basin holocene loess soil sequences on the gentle sloped lands were studied by measuring magnetic susceptibility particle size distribution caco3 and extraction and identification of the non dust materials the analytical results indicate that in the early holocene soil erosion and redeposition by overland flow occurred even on the loess lands with small ground gradient in response to climatic amelioration linked to global climatic change no obvious soil erosion and redeposition events were found to correspond with the climatic fluctuations recorded in the loess soil sequence during the holocene climatic optimum the primary neolithic farming did not cause apparent erosion and redeposition because the loess landscape was mantled by well developed ustic luvisols and probably by forest vegetation both provided adequate resistance to sheet erosion by overland flow enhanced soil erosion and redeposition are traceable back to ca 4000 a b p it is attributed to intensified land use of arable farming and human settlement from the early bronze age onward a major event of sheet erosion and redeposition by overland flow occurred in the loess landscape during 4000 3600 a b p in the xia dynasty soil degradation and reduced resistance caused by climatic aridity and intensified dust accumulation may have played a secondary role in promoting soil erosion since 3100 a b p these results provide new insights into the history of soil erosion in the semi arid and semi humid loess regions and into the evaluation of human induced accelerated soil erosion against the background of the holocene natural erosion forced by monsoonal climatic fluctuation

impact of monsoonal climatic change on holocene overbank flooding along sushui river middle reach of the yellow river china abstract in the semiarid loess regions slackwater deposition of overbank flooding over the piedmont alluvial plains was episodic and alternated with dust accumulation and soil formation throughout the holocene the records of past hydrological events are therefore preserved within the architecture of loess and soils and are protected from subsequent erosion and destruction several holocene loess soil sequences with the deposits of overbank flooding over the semiarid piedmont alluvial plains in the southeast part of the middle reaches of the yellow river drainage basin were investigated by field observation osl and c14 dating measurement of magnetic susceptibility particle size distribution and chemical elements this enables the reconstruction of a complete catalog of holocene overbank flooding events at a watershed scale and an investigation of hydrological response to monsoonal climatic change as well during the holocene there are six episodes of overbank flooding recorded over the alluvial plain the first occurred at 11 500 11 000 a bp i e the onset of the holocene the second took place at 9500 8500 a bp immediately before the mid holocene climatic optimum after an extended geomorphic stability and soil formation the third overbank flooding episode came at about 3620 3520 a bp i e the late stage of the mid holocene climatic optimum and the floodwater inundated and devastated a bronze age town of the xia culture built on the alluvial plain and therefore the town was abandoned for a period of ca 100 years during the late holocene the alluvial plain experienced three episodes of overbank flooding at 2420 2170 1860 1700 and 680 100 a bp respectively the occurrence of these overbank flooding episodes corresponds to the anomalous change in monsoonal climate in the middle reaches of the yellow river drainage basin when rapid climate change or climatic decline occurs during at least the last four episodes both extreme floods and droughts occurred and climate departed from its normal condition which was defined as a balanced change between the northwestern continental monsoon and southeastern maritime monsoon over time great floods occurred as a result of extreme rainstorms in summers caused by rare intensive meridianal airflows involving northwestward moving tropical cyclone systems from the pacific these results could be applied to improve our understanding of high resolution climatic change and of hydrological response to climatic change in the semiarid zones

evidence of frictional melting from disk shaped black material discovered within the taiwan chelungpu fault system 1 the taiwan chelungpu fault drilling project penetrated three fault zones as the chelungpu fault system which slipped during the 1999 chi chi earthquake discovering disk shaped black material bm disk within the middle and lower fault zones in hole b the microscopic features of the bm disks indicated that they were pseudotachylytes and they showed high magnetic susceptibility possibly the result of intense shearing or high temperature conditions inorganic carbon content of the bm disks was low possibly because of thermal decomposition of carbonate minerals the high temperatures might be related to frictional heating during the earthquake implying that the bm disks were produced under intense shearing with frictional heating that reached melting temperature because the disks which provide the only evidence of melting pre date the 1999 earthquake we concluded that frictional melting did not occur during the earthquake

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

illite smectite patterns in sheared pleistocene mudstones of the southern apennines and their implications regarding the process of illitization a multiscale analysis abstract the transformation of water rich smectite clay minerals into relatively anhydrous illite is a common reaction in sedimentary basins it is commonly thought to be driven by temperature increase with increasing burial depth this mineral transformation is also observed in the gouge of large faults and because it releases bound water from smectite it is thought to be a key control in hydrologic and mechanical processes at subduction complexes in this work the distribution of smectite and illite within a large fault zone of the southern apennines of italy is analysed at scales varying from outcrop to sub millimetre x ray diffraction analyses indicate a direct link between the darkening in colour of the sheared mudstone and the illitization of smectite the heterogeneous distribution of illite and smectite within this shear zone was studied by integrating outcrop scale observations with a peeling technique that allows microscope and sem observations to be made over areas in excess of 60 cm2 the observed patterns of smectite illitization suggest that temperature is not the primary cause of the mineral transformation inside the fault the distribution of illite along planes of the p foliation and in the infill of shears indicates that shear stress facilitates the mineral transformation

shear induced graphitization of carbonaceous materials during seismic fault motion experiments and possible implications for fault mechanics abstract carbonaceous materials often concentrate in fault zones developed in pelitic rocks among carbonaceous minerals graphite is known as a lubricant and possibly plays a key role in frictional properties of the fault graphite reported from slip localized zones suggests that graphitization can occur during seismogenic fault motion thus we performed friction experiments on amorphous carbon and graphite to investigate how graphite forms in association with fault motion and how these carbonaceous minerals affect frictional properties of faults experiments were done at normal stresses of 0 5 2 8 mpa and slip rates of 50 m s to 1 3 m s in atmospheres of air and n 2 gas using rotary shear apparatuses xrd and tem analyses revealed that graphitization can indeed occur during seismogenic fault motion perhaps due to large shear strain short lived flash heating and stress concentration at asperity contacts even at low temperatures and pressures under anoxic environments we found large differences in steady state friction coefficient ss between graphite ss 0 1 and amorphous carbon ss 0 54 at low slip rate but amorphous carbon exhibits marked velocity weakening at slip rate above 10 mm s and its steady state friction reduces to the same level as that of graphite at a slip rate of 1 3 m s faults with amorphous carbon are not weak at low slip rates but they can become dynamically weak to foster fault motion during the generation of large earthquakes enriched graphite in fault zones can lubricate at all slip rates even at great depths and should receive more attention

