sample scale carbon isotopic variability and diverse biomass in the paleoproterozoic zaonega formation russia abstract the stratigraphic record of organic matter in the c 1 97 ga zaonega formation zf onega basin northwestern russia exhibits a distinct negative 13c excursion 13corg from 25 to 40 vpdb which was previously interpreted either to reflect a disturbance in the global carbon cycle after the great oxidation event or to have been caused by an increase in basinal methanotrophic activity in order to assess the nature of primary biomass and the effects of post depositional alteration we here report the sample scale carbon isotopic characteristics of organic matter in two drill cores from the zf covering 500 m of stratigraphy by using secondary ion mass spectrometry sims the results confirm that the organic matter has to a large extent preserved the primary isotopic signatures whereas secondary effects are limited

stable isotope geochemistry of crude oils and of possible source rocks from new zealand 2 sulfur abstract the sulfur isotopic composition of new zealand low s crude oils and components asphaltenes absorptive filtration fractions and source rock components extracted hydrocarbons kerogen pyrite sulfates were determined oils from the taranaki basin have 34s values from 3 to 14 o the lower values possibly represent plant assimilation of fresh water sulphate higher values particularly those from the west coast basin around 20 suggest closed ocean basin conditions or fast sedimentation rate whereas negative 34s values from east coast basin suggest open ocean or low sedimentation rate conditions it is suggested than an oil source rock relation should show as a similarity in 34s values for total oil and source rock extract kerogen and pyrite shale samples analysed plot outside the corresponding oil range and cannot be considered as possible source rocks however coal samples from the maui 4 well and nelson outcrops show strong isotopic correlations with the taranaki oils

earthquakes drive focused denudation along a tectonically active mountain front abstract earthquakes cause widespread landslides that can increase erosional fluxes observed over years to decades however the impact of earthquakes on denudation over the longer timescales relevant to orogenic evolution remains elusive here we assess erosion associated with earthquake triggered landslides in the longmen shan range at the eastern margin of the tibetan plateau we use the m w 7 9 2008 wenchuan and m w 6 6 2013 lushan earthquakes to evaluate how seismicity contributes to the erosional budget from short timescales annual to decadal as recorded by sediment fluxes to long timescales kyr to myr from cosmogenic nuclides and low temperature thermochronology over this wide range of timescales the highest rates of denudation in the longmen shan coincide spatially with the region of most intense landsliding during the wenchuan earthquake across sixteen gauged river catchments sediment flux derived denudation rates following the wenchuan earthquake are closely correlated with seismic ground motion and the associated volume of wenchuan triggered landslides r 2 0 6 and to a lesser extent with the frequency of high intensity runoff events r 2 0 36 to assess whether earthquake induced landsliding can contribute importantly to denudation over longer timescales we model the total volume of landslides triggered by earthquakes of various magnitudes over multiple earthquake cycles we combine models that predict the volumes of landslides triggered by earthquakes calibrated against the wenchuan and lushan events with an earthquake magnitude frequency distribution the long term landslide sustained seismic erosion rate is similar in magnitude to regional long term denudation rates 0 5 1 mm yr 1 the similar magnitude and spatial coincidence suggest that earthquake triggered landslides are a primary mechanism of long term denudation in the frontal longmen shan we propose that the location and intensity of seismogenic faulting can contribute to focused denudation along a high relief plateau margin

organic geochemistry of petroleum from the green tuff basin japan abstract stable carbon isotopic composition and distribution of saturate hydrocarbons were analyzed for oils accumulated in volcanic vr and sedimentary sr rocks from the green tuff basin of northeast japan in order to investigate their origin the average 13 c values relative to pdb of the whole phase and saturate hydrocarbon fraction are identical for both the vr and sr oils within experimental error they lie within the range of 13 c of kerogen in the sediments from the same basin the distributions of saturate hydrocarbons of the vr and sr oils are similar to each other and not distinguished from that of a normal marine oil they include n alkanes as major components and acyclic isoprenoid alkanes such as pristane and phytane as the next abundant components these data indicate that the vr oils are biogenic i e pyrolysis products of kerogen just like the sr oils the abiogenic scenario assuming that the vr oils alone were derived from mantle carbon by the fischer tropsch reaction is not plausible

pore types and pore network evolution in upper devonian lower mississippian woodford and mississippian barnett mudstones insights from laboratory thermal maturation and organic petrology abstract pore evolution models from immature organic matter om rich barnett 0 42 r o and woodford 0 49 r o mudstones were compared with models previously developed from low maturity om lean boquillas eagle ford equivalent mudstones to investigate whether 1 different mineralogy siliceous vs calcareous exerts different catalytic and sorption effects and influences om pore origin and evolution and 2 different types of macerals show different om pore evolution history laboratory gold tube pyrolysis scanning electron microscopy sem and thin section petrography organic petrography and geochemical characterization were used to investigate the role of bulk mineralogy maceral type and thermal maturation on om pore evolution results suggest that mineralogy has little impact on om pore development and evolution macerals identified using both sem platy om particulate om organic mineral admixtures tasmanites and organic petrology vitrinite inertinite amorphous organic matter aom bituminite telalginite leiosphaeridia tasmanites do affect the origin and evolution of om pores owing to differences in chemical compositions generation kinetics and activation energy distributions between tasmanites matrix bituminite and other types of macerals leiosphaeridia and tasmanites in woodford mudstone samples exhibit a delay in onset and a shorter period of petroleum generation and pore development compared to the matrix bituminite in the barnett and woodford mudstone samples pre oil solid bitumen was observed to have migrated into initial primary mineral pore networks at the bitumen generation stage in both barnett and woodford samples at higher levels of thermal maturation the volume of primary mineral pores decreases and the pore volume composed of modified mineral pores and om pores becomes greater pore evolution and pore type heterogeneity in these mudstones is a function of the initial mineral pore network types of kerogen and macerals and generation kinetics of individual macerals upon thermal maturation

stable isotope geochemistry of organic matter alteration in animikie basin sediments within the thermal aureole of the duluth ccomplex abstract we have determined total organic carbon toc total carbonate carbon tcc and 13 c values for toc in samples from the early proterozoic animikie basin sediments virginia and biwabik iron formations that have been variably metamorphosed by the duluth complex toc values for the variably metamorphosed virginia formation show no systematic variation with distance from the intrusion toc from 0 06 to 2 54 in the biwabik iron formation samples outside the thermal aureole of the intrusion have toc generally below 1 compared to 1 7 6 2 for samples within the thermal aureole this enrichment may reflect extensive remobilization of organic carbon within the thermal aureole however 13 c org values measured for both the virginia and biwabik iron formations within the thermal aureole are not significantly different from those outside the thermal aureole it thus appears that in the iron formation the thermal shock caused by the intrusion induced migration of labile organic carbon that was isotopically similar to the residual kerogen the relatively low tcc in samples within the thermal aureole of the intrusion appear to indicate decarbonation of the iron formation also occurred

lower tertiary and upper cretaceous source rocks in louisiana and mississippi implications to gulf of mexico crude oil the lower tertiary sparta formation wilcox group and the midway group in southern louisiana include organic rich source facies that generate crude oil at relatively high thermal maturities the wilcox group is an important source of wilcox crude oil and regional kerogen variations explain two crude oil subfamilies wilcox crude oils in downdip areas of southern louisiana migrated short distances but long range lateral migration about 150 km best explains wilcox crude oils far updip from mature source rocks crude oils in oligocene and younger reservoirs in southern louisiana migrated vertically from deep lower tertiary source rocks some crude oils in upper cretaceous tuscaloosa reservoirs were emplaced by long range lateral migration from tuscaloosa source rocks g ven little evidence of upper tertiary source rocks and the overmaturity problems of mesozoic source rocks most crude oils in upper tertiary and pleistocene reservoirs of the gulf continental shelf are best explained by vertical migration from deep lower tertiary source rocks even so it is simplistic to assume an exclusive lower tertiary origin many tertiary and pleistocene crude oils of this study probably include an overprint of high maturity hydrocarbons from mesozoic sources

carbon isotopes as indicators of dispersal patterns in devonian mississippian shales of the appalachian basin measurement of the carbon isotopic composition of organic matter in about 200 samples from the devonian shale sequence of the eastern united states shows a definite transition from nonmarine values of around 25 through intermediate values in prodelta samples to distal basinal samples with values around 30 5 this trend matches very closely that found for paleocurrents in the sequence from sole markings on turbidite siltstone beds thus the carbon isotopes suggest that the organic matter and hence the enclosing shale had the same dispersal pattern as the silt stones furthermore the steady westward change to more marine values indicates that the cincinnati arch was never sufficiently positive to act as a source of organic matter the nonmarine carbon has an isotopic composition very similar to that of coal and so probably represents woody material the basinal values however are much lighter than modern marine plankton this may be a diagenetic effect or it may reflect a difference in the devonian plankton

calculation of average landslide frequency using climatic records aerial photographs are used to develop a relationship between the number of debris slides generated during a hydrologic event and the size of the event and the long term average debris slide frequency is calculated from climate records using the relation for a site in california with an average of 8 3 slides km 2 yr 1 a sequence of four photo sets representing 10 15 years 35 50 observed slides and 4 6 large storms is needed to estimate the long term debris slide frequency to within 30 of the actual value p 0 90 if climatic records are used a record length of 5 10 years 17 35 observed slides and 2 4 significant storms is sufficient to provide the same accuracy the climate based model suggests that debris slide frequency changed from approximately 1 6 to 8 3 slides km 2yr 1 during the late 1930s owing to an increased frequency of high intensity storms the model accurately predicts the change in slide scar density observed on sequential aerial photographs following the climatic shift

