the limitations of three dimensional kinematic vorticity analysis abstract the kinematic vorticity number wk can be calculated for three dimensional as well as two dimensional geologic deformations for steady state deformations wk can be correlated to and analyzed in terms of finite strains the analysis shows that assumptions commonly made for two dimensional deformations are not applicable to three dimensional deformations a single wk describes an infinite number of three dimensional deformations further even knowledge of flow apophyses orientation instantaneous stretching axes orientation and or wk are not sufficient to describe deformation three dimensional deformations also require knowledge of the deformation type or boundary conditions of deformation e g transpression hence in addition to being difficult to estimate the value of knowing wk for three dimensional deformations is greatly reduced compared with plane strain the most useful methods of determining wk from naturally deformed rocks are presented

a new model for the formation of a spaced crenulation shear band cleavage in the dalradian rocks of the tay nappe sw highlands scotland abstract the main conclusion of this study is that non coaxial strain acting parallel to a flat lying d 1 spaced cleavage was responsible for the formation of the d 2 spaced crenulation shear band cleavage in dalradian rocks of neoproterozoic lower ordovician age in the sw highlands scotland the cm dm scale d 2 microlithons are asymmetric have a geometrically distinctive nose and tail and show a thickened central portion resulting from back rotation of the constituent d 1 microlithons the current terminology used to describe crenulation cleavages is reviewed and updated aided by exceptional 3d exposures it is shown how embryonic d 2 flexural slip folds developed into a spaced cleavage comprising fold pair domains wrapped by anastomosing cleavage seams the bulk strain was partitioned into low strain domains separated by zones of high non coaxial strain this new model provides a template for determining the sense of shear in both low strain situations and in ductile higher strain zones where other indicators such as shear folds give ambiguous results analogous structures include tectonic lozenges in shear zones and flexural slip duplexes disputes over the sense and direction of shear during emplacement of the tay nappe and the apparently intractable conflict between minor fold asymmetry and shear sense appear to be resolved

orogen scale strain partitioning and an analogy to shear bands in the torngat orogen northeastern canadian shield abstract shear bands are discrete small scale shear zones oriented at an acute angle to the main plane of anisotropy of a foliated rock while this rock undergoes non coaxial deformation if the bulk direction of shear is not parallel to the main plane of anisotropy which in most cases is a preferential locus for gliding the strain will be partitioned between this plane and subsidiary slip planes namely shear bands as erogenic belts become intrinsically anisotropic after a severe deformation similar strain partitioning on a megascopic scale is expected when they undergo further bulk regional non coaxial deformation such a process occurred in the lower proterozoic torngat orogen of the northeastern canadian shield where gneisses with a regular planar foliation developed through regional sinistral non coaxial shear under granulitic conditions shearing during the waning stage of high grade metamorphism once the main planar fabric developed leads to partitioning of the strain increments into the main fabric and discrete map scale shear zones developed at an acute angle with the regional fabric coeval slip between these shears and reactivated main fabrics is supported by the oriented growth of hornblende upon stretched hypersthene crystals within both fabrics indicating that shearing occurred under the same metamorphic conditions along both the main fabric and the shear bands

simulation of a long runout rock avalanche triggered by the lushan earthquake in the tangjia valley tianquan sichuan china abstract only one long runout rock avalanche was triggered by the 2013 lushan earthquake in the tangjia valley tianquan sichuan china the rock avalanche involved the failure of 530 000 m3 of sandstone from the source area the displaced material travelled a horizontal distance of 1600 m with an elevation descent of 480 m equivalent to a fahrboschung of 16 7 based on a detailed field investigation we introduce basic characteristics of the rock avalanche and find that the rock avalanche resulted in one run up in the chunwojian valley a superelevation in the gangoutou valley and increase in volume due to the entrainment of path materials a numerical model dan3d was used to simulate the post failure behavior of the rock avalanche by means of trial and error a combination of the frictional model and voellmy model is found to provide the best performance in simulating this rock avalanche the simulation results reveal that of the rock avalanche lasted approximately 160 s and an average velocity of 10 m s

palghat gap a dextral shear zone from the south indian granulite terrain abstract the origin of palghat gap the most prominent discontinuity in the western ghats is controversial the rocks of the gap hornblende biotite gneiss mylonitic augen gneiss charnockite and amphibolite are characterised by three groups of folds formed during two deformations shear indicators like augens pull aparts rootless folds sheath folds minor shears and quartz fabric strongly suggest ductile dextral shearing kinematic analysis of structural elements supports shearing in a n s compressional field with xy being subvertical features on both mesoscopic and microscopic scales strongly favour palghat gap being treated as a ductile shear zone the present gap topography is the product of shearing and erosion

towards a holocene tephrochronology for the faroe islands north atlantic abstract the faroe islands hold a key position in the north atlantic region for tephra studies due to their relative proximity to iceland several tephras have been described over the last 50 years in peat and lake sediment sequences including the type sites for the saksunarvatn and mjauvotn tephras here we present a comprehensive overview of holocene tephras found on the faroe island in total 23 tephra layers are described including visible macrotephras such as the saksunarvatn and hekla 4 tephras and several cryptotephras the importance of tephras originally described from the faroe islands is highlighted and previously unpublished results are included in addition full datasets for several sites are published here for the first time the saksunarvatn ash now considered to be the result of several eruptions rather than one major eruption can be separated into two phases on the faroe islands one early phase with two precursor eruptions with lower mgo concentrations 4 5 5 0 wt than the main eruption and a later phase with higher mgo concentrations 5 5 6 0 wt including the visible saksunarvatn ash the tjornuvik tephra previously considered to be a primary deposit is now interpreted as a reworked tephra with material from at least two middle holocene eruptions of hekla several of the tephras identified on the faroe islands provide useful isochrons for climate events during the holocene

volcanic ash hazard climatology for an eruption of hekla volcano iceland abstract ash produced by a volcanic eruption on iceland can be hazardous for both the transatlantic flight paths and european airports and airspace in order to begin to quantify the risk to aircraft this study explored the probability of ash from a short explosive eruption of hekla volcano 63 98 n 19 7 w reaching european airspace transport dispersion and deposition of the ash cloud from a three hour explosive eruption with an initial plume height of 12 km was simulated using the met office s numerical atmospheric dispersion modelling environment name the model used operationally by the london volcanic ash advisory centre eruptions were simulated over a six year period from 2003 until 2008 and ash clouds were tracked for four days following each eruption results showed that a rapid spread of volcanic ash is possible with all countries in europe facing the possibility of an airborne ash concentration exceeding international civil aviation organization icao limits within 24 h of an eruption an additional high impact low probability event which could occur is the southward spread of the ash cloud which would block transatlantic flights approaching and leaving europe probabilities of significant concentrations of ash are highest to the east of iceland with probabilities exceeding 20 in most countries north of 50 n deposition probabilities were highest at scottish and scandinavian airports there is some seasonal variability in the probabilities ash is more likely to reach southern europe in winter when the mean winds across the continent are northerly ash concentrations usually remain higher for longer during summer when the mean wind speeds are lower

rotation of fabric elements in convergent shear zones with examples from the southern appalachians plane strain shear zones between rigid walls which do not rotate but which converge and move laterally relative to each other are here in referred to as convergent shear zones analysis of the deformation in convergent shear zones indicates the existence of two flow apophyses one parallel to the shear zone wall and the other inclined to the wall modeling of the development of fabrics in convergent shear zones indicates the occurrence of stable orientations in which s and c do not rotate and are oppositely inclined to the shear zone boundary the stable c orientation is parallel to the inclined flow apophysis and also is parallel to the approach velocity vector of the opposing walls of the shear zone if it can be demonstrated from field relationships that the walls of a shear zone were rigid and remained parallel then the occurrence of a flow apophysis inclined in the direction of shear is diagnostic of convergent shear s and c fabrics in the ridge road and gundy creek shear zones of the southern appalachian piedmont are interpreted to indicate a convergent shear regime with an approach velocity vector oriented 10 13 clockwise from the strike of the zones

multi centennial scale changes in east asian typhoon frequency during the mid holocene abstract this study reconstructs a record of typhoon frequency over the korean peninsula during the mid holocene using mineral components and diatom assemblages in deposits of lagoon hyangho located on the east coast of the peninsula the lagoon deposits confirm the occurrence of cyclical multi centennial scale episodes of low salinization induced by typhoon derived heavy rain although shifts in typhoon frequency broadly follow el nino southern oscillation enso conditions during the holocene evidence from the typhoon induced deposits in hyangho lagoon suggests that the path of the polar westerly jet controls the effect of enso on multi centennial scale typhoon patterns across the mid latitude region of east asia the influence of enso is limited when the westerly jet passes through low latitudes fluctuations in solar activity play a key role in regulating movement of the westerly jet multi centennial scale changes in typhoon frequency in mid latitude east asia are therefore influenced by changes in solar activity and enso conditions

