numerical models for planning landslide risk mitigation strategies in iconic but unstable landscapes the case of cinque torri dolomites italy abstract this study deals with the numerical modelling of large deep seated instability processes affecting the cinque torri group dolomites italy which is a unesco world heritage site the aim is to evaluate the role of intrinsic causal factors and to assess the failure mechanism proposed in previous investigations the geological model is based on topographic geological and geomechanical surveys complemented with mineralogical physical and geotechnical lab analyses for parameters determination the numerical simulations have been carried out using a distinct element method code on conceptual and site specific slope models a series of parametric analyses have been performed to characterize the role of the different predisposing factors potentially related with the ongoing rock spreading i load of the rocky pinnacles ii lithology stratigraphy and attitude of the geological units iii discontinuity sets in the rock mass iv degradation of the mechanical properties the results of this study suggest that the shear zone initiation is controlled by stress concentration due to the loading of the dolomitic pinnacles whereas its shape appears to be structurally controlled by the dip slope attitude of bedding in clay rich mudstones the interpretation of the modelling results has provided a better understanding of the ongoing deformation process which can help in targeting effective and low impact landslide risk mitigation strategies in this iconic landscape

depositional environments of late eocene lignite bearing strata east central texas late eocene lignites in the brazos river valley area occur in parasequence scale cycles containing mostly marine sediments lignite is present at the base of the marine interval and forms the base of the cycle in a majority of cases less frequently lignite is underlain by a thin interval of nonmarine deposits that form the base of the cycle in both situations the lignite is part of a thin transgressive interval cycles are separated by an exposure surface usually marked by plant rooting and or development of a paleosol in the top of the underlying sediments peat accumulated on top of these exposure surfaces and lignite is preserved where marine flooding allowed ocean waters to cover the peat deposits with fine grained sediments producing high ash lignite horizons of great lateral extent but variable thickness and quality this strandplain model of lignite occurrence provides a better understanding of late eocene lignites in texas than the deltaic or fluvial deltaic models previously used the strandplain model of lignite occurrence is appropriate for most of the yegua jackson lignites middle late eocene of texas and should be considered when evaluating depositional conditions of paleogene lignites in the northern gulf coast region a re evaluation of late eocene stratigraphy of the brazos valley area accompanies the documentation of depositional environments

seismogenic sources potentially responsible for earthquakes with m 6 in the eastern southern alps thiene udine sector ne italy summary new geomorphological and structural data permitted to define the active faulting framework of the eastern southern alps ne italy all the active faults detected in the investigated area are thrust segments of the complex thrust system which has been responsible for the latest building of the eastern southalpine chain esc geomorphological investigations were performed to identify the surficial traces of recent fault activity generally represented by gentle scarps connecting uplifted palaeolandscapes of quaternary age with the flat and lower areas of the venetian and friulian plains surficial and subsurficial data the latter from reflection seismic profiles available for the investigated faults indicate that the thrusts have been responsible for the displacement of the entire wedge of quaternary deposits in the western sector of the investigated area the six recognized fault segments represent portions of a 100 km long thrust system at the boundary between the alpine relief and the plain areas in the eastern sector active tectonics is the result of parallel thrust segments located both in the alpine mountainous area and in the friulian plain the 3 d geometry of the active thrust segments has been derived from new structural surficial surveys and the interpretation of reflection seismic profiles for a total length of 1700 km on this basis we defined the geometry of 10 seismogenic sources whose dimensions are consistent with the occurrence of earthquakes with m 6 the comparison between the source geometry and the highest intensity data point distribution of large historical earthquakes has permitted to make hypotheses on the association of past seismic events to specific seismogenic sources this procedure indicated that no large historical events can be attributed to three sources montello conegliano arba ragogna medea this may indicate an elapsed time since the last activation of more than eight centuries based on the completeness of the historical catalogues the available data define therefore sources and related areas for which a high level of seismic hazard may be invoked

application of the revised universal soil loss equation model on landslide prevention an example from n euboea evia island greece this study aims to evaluate the application of the revised universal soil loss equation rusle on predicting of sites susceptible to slope failures caused by the soil erosion it was carried out at the northern part of euboea island presenting one of the highest frequencies of landslide occurrence in greece all required datasets for the application of the rusle model were engaged to compile a potential soil erosion map of the study area in addition historical slope failure data were used to evaluate the produced map moreover the frequency ratio statistical analysis was applied for the verification of the soil erosion map the results showed a satisfactory agreement between the soil erosion intensity zones and distribution of landslides events therefore the rusle model can be applied for the localization of sites susceptible to landslides that were prepared or triggered by the soil erosion finally taking under consideration the contribution of erosion mechanisms over the landslides manifestation a combination of measures were proposed for preventing and supporting these catastrophic phenomena