large deep seated landslides controlled by geologic structures prehistoric and modern examples in a jurassic subduction accretion complex on the kii peninsula central japan abstract the relationship between large deep seated landslides and geologic structures characteristic of accretionary complexes were examined in the chichibu belt on the eastern part of the kii peninsula central japan in the chichibu belt bedrock consists of jurassic accretionary complexes composed of basalt limestone chert permian triassic boundary siliceous shale ptbs mudstone sandstone and melanges with sheared shale matrices the landslides treated in this paper include prehistoric examples involving volumes greater than one million cubic meters located in the karako sono kasagi and aso areas and the modern kasugadani landslide that was triggered by the typhoon meari on 29 30 september 2004 the age of the landslide in the sono area was estimated at 20 440 70 bp and 20 820 70 bp based on ams 14c ages of wood fragments embedded in the dammed lake sediments while ages of the other prehistoric slides are not known all of the landslides occurred on dip slopes the bedding foliation and fault planes of the rocks in the area generally trend e w and dip to the north although those in the kasugadani area dip to the south as a result of local folding the landslides selectively slid along the planes of 1 ptbs horizons that were less strong than those of underlying chert 2 lithologic boundaries with physical contrasts or 3 boundary faults between melange units these geologic structures including the north dipping bedding cleavage fault planes were formed during jurassic subduction accretion and later uplift processes the movement directions estimated for the 269 landslides and unstable slopes in this region are also n nne and their slip planes are subparallel to the general bedding cleavage planes in this area thus future slides are also likely to occur on north facing slopes

quantifying rainfall controls on catchment scale landslide erosion in taiwan landslide erosion is a dominant hillslope process and the main source of stream sediment in tropical tectonically active mountain belts in this study we quantified landslide erosion triggered by 24 rainfall events from 2001 to 2009 in three mountainous watersheds in taiwan and investigated relationships between landslide erosion and rainfall variables the results show positive power law relations between landslide erosion and rainfall intensity and cumulative rainfall with scaling exponents ranging from 2 94 to 5 03 additionally landslide erosion caused by typhoon morakot is of comparable magnitude to landslide erosion caused by the chi chi earthquake mw 7 6 or 22 24 years of basin averaged erosion comparison of the three watersheds indicates that deeper landslides that mobilize soil and bedrock are triggered by long duration rainfall whereas shallow landslides are triggered by short duration rainfall these results suggest that rainfall intensity and watershed characteristics are important controls on rainfall triggered landslide erosion and that severe typhoons like high magnitude earthquakes can generate high rates of landslide erosion in taiwan copyright 2012 john wiley sons ltd

the stable carbon isotopic composition of oil from the taranaki basin of new zealand abstract the average stable carbon isotope ratio of 21 oils from the taranaki basin of new zealand suggests that the source rocks date from the cretaceous period when sedimentation in this basin began stable carbon isotope ratios also confirm the grouping of these oils into the genetic families which were previously suggested by the correlation of source related biomarkers stahl isotope type curves for the oils also reflect the correctness of these relationships a plot of the saturate versus aromatic 13c values for the new zealand oils is particularly valuable for oil correlation in this basin and clearly demonstrates that the ahuroa and stratford oils while separated from the mckee field by some 30 km probably originate from the same oil source formation as do the oils of the mckee field the plot also indicates that the kaimiro mangahewa pukearuhe and waihapa oils are discrete in situ accumulations of petroleum which do not have the characteristics of oils from adjacent fields these conclusions are further supported by the values of the sofer canonical variable for all of the oils additionally the sofer plot provides clear evidence of the predominantly terrigenous origin of the oils in the taranaki basin consideration of the data for these oils leads to a hypothesis that three independent sources of organic material microbes gymnosperms and angiosperms gave rise to the oils in this region

use of hydrogen and carbon stable isotopes characterizing oils from the potiguar basin onshore northeastern brazil hydrogen and carbon isotopic abundances were measured in representative samples of marine evaporitic lacustrine and mixed oils from the onshore potiguar basin the isotopic data together with chemical compositions and geological information were used to investigate relationships among ddoil and d13coil and source thermal maturity biodegradation mixing and the distance of secondary migration of these oils the marine evaporitic oils are depleted in deuterium 135 to 114 and the lacustrine oils are enriched 101 to 88 values of dd for mixed oils are intermediate 113 to 104 between those of marine evaporitic and lacustrine oils showing that ddoil is a reliable tool to identify oils that differ genetically values of ddoil were not directly related to thermal maturation biodegradation or distance of the secondary migration hydrogen isotopic compositions of the oils can be related mainly to the ddwater in the paleoenvironments in which the primary producers lived therefore ddoil values can provide rough estimates of ddwater in the depositional environments of the source rocks and consequently may provide evidence about paleoclimatic conditions at the site marine evaporitic oils are enriched in 13c 26 5 to 25 7 and lacustrine oils are depleted 33 6 to 30 2 in 13c relative contributions of marine evaporitic and lacustrine sources to mixed oils thus can be calculated independently from carbon or hydrogen isotopic mixing models when these calculations are done independently the mixed oils separate into two families and a previously unrecognized component possibly associated with environments that formed during the lacustrine to marine transition is revealed the investigation thus demonstrates the superior resolving power of two element mixing systematics

simulated petroleum generation studies by hydrous pyrolysis of a tertiary coal from northern cambay basin in india in the northern cambay basin ahmedabad mehsana block abundant coal seams occur at depths of 1000 1700 m the role such coals can play in hydrocarbon hc generation has not been determined hydrocarbon generation from a core sample with a hydrogen index hi 268 mg hc g total organic carbon toc oxygen index oi 19 mg co2 g toc and vitrinite reflectance in oil vro 0 38 has been simulated by hydrous pyrolysis at a temperature of 325 c for 2 10 50 and 100 h it has been observed that generation is in accordance with the model kerogen asphaltenes hydrocarbons the peak oil generation stage is reached at 0 89 vro the peak oil expulsion stage occurs at 0 91 vro although hydrocarbons are generated from 0 75 vro onwards the results indicate that these coals have not contributed towards hydrocarbon reserves of northern cambay basin

potential for landsliding dependence on hyetograph characteristics 1 this paper examines the effect of hyetograph shape on the potential for landsliding in soil mantled landscapes an existing pore pressure response model iverson 2000 is used to study the effects of unsteady rainfall infiltration in hillslopes and the effect of slope and convergent topography is expressed using a steady state model of slope parallel subsurface flow slope stability is assessed using an infinite slope analysis this theoretical framework is coupled with simple hyetograph models and to intensity duration frequency functions to determine the return period of landslide triggering rainfall results also show that hyetographs with a peak at the end of a rainfall event have a stronger destabilizing effect than hyetographs with a constant rainfall or with a peak at the beginning of a storm thus the variability of hyetograph shapes adds uncertainty to the assessment of landsliding triggered by rainfall

stable sulfur and nitrogen isotopic compositions of crude oil fractions from southern germany abstract eleven samples of crude oil from the molasse basin of southern germany were fractionated and their contents of sulfur and nitrogen as well as the stable isotope compositions of these elements 34 s 32 s and 15 n 14 n resp investigated according to the 34s determinations all crude oils from the tertiary base of the western and eastern molasse belong to one oil family and differ significantly from the triassic and liassic oils in the western molasse an enrichment of 34s was observed with increasing polarity of crude oil fractions the isotope distributions of sulfur in the polar constituents of the biodegraded oils from the sandstones of ampfing however approach a homogeneous distribution the nitrogen isotope distribution is rather uniform in southern german oils a regional differentiation can be recognized although the overall isotopic variation is small the 15n values of the crudes and asphaltenes do not correlate

rainfall thresholds for landslide activity in portugal a state of the art rainfall is the most important physical process responsible for the landslide triggering in portugal results obtained worldwide have shown that control of rainfall on landslides differs substantially depending upon landslide depth and kinematics and the affected material therefore the critical rainfall conditions for failure are not the same for different types of landslides and may be strongly influenced by regional geologic and geomorphologic conditions rapid debris flows are typically triggered by very intense showers concentrated in just a few hours and shallow translational soil slips are usually triggered by intense precipitation falling within the 1 15 days long range on the contrary activity of deep seated landslides of rotational translational and complex types is related to periods of nearly constant rainfall lasting from several weeks to several months the different rainfall intensity duration conditions are associated with different hydrologic mechanisms for slope failure the generation of surface run off and high peak discharges in first order mountain catchments is a critical triggering mechanism for debris flows the intense rainfall allows the rapid growth of pore water pressure and the drop of capillarity forces that sustain the apparent cohesion of thin soils as a consequence shallow soil slips occur within the soil material or at the contact with the underlying less permeable bedrock long lasting rainfall episodes enable the steady rise of the groundwater table and the development of positive pore water pressures into the soil consequently deep seated failures occur in relation to the reduction of shear strength of affected materials in this work we present the state of the art concerning the proposition of empirical rainfall thresholds in portugal for different types of landslides observed in different zones of the country the lisbon region the douro valley and the nw mountains and the povoacao municipality in sao miguel island azores the empirical thresholds applied in portugal are based on the identification of past landslide events and include i the computation of antecedent rainfall threshold defined by linear regression ii the normalization of rainfall by the mean annual precipitation iii the definition of lower limit and upper limit rainfall thresholds and iv the definition of combined rainfall thresholds which integrates the rainfall event and the antecedent rainfall for different time periods

hydrocarbon generating potential of humic coals from dry pyrolysis for comparing the oil and gas generation potential of humic coals two immature subbituminous coals australia gippsland an oil prone eocene coal ro 0 37 hi 237 5 and a gas prone rocky mountain upper cretaceous coal ro 0 45 hi 110 5 as well as an exinite poor vitrinite dominant gulf coast wilcox lignite ro 0 32 hi 183 7 were selected for dry pyrolysis at 300 degrees c from 2 to 1000 hr the results indicate that australia gippsland eocene coal gec generated four times as much liquid hydrocarbon i e c 12 saturated and aromatic hydrocarbons as the rocky mountain coal rmc whereas both coals have the same potential for generation of gaseous hydrocarbons wilcox lignite wl generated as much liquid hydrocarbon as gec the two coals ge and rmc and lignite wl exhibit similar h c ratios have high pristane phytane ratios of 5 0 4 5 and 5 1 respectively and sigma 13 c values of 25 7 24 9 and 25 5 parts per mil in rmc gec and wl respectively the study suggests that the relative abundances of various macerals exinite vitrinite and inertinite are not critical to the hydrocarbon generating potential rather the amount of dispersed algae and bacterial material unidentified in the coal probably is more significant depositional environment of the source organic material also may be important because it could control preservation of organic constituents because of the small stable isotope variations in c h n in the original coal kerogen as well as residual kerogen after pyrolysis of the three coals it seems unlikely that isotopic composition can characterize coal depositional environments