high resolution studies of the oldest cultivated soils in the southern loess plateau of china abstract the holocene loess soil sequence on the chinese loess plateau constitutes an excellent record of evolution of soil formation monsoonal climate eolian dust accumulation and influences of arable farming of over 8000 years a high resolution soil profile on the zhouyuan loess tableland to the west of xi an was studied using particle size analysis measurement of magnetic susceptibility total fe toc and caco3 the results provide new insights into the roles of eolian dust deposition and human impact of cultivation on soil development in this environmentally sensitive zone several loess layers are found interbedded with cinnamon soils in the profile this has been caused by changes in rainfall and intensity of dust deposition that is forced by changes in balance between the northwest continental monsoon and southeast maritime monsoon of east asia during the holocene the processes of soil formation were interrupted several times by intensified dust fall and climatic aridity in the last 11 500 years the initial clearance of forest for arable farming occurred at ca 7500 years bp on the loess tableland it was contemporaneous with the arrival of the wetter and warmer climate of the holocene megathermal 8500 3100 years bp thereafter arable farming has been maintained during both the time of soil formation and that of intensified dust accumulation though there could be temporary cessation or reduced intensity of cultivation in the drier intervals because of lack of rainfall and soil moisture increased intensity of dust accumulation has been ongoing since ca 3100 years bp in the loess plateau a loess deposit of 40 80 cm has overlaid the multiple or single welded cinnamon soils on the flat land over the plateau

out of phase evolution between summer and winter east asian monsoons during the holocene as recorded by chinese loess deposits we analyzed climate proxies from loessic soil sections of the southern chinese loess plateau the early holocene paleosol s0 is 3 2 m thick and contains six sub soil units co eval soils from the central loess plateau are thinner 1 m consequently higher resolution stratigraphic analyses can be made on our new sections and provide more insight into holocene temporal variation of the east asian monsoon both summer and winter monsoon evolution signals are recorded in the same sections enabling the study of phase relationships between the signals our analyses consist of i measurements of magnetic properties sensitive to the production of fine grained magnetic minerals which reflect precipitation intensity and summer monsoon strength and ii grain size analyses which reflect winter monsoon strength our results indicate that the holocene precipitation maximum occurred in the mid holocene 7 8 3 5 cal ka bp with an arid interval at 6 3 5 3 cal ka bp the winter monsoon intensity declined to a minimum during 5 0 3 4 cal ka bp these results suggest that the east asian summer and winter monsoons were out of phase during the holocene possibly due to their different sensitivities to ice and snow coverage at high latitudes and to sea surface temperature at low latitudes

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

the gisp2 δ18o climate record of the past 16 500 years and the role of the sun ocean and volcanoes measured 18o 16o ratios from the greenland ice sheet project 2 gisp2 ice core extending back to 16 500 cal yr b p provide a continuous record of climate change since the last glaciation high resolution annual 18o 16o results were obtained for most of the current millennium a d 818 1985 and record the medieval warm period the little ice age and a distinct 11 yr 18o 16o cycle volcanic aerosols depress central greenland annual temperature 1 5 c maximally and annual 18o 16o for about 4 yr after each major eruptive event on a bidecadal to millennial time scale the contribution of solar variability to holocene greenlandic temperature change is 0 4 c the role of thermohaline circulation change on climate problematic during the holocene is more distinct for the 16 500 10 000 cal yr b p interval analogous to 14c age calibration terminology we express time in calibrated cal yr b p a d 1950 0 cal yr b p the oldest dryas bolling older dryas allerod younger dryas sequence appears in great detail bidecadal variance in 18o 16o but not necessarily in temperature is enhanced during the last phase of lateglacial time and the younger dryas interval suggesting switches of air mass transport between jet stream branches the branched system is nearly instantaneously replaced at the beginning of the bolling and holocene at 14 670 and 11 650 cal yr b p respectively by an atmospheric circulation system in which 18o 16o and annual accumulation initially track each other closely thermodynamic considerations of the accumulation rate temperature relationship can be used to evaluate the 18 o 16o temperature relationship the gisp2 ice layer count years of major gisp2 climate transitions also support the use of coral 14c ages for age calibration

strong velocity weakening and powder lubrication of simulated carbonate faults at seismic slip rates 1 high velocity friction tests were conducted on solid and hollow cylinders of carrara calcite marble dolomite marble silicate bearing calcite marble and calcite gouge to investigate the strength of carbonate faults during seismic slip the experiments performed at normal stresses of 0 6 14 7 mpa slip rates of 0 03 1 60 m s and room temperature in a rotary shear friction testing machine yielded an extraordinarily low steady state friction coefficient 0 1 at slip rates of 1 1 1 2 m s the slip weakening distance of 4 28 m became shorter at higher normal stress or frictional work rate strong velocity weakening was observed not only in steady state but also in nonsteady state friction while the slip rate was changing thus slip deceleration was accompanied by fault strength recovery large rapid temperature rises in narrow shear localization zones less than a few micrometers induced carbonate decomposition such as the breakdown of calcite into aggregates of cao nanograins and co2 in carrara marble scanning electron microscope observation revealed that the shear localization zone in the highly porous decomposition product was a layer of scattered small grains mostly 1 m in diameter these microstructures and the measured high permeability 10 14 m2 of the decomposed marble indicate that the dominant weakening mechanism in our experiments was possibly powder lubrication powder rheology at high slip rates is not yet well understood but the frictional behavior of nanograins appears to be strongly velocity dependent if decarbonation occurs during seismic slip in natural carbonate faults powder lubrication may make the faults slippery even under fluid drained conditions

experimental investigation of flash weakening in limestone abstract flash heating and weakening could operate during earthquake nucleation and propagation we performed 27 friction experiments in a compression torsion apparatus on ring shaped limestone samples at sub seismic to seismic slip rates 340 mm s centimetric displacements and normal stresses of 8 mpa friction decreases dramatically at slip rates of 50 150 mm s flash weakening was contemporaneous with a peripheral temperature rise of 90 c measured with an infrared camera the peripheral temperature yields a lower limit to the slipping zone temperature the decrease in friction may result from weakening of the asperity contacts due to decarbonation of calcite induced by 1 flash heating or 2 mechanically activated reactions however x ray powder diffraction and raman spectroscopy analyses do not reveal the presence of decarbonation products in the slipping zone instead white light interferometry and field emission scanning electron microscope observations reveal the presence of a smooth sliding surface made of nanometric particles the mechanical data can be fit by the rate and state dependent friction model or by a quadratic model the latter proposed for powder lubrication we conclude that flash heating and weakening and powder lubrication may operate together to decrease dynamic friction in limestone in experiments and for the conditions investigated here in nature

