submarine debris flow impact on pipelines part i experimental investigation estimating the impact forces exerted by a submarine debris flow on a pipeline is a challenge and there is room for considerably more work to advance the state of the art to this end an experimental program was performed to investigate the impact on two pipeline installation scenarios 1 suspended pipeline and 2 laid on seafloor pipeline the results and observations from the experimental investigation are discussed the definition of reynolds number was modified for non newtonian fluids and an ad hoc method was developed to estimate the drag force exerted by an impact perpendicular to the pipe axis the method may be used in prototype situations to estimate the drag force from submarine debris flow impact on pipelines the experimental program was complemented by computational fluid dynamics cfd analyses the details of which are discussed in the accompanying paper

low temperature hydrothermal maturation of organic matter in sediments from the atlantis ii deep red sea abstract hydrocarbons and bulk organic matter of two sediment cores no 84 and 126 chain 61 cruise located within the atlantis ii deep have been analyzed although the brines overlying the coring areas were reported to be sterile microbial inputs and minor terrestrial sources represent the major sedimentary organic material this input is derived from the upper water column above the brines both steroid and triterpenoid hydrocarbons show that extensive acid catalyzed reactions are occurring in the sediments in comparison with other hydrothermal guaymas basin or intrusive systems cape verde rise the atlantis ii deep exhibits a lower degree of thermal maturation this is easily deduced from the elemental composition of the kerogens and the absence of polynuclear aromatic hydrocarbons of a pyrolytic origin in the bitumen the lack of carbon number preference among the n alkanes suggests especially in the case of the long chain homologs that the organic matter of atlantis ii deep sediments has undergone some degree of catagenesis however the yields of hydrocarbons are much lower than those observed in other hydrothermal areas the effect of lower temperature and poor source rock characteristics appear to be responsible for the differences

understanding how volume affects the mobility of dry debris flows 1 the prediction of the runout length l of large dry debris flows has long been the subject of a considerable research effort primarily due to the obvious concern caused by their destructive power one seemingly well established feature is the increase of the mobility of a rock avalanche defined as the ratio of the runout distance to the fall height with its volume v the physical nature of this lubrication mechanism remains however controversial in this paper we analyse field data and discrete numerical simulations of granular flows and demonstrate the geometrical origin of the apparent enhancement of the mobility with the volume we evidence the intertwined role of volume and topography and show the existence of two contributions in the runout defining two flow regimes one dominated by sliding in which the runout is independent of v and another dominated by spreading in which the runout is strongly dependent on v in the light of these results the search of a volume dependent lubrication mechanism appears to be an ill posed problem

new isotopic evidence for the origin of groundwater from the nubian sandstone aquifer in the negev israel the geochemistry and isotopic composition h o s osulfate c sr of groundwater from the nubian sandstone kurnub group aquifer in the negev israel were investigated in an attempt to reconstruct the origin of the water and solutes evaluate modes of water rock interactions and determine mean residence times of the water the results indicate multiple recharge events into the nubian sandstone aquifer characterized by distinctive isotope signatures and deuterium excess values in the northeastern negev groundwater was identified with deuterium excess values of 16 which suggests local recharge via unconfined areas of the aquifer in the negev anticline systems the d 18 oh2o and d 2 h values 6 5 and 35 4 of this groundwater are higher than those of groundwater in the sinai peninsula and southern arava valley 7 5 and 48 3 that likewise have lower deuterium excess values of 10 based on the geochemical differences between groundwater in the unconfined and confined zones of the aquifer a conceptual geochemical model for the evolution of the groundwater in the nubian sandstone aquifer has been reconstructed the isotopic composition of shallow groundwater from the unconfined zone indicates that during recharge oxidation of pyrite to so4 d 34 sso4 13 d 18 oso4 7 7 and dissolution of caco3 87 sr 86 sr 0 70787 d 13 cdic 3 7 occur in the confined zone of the aquifer bacterial so4 reduction removes a significant part of dissolved so 2

highly isotopically depleted isoprenoids molecular markers for ancient methane venting abstract we propose that organic compounds found in a miocene limestone from marmorito northern italy are source markers for organic matter present in ancient methane vent systems cold seeps the limestone contains high concentrations of the tail to tail linked acyclic c20 isoprenoid 2 6 11 15 tetramethylhexadecane crocetane a c25 homolog 2 6 10 15 19 pentamethylicosane pme and a distinctive glycerol ether lipid containing 3 7 11 15 tetramethylhexadecyl phytanyl moieties the chemical structures of these biomarkers indicate a common origin from archaea their extremely 13c depleted isotope compositions 13c 108 to 115 6 pdb suggest that the respective archaea have directly or indirectly introduced isotopically depleted methane derived carbon into their biomass we postulate that a second major cluster of biomarkers showing heavier isotope values 13c 88 is derived from sulfate reducing bacteria srb the observed biomarkers sustain the idea that methanogenic bacteria in a syntrophic community with srb are responsible for the anaerobic oxidation of methane in marine sediments marmorito may thus represent a conceivable ancient scenario for methane consumption performed by a defined two membered bacterial consortium 1 archaea that perform reversed methanogenesis by oxidizing methane and producing co2 and h2 and 2 srb that consume the resulting h2 furthermore the respective organic molecules are unlike other compounds tightly bound to the crystalline carbonate phase the marmorito carbonates can thus be regarded as cold seep microbialites rather than mere authigenic carbonates

archaea mediate anaerobic oxidation of methane in deep euxinic waters of the black sea we evaluate anaerobic oxidation of methane aom in the black sea water column by determining distributions of archaea specific glyceryl dialkyl glyceryl tetraethers gdgts and 13c isotopic compositions of their constituent biphytanes in suspended particulate matter spm sinking particulate matter collected in sediment traps and surface sediments we also determined isotopic compositions of fatty acids specific to sulfate reducing bacteria to test for biomarker and isotopic evidence of a syntrophic relationship between archaea and sulfate reducing bacteria in carrying out aom bicyclic and tricyclic gdgts and their constituent 13c depleted monocyclic and bicyclic biphytanes down to 67 indicative of archaea involved in aom were present in spm in the anoxic zone below 700 m depth in contrast gdgt 0 and crenarchaeol derived from planktonic crenarchaeota dominated the gdgt distributions in the oxic surface and shallow anoxic waters fatty acids indicative of sulfate reducing bacteria i e iso and anteiso c15 were not strongly isotopically depleted e g 32 to 25 although anteiso c15 was 5 more depleted in 13c than iso c15 our results suggest that either aom is carried out by archaea independent of sulfate reducing bacteria or those sulfate reducing bacteria involved in a syntrophy with methane oxidizing archaea constitute a small enough fraction of the total sulfate reducing bacterial community that an isotope depletion in their fatty acids is not readily detected sinking particulate material collected in sediment traps and the underlying sediments in the anoxic zone contained the biomarker and isotope signature of upper water column archaea aom specific gdgts and 13c depleted biphytanes characteristic of the spm in the deep anoxic zone are not incorporated into sinking particles and are not efficiently transported to the sediments this observation suggests that sediments may not always record aom in overlying euxinic water columns and helps explain the absence of aom derived biomarkers in sediments deposited during past periods of elevated levels of methane in the ocean

