the alashan terrane did not amalgamate with north china block by the late permian evidence from carboniferous and permian paleomagnetic results abstract rock magnetic and paleomagnetic studies have been carried out on the early carboniferous limestones and the late permian purple sandstones sampled in the eastern alashan terrane alt northwest of china two components were isolated from the early carboniferous limestone by thermal progressive demagnetisation a low unblocking temperature component ltc of recent origin a pre folding medium temperature component mtc the paleomagnetic pole is 13 1 n 11 0 e a 95 7 0 that is probably the result of the hydrothermal fluids from the qilian orgenic belt acquired during the late carboniferous early permian also two components were separated from the late permian purple sandstone by thermal progressive demagnetisation the ltc with the recent viscous remanent magnetisation and the higher temperature component htc revealed from three sections which has passed a regional fold test at the 95 probability level and reversal test suggesting a primary characteristic magnetisation the corresponding paleomagnetic pole is 27 2 n 18 8 e a 95 12 0 the apparent polar wander path including early carboniferous late carboniferous early permian late permian and early middle triassic poles of the alt is significantly different with those of the ncb comparison of the apwps between the alt and ncb shows a strong similarity if the apwp of hexi corridor alashan rotated counterclockwise around an euler pole at 44 n 84 e by 32 then the coeval apw path of the alt overlaps to that of the ncb this result indicates that the alt migrated to the ncb after the early middle triassic along a tectonic boundary located between helanshan mountain and zhuozishan mountain and finally amalgamated to the ncb before the early cretaceous

new silurian and devonian palaeomagnetic results from the hexi corridor terrane northwest china and their tectonic implications summary a total of 239 orientated drill core samples from 23 sites were collected for palaeomagnetic study from silurian and devonian red beds marlaceous sandstone and limestone rocks in the eastern part of the hexi corridor southwest ningxia north china the characteristic high temperature component resides in both haematite and magnetite it clusters around a northwesterly and shallow to moderate downward direction and its antipode after tilt correction the primary origin of this characteristic remanent magnetization chrm is ascertained by positive fold and reversal tests at the 95 per cent confidence level the corresponding palaeopoles at 339 0 e 60 1 n with a 95 11 2 silurian and 336 0 e 56 0 n with a 95 9 2 devonian imply that the north china block ncb had a low palaeolatitude of around 15 n in the northern hemisphere during the silurian devonian period comparison with the early middle ordovician palaeopole of the ncb suggests that the ncb moved rapidly northwards by 30 8 10 9 to cross the palaeo equator during the early middle ordovician to silurian in combination with the palaeobiogeographical data from ningxia our palaeomagnetic results suggest that the ncb was located close to australia during the late devonian

further evidence for inclination shallowing in red beds red beds and related shallow marine siliciclastic sediments within the extensional catalan neogene basins offer a unique opportunity to study the relationship between sediment anisotropy remanence acquisition and inclination shallowing on the basis of the dominant fabric features sedimentary facies are grouped into laminated massive and bioturbated the bulk susceptibility appears to be dominated by paramagnetic phyllosilicates and clay minerals the magnetic susceptibility fabric is dominantly foliated while the degree of anisotropy is very variable and is dependent on the facies type strong foliation dominates in the laminated sediments whereas weak anisotropy characterizes the bioturbated and massive mass flow facies moreover we observe a correlation between facies type and remanence inclination the undisrupted thinly laminated facies provides the most biased inclination values 20 as opposed to 60 of the expected geomagnetic field steeper inclinations are reported from bioturbated muds while the best record of the geomagnetic inclination is found in the weakly anisotropic mass flow deposits

late cretaceous paleomagnetic results from southeastern china and their geological implication abstract a paleomagnetic study was carried out on late cretaceous red beds in central jiangxi province southeastern china stepwise thermal demagnetization was used to isolate the characteristic higher temperature component htc from the jishui d 355 7 i 34 8 95 6 3 and ganzhou d 15 6 i 35 6 95 5 5 areas respectively the htc direction from the jishui area passes enkin s fold test at 95 confidence level and indicates an 18 9 5 5 counter clockwise rotation relative to the referent pole of the stable south china block scb the htc direction from ganzhou passes both mcfadden s fold test at 95 confidence level and reversal test comparing these two new poles 81 0 n 322 2 e a95 5 8 from jishui and 74 4 n 225 1 e a95 5 2 from ganzhou with other coeval poles reported from south china these results demonstrate a significant difference in paleolatitude 9 9 4 1 between coastal and inland areas which might be either related to dextral shearing faulting between them or inclination shallowing conducted by sedimentation and or compaction however results obtained from both anisotropy of the isothermal remanence air method and corrected results of the elongation inclination model of tauxe and kent l tauxe d v kent a simplified statistical modal for the geomagnetic field and the detection of shallow bias in paleomagnetic inclinations was the ancient magnetic field dipolar in j e t channell d v kent w lowrie j meert eds timescales of the paleomagnetic field geophys monogr am geophys union 145 2004 101 115 indicate that a distinct inclination flattening occurred in our samples