geochemical characterization of qhd29 oils on the eastern margin of shijiutuo uplift bohai sea china insights from biomarker and stable carbon isotope analysis abstract toc and rock eval analyses were conducted on cutting samples 111 from various paleogene formations ed3 es1 and es3 in the qinnan sag the average values of total organic carbon toc content are 1 11 1 64 and 2 29 for ed3 es1 and es3 samples respectively the es1 and es3 source rocks are of relatively high s2 values ranging from 0 42 to 46 01 and 2 46 61 01mghc rock respectively the ed3 rocks have lower generative potential with s2 values ranging from 0 9 to 9 3 mg hc g rock moreover tmax values indicate that these source rocks are sufficiently mature for petroleum generation these analyses suggest that es1 and es3 are potential source rocks for oils produced from the qhd29 field eighteen oil samples from the qhd29 field were analyzed by gc and gc ms and 84 qhd29 oil 13 and source rock 71 samples were employed for stable carbon isotope analysis based on hierarchical cluster analysis of selected biomarker parameters the qhd29 oils can be identified into two groups group i and group ii oils are both derived from the eocene shahejie formation es1 and es3 displaying remarkable difference to the oligocene ed3 derived oils in comparison with group ii oils group i oils display relatively low 4msi and high g h indicating that group i oils have important contributions from es1 source rock deposited under more alkaline saline environment moreover these two group oils can be clearly separated by 13c values and group i oils are isotopically lighter than group ii oils difference occurs in stable carbon isotope distribution between es1 and es3 source rock extracts as well and es1 source rocks are characterized by relatively light carbon isotopic composition this implies that group i oil shares more es1 derived oil which is consistent with the results of biomarker analysis

multiple negative carbon isotope excursions during the carnian pluvial episode late triassic abstract the carnian pluvial episode was a phase of global climatic change and biotic turnover that occurred during the early late triassic in marine sedimentary basins the arrival of huge amounts of siliciclastic sediments the establishment of anoxic conditions and a sudden change of the carbonate factory on platforms marked the carnian pluvial episode the sedimentary changes are closely associated with abrupt biological turnover among marine and terrestrial groups as for example an extinction among ammonoids and conodonts in the ocean and a turnover of the vertebrate fauna and the flora on land multiple negative carbon isotope excursions were recorded during the carnian pluvial episode in both organic matter and marine carbonates suggesting repeated injection of 13c depleted co2 into the ocean atmosphere system but their temporal and causal links with the sedimentological and palaeontological changes are poorly understood we here review the existing carbon isotope records and present new data on the carbon isotope composition of organic carbon in selected sections of the western tethys realm that record the entire carnian pluvial episode new ammonoid conodont and sporomorph biostratigraphic data were collected and coupled to an extensive review of the existing biostratigraphy to constrain the age of the sampled sections the results provide biostratigraphically constrained composite organic carbon isotope curves for the carnian which sheds light on the temporal and causal links between the main carbon isotope perturbations and the distinct environmental and biotic changes that mark the carnian pluvial episode the carbon isotope records suggest that a series of carbon cycle perturbations possibly recording multiple phases of volcanic activity during the emplacement of the wrangellia large igneous province disrupted carnian environments and ecosystems repeatedly over a remarkably long time interval of about 1 million years

effects of forest harvesting on the occurrence of landslides and debris flows in steep terrain of central japan landslides and debris flows associated with forest harvesting can cause much destruction and the influence of the timing of harvesting on these mass wasting processes therefore needs to be assessed in order to protect aquatic ecosystems and develop improved strategies for disaster prevention we examined the effects of forest harvesting on the frequency of landslides and debris flows in the sanko catchment central japan using nine aerial photo periods covering 1964 to 2003 these photographs showed a mosaic of different forest ages attributable to the rotational management in this area since 1912 geology and slope gradient are rather uniformly distributed in the sanko catchment facilitating assessment of forest harvesting effects on mass wasting without complication of other factors trends of new landslides and debris flows correspond to changes in slope stability explained by root strength decay and recovery the direct impact of clearcutting on landslide occurrence was greatest in forest stands that were clearcut 1 to 10 yr earlier with progressively lesser impacts continuing up to 25 yr after harvesting sediment supply rate from landslides in forests clearcut 1 to 10 yr earlier was about 10 fold higher than in control sites total landslide volume in forest stands clearcut 0 to 25 yr earlier was 5 8 10 3 m 3 km 2 compared with 1 3 10 3 m 3 km 2 in clearcuts 25 yr indicating a fourfold increase compared with control sites during the period when harvesting affected slope stability because landslide scars continue to produce sediment after initial failure sediment supply from landslides continues for 45 yr in the sanko catchment to estimate the effect of forest harvesting and subsequent regeneration on the occurrence of mass wasting in other regions changes in root strength caused by decay and recovery of roots should be investigated for various species and environmental conditions copyright 2007 john wiley sons ltd

a seismologically consistent expression for the total area and volume of earthquake triggered landsliding we present a new seismologically consistent expression for the total area and volume of populations of earthquake triggered landslides this model builds on a set of scaling relationships between key parameters such as landslide spatial density seismic ground acceleration fault length earthquake source depth and seismic moment to assess the model we have assembled and normalized a catalog of landslide inventories for 40 shallow continental earthquakes low landscape steepness causes systematic overprediction of the total area and volume of landslides when this effect is accounted for the model predicts the total landslide volume of 63 of 40 cases to within a factor 2 of the volume estimated from observations r2 0 76 the prediction of total landslide area is also sensitive to the landscape steepness but less so than the total volume and it appears to be sensitive to controls on the landslide size frequency distribution and possibly the shaking duration some outliers are likely associated with exceptionally strong rock mass in the epicentral area while others may be related to seismic source complexities ignored by the model however the close match between prediction and estimate for about two thirds of cases in our database suggests that rock mass strength is similar in many cases and that our simple seismic model is often adequate despite the variety of lithologies and tectonic settings covered this makes our expression suitable for integration into landscape evolution models and application to the anticipation or rapid assessment of secondary hazards associated with earthquakes

oil source rock correlations in the polish flysch carpathians and mesozoic basement and organic facies of the oligocene menilite shales insights from hydrous pyrolysis experiments the oligocene menilite shales in the study area in the polish flysch carpathians are organic rich and contain varying mixtures of type ii type iis and type iii kerogen the kerogens are thermally immature to marginally mature based on atomic h c ratios and rock eval data this study defined three organic facies i e sedimentary strata with differing hydrocarbon generation potentials due to varying types and concentrations of organic matter these facies correspond to the silesian unit and the eastern and western portions of the skole unit analysis of oils generated by hydrous pyrolysis of outcrop samples of menilite shales demonstrates that natural crude oils reservoired in the flysch sediments appear to have been generated from the menilite shales natural oils reservoired in the mesozoic basement of the carpathian foredeep appear to be predominantly derived and migrated from menilite shales with a minor contribution from at least one other source rock most probably within middle jurassic strata definition of organic facies may have been influenced by the heterogeneous distribution of suitable menilite shales outcrops and producing wells and subsequent sample selection during the analytical phases of the study

organic geochemistry of the san vicente zinc lead district eastern pucara basin peru abstract isotopic and chemical studies of organic matter of the san vicente mississippi valley type zn pb district hosted in the dolomitic units of the eastern pucara basin peru provide insight into the source of organic matter and of the organic matter ore relationship a large scatter exists in the 13c and 15n values of the highly mature kerogens these bulk data were combined with 13c covariations of the saturated and aromatic fractions of the rock extracts to indicate a contribution of continental higher plant lipids to the marine algal source of the organic matter disseminated in the host carbonate rocks an enrichment in 15n of the kerogens of mineralized samples compared to barren samples suggests that isotopically heavy nitrogen compounds were introduced to the ore fluid the fluid likely leached these compounds from the underlying clastic rocks and other detrital units of the pucara the extracts from mineralized samples are enriched in 13c compared to the associated kerogens this suggests that the rocks in the mineralized areas were stained by a mixture of extrinsic and indigenous bitumens by the use of novel instrumentation such as a gas chromatograph gc coupled to a stable isotope ratio mass spectrometer irms through a combustion c interface gc c irms stable carbon isotope analyses of individual hydrocarbons were also obtained both the molecular and isotopic signatures of the individual hydrocarbons are related to mineralization the variability in the organic molecular parameters and the 13c values of the individual n alkanes and isoprenoids indicate mixing of indigenous hydrocarbons with extrinsic 13c depleted microbially derived hydrocarbons the extrinsic source hydrocarbons were introduced to the mineralization site by the ore fluid or later fluids using the same porosity network oxidative alteration of the migrating hydrocarbons was involved in the thermochemical reduction of sulfate to h2s and precipitation of pyrobitumen large differences 12 in the carbon isotope compositions of long chain c20 n alkanes can be utilized in distinguishing sources of organics in the barren and mineralized samples

recent advances in petroleum isotope geochemistry abstract organic matter is isotopically heterogeneous lipids tend to be depleted in the heavy carbon and hydrogen isotopes as compared to carbohydrates and lignite the c and h isotopic composition of kerogens is determined by many factors such as environmental conditions during formation and deposition and variability of sources of organic matter stable isotope concentrations in mature kerogens are not significantly altered during maturation and hence reflect the variability of the organic matter during deposition isotope variations in kerogens therefore reflect to some extent the paleogeographic situation and can be used for paleoreconstruction a basin facies with anoxia and a marginal facies with detrital input can be differentiated isotopically in the toarcian of central europe coals are isotopically heterogeneous due to different isotopic composition of macerals inertinite and vitrinite tends to be enriched in deuterium as compared to exinite also boghead coals tend to be depleted in dueterium which possibly reflects various lipid contents of respective precursor materials petroleums can be genetically classified through the patterns of covariance of their compound classes carbonate and shale sourced petroleums may be additionally differentiated through their deuterium content the general world wide applicability of such genetic differentiations needs still to be proved carbon and hydrogen isotope variations in methane are genetically controlled bacterial methane in freshwater environments is characteristically depleted in deuterium even complex origins of natural gases can be unraveled using compositional and isotopic variations new analytical developments led to the application of carbon isotope analyses of gaseous hydrocarbons desorbed from sediments for geochemical surface exploration a discussion reveals that processes such as isotope effects during degassing and bacterial oxidation as well as indigenous formation of hydrocarbons may completely obscure the results

