sedimentological effects of a moving terrain to investigate the sedimentologic effects of changing rheology and boundary conditions on lithospheri cflexure due to thrust loading the following simple linear models for flexure have been examined the infinite elastic plate to represent thrusting on the craton the semi infinite plate to represent thrusting near a plate boundary and the infinite viscoelastic plate to consider simple time dependent effects these models make the following sedimentological predictions 1 periodic thrust motion on the infinite and semi infinite elastic plates produces periodic regressions and transgressions on the orogenward and cratonward side of the basin respectively 2 periodic thrust motion on a viscoelastic plate with a small relaxation constant produces out of phrase transgressions and regressions on both sides of the basin and 3 for a given set of flexural parameters the flexure size for these models in order of decreasing amplitude are the semi infinite elastic plate the infinite viscoelastic plate

high resolution sequence stratigraphy of lower paleozoic sheet sandstones in central north america the role of special conditions of cratonic interiors in development of stratal architecture well known difficulties in applying sequence stratigraphic concepts to deposits that accumulated across slowly subsiding cratonic interior regions have limited our ability to interpret the history of continental scale tectonism oceanographic dynamics of epeiric seas and eustasy we used a multi disciplinary approach to construct a high resolution stratigraphic framework for lower paleozoic strata in the cratonic interior of north america within this framework these strata proved readily amenable to modern sequence stratigraphic techniques that were formulated based on successions along passive margins and in foreland basins settings markedly different from the cratonic interior parasequences parasequence stacking patterns systems tracts maximum flooding intervals and sequence bounding unconformities can be confidently recognized in the cratonic interior using mostly standard criteria for identification the similarity of cratonic interior and foreland basin successions in size geometry constituent facies and local stacking patterns of nearshore parasequences is especially striking this similarity indicates that the fundamental processes that establish shoreface morphology and determine the stratal expression of retreat and progradation were likewise generally the same despite marked differences in tectonism physiography and bathymetry between the two settings our results do not support the widespread perception that paleozoic cratonic interior successions are so anomalous in stratal geometries and constitute such a poor record of time that they are poorly suited for modern sequence stratigraphic analyses the particular arrangement of stratal elements in the cratonic interior succession we studied is no more anomalous or enigmatic than the variability in architecture that sets all sedimentary successions apart from one another thus paleozoic strata of the cratonic interior are most appropriately considered as a package that belongs in a continuum of variable stratigraphic packages reflecting variable controls such as subsidence and shelf physiography special conditions of exceptionally slow subsidence rate shallow bathymetry and nearly flat regional shelf gradient are manifest mostly by the presence of individual systems tracts of relatively long duration that extend for much greater distances across depositional strike than those that characterize successions deposited in more dynamic tectonic and physiographic settings these results suggest that if other cratonic interior successions are as anomalous as reported a low sediment supply may have played a primary role in development of their apparently condensed stratal architecture the results also lead us to suggest that a nonvegetated lower paleozoic landscape played a relatively insignificant role in the development of what are commonly perceived to be enigmatic stratigraphic features of sheet sandstones particularly their widespread yet thin geometry and a scarcity of shale and siltstone

worldwide review of seals for major accumulations of natural gas abstract about 62 of the caprock seals for the world s 176 giant gas fields are shales and about 38 are evaporites these two lithologies make up essentially all of the caprock for the 2 650 tcf of gas expected to be recovered from these fields caprock thickness data is lacking from many fields but 20 to several hundred meters are typical optimal conditions for seal preservation occur in areas which had a comparatively simple geologic evolution complex fold belts and overthrust belts are commonly subject to seal destruction of the world s 25 largest gas fields 21 are in cratonic settings and four in fold belts those in fold belts have evaporite seals lateral continuity of caprock has a favorable impact on the retention of gas over large areas such as the arabian platform gas hydrate accumulations illustrate both seal and reservoir seal destruction is caused by changes in the phase equilibrium considerable multidisciplinary research still needs to be done to quantify knowledge of seal prediction for giant gas fields end of article last page 933

carbonate deposition in mixed siliciclastic carbonate environments on top of an orogenic wedge late cretaceous northern calcareous alps austria abstract in the middle turonian to lower campanian lower gosau subgroup lgs of the northern calcareous alps austria in the highstand systems tract of mixed siliciclastic carbonate depositional sequences small carbonate shelves locally developed that were mainly controlled by a differentiated morphology of the substratum and siliciclastic input onto a storm dominated shelf the lgs was deposited above thrust nappes of the alpine orogen the transgressive systems tracts of depositional sequences consist of local fan delta or fluvial deposits overlain by a succession mainly of siliciclastics that records deepening from paralic to outer shelf environments locally rudist biostromes and coral rudist mounds accumulated in lagoonal bay to inner shelf environments but were buried by paralic siliciclastics along coastal sectors of low siliciclastic input because of a high relief truncation surface at the base of the lgs the transgressive systems tracts consist of an upward deepening succession of clastic carbonates deposited from gravelly to rocky carbonate shores the highstand systems tracts are dominated by siliciclastics and record shoaling to inner shelf depths and near the basin margins to lagoonal to marsh environments during highstand conditions delta progradation combined with shoreline compartmentalization by headlands locally led to establishment of inner shelf compartments of low siliciclastic input in these compartments carbonate shelves developed along strike the carbonate shelves were up to more than 10 km in length beyond limits of larger outcrops and about 1 km to possibly 10 km wide down dip the carbonate shelves consisted of a an inner shelf belt with coral rudist mounds rudist biostromes and bioclastic sand bodies b a dissipative shore zone of bioclastic sand bodies c open lagoons bays with radiolitid biostromes and d narrow micro tidal flats or lithoclastic bioclastic beaches up section inner shelf to shore zone carbonate parasequence tracts consist of a coral rudist mound a rudist biostrome and of shore zone bioclastic limestones parasequence tracts deposited in lagoons bays commonly shoaled incompletely and mainly consist of more or less marly limestones deposited in shallow subtidal environments with radiolitid biostromes substrata of bioclastic sand or lime mud and with local mass accumulations of gastropods or of epibenthic non rudist bivalves the carbonate shelf successions are up to 100 m thick and in vertical section consist of stacked parasequence tracts that become thinner up section and record a shoaling of mean depositional water depth carbonate deposition was confined to the actual inner shelf to tidal flat beach compartment down dip the coral rudist mounds scattered along the seaward fringe of the carbonate shelves graded into small haloes composed mainly of disoriented fragmented rudists and corals larger carbonate slope depositional systems were not individuated and the carbonate shelves interfingered with and pinched out into inner shelf siliciclastics the development of larger carbonate slopes was prevented by the low relief of the coral rudist mounds combined with high input and effective dispersal of siliciclastics ahead carbonate shelf progradation over a possible distance of up to a few kilometres was linked with aggradation of shelf siliciclastics

investigation about rainfall induced shallow landslides in cyl and twr watersheds taiwan landslides identified from aerial photos and satellite images between 1988 and 2009 in chenyulan cyl and tsengwen reservoir twr watersheds in taiwan were investigated these watersheds have similar area but different percentage of landslide area due to their own watershed characteristics and extreme triggers earthquakes and typhoons the chi chi earthquake in 1999 increased about 3 of landslide area in cyl had obvious influence on rainfall induced landslides in subsequent 5 years while the typhoon morakot in 2009 increased 2 53 of landslide area in twr the incremental landslide area by rainfalls especially brought by typhoons indicates that the rainfall induced shallow landslide depends not only on the rainfall amount but also on intensity two quadratic equations of the percentage of incremental landslide areas in terms of the rainfall erosivity factor that is composed of rainfall amount and intensity were developed the number and size of landslides caused typhoon morakot in cyl and twr were different but they followed a similar power law frequency area distribution extreme triggers play the most important roles in the evolution of landslides in these watersheds

the 2001 adana landslide and its destructive effects turkey the current study deals with a catastrophic landslide that occurred due to heavy rainfall in adana southern turkey in 2001 the research area which is one of the largest populated districts in adana and one of the most tropical places between the middle east and southern europe has about 25 000 people on the basis of geological and geotechnical surveys the landslide phenomena and the effects of landslide are examined to understand the slide mechanism of the landslide ground reconnaissance laboratory and in situ tests are conducted it is observed that the clayey and silty layers of the site are heavily saturated due to extreme rainfall in winter and consequently sheared the landslide consists of a block sliding in the upper portions and a debris flow soil flow component around the margins of the sliding blocks in the middle parts and at the toe although there was no loss of human life it has caused significant economic losses besides it is determined that if precautions are not taken around the landslide area larger landslides could definitely occur in the future

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

dolomitization induced aquifer heterogeneity evidence from the upper floridan aquifer southwest florida large variations in artesian flow and specific capacity encountered during the installation and testing of a well field completed in the upper floridan aquifer in collier county florida are related to differences in dolomite abundance among wells the wells produce primarily from some thin intervals of fractured crystalline and microsucrosic dolomite that have limited areal extent as evidenced by a strong boundary effect detected during an aquifer performance test microfacies and stable isotopic composition 1 8 o 1 39 1 57 1 3 c 0 15 1 70 peedee belemnite pdb indicate that the dolomite formed by the replacement of marine limestone in marine or brackish pore waters dolomite fracturing is likely related to folding that occurred no earlier than the late miocene the upper floridan aquifer behaves as a large scale dual porosity system in that the dolomite intervals with high hydraulic conductivities increase the specific capacities of some wells the dolomite intervals have little effect on the total volume of water that can be produced from the aquifer which is controlled by the surrounding lower hydraulic conductivity limestone the results of this interdisciplinary investigation reveal the high degree of heterogeneity and unpredictability that may occur in carbonate aquifers as the result of diagenesis because of uncertainty over fluid flow paths heterogeneities in aquifer hydraulics related to diagenesis may greatly impact projects requiring recovery of a specific volume of water such as pump and treat remediation and aquifer storage and recovery systems