paleogene clockwise tectonic rotation of the xining lanzhou region northeastern tibetan plateau 1 to help understand the deformational history of the northeastern tibetan plateau paleomagnetic samples were collected from 177 sites and two magnetostratigraphic sections at 16 localities distributed among upper jurassic lower cretaceous to pliocene sedimentary and subordinate volcanic rocks within the xining lanzhou region 34 37 n 101 105 e a total of 127 sites at 12 localities yielded primary magnetizations confirmed by fold reversal and conglomerate tests age control on sedimentary rocks is provided by regional synthesis of chronostratigraphic data and our own biostratigraphic and magnetostratigraphic analysis presented in the companion paper by horton et al 2004 analysis of paleomagnetic declination combined with results from previous studies yield a remarkably consistent trend of vertical axis tectonic rotations across the studied region whereas 19 0 7 2 to 37 8 10 6 clockwise rotations are recorded consistently in all paleomagnetic localities in lower cretaceous to eocene rocks all paleomagnetic localities in oligocene to pliocene rocks have recorded minor to insignificant rotations indicating that the xining lanzhou region has undergone a wholesale regional clockwise rotation during late paleogene time consistent with regional chronostratigraphic and thermochronologic results this late paleogene tectonic rotation confirms that deformation reached regions of the northern tibetan plateau shortly after the initial collision of india with asia when compared to rotational paleomagnetic results from adjacent regions several mechanisms can be proposed to explain the clockwise rotation on the basis of consistency with geologic data we prefer a model involving clockwise rotation of the xining lanzhou region through right lateral shear and associated shortening related to northward indentation of the qaidam basin index terms 1525 geomagnetism and paleomagnetism paleomagnetism applied to tectonics regional global 8102 tectonophysics continental contractional orogenic belts 9320 information related to geographic region asia 9604 information related to geologic time cenozoic keywords tectonics paleomagnetism tibetan plateau

paleomagnetic constraints on the tectonic relationship between the alashan hexi corridor terrane and the north china block we report paleomagnetic results for early middle ordovician limestone rocks from the eastern part of the hexi corridor northwest china the characteristic high temperature component b isolated from 74 out of 114 samples exhibited dual polarity and passed the fold and reversal tests at the 95 confidence level the corresponding paleopole at 326 5 e 31 8 n with a95 9 5 is in agreement with the coeval poles from the stable north china block ncb it implies that the alashan hexi corridor ahc terrane was part of the ncb since the early middle ordovician which is consistent with geological evidence the silurian and devonian paleomagnetic results from the ahc terrane may therefore be used to discuss the middle paleozoic tectonic displacement and paleogeographic reconstruction of the ncb

landslide movement in southwest colorado triggered by atmospheric tides the slumgullion landslide in the western united states has been moving almost continuously for over 100 years observations and numerical modelling show that air pressure changes from atmospheric tides trigger daily movement

seasonal reversals in groundwater flow direction and its role in the recurrent agwagune landslide problem a geophysical and geological appraisal the character of the shallow subsurface materials in the landslide and flood prone agwagune community has been investigated using geophysical electrical resistivity geological and geotechnical techniques arising from the continuous suffering of the people in the affected areas high occurrence rate and the desire to characterise the surficial materials two dimensional resistivity tomography vertical electrical sounding soil sampling and hydrodynamic monitoring were conducted results show that the surficial materials are dominated by two main lithologic units thin sandy materials with resistivity 30 m and thick argillaceous materials with resistivity 30 m particle size analyses confirm the dominance of argillaceous silty clay 56 2 and very fine 55 3 over arenaceous 9 2 materials bulk and particle densities of the surficial materials vary from 0 99 103 to 1 40 103 and 2 06 103 to 2 50 103 kg m3 respectively ph ec and porosity range from 4 46 to 6 68 8 0 to 23 0 ms cm and 34 0 to 60 0 respectively atterberg limits vary from 15 82 to 38 70 for liquid limit and 18 10 24 00 for plastic limit plasticity index varies from 11 92 to 15 70 shallow groundwater in the coastal area is always in hydrodynamic equilibrium with water inside the cross and efefa rivers and pond fields to sustain this equilibrium condition excess water inside the cross river is usually discharged into efefa river through both surface and underground flow processes however when water inside the cross river dries up a new hydraulic gradient which distorts the existing equilibrium is formed this results in the reversal of groundwater flow direction continuous flow of groundwater into the cross river channel crc without any corresponding recharge results in the formation of voids which gravitational force forces to collapse the collapsed materials usually roll toward the crc resulting in landslides models illustrating the main cause of the repeated landslide problem and suggested measures to minimise its occurrence rate have been included

silurian and devonian paleomagnetic poles from north china and implications for gondwana abstract we have obtained paleomagnetic results from silurian and devonian rocks on the western margin of the north china block ncb ages which previously were thought to be unrepresented throughout north china high unblocking temperature components of magnetization isolated from both the silurian and devonian strata pass fold and reversal tests suggesting that they are primary remanence the corresponding paleopoles at 228 4 e 26 2 n silurian and 228 7 e 34 2 n devonian imply low paleolatitude positions of north china during the middle paleozoic probably adjacent to east gondwana