early to mid holocene rapid sea level rise and coastal response on the southern yangtze delta plain china we used accelerator mass spectrometry ams 14 c dated sediments of the holocene basal supratidal flat to upper tidal flat facies in 11 cores on the southern yangtze delta plain to reconstruct relative sea levels of 8 5 8 0 cal ka bp three cores were further ams 14 c dated and used to examine the evolution of sedimentary geomorphological environments in response to the rapid sea level rise during the early to mid holocene results demonstrate relative sea level rise of around 30mm a 1 from 8 5 to 8 3 cal ka bp and around 10mm a 1 from 8 3 to 8 0 cal ka bp retrogradation from supratidal to lower tidal flat environments occurred in response to the rapid sea level rise at 8 5 8 3 cal ka bp and aggradation from middle to upper tidal flat occurred at 8 3 7 9 cal ka bp further retreat of the tidal flat at 7 9 7 2 cal ka bp implies a mean sea level rise rate exceeding 5mm a 1 at this time we suggest that the rapid relative sea level rise during 8 3 8 5 cal ka bp and subsequent slower rise caused drastic changes in the coastal zone and that these changes are key phenomena for understanding the coastal response to future sea level rise copyright 2013 john wiley sons ltd

land subsidence and earth fissures due to groundwater withdrawal in the southern yangtse delta china excessive extraction of groundwater has caused severe land subsidence and earth fissures in the southern yangtse delta china based on field data the temporal and spatial distribution of land subsidence is investigated and the causes for earth fissures are analyzed the areal distribution of the land subsidence is closely related to the cones of depression in the main exploited aquifers the compaction of a hydrostratigraphic unit depends on its mechanical behavior thickness compressibility and the piezometric level changing the primary subsidence layers in shanghai have been the first aquitard before 1990 and the third confined aquifer since then but the second aquitard unit was the primary subsidence layer in changzhou earth fissures trending in several directions occurred in the husu tectonic zone they were mainly caused by differential subsidence and horizontal displacement that resulted from tensile stress and shear stress in units the majority of fissures in the study area are tensile

paleotidal regime in the changjiang yangtze estuary the east china sea and the yellow sea at 6 ka and 10 ka estimated from a numerical model abstract two dimensional paleotidal simulations were carried out to investigate the paleotides and paleotidal currents in the changjiang yangtze estuary the east china sea and the yellow sea calculations were made for 10 ka 6 ka and the present an age of 10 ka corresponds to a period during the last deglaciation when the sea level was about 45 m below its present level at that time the changjiang estuary extended southeastward to the east china sea for about 400 km the second period 6 ka coincides with the maximum holocene transgression in eastern china the paleotopography around the changjiang estuary was reconstructed for 10 ka and 6 ka using available borehole datasets to remove the holocene strata at 10 ka the spatial distribution of m2 tides was different from today no amphidrome was present in the yellow sea and the current velocity was generally larger on the continental shelf strength and ellipticity of the simulated tidal currents indicated that the northern part of the moribund tidal sand ridge system in the east china sea might have been formed at around this period on the other hand the tidal field at 6 ka was similar to that at present except for the region within and adjacent to the paleo changjiang estuary a radial tidal flow pattern was originated from the estuary mouth which seemed to have enhanced tides and tidal currents in the estuary

exploring typhoon variability over the mid to late holocene evidence of extreme coastal flooding from kamikoshiki japan sediment cores from two coastal lakes located on the island of kamikoshiki in southwestern japan lake namakoike and lake kaiike provide evidence for the response of a backbarrier beach system to episodic coastal inundation over the last 6400 years sub bottom seismic surveys exhibit acoustically laminated parallel to subparallel seismic reflectors intermittently truncated by erosional unconformities sediment cores collected from targeted depocenters in both lakes contain finely laminated organic mud interbedded with coarse grained units with depths of coarse deposits concurrent with prominent seismic reflectors the timing of the youngest deposit at kamikoshiki correlates to the most recently documented breach in the barrier during a typhoon in 1951 ad assuming that this modern deposit provides an analog for identifying past events paleo typhoons may be reconstructed from layers exhibiting an increase in grain size a break in fine scale stratigraphy and elevated sr concentrations

mid to late holocene geomorphological and hydrological changes in the south taihu area of the yangtze delta plain china abstract the taihu plain of the lower yangtze valley china was a centre of rice agriculture during the neolithic period reasons for the rapid development of rice cultivation during this period however have not been fully understood for this coastal lowland which is highly sensitive to sea level change to improve understanding of the geomorphological and hydrological context for evolution of prehistoric rice agriculture two sediment cores dtx4 and dtx10 in the east tiaoxi river plain south taihu plain were collected and analysed for radiocarbon dating diatoms organic carbon and nitrogen stable isotopes 13c and 15n grain size and lithology these multiproxy analyses revealed that prior to ca 7500 cal yr bp the east tiaoxi river plain was a rapidly aggrading high salinity estuary the palaeo taihu estuary after ca 7500 cal yr bp low salinity conditions prevailed as a result of strong yangtze freshwater discharge subsequently seawater penetration occurred and saltmarsh developed between ca 7000 and 6500 cal yr bp due to accelerated relative sea level rise this transgression event influenced a large area of the taihu plain during the holocene as shown by multiple sediment records from previous studies persistent freshwater marsh or subaerial land formed due to dramatic shrinkage closure of the palaeo taihu estuary after ca 5600 cal yr bp when sea level was relatively stable we speculate that geomorphological and hydrological changes of the east tiaoxi river plain played an important role in agricultural development across the taihu plain during the neolithic period the closure of the palaeo taihu estuary and the formation of stable freshwater marsh or subaerial land after ca 5600 cal yr bp were critical preconditions encouraging the rapid rise of rice productivity in the liangzhu period 5500 4500 cal yr bp this development changed the landscape and river systems and thus provided adequate freshwater supply to the taihu plain

an overview of distal tephrochronology in northern europe during the last 1000 years several tephra layers from the last millennium have been identified in distal peat and lake sediment sequences in northern europe forming a framework of volcanic events of great value for palaeoenvironmental investigations most of the tephras within this framework have an origin in iceland but distal layers from jan mayen have also been identified the predominant transport pathway in an easterly southeasterly direction has led to the deposition of these tephras in a number of terrestrial deposits in northern europe ash from silicic eruptions 63 sio2 dominate at these sites even though many of the documentary records in distal areas report tephra fall from several basaltic eruptions here we provide an overview of the distribution shard concentration and geochemistry of these tephras to highlight the most important isochrones for addressing key dating issues in particular three horizons hekla 1 ad 1104 oraefajokull ad 1362 and askja ad 1875 are found at a number of different locations in northern europe and as such are valuable tie points for improving and validating chronological models and for synchronisation of records spanning the last 1000 years in addition we present new data identifying tephra from the grimsvotn volcanic system within the lomonosovfonna ice cap on svalbard demonstrating that some tephras have been transported 2000 km to as far north as 798 n along a northeasterly trajectory this discovery highlights the potential for utilising tephrochronology as a correlation tool for palaeoarchives located in more northerly areas and the complex nature of fall out from different eruptions copyright 2009 john wiley sons ltd

transatlantic distribution of the alaskan white river ash volcanic ash layers preserved within the geologic record represent precise time markers that correlate disparate depositional environments and enable the investigation of synchronous and or asynchronous behaviors in earth system and archaeological sciences however it is generally assumed that only exceptionally powerful events such as supereruptions 450 km3 of ejecta as dense rock equivalent recurrence interval of 105 yr distribute ash broadly enough to have an impact on human society or allow us to address geologic climatic and cultural questions on an intercontinental scale here we use geochemical age and morphological evidence to show that the alaskan white river ash eastern lobe a d 833 850 correlates to the ad860b ash a d 846 848 found in greenland and northern europe these occurrences represent the distribution of an ash over 7000 km linking marine terrestrial and ice core records our results indicate that tephra from more moderate size eruptions with recurrence intervals of 100 yr can have substantially greater distributions than previously thought with direct implications for volcanic dispersal studies correlation of widely distributed proxy records and volcanic hazard assessment

evidence for the presence of the vedde ash in central europe abstract as part of ongoing research to find distal tephra two lacustrine cores were analysed for the presence of volcanic ash layers not visible to the naked eye soppensee in switzerland and rotmeer in southern germany the laacher see tephra 12 900 ka bp is present as a visible layer in both sites in both cores we found a discrete tephra horizon with similar morphologies in the middle of the biostratigraphic units equivalent to the younger dryas stadial the vitreous components of these two tephra layers are geochemically identical comparison of the geochemical stratigraphical and chronological data from both sites strongly suggest that the tephra can be attributed to the icelandic vedde ash a widely distributed horizon found throughout the north atlantic and northern europe our results indicate that a precise and direct correlation between the greenland ice cores and central european sequences is now possible based on a co located tephra layer this means that there is now the potential to independently test climate synchronicity between greenland and europe as far south as the alps

northwest verging folds and the northwestward movement of the caledonian jotun nappe norway abstract a family of asymmetric northwest verging back folds and crenulations occur on a regional scale in the caledonian decollement zone in southwestern norway they are the result of reversal of the emplacement movement of the jotun and other nappes in early devonian time the back folds may have formed progressively by two different mechanisms actively by buckling of the layering and more passively by transfer of slip across the layering reverse slip crenulations to balance the thinning of the zone caused by foliation parallel slip and shear band formation the former mechanism is considered to be most important during the initial stages of fold development gradually giving way to the latter mechanism the hinge lines of these folds appear to have remained stationary during deformation this is explained by the observation that the hinge lines lie within or close to the shear plane i e the plane of no rotation in simple shear deformation integration of strain across the deformation zone indicates a magnitude of back movement in the order of ca 20 36 km and it is argued that the deformation was close to simple shear