the role of bitumen in strata bound copper deposit formation in the copiapo area northern chile in northern chile between 27 and 33 s there are numerous deposits where residual petroleum is associated with cu ag mineralisation the most famous being el soldado all of these deposits are hosted by lower cretaceous volcanic or volcanoclastic facies along the axis of a former backarc basin this close relationship suggests that the generation migration and emplacement of hydrocarbons in the cretaceous volcanic units is a regional process associated with the evolution of the cretaceous backarc basin and points to the importance of pyrobitumen as an exploration tool for similar cu ag deposits the present work analyses four small strata bound copper deposits located along a north south belt approximately 10 km east of copiapo in northern chile these deposits are typically hosted by pyrobitumen rich andesitic volcanic to volcanoclastic rocks intercalated with the marine carbonate pabellon formation the youngest formation within the chanarcillo group the strong genetic and spatial relationships between the pyrobitumen rich lavas and the mineral deposits allow us to define this volcanic belt as the ocoita pabellon metallotect two hydrothermal events can be distinguished based on the mineralogical textural fluid inclusion and isotope data of ore and gangue and on the optical properties of residual petroleum during the early event petroleum was mobilised from the source rocks into the primary and secondary porosity of the lavas by fe rich hydrothermal fluids which precipitated pyrite as an early sulphide phase the second event is characterised by cu rich hydrothermal fluids which induced three successive sub stages of cu sulphide precipitation the hydrothermal fluids chemically and thermally altered the first stage bitumen transforming it into pyrobitumen the present work documents similarities between the ocoita pabellon metallotect and the el soldado ore deposit and emphasises important differences in the el soldado host rocks a petroleum reservoir existed prior to the arrival of the mineralising hydrothermal fluids the framboidal pyrite was formed by assistance of bacteria the s of the cu sulphides was inherited from the pyrite and the fluid source was basin connate metamorphic brine in the ocoita pabellon metallotect the hydrocarbons were mobilised into the host rocks by hydrothermal fluids the pyrite is epigenetic the 34s values of pyrite and copper sulphides are very different with distinctive light 34s signature of cu sulphides 34s between 44 7 and 17 9 and the calculated 18o of hydrothermal fluids indicates the participation of meteoric water in the late phases of the hydrothermal system

nature and origins of internal sediments in jurassic limestones of burgundy franc and fnoud algeria numerous hard grounds and palaeo emersion surfaces in middle jurassic grainstones of burgundy france and upper jurassic micritic limestones of the fnoud region algeria exhibit a variety of diagenetic cements and internal sediments four types of internal sediments have been defined each being the product of a particular environment type 1 unsorted microbioclastic wackestone characterizes submarine hard grounds type 2 pelleted grainstone with inverse graded bedding occurs in microcaverns developed in palaeobeach rocks type 3 centrifugal micrite seems to characterize relatively dry supratidal substrates type 4 crystal silt is associated with early sparitic cements and dissolution phenomena indicating the influence of non marine waters within a given pore space a centripetal succession of various cements and internal sediments seems to reflect the lateral evolution of the tidal flat or beach at any given pore space interstitial waters have evolved progressively as the intertidal zone advanced or receded thus internal sediments and related early diagenetic phenomena are valid criteria both for particular environments and for the general evolution of the coastal plain finally although internal sediments may accumulate both within grainstones burgundy and mudstone substrates fnoud these textural differences may influence the type and frequency of internal sedimentation resume de multiples ciments diagenetiques et sediments internes precoces ont ete reconnus dans les nombreuses surfaces durcies et surfaces d emersion des calcaires grainstones du jurassique moyen de bourgogne france et des calcaires micritiques de la region des fnoud algerie quatre types principaux de sediments internes ont ete definis chacun etant le produit d un milieu diagenetique particulier le type 1 est un wackestone rnicrobioclastique non classe qui caracterise les surfaces durcies sousmarines le type 2 est un micrograinstone a pellets avec granoclassement inverse qui existe dans les microcavernes developpees dans les paleo gres de plage le type 3 est une micrite centrifuge qui se developpe dans des conditions supratidales le type 4 consiste en un silt a debris de cristaux associe aux ciments sparitiques precoces et aux phenomenes de dissolution caracterisant ainsi l influence d eaux non marines dans un pore donne la succession centripete entre ciment et sediments internes reflete i evolution laterale de la plaine cotiere ou de la plage suivant le regime sedimentaire dans cet espace poreux les eaux intersticielles evoluent progressivement au fur et a mesure que la zone intertidale s accro t ou se reduit ainsi les sediments internes et les phenomenes diagenetiques associes constituent de bons criteres pour la determination d un environnement particulier et pour retracer i evolution generale de la plaine cotiere enfin bien que les sediments internes se deposent au sein de calcaires grainstones bougogne ou de calcaires mudstones fnoud les differences texturales du sediment hote peuvent influencer sur le type et la frequence de la sedimentation interne

a view on some hydrological triggering systems in landslides abstract in this paper different types of hydrological triggering systems for debris flows shallow and deeper landslides are described the generation of surface run off and high peak discharges in first order alpine catchments is an important triggering mechanism for debris flows failure conditions in shallow landslides can occur when at a critical depth which is determined by the cohesion of the soil and the slope angle the moisture content in the soil becomes close to saturation resulting in a considerable reduction of soil strength deeper landslides 5 20 m depth are in most cases triggered by positive pore pressures on the slip plane induced by a rising ground water level the assessment of meteorological threshold conditions for shallow landslides 1 2 m needs more detailed meteorological information than for deeper landslides in the analyses of the hydrological triggering systems of deeper landslides the presence of a permeable top layer and fissures has to be taken into consideration

the determination of statistical and deterministic hydrological landslide triggering thresholds hydrological landslide triggering thresholds separate combinations of daily and antecedent rainfall or of rainfall intensity and duration that triggered landslides from those that failed to trigger landslides they are required for the development of landslide early warning systems when a large data set on rainfall and landslide occurrence is available hydrological triggering thresholds are determined in a statistical way when the data on landslide occurrence is limited deterministic models have to be used for shallow landslides directly triggered by percolating rainfall triggering thresholds can be established by means of one dimensional hydrological models linked to the infinite slope model in the case of relatively deep landslides located in topographic hollows and triggered by a slow accumulation of water at the soil bedrock contact simple correlations between landslide occurrence and rainfall can no longer be established therefore real time failure probabilities have to be determined using hydrological catchment models in combination with the infinite slope model

detection of petroleum heterogeneity in eldfisk and satellite fields using thermal extraction pyrolysis gc gc ms and isotope techniques abstract eldfisk field is one of several oil producing chalk fields of the north sea analysis was performed on core samples from 11 wells from the palaeocene cretaceous chalk reservoir analyses performed on cores included various pyrolysis techniques conventional gc ms was performed on 27 oils from the 2 7 block stable carbon isotope analysis was performed on bulk and n alkane fractions of the oils pyrolysis data could be used to detect the main producing section of the reservoir and show that there appear to be sections of the reservoir rich in waxes biomarker and pyrolysis data indicate that there are differences in maturity of the petroleum of eldfisk alpha and bravo structures and that there are lateral and vertical variations in composition within each structure based on both biomarker and isotopic data there is evidence for at least two phases of reservoir filling

vanadyl porphyrins in exploration maturity indicators for source rocks and oils abstract the porphyrin maturity parameter pmp which is derived from the vanadyl porphyrin distribution is an excellent parameter for 1 identifying the zone of hydrocarbon generation from marine source rock extracts and 2 determining from oils the thermal maturity of their source rocks at expulsion the pmp is measured using a methodology which is inexpensive reliable and faster than earlier methods allowing it to be used as a routine exploration tool the pmp may be a more reliable maturity indicator for marine organic matter than some conventional methods such as vitrinite reflectance unlike most conventional maturity parameters guided by processes other than kerogen conversion the reactions causing pmp evolution directly monitor the generation of bitumen and the concurrent thermal degradation of kerogen measurements on hydrous pyrolyzates from the monterey formation offshore california source rock bitumens from the devonian mississippian bakken shale williston basin and miocene monterey equivalent source strata san joaquin basin california illustrate the method in all cases reviewed so far pmp begins increasing at the onset of hydrocarbon generation and increases systematically and predictably as kerogen decomposition proceeds in oils generated from high s marine kerogens pmp reflects the maturity of the source rock at the time of oil expulsion provided that the oil does not undergo subsequent reservoior maturation or mixing with in situ bitumen

stochastic forcing of sediment supply to channel networks from landsliding and debris flow sediment influx to channel networks is stochastically driven by rainstorms and other perturbations which are discrete in time and space and which occur on a landscape with its own spatial variability in topography colluvium properties and state of recovery from previous disturbances the resulting stochastic field of sediment supply interacts with the topology of the channel network and with transport processes to generate spatial and temporal patterns of flux and storage that characterize the sedimentation regime of a drainage basin the regime varies systematically with basin area we describe how the stochastic sediment supply is generated by climatic topographic geotechnical and biotic controls that vary between regions the general principle is illustrated through application to a landscape where sediment is supplied by mass wasting and the forcing variables are deterministic thickening of colluvium random sequences of root destroying wildfires and random sequences of rainstorms that trigger failure in a population of landslide source areas with spatial variance in topography and colluvium strength landslides stop in channels or convert to scouring debris flows depending on the nature of the low order channel network sediment accumulates within these channels for centuries before being transferred downstream by debris flows time series of sediment supply transport and storage vary with basin scale for any combination of climatic topographic and geotechnical controls in a companion paper benda and dunne this issue we use simulations of timing volumes and locations of mass wasting to study the interaction between a stochastically forced sediment supply and systematic changes of storage and flux through channel networks