carbon isotope stratigraphy of the upper kharaib and shuaiba formations implications for the early cretaceous evolution of the arabian gulf region the carbon isotope profiles of shallow marine carbonates from the barremian aptian kharaib and shuaiba formations of the arabian gulf region range between 0 5 and 7 pmil dgr13c pdb peedee belemnite systematic variations can be correlated with isotope profiles reported from tethyan pelagic limestone sequences the detailed correspondence between the isotopic signature of the relatively well dated pelagic limestones and the poorly dated shallow water limestones from the arabian gulf region suggests that global marine carbon isotope changes apparently affected deep sea and shallow water carbonate sediments similarly and at a similar time resolution although oxygen isotopes have been reset during diagenesis carbon isotopes appear to have maintained their primary marine signature through time no evidence has been found to connect carbon isotope trends to subaerial exposure or later meteoric diagenesis in combination with other data the investigated carbon isotope profiles can be used for basin to platform and regional correlations beyond the current resolution of biostratigraphy in shallow water limestones carbon isotope stratigraphy confirms significant hiatuses in the investigated shallow water carbonate sequences using carbon isotope trends as a proxy for sea level fluctuations the carbon isotope cycles of the late early cretaceous of the arabian gulf region may represent four cycles of rising and falling sea level with a duration corresponding to that of third order sea level fluctuations regional correlations derived from isotope trends provide a scenario for the larger scale stratigraphic evolution of the arabian peninsula during the end of the early cretaceous differential rates of aggradation between realms influenced by siliciclastics and those characterized by siliciclastic poor clean carbonate deposition apparently caused the development of a pronounced basin platform topography during the early aptian shuaiba intrashelf basin and platform

a model for carbonate to terrigenous clastic sequences the development of carbonate sequences that grade toward a source region into terrigenous clastic sediment is poorly understood in both carbonate and terrigenous clastic regimes environments of rapid sedimentation have comparable rates of deposition 102 to 102 5 cm 1 000 yr slowest continuous rates are also comparable 100 5 to 101 cm 1 000 yr because of the inhibiting effect of terrigenous deposition on carbonate skeletal production the slowest rates in a transect tend to occur where mixed lithologies are deposited midway between coarse clastic and pure carbonate sediments this leads to a bimodal distribution of rapid depositional rates and invariably to the development of a basin in the intervening area to develop a model we combine concepts of depositional rate with knowledge of the middle ordovician carbonate to terrigenous clastic sequence of the southern appalachians deposition began on a shallow water ramp sloping gently eastward but everywhere within the photic zone an episode of tectonic subsidence differentiated this ramp into a shallow shelf on the northwest and a deep starved basin on the southeast separated by a linear shelf margin with organic build ups subsequent development of the sequence consisted of the filling of the deep basin first with pelagites then with turbidites during which the carbonate shelf was isolated from terrigenous deposition once the basin filled terrigenous deposition began to affect the shelf inhibition of carbonate deposition near the shelf edge led to formation of successively smaller basins within the old shelf area after the initial pulse of tectonic subsidence deposition of the sequence can be explained by sediment loading subsidence thus the ordovician sequence coupled with the concept of bimodal distribution of sedimentation rates in carbonate to terrigenous clastic facies patterns allows development of a model for basins adjacent to active tectonic lands five model stages are derived by application of calculated deposition rates and sediment loading along a transect away from the terrigenous source these stages are 1 an initial carbonate ramp stage followed by 2 a carbonate shelf starved deep basin stage 3 a carbonate shelf turbidite basin terrigenous shelf stage 4 a carbonate shelf narrowed and shallowed basin broad terrigenous shelf stage and finally 5 a stage in which the initial basin is filled a subsequent starved basin forms on the old carbonate shelf and a new carbonate shelf margin forms a few to tens of kilometres farther from the terrigenous source the model should be useful in predicting depositional facies in analogous basins

supply and removal of sediment in a landslide dominated mountain belt central range taiwan abstract a strong coupling between hillslope and valley systems is often inferred for mountain landscapes dominated by bedrock landsliding we reveal the nature of this link using data sets on landsliding and sediment transport from two montane catchments draining the eastern central range of taiwan here the magnitude frequency distribution of landslides can be modeled by a robust power law but this scale invariance is not mirrored in the sediment discharge at the mountain front instead downstream sediment loads reflect a complex response to both sediment supply and ambient hydraulic conditions the rivers do not transport significant amounts of sediment unless it is provided by hillslope mass wasting in the catchment removal of landslide debris is a function of the transport capacity of the stream at the site of entry thus there is a dual supply and transport control on sediment loads in bedrock floored streams over a monitoring period of 25 yr the bulk of the sediment leaving the mountain bel

polygonal faults and their implications for hydrocarbon reservoirs in the southern qiongdongnan basin south china sea the polygonal faults were identified in qiongdongnan basin south china sea by using the technique of time coherent slice and horizon flattening of high resolution 3d seismic data these polygonal faults occur in three tiers of the upper meishan formation and the huangliu formation the faults have lengths of 150 1500 m spacings of 50 3000 m throws of 10 40 m and dips of 50 90 degrees tectonic evolution in the qiongdongnan basin can be divided into a rifted stage and a post rifted stage tectonic faults are widely distributed in the rifted sequences but are not well developed in the post rifted stage few faults in the post rifted sequences might suggest the absence of a migration pathway for hydrocarbon or other fluids however the existence of polygonal faults in the post rifted sequences can serve as the pathway and promote the hydrocarbon migration and accumulation in the qiongdongnan basin during the post rifted stage c 2010 elsevier ltd all rights reserved

climate change and the episodicity of sediment flux of small california rivers abstract we studied the streamflow and sediment flux characteristics of the 20 largest streams entering the pacific ocean along the central and southern california coast extending for 750 km from monterey bay to just south of the u s mexico border drainage basins ranged in area from 120 to 10 800 km2 with headwater elevations ranging from 460 to 3770 m annual streamflow ranged from 0 to a maximum of documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape 1 times 10 9 end document m3 yr for the santa clara river in 1969 with a

triterpane and sterane biomarkers in the ya13 1 condensates from qiongdongnan basin south china sea triterpanes and steranes in condensates from the ya13 1 gas field qiongdongnan basin were monitored the ya13 1 condensates have unusual biomarker distributions dominated by terpanes and steranes derived from higher plants anomalously abundant 1 got oleanane and remarkably abundant bicadinanes are present in the ya13 1 condensates whereas the 17alpha hopane contents are extremely low taraxastane and significantly abundant 17alpha diahopanes occur in the condensates in addition a number of unknown c 29 and c 30 pentacyclic triterpanes including previously unreported compounds were detected in the condensates some of which are significantly abundant the unknown compounds may be terrestrial biomarkers c 29 homologues are relatively predominant among the regular and rearranged steranes the diasterane concentrations are markedly higher than those of regular steranes the maturity of the ya13 1 condensates is relatively high at the peak to late oil generation stage corresponding to 0 85 1 10 ro based on sterane and terpane and including bicadinane maturity parameters i e t t 1 r and 2t r bicadinane ratios the above maturity assessment result is different from that based on diamondoid maturity parameters ro 1 60 1 70 org geochem 25 1996 179 which can be explained by a contribution of hydrocarbons from two sources at different depths the ya13 1 condensates were probably generated from the yacheng and lingshui coal bearing source rocks buried both in the qiongdongnan basin 3400 5000 m and in the yinggehai basin 5000 m the possible contribution of lower maturity hydrocarbons from the yacheng and lingshui formations 3400 4100 m in the qiongdongnan basin to the ya13 1 gases and condensates should not be neglected c 2003 elsevier science b v all rights reserved

complex accumulation and leakage of yc21 1 gas bearing structure in yanan sag qiongdongnan basin south china sea abstract yc21 1 is a gas bearing structure found within the yanan sag in the qiongdongnan basin south china sea while the structure bears many geological similarities to the nearby yc13 1 gas field it nevertheless does not contain commercially viable gas volumes the main reservoirs of the yc21 1 structure contain high overpressures which is greatly different from those of the yc13 1 structure the pressure coefficients from drillstem tests wireline formation tests and mud weights are above 2 1 based on well log analysis illite content and vitrinite reflectance data of mudstones in well yc21 1 2 combining with tectonic and sedimentation characteristics the timing and causes of overpressure generation are here interpreted the results indicate the existence of two overpressure segments in the yc21 1 structure the first overpressure segment resides mainly within the lower and the middle intervals of the yinggehai formation and is interpreted to have been mainly caused by clay diagenesis while disequilibrium compaction and hydrocarbon generation may also have contributed to overpressure generation the second overpressure segment comprising the sanya formation pressure transition zone and the lingshui and yacheng formations hard overpressure zone is interpreted to owe its presence to kerogen to gas cracking according to petrography homogenization temperature and salinity of fluid inclusions two stages of oil gas charge occurred within the main reservoirs on the basis of overpressure causes and oil gas charge history combining with restored tectonic evolution and fluid inclusion characteristics a complex accumulation and leakage process in the yc21 1 gas bearing structure has been interpreted collective evidence suggests that the first oil charge occurred in the middle miocene circa 16 3 11 2 ma small amount of oil generation and absence of caprocks led to the failure of oil accumulation rapid subsidence in the pliocene and quaternary gave rise to a sharp increase in geotemperature over a short period of time leading to prolific gas generation through pyrolysis and consequently overpressure within the main reservoirs the second overpressure segment during this period the second gas charge occurred in the pliocene and quaternary circa 4 5 0 4 ma the natural gas migrated in several phases consisting of free and water soluble phases in a high pressure environment large amounts of free gas are considered to have been consumed due to dissolution within formation water in highly pressured conditions water soluble gas could not accumulate in high point of structure when the pore fluid pressures in main reservoirs reached the fracture pressure of formation free gas could leak via opened fractures within cracked caprocks a repeated fracturing of caprocks may have consumed natural gas stored in formation water and have made water soluble gas unsaturated therefore the two factors including caprocks fracturing and dissolution of formation water are interpreted to be mainly responsible for the failure of natural gas accumulation in the yc21 1 structure

shallow groundwater response to rainfall on a forested headwater catchment in northern coastal california implications of topography rainfall and throughfall intensities on peak pressure head generation the pore water pressure head that builds in the soil during storms is a critical factor for the prediction of potential slope instability we report findings from a 3 year study of pressure head in 83 piezometers distributed within a 13 ha forested catchment on the northern coast of california the study s primary objective was to observe the seasonal and storm based dynamics of pressure head at a catchment scale in relation to observed rainfall characteristics and in situ topography to better understand landscape patterns of pressure head an additional goal was to determine the influence of the interaction between rainfall and forest canopy in altering delivery of water and pressure head during the large storms necessary to induce landsliding we found that pressure head was highly variable in space and time at the catchment scale pore pressures peaked close to maximum rainfall intensity during the largest storms measured the difference between rainfall and throughfall delivered through the canopy was negligible during the critical landslide producing peak rainfall periods pore pressure was spatially variable within the catchment and did not strongly correlate with surficial topographic features only 23 of the piezometers located in a variety of slope positions were found to be highly responsive to rainfall topographic index statistically explained peak pressure head at responsive locations during common storms but not during the larger storms with potential to produce landslides drainage efficiency throughout the catchment increased significantly in storms exceeding 2 to 7 months peak pressure head return period indicated by slowing or cessation of the rate of increase of pressure head with increasing storm magnitude this asymptotic piezometric pattern persisted through the largest storm measured during the study faster soil drainage suppressed pressure head response in larger storms with important process implications for pore pressure development and landslide hazard modelling copyright 2012 john wiley sons ltd