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

early mid holocene sea level change and coastal environmental response on the southern yangtze delta plain china implications for the rise of neolithic culture abstract we used a series of holocene sediment cores with ams 14c dated basal saltmarsh peat and supratidal sediment to reconstruct early mid holocene sea level change on the southern yangtze delta plain we also synthesized results for ca 150 late quaternary cores as well as archeological data to reveal the unique interplay between coastal evolution and neolithic cultural response relative sea level was ca 16 5 to 14 5 m from 8600 to 8500 cal bp and ca 6 to 4 m from 7400 to 7200 cal bp reflecting the rate of eustatic sea level rise but being ca 10 m higher possibly because of the effect of hydro istostasy three late pleistocene interfluve terraces t3 to t1 were revealed at burial depths of

interaction between volcanic plumes and wind during the 2010 eyjafjallajokull eruption iceland 1 estimates of volcanic source mass flux currently deduced from observations of plume height are crucial for ash dispersion models for aviation and population hazard this study addresses the role of the atmospheric wind in determining the height at which volcanic plumes spread in the atmosphere and the relationship between source mass flux and plume height in a wind field we present a predictive model of volcanic plumes that describes the bending over of the plume trajectory in a crosswind and show that model predictions are in accord with a dataset of historic eruptions if the profile of atmospheric wind shear is described the wind restricts the rise height of volcanic plumes such that obtaining equivalent rise heights for a plume in a windy environment would require an order of magnitude increase in the source mass flux over a plume in a quiescent environment our model calculations are used to calibrate a semi empirical relationship between the plume height and the source mass flux that explicitly includes the atmospheric wind speed we demonstrate that the model can account for the variations in plume height observed during the first explosive phase of the 2010 eyjafjallajokull eruption using independently measured wind speeds and show that changes in the observed plume height are better explained by changing meteorology than abrupt changes in the source mass flux this study shows that unless the wind is properly accounted for estimates of the source mass flux during an explosive eruption are likely to be very significant underpredictions of the volcanic source conditions

sedimentary facies and holocene progradation rates of the changjiang yangtze delta china abstract the changjiang yangtze river one of the largest rivers in the world has formed a broad tide dominated delta at its mouth during the holocene sea level highstand three boreholes cm97 js98 and hq98 were obtained from the changjiang delta plain in 1997 1998 to clarify the characteristics of tide dominated delta sediments and architecture based on sediment composition and texture and faunal content core sediments were divided into six depositional units in ascending order they were interpreted as tidal sand ridge prodelta delta front subtidal to lower intertidal flat upper intertidal flat and surface soil deposits the deltaic sequence from the prodelta deposits to the delta front deposits showed an upward coarsening succession overlain by an upward fining succession from the uppermost part of the delta front deposits to the surface soil thinly interlaminated to thinly interbedded sand and mud sand mud couplets and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of changjiang deltaic facies sediment facies and their succession combined with ams 14c dating revealed that isochron lines cross unit boundaries clearly and delta progradation has occurred since about 6000 to 7000 years bp when the rising sea level neared or reached its present position the average progradation rate of the delta front was approximately 50 km kyear over the last 5000 years the progradation rate however increased abruptly ca 2000 years bp going from 38 to 80 km kyear the possible causes for this active progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid holocene

characterization and sources of sedimentary organic matter in xingyun lake jiangchuan yunnan china xingyun lake plays a particularly important role in the retention and processing of organic matter in yuxi city china in this study geochemical analyses grain size oc n 13c were carried out the april 2014 sediment was finer than the october 2013 sediment oc content was in the range of 1 07 2 68 showing a increasing oc content with decreasing percent sand from the october 2013 sediment to the april 2014 sediment tn distribution in surface sediments followed a similar distribution and was commonly correlated with oc the correlation of 13c values and n c ratios in sediment reflected a mixing of soil derived and terrestrial organic matters the ali aro ratios from the solid state 13c nmr spectra exhibited more aliphaticity for april 2014 sediments the isotopic analyses on the fatty acids of sediments from twenty sampling stations in xingyun lake indicated that terrigenous components can be assigned as the major sources of the organic matters in the lake sediments the low yields in lignin in sediment pointed to nontypical terrigenous inputs to the lake sediments ratios of p hydroxyacetophenone to p hydroxyl phenols pon p in the surface sediments 0 08 0 22 over the all sampling stations in xingyun lake further demonstrated a contribution from soil derived organic matters it was observed a plot of the ratio of s v versus c v exhibited an organic input attributed to angiosperm nonwoods the reworking of surficial sediments may result in a difference in organic input between the october 2013 sediment and the april 2014 sediment furthermore the associated ratios of ad al v p v s in sediment indicated that the april 2014 sediments had experienced the lower degree of oxidation of lignin than the october 2013 sediments this can be attributed to the higher fine particle content in the former sediments protecting organic matter than in the latter sediments as revealed by the lower alkyl c o alkyl c ratio a o a in solid state 13c nmr spectra of april 2014 samples

initiation of the changjiang yangtze delta and its response to the mid holocene sea level change abstract the changjiang yangtze delta in eastern china is one of the largest tide dominated deltas in the world to obtain a more detailed information on its initiation we drilled three sediment cores pk01 hg01 and xj03 from the uppermost region of the delta plain on the basis of sedimentary facies and ams 14c dating we identified three depositional systems 1 a fluvial system 2 an estuarine system and 3 a deltaic system including an initial delta estuary delta transition and a typical delta the maximum flooding surface separates the estuarine and deltaic systems and occurred at ca 8 0 cal kyr bp when brackish water intruded landward and reached the nanjing area the changjiang delta was initiated at the area between nanjing and yizheng when the sea level rise decelerated after the rapid rise in sea level during 9 0 8 2 cal kyr bp the subsequent evolution of the changjiang delta has been shown as a seaward development model of river mouth bars with shoreline migration the oldest river mouth bar called hongqiao sand body which is located most landward was dated at 6 0 5 5 cal kyr bp in this study nearly one thousand years younger than the previous estimates a tide dominated funnel shaped estuary was formed at 8 0 cal kyr bp and lasted until the hongqiao sand bar became exposed this stage is regarded as an aggradation dominated initial stage of the changjiang delta followed by a progradation dominated stage that is characterized by the formation of a series of seaward migrating river mouth bars a relative sea level highstand in the mid holocene may be associated with glacio hydro isostatic tilting

kinematics of rock flow and the interpretation of geological structures with particular reference to shear zones abstract current interpretations of structures are generally based on homogeneous and steady deformation models despite the fact that both the heterogeneity of rocks materially rheologically and geometrically and the time dependence of imposed geological conditions give rise to significant heterogeneous and non steady flow in concert with field observations we emphasize that the expectation of heterogeneity and non steadiness is the key to understanding natural deformation and that in order to carry out successful structural analysis and tectonic interpretation it is necessary to recognize the first order distinction between imposed boundary conditions typically used to define the tectonic regime e g transcurrent transpression and the response recorded by rocks within the zone structures and fabrics using s c fabric as an example it is demonstrated how flow with a non zero spinning component resulting from the rheological contrasts and or geologically realistic time dependent boundary displacement can drastically change the ideal geometric and kinematic relations between the fabric and the host zone in agreement with both theoretical analysis and field observation it is shown that natural flow regimes range from pure shear to pure rotation including super simple shear in consideration of the heterogeneity and non steadiness of natural deformation kinematic analysis is justifiable only within a homogeneous domain and steady period flow kinematics and mechanisms are interrelated in that firstly mechanisms provide internal constraints on kinematics ensuring that only certain flows are possible and secondly flow kinematics will favour development of certain mechanisms

a 7000 yr perspective on volcanic ash clouds affecting northern europe the ash cloud resulting from the a d 2010 eruption of eyjafjallajokull in iceland caused severe disruption to air travel across europe but as a geological event it is not unprecedented analysis of peats and lake sediments from northern europe has revealed the presence of microscopic layers of icelandic volcanic ash tephra these sedimentary records together with historical records of holocene ash falls demonstrate that icelandic volcanoes have generated substantial ash clouds that reached northern europe many times here we present the first comprehensive compilation of sedimentary and historical records of ash fall events in northern europe spanning the past 7000 yr ash fall events appear to have been more frequent in the past 1500 yr it is unclear whether this reflects a true increase in eruption frequency or dispersal or is an artifact of the records or the way in which they have been generated in the past 1000 yr volcanic ash clouds reached northern europe with a mean return interval of 56 9 yr the range of return intervals is between 6 and 115 yr probabilistic modeling using the ash records for the last millennium indicates that for any 10 yr period there is a 16 probability of a tephra fallout event in northern europe these values must be considered as conservative estimates due to the nature of tephra capture and preservation in the sedimentary record

