giant blocks in the south kona landslide hawaii a large field of blocky sea floor hills up to 10 km long and 500 m high are gigantic slide blocks derived from the west flank of mauna loa volcano on the island of hawaii these megablocks are embedded in the toe of the south kona landslide which extends 80 km seaward from the present coastline to depths of nearly 5 km a 10 15 km wide belt of numerous smaller 1 3 km long slide blocks separates the area of giant blocks from two submarine benches at depths of 2600 and 3700 m depth that terminate seaward 20 to 30 km from the shoreline similar giant blocks are found on several other major submarine hawaiian landslides including those north of oahu and molokai but the south kona blocks are the first to be examined in detail using high resolution bathymetry dredging and submersible diving dredging of two of the giant blocks brought up pillowed tholeiitic lava observations from the u s navy submersible sea cliff on the asymmetrically steep eastern flank of one block 10 km long and 300 m high revealed a succession of fractured massive basalt laminar lava flows hyaloclastite and pillow lavas chemical analyses of dredged lava identified 19 units that overlap compositionally with lavas from the south rift zone ridge of mauna loa sulfur content indicates that most of the lavas were erupted in subaerial and shallow submarine

structural analysis of coseismic normal fault zones of the 2011 mw 6 6 fukushima earthquake northeast japan the 2011 m w 6 6 fukushima earthquake occurred in iwaki city 250 km southwest of the epicenter of the 2011 m w 9 0 tohoku japan earthquake and produced two subparallel 15 23 km long surface rupture zones with distinct displacements along two pre existing normal faults the shionohira and yunodake faults which strike north northwest south southeast and northwest southeast both dipping southwest respectively field investigations and structural analysis of the coseismic shear zones developed within the shionohira and yunodake fault zones reveal that 1 the coseismic shear zones consist of a fault core that includes a narrow fault gouge zone of 10 cm in width generally 1 5 cm a fault breccia zone of 50 cm in width and a damage zone of 5 50 m in width that is composed of cataclastic rocks fractures and subsidiary faults 2 the foliations characterized by s c fabrics developed in the shear zones indicate a dominantly normal fault slip sense consistent with that observed along the coseismic surface ruptures and 3 veinlet cataclastic rocks composed of unconsolidated fault gouges and fine grained materials occur as simple discrete veinlets and multiple cross cutting interconnected networks of veinlets these newly documented structural characteristics for two coseismic fault shear zones and associated cataclastic rocks indicate that the locations of coseismic slip zones associated with the 2011 fukushima earthquake were controlled by pre existing fault shear zones central to the shionohira and yunodake faults which have repeatedly moved as seismogenic normal faults since the timing of formation of associated cataclastic rocks our results demonstrate that the structural analyses of coseismic shear fault zones provide a powerful tool to study the nature and active faulting history of seismological faults

slope stability change from late pleistocene to holocene in the ulleung basin east sea japan sea abstract a wide variety of mass movement deposits prevail along the entire margin of ulleung basin overlain by a hemipelagic mud unit 1 2 m thick the boundary between the lower turbidite sequence and the upper hemipelagic mud on the basin plain is distinct and approximately coincides with the well known basin wide ash layer ulleung ash of early holocene age in the absence of significant terrigenous sediment input the lithologic change from the turbidite to hemipelagic mud may reflect physical effects of glacio marine eustatic sea level change sea level lowering during the glacial period may have generated excess pore pressure within the sediments caused by reducing hydrostatic confining pressure and facilitated triggering of the deep water slope failure by earthquakes storm waves may also have affected the uppermost slope area to induce small scale slope instabilities during the lowered sea level stand these glacial factors destabilizing the slope appear to have enhanced large scale slope failures during the late pleistocene in contrast the topmost hemipelagic mud attests to a stable slope phase associated with raised sea level in the holocene consistent with the infinite slope stability analyses calculations of the sedimentation rates based on c 14 dates of several ash layers indicate that the pre holocene turbidites on the basin plain had accumulated at an average rate of 40 cm 1000 years with a minimum recurrence interval of 50 years during the late pleistocene mass flux estimations between the slumps and turbidites suggest a predominance of the nondisintegrative mode of slope failures in the ulleung basin in each event of slope failure most of the failed mass rested on the slope as slide slump blocks and only its meager portions were deposited on the basin plain as turbidite layers

