the landing s of philae and inferences about comet surface mechanical properties the philae lander part of the rosetta mission to investigate comet 67p churyumov gerasimenko was delivered to the cometary surface in november 2014 here we report the precise circumstances of the multiple landings of philae including the bouncing trajectory and rebound parameters based on engineering data in conjunction with operational instrument data these data also provide information on the mechanical properties strength and layering of the comet surface the first touchdown site agilkia appears to have a granular soft surface with a compressive strength of 1 kilopascal at least 20 cm thick possibly on top of a more rigid layer the final landing site abydos has a hard surface

rockfall susceptibility zoning at a large scale from geomorphological inventory to preliminary land use planning abstract rockfall up to several hundreds of cubic meters is a frequent and rapid landslide which menaces extensive areas in mountainous territories rockfall susceptibility zoning map at a large scale 1 5000 1 25 000 can be the first tool for land use planning in order to manage rockfall risk a methodology allowing to analyze susceptibility in extensive areas with optimum cost benefit relationship is needed this work analyzes rockfall susceptibility in an extensive rocky mountain of the principality of andorra pyrenees mountains first on the rock slope and then on the exposed area located below the rockfall record obtained by means of geomorphological analysis supplies the main data to analyze the susceptibility on the rock slope an additional historical inventory verifies the accuracy of rockfall sizes recorded by means of the geomorphological analysis according to the classification recommended by the guidelines of joint technical committee the density of rockfall features on the rock slope assesses susceptibility in four levels subsequently susceptibility on exposed areas has been analyzed by means of reach probability of rock blocks analysis using empirical models data acquired from thirteen recent events from 1999 to 2004 have been used to verify the accuracy of the two empirical models mainly used reach angle and shadow angle five reach probability limits 1 0 5 0 25 0 01 and 0 establish boundaries between susceptibility levels the resulting rockfall susceptibility zoning map allows a to identify land areas and human elements exposed to rockfalls and b to establish several exposition levels this map can be a useful and cost effective tool for administrations responsible to manage natural risk in order to guide urban grow in extensive areas or decide upon work programs based on in depth analysis hazard and risk

sea level changes and the continental freeboard concept general principles and application to the precambrian abstract eustatic sea level changes reflect variation in ocean water or ocean basin volume or changes to the hypsometric curve which is in itself geographically and chronologically variable freeboard the elevation of a continent above mean sea level is closely related to changes in both sea level and this curve relative sea level change occurs due to tectonism sediment supply compaction and eustatic movements hydroisostatic compensation modifies first order sea level variation by about one third short term and localised change in sea level may be ascribed to waves and tides storm winds hurricanes tsunamis and catastrophic sediment slumps wide gently sloping shelves with more uniform circulation systems inferred for the precambrian may have enhanced tide and wave induced sea level changes salinity and water temperature mutually dependent affect eustatic and relative sea levels elevated water temperatures postulated for the early precambrian would have been offset partly by enhanced evaporation and increased salinity longer term changes in sea level regional or eustatic may result from orogenesis volcanism sediment supply compaction and loading isostasy and thermal mechanisms glacioeustatic changes compounded by related salinity variations moderated by glacioisostatic effects and modified by hydroisostasy reach ca 150 m isostatic rebound in interglacial episodes will produce rapid and marked sea level drops up to ca 250 m this is a localised effect and contrasts with the global enhancement of sea level during interglacials however evidence for glaciation in the geological record is limited also for most of the precambrian sea level oscillations in non glacial episodes may reflect flexure of tectonic plates change up to 100 m or changes to earth s geoid 250 m eustasy up to 350 m will result from change to ocean basin volume due to variation in mid ocean ridge volume and spreading rates also related to supercontinent amalgamation and breakup intra plate hot spots and oceanic plateaus will change eustatic sea level more slowly up to 100 m higher heat flow in the archaean and concomitant enhanced volcanism suggest that these were important influences on precambrian sea levels the exponential elevation age relationship observed for phanerozoic oceanic lithosphere may have been more significant in the precambrian as continental crust grew from ca 4 0 ga declining heat flow and concomitant deepening of the ocean basins maintained an approximately constant freeboard during the archaean although still hotly debated there is strong support for episodic growth models inferring rapid formation of continental crust near the archaean proterozoic boundary this would imply constant freeboard conditions after 2 5 ga as well the constant freeboard model however is one based on average global conditions freeboard was still subject to geographic and chronologic variation and these potential changes lie within the bounds of eustatic and relative sea level change continental crustal growth the freeboard concept and sea level changes are thus interdependent variables in precambrian geology

proterozoic sedimentation and volcanism in the singhbhum crustal province india and their implications abstract the proterozoic volcano sedimentary succession comprising successively younger dhanjori chaibasa dhalbhum dalma and chandil formations of the singhbhum crustal province india records sedimentation and volcanism in a rapidly changing tectonic scenario cooling of the vast volume of archaean singhbhum granite possibly induced an isostatic readjustment the associated tensional regime and deep seated fractures controlled the formation of the proterozoic singhbhum basin the dhanjori formation unconformably overlies the singhbhum granite and is entirely terrestrial dominantly fluvial at the base the conglomerate deposits coarse grained sandstone and shale represent the distal fringe of an alluvial fan complex the rest of the formation including the volcaniclastic rocks consists almost entirely of fining upward fluvial cycles the base of the dhanjori formation is a sequence boundary and the formation itself represents a lowstand systems tract the dhanjori volcano sedimentary succession displays evidence of having passed through passive as well as active phases of continental rifting with an increasingly important influence of volcanism on the sedimentation through time the chaibasa formation sharply overlies the dhanjori formation and a transgressive lag demarcates their contact the basal part of the chaibasa formation immediately overlying the transgressive lag deposit represents a transgressive systems tract while offshore shales that sharply overlie the shallow marine sandstones up section represent marine flooding surfaces the shallow marine subtidal sandstones bear an excellent record of sandwave migration and provide a rare opportunity to unlock the late palaeoproterozoic lunar orbital periodicities unlike the chaibasa the overlying dhalbhum formation is entirely terrestrial fluvial aeolian indicating that the chaibasa dhalbhum contact is a sequence boundary the dalmas overlying the dhalbhum formation represents concordant lava outpourings without any break in sedimentation these lavas are genetically related to mantle plume upwelling in an intracontinental rift setting the volcano sedimentary package lying north of the dalma volcanic belt chandil formation is of mesoproterozoic age the entire late palaeoproterozoic volcano sedimentary package displays post depositional compressional deformation and greenschist to amphibolite facies metamorphism dated at ca 1600 ma forming the so called north singhbhum fold belt the volcano sedimentary package lying south of the dalma volcanic belt was pushed further south towards the singhbhum granite batholith complex as a result of uplift related to the dalma plume the singhbhum granite batholith acted as a rigid body this gave rise to a compressional stress regime that induced shearing thrusting at ca 1600 ma along the singhbhum shear zone the dalma plume magmatism was possibly part of a 1600 ma global tectono thermal event

comet 67p churyumov gerasimenko sheds dust coat accumulated over the past four years comets are composed of dust and frozen gases the ices are mixed with the refractory material either as an icy conglomerate1 or as an aggregate of pre solar grains grains that existed prior to the formation of the solar system mantled by an ice layer2 3 the presence of water ice grains in periodic comets is now well established4 5 6 modelling of infrared spectra obtained about ten kilometres from the nucleus of comet hartley 2 suggests that larger dust particles are being physically decoupled from fine grained water ice particles that may be aggregates7 which supports the icy conglomerate model it is known that comets build up crusts of dust that are subsequently shed as they approach perihelion8 9 10 micrometre sized interplanetary dust particles collected in the earth s stratosphere and certain micrometeorites are assumed to be of cometary origin11 12 13 here we report that grains collected from the jupiter family comet 67p churyumov gerasimenko come from a dusty crust that quenches the material outflow activity at the comet surface14 the larger grains exceeding 50 micrometres across are fluffy with porosity over 50 per cent and many shattered when collected on the target plate suggesting that they are agglomerates of entities in the size range of interplanetary dust particles their surfaces are generally rich in sodium which explains the high sodium abundance in cometary meteoroids15 the particles collected to date therefore probably represent parent material of interplanetary dust particles this argues against comet dust being composed of a silicate core mantled by organic refractory material and then by a mixture of water dominated ices2 3 at its previous recurrence orbital period 6 5 years the comet s dust production doubled when it was between 2 7 and 2 5 astronomical units from the sun14 indicating that this was when the nucleus shed its mantle once the mantle is shed unprocessed material starts to supply the developing coma radically changing its dust component which then also contains icy grains as detected during encounters with other comets closer to the sun4 5