overpressure retardation of organic matter maturation and petroleum generation a case study from the yinggehai and qiongdongnan basins south china sea three superimposed pressure systems developed in the yinggehai basin south china sea as indicated by seismic data well logs and direct pressure measurements the organic maturation profile is nonlinear with three nonparallel segments that correspond to the shallow normal pressured system the intermediate overpressured system and the deep strongly overpressured system respectively the intermediate and deep overpressured systems have abnormally low r0 gradients the organic maturity of these overpressured rocks is significantly lower than the maturity of normal pressured source rocks in nearby wells with similar thermal histories and does not match the thermal histories of the rocks such an organic maturity anomaly is distinctly different from those aused by variation in activation energies conductivity contrasts and hydrologic effects and is confirmed to be the result of overpressure retardation the degree to which the organic matter maturation is retarded expressed as the difference between predicted and measured vitrinite reflectance increases exponentially with increasing fluid pressure confirming that pressure increases the activation energies of organic matter maturation reactions overpressure retardation has been proven to be conditional and quite important for clearly understanding petroleum generation migration and accumulation in overpressured sedimentary basins

late cretaceous early tertiary sedimentation in a semi arid foreland basin neuquen basin western argentina abstract a late cretaceous transgression and a subsequent paleocene regression is recorded in the neuquen basin of western argentina in the sediments of the upper malargue group seven facies associations d through j representing different depositional subenvironments have been recognized in the younger depositional sequence facies association e green calcareous mudstones was deposited in the outer shelf facies association f bioclastic carbonates represents inner shelf deposits to littoral sediments facies association g sandy calcarenites corresponds to nearshore to coastal deposits facies association h oolitic calcarenites and facies association d evaporites composed a shallowing upward carbonate sequence facies association i cross bedded lithic sandstones and facies association j red mudstones are characterized as meandering fluvial deposits the lateral and vertical distribution of facies association changes from north to south in the basin according to several depositional controls the foreland setting of the neuquen basin at this time with different sediment input and paleoslopes on the retro arc vs the cratonic side of the basin influenced sedimentation basin embayment geometry caused differences in tidal regime which in turn affected depositional environments westerly winds generated clockwise tidal currents inside the basin which affected alongshore lateral facies association variation the semi arid climate favoured deposition of mixed carbonate siliciclastic lithologies and evaporites

the importance of earthquake induced landslides to long term slope erosion and slope failure hazards in seismically active regions abstract this paper describes a general method for determining the amount of earthquake induced landsliding that occurs in a seismically active region over time this determination can be used as a quantitative measure of the long term hazard from seismically triggered landslides as well as a measure of the importance of this process to regional slope erosion rates and landscape evolution the method uses data from historical earthquakes to relate total volume of landslide material dislodged by an earthquake to the magnitude m and seismic moment m0 of the earthquake from worldwide data a linear regression relation between landslide volume v and m0 is determined as v m0 1018 9 0 13 where v is measured in m3 and m0 is in dyn cm to determine the amount of earthquake generated landsliding over time this relation is combined with data on seismic moment release for a particular region which may be derived from either earthquake history or fault slip data the form of the m0 v relation allows the rate of production of earthquake induced landslides over time to be determined from total rate of seismic moment release without regard to the distribution of individual events thus simplifying and generalizing the determination application of the method to twelve seismically active regions with areas ranging from 13 275 to 2 308 000 km2 shows that erosion rates from earthquake induced landslides vary significantly from region to region of the regions studied the highest rates were determined for the island of hawaii new zealand western new guinea and the san francisco bay region of california significantly lower rates were determined for iran tibet the sierra nevada great basin region of california and central japan for the time period from 715 ad to the present intermediate rates were determined for peru southern california onshore california turkey and central japan for the time period from 1586 ad to the present to determine the relative long term importance of seismically triggered landslides these erosion rates are compared to erosion rates calculated for other slope processes and to rates calculated from fluvial sediment discharge comparisons with other slope processes indicate that earthquake induced landslides are the predominant agents of slope erosion on the island of hawaii in the san francisco bay region and in western new guinea for hawaii the san francisco bay region and sierra nevada great basin region of california the erosion rates calculated for earthquake induced landslides also exceed the regional erosion rates calculated from fluvial sediment discharge

the cap rocks sealing the reservoir in the weglowka oil field sub silesian unit polish outer carpathians petrographical approach the weglowka oil field is located in the outer carpathians the outer carpathians are a region where hydrocarbons were discovered and exploited at the end of the nineteenth century in several dozen oil fields which are relatively small the weglowka oil field is one of the largest in this region in the 150 yr or so of hydrocarbon exploration in the area more than 1 million t 1 237 000 tons 8 841 000 bbl of oil have been produced hydrocarbons are concentrated in lower cretaceous sandstones grodziszcze and lgota sandstones that form an anticline sealed by upper cretaceous marls called the weglowka marls these cap rocks are up to 600 m 2000 ft thick because of the thrust related exhumation they were exposed at the surface and represent the youngest deposits in the region the present work is focused on a detailed petrographic characterization of the weglowka marls this study allows petroleum geologists to better understand the evolution of porosity in these cap rocks and can serve as a foundation for the prediction of their sealing properties the marls appear as a succession of interbedded red and green varieties which occur in up to 2 m 6 ft thick beds these beds are nonarenaceous soft and bioturbated grain size corresponds to approximately 80 clay and less than 20 silt fractions x ray diffraction xrd reveals that the marls contain on average 54 clay 28 calcite 16 quartz up to 3 feldspars and in red marls 3 hematite the xrd patterns of clay are typical of mixed layer illite smectite i s 40 illite in i s the clay structures are dioctahedral with similar octahedral mg and relatively high fe3 contents both in the red and green intervals as revealed by standard petrography combined with high resolution petrography performed through the use of a field emission scanning electron microscope the marls have mudstone textures according to dunham s 1962 classification and are mostly composed of coccoliths and clay with rare nanoquartz this rock may be considered an impure chalk sealing properties of the weglowka marls are indicated by the specific surface area porosity pore size and permeability calculated using n2 gas adsorption helium and mercury porosimetry the sealing potential is postulated to result from a combination of the following 1 origin of components i e deposition of minute calcareous bioclasts and volcanic material as a source for clay 2 oxygenated sedimentary environment as a result of the presence of oxygen in the sediments burrowing caused the rocks to be homogenized and 3 tectonic induced clogging of pore space because of reorganization of clay flakes the rocks were strongly tectonically deformed which resulted in reduction of porosity in clay aggregates

effects of diagenesis and clays on compressional velocities in rocks experimental results at ultrasonic frequencies in brine or water saturated samples cut perpendicular to bedding demonstrate that compressional velocities vary linearly with porosity and volume fraction clay in detrital silicate rocks characterized by pores with low aspect ratios p wave velocity is more sensitive to porosity than clay content obeying the empirically derived expression vp 2 4c 8 6 5 8 at 800 bars confining pressure and 400 bars pore pressure where the units of vp are kilometers per second is the volume fraction pores and c is the volume fraction clay deviations from this equation are less than 2 with the exception of the high pore aspect ratio st peter sandstone which has a compressional velocity that is 17 higher than the predicted value the equation is insensitive to the chemical compostion of the dominant clay mineral and apparently insensitive to the location of the clay grains with respect to the mineral framework e g in free pore space or in contact zones between mineral grains of lower compressibilities

discussion of landslide self organized criticality and the initiation of debris flow the study contains descriptions of landslides and debris flows in a small upland catchment in taiwan between 1986 and 2004 this catchment the chushui creek is situated near the epicentre of the 1999 m7 6 chi chi earthquake this is an area with high background erosion rate the chi chi earthquake caused a sharp increase in the rate of mass wasting in the epicentral area and the data presented in this study illustrates the geomorphic change associated with the earthquake the measurements of the geometry of the trunk stream of the chushui catchment also show its change due to the impact of a strong typhoon in 1996 two channel reaches that were affected by separate debris flows during this event were identified each reach has three sections scour transfer and deposition cross profiles of these sections show a systematic change from v shaped bedrock channel in the scour areas to flat floored channel in the transfer and deposition areas debris flows also occurred on other occasions in this channel and their frequency has increased since the 1999 earthquake in addition this study contains precise geographic and statistical descriptions of the landslides triggered by three typhoons and an earthquake that affected the catchment since 1996 the total landslide area is measured for different time intervals and a marked increase in landslide incidence is found after the 1999 earthquake frequency area plots of the 126 landslides in the catchment indicate a power law scaling with an exponent of about 1 5 of these quantities as has been observed in other studies we propose that a link exists between landslide frequency area distributions and initialization of debris flow in the catchment it may be classified as a self organized criticality process with a critical frequency area distribution for the landslide population in this case the landslide frequency area distribution is useful in quantifying the severity of the trigger and the contribution of landslides to debris flow copyright 2006 john wiley sons ltd

the role of material properties and landscape morphology on landslide size distributions abstract it has been observed that landslide size distribution shows power law scaling for large landslide areas with a roll over for landslides below a certain threshold which frequently coincides with the modal peak of the distribution the physical reasons leading to this distribution are not yet fully understood the analysis of non cumulative size distribution of two landslide inventories in the italian alps confirms the existence of a power law scaling with exponent of 2 56 0 02 and demonstrates that the roll over is not due to under sampling since it occurs at landslide sizes significantly larger than mapping resolution the control of topography on landslide size distribution is investigated by a topographic analysis using the virtual tiling method we observe a power law scaling of topography with a roll over for finer scales which is comparable with that of landslide size distribution the control of material properties on landslide size and geometry is examined through deterministic and probabilistic 2d limit equilibrium slope stability analyses incoherent materials favour shallow landslides with no limitation in size cohesive materials favour deep landslides and show a limitation for small sizes multilayered materials with depth dependent strength show a limitation for both small and large landslides the joint probability of 1 the probability that a slope with a given size and slope gradient is unstable i e failure probability from probabilistic stability analysis and 2 the probability that a slope with a given size and slope gradient exists topographic analysis allows to build synthetic size distributions which show both power law scaling and roll over for multilayered materials we obtain a scaling exponent of the power law of 2 58 0 02 we suggest that the power law scaling in landslide size distribution results in the study area from the constraint of topography and the presence of multilayered materials or depth dependent strength the roll over is an intrinsic characteristic of the size distribution due to the contribution of cohesion to slope stability