paleobathymetric influence on the development of the late ediacaran yangtze platform hubei hunan and guizhou provinces china abstract a compiled facies map based on 48 sections positioned in three chinese provinces hunan guizhou and hubei and field data emphasize the changes in depositional environments on the shelf of the ediacaran yangtze platform the facies interpretation suggests three depositional environments 1 a deep water basin with a slope facies on its margins maoping and wuhe sections hubei province 2 intertidal or shoals environments subjected to wave energy yangjiaping and zhongling sections hunan province wengan section guizhou province 3 a shallow water subtidal shelf environment subjected to currents xikou section guizhou province during the doushantuo formation time period 635 ma 551 ma condon d zhu m y bowring s yang a jin y g 2005 u pb ages from the neoproterozoic doushantuo formation china science science 308 95 98 the shelf showed an irregular bathymetry interpreted as inherited from the rifting history of the yangtze platform following the break up of rodinia approx 700 ma the tilted blocks influenced the platform development and the facies distribution locally more than the doushantuo formation time period 84 ma has been necessary to compensate the variations of bathymetry inherited of the tilted blocks geometry

large scale slope instability at the southern margin of the ediacaran yangtze platform hunan province central china thirteen stratigraphical sections from the doushantuo formation hunan province central china indicate large scale mass wasting of the yangtze platform margin between the late neoproterozoic glaciation and the earliest cambrian numerous sedimentary discontinuities due to regional slides olistostromes and slumps have modified the stratigraphy between the shallow water carbonate platform margin and the siliciclastic slope slide blocks are predominantly gently deformed and are largely composed of shallow water dolomitized limestones slide sheets may reach a regional extent of up to 5000 km 2 and are embedded in anoxic shales at an unknown water depth

sliding and regional slope stability in active margins north aegean trough mediterranean continuous seismic air gun sub bottom profiling in the north aegean has revealed a large submarine slide the failure zone extends from a depth of about 300 m down to 850 m and covers an area of 85 km2 the mean thickness of the slide reaches about 55 m and an estimated total volume of 3 8 km3 of late pleistocene sediments has slid a distance of 6 7 km chronostratigraphic analysis of the acoustic reflectors imply that the major and secondary glide planes are the transitional zones between a lower sequence of strongly stratified reflectors stiff relatively coarser sediment layers and the overlying acoustically transparent and or poorly stratified sequence weaker muddy layers with higher water content and lower shear strength these weak transparent layers have been deposited during interglacial high sea level stands isotopic stages 7 5 3 the major glide plane is assumed to have been developed within a muddy layer that was deposited about 170 245 ka bp stratigraphic sedimentological data and ams dates indicate an early holocene age of the major failure event not earlier than about 5 5 ka bp and not later than 7 8 ka bp the regional seismic hazard and slope stability analysis shows that the north aegean marginal upper middle slopes are highly unstable the calculated values of horizontal ground acceleration able to initiate failures kc range from 80 to 300 gal downslope this is lower than what is expected within 50 yr especially in the upper middle slopes