organofacies and paleoenvironment of lower carboniferous mudstones dishuiquan formation in eastern junggar nw china abstract the sedimentary rocks of the dishuiquan formation represent an important potential source for volcanic rock reservoirs and record the transition of the depositional environment from marine to terrestrial during paleo junggar oceanic subduction the source rock potential and paleoenvironment of mudstones from dishuiquan formation in eastern junggar were determined by organic petrography rock eval molecular and stable carbon 13 c analyses toc s 2 and hydrogen index hi values suggest a fair to good organic richness in mudstone samples from the c 2 well moreover an early mature to mature state for all the samples is inferred based on the rock eval and biomarker parameters the maceral composition molecular geochemistry and carbon isotopic results for kerogen reveal that all the mudstone samples are characterized by a mixed organic matter assemblage types ii iii with relatively high percentages of terrigenous organic matter the low to intermediate values of pr ph and the high abundances of carotene and gammacerane indicate the presence of a dysoxic reducing high salinity sedimentary environment during the deposition of the dishuiquan formation numerous parameters derived from the organic geochemical analyses indicate that the terrigenous organic matter increased with decreasing salinity and oxidation in the sedimentary environment this study concludes that a warm wet climate provided a continuous fluvial input of terrigenous plant debris and fresh water the organic geochemical data combined with the tectonic setting reveal a restricted semi closed marine depositional environment during the deposition of the dishuiquan formation in the early carboniferous

the yarkon taninim groundwater basin israel hydrogeology case study and critical review abstract the late albian turonian judea group carbonate aquifer is one of the most important resources of fresh groundwater in the northern negev and in the central part of israel over three decades ago various hydrological hydrochemical hydrometeorological and geological aspects of this aquifer were thoroughly investigated and served to build up the professional background and data base for the management of this resource notwithstanding the accumulating structural hydrogeological and hydrochemical evidence the conceptual hydrogeological model of the yarkon taninim basin which constitutes the western part of the judea group aquifer has neither been questioned nor updated therefore the existing and accepted model of this basin should in the best case only depict general features and trends the present review critically examines the main hitherto accepted hydrogeological conventions points out puzzling and contradictory phenomena and emphasizes questionable issues although the present review deals with problems related to a specific groundwater basin the methods and effort for breaking long established conventions may serve as an example for similar situations in other places in which water resources are managed according to long established concepts and traditions without being periodically revised and reassessed in view of accumulating knowledge

global comparisons of organic matter in sediments across the cretaceous tertiary boundary a tract the cretaceous tertiary k t boundary is marked by extensive changes in the sedimentary fossil record of continental and marine life organic matter in sediments from above and below the k t boundary has been studied to identify consequences of the biotic extinctions and of the changes in biological productivity which occurred at this time data from locations encompassing a variety of marine paleoenvironments were examined to assess the global extent and local expressions of these biological changes characterizations of organic matter included rock eval pyrolysis stable carbon isotope ratios and distributions of extractable biomarkers in general organic carbon concentrations are a few tenths of a percent in the chalks and marls above and below the k t boundary in some boundary clay samples concentrations up to 5 are found the elevated amounts near the boundary result from oxidation of marine organic matter consequent dissolution of carbonates and concentration of the surviving organic matter at all locations the organic matter has been microbially reworked and evidently was deposited in oxidizing environments carbon isotope shifts in open marine sediments suggest biological productivity was depressed following the k t boundary repetition of these changes at different locations verifies the global extent of the boundary event yet local variations in its expression are evident

a perturbation solution for bingham plastic mudflows an analytical solution is proposed for laminar mudflows and debris flows that can be modeled by a bingham plastic law two dimensional unsteady nonuniform bingham flows released from a point source or a source of finite size dam break problem or mudslide problem on a steep slope are considered the method of matched asymptotic expansions was implemented to get a first order solution for the dam break problem the proposed model is found to be valid when the shock wave has advanced three reservoir lengths downstream also it is found that the bingham flow only propagates a finite distance downstream with the shock depth asymptotically approaching the yield depth and the shock velocity asymptotically falling to zero the hydrograph produced by a bingham flow is seen to have a slower and lower flood peak and a longer and higher flow tail than that produced by newtonian flow having the same dynamic viscosity comparison of the model predictions with laboratory observations shows reasonable agreement

geochemical and biological marker assessment of depositional environments using brazilian offshore oils abstract a combined geochemical and molecular characterization of a wide selection of oils from the major brazilian offshore basins has been undertaken the elemental sulphur nickel and vanadium and bulk oapi and 13c properties of each sample been considered together with its molecular composition determined using liquid and gas chromatography and quantitative biological marker investigations using gas chromatography mass spectrometry for alkanes the results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups the distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils each group is correlated tentatively with source rocks laid down in a specific depositional regime namely lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate or marine deltaic the diagnostic features that allow this classification are the relative abundance and carbon number distributions of n alkanes pristane phytane ratios sulphur nickel and vanadium contents carbon isotope data the absolute concentrations of hopanes and steranes and their abundance relative to 4 methylsteranes and also the occurrence and abundance of several specific biological markers including 18 h oleanane gammacerane carotane tricyclic terpanes higher acyclic isoprenoids 28 30 bisnorhopane and 25 28 30 trisnorhopane this investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils

sources and deposition of organic matter in cretaceous passive margin deep sea sediments a synthesis of organic geochemical studies from deep sea drilling project site 603 outer hatteras rise abstract the results of organic geochemical studies of rock samples from cretaceous strata at site 603 on the outer hatteras rise are reviewed and integrated with their lithostratigraphic information although most of the strata contain little organic carbon black shales enriched in organic matter were found in two settings these rocks exist as claystones in the aptian to turonian hatteras formation and as marlstones in the neocomian blake bahama formation terrigenous organic matter predominates in these deposits except in cenomanian and valanginian rocks where marine material becomes dominant organic carbon concentrations in cenomanian black claystones are higher than any previously reported from the western north atlantic but lower than the concentrations found in the eastern north atlantic black shales at site 603 appear to result from downslope transport and rapid reburial of coastal and ocean margin sediments by turbidity flows deep basin anoxia is not a major factor except during the cenomanian turonian when the entire atlantic ocean may have briefly become anoxic organic matter in the sediments from all locations is thermally immature

the fault pattern in the northern negev and southern coastal plain of israel and its hydrogeological implications for groundwater flow in the judea group aquifer abstract on the basis of a broadly expanding data base the hydrogeological properties of the judea group sequence in the northern negev and southern coastal plain of israel have been reassessed the updated subsurface model is based on data derived from water and oil wells and on recent large scale geophysical investigations a new regional pattern of the reassessed geological through the subsurface of the study area has been revealed in view of the reassessed geological and hydrological subsurface setting it appears that the judea group aquifer should not be regarded as one continuous and undisturbed hydrological unit owing to the occurrence of regional faults its subaquifers are locally interconnected these subaquifers which contain mainly high quality water are juxtaposed as a result of faulting against kurnub group sandstones containing brackish paleowater the latter group is faulted against late jurassic formations containing highly saline groundwater in the beer sheva area the judea group aquifer is vertically displaced against the senonian and eocene mt scopus and avdat groups which also contain brackish and saline water in the southern coastal plain major faults locally dissect also the pleistocene kurkar group facilitating inflow of mg rich groundwater deriving from judea group dolomites the new geological evidence and its hydrogeological implications provide new solutions for previously unexplained salinization phenomena

