karst collapse susceptibility assessment a case study on the amalfi coast southern italy abstract this paper presents a study to evaluate the collapse susceptibility of a karst cave located along a slope on the amalfi coast southern italy and the presumable geomorphological evolution of the whole slope as a result of cave roof collapse in the study area several natural karst caves with volumes varying between 1000 and 10 000 m 3 were inventoried and the most likely genetic processes were identified some of them proved to be remnants of already collapsed caves while others were in precarious stability conditions the caves are usually located upslope or very close to the main populated resorts a detailed geological geomorphological and geostructural study was performed on a very wide deep cave called the saraceno cave on which the resort town of conca de marini has been built the study was carried out through a multidisciplinary approach which included classical field geological observations sometimes requiring the support of rock climbing geologists experts in photogrammetric surveys and terrestrial laser scanning techniques tls tls surveys allowed the reconstruction of an accurate geometric and geostructural model of the cave and its relationship with the upslope conca de marini resort furthermore it allowed the thickness of the cave overburden to be determined in detail ground surfaces most susceptible to collapse were also identified in the event of possible widespread collapse several buildings and transportation infrastructures could be involved as the cave is located on a very steep slope a debris avalanche could be triggered in the event of a catastrophic failure and the landslide debris characterized by a presumably high magnitude and velocity could involve a wide slope area down to the coast the failure evolution could be very similar to that which took place in amalfi in the late 19th century

magnetic susceptibility of the rock matrix related to magnetic fabric studies non ferromagnetic minerals constitute what is called the rock matrix whose susceptibility k1 is directly accessible using only high magnetic fields measurements on minerals and a wide range of rock types show that k1 is mainly due to paramagnetism and hardly exceeds 10 3 si with an anisotropy degree p less than 1 35 different methods to estimate the role of the matrix component in low field susceptibility k and its anisotropy include petrological and chemical analysis evolution of p vs k low temperature studies and comparison of k with remanent magnetizations

morphostructural evolution and related kinematics of rockfalls in campania southern italy a case study abstract on the southern slope of the sorrentine peninsula there are many subtriangular depressions in which the main townsof the area are located the depressions are linked to block rotation during strike slip fault activity and are oftenmarked by high subvertical cliffs and related rockfall phenomena with consequent damage to the underlying towns on the basis of back analyses carried out using hoek s method an in depthstudy of some of the rockfalls enabled us todefine for one of these towns the most suitable shock restitution coefficients of the detritical pyroclastic deposits present on the terraces situated at the foot of the cliffs on the basis of the main kinematic parameters of actual rockfalls and approximately 6600 simulated rockfalls a planning of the high level rockfall risk valley bottoms was drawn up the size of the high level rockfall risk sites depends above all on the presence number and size of the terracings wherecitrus fruit trees are cultivated the calculation method suggested by paronuzzi was also adopted in order to make a detailed evaluation of the role the terraces play in modifying the trajectory height the translation velocity and the endpoint of the boulders although there are methodological and statistical differences between the two methods results from both studies showed sufficient correlation in particular concerning the trajectories endpoints

high resolution mapping of rock fall instability through the integration of photogrammetric geomorphological and engineering geological surveys abstract a semi quantitative methodology for rock fall susceptibility assessment is presented the test area is located along the amalfi coast sorrento peninsula southern italy which is characterized by high relief energy and very steep slopes made up of dolomite limestone of mesozoic age generally the cliffs are strongly jointed and affected by karst processes for this reason rock falls rock slides and more seldom topples are very frequent in the area the study took a multidisciplinary approach mixing classical field geology observations with typically geo mechanical ones and required the support of highly professional staff such as applied geologists experts in photogrammetric survey techniques and engineers for stabilization works planning the acquisition of the data involves a detailed large scale study scale 1 500 this methodology is mainly suitable for the study of single cliffs or slope with limited dimensions cartographic representation is a main problem in the study of a vertical cliff a frontal topographic survey terrestrial photogrammetry was first carried out after this different geo thematic maps showing the main geological geomorphological and geostructural information were elaborated and then compared allowing the elaboration of the triggering susceptibility map the semi quantitative proposed method has a good accuracy in the realization of the potential detachment area of rock falls in order to predispose stabilization works and to rationalize the disposal resources for the hazard mitigation in the unstable areas near human utilization urban centres roads etc

the neogene xiyu formation a diachronous prograding gravel wedge at front of the tianshan climatic and tectonic implications the tarim and junggar basins in central asia are capped by a thick pile of conglomerates called the xiyu formation that are commonly linked to a change in climate and or accelerated uplift near the plio pleistocene boundary in order to better understand their origin and significance we carried out a combined structural and magnetostratigraphic study in the quilitage syncline southern tianshan where the base of the xiyu conglomerates is observed at both sides of the syncline a balanced cross section shows that even at a local scale the base of the xiyu conglomerates cannot be regarded as a single continuous stratigraphic layer on the southern flank of the quilitage syncline we collected 172 samples collected for magnetostratigraphic dating identify 17 polarity chrons that date the new section from 5 2 to 1 7 ma and constrain the base of the xiyu conglomerate here at 1 7 ma this is 4 2 ma younger than the age of the xiyu previously found on the northern limb of the same syncline together with other magnetostratigraphic studies carried out around the tianshan our study unambiguously demonstrates that the onset of deposition of the xiyu conglomerates is diachronous and that the conglomerates are systematically younger toward the basin consequently the xiyu formation should not be considered as a chronostratigraphic marker related to any particular tectonic or climatic event but is instead a prograding gravel wedge that has prograded over the underthrusting forelands a synthesis of chronologic and structural results yields progradation rates over the last 10 ma on the order of 2 0 mm yr and 3 9 mm yr south and north of the tianshan mountains respectively these rates are comparable to the shortening rate across the tianshan range suggesting that underthrusting is the main factor governing the progradation rate of the xiyu formation

effect of impact velocity block mass and hardness on the coefficients of restitution for rockfall analysis abstract one of the most significant input parameters in rockfall trajectory modelling is the coefficient of restitution which controls block rebound in particular in the design of rockfall barriers it can significantly affect their height in practice the coefficients of restitution are acquired by field or laboratory tests back analyses of known events experience or most commonly suggested values connected to the slope material furthermore to account for the effect of impact velocity or block mass scaling factors are available however the suggested values are based on a qualitative description of the slope material and the scaling factors are not well documented nor do they account for the effects of impact velocity and block mass simultaneously in this paper a semi empirical correlation is proposed that takes into account the schmidt hammer rebound value of both the slope and block material as well as the impact velocity and block mass this was derived by an extensive laboratory experimental study 445 impact tests of a one dimensional drop of spherical blocks onto planar surfaces the semi empirical correlation proposed adequately describes the responses observed under the circumstances imposed in the laboratory