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

paleomagnetic constraints on the geodynamic history of the major blocks of china from the permian to the present paleomagnetic study of china and its environs has been the center of a major international effort for the last 10 years in this paper we critically review all available paleomagnetic poles of upper permian to tertiary age from the main blocks of china with the goal of placing constraints on models of the formation and the subsequent deformation of the region after selecting reliable poles by applying objective criteria we divide our analysis into first order motions of blocks and second order deformation within blocks for first order analysis apparent polar wander paths are constructed for the major blocks we discuss the compatibilities and contradictions between the geological and paleomagnetic records a sequence of paleogeographic configurations taking into account geological constraints but remaining within paleomagnetic uncertainties is presented in general the major blocks were probably in contact throughout the permian and triassic but the jurassic was the key age during which most of the movement toward china s present configuration took place our reconstructions include certain details which are suggested by the paleomagnetic record but whose geological signatures seem to have been hidden by subsequent events during the cretaceous chinese poles agree with poles from other continents transferred onto eurasia at the second order we observe that for almost each period with sufficient data the paleomagnetic poles are streaked along a small circle centered on the sampling region indicating that much of china has been affected by small 20 differential rotations this we interpret as deformation caused in part by the extrusion of the chinese blocks away from the indian collision the complete annotated list of poles is given as an appendix

large n s convergence at the northern edge of the tibetan plateau new early cretaceous paleomagnetic data from hexi corridor nw china abstract nine early cretaceous paleomagnetic sites have been collected in the yumen area of the hexi corridor nw china magnetic directions isolated at lower temperatures fail the fold test and lie close to the geocentric axial dipole field direction before tilt correction high temperature components are carried by magnetite and or hematite all with normal polarity and pass the fold test the average paleomagnetic pole from the nine sites is at 75 5 n 169 9 e a 95 7 7 these results are consistent with those from other areas of the north china block ncb but significantly different from those from the qaidam basin on the southern side of the qilian mountains they suggest that 1 the yumen region behaved as a rigid part of the ncb since at least the early cretaceous 2 740 500 km of north south directed convergence has taken place between the ncb and qaidam within the qilian mountains and 3 extrusion of qaidam was accompanied by a 23 5 relative rotation with respect to north china this is larger than implied by the maximum left lateral slip on the altyn tagh fault system the same data imply some 1000 800 km of cenozoic motion between the tarim and ncb blocks which were so far believed to have formed a rigid entity since at least the jurassic one interpretation could be that all tarim and qaidam cretaceous paleomagnetic samples from red beds but not those from yumen and the ncb suffered significant inclination shallowing as observed in cenozoic red beds from central asia so far we do not find support for this possibility possible tectonic interpretations include 1 the existence of a large as yet uncharted tectonic discontinuity between tarim and the ncb in the vicinity of the desert corridor near 95 100 e longitude 2 the occurrence of significant deformation within southwestern tarim to the north of yingjisha where paleomagnetic sites were obtained or 3 persistent clockwise rotation of tarim with respect to the ncb for at least 20 ma at the rate found for current block kinematics

a chronology of post glacial landslides suggests that slight increases in precipitation could trigger a disproportionate geomorphic response large deep seated landslides are common throughout the southeastern san juan mountains of colorado and new mexico but their timing and initiation are not well understood determining when the landslides occurred would aid in clarifying the mechanisms for initiating landslides in the region and would help us to understand post glacial landscape evolution we studied seven prehistoric landslides located within the tertiary volcanic rocks of the san juan volcanic field the landslides range in area from 0 8 km2 to 11 3 km2 and most are located in areas that were previously mapped as having been ice covered during the last glaciation landslide deposits were dated using a variety of methods including surface exposure dating 36cl radiocarbon dating of basal bog sediments and organic material buried in soils and relative soil development the resulting limiting ages range from approximately 14 ka to 2 ka and show that deep seated landsliding has occurred throughout the post glacial period this broad range in ages is inconsistent with our initial hypothesis which proposed that landslides were likely the result of debuttressing of glacial walls during glacial retreat furthermore the timing of landslides does not seem to correlate with documented post glacial climatic shifts therefore we conclude that landsliding in the region was the result of wetter than normal periods lasting months to years acting on weak bedrock pre conditioned to failure and prepared by glacial debuttressing our findings suggest that the study area is likely still susceptible to deep seated landsliding and may become even more prone to large scale slope failure if future climate change increases precipitation in the san juan mountains

internal kinematics of the slumgullion landslide usa from high resolution uavsar insar data abstract landslides represent one of the most damaging natural hazards and often lead to unexpected casualties and property damage they also continually modify our natural environment and landscapes knowledge of landslide systems is largely restricted by the stochastic nature subjective interpretation and infrequent or spatially sparse surveying of landslides characterized by persistent daily movements of a couple of centimeters over multi centennial timescales and a long narrow shape as long as 4 km the slumgullion landslide in colorado usa represents an ideal natural laboratory to study slow moving landslides here we demonstrate the capability of the highly accurate spatially continuous airborne synthetic aperture radar sar system of the nasa uninhabited aerial vehicle sar uavsar to characterize the kinematic details of internal deformation of the slumgullion landslide using sar interferometry insar we develop a phase based approach to automatically extract the boundaries of the mobile geological structures without unwrapping comparison with historic field observations from 1991 reveals the 40 m advance of the frontal toe and shift of an internal fault the uavsar data also resolve an internal minislide 100 by 70 m which moves more southerly than the main body at 5 mm day in the lower part of the landslide a light detection and ranging lidar digital elevation model dem shows that the minislide is associated with the opening of a 30 by 10 m pull apart basin and bounding strike slip faults these extensional structures nearby incised streams and steepened local slopes helped establish the kinematic environment for the formation of the secondary minislide the disparity between the uavsar insar derived horizontal moving directions and the lidar dem derived slope aspects suggest that while the surface topography governs the first order orientation the local kinematics is also subject to the variable nature of heterogeneous landslide materials and the irregular basal bedrock surface the landslide velocity and precipitation show similar multi annual variations our study demonstrates that the freely available high resolution uavsar data have great potential for characterizing landslide kinematics and other small scale geological and geomorphological processes