an organic geochemical profile of the toarcian anoxic event in northern italy abstract a suite of black shales calcareous shales and limestones representing the toarcian anoxic event jurassic 192 ma was collected from a 14 m length of core taken from the belluno trough northern italy and examined in detail to assess variations in depositional environment during this interval geochemical and optical data indicate organic matter of algal and bacterial origin with only trace contribution from terrestrial sources detailed biological marker data interpreted with the aid of multivariate statistics demonstrate fluctuations in primary producers and bacterial populations during black shale deposition the onset of the anoxic event was not abrupt but characterized by an apparent gradual development of anoxia and consequent enhanced organic matter preservation different hopane biomarkers proved especially useful in recognizing preservation potential in the section and correlate well with other preservation indicators increased oxygenation at the end of the event may have been associated with changes in primary productivity

stereochemical studies of acyclic isoprenoids xii lipids of methanogenic bacteria and possible contributions to sediments abstract abundant volatile lipids of methanobacterium thermoautotrophicum and methanosarcina barkeri include isoprenoid hydrocarbons c30 and c15 c20 and c25 isoprenoid alcohols m barkeri contains 2 6 10 15 19 pentamethyleicosane whose relative stereochemistry is the same as found in marine sediments indicating that it is a marker of methanogenic activity the c20 c30 and c25 alkenes in m thermoautotrophicum also have a preferred sterochemistry the latter have the 2 6 10 14 18 pentamethyleicosanyl skeleton suggesting that the alkane in marine sediments may derive from methanogens the stereochemistry of squalane in a marine sediment is also compatible with an origin in methanogens in contrast the stereochemistry of pristane in m thermoautotrophicum indicates a fossil fuel contaminant origin suggesting that this and certain other alkanes reported in archaebacteria might also be of contaminant origin there is therefore little evidence at present that the pristane in immature marine sediments originates in methanogens the c15 and c20 saturated alcohols in m thermoautotrophicum have mainly the all r configuration if this is generally true for methanogens the c20 alcohol in the messel shale may originate mainly from methanogens whereas that in the green river shale may originate mainly from photosynthetic organisms

sulfuric acid speleogenesis sas close to the water table examples from southern france austria and sicily caves formed by rising sulfuric waters have been described from all over the world in a wide variety of climate settings from arid regions to mid latitude and alpine areas h2s is generally formed at depth by reduction of sulfates in the presence of hydrocarbons and is transported in solution through the deep aquifers in tectonically disturbed areas major fractures eventually allow these h2s bearing fluids to rise to the surface where oxidation processes can become active producing sulfuric acid this extremely strong acid reacts with the carbonate bedrock creating caves some of which are among the largest and most spectacular in the world production of sulfuric acid mostly occurs at or close to the water table but also in subaerial conditions in moisture films and droplets in the cave environment these caves are generated at or immediately above the water table where condensation corrosion processes are dominant creating a set of characteristic meso and micromorphologies due to their close connection to the base level these caves can also precisely record past hydrological and geomorphological settings certain authigenic cave minerals produced during the sulfuric acid speleogenesis sas phase allow determination of the exact timing of speleogenesis this paper deals with the morphological geochemical and mineralogical description of four very typical sulfuric acid water table caves in europe the grotte du chat in the southern french alps the acqua fitusa cave in sicily italy and the bad deutsch altenburg and kraushohle caves in austria

gc ms detection and significance of crocetane and pentamethylicosane in sediments and crude oils abstract the occurrence of the archaeal biomarkers crocetane and pentamethylicosane pmi in sediments and crude oils was investigated using gc ms and gc ms ms selected ion monitoring sim and multiple reaction monitoring mrm protocols designed to detect the c 20 and c 25 irregular isoprenoids were evaluated a method for the preferential detection of crocetane over phytane its more abundant isomer was refined using authentic compounds crocetane was found to be present in modern sediments from both aerobic and anaerobic water columns and in sediment from the 1640 ma barney creek formation providing evidence for the antiquity of its biosynthesis crocetane was also detected in several perth basin crude oils and in the kockatea shale their putative source rock and in canning basin oils although mrm analysis could only verify its occurrence in canning oils of devonian age equivocal data from ordovician and carboniferous canning basin oils highlight the need for extreme caution when attempting to distinguish between acyclic isoprenoid isomers pmi was identified by mrm in a miocene monterey sediment and in a modern antarctica sediment on the other hand the c 25 isoprenoid hydrocarbon peak detected in triassic and older sediments was consistently identified as the regular isomer i 25 reg whenever it was sufficiently abundant for mrm to be applied

submarine debris flow impact on pipelines part ii numerical analysis computational fluid dynamics cfd numerical analysis was employed to analyze the situations tested experimentally as described in part i the methodology and results of the cfd analyses are discussed and compared with the observations made from the experiments the numerical model performed satisfactorily with regard to obtaining the impact forces exerted on the model pipe as well as simulating the hydroplaning phenomenon and estimating slurry flow heights the experimental results were combined with the results of the cfd analyses to develop a practical method to compute the drag force caused by a submarine debris flow impact on a pipeline the cfd analyses provided some insight to the separated region characterization but the attempt to analyze the vortex shedding phenomenon as observed in the experiments was unsuccessful additional studies are required for better understanding of both the separated region characteristics and vortex shedding

late pleistocene palaeoclimatic and palaeoenvironmental reconstruction of the dead sea area israel based on speleothems and cave stromatolites abstract calcite speleothems are a hitherto hardly documented occurrence in the nowadays arid to hyper arid rain shadow dead sea area of eastern israel speleothem ages u th from two caves on the dead sea fault escarpment and two caves from arid rain shadow areas surrounding the dead sea span the last three glacial cycles from ca 354 to 12 ka and suggest episodic moist local palaeoclimate mainly during glacial periods of marine isotopic stages mis 6 and 4 to 2 previously reported u th ages of stromatolites deposited in the late pleistocene lake lisan and preserved in caves of the dead sea fault escarpment suggest that regional relatively moist climate affected the lake catchment area during the late part of relatively warm mis 3 lasting until middle cold mis 2 as well as at the mis 5 to 4 interglacial glacial transition speleothem deposition periods spanning the 38 4 0 5 to 16 4 0 3 ka time interval i e late mis 3 to early mis 2 representing moist periods in the lake area are coeval to regional moist conditions inferred by the stromatolite record a direct connection is thus implied between local and regional climate at the latest pleistocene based on correlation between two independent data sets this connection implies that glacial climate has generally been moister than interglacial climate during the last glacial interglacial cycle at both local and regional scales around the dead sea and its predecessors

the role of minerals in the thermal alteration of organic matter iv generation of n alkanes acyclic isoprenoids and alkenes in laboratory experiments a series of pyrolysis experiments utilizing two different immature oil prone kerogens type i green river formation kerogen type ii monterey formation kerogen mixed with common sedimentary minerals calcite illite or na montmorillonite was conducted to study the effects of minerals on the generation of n alkanes acyclic isoprenoids and alkenes during laboratory simulated catagenesis of kerogen the influence of clay minerals on the aliphatic hydrocarbons is critically dependent on the water concentration during laboratory thermal maturation under extremely low contents of water i e dry pyrolysis where only pyrolysate water is present c12 range n alkanes and acyclic isoprenoids are mostly destroyed by montmorillonite but undergo only minor alteration with illite both clay minerals significantly reduce alkene formation during dry pyrolysis under hydrous conditions mineralwater 2 1 the effects of the clay minerals are substantially reduced in addition the dry pyrolysis experiments show that illite and montmorillonite preferentially retain large amounts of the polar constituents of bitumen but not n alkanes or acyclic isoprenoids therefore bitumen fractionation according to polarity differences occurs in the presence of these clay minerals by this process n alkanes and acyclic isoprenoids are concentrated in the bitumen fraction that is not strongly adsorbed on the clay matrices the extent of these concentration effects is greatly diminished during hydrous pyrolysis in contrast calcite has no significant influence on the thermal evolution of the hydrocarbons in addition calcite is incapable of retaining bitumen therefore the fractionation of n alkanes or acyclic isoprenoids relative to the polar constituents of bitumen is insignificant in the presence of calcite

