microbial sulfate reduction in deep sea sediments at the guaymas basin hydrothermal vent area influence of temperature and substrates abstract microbial sulfate reduction was studied by a 35 s tracer technique in sediments from the hydrothermal vent site in guaymas basin gulf of california mexico in situ temperatures ranged from 2 7 c in the overlying seawater to 120 c at 30 cm depth in the hydrothermal sediment sulfate reduction was measured in intact cores of hydrothermal sediment at 3 20 35 50 70 and 90 c the maximum rates of sulfate reduction were found in the upper 0 2 cm of the sediment and ranged from 32 nmol cm 3 d 1 at 90 c to 1563 nmol cm 3 d 1 at 70 c the rates of sulfate reduction rapidly decreased with depth in the upper 0 10 cm of the sediment and the maximal depth integrated rate 0 10 cm was 70 3 mmol so 4 2 m 2 d 1 at 70 c in comparison the sulfate reduction rate in nonhydrothermal sediment from the vent area was 0 85 mmol m 2 d 1 at the in situ temperature of about 3 c the high subsurface rates of sulfate reduction in the hydrothermal vent area was attributed to an enhanced local substrate availability in slurries of hydrothermal sediment incubated at 10 120 c microbial sulfate reduction extended to 102 c and different temperature groups of microbial sulfate reducers had optimum temperatures at around 34 70 and 80 88 c the overall temperature response of thermophilic sulfate reduction was similar in hydrothermal sediment sampled at different sites addition of short chain fatty acids and yeast extract to the sediment slurries stimulated sulfate reduction rates at all incubation temperatures no sulfate reduction was detected in the temperature range from 102 120 c microbial rather than thermochemical sulfate reduction could be a possible source of h 2 s in sulfide deposits with formation temperatures at about 100 c

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

first evidence of benthic communities based on chemosynthesis on the napoli mud volcano eastern mediterranean abstract some molluscan valves attributed to myrtea sp lucinidae vesicomya sp and another undetermined vesicomydae were sampled in 1993 cruise ttr3 leg2 and 1994 cruise um94 by coring on the top of the napoli dome a mud volcano located on the mediterranean ridge at about 1900 m of water depth these bivalves belong to an unknown apparently rich benthic community associated to the sulphides and methane rich emissions that characterize the napoli dome outside the mediterranean deep sea lucinidae and vesicomyidae are associated with cold seeps and hydrothermal vents and are known to be sustained by bacterial chemosynthetic activity based on sulphide and or methane oxidation the same explanation is given for this newly discovered deep mediterranean fauna firstly described here

the distinct morphological and petrological features of shock melt veins in the suizhou l6 chondrite the morphology and petrology of distinct melt veins in the suizhou l6 chondrite have been investigated using scanning electron microscopy electron microprobe analyses and raman spectroscopy synchrotron energy dispersive diffraction and transmission electron microscopy it is found that the melt veins in the suizhou meteorite morphologically are the simplest straightest and thinnest among all shock veins known from meteorites at first glance these veins look like fine fractures but petrologically they are solid melt veins of chondritic composition and consist of fully crystalline materials of two distinct lithological assemblages with no glassy material remaining the suizhou melt veins contain the most abundant high pressure mineral species when compared with all other veins known in chondrites thus these veins in suizhou are classified as shock veins all rock forming and almost all accessory minerals in the suizhou shock veins have been transformed to their high pressure polymorphs and no fragments of the precursor minerals remain in the veins among the 11 high pressure mineral phases identified in the suizhou veins three are new high pressure minerals namely tuite after whitlockite xieite and the cf phase after chromite on the basis of transformation of plagioclase into maskelynite it is estimated that the suizhou meteorite experienced shock pressures andmore shock temperatures up to 22 gpa and 1000 c respectively shearing and friction along shock veins raised the temperature up to 1900 2000 c and the pressure up to 24 gpa within the veins hence phase transition and crystallization of high pressure minerals took place only in the suizhou shock veins fast cooling of the extremely thin shock veins is regarded as the main reason that up to 11 shock induced high pressure mineral phases could be preserved in these veins less

petrography and reservoir physics ii relating thin section porosity to capillary pressure the association between pore types and throat size porosity in reservoir rocks is configured into a few types of pores whose size and shape are controlled by depositional fabric and postdepositional processes the size shape and abundance of each pore type can be objectively determined from thin section using image analysis and pattern recognition procedures each pore type tends to be associated with a limited range of throat sizes the association between pore type and throat size can be determined using regression procedures linking pore type data obtained from thin section with capillary pressure data to do so a set of samples is required wherein the association between pore type and throat size is fixed but where pore type proportions vary between samples this condition is met by a sample suite representing res rvoir facies from a single core or in many cases from a single field the relationship between pore type and throat size is an effective means to relate reservoirs in terms of the efficiency of the porous microstructure to multiphase flow parameters derived from the relationship can be used to construct accurate physical models that subdivide physical response in terms of the contributions of each pore type

