sedimentation of organic rich limestones in the late precambrian of southern norway abstract organic rich laminated limestones are a major facies of the late precambrian biri formation deposited around the margins of the sparagmite basin of southern norway the laminated limestones consist of an alternation of calcitic laminae and clay laminae trace element and stable isotope analyses confirm a marine origin for the carbonate and suggest that the original precipitate was aragonite the organic matter reaches 3 weight loss on ignition and apparently is finely dispersed within the sediment both cm thick limestone beds of probable storm origin and thin disrupted and folded horizons of slump origin occur within the laminated facies the organic rich laminated limestones occur at several horizons and are interbedded with carbonate grainstones of shallow water origin basinwards they pass into light to dark grey to green organic deficient mudrocks with resedimented and slumped units the facies context of the organic rich laminated limestones suggests deposition in an outer shelf setting at times of higher sea level stands the transgressive events possibly induced by changes in glacial ice cover of near or distant landmasses led to increased organic productivity through seasonal blooms of phytoplankton preservation of the organic matter in the sediments resulted from the development of anoxic or at least oxygen depleted bottom waters some physical constriction of water circulation in the sparagmite basin may have contributed towards the anoxic events the development of precambrian organic rich black shales in the sparagmite basin of southern norway does show that potential hydrocarbon source rocks were formed in the pre phanerozoic in situations comparable to some mesozoic and tertiary oil source rocks

aragonite relic preservation in jurassic calcite replaced bivalves shells of the aragonite bivalve neomiodon great estuarine group jurassic scotland replaced by coarse neomorphic calcite contain oriented relics of the original aragonite ultrastructure the presence of these relics in such old altered shells as well as the high sr content of the replacement calcite indicate that the process of calcite replacement of aragonite is not a cumulative slow process involving repeated alteration events but rather a rapid one step process aragonite relics once encased in neomorphic spar will survive as unequivocal evidence of original aragonite mineralogy barring total remobilization of the enclosing stable calcite a generally unlikely event the retention of this residual aragonite and high sr calcite supports recent isotopic studies which suggest that the multiple phases of alteration recrystallization invoked in earlier literature are unlikely events in the diagenesis of most undolomitized limestones retention of aragonite relics appears to be independent of whether alteration occurs in shallow meteoric or as in the case of our neomiodon material deeper burial environments pseudopleochroism of the replaced neomiodon shells appears to be due to organic largely graphitic relics not to the aragonite relics

paleolatitude distribution of phanerozoic marine ooids and cements opdyke b n and wilkinson b h 1990 paleolatitude distribution of phanerozoic marine ooids and cements palaeogeogr palaeoclimatol palaeoecol 78 135 148 data on 493 phanerozoic marine ooid and cement occurrences indicate that the dominance of calcite versus aragonite in tropical marine settings has changed in response to variation in atmospheric co2 and or oceanic temperature gradient holocene ooid and cement precipitation occurs over similar latitudes with means centered around 24 and 28 respectively aragonite and calcite also display roughly comparable distributions with average occurrences between 25 and 28 surface seawater saturation values requisite for ooid cement carbonate precipitation are at least 3 8 rs for aragonite and 3 4 a s for calcite ancient ooid cement occurrences vary in space and time with depositional zones generally closer to the equator during continental emergence greatest extent correlates with periods of maximum transgression aragonite formation is favored in more equatorial localities than calcite when cement ooid distributions are narrow and continents are emergent similarity of latitude distribution of marine ooids cement and biogenic carbonate suggests that physicochemical processes that control levels of carbonate saturation were more important in predicating sites of limestone accumulation in phanerozoic seas than biological processes related to net productivity of various carbonate platform communities continental position and tropical shelf area available for carbonate accumulation dictates the relative abundance of shallow water inorganic carbonate precipitates in space and time

oceanography bathymetry and syndepositional tectonics of a precambrian intracratonic basin integrating sediments storms earthquakes and tsunamis in the belt supergroup helena formation ca 1 45 ga western north america abstract the carbonate dominated helena formation of the mesoproterozoic belt supergroup of western north america provides an instructive example of how a range of regional depositional and environmental characteristics of an ancient sea can be deduced on the basis of micron to metre scale features particularly revealing is the window opened by the presence of abundant molar tooth structure onto the paleoceanography paleobathymetry paleoclimate and tectonic regime of this intracratonic precambrian basin the facies hosting molar tooth structure is composed dominantly of lime mud with substantial subangular quartz and feldspar silt and clay derived from the western and southwestern side of the basin these are low energy tempestites deposited on a remarkably flat sea bottom at the limit of storm wave base at about 50 m sporadic domical stromatolite patch reefs confirm that the sea bottom was normally within the photic zone the ubiquity of molar tooth structure suggests frequent near field seismic activity during subsidence which generated ground motion sufficient to liquefy granular lime mud and terrigenous silt sporadic tsunamis from major submarine faults far to the west pounded the shallow water platform to the east tsunami off surge swept ooids and rounded coarse grained feldspathic quartz sand westward into deeper water and created strongly erosive currents that left gutter casts composed of lags of preferentially cemented molar tooth structure in otherwise relatively low energy facies mineralogical and geochemical evidence confirms that the belt basin was marine organic matter was essentially fully oxidized in the water column original high mg composition and cementation of lime mud in molar tooth structure indicate that calcite precipitated above the thermocline in supersaturated seawater under tropical conditions scattered bimineralic ooids in allochthonous grainstones indicate that shoals on the platform to the east were intermittently above a shallow aragonite compensation depth in warm water rare vestiges of halite and gypsum demonstrate occasional temporary salinity stratification for periods of up to a few years unaltered feldspar and mica grains point to a generally arid climate but the large volume of clay is suggestive of protracted weathering and transport

an oscillating trend in phanerozoic non skeletal carbonate mineralogy textural and compositional data on ancient ooids and cements suggest the existence of an oscillating phanerozoic temporal trend in non skeletal carbonate mineralogy the trend shows good correlation with eustatic climatic oscillations proposed by others the most likely mechanism appears to be plate tectonically influenced oscillations in pco2 the vapour pressure of co2 rather than change in oceanic mg ca ratio

electrical resistivity tomography applied to groundwater aquifer at downstream of chih ben creek basin taiwan groundwater resource investigations primarily involve inferring groundwater levels and recharge sources from factors such as the distributed location and range subsurface geological structure and flow paths of groundwater sources this study conducted an investigation on the underground aquifer at the downstream of the chih ben creek basin taiwan in addition convenient rapid and accurate two dimensional electrical resistivity tomography ert was employed for evaluations the cross sectional ert image indicates that the low resistivity region in the stratum at survey line cb01 may be a groundwater deposit or fracture zone this region can be divided into three major segments the segment that is 0 50 m from the survey line exhibits a decreasing trend and is thus inferred to be a recharge source survey line cb02 can be generally divided into four layers with the second layer containing a greater amount of groundwater this layer is an aquifer with a depth of approximately 25 100 m below the ground surface and 75 100 m in thickness the base of the aquifer slopes toward the east and primarily possesses a lithological composition of slate and sandstone with explicit and fractured joints

giant ooids in a neoproterozoic carbonate shelf simla group lesser himalaya india an analogue related to neoproterozoic glacial deposits abstract this study is the first comprehensive documentation of giant ooids and related facies associations in the kunihar formation proterozoic simla group lesser himalaya himachal pradesh analysing the understanding of processes and controls on development of giant ooids based on field observations supplemented by outcrop based facies analysis petrography and delineation of environmental variations four facies associations have been delineated i peritidal siliciclastic carbonate fa1 ii shelf lagoon fa2 iii reef complex fa3 iv fore reef slope fa4 deposition of giant ooids and associated facies associations of kunihar formation occurred in a carbonate rimmed shelf with high tidal influence size of giant ooids from kunihar formation is the largest as compared to giant ooids from other geological formations kunihar giant ooids developed when normal ooids were washed from ooid shoals intertidal into slightly deeper regions shallow subtidal resulting in the increased dimension of ooids in suspension due to higher hydrodynamics scanning electron microscopy sem studies support microbial origin of ooids giant ooids and stromatolites of kunihar formation increased microbial activity in kunihar formation is attributed to increase in nutrients by virtue of weathering of underlying darla volcanics abundant carbonate and microbially induced sedimentary structures miss deposition in lower part of simla group points to increased microbial activity which likely increased the volume of oxygen in neoproterozoic atmosphere ushering in ice house conditions during the subsequent deposition of blaini group giant ooids associated with neoproterozoic glacial deposits throughout the world occupy stratigraphic positions below above or between glaciations simla group is another example where giant ooids lie stratigraphically below marinoan blaini tillites increased magmatic activity and weathering before and during the neoproterozoic glaciations increased nutrients in marine waters which increased algal growth thus giant ooids were deposited due to such phases of increased microbial activity before after glaciation and during interglacial periods