characterization and comparison of landslide triggering in different tectonic and climatic settings 1 the spatial and temporal distributions of landslides in six catalogues are analyzed in order to better understand landslide triggering mechanisms the six landslide catalogs are new zealand yosemite california grenoble french alps val d arly french alps australia and wollongong new south wales australia landslides are clustered in time for all catalogs for new zealand yosemite australia and wollongong the frequency of landslides varies between 1 and 1000 events per day and is well fitted by a power law there is no characteristic scale for daily rates when the large rates of daily landslides are known to be rain or earthquake triggered our results suggest the same triggering may hold for the small daily rates earthquakes are found to trigger landslides for the new zealand yosemite and australia areas at distances as large as 20 times their fault lengths there is no evidence of landslides triggered by earthquakes for the three other catalogs small m 4 earthquakes have little influence on landslide triggering if any for all catalogs for new zealand yosemite val d arly australia and wollongong the number of landslides per month is significantly correlated with monthly rainfall a correlation with temperature is found only for grenoble and new zealand landslide triggering strong clustering in time and space is more important in new zealand than in grenoble probably because the forcing seismicity and climate is stronger in new zealand than in the french alps but possibly also because of a high sensitivity to landslides in new zealand we suggest that intensity of clustering in space and time can be used to assess the importance of landslide triggering and the processes responsible for triggering

far field tilting of laurentia during the ordovician and constraints on the evolution of a slab under an ancient continent during a brief period of 10 to 15 million years in the middle ordovician the michigan basin departed from its bull s eye subsidence pattern and tilted toward the east opening to the appalachian basin this tilting is observed in maps of tectonic subsidence estimated for the black river and trenton formations and extends over 300 km across the michigan basin and into eastern wisconsin contours of constant tectonic subsidence rate are approximately parallel to the inferred position of the laurentian iapetus convergent margin the distance between the inferred position of the subduction zone to the limit of tilting is approximately 1000 km three alternative models for the tilting are tested two relying on the rigidity of the continental lithosphere and a third on the viscous flow generated by a subducted slab in the first elastic model we assume the edge of the elastic plate is simply loaded from above by a fold and thrust sheet volcanic pile etc this model however cannot simultaneously satisfy the space of tectonic subsidence and subsidence rate even for lithospheres which have a rigidity of 10 28 nm in the second elastic model the laurentian continental margin descends into a trench of an eastward dipping slab that is a slab descending under the iapetus ocean this process cannot generate any significant far field displacements even for extremely rigid plates and must be rejected for the third model we use finite element solutions of a negatively buoyant slab in a viscous medium with a faulted lithosphere such slabs can easily generate not only realistic trenches on the under thrusting plate but also significantly tilt the lithosphere as much as 1000 km from the plate margin the magnitude and distribution of far field displacements depend on the age length and dip angle of the slab in contrast to the elastic models penetration of a west dipping slab beneath the continent can reproduce both the extent magnitude and rate of tectonic subsidence observed in the trenton and black river formations the observed data are best fit by an old slab 140 ma which initially descended at a moderate dip 20 30 for 10 15 m y which then steepened as the slab penetrated deeper into the mantle at the position of the previous ordovician plate margin there are narrow block faulted basins which underwent rapid subsidence 10 m y before the michigan basin tilted toward the east we propose that these earlier subsidence events were caused by the initial descent of the slab under the preexisting cambro ordovician passive margin the time lag of 10 m y may be due to the time it takes the slab to penetrate the upper mantle this result is important for understanding the time evolution of mantle convection and mechanisms for the initiation of subduction

carbonate siliciclastic facies transition and reef growth on the northeast coast of barbados west indies abstract on most of the insular shelf around barbados carbonate sediments are now accumulating from the growth of reefs the contributions of the skeletons of carbonate secreting organisms and the erosion of the pleistocene coral cap that covers six sevenths of the island however after heavy rains water laden with siliciclastic sediment eroded from the scotland district where the coral cap is breached is discharged from four main rivers onto the northeast coast insular shelf the coarse grained material is transported as bedload onto an offshore sand ramp over the shelf break into deeper water or is incorporated into adjacent beaches the fine grained sediment is directed northward along the shore within a sediment plume by the equatorial current fine sediment settling out of the plu e is deposited on a spur and groove system and reefs growing on a deeper water platform north of the sand ramp nearshore the transition from the siliciclastic sediments to carbonate sediments is located on a submerged barrier reef at the seaward margin of a shallow water platform the facies transition on the deeper water platform is gradual near the southern edge of the deeper water reefs distribution of benthic biota and the growth of reefs are controlled by a combination of siliciclastic influx and shelf floor topography the deeper water reefs grow despite the periodic blanketing by fine siliciclastic sediment settling from the sediment plume that accumulates around them

characterization of pore systems in seal rocks using nitrogen gas adsorption combined with mercury injection capillary pressure techniques abstract porous microstructure parameters of seal rock samples originating from different depths within brazilian geological formations were correlated to empirical models which predict the intrinsic permeability mercury injection capillary pressure micp and nitrogen gas adsorption n 2 ga were applied in combination as complementary techniques micp to obtain the porosity values and the size distribution of meso and macropores and n 2 ga associated with the brunauer emmett and teller bet theory to determine the specific surface area s o the barret joyner and hallenda bjh theory was applied to find the size distribution of the micro and mesopores the combination of the micp and n 2 ga curves showed that the samples analyzed present a polymodal pore size distribution psd and a total porosity ranging from 0 33 to 10 44 the s o values measured by n 2 ga were higher than those calculated by micp due to the majority of the samples having a mean pore size of 20 1000 a the intrinsic permeability could also be predicted applying the measured parameters s o psd curves and total porosity in the carman kozeny and series parallel models the ranges of permeability values obtained were 4 09 10 24 4 96 10 21 m 2 and 9 48 10 27 9 14 10 22 m 2 respectively these results were compared with values reported in the related literature and those obtained for four samples submitted to pressure pulse decay permeability pdp tests

mixed siliciclastic and carbonate sediments a proposed first order textural and compositional classification sediments that are composed of mixtures of siliciclastic and carbonate material occur in both the modern and the ancient to date there is no commonly used classification of this type of sediment a descriptive first order classification system is proposed here that is applicable to most mixed sediments and their lithified equivalents the sediments are composed of four components 1 siliciclastic sand sand sized quartz feldspar etc 2 mud mixtures of silt and clay 3 allochems carbonate grains such as peloids ooids bioclasts and intraclasts 20 m in size and carbonate mud or micrite 20 m in size these components define a tetrahedra whose subdivision produces eight general classes of mixed sediment the name of a class reflects both the dominant grain type and the most abundant antithetic component for example a rock that contains greater than 50 siliciclastic material of which most is sand sized and subordinate allochems is termed an allochemic sandstone other rock names include micritic sandstone allochemic and micritic mudstone sandy or muddy allochem limestone and sandy or muddy micrite prefixes and adjectives can be added to these terms to include dolomitic sediments conglomeratic textures and biogenic constituents

the cambro ordovician bliss formation southwestern new mexico u s a progradational sequences on a mixed siliciclastic and carbonate shelf abstract the bliss formation was deposited during the basal cambrian transgression over an undulose precambrian igneous and metamorphic terrain the strata comprising the bliss formation can be readily divided into five genetic sequences a lowermost transgressive unit and four progradational units progradation occurred both along the cratonic shoreline due to the influx of terrigenous material and also from the offshore portion of the shelf toward the craton due to the development and growth of an offshore carbonate bank the progradational sequences are separated by pronounced transgressive shifts in the depositional environment represented by thin or no strata the ideal progradational sequence begins with an essentially quartz free shallow shelf accumulation of bioturbated biosparites and biomicrites these grade upward into finely laminated dolomites which contain zones of rip up clasts and which are cut by small channel fill deposits this change represents shoaling of the subtidal site to a tidal flat environment by growth of an offshore bank the carbonates contain a greater admixture of terrigenous material upsection and grade into glaucarenites the glaucarenites become thicker bedded and thoroughly cross stratified upward accompanied by an increase in quartz grain size these glaucarenites are gradationally overlain by a thoroughly trough cross stratified very coarse to conglomeratic sandstone bedding thickness size of trough cross stratification and quartz grain size have increased and silica has become the dominant cementing agent the depositional environment shifted from the shallow shelf and offshore bank with a paucity of terrigenous material to a subtidal site of moderate energy to the turbulent surf zone with a paucity of carbonate material the topmost part of the progradational sequence is represented by trough cross stratified calcitic and hematitic coarse quartzarenites bedding thickness trough size and quartz grain size all represent a definite though minor decrease in the energy level of the depositional environment this decrease in energy level was due to the shoaling of the shelf shallow shelf carbonates essentially quartz free immediately overlie the hematitic quartzarenites indicating a marked shift in depositional environment with thin or no strata representing this transgression a decrease in the rate of sedimentation is represented by the shift from carbonates which were deposited on tidal flats on top of an offshore bank to the superjacent glaucarenites which were deposited in a shallow marine realm the increase in water depth is the result of a decrease in the rate of carbonate production and therefore accumulation due to the negative influence that the influx of fine siliciclastics had on the carbonate factory

linkage of sediment supply and transport processes in miyagawa dam catchment japan 1 linkages between sediment supply by episodic geomorphic processes obtained from aerial photographs and field surveys and sediment transport estimated from changes in sediment deposition behind a large dam were investigated in the miyagawa dam catchment central japan a total of 6667 landslides were confirmed in the period from 1965 to 2000 on the basis of seven temporal pairs of aerial photographs both the occurrence of landslides and discharge into the dam lake affect sediment yield indicating that fluvial systems in miyagawa dam catchment are supply limited with respect to sediment sediment yields are affected by not only the initial failed volume of landslides but also the mobility of landslides and debris flows in miyagawa dam catchment percentages of landslides reaching channels varied from 56 in 1997 2000 to 75 in 1976 1981 and were correlated with maximum hourly rainfall in addition the mobility of debris flows was higher during periods with high maximum instantaneous discharge compared to lower discharge suggesting that the water content both in initially failed materials and transported sediment controlled their mobility topography also affected the mobility of landslides debris flows for catchments 0 1 km2 the percentage of channel network length impacted by debris flows decreased with increasing catchment area due to reduced channel gradient thus both the magnitude of rainfall runoff events and the catchment topography affect how landslide sediment contributes to sediment yield at the large catchment scale