archaeal lipids and anaerobic oxidation of methane in euxinic water columns a comparative study of the black sea and cariaco basin abstract the black sea and the cariaco basin are both large euxinic marine basins in which methane concentrations are high and where anaerobic oxidation of methane aom is an important part of the carbon cycle aom can be recognized by lipid biomarkers that are specific to methanotrophic archaea involved and by strongly 13c depleted isotope compositions consistent with uptake of 13c depleted methane derived carbon the working hypothesis for our investigation was that aom in both the black sea and cariaco basin would generate measurable diagnostic biomarkers and isotope depletions to test this hypothesis we analyzed particulate matter and surface sediments for intact glycerol dialkyl glycerol tetreaethers gdgts components of archaeal membrane lipids and measured stable carbon isotope compositions of their constituent biphytanes several gdgts and strongly 13c depleted biphytanes indicative of aom were present in the deep anoxic region of the black sea 700 m unexpectedly this biomarker signal was not detected in the upper anoxic zone of the black sea or in the entire water column of the cariaco basin even though previous studies had shown high rates of aom to occur in both basins it is possible that the aom derived biomarker signal is masked by archaeal lipids derived from non methanotrophic archaea which utilize 13c enriched carbon substrates alternately we speculate that the methanotrophic community may be highly diverse in euxinic basins possibly producing another suite of biomarkers that we did not measure this conclusion will require further testing by coordinated organic geochemical microbial ecology studies

the chemical evolution of kurnub group paleowater in the sinai negev province a mass balance approach abstract the chemical evolution of the kurnub group paleowater was studied starting from rainwater in recharge areas of the sinai and along groundwater flowpaths leading to the natural outlets of this regional aquifer this was achieved by investigating the chemical composition of groundwater ionic ratios degrees of saturation with common mineral species normative analysis of dissolved salts and by modeling of rock water interaction and mixing processes occurring along groundwater flow paths the initial groundwater composition used is from the nakhel well in sinai it evolves from desert rainwater percolating through typical kurnub group lithology in sinai this rainwater dissolves mainly gypsum halite and dolomite together with smaller amounts of marine aerosol and k feldspar at the same time it precipitates calcite sio 2 smectite and degasses co 2 between the area of nakhel and the northern negev the chemistry of kurnub group waters is influenced by dissolution of halite and lesser amounts of gypsum of surficial origin in recharge areas small amounts of feldspars and of dolomite cement in sandstones eroded from the arabo nubian igneous massif of sinai and organic degradation derived co 2 concomitantly there is precipitation of calcite smectite sio 2 and probably analcime characteristic of sediments in continental closed basins north of the negev the kurnub group fluids are diluted and altered by mixing with judea group aquifer groundwaters on the e there is mixing with residual brines from the water body ancestral to the dead sea prior to discharge into the arava valley rock water interaction indicated by netpath and phreeqc modeling is in agreement with lithology and facies changes previously observed in the kurnub group sequence

field and laboratory analysis of the runout characteristics of hillslope debris flows in switzerland abstract hillslope debris flows are unconfined flows that originate by shallow failures in unconsolidated material at steep slopes in spite of their significant hazard for persons and infrastructure in mountainous regions research on hillslope debris flows is rather scarce in comparison to other landslide types this study focusses on the runout characteristics of hillslope debris flows applying two different approaches first detailed landslide inventories which include field measurements of 548 slope failures that occurred during the last two decades in seven parts of switzerland were analysed second laboratory tests were carried out to study the effect of the soil water content grain size distribution and mobilized volume on the runout behaviour of hillslope debris flows most of the failures in the field started as shallow translational slides at terrain slopes between 25 and 45 and involved volumes of some tens to a few hundred cubic meters an analysis of the runout distance of 117 hillslope debris flows showed that they normally travelled some tens of meters but sometimes the runout exceeded 300 m a positive relation between volume and runout distance and between volume and affected area was observed although there is considerable scatter in the data the affected area of 63 hillslope debris flows ranged from 100 to 1500 m2 based on the field data a 7 5 m long laboratory hillslope was designed with a geometrical scale factor of 20 a total of 75 runs with volumes from 4 to 20 dm3 water contents from 18 to 38 and four grain size distributions were carried out the laboratory tests revealed that water content is the dominant control but also the clay content strongly influences the runout distance and the affected area even a small increase in water or clay content produces a considerably larger or smaller runout distance respectively in contrast the influence of the volume on the runout was smaller and a positive relation was observed between these two parameters the field and laboratory results are in general agreement and consistent with the results of other studies the results of this work improve the understanding of hillslope debris flows and may aid in the hazard assessments of these processes

jurassic and mid cretaceous carbonaceous claystones in the western dsdp leg 76 and eastern dsdp leg 79 north atlantic abstract deep sea drilling in the blake bahama basin dsdp leg 76 site 534 and at the mazagan escarpment off morocco dsdp leg 79 site 547 recovered carbonaceous claystones of mid cretaceous and middle late jurassic age although there are differences in the sedimentological and organic geochemical characteristics of these sediments from opposite margins of the north atlantic the preservation of the organic matter in both cases appears to be controlled by the intensity of the terrigenous organic matter supply downslope transport events and local oxygen depletion

effects of thermal maturity on biomarker distributions in gondwana coals from the satpura and damodar valley basins india abstract organic geochemistry of gondwana coals especially the distribution of molecular fossils or biomarkers is not well constrained throughout the world in this study we have therefore evaluated biomarker signatures along with bulk organic matter and petrographic characteristics in coal samples collected from two gondwana basins in india satpura basin kanhan coalfield and damodar valley basin jharia coalfield from both coalfields the samples were collected from the lower permian barakar formation which is one of the major coal bearing strata in india a significant variation in thermal maturity levels in the samples is indicated by rock eval pyrolysis and petrographic analysis with the kanhan samples generally belonging to immature to early mature stage while the jharia samples display characteristics of overmature coals this variation in the thermal maturity strongly affects the biomarker distributions especially the terpenoids hopanes and steranes were considerably degraded due to thermal maturation and were below detection limit in the overmature samples presence of aliphatic diterpanes ent 16 h kaurane 16 h phyllocladane as well as aromatic diterpanes retene methylretenes tetrahydroretene simonellite and bisnorsimonellite in low maturity samples indicate terrestrial input possibly from the primitive conifers however the aliphatic and aromatic diterpanes were below detection limit in overmature samples making it difficult to infer their source distributions of polycyclic aromatic hydrocarbons pahs are also controlled by thermal maturity levels as evident from difference in pah ratios in the low and high maturity samples

geological evolution of the afro arabian dome abstract the afro arabian dome includes the elevated continental regions enclosing the red sea gulf of aden and the ethiopian rift system and extends northwards as far as jordan it is more than an order of magnitude larger than other african uplifts both the structures and the igneous rocks of the dome appear to be products of the superimposition of two perhaps three semi independent generating systems initiated at different times but all still active a strain pattern dominated by nw trending basins and rifts first became established early in the cretaceous by the end of the oligocene much of the extensional strain had been taken up along the red sea and gulf of aden axes which subsequently developed into an ocean palaeogene trap volcanism of mildly alkaline to transitional character was related to this horizontal extension rather than to doming further west the east sahara swell has a history of intermittent alkaline volcanicity which began in the mesozoic and was independent of magmatism in the afro arabian dome volcanicity specifically related to doming began in the miocene along a n s zone of uplift extending from ethiopia to syria this elongated swell forms the northern termination of the east african system of domes and rifts characterized by episodic vertical uplift but very little extension superimposition of epeirogenic uplift upon structures formed by horizontal extension took place in the neogene volcanicity related to vertical tectonics is mildly alkaline in character whereas transitional and tholeiitic magmas are found along the spreading axes