self repair of compacted vertisols from central queensland australia vertisols have the inherent ability to self repair because of high clay contents and clay type that govern volume change a study was undertaken to correlate soil inherent properties with two indicators of structure improvement based on tensile strength and clod porosity of compacted soil cores before and after wet dry cycles in order to minimize inter soil differences vertisols under similar cropping regimes and from the same climatic region in queensland australia were selected a soil repair index rt 1 based on compressive strength of soil cores was related to soil inherent properties and shrinkage indices colestd and lsmod using multiple regression results showed that compressive strength of soil cores after a single wet dry cycle after compaction was sufficient to rank vertisols in terms of their capacity to improve structure after compaction clay content and clay activity cec clay on their own were poor indicators of soil repair fine sand was shown to be an important component in the repair process lsmod and colestd predicted rt 1 equally well and indicated that vertisols with colestd values 0 15 and lsmod 12 would be expected to have sharper reductions in tensile strength compared to those with lower values after just one wet dry cycle clod porosity was poorly related to soil inherent properties 2008 elsevier b v

comparison of the implementation of rock engineering system and analytic hierarchy process methods upon landslide susceptibility mapping using gis a case study from the eastern achaia county of peloponnesus greece as landslides are very common in greece causing serious problems to the social and economic welfare of many communities the implementation of a proper hazard analysis system will help the creation of a reliable susceptibility map his will help local communities to define a safe land use and urban development the purpose of this study is to compare the implementation of two semi quantitative landslide assessment approaches using landslide susceptibility maps compiled in a gis environment the compared methods are rock engineering system res and the analytic hierarchy process ahp for the landslide susceptibility analysis the northeastern part of the achaia county was examined this area suffers from many landslides because of its neighborhood with the tectonically active corinthian gulf and its geological setting neogene sediments flysch and other bedrock formations with local overthrusts ten parameters were used in both methodologies and each one was separated into five categories ranging from 0 to 4 representing their specific conditions derived from the investigation of the landslides in the western part of the study area ranking area a layer map was generated for each parameter using gis while the weighting coefficients of each methodology were used for the compilation of res and ahp final maps of the eastern part of the study area validating area by examining these two maps it is revealed that even though both correctly show the landslide status of the second site the res map reveals a better behavior in the spatial distribution of the various landslide susceptibility zones

evaluation of meteorological controls of reconstructed rockfall activity in the czech flysch carpathians the spatio temporal characteristics of rockfall activity were studied at four localities representative of old landslides in the highest part of the czech flysch carpathians moravskoslezske beskydy mountains historical activity chronology and spatial context of rockfall activity were reconstructed using dendrogeomorphic techniques and rockfall rate index rr a total of 1132 increment cores from 283 trees growing in the rockfall transport and accumulation zones enabled the dating of 989 rockfall events reconstruction of a 78 year long rr chronology suggests similar rockfall histories and trends at all study sites indicating the existence of major common factors driving rockfall dynamics in the region temporal analysis and correlation of the rr series obtained with monthly mean temperatures numbers of days with temperature transitions through 0 deg c and monthly precipitation totals show that meteorological characteristics have evident but variable influence on rockfall activity

assessment of rockfall susceptibility by integrating statistical and physically based approaches in val di fassa dolomites eastern italian alps rockfalls constitute the most significant gravity induced natural disaster that threatens both the inhabitants of the valley who are few and the thousands of tourists who populate the area in summer and winter to assess rockfall susceptibility we developed an integrated statistical and physically based approach that aimed to predict both the susceptibility to onset and the probability that rockfalls will attain specific reaches through field checks and multi temporal aerial photo interpretation we prepared a detailed inventory of both rockfall source areas and associated scree slope deposits using an innovative technique based on gis tools and a 3d rockfall simulation code grid cells pertaining to the rockfall source area polygons were classified as active or inactive based on the state of activity of the associated scree slope deposits the simulation code allows one to link each source grid cell with scree deposit polygons by calculating the trajectory of each simulated launch of blocks by means of discriminant analysis we then identified the mix of environmental variables that best identifies grid cells with low or high susceptibility to rockfalls among these variables structural setting land use and morphology were the most important factors that led to the initiation of rockfalls we developed 3d simulation models of the runout distance intensity and frequency of rockfalls whose source grid cells corresponded either to the geomorphologically defined source polygons geomorphological scenario or to study area grid cells with slope angle greater than an empirically defined value of 37 empirical scenario for each scenario we assigned to the source grid cells an either fixed or variable onset susceptibility the latter was derived from the discriminant model group active inactive membership probabilities comparison of these four models indicates that the geomorphological scenario with variable onset susceptibility appears to be the most realistic model nevertheless political and legal issues seem to guide local administrators who tend to select the more conservative empirically based scenario as a land planning tool