controls on precambrian sea level change and sedimentary cyclicity abstract although uniformitarianism applies in a general sense to the controls on relative and global sea level change some influences thereon were more prominent in the precambrian short term base level change due to waves and tides may have been enhanced due to possibly more uniform circulation systems on wide low gradient precambrian shelves the lack of evidence for global glacial events in the precambrian record implies that intraplate stresses and cyclic changes to earth s geoid were more likely explanations for third order sea level change than glacio eustasy higher heat flow in the earlier precambrian may have led to more rapid tectonic plate formation transport and destruction along with an increased role for hot spots aseismic ridges and mantle plumes superplumes all of which may have influenced cyclic sedimentation within the ocean basins a weak cyclicity in the occurrence of plume events has an approximate duration comparable to that of first order supercontinental cycle sea level change second order cyclicity in the precambrian largely reflects the influences of thermal epeirogeny changes to mid ocean ridge volume as well as to ridge growth and decay rates and cratonic marginal downwarping concomitant with either sediment loading or extensional tectonism third order cycles of sea level change in the precambrian also reflected cyclic loading unloading within flexural foreland basin settings and filling deflation of magma chambers associated with island arc evolution the relatively limited number of studies of precambrian sequence stratigraphy allows some preliminary conclusions to be drawn on duration of the first three orders of cyclicity archaean greenstone basins appear to have had first and second order cycle durations analogous to phanerozoic equivalents supporting steady state tectonics throughout earth history in direct contrast however preserved basin fills from neoarchaean palaeoproterozoic cratonic terranes have first and second order cycles of considerably longer duration than phanerozoic examples supporting less evolved tectonism affecting cratonic plates it is possible that oceanic tectonic realms underwent more rapid and dynamic plate movements and arc generation whereas early continental cratonic plates offered more stable platforms and may have been subject to slower migration rates the wide range of controls on precambrian sea level change allied to their apparent variability in rates and periodicity through precambrian time supports the conclusion that each order of cyclicity is relative and must be defined within the stratigraphic context of each individual case study this underlines the importance of establishing a hierarchical order of cyclicity in sequence stratigraphic interpretations of precambrian basins based on the relative importance of sequences rather than their temporal duration

the 28 october 1996 landslide and analysis of the stability of the current huashiban slope at the liangjiaren hydropower station southwest china on 28 october 1996 a landslide occurred on the huashiban slope near the liangjiaren hydropower station the landslide was caused by a failure mechanism induced by an earthquake mw 7 0 at lijiang on 3 february 1996 after which a tensile fracture zone formed on the huashiban slope the subsequent impact of several small earthquakes on the slope increased the tension crack connectivity and the tensile strength gradually decreased severe rainfall in the rainy season between may and october especially in july and august decreased the shear strength of the bottom sliding surface resulting in a landslide on the huashiban slope on 28 october 1996 the stability of the huashiban slope is important for plant site selection if a further landslide occurs on the slope the liangjiaren hydropower station project will be critically affected so analysis of the current slope stability is extremely important at present the huashiban slope can be divided into five subzones 1 a landslide deposit zone 2 a landslide zone 3 a tensile fracture zone 4 a crescent shaped zone and 5 an upper slide zone using historic landslide data for 28 october 1996 retrospective analysis of the landslide process revealed shear strength parameters for the huashiban slope the cohesion strength is 0 024 mpa the friction angle at the bottom sliding surface is 14 and the tension crack connectivity is 50 these parameters were used to compute the stability of the huashiban slope under the same conditions the stability of the whole slope is better than that of part of the slope and the overall stability is dominated by the tensile fracture zone under earthquake and rainfall conditions it is possible that failure will occur in the tensile fracture zone thus the huashiban slope should be reinforced for construction and operation of the liangjiaren hydropower station

reconstructing sea level change from the internal architecture of stromatolite reefs an example from the mesoproterozoic sulky formation dismal lakes group arctic canada the mesoproterozoic dismal lakes group arctic canada contains a relatively thin yet regionally extensive stromatolitic reef complex that developed subtidally during a major transgression shoaled to sea level and was overlain by intertidal to supratidal carbonate and evaporite strata the september lake reef complex exhibits a complex internal architecture that records the interaction between stromatolite growth and changes in accommodation space derived from both higher order 4th or 5th order parasequence scale changes in sea level and the variable bathymetry of the sea floor reef growth which was initiated during three sea level cycles records progressive marine transgression over depositional lows that were formed during pre reef subaerial exposure and erosion of the underlying strata a fourth sea level cycle represented by spectacular coniform stromatolites with 10 m of synoptic relief marks a more dramatic rise in sea level and establishment of the main reef complex aggradation and ev

identifying rock slope failure precursors using lidar for transportation corridor hazard management abstract in the thompson and fraser river valleys rockfall and rockslides are a hazard for railway traffic in the region in june 2013 a 2600 m 3 rockslide occurred in the white canyon causing damage to infrastructure and interruption to service in the year preceding this failure the slope was monitored using terrestrial light detection and ranging lidar as part of the railway ground hazards research program initiative the purpose of this study is to evaluate a hazard management strategy for transportation corridors exposed to steep slopes involving the identification of rockfall precursors prior to significant slope failures for this failure deformation was observed in the seven months preceding collapse with an accelerating period occurring in the final 28 days a distinct pattern of smaller rockfalls was observed around the perimeter of the deforming rock block as well as loss of surficial material over the slides tension crack this study shows that with lidar monitoring precursors to rock slope failures can be identified allowing for better rock slope hazard management by focusing attention on areas with the highest probability of failure

seismically induced rock slope failures resulting from topographic amplification of strong ground motions the case of pacoima canyon california abstract the 1994 northridge earthquake mw 6 7 triggered extensive rock slope failures in pacoima canyon immediately north of los angeles california pacoima canyon is a narrow and steep canyon incised in gneissic and granitic rocks peak accelerations of nearly 1 6 g were recorded at a ridge that forms the left abutment of pacoima dam peak accelerations at the bottom of the canyon were less than 0 5 g suggesting the occurrence of topographic amplification topographic effects have been previously suggested to explain similarly high ground motions at the site during the 1971 mw 6 7 san fernando earthquake furthermore high landslide concentrations observed in the area have been attributed to unusually strong ground motions rather than higher susceptibility to sliding compared with nearby zones we conducted field investigations and slope stability back analyses to confirm the impact of topographic amplification on the triggering of landslides during the 1994 earthquake our results suggest that the observed extensive rock sliding and falling would have not been possible under unamplified seismic conditions which would have generated a significantly lower number of areas affected by landslides in contrast modelling slope stability using amplified ground shaking predicts slope failure distributions matching what occurred in 1994 this observation confirms a significant role for topographic amplification on the triggering of landslides at the site and emphasises the need to select carefully the inputs for seismic slope stability analyses