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

selective and reversible carbonate silica replacements in lower cretaceous carbonate bearing turbidites of the eastern alps in the diagenetic history of calcareous sandstones silicacementation and silicification may be followed by carbonatecementation and replacement and vice versa and the change over from one to the other may occur more than once this is well illustrated by calcareous and siliciclastic turbidites of the gault formation aptian to albian of the eastern alps which have been interpreted as deep sea trench plain and deep sea fan deposits in these turbidites silicification selectively affects ooids and a few other biogenic carbonate fragments rich in organic matter algae and bryozoans which form a small fraction of the bulk sediment the type and sequence of diagenetic changes are largely controlled by host rock composition and may vary vertically within individual beds as a result of compositional grading in the carbonate turbidites silicification follows widespread calcite cementation the process is slow resulting in relatively coarsely crystalline replacement quartz in ooids with quartz nuclei rim quartz forms mostly monocrystalline overgrowths by outward replacement of the concentrically laminated carbonate cortex this type of silicification is often incomplete leaving parts of the ooid cortices unaffected in quartz arenites and sublitharenites silicification precedes calcite cementation there the process is rapid forming microcrystalline quartz even if the ooid nucleus consists of quartz a syntaxial overgrowth does not normally form the replacement quartz is almost always polycrystalline late stage diagenetic calcite and dolomite which develop euhedral crystal shapes and cut across grain boundaries may replace the earlier secondary rim quartz of the ooids as well as other minerals possible sources of the silica are pressure solution of quartz dissolution of opaline silica of radiolarian tests and of sponge spicules and feldspar in the host bed in a number of examples an increase in the degree of silicification can be observed towards the lower bedding planes of individual turbidites requiring an additional external source of silica which seems to necessitate cross formational flow of pore solutions silicification in both the carbonate and the siliciclastic turbidites probably took place at about the same time in the carbonate turbidites it was preceded however by calcite cementation which significantly reduced porosity and permeability before silicification took place the greater degree of alteration experienced by the gault turbidites of the falknis and tasna nappes which are more internal structural units of the alps compared to the flysch zone of the eastern alps is reflected by the growth of quartz beards and spikes from the ooids in the direction perpendicular to maximum stress this is the only case observed where the rim quartz of the ooids grows beyond the original grain boundaries

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

thickness distribution texture and stratigraphy and a simple probabilistic model for dynamical thickening of sea ice in the southern sea of okhotsk 1 sea ice thickness data and sea ice samples were analyzed to examine the characteristics of the ice thickness distribution and ice texture and to understand ice growth processes in the southern sea of okhotsk ice thickness data and samples were obtained aboard the icebreaker soya in early february the ice growth season ice thickness data which were obtained with a video monitoring system installed on the side deck of the ship each winter from 1991 to 2000 except 1995 show that the average thickness ranges from 19 7 to 55 23 cm and that it matches the characteristics of a poisson distribution ice structure analysis reveals that granular texture occupies about three quarters of the total ice thickness and that the ice exhibits a layered structure with unit thickness averaging 5 to 10 cm stratigraphy and stable isotopic composition of the ice indicate that snow ice accounts for 10 and frazil ice accounts for 64 of the total ice thickness this suggests that dynamic ice thickening processes such as frazil ice growth and piling up are more significant than congelation growth on the basis of these characteristics which resemble more those of antarctic than arctic sea ice we propose a conceptual model for the ice thickening process in this region it is shown that this model can explain the shape of the ice thickness distribution well and is analogous with the concept of the pancake cycle and multiple rafting of antarctic sea ice growth and thickening

ultra rapid topographic surveying for complex environments the hand held mobile laser scanner hmls terrestrial laser scanning is the current technique of choice for acquiring high resolution topographic data at the site scale i e over tens to hundreds of metres for accurate volume measurements or process modelling however in regions of complex topography with multiple local horizons restricted lines of sight significantly hinder use of such tripod based instruments by requiring multiple setups to achieve full coverage of the area we demonstrate a novel hand held mobile laser scanning technique that offers particular promise for site scale topographic surveys of complex environments to carry out a survey the hand held mobile laser scanner hmls is walked across a site mapping around the surveyor continuously en route we assess the accuracy of hmls data by comparing survey results from an eroding coastal cliff site with those acquired by a state of the art terrestrial laser scanner tls and also with the results of a photo survey processed by structure from motion and multi view stereo sfm mvs algorithms hmls data are shown to have a root mean square rms difference to the benchmark tls data of 20 mm not dissimilar to that of the sfm mvs survey 18 mm the efficiency of the hmls system in complex terrain is demonstrated by acquiring topographic data covering 780 m2 of salt marsh gullies with a mean point spacing of 4 4 cm in approximately six minutes we estimate that hmls surveying of gullies is approximately 40 times faster than using a tls and six times faster than using sfm mvs 2013 the authors earth surface processes and landforms published by john wiley sons ltd

isotopic evidence for the paleoenvironmental evolution of the mesoproterozoic helena formation belt supergroup montana usa high resolution isotopic and geochemical data constrain long debated marine vs lacustrine depositional models for the helena formation a carbonate unit within the mesoproterozoic belt supergroup montana paired carbon and oxygen isotope and minor element analyses of microsamples from a diverse array of petrographic components effectively distinguish between primary and secondary isotopic signatures 13c values reflecting primary depositional conditions increase progressively from an average of 0 near the base of the helena formation to an average of 1 4 near the top over a stratigraphic thickness of 100 200 m because the base of this 1 6 shift coincides with a basin wide facies change marked by the appearance of stromatolitic units and an increased occurrence of features indicative of evaporative conditions and subaerial exposure the shift toward more positive 13c values is interpreted to reflect an increase in biologic productivity coupled with increasingly evaporative conditions in the eastern part of the belt basin 13c values from the lower part of the helena formation are similar to those from other marine carbonates of similar age and suggest that the belt basin was marine during deposition of the helena formation taken as a whole these relations suggest that helena sediments were deposited in a shallow marine basin that was increasingly isolated from the open mesoproterozoic ocean original 13o values have been retained only in syndepositional and early diagenetic intergranular cements in oolitic grainstones that occur in the upper part of the helena formation the most positive 13o values derived from these cements 6 1 pdb are up to 3 higher than previous estimates for the 13o value of mesoproterozoic marine calcite however because these phases are associated with facies deposited under restricted marine conditions interpretation of 13o values from these cements with regard to the composition of the open mesoproterozoic ocean awaits study of additional coeval marine carbonate successions

landslide susceptibility mapping of vicinity of yaka landslide gelendost turkey using conditional probability approach in gis on 19 february 2007 a landslide occurred on the alaardic slope located 1 6 km south of the town of yaka gelendost turkey subsequently the displaced materials transformed into a mud flow in eglence creek and continued 750 m downstream towards the town of yaka the mass poised for motion in the yaka landslide source area and its vicinity which would be triggered to a kinetic state by trigger factors such as heavy or sustained rainfall and or snowmelt poise a danger in the form of loss of life and property to yaka with its population of 3 000 this study was undertaken to construct a susceptibility mapping of the vicinity of the yaka landslide s source area and to relate it to movement of the landslide mass with the goal of prevention or mitigation of loss of life and property the landslide susceptibility map was formulated by designating the relationship of the effecting factors that cause landslides such as lithology gradient slope aspect elevation topographical moisture index and stream power index to the landslide map as determined by analysis of the terrain through the implementation of the conditional probability method it was determined that the surface area of the goksogut formation which has attained lithological characteristics of clayey limestone with a broken and separated base and where area landslides occur possesses an elevation of 1 100 1 300 m a slope gradient of 15 35 and a slope aspect between 0 67 5 and 157 247 loss of life and property may be avoided by the construction of structures to check the debris mass in eglence creek the cleaning of the canal which passes through yaka the broadening of the canal s base area elevating the protective edges along the canal and the establishment of a protective zone at least 10 m wide on each side of the canal to deter against damage from probable landslide occurrence and mud flow

evidence for initial calcite aragonite composition of lower algal chert member ooids and stromatolites paleoproterozoic gunflint formation ontario canada the chert members of the paleoproterozoic gunflint formation ontario canada are commonly regarded as examples of primary silica chemical sediments this interpretation is founded upon the ubiquitous nature of silica high fidelity of preservation of microfossils found within and lack of observed primary carbonate previous arguments for silica replacement of carbonate are based on indirect evidence and are largely dismissed thus gunflint microfossils are regarded as having lived in a silica rich environment which makes them unusual compared to most other pre phanerozoic microfossils that are known from silicified carbonates we present evidence that carbonate was a primary mineral species of the lower algal chert member where most of the microbiota are found most compelling are iron stained low mg calcite ooids containing 1 well preserved growth laminae 2 textures indicating a disrupted tan gential fabric of growth laminae and 3 quartz crosscutting the growth laminae these indicate the initial mineral was a carbonate possibly aragonite less compelling evidence is found in stromatolite columns specularite crystals in low mg calcite display crosscutting relationships with calcite and quartz indicating that calcite was primary specularite sec ondary and quartz tertiary the crosscutting relations show that silicification took place in at least two stages one of the silicification events took place very early in diagenesis thus the gunflint microbiota may not have existed in a radically different environment silica precipitating than those of most other known proterozoic microbiota high fidel ity of preservation of microfossils does not always indicate that the mineral entombing them was the primary mineral precipitated from aqueous solution