cross formational rising groundwater at an artesian karstic basin the ayalon saline anomaly israel it is proposed that a geothermal artesian karstic system at the central part of the yarkon taninim aquifer creates the ayalon saline anomaly asa whose mechanism has been under debate for several decades a 4 year long detailed groundwater monitoring was carried out at 68 new shallow boreholes in the ayalon region accompanied by a comprehensive survey of karstic voids results indicate the rising of warm brackish groundwater through highly permeable swarms of karstic shafts serving as an outflow of the artesian geothermal system the asa area contains hot spots where groundwater contrasts with normal water hundreds of meters away the asa temperature reaches 30 8 c w5 8c warmer than its surroundings chloride concentration reaches 528 mg l 50 100 mg l in the surrounding h2s concentration reaches 5 6 mg l zero all around and ph value is 7 0 compared with 7 8 around subsequently the hydrothermal water flows laterally of at the watertable horizon through horizontal conduits mixing with normal fresh water which had circulated at shallow depth following rainy seasons maximal watertable rise is observed in the asa compared to its surroundings regional hydrogeology considerations suggest that the replenishment area for the asa water is at the samaria mountains east of the asa the water circulates to a great depth while flowing westward and a cross formational upward flow is then favored close the upper sub aquifer s confinement border

identification of aryl isoprenoids in source rocks and crude oils biological markers for the green sulphur bacteria abstract a series of c13 to c31 aryl isoprenoids 1 alkyl 2 3 6 trimethylbenzenes have been identified in reef hosted oils and their source rocks from the middle and upper silurian of the michigan basin and middle devonian of the alberta basin canada their structure has been confirmed by unambiguous synthesis of the c14 member of the series their structure and isotopic composition indicate that they are derived from isorenieratene from the chlorobiaceae family of sulphur bacteria these results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns the distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment in conjunction with the aryl isoprenoids they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation this reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils

scaling behaviour of clay rich submarine debris flows we perform a statistical study of submarine debris flows based on recent data from the storegga area off the western coast of norway due to the high quality of the data and the uniformity of materials the data from the storegga database are far less dispersed than world wide compilations available so far allowing for a fit with good statistical significance we find that both the run out and the ratio between fall height and run out are best described as a power law function of the volume for small to moderate volumes visco plastic models are able to reproduce the power law in contrast to granular frictional models however either progressive mixing of the shear layer with ambient water or hydro planing must be invoked in order to explain the extreme run out distances of larger debris flows

10be exposure ages of ancient desert pavements reveal quaternary evolution of the dead sea drainage basin and rift margin tilting abstract early to late pleistocene 10 be exposure ages of abandoned surfaces in the negev desert reveal the regional drainage evolution history and its relationship with the subsidence of the western margin of the dead sea rift the dated desert paved surfaces have developed over originally westward flowing rivers which were abandoned by early pleistocene and whose relicts are now progressively tilted towards the rift axis the slow and non destructive subsidence coupled with extreme hyperaridity enabled the preservation of these ancient surfaces along some of the main water divides in the negev nearly irrespective of their distance from the rift axis constraints on the tilting history are obtained from analyzing the spatial pattern of the exposure ages suggesting subsidence rates as low as 120 300 m ma 1 in the southern arava valley since the late pliocene it is shown that the transition from the pliocene to current drainage pattern occurred over a short period during the early pleistocene and that the governing fluvial response that followed the delineation of current basins is represented by a continuous spectrum of ages of inset terraces

the nubian sandstone aquifer in the central and northern negev israel delineation of the hydrogeological model under conditions of scarce data abstract the cl content of ground water in the central and northern negev ranges between 250 mg 1 1 in the beer sheva area and 1600 mg 1 1 near the egyptian border where the water is also thermal with high concentrations of sulphates and iron during the last few years groundwater resources in the heavily populated beer sheva area have become endangered by a continuing process of salinization in the course of the present work it was found that in the study area ground water flows through a multiple aquifer system including the jurassic lower cretaceous kurnub group and the upper cretaceous judea group aquifers because of the absence of impermeable beds at the boundary between the two groups brackish ground water flows from the kurnub group into the overlying judea group aquifer moreover numerous faults discovered in the subsurface facilitate lateral inflow of kurnub ground water into the judea aquifer by interpreting new lithostratigraphic data from the kurnub group and seismic surveys made in the study area it is shown that the kurnub aquifer extends far beyond the hitherto known boundaries and contains an additional estimated volume of 51 10 9 m 3 of paleowater the limiting factors of its exploitability are groundwater depth and salinity the rational exploitation of the kurnub paleowater may prevent salinization of the overlying judea group aquifer

the interaction of two major old water bodies and its implication for the exploitation of groundwater in the multiple aquifer system of the central and northern negev israel abstract in the beer sheva region of the negev desert the only significant fresh groundwater is contained within the judea group carbonate aquifer it is found that this aquifer holds two distinctly different old water bodies one such groundwater body has evolved in equilibrium with the carbonate aquifer rocks after being recharged during the holocene in the hebron mountains north of the study area at present modern recharge as denoted by the tritium and radiocarbon contents is very minor a subtle piston effect generated by contemporary replenishment is discussed in representative hydrographs in beer sheva wells another groundwater body identified in the judea group aquifer derives from the underlying kurnub group aquifer the regional artesian kurnub group aquifer nubian sandstone contains an older and brackish groundwater body which has been recharged in sinai during pleistocene pluvials faulting in the beer sheva region facilitated hydrologic contact between the two aquifers exploitation of the judea group has released confining pressures and resulted in the intrusion of kurnub group water into the overlying judea group carbonate aquifer this process is most significant in those wells drilled close to major faults where salinity increases with pumping the intruding water originating from the kurnub group sandstone aquifer has not yet equilibrated chemically with the carbonate host the low ph and high temperatures that have been encountered indicate continuing and very recent intrusion in the beer sheva area in the absence of direct significant modern recharge as determined from tritium and 14 c values all waters should be considered as paleowaters that are being mined a complete revision of the hydrologic concept by which the multiple aquifer system can be exploited is required to take into account the fact that the fresh judea group groundwater is actually an old holocene water body intruded by brackish and older pleistocene water along fault zones

algal and archaeal polyisoprenoids in a recent marine sediment molecular isotopic evidence for anaerobic oxidation of methane 1 analyses of 13c contents of individual organic molecules in a marine sediment show that crocetane 2 6 11 15 tetramethylhexadecane an isomer of phytane is produced by microorganisms that use methane as their main source of carbon the sediments lie at a water depth of 68 m in the kattegat the strait between denmark and sweden crocetane appears first 185 cm below the sediment water interface in the zone marking the transition from sulfate reduction to methanogenesis its 13c value is 90 10 versus vienna pee dee belemnite vpdb its structure which includes four isoprene units arranged symmetrically around a tail to tail linkage suggests that it is produced by a member of the archaea growing at the intersection of the diffusion gradients for sulfate and methane in sedimentary pore waters the source organism apparently functions as a methane consuming member of the microbial consortium responsible for the anaerobic oxidation of methane hoehler et al 1994 in which as first demonstrated quantitatively in these sediments iversen and jorgensen 1985 electrons are transferred from methane to sulfate the presence of archaeal biomass throughout the sediment section is indicated by significant concentrations of 2 6 10 15 19 pentamethylicosane pmi and of ether bound phytane and biphytane the pmi reaches a minimum value of 47 well below the transition zone its isotopic depletion could reflect either methanogenic or methanotrophic sources the ether bound lipids are isotopically uniform throughout the section and are presumed to derive from archaea that utilize a carbon source unaffected by the oxidation of methane