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

whence the gosport sand upper middle eocene alabama the origin of glauconitic shell beds in the paleogene of the u s gulf coastal plain abstract an explanation for the depositional history of the gosport sand has proven to be as puzzling as its diverse mollusk fossils is beguiling we propose that shifting delta lobes produced patchy environments which accumulated to form the gosport sand and likely other glauconite and fossil rich shell beds of the gulf coastal plain of the paleogene we present facies and mineralogical data to suggest glauconite in the gosport sand was deposited during relatively stable environmental conditions increased glauconite maturity and taphonomic alteration in the gosport sand are attributed to eustatic transgression resulting in decreased deposition enhanced winnowing and increased exposure at the sediment water interface increased fossil diversity and abundance likely result from time averaging and accumulation of shells from ancient patchy habitats analogous to modern inner shallow shelf and open sound environments delta progradation and subsidence would have determined the migration of these environments we evoke a similar depositional model for glauconite rich shell beds distributed throughout the paleocene and eocene of the gulf coastal plain based on their transgressive nature and roughly equivalent facies these shifting environmental conditions may have played a partial role in generating the high molluscan diversity of the gulf coastal plain of the paleogene

paleoecology of the eocene wheelock member of the cook mountain formation in western houston county texas abstract eighty five species of foraminifera and forty nine molluscan species were recovered from the wheelock member of the cook mountain formation in the porter springs area of houston county texas and along the little brazos river in brazos county texas the wheelock member is primarily a regressive unit a thin shell lag deposit at the base of the member is all that remains of the transgressive part of the sequence above the shell lag deposit the lower part of the member consists dominantly of bioturbated glauconitic fossiliferous mudstone the percentage of planktic foraminifers and the diversity of benthic foraminifers suggests deposition in an inner or inner middle shelf environment the low diversity and equitability of the molluscan population and the abundance of opportunistic corbulid bivalves suggest that the environment was at least periodically unstable the upper part of the wheelock member consists dominantly of regularly layered or laminated mudstone and siltstone and contains only a low diversity assemblage of agglutinated foraminifera this part of the member was probably deposited in a shallow brackish water environment with a high sedimentation rate planktic foraminifers recovered from the wheelock member support an age correlation with the late middle eocene morozovella lehneri or orbulinoides beckmanni zones according to berggren and others 1985 this corresponds to an absolute age of between 42 and 46 million years b p

sedimentary organic matter sources and depositional environment in the yegua formation brazos county texas abstract the complex depositional environment of the eocene yegua formation brazos county texas can be better understood by integrating organic matter om geochemistry with stratigraphy yegua sediments represent parasequences separated by exposure surfaces organic petrography and geochemistry biomarkers c n ratios and carbon isotopes indicate the presence of both terrestrial and marine om in transgressive sediments in contrast regressive sediments contain only terrestrial om these differences relate to contrasting om sources and depositional styles on the shelf om in the sediments is immature and the potential for generating hydrocarbons is poor the study suggests that organic geochemical data can help in distinguishing transgressive and regressive environments in sedimentary formations

tectonics of the dolomites southern alps northern italy abstract in post variscan times the dolomites underwent a number of tectonic events which may be summarized as follows permian and triassic rifting phases broke the area into n s trending basins with different degrees of subsidence a middle triassic transpressive event then deformed the region along a n70 e axis generating flower structures within the basement volcano tectonic domal uplift and subsequent caldera formation occurred at the same time as the late ladinian magmatism early jurassic rifting also controlled the subsidence which increased eastward this long period of deformation was followed by a pre neogene late cretaceous palaeogene e w ene wsw compression which generated a w vergent belt possibly equivalent to the folded foreland of the dinaric chain a 70 km e w section of the dolomites indicates shortening of at least 10 km during the neogene the dolomites as far north as the insubric lineament were the innermost part of a s vergent thrust belt the basement of the dolomites was thrust southwards along the valsugana line onto the sedimentary cover of the venetian prealps for at least 10 km this caused a regional uplift of 3 5 km the valsugana line and its backthrusts on the northern side of the central dolomites generated a 60 km wide pop up in the form of a synclinorium within which the sedimentary cover adapted itself mainly by flexural slip often forming triangle zones the shortening linked to this folding is about 5 km with neogene thrusts faulting and folding pre existing thrust planes on the north eastern side of the dolomites neogene deformation is apparently more strictly controlled by the transpressive effects of the insubric lineament and shortening of the sedimentary cover may be greater than in the central dolomites minor deformation linked to the giudicarie belt is present in the western dolomites the present structure of the dolomites is thus the result of a number of tectonic events of different significance and different strike only a 3 dimensional restoration can unravel the true structure of the dolomites

the thurwieser rock avalanche italian alps description and dynamic analysis a rock avalanche of about 3 106 m3 detached from the south east flank of the punta thurwieser ridge italian central alps on the 18th of september 2004 due to the characteristics of the moving material i e rock debris ice snow and the path of propagation e g presence of a glacier the mass was able to rapidly cover long distances about 3000 m among the possible causes of the event attention is mainly focused on permafrost degradation and changes in glacier extension due to global warming in the present work the dynamics of the event and the role played by characteristics of the propagation path are numerically investigated with the rash3d code based on a continuum mechanics approach results obtained with two rheological hypotheses frictional and voellmy are compared and discussed in particular it emerges that 1 the use of a voellmy rheology with a reduced friction angle on the glacier is necessary to reproduce the dynamics of the thurwieser event and 2 a lack in knowledge of geometrical and geomechanical information may lead to wrong interpretations of the event and inaccurate calibration of numerical models