distribution of landslides in the upper tiber river basin central italy abstract a comprehensive analysis of the distribution of landslides was completed in the upper tiber river basin central italy landslide occurrence was ascertained through a large scale inventory obtained through air photo interpretation api and local field surveys lithological and bedding information was obtained through photo geological and field mapping aided by the review of geological maps and reports the probability density of landslide areas was found comparable to statistics obtained by investigators in other areas of the world adoption of empirical relationships to link landslide area and volume allowed estimating the total volume of landslide material in the 4098 km2 catchment in excess of 5 9 109 m3 statistics of terrain elevation and slope in stable areas were found different from those in landslide areas in particular modal terrain slope in landslide areas was less steep 11 9 than that in areas where landslides were not mapped 13 3 analysis of the landslide and slope areas revealed that a relationship exists between the size of the slope and the size of the most common landslide analysis of the spatial relationship between landslides and the geological setting revealed that slope failures are most abundant where soft and weak rocks crop out and where bedding is chaotic or disorganized where rocks are regularly bedded landslide abundance is largest in dip slopes these new findings are important to understand the long term evolution of the upper tiber river basin and may prove useful in the assessment of landslide hazard and risk

velocity porosity clay content systematics of poorly consolidated sandstones compressional velocities have been measured as a function of confining pressure for 14 west delta block louisiana sandstone cores the dry velocity data for these poorly consolidated sandstones at 10 mpa confining pressure plot on a linear velocity density trend with well consolidated sandstones but not loose sands the dry velocity data also show linear trends of decreasing velocity with increasing porosity along contours of constant clay content similar to those obtained at 40 mpa by tosaya and nur 1982 for saturated sandstones the spacing between clay contours indicates that a large portion of the velocity variation with clay content is due to microporosity which is not included in point counting within the clays the slope of the velocity porosity trends indicates that cementation increases with decreasing porosity

middle miocene mound shaped sediment packages on the slope of the xisha carbonate platforms south china sea combined result of gravity flow and bottom current deep water mound shaped sediment packages on the northern slope of the xisha carbonate platforms in the northern south china sea were analyzed by integrating high resolution multi channel seismic and drilling data the mounds are distributed in the beijiao depression of the qiongdongnan basin within the t41 t40 seismic horizons which correspond to the middle miocene mound shaped reflections were identified both in the ne sw and nw se oriented seismic profiles the mound shapes are most prominent in the center of the nw se oriented seismic profiles and the undulating tops flatten out towards the nw and se similar reflections are mostly asymmetric with steeper eastern flanks in the ne sw oriented seismic profiles and they are mostly round in shape the wave impedance from the inversion calculation is 6 8 x 10 6 kg m 2 s it is much lower than that of the reef reservoir in the lh11 1 reef oilfield paleogeographic analysis shows that the xisha uplift was dominated by tropical shallow carbonate platforms while the beijiao depression became a bathyal environment in the middle miocene drilling data confirmed that the mound shaped sediment packages are mainly composed of calcareous mudstone therefore we infer that the mound shaped sediment packages could be reef complexes or they were presumably built by combined gravity flow and bottom current c 2015 elsevier ltd all rights reserved

diffusion of methane and ethane through the reservoir cap rock implications for the timing and duration of catagenesis to maintain natural gas reserves for even short periods of geologic time there must be an influx of gas to the reservoir to balance any loss because molecular diffusion through the reservoir cap rock is generally regarded as the slowest loss mechanism the minimum influx rate necessary to maintain the reserves is the same as the diffusive loss rate fick s first law of diffusion modified with the stokes einstein relation and the archie equation provides a conservative estimate for the rate of diffusion through a porous medium such as the reservoir cap rock as an example the diffusive flux of methane and ethane through the cap rock of the mcclave field in southeastern colorado was calculated assuming a shale cap rock porosity of only 5 the entire volume of methane would have to be replaced in less than 2 3 m y and 5 3 m y for ethane to maintain the reserves using 10 porosity the replacement time falls to less than 500 000 yr for methane and 1 2 m y for ethane unless natural gas fields are short lived ephemeral phenomena there must be ongoing generation and migration of gas to the reservoir to at least balance the diffusional loss this balance requires that catagenesis be an ongoing and recent phenomenon

petrophysical analysis of the cajon pass scientific well implications for fluid flow and seismic studies in the continental crust in the framework of the cajon pass scientific drilling project in the vicinity of the san andreas fault system petrophysical analysis of the retrieved core was focused on elastic properties density porosity and permeability simultaneous study of rock mineral composition texture degree of metamorphism and fracture filling yielded a petrophysical classification of the studied rock that is convenient for the interpretation of the downhole logging data given the small percentage of the hole drilled with coring the geophysical data were used to construct a lithologic petrophysical column of the well most of the petrophysical variability seen in this column is the result of laumontite alteration of granitoids during retrograde metamorphism in the zeolite facies the intensity peaks of the alteration process are spatially confined to the oblique reverse faults 25 40 dip angles as observed in the core and borehole televiewer images accompanied by brittle deformation of the adjacent granitoids the marked drop in density velocity and elastic moduli and the noticeable increase in porosity and permeability of these altered fault zone rocks are enhanced owing to in situ stress shielding the low velocity and density and higher permeability associated with these faults makes them detectable seismic reflectors and hydrologic conduits in the upper crust by contrast based on our data analysis the matrix of the intact crystalline rock in situ is inferred to be essentially free of microcracks and interconnected channels with free water a detailed analysis of the various factors affecting the microcrack introduction into the cores retrieved from deep and superdeep holes is presented to show that a unique interpretation of in situ stresses from analysis of microcracks in cores is not possible without a better understanding of the mechanisms of crack formation

the early cretaceous platform off northwest florida controls on morphologic development of carbonate margins abstract an analysis of approximately 3500 km of multifold and 1000 km of singlefold seismic reflection data correlated with two exploration wells and other available geologic information records the morphologic development of the early cretaceous carbonate platform margin off northwest florida early cretaceous depositional patterns apparently controlled the concurrent formation of gently dipping declivities 10 carbonate platform margin slopes in the vicinity of desoto canyon northeastern gulf of mexico we suggest that the pronounced along strike change in morphology reflects variations in platform width input of terrestrial clastics and overall sediment availability to the platform s seaward margin slope southeast of the canyon the early cretaceous slope bordered a relatively broad platform removed from terrigenous sediment input environmental conditions favored the uninterrupted development of skeletal and nonskeletal buildups along the paleo shelf edge which effectively prevented large quantities of shelf derived clastic sediments from moving seaward consequently as the carbonate platform grew and its height increased the declivity of its seaward slope also increased as predicted by models of long term carbonate platform development in contrast northwest of the canyon the slope bordered a narrower platform adjacent to a source of terrigenous clastics more vigorous cross platform transport of clastics and resultant adverse environmental conditions at the paleo shelf edge inhibited consistent development of carbonate buildups thereby creating only an intermittent sediment barrier to the adjacent slope resultant higher sedimentation rates on the slope caused it to aggrade and prograde along with the carbonate platform allowing the margin slope to maintain its gentle morphology throughout the early cretaceous

numerical modeling of percolating flow path in a caprock formation during aquifer pressurization and its implication for co2 sequestration spatial distribution of sand bodies in caprock is important to its sealing potential in the evaluation of a potential waste disposal site a numerical investigation was conducted to investigate the roles of sand bodies in caprock integrity and a new leaking mechanism associated with the embedded sand bodies has been identified for the first time this numerical model is characterized by a low proportion of sand bodies in caprock formation and stochastic permeability assignments to the shale facies with a consideration of stress sensitive permeability the research revealed that sand bodies in caprock even initially unconnected due to their low concentration represent the foundation for creating a percolating flow path if certain conditions are met these conditions include a relatively high pore pressure gradient across the caprock which may occur during fluid injection and a favorable geometric configuration of these sand bodies sand bodies of different shapes play different roles in forming a percolating flow path sand bars dykes can lead pore pressure front to cover a considerable vertical thickness quickly while thin sand sheets tend to transfer the pore pressure front across a large horizontal range and thus increase the possibility of involving other local sand bodies in the evolution of percolating flow paths on the other hand the presence of percolating flow path in caprock can limit the pore pressure increase in the aquifer formation during fluid injection the more active the flow paths the less increase the pore pressure that occurs in the aquifer stress dependent permeability can facilitate the formation of percolating flow path but evaluating how much impact it may have remains a question for future research the modeling results indicate that the underlying geologically based discrete structure of permeable domains even when masked by a low permeable rock matrix exerts a significant influence on the location and magnitude of fluid flow within the system during fluid injection

role of diffusion in primary migration of hydrocarbons the following effective diffusion coefficients d cm2 sec were determined for the diffusion of light hydrocarbons through the water saturated pore space of shales methane 2 12 10 6 ethane 1 11 10 6 propane 5 55 10 7 iso butane 3 75 10 7 n butane 3 01 10 7 n pentane 1 57 10 7 n hexane 8 20 10 8 n heptane 4 31 10 8 and n decane 6 08 10 9 on the basis of these new data a deterministic dynamic model was set up to simulate the diffusive transport of light hydrocarbons c1 to c10 from source rocks for eight documented source rock units representing a wid range of geologic conditions maturities of 0 40 to 1 35 mean vitrinite reflectance oil to gas prone kerogens the cumulative amounts of hydrocarbons escaping with time were calculated thus it was shown that diffusion represents an effective process for primary migration of gas but not for oil the rate of mass transport for gas from source rocks with geologic time can be sufficiently high to account for the origin of commercial size gas fields for example a cumulative amount of 109 kg of methane 1 5 109 std m3 or 5 3 1010 scf has escaped by diffusion in 540 000 years from a certain volume 1 000 km2 by 200 m thick of a high mature gas prone mesozoic source rock in western canada the origin of hydrocarbon accumulations with high gas to oil ratios in low mature sediments in geologically young basins early gases and condensates can be explained by an early phase of primary migration predominantly based on diffusion during the initial stages of the accumulation history of those fields extending up to millions of years under certain conditions the reservoir gas changes with geologic time from a methane rich to a wet gas composition at low maturity levels below about 0 6 rm even oil prone source rocks yield methane rich light hydrocarbon mixtures by migration through diffusion compositional trends among reservoir gases of several multiple pay gas fields in louisiana represent evidence for diffusive transport of hydrocarbons the variation in gas composition between the individual pay zones is controlled by increasing distances of diffusive transport of the hydrocarbons from a uniform source rock at depth to their present accumulation sites in the shallow pay zones compounds of high diffusivity are enriched for example in the sligo gas field of louisiana the methane ethane and the iso butane n butane ratios increase from 10 2 to 36 0 and from 0 86 to 1 13 respectively from the deepest to the shallowest of the five productive reservoir sands which are spread over a a depth interval of 5 500 ft 1 676 m diffusion of light hydrocarbons in the subsurface can also have economically adverse effects for example existing gas accumulations can be destroyed by dissipation the rate of this destruction was calculated for the harlingen gas field holland by diffusive loss through 400 m of shale cap rock the initial amount of methane in place of 1 93 109 std m3 6 8 1010 scf is reduced by one half over a period of 4 5 million years this leads us to propose the concept that large gas accumulations can persist through extended periods of geologic time only as dynamic systems reaching some kind of steady state equilibrium between diffusive loss through the cap rock and continuous replenishment from the source rock