analysis of lidar derived topographic information for characterizing and differentiating landslide morphology and activity abstract this study used airborne laser altimetry lidar to examine the surface morphology of two canyon rim landslides in southern idaho the high resolution topographic data were used to calculate surface roughness slope semivariance and fractal dimension these data were combined with historical movement data global positioning systems gps and laser theodolite and field observations for the currently active landslide and the results suggest that topographic elements are related to the material types and the type of local motion of the landslide weak unconsolidated materials comprising the toe of the slide which were heavily fractured and locally thrust upward had relatively high surface roughness high fractal dimension and high vertical and lateral movement the body of the slide which predominantly moved laterally and consists mainly of undisturbed older canyon floor materials had relatively lower surface roughness than the toe the upper block consisting of a down dropped section of the canyon rim that has remained largely intact had a low surface roughness on its upper surface and high surface roughness along fractures and on its west face unrelated to landslide motion the upper block also had a higher semivariance than the toe and body the topographic data for a neighboring older and larger landslide complex which failed in 1937 are similarly used to understand surface morphology as well as to compare to the morphology of the active landslide and to understand scale dependent processes the morphometric analyses demonstrate that the active landslide has a similar failure mechanism and is topographically more variable than the 1937 landslide especially at scales 20 m weathering and the larger scale processes of the 1937 slide are hypothesized to cause the lower semivariance values of the 1937 slide at smaller scales

molar tooth structures of the neoarchean monteville formation transvaal supergroup south africa i constraints on microcrystalline caco3 precipitation molar tooth mt structures are enigmatic contorted millimetre to decimetre long veins and spheroids of microcrystalline calcite that formed during very early diagenesis in precambrian sediments mt structures in the ca 2 6 ga monteville formation are 600 800 myr older than previously reported occurrences and establish that conditions necessary for mt genesis were met locally throughout much of the precambrian in the monteville formation mt structures were formed shallow subtidally extending to depths near storm wave base in shale host sediments intercalated with storm generated carbonate sand lenses they are filled with microcrystalline calcite and rare pyrite microcrystalline calcite identical to that in mt structures fills other pore space including porosity between grains in carbonate sand lenses moldic porosity in sand grains sheet cracks in columnar stromatolites and shallow cracks on sandy bedding planes relationships in the monteville formation demonstrate that microcrystalline caco3 precipitated in fluid filled cracks and pores microcrystalline calcite characteristics as well as the paucity of carbonate mud in host rocks are inconsistent with injection of lime mud as the origin of mt structures locally mt cracks were filled by detrital sediment before or during precipitation precipitation occurred in stages and mt caco3 evolved from granular cores to a rigid mass of cores with overgrowths allowing both plastic and brittle deformation of mt structures as well as reworking of eroded mt structures as rigid clasts and lime mud crystal size distributions and morphology suggest that cores precipitated through nucleation ostwald ripening and size dependent crystal growth whereas overgrowths formed during size independent crystal growth

zoned calcites in jurassic ammonite chambers trace elements isotopes and neomorphic origin zoned calcites were found in the phragmacone chambers of three sonniniid ammonites from marine middle jurassic sandstones isle of skye u k each ammonite has a unique sequence of up to nine zones of calcite which fill or partially fill the chambers zones are defined by changes in the density of minute opaque inclusions and variation in trace element composition proximal early calcites have undulose extinction and some exhibit the specific fabrics of fascicular optic and radiaxial fibrous calcites microdolomite inclusions are found in one specimen early calcites interpreted as replacements after a single isopachous fringe of acicular carbonate probably high magnesium calcite are succeeded by blocky ferroan calcite cement in one specimen there are two distinct generations of calcite in the others there is a continuous mosaic incorporating both early calcites and late cement isotopic composition of the early calcite zones demonstrates the initial importance of organic derived carbon 13c 26 18o o further cementation and mineralogical stabilization took place at increased temperatures and probably after modification of the pore water isotopic composition calcites with 13c o 18o 10 the distinctive fabrics and zonal patterns probably developed during the replacement of the precursor cement and are not primary growth features reversals in isotopic and trace element trends are believed to be related to the rate of neomorphic crystal growth and hence to the degree of exchange with external pore waters further increase in temperature probably during tertiary igneous activity gave rise to the extremely light 18o values of the late cements in the ammonite which had previously had least contact with external waters cements with 13c o 18o 20

shallow and deep seated regolith slides on deforested slopes in canakkale nw turkey abstract this study deals with the stripping of regolith on a steep slope by surface wash and shallow landslides and a deep seated landslide at a lower slope that took place on 17 february 2003 at the village of mazilik east of canakkale turkey soil loss and shallow slides dominate on the deforested steep slopes in the study area and occur preferentially along slope parallel sub horizontal joint planes with clay coatings particularly oxyhydroxides that are rich in fe but poor in mn as a result of weathering under well drained conditions gully erosion also occurs where the regolith cover is relatively thick up to 4 m the area of the deep seated landslide however is dominated by silty clay 46 a geoelectrical resistivity survey revealed a clay rich zone at depths of 3 10 m corresponding to the slip surface of the slide which was associated with excessive water content after the snowy day of 14 february 2003 with a daily precipitation of 16 4 mm based on thornthwaite s water budget analysis the study area has a slide prone condition with excess soil moisture content heavy rainfall events snow accumulation and snow melting in winter months and low soil permeability also favouring slope instability

ice thickness in the arctic ocean the statistical reliability of experimental data the statistical reliability of ice thickness distributions derived from submarine sonar data sets of finite length is examined focusing on the standard error eh l in the mean ice draft h derived from a record of length l km this is important in assessing the significance or otherwise of quoted temporal or spatial differences in mean ice draft estimates for eh 50 are derived from four different submarine surveys each of which involved repeated sampling of apparently homogeneous ice fields values ranged from 7 18 to 15 29 of the mean for climate related comparisons of data sets from different years in the same location a value of 12 75 is recommended derived from data gathered at the north pole this value is used to reassess the significance of published data on ice draft variability quoted variability at the north pole over the 1977 1990 period is found to be not statistically significant but a difference in area averaged ice draft over the eurasian basin between 1976 and 1987 remains highly significant using hitherto unreported 1987 data from the north pole area the statistical variability of other parameters of the ice cover is examined the frequency of lead occurrence the width of leads the fractional cover of smooth ice and the frequency of keel occurrence all show standard errors of 22 24 in their mean values while mean keel draft has a 4 error all over a 50 km track length finally unreported 1987 data for an area extending from the pole to 72 n along the prime meridian and the east greenland shelf break are examined in 1 bins using eh l to assess the significance of variations in the mean a statistically significant decline in mean ice draft is observed starting at 86 n and continuing to 72 n a linear regression gives a thinning rate of 0 22 m deg the decline within the arctic basin itself is tentatively ascribed to a mixture of under ice melt and mixing of ice types since data on young ice occurrence show that divergence did not occur north of fram strait

sea ice type maps from alaska synthetic aperture radar facility imagery an assessment synthetic aperture radar sar imagery received at the alaska sar facility is routinely and automatically classified on the geophysical processor system gps to create ice type maps we evaluated the wintertime performance of the gps classification algorithm by comparing ice type percentages from supervised classification with percentages from the algorithm the rms difference for multiyear ice is about 6 while the inconsistency in supervised classification is about 3 the algorithm separates first year from multiyear ice well although it sometimes fails to correctly classify new ice and open water owing to the wide distribution of backscatter for these classes our results imply a high degree of accuracy and consistency in the growing archive of multiyear and first year ice distribution maps these results have implications for heat and mass balance studies which are furthered by the ability to accurately characterize ice type distributions over a large part of the arctic

estimates of sea ice thickness distribution using observations and theory the thickness distribution of sea ice is maintained by a balance of thermal and mechanical processes observations now exist that make it possible to quantify this balance and to test models of the individual physical processes in particular the observed distributions used with fairly well established thermodynamic growth rates give an estimate of the redistribution process that models the formation of pressure ridges to highlight the main ideas the evolution of the thickness distribution is recast as a markov process forced by the mean velocity divergence and a measure of the random short term deformation this model reproduces features of the observed thickness distribution such as the peak near 3 m the mean thickness somewhat greater than 3 m the long tail and the variable shape of the thin side of the distribution analytical expressions for the mean and variance of the ice thickness are given showing how they depend on the growth rates for thick and thin ice the equilibrium thickness the ice deformation and the rule for building pressure ridges these are sensitive to the mean divergence and the melt rate for thick ice with large amounts of data now available for both the ice thickness and the ice motion further progress is anticipated toward understanding the processes which shape the thickness distribution

lidar derived dem evaluation of deep seated landslides in a steep and rocky region of japan abstract in steep and rocky terrains their rough surfaces make it difficult to create landslide inventories even with detailed maps images produced from airborne lidar data to provide objective clues in locating deep seated landslides the surface textures of a 5 km2 steepland area in japan was investigated using the eigenvalue ratio and slope filters calculated from a very high resolution lidar derived dem the range of filter values was determined for each of a number of surface features mapped in the field and these included cracked bedrock outcrops coarse colluvial deposits gently undulating surfaces and smooth surfaces recently active slides commonly contained patches of ground in which deposition and erosion occurred together near the erosion front or where cracked bedrock outcrops and coarse colluvial deposits coexisted under a gently undulating surface the characteristic eigenvalue and slope filter values representing this sliding process were applied to maps of the dem derived filter values to extract potential sites of recent landslide activity in addition the relationships between the filter values of deep seated landslides at various stages of evolution within the field mapped area were extended to the entire study area to assess the contribution that landslide evolution makes to change in the landscape as a whole while landslide components made up the steepest as well as the gentlest parts of the landscape depending on their evolutionary stage landslides were constantly coarsened and steepened by progressive erosion probably initiated by river bank erosion at the foot of slopes