fluidization and melting of fault gouge during seismic slip identification in the nojima fault zone and implications for focal earthquake mechanisms 1 the record of physical processes that occur during seismic slip events is well preserved in fault rocks from the active nojima fault in japan the fault rocks formed at about 3 km depth and comprise thin alternating layers of very fine gouge and pseudotachylyte derived from granite each layer is thinner than a few millimeters and corresponds to one seismic slip event the very thin slip zone width suggests that some mechanisms of slip weakening operated and our studies of the fault rocks suggest that fluidization and melting of gouge were particularly important fluidized and nonfluidized gouges were distinguished using the detection probability of fragmented counterparts method it is known from granular material science that the phase transition from a grain friction regime to fluidization of granular materials can occur only by a very small decrease in volume fraction of solid grains once fluidization occurs the frictional resistance decreases abruptly to nearly zero even before thermal pressurization reaches its extreme state when fault gouge is melted frictional resistance is governed by the viscosity of melt which depends mainly on temperature chemical composition h2o concentration and the volume fraction of unmelted grains for each pseudotachylyte layer we estimated the temperature of melt using various temperature indices and measured volume fraction of unmelted grains we synthesized these data to reconstruct the change in viscosity during seismic slip events the melt viscosity is very high 107 9 pas during initial melting due to the combined effect of low temperature 750 800 c and large volume fraction of solid grains thus seismic slip is inevitably restrained instantaneously once this mechanical barrier is overcome the viscosity reduces continuously and dramatically as slip increases at 1000 c the viscosity reduces to 104pas and eventually to 10pas at 1280 c thus stress drops almost completely and rupturing tends to run away

simultaneous reactivation of two subparallel inland normal faults during the mw 6 6 11 april 2011 iwaki earthquake triggered by the mw 9 0 tohoku oki japan earthquake the gigantic m w 9 0 11 march 2011 tohoku oki earthquake suddenly changed the overriding inland area to an extensional stress regime and triggered massive seismic swarms in the coastal region the largest earthquake of m w 6 6 struck southern fukushima on 11 april 2011 and ruptured two previously mapped faults the northwest nw trending yunodake fault and the north northwest nnw trending itozawa fault clear 15 km long and 14 km long surface ruptures appeared along both faults respectively exhibiting a predominantly normal sense of slip down to the west the maximum vertical offset on the yunodake fault is 0 8 m whereas that on the itozawa fault is 2 1 m the itozawa fault rupture is in part marked by uphill facing scarps which is discordant with the large scale topography but consistent with saddled ridges and ponded alluvium the yunodake fault which bounds a neogene half graben structure juxtaposing mesozoic metamorphic rocks against neogene sedimentary rocks shows left lateral deflections of streams seismological data and interviews of local residents revealed that the two subparallel faults ruptured simultaneously based on the location of its hypocenter we however interpret that the itozawa rupture was primary and then triggered normal faulting on the yunodake fault under the heightened coulomb stress caused by the preceding tohoku oki earthquake our paleoseismic trench across the itozawa fault exposed evidence for a penultimate earthquake that occurred sometime between 12 620 and 17 410 cal yr b p there is no evidence that the itozawa fault ruptured during or immediately after the a d 869 jogan earthquake which is believed to be the penultimate giant megathrust earthquake along the japan trench

towards an orbital time scale for chinese loess deposits abstract in this study we analyzed the grain size of the baoji loess soil sequence at 10 cm intervals results show that grain size variations are very sensitive to loess soil alternations with loess units being much coarser than soils such a change in loess soil grains is interpreted as the result of the glacial interglacial cyclic variations in the intensity of the winter monsoon winds out of siberia the grain size record is thus employed as a proxy indicator of the winter monsoon circulation and tuned to the orbital records calculated recently by berger and loutre 1991 under the control of major magnetic reversals the tuning is independent of any correlation with 18o signals in the deep sea sediments the resulting grain size time scale is tightly constrained as suggested by the following facts 1 the filtered obliquity and precession components from the grain size data on the orbital time scale closely match the theoretical orbital records 2 ages of the major magnetic reversals estimated from the grain size time scale are in good agreement with the k ar dated ages 3 there is close coherence between the baoji grain size time series and the orbital variations at the orbital frequency bands over the entire 0 2 5 ma period and 4 the grain size record on the orbital time scale shows a close similarity to the orbitally tuned dsdp site 607 and odp site 677 18o records examination of time dependent characteristics of the grain size record suggests that there are two major shifts of dominant periodicities in the long term monsoonal cycles one occurring at about 0 8 ma bp and the other around 1 7 ma bp

convective contribution to the genesis of hurricane ophelia 2005 abstract the convection occurring in the tropical depression that became hurricane ophelia 2005 was investigated just prior to tropical storm formation doppler radar showed a deep wide intense convective cell of a type that has been previously thought to occur in intensifying tropical depressions but has not heretofore been documented in detail the updraft of the cell was 10 km wide 17 km deep had updrafts of 10 20 m s 1 throughout its mid to upper levels and contained a cyclonic vorticity maximum the massive convective updraft was maintained by strong positive buoyancy which was maximum at about the 10 km level probably aided by latent heat of freezing evaporative cooling and precipitation drag occurred in the rain shower of the cell but were insufficient to produce a strong downdraft or gust front outflow to force the updraft the convective updraft was fed by a layer of strong inflow that was several kilometers deep wind induced turbulence just above the ocean surface enriched the equi

dry damp or drenched the effect of water saturation on the frictional properties of clay fault gouges abstract clay minerals often constitute a significant proportion of fault cores yet the physics of clay friction in particular the effect of free and interstitial bound interlayer water is poorly understood understanding the behaviour of this typically frictionally weak component is fundamental to constraining the larger scale behaviour of fault zones in this study laboratory experiments were conducted on synthetic clay fault gouges under carefully controlled saturation states samples were sheared at room temperature under triaxial pressure at the following conditions water saturated room humidity thermally dried then sheared at room humidity in a vacuum at room humidity thermally dried then sheared in a vacuum in a vacuum and thermally dried within the pressure vessel friction coefficient is shown to increase with dryness by a factor of 3 in 2 1 smectite and a factor of 2 in 1 1 sheet silicate with largest increases in thermally dried samples analysis of constitutive frictional parameters a b show that gouges become less stable with dryness the amount of displacement or time required to establish a new steady state upon a change in sliding velocity dc decreases markedly in drier samples results suggest that the presence of water is key in promoting time and slip dependent frictional changes constraining operative grain scale deformation mechanisms to those that are fluid assisted they also highlight the optimum laboratory procedures to investigate the frictional properties of clay bearing materials

