saurornitholestes robustus is a troodontid dinosauria theropoda the holotype of saurornitholestes robustus smp vp 1955 from the upper kirtland formation de na zin member originally identified as a dromaeosaurid is here re identified as an indeterminate troodontid theropod the frontal has no diagnostic dromaeosaurid characters but is shown to have several features unique to troodontids among deinonychosaurs including the shallow lateral wall defining the fossae for the olfactory system the exclusion of the supratemporal fossa from the dorsal surface of the frontal and a raised orbital rim the size and morphology of smp vp 1955 is also consistent with better known troodontid material from the late campanian of alberta and as preserved the kirtland specimen is indistinguishable from comparable alberta material the revised identification of smp vp 1955 provides the first non dental skeletal record of a troodontid from the kirtland formation and a rare record of this clade from the kirtlandian land vertebrate age

numerical study on deep seated gravitational slope deformation in a shale dominated dip slope due to river incision abstract based on numerical simulation this study investigates the triggering factors and evolution of deep seated gravitational deformation in a dip slope consisting of a shale dominated sequence of sediments results from continuum based finite difference numerical modeling demonstrate that long term strength degradation of a rock mass is a prerequisite for the development of gravitational slope deformation and that river incision resulting in change of slope geometry and corresponding stress concentration and redistribution is a major driving mechanism for the progressive evolution of deep seated gravitational slope deformation dsgsd numerical simulation considering the influence of weak planes indicates that the bedding planes control the strength of rock mass and form a structural constraint on the development of gravitational slope deformation a satisfactory correlation between the distribution of numerically simulated plastic shear bands and weak zones in drill cores demonstrates that the weak zones within the slope are formed due to gravitational slope deformation furthermore numerical simulation shows a link between geomorphological development and internal deformation of the slope which aids in the understanding of relationships between interior deformation of the slope the exterior geomorphology and related effect factors including river incision and strength degradation

1891 1883 ma southern bastar cuddapah mafic igneous events india a newly recognized large igneous province abstract a newly recognized remnant of a paleoproterozoic large igneous province has been identified in the southern bastar craton and nearby cuddapah basin from the adjacent dharwar craton india high precision u pb dates of 1891 1 0 9 ma baddeleyite and 1883 0 1 4 ma baddeleyite and zircon for two se trending mafic dykes from the bd2 dyke swarm southern bastar craton and 1885 4 3 1 ma baddeleyite for a mafic sill from the cuddapah basin indicate the existence of 1891 1883 ma mafic magmatism that spans an area of at least 90 000 km2 in the south indian shield this record of 1 9 ga mafic ultramafic magmatism associated with concomitant intracontinental rifting and basin development preserved along much of the south eastern margin of the south indian shield is a widespread geologic phenomenon on earth similar periods of intraplate mafic ultramafic magmatism occur along the margin of the superior craton in north america 1 88 ga molson large igneous province and in southern africa along the northern margin of the kaapvaal craton 1 88 1 87 ga dolerite sills intruding the waterberg group existing paleomagnetic data for the molson and waterberg 1 88 ga large igneous provinces indicate that the superior and kalahari cratons were at similar paleolatitudes at 1 88 ga but a paleocontinental reconstruction at this time involving these cratons is impeded by the lack of a robust geological pin such as a limpopo like 2 0 ga deformation zone in the superior province the widespread occurrence of 1 88 ga intraplate and plate margin mafic magmatism and basin development in numerous archean cratons worldwide likely reflects a period of global scale mantle upwelling or enhanced mantle plume activity at this time

the plutonic alkaline series the problem of their origin and differentiation the role of their mineralogical assemblages abstract the plutonic alkaline ring complexes present several different trends of differentiation the two more important being the silica oversaturated one and the silica undersaturated one a hiatus appears in the silica oversaturated association for monzonitic compositions which may be compared with the galy gap in volcanic series characteristics of the plutonic series as the cumulative features of the basic rocks the differentiated patterns of the acid rocks and the monzonites which present ree patterns of initial liquid lead one to propose the existence of a magma of monzonitic composition its vanishing is owing to cumulation of the early mineral phases and to consequent evolution of the residual liquid the trends of differentiation can be explained by a multistage model where mineral phases are both controllers of the differentiation and images of this differentiation the path from monzonites to syenites is governed by calcic plagioclase bowen s plagioclase effect olivine and calcic clinopyroxene which have effects upon iron enrichment and increase in alkalies calcic amphiboles and more modestly biotite play a significant role for the silica level of the liquids the path from syenites to late stage differentiates is governed by alkali feldspars and calcic amphiboles late iron rich sodic amphiboles and pyroxenes and potassic annite siderophyllite minerals are reflecting the mode of the differentiation one must also consider opaque minerals marks of fo 2 and zircons marks of temperature and agpaitic index in the alkaline plutonic series the controls of the differentiation by minerals can explain the coexistence of silica saturated and undersaturated series and of peralkaline and peraluminous trends the role of calcic amphiboles seems fundamental and we suggest that their stability is controlled by the characteristics of surrounding lithosphere water amounts porosity and permeability thus can be understood differences observed between oceanic and continental alkaline series between complexes emplaced in cratonic environments or in youthful mountain belts and specially coexistence of granites and nephelinic syenites subsolvus granites and albitic granites with their features showing a crustal signature