persistently low asian paleolatitudes implications for the india asia collision history 1 paleomagnetism provides independent paleolatitude constraints on the india asia convergence however implied cenozoic latitudinal convergence within asia thousands of km largely exceeds geologic estimates of tectonic shortening hundreds of km this discrepancy may result from a notoriously low bias in paleomagnetically determined cenozoic paleolatitudes in asia we provide here new paleomagnetic data from cenozoic mongolian volcanic rocks and from chinese paleogene sediments corrected from the depositional bias of inclination shallowing these results combined with similar asian data sets confirm that paleolatitudes are still 5 10 lower than predicted by the paleomagnetic apparent polar wander path apwp for asia between 50 and 20 ma inclination shallowing being excluded from the selected data sets we investigate the likeliness of other proposed mechanisms for this discrepancy 1 more southerly positions of asia than expected by the apwp due to apwp inaccuracies rather than eurasian non rigidity or 2 non dipolar geomagnetic field contributions fully explaining this discrepancy by only one of these mechanisms would imply either unrealistically large 10 apwp inaccuracies or unrealistically large octupolar field contributions up to 16 a combination of these mechanisms is found more likely to have produced the observed latitudinal discrepancy but their respective contributions cannot be quantified given the still relatively low amount and poor quality of cenozoic paleomagnetic data from stable cratons of asia india and europe by allowing for reasonable time dependant non dipolar contributions and a slight 5 apwp bias the latitudinal discrepancy can be resolved and the excessive amounts of intra asian shortening decrease to values in line with tectonic shortening from structural studies

magnetostratigraphic dating of hominoid bearing sediments at zhupeng yuanmou basin southwestern china abstract the hominoid fossils found in the yuanmou basin southwestern china are among the key fossils for understanding the evolution of early hominoids in eastern asia and their relationship with coeval hominoids in europe and africa however their exact ages have not yet been well determined we provide a new high resolution magnetostratigraphy for the zhupeng profile which is one of the fossil bearing type sections in the region based on magnetostratigraphy of 227 remanent directions together with the age of micromammalian fauna indicate that the hominoid bearing layer is dated within polarity chron 3br 2r or 3br 1r i e within the interval 7 43 7 38 ma or 7 34 7 17 ma this unambiguously indicates that the yuanmou hominoid has a late miocene age which therefore makes it the youngest hominoid found in eurasia it is possible that the yuanmou basin provided a refuge for hominoids during a time of major environmental changes

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

exposure history and terrestrial ages of ordinary chondrites from the dar al gani region libya we measured the concentrations of noble gases in 32 ordinary chondrites from the dar al gani dag region libya as well as concentrations of the cosmogenic radionuclides 14c 10be 26al 36cl and 41ca in 18 of these samples although the trapped noble gases in five dag samples show ratios typical of solar or planetary gases in all other dag samples they are dominated by atmospheric contamination which increases with the degree of weathering cosmic ray exposure cre ages of dag chondrites range from 1 myr to 53 myr the cre age distribution of 10 dag l chondrites shows a cluster around 40 myr due to four members of a large l6 chondrite shower the cre age distribution of 19 dag h chondrites shows only three ages coinciding with the main h chondrite peak at 7 myr while seven ages are 5 myr two of these h chondrites with short cre ages dag 904 and 908 show evidence of a complex exposure history five of the h chondrites show evidence of high shielding conditions including low 22ne 21ne ratios and large contributions of neutron capture 36cl and 41ca these samples represent fragments of two or more large pre atmospheric objects which supports the hypothesis that the high h l chondrite ratio at dag is due to one or more large unrecognized showers the 14c concentrations correspond to terrestrial ages 35 kyr similar to terrestrial ages of chondrites from other regions in the sahara but younger than two dag achondrites despite the loss of cosmogenic 36cl and 41ca during oxidation of metal and troilite concentrations of 36cl and 41ca in the silicates are also consistent with 14c ages 35 kyr the only exception is dag 343 h4 which has a 41ca terrestrial age of 150 40 kyr this old age shows that not only iron meteorites and achondrites but also chondrites can survive the hot desert environment for more than 50 kyr a possible explanation is that older meteorites were covered by soils during wetter periods and were recently exhumed by removal of these soils due to deflation during more arid periods such as the current one which started 3000 years ago finally based on the 26al 21ne and 10be 21ne systematics in 16 dag meteorites we derived more reliable estimates of the 10be 21ne production rate ratio which seems more sensitive to shielding than was predicted by the semi empirical model of graf et al 1990 but less sensitive than was predicted by the purely physical model of leya et al 2000

northeastward growth of the tibet plateau deduced from balanced reconstruction of two depositional areas the qaidam and hexi corridor basins china we address the problem of late cenozoic uplift erosion and growth of northeastern tibet by reconstructing from isopach maps and drill holes the volumes and masses of sediments deposited in the qaidam and hexi corridor basins since 35 myr ago the mass budget is based on simple geometrical assumptions such as regional similarity of the thickness ratios between strata of different ages in the qaidam where our record extends back to the oligocene the budget shows a huge rise of the accumulation rates after the beginning of the pliocene 5 3 ma the early pliocene seems to be the period of maximum deposition with accumulation rates in excess of 1 mm yr 1 2 7 kg m 2 yr 1 of compacted rocks throughout the basin there also seems to be a southeastward shift of the largest depocenters between the upper pliocene 3 4 1 6 ma and the quaternary in the hexi corridor sedimentation is confined to small foreland flexural depressions associated with the frontal thrusts of the qilian shan and occurs at an average rate one order of magnitude smaller than in the qaidam basin the accumulation rate is maximum in the quaternary the sedimentation history appears to support a plateau building mechanism resulting from the combination of two geologicallly common processes crustal scale thrusting and sedimentary basin infilling the time needed to completely fill the qaidam basin and make its catchment a plateau closely resembling that of the highest part of tibet qangtang is of the order of 9 myr the mechanism now at work north of the kunlun which involves rapid infilling of broad flat areas separated by relatively narrow mountain ranges has thus probably been important in producing the high smooth topography that characterizes much of central tibet

mineral magnetic properties of loess paleosol couplets of the central loess plateau of china over the last 1 2 myr 1 we have conducted a multiparameter investigation of 15 loess paleosol couplets s0 l1 to s14 l15 from the jiaodao section in the central loess plateau of china using environmental magnetic approaches coupled with soil science techniques the magnetic parameters display systematic variations that seem to be closely related to paleoclimate variations and intensity of pedogenesis high temperature susceptibility curves of paleosols show a generally decreasing trend in reversibility from the base of the lishi formation to the holocene black loam possibly indicating a decrease in weathering intensity this may reflect a long term increase in aridity and or a general long term cooling trend of the interior of the asian continent from 1 2 ma to the present several samples display wasp waisted hysteresis loops these are most pronounced in moderately enhanced paleosols less pronounced in the practically unaltered loess and subdued in the well developed paleosols but wasp waistedness reappears in the most developed paleosols this wasp waistedness sequence suggests that the composition concentration and grain size of magnetic minerals all contribute to the hysteresis behavior of samples from the studied loess paleosol sequence but each factor has a different effect at different stages of pedogenesis