geochronology and paleoenvironment of the taoshan site northeastern china and archaeological implications abstract the taoshan archaeological site located in northeastern china was found in 2011 and an area of 36 m 2 was excavated in 2013 and 2014 2908 stone artifacts 71 pottery fragments and five ornaments were excavated from three cultural layers similar sites with both stone artifact and pottery at least in heilongjiang province of china have not been reported the dating results showed that the optically stimulated luminescence technique is of great utility for such archaeological deposits and the three cultural layers were dated to 16 5 13 4 ka 13 4 8 7 ka and 8 7 5 6 ka respectively the climate proxies magnetic susceptibility total organic content and pollen indicate that the local climate was cold and dry for the period of 16 5 13 4 ka warm and wet for the period of 13 4 8 7 ka and warm and dry for the period of 8 7 5 6 ka respectively the types and amount of archaeological findings from each layer period reflect the human response to the past climate change implying that the human related processes identified at taoshan are associated with climatic and environmental changes the investigations of the site are very important for developing a better understanding of the colonization of this region by humans the transmission of technologies and the processes of economic and social change the local societies underwent the presence of microblades and pottery is the most significant for our reconstructing of the archaeology of the northernmost parts of northeast china

clay mineral anomalies in the fault zone of the chelungpu fault taiwan and their implications 1 the taiwan chelungpu fault drilling project tcdp hole a recovered continuous core samples across the rupture zone of the 1999 chi chi earthquake mw7 6 studying in situ chemical properties sequentially from fresh fault zone materials of the chelungpu fault provides insight into possible faulting mechanisms distinct anomalies of mineral assemblages at the 1111 m fault zone of tcdp hole a are found to be 1 a decrease in clay content within the primary slip zone psz and 2 a significant decline of illite disappearance of chlorite and kaolinite and spike in smectite within the psz meanwhile features relating to melting or amorphous material in the psz have been observed by sem and tem the results suggest that the psz might have experienced generation of glassy materials such as pseudotachylyte by the expense of clay minerals due to strong shear heating then prompt alteration of pseudotachylyte into smectite characteristics of clay minerals and images obtained from electronic microscopes in the psz thus imply that pseudotachylyte possibly developed during the 1999 chi chi earthquake but quickly altered into smectite this particular phenomenon may explain why pseudotachylyte is rarely found in exhumed hydrated fault zones

anthropogenic hillslope terraces and swidden agriculture in jiuzhaigou national park northern sichuan china abstract small irregular terraces on hillslopes or terracettes are common landscape features throughout west central china despite their prevalence there is limited understanding of the nature of these topographic features the processes that form them and the role humans played in their formation we used an interdisciplinary approach to investigate the geology ecology and cultural history of terracette development within jiuzhaigou national park sichuan province china terracettes occur on south facing 20 slopes at 2500 m elevation which appears to coincide with places people historically preferred to build villages ethnographic interviews suggest that traditional swidden agricultural cycles removed tree roots causing the loess sediments to lose cohesion slump and the terrace risers to retreat uphill over time this evidence is supported by landslide debris at terracette faces archaeological analysis of terracette sites reveal remains of rammed spread soil structures bones stone tools and ceramics dating from at least 2200 years before present within a distinct paleosol layer radiocarbon and optically stimulated luminescence dating of terracette sediments ranged in age from between 1500 and 2000 14 c yr bp and between 16 and 0 30 ka respectively these multiple lines of evidence indicate a long history of human habitation within jiuzhaigou national park and taken together suggest strong links between terracette formation and human landuse interactions

coseismic thickness of principal slip zone from the taiwan chelungpu fault drilling project a tcdp a and correlated fracture energy abstract direct observations of the physical structures of the seismogenic zones of active faults are rare due to the difficulty in reaching the fault zone at depth current geological evidences mostly from the surface suggest that principal slip zone psz accommodated most shear displacement and was the place where physico chemical processes occurred during an individual coseismic event and the thickness of psz is a few millimeter to tens of centimeter wide however the actual thickness of psz of a large earthquake a key parameter of seismology in understanding energy dissipation and rupture processes remains largely unknown the chelungpu fault that ruptured during the 1999 mw 7 6 chi chi earthquake taiwan was drilled to a depth of 2003 m providing a unique opportunity to sample an active fault that slipped in a recent large earthquake the psz corresponding to the 1999 chi chi earthquake was well characterized within cores at a borehole depth of 1111 m from the taiwan chelungpu fault drilling project a tcdp a here we determine the interval of clay anomaly that resulted from frictional melting thermal decomposition process by state of art in situ synchrotron xrd analysis providing very high spatial resolution for mineralogy combined with the interval of the presence of vesicles from microstructural observation the thickness of chi chi psz is estimated to be 1 mm thus the correlated contribution of surface fracture energy to earthquake breakdown work at least in this locality is quantified to be 1 9 the huge remaining part of the breakdown work seems to be turned into heat associated with fault dynamic processes during the 1999 chi chi earthquake

late quaternary climate change loess sedimentation and soil profile development in the central great plains a pedosedimentary model research on soil genesis often assumes a top down model in which the soil profi le develops downward from a stable land surface this model is inapplicable to upland landscapes affected by frequent dust deposition where soils grow upward as they develop on the central great plains late quaternary loess sections proximal to immediate source areas contain the brady soil a prominent marker separating late pleistocene peoria loess from holocene bignell loess farther from immediate dust source areas the brady soil and bignell loess are not recognizable in the fi eld on loess tablelands in these distal regions surface soils typically contain a prominent clay rich b horizon below a thick silty a horizon assuming top down pedogenesis this could be interpreted as a postglacial soil profi le formed in peoria loess with the b horizon produced by weathering and clay illuviation we propose a strikingly different interpretation in which the upper b horizon at distal sites is the brady soil a horizon that has been transformed by burial organic matter loss and modern subsoil structure formation processes the overlying modern a horizon represents bignell loess properties of the brady soil at proximal sites a distinctive burrowed zone high clay content and tio 2 zro 2 and low volcanic glass content can be traced to the b horizon in distal soils a decrease in smectite abundance above the brady soil at proximal sites is identifi able at the top of the clay rich b horizon in distal soils the spatial variation of clay content in loess and soil horizons is best explained by eolian sedimentation patterns the higher clay content in the brady soil and distal b horizons defi nes a fi ne grained zone that represents a late phase of peoria loess accumulation evidence of chemical weathering is minimal and illuvial clay is rare to absent in the clay rich b horizons illuvial clay does often occur deep in the solum and is related to the depth below the top of the brady soil the depth of occurrence of illuvial clay is not related to modern climate parameters although depth to secondary carbonate appears to be in equilibrium with modern climate upland soils in the central great plains are composite soils their properties are the result of a pedosedimentary history linked to regional climate change that has infl uenced sedimentation and pedogenesis since the late pleistocene