climate controlled variations in scree production southern alps new zealand the interaction of fluvial glacial and hillslope processes controls the development of mountain belts and their response to tectonic and climatic forcing studies on the contribution of hillslope processes to mountain erosion have focused on bedrock landslides as they have a profound and readily observed impact on sediment yield and slope morphology despite the ubiquity of scree or talus mantled slopes in mountainous terrain the role of frequent low magnitude 100 m 3 rockfall events is seldom addressed in the context of landscape evolution here we quantify the contribution of rockfall erosion across an 80 by 40 km transect in the southern alps new zealand by analyzing the spatial extent of scree slopes mapped from aerial photographs and estimating long term 10 15 k y rockfall erosion rates from the accumulation of slope deposits below bedrock headwalls and in debris and alluvial fans along the rapidly uplifting high rainfall western margin where high rates of bedrock landsliding have been previously documented scree mantled slopes are sparse rainfall decreases exponentially east of the main divide and the proportion of slopes mantled by scree increases monotonically attaining a maximum value of 70 the systematic distribution of scree deposits cannot be attributed to lithologic variation seismicity or the legacy of glaciation instead climate may serve as a primary control on scree production as nearly 70 of the mapped scree deposits in our transect are confined to a narrow elevation range of 1200 1600 m above sea level masl our analysis of altitudinal controls on annual temperature variations indicates that scree production via frost cracking processes may be maximized between elevations of 1600 and 2300 masl as higher elevations are subject to persistent permafrost which obviates the frost cracking process rates of rockfall erosion near the rapidly uplifting main divide are low 0 1 mm yr whereas rates in the scree dominated eastern areas average 0 6 mm yr and may approximately balance rock uplift

palynology and paleoecology of lignites from the manning formation jackson group outcrop in the lake somerville spillway of east central texas abstract four palynomorph assemblages whose parent plants contributed to the formation of the lignite occur in the lignite seams and associated sediments from the manning formation jackson group outcrop in the lake somerville spillway of texas the cicatricosisporites laevigatosporites fern assemblage occurs in the middle and upper seam and probably derived from a freshwater herbaceous mire community the momipites coryloides arecipites columellus liliacidites assemblage occurs in all three seams and probably derived from a freshwater mire forest with an open canopy or shrub community the momipites coryloides nyssa rhoipites angustus assemblage occurs in the lower and middle seams and probably derived from a different freshwater mire forest the cupuliferoipollenites cupuliferoidaepollenites liblarensis siltaria cf s scabriextima assemblage occurs at the top of the lower and middle seams which are overlain by marine sediments the association between cupuliferoipollenites dominance and the presence of marine diatoms and brackish or marine trace fossils in the lignite suggests that this assemblage may have derived from a mangrove i e marine or brackish mire forest however other factors may influence its distribution ailanthipites berryi possibly derived from a tree or shrub related to the tree of heaven predominates in the claystone underlying the lower lignite seam and may have colonized the coastal plain prior to the initiation of peat accumulation we can differentiate lignite samples dominated by fern spores momipites pollen and cupuliferoipollenites pollen based on gas chromatography mass spectrometry gc ms fragmentograms of triterpanes m z 191 and steranes m z 217 the lignite layers dominated by each palynomorph assemblage appear to have distinct sources and different early diagenetic pre coalification histories

a regional rockfall database the eastern alps test site landslide databases are essential tools for risk assessment in the italian portion of the south eastern alps these archives are managed by the veneto region and by the provinces of bolzano and trento as part of the italian inventory of landslides about 750 rockfall events recorded in these archives were checked put together and completed to create a new integrated database information on 24 new rockfalls were added from different research sources descriptive statistic shows that the most affected slopes with the highest frequency of rockfall are the southern ones the distribution of rockfalls during the year presents three peaks in march june and november the most commonly affected lithologies are massive dolomites effusive rocks and mica schists roads proved to be the most commonly involved feature the hypsographic curves obtained from the dems of the provinces of belluno bolzano and trento have shown that the different areas potentially affected by periglacial processes experience rockfalls during summer and autumn thus representing a risk to tourists and hikers this study is the first attempt to collate and extend the available information in the various rockfall databases in the eastern italian alps with the aim at creating uniform data collection for the whole alpine range

