the evolution of tungsten sources in crustal mineralization from archean to tertiary inferred from lead isotopes lead isotope compositions of 31 tungsten bearing mineral occurrences worldwide with ages ranging be tween archean and tertiary have been determined to assess the evolution of tungsten sources in crustal min eralization through time the data indicate that tungsten of crustal mineralization was mainly supplied by the mantle between 3 0 and 2 4 ga the possibility of increasing contributions from the newly formed crust to tungsten mineralization throughout the archean is suggested by the available data although this suggestion needs to be tested by additional measurements the tungsten occurrences of proterozoic age contain mature crustal lead reflecting their association with crustal reworking through metamorphism and magmatism in the proterozoic mobile belts from 0 5 ga onward tungsten mineralization displays a renewed mantle lead con tribution owing to the direct or indirect association of post 0 5 ga tungsten occurrences with subduction re lated magmatic rocks of the phanerozoic orogenic cycles the data presented also suggest that several tungsten mineralization pulses may have recycled tungsten from older reservoirs

landslides and climate change in the italian dolomites since the late glacial abstract the paper deals with the relationship between the temporal occurrence of landslides and climatic changes in the italian dolomites since the late glacial after an introduction on the state of the art with particular reference to the alpine region the results of recent investigations in the two study sites are illustrated at cortina d ampezzo several landslides were dated mainly by the radiocarbon method the most ancient landslide event there involved large rock slides which affected the dolomitic slopes following the withdrawal of glaciers after the last glacial maximum lgm and also slides and flows mainly occurring in pelitic materials of the valley floors from 13 000 to 10 000 cal bp a later series of flows occurred between 5500 and 2500 cal bp in the upper badia valley alta badia the most ancient events go back to 10 000 and 9000 cal bp and correspond with earth flows that followed vast rotational slides affecting the bedrock up to a depth of about 50 m more recent earth flows involving more modest amounts of material took place between 6500 and 2300 cal bp by analysing the dates from the two study areas it was possible to correlate the recorded increase of landslide activity with the climatic changes occurring at the boundary between the late glacial and the holocene and between the atlantic and the subboreal and to compare the results with those derived from other european regions the types and causes of landslides taking place in these two periods were substantially different reflecting the different morphoclimatic conditions that existed in the two areas when these mass movements were triggered finally notwithstanding the importance of non climatic causes such as geological structural factors and possible human influences it is concluded that many of the dated landslides can be considered as indicators of climatic change

slope development reconstruction at two sites in the bohemian forest mountains although the bohemian forest is generally considered to be geomorphologically a rather stable region there are localities which bear proof of a surprisingly high intensity of recent and even present day processes a multidisciplinary methodology based on the analysis of slope systems was used for researching the present and past dynamics of two hillslopes using the results of direct dilatometric monitoring the slow creep of rock blocks reached a maximum of 1 mm year 1 gps field mapping sedimentology geodetic measurements and dem analyses several common rules have been observed for the behaviour of two model localities and a likely polycyclic development established with recurrence of mass wasting cycles related to material supply thresholds radiometric dating of debris flow activity showed that the cycles span approximately 4000 years in this area of rather stable bedrock conditions at least two factors that decrease slope stability need to act together to activate slope processes i e a favourable structural predisposition dip of major joint or bedding planes and an increase in relief through either glaciation or river incision copyright 2010 john wiley sons ltd

surface and sub surface schmidt hammer rebound value variation for a granite outcrop this study presents rock strength variations at granite outcrops and in subsurface vertical profiles in the jizerske hory mountains czech republic schmidt hammer rebound values in subsurface profiles change gradually from the bedrock surface downward an exponential relation has been observed between the r values and depth in rock outcrops to a depth of around 4 5 m the exponential nature of the curve indicates that rock hardness increases more rapidly with depth in the uppermost 1 m section of the rock profile a detailed study of rebound values obtained from both intact and polished rock exposures reveal effects of surface grinding on results of the schmidt hammer method the range of data collected increases after grinding allowing more precise discrimination of rock surfaces in respect of age and weathering the schmidt hammer method may be used effectively as a relative age dating tool for rock surfaces that originated during the late pleistocene it is concluded that this time limitation can be significantly mitigated by surface grinding before measurement copyright 2010 john wiley sons ltd

a regional inventory of rock glaciers and protalus ramparts in the central italian alps abstract we present a regional inventory of rock glaciers n 1514 and protalus ramparts 228 for the lombardy region central italian alps to identify and classify the landforms we inspect three sequential air orthophoto mosaics and a 2 m dsm and conduct confirmatory field work the inventory forms an empirical basis to analyze i the relative contribution of hillslope i e talus slopes and glacial i e moraines sediment stores to rock glacier sediment supply ii linkages between the landforms inventoried and local topographic attributes iii the spatial variability of periglacial activity in relation to a parsimonious set of environmental variables i e elevation precipitation and lithology and iv the effects of the pleistocene holocene climatic transition on the distribution of intact and relict landforms this analysis reveals that the elevation of rock glacier termini can vary over 200 m as a function of slope aspect in turn the distribution of rock glaciers among aspect categories is controlled by the structure of the valley network that promotes nw and se exposures talus rock glaciers prevail numerically over the glacier related typology even though the latter population appears to have increased during the holocene relict and intact rock glaciers have distinct spatial patterns in that the former display on average a 400 m elevation drop and a less clustered distribution towards northern aspects suggesting that they have developed in more permafrost prone climatic conditions analyzing the study region through a 27 5 km grid has been instrumental for showing that the rock glacier specific area and terminus elevation are i positively correlated with terrain elevation and ii negatively correlated with mean annual precipitation as a consequence in relation to holocene generalized atmospheric temperature rise intact rock glaciers have progressively disappeared from the wetter and milder portions of the central italian alps analysis of rock glacier occurrence across litho tectonic sectors does not provide conclusive dependences and requires further analysis this inventory which represents a necessary preliminary step for modelling the spatial distribution of discontinuous permafrost at the regional scale fills a critical geographic gap in the context of ongoing permafrost research in the european alps e g permanet

application of field geophysics in geomorphology advances and limitations exemplified by case studies abstract during the last decade the use of geophysical techniques has become popular in many geomorphological studies however the correct handling of geophysical instruments and the subsequent processing of the data they yield are difficult tasks furthermore the description and interpretation of geomorphological settings to which they apply can significantly influence the data gathering and subsequent modelling procedure e g achieving a maximum depth of 30 m requires a certain profile length and geophone spacing or a particular frequency of antenna for more than three decades geophysical techniques have been successfully applied for example in permafrost studies however in many cases complex or more heterogeneous subsurface structures could not be adequately interpreted due to limited computer facilities and time consuming calculations as a result of recent technical improvements geophysical techniques have been applied to a wider spectrum of geomorphological and geological settings this paper aims to present some examples of geomorphological studies that demonstrate the powerful integration of geophysical techniques and highlight some of the limitations of these techniques a focus has been given to the three most frequently used techniques in geomorphology to date namely ground penetrating radar seismic refraction and dc resistivity promising applications are reported for a broad range of landforms and environments such as talus slopes block fields landslides complex valley fill deposits karst and loess covered landforms a qualitative assessment highlights suitable landforms and environments the techniques can help to answer yet unsolved questions in geomorphological research regarding for example sediment thickness and internal structures however based on case studies it can be shown that the use of a single geophysical technique or a single interpretation tool is not recommended for many geomorphological surface and subsurface conditions as this may lead to significant errors in interpretation because of changing physical properties of the subsurface material e g sediment water content in many cases only a combination of two or sometimes even three geophysical methods gives sufficient insight to avoid serious misinterpretation a good practice guide has been framed that provides recommendations to enable the successful application of three important geophysical methods in geomorphology and to help users avoid making serious mistakes