pleistocene loess in the humid subtropical forest zone of east asia 1 loess deposits in asia have been used as indicators of palaeoclimate because they are usually found bordering deserts this paper reports extensive and thick deposits of loess in tropical southwest china between latitudes 18 and 23 30 n which is 1300 km south of known and extensively researched loess deposits in north china the present climate of the reported loess areas is hot and humid with mean annual rainfall of 1000 2000 mm and vegetation of subtropical evergreen broadleaf forest this compares with less than 400 mm rainfall and vegetation of semi desert steppe in areas of current loess accumulation on desert margins in north china the source area of the loess which is dated by optical luminescence to the late pleistocene from 90 222 ka is thought to be the exposed east asian shelf which was up to 140 m below present sea level during quaternary arid phases recent research on the nature of the shelf environment and the relatively large particle size of the loess suggests a local origin the reported loess is not interbedded with palaeosols and small amounts of soil cover the loess compared with well developed soils in loess in semiarid regions in north china this is explained by elimination of the supply source by sea level rise following each arid phase as continued dust supply appears necessary for soil to form this preliminary report of loess in southwest china conflicts with palynological evidence and suggests that recent reconstructions of pleistocene aridity in east asia may be conservative

episode of strengthened summer monsoon climate of younger dryas age on the loess plateau of central china abstract the baxie loess section just east of the tibetan plateau contains evidence showing that the asian monsoon climate experienced an abrupt reversal near the end of the last glacial age rapid deposition of dust under cool dry full glacial conditions gave way to an interval of soil development and reduced dust influx attributed to a strengthening of the warm moist summer monsoon a subsequent abrupt increase in dust deposition a response to a weakening of the summer monsoon was later followed by renewed soil formation as summer monsoon circulation again intensified during the early holocene by one interpretation the thin upper loess is a manifestation of the european younger dryas oscillation however in this case the available 14c ages require either that 1 onset of loess deposition lagged the beginning of the younger dryas event in europe by as much as 2000 calibrated 14c years or 2 all the 14c ages are too young possibly due to contamination alternatively the late glacial paleosol the top of which is synchronous with the abrupt end of the late glacial 18o anomaly in the dye 3 greenland ice core records the younger dryas event such an interpretation is consistent with general circulation model simulations of younger dryas climate that show strong seasonality and a strengthened summer monsoon and with marine cores from the western pacific ocean that contain evidence of pronounced cooling of surface waters during younger dryas time

the cold event 8200 years ago documented in oxygen isotope records of precipitation in europe and greenland stable oxygen isotope ratios of ostracod valves in late glacial and holocene sediments of core as 92 5 from deep lake ammersee southern germany reflect variations of mean oxygen isotope ratios in past atmospheric precipitation the record reconfirms the strong similarity of climate evolution in europe and greenland during the last deglaciation for the first time in europe we find a 200 year long negative 18o excursion which is contemporaneous with the strongest negative 18o excursion in the greenland ice around 8 2 ky before present the 8 2 ky isotopic event on both sides of the north atlantic ocean is interpreted as a cold period most probably induced by a perturbation of the north atlantic thermohaline circulation we discuss two possible triggering mechanisms 1 weak forcing as proposed by alley et al and 2 forcing by a strong and sudden freshwater pulse from the collapse of the hudson ice dome

reinterpreting climate proxy records from late quaternary chinese loess a detailed osl investigation abstract numerous authors have utilised physical properties of chinese loess and red clay deposits to develop apparently detailed and continuous past climate records from the miocene into the holocene many of these studies have further suggested that the principal climatic agent responsible for the aeolian emplacement and diagenesis of chinese loess the east asian monsoon has fluctuated rapidly on millennial to sub millennial timescales in concert with dramatic changes in the north atlantic dansgaard oeschger cycles and heinrich events and the western pacific el nino southern oscillation much of this evidence is based on reconstructions and age models that are tied to assumptions concerning the nature of loess sedimentation and diagenesis for example the belief that loess sedimentation can be viewed as essentially continuous some authors have however cast doubt on these assumptions and suggest that the application of radiometric techniques may be required to determine their validity recent studies utilising optically stimulated luminescence osl methods have reinforced these doubts and here osl dates obtained at 10 cm intervals from three sites along a transect across the chinese loess plateau have been used in combination with climate proxy evidence to test the existing assumptions that underpin many palaeoclimatic reconstructions from loess in this way the first time continuous and independently dated late quaternary climate reconstruction is developed from loess the data indicate that sedimentation is episodic and that once emplaced loess is prone to pedogenic disturbance diagenetic modification and in some cases erosion the relationships between proxies and sedimentation rates are also assessed and climatic interpretations based on different age models compared the implications of these findings for reconstructions of climate from loess are explored and comparisons are made between the developed palaeoclimate records and evidence from ice and ocean cores this exercise also highlights important information concerning the relative influence of forcing mechanisms behind east asian monsoon change over the late quaternary