the influence of environmental and lithologic factors on rockfall at a regional scale an evaluation using gis abstract analysis of the spatial distribution of rockfall deposits at a regional scale over an area of 250 km2 of northern spain using a cartographic database supported by a geographic information system gis reveals several relationships between rockfall activity and environmental variables recent rockfall activity is inferred when recent scree is preserved at the bottom of the rock slopes in order to identify the slope source areas of the scree we have mapped the deposit s drainage basin applying topographic criteria and we have combined these basins with the rock slopes map a method for setting the basin boundaries automatically will replace manual cartography this method is based on algorithms available within many commercial software programs and originally planned to analyse the behaviour of fluids over a topographic surface the results obtained by combining the rockfall area source map with the geology and dtm show the relationships between the distribution of rockfall deposits and lithology elevation and slope of the rockwall and a strong control of the joint type and density elevation influence on rockfall has been associated with climatic variations with elevation other variables such as orientation show complex influences that are difficult to interpret

shrinkage and atterberg limits in relation to other properties of principal soil types in israel abstract soil samples collected from 32 sites across israel representing major types were analyzed for their pedological characteristics and mechanical properties correlative relationships between shrinkage measured by the coefficient of linear extensibility cole atterberg limits liquid and plastic and the physical and chemical properties were established and indicate possibilities of estimating mechanical properties from known pedological data strong correlations were noted between mechanical properties and the pedological characteristics reflecting clay mineralogy and texture e g cation exchange capacity specific surface area hygroscopic moisture and clay content these relationships are useful inasmuch as clay mineralogy is usually evident from soil classification sodicity and salinity common in dry soils of semi arid regions may introduce complicating factors such as raising or lowering atterberg limits respectively shrinkage is similarly affected being accentuated at high sodium low salt levels and reduced in highly saline sodic soils organic matter was correlated with liquid and plastic limits but no relationship with shrinkage was noted calcium carbonate also had little influence on atterberg limits the relationships presented may serve as first approximations mechanical properties of the soil groups illustrate the range of values encountered among regions with differing environmental conditions

stable seafloor conditions sea level and food supply during the latest maastrichtian at brazos river texas abstract the cretaceous paleogene k pg boundary extinction event is inextricably linked to the chicxulub impact environmental changes like sea level changes and changes in food supply prior to or after the impact could however have contributed to the biotic turnover in this study benthic foraminifera from two cores from the brazos river area in texas are quantitatively analyzed in order to reconstruct environmental changes across the k pg boundary cluster analysis as well as non metric multidimensional scaling reveals three distinct benthic foraminiferal assemblages an upper maastrichtian assemblage a post impact assemblage and a lower danian assemblage the rather uniform upper maastrichtian assemblage at brazos river composed of e g clavulinoides midwayensis gavelinella dumblei cibicidoides harperi gyroidinoides aequilateralis and bulimina kickapooensis indicates a stable paleodepth of about 75 100 m up to the k pg boundary food supply indicators such as percentage buliminaceae and foraminiferal numbers suggest a relatively low and stable food supply during this interval environmental disruption caused by the chicxulub impact led to the settlement of a typical pioneer assemblage characterized by endobenthic morphotypes such as ammobaculites spp and pseudouvigerina naheolensis during the early danian the typical midway type benthic foraminiferal shelf fauna e g alabamina midwayensis anomalinoides acutus gyroidinoides subangulatus praebulimina carseyae and cibicidoides alleni developed indicating a paleodepth of 75 100 m no clear water depth changes can be derived from the benthic foraminiferal record during this interval although the sedimentary record suggests a shallowing followed by a transgressive pulse in zone p1a food supply indicators suggest a lower food supply in the early danian than during the upper maastrichtian because of the stability of the late maastrichtian environment we conclude that environmental disruption caused by the impact was most likely the principal cause of the benthic foraminiferal turnover across the k pg boundary observed at brazos river

paleocene sequence stratigraphy of southwestern alabama abstract in southwestern alabama the paleocene consists of about 1 300 ft of marginal marine and marine terrigenous and carbonate sediments based on regional stratigraphic sedimentologic and paleontologic data eight unconformity bounded depositional sequences resulting from relative changes in coastal onlap during the paleocene are recognized in these strata these sequences are in ascending order the tp1 1a pine barren member of the clayton formation the tp1 1b turritella rock beds of the pine barren member and mcbryde limestone member of the clayton formation and calcareous clays and limestones of the lower member of the porters creek formation the tp1 1c marls and clays of the lower member of the porters creek formation the tp1 2 cross bedded sands of the lower member and matthews landing marl member of the porters creek formation and oak hill member of the naheola formation the tp1 3 coal bluff marl member of the naheola formation the tp2 1 gravel creek sand ostrea thirsae beds and grampian hills members of the nanafalia formation and lower beds of the tuscahoma sand the tp2 2 greggs landing marl member and middle beds of the tuscahoma sand and the tp2 3 bells landing marl member and upper beds of the tuscahoma sand planktonic foraminiferal zone boundaries recognized for these strata correspond to relative rises in sea level and usually occur at sequence boundaries or transgressive surfaces zonal boundaries occurring in this fashion include subbotina pseudobulloides interval zone morozovella uncimata interval zone morozovella angulata interval zone planorotalites pusilla pusilla interval zone planorotalites pseudomenardii range zone and morozovella velascoensis interval zone the zonal boundary for the subbotina trinidadensis interval zone also corresponds to a relative rise in sea level and occurs in transgressive or condensed section deposits