geochemical criteria for a refined tectonic discrimination of orogenic andesites abstract minor trace element and sr isotope data are compiled for tertiary recent orogenic andesites of three tectonic settings 1 oceanic island arcs divided into low k and other andesites 2 continental island arcs and thin continental margins and 3 thick continental margins andean from 1 to 3 there is a steady overlapping increase in la ce ree la yb la y th th u zr y hf yb and ni co and a decrease in k la p la sc cr and sc ni optimum discriminationis achieved with a plots of la yb vs th and la yb vs sc ni and b cluster analysis using the critical parameters listed above shoshonitic andesites and high mg andesites boninites are considered separately orogenic andesites are distinguished from non orogenic andesites by high contents of al low contents of ti zr ree y nb ta and ga and the absence of pronounced negative eu anomalies

late quaternary sackungen in the highest mountains of the carpathians sackungen represents a common mode of deep seated rock slope failures in alpine landscapes but proof of their temporal and causal relationship to extrinsic factors such as climatic changes glacier retreat or seismic activity remains elusive based on the terrestrial cosmogenic nuclide tcn dating of 18 sackung scarps supported by one radiocarbon dated scarp we reconstructed the post glacial chronology of sackungen in the tatra mts central europe slovakia and poland the highest part of the carpathians the obtained ages 15 7 4 3 ka indicate that sackungen post date the regional lgm and some of them originated soon after the glacier withdrawal from adjacent valleys furthermore systematic decrease of scarp ages with their increasing altitude suggests a direct link between sackung origin and post lgm glacier thinning however substantial lag 5 ka of some sackungen in respect to glacier retreat implies complex relationships between sackung onset and deglaciation where retreat of glaciers acted predominantly as a preparatory not a triggering factor during the genesis of these slope deformations they originated either as a consequence of stress relaxation within the rock mass lasting several ka or alternatively could be triggered by climatic processes or seismicity indeed a significant part of sackung activity took place during predominantly warmer and more humid periods with some dates coinciding with the belling allerod chronozone but especially with the onset of the holocene and the holocene climatic optimum earthquake triggering is less probable as the tatra mts lack significant modern and historic seismic activity and there is no geomorphic evidence of fault offsets on the late quaternary landforms in concert with other recent studies we propose that large rock slope failures in high mountains seldom react immediately to glacier withdrawal but could display temporal delay lasting up to several millennia c 2017 elsevier ltd all rights reserved

surface faulting accompanying the borah peak earthquake and segmentation of the lost river fault central idaho on the morning of 28 october 1983 the ms 7 3 borah peak earthquake struck central idaho and formed a y shaped zone of surface faults that is divided into a southern a western and a northern section the total length of the surface faults is 36 4 3 1 km and the maximum net throw is 2 5 to 2 7 m the near surface net slip direction determined from the rakes of striations in colluvium averaged 0 17 m of sinistral slip for 1 00 m of dip slip the 20 8 km long southern section is the main zone of surface faulting and coincides with the thousand springs segment of the lost river fault it has the largest amount of net throw most complex rupture patterns and best evidence of sinistral slip the surface faults include zones of ground breakage as much as 140 m wide en echelon scarps with synthetic and antithetic displacements and individual scarps that are nearly 5 m high the 14 2 km long western section diverges away from the lost river fault near the northern end of the southern section the net throw on this section is generally less than 0 5 m but locally is as much as 1 6 m the new ruptures are poorly developed across the crest and north flank of the willow creek hills they are mostly downhill facing arcuate scars perhaps incipient landslides that may overlie a deeper zone of tectonic movement the northern section at least 7 9 km long is on the warm spring segment of the lost river fault and has a maximum net throw of about 1 m the pattern of surface faulting on this section is simple compared to the other sections a 4 7 km long gap in 1983 surface faults separates the northern and southern sections but contains an older scarp of late pleistocene age geologic seismologic and geodetic data from the earthquake suggest that barriers confined the primary coseismic rupture to the thousand springs segment of the fault the rupture propagated unilaterally to the northwest from a hypocenter near the southeastern end of the segment the southeastern boundary of the segment is marked by an abrupt bend in the range front a 4 km long gap in late quaternary scarps and transverse faults of eocene age that intersect the lost river fault the northwestern boundary of the thousand springs segment is at the junction of the willow creek hills and the lost river fault here the southern and western sections of surface faults diverge and there is a gap in the 1983 scarps during the first few weeks after the main shock the large magnitude and large stress drop aftershocks clustered near this barrier later aftershocks were mainly northwest of the barrier on the warm spring and challis segments and showed that strain adjustments eventually affected the entire northern part of the lost river fault fault scarp morphology and the bedrock geology suggest that the boundary between the thousand springs and warm spring segments has probably ruptured less frequently and had less net slip during much of the late cenozoic than the interior of the adjacent segments the 1983 faulting shows that although segment boundaries can stop or deflect primary ruptures secondary surface faulting can occur on adjacent segments of the main fault a late pleistocene scarp in the 1983 gap suggests that infrequent earthquakes perhaps larger than the 1983 event might break through a segment boundary and thus release strain on two adjacent segments