holocene dust accumulation and the formation of polycyclic cinnamon soils luvisols in the chinese loess plateau chinese loess palaeosol sequences are well known for their records of monsoonal climatic variations however the modern processes of dust accumulation and soil formation remain poorly understood a high resolution investigation on modern soils including the measurement of magnetic susceptibility particle size distribution total fe total organic carbon caco3 content and optical stimulated luminescence osl dating was carried out on the zhouyuan loess tableland in the southern loess plateau the results indicate that modern cinnamon soils luvisols have developed on contemporarily accumulated aeolian dust during the holocene the aeolian loess accumulated during the younger dryas was identi ed in the top part of the malan loess that underlay the modern soil by osl dating and proxy climatic data it indicates that the malan loess accumulated during the last glaciation marine isotope stages 2 4 does not serve as the parent material for the modern soils pedogenesis of the soils started with the increased precipitation and soil moisture that have occurred on the loess tableland since the early holocene precipitation driven pedogenesis and organic activities are responsible for the leaching of caco3 decomposition of mineral dust and the production of clay and ferromagnetic minerals drier intervals have interrupted soil formation several times and therefore pro les with multiple soils have been developed at many sites on the loess tableland at places where soil erosion was relatively strong either a single soil or welded soils are preserved in the holocene pro les this does not necessarily mean however that modern soils over the plateau have been developed without interruption under a constantly warmer moister climate this is signi cant for understanding the surface processes and climatic variation during the formation of the numerous palaeosols over the loess plateau in the quaternary copyright 2003 john wiley sons ltd

holocene wildfires related to climate and land use change over the weihe river basin china abstract charcoal particles preserved in the loess palaeosol profiles provide records of wildfires during the holocene total organic carbon magnetic susceptibility and charcoal analysis and osl dating were carried out in the holocene loess palaeosol profiles at two sites in the weihe river basin the analytical results show that natural wildfires occurred frequently during the last glaciation when climate was dominated by northwest continental monsoon and steppe vegetation expanded southerly to the weihe river basin wildfire occurrence decreased during climatic amelioration in the early holocene during the holocene climatic optimum between 8500 b p and 3100 b p natural wildfire occurrence was reduced greatly pedogenic alteration to the accumulated dust was intensified because of the humid warm climate brought on by southeast maritime monsoon localized fire events in connection with human activities of the neolithic occurred in several episodes over the region during the late holocene when climate become drier wildfire occurrence over the upland hills shows a pattern different from that in the guanzhong basin over the upland hills in the north charcoal concentrations show a decreasing trend in the recent loess and topsoil it indicates infrequent biomass burning during the last 3100 years this is attributable to nomadic occupation of the loess hills during the bronze age and the development of a land use pattern of livestock farming in most part of the history over the loess tableland in the guanzhong basin in the south abruptly increased charcoal concentrations in the recent loess and topsoil show very high level of biomass burning this is attributable to the increasingly intensified land reclamation for cereal cultivation from the bronze age this study provides new insights into wildfires over the semi arid and sub humid regions in connection with climate and land use change

east asian monsoon evolution during the eemian as recorded in the western chinese loess plateau abstract we present a high resolution environmental magnetic record of the east asian summer monsoon spanning paleosol s1 corresponding to marine oxygen isotope mis 5 from the jiuzhoutai jzt loess section in lanzhou on the northwestern edge of the chinese loess plateau we use a chronology based on a sediment grain size age model frequently used for chinese loess the eemian is dated to 127 37 121 31 ka bp and can be divided into three sub stages based on variations in summer monsoon intensity early eemian 127 37 125 67 ka bp with an intermediate summer monsoon intensity mid eemian 125 67 124 24 ka bp with weakest summer monsoon intensity and late eemian 124 24 121 31 ka bp with the strongest summer monsoon intensity contrasting the winter monsoon weakened at the beginning of mis5e reached its weakest intensity during the late eemian 121 ka bp and then commenced an irreversible strengthening trend furthermore the eemian exhibits a similar climatic trend to the holocene optimum since both are divided into two parts by an intervening arid interval and the most humid period occurs in the secondary pedogenic stage therefore we suggest that the climate evolution during eemian and later may provide useful information about climate forecast in the future

archaeology of the anthropocene in the yellow river region china 8000 2000 cal bp although archaeological analysis emphasizes the importance of climatic events as a driver of historical processes we use a variety of environmental and archaeological data to show that human modif

effects of sample preparation on the microstructural signatures of faulting in clay bearing fault gouge abstract clay rich fault gouge in the principal slip zones of faults stores abundant water within pores and between clay interlayers during the preparation of thin sections and rock chips for microstructural observations fault gouge samples are commonly air dried at room temperature or in an oven however during the drying process remnant liquid water between gouge grains produces an inter particle adhesion force liquid bridge force which rearranges the grain to grain structure likely resulting in a disturbance of the original fabric for this study we prepared gouge samples from the itozawa fault northeastern japan using a t butyl alcohol freeze drying method that mitigates drying induced fabric disturbance we then compared the microstructure of our samples with those prepared using the conventional air drying method the freeze dried samples preserve a smooth fault plane clearly defined nanoparticles and well developed shear sense indicators including slickenlines and riedel shear planes in contrast the air dried samples underwent shrinkage during drying which distorted the geometry of the fault plane these air dried samples lack nanoparticles and display only a weak shear fabric we conclude that microstructural observations on samples prepared using the t butyl alcohol freeze drying method compared with conventional air drying could preserve more evidence for the retrieval of fault information including the kinematics slip stability and dynamic weakening mechanism of a fault

spatial and temporal reconstructions of changes in the asian palaeomonsoon a new mineral magnetic approach abstract a new quantitative approach is proposed for estimating palaeoprecipitation across the chinese loess plateau at present there is a strong rainfall gradient across the plateau from 300 mm yr in the near desert conditions in the northwest to over 750 mm yr in the southeast just 700 km distant we find that the concentration of ferrimagnetic iron oxide minerals in nine modern soil types represented by 37 individual soil profiles is strongly correlated with this contemporary rainfall gradient the ferrimagnetic concentration rises along this gradient from 0 01 in the northwest to over 0 2 in the southeast the nine modern soil types have been used in the construction of a rainfall vs magnetic susceptibility least squares regression climofunction past variations of loess soil iron oxide content are easily established through magnetic susceptibility measurements and so can be used to reconstruct the rainfall of former interglacial and glacial periods the physical and pedological basis of the rainfall vs susceptibility relationship is discussed and potential limitations of our rainfall reconstruction method are explored our palaeoclimate reconstructions indicate dramatic changes in rainfall due to variations in the structure of the asian monsoon the rainfall variations are about four times greater than has been suggested for this region by atmospheric general circulation modelling our data indicate increased rainfall throughout central china both in interglacial periods and in the early holocene the increases in monsoonal rain were particularly pronounced at our westernmost sites adjacent to the northeastern edge of the tibetan plateau in contrast for glacial periods a reduction in rainfall is found across the whole loess area with the greatest decreases in the southeast