an examination of seasonal deformation at the portuguese bend landslide southern california using radar interferometry 1 the portuguese bend landslide located on the palos verdes peninsula in southern california is a slow moving landslide whose activity is closely tied to infiltration from rainfall we use radar interferometry to constrain the seasonal kinematics of the landslide from 1995 to 2000 traditional interferometric synthetic aperture radar methods estimate an average downslope displacement rate of 1 00 m yr with an uncertainty range of 0 39 2 57 m yr during the summer months interferograms show a consistent loss in phase coherence over the landslide for epochs greater than 6 months especially in the winter interferograms become incoherent as a result of large displacement and decorrelation is used to map the spatial extent of slide movement through time the displacement rate increases sharply several weeks after the beginning of the rainy season as rainwater percolating into the slide elevates pore pressures phase coherence is lost when the slide velocity surpasses 2 6 m yr for interferograms with durations of a few months a physically based model based on rainfall driven landslide movement incorporates these observations to constrain hydraulic diffusivity to between 0 9 and 3 5 10 6 m2 yr

historic drought puts the brakes on earthflows in northern california california s ongoing unprecedented drought is having profound impacts on the state s resources here we assess its impact on 98 deep seated slow moving landslides in northern california we used aerial photograph analysis satellite interferometry and satellite pixel tracking to measure earthflow velocities spanning 1944 2015 and compared these trends with the palmer drought severity index a proxy for soil moisture and pore pressure that governs landslide motion we find that earthflow velocities reached a historical low in the 2012 2015 drought but that their deceleration began at the turn of the century in response to a longer term moisture deficit our analysis implies depth dependent sensitivity of earthflows to climate forcing with thicker earthflows reflecting longer term climate trends and thinner earthflows exhibiting less systematic velocity variations these findings have implications for mechanical hydrologic interactions that link landslide movement with climate change as well as sediment delivery in the region

a view on some hydrological triggering systems in landslides abstract in this paper different types of hydrological triggering systems for debris flows shallow and deeper landslides are described the generation of surface run off and high peak discharges in first order alpine catchments is an important triggering mechanism for debris flows failure conditions in shallow landslides can occur when at a critical depth which is determined by the cohesion of the soil and the slope angle the moisture content in the soil becomes close to saturation resulting in a considerable reduction of soil strength deeper landslides 5 20 m depth are in most cases triggered by positive pore pressures on the slip plane induced by a rising ground water level the assessment of meteorological threshold conditions for shallow landslides 1 2 m needs more detailed meteorological information than for deeper landslides in the analyses of the hydrological triggering systems of deeper landslides the presence of a permeable top layer and fissures has to be taken into consideration

deciphering the effect of climate change on landslide activity a review abstract increased landslide activity is commonly listed as an expected impact of human induced climate change this paper examines the theoretical and empirical bases for this assertion it identifies the mechanisms by which climate can induce landsliding and examines the manner in which these mechanisms may respond to changes in a range of climatic parameters it is argued that inherent limiting stability factors which vary with different terrain conditions and landslide types ultimately govern the nature of response to changing climate several modelling approaches are evaluated on the basis of their potential to predict landslide response to climate projections given reliable input data of appropriate form and resolution the existing slope stability hydrological and statistical models are for the most part capable of yielding useful prognoses on occurrence reactivation magnitude and frequency of landsliding while there is a strong theoretical basis for increased landslide activity as a result of predicted climate change there remains a high level of uncertainty resulting from the margins of error inherent in scenario driven global climate predictions and the lack of sufficient spatial resolution of currently available downscaled projections examples from new zealand are used to illustrate the extent to which changes resulting from human activity have affected slope stability changes resulting from human activity are seen as a factor of equal if not greater importance than climate change in affecting the temporal and spatial occurrence of landslides

new early and late carboniferous paleomagnetic results from the qaidam block nw china implications for the paleogeography of central asia abstract there is an ongoing debate regarding the paleogeographic evolution of the qaidam block 37 3 n 96 4 e in northwest china during the late paleozoic to provide a reliable constraint on the paleogeographic reconstruction and to determine the relationship with the adjacent area we performed a paleomagnetic investigation of early and late carboniferous sediments from the qaidam block stepwise thermal demagnetization successfully isolated high unblocking temperature characteristic directions from the samples the tilt corrected mean direction of the early carboniferous sediments is ds is 298 6 46 4 with 95 4 7 and n 15 sites corresponding to a paleopole at 3 2 n 147 5 e with a95 4 8 the late carboniferous paleomagnetic direction is ds is 320 1 46 1 with 95 5 3 and n 8 sites corresponding to a paleopole at 15 1 n 132 2 e with a95 5 4 a positive fold test for the early carboniferous paleomagnetic directions and consistency with the kiaman reversed superchron for the late carboniferous paleomagnetic directions indicates the primary origin of the characteristic remanence of the studied section the new paleomagnetic results suggest that the qaidam block was located at about 27 n and did not undergo significant n s movement during the carboniferous however the qaidam block experienced a counter clockwise rotation of about 21 during this period comparisons of the paleomagnetic results from the major blocks of central asia suggest that the qaidam block may have experienced a relatively rapid northward movement and collided with the tarim block after the late permian based on the paleomagnetic poles of the qaidam block and adjacent blocks we present a tentative paleogeographic reconstruction for central asia during the early and late carboniferous