intraplate stresses and dynamical aspects of rifted basins abstract intraplate stresses play a important role during the syn and post rift evolution of sedimentary basins deviations from long term thermal patterns of post rift subsidence as well as the development of unconformities within rifted basins reflect to a large extent the temporal fluctuations of the regional stress fields in the lithosphere it appears that incorporation of intraplate stresses in dynamical models for basin development together with a quantification of the role of petrological changes in the crust lithosphere system can explain some of the observed shortcomings of thermal models of post rift basin subsidence late neogene accelerations in tectonic subsidence in the deeper parts of rifted basins in the northern atlantic and mediterranean regions could reflect a change in the level of intraplate stress over large areas of the globe non thermal contributions to the subsidence record affect estimates of crustal extension and consequently influence the depth at which hydrocarbon source rocks enter the maturity window stress induced changes in basement topography have also important consequences for the budget of fluid flow in the deeper parts of the sediment fill of the rifted basins as well as on the dynamics of diapirism

dynamic stratigraphy of an evaporite to red bed sequence gipskeuper triassic southwest german basin abstract the dynamics of evaporite accumulation are studied in the gipskeuper triassic of the southwest german epicontinental basin based on a hierarchical three level stratigraphic analysis 1 among the various stratification types the following are most important a thin carbonate intervals with marine faunas b massive sulfates with selenite indicating very shallow subaqueous gypsum precipitation c thin bedded gypsarenites with a variety of sedimentary structures suggesting clastic evaporite accumulation during high energy events gypsum tempestites d laminated gypsum with spectacular tepee structures testifying inter to supratidal settings e green grey and reddish claystones with nodular gypsum indicating evaporitic playa mudflats 2 facies sequences occur in several varieties and commonly form 1 4 m thick transgressive regressive cycles with shallowing upwards trends the long recognized carbonate marker beds represent short term trans or ingressions into the almost flat keuper basin highly disturbed tepee horizons form widely correlatable regressive peaks these sequences form evaporite equivalents to the ubiquitous shallowing upward cycles known from carbonate systems 3 the basin fill consists of a small scale cycles being vertically stacked upon each other to form the basic building block of the layer cake architecture of the gipskeuper succession the stacking of small scale cycles is superimposed onto a larger scale regressive cycle which records a general shift from restricted marginal marine to hypersaline marine to the more continental red bed deposition of the overlying keuper this hierarchy of cycles probably reflects various orders of eustatic sealevel fluctuations the gipskeuper thus exemplifies dynamics of evaporite accumulation and allows us to understand some of the processes that produce a layer cake stratigraphy its cycle hierarchy is a common motif in the entire southwest german basin fill and appears typical for epicontinental basins

subsidence of the paris basin we discuss the main results of a systematic quantitative analysis of the subsidence of the paris basin made on 100 wells backstripping techniques with decompaction as well as sea level and water depth corrections are used to derive tectonic subsidence curves in the absence of water and sediment loading assuming local as well as regional compensation a best fitting sea level variations curve is derived for the deepest central part on the basis of the resulting tectonic subsidence curve the adopted amplitude of the regression since upper cretaceous is 330 m the spatial and temporal distribution of tectonic subsidence is reconstructed and discussed it is shown that rigidity of the lithosphere with an adopted 50 km flexural parameter plays a significant role these results are then quantitatively interpreted in terms of the lithospheric stretching model this interpretation is reasonable provided it is made in terms of volumetric subsidence over the whole basin because of the thermal conduction and the rigidity low pass filtering effects the subsidence can be explained if the axial zone was thinned during permo triassic by a factor of about 1 3 with respect to the adjacent lithosphere it is shown that either the initial altitude was more than 500 m above sea level or the lower part of the lithosphere was lost at the beginning of the permo triassic phase of extension resulting in a rapid uplift of several hundreds of meters the similarity of the permo triassic initiating extensional phase with active continental rifting is shown

lithofacies and cyclicity of mohilla evaporite basins on the rifted margin of the levant in the late triassic makhtesh ramon southern israel marine connected basins with evaporites occur beneath most extensional continental margins that originated at low latitudes and often are of major economic significance cyclicity in the evaporite lithofacies reflects the degree of restriction of the basin overprinted by sea level changes and caused by structural movements in the barrier region whether by fault block rotation footwall uplift or hanging wall subsidence in both extensional and compressional basins the upper triassic evaporites of the ramon section in southern israel model cyclic sedimentation in such environments the mohilla formation is a carbonate evaporate siliciclastic succession of carnian age that fills a chain of basins extending along the levant margin from southern israel to jordan and syria the basins developed in half grabens adjacent to normal faults that formed during a period of regional extension evaporites of this formation are well exposed in outcrops at makhtesh ramon the southernmost of these basins the m2 member of the mohilla formation is composed of 42 sub metre cycles of alternating dolostone gypsum and calcareous shales field and microfacies analysis showed these cycles to conform mostly to restricted shallow and marginal marine environments spatially limited by the uplifted shoulders of the half graben systems a total of 10 facies types belonging to six depositional environments have been identified from stacking patterns and analysis of bed to bed change cycles can be categorized into three groupings i low frequency exposure to exposure cycles that developed under eustatic or climate control ii high frequency deepening shallowing upward cycles characterized by gradual transitions due to short term sea level or runoff event oscillations possibly referable to orbital forcing and iii high frequency shallowing upward cycles characterized by abrupt transitions attributable to sporadic tectonic events affecting accommodation space or barrier effectiveness the way facies and cycling of the sedimentary environments was deciphered in the mohilla evaporite basin can be used to unravel the genesis of many other evaporite basins with barriers of tectonic origin

interpretation age and significance of a relict paraglacial and periglacial boulder dominated landform assemblage in alnesdalen romsdalsalpane southern norway abstract a boulder dominated landform assemblage in an alpine setting in norway is described interpreted and dated using a combination of schmidt hammer exposure age dating shd and cosmogenic 10be surface exposure dating the origin and formation of these features is determined from their morphology topographic setting and age three main components of the assemblage are recognized first a 300 m long and 160 m wide tongue shaped rock slope failure with a shd age of 11 49 0 82 12 96 0 86 ka is identified on the basis of its planform thickness runout distance and association with a fractured backing scarp this is interpreted as a relict paraglacial landform triggered by deglaciation second a 400 m long unequivocal pronival protalus rampart with an shd age of 6 95 0 97 8 35 1 21 ka is identified on the basis of its narrow ridge form aligned close to the foot of an extensive talus slope although formation of the rampart probably commenced with deglaciation the younger shd ages indicate formation at a diminishing rate through the holocene third a 550 m by 150 m lobate component with transverse ridges longitudinal and transverse depressions and enclosed pits previously identified as a rock glacier is dated to 11 33 0 83 13 33 0 90 ka with the schmidt hammer and between 13 3 2 0 14 7 2 0 ka with 10be this third component may also be a product of rock slope failure but attribution to rock glacier creep associated with either interstitial ice permafrost or buried glacier ice during the allerod interstadial younger dryas stadial and to which one or more rock slope failures contributed debris cannot be rejected the advantages and limitations of compiling such evidence for identifying differentiating and classifying apparently similar boulder dominated colluvial landforms are exemplified

internal structure and permafrost distribution in two alpine periglacial talus slopes valais swiss alps in order to determine the spatial extension and the characteristics of permafrost within alpine talus slopes two sites located in the western part of the swiss alps were studied using borehole drilling and electrical resistivity tomography ert profiles three boreholes were drilled along an upslope downslope transect in both talus slopes in both sites frozen sediments are present only in the two lowest boreholes whereas the upper borehole does not present ice this stratigraphy is confirmed by ground temperatures registered in the boreholes in each site three upslope downslope ert profiles were crossed with five respectively four horizontal ert profiles all the upslope downslope profiles show a difference in resistivities between the upper and lower parts of the slope where a large resistive body with values higher than 35 k m is present in the uppermost part of the profiles the resistivities are lower than 10 15 k m the borehole data allowed the stratigraphy obtained from the ert inverted profiles to be validated with regards to the distribution of frozen sediments as well as the depth of the detected structures the results confirm that in the two studied sites permafrost is present in the lower sections of the talus slopes whereas it is absent in the upper parts finally the analysis of the talus structure showed that the permafrost stratigraphy and in particular the ice content may be an important element of interpretation of the palaeoclimatic significance of an alpine talus slope