a thermal and chemical degradation approach to decipher pristane and phytane precursors in sedimentary organic matter a thermal and chemical degradation approach was followed to determine the precursors of pristane pr and phytane ph in samples from the gessoso solfifera ghareb and green river formations hydrous pyrolysis of these samples yields large amounts of pr and ph carbon skeletons indicating that their precursors are predominantly sequestered in high molecular weight fractions however chemical degradation of the polar fraction and the kerogen of the unheated samples generally does not release large amounts of pr and ph additional information on the precursors of pr and ph is obtained from flash pyrolysis analyses of kerogens and residues after hydrous pyrolysis and after chemical degradation multiple precursors for pr and ph are recognised in these three samples the main increase of the pr ph ratio with increasing maturation temperature which is associated with strongly increasing amounts of pr and ph is probably due to the higher amount of precursors of pr compared to ph and not to the different timing of generation of pr and ph

effects of debris flow composition on runout depositional mechanisms and deposit morphology in laboratory experiments predicting debris flow runout is of major importance for hazard mitigation apart from topography and volume runout distance and area depends on debris flow composition and rheology but how is poorly understood we experimentally investigated effects of composition on debris flow runout depositional mechanisms and deposit geometry the small scale experimental debris flows were largely similar to natural debris flows in terms of flow behavior deposit morphology grain size sorting channel width depth ratio and runout deposit geometry lobe thickness and width in our experimental debris flows is largely determined by composition while the effects of initial conditions of topography i e outflow plain slope and channel slope and width and volume are negligible we find a clear optimum in the relations of runout with coarse material fraction and clay fraction increasing coarse material concentration leads to larger runout however excess coarse material results in a large accumulation of coarse debris at the flow front and enhances diffusivity increasing frontal friction and decreasing runout increasing clay content initially enhances runout but too much clay leads to very viscous flows reducing runout runout increases with channel slope and width outflow plain slope debris flow volume and water fraction these results imply that debris flow runout depends at least as much on composition as on topography this study improves understanding of the effects of debris flow composition on runout and may aid future debris flow hazard assessments

landslide hazard assessment by smoothed particle hydrodynamics with spatially variable soil properties and statistical rainfall distribution rainfall induced landslide has caused significant damage to structures and casualties in the past decades and it is of great importance to assess the post failure behavior of slopes this study pr

arid hypogene karst in a multi aquifer system hydrogeology and speleogenesis of ashalim cave negev desert israel

the rate of flushing as a major factor in determining the chemistry of water in fossil aquifers in southern israel abstract issar a 1981 the rate of flushing as a major factor in determining the chemistry of water in fossil aquifers in southern israel in w back and r letolle guest editors symposium on geochemistry of groundwater 26th international geological congress j hydrol 54 285ndash 296 a parallel trend has been found to exist between the isosalinity lines and the isopiezo metric lines in the fossil aquifers of the nubian sandstones in southern israel and the central sinai the flow pattern in these aquifers determines the rate of mixing between paleo seawater and paleo meteoric water this flowpattern is determined by the spatial relations between the nubian sandstone outcrops in the central sinai and the major fault lines of the dead sea and suez rift valleys a cumulative chemical composite diagram in which 18o stable isotope data were plotted makes it possible to classify the water and to trace the ratios in the mixture

the perfect debris flow aggregated results from 28 large scale experiments 1 aggregation of data collected in 28 controlled experiments reveals reproducible debris flow behavior that provides a clear target for model tests in each experiment 10 m3 of unsorted water saturated sediment composed mostly of sand and gravel discharged from behind a gate descended a steep 95 m flume and formed a deposit on a nearly horizontal runout surface experiment subsets were distinguished by differing basal boundary conditions 1 versus 16 mm roughness heights and sediment mud contents 1 versus 7 percent dry weight sensor measurements of evolving flow thicknesses basal normal stresses and basal pore fluid pressures demonstrate that debris flows in all subsets developed dilated coarse grained high friction snouts followed by bodies of nearly liquefied finer grained debris mud enhanced flow mobility by maintaining high pore pressures in flow bodies and bed roughness reduced flow speeds but not distances of flow runout roughness had these effects because it promoted debris agitation and grain size segregation and thereby aided growth of lateral levees that channelized flow grain size segregation also contributed to development of ubiquitous roll waves which had diverse amplitudes exhibiting fractal number size distributions despite the influence of these waves and other sources of dispersion the aggregated data have well defined patterns that help constrain individual terms in a depth averaged debris flow model the patterns imply that local flow resistance evolved together with global flow dynamics contradicting the hypothesis that any consistent rheology applied we infer that new evolution equations not new rheologies are needed to explain how characteristic debris flow behavior emerges from the interactions of debris constituents

morphometry and distribution of isolated caves as a guide for phreatic and confined paleohydrological conditions isolated caves are a special cave type common in most karst terrains formed by prolonged slow water flow where aggressivity is locally boosted the morphometry and distribution of isolated caves are used here to reconstruct the paleohydrology of a karstic mountain range within a homogenous karstic rock sequence two main types of isolated caves are distinguished and each is associated with a special hydrogeologic setting maze caves form by rising water in the confined zone of the aquifer under the mt scopus group israel confinement while chamber caves are formed in phreatic conditions apparently by lateral flow mixing with a vadose input from above

the uplift history of the arabian plateau as inferred from geomorphologic analysis of its northwestern edge abstract the arabian plateau ap is an oligocene sub horizontal regional planation surface extending throughout the western half of the arabian peninsula its present elevation of about 1 km required a prominent uplift since the late eocene in order to reconstruct the uplift history we documented abundant abrasive and fluvial terraces that were left along and across the raised judea mountains jm which comprised the nw edge of the ap using the ages of those terraces and the differences in height between them we found that the jm was uplifted in three major phases a few hundred meters during the late eocene early oligocene 500 m during the early miocene early middle miocene and 350 m during the late pliocene the two earliest uplift phases predate the formation of the dead sea transform dst which today separates the jm from the ap meaning that these two phases affected the continuous rigid lithosphere extending southeastwards to the ap interiors moreover restoration of the paleogeography predating the lateral offset along the dst eliminates the main height differences across it and suggests that the dst does not play a major role in the vertical position of its bordering plates but rather forms a relatively narrow deformation strip within the ap those two early phases of uplift can be corroborated by previous thermochronology studies which exhibit similar ages around the red sea but may reflect the uplift age of the entire region the present sub horizontal morphology of the ap is in contrast to the presumed original northeastward drainage and may suggest a subsequent long wave moderate tilting to the sw three possible mechanisms were suggested for the uplift of the ap a long wavelength flexure of the arabian plate during early stages of the uplift and lithospheric thinning or dynamic topography during later stages of the uplift