overview of some geological hazards in the saudi arabia the saudi arabia has harsh environmental conditions which enhance some geomorphologic geological processes more than in other areas these processes create different geological hazards the general physiography of the saudi arabia is characterized by the red sea coastal plains and the escarpment foothills called tihama followed by the arabian shield mountains the arabian shelf plateau and finally the arabian gulf coastal plains these types of geological hazards can be categorized into sand accumulations earth subsidence and fissures flash floods problematic soils slope stability problems and karst problems the current study gives an overview of all these hazards with examples as well as develops a geo hazard map for the saudi arabia our findings indicate that the desert environment needs much concern and care national and international agencies have to join together with other people to keep the system balanced and to reduce the resulting geological hazards also remedial measures should be proposed to avoid and reduce these natural hazards

surface electrical resistivity tomography and hydrogeological characterization to constrain groundwater flow modeling in an agricultural field site near ferrara italy a portion of an unconfined alluvial aquifer located in the padana plain italy was characterized following an integrated hydro geophysical approach initially an electrical resistivity tomography ert survey was employed to localize the boundaries of a modest paleo channel body and to design the installation of a groundwater monitoring network multilevel slug tests were performed to estimate the aquifer s saturated hydraulic conductivities determined permeability values together with electrical resistivity data were correlated the correlation resulted in a site specific bi logarithmic linear relationship based on this relationship punctually determined hydraulic conductivities were spatially extended over the studied flow domain finally continuously measured piezometric heads were used to calibrate a 3d flow model sensitivity analysis was performed to confirm the reliability of the reconstructed permeability field as well as to assess the minimum number of direct measurements needed to safely characterize the selected aquifer portion the integration of the ert survey results with the classical hydrogeological tests can be conveniently applied to constrain the permeability field during flow model calibration although the applicability of the determined relationship is site specific the followed procedure is useful especially when there is a need to optimize the available resources and in case of small scale pilot studies

land subsidence in konya closed basin and its spatio temporal detection by gps and dinsar konya closed basin that includes two depression blocks konya and tuz golu is the biggest endorheic basin in turkey a lowering in the ground levels of the depositional areas has been shown with respect to the surrounding mountains in the past this process was controlled by geological and hydrogeological phenomena nowadays it has gained a new dimension due to the excessive pumping of groundwater to the earth s surface the geodetic techniques such as global positioning system gps and interferometric synthetic aperture radar insar reveal a considerable land subsidence resulting in the rate of 1 4 cm year in konya sub basin it seems that the calculated amounts are responsible for changing environmental conditions like seasonality both gps and differential insar techniques verify these relatively small fluctuations in the subsidence development target districts that should be observed primarily are agricultural zones where groundwater is overused for irrigation and regions where human population density is high the geocoded interferogram and vegetation index map verify the spatial relation between the subsidence and green areas in this study a project dealing with the investigation of the land subsidence occurrences and of their possible causes and consequences within a specific part of konya closed basin is introduced

determination of mechanisms and hydrogeological environments of gangxianlane landslides using geoelectrical and geological data in central taiwan electrical resistivity tomography ert single point resistance logging with time lapse and geological and groundwater level data are utilized to determine the mechanism of and a hydrogeological model of the gangxianlane landslide in the west central part of taiwan the rock surface and geometry of the colluviums were found by integrating ert and borehole data the iso resistivity line in the bedrock broadly followed the bedding plane indicating that the contribution of lithology to resistivity exceeds that of groundwater the results of single point resistance logging with time lapse and borehole data reveal that the bedrock has low permeability which is associated with poorly developed joints and fractures the fine grain content part including the clayey layer almost parallel to the bedding plane of the bedrock and between the colluvium and the bedrock in the upper part of the landslide served as the slip surface and is believed to have been recently produced it can block and retain water in the colluviums accordingly this slip surface has the potential to re slip in the future another slope failure involved rock collapse by a well developed open release joint close to the huoshaoping terrace it is also related to groundwater flow over a large gradient from the huoshaoping terrace it is a key to determining whether this landslide will expand in the future

sea ice is a mushy layer sea ice is a two phase two component reactive porous medium an example of what is known in other contexts as a mushy layer the fundamental conservation laws underlying the mathematical description of mushy layers provide a robust foundation for the prediction of sea ice evolution here we show that the general equations describing mushy layers reduce to the model of maykut and untersteiner 1971 under the same approximations employed therein

sea ice topography of the arctic ocean in the region 70 degrees w to 25 degrees e in october 1976 a cooperative experiment was made to survey the sea ice topography in the european sector of the arctic ocean h m submarine sovereign acquired 4000 km of ice draft data by using an upward looking sonar while a canadian forces aircraft flew along the submarine s track and acquired 2200 km of ice elevation data by using a laser profilometer the two types of profile were processed in corresponding 100 km section lengths and the following statistical analyses and comparisons were made i probability density functions o f ice draft and elevation each distribution shows a peak for young ice and for undeformed multi year ice at large ice thicknesses the distributions take the analytical form of a negative exponential the mean drafts enable two distinct geographical ice regimes to be identified there is an offshore zone of very heavy pressure ridging extending up to 400 km from the coasts of ellesmere island and of north greenland with mean ice draft in the range 5 0 to 7 5 m while out in the central arctic ocean the mean ice draft is lower 3 9 5 1 m and the characteristics of the ice cover remain homogeneous over a length scale of 1000 km the transition between the two regimes is abrupt taking place in less than 25 km data from the same part of the central arctic taken in march 1971 showed a mean ice draft 0 3 m lower while data from the central beaufort sea showed a mean draft more than 0 8 m lower ii level ice distributions ice with a local gradient of less than 1 in 40 was defined as level ice and used as an indicator of the quantity and thickness distribution of undeformed i e thermodynamically grown ice in the arctic ocean the distribution has a mode at 3 0 3 1 m draft and level ice percentages are in the range 30 40 bottom side and 70 80 top side in the offshore zone and 45 55 bottom and 85 95 top in the central arctic thus about half of the arctic ice cover consists of deformed ice iii pressure ridge spacings the spacings of ridge keels fit a negative exponential distribution characteristic of randomness except at close spacings where there is a deficit of keels explained as a geometrical effect and at very large spacings where there is an excess due to the contribution of polynyas the distribution of sail spacings exhibits these two effects but also differs from a random distribution at moderate sail separations iv ridge elevations and drafts keel drafts fit a law of form p h d oc exp ah 2 d h except for an excess of keels at drafts beyond 20 m there is a positive correlation between mean keel draft and keel frequency there are 3 5 4 5 keels per kilometre with draft exceeding 9 m in the offshore zone and 2 3 in the central arctic sail elevations fit a law of form p h d h x exp a h d h with a positive correlation between mean sail elevation and sail frequency the sail elevation and ice elevation distributions can be related by assuming that all thick ice is contained in pressure ridges of triangular cross section v keel sail comparison for the 21 corresponding 100 km sections there are positive correlations between mean sail height and mean keel draft and between keel frequency and sail frequency from these it is possible to convert a sail distribution computed from a laser profile into a keel distribution enabling sea ice bulk characteristics to be derived from airborne surveys alone vi leads and polynyas a lead was defined as a continuous sequence of depth points greater than 5 m long and not exceeding 1 m draft the number density n d of leads per kilometre of width d m fits the power law n d 15 d 2 exceptionally wide leads were concentrated in the offshore zone and in the marginal ice zone close to the open water of the greenland sea

coastal lithofacies and biofacies associated with syndepositional dolomitization and silicification draken formation upper riphean svalbard the draken formation 120 250 m of northeast spitsbergen svalbard forms part of a thick upper proterozoic carbonate platform succession it consists predominantly of intraformational dolomitic conglomerates with excellent textural preservation six main lithofacies were recognized in the field quartz sandstones stromatolitic mats conglomerates with silicified intraclasts dolostone conglomerates with desiccated mudrocks oolitic pisolitic grainstones and fenestral dolostones a series of five main gradational biofacies were recognized from silicified and rare calcified microfossils biofacies 1 represents low energy subtidal benthos erect filaments and plankton acritarchs and vase shaped microfossils whereas biofacies 2 to 5 are microbial mat assemblages with filamentous mat builders and associated dwellers and washed in plankton ranging from basal intertidal to high intertidal supratidal colour values a measure of the lightness of the colour shade of sawn rock samples were quantified using a munsell chart and exhibit a pronounced variation means of major groups varying from 4 0 to 5 95 across the spectrum of subtidal to supratidal sediments as inferred from other criteria the lightening in progressively more exposed sediments is related to lowering of organic carbon contents probably mainly by oxidation six types of early cement have been recognized calcite microspar type 1 is common as a subtidal cement in many proterozoic formations whereas types 2 subtidal isopachous fringes 3 subtidal hardground dolomicrite and 4 intertidal meniscus dolomicrite are very similar to phanerozoic examples except for their dolomitic mineralogy types 5 and 6 are complex and variable dolomite growths associated with expansion and replacive phenomena they characterize the fenestral lithofacies and compare with modern supratidal cements consideration of diagenetic fabrics and truncation textures of intraclasts indicates that leaching dolomitization silicification were all significant syndepositional processes altering the original metastable carbonates the data set provides evidence for a spectrum of peritidal environments including ooid shoals protected subtidal tidal sandflats and protected carbonate mudflats different sections show a preponderance of particular facies the coastal lithofacies continuum was completely dolomitized unlike offshore to ooid shoal facies of adjacent formations dolomitization thus bears a relationship to depositional bathymetry although hydrodynamics clearly have a role the potential importance of whiting precipitation in raising mg ca in marginal marine environments is also stressed