diagnostic characteristics and paleodynamics of supraglacial rock avalanches innerdalen western norway abstract misinterpretation of rock avalanche deposits in mountain environments is not uncommon because of the complex interactions between rock avalanches and glaciers this paper for the first time presents a detailed description of suspicious rock boulder deposits which are remnants of a rock avalanche onto a late pleistocene glacier the boulder deposits cover around 1 1 km 2 and are distributed over an area of around 7 5 km 2 and a variety of landforms three closely nested distinct terminal moraines 0 45 km 2 and dislocated terminal moraines 0 34 km 2 entirely built up of large boulders lateral moraines that decrease in elevation over a short distance and connect to the terminal moraines small patches 0 02 km 2 of boulders that occur in islands on a peat dominated valley floor and large patches of boulder fields 0 25 km 2 in size hanging 350 m above the valley floor the latter are disconnected from any potential source area 10 be cosmogenic nuclide ages of the three terminal moraines give an indistinguishable late pleistocene age of 13 6 1 4 ka whereas the largest boulder field that is located on the opposite side of the valley from the failed mountain yields a 10 be age of 14 1 0 4 ka which is slightly older but indistinguishable from the moraine deposits within uncertainty margins all boulder deposits add up to a volume of 31 10 6 m 3 the interpretation of a single rock avalanche source for those landforms is further confirmed by numerical runout modeling using dan3d a failure of the entire volume from skarfjellet mountain would result in a runout pattern that is identical to that of the distributed boulder fields when considering that the valley was filled with a glacier around 350 m thick the rock avalanche would not reach the position of the terminal moraines however a glacial re advance could have transported the boulders to that position the late pleistocene rock avalanche was followed by a holocene rock avalanche with a volume of 23 10 6 m 3 and a typical lobate deposit damming the innerdalen valley and creating a lake 10 be ages indicate that this event occurred 7 97 0 94 ka ago structural measurements performed on high resolution lidar scans show a strongly jointed source rock with three joint sets with dip dip direction 81 034 86 331 and 77 354 and a foliation with 22 003 the kinematic of the failures can thus be a combination of small scale wedge failures and planar sliding on shallow dipping foliation our detailed description can enable a better identification and interpretation of similar deposits in other mountain areas

keuper stratigraphic cycles in the paris basin and comparison with cycles in other peritethyan basins german basin and bresse jura basin abstract high resolution sequence stratigraphy of the keuper paris basin is used to establish correlations between the basin centre evaporite series and the basin margin clastics series the high resolution correlations show stratigraphic cycle geometries the keuper consists of five minor base level cycles whth occur in the upper portion of the scythian carnian major base level cycle and the lower part of the carnian liassic major base level cycle the maximum relative rate of subsidence for the base level fall phase of the scythian carnian major cycle occurs in the eastern part of the paris basin during the base level rise phase of the carnian liassic major cycle the area of highest rate of subsidence shifted westwards and northwards this shift records the first occurrence of an independent paris basin which was no longer merely the western margin of the german basin two phases of tectonic movement influenced evaporite sedimentation and sequence geometries by creating areas of subsidence where halite could accumulate the second within the marnes irisees superieures induced a general westward and northward tilt of the basin concurrent migration of depocentres to the west and north produced an intra marnes irisees superieures truncation comparison of the stratigraphic records of the paris basin and of other triassic peritethyan basins german basin bresse jura basin and south east basin reveals numerous similarities the coastal onlap curve of the german keuper aigner and bachmann 1992 exhibits many similarities with the sequence evolution of the paris basin but the triassic succession is more complete in the german basin and more cycles are observed the major difference between these two basins during the keuper is that the marnes irisees inferieures minor base level cycle does not occur in the german basin in the bresse jura basin the major difference concerns the lettenkohle one minor base level cycle is recorded in the paris basin while no cycle is observed in the bresse jura basin

classic and new dating methods for assessing the temporal occurrence of mass movements abstract establishing landslide chronologies is essential both for understanding causes of mass movements as part of fundamental geomorphological research and for the assessment of landslide hazards as part of applied geomorphology we discuss the applicability of different methods for determining landslide chronologies frequencies and dynamics in relation to the type of material being dated sampling location and type of mass movement the emphasis is on the possibilities and limitations of the different dating methods established methods such as radiocarbon dating lichenometry and dendrochronology are briefly discussed the paper focuses however on 1 new analytical techniques like accelerator mass spectrometry ams thermally ionising mass spectrometry tims and laser fusion which have led to significant improvements of established dating methods and on 2 new dating methods like optically stimulated luminescence osl dating and alpha recoil track art dating

sensitivity to long term climate change of subpermafrost groundwater systems in svalbard deep subpermafrost aquifers are highly climate dependent with the permafrost as an aquitard preventing groundwater recharge and discharge a study from the high arctic island of spitsbergen svalbard shows that during a glacial to interglacial phase both the permafrost and the glacier regime will respond to climatic changes and a glacier fed groundwater flow system will vary accordingly a full glaciation results in the melting of permafrost and groundwater can flow through pores and fracture systems in the rocks and sediments below the temperate zones of glaciers these groundwater flow systems will mainly be localized to fjords and valleys and form low lying terrestrial springs when the relative sea level drops during deglaciation due to glacio isostatic rise during an interglaciation permafrost develops and thickens and the groundwater recharge and discharge areas will thereby be gradually reduced to a minimum reached at the warmest part of an interglaciation an already frozen spring system cannot reopen before the permafrost melts only groundwater springs related to permanently warm based glacial ice will persist into the next glaciation during a new glaciation flow systems that terminated during the previous interglaciation may become revitalized if overridden by warm based ice causing permafrost thawing

rockfall hazard analysis using lidar and spatial modeling abstract rockfalls have been significant geohazards along the canadian class 1 railways cn rail and cp rail since their construction in the late 1800s these rockfalls cause damage to infrastructure interruption of business and environmental impacts and their occurrence varies both spatially and temporally the proactive management of these rockfall hazards requires enabling technologies this paper discusses a hazard assessment strategy for rockfalls along a section of a canadian railway using lidar and spatial modeling lidar provides accurate topographical information of the source area of rockfalls and along their paths spatial modeling was conducted using rockfall analyst a three dimensional extension to gis to determine the characteristics of the rockfalls in terms of travel distance velocity and energy historical rockfall records were used to calibrate the physical characteristics of the rockfall processes the results based on a high resolution digital elevation model from a lidar dataset were compared with those based on a coarse digital elevation model a comprehensive methodology for rockfall hazard assessment is proposed which takes into account the characteristics of source areas the physical processes of rockfalls and the spatial attribution of their frequency and energy

the schmidt hammer in rock material characterization the schmidt hammer provides a quick and inexpensive measure of surface hardness that is widely used for estimating the mechanical properties of rock material however a number of issues such as hammer type normalization of rebound values specimen dimensions surface smoothness weathering and moisture content and testing data reduction and analysis procedures continue to influence the consistency and reliability of the schmidt hammer test results this paper presents a a critical review of these basic issues and b the results of tests conducted on granitic rocks of various weathering grades in the light of the conclusions of this review it was found that a very good correlation exists between l and n hammer rebound values and that both hammers are fairly sensitive to the physical properties particularly to dry density though less so to effective and total porosities the n hammer producing a lesser scatter in the data proved to be more efficient than the l hammer in predicting uniaxial compressive strength and young s modulus the exponential form of the correlation curves was found to reflect microstructural changes during the course of weathering and the differences in the probing scales or mechanisms in the means of measuring these mechanical properties and could be generalized to other crystalline igneous rocks the possibility of predicting weathering grades from rebound values was also explored the changes in the rebound values during multiple impacts at a given point produced a better indication of the weathering grade than a single impact value it was concluded that increasing the impact energy and plunger tip diameter should significantly reduce the scatter in coarse grained weathered rocks and hence improve the reliability of the schmidt hammer as a rock material characterization tool