new cretaceous and early tertiary paleomagnetic results from xining lanzhou basin kunlun and qiangtang blocks china implications on the geodynamic evolution of asia we present the results of a paleomagnetic study of 360 cores drilled at three different areas from the tibetan plateau 13 sites from lower cretaceous red beds in the xining lanzhou basin around xining and lanzhou cities southwest of the qilian mountains 36 2 n 103 5 e 13 sites from cretaceous red beds in the kunlun block near maqin 34 5 n 100 1 and 9 sites from paleocene lower eocene red beds in the qiangtang block near fenghuoshan 34 5 n 92 8 e thermal demagnetization of the samples allowed us to isolate a high temperature component which passes both positive reversal and fold tests for all formations the corresponding paleopoles lie at 50 3 n 195 5 e a95 4 6 for xining lanzhou 80 1 n 281 2 e dp 7 8 dm 12 7 for maqin and 62 6 n 210 5 e dp 3 9 dm 6 8 for fenghuoshan we discuss these in the frame of a new paleogeographic reconstruction of the cretaceous paleoposition of the blocks forming the asian mosaic we conclude that the xining lanzhou area could not be part of the north china block but rather was associated with the tarim qaidam assemblage paleomagnetic data argue in favor of a qaidam kunlun tarim junggar assemblage in the cretaceous significantly to the south of its current position with respect to the asian continent siberia mongolia and north china the large n s convergence 800 500 km implied since the cretaceous appears to be far larger than could be absorbed in the altay range to the north and qilian shan to the east of the order of 300 km part of this motion could have occurred along a large left lateral strike slip fault system which may connect with the mongol okhotsk suture to the northeast verifying this hypothesis will require new geologic and paleomagnetic data from these remote regions

statistical significance of the fold test in palaeomagnetism summary the significance of the change in direction dispersion on applying the fold test in palaeomagnetism is used as the criterion for deciding whether or not the fold test has statistical significance a set of tables is compiled which can be used for quick application of the test

petrography and zircon u pb isotopic study of the bayanwulashan complex constrains on the paleoproterozoic evolution of the alxa block westernmost north china craton abstract the bayanwulashan metamorphic complex bmc exposes along the eastern margin of the alxa block the westernmost part of the north china craton ncc bmc is principally composed of metamorphic rocks with amphibole plagiogneiss biotite plagioclase gneiss and granitic gneiss our research has been focused on the petrography and zircon u pb geochronology of the bmc to better understand the evolution of the alxa block and its relationship with the ncc evidences from field geology petrography and mineral chemistry indicate that two distinct metamorphic assemblages the amphibolite and greenschist facies had overprinted the preexisting granitic gneiss and suggest that the bmc experienced retrograde metamorphic episodes the la icp ms zircon u pb ages reveal that the primary magmatic activities of bmc were at ca 2 30 2 24 ga and the two metamorphic events were at ca 1 95 1 91 ga and ca 1 88 1 85 ga respectively these ages indicate that bmc initially intruded during paleoproterozoic not as previously suggested at archean period the early paleoproterozoic metamorphic records and the magmatic thermochronological data in bmc exhibit different evolution paths between the alxa block and the ncc the alxa block was most likely an independent early paleoproterozoic terrain following different amalgamation processes the alxa block combined with western block at ca 1 95 ga and then united with ncc at ca 1 85 ga

regional moisture balance control of landslide motion implications for landslide forecasting in a changing climate i correlated 12 years of annual movement of 18 points on a large continuously moving deep seated landslide with a regional moisture balance index moisture balance drought index mbdi i used mbdi values calculated from a combination of historical precipitation and air temperature data from a d 1895 to 2010 and downscaled climate projections using the intergovernmental panel on climate change a2 emissions scenario for 2011 2099 at the landslide temperature is projected to increase 0 5 c 10 yr between 2011 and 2099 while precipitation decreases at a rate of 2 mm 10 yr landslide movement correlated with the mbdi with integration periods of 12 and 48 months the correlation between movement and mbdi suggests that the mbdi functions as a proxy for groundwater pore pressures and landslide mobility i used the correlation to forecast decreasing landslide movement between 2011 and 2099 with the head of the landslide expected to stop moving in the mid 21 st century the mbdi or a similar moisture balance index that accounts for evapotranspiration has considerable potential as a tool for forecasting the magnitude of ongoing deep seated landslide movement and for assessing the onset or likelihood of regional deep seated landslide activity