numerical simulation of mid holocene tidal regime and storm tide inundation in the south yangtze coastal plain east china abstract coastal flooding is reported as one of the major causes for the interruptions of neolithic cultures inhabiting the south yangtze coastal plain china during the middle holocene the archaeologically sterile transgressive sedimentary layers could be the results of extreme events or relative sea level rise induced by the enlargement of the local tidal range or global regional sea level rise to clarify the mechanism of the transgressive deposits at typical neolithic sites and the termination of neolithic liangzhu culture in the south yangtze coastal plain this study reconstructed the paleo topography at 7 6 6 4 and 4 5 cal ka bp on the basis of a database including 107 sediment cores and 644 radiocarbon ages and simulated the paleo tidal regimes and the inundation areas induced by typhoon events under the paleo topography and sea levels using a hydrodynamic model of high resolution changjiang estuary finite volume community ocean model ce fvcom the simulation results of tidal regimes showed that the tidal amplitude increased from 1 6 m to 2 2 m in the head of hangzhou bay induced by the paleo topographic change during the period 7 6 4 5 cal ka bp by contrast it reduced from 1 6 m to 1 0 1 2 m in the ningbo plain southeast of the bay which was unable to explain the long lasting marine inundation there and supported our previous assumption of an event of abrupt sea level rise at 4 5 4 4 cal ka bp simulation of the storm induced inundation further suggested that coastal flooding mainly occurred along the coastline of the taihu plain under the combined effect of tidal amplification and typhoon events at 4 5 cal ka bp while the inundation almost covered half of the taihu plain if all factors including tidal amplification extreme event and the abrupt sea level rise were considered we therefore suggest that the obvious increase in flood risk under the backdrop of sea level rise was a major cause for the abandonment of the liangzhu culture in the south yangtze coastal plain at around 4 4 cal ka bp

mechanisms for folding of high grade rocks in extensional tectonic settings abstract this review of structures developed in extensional high grade terrains combined with results of centrifuge analogue modelling illustrates the range of fold styles and mechanisms for folding of amphibolite to granulite facies rocks during rifting or the collapse of a thrust thickened orogen several extensional fold mechanisms such as folding within detachment shear zones are similar to those in contractional settings the metamorphic p t t path and not fold style or mode of formation is therefore required to determine the tectonic setting in which some folds developed other mechanisms such as rollover above and folding between listric normal shear zones and folding due to isostatic adjustments during crustal thinning are unique to extensional tectonic settings several mechanisms for folding during crustal extension produce structures that could easily be misinterpreted as implying regional contraction and hence lead to errors in their tectonic interpretation it is shown that isoclinal recumbent folds refolded by open upright folds may develop during regional extension in the deep crust folds with a thrust sense of asymmetry can develop due to high shear strains within an extensional detachment or from enhanced back rotation of layers between normal shear zones during back rotation folding layers rotated into the shortening field undergo further buckle folding and all may rotate towards orthogonality to the maximum shortening direction this mechanism explains the presence of many transposed folds folds with axial planar pegmatites and folds with opposite vergence in extensional terrains examples of folds in high grade rocks interpreted as forming during regional extension included in this paper are from the grenville province of canada norwegian caledonides albany mobile belt and leeuwin complex of western australia ruby mountains in the basin and range province of nevada the at sund area of greenland the napier complex of enderby land in east antarctica and the kigluaik mountains in western alaska

insights into the 3d architecture of an active caldera ring fault at tendurek volcano through modeling of geodetic data abstract the three dimensional assessment of ring fault geometries and kinematics at active caldera volcanoes is typically limited by sparse field geodetic or seismological data or by only partial ring fault rupture or slip here we use a novel combination of spatially dense insar time series data numerical models and sand box experiments to determine the three dimensional geometry and kinematics of a sub surface ring fault at tendurek volcano in turkey the insar data reveal that the area within the ring fault not only subsides but also shows substantial westward directed lateral movement the models and experiments explain this as a consequence of a sliding trapdoor ring fault architecture that is mostly composed of outward inclined reverse segments most markedly so on the volcano s western flanks but includes inward inclined normal segments on its eastern flanks furthermore the model ring fault exhibits dextral and sinistral strike slip components that are roughly bilaterally distributed onto its northern and southern segments respectively our more complex numerical model describes the deformation at tendurek better than an analytical solution for a single rectangular dislocation in a half space comparison to ring faults defined at glen coe fernandina and bar arbunga calderas suggests that sliding trapdoor ring fault geometries may be common in nature and should therefore be considered in geological and geophysical interpretations of ring faults at different scales worldwide

volcanic aerosol records and tephrochronology of the summit greenland ice cores the recently collected greenland ice sheet project 2 gisp2 and greenland ice core project ice cores from summit greenland provide lengthy and highly resolved records of the deposition of both the aerosol h2so4 and silicate tephra components of past volcanism both types of data are very beneficial in developing the hemispheric to global chronology of explosive volcanism and evaluating the entire volcanism climate system the continuous time series of volcanic so42 for the last 110 000 years show a strong relationship between periods of increased volcanism and periods of climatic change the greatest number of volcanic so42 signals many of very high magnitude occur during and after the final stages of deglaciation 6000 17 000 years ago possibly reflecting the increased crustal stresses that occur with changing volumes of continental ice sheets and with the subsequent changes in the volume of water in ocean basins sea level change the increase in the number of volcanic so42 signals at 27 000 36 000 and 79 000 85 000 years ago may be related to initial ice sheet growth prior to the glacial maximum and prior to the beginning of the last period of glaciation respectively a comparison of the electrical conductivity of the gisp2 core with that of the volcanic so42 record for the holocene indicates that only about half of the larger volcanic signals are coincident in the two records other volcanic acids besides h2so4 and other so42 sources can complicate the comparisons although the threshold level picked to make such comparisons is especially critical tephra has been found in both cores with a composition similar to that originating from the vatnaoldur eruption that produced the settlement layer in iceland mid a d 870s from the icelandic eruption that produced the saksunarvatn ash 10 300 years ago and from the icelandic eruption s that produced the z2 ash zone in north atlantic marine cores 52 700 years ago the presence of these layers provides absolute time lines for correlation between the two cores and for correlation with proxy records from marine sediment cores and terrestrial deposits containing these same tephras the presence of both rhyolitic and basaltic shards in the z2 ash in thegisp2 core and the composition of the basaltic grains lend support to multiple icelandic sources torfajokull area and katla for the z2 layer deposition of the z2 layer occurs at the beginning of a stadial event further reflecting the possibility of a volcanic triggering by the effects of changing climatic conditions

coastal gia processes revealed by the early to middle holocene sea level history of east china abstract in order to examine relative sea level responses to the postglacial ice volume change and the glacio hydro isostatic adjustments gia this study investigated the inner part of the hangzhou bay east china a tectonically relatively stable far field location and reconstructed the early to middle holocene sea level history this investigation has established the elevational relationship between modern saltmarsh mudflat and tidal levels based on diatom analysis for sea level indicative meaning estimates produced 17 high quality sea level index points and simulated gia processes for the study site these results reveal that the relative sea level rose from 38 3 1 6 m in c 10 000 cal a bp to the present height by c 7000 cal a bp and the average rate of sea level rise decreased gradually from 19 6 2 6 mm a to 2 3 1 5 mm a during the 3000 years this period of sea level history was punctuated by two episodes of accelerated rise around 8200 and 7500 cal a bp the relative sea level rose to 0 8 1 4 m above msl by c 6500 cal a bp followed by a gradual fall back to the present height at 4500 cal a bp implying a different response to the potential additional ice melting between 7000 and 4000 cal a bp a comparison of the sea level histories between the inner and outer hangzhou bay indicates the coastal levering effect due to the marine inundation of the continental shelves a further comparison between sea level data from china and malay peninsula reveals different gia effects between the cathaysia yangtze blocks and the sundaland block

distal deposition of tephra from the eyjafjallajokull 2010 summit eruption the 2010 eyjafjallajokull lasted 39 days and had 4 different phases of which the first and third 14 18 april and 5 6 may were most intense most of this period was dominated by winds with a northerly component that carried tephra toward europe where it was deposited in a number of locations and was sampled by rain gauges or buckets surface swabs sticky tape samples and air filtering in the uk tephra was collected from each of the phases 1 3 with a combined range of latitudes spanning the length of the country the modal grain size of tephra in the rain gauge samples was 25 mu m but the largest grains were 100 mu m in diameter and highly vesicular the mass loading was equivalent to 8 218 shards cm 2 which is comparable to tephra layers from much larger past eruptions falling tephra was collected on sticky tape in the english midlands on 19 20 and 21st april phase 2 and was dominated by aggregate clasts mean diameter 85 mu m component grains 10 mu m sem eds spectra for aggregate grains contained an extra peak for sulphur when compared to control samples from the volcano indicating that they were cemented by sulphur rich minerals e g gypsum caso4 center dot h2o air quality monitoring stations did not record fluctuations in hourly pm10 concentrations outside the normal range of variability during the eruption but there was a small increase in 24 hour running mean concentration from 21 24 april phase 2 deposition of tephra from phase 2 in the uk indicates that transport of tephra from iceland is possible even for small eruption plumes given suitable wind conditions the presence of relatively coarse grains adds uncertainty to concentration estimates from air quality sensors which are most sensitive to grain sizes 10 mu m elsewhere tephra was collected from roofs and vehicles in the faroe islands mean grain size 40 mu m but 100 mu m common from rainwater in bergen in norway 23 91 mu m and in air filters in budapest hungary 2 6 mu m a map is presented summarizing these and other recently published examples of distal tephra deposition from the eyjafjallajokull eruption it demonstrates that most tephra deposited on mainland europe was produced in the highly explosive phase 1 and was carried there in 2 3 days