decoding the mechanism of formation in marine ooids a review abstract ooid shoals sedimentary structures consisting of carbonate grains are often used as proxies to explore changes in seawater chemistry over earth history despite their importance as contributors to the global carbonate budget and as paleo environmental indicators for water depth ph temperature and water energy the mechanism of formation of these concentric sub spherical concretions of tangentially or radially arranged aragonite or calcite crystals is still the subject of intense debate unlike oncoids whose microbial origins are well acknowledged ooids are traditionally viewed as abiotic grains mainly produced in suspension by agitated warm waters that are supersaturated with respect to caco3 yet there is considerable evidence including geochemical bio signatures and detection of viable microbes capable of mineralization and biofilm production and degradation to suggest otherwise the emergence of new and sophisticated technologies reveals that the level of microbial diversity of these sedimentary grains exceeds that of some microbialite systems these findings have refined our understanding of ooid genesis and ooid accretion processes and argue toward microbial mediation both as a direct result of metabolic activities inducing changes in the environment conducive to precipitation and by a passive mechanism in which mucilaginous extracellular polymeric substances eps act as a template for mineral nucleation furthermore new developments in the field indicate that carbonate mineralization in marine ooids occurs through sequential precipitations that involve an amorphous calcium carbonate phase acc which some argue are of biotic origins herein we discuss the most relevant theories of ooid formation including some of the early pioneering studies that laid the groundwork for new theories attempting to decode the origins of these controversial grains

a middle proterozoic palaeokarst unconformity and associated sedimentary rocks elu basin northwest canada a major palaeokarst erosion surface is developed within the middle proterozoic elu basin northwestern canada this palaeokarst is named the sub kanuyak unconformity and truncates the parry bay formation a sequence of shallow marine dolostones that were deposited within a north facing carbonate platform under a semi arid climate the sub kanuyak unconformity exhibits up to 90 m of local relief and also formed under semi arid conditions when parry bay dolostones were subaerially exposed during a relative sea level drop of about 180 m caves and various karren developed within the meteoric vadose and phreatic zones their geometry size and orientation were largely controlled by northwest and northeast trending antecedent joints bedding and lithology near surface caves later collapsed forming valleys and intervening towers or walls and plains minor terra rossa formed on top of highs karstification was most pronounced in southern parts of bathurst inlet but decreased northward probably reflecting varying lengths of exposure time along a north dipping slope the kanuyak formation is up to 65 m thick and partially covers the underlying palaeokarst it consists of six lithofacies i breccia formed during collapse of caves as reworked collapse breccia and regolith ii conglomerate representing gravel dominated braided fluvial deposits iii sandstone deposited as braided fluvial and storm dominated lacustrine deposits iv interbedded sandstone siltstone and mudstone of sheet flood origin v dolostones formed from dolocretes and quiet water lacustrine deposits and vi red beds representing intertidal marine mudflat deposits rivers flowed toward the northwest and northeast within karst valleys and caves lakes were also situated within valleys marine mudflat sediments completely cover the palaeokarst to the north a regional correlation of the sub kanuyak unconformity with the intra greenhorn lakes disconformity within the coppermine homocline suggests that similar styles of karstification occurred over an extensive region the elu basin palaeokarst however was developed more landward and was exposed for a longer period of time than the coppermine homocline palaeokarst

application of electrical resistivity tomography technique for investigation of landslides a case from turkey electrical resistivity imaging is a widely used tool in near surface geophysical surveys for investigation of various geological environmental and engineering problems including landslide in this study an electrical resistivity tomography ert survey was conducted in a landslide area located in the soke district of aydin turkey in 2003 the neogene aged units on the slope next to a newly built school building became unstable due to an excavation work and moved after a heavy rainfall the resulting landslide partly covered the school the authors carried out a 2 d resistivity survey along three profiles over the landslide mass using a wenner configuration it yielded useful information about the geometry and characteristics of the landslide in addition a 2 d synthetic resistivity modelling study was carried out to understand the response of the resistivity method to a landslide problem before the field surveys eight boreholes were also drilled in the landslide area both the drilling and resistivity results indicated the presence of a fault in the site also the resistivity data from the line measured along the axis of the landslide revealed the surface of rupture

the relation between ice deformation oceanic heat flux and the ice thickness distribution in the arctic ocean a one dimensional ocean model coupled with an ice model where the ice cover is partitioned into a number of thickness categories is used to investigate how the ice thickness distribution in the arctic ocean depends on the two deformation processes export net divergence and ridging the model standard case generates vertical profiles of temperature salinity and an ice thickness distribution similar to the observations the standard case oceanic heat flux agrees well with recently deduced heat fluxes from arctic ice dynamics joint experiment aidjex data the oceanic heat flux is about 18 w m 2 during summer and about 1 w m 2 during winter it is found that the mean ice thickness decreases with increasing ice export in close agreement with other investigations however the dependence of the mean ice thickness on ridging activity is found to be very weak the change of the mean ice thickness is only 12 cm when increasing the ridging activity in the model from 0 to 0 4 yr 1 where the larger value represents an estimate of the actual ridging activity in the arctic ocean in a sensitivity study different types of ridging and albedo parameterizations are tested and this weak dependence is found to be very robust other properties of the model ice cover are sensitive to ridging though the equilibrium thickness of undeformed ice decreases with both export and ridging activity the annual maximum open water fraction and the amplitude of the seasonal thickness variation increases with export and ridging

petrographic and geochemical evidence for original aragonite mineralogy of upper jurassic carbonates mozduran formation sarakhs area iran abstract diverse skeletal and non skeletal grains with abundant red and blue green calcareous algae evaporites and early diagenetic dolomites in the mozduran carbonates are similar to those of modern warm water shallow marine carbonates isopachous and fibrous intragranular sparry calcite cements resemble modern aragonite morphologies concentric and radial ooids are like modern aragonitic forms which are formed in turbulent and in low energy environments respectively deformed ooids shattered micritic envelopes and spalled ooids indicate aragonite dissolution during meteoric diagenesis meteoric cements are equant mosaic to drusy calcites burial cements only occur as vein fillings sr and na covariance with mn supports evidence of inversion of aragonite to calcite with subsequent open phreatic diagenesis fe concentrations are a magnitude higher than mn due to a reducing phreatic environment high sr na ratios suggest original aragonite mineralogy the 18 o and 13 c field of mozduran limestone lies at the edge of the modern shallow marine field indicating a range from marine to meteoric cements differences in 18 o values between marine calcites and meteoric derived calcites is similar to that in the modern tropics the surface marine diagenetic trend line that passes through shallow marine modern whole carbonates cuts the mozduran limestone isotope field due to their formation in warm shallow marine waters given that atmospheric co 2 levels were similar to those at present increasing mn and fe values decreasing na and uniform sr values with increasingly lighter values of both 18 o and 13 c are exlained by extensive meteoric diagenesis the least altered marine calcite 18 o value of 2 6 pdb corresponds to 29 or 24 c depending on whether 0 of present seawater and 1 2 of ancient seawater with no ice caps are taken as a base an original calcite mineralogy postulated for some jurassic limestones is related to a non tropical origin

secular variation of calcium carbonate mineralogy an evaluation of ooid and micrite chemistries three ooid types are recognized from the lower tournaisian kohlenkalk shelf facies at velbert germany ooids from this unit have a predominantly concentric laminae fabric radial concentric and small radial fibrous ooids are minor components to this oolite the diagenetic response of kohlenkalk ooid chemistry is significantly different from that observed in contemporaneous crinoid and brachiopod material fabric evidence suggests that radial concentric and radial fibrous ooids were probably originally aragonite high mg calcite and high mg calcite respectively fabric and trace elemental chemistries of the concentric fabric ooids suggests that they were originally precipitated as aragonite and subsequently altered to low mg calcite

ooid cortical stratigraphy reveals common histories of individual co occurring sedimentary grains ooids are a common type of carbonate sand grain that form through a combination of constructive and destructive mechanisms growth via precipitation and diminution via physical abrasion because growth and abrasion obey distinct morphometric rules we developed an approach to quantitatively constrain the history of growth and abrasion of individual ooid grains using the record of evolving particle shape preserved by their cortical layers we designed a model to simulate 10 possible growth abrasion histories for each pair of cortical layer bounding surfaces in an individual ooid estimates for the durations of growth and abrasion of each cortical layer were obtained by identifying the simulated history that best fit the observed particle shape we applied this approach to thin sections of modern lacustrine ooids collected from several locations in the great salt lake gsl ut to assess the spatial and temporal variability of environmental conditions from the perspective of individual grains within a single deposit we found that gsl ooids do not all share the same histories clustering ooid histories by a frechet distance metric revealed commonalities between grains found together locally within a deposit but distinct differences between subpopulations shared among localities across the gsl these results support the tacit view that carbonate sedimentary grains found together in the environment do reflect a common history of sediment transport this general approach to invert ooid cortical stratigraphy can be applied to characterize environmental variability over 1 000 year timescales in both marine and lacustrine ooid grainstones of any geologic age

ooid cortices composed of neomorphic pseudospar possible evidence for ancient originally aragonitic ooids cortices of ooids in a bed in the upper part of the bangor limestone upper mississippian in northwestern georgia are composed of neomorphic pseudospar which is mostly in a mosaic pattern but also occurs as single crystals in crystallographic continuity with nuclei consisting of echinoderm fragments locally common are single crystals of neomorphic spar which are shared by cortices of adjoining ooids a void filling origin for the calcite in the ooid cortices is ruled out for the most part because of good preservation of concentric structure in the ooids the tentative conclusion is drawn that the cortices of the ooids originated as aragonite and that echinoderm fragments where present as nuclei of ooids or as uncoated grains adjacent to ooids strongly influenced the crystallographic orientation of neomorphic calcite in the cortices