scaling and design of landslide and debris flow experiments abstract scaling plays a crucial role in designing experiments aimed at understanding the behavior of landslides debris flows and other geomorphic phenomena involving grain fluid mixtures scaling can be addressed by using dimensional analysis or more rigorously by normalizing differential equations that describe the evolving dynamics of the system both of these approaches show that relative to full scale natural events miniaturized landslides and debris flows exhibit disproportionately large effects of viscous shear resistance and cohesion as well as disproportionately small effects of excess pore fluid pressure that is generated by debris dilation or contraction this behavioral divergence grows in proportion to h3 where h is the thickness of a moving mass therefore to maximize geomorphological relevance experiments with wet landslides and debris flows must be conducted at the largest feasible scales another important consideration is that unlike stream flows landslides and debris flows accelerate from statically balanced initial states thus no characteristic macroscopic velocity exists to guide experiment scaling and design on the other hand macroscopic gravity driven motion of landslides and debris flows evolves over a characteristic time scale l g 1 2 where g is the magnitude of gravitational acceleration and l is the characteristic length of the moving mass grain scale stress generation within the mass occurs on a shorter time scale h gl 1 2 which is inversely proportional to the depth averaged material shear rate a separation of these two time scales exists if the criterion h l

archaeal and bacterial lipids in authigenic carbonate crusts from eastern mediterranean mud volcanoes abstract we investigated the distributions and 13 c values of lipid biomarkers in authigenic methane related carbonate crusts formed on eastern mediterranean mud volcanoes a highly diverse suite of microbial membrane lipids was detected strongly 13 c depleted lipids diagnostic for archaea include isoprenoid glycerol diethers isoprenoid glycerol dialkyl glycerol tetraethers and several c 20 c 35 isoprenoid hydrocarbons bacterial lipids mainly consist of dialkyl glycerol diethers branched fatty acids and hopanoids showing important 13 c depletions albeit less than archaeal lipids the data provide further evidence for the involvement of archaea and bacteria in the anaerobic oxidation of methane aom and in the sequestration of methane derived carbon in authigenic carbonate crusts varying distributions and isotopic compositions of 13 c depleted lipids argue for heterogeneous aom related microbial consortia expanding on existing work at cold seeps distinctive biomarker features and inferred microbial assemblages are observed in these crusts in agreement with available phylogenetic data for the samples our results support the potential of lipids for distinguishing methanotrophic communities despite the observed variances conservative features in the abundances and isotopic offsets of microbial biomarkers occur likely reflecting the overall relationships between archaea and bacteria and the nature of carbon flow between them

pliocene pleistocene climate of the northern margin of saharan arabian desert recorded in speleothems from the negev desert israel abstract the middle late pliocene climate was 2 3 c warmer than today but with similar levels of atmospheric co2 this period reflects climate conditions expected in the near future and is therefore an important target for current data modeling studies this study reconstructs the pliocene quaternary evolution of arid conditions on the northern margin of the saharan arabian desert using radiometrically u pb dated periods of speleothem deposition from three caves of the negev desert israel speleothem growth started between 3 75 and 3 ma at the end of the first significant tectonic uplift of the western shoulder of the dead sea rift major speleothem deposition indicating wet conditions occurred during the pliocene around 3 1 ma with subsequent aridity during the last 3 myr punctuated by short wet episodes the pleistocene negev humid periods nhp the oldest dated nhp occurred between 1 7 and 1 25 ma and other short humid episodes continued intermittently later speleothem 18o values 6 9 to 11 2 show that the humid episodes were associated with periods of low global ice volume and warm temperatures after correction for rainfall 18o changes associated with ice volume and temperature effects the observed relative constancy of speleothem 18o values from pliocene to late pleistocene indicates rainfall was from a common source most probably the eastern mediterranean sea the humid pliocene conditions could be generated by more southerly position of the mediterranean coast allowing the access of mediterranean precipitation to the negev as well as by warmer atlantic sea surface temperatures that weakened the azores high pressure cell maximum amounts of precipitation were 500 600 mm a during the pliocene and 300 mm a during pleistocene nhp the pliocene and the earliest pleistocene nhp are associated with formation of lakes in the negev low 87sr 86sr ratios of 0 7078 in the pliocene speleothems are indicative of low dust supply low water residence time in the vadose zone and relatively high weathering rates of the cave host rock increase of 87sr 86sr ratios to 0 7082 0 7083 in the pleistocene suggest an increased supply of desert dust high water residence time in the vadose zone and reduced host rock weathering

slow unconfined spreading of a mudflow mudflows are natural highly concentrated water clay grain mixtures that flow in mountain streams after long or intense rainy periods and may cause considerable damage if they overflow on the alluvial fan the possibility of predicting the extent of these flows on the basis of material and flow parameters is examined the simplest realistic case of a yield stress mudflow moving through a narrow open channel followed by a wide long plane is considered it is demonstrated that the unconfined flow of a yield stress fluid over an inclined plane cannot be uniform even in steady state the flow width should increase continuously from the channel exit a complete treatment of the flow equation on the basis of the long wave approximation including an appropriate three dimensional expression for the constitutive equation makes it possible to establish a system of equations from which flow characteristics at any point longitudinal and lateral mean velocities and fluid depth can be deduced in particular for a herschel bulkley fluid with a flow index of 1 3 it is found that the lateral extent will increase proportionally to the distance from the channel exit to the power 9 20 and that in the sheared part the fluid depth in a cross section will have a parabolic distribution experiments have been carried out with fine mud suspensions at different solid fractions whose rheological behavior is similar to that of natural mudflows the theory is in fair agreement with experimental data concerning fluid depth distribution but systematically overestimates lateral extent by 30 this is certainly due to the fact that the assumption of lateral extent much smaller than flow length is not respected in our tests

organic geochemistry of cretaceous black shales from the galicia margin ocean drilling program leg 103 organic carbon rich black shales from three different cretaceous episodes sampled during ocean drilling program leg 103 have been studied by organic geochemical methods rock eval analysis carbon isotope data and lipid biomarkers show organic matter to contain varying proportions of marine and continental materials in hauterivian barremian organic carbon rich turbiditic marlstones major amounts of land derived organic matter are found aptian albian black colored shales are interspersed within green claystones from which they differ by containing more marine organic matter an abbreviated layer of black shale from the cenomanian turonian boundary is dominated by well preserved marine organic matter downslope transport and rapid reburial within a predominantly oxygenated dcepwater setting created most of these examples of black shales except for the cenomanian turonian deposits in which decpwater anoxia may have been involved

anaerobic bacterial degradation of pristenes and phytenes in marine sediments does not lead to pristane and phytane during early diagenesis abstract anaerobic degradation of mixtures of isomeric pristenes and phytenes by sedimentary bacterial communities was investigated these isoprenoid alkenes were quickly metabolized without formation of the corresponding alkanes identification of several bacterial metabolites allowed us to confirm the key role played by hydration in the metabolism of alkenes despite the increasing production of 5 stanols during incubation attesting to the involvement of biohydrogenation this process did not act significantly on the double bond of pristenes and phytenes their resistance is attributed to the lack of binding polar group s to anchor the substrate to the enzyme and thus allow the double bond to reach the reductive catalytic site it therefore seems that microbial hydrogenation of pristenes and phytenes does not account for the presence of pristane and phytane in recent sediments during early diagenesis

shallow viscoplastic flow on an inclined plane evolving viscoplastic flows upon slopes are an important idealization of many flows in a variety of geophysical situations where yield stress is thought to play a role for such models asymptotic expansions suitable for slowly moving shallow fluid layers lubrication theory reduce the governing equations to a simpler problem in terms of the fluid thickness we consider the version of the theory for fluids described by the herschel bulkley constitutive law and provide a variety of solutions to the reduced equation both numerical and analytical for extruded inclined domes we derive the characteristic temporal behaviour of measures of the dome s dimensions