stratigraphic evidence for an early collision between northwest india and asia the collision of india with asia1 had a profound influence on late cretaceous and cenozoic oceanography2 climate3 fauna extinctions4 and the motion of at least some of the earth s litho spheric plates5 as the collision ended a period of rapid indo asian convergence6 a precise knowledge of its timing when the crust of the neo tethys ocean was completely subducted7 at some point along the plate boundary is important for understanding its wider consequences but current estimates of the collision age range from 65 to 38 myr before present6 8 11 here we report the results of extensive biostratigraphic analyses from waziristan and kurram in northwest pakistan which show that accretionary prism and trench strata were first thrust onto the northwest indian passive margin after 66 myr but before 55 5 myr after this time volcanic arc fragments the accretionary prism trench material and imbricates of the north indian slope were raised to shallow water depths and overlapped by upper palaeocene shallow water carbonates and shales12 14 indicative of post collision thrusting in this region finally both the suture and the indian craton were overlapped by continuous unconformable upper lower eocene shallow marine strata demonstrating that suturing was complete by 49 myr

northwest trending middle cenozoic left lateral faults in southern yunnan china and their tectonic significance abstract the northwest striking jianshui qujiang and chuxiong faults and probably the zhongdian fault south china show evidence for different amounts of middle cenozoic pre pliocene and post early paleogene left lateral displacement that range from 6 to 25 km the age and orientation of the left lateral faults suggest that the faults are related to a regional deformational event associated with important left lateral shear on the ailao shan shear zone which lies 50 70 km to the south identification of these faults extends left lateral shear during this deformational event farther to the northeast than previously recognized unlike the ailao shan shear zone these faults do not appear to be part of a through going nw trending shear zone these faults are interpreted to be the northernmost part of a nw trending boundary whose main structure the left lateral ailao shan shear zone forms a broad zone of mylonitic rocks bounding a crustal fragment that rotated clockwise around the eastern himalayan syntaxis following middle cenozoic left lateral displacement only the jianshui and qujiang faults exhibited a reversal of displacement in post miocene time this reversal is interpreted to be the result of counterclockwise rotation within the broad n s striking left lateral xiaojiang fault zone none of the post miocene displacement on these two faults appears to be related to post miocene right lateral displacement on the red river fault system the chuxiong fault may have reversed its early left lateral displacement but evidence from surface geology for young and active right lateral displacement is not clear the zhongdian fault appears to have undergone only left lateral displacement some of which may be middle cenozoic in age and some post miocene in age active displacement on the zhongdian fault is interpreted to mark the eastern boundary for a small crustal fragment that rotates clockwise around the eastern himalayan syntaxis

combining field and modelling techniques to assess rockfall dynamics on a protection forest hillslope in the european alps adequate management of a mountain forest that protects downslope areas against impacts of rockfall requires insight into the dynamics of the hillslope environment therefore we applied a combined approach using field and modelling techniques to assess the determining factors for rockfall source areas rockfall tracks and rockfall runout zones on a forested slope in mountainous terrain the first objective of this study was to understand why rockfall occurs in the study area the second objective was to translate the knowledge obtained in the field into a model that simulates rockfall dynamics on a forested slope realistically the third objective was to assess which hillslope characteristics primarily determine the distribution of active rockfall tracks to achieve these objectives we made a geomorphological map of the whole study area and we measured the major discontinuity planes in the bedrock that are exposed in the rockfall source areas furthermore a test site for simulation modelling within the larger study area was defined in which both a forest and a hillslope inventory were carried out the available data and our developed rockfall simulation model allowed us to assess the slope characteristics that mainly determine the distribution of areas affected by rockfall we found that in decreasing order of importance both standing and felled trees the surface roughness and rockfall resistant shrubs primarily determine the distribution of rockfall affected areas simulation tests without a forest cover produced similar rockfall runout zones as fossil rockfall events identified in the field we believe that the combined field and modelling approach is a prerequisite for understanding how forests can protect against rockfall

magnetic enhancement paths in loess sediments from tajikistan china and hungary saturation magnetization and saturation remanence of 139 loess and paleosol samples from tajikistan china and hungary increase linearly with low field susceptibility in all sections investigated thus magnetic enhancement is caused by increasing quantities of ferrimagnetic minerals the observed variations of high field susceptibility h are attributed to variations in the amount of clay minerals as h is linearly correlated with the 2 m grain size mineral fraction the magnetic enhancement process is compared with a theoretical mixing model based on two magnetic mineral assemblages with different but invariable coercivities the two component model provides a good approximation to the data from hungary and the magnetically enhanced paleosol samples in tajikistan and china discrepancies between model calculation and data arise in the behaviour of the loess samples in tajikistan here a three component model improves the agreement between data and mixing calculation the magnetic enhancement in the loess in tajikistan and china is different from the one in the paleosols and the link between paleoclimate and susceptibility is not as straightforward as in the hungarian loess paleosol sequence

assessment of rockfall hazard around afyon castle turkey the afyon castle is a tourist destination and a historical site in the city of afyon in turkey the castle is located on a steep hill with a height of 226 m in close proximity to the castle there are settlements the hill consists of trachitic andesite the rock contains columnar joints and flow layering owing to these discontinuities blocks of varying sizes had fallen down the settlement areas near the castle are now in danger because of the rockfall risk in this study rockfall analysis was carried out along nine profiles of the hill fall out distance bounce height kinetic energy and velocity of the rocks along each profile were investigated the results of the analyses were evaluated and the areas delineated as susceptible to rockfall risk are highlighted remedial measures including rock bolts and protective fences were suggested on the basis of the field observations and the rockfall risk evaluation

magnetostratigraphy of the dali basin in yunnan and implications for late neogene rotation of the southeast margin of the tibetan plateau 1 the rotation pattern and fault activity in the southeast margin of the tibetan plateau semtp provide meaningful constraints on the geodynamic evolution of the plateau however the lack of cenozoic paleomagnetic studies and accurate age constraints on neogene sediments prevents a better understanding of the late cenozoic tectonic activity in this area to clarify the tectonic rotation pattern and deformation history of the semtp we report new magnetostratigraphic data from a late neogene sedimentary sequence in the dali basin northwestern yunnan province china rock magnetic analyses indicate that both magnetite and hematite are the main carriers of the characteristic remanent magnetizations chrms magnetostratigraphic results show that the sedimentary profile spans from chron c4n 1r to chron c2n the age of the sedimentary sequence in the dali basin can thus be paleomagnetically constrained to an interval from late miocene to early pleistocene the basal age of the sediments is 7 6 ma which indicates that the unroofing of diancang shan and activation of the dali fault system were initiated at this time the appearance of conglomerates and syntectonic sediments suggests the reactivation of the dali fault system at 2 5 ma moreover the overall mean chrm direction suggests that the dali basin experienced significant 4 4 2 5 but minor post late miocene rotation this indicates that most of the clockwise rotation demonstrated by previous paleomagnetic studies in the semtp occurred prior to late miocene and may be concentrated between eocene and miocene which is contemporaneous with the sinistral slip of the ailao shan red river fault