preliminary early cretaceous paleomagnetic results from the gansu corridor china we report results from our paleomagnetic study of lower cretaceous redbeds from the gansu corridor northwestern china the characteristic remanent magnetization chrm resides in hematite often at very high unblocking temperatures 660 c the directions associated with this component exhibit only reversed polarities from locality a sunan area but the samples from locality b lanzhou area 480 km to the southeast show roughly antipodal normal and reversed polarities the combined sample directional data from both localities pass a fold test at the 99 confidence level the mean paleomagnetic pole is located at 48 7 n 199 7 e with a 95 4 1 which is discordant with poles of similar age elsewhere from neighboring regions in china although represented by relatively few samples n 21 this pole suggests that significant post cretaceous motion may have occurred between the gansu corridor and adjacent blocks relative to eurasia or north china the discordance corresponds to 28 1 5 2 or 35 6 9 7 clockwise rotation and 9 5 4 5 or 9 8 8 2 northward displacement respectively the rotations support but do not yet distinguish between several neotectonic models assumed to have acted over the past 15 40 m y the displacement is not predicted by any of these models if real it may have occurred early in the history of the india asia collision or even before

late permian paleomagnetic pole from dikes of the tarim craton china we have obtained a late permian paleomagnetic pole from dikes in the tarim craton of china directions of magnetization from 21 mafic and ultramafic dikes at three localities pass a fold test at the 95 confidence level the new paleomagnetic pole lies at lat 66 n long 181 e n 21 k 61 and 95 3 9 on the basis of a comparison with paleomagnetic data from adjacent tectonic units we conclude that 1 the late permian paleolatitude of the tarim craton differs from that of the sino korean craton suggesting that the two cratons were distinct tectonic units in late permian time 2 there was relative motion between the tarim craton and the siberian craton after late permian time and 3 negligible relative motions have occured between different thrust sheets in the keping bachu area of the north western tarim craton

paleomagnetic constraints on the paleogeography of the east asian blocks during late paleozoic and early mesozoic times abstract although the axial and dominant geocentric character of the earth s magnetic field means that paleolongitude is indeterminate paleomagnetism is otherwise the only truly quantitative method available to the earth scientist for constraining paleogeography and reconstructing the kinematic evolution of continental blocks during the past half century numerous paleomagnetic results have provided substantial quantitative constraints on the origin and tectonic evolution of the major tectonic divisions now comprising eastern asian in this paper we first assess the available early paleozoic to early cretaceous paleomagnetic results from the south china north china and tarim blocks using internationally recognized reliability criteria we then construct a running mean through a 20 ma window by weighting the poles according to their q factors and fit a spherical spline with smoothing factor of 300 to derive apparent polar wander apw paths for these three major blocks during this early paleozoic to late mesozoic time interval together with late paleozoic to early mesozoic paleomagnetic poles from the qaidam qiangtang lhasa sibumasu indochina and some other smaller blocks terranes of east asia we produce a series of paleogeographic reconstructions for these major blocks and lesser terranes of east asia between mid ordovician and late jurassic times 460 160 ma which although based primarily upon paleomagnetic evidence aim to embrace the geological constraints finally we discuss the current evidence for closure times of the paleo asian mianlue and east paleo tethyan oceans which incorporate fundamental issues concerning the formation of the east asian continental collage and collision with the northern main body of the pangean supercontinent we use the collective evidence to argue that these major paleo oceans had closed by the late triassic and that the east asian sector of the supercontinent had united to become an integral part of pangea by that time 220 ma

permo triassic magnetostratigraphy in china northern tarim abstract the upper boundary of the permo carboniferous reversed polarity superchron has been identified in a palaeomagnetic study of the permo triassic of the northern part of the tarim basin china this boundary serves as an important marker horizon for correlation with other permo triassic sequences both in china and world wide a permo triassic palaeomagnetic pole for the tarim block is estimated to be at 71 8 n 187 6 e comparison with similar age poles from the adjacent blocks of china and asia suggests that the tarim was widely separated from the sino korean block in permo triassic times but was not yet sutured to kazakhstan

three dimensional surface deformation derived from airborne interferometric uavsar application to the slumgullion landslide author s delbridge bg burgmann r fielding e hensley s schulz wh abstract 2016 american geophysical union all rights reserved in order to provide surface geodetic measurements with landslide wide spatial coverage we develop and validate a method for the characterization of 3 d surface deformation using the unique capabilities of the uninhabited aerial vehicle synthetic aperture radar uavsar airborne repeat pass radar interferometry system we apply our method at the well studied slumgullion landslide which is 3 9 km long and moves persistently at rates up to 2 cm day a comparison with concurrent gps measurements validates this method and shows that it provides reliable and accurate 3 d surface deformation measurements the uavsar derived vector velocity field measurements accurately capture the sharp boundaries defining previously identified kinematic units and geomorphic domains within the landslide we acquired data across the landslide during spring and summer and identify that the landslide moves more slowly during summer except at its head presumably in response to spatiotemporal variations in snowmelt infiltration in order to constrain the mechanics controlling landslide motion from surface velocity measurements we present an inversion framework for the extraction of slide thickness and basal geometry from dense 3 d surface velocity fields we find that the average depth of the slumgullion landslide is 7 5 m several meters less than previous depth estimates we show that by considering a viscoplastic rheology we can derive tighter theoretical bounds on the rheological parameter relating mean horizontal flow rate to surface velocity using inclinometer data for slow moving clay rich landslides across the globe we find a consistent value for the rheological parameter of 0 85 0 08