kaapvaal craton changing first and second order controls on sea level from c 3 0 ga to 2 0 ga abstract well preserved supracrustal basin fills including the oldest large depository witwatersrand known makes the kaapvaal craton an ideal example for studying controls on first and second order stratigraphic cyclicity the duration of the three basins studied witwatersrand ventersdorp and transvaal from c 3 0 to c 2 0 ga is almost twice that of the entire phanerozoic period from which the paradigms of classical sequence stratigraphy have been derived amongst these is an assumption that cyclicity at specific hierarchical levels is predictable and repetitive through earth history this does not appear to be borne out by the precambrian record studied here instead a hierarchical order of cycles based on relative importance of sequences allied to a more flexible approach to controls on stratigraphic cyclicity at first and second orders is preferred first order cycles within the c 3 0 2 0 ga period on kaapvaal are synonymous with the entire evolution of a supracrustal basin fill defined by a specific basin type second order cycles define basin fill packages of unique character which reflect large scale shifts in the accommodation sedimentation balance early to middle archaean evolution of the kaapvaal craton encompassed amalgamation of a mosaic of subdomains to produce an early south southeastern nucleus by c 3 1 ga accretion of composite terranes from both north and west followed from c 3 0 2 7 ga this was contemporaneous with evolution of the c 3 0 2 8 ga witwatersrand basin the high grade limpopo terrane was amalgamated with the kaapvaal craton between 2 95 and 2 69 ga although a younger age for this orogensis is also possible the witwatersrand first order depositional cycle was controlled largely by subduction related tectonic loading and had a duration of c 190 my the c 5 my first order cycle of the c 2 7 ga ventersdorp basin was essentially controlled by thermal uplift induced extensional subsidence and that of the c 650 my transvaal basin by extensional and subsequent thermal subsidence it is noteworthy in the three basins examined that first order cycles controlled by plate tectonics witwatersrand and transvaal basins were about two orders of magnitude longer relative to the ventersdorp plume tectonic cycle second order cycles also varied greatly from c 100 my to c 1 my within the witwatersrand and transvaal basins subsidence allowed extensive seaways to develop within which classical sequence stratigraphic systems tracts can be recognized reflecting different stages of shoreline shifts within the short lived ventersdorp continental basin system sedimentological criteria can be used to discriminate high and low accommodation systems tracts the transvaal first order cycle was terminated at c 2 0 ga by the bushveld complex plume event

late visean early serpukhovian conodont succession at the naqing nashui section in guizhou south china this study reports the conodont succession across the visean serpukhovian v s boundary interval at the naqing section south china continuous centimetre scale sampling of the relatively deep water section in recent years has provided new data for a more detailed biostratigraphy of conodonts across the visean serpukhovian boundary three conodont zones were described in ascending order the gnathodus bilineatus lochriea nodosa and lochriea ziegleri zones the first appearance datum fad of l ziegleri has been moved down to 60 1 m above the base of the naqing section the correlation of the conodont succession across the visean serpukhovian boundary in the naqing section with other sections in eurasia is discussed

sea level curve for pennsylvanian eustatic marine transgressive regressive depositional cycles along midcontinent outcrop belt north america at least 55 cycles of marine inundation and withdrawal are recognized in the mid desmoinesian to mid virgilian midcontinent outcrop sequence in north america they range from widespread major cycles classic cyclothems with deep water facies extending across the northern shelf through intermediate cycles persisting as marine horizons across the shelf to minor cycles developed on the lower shelf or as parts of major cycles biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems but they may be obscured by the distinctness of the major cyclothems estimates of cycle periods range from about 40 to 120 x 10 sup 3 yr for the minor cycles up to about 235 to 400 x 10 sup 3 yr for the major cyclothems the range for all cycles corresponds well to the range of periods of earth s orbital parameters that constitute the milankovitch insolation theory for the pleistocene ice ages and it further supports gondwanan glacial control for the pennsylvanian cycles even though the dominant period of the major pennsylvanian cyclothems is up to four times longer than the dominant 100 000 yr period inmore the pleistocene the shapes of both curves display rapid marine transgression rapid melting of ice caps and slow interrupted regression slow buildup of ice caps which suggest similar linkages between the climatic effects of the orbital parameters and ice cap formation and melting at the two different scales widely separated in time 28 references 3 figures less

radar probing of jovian icy moons understanding subsurface water and structure detectability in the juice and europa missions abstract radar probing of jovian icy satellites is fundamental for understanding the moons origin and their thermal evolution as potential habitable environments in our solar system using the current state of knowledge of the geological and geophysical properties of ganymede europa and callisto we perform a comprehensive radar detectability study to quantify the exploration depth and the lower limit for subsurface identification of water and key tectonic structural elements to achieve these objectives we establish parametric dielectric models that reflect different hypotheses on the formation and thermal evolution of each moon the models are then used for fdtd radar propagation simulations at the 9 mhz sounding frequency proposed for both esa juice and nasa europa missions we investigate the detectability above the galactic noise level of four predominant subsurface features brittle ductile interfaces shallow faults brine aquifers and the hypothesized global oceans for ganymede our results suggest that the brittle ductile interface could be within radar detectability range in the bright terrains but is more challenging for the dark terrains moreover understanding the slope variation of the brittle ductile interface is possible after clutter reduction and focusing for europa the detection of shallow subsurface structural elements few kilometers deep such as fractures faults and brine lenses is achievable and not compromised by surface clutter the objective of detecting the potential deep global ocean on europa is also doable under both the convective and conductive hypotheses finally for callisto radar waves can achieve an average penetration depth of 15 km although the current understanding of callisto s subsurface dielectric properties does not suggest sufficiently strong contrasts to produce unambiguous radar returns

the 2 7 2 0 ga volcano sedimentary record of africa india and australia evidence for global and local changes in sea level and continental freeboard abstract the 2 7 2 0 ga volcano sedimentary records of the african indian and australian cratons indicate two broadly defined periods of extensive drowning of the emergent continental areas concomitant with lowered freeboard carbonate banded iron formation bif platforms characterised the first such event at ca 2 6 2 4 ga africa and australia to 2 7 ga india these earlier globally enhanced sea levels are ascribed to increased mid ocean ridge activity possibly related to breakup of a postulated late archaean southern supercontinent alternatively a transition from global scale catastrophic mantle overturn events to the onset of plate tectonics may have occurred in the late archaean nelson 1998 earth planet sci lett 158 109 119 both explanations of increased mid ocean ridge activity are compatible with significant early to middle archaean crustal growth armstrong 1981 phil trans r soc london a 301 443 472 with the emergent high freeboard cratons being subjected to aggressive weathering and erosion enhanced continental crustal growth near the archaean proterozoic boundary mclennan and taylor 1982 j geol 90 347 361 related to the development of significant island arc complexes would have resulted in common lowered freeboard enhanced sea level conditions at the passive margins of the southern cratons the diachronous nature of these earlier transgressions in the various cratons may reflect the effect of local tectonic movements and or the thermal state of the cratons from ca 2 4 2 2 ga cratons that make up the present day continents of india africa and australia had relatively high continental freeboard and lowered sea levels glacigenic deposits are preserved on the kaapvaal africa singhbhum india and pilbara australia cratons the second broadly defined drowning event at ca 2 15 ga was probably due to post glacial climatic amelioration freeboard was reduced by the combination of eustatic rise and the reestablishment of aggressive weathering as warmer palaeoclimates returned in india carbonates were more prominent than the siliciclastic sediments including prominent black shales seen in africa and australia

sequence stratigraphy of the middle cambrian daegi formation korea and its bearing on the regional stratigraphic correlation abstract the sediments that comprise the middle cambrian daegi formation in eastern central korea are interpreted to have been deposited in a carbonate ramp setting the daegi formation consists of nine lithofacies argillaceous rock ribbon rock oolitic limestone skeletal limestone microbial limestone intraclastic limestone micritic limestone bioturbated limestone and crystalline limestone which are grouped into three facies associations presenting from base up outer ramp grain shoal and inner ramp facies associations two depositional sequences can be distinguished in the daegi formation sequence 1 in the lower part of the daegi formation comprises a lower transgressive systems tract tst and an upper highstand systems tract hst the tst consists of terrigenous deposits with subordinate limestones while the hst contains various types of limestone sequence 2 comprises the upper half of the daegi formation and was deposited during a tst the sequence stratigraphic analysis of the daegi formation suggests that the sediments were deposited during one 3rd order sea level change during the middle to late middle cambrian the sequence stratigraphic framework of the daegi formation can be excellently correlated with coeval deposits in north china the zhangxia and the lower part of the overlying gushan formations which belong to the same tectonic block as the korean peninsula the sino korean block skb the almost identical sequence stratigraphic frameworks in two separate basins suggest that the sequence stratigraphic development on the skb was mainly influenced by eustatic changes during the middle cambrian