duration of strike slip movements in large shear zones the red river belt china abstract sixty four size fractions of zircon monazite xenotime and titanite were dated by the u pb method to temporally and spatially constrain left lateral movements in the red river shear zone between the depths of 15 and 20 km the shearing led to the formation of the high grade metamorphic gneisses that form the bulk of the 4200 m high diancang shan and 3100 m high ailao shan mountain ranges the omnipresence of melt layers and pockets in these gneisses shows that temperatures associated with tectonometamorphism lie at and above the solidus of continental crust and deformation patterns are very homogeneous over the entire length of the belt north of the gneisses subvolcanic bodies intrude unmetamorphosed cover rocks in particular eocene red beds along the projected trend of the red river shear zone for a leucogranitic layer in the diancang shan gneisses an age of 24 2 0 2 ma 2 is obtained for monazite and 22 4 0 2 ma is obtained for xenotime whereas zircon formed through two growth stages at 24 23 ma these ages record solidification of the anatectic melts over a period of at least 1 8 0 4 ma during which left lateral shear was continuously active in the ailao shan gneisses zircon and titanite ages are 26 3 0 3 and 26 1 0 2 ma for two monzonitic bodies and 24 1 0 2 and 22 4 0 2 ma for two pegmatitic layers that occur within the monzonitic intrusions these results show that zircon monazite titanite and probably also xenotime are closed systems for u and pb under melting conditions 650 c therefore the ages date mineral formation in the melt rather than cooling below certain closure temperatures a significantly older age of 35 0 0 1 ma is obtained for a monzonitic subvolcanic intrusion north of the diancang shan gneisses because these intrusions follow the trend of the shear zone they most likely represent the surface expression of early activity along that zone indicating that strike slip movement had already occurred in latest eocene time the total set of u pb ages shows that magmatic and metamorphic activity occurred from 35 to 20 ma strengthening the idea that the red river shear zone absorbed most of the intraplate movements required to compensate the opening of the south china sea between 32 and 16 ma the existence of monzonitic syenitic intrusions along the red river zone implies that melting affected source rocks other than the diancang shan and ailao shan gneiss protoliths potential sources to produce such rocks lie in the deep crust possibly including melts from the mantle consequently the red river shear zone must be a deep rooted structure along which melts migrated to the surface moreover the contemporaneity of shear motion and magma generation suggests that melting occurred in direct relation to strike slip activity

rockfall susceptibility map for athinios port santorini island greece abstract this article analyzes rockfall susceptibility in the steep caldera slopes upstream of athinios port santorini island greece the study area is situated in the internal rim of a submarine caldera where the most important problem that is recorded is the frequent rockfalls that not only cause damages to roads and vehicles but also pose a threat to people that are transported or located on the port as a result a methodology which combines information relatively to surficial and engineering geology geomorphological processes and structural analysis was adopted the methodology incorporates evenly a maximum runout map generated by means of reach probability of rock block analysis using the empirical model of reach angle additionally volumes of rockfall events categorized and presented through a map to assist the compilation of rockfall susceptibility map which allows us to identify areas and human activities exposed to these incidents and set up several protection meters

coastal hazard assessment and mapping in northern campania italy abstract in the northern campanian coastal zone over 150 km long three geomorphic units are recognised 1 sandy beaches that are well developed in the northern area where a prominent river mouth volturno river is also present 2 steep and rocky shores often with gravelly beaches or debris cones at their base are mainly diffuse in the southern area sorrentine peninsula and lastly 3 techno coast shorelines stabilized with revetments and seawalls as well as former natural environments no longer clearly operational because of urbanization as is visible in naples and in the vesuvian coast six primary hazards are considered in this investigation shoreline erosion riverine flooding storms landslides seismicity and volcanism and man made structures these hazards do not have a uniform distribution along this coast in terms of their frequency and intensity moreover both their interaction and the intensive action of humans often uncontrolled makes it difficult to assess the overall coastal hazard in this paper a semi quantitative method with which to quantify rank and map the distribution of hazard is applied along this particular stretch of coast in such a stretch previously characterized in terms of types and processes and compartmentalized into geomorphic units the effect of individual hazards based on their magnitude and recurrence is evaluated dominant and subordinate hazards for each geomorphic unit are identified assigning a rank that is also a weighting comparison of each weighting through an interaction matrix permits the calculation of a resultant which is the overall hazard assessment and which can be expressed cartographically the results obtained for a coastal zone with one of the highest pressures from urbanization in the world help us to recognise that this approach could become a useful tool to aid decision making regarding coastal land use and planning

continuous deformation of the tibetan plateau from global positioning system data global positioning system velocities from 553 control points within the tibetan plateau and on its margins show that the present day tectonics in the plateau is best described as deformation of a continuous medium at least when averaged over distances of 100 km deformation occurs throughout the plateau interior by ese wnw extension and slightly slower nne ssw shortening relative to eurasia material within the plateau interior moves roughly eastward with speeds that increase toward the east and then flows southward around the eastern end of the himalaya crustal thickening on the northeast ern and eastern margins of the plateau occurs over a zone 400 km wide and cannot be the result of elastic strain on a single major thrust fault shortening there accommodates much of india s penetration into eurasia a description in terms of movements of rigid blocks with elastic strain associated with slip on faults between them cannot match the velocity field

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

characteristics of the active xiaojiang fault zone in yunnan china a slip boundary for the southeastward escaping sichuan yunnan block of the tibetan plateau abstract the xiaojiang fault zone within the yunnan province china is one of the most active fault zones of the southeastern edge of the tibetan plateau this n s trending 400 km long fault zone defines the southern part of the eastern boundary of the sichuan yunnan block which is escaping southeastward from the tibet plateau and rotating around the eastern himalayan syntaxis the middle section of the fault zone splits into two branches each branch fault consists of several en echelon faults basins of various ages have developed on the step overs between the secondary faults the left lateral strike slip rate along the eastern branch is up to 9 mm a and that on the western branch is 7 mm a more than 10 m 6 historic earthquakes have occurred along the fault zone the largest was the 1833 songming earthquake of m 8 four earthquake rupture zones were discovered along the fault zone 15 trenches have been excavated along every major segment of the fault zone and 4 5 paleoearthquakes have been distinguished along the xiaojiang fault zone the average strong earthquake recurrence interval is 2000 2500 years

the significance of geology for the morphology of potentially unstable rocks abstract from a consideration of the concepts of geological weathering and structure it can be expected that rockfall hazards should be characteristically different in different geological environments this paper tests this idea by looking at the geometric characteristics of rock fragments formed on natural slopes in four different geological environments in eastern australia where rockfall phenomena are often characterised by rolling of pre detached debris by measuring the three principle dimensions and making a systematic assessment of the shape characteristics of samples of rock debris in significant geological environments it is found that the distributions of size and shape for the surface debris are statistically different from the results it is shown that the size and shape of debris is directly controlled by the rock type its weathering characteristics and the structure of the parent rock mass the severity of rockfall hazards is shown to be relatively lower in areas of tertiary basalt as the size of rolling fragments is limited by closely spaced fracturing inherited from its formation and the tendency to deteriorate further as it weathers deeply and rapidly it is also lower in areas of palaeozoic volcanics since these tend to produce relatively angular fragments with higher proportions of fragments that are inherently more resistant to rolling by contrast thickly bedded sandstones form larger blocks with a larger proportion of shapes that are more prone to rolling the size distribution of fragments is shown to be well approximated by a log normal statistical distribution and using the data provided in this study it is possible to generate the size and shape data needed to undertake a stochastic assessment of rockfall trajectories in different geological environments