the neoproterozoic of southwestern africa with emphasis on platform stratigraphy and paleontology abstract neoproterozoic sediments in southwestern africa occur in the pan african kaoko khomas gariep vanrhynsdorp and saldania belts they were deposited in response to rifting break up of a supercontinent formed at 1000 ma and subduction and collisions of the congo kalahari rio de la plata and malvinas plates these collisions led to the formation of a neoproterozoic cambrian supercontinent this paper deals with the geology of the platform successions of the kaoko khomas gariep and vanrhynsdorp belts deposition of the sediments occurring in these belts commenced 900 to 1000 ma ago and probably ended between 500 and 520 ma the sediments record wilson cycles that ended with the deposition of red beds palaeontological and carbon isotope studies on the damara sequence gariep complex nama group and vanrhynsdorp group make intra and inter basinal correlations possible prior to deposition of the nama group two or perhaps three glaciations took place over an extensive area in southwestern africa these being the kaigas chuos 725 700 ma numees 650 600 ma or 610 590 ma and possibly the varianto 745 725 ma glaciations the numees tillite is overlain by a stratigraphic unit containing pinkish dolomite during deposition of the nama group the minor vingerbreek 600 545 ma glaciation or cold water period occurred the major kaigas chuos and numees and minor vingerbreek glaciations correspond with low 13c isotope ratios and appear to have taken place at relatively low palaeolatitudes the riphean sediments were deposited predominantly during rifting and break up of a supercontinent during the late vendian to early cambrian deposition of the nama group in southern namibia and the penecontemporaneous vanrhynsdorp group in the republic of south africa took place in the nama foreland basin detrital micas indicate that deposition of the nama group took place between 635 and 530 ma the nama foreland basin which was connected to a major ocean to the south formed as a result of collisions between the congo kalahari and rio de la plata plates with the exception of the nama group little is known about the palaeontology of the neoproterozoic in southwestern africa the lower nama group is latest proterozoic in age it contains an ediacaran fauna a depauperate assemblage of organic walled microfossils and a relatively well diversified ichnofauna with brooksella diplocraterion and nereites which are atypical of vendian strata many trace fossils are exceptionally small the occurrence of the shelly fossil cloudina and probable calcified metaphytes in the lower nama group suggest that skeletalization in animals and metaphytes occurred almost simultaneously towards the end of the proterozoic the upper nama group is early cambrian in age as indicated by the occurrence of the trace fossil phycodes pedum the upper nama group dominated by red beds contains a low diversity ichnofauna with trace fossils of normal size bio and chemostratigraphy combined with sequence stratigraphy will probably establish how the prominent unconformities which occur in the neoproterozoic of southwestern africa are related to the periods of formation of the wonoka canyons in south australia

retreat of carbonate platforms response to tectonic processes a seamarc ii and seismic reflection investigation of the deep water margins of carbonate banks in the southeast bahamas has documented the retreat of these isolated platforms since mid cretaceous time this retreat is in sharp contrast to prograding carbonate platforms in the passive northwest bahamas and provides an initial framework within which to view the response of carbonate platforms to tectonic processes processes of retreat include large scale 50 60 km step back of platform margins during the mid cretaceous tectonic subsidence and downfaulting during the late tertiary and large scale collapse of platform margins which may be an active process step back during the mid cretaceous correlates with a global tectonic pulse of ocean crust formation and relative sea level rise downfaulting may be a response to either late tertiary lithospheric bending during subduction and or block rotation along the north american caribbean plate boundary and collapse may be related to earthquake shocks generated by active plate tectonic collision between the southeast bahamas and hispaniola

middle cambrian carbonate platform collapse southeastern canadian rocky mountains regional erosion features termed megatruncation surfaces at the seaward margin of a middle cambrian carbonate platform in southeastern british columbia are inferred to be the proximal parts of gravity slide scars comparable in scale and morphology to modern examples in the caribbean region the surfaces truncate up to 200 m of outer platform strata and have low angle to near vertical headwalls they can be traced a minimum of 56 km along depositional strike and appear to extend at least 8 km basinward of the platform edge they therefore profoundly affect regional stratigraphy