dynamic sedimentation of paleoproterozoic continental margin iron formation labrador trough canada paleoenvironments and sequence stratigraphy abstract the paleoproterozoic sokoman formation ca 1 88 ga of the labrador trough eastern canada is a ca 100 m thick succession of interbedded iron formation and fine grained terrigenous clastic sedimentary rocks detailed examination of drill cores and outcrops indicates a dynamic paleoshelf where an oxygen stratified water column coastal upwelling of hydrothermally derived fe and si as well as tide and storm generated currents controlled lithofacies character vertical and lateral facies stacking patterns record deposition through two relative sea level cycles that produced seven distinct lithofacies comprising two unconformity bounded sequences sequence 1 reflects deposition of hematitic peritidal iron formation as deep as the upper shoreface sequence 2 is truncated by later erosion and encompasses the change to deeper water accumulation of magnetite and fe silicate rich iron formation the character and lateral distribution of redox sensitive facies indicate that iron formation accumulation was controlled as much by shelf hydraulics as oxygen levels the development of a suboxic surface ocean is interpreted to reflect photosynthetic oxygen production from a combination of peritidal stromatolites and cyanobacterial phytoplankton that flourished in nutrient rich upwelled waters offshore deposition of other continental margin iron formations also occurred on paleoproterozoic shelves that were favorably positioned for coastal upwelling variability between iron formations reflects intrinsic factors such as shelf profile fluvial contribution eolian input evaporation rates and coastal current systems which influenced upwelling dynamics and the delivery of fe si and nutrients aridity onshore was a primary depositional control since it governed the transport and type of diluting terrigenous clastics as well as evaporative precipitation along the coastline as in the phanerozoic unconformities and transgressive and maximum flooding surfaces frame iron formation sequences but with important differences the absence of trace and body fossils as well as lack of terrestrial vegetation can make the recognition of these surfaces difficult transgressive surfaces can also be easily mistaken for phanerozoic style maximum flooding surfaces since stratigraphic condensation was restricted to inboard environments during ravinement outboard the accumulation of fresh precipitates increased sedimentation to produce a maximum flooding surface not usually marked by a prominent depositional hiatus understanding these differences is essential for establishing an accurate sequence stratigraphic framework such context is the backdrop for properly interpreting the sedimentology oceanography microbial ecology and geochemistry of continental margin iron formations

radar sounding of temperate permafrost in alaska analogy to the martian midlatitude to high latitude ice rich terrains 1 radar detection of subsurface ice on mars has been widely debated in part because the dielectric signature of ice as deduced from the dielectric constant can be confused with dry silicate rich materials to identify the ice dielectric signature it is crucial to estimate the imaginary part of the dielectric permittivity inferred from the dielectric attenuation after removing the scattering loss unfortunately the latter remains poorly quantified at both mars advanced radar for subsurface and ionospheric sounding marsis and shallow subsurface radar sharad frequencies to address this ambiguity we conducted multiple frequency ground penetrating radar and resistivity investigations in well characterized temperate permafrost in fairbanks alaska the area shows several geomorphologic similarities to midlatitude and high latitude terrains on mars this approach allowed us to quantify the dielectric and scattering losses in temperate permafrost over the 10 to 1000 mhz frequency band at 20 mhz our results suggest an average dielectric loss rate of 0 25 0 03 db m whereas the corresponding average scattering loss rate is 0 94 0 37 db m the scattering loss was found to represent 69 of the total signal attenuation considering this result and the study by heggy et al 2006a in volcanic environments we revised the interpretation of the attenuation coefficient calculated from sharad data over the deuteronilus mensae region and amazonis planitia we then used the reevaluated dielectric loss to estimate the imaginary part of the dielectric permittivity our results suggest that even if deuteronilus mensae deposits and the vastitas borealis formation may have similar dielectric constants their imaginary parts are different this implies that the two regions have different bulk compositions with the former being ice rich sediments and the latter being nonconsolidated volcanic deposits

stability analysis of earthquake induced rock slope based on back analysis of shear strength parameters of rock mass abstract high steep rock slopes are much more likely to collapse and form weir body due to earthquake converting the weir body to hydraulic engineering is a good way to deal with natural disasters however it is difficult to evaluate the stability of earthquake induced rock slope due to the lack of shear strength parameters of rock mass based on three dimension nonlinear finite elements deformation reinforcement theory was adopted in which plastic complementary is used to measure the global stability of slope and unbalanced forces is utilized to identify the damage region the shear strength parameters has been determined through back analysis based on stability and failure status before and after earthquake and monitoring data after earthquake then the stability evaluation under static conditions dynamic conditions and rainfall conditions has been carried out respectively the results show that failure mode of the slope under seismic load is consistent with the actual situation when the lowest material parameters are used the major failure mode of the slope is sliding along the fault f5 and local collapse of the hanging body at the top of the slope under dynamic or rainfall load the local stability can be improved effectively by excavating and taking bolt anchorages on the top of the slope

extension of the astronomically calibrated polarity time scale to the miocene pliocene boundary the early pleistocene to late pliocene astronomically calibrated time scale of shackleton et al 1 and hilgen 2 is extended to the miocene pliocene boundary this is done by correlating the detailed record of caco3 cycles in the trubi and the lower part of the overlying narbone formation rossello composite section sicily to the astronomical record using 1 inferred phase relations between these caco3 cycles and the corresponding orbital cycles of precession and eccentricity and 2 calibration points provided by the previously established astronomical calibration of sapropelitic layers which occur in the topmost part of the caco3 record 2 this correlation allows all small scale caco3 cycles in the rossello composite section to be coded after the correlative precession peak and to be dated astronomically with an accuracy of 1 ky in combination with the available high resolution magnetostratigraphy it further allows the construction of an astronomically calibrated geomagnetic polarity time scale for the major part of the gilbert and gauss chrons this new time scale gives ages for the reversal boundaries of the kaena 3 04 3 11 ma and mammoth 3 22 3 33 ma the gilbert gauss chron boundary 3 58 ma and the reversal boundaries of the cochiti 4 18 4 29 ma nunivak 4 48 4 62 ma sidufjall 4 80 4 89 ma and thvera 4 98 5 23 ma these ages are significantly older than the ages given by conventional time scales age discrepancies gradually increase with increasing age the age of 5 32 ma for the miocene pliocene boundary as defined by the base of the trubi on sicily is almost 0 5 m y 9 5 older than the presently accepted age of 4 86 ma 3 these considerable discrepancies with the conventional time scale can either be explained by an consistent error in the decay constants used in k ar radiometric dating or more likely by diffusional loss of radiogenic argon

global tectonics and eustasy for the past 2 billion years abstract continental freeboard and eustasy as gauged by the relative position of the world shelf break with respect to sea level have varied by 250 m from today s ice free shelf break depth of 200 m during the past 600 ma assuming constant or uniformly accreting continental crust and ocean water volume in an ice free world sea level fluctuations can be attributed to variation in the world ocean basin volume caused by changes in either its area or its depth relative to the world shelf break an increase in volume and lowering of sea level occur as 1 the world ocean floor ages cools and subsides 2 accreting continents collide thicken and decrease in area and 3 poorly conductive continental platforms become thermally elevated due to a size induced stasis over the mantle conversely a decrease in the age of the world ocean floor attenuation of continental crust during rifting and an increase in continent number and mobility will reduce the world ocean basin volume and raise sea level theoretical sea level calculated from these principles correlates well with calibrated first order cycles of eustatic sea level change for the phanerozoic the record closely fits a simple model of retardation and acceleration of terrestrial heat loss during alternating periods of supercontinent accretion and fragmentation calibrated to sea level highstands successive first order marine transgressions and orogenic pangea regressions characterize a self sustaining 440 ma plate tectonic cycle for the late precambrian and phanerozoic the cycle can be recognized as far back as 2 ga from the tectonic evidence of continental collision and rifting recorded in global orogenic peaks and mafic dike swarms and may be related to major episodes of glaciation and evolutional biogenesis