the precambrian cambrian boundary seawater chemistry ocean circulation and nutrient supply in metazoan evolution extinction and biomineralization this paper reviews the evidence for changes in the global environment from the late precambrian into the cambrian against which the evolution of many metazoan groups and the development of biomineralization should be seen with higher carbon dioxide levels precambrian seawater was more supersaturated with respect to caco 3 than phanerozoic seawater and carbonates were precipitated easily from the late precambrian to the early cambrian there was a decrease in the mg ca ratio and an increase in the a co 2 of seawater changes in global climate icehouse to greenhouse and increased plate tectonic activity resulted in major changes in ocean circulation and nutrient levels a rise in global temperature and the formation of extensive shallow seas the vendian cambrian radiation events and onset of biomineralization must have been strongly influenced if not driven by these global environmental changes

a comparative study of frequency ratio weights of evidence and logistic regression methods for landslide susceptibility mapping sultan mountains sw turkey abstract this study evaluated and compared landslide susceptibility maps produced with three different methods frequency ratio weights of evidence and logistic regression by using validation datasets the field surveys performed as part of this investigation mapped the locations of 90 landslides that had been identified in the sultan mountains of south western turkey the landslide influence parameters used for this study are geology relative permeability land use land cover precipitation elevation slope aspect total curvature plan curvature profile curvature wetness index stream power index sediment transportation capacity index distance to drainage distance to fault drainage density fault density and spring density maps the relationships between landslide distributions and these parameters were analysed using the three methods and the results of these methods were then used to calculate the landslide susceptibility of the entire study area the accuracy of the final landslide susceptibility maps was evaluated based on the landslides observed during the fieldwork and the accuracy of the models was evaluated by calculating each model s relative operating characteristic curve the predictive capability of each model was determined from the area under the relative operating characteristic curve and the areas under the curves obtained using the frequency ratio logistic regression and weights of evidence methods are 0 976 0 952 and 0 937 respectively these results indicate that the frequency ratio and weights of evidence models are relatively good estimators of landslide susceptibility in the study area specifically the results of the correlation analysis show a high correlation between the frequency ratio and weights of evidence results and the frequency ratio and logistic regression methods exhibit correlation coefficients of 0 771 and 0 727 respectively the frequency ratio model is simple and its input calculation and output processes are easily understood the interpretations of the susceptibility map reveal that geology slope steepness slope aspect and elevation played major roles in landslide occurrence and distribution in the sultan mountains the landslide susceptibility maps produced from this study could therefore assist planners and engineers during development and land use planning

lower triassic oolites of the nanpanjiang basin south china facies architecture giant ooids and diagenesis implications for hydrocarbon reservoirs lower triassic platforms in the nanpanjiang basin contain extensive oolites interior oolites are stacked in meter scale cycles arranged into larger coarsening upward sequences oolites thicken toward margins to include grainstones up to 50 m 164 ft thick and contain giant ooids up to 1 cm 0 4 in and composite coated grains cross bedding ripples and abraded ooids indicate deposition in high energy shoals apparent layer cake correlation across interiors indicates amalgamation of shoals thinner interior lenses represent spillover lobes ooids are interpreted to have originally been bimineralic with cortices of radial or micritic fabrics high magnesium calcite alternating with coarse pseudospar or brickwork originally aragonite distorted ooids formed by brittle compaction of micritic cortices around voids are interpreted to have been dissolved aragonite abundant potential nuclei indicate that limited supply was not a factor contributing to the large ooid size high energy and abnormally high seawater caco3 saturation are interpreted to be causes of the giant ooids most previous reports of giant ooids come from the neoproterozoic a period of increasing surface water oxygenation and high caco3 saturation caused by a minimal skeletal carbonate precipitation we interpret similar seawater chemistry in the aftermath of the end permian extinction to explain the genesis of the giant ooids in the early triassic the genesis of bimineralic ooids during an early triassic period of rapidly increasing pco2 and low indicates that an increasing ca mg ratio was the primary mechanism driving the change from aragonite to calcite seas the architecture textures and diagenesis of the lower triassic oolites of the nanpanjiang basin provide useful analogs for coeval reservoirs in sichuan and the middle east

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

geometrical constraints on the evolution of ridged sea ice 1 a numerical model of the evolving draft distribution of seasonal pack ice is driven by freezing and ice field compression in one dimension spatial transects of sea ice draft acquired during winter in the beaufort sea are used to evaluate the model histograms obtained by ice profiling sonar on subsea moorings reveal changes in the draft distribution while observations of ice velocity by doppler sonar allow calculation of the strain to which the draft distribution is responding numerical diffusion in thermal ice growth is controlled using a remapping algorithm mechanical redistribution algorithms in common use generate much more deep ridged ice than is observed geometric constraints on ridge keel development that reflect the finite extent of level floes available for ridge building and the true average shape of keels produce more realistic results in the seasonal pack ice of the beaufort sea 75 of all floes are too small to provide a volume of ice sufficient to construct a keel of draft equal to that commonly assumed in ice dynamics modeling on average the distribution of draft within keels has a negative exponential form implying a cusped keel shape with more area on the thinner flanks than at the crest models commonly assume a uniform redistribution of ice into a keel of triangular shape clearly the spatial organization of ice within seasonal pack or equivalently the existence of ridges and floes should be an acknowledged factor in redistribution theory for pack ice thickness

sedimentary characteristics and origin of dolomitic ooids of the terminal ediacaran dengying formation at yulin chongqing south china abstract the ediacaran was a crucial transition period in the evolutionary history of the earth ediacaran ooids in the dengying formation from the yulin section in southwestern china are important archives of paleoenvironmental information although these ooids have been totally dolomitized the cortical fabric characteristics are locally preserved well indicating that these ooids were mimetically replaced the common occurrence of concentric radial fabrics and low level of sr concentrations 60 3 8 8 ppm in the studied ooid cortex is more likely suggestive of a primary low mg calcite mineralogy and that a calcite sea might exist during deposition of the second member of the dengying formation in situ geochemical data for the ooid cortices obtained by laser ablation inductively coupled plasma mass spectrometry show that these ooids have middle rare earth element enrichment prn smn 0 7 0 1 and smn ybn 1 5 0 4 and high fe contents 8200 1800 ppm this suggests ferruginous pore waters which were related to the selective or preferential absorption and release of rees by fe mn oxyhydroxides

carbon isotope record for the onset of the lomagundi carbon isotope excursion in the great lakes area north america carbonate units of the chocolay group in the lake superior area usa and the gordon lake formation of the correlative upper huronian supergroup ontario canada were deposited after the last paleoproterozoic glacial event and an episode of intense chemical weathering the huronian supergroup contains at the base 2 45 ga volcanics and is intruded by the 2 22 ga nipissing diabase dykes and sills while the chocolay group is bracketed in age between 2 29 and 2 20 ga the lomagundi 2 22 2 1 ga carbon isotope excursion started after the paleoproterozoic glacial epoch and before a plume breakout event at 2 22 ga therefore the chocolay and upper huronian carbonates were deposited either before or during the onset of the lomagundi event notably thin carbonates of the basal gordon lake formation and thick carbonate succession of the kona dolomite in the northeastern exposures of the chocolay group record 13 c values as high as 9 5 versus v pdb similar to other successions deposited during the lomagundi event both units contain pseudomorphs and molds after sulfates this observation suggests that seawater sulfate contents rose dramatically in association with the onset of the lomagundi event and the rise of atmospheric oxygen carbonates in the western and southern exposures of the chocolay group randville and bad river dolomites and saunders formation previously assumed to be equivalent to the gordon lake formation and kona dolomite have carbon isotope values close to 0 based on basin analysis we infer that these carbonate units were deposited during a negative carbon isotope excursion after the lomagundi event started and are slightly younger than the kona dolomite and gordon lake formation this interpretation implies that the carbonate platform in the great lakes area transgressed to the west over shallow marine and fluvial deposits the negative carbon isotope excursion in the lake superior area might correspond to similar 13 c values of the mooidraai dolomite in the griqualand west basin south africa supporting correlation between paleoproterozoic successions of north america and south africa and the notion of three global glaciations in the paleoproterozoic era carbonates of the mille lacs group trout lake glen township and denham formations in minnesota have 13 c values ranging from 1 2 to 2 5 combined with geochronologic constraints these data suggest that these units were deposited after the lomagundi excursion and are related to the rifting event that led to development of the so far unrecognized 2 0 ga passive margin in the lake superior area 2006 elsevier b v all rights reserved

petrology and diagenetic evolution of neoproterozoic ooids libby formation western montana u s a abstract radial concentric and twinned sparry ooids from the upper belt supergroup originally formed as mixed mg calcite and aragonite and aragonite textural evidence suggests that mg calcite ooids may have formed along with the ooids having an original aragonite mineralogy strontium concentrations of 2400 to 2900 ppm support an aragonitic precursor to the twinned sparry ooids and sr values of 2500 ppm strongly suggest that the radial concentric ooids had an aragonitic component in addition to the mg calcite suggested by the preserved fabric trace element mn mg fe and sr values of ooids and early carbonate cements suggest that diagenetic trends for these proterozoic carbonates are similar to those established for their phanerozoic and archean counterparts mg fe and mn increase and sr decreases with successively later carbonate phases