rapid tectonic exhumation detachment faulting and orogenic collapse in the caledonides of western ireland collision of the oceanic lough nafooey island arc with the passive margin of laurentia after 480 ma in western ireland resulted in the deformation magmatism and metamorphism of the grampian orogeny analogous to the modern taiwan and miocene new guinea orogens after f470 ma the metamorphosed laurentian margin sediments dalradian supergroup now exposed in connemara and north mayo were cooled rapidly 35 jc m y and exhumed to the surface we propose that this exhumation occurred mainly as a result of an oceanward collapse of the colliding arc southwards probably aided by subduction rollback into the new trench formed after subduction polarity reversal following collision the achill beg fault in particular along the southern edge of the north mayo dalradian terrane separates very low grade sedimentary rocks of the south mayo trough lough nafooey forearc and accreted sedimentary rocks of the clew bay complex from high grade dalradian meta sedimentary rocks suggesting that this was a major detachment structure in northern connemara the unconformity between the dalradian and the silurian cover probably represents an eroded major detachment surface with the renvyle bofin slide as a related but subordinate structure blocks of sheared mafic and ultramafic rocks in the dalradian immediately below this unconformity surface probably represent arc lower crustal and mantle rocks or fragments of a high level ophiolite sheet entrained along the detachment during exhumation orogenic collapse was accompanied in the south mayo trough by coarse clastic sedimentation derived mostly from the exhuming dalradian to the north and to a lesser extent from the lough nafooey arc to the south sediment flow in the south mayo trough was dominantly axial deepening toward the west volcanism associated with orogenic collapse rosroe and

geometry classification and kinematics of s c and s c fabrics in the mushandike area zimbabwe planar fabrics in small dextral shear zones in the mushandike area of the zimbabwe archaean craton consist of a sigmoidal primary foliation s displaced by discrete shears c or c these planar fabrics can be divided into porphyroclastic megacrystic and banded types depending mainly on the values of the angles between s and c or c surfaces the structures that define s surfaces and the spacing of c or c surfaces the values of the angles between the foliations are proposed as the basis for a general classification of planar fabrics in shear zones the values of the angles depend on microstructures and strain microstructural evidence shows that slip did not occur on s surfaces but only on c or c surfaces a model for the development of the fabrics proposes that s surfaces lie parallel to the xy plane of the local finite strain ellipsoid in domains of simple shear between c or c surfaces c surfaces may form in the orientation of a coulomb failure surface the field evidence suggests that an increase in bulk strain is at least partly accommodated by an increase in local strain in domains between c or c surfaces as the s surfaces rotate with the local finite strain ellipsoid

brittle origins for disseminated gold mineralization in mylonite gaocun gold deposit hetai goldfield guangdong proince south china gold mineralization in the hetai goldfield in south china is almost entirely confined to a series of steeply dipping ductile shear zones generated during hercynian indosinian orogenesis of sinian host rocks approximately half of the mineralization is in the form of disseminations in the mylonite and the remainder was clearly emplaced as a result of brittle deformation in einlets and as sulfide cement to brecciated mesoscopic quartz eins heaily influenced by the presence of disseminated mineralization all publications on hetai determine a major role for ductile deformation in the introduction of gold into the deposit the brittle deformation is typically regarded as redistributing within the host structures the gold initially introduced as a result of ductile deformation mechanisms howeer textures of the sulfides associated with the gold indicate an entirely postductile deformation timing as they display none of the features attributed to ductile deformation during the eident brittle deformation phase competence contrasts at the microscopic scale allowed fracturing to focus on the quartz sericite domain boundaries of the mylonite foliation thus permitting the introduction of auriferous fluid into the mylonite to create disseminated mineralization the control exerted by preexisting structures is further reflected in the restriction of disseminated mineralization to the quartz domains presumably because the sericite domains accommodated the deformation in a more distributed fashion seeral other lines of eidence support an origin of the hetai deposit in an upper crustal regime a similar style of disseminated mineralization to that seen in the mylonite surrounds microeinlet terminations in the brecciated quartz eins as well as oerprinting pseudotachylite which is associated with cataclasite there are also large olumes of unmineralized mylonite indicating no connection between the intensity of strain and gold grade we conclude that in structurally controlled deposits the textural category of disseminated gold mineralization can be generated either under entirely ductile or entirely brittle conditions and that microtextural eidence has to be carefully analyzed to determine the mode of formation of a deposit

structural and stratigraphic relationships across the continuation of the highland boundary fault in western ireland t he relationship between the dalradian supergroup and the highland border complex in scotland has remained contentious for over a century in western ireland the contact between the dalradian supergroup and the clew bay complex a correlative of the highland border complex is superbly exposed on the island of achill beg on the north mayo coast the unfossiliferous south achillbegsuccessionhasbeentraditionally assignedtotheclewbaycomplex andthisinterpretation is supported by a combination of sm nd model age data heavy mineral analysis and lithostratigraphic correlation tdm ages range from 1 99 2 66 ga mean 2 28 ga n 6 detailed structural mapping shows that both the dalradian and the clew bay complex share the same structural history a d1 high strain event is common to both units and is associated with the development of tectonic slides the d2 event is responsible for the formation of crustal scale nappes in both units beds are consistently downward facing on the s2 foliation later dextral shearing d3 resulted in the tilting of the originally recumbent s facing d2 nappes into this downward facing orientation rb sr and 40 ar 39 arradiometricdatingofmuscoviteconfirmsthatbothunitsweredeformedcontemporaneously as the s2 nappe fabric in each is dated at c 460 ma this middle ordovician age for deformation of the clew bay complex is highly significant not least because published microfossil data suggest a silurian age

the impact of the atmosphere on the eyjafjallajokull 2010 eruption plume 1 the eruption of eyjafjallajokull volcano in 2010 lasted 39 days 14 april 23 may the eruption had two explosive phases separated by a phase with lava formation and reduced explosive activity during the explosive phases there were episodes of strong winds that advected ash to the south and southeast leading to widespread disruptions in air traffic the height of the eruption plume was monitored with a weather radar and with web cameras mounted with a view of the volcano three different types of the impact of the ambient atmosphere on the eruption plume are described first the weather situation throughout the eruption has been analyzed the frequency of northerly wind component is found to be unusually high or 71 in comparison to 49 on average in spring secondly during the effusive phase of the eruption diurnal variation was observed in the plume altitude and there is evidence that suggest that nocturnal inversions may have played a role limiting the rise of the weak plume thirdly images from a web camera were analyzed and the rise of individual cloud heads associated with explosions at the volcano vent mapped the velocity profiles obtained largely agree with conceptual models of volcanic plumes

on resolving shear direction in foliated rocks deformed by simple shear we present a three dimensional model for the formation of crenulations in ductile shear zones based on compatibility conditions infinitesimal displacement equations and our own field observations in many shear zones at least two and probably three mesoscopic slip systems are active crenulation slip is interpreted to compensate for the displacement component of foliation slip normal to the shear zone wall in zones in which foliation slip is an important mode of deformation foliation and crenulation slip vectors do not necessarily lie in the same plane nor are they necessarily perpendicular to crenulation axes solutions for the orientation of the crenulation plane crenulation slip vector and magnitude of the crenulation slip shear strain belong to one of two possible solution sets given the orientation of slipping foliation the foliation slip vector and the magnitude of slip on foliation hence shear sense may be reliably interpreted from composite planar fabrics in ductile shear zones but more specifically shear direction cannot these results have broad implications in the interpretation of the kinematic significance of mineral lineations oblique to crenulation axes and in the deduction of shear strain from angular relations between planar fabric elements

mid holocene coastal hydrology and salinity changes in the east taihu area of the lower yangtze wetlands china abstract during the mid holocene the eastern taihu area on china s yangtze delta plain was populated by advanced late neolithic cultures supported by intensive domesticated rice cultivation this agricultural system collapsed around 4200 cal yr bp with severe population decline the end of the liangzhu culture and about half a millennium of very low scale human activity in the area before the re establishment of agricultural production microfossil analyses from six sedimentary sequences supported by ams 14c dating has allowed reconstruction of mid holocene hydrological conditions and salinity changes which would have had a major influence on agricultural viability and cultural history in the coastal wetlands these data allied to existing stratigraphic and sea level records show that chenier ridges that developed after ca 7000 cal yr bp in the east of the area sheltered it from marine inundation and although still connected to the sea through tidal creeks low salinity conditions persisted throughout the neolithic period there is no evidence that marine flooding caused the collapse of liangzhu culture marine influence was stable and evolved slowly social and cultural causes may also have been important but if environmental change triggered the collapse of neolithic agricultural society here other natural forces must be sought to explain this event