coeval versus reciprocal mixed carbonate siliciclastic deposition middle devonian baltic basin eastern europe implications from the regional tectonic development the middle devonian narva succession in the baltic basin represents a significant turnaround in the history of the basin the detailed study of core and outcrop sections and the three dimensional correlations across the baltic basin reveal a carbonate dominated mixed retrogressive succession overlain by a siliciclastic dominated progradational succession the palaeogeographic reconstructions show how the shallow tide influenced basin expanded from south west to north east and later during the transgression also to the north south and east the transgressive portion of the basin fill is dominated by carbonate rich sabkha and supratidal to intertidal deposits on the basin margins and subtidal carbonates in the basin centre siliciclastic material was derived by tidal currents and storm waves from the south west through a tidal inlet and flood tidal delta complex this initial transgressive phase is characterized by the lack of subsidence or even episodic uplifts in the northern north western part of the basin margin shown by convergence of timelines and the thin 30 m transgressive succession in contrast on the southern margin the facies associations stack vertically into a 70 to 80 m thick succession indicating significantly higher subsidence rates the upper part of the transgressive phase indicates subsidence across the whole basin the upper progradational portion of the basin fill is dominated by coarse siliciclastic tide influenced deltaic deposits that rapidly prograded from north west to south east this detailed study on the narva succession shows that siliciclastic and carbonate deposition was coeval and that mixing occurred at different temporal and spatial scales the mixing was controlled by grain size volume and location of siliciclastic input rather than relative sea level changes as suggested in widely used reciprocal mixing models it is suggested that the forebulge of the scandinavian caledonian fold and thrust belt migrated to the north western margin of the baltic basin during the earliest eifelian as indicated by the lack of subsidence and probable uplift in the northern north western margin during the early transgressive phase the forebulge migration ceased although the forebulge had already started to subside during the later stages of the transgressive phase the deltaic progradation is interpreted to be associated with the orogenic collapse and uplift in the scandinavian caledonides that caused the erosion of the foreland basin fill and the coarse sediment transport into the baltic basin

stability analyses of rainfall induced landslides the slope stability issues concerning rainfall induced slope failures are investigated and presented specifically the effect of both negative and positive pore water pressures on the stability of initially unsaturated slopes are carefully explained and coupled with infinite slope analysis methods in order to present a predictive formulation of slope failures that occur as a result of rainfall events the formulation serves as a baseline analysis method for evaluating potentially unstable soil slopes that are subject to surface infiltration and explains the various triggering mechanisms that may occur based on individual combinations of the slope geometry soil strength and infiltration parameters a procedural method is outlined for utilizing the analytical formulation to predict the change in the factor of safety for a slope subject to infiltration and a detailed analysis of a case study is presented to verify the method quantitative statements are made concerning the time and depth of failure in relationship to the soil slope and rainfall parameters

the relationship of rainfall energy with landslides and sediment delivery abstract in tropical mountainous areas typhoon induced rainstorms trigger extensive landslides and deliver huge amounts of sediment to river basins two mountainous catchments in central taiwan with 0 8 13 5 of their catchment areas disturbed by landsliding induced by a series of typhoons were selected for the purpose of quantifying the impact of typhoon induced rainfall kinetic energy on landslides and sediment transport during 1994 2008 distribution analysis of the rainfall kinetic energy required to trigger landslides revealed the threshold at which rainfall kinetic energy ek induces landslides in the mountainous catchments of central taiwan to be approximately 2000 j m 2 the present study demonstrates that higher rainfall kinetic energy causes more sediment to be delivered to rivers and finds a positive relationship between ek and sediment transfer during typhoon periods we postulate that real time monitoring of rainstorms can be used to predict the impact of typhoon events by applying the threshold of rainfall kinetic energy needed to trigger landslides and transport of huge amounts of sediment

impacts of the chi chi earthquake on subsequent rainfall induced landslides in central taiwan abstract the influence of the chi chi earthquake on subsequent rainfall induced landslides was evaluated by comparing the occurrence of landslides in the choushui river watershed through eight spot images that covered the period from 1996 to 2001 the chi chi earthquake not only triggered serious coseismic landslides itself but also extensively disturbed surface strata around the epicentral area after surface strata have been highly disturbed heavy rainfalls in 2000 and 2001 have triggered more landslides than the earthquake itself compared with the data obtained from images before the earthquake it is obvious that the density of rainfall induced landslides increased significantly after the earthquake and the places where landslides occurred changed as well although typhoon herb in 1996 brought more precipitation than typhoon toraji in 2001 only 9 77 km 2 landslides were induced by herb while 48 8 km 2 landslides almost five times larger than those caused by herb were triggered by toraji besides landslides induced by herb were mainly distributed in mid slope areas with slopes of 20 30 after the chi chi earthquake the rainfall induced landslides occurred mainly in places with slopes between 40 and 50

bedrock fracturing threshold hillslopes and limits to the magnitude of bedrock landslides abstract bedrock fracturing and rock strength are widely believed to influence landscape morphology and erosional resistance yet understanding of the quantitative relationship between rock mass strength and landscape evolution remains limited here we present a new application of seismic refraction surveys that uses variations in seismic velocity to interpret differences in bedrock fracture density with depth we use a comparative study of fiordland and the western southern alps of new zealand to examine how differences in rock type and bedrock fracturing influence landscape morphology and landslide response to rock uplift in both regions slopes appear invariant with differential rock uplift rates and slope distributions reveal modal hillslope angles of 32 the majority of landslides initiate on slopes steeper than the modal hillslope angle however landslide magnitude frequency distributions reveal order of magnitude differences between the regions with fiordland experiencing considerably smaller and less frequent landsliding events landslide driven denudation rates of 9 mm yr in the western southern alps and between 0 1 and 0 3 mm yr in fiordland approximate estimates of long term rock uplift rates for each region the invariance of hillslope angles near normal slope distributions predominance of landslide initiation on slopes steeper than modal values and the apparent balance between rates of uplift and landslide driven erosion suggest that hillslopes in both regions are at threshold angles their similar modal slopes further suggest that both ranges are characterized by equivalent rock mass strength despite striking differences in lithology additionally our seismic analysis reveals nearly identical surface p wave velocities the unexpected equivalence of both modal slopes and surface velocities between these lithologically distinct ranges is attributed to contrasting degrees of surface fracturing that have differentially affected the intact rock properties such that they now yield equivalent surface velocities and hillslope scale strengths given that surface fractures help regulate threshold angles by modulating hillslope strength we propose that shallow seismic velocities may provide a quantitative proxy for rock mass strength we define two contrasting fracture and landsliding environments in fiordland dense geomorphic fracturing that is focused within the shallow subsurface appears to limit the depth and magnitude of most bedrock landslides conversely in the western southern alps tectonic forces produce pervasive fracturing with depth that results in larger and deeper landslides our data suggest that bedrock fracturing at the earth s surface modulates threshold hillslope angles whereas the depth of bedrock fracturing influences the magnitude and frequency of landslide response to tectonic rock uplift

effects of porosity and clay content on wave velocities in sandstones the ultrasonic compressional vp and shear vs velocities and first arrival peak amplitude ap were measured as functions of differential pressure to 50 mpa and to a state of saturation on 75 different sandstone samples with porosities ranging from 2 to 30 percent and volume clay content c ranging from 0 to 50 percent respectively both vp and vs were found to correlate linearly with porosity and clay content in shaly sandstones at confining pressure of 40 mpa and pore pressure of 1 0 mpa the best least squares fits to the velocity data are vp km s 5 59 6 93 2 18c and vs km s 3 52 4 91 1 89c deviations from these equations are less than 3 percent and 5 percent for vp and vs respectively the velocities of clean sandstones are significantly higher than those predicted by the above linear fits about 7 percent for vp and 11 percent for vs which indicates that a very small amount of clay 1 or a few percent of volume fraction significantly reduces the elastic moduli of sandstones for shaly

sequence stratigraphy of a carbonate evaporite succession zechstein 1 hessian basin germany the evaporitic hessian zechstein basin is a sub basin of the southern zechstein basin situated at its southern margin twelve facies groups were identified in the zechstein limestone and lower werra anhydrite in order to better understand the sequence stratigraphic evolution of this sub basin which contains economically important potassium salts four different paleogeographic depositional areas were recognized based on the regional distribution of facies siliciclastic carbonate carbonate carbonate evaporite and evaporite shallowing upward successions are developed these allow the establishment of parasequences and sequences as well as correlation throughout the hessian basin and into the southern zechstein basin two depositional sequences are distinguished zechstein sequence 1 and zechstein sequence 2 the former comprises the succession from the variscan basement up to the lowermost part of the werra anhydrite including the kupferschiefer as part of the transgressive systems tract the highstand systems tract is defined by the zechstein limestone in which two parasequences are developed in large parts of the hessian basin zechstein sequence 1 is capped by a karstic subaerial exposure surface interpreted as recording a type 1 sequence boundary that formed during a distinct brine level fall low lying central areas central hessian sub basin werra sub basin however were not exposed and show a correlative conformity topography was minimal at the end of sequence 1 widely developed perilittoral sabkha and salina shallowing upward successions indicate a renewed rise of brine level interpreted as a transgressive systems tract because of inflow of preconcentrated brines from the southern zechstein basin to the north this marks the initiation of zechstein sequence 2 which comprises most of the lower werra anhydrite in the central hessian sub basin situated proximal to the brine inflow and on the ridges within the hessian basin physico chemical conditions were well suited for sulphate precipitation to form a thick cyclic succession it consists of four parasequences that completely filled the increased accommodation space in contrast only minor sulphate accumulation occurred in the werra sub basin situated further southwards and distal to the inflow as a result of substantially different sulphate precipitation rates during increased accommodation water depth in the region became more variable the werra sub basin characterized by very low sedimentation rates became increasingly deeper through time trapping dense halite brines and precipitating rock salt deposits werra halite this self organization model for an evaporitic basin in which depositional relief evolves with sedimentation and relief is filled by evaporite thereafter contradicts earlier interpretations that call upon the existence of a tectonic depression in the werra area which controlled sedimentation from the beginning of the zechstein