field investigation and rockfall hazard zonation at the shijing mountains sutra caves cultural heritage china sutra inscriptions have been a main means for buddhistic monks to pass on their teachings nine sutra caves used to store about 5 000 pleromas carved during the sui dynasty of china more than 1 000 years ago were found in the shijing mountains close to beijing these sutra caves area have been affected by past failures and are subject to serious potential rockfall hazard from the relatively low rocky cliffs where caves are located the aim of this study was a preliminary assessment of rockfall hazard for this cultural heritage site to support the design of safe tourist paths the slope geometry has been surveyed by means of a laser profiler these slope profiles have been used for two dimensional distinct elements and rockfall simulations the volumes of more probably unstable rock blocks were measured in situ the results show that the runout distance ranges between 1 6 and 12 5 m affecting the most important tour route the rockfalls threaten the life safety of tourists walking around and waiting for visiting the sutra caves based on the analysis mentioned above a zonation map of runout distance was accomplished in the map the range between the release points of the potential rockfalls and the minimum runout distance is defined as the most dangerous zone the range between the maximum and the minimum runout distance is defined as danger zone the range beyond the runout distance is defined as a safe zone the map provides the guidance to the selection of safe tour routes at the scenic site finally to reduce the rockfall hazard remedial measures including rock bolts placement of an absorbing layer of loose material and flexible barriers are suggested

paleomagnetism of miocene sediments from the turfan basin northwest china no significant vertical axis rotation during neotectonic compression within the tian shan range central asia abstract paleomagnetic results are reported from 377 samples of miocene red sediments in the turfan basin of east tian shan northwest china thermal demagnetization for most specimens isolates a low temperature component that groups around the present geomagnetic field a high temperature characteristic component is isolated from four localities and interpreted as primary remanent magnetization from apparent pre folding origin and positive reversal test as for previous results obtained from tertiary rocks in central asia the magnetic inclination is significantly shallower than the reference field computed from the eurasian apw path at 10 and 20 ma magnetic susceptibility measured in 324 specimens exhibits low anisotropy of less than 1 05 for 80 of the sample the low anisotropy degrees ams shape and orientations suggest that the studied rocks are unlikely to have undergone significant strain during compaction or tectonism we argue that the shallow inclination is likely to result from an initially shallow detrital remanent magnetization comparison of the paleomagnetic declination from eurasia north china and tarim suggests that the turfan basin has been subjected to little or no vertical axis rotation since the miocene together with paleomagnetic declinations on both sides of the talas ferghana fault we propose that the tian shan to the east of the talas ferghana fault has remained relatively stationary with respect to adjacent blocks since the miocene

paleomagnetism of the yuanmou basin near the southeastern margin of the tibetan plateau and its constraints on late neogene sedimentation and tectonic rotation abstract new paleomagnetic investigation was carried out on the late neogene fluviolacustrine sequence of the yuanmou basin located near the southeastern margin of the tibetan plateau magnetostratigraphic results indicate nine reverse magnetozones r1 to r9 and eight normal magnetozones n1 to n8 in the sedimentary profile which can be correlated to the geomagnetic polarity timescale from c3n 3r to c1r 1r the age of the sedimentary sequence of the yuanmou basin can thus be paleomagnetically constrained to an interval from early pliocene to pleistocene with sedimentation rates varying from 12 5 to 55 cm kyr in addition to its highly resolved magnetostratigraphic sequence the yuanmou basin provides a record of plio pleistocene tectono and climato sedimentary processes the mean declinations of the seventeen polarity units excluding samples with transitional directions can be grouped into three distinct directional intervals group i 2 58 1 37 ma group ii 4 29 2 58 ma and group iii 4 91 4 29 ma these directions indicate that the yuanmou basin has probably experienced vertical axis clockwise rotation of about 12 from 1 4 ma to 4 9 ma which may be related to slip activity of the red river fault to the southwest and the xianshuihe xiaojiang fault to the east

large river offsets and plio quaternary dextral slip rate on the red river fault yunnan china using multispectral spot images and 1 100 000 topographic data we present an improved map of the active red river fault zone between midu yunnan china and hanoi vietnam the fault zone is composed of parallel strands one of which the yuanjiang fault was previously undetected there also appears to be a component of extension all along the fault zone such extension increases toward the se from yunnan to the south china sea coast and the vector describing the motion of south china relative to indochina points within the n45 135 e quadrant we attempt to assess the plio quaternary dextral slip rate on the red river fault rrf by restoring large river offsets and searching for the largest plausible one across much of yunnan the fault is perpendicular to local catchments that drain into the red river from precise mapping of the river courses on spot satellite images and on 1 100 000 topographic maps numerous multiple offsets along the fault can be detected and reconstructed the lack of correlation between the apparent offsets and the lengths of the rivers upstream from the fault suggests either that the drainage system was in large part established prior to the onset of dextral slip along the fault or that frequent captures have occurred we thus try to find the best fit between series of river channels upstream and downstream from the fault by progressively restoring the dextral displacement in increments of 500 m up to an offset of 50 km for each increment we measure the misfits root mean squares rms between the upstream and downstream channels the best fit and smallest rms are obtained for an offset of 25 0 5 km that we interpret to represent the clearest large right lateral displacement recorded in the geomorphology along the active red river fault since dextral motion is likely to have started around 5 myr the most probable average plio quaternary slip rate on the fault is of order of 5 mm yr we attribute the apparent lack of seismic activity on a large stretch of the fault to millennial recurrence times between great earthquakes our study shows that relatively small drainage systems can keep a good record of fairly large cumulative fault offsets

paleomagnetism of the jianshui basin in yunnan sw china and geomorphological evolution of the yunnan plateau since the neogene abstract there are still a lot of uncertainty on the process of the tibetan plateau uplift and the response of the yunnan plateau in the cenozoic in order to have a further understanding on the yunnan plateau uplift process we combine the studies on the sedimentary history of the jianshui basin and other basins and faults in the yunnan plateau we established magnetostratigraphy for the wanyao wy and qingyunshuiku qs fluviolacustrine sections in the northern and middle parts of the jianshui basin which indicates eight reverse magnetozones r1 r8 and seven normal magnetozones n1 n7 correlating to chrons c1r 3r through c3n 2r the strata are constrained to a span from 4 77 to 1 73 ma representing an early pliocene to early pleistocene age the accumulation rate of the wy section has accelerated trend stopping deposit earlier than the qs section the stratigraphic characteristics of the two sections and their nearby regions indicate the shiping jianshui sj and xiaojiang faults have already existed and affected the accumulation of the basin at least since the early pliocene according to the history of faults activities and the sedimentary strata of basins we established the geomorphological evolution process of the yunnan plateau since the neogene

rockfall induced block propagation on a soil slope northern italy this paper reports the field evidence and the kinematical study of the motion of two blocks a and b mobilised by a rockfall in lavone valtrompia northern italy on 14 february 1987 the two sequences of impact marks left by the blocks on the ground surface were measured and the lithostratigraphical features of the debris slope were surveyed on the basis of the field collected input data several computer simulations were carried out to calculate the coefficients of restitution e satisfying the trajectory conditions the computed output values show that rebound trajectories require high coefficients of restitution 0 8 e 0 9 back calculated impact velocities range from 9 2 to 19 8 m s trajectory heights vary from 0 to 2 4 m above the slope surface block trajectories differ considerably according to the circumstances of initial air projection i e to initial rebound angle r the calculated values of r denote a considerable range 36 emphasising the random nature of this parameter the described case history shows that rockfall computer analyses can be an effective tool to describe the bouncing propagation of single blocks but care must be taken in choosing the restitution coefficient e and the geometrical parameters of initial air projections