petroleum system analysis of the hunton group in west edmond field oklahoma west edmond field located in central oklahoma is one of the largest oil accumulations in the silurian devonian hunton group in this part of the anadarko basin production from all stratigraphic units in the field exceeds 170 million barrels of oil mmbo and 400 billion cubic feet of gas bcfg of which approximately 60 mmbo and 100 bcfg have been produced from the hunton group oil and gas are stratigraphically trapped to the east against the nemaha uplift to the north by a regional wedge out of hunton strata and by intraformational diagenetic traps hunton group reservoirs are the bois d arc and frisco limestones with lesser production from the chimneyhill subgroup haragan shale and henryhouse formation hunton group cores from three wells that were examined petrographically indicate that complex diagenetic relations influence permeability and reservoir quality greatest porosity and permeability are associated with secondary dissolution in packstones and grainstones forming hydrocarbon reservoirs the overlying devonian mississippian woodford shale is the major petroleum source rock for the hunton group in the field based on one dimensional and four dimensional petroleum system models that were calibrated to well temperature and woodford shale vitrinite reflectance data the source rock is marginally mature to mature for oil generation in the area of the west edmond field and migration of woodford oil and gas from deeper parts of the basin also contributed to hydrocarbon accumulation

characterizing thermogenic coalbed gas from polish coals of different ranks by hydrous pyrolysis abstract to provide a better characterization of origin and volume of thermogenic gas generation from coals hydrous pyrolysis experiments were conducted at 360 c for 72 h on polish coals ranging in rank from lignite 0 3 r r to semi anthracite 2 0 r r under these conditions the lignites attained a medium volatile bituminous rank 1 5 r r high volatile bituminous coals attained a low volatile bituminous rank 1 7 r r and the semi anthracite obtained an anthracite rank 4 0 r r hydrous pyrolysis of a coal irrespective of rank provides a diagnostic 13 c value for its thermogenic hydrocarbon gases this value can be used quantitatively to interpret mixing of indigenous thermogenic gas with microbial methane or exogenous thermogenic gas from other sources thermogenic methane quantities range from 20 dm 3 kg of lignite 0 3 r r to 0 35 dm 3 kg of semi anthracite 2 0 r r at a vitrinite reflectance of 1 7 r r approximately 75 of the maximum potential for a coal to generate thermogenic methane has been expended at a vitrinite reflectance of 1 7 r r more than 90 of the maximum potential for a coal to generate co 2 has been expended assuming that these quantities of generated co 2 remain associated with a sourcing coal bed as uplift or erosion provide conditions conducive for microbial methanogenesis the resulting quantities of microbial methane generated by complete co 2 reduction can exceed the quantities of thermogenic methane generated from the same coal bed by a factor of 2 5

rock type leaves topographic signature in landslide dominated mountain ranges 1 the idea that hillslopes in active mountain belts are limited to a threshold inclination by the rate of landsliding has guided landscape evolution models for over a decade however widely applied topographic diagnostics of threshold hillslopes remain debated and unverified this study relates landslide occurrence to hillslope metrics of several active mountain ranges throughout new zealand which are formed in uniform greywacke and its schist derivative all these ranges share a distinctive peak in hillslope inclination despite order of magnitude variations in rates of rock uplift and precipitation landslide density and extent of quaternary glaciation comparison with landslide dominated terrain in different lithologies highlights this peak as diagnostic of rock type reflecting a conspicuous tendency in hillslope evolution to adjust to rock mass strength irrespective of the intensity of tectonic and climatic forcing this finding expands the model perspective that only undisturbed strength equilibrium slopes may adjust to their rock mass strength

seismic recordings of landslides caused by typhoon talas 2011 japan 1 large deep seated landslides occurred in nara wakayama and mie prefectures of western japan when typhoon talas passed through the region on september 3 4 2011 signals of large landslides have been recorded by seismic networks around the world and overall force estimates have been previously determined for large landslides using long period waves this study focuses on the high frequency waveforms and presents signals of 18 landslides caused by typhoon talas 2011 the location of the landslides can be determined by a seismological back projection technique and these locations correlate with the observed surface features we have found that the volumes of the landslide correlated with an energy parameter derived from the seismic records

impact of maturity on producible shale oil volumes in the silurian llandovery hot shales of the northern arabian plate southeastern turkey the silurian llandovery hot shales in southeastern turkey have excellent source rock potential with an average total organic carbon toc of 5 9 wt and generation potential values of 14 9 mg hc g toc the hot shales contain type ii organic matter and demonstrate oil and secondary gas generation potential hydrogen indices range from 36 to 510 mg hc g toc depending on maturity the hot shales in the gulf kevan 1 and turkish petroleum tp dogan 1 wells are immature early mature with a vitrinite reflectance equivalent requ of 0 58 0 76 the hot shales in the tp soguktepe 1 and tp k migo 2 wells are mature and in the oil window at 0 78 0 92 requ the hot shales are interpreted to be in the wet gas condensate maturity window with 1 08 1 30 requ in the tp g hazro 2 and tp arco abdulaziz 1 wells corrected evaporation loss restored using oil api gravity values oil saturation index values osic within the gulf kevan 1 tp dogan 1 and tp arco abdulaziz 1 wells are less than 100 mg hc g toc which indicates that unconventional commercial oil production is not probable the osic values of the mature hot shales at the tp soguktepe 1 tp k migo 2 and tp g hazro 2 wells all exceed 100 mg hc g toc indicating potentially producible oil and wet gas condensate thus producible oil and wet gas condensate in the hot shale play appear present in areas that have been assessed as having between 0 8 and 1 1 requ

organic geochemistry of the silurian tanezzuft formation and crude oils nc115 concession murzuq basin southwest libya abstract thirty six silurian core and cuttings samples and 10 crude oil samples from ordovician reservoirs in the nc115 concession murzuq basin southwest libya were studied by organic geochemical methods to determine source rock organic facies conditions of deposition thermal maturity and genetic relationships the lower silurian hot shale at the base of the tanezzuft formation is a high quality oil gas prone source rock that is currently within the early oil maturity window the overall average toc content of the hot shale is 7 2 wt with a maximum recorded value of 20 9 wt by contrast the overlying deposits of the tanezzuft formation have an average toc of 0 6 wt and a maximum value of 1 1 wt the organic matter in the hot shale consists predominantly of mixed algal and terrigenous type ii iii kerogen whereas the rest of the formation is dominated by terrigenous type iii organic matter with some type ii iii kerogen oils from the a b and h oil fields in the nc115 concession were almost certainly derived from marine shale source rocks that contained mixed algal and terrigenous organic input reflecting deposition under suboxic to anoxic conditions the oils are light and sweet and despite being similar were almost certainly derived from different facies and maturation levels within mature source rocks the b oils were generated from slightly less mature source rocks than the others based on hierarchical cluster analysis hca principal component analysis pca selected source related biomarkers and stable carbon isotope ratios the nc115 oils can be divided into two genetic families family i oils from ordovician mamuniyat reservoirs were probably derived from older palaeozoic source rocks whereas family ii oils from ordovician mamuniyat hawaz reservoirs were probably charged from a younger palaeozoic source of relatively high maturity a third family appears to be a mixture of the two but is most similar to family ii oils these oil families were derived from one proven mature source rock the early silurian rhuddanian hot shale there is a good correlation between the family ii and iii oils and the hot shale based on carbon isotope compositions saturated and aromatic maturity parameters indicate that these oils were generated from a source rock of considerably higher maturity than the examined rock samples the results imply that the oils originated from more mature source rocks outside the nc115 concession and migrated to their current positions after generation

mineralogical chemical and k ar isotopic changes in kreyenhagen shale whole rocks and 2 μm clay fractions during natural burial and hydrous pyrolysis experimental maturation abstract progressive maturation of the eocene kreyenhagen shale from the san joaquin basin of california was studied by combining mineralogical and chemical analyses with k ar dating of whole rocks and hydrous pyrolysis was intended to alleviate the problem of mineral and chemical variations in initially deposited rocks of naturally matured sequences however experiments on aliquots from thermally immature kreyenhagen shale outcrop sample did not mimic the results from naturally buried samples experiments conducted for 72 h at temperatures from 270 to 365 c did not induce significant changes at temperatures above 310 c in the mineralogical composition and k ar ages of the rock and large amounts of smectite layers in the illite smectite mixed layers of the pyrolyzed outcrop

carbon isotope composition of lower palaeozoic kerogen effects of maturation abstract the carbon isotope composition of type i kerogen from a marine organic rich black shale deposit of late cambrian age the alum shale formation of southern scandinavia varies from 28 to 30 pdb the thermal maturity is rated by hi oi index t max pi and vitrinite reflectance values and published conodont alteration data the results range from immature conditions with regard to oil generation in central sweden to overmature and submetamorphic conditions in southern sweden denmark and norway in the immature areas the shale is found to be extremely hydrogen rich and oil prone hydrocarbon potential up to 85 kg per ton rock the observed 13 variations are not correlated with maturity it is therefore concluded that thermal maturation processes have no influence on the isotopic composition of a purely marine kerogen the observed range in lower palaeozoic 13 kerogen values 27 to 31 is in accordance with published results from other sedimentary basins