investigation of mass wasting on the continental slope and rise abstract a methodology is presented for the investigation of submarine slope instability this approach integrates the results of a variety of tools and methods including multibeam side scan and subbottom acoustic data geotechnical sampling and testing and advanced dating techniques for slides slumps that have the potential for causing tsunamis the use of long large diameter piston corers is a cost effective way of obtaining good quality sediment samples using a multi sensor core logger and geotechnical analyses a baseline of sediment properties is developed from nearby stable unfailed regions which is then compared to more active areas where faulting and instability is suspected clear evidence of past and recent slope failures can often be obtained from the stress history of the sediment derived from consolidation test results and from careful identification of naturally deposited sediments overlying relic failures this methodology was applied for the investigation of slope failures along a study corridor in deepwater gulf of mexico large failures were identified from multibeam data and coring locations were chosen based on subbottom and side scan data obtained with a deep tow system buried failures were identified from detailed bulk density measurements geotechnical test results and paleomagnetic and 14 c dating techniques dating of these failures can provide information regarding the triggering mechanisms of these events which can be used to assess the current risk of new instabilities

slip sliding away the side of an oceanic volcano one of the hawaiian islands has been caught sliding towards the sea the distance concerned was only a few centimetres but it could be an indicator of a huge landslip to come

sulfur redox reactions hydrocarbons native sulfur mississippi valley type deposits and sulfuric acid karst in the delaware basin new mexico and texas hydrocarbons native sulfur mississippi valley type mvt deposits and sulfuric acid karst in the delaware basin southeastern new mexico and west texas usa are all genetically related through a series of sulfur redox reactions the relationship began with hydrocarbons in the basin that reacted with sulfate ions from evaporite rock to produce isotopically light 34s 22 to 12 h2s and bioepigenetic limestone castiles this light h2s was then oxidized at the redox interface to produce economic native sulfur deposits 34s 15 to 9 in the castiles paleokarst and along graben boundary faults this isotopically light h2s also migrated from the basin into its margins to accumulate in structural anticlinal and stratigraphic yates siltstone traps where it formed mvt deposits within the zone of reduction 34s 15 to 7 later in time in th zone of oxidation this h2s reacted with oxygenated water to produce sulfuric acid which dissolved the caves e g carlsbad cavern and lechuguilla cave guadalupe mountains massive gypsum blocks on the floors of the caves 34s 25 to 4 were formed as a result of this reaction the h2s also produced istopically light cave sulfur 34s 24 to 15 which is now slowly oxidizing to gypsum in the presence of vadose drip water

high resolution 2 7 khz acoustic and geometric characters of submarine creep deposits in the south korea plateau east sea a synthesis of high resolution chirp 2 7 khz seismic profiles in the south korea plateau reveals that large masses of wavy stratified sediment 60 90 m thick cover broad gently sloping 0 5 ridges in water depths of 1000 2000 m the wavy stratified sediment wss is characterized by wavy 0 2 5 km in wavelength and 15 m in relief continuous reflective layers with a basal deformed zone that overlies undeformed strong reflectors the wss exhibits systematic variation in wave dimensions and thickness of internal reflective layers with changes in slope gradient the troughs of the waves are commonly associated with internal growth faults and wave amplitude generally increases with subbottom depth on steep slopes around the ridges the wss masses are bounded downslope by slide and slump deposits including slightly translated or rotated wss blocks the acoustic and geometric characters and association with downslope slides and slumps on the steeper slopes suggest that the wss masses were most probably formed by slow creep movement before slope failure in the absence of significant sediment input to the south korea plateau the deep 1000 2000 m in water depth mass movements were probably triggered by earthquakes that have occurred frequently in this region some slightly displaced intact wss blocks in the associated slides and slumps downslope reflect a progressive evolution from submarine creep into slide and slump

facies and depositional processes in an upper jurassic to lower cretaceous pelagic sedimentary sequence antarctica the nordenskjold formation oxfordian berriasian age is exposed on the east coast of the antarctic peninsula where it consists of interbedded ash layers and biosiliceous mudstones which accumulated under anaerobic to dysaerobic bottom waters the mudstones were deposited by pelagic settling and the ash layers by pelagic settling from suspension or as fallout from subaerial eruption columns the lower part of the succession accumulated in a basinal setting under anaerobic bottom waters and is characterized by parallel bedding mudstones deposited in this setting preserve abundant zooplankton faecel pellets compaction of these pellets has given rise to a bedding parallel fissility the upper part of the succession accumulated under dysaerobic bottom waters in a slope setting the sequence is wavy bedded and contains abundant evidence of post depositional sediment instability and resedimentation much of which was caused by tectonic activity discrete slide masses are absent from the slope sequence and it appears that slope processes were dominated by creep examination of the mudstones shows that as levels of dissolved oxygen in bottom waters increase pelleted mudstones give way to structureless mudstones before visible bioturbation is noted