mineral magnetic variation of the jiaodao chinese loess paleosol sequence and its bearing on long term climatic variability 1 to retrieve reliable long term paleoclimatic signals from the chinese loess paleosol sequences deposited over the past 2 6 myr multiparameter mineral magnetic investigations have been conducted on the jiaodao section on the chinese central loess plateau first the lithogenic magnetic components and the pedogenic overprinting were chemically separated by the citrate bicarbonate dithionite cbd method the magnetic properties of the least pedogenically altered loess units and post cbd loess paleosols are dominated by coarse grained lithogenic magnetite increasing degree of pedogenesis increases both the concentration and grain size of pedogenic magnetite maghemite long term changes of the pre cbd magnetic properties suggest a long term decrease in summer monsoon intensity and a long term increase in winter monsoon intensity from the late pliocene to the late pleistocene long term variations of the post cbd magnetic properties suggest an increase in both concentration and grain size of coarse grained lithogenic psd md magnetite grains and hence indicate a long term increase in winter monsoon intensity over that period the coercivity decrease of the lithogenic component for the loess unit l15 may be related to the accelerated uplift of the tibetan plateau and its adjacent regions during the period of l15 deposition from paleosol s5 to loess l1 higher values of coercivity of the lithogenic component occur in typical loess and paleosols and lower values are found at the loess paleosol transition these coercivity variations are thought to be related to significant changes in the source region as well as dust deposition in the loess plateau caused by changes in ice snow or vegetational cover these new results lead to a better understanding of the relationships between the effects of tectonic paleoclimatic and paleoenvironmental processes in northwestern china

oligo miocene magnetostratigraphy and rock magnetism of the xishuigou section subei gansu province western china and implications for shallow inclinations in central asia magnetostratigraphy of 222 remanent directions together with late oligocene to early miocene mammal and charophyte paleontology suggest that 2179 m of the xishuigou section subei gansu province china were deposited from 26 to 19 ma stratigraphic patterns of bulk susceptibility anisotropy of magnetic susceptibility parameters and natural and anhysteretic remanent magnetization intensities demonstrate that 1 faulting does not significantly affect the record 2 sediment deposition was relatively continuous 3 sediment source changed around 23 ma and 4 rapid uplift near subei occurred at 21 ma subei rotated 27 5 counterclockwise with respect to the 20 ma pole from the eurasian synthetic apparent polar wander path folding and rotation of the section took place after 19 ma the paleolatitude of subei is 14 less than at present and 19 3 less than predicted from the reference pole both rock magnetic and paleomagnetic data sets suggest that the unusually low paleolatitude is the result of synsedimentary inclination shallowing a phenomenon which has likely affected other paleomagnetic data from central asia

a new late cretaceous to present apwp for asia and its implications for paleomagnetic shallow inclinations in central asia and cenozoic eurasian plate deformation based on a compilation of 533 cretaceous to present day palaeomagnetic poles obtained from both sedimentary and igneous rocks we present a new analysis of the so called asian inclination anomaly and demonstrated the anomaly to be twofold a 2nd order anomaly characterized by high palaeolatitudes in indochina and low palaeolatitudes over tibet and central asia is superimposed on a 1st order anomaly characterized by cenozoic low palaeolatitudes found all over northeastern asian stable blocks the analysis herein convincingly shows that the europe apparent polar wandering path apwp can no longer be used to interpret palaeomagnetic data east of the urals including interpretation of asian tertiary deformation related to the india asia collision we thus construct a new apwp for east asia based on palaeopoles from blocks assumed to be stable this new apwp is consistent with and reinforces previous analyses of asian tectonics such as the age 55 ma and locus 5 10 n of the indo asian collision the lateral extrusion of se asian continental blocks and the intracontinental shortening in central asia possible origins of the 1st order palaeolatitude anomaly are 1 a geomagnetic origin due to long lasting non dipolar contribution to the magnetic field and 2 a tectonic hypothesis in which a newly defined east asia plate was located 10 farther south than expected from the current europe apwp based on a set of six new reconstructions from 90 ma to present we show that our tectonic model reconciles geophysical geological and tectonic observations throughout eurasia from siberia to europe including kinematics in the arctic ocean up to northwestern arctic alaska beyond possible occurrences of non dipolar field contribution and or local inclination flattening in the sedimentary data our model leads us to conclude that cenozoic tectonics is the dominant contributor to the observed 1st order 10 low palaeolatitude anomaly over asia during the tertiary

oligocene deformation of the chuandian terrane in the se margin of the tibetan plateau related to the extrusion of indochina mechanisms driving the tectonic evolution of the southeast se margin of tibet include the paleogene extrusion of the coherent indochina lithospheric block and the continuous deformation caused by lower crustal flow since the middle miocene the timing and style of regional deformations are key to determining the role of each mechanism fault bounded and controlled cenozoic basins within the se margin of tibet record regional deformation surface uplift and variations in paleoclimate but often are poorly dated new magnetostratigraphy and 40ar 39ar dating of volcanic ashes constrain precisely the timing of sedimentation within the luhe basin to between 35 and 26 5 ma the basin is located in the chuandian terrane along the chuxiong fault which lies 70 km north of and parallel to the ailao shan red river fault the asymmetric syncline of the luhe basin suggests syn contractional sedimentation and the basal age of the basin represents the initiation of the chuxiong fault and crustal shortening at 35 ma this is coincident with the onset of the ailao shan red river fault and supports a kinematic link between them our study suggests that like the ailao shan red river fault the chuxiong fault is a paleogene transpressional structure that developed during the extrusion and clockwise rotation of indochina around the eastern himalayan syntaxis which caused the late paleogene deformation and surface uplift of the chuandian terrane and indochina our revised chronostratigraphy of the luhe basin provides further evidence that many of the neogene sedimentary basins in the se margin of tibet may be much older than previously thought

the role of maghemite in the enhancement of magnetic signal in the chinese loess paleosol sequence an extensive rock magnetic study combined with citrate bicarbonate dithionite treatment we have conducted a rock magnetic study of selected chinese loess samples before and after citrate bicarbonate dithionite cbd treatment our study is more extensive than previous ones and reveals new details of the magnetic carriers which are related to paleoclimate change three pairs of paleosol s1 the top paleosol layer in the lishi formation and loess l2 underlying s1 from three localities xining xifeng and jixian were investigated by using a variety of magnetic methods after the paleosols were treated with cbd which removes all maghemite grains and the finest grains of magnetite magnetic susceptibility decreased from 77 10 8 to 20 10 8 m3 kg in xining from 165 10 8 to 30 10 8 m3 kg in xifeng and from 180 10 8 to 25 10 8 m3 kg in jixian anhysteretic remanent magnetizations arm were reduced to less than one tenth of the original values in the three sites and saturation magnetization js decreased by about 60 in xining and 70 in xifeng and jixian these reduced values in the paleosols after cbd treatment are similar to those of the corresponding underlying loess samples which however did not show significant decrease after cbd treatment room temperature frequency dependence of susceptibility high temperature dependence of susceptibility and low temperature sirm demagnetization of the paleosol and loess samples before and after cbd treatment confirm that in addition to superparamagnetic sp particles magnetite and or maghemite the cbd removable magnetic carriers also include maghemite of grain sizes larger than sp