production preservation and prediction of source rock facies in deltaic settings abstract this article hypothesizes that production and preservation of source rock type facies in deltaic systems both landward and seaward of a coastline is mutually exclusive time successive and related to the dynamics of relative sea level sedimentologic research in the holocene mississippi and rhone delta complexes suggests that rheotrophic peats and associated organic rich beds preferably accumulate in the accommodation space created behind landward stepping shorelines in a transgressive systems tract tst such a setting also allows for a sufficient supply of recharging fresh nutrient rich groundwater into the peat forming mires kosters e c suter j r 1993 facies relationships and systems tracts in the late holocene mississippi delta plain journal of sedimentary petrology 63 4 727 733 independently carried out quantitative paleoecological studies in the same delta systems and in addition in the orinoco and po deltas suggest that in a progradational setting highstand systems tract hst seasonally discharged nutrient and sediment laden river waters on the shelf may give rise to anoxia or dysoxia subsequent overfertilization of the shelf leads to accumulation of organic rich mud belts on the shelf vanderzwaan g j jorissen f j 1991 biofacial patterns in river induced anoxia in tyson r v pearson t h eds modern and ancient continental shelf anoxia geological society of london special publication no 58 pp 65 82 thus production and preservation of source rock type facies landward of a shoreline as peats and related sediments is preferred in a tst when accommodation space and nutrient supply are landward of the shoreline vice versa production and preservation of such facies seaward of a shoreline as organic rich shelf muds occurs preferentially in a highstand systems tract in that situation accommodation space is on the shelf where river fed nutrients are supplied as well this hypothesis suggests further potential for application of sequence stratigraphic concepts for improved understanding of the occurrence of source rock type facies

a hierarchical tectonic model of the gulf of mexico and caribbean region abstract a quantitative computer graphic methodology hierarchical tectonic analysis has been used to model the tectonic evolution of the gulf of mexico and caribbean region this method employs a highly structured hierarchical description of the relative motions of pairs of tectonic elements in order to quantify the timing and style of plate interactions the main features described in this model are 1 1 a revised fit of pangea 2 2 the opening of the gulf of mexico in the middle late jurassic 3 3 the formation of a proto caribbean ocean due to the separation of north and south america during the early cretaceous 4 4 the formation of the greater antilles arc along the western margin of the proto caribbean ocean 5 5 the insertion of the farallon plate between north and south america during the middle cretaceous resulting in the northeastward advance of the greater antilles arc and the subduction of proto caribbean oceanic crust 6 6 the complete subduction of the proto caribbean ocean and the collision of the greater antilles arc with the bahamas platform in the late cretaceous 7 7 the truncation of the caribbean section of the farallon plate from its pacific counterpart and the formation of the panama arc latest cretaceous and 8 8 the westward movement of north and south america with respect to the caribbean plate resulting in the opening of the yucatan basin paleocene and subsequently in the evolution of the cayman trough and e w zone of strike slip

eustatic cyclicity in the paleocene and eocene data from the brazos river valley texas abstract documentation of the geologic history of global sea level change requires the analysis of numerous geographically diverse sections the paleocene through eocene section of the brazos river valley eastern texas is an area suitable for such analysis which has yet to be studied analysis of the brazos river valley section for sea level changes during the paleocene and eocene was accomplished by the application of sequence stratigraphie analysis using seismic well log and outcrop data the information obtained from this study was then used in evaluating the published sea level record a total of fifteen sequence boundaries and ten maximum flooding surfaces indicating conditions of falling and rising sea level respectively were identified in the paleocene and eocene strata of the brazos river valley results of this study show an excellent correlation with the published record of sea level change in the paleocene poor correlation in the early eocene good correlation in the middle eocene and fair correlation in the late eocene the excellent correlation between the results of this study and the published record during the paleocene provide strong support for eustalic nature of these events poor to fair correlation during the early and late eocene is attributed to the resolution of the data base and neither supports nor refutes the published record results of this study in the middle eocene provide strong support lor the published record with two important exceptions published records show a cycle of sea level change in the earliest part of the middle eocene which was not observed in this study and a rise in sea level near the end of the middle eocene bartonian may have occurred earlier than that indicated by the published record