massive co2 ice deposits sequestered in the south polar layered deposits of mars shallow radar soundings from the mars reconnaissance orbiter reveal a buried deposit of carbon dioxide co2 ice within the south polar layered deposits of mars with a volume of 9500 to 12 500 cubic kilometers about 30 times that previously estimated for the south pole residual cap the deposit occurs within a stratigraphic unit that is uniquely marked by collapse features and other evidence of interior co2 volatile release if released into the atmosphere at times of high obliquity the co2 reservoir would increase the atmospheric mass by up to 80 leading to more frequent and intense dust storms and to more regions where liquid water could persist without boiling

out of our depth on the impossibility of fathoming eustasy from the stratigraphic record the evolution of a sedimentary basin s gross morphology depends upon 1 basement movement 2 sediment accumulation and compaction and 3 variations of eustasy with time thus if an accurate history of eustasy could be derived it would aid in our understanding of basin stratigraphy and help in the prediction of sediment geometry from described areas techniques which attempt to determine the magnitude of eustatic sea level excursions include the measurement of 1 the amount of sedimentary onlap onto the continental margins with and without the use of hypsometric curves 2 the thickness of marine sedimentary cycles and the elevation and distance between indicators of old strandlines 3 the perturbations on individual thermo tectonic subsidence curves and stacked crustal subsidence curves 4 the variations in deep ocean oxygen isotopes found in sediments and 5 the size of variables used in graphical and numerical simulations of basin fill in terms of tectonic behavior rates of sediment accumulation and eustasy which invert the problem to date a combination of the use of relative sea level charts derived from sediment onlap of the continental margin with dimensioning by oxygen isotopes responding to glacial events offers the best potential for relative tectono eustatic sea level curves but even this method can not produce a unique solution for absolute eustatic variations mathematical modelling shows that at best it is possible to obtain only the sum of tectonic basement subsidence and sea level variations from the above methods and at worst not even that simple a combination thus every proposed scheme to measure eustatic sea level excursions assumes some behavior for two of the three underlying processes tectonic movement of the basement sedimentary accumulation and eustatic sea level each scheme then determines the third process relative to the assumed model behavior of the other two it would seem that like king canute we cannot command the sea though we can still use undifferentiated relative tectono eustatic sea level curves to generate a family of solutions which are the product of a variety of absolute sea level curves and tectonic models each solution has then to be assessed in terms of geologic setting and the hypotheses it generates

evidence for geologic processes on comets spacecraft missions have resolved the nuclei of six periodic comets and revealed a set of geologically intriguing and active small bodies the shapes of these cometary nuclei are dominantly bilobate reflecting their formation from smaller cometesimals cometary surfaces include a diverse set of morphologies formed from a variety of mechanisms sublimation of ices driven by the variable insolation over the time since each nucleus was perturbed into the inner solar system is a major process on comets and is likely responsible for quasi circular depressions and ubiquitous layering sublimation from near vertical walls is also seen to lead to undercutting and mass wasting fracturing has only been resolved on one comet but likely exists on all comets there is also evidence for mass redistribution where material lifted off the nucleus by subliming gases is deposited onto other surfaces it is surprising that such sedimentary processes are significant in the microgravity environment of comets there are many enigmatic features on cometary surfaces including tall spires kilometer scale flows and various forms of depressions and pits furthermore even after accounting for the differences in resolution and coverage significant diversity in landforms among cometary surfaces clearly exists yet why certain landforms occur on some comets and not on others remains poorly understood the exploration and understanding of geologic processes on comets is only beginning these fascinating bodies will continue to provide a unique laboratory for examining common geologic processes under the uncommon conditions of very high porosity very low strength small particle sizes and near zero gravity

coastal cliff monitoring and analysis of mass wasting processes with the application of terrestrial laser scanning a case study of rugen germany abstract an active landslide affecting a composite sea cliff section of the island of rugen germany was investigated and monitored using terrestrial laser scanning biannual surveys were performed from 2006 to 2011 high resolution scans were used to delineate landslide extensions monitor the spatial and temporal changes and evaluate the processes of mass wasting along the cliff section between may 2006 and may 2011 the multi temporal analysis documents a strong landward progression of the landslide that resulted in an increase in the planimetric area by 32 in the same period 9365 m 3 of soil volume has been removed primarily due to rainfall triggered surface runoff erosion and the resulting slumping this volume loss correlates with the preferential erosion of weak and unconsolidated sediments building up the major part of the cliff face this produced a maximum cliff top retreat of 17 32 m with an average retreat rate of 3 46 m yr 1 the quantification of the mass wasting processes and cliff top retreat demonstrates the substantial effect of local cliff lithology on slope stability and supports a prognosis of the near future development of the landslide furthermore the absence of local wave attack indicators or human activity highlights the major role of subaerial processes in the erosion of the sea cliff these results can be transferred to cliff locations in the urbanised cliff top area nearby that currently suffer similar cliff erosion processes and episodic events of large cliff top retreats the study therefore provides reliable data for the local authorities in charge of hazard assessment and planning and implementation of adaptive countermeasures

testing for eustatic sea level control in the precambrian sedimentary record abstract stratigraphic successions are deposited under the influence of three primary controls which tend to vary systematically through time these controls are tectonism basin subsidence and uplift sea level change and sediment supply the development of sequence stratigraphy has enabled the introduction of systematic quantitative methods for the analysis of these controls the use of the sequence approach requires the establishment of a regional sequence framework and detailed chronostratigraphic control working with the phanerozoic record this approach has revealed a variety of sequence types reflecting long term tectonostratigraphic processes caused by continental rifting continental collisions and cratonic dynamic topography high frequency thrust loading cycles in foreland basins and high frequency cycles caused by orbital forcing glacioeustasy 104 5 year periodicity and eustasy driven by changing rates of sea floor spreading 107 8 year periodicity have emerged as two significant global processes documenting the sequence record in the precambrian has proved difficult owing to fragmentary preservation and structural deformation methods of dating are at present not precise enough to permit reliable regional correlation or testing of high frequency sequence generating mechanisms some studies of precambrian sequence architecture have been achieved but these indicate tectonic processes acting at a much slower rate than during the phanerozoic further analysis of this problem is required

depositional sequences in a foreland basin north western domain of the continental duero basin spain abstract the cenozoic record of the north western domain of the duero basin is articulated at the surface through a set of continental depositional sequences called from base to top the vegaquemada sequence the candanedo sequence and the barrillos sequence these depositional sequences were deposited in continental sedimentary environments the deposition of the first sequence occurred through a fluvial system with floodplains cut by low sinuosity channels the vegaquemada sequence was developed between the middle eocene and the early agenian the second sequence was formed by a set of highly efficient transport alluvial fans that evolved laterally towards fluvial systems with low sinuosity fluvial channels and an extensive floodplain where several types of palaeosols were formed this sequence developed between the early agenian and the late vallesian the third unit the barrillos sequence between the late vallesian and the turolian ruscinian transition was generated by a set of highly efficient transport alluvial fans dominated by low sinuosity fluvial channels in subsurface geology seismic and well data are used to rebuild the stratigraphic architecture the two basal depositional sequences can be identified with two seismic units the palaeogene seismic unit pgsu and the neogene seismic unit ngsu respectively in the present work we obtained the isovelocity isochron and isobath maps for the top and base of the two cenozoic units the palaeozoic pzsu and mesozoic mzsu seismic units are found under these two units through study of the logs of the various boreholes it was only possible to analyse the upper 700 m of the candanedo sequence ngsu without encompassing the total thickness of the unit several middle order sequences were differentiated in general showing a sequential fining upwards evolutionary character additionally for the boreholes analysed two main types of electrofacies were identified both representing fluvial channels and floodplain deposits the north western domain of the duero basin is interpreted to have been formed in response to the tectonic uplifting of the cantabrian mountains since middle eocene times integration of the data concerning the surface and subsurface geology in this domain reveals that this basin edge behaved as a foreland basin during cenozoic stages the foredeep with a depth of 2800 m is oriented east west and has a sediment thickness of up to 3500 m the forebulge is located in the southwestern zone and represents an area of basement uplifting in which a minimum thickness of materials from the cenozoic depositional sequences has accumulated