sediment flux from a mountain belt derived by landslide mapping in humid uplands landsliding is the dominant mass wasting process in the western southern alps of new zealand landslides are scale invariant and have a power law magnitude frequency distribution independent studies from other regions suggest that this is a general property of landsliding this observation is of critical importance to the evaluation of the impact of events of different length scales over different time intervals on landscape evolution it is particularly useful when estimating regional geomorphic rates because it constrains the frequency and overall significance of extreme events which cannot otherwise be evaluated by integrating the complete response of the system we estimate the regional denudation rate due to landsliding to be 9 4 mm yr 1 sediment discharge from the western southern alps is dominated by landslide derived material

the simulation of the sedimentary fill of basins an interactive computer simulation which erects models of sedimentary geometries by filling in a two dimensional basin from both sides with a combination of clastic sediment and or in situ and transported carbonate sediments is described the simulation program is implemented in c using graphical plotting functions data entry including the initial basin configuration the local tectonic behavior the sea level curves the amount and source direction of clastic sediment and the growth rates of carbonates as a function of water depth is performed interactively geometries of clastic and carbonate sediments evolve through time and respond to tectonic movement eustasy and sedimentation clastic modeling includes sedimentary bypass and erosion and sedimentation in alluvial and coastal plains marine shelf basin slope and basin floor settings carbonate modeling includes progradation the development of hard grounds downslope aprons keep up catch up back step and drowned reef settings as well as lagoonal and epeiric settings also included in the model are extensional vertical faulting of the basin sediment compaction and isostatic response to sediment loading sediment geometries are plotted on a graphics terminal as they are computed so the user can immediately view the results based on these observations parameters can be changed and the program rerun until the user is satisfied with the resultant geometry this paper includes output showing the simulation s sensitivity to eustatic sea level variations and variations in sedimentation and subsidence rates also shown are outputs demonstrating the modeling of some examples from the geologic section in the permian basin of west texas and the upper permian of the sichuan basin

ordovician collision of the argentine precordillera with gondwana independent of laurentian taconic orogeny abstract the argentine precordillera a rifted fragment of laurentian crust and sedimentary cover collided with gondwana in middle ordovician time the time of collision ocloyic orogeny is similar to that of the taconic orogeny of eastern laurentia three hypotheses have been proposed to explain ordovician docking of the precordillera with western gondwana a the precordillera microcontinent was rifted from laurentia in cambrian time and following solitary drift collided with gondwana independent of the laurentian taconic orogeny b a continent continent collision of laurentia with gondwana producing a continuous taconic ocloyic orogenic belt was followed by rifting that left the precordillera attached to gondwana and c the precordillera at the tip of a distal plateau on greatly stretched laurentian crust collided with gondwana and subsequently separated from laurentia contrasts in several aspects of taconic and ocloyic orogenic history provide for discrimination between the microcontinent and continent continent collision hypotheses stratigraphic gradients and lithologic assemblages within the synorogenic clastic wedges are incompatible with a single continuous orogenic belt which in palinspastic location places the thin fine grained southern fringe of the taconic clastic wedge adjacent to the thickest and coarsest part of the ocloyic clastic wedge separate temporal and spatial distribution patterns of volcanic ash bentonite beds in laurentia and the precordillera indicate originally separate dispersal systems late ordovician hirnantian gondwanan glacial deposits in the precordillera indicate substantial latitudinal separation from laurentia post collision faults with large vertical separation in the precordillera have no coeval counterparts on the laurentian foreland these contrasts indicate originally separate not initially continuous and subsequently dismembered orogenic belts favoring the microcontinent hypothesis and eliminating the continent continent collision hypothesis initial taconic tectonic loading near the southern corner of the alabama promontory of laurentia and the lack of post taconic extension there are inconsistent with the tectonic history required by the plateau hypothesis but are consistent with the tectonic history required by the microcontinent hypothesis paleobiogeography distribution of bentonite beds and the hirnantian glacial deposits all indicate wide separation iapetus ocean between the precordillera and southern laurentia at the time of the ocloyic and taconic orogenies further favoring the microcontinent hypothesis

landslide volumes and landslide mobilization rates in umbria central italy abstract a catalogue of 677 landslides of the slide type was selected from a global database of geometrical measurements of individual landslides including landslide area al and volume vl the measurements were used to establish an empirical relationship to link al in m2 to vl in m3 the relationship takes the form of a power law with a scaling exponent 1 450 covers eight orders of magnitude of al and twelve orders of magnitude of vl and is in general agreement with existing relationships published in the literature the reduced scatter of the experiential data around the dependency line and the fact that the considered landslides occurred in multiple physiographic and climatic environments and were caused by different triggers indicate that the relationship between vl and al is largely independent of the physiographical setting the new relationship was used to determine the volume of individual landslides of the slide type in the collazzone area central italy a 78 9 km2 area for which a multi temporal landslide inventory covering the 69 year period from 1937 to 2005 is available in the observation period the total volume of landslide material was vlt 4 78 107 m3 corresponding to an average rate of landslide mobilization l 8 8 mm yr 1 exploiting the temporal information in the landslide inventory the volume of material produced during different periods by new and reactivated landslides was singled out the wet period from 1937 to 1941 was recognized as an episode of accelerated landslide production during this 5 year period approximately 45 of the total landslide material inventoried in the collazzone area was produced corresponding to an average rate of landslide mobilization l 54 mm yr 1 six times higher than the long term rate the volume of landslide material in an event or period was used as a proxy for the magnitude of the event or period defined as the logarithm base 10 of the total landslide volume produced during the event or period with this respect the new relationship to link al and vl is a starting point for the adoption of a quantitative process based landslide magnitude scale for landslide events

geophysical properties of cap rocks in qiongdongnan basin south china sea abstract based on measured petrophysical properties and statistical methods relationship between petrophysical properties and well log and seismic parameters are established empirically to evaluate the quality of cap rocks in qiongdongnan basin good cap rocks show high density and low sonic travel time four zones can be divided vertically according to displacement pressures in qiongdongnan basin best seal quality is found in the depth range of 2000 4000 m the ya 13 1 structure has excellent cap rock which contributes to its abundant gas accumulation

denudation processes and rates in the transverse ranges southern california erosional response of a transitional landscape to external and anthropogenic forcing 1 quantification of denudation in the transverse ranges of california permits reconstruction of spatial and temporal variations in erosion that represent both the response and evolution of interacting hillslopes and channels on the southern front of the san gabriel mountains observational records of the infilling of debris basins and dams define twentieth century landscape erosion rates averaging 1 6 and 0 9 mm yr 1 respectively although all major sediment transport occurs during intense winter storms debris production on hillslopes is greatly enhanced by recurrent fires consequently in this populated region anthropogenic fires have augmented the natural erosion rates we perform a global inversion to estimate the role of precipitation intensity burned areas and local slope on catchment denudation rates after subtracting the effects of anthropogenic fires we estimate landscape denudation rates given natural fire ignition rates increased fire during the past century has augmented sediment production in debris basins by an average of 60 and individual basins show increases up to 400 to identify the dominant hillslope erosion processes the volumetric contribution of landslides was estimated using repeat aerial photographs for the same time interval over which the debris basins have been operative between 1928 and 1973 landsliding produced only 10 of the sediment in debris basins even in the long term when infrequent but volumetrically important landslides occur bedrock landslides appear to contribute a maximum of 50 to the long term landscape denudation previous mapping of soil slippage in the san dimas experimental forest within the san gabriel mountains rice et al 1969 rice and foggin 1971 indicates that shallow landsliding is likely to be the dominant modern hillslope erosion process when compared to incision rates derived from a fluvial shear stress model and to exhumation rates based on low temperature thermochronological data blythe et al 2000 modern natural erosion rates are comparable to denudation rates since the pliocene comparisons of modern erosion rates suggest that debris production on hillslopes and first order channels is directly dependent on vegetation cover and precipitation intensity for higher order channels drainage areas 2 km2 only major storms convey the sediments down valley during the past century some temporal decorrelation occurs between small scale and large scale catchments because hillslope produced sediment is stored in second order and higher channels until major storms mobilize it thus the larger fluvial network damps the episodic fire induced hillslope sediment pulses that occur within small watersheds at a longer temporal scale however uplift and denudation may have been sustained sufficiently long in much of the san gabriel mountains for the topography to reach a macroscale steady state in contrast to rapidly eroding 2 mm yr 1 ranges for which quantification of bedrock landsliding will approximate the sediment flux the san gabriel mountains occupy a niche of intermediate rates 0 1 1 0 mm yr 1 in which a broad suite of hillslope processes including shallow seated and deep seated landslides debris flows and wet and dry ravel contribute to the sediment flux

earthquake triggered increase in sediment delivery from an active mountain belt in tectonically active mountain belts earthquake triggered landslides deliver large amounts of sediment to rivers we quantify the geomorphic impact of the 1999 mw 7 6 chi chi earthquake in taiwan which triggered 20 000 landslides coseismic weakening of substrate material caused increased landsliding during subsequent typhoons most coseismic landslides remained confined to hillslopes downslope transport of sediment into the channel network occurred during later storms the sequential processes have led to a factor of four increase in unit sediment concentration in rivers draining the epicentral area and increased the magnitude and frequency of hyperpycnal sediment delivery to the ocean four years after the earthquake rates of hillslope mass wasting remain elevated in the epicentral area

power law correlations of landslide areas in central italy abstract we have studied the frequency area statistics of landslides in central italy we consider two data sets data set a contains 16 809 landslide areas in the umbria marche area of central italy they represent a reconnaissance inventory of very old old and recent modern landslides the noncumulative frequency area distribution of these landslides correlates well with a power law relation exponent 2 5 over the range 0 03 km 2 a l 2 data set b contains 4233 landslides that were triggered by a sudden change in temperature on 1 january 1997 resulting in extensive melting of snow cover an inventory of these snow melt triggered landslides was obtained from aerial photographs taken 3 months after the event these landslides also correlate well with a power law relation with exponent 2 5 over the range 0 001 km 2 a l 2 we show that the correlation of data set b is essentially identical to the correlation of 11 000 landslides triggered by the 17 january 1994 northridge california earthquake we attribute a rollover for small landslides in data set a to incompleteness of the record due to erosion and other processes and to limitations in the reconnaissance mapping technique used to complete the inventory on the other hand we conclude that rollovers for small landslides in data set b and the california earthquake data are real and are associated with the surface morphology we conclude that the power law distribution is valid over a wide range of landslide areas and discuss possible reasons we also discuss the contribution of the snow melt and earthquake triggered landslide events to the total landslide inventory