baoji type pedostratigraphic section loess plateau north central china abstract the baoji section is judged to be the most complete pedostratigraphic section on the loess plateau of north central china it is located about 5 km north of the city of baoji and consists of 37 paleosols formed during more than the last 2 5 ma it is designated here as the type pedostratigraphic section with formally named geosols following the rules of the north american commission on stratigraphic nomenclature geochronological control is based largely on magnetostratigraphy with the brunhes matuyama and gauss epochs and jaramillo and olduvai events clearly recognized the baoji geosols can be correlated with equivalent pedostratigraphic units throughout the loess plateau by a combination of magnetostratigraphy and character position and the association of the pedostratigraphic units within the quaternary succession the variation of the geosols suggests climatic cycles of varying intensity and duration but generally warmer and moister conditions when compared with the loess units that suggest colder and drier periods

changes in paleostress and its magnitude related to seismic cycles in the chelung pu fault taiwan paleostress analysis was conducted through a multiple stress inversion method using slip data recoded for the core samples from the taiwan chelung pu fault drilling project tcdp two stress fields were obtained one of these had horizontally plunging 1 and the other has horizontally plunging 2 or 3 in the compressional stress direction of the chi chi earthquake stress magnitude for both the stress fields was constrained by stress polygons which indicated larger shmax for horizontally plunging 1 than that in the case of horizontally plunging 2 or 3 these differences in stress orientations and stress magnitude suggest that the change in stress filed can be caused by stress drop and stress buildup associated with seismic cycles the seismic cycles recoded in the core samples from tcdp could include many events at geological timescale and not only the 1999 chi chi earthquake

constitutive properties of clayey fault gouge from the hanaore fault zone southwest japan velocity step tests at a range of slip rates 0 0154 155 54 m s 1 are performed using natural fault gouge containing smectite mica and quartz collected from an outcrop of the hanaore fault southwest japan field and microscopic observations reveal that the shear deformation is localized to a few centimeters or thinner layer of black clayey fault gouge this layer is formed by multiple stages and determining the width of the shear zone due to a single event is difficult to determine the experimental data on the abrupt jumps in the load point velocity are fitted by a rate and state dependent frictional law coupled with the spring slider model the stiffness of which is treated as a fitting parameter this treatment is shown to be essential to determine the constitutive parameters and their errors the velocity steps are successfully fit with typically two state variables larger b 1 with shorter d c1 and smaller b 2 with longer d c2 at slip rates higher than 1 m s 1 negative b 2 is required to fit the data in most of the cases thin gouge layers 200 m in the experiment enables us to simulate large averaged shear strain which is important to recognize the evolution of the state variable associated with negative b 2 and long d c2 observation of microscopic structure after experiments shows poor development of y planes this may be consistent with the mechanical behavior observed weak occurrence of initial peak strength at yielding and displacement hardening throughout the experiments

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

do scaly clays control seismicity on faulted shale rocks abstract one of the major challenges regarding the disposal of radioactive waste in geological formations is to ensure isolation of radioactive contamination from the environment and the population shales are suitable candidates as geological barriers however the presence of tectonic faults within clay formations put the long term safety of geological repositories into question in this study we carry out frictional experiments on intact samples of opalinus clay i e the host rock for nuclear waste storage in switzerland we report experimental evidence suggesting that scaly clays form at low normal stress 20 mpa at sub seismic velocities 300 m s and is related to pre existing bedding planes with an ongoing process where frictional sliding is the controlling deformation mechanism we have found that scaly clays show a velocity weakening and strengthening behaviour low frictional strength and poor re strengthening over time conditions required to allow the potential nucleation and propagation of earthquakes within the scaly clays portion of the formation the strong similarities between the microstructures of natural and experimental scaly clays suggest important implications for the slip behaviour of shallow faults in shales if natural and anthropogenic perturbations modify the stress conditions of the fault zone earthquakes might have the potential to nucleate within zones of scaly clays controlling the seismicity of the clay rich tectonic system thus potentially compromising the long term safeness of geological repositories situated in shales

gouge graphitization and dynamic fault weakening during the 2008 mw 7 9 wenchuan earthquake the longmenshan fault that ruptured during the 2008 mw 7 9 wenchuan china earthquake was drilled to a depth of 1200 m and fault rocks including those in the 2008 earthquake slip zone were recovered at a depth of 575 595 m we report laboratory strength measurements and microstructural observations from samples of slip zone fault rocks at deformation conditions expected for coseismic slip at borehole depths results indicate that the longmenshan fault at this locality is extremely weak at seismic slip rates in situ synchrotron x ray diffraction analysis indicates that graphite was formed along localized slip zones in the experimental products similar to the occurrence of graphite in the natural principal slip zone of the 2008 wenchuan rupture we surmise that graphitization occurred due to frictional heating of carbonaceous minerals because graphitization was associated with strong dynamic weakening in the experiments we further infer that the longmenshan fault was extremely weak at borehole depths during the 2008 wenchuan earthquake and that enrichment of graphite along localized slip zones could be used as an indicator of transient frictional heating during seismic slip in the upper crust

magnetic properties of modern soils and quaternary loessic paleosols paleoclimatic implications the magnetic properties of paleosols developed in quaternary sequences of loess have been used for stratigraphic definition correlation with other terrestrial and deep sea sequences and paleoclimatic paleorainfall reconstruction in some loess paleosol sequences including those of the chinese loess plateau tajikistan and the czech republic maxima in magnetic susceptibility values correspond with the paleosol horizons and minima with the least weathered loess layers in other loess soil sequences including those of siberia alaska and argentina the relationship is completely opposite with susceptibility minima associated with the most developed paleosols to account for these opposite relationships the respective roles of 1 magnetic enhancement and 2 magnetic depletion and or dilution in determining soil magnetic properties are investigated for a range of modern soil types most magnetic enhancement is seen in the upper horizons of well drained cambisols absence or loss of magnetic iron oxides is apparent in acid podsol profiles and waterlogged soils for the cambisol profiles significant correlation is found between susceptibility and organic carbon cation exchange capacity and clay content the mineralogy morphology and grain size of soil magnetic carriers extracted from three modern enhanced soils and a paleosol from the chinese loess plateau are also identified by independent petrographic means microscopy and x ray diffraction of magnetic extracts magnetite and maghemite of ultrafine grain size from 0 4 to 0 001 i m are the major contributors to the magnetically enhanced soils weathering can concentrate detrital magnetic grains especially in the fine silt size fractions of soils the magnetic data from the modern soils indicate that interpretation of paleosol magnetic properties must be done on a site specific basis taking into account the possibilities of pedogenic enhancement pedogenic dilution or depletion and allochthonous inputs of magnetic minerals excessively arid wet or acid soils are unable to form significant amounts of pedogenic ferrimagnets well drained intermittently wet dry soils with reasonable buffering capacity and a substrate source of fe show most magnetic enhancement for those soils which favour magnetic enhancement processes correlation has been found between the maximum value of the pedogenic susceptibility and the annual rainfall the almost unique pedogenic system in the chinese loess plateau where variation in soil forming factors other than climate is reduced to a global minimum allows use of the paleo susceptibility values as proxy paleorainfall values to identify the mechanism of any link between magnetic properties for example susceptibility and climate change the mineralogy and grain size of soil magnetic carriers requires detailed investigation given the prospect of 1 quantitative paleorainfall records from continental loess records 2 predictions of present and future climate change and 3 the value of paleoclimate data for testing of numerical climate models such magnetic investigations can contribute significantly to our understanding of past and future environmental change