terrestrial laser scanning used to determine the geometry of a granite boulder for stability analysis purposes abstract in this paper we analyze the use of terrestrial laser scanning tls technologies to determine the geometric features of a granite boulder accurate determination of these features is a key to performing a reliable stability analysis of the boulder tls has been demonstrated to have important advantages over traditional measurement techniques such as for example direct methods based on the use of tapes or indirect methods such as topography or close range photogrammetry tls equipment enables thousands of points to be accurately measured in minutes in our study tls measured points were used to model the surface of a boulder geometric parameters were then calculated namely centre of gravity volume of the boulder and dimensions of the boulder contact area with the ground taking into account mechanical and environmental factors these parameters were used to calculate the safety factor of the boulder against toppling and sliding our results show that when seismic activity in the region is taken into consideration the boulder is borderline stable unstable

quantitative assessment for the rockfall hazard in a post earthquake high rock slope using terrestrial laser scanning abstract geometric information and discontinuity characterization of rock masses are the key aspects of the analysis of the evolution and failure mechanisms of rockfalls with the advantageous use of terrestrial laser scanning tls the accurate three dimensional 3d spatial information of rock slopes can be obtained without contact by conducting a fuzzy k means algorithm in this study the automatic identification of discontinuity sets is achieved and dominant occurrences of rock mass discontinuities in each local region can be acquired in great detail this automatic identification method permits the user to visually identify the discontinuity sets and acquire their spacial distribution features e g occurrences spacings trace lengths and their geometric compounding relationships at the same time based on the shortest distance sd algorithm and the surface to plane volume calculation algorithm the distributions shapes volumes and scars of the rockfalls can be accurately detected over the monitored time interval these methods are able to provide adequate investigations and quantitative assessment for the rockfall failure mechanisms and evolutions of the hongshiyan post failure rock slope after the 2014 ludian earthquake the topography of the landslide surface mechanical properties scales and the structural features of the discontinuities have a significant effect on the failure mechanisms distributions and volumes of rockfalls the main failure mechanisms of the rockfall investigated in this rock slope can be divided into plane failure wedge failure and toppling failure the plane and wedge failures mainly occurred in the landslide surface while the toppling failures are mainly observed along the edge of the post failure slope which is obviously responded by preferred discontinuities the reverse dip stratified structure characteristics and the excavation disturbances during the recovering and slope treatment stage induce numerous progressive and continuous failures of rockfalls the results are beneficial for the design and optimization of rockfall treatments

comprehensive examination of large mineral and rock fragments in stardust tracks mineralogy analogous extraterrestrial materials and source regions abstract transmission electron microscopy examination of 87 large fragments from 16 carrot shaped and bulbous stardust sd tracks was performed to study the range and diversity of materials present in comet wild 2 olivines and low ca pyroxenes represent the largest proportions of fragments observed however a wide range of minerals and rocks were found including probable ferromagnesian al rich and si rich chondrule fragments a refractory inclusion possible matrix mineral lithic clasts and probable condensate minerals these materials combined with fine grained components in the tracks are analogous to components in unequilibrated chondrite meteorites and cluster interplanetary dust particles idps two unusual lithologies in the bulbous tracks are only observed in chondritic porous idps and may have direct links to idps the absence of phyllosilicates indicates that comet wild 2 may be a dry comet that did not accrete or form significant amounts of hydrated phases some large mineral fragments in the sd tracks are analogous to large mineral idps the large variations of the coarse grained components within and between all 16 tracks show that comet wild 2 is mineralogically diverse and unequilibrated on nearly all scales and must have accreted materials from diverse source regions that were widely dispersed throughout the solar nebula

oxygenation of the earth s atmosphere ocean system a review of physical and chemical sedimentologic responses abstract the great oxidation event goe is one of the most significant changes in seawater and atmospheric chemistry in earth history this rise in oxygen occurred between ca 2 4 and 2 3 ga and set the stage for oxidative chemical weathering wholesale changes in ocean chemistry and the evolution of multicelluar life most of what is known about this important event and the subsequent oxygenation history of the precambrian earth is based on either geochemistry or data mining published literature to understand the temporal abundance of bioelemental sediments bioelemental sediments include iron formation chert and phosphorite which are precipitates of the nutrient elements fe si and p respectively because biological processes leading to their accumulation often produce organic rich sediment black shale can also be included in the bioelemental spectrum thus chemistry of bioelemental sediments potentially holds clues to the oxygenation of the earth because they are not simply recorders of geologic processes but intimately involved in earth system evolution chemical proxies such as redox sensitive trace elements cu cr v cd mo u y zn and ree s and the ratio of stable isotopes 56fe 53cr 97 95mo 98 95mo 34s 33s in bioelemental sediments are now routinely used to infer the oxygenation history of paleo seawater the most robust of these is the mass independent fractionation of sulfur isotopes mif which is thought to have persisted under essentially anoxic conditions until the onset of the goe at ca 2 4 ga since most of these proxies are derived from authigenic minerals reflecting pore water composition extrapolating the chemistry of seawater from synsedimentary precipitates must be done cautiously paleoenvironmental context is critical to understanding whether geochemical trends during earth s oxygenation represent truly global or merely local environmental conditions to make this determination it is important to appreciate chemical data are primarily from authigenic minerals that are diagenetically altered and often metamorphosed because relatively few studies consider alteration in detail our ability to measure geochemical anomalies through the goe now surpasses our capacity to adequately understand them in this review we highlight the need for careful consideration of the role sedimentology stratigraphy alteration and basin geology play in controlling the geochemistry of bioelemental sediments such an approach will fine tune what is known about the goe because it permits the systematic evaluation of basin type and oceanography on geochemistry this technique also provides information on how basin hydrology and post depositional fluid movement alters bioelemental sediments thus a primary aim of any investigation focused on prominent intervals of earth history should be the integration of geochemistry with sedimentology and basin evolution to provide a more robust explanation of geochemical proxies and ocean atmosphere evolution

investigation of rock fragmentation during rockfalls and rock avalanches via 3 d discrete element analyses this paper investigates the characteristics of dynamic rock fragmentation and its influence on the postfailure fragment trajectory a series of numerical simulations by discrete element method dem were performed for a simple rock block and slope geometry where a particle agglomerate of prismatic shape is released along a sliding plane and subsequently collides onto a flat horizontal plane at a sharp kink point the rock block is modeled as an assembly of bonded spherical particles with fragmentation arising from bond breakages bond strength and stiffness were calibrated against available experimental data we analyzed how dynamic fragmentation occurs at impact together with the generated fragment size distributions and consequently their runout for different slope topographies it emerges that after impact the vertical momentum of the granular system decreases sharply to nil while the horizontal momentum increases suddenly and then decreases the sudden boost of horizontal momentum can effectively facilitate the transport of fragments along the bottom floor the rock fragmentation intensity is associated with the input energy and increases quickly with the slope angle gentle slopes normally lead to long spreading distance and large fragments while steep slopes lead to high momentum boosts and impact forces with efficient rock fragmentation and fine deposits the fragment size decreases while the fracture stress and fragment number both increase with the impact loading strain rate supporting the experimental observations the fragment size distributions can be well fitted by the weibull s distribution function

structural analysis of turtle mountain alberta using digital elevation model toward a progressive failure abstract in 1903 the eastern slope of turtle mountain alberta was affected by a 30 m m 3 rockslide named frank slide that resulted in more than 70 casualties assuming that the main discontinuity sets including bedding control part of the slope morphology the structural features of turtle mountain were investigated using a digital elevation model dem using new landscape analysis techniques we have identified three main joint and fault sets these results are in agreement with those sets identified through field observations landscape analysis techniques using a dem confirm and refine the most recent geology model of the frank slide the rockslide was initiated along bedding and a fault at the base of the slope and propagated up slope by a regressive process following a surface composed of pre existing discontinuities the dem analysis also permits the identification of important geological structures along the 1903 slide scar based on the so called sloping local base level slbl an estimation was made of the present unstable volumes in the main scar delimited by the cracks and around the south area of the scar south peak the slbl is a method permitting a geometric interpretation of the failure surface based on a dem finally we propose a failure mechanism permitting the progressive failure of the rock mass that considers gentle dipping wedges 30 the prisms or wedges defined by two discontinuity sets permit the creation of a failure surface by progressive failure such structures are more commonly observed in recent rockslides this method is efficient and is recommended as a preliminary analysis prior to field investigation