stratigraphic architecture and gamma ray logs of deeper ramp carbonates upper jurassic sw germany abstract the objective of this paper is to contribute to the development of sequence stratigraphic models for extensive epicontinental carbonate systems deposited over cratonic areas epicontinental carbonates of the sw german upper jurassic were analysed in terms of microfacies sedimentology and sequence stratigraphy based on 2 5 km of core 70 borehole gamma ray logs and 24 quarries facies analysis revealed six major facies belts across the deeper parts of the carbonate ramp situated generally below fair weather wave base and mostly below average storm wave base but in the reach of occasional storm events observed stratigraphic patterns differ in some aspects from widely published sequence stratigraphic models 1 elementary sedimentary cycles are mostly more or less symmetrical and are thus referred to as genetic sequences or genetic units aaapg bull 55 1971 1137 frazier d e 1974 depositional episodes their relationship to the quaternary stratigraphic framework in the northwestern portion of the gulf basin university of texas austin bureau of economic geology geologicalo circular 71 1 aapg bull 73 1989 125 galloway w e hobday d k 1996 terrigenous clastic depositional systems 489 pp springer cross t a baker m r chapin m s clark m s gardner m h hanson m s lessenger m a little l d mcdonough k j sonnenfeld m d valasek d w williams m r witter d n 1993 applications of high resolution sequence stratigraphy to reservoir analysis edition technip 1993 11 33 bull cent rech explor prod elf aquitaine 16 1992 357 homewood p mauriaud p lafont f 2000 best practices in sequence stratigraphy elf ep mem 25 81 pp homewood p eberli g p 2000 genetic stratigraphy on the exploration and production scales elf ep mem 24 290 pp in contrast to the asymmetrical shallowing upward parasequences of the exxon approach 2 neither sequence boundaries nor maximum flooding surfaces could be clearly delineated cycle boundaries are generally not represented by sharp stratal surfaces but are always transitional and thus referred to as turnarounds nor pet soc spec publ 8 1998 171 several types of genetic sequences were delineated both major types of facies and sequences show characteristic gamma ray log signatures based on the cycle stacking and the gamma ray patterns a hierarchy of sequences was recognized probably driven in part by 100 000 and 400 000 year milankovitch signals the cyclicity allowed regional correlations across various depositional environments such as sponge microbial bioherms and coeval basins the basin wide correlation revealed evidence for a subtle clinoform type stratigraphic architecture along very gentle slopes rather than a so far assumed simple layer cake pattern

development of tongue shaped and multilobate rock glaciers in alpine environments interpretations from ground penetrating radar surveys abstract rock glaciers occur as lobate or tongue shaped landforms composed of mixtures of poorly sorted angular to blocky rock debris and ice these landforms serve as primary sinks for ice and water storage in mountainous areas and represent transitional forms in the debris transport system accounting for 60 of all mass transport in some alpine regions observations of active flowing alpine rock glaciers indicate a common association between the debris that originates from cirque headwalls and the depositional lobes that comprise them the delivery of this debris to the rock glacier is regulated primarily by the rate of headwall erosion and the point of origin of debris along the headwall these factors control the relative movement of individual depositional lobes as well as the overall rate of propagation of a rock glacier in recent geophysical studies a number of alpine rock glaciers on prins karls forland and nordenskioldland svalbard norway and the san juan mountains of southwest colorado usa have been imaged using ground penetrating radar gpr to determine if a relationship exists between the internal structure and surface morphology results indicate that the overall morphologic expression of alpine rock glaciers is related to lobate deposition during catastrophic episodes of rockfall that originated from associated cirque headwalls longitudinal gpr profiles from alpine rock glaciers examined in this study suggests that the difference in gross morphology between the lobate and tongue shaped rock glaciers can be attributed primarily but not exclusively to cirque geometry frequency and locations of debris discharge within the cirque and the trend and magnitude of valley gradient in relation to cirque orientation collectively these factors determine the manner in which high magnitude debris discharges which seem to be the primary mechanism of formation accumulate to form these rock glaciers

from a mountain belt collapse to a sedimentary basin development 2 d thermal model based on inversion of stratigraphic data in the paris basin abstract the thermal mineralogical and mechanical behaviour of the lithosphere determines the genesis and evolution of sedimentary basins subsidence amplitude geometry of sediment bodies sedimentary processes using the large stratigraphic database available for the paris basin we constrain the lithosphere thermal evolution thickness and rigidity as well as the mechanism that gave birth to this wide intracontinental basin the thermal subsidence calculated with a two dimensional thermal model is adjusted to the estimated tectonic subsidence by optimization of three parameters extension profile crustal thickness profile and average mantle heat flow the best fits for the paris basin lithosphere are obtained for a mantle heat flow of 23 mw m 2 and for an elastic thickness lower than 20 km preferred value te 5 km two mechanisms for the origin of the basin subsidence have been tested a pure extensional collapse of the variscan belt and a delamination of the mantle lithosphere at the end of carboniferous it appears that in both cases inverted extension factors are large in the range 1 2 1 85 in the first case and in the range 1 0 1 85 in the second case both cases involve the presence of a thick variscan crustal wedge and a mountain belt elevation of 1500 3500 m located in the paris basin centre the maximum extensional rates are obtained in the centre part of the basin in addition lithospheric delamination at around 300 ma allows for both crustal and mantle melting in agreement with the widespread existence of permian bimodal magmatism in france at the end of extension the basin centre kept a high elevation of about 1000 m before subsiding around 40 my later below sea level

high resolution sequence stratigraphy of an alluvial fan fan delta environment stratigraphic and geodynamic implications an example from the keuper chaunoy sandstones paris basin abstract facies analysis of the chaunoy formation conducted as the first stage of this study reveals that the corresponding fluvial system essentially involved bedload deposition 2 d and 3 d megaripple migration and debris flow deposition such processes are characteristic of alluvial fan depositional environments these alluvial fan deposits pass laterally eastward into a shallow lacustrine environment in stage 2 of the study electrofacies are defined by well log analysis and then matched with sedimentary facies defined by core analysis electrofacies associations and depositional environments are then inferred directly from well logs on this basis six electrofacies characterizing the main sedimentary facies associations and depositional environments within the chaunoy formation are defined channel lag deposits channel infilling lake or flood plain overflow deposits and paleosols stage 3 involves establishing correlations based on high resolution sequence stratigraphy within these continental deposits the procedure consists in analysing high frequency fluctuations in baselevel defined from sedimentological studies and calibrated on well log signatures the correlations show that the top of the chaunoy formation is diachronous the formation is subdivided here into three stratigraphic units from base to top chaunoy i ii and iii this study shows that the degree of preservation of continental deposits varies with stratigraphic cycle genetic sequences and genetic sequence sets are asymmetrical with the baselevel rise being better preserved than the baselevel fall while for minor cycle deposits may be similarly preserved during baselevel rise and fall the sequence stratigraphy pattern of the genetic sequences and the genetic sequence sets can result from climatic and or tectonic factors but their effects are difficult to distinguish at the scale of the minor chaunoy i cycle or the chaunoy ii cycle preservation is similar during the baselevel rise and fall that implies that the chaunoy minor cycles were influenced by load discharge resulting in greater accommodation space which could result from climatic or tectonic fluctuations the chaunoy formation was deposited as part of a major baselevel rise during the carnian liassic cycle during this cycle the paris basin was generally tilted to the northwest producing the intra marnes irisees superieures truncation which seems to have been induced by large scale wavelength tectonic deformation detailed isopach maps of minor baselevel cycles in chaunoy i with inferred depositional environments are used to define the extent of depositional environments and fault activity during baselevel rise and fall during emplacement of the braided alluvial fan and lacustrine deposits of the chaunoy formation fault activity which was confined to the western part of the basin controlled the preservation potential i e the thickness of the deposits and depositional environment profiles within the chaunoy i and ii cycles the increased thickness of the sandstone deposits to the northeast and the onlap at the top of chaunoy i can be explained by local fault activity and by the general tilting of the basin the chaunoy iii sandstones are confined to the western part of the basin and seem to have been controlled by local factors only