platform margin collapses and sequence stratigraphic organization of carbonate slopes cretaceous eocene gargano promontory southern italy we describe the sequence stratigraphic organization and the associated sedimentological characteristics of cretaceous to eocene slope and base of slope carbonate successions the study area is located in the gargano promontory which belongs to the stable foreland of southern italy the succession consists of three superimposed depositional sequences separated by major unconformities the upper two sequences are clear examples of sequence stratigraphic organization in fact they both start with huge megabreccia wedges lst followed upward by thin pelagic units tst and a thick package of calciturbidites and debrites that alternate with pelagic mudstone hst the cretaceous highstand systems tract is clearly arranged in a number of coarsening upward cycles while the eocene one which also comprises a toplap shallow water unit is not the gargano stratigraphic palimpsest and the entire margin of the apulia platform show remarkable similarities with present day carbonate platform margins and slopes where irregular convex bankward embayments suggest large scale failures it is clear that classic sequence stratigraphic organization can result from simple platform dismantling having no or little time relation with global sea level fluctuations in fact as the margin failure lst interrupts the carbonate production a period of starvation tst along the entire slope and base of slope follows necessarily finally when the margin once again becomes active and productive sediment exportation starts again and the system begins to prograde hst

soft sediment deformation at the base of the neoproterozoic puga cap carbonate southwestern amazon craton brazil confirmation of rapid icehouse to greenhouse transition in snowball earth stratigraphic and isotopic data identify the lower 45 m of the araras group on the southwest margin of the amazon craton as a neoproterozoic platform cap carbonate deposited below wave base upon varanger glacial diamictites of the puga formation the basal beds consist of moderately deep water pinkish dolomudstone with stratiform to wavy fenestral microbialites locally cut by tube like structures and fenestral nonmicrobial planar laminites with tepee like features above the basal carbonates are deep water bituminous lime mudstones with alternating thin calcite crusts and lime mudstone laminae commonly disrupted by calcite crystal fans pseudomorphs after aragonite the basal contact of the puga cap exhibits soft sediment deformational structures principally load casts that are here attributed to rebound induced seismicity acting upon both recently deposited carbonate sediments and underlying unconsolidated diamictite these features constitute the first clearly recognized sedimentological evidence for the rapid change from icehouse to greenhouse conditions as postulated in the snowball earth model of neoproterozoic glaciation

genesis of limestone megabreccias and their significance in carbonate sequence stratigraphic models a review a re appraisal of the factors controlling the deposition of carbonate megabreccias and their sequence stratigraphic significance is presented based on an examination of the mechanisms for instigating carbonate seafloor slope instability and a review of the depositional settings of these distinctive rock deposits limestone megabreccias have classically been interpreted as formed by the catastrophic collapse of high angle metastable oversteepened carbonate platform margins however a review of megabreccia occurrence shows that these deposits formed on a broad range of carbonate slope angles and that metastable oversteepened slopes are not necessary for their genesis a re evaluation constructed from first principles of mechanisms promoting submarine gravitational instability indicates that pore water overpressure of confined aquifer horizons beneath the seafloor rather than slope oversteepening is the critical control on megabreccia deposition catastrophic release of overpressure may initiate gravitational instability of previously kinematically stable slopes the relative importance of endogenic processes intrinsically linked to the depositional system and exogenic processes operating independently in generating megabreccias is assessed two particularly important mechanisms in generating megabreccias are endogenic processes causing overpressure at discrete hydrologically confined horizons beneath the seafloor during relative sea level falls and increases in stress as pore fluid drains from the sediment when the platform top becomes subaerially exposed during relative lowstands of sea level the increased likelihood of megabreccia genesis during relative sea level falls is supported by an empirical trend identified from a review of the stratigraphic distribution of documented megabreccias exogenic causes of gravitational instability with inherently random periodicity especially seismicity may account for the small number of documented megabreccias that do not conform to this underlying trend the proposed endogenic pattern favouring megabreccia deposition during relative sea level falls is important in a sequence stratigraphic context megabreccia deposits may build volumetrically significant toe of slope wedges and aprons during relative lowstands of sea level partially compensating for the decrease loss in the supply of fresh granular sediment as the platform top carbonate factory contracts lowstand wedges and aprons in carbonate systems therefore generally differ in composition from equivalent highstand deposits in being composed not of calciturbidite deposits but of megabreccias cannibalized from the upper slope