rainfall conditions typhoon frequency and contemporary landslide erosion in japan dealing with predicted increases in extreme weather conditions due to climate change requires robust knowledge about controls on rainfall triggered landslides we explore relationships between rainfall and landslide size throughout the japanese archipelago we test whether the total volume of landslides can be predicted directly from rainfall totals intensity and duration using a nationwide inventory of 4744 rainfall triggered landslides recorded from a d 2001 to 2011 we find that larger landslides were more abundant at the expense of smaller ones when total maximum and mean rainfall intensity exceeded 250 mm 35 mm h and 4 mm h respectively frequency distributions of these rainfall parameters are peaked and heavily skewed yet neither the most frequent nor the most extreme values of these rainfall metrics coincide consistently with the maximum landslide volumes a striking decrease of landslide volumes at both mean and maximum rainfall intensity as well as duration points to an exhaustion in hillslope geomorphic response regardless of sample size landslide type mobilized volume dominant lithology or reporting bias our results underscore substantial offsets between the peaks of rainfall metrics and maximum associated landslide volumes thus complicating straightforward estimates of geomorphic work from metrics of rainstorm magnitude or frequency only the rainfall total appears to be a suitable monotonic predictor of landslide volumes mobilized during typhoons and frontal storms

basin internal derivation of hydrocarbons in the witwatersrand basin south africa evidence from bulk and molecular δ13c data abstract gold in the quartz pebble conglomerates of the late archean witwatersrand basin south africa is often intimately associated with carbonaceous matter of organic biogenic origin which occurs in the form of stratiform carbon seams and paragenetically late bitumen nodules both carbon forms are believed to be formed by solidification of migrating hydrocarbons this paper presents bulk and molecular chemical and stable carbon isotope data for the carbonaceous matter all of which are used to provide a clue to the source of the hydrocarbons these data are compared with those from intra basinal shales and overlying dolostone of the transvaal supergroup the 13c values of the extracts from the witwatersrand carbonaceous material show small differences up to 2 4 compared to the associated insoluble organic matter this suggests that the auriferous rocks were stained by mobile hydrocarbons produced by thermal and oxidative alteration of indigenous bitumens a contribution from hydrocarbons derived from intra basinal witwatersrand shales cannot be excluded individual aliphatic hydrocarbons of the various carbonaceous materials were subjected to compound specific isotope analysis using on line gas chromatography combustion stable isotope ratio mass spectrometry gc c irms the limited variability of the molecular parameters and uniform 13c values of individual n alkanes 31 1 1 7 and isoprenoids 30 7 1 1 in the witwatersrand samples exclude the mixing of oils from different sources carbonaceous matter in the dolostones shows distinctly different bulk and molecular isotope characteristics and thus cannot have been the source of the hydrocarbons in the witwatersrand deposits all the various forms of witwatersrand carbon appear indigenous to the witwatersrand basin and the differences between them are explained by variable in general probably short centimeter to meter scale hydrocarbon migration during diagenesis and subsequent hydrothermal infiltration

carbon and hydrogen isotopic compositions of n alkanes as a tool in petroleum exploration compound specific isotope analysis csia of individual organic compounds is a powerful but underutilized tool in petroleum exploration when integrated with other organic geochemical methodologies it can provide evidence of fluid histories including source maturity charge history and reservoir processes that can support field development planning and exploration efforts the purpose of this chapter is to provide a review of the methodologies used for generating carbon and hydrogen isotope data for mid and high molecular weight n alkanes we discuss the factors that control stable carbon and hydrogen isotope compositions of n alkanes and related compounds in sedimentary and petroleum systems and review current and future applications of this methodology for petroleum exploration we discuss basin specific case studies that demonstrate the usefulness of csia either when addressing particular aspects of petroleum exploration e g charge evaluation source rock oil correlation and investigation of maturity and in reservoir processes or when this technique is used to corroborate interpretations from integrated petroleum systems analysis providing unique insights which may not be revealed when using other methods csia of n alkanes and related n alkyl structures can provide independent data to strengthen petroleum systems concepts from generation and expulsion of fluids from source rock to charge history connectivity and in reservoir processes

theoretical research on the relationship between return period of rainfall and shallow landslides a hydrogeomorphological model for shallow landslide prediction that considers both the stochastic character of rainfall intensity and duration and the deterministic aspects controlling slope stability is presented the probability of shallow subsurface flow i e the process triggering shallow landsliding is expressed by a lognormal distribution the short term probability of landsliding is defined as the probability that the saturated depth exceeds a critical value the average recurrence interval of landsliding tav can be defined as the expected value of the recurrence interval of landsliding this model was applied to a field site in japan where extensive shallow landsliding occurred as a consequence of a heavy rainstorm in 1988 a digital elevation model was utilized to calculate tav for every grid cell it was found that tav is a useful index to correlate to the susceptibility to shallow landsliding a time series of landsliding was then simulated using this model a series of values of return periods of rainfall and consequently of saturated throughflow were randomly generated for 10 000 years one rainstorm event per year it was found that the spatial extent of landsliding expressed as a percentage of scar area associated with each rainstorm event was strongly influenced not only by rainfall but also by the historical sequence of landsliding the effective return period of rainfall for shallow landsliding was then estimated using the same model it was found that rainfall events with return periods 500 years and 1000 years trigger about 50 and 65 respectively of the total number of landslides over the long term copyright 2004 john wiley sons ltd

the mass balance of earthquakes and earthquake sequences large compressional earthquakes cause surface uplift as well as widespread mass wasting knowledge of their trade off is fragmentary combining a seismologically consistent model of earthquake triggered landsliding and an analytical solution of coseismic surface displacement we assess how the mass balance of single earthquakes and earthquake sequences depends on fault size and other geophysical parameters we find that intermediate size earthquakes mw 6 7 3 may cause more erosion than uplift controlled primarily by seismic source depth and landscape steepness and less so by fault dip and rake such earthquakes can limit topographic growth but our model indicates that both smaller and larger earthquakes mw 7 3 systematically cause mountain building earthquake sequences with a gutenberg richter distribution have a greater tendency to lead to predominant erosion than repeating earthquakes of the same magnitude unless a fault can produce earthquakes with mw 8 or more

a seismic landslide susceptibility rating of geologic units based on analysis of characteristics of landslides triggered by the 17 january 1994 northridge california earthquake abstract one of the most significant effects of the 17 january 1994 northridge california earthquake m 6 7 was the triggering of thousands of landslides over a broad area some of these landslides damaged and destroyed homes and other structures blocked roads disrupted pipelines and caused other serious damage analysis of the distribution and characteristics of these landslides is important in understanding what areas may be susceptible to landsliding in future earthquakes we analyzed the frequency distribution and geometries of triggered landslides in the santa susana 7 5 quadrangle an area of intense seismic landslide activity near the earthquake epicenter landslides occurred primarily in young late miocene through pleistocene uncemented or very weakly cemented sediment that has been repeatedly folded faulted and uplifted in the past 1 5 million years the most common types of landslide triggered by the earthquake were highly disrupted shallow falls and slides of rock and debris far less numerous were deeper more coherent slumps and block slides primarily occurring in more cohesive or competent materials the landslides in the santa susana quadrangle were divided into two samples single landslides 1502 and landslide complexes 60 which involved multiple coalescing failures of surficial material we described landslide morphologies by computing simple morphometric parameters area length width aspect ratio slope angle to quantify and rank the relative susceptibility of each geologic unit to seismic landsliding we calculated two indices 1 the susceptibility index which is the ratio given as a percentage of the area covered by landslide sources within a geologic unit to the total outcrop area of that unit and 2 the frequency index given in landslides per square kilometer ls km2 which is the total number of landslides within each geologic unit divided by the outcrop area of that unit susceptibility categories include very high 2 5 landslide area or 30 ls km2 high 1 0 2 5 landslide area or 10 30 ls km2 moderate 0 5 1 0 landslide area or 3 10 ls km2 and low

regional patterns of earthquake triggered landslides and their relation to ground motion 1 we have documented patterns of landsliding associated with large earthquakes on three thrust faults the northridge earthquake in california chi chi earthquake in taiwan and two earthquakes on the ramu markham fault bounding the finisterre mountains of papua new guinea in each case landslide densities are shown to be greatest in the area of strongest ground acceleration and to decay with distance from the epicenter in california and taiwan the density of co seismic landslides is linearly and highly correlated with both the vertical and horizontal components of measured peak ground acceleration based on this observation we derive an expression for the spatial variation of landslide density analogous with regional seismic attenuation laws in its general form this expression applies to our three examples and we determine best fit values for individual cases our findings open a window on the construction of shake maps from geomorphic observations for earthquakes in non instrumented regions

isotopic evidence for massive oxidation of organic matter following the great oxidation event the stable isotope record of marine carbon indicates that the proterozoic eon began and ended with extreme fluctuations in the carbon cycle in both the paleoproterozoic 2500 to 1600 million years ago ma and neoproterozoic 1000 to 542 ma extended intervals of anomalously high carbon isotope ratios 13c indicate high rates of organic matter burial and release of oxygen to the atmosphere in the neoproterozoic the high 13c interval was punctuated by abrupt swings to low 13c indicating massive oxidation of organic matter we report a paleoproterozoic negative 13c excursion that is similar in magnitude and apparent duration to the neoproterozoic anomaly this shunga francevillian anomaly may reflect intense oxidative weathering of rocks as the result of the initial establishment of an oxygen rich atmosphere

a stochastic hydro geomorphological model for shallow landsliding due to rainstorm abstract a prediction model of shallow landsliding is proposed it considers not only the deterministic aspects containing slope stability saturated throughflow and a soil regolith depth development but also the stochastic aspects of intensity and duration of rainfall it turns out that the probability of saturated throughflow which is the direct trigger mechanism to shallow landsliding can be expressed by a log normal distribution the short term probability of landsliding is defined as the excess probability that the depth of saturated throughflow surpasses the critical value the average recurrence interval t av of landsliding can be calculated as the expected value this model was applied to a test field where a lot of shallow landsliding occurred at a heavy rainstorm in 1988 then a dem of 5 m grid interval was utilized to calculate t av at every grid point consequently it was found that the percentage of the landslide grid number to the total grid number for every t av rank increases when t av decreases therefore it is confirmed that t av is an index of the susceptibility to shallow landsliding and the distribution map of t av can be regarded as a kind of hazard map the spatial distribution of t av reveals its significant dependence on the topography