a new approach to lichenometry dating single age and diachronous surfaces a new approach to lichenometry based on large samples of the single largest lichen on each boulder is presented on surfaces of uniform age lichen sizes measured in this way are near normally distributed so the mean value can be used in constructing lichenometric dating curves by combining mean values from several sites statistically defined confidence limits can be assigned to predicted dates in a pilot study dates obtained for little ice age moraines of two glaciers in southern norway are consistent with those obtained using other approaches unlike standard lichenometry the new approach can be used to investigate the age frequency of boulders on diachronous surfaces formed by continuous or periodic accretion or disturbance it has been used successfully to access the record of late holocene snow avalanche activity retained on avalanche boulder ramparts in upper jostedalen western norway pilot studies are also presented of its use on a talus slope solifluction lobes and periglacial pattern

rock slope failure following late pleistocene deglaciation on tectonically stable mountainous terrain the ages of 31 postglacial rock slope failures rsfs in scotland and nw ireland derived from 89 cosmogenic isotope exposure ages are employed to analyse the temporal pattern of failure and its relationship to the timing of deglaciation rates of glacio isostatic crustal uplift and periods of rapid climate change rsf ages span almost the whole period since ice sheet retreat from 18 2 1 2 ka to 1 7 0 2 ka or from 17 1 1 0 ka to 1 5 0 1 ka depending on the production rate used in 10 be age calculation but catastrophic failure of rock slopes was w4 6 times more frequent prior to w11 7 ka than during the holocene 95 of dated rsfs at sites deglaciated during retreat of the last ice sheet occurred within w5400 years after deglaciation with peak rsf activity 1600e1700 years after deglaciation this time lag is inferred to represent 1 stress release initiated by deglacial unloading leading to 2 time dependent rock mass strength degradation through progressive failure plane development and ultimately 3 to either spontaneous kinematic release or failure triggered by some extrinsic mechanism by contrast 11 dated rsfs at sites reoccupied by glacier ice during the younger dryas stade yds of w12 9e11 7 ka exhibit no clear temporal pattern suggesting that glacial reoccupance during the yds was ineffective in preconditioning a renewed cycle of enhanced rsf activity comparison of timing of individual rsfs with that of deglaciation and rapid warming events at w14 7 ka and w11 7 ka suggests that glacial debuttressing enhanced joint waterpressuresduringdeglaciationandthawofpermafrosticeinrockjointscouldhavetriggeredfailurein only a small number of cases conversely the timing of maximum rsf activity following ice sheet deglaciation corresponds broadly with maximum rates of glacio isostatic crustal uplift suggesting that the two are linked by enhanced seismic activity a seismic failure trigger is consistent with full slope failure at all sites where failure planes are clearly defined our results indicate that numerous rsfs must have occurred in areas that were reoccupied by glacier ice during the yds but have not been identified because runout debris was removed by yds glaciers more generally they provide the first reliably dated body of evidence to support the view that retreat of the last ice sheets in tectonically stable mountainous terrain initiated a period of enhanced rock slope failure due to deglacial unloading and probably lateglacial seismic activity implying that most undated rsfs in such areas are probably of lateglacial or veryearly holocene age they also demonstrate however that a low frequency of rsf activity extended throughout the holocene

growth and demise of the jurassic carbonate platform in the intracratonic paris basin france interplay of climate change eustasy and tectonics it is usually very difficult to identify and quantify the relative influence of tectonics eustasy and climateon carbonate system evolution from sedimentary records in order to improve our understanding of these mechanisms we have traced for the first time the evolution of the eastern paris basin platform throughout the entire jurassic period this carbonate platform underwent eight successive growth and demise phases with different depositional profiles ranging from ramps to flat topped geometries the eight carbonate growth periods are compared with the standard sea level curves local tectonic regimes and recently published oxygen isotope and or clay mineralogy databases prograding heterozoan facies along ramp profiles mark periods dominated by second order eustatic sea level rise relatively cool sea surface temperatures and mesotrophic and humid conditions hettangian pliensbachian late oxfordian tithonian during these periods variable detrital contents in the sedimentary succession hampered the efficiency of shallow marine carbonate factories higher sea surface temperatures oligotrophic and humid conditions associated with either eustatic sea level rise or very high local subsidence occurred during the early bajocian and the mid oxfordian these seawater properties seem to have favoured the aggradation of scleractinian corals forming dome shaped bioherm buildups an oolitic and lime mud carbonate system deposited during the bathonian second order eustatic sea level fall is characterised by miliolid rich micritic facies on a rimmed ramp under stable cooler and drier conditions the secondorder maximum flooding associated with a sea surface temperature decline and or a seawater eutrophication caused at least five carbonate demise periods i e toarcian earliest late bajocian callovian oxfordian transition earliest late oxfordian and kimmeridgian

effect of the thermal gradient variation through geological time on basin modeling a case study the paris basin many studies investigated the thermal modeling of the paris basin for petroleum interests during the 1970s most of the softwares developed by oil companies or research centers were based on the assumption of a constant thermal gradient in order to take into consideration the variation of the thermal gradient during basin evolution we developed the thermo s visual basic 1d program we applied our model to twenty boreholes located along a cross section roughly running ew over 150 km in the center of the paris basin the numerical results were calibrated with organic matter maturity data thermo s simulates the amount of heat provided to the sedimentary organic matter the heat parameter simulated shows lateral variation along the cross section it decreases from rambouillet to trou aux loups boreholes 87 66 mw m2 at about 100 km more to the east whereas the heat flux value simulated is 73 mw m2 in st loup borehole the mean thermal gradient calculated for liassic horizons at 87 my for the rambouillet well is 50 4 c km this value is similar to previously published results by integrating the calculation of the thermal gradients and conductivities related to the burial of each stratigraphic sequence our approach points out variations in the thermal regimes the sedimentary organic matter som has been subjected to through geological time

rock glaciers and the geomorphological evolution of deglacierizing mountains abstract rock glaciers are an important geomorphic element of glaciated mountain landscapes but our understanding of their distribution and ages controls on their development and their importance in regional mountain hydrology and mountain geomorphic evolution is incomplete in part this incomplete knowledge arises through problems associated with identifying rock glaciers on a morphological basis alone amplified by the multiple ways in which rock glaciers can form in different glacial periglacial and paraglacial settings this study focuses on rock glaciers as a paraglacial mountain landscape element and considers the relationships between rock glaciers and glacial periglacial and paraglacial processes new geomorphic and sedimentary data on different rock glaciers from the khumbu region of nepal are presented these data show that even within a single region rock glaciers may have varied origins and thus likely ages and different climatic and environmental controls we argue that rock glaciers in deglacierizing mountains may have a long residence time in the landscape unlike many other glacially influenced mountain landforms and can undergo significant morphodynamic changes as glaciated landscapes transition into paraglacial landscapes

three dimensional accommodation analysis of the keuper of the paris basin discrimination between tectonics eustasy and sediment supply in the stratigraphic record abstract during the keuper the paris basin was an intracratonic sedimentary basin filled by continental deposits using paleo environmental isopach and paleo altitude maps we estimate the variations of accommodation rate at the scale of stratigraphic minor hemi cycle 1 3 ma an analysis of the short and long wavelength accommodation variations allows us to assess the relative influence of tectonics eustasy and sediment supply on the stratigraphic record our data suggest a pattern of subsidence along three trends e w in the carnian e w to nne ssw in the norian and ne sw in the norian rhaetian during the keuper the paris basin accurately records the different phases of the opening of the tethys ocean associated with a rotation of the extension direction the norian cycle could thus reflect the intraplate stresses in a transitional period between the triassic and the liassic