deep seated failure propagation in a fractured rock slope over 10 000 years the la clapiere slope the south eastern french alps abstract the la clapiere area tinee valley alpes maritimes france is a typical large complex unstable rock slope affected by deep seated gravitational slope deformations dgsd with tension cracks scarps and a 60 106 m3 rock slide at the slope foot that is currently active the slope surface displacements since 10 ka were estimated from 10be ages of slope gravitational features and from morpho structural analyses it appears that tensile cracks with a strike perpendicular to the main orientation of the slope were first triggered by the gravitational reactivation of pre existing tectonic faults in the slope a progressive shearing of the cracks then occurred until the failure of a large rock mass at the foot of the slope by comparing apertures variations and changes in direction between cracks of different ages three phases of slope surface displacement were identified 1 an initial slow slope deformation spreading from the foot to the top characterized by an average displacement rate of 4 mm yr 1 from 10 5 6 ka bp 2 an increase in the average displacement rate from 13 to 30 mm yr 1 from the foot to the middle of the slope until 3 6 ka bp and 3 development of a large failure at the foot of the slope with fast displacement rates exceeding 80 mm yr 1 for the last 50 years the main finding of this study is that such a large fractured slope destabilization had a very slow displacement rate for thousands of years but was followed by a recent acceleration the results obtained agree with several previous studies indicating that in situ monitoring of creep of a fractured rock slope may be useful for predicting the time and place of a rapid failure

zircon u pb ages of rocks from the rio apa cratonic terrane mato grosso do sul brazil new insights for its connection with the amazonian craton in pre gondwana times abstract this paper presents 14 zircon u pb determinations shrimp and la mc icp ms for key geological units from the rio apa cratonic terrane ract which is considered the southernmost exposed part of the amazonian craton in southwestern brazil the zircon u pb ages and geological data indicate that the ract was formed by the accretion of magmatic arcs in a continental margin active from 1950 to 1720 ma the ract is composed of three major terranes western eastern and southeastern terranes with distinct evolution histories the western terrane presents orthogneisses and granites formed at 1950 1940 ma and subduction related granites and volcanic rocks formed at 1900 1880 ma and 1840 1830 ma these basement rocks are covered by a greenschist facies metavolcano sedimentary succession rio naicata formation with basal volcanic rocks formed at 1813 18 ma a gabbronoritic dyke of the rio perdido suite hosted by the rio naitaca formation yields an age of 1589 44 ma the eastern and southeastern terranes present deformed leucogranites generated within the intervals 1780 1720 ma and 1810 1790 ma respectively both terranes are covered by a metavolcano sedimentary succession alto terere formation dominated by barrovian type amphibolite facies metamorphic assemblages suggestive of a collisional event available 40 ar 39 ar data hornblende muscovite and biotite indicate that the proto ract evolved to a collisional orogen between 1310 and 1270 ma and behaved as a cratonic mass after 1270 ma preceding the assembly of rodinia the available data allow us to interpret the ract as a part of the ventuari tapajos province of the amazonian craton which was fragmented and dispersed as a microcontinent it was subsequently reincorporated into the sw amazonian craton along the sunsas belt as an allochthonous terrane in a global perspective the tectono magmatic events of the ract are consistent with a long lived accretionary orogen possibly related to an active margin of columbia

paraglacial gravitational deformations in the sw alps a review of field investigations 10be cosmogenic dating and physical modelling catastrophic deep seated landslides dsl are generally considered to be the result of large slope deformations also known as deep seated gravitational slope deformation dsgsd this paper aims to build a synthesis of multiple studies made in the tinee valley southern french alps to assess the geometrical kinematical mechanical and chronological relationships between these two gravitational processes at the scale of the valley data issued from geological geomorphological and 10be dating indicate a clear geometrical link between dsgsd and dsl occurring at the base of the slope and suggest that gravitational slope evolution began after the glacial retreat 13 ka bp this is supported by the example of the well documented la clapiere slope a continuous evolution process is characterized geometrically and temporally from geomorphic observations and analogue modelling coupling structural geomorphological physical and chronological studies allowed us to propose a four dimensional 4d deformation model mechanically correlated with progressive failure concept the validity and variability of this reference site are discussed at the valley scale taking isola and le pra slope deformation as examples it allows a rough estimation of the state of slope deformation at the valley scale to be constructed and the slope evolution with time to be considered this 4d model could then be considered as a reference for other deep seated gravitational slope deformations in comparable alpine valleys