implications of continental crust extension for plate reconstruction an example from the gulf of mexico the prerift reconstruction of continental plates bounded by rifted margins requires the closure of relative motion accomplished both by seafloor spreading and by the extension of continental crust during the rift phase of continental breakup continental extension is not expected to be pervasive throughout the plate but to be confined to a zone of up to several hundred kilometers in width the direction of particle motion in this zone is expected to be parallel to flow lines followed by the rigid portions of the plates the best fit between rifted continental margins is then described by the rotation angle about an euler pole which best closes both the oceanic crust and the extension within the continental crust along small circles about the euler pole as an example application of these concepts the pattern of late mesozoic crust extension within the gulf of mexico basin is used to constrain the location of the euler pole and angle of rotation of the yucatan block with respect to north america both crust type and the degree of extension within the transitional crust surrounding the basin are estimated on a point by point basis from bathymetry and basement depth the root mean square rms misfit in the apparent total closure of both oceanic crust and extension within the continental crust is computed for a range of possible poles of opening a contour map of misfit versus pole location reveals a global minimum rms misfit of 47 km for a 45 counterclockwise opening of the gulf of mexico basin about an euler pole at 25 n 79 w an elongate trend of poles for which the misfit is less than 100 km extends from the bahama islands eastward across the atlantic and through north africa the reconstruction of the gulf of mexico for the best fit pole places the palinspastically restored yucatan block in contact with north america along the texas and louisiana shelf the resulting restored southern margin of north america fits against the the northern margin of south america in its prerift position to within the uncertainty in the north america africa south america plate circuit we conclude that the prerift placement of the yucatan block between north and south america along the texas louisiana shelf is consistent with both the pattern of extension within the gulf of mexico basin and seafloor spreading history of the central atlantic basin

influence of daily surface temperature fluctuations on rock slope stability case study of the rochers de valabres slope france the present paper describes a rockfall that has affected the rochers de valabres slope france s southern alps region and discusses one possible mechanism for the occurrence of this rockfall along with the potential for future ones in the absence of an obvious explanatory trigger factor we set out to examine whether natural daily surface temperature changes could have played a role in this event in particular it is suspected that these slight yet repeated perturbations may be a preparatory factor for rockfalls with a day to day cumulative effect a numerical model strengthens this hypothesis by showing that thermally induced deformations can be sufficient to cause the gradual downward creep of a rock block located in an awkward position to investigate this notion more thoroughly a currently vulnerable part of the rochers de valabres slope has been instrumented with a high precision geodetic monitoring system total station it is believed that this device is able to capture thermally induced movements if specific precautions are taken the instrumented rock volume is used as a test site in the aim of better understanding the consequences of surface temperature changes on slope stability measured data with a precision level never before achieved on rock slopes are compared herein with numerical modelling results the initial conclusions of the long term study we are conducting indicate that surface temperature changes play an important while not easily quantifiable role in preparing rockfalls

rockfall activity from an alpine cliff during thawing periods abstract rockfall activity during thawing periods was investigated by collecting rockfall debris fallen on the snow covered talus slope in a cirque in the japanese alps near surface rock temperature was also monitored on the cirque wall maximum rockfall activity occurs on average about 10 days after the meltout of the cirque wall the intensive activity is rarely associated with precipitation events or diurnal frost cycles on the rockface a thermal conduction model suggests that rockfalls at this site occur most frequently when the seasonal thawing front penetrates to a depth of about 1 m in the bedrock while the freeze thaw penetration controls the maximum dimensions of detachable rock mass joint spacing on the rockface affects the size distribution of rockfall debris boulder falls resulting from seasonal frost weathering are considered to be the most important process responsible for the contemporary modification of the cirque wall the rockfall volume during a thawing period is usually 1 3 m3 which is equivalent to the rate of cirque wall retreat of the order of 0 01 mm year 1 however big boulder falls that occur once per decade can increase the retreat rate significantly

karst collapse susceptibility mapping considering peak ground acceleration in a rapidly growing urban area abstract karst collapse occurrences represent a geological hazard that can cause damage to man made structures in the present study a karst collapse susceptibility map was produced using a multivariate statistical method and a geographical information system the case under study is the northern suburbs of athens greece the karstic features of the study area were recorded physical processes slope angle and aspect hydrographic network springs lithology tectonic features along with anthropogenic road network and land use parameters were chosen as major factors affecting the karst collapse occurrences the innovative method was combining karst collapse occurrences with seismic hazard assessment which was achieved by calculating peak ground acceleration pga the pga was determined for a return period of 475 years corresponding to a 90 probability of not being exceeded in 50 years the logistic regression lr method was applied to evaluate these factors slope angle pga lithology and distance to springs and roads were statistically significant for the applied model among these factors the slope angle and pga have a negative effect while the lithology and distance to springs and roads have a positive effect on the karst collapse occurrences the validation of the applied lr model indicated that the results are reliable and that the produced map is accurate the karst collapse susceptibility map was classified into four classes the areas of very high and high susceptibility were observed mainly in the eastern and southwestern parts of the study area almost 30 of the existing urban growth boundary of the study area is located in areas of very high and high susceptibility the karst collapse susceptibility map can be used by planners and engineers for sustainable urban development