lichen dating of earthquake generated regional rockfall events southern alps new zealand synchronous regional rockfall events triggered by large earthquakes in the southern alps of new zealand were used to evaluate and improve the lichenometry method for surface exposure dating digital calipers were used to measure the maximum diameter of the largest lichen on many rockfall blocks using a fixed area largest lichen fall sampling strategy regional significance of fall peaks can be tested by confirming the occurrence of a coeval peak at multiple sites and by showing an increase in peak size toward the earthquake epicenter significance of fall peaks at a local site can be described in terms of peak size relative to a uniform density of fall sizes measurements of 34 000 fall sizes on fully exposed rockfall blocks and outcrop joint faces at 90 sites allow precise dating of geomorphic events of the past 300 to 500 yr uncertainties at the 95 confidence interval can be reduced to a level better than 10 yr for ages within the calibrated time range represented by the lichen growth equation recognition of prehistorical regional rockfall events in 1833 1836 and 1840 demonstrates the excellent resolution of this dating method precise dates result from exceptionally low measurement errors of lichen sizes relative to their growth rate tightly clustered fall sizes for earthquake induced rockfall events and substrate exposure times for calibration sites that are known to the year or day fall peaks for synchronous rockfall events are the same for 20 sites with diverse climate altitude and substrate lithology a regionally consistent lichen growth rate allows use of a single growth rate equation for most species of rhizocarpon subgenus rhizocarpon on the south island of new zealand a nonlinear growth equation suggests that the first colonization on average occurs in the 5th yr after formation of new rock surfaces 0 5 m 2 unit areas and is followed by rapid exponentially declining growth for about 20 yr greatgrowth phase that is largely completed by the 24th yr then linear growth persists at about 15 mm per century uniform growth phase

rock avalanche and rock glacier a compound landform study from hornsund svalbard abstract on the northern coast of the hornsund fjord at sw svalbard numerous rock block accumulations flank the foot of rotjesfjellet ridge whereas these accumulations are widely described as rock glaciers this study shows that other factors also influence formation of these landforms in this study morphometric profiling and terrain analyses lichenometry optical granulometry schmidt hammer measurements geophysical measurements using electric resistivity tomography geodetic measurements using terrestrial lidar and rockfall modelling were used to clarify the formation of one unusual block accumulation the morphometric analysis of a detailed 0 5 m dem and relief profiles showed distinctly different morphology of one of four studied block accumulations the electric resistivity tomography revealed an ice core in the accumulation the schmidt hammer sampling helped to establish relatively younger age of the lobe like left part of accumulation and finally the lichenometry was employed to place the event on the approximate position on the timescale in conclusion the unusual block accumulation is a result of two consequent processes first a typical foothill rock glacier has developed and consequently a large rock avalanche occurred adding material and deforming the nw part of the accumulation based on the results of lichenometry the rock avalanche was estimated to be 250 50 years old the study thus presents one of the few reported slope deformation events from the recently deglaciated arctic areas

application of schmidt hammer relative age dating to late pleistocene moraines and rock glaciers in the western tatra mountains slovakia abstract in order to evaluate the potential of the schmidt hammer for relative age dating of late pleistocene moraines and rock glaciers rebound r values were collected at 38 sites in two formerly glaciated valleys in the western tatras in northern slovakia a large statistical population of measurements obtained from moraine and rock glacier surfaces was used to analyze the variability of mean r values in the same lithology and overall southern valley exposition four separate sets of glacial periglacial morphosystems are present at different positions in the western tatras starting from valley outlets to the highest cirques which represent successive phases of deglaciation r value means and 95 confidence intervals for selected last glacial maximum lgm and late glacial lg 1 lg 2 and lg 3 stages respectively 40 1 1 1 46 0 5 53 5 1 0 and 60 5 0 3 are significantly statistically different and values for each age category are comparable for the two analyzed valleys the results of weathering indexes used in conjunction with geomorphological relationships were taken together to reconstruct the pattern of deglaciation on southern tatra slopes it is stated that the schmidt hammer technique may be successfully used as a relative age dating tool for late pleistocene glacial and periglacial deposits and with this method it is possible to differentiate between late glacial moraines and rock glacier systems of different age

sequence stratigraphic framework of the german triassic abstract the sequence stratigraphic methodology can be readily applied to the cratonic basin fill of the classic german triassic consisting of shallow marine to terrestrial mixed carbonate siliclastic rocks the whole triassic succession represents a second order transgression regression cycle built by third order depositional sequences systems tracts and parasequences many bounding surfaces represent widely used marker beds long used in classical lithostratigraphy using a synthesis of outcrop well log and literature data on stratal geometry facies cycle stacking patterns and paleogeography a regional chart of coastal onlap was constructed within the limitations of the presently available biostratigraphic data the observed cycles appear to correlate fairly well with those in other areas but include a number of additional sequences not included in the haq et al 1988 chart comparative analysis of regional onlap curves from different globally spread triassic basins together with an improved biostratigraphy will be necessary to relate the accommodation changes to eustatic versus tectonic and climatic controls and to produce a refined eustatic chart the german basin could provide a favourable reference point for such an analysis

comparing geophysical methods for talus slope investigations in the turtmann valley swiss alps three geophysical methods ground penetrating radar 2d resistivity and seismic refraction were applied to two landform complexes in a high alpine valley in switzerland to investigate their internal structure results of the different methods were analysed separately before conclusions about sediment thickness and geomorphologic implications were drawn the results from the three methods were compared to focus on the quality of the methods and their field utility with respect to portability of equipment required man power and measurement time in this study ground penetrating radar and seismic refraction proved to be the most suitable with respect to the quality and resolution of the subsurface information and the level of field utility sediment thicknesses of 15 m on a rectilinear slope and more than 30 m on a talus cone have been measured a backweathering rate of approximately 700 mm ka 1 was established furthermore the radar delivered detailed internal sediment structure as well as interfaces between talus and rock glacier the combined geophysical investigation produced a detailed image of the subsurface composition of the two landform complexes that enhance the understanding of the paraglacial landform evolution in this hanging valley

large rock slope failures in the highlands of scotland characterisation causes and spatial distribution abstract a comprehensive database of larger rock slope failures rsfs has been compiled and characterised for a whole mountain range possibly for the first time apart from iceland most rsfs in the scottish highlands occurred soon after deglaciation a threshold size of 0 25 km 2 focuses on rsfs which contribute significantly to gross erosion in the glacial paraglacial cycle and on the spatial concentration of this poorly recognised process database verification indicates that at least 90 of the total extant population in the highlands is covered standard mass movement typologies are broadly applicable but require some refinement to characterise rsfs in a passive margin glaciated mountain range comprised mainly of ancient metasediments most larger rsfs here are complex and difficult to categorise a continuum from cataclasmic failures including rock avalanches through arrested translational slides to almost in situ slope deformations is identified the prevailing modes of large rsf are arrested short travel translational sliding and gravitational sagging cataclasmic failure is rare and sub cataclasmic outcomes are more evident a significant class of deformations exhibits compressional rather than extensional features and may be responding to localised glacio isostatic rebound stresses the large rsf population is widely but very unevenly distributed across the main mountain areas 65 are in seven main clusters with the rest non randomly scattered previous glaciological lithological and seismotectonic explanations are insufficient to explain this spatial pattern and overlook the basic engineering geology prerequisites for failure massifs of similar relief and lithology can display intense or sparse rsf incidence geomorphological appraisal suggests an association with recently active glacial breaches of main and secondary watersheds with rsf being scarce or absent in valleys inherited from tertiary uplift and in mountain groups away from the main watersheds valleys which adapted early to ice discharge are seen as stress hardened with their slopes unlikely to reach critical thresholds for failure after subsequent reoccupations by ice concentrated erosion in the last glaciations is most likely to be found close to where breaches are actively forming or enlarging such erosion in the slope foot and valley floor may have daylighted failure planes or generated rebound stresses augmenting those from other endemic sources sufficiently to provoke widespread paraglacial rsf slope stress models for deglaciated valleys and comparative studies in other glaciated mountain ranges are required to test this concept and may assist in geohazard assessments