granular nanoparticles lubricate faults during seismic slip nanoparticles are known to form in narrow slip zones in natural and experimental fault zones but their possible role in dynamic weakening of faults during seismic slip remains almost unexplored we conducted friction experiments on periclase mgo nanoparticles 50 nm in average size at rates as high as 1 3 m s 1 a typical speed of seismic slip the nanoparticles were used as the initial gouge to avoid complexities arising from comminution and fluid release the dynamic friction decreased with increasing slip rate and the steady state frictional coefficient reduced to as low as 0 1 at a slip rate of 1 3 m s 1 flash heating is not effective for nanoparticles and we propose that development of slickensides and dominant operation of nanoparticle rolling cause such a weakening nanoparticle lubrication appears to be as effective as melt lubrication and thermal pressurization and the formation of nanoparticles in slip zones may be an important fault lubrication process

wildfire history and climatic change in the semi arid loess tableland in the middle reaches of the yellow river of china during the holocene evidence from charcoal records high resolution macroscopic charcoal and sediment analysis was used to reconstruct fire history and environmental changes from three loess paleosol profiles on the semi arid loess tableland landsca

a radar and electrical study of tropical hot towers abstract radar and electrical measurements for deep tropical convection are examined for both break period and monsoonal regimes in the vicinity of darwin australia break period convection consists primarily of deep continental convection whereas oceanic based convection dominates during monsoonal periods associated with the monsoon trough over darwin order of magnitude enhancements in lightning flash rates for the break period regime are associated with 10 20 db enhancements in radar reflectivity in the mixed phase region of the convection compared with the monsoonal regime the latter differences are attributed to the effect of convective available potential energy cape and its nonlinear influence on the growth and accumulation of ice particles aloft which are believed to promote charge separation by differential particle motions cape in turn is largely determined by the boundary layer wet bulb temperature modest differences 1 3 c in wet bulb potential temperature between land and s

late pleistocene tropical pacific temperature sensitivity to radiative greenhouse gas forcing understanding how global temperature changes with increasing atmospheric greenhouse gas concentrations or climate sensitivity is of central importance to climate change research climate models provide sensitivity estimates that may not fully incorporate slow long term feedbacks such as those involving ice sheets and vegetation geological studies on the other hand can provide estimates that integrate long and short term climate feedbacks to radiative forcing because high latitudes are thought to be most sensitive to greenhouse gas forcing owing to for example ice albedo feedbacks we focus on the tropical pacific ocean to derive a minimum value for long term climate sensitivity using mg ca paleothermometry from the planktonic foraminifera globigerinoides ruber from the past 500 k y at ocean drilling program odp site 871 in the western pacific warm pool we estimate the tropical pacific climate sensitivity parameter to be 0 94 1 06 c w m 2 1 higher than that predicted by model simulations of the last glacial maximum or by models of doubled greenhouse gas concentration forcing this result suggests that models may not yet adequately represent the long term feedbacks related to ocean circulation vegetation and associated dust or the cryosphere and or may underestimate the effects of tropical clouds or other short term feedback processes

variations in loess and palaeosol properties as indicators of palaeoclimatic gradients across the loess plateau of north china abstract new data are presented on micromorphology magnetic susceptibility and particle size characteristics of three soil sediment units at four locations along a wnw ese transect across the loess plateau of north china differences and spatial trends are used to assess the sensitivity of such data as proxies of regional palaeoclimatic gradients the steepest climatic gradient suggested by the magnetic susceptibility for the s1 palaeosol is at the eastern humid end of the traverse micromorphology and particle size analysis show that the loess units in the east are richer in clay than the best developed palaeosols in the semi arid west and that particle size in the west appears to provide a more sensitive record of climatically driven changes than magnetic susceptibility the use of surface and near surface soils as a datum for inferring palaeoprecipitation values is reviewed in the light of recent evidence of substantial degradation of such soils micromorphological and particle size analysis of closely spaced samples from loess palaeosol sequences is a sensitive addition to magnetic susceptibility stratigraphy and correlation

scale interactions during the formation of typhoon irving the development of typhoon irving is investigated using a variety of data including special research aircraft data from the tropical cyclone motion tcm 92 experiment objective analyses satellite data and traditional surface and sounding data the development process is treated as a dry adiabatic vortex dynamics problem and it is found that environmental and mesoscale dynamics mutually enhance each other in a cooperative interaction during cyclone formation synoptic scale interactions result in the evolution of the hostile environment toward more favorable conditions for storm development mesoscale interactions with the low level large scale circulations and with other midlevel mesoscale features result in development of vorticity in the midlevels and enhancement of the low level vorticity associated with the developing surface cyclone multiple developments of mesoscale convective systems after the storm reaches tropical depression strength suggests both an increase in low level confluence and a tendency toward recurrent development of associated mesoscale convective vortices this is observed in both aircraft data and satellite imagery where subsequent interactions including mergers with the low level tropical depression vortex are observed a contour dynamics experiment suggests that the movement of mesoscale convective systems in satellite imagery corresponds well to the movement of their associated midlevel vortices results from a simple baroclinic experiment show that the midlevel vortices affect the large scale low level circulation in two ways 1 initially interactions between midlevel vortices produce a combined vortex of greater depth 2 interaction between midlevel vortices and the low level circulation produces a development downward of the midlevel vorticity this strengthens the surface vortex and develops a more cohesive vortex that extends from the surface through the midtroposphere