geological and geomorphic evidence for activity of the mengzi fault along the southeastern margin of the tibetan plateau abstract few studies have been conducted on the activity of the mengzi fault system which is located to the southeast of the sichuan yunnan block the mengzi fault is distributed along the eastern margin of the mengzi basin however little is known about the location length and activity of the fault or the occurrence of paleo earthquakes during the late quaternary this paper studies the geometric distribution and activity of the fault via remote sensing imagery interpretation fault outcrops in the area faulted landforms and chronological analyses the results show that the mengzi fault extends from nandong kaiyuan basin in the north through the eastern margin of the mengzi basin to pingbian in the southeast eventually intersecting with the honghe fault the mengzi fault is approximately 250 km long and is characterized as a reverse strike slip fault we survey and calculate the offset gullies and terraces dislocated by the fault combined with sample dating we calculate the horizontal slip rate of the fault since 30 ka bp to be 0 91 1 56 mm a three paleo events since 30 40 ka bp are observed with a 10 ka major earthquake recurrence period we analyze the relationships among the mengzi fault southern xiaojiang fault and qujiang jianshui fault and note a slip rate loss of 8 mm a from the southern xiaojiang fault that was absorbed by reverse dextral strike slip faulting and lateral shortening of the qujiang jianshui fault and the mengzi fault the mengzi fault plays an important role in the adjustment of the large slip rate reduction along the southern xiaojiang fault moreover the mengzi fault has a similar tectonic position to the seismogenic faults of the 2008 wenchuan earthquake 2013 lushan earthquake and 2014 ludian earthquake and the mengzi fault and southern xiaojiang fault both accumulate the energy generated by the southeastward movement of the sichuan yunnan block studies on the mengzi fault are helpful for renewing our understanding of the tectonic patterns of the southeastern sichuan yunnan block and delimiting the boundary of the southeastern block margin furthermore because the cities of mengzi and kaiyuan are located along the mengzi fault this study has practical significance for earthquake disaster mitigation

meteorites from the united arab emirates description weathering and terrestrial ages we report on the first meteorite search campaign in the united arab emirates uae the geology and proximity of our search region suggest that it is the north western extension of the oman meteorite fields we found 26 ordinary chondrites bringing the total number of official meteorites from the uae to 28 the campaign was organized and conducted in close cooperation with the uae government and the main masses of the meteorites remained in the country where they will become part of an exhibition the bulk composition of five meteorite and three soil samples indicates an uptake of u mo sr ba li and pb from the soil into the meteorites during terrestrial weathering terrestrial ages determined from 14c decay of 21 meteorites range from recent falls to 24 4 ka with two meteorites having 37 ka and approximately 39 ka respectively weak correlations between weathering degree meteorite bulk chemical composition and terrestrial age suggest highly localized weathering conditions possibly related to abundant occurrences of sabkhas in the search region

pliocene uplift of the northern tibetan plateau neogene redbeds passing upward into upward coarsening conglomerate and debris flow deposits at the foot of the kunlun mountains record the change in paleoslope related to uplift of the surface of the northern tibetan plateau detailed magnetostratigraphy of a 4 5 km section near yecheng in the western kunlun mountains shows that the change from deposition on distal alluvial plains to proximal alluvial fans occurred during the gilbert reversed chron 4 5 3 5 ma the change in depositional facies was accompanied by an increase in sedimentation rate from an average 0 15 mm yr between the earliest oligocene and the earliest pliocene to 1 4 mm yr in the gauss normal chron 3 6 2 6 ma we interpret the change in depositional facies and increase in sedimentation rate as indicating that the main uplift of the northwestern tibetan plateau began ca 4 5 ma

normal faulting in central tibet since at least 13 5 myr ago tectonic models for the evolution of the tibetan plateau interpret observed east west thinning of the upper crust to be the result of either increased potential energy of elevated crust1 or geodynamic processes that may be unrelated to plateau formation2 3 4 5 6 a key piece of information needed to evaluate these models is the timing of deformation within the plateau the onset of normal faulting has been estimated to have commenced in southern tibet between about 14 myr ago7 and about 8 myr ago8 and in central tibet about 4 myr ago9 here however we report a minimum age of approximately 13 5 myr for the onset of graben formation in central tibet based on mineralization ages determined with rb sr and 40ar 39ar data that post date a major graben bounding normal fault these data along with evidence for prolonged activity of normal faulting in this and other tibetan grabens support models that relate normal faulting to processes occurring beneath the plateau thinning of the upper crust is most plausibly the result of potential energy increases resulting from spatially and temporally heterogeneous changes in thermal structure and density distribution within the crust and upper mantle beneath tibet this is supported by recent geophysical and geological data10 11 12 13 14 15 16 17 which indicate that spatial heterogeneity exists in both the tibetan crust and lithospheric mantle

paleomagnetic age of the tangxian planation surface northwestern zhongtiao shan of the shanxi graben system north china abstract a numerical formation age for the tangxian planation surface txps in north china is still controversial the txps beveled across paleoarchean basement rocks is overlain by late cenozoic conglomerate aeolian red clay and loess the magnetostratigraphy of two late cenozoic deposition sections is established and two other sections are recorded and measured in this work the magnetostratigraphy indicates six normal magnetozones n1 to n6 and six reverse magnetozones r1 to r6 these magnetozones are correlated to chron c1n through c2an 1r indicating that the txps was formed at 3 12 3 03 ma the characteristics of the zhongtiao shan tectonic uplift and its relationship with the tibetan plateau and ordos block are discussed in terms of tectonic uplift the txps formation and accumulation of the late cenozoic sediments are mainly controlled by tectonic activities the formation and uplift of the txps with a lag in the shanxi graben system is consistent with the activities of the tibetan plateau and ordos block implying that the ne extension of the tibetan plateau epeirogenic uplift advances successively