a highstand oolitic sequence and associated facies from a late triassic lake basin south west england high energy lake shoreline carbonate sequences are rarely documented in the geological record however one example occurs in the upper triassic mercia mudstone group mmg of southern britain the mmg is one of a number of thick non fossiliferous mudstone deposits associated with north atlantic mesozoic rift basins the origin of the mmg mudstones is the subject of current debate with marine playa lacustrine and alluvial aeolian models having been proposed shoreline features have been documented from the northern margin of the basin but the rarity of such features elsewhere in the mmg has led many workers to doubt a lacustrine origin for the mudstones wave dominated lake shoreline deposits have been recognized in several sections from the southern basin margin in the clevedon area of the bristol channel in south west england these deposits provide evidence for the development of a sizeable perennial to semi perennial hypersaline lake in which the mmg mudstones accumulated shoreline sediments overlie alluvial stream and sheet flood deposits and pass from transgressive gravel conglomerate beach units with bioclasts influenced by shore normal waves deposited under semi humid conditions to lower gradient highstand oolitic sands affected by more varied wave approach deposited under progressively more arid conditions which culminated in lowstand oolitic strand plain deposits overlain by a playa mudflat unit shoreline deposits record a simple shallowing upward transgressive highstand lowstand sequence however a change from a reflective transgressive to dissipative highstand shoreline is believed to represent a climatically induced change in prevailing wind direction shoreline features recognized in the mmg are similar to those of recent playa lacustrine basins of the western united states ooids display a variety of size fracture and dissolution features in addition to beachrock fabrics suggesting that they were originally composed of radial aragonite similar to modern ooids from the great salt lake utah

landslides as a geomorphological proxy for climate change a record from the dolomites northern italy abstract this study investigates the relationships between climate changes and hillslope evolution in the dolomites eastern alps italy during the late quaternary with particular attention paid to landslide processes the basic premise is that modifications in landslide frequency may be interpreted as changes in the hydrological conditions of slopes which are in turn controlled by climate after the statistical analysis of a data set composed of 73 conventional radiocarbon ages obtained from 24 landslides four periods of enhanced landsliding have been identified i from 10 700 to 8400 cal bp between younger dryas and the preboreal ii from 8200 to 6900 cal bp during the older atlantic iii from 5800 to 4500 cal bp between atlantic and subboreal and iv from 4000 to 2100 cal bp between subboreal and subatlantic these periods have been compared with different lateglacial and holocene paleoclimatic records to check the correspondence between periods of enhanced landslide activity and cold and humid spells recognized at different spatial scales as the records show in the study areas slope instability processes can be considered geomorphological indicators of climatic changes and to a certain extent reliable proxies of environmental evolution

a comparison of the styles of deformation associated with two recent push moraines south van keulenfjorden svalbard in this paper two push moraine systems associated with two small subpolar glaciers finsterwalderbreen and penckbreen were investigated this study showed that at these glaciers the push moraines were formed in association with surges which produced a different style of moraine depending on the rheology of the deformed material and the glacial history the moraines are similar in that they are formed by folded outwash sediments and contain little till however the forms of these moraines are very different the penckbreen moraine is composed of a lower shallow marine sand silt and clay and an upper fluvial sand and gravel deformation at this site led to the formation of large anticlines in the silts and clays with disharmonic smaller folds and thrusts in the upper gravels above a detachment surface between the fine grained and overlying coarse grained lithologies this deformation decreases towards the foreland with marine and fluvial sediments responding differently because of their different rheological properties this moraine was formed during one surge event which occured during the early 19th century in contrast the finsterwalderbreen moraine is composed of outwash sand and gravel and was formed as the result of a series of surge events these advances all reached a similar limit and occurred at regular intervals 1997 john wiley sons ltd

sequence stratigraphy of middle triassic carbonates and terrigenous deposits muschelkalk and lower keuper in the sw germanic basin maximum flooding versus maximum depth in intracratonic basins abstract we analyze the sequence stratigraphy of the middle muschelkalk to the lower keuper strata middle triassic in the sw germanic basin the sequences are interpreted on the basis of a synthesis of facies in the neritic carbonates terrigenous sediments and evaporites along a basin margin to center transect continental sediments cs lower middle muschelkalk occur at the base of the middle upper muschelkalk sequence thick retrogradational marginal marine sediments overlain by open marine deposits middle middle muschelkalk to lower upper muschelkalk form the transgressive systems tract in the basin center only bathymetric criteria are available for recognition of this systems tract the maximum flooding surface mfs at the basin margin differs in age from the maximum depth interval in the basin center maximum depth surfaces or intervals mdi new term should be recognized in many deep basins where flooding is not recorded the highstand systems tract upper upper muschelkalk is strongly progradational the upper sequence boundary muschelkalk keuper boundary is characterized by subaerial exposure at the basin margin and submarine erosion in most other sections along this boundary the low paleo relief resulted in a lack of coarse grained clastic deposits in the basin center a strongly regressive succession lower lower keuper allows possibly for the first time in an intracratonic basin the distinction of an early or late lowstand systems tract elst or llst high frequency low amplitude sea level fluctuations resulted in parasequences in the open marine upper muschelkalk but in high frequency sequences in the coastal plain sediments of the overlying parts of the lower keuper

palaomagnetische untersuchungen im schilfsandstein trias km2 westeuropas von insgesamt 46 beprobten profilen aus dem schilfsandstein trias km2 westeuropas wurden bislang 41 profile mit 343 einheiten und 870 handstucken mit 1897 einzelkernen auf ihren palaomagnetischen inhalt untersucht

a new model of rock glacier dynamics abstract rock glaciers have traditionally been described as periglacial landforms and thus associated genetically with the presence of permafrost and a seasonal active layer they have also been described as glacigenic in origin in which the main rock glacier body contains glacier ice at depth other rock glaciers can be considered as relict where they contain no interstitial ice and are functionally inactive although all rock glaciers are to some extent polygenic there is no clear simple test that can be used to distinguish between different rock glacier types this study proposes a simple and testable model for rock glacier classification based on their behaviour from evidence reported from the literature the study then proposes an interpretive evolutionary model describing the temporal evolution of rock glacier surface movement through the year that can inform on its dynamical controls this analysis provides an easily deployed interpretive framework for the origins of rock glaciers

lithospheric necking and regional isostasy at extensional basins 2 stress induced vertical motions and relative sea level changes we investigate long wavelength differential vertical motions at extensional basins which are the result of temporal changes in the intraplate stress field in the lithosphere these stress induced vertical motions are intimately coupled to the state of flexure flexural curvature of the lithosphere we compare a previous model of flexure under the sediment load only fsl model and a recent more consistent model which incorporates regional compensation of other vertical loads induced by lithospheric extension as well these additional loads are controlled by the depth at which the necking of the lithosphere occurs don model tlie fsl model and models assuming a shallow level of necking 15 km are very similar they predict tilting of the basin with the hinge point landward of the shelf edge compression results in uplift of the landward pan of the basin which generally corresponds to the coastal plain or inner to middle shelf and downwarping of the outer shelf and slope the differential vertical motions correspond to relative sea level cycles which are out of phase in different parts of the basin internal architecture of systems tracts can be different from predictions by eustasy by contrast deeper levels of necking 20 km predict a uniform sense of motion landward of the shelf edge type i sequence boundaries can be very easily induced for these conditions and sequence stratigraphie features are probably hard to distinguish from predictions by eustasy these results are for a pure elastic plate rheology stress induced vertical motions for a more realistic depth dependent rheology are more complicated because of the additional effect of stress induced reduction of flexural rigidity for these conditions gradual buildup of tension causes a complete relative sea level cycle for high tensional stress levels total vertical motions become rather similar to vertical motions for compression this may be of importance for the issue of global synchroneity of relative sea level changes