the eyjafjallajokull ad 2010 eruption and the preservation of medium sized eruptions in marine surface sediment offshore southern iceland the recent volcanic eruptions of eyjafjallajokull 2010 and grimsvotn 2011 demonstrated the risks that mediumsized explosive icelandic eruptions pose to the north atlantic region using the eyjafjallajokull 2010 eruption as a case study we assess how traceable such eruptions are in the marine sedimentary record at medial distances from the source and investigate which factors have affected the particle transport to the marine sedimentary archive during r v poseidon cruise 457 we recovered 13 box cores at 100 1600 m water depths and distances of 18 180 km southwest south and east of iceland volcanic glass shards from the uppermost surface sediment were analyzed for their major element composition by electron microprobe and assigned to their eruptive source by geochemical fingerprinting the predominantly basaltic particles are mostly derived from the katla grimsvotn lakagigar and bar arbunga vei ivotn volcanic systems we also identified rhyolitic particles from the askja 1875 and oraefajokull 1362 eruptions only three out of almost 900 analyzed glass shards are derived from the recent eyjafjallajokull 2010 eruption suggesting that medium sized eruptions are only poorly preserved in marine sediments located at medial distances southwest to east of iceland we conclude that the frequency of past medium sized eruptions is likely higher than detectable in this archive

neolithic agriculture freshwater resources and rapid environmental changes on the lower yangtze china analyses of sedimentary evidence in the form of spores pollen freshwater algae dinoflagellate cysts phytoliths and charcoal from ams 14c dated holocene aged sequences provide an excellent opportunity to examine the responses of neolithic agriculturalists in the lower yangtze to changing environments evidence from two sites close to the southern margin of the yangtze delta and separated by what is now hangzhou bay attests the critical importance to early attempts at food production of access to freshwater resources more readily if episodically available freshwater resources during the early to mid holocene on the hangjiahu plain may have encouraged an early reliance on rice based agriculture which in turn facilitated the accumulation of agricultural surpluses and cultural diversification cultural change was relatively attenuated and human population pressures possibly lower on the ningshao plain seemingly because of much more profound environmental impacts of variations in local hydrological conditions and because predominantly saline conditions associated with rising relative sea level hampered the early development of irrigated agriculture the evidence although largely dating to the early and middle parts of the holocene provides a timely warning of the complexity of vulnerability to climate change induced processes of agriculture and indeed human activities more generally on megadeltas in asia

folding in high grade rocks due to back rotation between shear zones abstract folds with a sense of asymmetry opposite to the bulk shear sense may form in high grade rocks due to back rotation between ductile shear zones layers back rotated into the shortening field can undergo additional buckle folding with progressive deformation shear zones and domains of back rotated foliation between shears rotate towards the x y flattening plane of the finite strain ellipsoid in high grade gneiss the migration of melt into shear zones may facilitate displacement along them and accentuate back rotation of material between shear zones folding during back rotation occurs when the spacing between shear zones does not increase sufficiently to accommodate the length of back rotated layers or between non parallel shear zones folds formed by back rotation between shear zones commonly have pegmatites sub parallel to their axial planes thickened overturned limbs and occur in localised packages associated shear zones have the same sense of shear on both attenuated limbs of folds formed by back rotation examples are given for folds between transcurrent and normal ductile shear zones in the albany mobile belt and leeuwin complex western australia and the dharwar craton india

the grain size distribution and composition of the touzhai rock avalanche deposit in yunnan china abstract the september 23 1991 rock avalanche that occurred in touzhai zhaotong yunnan province of china claimed 216 lives and caused heavy property losses the touzhai avalanche possesses typical and representative feature of high mobility field surveys are applied in the exploration of the grain size distribution and deposit composition and the lab analyses provide important information about the occurrence mechanism of the rock avalanche flow the touzhai rock avalanche has a volume of 9 million m3 that traveled about 3 4 km along touzhai valley within 3 min with an effective coefficient of friction of 0 22 the deposit of the touzhai rock avalanche contains a wide spectrum of grain sizes 50 cm outcropped in the deposit surface is 0 2 compared with the upper reaches a greater number of boulders are found to exist in the middle and lower reaches of the rock avalanche flow the non uniformity coefficient curvature coefficient and fractal dimension of the deposit

aggregation dominated ash settling from the eyjafjallajokull volcanic cloud illuminated by field and laboratory high speed imaging the recent eyjafjallajokull iceland eruption strikingly underlined the vulnerability of a globalized society to the atmospheric dispersal of volcanic clouds from even moderate size eruptions ash aggregation controls volcanic clouds dispersal by prematurely removing fine particles from the cloud and depositing them more proximally physical parameters of ash aggregates have been modeled and derived from ash fallout deposits of past eruptions yet aggregate sedimentation has eluded direct measurement limiting our ability to predict the dispersal of volcanic clouds here we use field based high speed video analysis together with laboratory experiments to provide the first in situ investigation and parameterization of the physical features and settling dynamics of ash aggregates from a volcanic cloud in may 2010 high speed video footage was obtained of both ash particles and aggregates settling from the eyjafjallajokull volcano eruption cloud at a distance of 7 km from the vent fallout samples were collected simultaneously experimental laboratory determinations of the density morphology and settling velocity of individual ash particles enable their distinction from aggregates the combination of field and experimental analyses allows a full characterization of the size settling velocity drag coefficient and density distributions of ash aggregates as well as the size distribution of their component particles we conclude that ash aggregation resulted in a tenfold increase in mass sedimentation rate from the cloud aggravating the ash hazard locally and modifying cloud dispersal regionally this study provides a valuable tool for monitoring explosive eruptions capable of providing robust input parameters for models of cloud dispersal and consequent hazard forecast

the table a flat topped volcano in southern british columbia revisited more than 65 years ago w h mathews published a seminal paper in american journal of science describing the table an iconic flat topped volcano in southern british columbia canada the table is recognized as the type example of a glaciovolcanic lava dominated tuya we use field mapping 3 d photogrammetry lithofacies identification and 40ar 39ar geochronology to re examine the emplacement origins of this unique volcanic edifice the table is a steep sided flat topped mass of dense porphyritic andesite preserving a near original outer surface of hackly fractured aphanitic material the age of the edifice is 100 12 ka a new model for the emplacement involves dike injection and endogenous inflation within an overlying ice mass that is estimated to have been 250 to 350 m thick the model assumes that the edifice expanded outwardly as an elliptical cylinder endogenously inflating and melting an equal volume of ice the thermal exchange between the expanding massif and the melting ice operates across a subvertical well drained enveloping carapace of quench breccia for effusion rates of 0 5 to 2 m3 s 1 marginal heat fluxes are 43 to 186 w m 2 implying low overall heat transfer coefficients 0 04 to 0 18 w m 2 k 1 the total volume of ice melted serves as a calorimeter and constrains the average thickness 3 m and properties thermal conductivity 0 1 0 4 w m 1 k 1 of the breccia carapace the heat transfer efficiency of intermediate lava dominated tuyas is significantly lower 2 than reported for other glaciovolcanic systems commonly 45 77 but similar to that found for block lava flows and lava tubes

late quaternary evolution of the yellow east china sea tidal regime and its impacts on sediments dispersal and seafloor morphology the evolution of a tidal current field in the yellow sea and east china sea yecs in response to the sea level rise since the last glacial maximum lgm was investigated using a two dimensional tidal model with special attention to changes in the sedimentary environment of the continental shelf region it was found that tidal currents on the yecs shelf have generally been semi diurnal throughout the post glacial stages with f ratio index of diurnal inequality and s2 m2 ratio index of spring neap cycle remaining similar to present on the other hand the spatial distribution of the tidal bottom stress associated with m2 and m4 tidal currents changed greatly during the transgression as the sea level rose two core regions showing high bottom stress values migrated shoreward from cheju island toward the west coast of korea and along the retreat path of the paleo changjiang estuary distribution of extremely intense tidal bottom stress suggested that intense tidal reworking may have occurred at sea levels from 90 to 45 m in the southeast yellow sea and at 75 to 60 m off the paleo changjiang estuary the latter of which agreed with the timing of a large terrigenous organic c flux observed on the shelf slope distribution of slightly weaker bottom stress indicated that the sand ridges off the changjiang estuary and in the southeast yellow sea also might have formed at during those periods on the other hand when the sea level was between 45 and 15 m the tidal bottom stress was generally not strong enough to invoke significant reworking even though the stress intensity may be stronger than present correlation with modern and relict sedimentary features suggested that the tidal process have played a significant role on the reworking and deposition of sediments on the yecs shelf