petrology geochemistry and la icp ms u pb geochronology of paleoproterozoic basement rocks in bangladesh an evaluation of calc alkaline magmatism and implication for columbia supercontinent amalgamation abstract the paleoproterozoic 1 7 ga basement rocks from maddhapara bangladesh show a large range of chemical variations e g sio2 50 7 74 7 and include diorite quartz diorite monzodiorite quartz monzonite and granite the pluton overall displays metaluminous calc alkaline orogenic suite mostly i type suites formed within subduction related magmatism the observed major elements show general trends for fractional crystallization trace element contents also indicate the possibility of a fractionation or assimilation explain the entire variation from diorite to monzonite even granite the pluton may have evolved the unique chemical features by a process that included partial melting of calc alkaline lithologies and mixing of mantle derived magmas followed by fractional crystallization and by assimilation of country rocks the pluton shows evidence of crystal fractionation involving largely plagioclase amphibole and possibly biotite some of the fractionated magmas may have mixed with more potassic melts from distinct parts of the continental lithosphere to produce granites and or pegmatites new geochronological results of granitic pegmatite 1722 10 ma are indisputably consistent with diorite and tonalite and those data showing credible geochronological sequence i e diorite tonalite granitic pegmatite identical paleoproterozoic age 1 7 ga with distinctive magmatism of the maddhapara basement rocks have agreeable relationship with the citz india the consistent magmatism is also common in the transamazonian of south america trans hudson orogeny in north america bohemian massif and the svecofennian poland have identified the sequential growth of the continent through the amalgamation of juvenile terrains succeeded by a major collisional orogeny such paleoproterozoic subduction related orogens in australia have similar counterparts in antarctica and other part of the world these types of paleoproterozoic magmatism dominantly contributed to assemble amalgamation and breakup of the enormous columbia supercontinent

step like displacements of a deep seated gravitational slope deformation observed during the 2016 2017 seismic events in central italy abstract deep seated gravitational slope deformations are characterized by low deformation rates although they can experience partial collapse phases or more rapid movements especially in presence of active tectonic structures in the central italy considering the high seismicity rate seismic activity must be considered to be an important trigger of deep slope movements we aim to contribute to the research in this field by reporting the results of a monitoring program on a deep seated gravitational slope deformation in this region that involves marly calcareous rocks we documented the pre earthquakes evolution of the phenomenon and measured its displacements during the seismic sequence in 2016 and 2017 in central italy which largest events were mw 5 0 to 6 5 a multidisciplinary approach that combines a field geomorphological survey installation of permanent gps stations and insar elaborations was adopted for this study the average ground motion rate of the slope deformation before the earthquakes was very low on the other hand gps and insar recorded significant step like movements one to ten times higher than the normal activity rate triggered by the mw 5 0 to 6 5 earthquakes in detail the movement mainly depended on the magnitude of the earthquake and the distance from the epicenter and only secondarily on the number of larger magnitude earthquakes on a given day in conclusion we furnished monitoring data on the activity rate of a deep seated gravitational slope deformation in seismic context we indicated two sectors of the investigated deformation that resulted more unstable and we proved that the combination of insar and gps data is a useful monitoring system for earthquake activated slow moving slope instabilities

asynchroneity of maximum glacier advances in the central spanish pyrenees the deglaciation history of the escarra and lana mayor glaciers upper gallego valley central spanish pyrenees had been reconstructed on the basis of detailed geomorphological studies of glacier deposits sedimentological and palynological analyses of glacial lake sediments and an accelerator mass spectrometry ams 14c chronology based on minimum ages from glacial lake deposits the maximum extent of the pyrenean glaciers during the last glaciation was before 30 000 yr bp and pre dated the maximum advances of the scandinavian ice sheet and some alpine glaciers a later advance occurred during the coldest period around 20 000 yr bp synchronous with the maximum global ice extent but in the pyrenees it was less extensive than the previous one later there were minor advances followed by a stage of debris covered glaciers and a phase of moraine formation near cirque backwalls the deglaciation chronology of the upper gallego valley provides more examples of the general asynchroneity between mountain and continental glaciers the asynchroneity of maximum advances may be explained by different regional responses to climatic forcing and by the southern latitude of the pyrenees copyright 2002 john wiley sons ltd

cosmogenic 10be dating of a sackung and its faulted rock glaciers in the alps of savoy france sackungs are the largest gravitational deformation observed in mountains they are characterized by the long term slowness of the movements but their mechanism is still not well understood nowadays cosmic ray exposure cre dating methods allow dating the morphologic structures involved in sackung and can contribute at the understanding of their origin in the alps the 5 3 km long arcs sackung initiated during the activity of rock glaciers three samples from these faulted rock glaciers provide their first cre ages and show that at 2000 m elevation these block accumulations moved during the younger dryas and stopped in early holocene six 10be ages of fault scarps show that the arcs sackung lasted only a few thousand years and stopped at about 8462 432 10be yr they also reveal that deformation migrated upslope in agreement with a mechanism of flexural toppling of vertical layers this unique and long gravitational event characterized by migration of the deformation does not support earthquake shaking as triggering mechanism for individual faults it shows that in the upper isere valley slope deformation was delayed of several thousand years after glacial debuttressing and is not anymore active despite its fresh morphology