applicability of power law for describing the rheology of soils of different origins and characteristics the rate dependent rheological behaviour of soils of different origins and characteristics was studied and the applicability of the power law model was examined the studied soils were divided into

experimental study of the grain flow fluid mud transition in debris flows abstract we have performed a series of laboratory experiments that clarify the nature of the transition between fluid mud and grain flow behavior the surface velocity structure and the speed of the nose of debris flows in channels with semicircular cross sections were measured with several cameras and visual tracers while the mass flow rate was recorded using a load cell at the exit chamber other rheological tests were used to calculate independently the yield strength and matrix viscosity of the debris flow mixture shear rates were varied by nearly an order of magnitude for each mixture by changing the channel radius and slope shear rates were significantly higher than expected 6 55 s 1 given the modest slopes examined 10 7 15 2 the large values were primarily a result of the concentration of shear into narrow bands between a central nondeforming plug and the sidewall as a result the shear rate of interest was calculated by using the width of the shear band and the plug velocity as oppose

grain size segregation and levee formation in geophysical mass flows 1 data from large scale debris flow experiments are combined with modeling of particle size segregation to explain the formation of lateral levees enriched in coarse grains the experimental flows consisted of 10 m3 of water saturated sand and gravel which traveled 80 m down a steeply inclined flume before forming an elongated leveed deposit 10 m long on a nearly horizontal runout surface we measured the surface velocity field and observed the sequence of deposition by seeding tracers onto the flow surface and tracking them in video footage levees formed by progressive downslope accretion approximately 3 5 m behind the flow front which advanced steadily at 2 m s 1 during most of the runout segregation was measured by placing 600 coarse tracer pebbles on the bed which when entrained into the flow segregated upwards at 6 7 5 cm s 1 when excavated from the deposit these were distributed in a horseshoe shaped pattern that became increasingly elevated closer to the deposit termination although there was clear evidence for inverse grading during the flow transect sampling revealed that the resulting leveed deposit was strongly graded laterally with only weak vertical grading we construct an empirical three dimensional velocity field resembling the experimental observations and use this with a particle size segregation model to predict the segregation and transport of material through the flow we infer that coarse material segregates to the flow surface and is transported to the flow front by shear within the flow head coarse material is overridden then recirculates in spiral trajectories due to size segregation before being advected to the flow edges and deposited to form coarse particle enriched levees

deep confined karst detection analysis and paleo hydrology reconstruction at a basin wide scale using new geophysical interpretation of borehole logs summary deep karst voids can be identified by a new method of geophysical interpretation of commonly used borehole logs in deeply confined carbonate aquifers we show that deep buried karst voids can be characterized by combining this geophysical interpretation together with geological and hydrological data and with known speleological constraints we demonstrate how this characterization can reveal past hydrological regimes and allow mapping of karst distribution on a basin wide scale a combined analysis of geophysical geological hydrological and speleological data in the confined yarkon taninim aquifer israel led us to reconstruct past groundwater levels at different relief and sea levels with the karst voids as a marker for long term flow close to the water table paleo canyons along the mediterranean sea shoreline strongly affected the region s paleo hydrology by serving as major outlets of the aquifer during most of the cenozoic we conclude that intensive karstification was promoted by flow periods of longer duration and or higher flux and flow velocities close to the aquifer s past and present outlets in addition we suggest that karst voids found under shallow confinement were developed by renewed aggressivity due to hypogene water rising in cross formational flow becoming mixed with fresh lateral water flow from the east

mobility of long runout rock flows a discrete numerical investigation summary in the perspective of studying the mobility and deposit geometry of long runout flows discrete numerical simulations of model granular avalanches over simple topography are performed analysing the behaviour of the ratio h l depending on the parameters varied in the simulations we show its poor sensitivity to the topographic parameters namely the initial height of the flowing mass and the slope on the contrary a correlation between h l and the frictional properties of the material is established however the existence of variations of the effective friction induced by the dynamics are not reflected by the value of h l as an alternative to the h l description of the flow behaviour we propose a new scaling for the runout distance taking into account the lateral extension l0 of the relief forming the normalized runout l l0 and defining the aspect ratio a of the topography we show the dependence of l l0 on a thus generalizing previous analysis of martian data analysing the correlation between the normalized runout and the front velocity for the numerical simulations we show how l l0 depends both on the frictional properties of the material and on the dynamics of the flow this result suggests the necessity of evaluating the lateral extension of the relief l0 in the case of natural flows in order to define a horizontal travel index including the topography in an attempt to better understand the flow dynamics analysing the deposit for both simulations and real flow data we evidence a common behaviour suggesting that the geometric factors prevail in the spreading dynamics irrespective of the details of the flow context and conditions we moreover assert the relevance of discrete simulations to the discussion of real cases

channeled flow analytic solutions laboratory experiments and applications to lava flows although channeled lava flows are common in basaltic volcanism relationships between channel morphology eruption and emplacement parameters and lava properties are not well understood several models have commonly been used to constrain these relations but they have not been well tested on natural or simulated lava flows over a wide range of parameter space here we test the accuracy and assumptions of a moderately simple analytic rectangular channel solution by comparing the behavior of well controlled laboratory polyethylene glycol peg channeled flows to the analytic solution for isothermal steady newtonian flow in a rectangular channel with constant dimensions this analytic solution agrees well with laboratory measurements volumetric effusion rates q m3 s 1 calculated from the analytical model using measured peg flows as input yield ratios of qcalculated qpumped of 0 2 to 3 6 and flow rates calculated from a best fit surface velocity profile to measured velocities give more accurate ratios of 0 8 to 1 2 we find a very weak dependence of solution accuracy on slope attributable to flow front effects within the laboratory flows we subsequently apply the solution to several subaerial and submarine terrestrial flows as well as extraterrestrial channeled flows over a wide range of flow parameters viscosity ranges and flow rates obtained using measured channel dimensions and assumed lava properties are plausible interestingly the resulting extraterrestrial estimates of viscosities and flow rates tend to fall closer to known terrestrial measurements and estimates of channel flow than to previous planetary estimates we therefore suggest that the analytic newtonian rectangular channel flow model is a more appropriate physical model for many channeled terrestrial and planetary flows than the newtonian infinite sheet flow and approximation to bingham channel flow widely used previously

unraveling rift margin evolution and escarpment development ages along the dead sea fault using cosmogenic burial ages abstract the dead sea fault dsf is one of the most active plate boundaries in the world understanding the quaternary history and sediments of the dsf requires investigation into the neogene development of this plate boundary dsf lateral motion preceded significant extension and rift morphology by 10 ma sediments of the sedom formation dated here between 5 0 0 5 ma and 6 2 2 1 inf ma yielded extremely low 10be concentrations and 26al is absent these reflect the antiquity of the sediments deposited in the sedom lagoon which evolved in a subdued landscape and was connected to the mediterranean sea the base of the overlying amora formation deposited in the terminal amora lake which developed under increasing relief that promoted escarpment incision was dated at 3 3 0 8 0 9 ma burial ages of fluvial sediments within caves 3 4 0 2 ma and 3 6 0 4 ma represent the timing of initial incision initial dsf topography coincides with the earliest red sea morb s and the east anatolian fault initiation these suggest a change in the relative arabian african plate motion this change introduced the rifting component to the dsf followed by a significant subsidence margin uplift and a reorganization of relief and drainage pattern in the region resulting in the topographic framework observed today