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

tectonic controls of phanerozoic sedimentary rock cycling the cyclic nature of the phanerozoic sedimentary rock distribution carbon sulphur coupling and material transfer among sedimentary reservoirs appears to be controlled by tectonic factors the distribution of preserved sedimentary mass in terms of rock mass remaining u geologic age shows a minimum c 300 350 ma ago which separates two subcycles of erosion and deposition of sedimentary rocks the older subcycle was interrupted because of the major continental collisions of the devonian and late carboniferous these collisions resulted in a reduction of outcrop areas of rocks of the older cycle relative to their masses leading to a decline in the probability of destruction and an increase in half life of these older sediments a strong correlation exists between the long term cyclicity in the phanerozoic global sea level curve and the distribution of carbon and sulphur among their major exogenic reservoirs this correlation is related to two principal tectonic modes of the phanerozoic oscillatory and submergent it is postulated that the submergent mode of active plate convergence obduction and subduction of sediments large ridge volume and high sea level gave rise to low erosion and sedimentation rates less restricted environments of carbonate deposition and relatively high atmospheric co 2 levels high temperatures resulting from an increased rate of production of co 2 from diagenetic and metamorphic reactions at subduction zones as sea level rose carbon was transferred from the sedimentary reservoir of reduced organic carbon to that of oxidized inorganic carbon in limestones whereas sulphur moved from the oxidized sulphate reservoir to the reduced sulphide reservoir as sea level fell reservoir transfers were opposite to those above culminating in the oscillatory mode of generally elevated continental interiors these reservoir transfers are consistent with secular changes observed in the distribution of 13 c and 34 s in sedimentary materials during the phanerozoic petrographic examination of phanerozoic oolite formations shows that ooids with preserved calcitic relict textures are characteristic of pre carboniferous carbonate rocks whereas ooids with relict textures indicative of initial aragonite mineralogy are dominant in rocks of younger age these changes in ooid mineralogy may be interpreted as reflecting changes in co 2 levels of the ocean atmosphere system consistent with the above tectonic considerations atmospheric co 2 levels were higher prior to carboniferous time favouring formation of calcitic ooids and skeletal parts after the carboniferous co 2 levels fell and aragonite and mg calcites of greater than 8 mol mg increased in abundance as precipitates

the tonian beck spring dolomite marine dolomitization in a shallow anoxic sea abstract the reason for the abundance of dolomite lithologies in earth s early geological record compared to modern environments remains contentious this study provides new insight into this precambrian dolomite problem by revisiting one of the most controversial dolomite localities the beck spring dolomite of death valley usa consistent with some previous studies petrographic evidence indicates that although the beck spring dolomite now consists almost entirely of dolomite it was originally precipitated largely as aragonite and high mg calcite depositional constituents microbialites and ooids were likely originally aragonitic and early marine length fast cements now dolomite are suggested to have precipitated as high mg calcite then replaced syntaxially by dolomite based on petrographic and geochemical evidence we suggest that marine dolomitization was the dominant synsedimentary diagenetic process in the unit and for the most part involved syntaxial and mimetic replacement further a length slow fibrous dolomite generation was precipitated during the later stages of marine diagenesis as a primary marine dolomite cement this is indicated by the length slow crystallographic structure of the cement and from its preserved geochemical and cathodoluminescence growth zonation this new evidence for tonian marine dolomite precipitation reinforces the idea of precambrian marine environmental conditions including the chemical composition of seawater promoting dolomite formation at this time the trace metal geochemical composition of well preserved marine components especially dolomite marine cements reveals information about redox conditions in this tonian shallow seawater in terms of rare earth element geochemistry the beck spring dolomite has no significant ce anomaly and a ubiquitous positive eu anomaly consistent with widespread oceanic anoxia during deposition furthermore the relatively low levels of iron and chalcophile elements co cu pb and zn in marine components compared to other neoproterozoic carbonates suggest euxinic conditions both anoxic and sulphidic prevailed during deposition of the beck spring dolomite

silicification in the belt supergroup mesoproterozoic glacier national park montana usa nodular cherts can provide a window on the original sediment composition diagenetic history and biota of their host rock because of their low susceptibility to further diagenetic alteration the majority of phanerozoic cherts formed by the intraformational redistribution of biogenic silica particularly siliceous sponge spicules radiolarian tests and diatom frustules in the absence of a biogenic silica source precambrian cherts necessarily had to have had a different origin than phanerozoic cherts the mesoproterozoic belt supergroup in glacier national park contains a variety of chert types including silicified oolites and stromatolites which have similar microtextures and paragenesis to phanerozoic cherts despite their different origins much of the silicification in the belt supergroup occurred after the onset of intergranular compaction but before the main episode of dolomitization the belt supergroup cherts probably had an opal ct precursor in the same manner as many phanerozoic cherts although it is likely that precambrian seas had higher silica concentrations than at present because of the absence of silica secreting organisms no evidence was observed that would suggest that high dissolved silica concentrations in the belt sea had a significant widespread effect on silicification the rarity of microfossils in belt supergroup cherts indicates that early silicification if it occurred was exceptional and restricted to localized environments the similarity of microtextures in cherts of different ages is evidence that the silicification process is largely controlled by host carbonate composition and dissolved silica concentration during diagenesis regardless of the source of silica

lifestyles of the palaeoproterozoic stromatolite builders in the vempalle sea cuddapah basin india abstract the distribution and changing pattern of stromatolites in the vempalle formation of the cuddapah basin india have been investigated with emphasis on external morphologies internal fabrics growth patterns and sediment associations the stromatolitic limestone occurs in a low angle ramp type carbonate platform with complete exposures from shallow shelf to basinal facies provides record of changes in reef building capacity of stromatolites with change in the depositional milieu changing pattern and style of the stromatolites clearly reflect depth partitioned growth of the microbial community small and scattered stromatolites commonly with wavy parallel laminations or stratifications occurred in inner ramp settings where they are build up to the sea level tepee structure and desiccation cracks in associated sediments and salt pseudomorphs point to shallow water to occasional exposure condition large bioherms with columnar and conical stromatolites developed in the headland mid ramp which were in continuous interaction with strong waves of the open sea growth of the bioherms changed the landform with time and generated a high sloping edge with a sheer drop that extended out into the sea forming distally steepened ramp outer ramp lithofacies characterized by thick layers of shale succession with thin beds of laterally persistent stromatolitic beds with low synoptic relief build ups these biotic components along with the absence of wave related structures place the outer ramp below the base of wave action zone ooid banks developed in the mid ramp area are in the high surfing zone high flux of nutrients and high light show positive correlation thus the high growth pattern is best observed within the photic zone where wave action is maximum the ability to change from low synoptic relief algal laminites to high synoptic relief columnar stromatolites point to their adaptive power the key factor that controlled the shape of these palaeoproterozoic stromatolites is the dynamic interactions between mat growth currents and sediment supply presence of concentric and radial fibrous ooids indicates change in climate and salinity of the sea

carbonate minerals major and minor elements and oxygen and carbon isotopes and their variation with water depth in cool temperate carbonates western tasmania australia cool temperature bryomol carbonates predominate on shallow shelves around western tasmania many samples are bored and encrusted due to the occurrence of submarine hardgrounds and to slow rates of sedimentation intragranular caco3 cementation is common tasmanian whole carbonates are mainly mixtures of high mg calcite hmc and low mg calcite lmc with minor amounts of aragonite hmc and aragonite contents decrease while lmc content increases with increasing water due to a decrease in water temperature mg concentrations in calcite correspond to temperatures of 10 c sr and na concentrations in bryozoa decrease due to calcite cementation whereas their concentrations increase with aragonite content mn and fe concentrations are higher than in warm shallow marine counterparts and increase with increasing aragonite percentage sr and na concentrations in calcite slightly increase with increasing lmc percentage due to decreasing water temperatures mn and fe values in calcite are independent of water temperature hmc percentage and hmc lmc ratios decrease while lmc percentage increases with increasingly heavier 18o values due to decreasing temperatures lmc is a marine mineral and not a product of meteoric diagenesis unusually high concentrations of sr na mn and fe in aragonite are due either to the tendency of aragonite formed in cold seas to incorporate more of these elements or to aragonite formation by transformation of metastable cold water caco3 minerals such as vaterite or hydrous calcite sr contents decrease with increasing water depth due to a decrease in aragonite and increase in low mg calcite na values increase with increasing water depth due to increasing salinity mn and fe concentrations decrease with increasing water depth due to decreasing continental terrigenous input depth related variations in mg sr na mn and fe are due to marine diagenesis and are unrelated to meteoric diagenesis 18o and 13c values are positively correlated and this isotopic field is bisected by the diagenesis trend line for upwelling water that passes through the point 1 18o 0 13c the 18o values become heavier and mg values decrease with increasing water depth due to decreasing temperatures from about 17 to 6 c for normal seawater and from 13 to 2 c for upwelling water these temperatures are lower than measured summer values because of the strong seasonal effect of surface waters influx of subantarctic water in winter and mixing of cold upwelling waters in the bottom water as carbonates in upwelling regions are in equilibrium with upwelling water having 18o values of 1 in paleotemperature determinations seawater values that are lower by 1 than those postulated for different geological periods should be considered for those carbonates suspected of being non tropical in origin on the basis of geological and geochemical evidence originally calcitic limestonesare abundant in ancient sequences and their temperatures of formation and diagenesis can be better understood by using the data base provided by this study