influence of pre existing plate margin structures on foredeep filling insights from the taconian blountian clastic wedge southeastern usa break up of continents gives rise to conjugate margins with irregular shapes and with thermal histories and sedimentary records that differ along strike these elements need to be considered in the integrated study of a foreland basin orogenic belt pair that formed during subsequent contractional events this paper relates the promontory and embayment configuration of southeastern laurentia north american craton to 1 along strike variations in width of the initial depositional profile of the middle to upper ordovician taconian blountian foredeep 2 northeastward toward the embayment along strike thickening and migration of siliciclastic depocenters in the foredeep that favored the resumption of carbonate ramp deposition on the promontory during the late ordovician and 3 variation in intensity of deformation of intrabasinal structures as recorded by reactivation of across strike structures located on the transition zone between the promontory and embayment geometry and composition of the blountian foreland strata indicate that the foredeep slope was narrower and steeper on the alabama promontory than on the southwestern flank of the tennessee embayment differential slope geometries were accommodated by reactivation of transverse basement faults which controlled local conglomerate deposition in deep water settings on the transition zone between the promontory and embayment in contrast conglomerate beds at the top of coarsening upward successions on the southwestern flank of the tennessee embayment record the cratonward progradation of deltaic depositional systems the results presented here may have relevance to other peripheral foreland basins formed over rifted continental margins or retro arc foreland basins formed adjacent to inverted intracratonic rifts

upper cretaceous muti formation transition of a mesozoic nate platform to a foreland basin in the oman mountains the upper cretaceous turonian campanian muti formation sayja member documents the transition from a passive continental margin to a foreland basin related to overthrusting of continental margin and ophiolitic nappes derived from the tethys ocean upper cretaceous northeastward subduction culminated in collision of a trench with the arabian margin as the trench docked with the margin the lithosphere was flexed forming a peripheral bulge that migrated cratonward with time the platform edge was initially uplifted turonian and deeply eroded creating the wasia aruma break after passage of the peripheral bulge subsidence began with accumulation first of ferruginous crusts on hardgrounds lime muds were then deposited on a deepening unstable sea floor along with phosphatic nodules and crusts turonian coniacian passage of the overthrust load over the arabian continental margin edge downflexed the lithosphere santonian campanian resulting in drastic foundering of the old shelf edge to form a foredeep upper platform horizons collapsed as slump sheets and debris flows limestone blocks and lithoclastic debris flows were shed by mass wasting of the already deeply eroded old platform edge mud and silt were derived from the uplifted arabian continent and deposited by mainly gravitational processes in a foredeep below the c c d subsidence of the arabian platform edge allowed the semail ophiolite nappe finally to override the muti basin late campanian with little internal deformation submarine emplacement is suggested by the absence of ophiolitic detritus in the muti formation the stratigraphic evolution of the muti formation is in good general agreement with a model of the transition of an old thermally mature passive continental margin to a foreland basin where the emplaced load is submerged

posteruption suspended sediment transport at mount st helens decadal scale relationships with landscape adjustments and river discharges received 11 december 2002 revised 30 september 2003 accepted 18 november 2003 published 17 january 2004 1 widespread landscape disturbance by the cataclysmic 1980 eruption of mount st helens abruptly increased sediment supply in surrounding watersheds the magnitude and duration of the redistribution of sediment deposited by the eruption as well as decades to centuries old sediment remobilized from storage have varied chiefly with the style of disturbance posteruption suspended sediment transport has been greater and more persistent from zones of channel disturbance than from zones of hillslope disturbance despite the severe landscape disturbances caused by the eruption relationships between discharge magnitudes and frequencies and suspended sediment transport have been remarkably consistent discharges smaller than mean annual flows generally have transported 5 but locally 15 of the annual suspended sediment loads and infrequent p 0 01 large floods have transported as much as 50 of the annual suspended sediment loads in a single day however moderate magnitude discharges those greater than mean annual flows but less than 2 year floods have transported the greatest amounts of sediment from all disturbance zones such discharges have transported on average 60 to 95 of the annual suspended sediment loads usually within cumulative periods of 1 3 weeks each year although small magnitude and largemagnitude discharges have locally and episodically transported considerable amounts of suspended sediment there has not been any notable change in the overall nature of the effective discharges moderate magnitude flows have been the predominant discharges responsible for transporting the majority of suspended sediment during 20 years of posteruption landscape adjustment index terms 1824 hydrology geomorphology 1625 1815 hydrology erosion and sedimentation 1860 hydrology runoff and streamflow keywords sediment yield suspended sediment transport mount st helens erosion volcano geomorphology

stratigraphic simulation of sedimentary basins concepts and calibration a two dimensional stratigraphic simulation program based on semiempirical algorithms has been successfully applied to clastic carbonate and mixed clastic carbonate depositional regimes the program may be used to predict reservoir distribution to constrain interpretations of well and seismic data to test exploration scenarios in frontier basins and to evaluate the fundamental controls on basin stratigraphy applications to seismic and well log data sets from main pass u s gulf coast offshore sarawak malaysia and the baltimore canyon u s east coast demonstrate that the program simulates stratigraphy on a basin wide scale as well as on the scale of individual prospects the main pass section is an offlapping sequence of neogene clastics the model simulates 17 m y of geologic history at a 200 000 yr resolution and reproduces gross basin geometry major sequence boundaries depth and location of nearshore marine sands intervals of sediment bypass into deep water shelf margin positions and paleobathymetry three neogene carbonate buildups of central luconia offshore sarawak malaysia were simulated using a sea level history optimized to reproduce the carbonate growth anatomy the model reproduced observed seismic reflection geometries and transgressive aggradational progradational retrogradational and subaerial exposure phases the program has also simulated jurassic pleistocene basin and stratigraphic sequence geometries and mixed clastic carbonate facies distribution along a 300 km regional dip line of the baltimore canyon trough modeled features of interest include a progradational middle jurassic carbonate margin punctuated by clastic deposition during sea level lowstands and a late jurassic early cretaceous aggradational carbonate margin culminating in the development and subsequent drowning of isolated carbonate buildups simulated bathymetries facies relations and subaerial exposure surfaces for the early cretaceous aggradation margin are consistent with detailed petrographic paleontologic and seismic stratigraphic interpretations

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

early depositional history of a rift basin miocene in western sinai abstract the cenozoic stratigraphic record in the gulf of suez provides a model of six events for the early sedimentologic history of a rifted basin classic exposures on the east coast of the suez in the western sinai yield a composite section of the miocene succession 1 1 oligocene early miocene nukul formation terrigenous clastics in fluvial fandelta and littoral environments filled local valleys 2 2 during early miocene transgression lower rudies member nearshore and shelf sediments accumulated at a rate no less than 4 cm 1000 yrs rates of accumulation increased dramatically at the beginning of the middle miocene 3 3 during the early part of the middle miocene basinal muds and evaporites upper rudeis member kareem formation and part of belayim formation accumulated at a rate of 106 146 cm 1000 yrs 4 4 rates slowed during short term shoaling periods when shelf carbonates hammam faraun member were deposited 5 5 a fifth event is represented by more than 2 km of late miocene evaporites zeit south gharib formations which accumulated at a minimum rate of 32 cm 1000 yrs 6 6 the post evaporite event of alluvial and shallow deep marine sedimentation began in the pliocene and is continuing today local carbonate buildups developed upon fault blocks during the second and fourth stages evaporite deposition can be a very rapid process in the filling of rifted basins

depositional response to foreland deformation in the carboniferous of eastern kentucky the appalachian basin is a typical foreland basin that has subsided episodically under the loads of successive thrust sheets the dynamics of basin subsidence and upwarping of basin margin arch systems reflects the flexural properties of the lithosphere quantitative models of the lithosphere depend on assumed rheological properties this study attempts to test these geodynamic models in a part of the appalachian basin mississippian deposition is correlated with waning acadian tectonism orogenic quiescence coincided with basin overdeepening and uplift of the cincinnati arch or forebulge although the foreland basin was mudstone dominated shoaling along the crest of the basin margin arch system resulted in reworking and wedges of unconformities in contrast the onset of alleghenian orogenesis during the pennsylvanian is reflected in a thick wedge of terrigenous clastic sediments the pennsylvanian basin fluctuated between underfilled restricted marine and overfilled nonmarine conditions rapid response of the basin to thrust sheet loading is inferred these characteristics of mississippian and pennsylvanian deposition support a viscoelastic model of the lithosphere

mixed siliciclastic carbonate upward deepening cycles of the upper cambrian inner detrital belt of laurentia abstract high resolution sedimentological and biostratigraphic data recently recovered from upper cambrian strata in the northern rocky mountain and central appalachian regions reveal that meter scale cycles of very different character developed synchronously during deposition of the basal subzones of the ibexian series in both the carbonate facies belt and the distal part of the inner detrital mixed siliciclastic carbonate facies belt of the laurentian paleocontinent a typical mixed siliciclastic carbonate cycle in the snowy range formation of wyoming and montana consists of the following lithofacies in ascending order shale shale with very thin grainstone interbeds grainstone with subordinate thin shale interbeds flat pebble conglomerate and in some cycles thrombolitic bioherms internal transitions between the constituent lithofacies are mostly gradational but cycle boundaries are sharp with shale directly overlying flat pebble conglomerate and or thrombolitic boundstone we postulate that these mixed siliciclastic carbonate cycles developed in response to different depositional dynamics than meter scale cycles developed in carbonate belt facies specifically cycles in the carbonate belt were produced largely by temporal variation in accommodation space and associated filling of that space through progradation of the carbonate system and aggradation to sea level in contrast cyclic deposition within the inner detrital belt was controlled by variations in terrigenous sediment input and resulting effects on carbonate productivity in this case enhanced delivery of siliciclastic mud by rivers was triggered by regression and or a shift to more humid climatic conditions an upward increase of carbonate in the main part of the cycles reflects enhanced carbonate production in response to the reduction of terrigenous clay supply during shoreline retreat widespread cementation of fine grainstone substrates led to deposition of extensive beds of flat pebble conglomerate possibly in association with elevated sea surface temperatures and enhanced storm intensity thrombolites formed at times of maximum transgression as microbial communities thrived in the absence of turbidity colonizing the irregular surfaces of flat pebble conglomerate beds we thus interpret these wholly subtidal cycles to record full changes in paleobathymetry with the bulk of the cycles recording upward deepening rather than shoaling associated with regression comparison with age equivalent shoaling cycles of the conococheague formation of the carbonate belt of the appalachian mountains highlights the different depositional dynamics in the mixed siliciclastic carbonate systems and underscores the peril in extrapolation of depositional models derived from carbonate systems to mixed systems regardless of age or paleogeographic setting