are sackungen diagnostic features of de glaciated mountains abstract deep seated gravitational slope deformations dsgsds with characteristic sackung landforms e g double crests trenches uphill facing scarps and toe bulging are considered by some researchers to be diagnostic features indicating past mountain glaciations however an extensive literature review on sackung features throughout the world reveals that in some regions paraglacial processes are not the causes of such phenomena sackungen occur across a diverse spectrum of mountain types with different morphoclimatic histories including regions that have never experienced glaciation to reinforce that sackungen may originate independently of glaciation we also include two case studies from the western carpathians czech republic and slovakia which are supported by detailed geomorphic mapping trenching and absolute dating 10 be 14 c and osl on the ond ejnik ridge outer western carpathians czech republic sackungen occur in the mid holocene in the medium high mountains which are beyond the pleistocene glacial limits on the salatin mt tatra mts slovakia the sackungen which occur in formerly glaciated terrain date between 7 5 and 4 2 ka bp representing a 4 ka time lag after the disappearance of glaciers this suggests that the direct link between the ice retreat and the onset of sackung formation is not obvious even in the case of the once glaciated mountain range although paraglacial stress release is undoubtedly one of the crucial causes of sackung genesis in many mountain regions it is not the only important mechanism therefore despite occurring in numerous de glaciated mountains sackung features cannot be considered as proof of past mountain glaciations e g during analysis of extra terrestrial settings

the nature of mesoproterozoic central indian tectonic zone with exhumed and reworked older granulites abstract the ese wnw trending central indian tectonic zone citz divides the indian subcontinent into southern and northern crustal provinces its narrow northern belt consists of closed early proterozoic mahakoshal rift zone which is presently confined between two moho reaching faults that characterize the son narmada sona lineament the mesoproterozoic sausar mobile belt smb the chhotanagpur granite gneiss complex cggc and the gneissic complex of northeast india represent the wider southern belt the mahakoshal rift belt has a thick pile of mafic ultramafic rocks and possibly oceanic components the basin closed due to a south directed subduction creating a magmatic arc that was sutured to its southern boundary during 1 8 1 7 ga a south dipping ductile shear zone known as the son narmada south fault affects both its supracrustals and intrusive granitoids the son narmada south fault generally delimits the northern boundary of the gondwana basins whereas the son narmada north fault delineates the northern boundary of the mahakoshal mobile belt and the southern boundary of the meso neoproterozoic vindhyan basin the smb representing the southern belt of the citz in the central sector comprises strongly folded and metamorphosed non volcanic and mn rich sausar sediments intermixed with reworked basement gneisses migmatites and granulites representing the pre sausar assemblage the sausar orogeny closed during terminal mesoproterozoic ca 1 0 ga on the other hand metamorphism in the basement gneiss migmatites and northern and southern granulite belts pre dates the sausar orogeny the earliest structure of the smb truncates and rotates the n s oriented structures of the southward located sakoli and the dongargarh belts of neoarchaean palaeoproterozoic age the northern granulite belt of the smb and the cggc and the high grade supracrustals from the sonapahar area in ne india all indicate very high p t conditions during 1 7 1 5 ga peak metamorphism which was followed by decompressional cooling the setting resembles continental collision which was followed by tectonic exhumation and denudation on the other hand the southern granulite belt from the smb documents a late archaean 2 6 ga event and a later 1 4 ga event the dalma volcanic belt located close to the southern tectonized boundary of the cggc belt and possibly the assemblage of copious mafic enclaves within the ca 550 ma granite plutons from ne india represent back arc like setting during 1 6 1 5 ga the setting is caused due to the southward subduction of the north indian block beneath the southern block leading to continental collision the metasedimentary belt located further to the south of the dalma volcanic belt and flanking the archaean singbhum craton to the north on the other hand is palaeoproterozoic in age but has been metamorphosed during ca 1 6 ga because of the northern collision related orogeny reworking and incorporation of basement gneisses and granulites from the mid crust level to the younger sausar cover sediments denote renewed spell of thrust tectonics that remobilized the collision zone rocks of the earlier orogeny the tectonic transport was from the north to the south with north dipping thrusts thus there was a reversal in the direction of convergence from the preceding orogeny the sausar orogeny closed during ca 1 0 ga it caused anatectic event producing granitoid plutons migmatites and charnockites in the cggc belt and migmatites in the gneissic complex in ne india