depositional trends in siliciclastic deposits of the stone city transgressive systems tract middle eocene texas abstract strata exposed at stone city bluff texas contain shelf sediments deposited during progressive marine deepening from shallow water depths and then capped by a maximum flooding horizon they are part of the early bartonian np16 cook mountain transgressive systems tract exposed in the type section of the stone city member of the crockett formation this locality lies on the inner portion of a shelf transect about 175 km 110 mi shoreward of the late eocene shelf slope margin and probably never farther than 80 km 50 mi from the shoreline sedimentary structures in the sediments change upward reflecting a shift from tidal current dominated to storm dominated deposition in lower intervals tidal control is dominant the transition interval contains isolated storm sands as sheets with lenses 40 cm 15 in thick in mudstones with tidal bedding these storm beds contain teeth bone concentrates and some gravel size clasts at the bases of larger lenses in higher intervals storm deposition is dominant in all units mostly as thin distal layers of very fine sand or silt amalgamated storm deposits form larger units e g the moseley bed local hardground surfaces are developed where storm washing exposed concretionary layers or on condensed winnowed zones glauconite occurrence and siderite concretion formation are most common in the upper intervals storm deposits have dual sediment sources and contain 1 skeletal remains shells fish bone and glauconite pellets concentrated by in place winnowing or 2 fine quartzose sand washed in from shallower water settings alternation of amalgamated storm deposits and mudstone units with thin storm deposits indicate a cyclic record of storm activity

prograding muddy shelves in the paleogene wilcox deltas south texas gulf coast abstract core facies analysis integrated with subsurface well log correlations and seismic horizon mapping document two thick mudstone dominated deltaic successions in the wilcox group along the south texas gulf coast meters to tens of meter thick upper slope to outer shelf mudstones form units that lie at the base of upward coarsening successions which are interpreted as fluvial or storm wave dominated shelf deltas the muddy character of the deposits is observed in cores and inferred from well logs whereas the larger depositional architecture is interpreted from well log correlations and seismic data physical sedimentary structures described from a lower wilcox core reflect deposition on a mud dominated prodelta controlled by hyperpycnal processes normally and inversely graded beds are present indicating sustained flows that waxed and waned upward coarsening facies successions contain current ripples organic matter and siderite cemented bands low trace fossil abundance and low diversity which suggest deposition in a fluvial prodelta to shelf environment centimeter thick interbeds of normal and inversely graded mudstones siltstones and very fine grained sandstones with low intensities of bioturbation reflect the high physical and chemical stresses of hyperpycnal environments heterolithic stratification with lenticular wavy and flaser bedding indicates some tidal influence on the other hand cores of the middle wilcox reflect deposition on a muddy wave storm dominated shelf bioturbation intensities tend to be high with unstressed fully marine ichnological suites pervasively bioturbated sandy mudstones and muddy sandstones with cruziana ichnofacies wavy parallel and low angle lamination and structureless sandstones with ophiomorpha record deposition in a wave influenced prodelta to shelf environment hyperpycnal flows associated with river floods might have transported mud across the shelf to the outer shelf where prevailing wave and storm conditions facilitated suspension and transport of mud beyond the shelf edge previous studies have shown that wilcox delta sandstones are largely trapped on the shelf by contemporaneous growth faults however this paper illustrates that at times the wilcox shelf margin prograded through mud accretion

relationships between shrinkage indices and soil properties in some new zealand soils abstract shrinkage is a physical process that has profound effects on the agricultural and engineering use of soil this study was undertaken to assess the shrinkage potential of different new zealand soils using the coefficient of linear extensibility cole and to examine relationships between soil shrinkage and selected chemical physical and mineralogical soil properties results indicate that there is a wide range in the shrinkage capacities of different soils with cole values between 0 050 and 0 313 allophane dominated soil samples showed the largest soil shrinkage followed by montmorillonite and halloysite samples with the least shrinkage occurring in the kaolinite vermiculite and chlorite illite dominated samples there was a significant statistical relationship found between cole std determined using natural soil aggregates and cole rod determined using remoulded soil samples r 2 0 85 p std and cole rod were found to be significantly related to specific surface area and soil clay content and inversely related to bulk density cole rod was also significantly related to cec no relationships were found between shrinkage indices and organic matter multiple regression models with terms for specific surface area and clay content could explain 76 and 81 of the variance in shrinkage determined by cole rod and cole std respectively

magnitude and frequency of rock falls and rock slides along the main transportation corridors of southwestern british columbia the two main transportation corridors of southwestern british columbia are subject to a range of rock slope movements rock falls rock slides and rock avalanches that pose significant risks to r

self healing in fractured fine grained soils fine grained soils when exposed to cyclic freezing and thawing generally but not always experience considerable increases in hydraulic conductivities due to the formation of a system of fissures and cracks some soils such as nonplastic or very low plastic soils on the one hand or very highly swelling soils on the other hand do not experience such changes in permeability even though after the freezing stages ice filled separation zones can be commonly observed in the soil matrix self healing of these cracks occurs during subsequent thawing and permeation to identify possible self healing mechanisms and to understand when they can be expected data from freezet ii cloggi