chromium isotope stratigraphy of ediacaran cap dolostones doushantuo formation south china abstract the yangtze platform in south china is considered a key site for studying neoproterozoic ocean oxygenation comprehensive cr concentration and isotopic signatures are presented from cap dolostones of the doushantuo formation from a deep water and a shallow marine carbonate section that have previously been used to constrain the redox evolution of ediacaran seawater in space and time employing major and trace element abundances as well as sr o and c isotope compositions the majority of the studied samples yield elevated cr concentrations and negatively fractionated 53 cr signals due to i detrital contamination consistent with cr signatures of other post marinoan cap dolostones ii diagenetic carbonate alteration and post depositional remobilization of cr al concentrations were used as indicator of detrital contamination and to calculate authigenic cr concentration and isotope signatures when the detrital contribution of cr was 18 o carb signals that correlate with low cr concentrations and negatively fractionated 53 cr values post depositional remobilization of cr results in the loss of heavy cr isotopes and consequently light cr isotopes are retained during precipitation of secondary carbonates however some samples might still show pristine ediacaran seawater signals two samples pertaining to the deep water cap dolostone section at yanwutan and one sample pertaining to the shallow water section at jijiawan yield slightly positively fractionated 53 cr signals particularly when corrected to presumably authigenic signals 53 cr auth these values are consistent with those from other neoproterozoic carbonate sections deposited in an oxygenated environment this short sequence of positively fractionated 53 cr auth is concurrent with a cap dolostone 87 sr 86 sr signal close to ediacaran seawater values with relatively high sr and cr concentrations with decreased detrital contamination and with a pronounced negative ce anomaly they indicate either light pulses of enhanced oxidative weathering or inferred from a few least altered samples prevailing oxic conditions during cap dolostone deposition the cr isotopic composition of ediacaran cap dolostones pertaining to the doushantuo formation reveals fine scale fluctuations in post glacial detrital contamination and diagenesis balanced against a clear signal of oxidative weathering cr isotopes have the potential to further enhance our understanding of neoproterozoic weathering regimes and past ocean oxygenation however before the cr isotope system can be faithfully applied to delineate changes in redox conditions recorded in ancient marine carbonates possible diagenetic alteration of the cr signal as well as cr contribution from detrital contamination need to be taken into consideration