deep seated gravitational slope deformations in the european alps abstract deep seated gravitational slope deformations dsgsd are widespread phenomena recognized in different mountain ranges worldwide the distribution of such phenomena at the scale of a mountain belt has rarely been systematically analysed in the past aim of the paper is to present and discuss an inventory map of dsgsd at the scale of the entire european alps in order to review existing knowledge and investigate general controls on these phenomena the criteria adopted for their classification and distinction are presented a total of 1033 dsgsds ranging in size between 0 03 and 108 km 2 have been mapped the inventory has been validated against available local or regional landslide inventories at different scales and prepared by different authors using different approaches the frequency area relationship for the mapped features is presented the spatial distribution of the mapped dsgsd has been quantified by discretizing the study area into regular square grids with different resolution and analysed with respect to a variety of geological geomorpohological and morphometric variables and of their clustering discriminant principal component and cluster analyses have been performed to define the most important controlling and predisposing factors results suggest that the occurrence of foliated metamorphic rocks lgm ice thickness local relief and related parameters slope size drainage density and river stream power are the local parameters most positively correlated to dsgsd occurrence the impact of these phenomena on slope morphology in terms of hypsometry and slope gradient adjustment is also discussed

two cases of continental collisions and related tectonics during the proterozoic period in india insights from gravity modelling constrained by seismic and magnetotelluric studies abstract the aravalli delhi mobile belt admb in nw india includes the proterozoic aravalli and delhi rifts and fold belts a seismic profile and gravity modelling across the admb shows several dipping reflections and suggests a thick crust 45 46 km and a high density 3 04 g cm 3 dome shaped body in the lower crust this high density body in the lower crust may represent underplated lower crust caused by extension during evolution of the proterozoic rifts part of the gravity high observed over the admb is attributed to the upthrust blocks of high density lower crustal granulite rocks the gravity low along the eastern margin of the admb is modelled as being due to a westerly dipping 45 low density body in the crust in accordance with seismic reflectors which may represent remanents of the subducted crustal rocks the hindoli group of rocks above this body is characterized by high conductivity indicating a high fluid content and a fractured nature which may be related to the collisional tectonism of this region a sharp gravity high along the western margin of the admb is attributed to the basic rocks of an ophiolite melange the gravity low and high west of the admb are attributed to plutonic activity and bimodal calc alkaline volcanics in linear basins and are related to arc and back arc rift magmatism respectively the admb therefore represents a proterozoic collision zone between the bundelkhand craton towards the east and the rajasthan craton towards the west with a plausible subduction towards the west along the eastern margin of the admb the thrusting is mainly confined to the obducted block towards the west although some thrusting is inferred even in the subducted block the central indian suture cis is located at the southern margin of the satpura mobile belt smb in central india and separates high grade metasediments and granulite towards the north from low grade proterozoic volcanogenic successions towards the south a seismic profile and gravity modelling across the cis show a thick crust with a thicker crust north of the cis compared to the south and a contact in the lower crust whose projection on the surface coincides with the cis the cis at the surface coincides with a low density 2 65 g cm 3 and conductive body that is interpreted to be fluid filled and fractured in nature the high density 2 81 g cm 3 body modelled in the upper crust north of the cis coinciding approximately with a highly conductive body and dome shaped seismic reflectors may represent an upthrust block from the lower crust as high density granulite rocks are exposed in this region short wavelength gravity highs and lows south of the cis represent exposed metavolcanics and granite intrusions which represent tholeiitic series rocks to calc alkaline series rocks associated with island arcs and back arc magmatism therefore the large wavelength gravity low south of the cis is modelled as a low density body below the moho which conforms with seismic reflectors and may represent crustal rocks subducted towards the south thrusting in this case is indicated in the subducted block towards the north of the cis the bipolar gravity anomaly across the cis therefore indicates a collision zone between the bundelkhand craton towards the north and bhandara deccan cratons towards the south

temporal behavior of deep seated gravitational slope deformations a review abstract deep seated gravitational slope deformations dsgsds are slow moving hillslope scale mass movements featuring characteristic landforms such as double crested ridges and upslope facing scarps that occur in diverse landscapes throughout the world although these deformations have been studied since the 1960s significant insights to the rates of dsgsds have only been gained within the last two decades owing to progress in geochronology remote sensing and instrumental monitoring absolute age and monitoring data indicate that dsgsd movements are observable over long term 102 years and short term future research directions include constraining the lifespan of dsgsds with absolute age dating and precise high resolution monitoring of spatio temporal displacement across dsgsd bodies it is of great importance to include absolute time scales in the numerical models of dsgsds furthermore combining remote sensing techniques such as synthetic aperture radar interferometry with high resolution lidar scanning and near surface geophysics offers a promising toolkit for collecting very detailed and accurate data on the short term deformation rates of dsgsds