geochronology of the baye mn oxide deposit southern yunnan plateau implications for the late miocene to pleistocene paleoclimatic conditions and topographic evolution 40ar 39ar laser incremental heating analyses of supergene k mn oxides from weathering profiles at the baye mn deposit southern yunnan plateau sw china were carried out to place constraints on the timing of weathering and derive insights into local paleoclimatic and landscape evolution weathering profiles in the baye mn mine are dominated by 20 30 m thick saprolites which are locally covered by unconsolidated alluvial deposits we analyzed 70 grains from 35 hand samples collected from four sites located at distinct elevations in most cases different grains from the same hand sample and different samples from the same site have reproducible 40ar 39ar plateau ages the plateau ages of individual grains are also consistent with the respective isochron integrated and ideogram ages this age consistency attests to the reliability of the geochronological results as numerical constraints on the formation and evolution of these weathering profiles sixty four grains from 32 hand samples collected from weathering profiles at four sites a to d yield well defined plateau or pseudoplateau ages ranging from 2 98 0 07 to 0 16 ma 2 the age results show that mn oxides become progressively younger towards lower elevations samples collected from the highest elevation site 1855 m a s l have the oldest ages at 2 98 0 07 to 2 83 0 13 ma samples from intermediate elevations 1821 to 1815 m a s l yield ages ranging from 2 91 0 10 to 2 08 0 11 ma and those from the lowest sites 1768 to 1753 m a s l are younger than 1 25 0 08 ma the age versus elevation relationship indicates fast downward propagation of weathering front since the late pliocene and permits estimating the weathering rates at 3 3 3 8 6 6 1 2 and 11 1 1 9 m myr 1 during the time periods of 2 98 2 83 2 91 2 08 and 1 25 to 0 16 ma respectively the average river incision rates estimated from the surface exposed ages range from 235 10 to 416 19 m myr 1 during the past 3 million years the incision rate calculated from minimum exposed ages at sites b d is 33 2 m myr 1 for the time period of 2 91 1 25 ma which is consistent with the slow incision of streams on the ridges over the yunnan plateau since the early pleistocene three mn oxide pebbles contained in the alluvial deposits overlying the saprolite dominated weathering profiles at the two highest sites provided additional information on the timing of weathering four grains from two pebbles yield plateau ages of 6 32 0 19 to 5 27 0 10 ma whereas the other two grains from the third pebble indicate the minimum formation ages of 8 2 0 4 and 9 3 0 3 ma these ages confirm the existence of older weathering profiles now dismantled in the region manganese oxide 40ar 39ar ages of the baye deposit when combined with results from other localities indicate that lateritic weathering and supergene mn enrichment and by inference warm and humid climates conducive to intense weathering have prevailed over the plateau since the middle to late miocene the climatic conditions inferred from the weathering geochronology are consistent with multiple independent marine and terrestrial sedimentary and paleontological records confirming that supergene mn oxides can be used as a useful proxy for past climate age clusters of mn oxides at 2 9 2 4 1 2 0 8 and 0 6 0 4 ma are broadly coincident with and thus likely reflect intensification events of the indian summer monsoon that brings moisture and abundant precipitation to the yunnan plateau these clusters also coincide with the periods of significant surface uplift in the yunnan plateau demonstrating a causal link between topographic evolution plateau uplift and intensification of the monsoonal climate

rockfall rebound comparison of detailed field experiments and alternative modelling approaches the accuracy of rockfall trajectory simulations mainly rests on the calculation of the rebound of fragments following their impact on the slope this paper is dedicated to the comparative analysis of two rebound modelling approaches currently used in rockfall simulation using field experiments of single rebounds the two approaches consist in either modelling the rock as a single material point lumped mass approach or in explicitly accounting for the fragment shape rigid body approach a lumped mass model accounting for the coupling between translational and rotational velocities and introducing a slope perturbation angle was used a rigid body approach modelling the rocks as rigid locally deformable in the vicinity of the contact surface assemblies of spheres was chosen the comparative analysis of the rebound models shows that both of them are efficient with only a few parameters the main limitation of each approach are the calibration of the value of the slope perturbation roughness angle for the lumped mass approach and the estimation of the rock length and height from field geological and historical analyses for the rigid body approach finally both rebound models require being improved in a pragmatic manner to better predict the rotational velocities distribution copyright 2012 john wiley sons ltd

geotechnical characterization and rockfall simulation of a slope a practical case study from south tyrol italy abstract rockfalls occur often along the state road ss241 val d ega in the val d ega valley south tyrol italy in order to protect the road and the traffic stabilization works are necessary detailed geological and geomorphologic mapping along structural and geomechanic sections was carried out and experimental rockfall trails were examined on the slope above the state road between km 3 550 and 3 830 rockfall simulation rock mass classification and an interpretation of field data especially concerning joints wrapped up the investigations they helped find the specific need for stabilization work and its positioning along the slope the stabilization works were completed on february 2002 another important aspect concerns ongoing geotechnical investigations and stabilization works urgently realised during autumn 1999 this paper is a practical approach in solving rockfall problems along public roads it should be considered as a workbook for university personnel and also for professional geologists

late neogene structural inversion around the northern gulf of tonkin vietnam effects from right lateral displacement across the red river fault zone continental extrusion may take up much of the deformation involved in continental collisions major strike slip zones accommodate the relative extrusion displacement and transfer deformation away from the collision front the red river fault zone rrfz accommodated left and right lateral displacements when indochina and south china were extruded during the indian eurasian collision the northern song hong basin onshore and offshore in the gulf of tonkin delineates the direct extension of the rrfz and thus records detailed information on the collision induced continental extrusion we assess the rapidly evolving kinematics of the fault zone buried within the basin based on seismic analysis contrary to previous studies we do not identify indications for latest miocene left lateral motion across the rrfz we tentatively consider the shift from left to right lateral motion to have occurred already during the middle late miocene as indicated by inversion of ne sw striking faults in the bach long vi area right lateral displacement terminated around the end of the miocene in the song hong basin however continued inversion in the bach long vi area and nnw sse striking normal faulting suggests a stress regime compatible with right lateral motion across the onshore part of the rrfz continuing to the present inversion around the bach long vi island may have accommodated up to a few kilometers of right lateral displacement between the indochina and south china blocks comparable ne sw striking fault zones onshore may have accommodated a larger fraction of the right lateral slip across the rrfz thus accounting for the restricted transfer of lateral displacement to the offshore basins

alternating field demagnetization single domain like memory and the lowrie fuller test of multidomain magnetite grains 0 6 356 μm 1 a fundamental question in paleomagnetism is how magnetite grains much larger than single domain size preserve stable remanence over millions of years in an effort to answer this question we measured alternating field af demagnetization of thermoremanent magnetization trm and saturation isothermal remanent magnetization sirm before and after low temperature demagnetization ltd ltd zero field cycling through 120 k unpins or nucleates domain walls reducing the remanence of multidomain grains we used two sets of sized crushed magnetites 0 6 1 3 6 9 14 20 110 and 135 m one set unannealed and the other annealed and a set of hydrothermally grown magnetites 0 8 6 3 25 64 94 and 356 m for all sizes trm and sirm memories after ltd are much harder to af demagnetize than the original remanences af demagnetization curves after ltd are flat for the first 10 mt such initial plateaus are one hallmark of single domain behavior in high stress unannealed grains after ltd response depends on grain size larger grains demagnetizing more easily than smaller ones in low stress annealed and hydrothermal magnetites after ltd response is almost independent of grain size over nearly 3 decades in grain size this size independent behavior could be due to grains in metastable single domain states in the smaller sized samples but in 100 m grains there must be a source of single domain like af behavior within the multidomain grains themselves we propose an ad hoc model in which ltd triggers domain wall unpinning and nucleation events up to a coercivity threshold producing the observed initial plateaus in af demagnetization curves of trm and sirm memories the size independent demagnetization behavior of memory in hydrothermal and annealed magnetites is ascribed to nucleation events above the threshold level and the additional size dependent af demagnetization of memory in high stress unannealed grains is explained by wall unpinning from strong stress centers in both cases the af properties merely mimic single domain behavior although ltd memory has single domain like af curves and erased remanence has multidomain like curves in grains of all sizes the lowrie and fuller 1971 test still works for the annealed samples for memory erased fraction and pre ltd remanence alike trm is more stable than sirm in fine grains 1 m less stable in large grains 135 m and of comparable stability in medium size grains 9 and 20 m