tectonic implications of early middle triassic palaeomagnetic results from hexi corridor north china summary a palaeomagnetic study was carried out on low middle triassic red beds at jingtai area of hexi corridor the characteristic higher temperature component htc ds 304 1 is 38 4 ks 33 2 a95 5 2 n 24 sites isolated by stepwise thermal demagnetization exhibits dual polarity which passes the mcfadden s fold test at the 99 per cent confidence level and reversal test with classification c compared with coeval palaeomagnetic results from the north china block ncb this result suggests insignificant palaeolatitude differences p between the observed and that expected at jingtai area p 0 9 4 9 in the early triassic or p 4 9 4 1 in the middle triassic this implies that the hexi corridor was the extension of the ncb by the middle triassic however in comparison with early and middle triassic results from the ncb an anticlockwise rotation of studied area relative to the ncb with rd 25 4 5 2 or rd 26 6 4 5 is detected our result also suggests that jingtai area of the western part of ncb was not connected with the tarim block by the early middle triassic

new mesozoic apparent polar wander path for south china tectonic consequences a new paleomagnetic study in the south sichuan basin south china block has been carried out on sediments of early triassic to middle jurassic age detailed stepwise thermal and alternating field demagnetizations allowed us to isolate two to three components a low temperature component component a falls close to the local present earth field direction a middle temperature component component b is found both in limestone and red beds of early triassic age in limestones of middle triassic age and finally in red beds of jurassic age the component b directions failed the fold test but show a significant increase of the ks kg ratio at 60 when a progressive stepwise unfolding is applied the directions obtained at 60 unfolding are grouped best and yield a pole position at 76 5 n 174 1 e a95 3 7 that is close to the late cretaceous pole of the south china block scb or the early tertiary pole of the eurasian plate characteristic directions are finally obtained component c for early triassic and early to middle jurassic sediments only both with reversal and fold tests they yield pole positions at 44 1 n and 217 2 e a95 4 9 and 79 n and 227 e a95 4 5 respectively the early triassic result well fits other data of the same age from the scb the revised late permian to cretaceous paleopole data provide a new mesozoic apparent polar wander path for south china the successive pole positions from late permian to early triassic indicate motion of the south china block as a whole rather than local rotations linked to important strain within the block the early to middle jurassic pole is statistically indistinguishable from the compiled north china block ncb poles and indicates that final suturation between the two blocks occurred by the end of the triassic which is coherent with the age of ultra high pressure metamorphism in the dabie sulu areas of eastern china the asian plate including the mongol central asian block ncb and scb however was probably separated from siberia by the mongol okhotsk ocean during jurassic time

rainfall ground water flow and seasonal movement at minor creek landslide northwestern california physical interpretation of empirical relations simple ground water flow analyses can clarify complex empirical relations between rainfall and landslide motion here we present detailed data on rainfall ground water flow and repetitive seasonal motion that occurred from 1982 to 1985 at minor creek landslide in northwestern california and we interpret these data in the context of physically based theories we find that landslide motion is closely regulated by the direction and magnitude of near surface hydraulic gradients and by waves of pore pressure caused by intermittent rainfall diffusive propagation of pore pressure waves accompanies downward ground water flow along nearly vertical hydraulic gradients that exist in most of the landslide field data combined with a pore pressure diffusion analysis show that single rainstorms typically produce short period waves that attenuate before reaching the landslide base in contrast seasonal rainfall cycles produce long period waves that modify basal pore pressures but only after time lags that range from weeks to months such tune lags can depend on antecedent moisture storage and can explain variable delays between the onset of the wet season and seasonal landslide motion limit equilibrium analysis shows that when seasonal pressure waves reach the landslide base they establish a critical distribution of effective stress that delicately triggers landslide motion the critical effective stress balance is extremely sensitive to the direction and magnitude of hydraulic gradients although pervasively downward gradients instigate seasonal motion we infer from theory and limited data that ground water also may circulate locally in near surface cells the circulation can further reduce the landslide s frictional strength particularly in areas of nearly horizontal ground water flow that occur beneath steep faces of hummocks hummocky topography that results from slope instability may therefore cause ground water flow that perpetuates instability

controls on the seasonal deformation of slow moving landslides article history precipitation drives seasonal velocity changes in slow moving landslides by increasing pore water pressure and reducing the effective normal stress along basal shear zones this pressure change is often modeled as a pore water pressure wave that diffuses through the landslide body such that the minimum time required for landslides to respond to rainfall should vary as the square of landslide depth which often approximates the saturated thickness and inversely with hydraulic diffusivity here we assess this model with new observations from the landslide prone eel river catchment northern california using satellite radar interferometry insar time series precipitation data and high resolution topographic data from airborne lidar we quantify the seasonal dynamics of 10 slow moving landslides which share the same lithologic tectonic and mediterranean climate conditions these slope failures have areas ranging from 0 16 to 3 1 km 2