large sackung along major tectonic features in the central italian alps deep seated gravitational slope deformation sackung is common in alpine mountain belts it is controlled by lithological geomorphological and structural features we describe and discuss five examples of dsgsd along the insubric line periadriatic fault in the central italian alps the five examples are different in morphology size state of activity and distribution and are located along both primary and secondary valleys we demonstrate relations between structural and gravitational features and discuss the possibility that structural has both passive and active roles in sackung development analysis of ps sar data shows that the studied examples are not active today numerical modelling demonstrates the importance of lithological and structural constraints postglacial debuttressing groundwater fluctuations and weathering on sackung triggering and development

topographic precursors and geological structures of deep seated catastrophic landslides caused by typhoon talas abstract typhoon talas crossed the japanese islands between 2 and 5 september 2011 causing more than 70 deep seated catastrophic landslides in a jurassic to paleogene lower miocene accretion complex detailed examination of the topographic features of 10 large landslides before the event recorded on 1 m dems based on airborne laser scanner surveys showed that all landslides had small scarps near their future crowns prior to the slide and one landslide had linear depressions along its future crown as precursor topographic features these scarps and linear depressions were caused by gravitational slope deformation that preceded the catastrophic failure although the scarps may have been enlarged by degradation their sizes relative to the whole slopes suggest that minimal slope deformation had occurred in the period immediately before the catastrophic failure the scarp ratio defined as the ratio of length of a scarp to that of the whole slope both measured along the slope line ranged from 5 to 21 careful examination of aerial photographs from another four large landslides for which no high resolution dems were available suggested that they also developed scarps at their heads beforehand twelve of the 14 landslides we surveyed in the field had sliding surfaces with wedge shaped discontinuities that consisted of faults and bedding suggesting that the buildup of pore pressure occurs readily on wedge shaped discontinuities in a gravitationally deformed rock body most of the faults were undulatory and were probably thrust faults that formed during accretion other types of gravitational deformation were also active e g flexural toppling and buckling were observed to have preceded one landslide

postglacial deformation history of sackungen on the northern slope of pic d encampadana andorra abstract slopes undergoing deep seated gravitational deformation create surface landforms that if trenched and dated yield critical data on slope kinematics the northern slope of pic d encampadana descends steeply 800 m down into the glaciated valira d orient of andorra and has long been known for its numerous antislope scarps sackungen indicative of deep seated gravitational slope deformation dsgsd we excavated three trenches across antislope scarps and their adjacent troughs to date the deformation structures and to infer slope kinematics trough deposits have been disrupted by normal and reverse faulting with the largest fault zone underlying the antislope scarp and dipping into the slope at 40 80 trenches in the troughs expose fining upward sequences of strata from which we interpret several cycles of 1 episodic downdropping along graben faults and deepening of the topographic trough 2 filling the trough with marginal colluvial and axial sag pond sediments followed by 3 a hiatus of soil profile development the average time between deformation events in any one trench in the past 12 15 ka is about 3 3 5 ka deformation seems to have begun first in the lower part of the northern slope 1935 m elevation about 15 3 ka and had spread to the upper parts of the slope 2320 m by 11 6 ka deformation in the lower slope ceased after 5 5 ka but continued higher on the slope into the mid late holocene the youngest deformation dated 1 4 1 6 ka occurred in the highest trench on the slope this pattern of younger deformation with increasing elevation has been documented at several other sites and has been ascribed to an upslope migrating extensional stress field which originated at the base of the slope from glacial oversteepening and end glacial debuttressing

synchronized gravitational slope deformation and active faulting a case study on and around the neodani fault central japan abstract earthquakes are considered to be important triggers of deep seated gravitational slope deformation dgsd in seismically active regions and if that is the case dgsd features could be candidates for off fault paleoseismology investigations on the basis of pit excavations and sediment cores at an off fault dgsd site and a trench excavation across the active neodani fault at a nearby site we examined the records of dgsd and surface rupturing paleoearthquakes of the neodani fault the four most recent dgsd events were dated at after 240 cal bp 1710 340 cal bp 4730 3970 cal bp and 5570 5340 cal bp the four most recent surface rupturing earthquakes were dated at 1891 ce the nobi earthquake 2010 1220 cal bp 7180 2110 cal bp and before 9540 cal bp we conclude that the ages of the four dgsd events are consistent with surface rupturing earthquakes on the adjacent neodani fault we infer that static crustal strain from repeated seismogenic faulting plays an important role in the occurrence of dgsd events at least in the immediate vicinity of active faults although coseismic severe shaking would have at least some effect on them our case study suggests that off fault dgsds can be used to reconstruct or refine the paleoseismic history of a nearby active fault we propose that an ideal dgsd for that purpose would be located in an area of concentrated strain near a termination bend or stepover of the target fault