detection and spatial prediction of rockfalls by means of terrestrial laser scanner monitoring abstract a rock face affected by small rockfalls has been monitored using a ground based remote sensing apparatus terrestrial laser scanner tls the pilot study area corresponds to the main scarp of the 1881 puigcercos landslide pallars jussa catalonia spain four datasets of the slope were acquired from september 2007 to july 2008 in an ongoing project the geomorphological evolution of the rock face in terms of volume and frequency of rockfall was studied by the comparison of sequential datasets in addition to the detection of past events this study deals with the spatial prediction of rockfalls through the detection of pre failure deformation as a precursory indicator the high resolution and accuracy and the maximum range of the tls offer interesting prospects for both spatial location and prediction of rockfall

a modified inverse velocity method for predicting the failure time of landslides abstract prediction of the failure time of landslides is always an important issue based on fukuzono s theory which suggests that the logarithm of the surface displacement velocity is proportional to the logarithm of the surface displacement acceleration in the final stage of the slope movement just before failure a modified inverse velocity method was proposed by introducing a controllable variable one landslide was detected in the certain open pit coal mine and four landslides were detected in the certain open pit iron mine by using ground based radar in the four landslides in the certain open pit iron mine the acceleration obviously decreased a few hours before failure which is inconsistent with the existing creep theory the traditional inverse velocity method and the modified inverse velocity method were employed to analyze the five landslides the analysis results show that the modified inverse velocity method can improve the effectiveness of prediction by reducing the prediction error caused by the acceleration decrease before failure the modified inverse velocity method proposed in this paper not only improves the prediction accuracy but also provides a study direction to improve the inverse velocity method that is it introduces controllable variables to improve the prediction accuracy

the application of a long range laser scanner for monitoring volcanic activity on mount etna abstract there is a requirement for rapid remote monitoring of ground deformation of volcanoes especially during eruptions a long range reflector less laser scanning instrument manufactured by riegl laser measurement systems was used on mount etna in october 2000 and its potential for monitoring ground surface changes associated with volcanic activity was evaluated the 3dlm lr1 scanner system can measure distances up to 2 km with an accuracy of 25 mm in typical conditions measurement rates range from 1 point per second at 2 km to 4 points per second at 10 m the system also records reflective intensity and this proved useful in distinguishing between different types of volcanic material cloud and gas obscured some measurements but the scanning nature of the instrument coupled with effective data filtering software allowed robust digital terrain models to be created

application of a long range terrestrial laser scanner to a detailed rockfall study at vall de nuria eastern pyrenees spain abstract in this study we show the application of a long range terrestrial laser scanner tls to a detailed rockfall study in a test zone at vall de nuria located in the eastern pyrenees data acquisition was carried out using tls ilris3d the new generation of reflector less laser scanners with a high range accuracy and velocity of measurements eight scans were performed at 3 stations to acquire coordinates of almost 4 million points the results from the acquired data are a high accuracy digital elevation model dem and the reconstruction of the joint geometry the former is used for inventory of rockfalls and for more accurate rockfall simulation trajectories and velocities the latter allows us to model the geometry and volume of the source area in recent rockfalls our findings suggest that tls technology could be a tool of reference in rockfall studies in the near future

the philae lander reveals low strength primitive ice inside cometary boulders on 12 november 2014 the philae lander descended towards comet 67p churyumov gerasimenko bounced twice off the surface then arrived under an overhanging cliff in the abydos region the landing process provided insights into the properties of a cometary nucleus1 3 here we report an investigation of the previously undiscovered site of the second touchdown where philae spent almost two minutes of its cross comet journey producing four distinct surface contacts on two adjoining cometary boulders it exposed primitive water ice that is water ice from the time of the comet s formation 4 5 billion years ago in their interiors while travelling through a crevice between the boulders our multi instrument observations made 19 months later found that this water ice mixed with ubiquitous dark organic rich material has a local dust ice mass ratio of formula see text matching values previously observed in freshly exposed water ice from outbursts4 and water ice in shadow5 6 at the end of the crevice philae made a 0 25 metre deep impression in the boulder ice providing in situ measurements confirming that primitive ice has a very low compressive strength less than 12 pascals softer than freshly fallen light snow and allowing a key estimation to be made of the porosity 75 7 per cent of the boulders icy interiors our results provide constraints for cometary landers seeking access to a volatile rich ice sample

origin of the pluto charon system constraints from the new horizons flyby abstract new horizon s accurate determination of the sizes and densities of pluto and charon now permit precise internal models of both bodies to be constructed assuming differentiated rock ice structures we find that pluto is close to 2 3 solar composition anhydrous rock by mass and charon 3 5 solar composition anhydrous rock by mass pluto and charon are closer to each other in density than to other large 1000 km diameter kuiper belt bodies despite this we show that neither the possible presence of an ocean under pluto s water ice shell and no ocean within charon nor enhanced porosity at depth in charon s icy crust compared with that of pluto are sufficient to make pluto and charon s rock mass fractions match all four small satellites styx nix kerberos hydra appear much icier in comparison with either pluto or charon in terms of a giant impact origin both these inferences are most consistent with the relatively slow collision of partly differentiated precursor bodies canup astrophys j 141 35 2011 this is in turn consistent with dynamical conditions in the ancestral kuiper belt but implies that the impact precursors themselves accreted relatively late and slowly to limit 26 al and accretional heating the iciness of the small satellites is not consistent with direct formation of the pluto charon system from a streaming instability in the solar nebula followed by prompt collapse of gravitationally bound pebble piles a proposed formation mechanism for kuiper belt binaries nesvorn et al astron j 140 785 793 2010 growth of pluto scale bodies by accretion of pebbles in the ancestral kuiper belt is not ruled out however and may be needed to prevent the precursor bodies from fully differentiating due to buried accretional heat prior to the charon forming impact

structural and geomorphological features of landslides in the bhutan himalaya derived from terrestrial laser scanning abstract this study presents data on landslides affecting the main west east transport corridor in the himalaya of eastern bhutan close to the main central thrust the study focuses on the extraction of structural and geometrical information from terrestrial laser scanning tls data utilising a case study landslide the namling landslide analyses of the tls data allow extraction of slide geometry discontinuity orientations and identification of the mode of failure the tls results are compared to a traditional engineering geological survey and prove to yield considerable added value and should form the basis of new approaches to geomorphological studies and site assessment macro scale geomorphological reconnaissance findings are outlined and interpreted within a conceptual model of the evolution of landslide features here termed hierarchical landsliding it is concluded that the nam ling landslide is indicative of deeper seated deformation and is not purely a function of road construction

properties of the 67p churyumov gerasimenko interior revealed by consert radar the philae lander provides a unique opportunity to investigate the internal structure of a comet nucleus providing information about its formation and evolution in the early solar system we present comet nucleus sounding experiment by radiowave transmission consert measurements of the interior of comet 67p churyumov gerasimenko from the propagation time and form of the signals the upper part of the head of 67p is fairly homogeneous on a spatial scale of tens of meters consert also reduced the size of the uncertainty of philae s final landing site down to approximately 21 by 34 square meters the average permittivity is about 1 27 suggesting that this region has a volumetric dust ice ratio of 0 4 to 2 6 and a porosity of 75 to 85 the dust component may be comparable to that of carbonaceous chondrites