two oil types on north slope of alaska implications for exploration forty oil samples from across the north slope of alaska have been analyzed by the u s bureau of mines and the u s geological survey results of these analyses suggest two separate genetic oil types the first the simpson umiat oil type occurs in reservoir rocks of cretaceous and quaternary age and includes oil from seeps in the skull cliff cape simpson manning point and ungoon point areas and oils from wolf creek test 3 and the cape simpson and umiat oil fields these are higher gravity low sulfur oils with no or slight odd numbered n alkane predominance and pristane to phytane ratios greater than 1 5 also these oils have dgr13c values ranging from 29 1 to 27 8 parts per thousand ppt and dgr34s values from 10 3 to 4 9 ppt the s cond type the barrow prudhoe oil type occurs in reservoir rocks of carboniferous to cretaceous age and includes oils from south barrow gas field prudhoe bay oil field and the fish creek test well 1 physical properties of barrow prudhoe oils are variable but in general the oils are medium gravity high sulfur oils with slight even numbered n alkane predominance and pristane to phytane ratios less than 1 5 also these oils have dgr13c values of 30 3 to 29 8 ppt and dgr34s values from 30 0 to 2 1 ppt the two types are believed to originate from different source rocks the barrow prudhoe type may have originated from a carbonate or other iron deficient source rock and the simpson umiat type from a siliciclastic source rock occurrences of the two oil types when outlined on a map indicate at least two areas for additional exploration for the barrow prudhoe type in stratigraphic traps along and adjacent to the barrow arch and for the simpson umiat type in cretaceous rocks along the trend between the simpson and umiat oil fields and in cretaceous and tertiary rocks from prudhoe bay field to the william o douglas arctic wildlife range

carbon isotope geochemistry of paleozoic oils from big horn basin abstract twenty crude oils from paleozoic reservoirs in the big horn basin wyoming were fractionated into light hydrocarbons saturates monoaromatics diaromatics polyaromatics and polars and asphaltenes amounts and isotopic composition of each fraction were found to be internally consistent with the degree of maturation of the oil confirming the established single source origin for these oils a variation of approximately three per mil in the carbon isotopic composition of the whole oil and individual fraction was explained as being caused by maturation the isotope type curves for these oils the variations in isotopic composition as a function of compound group type were not found to be as simple as commonly believed other alteration processes such as migration and deasphalting might have influenced the pattern of the isotope distributions among fractions the conservative nature of mass balance and subsequent isotope flows among various fractions of crude oil showed that the maturation of crude oil consists of consecutive processes leading from larger and more polar components into smaller and less polar components culminating in natural gas calculations were made to project the amount of condensates associated with the crude oils and the amount of natural gas which had been generated from crude oils of a given maturity

sulphur and carbon isotopic composition of power supply coals in the pannonian basin hungary abstract the present work is an attempt to establish the stable isotope database for mesozoic to tertiary coals from the pannonian basin hungary maceral composition proximate analysis sulphur form sulphur isotopes organic and pyritic and carbon isotopes were determined this database supports the assessment of the environmental risks associated with energy generation the characterization of the formation and the distribution of sulphur in the coals used the maceral composition the sulphur composition the c s isotopic signatures and some of the geological evidences published earlier show that the majority of these coals were deposited in freshwater and brackish water environments despite the relatively high average sulphur content however the upper cretaceous eocene and lower miocene formations also contain coal seams of marine origin as indicated by their maceral composition and sulphur and carbon chemistry the majority of the sulphur in these coals occurs in the organic form all studied sulphur phases are relatively rich in 34s isotopes 34sorganic 12 74 34spyrite 10 06 on average this indicates that marine bacterial sulphate reduction played a minor role in their formation in the sense that isotopic fractionation was limited it seems that the interstitial spaces of the peat closed rapidly during early diagenesis due to a regime of high depositional rate leading to a relative enrichment of the heavy sulphur isotopes

multiple sulphur isotope records tracking basinal and global processes in the 1 98 ga zaonega formation nw russia abstract the exceptionally organic rich rocks of the 1 98 ga zaonega formation deposited in the onega basin nw russia have refined our understanding of earth system evolution during the paleoproterozoic rise in atmospheric oxygen these rocks were formed in vent or seep influenced settings contemporaneous with voluminous mafic volcanism and contain strongly 13c depleted organic matter here we report new isotopic 34s 33s 36s 13corg and mineralogical major element total sulphur and organic carbon data for the upper part of the zaonega formation which was deposited shortly after the termination of the lomagundi jatuli positive carbon isotope excursion the data were collected on a recently obtained 102 m drill core section and show a 13corg shift from 38 to 25 sedimentary sulphides have 34s values typically between 15 and 25 reflecting closed system sulphur isotope behaviour driven by high rates of microbial sulphate reduction high sulphate demand hydrothermal activity and hydrocarbon seepage four intervals record 34s values that exceed 30 we interpret these unusually 34s enriched sulphides to be a result of limited sulphate diffusion into pore waters due to changes in sedimentation and or periods of basinal restriction additionally there are four negative 34s excursions that are interpreted to reflect changes in the open closed system behaviour of sulphate reduction or availability of reactive iron our findings highlight the influence of basinal processes in regulating sulphur isotope records and the need for care before interpreting such signals as reflecting global conditions

organic geochemistry and petrology of posidonia shale lower toarcian western europe the evolution from immature oil prone to overmature dry gas producing kerogen abstract kerogen concentrates as well as whole rock samples of the lower jurassic posidonia shale representing a complete maturity series from immature to highly overmature were analyzed using organic petrography palynology bulk geochemical analysis ft ir and curie point pyrolysis gc ms cp py gc ms in order to investigate changes in kerogen composition with increasing maturation vitrinite reflectance vrr ranges from 0 5 to 3 hi values reflect the maturity trend very well with little scatter in contrast tmax oi and pi values show more scatter and greater differences between kerogen concentrates and whole rock samples ft ir spectra show a decrease in functional group bands with increasing maturation which has been quantified cp py gc ms analyses indicate an increase in hydrocarbons especially for short and medium length n alkanes with a strong predominance of short length alkanes at highest maturities about 3 vrr this effect however depends also on the applied pyrolysis temperature where higher temperatures 920 c as compared to 650 c favor generation of short length n alkanes especially for samples at high levels of maturation ratios of aromatic over aliphatic hydrocarbons or alkenes over alkanes show a non steady evolution depending also on the applied pyrolysis temperatures indicating that higher pyrolysis temperatures are needed for pyrolytic alkene formation with a maximum alkene formation for samples within early overmature maturities 1 4 vrr aromaticity first decreases but increases at high levels of maturation finally weathering of the highly overmature sample 3 vrr resulted in strong oxidation of organic matter with impact on rock eval ftir and curie point pyrolysis data

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

landslide patterns reveal the sources of large earthquakes the distribution of fault slip in an earthquake controls seismic surface deformation and ground shaking and is the most direct record of fault response to tectonic stress detailed information about slip patterns in large earthquakes is only available where a dense local network of seismometers is in place elsewhere the evaluation of earthquake source and mechanism relies on observation of proxies such as surface change or damage intensity in upland areas the density of seismically induced landslides is strongly influenced by the intensity and duration of strong ground motion and therefore contains information about the earthquake source mechanism here we show that density patterns of co seismic landslides closely track the distribution of fault slip in two large thrust earthquakes in japan when adjusted for site effects landslide distributions readily obtained from remote sensed images can supplement or replace instrumental records of earthquakes opening historical and remote events for close geophysical investigation

stable carbon isotope variation of n alkanes in central graben oils while isotope analysis of bulk fractions is a well tried and useful tool in oil correlation use of compound specific isotope ratio mass spectrometry cs irms of individual hydrocarbons is still in its infancy this technique has been developed over the past few years as a useful research tool but its potential in petroleum exploration has yet to be demonstrated in this paper both bulk fraction and individual hydrocarbon isotopic data were acquired their use was evaluated and compared with traditional geochemical measurements such as gas chromatography and gc ms data on 72 oils from the norwegian sector of the central graben were acquired data include 13c isotope composition of whole oil and topped oil as well as saturated and aromatic hydrocarbon nso and asphaltene fractions and 13c isotopic composition of individual n alkanes in the range nc4 to nc35 the same samples were also analysed by capillary gc and gc ms gc gc ms and bulk fraction isotope data suggest that many of the analysed greater ekofisk oils e g valhall edlfisk i e within the lindesnes ridge inversion zone have more than one source facies outside of this area particularly towards the northwest oils are probably mainly from a single source facies the isotopic compositions of individual hydrocarbon compounds also reveal the same divisions in addition several further features were observed the normal alkanes of many of the greater ekofisk oils are more depleted in 12c between nc20 nc25 than at higher or lower molecular weight possibly representative of the original microbial precursors other oils have relatively uniform n alkane isotope profiles with n alkanes which are enriched in 12c relative to the n alkanes of oils with the other type of profile the two different isotope profiles are interpreted as being separate source facies the least mature greater ekofisk oils also become more enriched in 12c with decreasing molecular weight mature oils from this area tend to have very similar n alkane isotope values throughout the measured n alkane range the higher maturity oils and condensates have n alkanes nc8 the tentative interpretation of this is that the highly mature oils condensates are sourced only from highly mature source rocks i e of a condensate window maturity and are not products of thermal alteration in the reservoir

landslide erosion controlled by hillslope material landslide erosion is a primary control of landscape relief a wide ranging analysis of landslide geometry shows that soil based landslides are generally less voluminous than landslides that involve the failure of bedrock and provides refined metrics for estimating the volume of a landslide from the area of the failure