paraglacial slope failures in the aran valley central pyrenees abstract slope failures are widespread phenomena in mid latitude mountain environments that were glaciated during the last glacial cycle this is the case of the aran valley in the upper garonne catchment central pyrenees that included glaciers several hundred meters thick following postglacial warming and ice thinning the recently deglaciated slopes were subject to intense stress readjustments the so called paraglacial dynamics we have identified up to 135 major slope failures in the aran valley with only 10 units occurring outside the glaciated domain of the maximum ice extent of the last glacial the presence of polished bedrock surfaces till and moraine ridges next to some of these features evidence a close connection between glacial and slope processes we have detected different types of slope failures affecting both bedrock 12 large catastrophic rock slope failures 16 rock slope deformation 34 rockfalls and 49 rockslides and unconsolidated glacial sediments 14 slope readjustments on drift mantled slopes the average altitude of rock slope failures oscillates between 1551 and 1991 m with a mean length ranging from 147 to 905 m and a width between 247 and 513 m the affected surface is also highly variable oscillating between 0 02 and 126 2 ha slope failures occur in different lithological settings but they are most frequent in slate lutite and limestone bedrocks we conclude that most of the failures show a paraglacial origin though other factors i e lithology and topography promoted slope instability

september 2005 rain induced catastrophic rockslides on slopes affected by deep seated gravitational deformations kyushu southern japan river rejuvenation forms convex slope breaks that can destabilize nearby slopes leading to gravitational deformation and in some cases catastrophic sliding of the slopes during heavy rainstorms such landslides were induced by typhoon 0514 which passed to the west of kyushu island japan on 6 september 2005 five large catastrophic rockslides occurred aligning along convex slope breaks 150 to 300 m above the present river bed of the mimi river the slope breaks are inferred to have been formed by rejuvenation of the river geological and geomorphological investigation revealed that these slides occurred in sandstone and mudstone of the cretaceous shimanto group and were preceded by slope deformation which generated gravitational folds and faults that appeared as scarplets at the tops of the deformed areas the slopes seem to have been in critical condition just before catastrophic failure which was triggered by the rainstorm

did pyrenean glaciers dance to the beat of global climatic events evidence from the wurmian sequence stratigraphy of an ice dammed palaeolake depocentre in andorra the ice marginal depositional sequence of la massana provides a chronostratigraphic benchmark for reconstructing the wurmian glacial evolution of the valira catchment in andorra se pyrenees the sedimentary record of andorra confirms the asynchronous chronology of glacier fluctuations in different parts of the pyrenean mountain range a major ice recession occurred at the end of marine isotope stage mis 4 high magnitude valley glacier fluctuations during mis 3 constitute another important finding major readvances occurred toward the end of mis 3 whereas mis 2 in particular the global last glacial maximum or lgm featured sharp contrasts in ice recession rates between pyrenean valleys substantial distances separated mis 4 glacier fronts the wurmian maximum ice extent or mie from those reached during the global lgm in contrast to situations in the eastern pyrenees where wurmian mie and global lgm ice fronts nearly coincided overall the valira glaciers reveal patterns that are more similar to those recorded elsewhere in the western and central pyrenees than in the eastern pyrenees the rapid fluctuations recorded by andorran glaciers during the second half of the wurm also suggest a response to global forcing events such as heinrich events in the north atlantic

palaeogeography and 10be exposure age chronology of middle and late pleistocene glacier systems in the northern pyrenees implications for reconstructing regional palaeoclimates abstract we present constraints on the chronology palaeogeography and palaeoclimatic implications for western europe of middle and late pleistocene glaciation in the ariege catchment north eastern pyrenees based on 37 cosmogenic 10 be exposure ages obtained from moraines and glacially scoured bedrock exposures we have dated six regional glacial stades the chronology emphasises several conclusions that are new to the region i in the pyrenees the global lgm occurred several thousands of years after the maximum ice extent of the wurmian glaciation ii almost full glacier extent occurred again during the global lgm but only in the eastern pyrenees iii valley glaciers such as in the ariege trunk valley attained lengths of 25 km during the oldest dryas stadial the cosmogenic exposure ages additionally provide the first direct evidence of 10 km scale fluctuations of ice front positions during the late pleistocene glacial cycle probably at the time of marine isotope stage 3 as well as rare insights into middle pleistocene ice margin positions compared with existing evidence of glacial palaeogeography in other catchments of the pyrenan range the data also reveal a sharp contrast in relative ice extent between the glacierized catchments of the eastern pyrenees ariege carol malniu tet where wurmian mie and lgm ice fronts reached similar positions and the rest of the range where ice fronts at the time of the mis 2 and global lgm palaeotemperature minima lagged far behind the wurmian mie terminal moraines we ascribe this non uniform behaviour among catchments to non uniform palaeoclimatic conditions along the strike of the pyrenees a range of palaeoenvironmental proxies reviewed in the literature highlight a sharp difference in sea surface temperatures between the warmer western mediterranean and the cooler bay of biscay the consequences of such an e w temperature gradient on weather patterns during the global lgm are compatible with a strengthening of mediterranean low pressure systems particularly the semi permanent balearic low generating greater precipitation over the eastern pyrenees compared to atlantic weather systems further west