semi automatic extraction of rock mass structural data from high resolution lidar point clouds abstract in this paper a matlab tool called diana discontinuity analysis for the 2d and 3d geo structural analysis of rock mass discontinuities on high resolution laser scanning data is presented the proposed approach is able to semi automatically retrieve some relevant rock mass parameters namely orientation number of sets spacing frequency and derived rqd persistence block size and scale dependent roughness by analyzing high resolution point clouds acquired from terrestrial or aerial laser scanners in addition with a specific diana option called filterveg we are able to remove vegetation or other disturbing objects from the point cloud which is one of the main problems in lidar data processing some examples of the proposed method have demonstrated its ability to investigate rock masses characterized by irregular block shapes and suggest applications in the field of engineering geology and emergency management when it is often advisable to minimize survey time in dangerous environments and in the same time it is necessary to gather all the required information as fast as possible

the sequence stratigraphic concept and the precambrian rock record an example from the 2 7 2 1 ga transvaal supergroup kaapvaal craton abstract sequence stratigraphic concepts are applied to the 2 7 2 1 ga transvaal supergroup which constitutes the sedimentary floor to the bushveld igneous complex the transvaal succeeds the foreland fill of the witwatersrand supergroup and in its lowermost portions is partly synchronous with the ventersdorp supergroup lavas that followed upon the witwatersrand sediments in the stratigraphic record the unconformable contacts at the base and the top of the transvaal supergroup mark significant changes in the overall tectonic setting which qualifies them as first order sequence boundaries sedimentation within the transvaal basin was controlled by cycles of extensional and or thermal subsidence resulting in the accumulation of sequences separated by stages of base level fall generating sequence bounding subaerial unconformities the transvaal first order sequence is subdivided into five second order unconformity bounded depositional sequences i e the protobasinal black reef chuniespoort rooihoogte timeball hill and boshoek houtenbek sequences the span of time of these second order sequences averaging 130 ma is much longer than the duration of the second order phanerozoic cycles which is explained by the less evolved and thus slower plate tectonic processes that dominated the late archaean early proterozoic times each transvaal second order sequence preserves a variable number of systems tracts mainly as a function of the strength of the erosional processes associated with the ravinement surfaces and subaerial unconformities in a complete succession a sequence would include a basal lowstand systems tract lst followed by transgressive tst highstand hst and falling stage fsst systems tracts the protobasinal and rooihoogte timeball hill sequences only preserve the lst and tst due to the strong post depositional erosion the black reef sequence is composed of lst tst and hst the chuniespoort sequence preserves the tst hst and fsst but lacks the lst due to ravinement erosion the boshoek houtenbek sequence develops the complete succession of systems tracts common features may be emphasized between the same types of systems tract developed within different sequences the lst includes high energy coarse prograding facies such as alluvial fans and fan delta systems that fill the irregularities of the pre existing topography and lead to the peneplanation of the depositional areas the tst may be recognized from retrogradational stacking patterns that are associated with the transgression of marine environments the hst marks the normal regression of the previous marine environments which assumes coeval aggradation of fluvial and basinal facies within an overall progradational framework the fsst would normally include only basinal facies age equivalent with the correlative subaerial unconformities in our case study the stages of base level fall resulted invariably in fully nonmarine environments within the transvaal area generally leading to the development of subaerial unconformities in particular circumstances the nonmarine environment may still accumulate and preserve fluvial alluvial fan or lacustrine sediments as a function of the relative position between topography and local equilibrium profiles and base levels the interpretations of base level rise and fall resulting from the application of the sequence stratigraphic concept to the 2 7 2 1 ga transvaal supergroup enable estimation of sea level changes during deposition of this succession with an understanding of local tectonic conditions on the kaapvaal craton and of coeval sedimentation elsewhere in africa eustatic and relative sea level changes and variation in continental freeboard conditions may be suggested for the transvaal supergroup

time transgressive archean unconformities underlying molasse basin fill successions of dissected oceanic arcs superior province canada abstract late archean diachronous unconformities underlying tectonically controlled coarse clastic successions are located throughout the superior province of canada examples studied in detail include hiatuses at the base of the timmins and kirkland basins in the abitibi greenstone belt and the crowduck and stormy basins in the wabigoon subprovince the timmins molasse basin fill succession overlies a high angle subaerial unconformity separating deepwater turbiditic deposits from fluvial conglomerates a subaerial erosional unconformity defines the contact between mafic flows and overlying felsic volcaniclastic deposits and fluvial conglomerates of the kirkland basin the crowduck and stormy successions are characterized by shallow water and subaerial unconformities between quartz feldspar porphyry stocks and clastic deposits the pronounced characteristics of the molasse basins which include 1 basal unconformities with older sedimentary volcanic or plutonic rocks 2 bounding fault systems 3 ba

patterns of sedimentation in the precambrian abstract the principle of uniformitarianism may be applied to precambrian basin evolution and to the sedimentary record as a whole the major difference in the precambrian eon lay in variability of rates and intensities of processes controlling weathering erosion transport deposition lithification and diagenesis this paper examines precambrian sedimentation patterns within the larger framework of earth evolution pre rock record sedimentation probably comprised deep water oceanic realms within which meteoritic and cometary impact events generated very large tsunamis resulting in very coarse volcaniclastic detritus combined with fine dust settling out of suspension all reworked by marine current systems and localised turbidites from c 4 to 3 2 ga greenstone belts provided the predominant settings for the thin passive margin carbonates bif stromatolitic evaporites pelites and quartzites and lesser synorogenic turbidites conglomerates and sandstones that accompanied the volcanic and volcaniclastic rocks typical of these settings common palaeoenvironments were high gradient alluvial fans low sinuosity braided rivers and relatively shallow marine settings subject to wave and tidal action and turbidity currents although continental crustal growth continued largely through greenstone belts until c 2 7 ga the witwatersrand basin c 3 0 2 7 ga kaapvaal craton south africa reflects initial stabilisation of the oldest craton with an epeiric sea accumulating largely fluvial detritus subject to tidal inland and storm wave craton marginal reworking within a retroarc foreland basin setting neoarchaean palaeoproterozoic sedimentation is discussed within a framework of two global superevents at c 2 7 ga and 2 2 1 8 ga each encompassing major changes in earth s evolution related to the supercontinent cycle mantle superplumes peaks in crustal growth rates and significant biochemical changes within the atmosphere hydrosphere system concomitant globally raised sea levels led to chemical and clastic epeiric seas within which the first giant carbonate platforms developed and deposition of iron formation peaked globally at c 2 5 ga the first global glaciation at c 2 4 2 2 ga provides little support for the snowball earth theory but does suggest a negative feedback loop model whereby intraglacial co 2 related warming and synglacial decreases in weathering alternated up to three times models for palaeo atmospheric and oceanic evolution are mutually exclusive but by c 1 8 ga the existence of large landmasses and free oxygen in earth s atmosphere enabled erg development and red bed sedimentation globally the full spectrum of phanerozoic modern sedimentary environments was thus present on earth a third postulated superevent at c 0 8 0 6 ga essentially recreated conditions experienced at c 2 2 1 8 ga with additionally at least three global refrigeration events

synchronous global sequence boundaries sedimentary sequences in marine basins develop in response to relative changes in sea level sequence development in individual basins may be satisfactorily explained by a combination of tectonic subsidence and long period changes in global sea level it has been argued however that apparently synchronous shoreline shifts in widely separated basins require actual fluctuations in the global sea level curve with a period of 1 10 m y we suggest a mechanism for producing synchronous relative sea level changes in widely separated and geologically independent basins without producing changes in all basins and without requiring short period fluctuations in the global sea level curve the same mechanism can produce nonsynchronous but related shoreline shifts in separate bas ns while the rate of global sea level change remains constant

radar soundings of the subsurface of mars the martian subsurface has been probed to kilometer depths by the mars advanced radar for subsurface and ionospheric sounding instrument aboard the mars express orbiter signals penetrate the polar layered deposits probably imaging the base of the deposits data from the northern lowlands of chryse planitia have revealed a shallowly buried quasi circular structure about 250 kilometers in diameter that is interpreted to be an impact basin in addition a planar reflector associated with the basin structure may indicate the presence of a low loss deposit that is more than 1 kilometer thick