taylor mill analogues for patterns of flow and deformation in rocks abstract the giesekus design of taylor s four roll mill has been restored and is here used in novel flow visualizations of both pulsating and monotonously increasing strains the particle movement paths and progressive deformation patterns visualized in these physical experiments are in agreement with those previously calculated analytically and constructed graphically the progressive deformation of passive material markers is guided by flowlines circular flowlines accommodate rigid body rotations without deformation elliptical flowlines result in pulsating strains the maximum strain occurs when material particles which were initially at the short axis of the elliptical flowlines reach the long axis of the flow patterns monotonically increasing strains occur when flowlines are hyperbolic the insight thus gained is extrapolated to suggest practical methods and assumptions that allow the reconstruction of particle movement paths from deformation features commonly observed in rocks

caledonian compressional and late orogenic extensional deformation in the staveneset area sunnfjord western norway abstract the studied area in western norway constitutes part of the hangingwall of the extensional kvamshesten detachment zone kdz the kdz separates eclogite bearing lower crust from a hangingwall consisting of a precambrian basement cover pair silurian continental margin sediments a silurian obduction melange a late ordovician ophiolite and the devonian kvamshesten basin deposited unconformably on the pre devonian rocks contractional deformation related to ophiolite obduction and to the caledonian scandian orogeny produced a suite of se verging structures developed under greenschist facies conditions as orogenic collapse commenced extensional shear zones were formed in the upper and middle crust re activating contractional shear zones and fabrics the direction of transport on the inherited fabrics was reversed from top to southeast to top to northwest and structures related to the regional extension were superimposed on the contractional structures back folding of the main contractional foliation by asymmetric w vergent folds together with nw and w directed shearing along weak lithologies and semi ductile faulting in the melange are the main structural expressions of early stages of the orogenic collapse in the staveneset area there is apparently no metamorphic break between the contractional fabrics and the earliest extensional structures the extensional structures developed however under progressively more brittle conditions the devonian sediments were deposited upon a sequence of rocks in the upper plate of the kvamshesten detachment that had already undergone significant extensional deformation and tectonic exhumation in the late silurian early devonian the extensional deformation in the upper plate of the western norwegian extensional detachments has up to recently been largely ignored in the discussion of the structural control of the formation of the devonian basins

widespread dispersal of icelandic tephra how does the eyjafjoll eruption of 2010 compare to past icelandic events widespread dispersal of icelandic tephra how does the eyjafjoll eruption of 2010 compare to past icelandic events

deformation progressive or multiphase abstract complexly deformed rocks that exhibit refolded folds and overprinting planar fabrics are often interpreted as the result of polyphase deformation and described in a scheme of deformation phases d 1 d 2 d n at the same time a number of models have been presented over the last decades that explain how complex and overprinting structures can form by single phase progressive deformation as strain accumulates strain generally accumulates heterogeneously in a deforming region depending on strain intensity and geometry flow parameters rheology and lithology the result is regions of different structural complexity fabrics and fabric orientations that can be sorted into different structural facies such structural pattern should be mapped and presented before defining a scheme of deformation phases and attempts should be made to explain them by a single structural kinematic model such as partitioned transpression only if this is not possible or if independent geochronologic data reveals a more punctuated history should we define an additional tectonic regime and deformation phase multiphase and progressive deformation histories are not mutually exclusive and it is important that both possibilities are considered when describing the deformation history of any complexly deformed region when the concept of deformation phases is employed the number of phases should be minimized and be related to major tectonic event of external character uncritically defining deformation phases can easily generate a complicated discrete deformation history with no link to tectonic reality

analytical description of tidal dynamics in convergent estuaries analytical solutions of the one dimensional hydrodynamic equations for tidal wave propagation are now available and in this paper presented in explicit equations for given topography friction and tidal amplitude at the downstream boundary the velocity amplitude the wave celerity the tidal damping and the phase lag can be computed the solution is based on the full nonlinearized st venant equations applied to an exponentially converging channel which may have a bottom slope two families of solutions exist the first family consists of mixed tidal waves which have a phase lag between zero and 2 which occur in alluvial coastal plain estuaries with almost no bottom slope the second family consists of apparent standing waves which develop in short estuaries with a steep topography asymptotic solutions are presented for progressive waves frictionless waves waves in channels with constant cross section and waves in ideal estuaries where there is no damping or amplification the analytical method is accurate in the downstream marine part of estuaries and particularly useful in combination with ecological or salt intrusion models the solutions are compared with observations in the schelde elbe and mekong estuaries

tidal amplitude decreases in response to estuarine shrinkage tokyo bay during the holocene abstract tidal changes in tokyo bay during the last 10 000 years were investigated by combining a numerical model with newly compiled model bathymetries for the present day the early 20th century and every 1000 years from 4000 to 10 000 years ago over this time period sea level has changed by more than 30 m and the coastline has shifted 50 60 km tides during the early 20th century and 4000 9000 years ago were larger than those at present from 9000 to 4000 years ago the bay setting was mesotidal in contrast to the modern microtidal setting the maximum tidal level at the head of the bay was 72 higher 7000 years ago than at present and m2 tidal currents at the bay mouth from 10 000 to 9000 years ago were three times stronger than those at present when tides were compared at a fixed location the greatest tidal enhancement was found to have occurred 9000 years ago the weakening of tides over the last 9000 years can be explained by introducing the concept of estuarine shrinkage together with quarter wavelength resonance theory tidal weakening occurred in two phases during the first phase 9000 7000 years ago it was due to the rise in sea level type 2 shrinkage and during the second phase a decrease in the length of the bay was responsible type 1 shrinkage these findings can be applied to the assessment of both past tidal changes and potential future tidal changes in other elongated estuaries with lengths of several tens of kilometers

temporal monitoring of subglacial volcanoes with tandem x application to the 2014 2015 eruption within the barðarbunga volcanic system iceland on august 29 2014 a lava eruption commenced in the holuhraun plain north east of the bar arbunga caldera in iceland the eruption ended on february 27 2015 thus lasting for a period of about 6 months during these months the magma chamber below the caldera gradually deflated feeding the eruption and causing the rare event of a slow caldera collapse in this scenario tandem x remote sensing data are of particular interest by producing medium high resolution and accurate elevation models of the caldera it is possible to evaluate volume losses and topographical changes to increase the knowledge about the ongoing activity in particular five tandem x bistatic acquisitions have been commanded between august 01 2014 and november 08 2014 two of them before the volcanic eruption and three of them during the event additionally to fully cover the volcanic activity the lava field 48 km north east of the caldera has also been monitored in the first part of the paper the expected elevation accuracy is studied on two levels absolute and relative height accuracies are analyzed by inspecting the x band signal propagation into snow and by investigating the impact of the main geometrical system parameters and the local geomorphology in the second part of the paper the analysis is applied to the bar arbunga volcanic system including a validation performed using complementary altimeter data the main geophysical outcome is the accurate temporal height tracking of the entire caldera and the glacial volcanic system the measured volume loss at the caldera location is about 1 billion cubic meters in two months with an average rate of subsidence of nearly 50 cm day these numbers confirm other independent sources and can be compared to lava volume measurements finally the last segment of the dyke that propagated from the bar arbunga caldera to the holuhraun lava field is mapped and a graben structure with a width of up to 1 km and a sinking of a few meters is reported

composite fabrics in mid crustal gneisses observations from the oygarden complex west norway caledonides subhorizontal caledonian shear zones that transform migmatitic gneisses into layered gneissic tectonites in the western part of the oygarden complex show a number of composite fabrics the associated structures consist of two sets of related planar surfaces showing a consistent top to the west sense of shear the development of these structures depends mainly on the nature and variation of finite strain rheology strain heterogeneities and extent of metamorphic mineral growth and recrystallization in the shear zones the structures have one set of surfaces represented by slip surfaces or narrow high strain zones oblique to this is a complementary set of surfaces representing either a plane of mineral flattening or aligned metamorphic minerals in s c structures or rotated gneissic foliation in contractional and extensional composite structures rotation by folding and subsequent slip along limbs or axial planar cleavage results in contractional composite structures while rotation by downward cutting extensional type slip surfaces form extensional composite structures contractional and extensional composite structures involve slip transfer across the mylonitic layering commonly between terminating weak layers within strongly anisotropic layered tectonites combinations of the different types of composite structures are common but the method of shear sense identification is always the same

development of a shear band cleavage as a result of strain partitioning abstract microstructural analyses of shear band cleavages in a centimeter scale shear zone within a metasomatic biotite band in the teshima granite ryoke metamorphic belt southwest japan show that strain partitioning occurred between quartz and biotite feldspar domains within the shear zone pre tectonic hydrothermal alteration within the granite caused biotite replacement of both plagioclase and k feldspar resulting in the development of biotite feldspar domains where k feldspar mantles dominantly biotite plagioclase aggregates subsequently the altered granite was plastically deformed in simple shear so that intra layer shear band cleavages were passively developed within the biotite feldspar domains whereas intense dynamic recrystallization occurred in the quartz domains the rotation and orientation of the intra layer shear band cleavages can be explained by a finite strain ellipse model which shows that strain in the biotite feldspar domain requires only 10 20 of the bulk simple shear strain for the development of such cleavages so that most of strain could be accommodated by deformation in the quartz domain consequently the model suggests that the development of the shear zone resulted in strain partitioning between the quartz and the biotite feldspar domains due to compositional variations via hydrothermal alteration within the granite