the relationships between soft sediment deformation structures and synsedimentary extensional tectonics in upper triassic deep water carbonate succession southern tethyan rifted continental margin central sicily abstract we describe soft sediment deformation structures into the upper triassic cherty limestone outcropping in the pizzo lupo section central sicily italy pertaining to the deep water palaeodomain of the southern tethyan margin in the study section mainly consisting of thin bedded mudstone marl alternations with bedded chert intercalations some lithofacies have been separated on the basis of the abundance of the calcium carbonate clay content and the overall textural features the deformational structures displaying different deformational styles as folded and faulted beds disturbed layers clastic dikes and slumps occur mainly in the deformed horizons that involve marl dominated lithofacies small scale water escape structures involve beds with nodular fabric synsedimentary faults affect the mud limestone dominated lithofacies which are characterized by fault rotating blocks producing lateral thinning these bodies appear to have moved coherently along an overall planar surface we relate these soft sediment deformations to slump sheets associated with down slope sliding of sedimentary masses the deformation mechanism and driving force for these soft sediment deformations are due essentially to gravitational instability and dewatering detailing rotational slump and translational glide slides and water escape are the main processes causing the distinguished deformational styles the synsedimentary extensional tectonics that affected the upper triassic pelagic deposits was the triggering process responsible for the instability of the seafloor inducing loss of coherence of the unconsolidated sediments on the sea bottom developing a large number of gravity driven slides the analysis of both of these ssdss and their relationships with the structural scenario allow us to hypothesise that they are seismically induced

characterisation of a volcanic residual soil and its implications for large landslide phenomena application to tenerife canary islands large landslides are common processes during the evolution of volcanoes and individual events can exceed several cubic kilometres in volume volcanic slope failures are a significant risk for the neighbouring population due to their huge volumes and great runout distances around the canary archipelago a total of seventeen deposits of large landslides have been found and on tenerife seven large landslides have affected the subaerial and submarine morphology during the last 6 ma however the causes of such mass movements are still poorly understood this work analyses the events around the canary islands and focuses on the ones that occurred on tenerife in order to obtain new insights into the mechanisms of large volcanic landslides the study is divided into a first part that includes site investigations examining the general features favouring large scale failures at volcanoes the second part describes the laboratory tests used to analyse a residual soil that may be the potential slip surface of the slides on tenerife the site investigation revealed that regional tectonics and the climate have a significant influence on the spatial distribution of the landslides moreover morphological and geological features such as deep fluvial canyons a high coastal cliff and persistent dike intrusion may favour the initiation of slope failure a typical residual soil sample from the lateral scarp of the la orotava amphitheatre on tenerife was studied by carrying out standard laboratory tests the microstructure was analysed using environmental scanning electron microscopy and a particular bonding was found this bonding was also detected by the geotechnical tests consolidation tests and direct shear tests revealed that the mechanical behaviour of the residual soil changes greatly if the bonding of the soil is broken the bonded structure generally fails when the effective normal stress surpasses the yield strength of the bonding in the case of large volcanic landslides with thicknesses up to several hundred meters the high overburden easily exceeds this yield strength and generates a broken bonding therefore volcanic residual soils such as the one analysed in this study are perfect candidates for the potential failure surfaces of large volcanic landslides referring to the la orotava events we assume that residual soil layers and morphological geological and climatic features reduced the slope stability to critical conditions whereas a strong earthquake associated with a caldera collapse episode may have finally triggered the landslide the results obtained indicate that the residual soils play an important role in affecting the stability of volcano slopes and their destabilising influence significantly favours large scale sliding we suggest that the results obtained from this study can be applied to other locations since volcanic residual soils are common in volcanic areas

precambrian cambrian transition death valley united states the death valley region contains one of the best exposed and often visited precambrian cambrian successions in the world but the chronostratigraphic framework necessary for understanding the critical biologic and geologic events recorded in these sections has been inadequate the recent discovery of treptichnus phycodes pedum within the uppermost parasequence of the lower member of the wood canyon formation allows correlation of the precambrian cambrian boundary to this region and provides a necessary global tie point for the death valley section new carbon isotope chemostratigraphic profiles bracket this biostratigraphic datum and record the classic negative carbon isotope excursion at the boundary for the first time biostratigraphic chemostratigraphic and lithostratigraphic information from pretrilobite strata in this region can be directly compared with similar data from other key sections that record the precursors of the cambrian explosion few precambrian cambrian boundary sections contain both the facies restricted boundary fossil t pedum and carbon isotope data as found in death valley thus the death valley succession provides a critical link toward our understanding of the correlation between siliciclastic dominated and carbonate dominated precambrian cambrian transition sections