solid bitumens an assessment of their characteristics genesis and role in geological processes familiar since antiquity and subject in contemporary times to various characterization schemes the exact nature of solid bitumen is not yet fully known bitumens have random polymer like molecular structures are mobile as highly viscous fluids or were once fluids but have since turned into solids solid bitumens consist mainly of large moieties of polyclyclic aromatic hydrocarbons occasionally with finely admixed fine grained cryptocrystalline graphite solid bitumens are distinguished from kerogen which is the syngenetic and generally finely dispersed particulate organic matter in sedimentary rock that virtually does not migrate following its deposition occurrences of solid bitumens are relevant to petroleum exploration as well as the search for and evaluation of a variety of metallic mineral deposits genesis of bitumen is in many cases linked to the thermal and hydrothermal history of organic matter in sedimentary rock apparently bitumen or more specifically organic acids generated along with bitumen during diagenesis may alter porosity of reservoir rocks or otherwise prepare the ground for ore deposition bitumen is also relatively sensitive to alteration processes some of which such as oxidative weathering water leaching biodegradation contact metamorphism and ionizing radiation may likewise affect its nature elemental composition of bitumen commonly reflects the nature of mineral deposits is is possible that in petroleum exploration trace metal abundances of bitumen may eventually allow prediction of crude oil types and volumes anticipated from a given source rock beside transition elements notably ni and v highly anomalous concentrations of u pt and au occur in some solid bitumens during the generation of petroleum from kerogen the trend in 13c is toward lighter values the opposite seems to occur when liquid petroleum is subjected to thermal cracking and or related processes yielding solid bitumen enriched in 13c and isotopically light methane in fact except for deasphalting and possibly some irradiation processes the result of thermal cracking oxidation water leaching inspissation drying and bacterial degradation of crude oil is that lower molecular weight hydrocarbons are removed leaving bitumen residues enriched in aromatic hydrocarbons heteroatomic compounds nso and 13c such phenomena are relevant to bitumen paragenesis in petroleum reservoir rocks to certain phanerozoic occurrences of multiple generations of bitumens and to bitumens in mineral deposits

stable carbon isotopes in source bed organic matter of west and east siberia abstract 13 c 12 c ratios were measured for 157 insoluble organic matter samples and for 47 kerogenbitumoid chloroform extract syngenetic pairs from facially different sediments of main oil bearing complexes in west and east siberia the 13 c of organic matter of marine and continental sediments ranges from 32 2 to 27 5 and from 28 0 to 23 5 respectively the carbon isotope composition of sopropelic bitumoids is insignificantly lighter or equal to 13 c of related kerogens while the difference in 13 c between humic kerogens and syngenetic bitumoids is about 2 3 for kerogens of both types the linear dependence of 13 c vs h c atomic ration is observed sapropelic kerogens h c atomic ratio is 1 5 2 times greater than that in humic insoluble organic matter the organic matter of recent lacustrine sediments the main precursor of which was algal plankton has 13 c values between 27 1 for 26 3 0 for both the insoluble and dissolved parts of organic matter there is considerable difference in 13 c between insoluble 13 c from 28 8 to 26 3 0 and dissolved 13 c from 35 3 to 28 5 0 organic matter in sediments of those lakes in which higher aquatic plants accumulated and the contribution of terrestrial organic debris to sediments was significant in present day biota the 12 c concentration is lower in marine plankton and higher aquatic plants as compared to higher land plants the results showed that the isotopic differentiation similar to that found in living organisms is observed in recent sediments this differentiation is not applicable to sedimentary organic matter evaluation of the data suggests that the different types of kerogen forming reactions different pathways of organic matter transformation during decay burial and protocatagenesis in marine and continental environments result in different 13 c distributions in sedimentary organic matter than in living organisms and recent sediments the relationship between carbon isotopic composition of jurassic oils from west siberia and the different types of om from source beds of one and the same age in this region is established

density distribution of landslides triggered by the 2008 wenchuan earthquake and their relationships to peak ground acceleration the distribution of landslides induced by the 2008 m w 7 9 wenchuan earthquake was investigated following the method of meunier et al 2007 to examine the relationships to peak ground acceleration pga results suggest that landslide densities are quantifiably related to pga thresholds of pgacr for landslide failure are graphic 1 for average horizontal pga and graphic 2 for average vertical pga as with other earthquakes the distribution of the wenchuan earthquake triggered landslides can be described by two equations based on area and source densities respectively the similar damping factors of 20 in these two equations suggest that both density distribution patterns of landslides reflect the dissipation of seismic energy landslide derived pga equations were then produced for the hanging wall region of the earthquake affected area the results indicate that it should be possible to produce an earthquake shake map from the distribution of earthquake triggered landslides in an area where there are few or no seismic instruments but many landslides 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif

estimating the timing and location of shallow rainfall induced landslides using a model for transient unsaturated infiltration 1 shallow rainfall induced landslides commonly occur under conditions of transient infiltration into initially unsaturated soils in an effort to predict the timing and location of such landslides we developed a model of the infiltration process using a two layer system that consists of an unsaturated zone above a saturated zone and implemented this model in a geographic information system gis framework the model links analytical solutions for transient unsaturated vertical infiltration above the water table to pressure diffusion solutions for pressure changes below the water table the solutions are coupled through a transient water table that rises as water accumulates at the base of the unsaturated zone this scheme though limited to simplified soil water characteristics and moist initial conditions greatly improves computational efficiency over numerical models in spatially distributed modeling applications pore pressures computed by these coupled models are subsequently used in one dimensional slope stability computations to estimate the timing and locations of slope failures applied over a digital landscape near seattle washington for an hourly rainfall history known to trigger shallow landslides the model computes a factor of safety for each grid cell at any time during a rainstorm the unsaturated layer attenuates and delays the rainfall induced pore pressure response of the model at depth consistent with observations at an instrumented hillside near edmonds washington this attenuation results in realistic estimates of timing for the onset of slope instability 7 h earlier than observed landslides on average by considering the spatial distribution of physical properties the model predicts the primary source areas of landslides

plate tectonic trigger of changes in pco2 and climate in the oxfordian late jurassic carbon isotope and modeling evidence abstract the transition from the middle to the late jurassic was characterized by significant changes in oceanography and climate and by changes in global carbon cycle as shown in the c isotope record a prominent mid oxfordian positive excursion in bulk carbonate carbon isotope values 13 c carb with an amplitude of more than 1 has been documented from many sections in the northern tethys realm in this study we present new bulk organic matter c isotope data 13 c org from northwestern tethys that do not record the mid oxfordian positive excursion in carbonate carbon on the contrary 13 c org decreases during the interval of the most rapid increase in 13 c carb we demonstrate that this decrease is not due to a changing marine terrestrial organic carbon partitioning but that the contrasting isotope trends record peculiar environmental and climate changes which occurred near the beginning of the late jurassic using a simple carbon cycle model we show that an increase in atmospheric p co 2 starting at modern levels could be the cause of contrasting trends in 13 c carb and 13 c org we suggest that a reorganisation of ocean currents related to the opening and or widening of the tethys atlantic pacific seaway and a massive spread of shallow sea carbonate production led to higher p co 2 model simulations indicate that this increase in p co 2 may have triggered changes in the biological carbon pump and in organic carbon burial that can explain the middle oxfordian c isotope record

effects of thermal maturation on stable organic carbon isotopes as determined by hydrous pyrolysis of woodford shale acquiring crude oils that have been expelled from the same rock unit at different levels of thermal maturation is currently not feasible in the natural system this prevents direct correlation of compositional changes between the organic matter retained in a source rock and its expelled crude oil at different levels of thermal maturation alleviation of this deficiency in studying the natural system requires the use of laboratory experiments natural generation of petroleum from amorphous type ii kerogen in the woodford shale may be simulated by hydrous pyrolysis which involves heating crushed rock in contact with water at subcritical temperatures 374 c four distinct stages of petroleum generation are observed from this type of pyrolysis 1 pre oil generation 2 incipient oil generation 3 primary oil generation and 4 post oil generation the effects of thermal maturation on the 13c values of kerogen bitumen and expelled oil like pyrolysate from the woodford shale have been studied through these four stages of petroleum generation similar to the natural system the kerogens isolated from the pyrolyzed rock showed no significant change in 13c this suggests that the 13c value of kerogens may be useful in kerogen typing and oil to source rock correlations 13c values of bitumens extracted from the pyrolyzed rock showed an initial decrease during the incipient oil generation stage followed by depletion during the primary and post oil generation stages this reversal is not favorable for geochemical correlation or maturity evaluation saturated and polar components of the bitumen show the greatest 13c variations with increasing thermal maturation the difference between the 13c of these two components gives a unidirectional trend that serves as a general indicator of thermal maturation and is referred to as the bitumen isotope index bii 13c values of the expelled pyrolysates show a unidirectional increase with increasing thermal maturation the constancy and similarity of 13c values of the aromatic components in the expelled pyrolysates and bitumens with increasing thermal maturation encourages their use in oil to oil and oil to source rock correlations isotopic type curves for expelled pyrolysates indicate that they may be useful in oil to oil correlations but have a limited use in oil to source rock correlations

a process based model for colluvial soil depth and shallow landsliding using digital elevation data a model is proposed for predicting the spatial variation in colluvial soil depth the results of which are used in a separate model to examine the effects of root strength and vertically varying saturated conductivity on slope stability the soil depth model solves for the mass balance between soil production from underlying bedrock and the divergence of diffusive soil transport this model is applied using high resolution digital elevation data of a well studied site in northern california and the evolving soil depth is solved using a finite difference model under varying initial conditions the field data support an exponential decline of soil production with increasing soil depth and a diffusivity of about 50 cm 2 yr the predicted pattern of thick and thin colluvium corresponds well with field observations soil thickness on ridges rapidly obtain an equilibrium depth which suggests that detailed field observations relating soil depth to local topographic curvature could further test this model bedrock emerges where the curvature causes divergent transport to exceed the soil production rate hence the spatial pattern of bedrock outcrops places constraints on the production law the infinite slope stability model uses the predicted soil depth to estimate the effects of root cohesion and vertically varying saturated conductivity low cohesion soils overlying low conductivity bedrock are shown to be least stable the model may be most useful in analyses of slope instability associated with vegetation changes from either land use or climate change although practical applications may be limited by the need to assign values to several spatially varying parameters although both the soil depth and slope stability models offer local mechanistic predictions that can be applied to large areas representation of the finest scale valleys in the digital terrain model significantly influences local model predictions this argues for preserving fine scale topographic detail and using relatively fine grid sizes even in analyses of large catchments