planation surfaces of the armorican massif western france denudation chronology of a mesozoic land surface twice exhumed in response to relative crustal movements between iberia and eurasia the armorican massif an extensive outcrop of variscan basement in western france is shaped by several planation surfaces of debated origin and age we propose an evolution model for these landforms and their deformation based on detailed mapping of the planation surfaces their relative chronology and their relationships with dated outcrops of sediments and weathering products the armorican landscape consists of six stepped planation surfaces labelled ps1 to ps6 later incised by two successive river networks these landforms are pediments and pediplains or polygenic landforms armorican planation surface ps5 resulting from two periods of etchplanation these planation surfaces are mostly pre late cretaceous in age based on the age of the sediments overlapping these pediments the three older ones ps1 to ps3 are pre pliensbachian 191 183 ma ps4 is pre bajocian 170 168 ma ps5 here called the armorican planation surface is polygenic and ranges from the base of the early cretaceous to the base of the bartonian 140 40 ma and the youngest ps6 which is poorly constrained is older than 40 ma base of the bartonian or 15 ma base of the middle miocene most of these old landforms are exhumed i e they were buried by sediments and later re exposed by denudation at least two phases of burial and exhumation have been identified 1 burial in jurassic time followed by denudation during the early cretaceous and 2 burial in late cretaceous time followed by denudation during the latest cretaceous to early eocene the depth of burial is unknown but is probably low due to the small amount of coeval siliciclastic sediments in the surrounding basins the two periods of exhumation correspond to critical periods in the plate movements between africa iberia and eurasia the first is probably related to the initiation and breakup of the rift between iberia and eurasia and the second to the convergence between these two plates

timing and periodicity of paraglacial rock slope failures in the scottish highlands abstract many formerly glaciated mountains exhibit a high density of postglacial rock slope failures rsfs in the form of rockslides rock avalanches or deep seated gravitational slope deformations such rsfs are often termed paraglacial as they reflect pre conditioning by glaciation and deglaciation the temporal pattern of paraglacial rsfs is unknown we employ 47 cosmogenic isotope exposure ages obtained for 17 catastrophic rsfs in the scottish highlands to test models of changes in rsf frequency since deglaciation our results show that rsf activity spans almost the entire postglacial period from 17 ka until 1 5 ka and that the periodicity of sampled postglacial rsfs is statistically indistinguishable from a pattern of uniform periodicity 1 ka 1 our data do not conform to proposed models of declining rsf frequency with time elapsed since deglaciation but suggest that the temporal distribution of postglacial rsfs is best described by a combination of rapid response enhanced rsf frequency during or immediately after deglaciation followed by approximately constant periodicity our findings are consistent with near surface fracturing of rock when glacially induced confining stresses are removed causing some failures during or immediately after deglaciation and reducing other slopes to critical conditional stability so that failure is triggered by progressive rock mass weakening or by transient triggering mechanisms neither permafrost degradation thaw of ice in joints nor seismic activity offers a general explanation for triggering scottish rsfs but could be contributory in some cases the quasi constant periodicity inferred for holocene rsfs implies that the probability of rsfs in this seismically quiescent intraplate area has not changed in the past 10 ka and that further though infrequent catastrophic rsfs are likely to occur in the future

rock avalanches on a glacier and morainic complex in haut val ferret mont blanc massif italy abstract deposits in upper val ferret mont blanc massif italy have been attributed to glacier advances and to a rock avalanche of 12 september ad 1717 we review evidence for the timing and mode of emplacement of the deposit and present a new geomorphic interpretation and relative and absolute dating to show that the ad 1717 deposit is less extensive than previously thought the landslide was deflected along one side of the valley floor preserving older slope and morainic sediments along the other side an earlier rock avalanche onto the triolet glacier occurred before ad 1000 the deposits of these landslides partly cover older moraine several kilometres downstream from the present glacier front and have affected the glacier regimen and construction of its moraines this study highlights the geomorphic impact of rock avalanches in glacierized high mountains

climatic and biotic change in the late triassic generally arid conditions that pervaded much of europe and north america during the late triassic were interrupted by a wet monsoonal climatic phase during middle and late carnian times extensive fluviatile sandstones deposited at this time throughout the region occur within a thick sequence of playa lake mudstones the sandstones occasionally contain kaolinite suggesting a humid climate an extreme 13 c depletion in a shallow marine sequence of this age in israel has been interpreted as evidence for an influx of freshwater a widespread change from carbonates to clastics in marine sequences at this time may also be climate related water course cave systems in limestone areas exposed during the late triassic indicate high levels of runoff during the middle and late carnian the marine invertebrate fauna shows a significant turnover at the end of the early carnian the terrestrial fauna and flora were relatively unaffected at this time but subsequently diversified prior to a major biotic turnover at the carnian norian boundary these periods of biotic change appear to be synchronous with the onset and cessation of a carnian humid phase the change to a monsoonal climate during this interval has been documented over more than 90 of longitude between 5 and 50 north of the triassic equator it may have been caused by rising atmospheric co 2 levels due to volcanism associated with the incipient dispersal of pangaea

the internal structure of rock glaciers and recently deglaciated slopes as revealed by geoelectrical tomography insights on permafrost and recent glacial evolution in the central and western alps italy france abstract ground ice of permafrost origin and sedimentary ice of glacial origin can coexist in locations where rock glaciers and glaciers interacted as well as in glacigenic sediments abandoned by a retreating glacier and subsequently exposed again to atmospheric cooling some of these geomorphological settings in the central foscagno rock glacier and western alps marinet and schiantala rock glaciers schiantala debris covered glacier maledia glacier were explored by means of geoelectrical tomographies the aim was that of inferring the presence of ice and cryologically interpreting electrical stratigraphies in order to test whether or not the internal structure of these landforms can be used for the reconstruction of recent permafrost and glacier evolution geomorphological data assisted these reconstructions and available borehole stratigraphies were used to calibrate the resistivities along with the ice debris mixture massive ice has also been found as lenses both at the apex and the front of the studied rock glaciers these lenses of sedimentary origin are thought to be transferred from a glacier snout to sectors of rock glacier and eventually embedded into the permafrost creep the scarcity of frozen debris in the mid upper part of the rock glaciers as revealed by low resistivity values can be due to the disruptive effect of the over riding glacier over the permafrost the near surface sedimentary ice masses detected along the slopes of the studied glacial cirques are interpreted as or debris covered terminations of the glaciers still visible upward or as fragments of it detached by the main bodies these ice masses are locally associated to medium high resistive sediments consistent with permafrost occurrence this indicates that the non glacial environment established during the deglaciation allowed the onset of frozen sediments formation overall the results indicate that internal structure of rock glaciers and recent deglaciated slopes can store the different climate related episodes occurred in a specific area such as those linked to the shifting between glacial to criotic condition and vice versa

overview of the subsurface structural pattern of the paris basin france insights from the reprocessing and interpretation of regional seismic lines abstract the study presents the methodology used by the french geological survey brgm for the building reprocessing and interpretation of selected regional seismic lines in the paris intracratonic basin france the 14 constructed e w and n s regional transects represent a total of 2 516 km length and are based on the merge of 240 seismic single profiles recorded by petroleum operators between 1971 and 1995 the regional lines have been selected to cross the main oil fields of the paris basin as well as high potential areas for oil exploration a first difficulty was to recover the raw data necessary to build up the regional transects the signal reprocessing harmonization and merge of the single seismic lines constituent of the regional transects are then described these operations represent the cornerstone of the study we put the emphasis on the primary static corrections as the targeted structures are commonly spatially associated with large seismic velocity variations in the upper cretaceous chalk and tertiary sedimentary cover the interpreted regional transects definitely give complementary information to the existing studies which generally lack seismic and therefore structural data we give an overview of the main structural and geometrical features of the paris basin inversion structures major unconformities as well as permo carboniferous basins we also describe the structural pattern and show the close relationships between the faults geometry the faults density and the geological evolution of the paris basin we distinguish 1 few large scale polyphase faults with a variscan origin representing the first order structural frame of the paris basin 2 monophase normal faults with strike slip features representing the subsurface prolongation of cenozoic grabens cropping out in the neighbourhood 3 deep normal faults sealed by the base calcareous dogger sequence related to the permo liassic extensional tectonic regime this large scale view of the paris basin has highlighted several potential exploration targets