resolving the problem of shallow magnetizations of tertiary age in asia insights from paleomagnetic data from the qiangtang kunlun and qaidam blocks tibet china and a new hypothesis we present new paleomagnetic results obtained at 39 sampling sites from five sections of tertiary red bed formations two eocene formations from the qiangtang block of tibet xialaxiu locality 32 8 n 96 6 e and the xining basin of qaidam xining locality 36 5 n 102 0 e and three neogene formations from the xining basin jungong locality 34 7 n 100 7 e and the kunlun block tuoluo lake and west yushu localities 35 3 n 98 6 e and 33 2 n 96 7 e respectively thermal demagnetization of the rocks isolated a high temperature component that we interpret as the primary magnetization in four localities the paleopoles lie at 52 6 n 352 e dp dm 6 0 10 7 for xialaxiu 61 6 n 211 3 e dp dm 9 7 16 1 for xining 66 0 n 228 6 e dp dm 3 6 6 9 for jungong and 53 9 n 205 4 e dp dm 5 6 10 0 for west yushu as in previous studies of tertiary formations from asia the inclinations we obtained are shallower by 18 to 26 than the magnetic field computed from the eurasian apparent polar wander path apwp at 10 and 20 ma for neogene rocks and at 40 and 60 ma for eocene rocks on the basis of a compilation of eocene data from the south china block tibet central asia and kyrgyzstan we conclude that this inclination anomaly reflects erroneous predictions of positions of the siberian craton when based on the apwp of eurasia the main reason for this discrepancy might be nonrigid behavior of the eurasian plate in the tertiary combination of this with intracontinental shortening of asia under the penetration of india provides a full explanation for the anomaly verification of this new interpretation of the inclination anomaly will require new geologic and paleomagnetic data from the northern parts of these remote regions in mongolia and siberia

a new paleogeographic configuration of the eurasian landmass resolves a paleomagnetic paradox of the tarim basin china 1 new paleomagnetic data from permian red beds and middle jurassic limestones from the tarim basin pose a paradox their declinations are similar to upper carboniferous to neogene rocks collected from the same sections and their inclinations parallel present values when assuming that lower than expected inclinations in continental sedimentary rocks arise from inclination shallowing effects then the paleolatitudes of all upper carboniferous to present rocks from tarim are indistinguishable local vertical axis block rotations occurring in the last 20 million years explain why declinations vary at different localities in the basin our middle jurassic data positions tarim 23 6 8 4 farther south than that predicted from the coeval reference pole for eurasia however no geologic argument exists to support the closure of a large ocean basin between tarim and siberia since the middle jurassic thus the paradox are the rocks from tarim totally overprinted or is the middle mesozoic part of the reference eurasian apparent polar wander path erroneous several lines of evidence suggest the tarim rocks are not remagnetized we conclude that tarim has experienced little or no apparent polar wander since the carboniferous moreover our middle mesozoic reconstruction of eurasia using the new middle jurassic pole from tarim results in a more geologically compatible solution for the eastern asian blocks over previous reconstructions

seasonal movement of the slumgullion landslide determined from global positioning system surveys and field instrumentation july 1998 march 2002 abstract measurements of landslide movement made by global positioning system surveys and extensometers over a 3 5 year period show that the slumgullion landslide in the san juan mountains of southwest colorado moved throughout the monitoring period but that daily velocities varied on a seasonal basis landslide velocities peaked in the early spring and summer in response to snowmelt and summer thunderstorms respectively velocities were slowest in mid winter when air and soil temperatures were coldest and precipitation was generally low and or in the form of snow with a low water content we hypothesize that the seasonal variability in velocities is due to ground water levels and corresponding pore pressures that decrease when surface water is unavailable or cannot infiltrate frozen landslide material and increase when surface water from melting snow or rainfall infiltrates unfrozen landslide material we also suggest that patches of bouldery debris and fractures created by continuous movement of the landslide are conduits through which surface water can infiltrate regardless of the frozen or unfrozen state of the landslide matrix material therefore the availability of surface water is more important than landslide temperature in controlling the rate of landslide movement this hypothesis is supported by field instrumentation data that show 1 landslide velocities coinciding with precipitation amounts regardless of the depth of freezing of landslide material 2 spring and annual landslide velocities that were greatest when the depth of freezing was also the greatest and 3 a rapid several weeks or less velocity and pore pressure response to rainfall the persistent but seasonally variable movement of the landslide fits the bathtub model for landslide movement described by baum and reid baum r l reid m e 2000 ground water isolation by low permeability clays in landslide shear zones in bromhead e n dixon n ibsen m l eds landslides in research theory and practice proc 8th int symp on landslides cardiff wales vol 1 139 144 in their model the landslide is isolated both mechanically and hydrologically from adjacent materials by low permeability clays these clays cause the landslide to retain water our data support this model by suggesting that pore pressures at the basal landslide surface are always adequate to maintain landslide movement and that any infiltration of water at the surface of the landslide is adequate to rapidly increase landslide velocity

living stained and dead foraminifera from the newly ice free larsen ice shelf weddell sea antarctica ecology and taphonomy within the past 7 years the northern larsen ice shelf has broken up so it is now possible to sample the sea floor that formerly lay beneath it box cores have yielded surface sediment samples 0 1 cm that give information on living and dead foraminiferal assemblages the living assemblages are of moderate diversity and four have 50 calcareous tests while five have 50 agglutinated tests this is an area of high primary production and the standing crops of the benthic foraminiferal assemblages are high all the dead assemblages are much enriched in agglutinated tests often 90 they give a time averaged record of the past 7 ice free years and several decades of ice cover the loss of permanent ice cover there is still seasonal ice cover may have caused some response from the fauna but it is likely that it was mainly changes in relative absolute abundance of the existing fauna the differences between the live and dead assemblages in the surface 1 cm are attributed mainly to taphonomic effects dissolution of calcareous tests and loss of fragile agglutinated tests subsurface samples down to 5 cm show that dissolution of calcareous tests is widespread and there may be some loss of fragile agglutinated forms such as reophax subdentaliniformis for these reasons in this area it may be best to make palaeoecological interpretations on the agglutinated component of the fossil assemblages