caution in cryptotephra correlation resolving lateglacial chemical controversies at sluggan bog northern ireland tephra layers are valuable stratigraphic and chronological markers in palaeoenviromental studies establishing robust linkages requires complete comparative databases of eruptive events to ensure that potential correlatives are not overlooked this is achieved through the construction of tephrostratigraphical inventories from exposures proximal to the volcanic source proximally characterized ash layers are frequently detected thousands of kilometres from source alongside a limited number of tephras with no apparent proximal correlative despite the inability to correlate with a specific eruption source volcanoes can be proposed and many of these far field occurrences have become well established stratigraphic markers however careful scrutiny is essential to verify the primary and instantaneous fallout origin of these distant occurrences here we present new data which provide an explanation for the long standing controversy surrounding the source of lateglacial age cryptotephras within sluggan bog northern ireland chemical analysis of glass shards detected within this sequence suggests they originate from an obsidian exposure located 11 km from the site rather than from a contemporaneous eruptive event this discovery highlights the importance of giving appropriate consideration to the enclosing geology of a particular palaeorecord we suggest locations where geological sources might complicate air fall records of tephra deposition and propose a means by which to address this challenge

an inflection in the rate of early mid holocene eustatic sea level rise a new sea level curve from singapore this study presents a sea level curve from 9500 to 6500 cal bp for the farfield location of singapore on the sunda shelf in southeast asia the curve is based on more than 50 radiocarbon dates from elevations of 1 43 m to 15 09 m representing sea level index points in intertidal mangrove and shallow marine sediments deposited by sea level rise accompanying deglaciation the results indicate that mean sea level rose rapidly from around 17 m at 9500 cal bp to around 3 m by 8000 cal bp after this time the data suggest but do not unequivocally prove that the rate of sea rise slowed for a period of 300 500 years centred on 7700 cal bp shortly after the cessation of meltwater input to the oceans from the northern hemisphere renewed sea level rise amounting to 3 5 m began around 7400 cal bp and was complete by 7000 cal bp the existence of an inflection in the rate of sea level rise with a slow down centred on 7700 cal bp is broadly consistent with other available sea level curves over this interval and is supported by evidence of stable shorelines and delta initiation elsewhere at this time as well as evidence of comparatively rapid retreat of the west antarctic ice sheet beginning around 7500 cal bp stepped sea level rise occurring shortly after 7500 cal bp and also earlier during deglaciation may have served to focus significant post glacial episodes of human maritime coastal dispersal into comparatively narrow time intervals

correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods review and evaluation abstract we define tephras and cryptotephras and their components mainly ash sized particles of glass crystals in distal deposits and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental geological and archaeological research we then document and appraise recent advances in analytical methods used to determine the major minor and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures a narrow electron beam diameter 3 5 m can now be used to analyze smaller glass shards than previously attainable reliable analyses of microshards defined here as glass shards in part 2 of the review we describe critically assess and recommend ways in which tephras or cryptotephras can be correlated in conjunction with other information using numerical or statistical analyses of compositional data statistical methods provide a less subjective means of dealing with analytical data pertaining to tephra components usually glass or crystals phenocrysts than heuristic alternatives they enable a better understanding of relationships among the data from multiple viewpoints to be developed and help quantify the degree of uncertainty in establishing correlations in common with other scientific hypothesis testing it is easier to infer using such analysis that two or more tephras are different rather than the same adding stratigraphic chronological spatial or palaeoenvironmental data i e multiple criteria is usually necessary and allows for more robust correlations to be made a two stage approach is useful the first focussed on differences in the mean composition of samples or their range which can be visualised graphically via scatterplot matrices or bivariate plots coupled with the use of statistical tools such as distance measures similarity coefficients hierarchical cluster analysis informed by distance measures or similarity or cophenetic coefficients and principal components analysis pca some statistical methods cluster analysis discriminant analysis are referred to as machine learning in the computing literature the second stage examines sample variance and the degree of compositional similarity so that sample equivalence or otherwise can be established on a statistical basis this stage may involve discriminant function analysis dfa support vector machines svms canonical variates analysis cva and anova or manova or its two sample special case the hotelling two sample t2 test randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices hierarchical cluster analysis and pca such transformations may make the assumption of multivariate normality more appropriate a sequential procedure using mahalanobis distance and the hotelling two sample t2 test is illustrated using glass major element data from trachytic to phonolitic kenyan tephras all these methods require a broad range of high quality compositional data which can be used to compare unknowns with reference training sets that are sufficiently complete to account for all possible correlatives including tephras with heterogeneous glasses that contain multiple compositional groups currently incomplete databases are tending to limit correlation efficacy the development of an open online global database to facilitate progress towards integrated high quality tephrostratigraphic frameworks for different regions is encouraged

the respiratory health hazards of volcanic ash a review for volcanic risk mitigation studies of the respiratory health effects of different types of volcanic ash have been undertaken only in the last 40 years and mostly since the eruption of mt st helens in 1980 this review of all published clinical epidemiological and toxicological studies and other work known to the authors up to and including 2005 highlights the sparseness of studies on acute health effects after eruptions and the complexity of evaluating the long term health risk silicosis non specific pneumoconiosis and chronic obstructive pulmonary disease in populations from prolonged exposure to ash due to persistent eruptive activity the acute and chronic health effects of volcanic ash depend upon particle size particularly the proportion of respirable sized material mineralogical composition including the crystalline silica content and the physico chemical properties of the surfaces of the ash particles all of which vary between volcanoes and even eruptions of the same volcano but adequate information on these key characteristics is not reported for most eruptions the incidence of acute respiratory symptoms e g asthma bronchitis varies greatly after ashfalls from very few if any reported cases to population outbreaks of asthma the studies are inadequate for excluding increases in acute respiratory mortality after eruptions individuals with pre existing lung disease including asthma can be at increased risk of their symptoms being exacerbated after falls of fine ash a comprehensive risk assessment including toxicological studies to determine the long term risk of silicosis from chronic exposure to volcanic ash has been undertaken only in the eruptions of mt st helens 1980 usa and soufriere hills montserrat 1995 onwards in the soufriere hills eruption a long term silicosis hazard has been identified and sufficient exposure and toxicological information obtained to make a probabilistic risk assessment for the development of silicosis in outdoor workers and the general population a more systematic approach to multi disciplinary studies in future eruptions is recommended including establishing an archive of ash samples and a website containing health advice for the public together with scientific and medical study guidelines for volcanologists and health care workers

geometry of the pamir hindu kush intermediate depth earthquake zone from local seismic data 1 we present new seismicity images based on a two year seismic deployment in the pamir and sw tien shan a total of 9532 earthquakes were detected located and rigorously assessed in a multistage automatic procedure utilizing state of the art picking algorithms waveform cross correlation and multi event relocation the obtained catalog provides new information on crustal seismicity and reveals the geometry and internal structure of the pamir hindu kush intermediate depth seismic zone with improved detail and resolution the relocated seismicity clearly defines at least two distinct planes one beneath the pamir and the other beneath the hindu kush separated by a gap across which strike and dip directions change abruptly the pamir seismic zone forms a thin approximately 10 km width curviplanar arc that strikes east west and dips south at its eastern end and then progressively turns by 90 to reach a north south strike and a due eastward dip at its southwestern termination pamir deep seismicity outlines several streaks at depths between 70 and 240 km with the deepest events occurring at its southwestern end intermediate depth earthquakes are clearly separated from shallow crustal seismicity which is confined to the uppermost 20 25 km the hindu kush seismic zone extends from 40 to 250 km depth and generally strikes east west yet bends northeast toward the pamir at its eastern end it may be divided vertically into upper and lower parts separated by a gap at approximately 150 km depth in the upper part events form a plane that is 15 25 km thick in cross section and dips sub vertically north to northwest seismic activity is more virile in the lower part where several distinct clusters form a complex pattern of sub parallel planes the observed geometry could be reconciled either with a model of two sided subduction of eurasian and previously underthrusted indian continental lithosphere or by a purely eurasian origin of both pamir and hindu kush seismic zones which necessitates a contortion and oversteepening of the latter

rising waters new geoarchaeological evidence of inundation and early agriculture from former settlement sites on the southern yangtze delta china new pollen phytolith charcoal and diatom data from 14c ams dated sediments from three clusters of former occupation sites on the southern yangtze delta liangzhu majiabang and chuodun reveal

holocene cheniers in the yangtze delta china abstract nineteen cheniers formed in the middle and late holocene have been distinguished and studied in fair weather the wave action along the yangtze delta is weak with a wave height of 0 5 1 0 m and average wave energy of 0 127 erg s however in late summer and early autumn the coastal area is usually swept by typhoons which sometimes are extremely violent the development of cheniers is mainly controlled by these strong typhoons as a result a number of the sedimentary characteristics of the cheniers are related to the typhoon generated high energy environment moreover the study shows that the top elevation of a fully developed chenier indicates the spring high water level during a violent typhoon 11 12 on the beaufort scale