major minerals elemental and isotopic composition in modern temperate shelf carbonates eastern tasmania australia implications for the occurrence of extensive ancient non tropical carbonates eastern tasmanian shelf sediments range from siliciclastics mixed carbonates to pure carbonates carbonates consist mainly of skeletal bryozoa hashes with variable amounts of intragranular caco3 cement minerals detected by xrd are mainly mixtures of low to high mg calcites and quartz with variable amounts of aragonite four factors account for 95 of total variance of mineral components and elemental composition and are related to elements in carbonate fraction factor 1 positive relationship between mn and mg with latitude factor 2 to calcite types from d spacing variation factor 3 and to longitudinal i e distance from coast variation of carbonate and siliciclastic contents factor 4 factorial plots indicate residue carbonate plane with elements associated with them and that mg mn and aragonite contents and calcite d spacings are related to latitude and vary with water temperatures ca values reflect variable amounts of carbonate mg content indicates water temperatures of 10 c sr and na are positively correlated and increase with both calcite and aragonite contents and the ratio of srna is 1 unlike high ratios found in warm water carbonates mn concentrations are higher than in warm shallow marine carbonates and similar range of sr and na contents in both calcite and aragonite may be due to the formation of impure phases of caco3 the 18o and 13c values are positively correlated and tend to fall between the trend lines of seafoor diagenesis and upwelling water positive correlation between 13c and sr and na is due to both calcite and aragonite contents or due to the occurrence of vaterite the 18o values of whole sediments indicate water temperature from 14 to 8 c normal seawater or 10 4 c upwelling water these temperatures are slightly higher than those obtained from 18o of eastern tasmanian brachiopods originally calcitic ancient carbonates are abundant in stratigraphic sequences and can be better understood by comparison with modern temperature calcitic carbonates rather than with aragonitic modern tropical carbonates many of these ancient originally calcitic carbonates are of non tropical origin as coeval tropical aragonitic carbonates occur elsewhere low srna ratios and high mn contents are indicative of temperate origin heavy 13c values can be used in calculating water temperatures the non tropical carbonates form at low co2 levels in regions of upwelling waters which maintain saturation of caco3 and provide nutrients for a luxuriant growth of fauna

ooids in purbeck limestones lowermost cretaceous of the swiss and french jura ooids occurring in the shallow water purbeckian carbonate sediments of the jura mountains can be grouped into six types gradations from one type to another and coexistence of the various types are common type 1 ooids are small and well rounded they display fine concentric micritic laminae in many cases their cortices are dissolved and replaced by void filling spar microsparitic neomorphic replacement occurs locally type 2 ooids are large and have irregular shapes they show fine micritic laminae and occasional layers of fine radial crystals they commonly evolve into oncoids ooids of type 3 display many fine radial cortical laminae and are patchily micritized they are medium in size and mostly well rounded this type of ooid may pass into large irregularly shaped coated grains type 4 ooids have 1 to 4 cortical laminae with a fine radial structure and patchy micritization they are medium in size and well rounded type 5 ooids have only one lamina with a coarse radial structure they are small and well rounded associated are spherical grains containing bundles of elongate crystals ooids of type 6 show superpositions of two or more different radial and or fine micritic laminae the cortical structure may also change laterally in the same lamina the preferential dissolution of type 1 ooid cortices to form oomoulds indicates a primary composition of unstable carbonate sedimentological features and comparison with modern ooid occurrences point to formation on high energy sandbars in normal marine waters type 2 ooids grew in marine lagoonal environments with quiet water and abundant cyanobacteria the radially structured ooid cortices of types 3 4 and 5 show no dissolution features this implies that they were originally composed of stable carbonates or that an unstable carbonate phase was transformed into a stable one at an early stage of diagenesis type 3 ooids occur together with marine faunas and indicate high water energy ooids of type 4 and type 5 originated probably from relatively quiet water of variable salinity coexistence of different ooid types and mixed forms of type 6 implies gradual or rapid changes in hydrodynamic geochemical and microbiological conditions which were a feature of the purbeckian depositional environments

integrated application of geophysical methods for investigation of the al berktain archaeological site in the city of jerash jordan the application of electrical resistivity tomography ert techniques involving the wenner and schlumberger electrode configurations was conducted at the ancient site of al berktain of jerash n jordan during june 2011 it may be considered as the first archaeogeophysical survey at this site the city lived by succession of ancient cultures and still has archaeological remains e g water pools which gave it historical value and boosted the archaeological interest to make this study the objective of the work was to determine the layout dimension and the depth of expected buried structures i e water channels related to the pool structure within the site and to provide recommendations for future excavation projects the results showed high resistivity anomalies red color located within the site these anomalies were interpreted as a part of a general infrastructure of ancient man made buried channels or supporting basins draining out or feeding water to the two the water pools especially at the western and eastern sides inside the pool the main structure in the site results of the survey showed anomalous thin shallow zone interpreted as a layer limestone pavement of a thickness of 1 m the ert successfully determined the dimensions of the buried features and proved that this site was water reservoirs to serve the ancient city of jerash or irrigations purposes beside its use for leisure i e presence of the theatre roman path and the pools

monitoring landslides with geophysical and geodetic observations the objective of this study was to evaluate and predict land movement by integrating geodetic geophysical and meteorological data in a landslide area specifically electrical resistivity tomography surveying global navigation satellite system and terrestrial laser scanning techniques were integrated to monitor a landslide the study area lies to the southeast of the town of taskent in southern turkey close to balcilar in the central taurus mountain chain landslides result in considerable damage to structures farmland and the environment in this area therefore it is important to characterise the size extent and timing of past land movements in order to mitigate damage from future landslides analysis presented in this paper shows that the greatest land movements in the region occur in spring when average motions can be up to 1 5 m per month it is demonstrated that integrated techniques provide a better means for monitoring landslide processes and gathering data for predictions of future movements mapping landslide movements by integrating geophysical and geodetic observations can provide a meaningful evaluation of a landslide and its dynamics

secular variations in precambrian seawater chemistry and the timing of precambrian aragonite seas and calcite seas an extension of the seawater secular variation model that successfully predicted the observed timing of phanerozoic mgso 4 vs kcl marine evaporites and aragonite seas vs calcite seas has been applied to the prediction of the secular variations in the major ion chemistry of seawater and aragonite seas vs calcite seas during the precambrian testing of the predictions was based on those precambrian seafloor carbonate precipitates that have been interpreted by others to have formed originally as aragonite of 16 examples of precambrian seafloor aragonite 14 fall within the 6 periods of aragonite seas predicted for the late archean proterozoic by the model 1 falls on the transition between an aragonite sea and calcite sea and 1 falls in a period of calcite seas this strong correlation supports the following predictions of the model 1 precambrian seawater was a saline nacl water with ca hco 3 since at least the late archean 2 the major ion compositions of precambrian seawater chemistry and their secular variations are in the same ranges as those of phanerozoic seawater 3 the mg ca mole ratio in seawater has controlled the types of caco 3 polymorphs that have precipitated from earth9s oceans throughout the phanerozoic and most if not all of the precambrian

calcitic aragonitic and mixed calcitic aragonitic ooids from the mid proterozoic belt supergroup montana a great variety of ooid types occurs within the siyeh and snowslip formations of the mid proterozoic belt supergroup montana cortical layers are inferred to have been composed either of calcite in a radial concentric or radial with dark rays fabric or aragonite in a radial or concentric fabric the calcitic cortical layers record their original fabrics but the originally aragonitic cortical layers have been replaced by calcite in a range of textures and by quartz and dolomite some formerly aragonitic cortical layers are replaced by calcite spar which contains relics of the original cortical structure others consist of calcite spar without inclusions or columnar calcite which grew radially from the nucleus commonly a calcitic ooid some ooids were wholly composed of calcite others were of aragonite but two phase ooids were common mostly consisting of an inner calcitic part and an outer aragonitic part probable microdolomite inclusions suggest a high mg content of the calcitic cortical layers the depositional environment of these oolites was probably analogous to baffin bay texas where a similar range of ooid types is forming today

using global positioning system techniques in landslide monitoring the precise determination of point coordinates with conventional global positioning system gps techniques often required observation times of one to several hours in the last few years new gps methods have been developed among them the fast static and real time kinematic with higher productivity and good theoretical precision the main objective of this paper is to ascertain the performance of these methods in landslide monitoring practice we present first of all the basic principles of the gps the equipment and working procedures we discuss afterwards the applicability of the gps to the monitoring of landslide surface displacements compared with the classical surveying methods the gps allows a larger coverage and productivity with similar accuracy furthermore it can work in all kinds of weather conditions and a direct line of sight between stations is not required finally we present an example of the performance of the gps equipment in the landslide of vallcebre eastern pyrenees spain this landslide has been periodically monitored since 1987 with terrestrial photogrammetry and geodetic measurements theodolite electronic distance metres edm the movement extends over an area of 0 8 km2 and has experienced displacements as large as 1 6 m during the period 1996 1997 14 campaigns over a period of 26 months using both static and kinematic gps methods have been carried out the gps measurements have been compared with the results obtained with the edm inclinometers and wire extensometers and checked against fixed stable points the precision achieved with the gps measurements is 12 to 16 mm in the horizontal plane and 18 to 24 mm in elevation 2000 elsevier science b v all rights reserved