sedimentary geochemistry of hydrothermal vents in guaymas basin gulf of california mexico abstract surface sediments from 4 contrasting environmental settings in the southern trough of guaymas basin were analysed to determine their texture total organic matter tom p tp and n tn content as well as the spatial variation in their c n p atomic ratios in hydrothermally altered sediments particle size analysis revealed a marked spatial heterogeneity among sites cores taken at beggiatoa bacterial mats and at clam fields contained significant silt and clay content while those obtained near venting sites had sand and gravel as the main components because no fine sedimentary materials are deposited at these sites fine grain sediments were common farther away from vents high levels of organic c 3 4 to 12 4 were recorded in the upper 8 cm but no clear trends of decreasing toc with depth were noted the presence of hydrothermally generated petroleum in some cores increased the organic c content between 8 and 12 cm tn was generally high 456 3 4356 g g and sustained a significant correlation with tom r 0 834 p beggiatoa or vesicomyd clams are predominant

vent type taxa in a hydrocarbon seep region on the louisiana slope recent discoveries on the northern gulf of mexico continental slope have altered our understanding of biological and chemical processes occurring in the deep ocean a biological community of hydrothermal vent type organisms was recently discovered at the base of the florida escarpment1 where the fauna are apparently nourished by hydrogen sulphide rich hypersaline water seeping out onto the sea floor dense colonies of deep living chemosynthetic benthic organisms were first discovered during investigations of warm water anomalies along the axis of the galapagos rift in the pacific ocean in 19772 4 and this first discovery of clusters of clams tube worms and other filter feeders in the immediate proximity of warm water vents has been followed by the discovery of a number of other hydrothermal vent sites for example guaymas basin east pacific rise at 21 n the dense population assemblages at these sites are apparently restricted to small areas of the ocean floor where hydrogen sulphide rich water is escaping from spreading centres but the florida escarpment discovery indicates that these communities can also exist on passive margins here we report the discovery of dense biological communities associated with regions of oil and gas seepage on the louisiana continental slope these communities of large epi and infaunal organisms are similar to those associated with the vents of the pacific and the hypersaline brine seeps of the florida escarpment carbon isotope analyses suggest that these communities are chemosynthetic and derive their energy from hydrogen sulphide and or hydrocarbons similar communities may be widely distributed on the sea floor in other oil producing regions of the ocean

high molecular weight polycyclic aromatic hydrocarbons in hydrothermal petroleums from the gulf of california and northeast pacific ocean hydrothermal petroleums and heavy tars have been analyzed for polycyclic aromatic hydrocarbons pah with molecular weights greater than that of coronene 300 da samples from the hydrothermal systems in the guaymas basin gulf of california and in the escanaba trough and middle valley northeastern pacific were analyzed by gas chromatography mass spectrometry and high pressure liquid chromatography with diode array absorbance detection mass spectra and fluorescence spectra were used to characterize the compounds several large pahs with six and more rings were identified among the heavy pah production routes via one ring build up and scholl condensation are proposed to explain the observed structures the variations in pah concentrations and distributions between samples from different locales are a consequence of the hydrothermal conditions of generation migration and post depositional alteration

erratum to back transformation of high pressure phases in a shock melt vein of an h chondrite during atmospheric passage implications for the survival of high pressure phases after decompression earth planet sci lett 217 2003 141 150

a new methodological approach to assess the stability of discontinuous rocky cliffs using in situ surveys supported by uav based techniques and 3 d finite element model a case study abstract this paper aims to present a new methodological approach for the stability assessment of coastal cliffs constituted of discontinuous rock masses the method entails in situ specific geostructural and geomechanical surveys three dimensional uav based photogrammetric structural models laboratory geotechnical tests and two and three dimensional finite element analysis fem the application of the method to a case study is then presented and discussed it regards a 600 m long sea rocky cliff located at sant andrea melendugno south of apulia se italy and faced to the southern adriatic sea here the cliff is made up of an about 15 m thick sequence of laminate calcisiltites alternate with bioturbated calcarenites belonging to the uggiano la chiesa fm middle upper pliocene the structural discontinuities detected with photogrammetry techniques were compared and validated with those derived from conventional in situ survey methods later on the paper discusses assumptions and results of two and three dimensional finite element models developed to investigate the potential failure mechanisms of the sea cliff accounting for pre existing weak planes or discontinuities with unfavourable orientation the failure mechanisms obtained by both fem analysis agree well with those typically observed in the study area

petrology and raman spectroscopy of high pressure phases in the gujba cb chondrite and the shock history of the cb parent body abstract high pressure phases majorite possibly majorite pyropess wadsleyite and coesite are present in the matrix and in barred olivine fragments in the gujba cb chondrite grossular pyrope was also observed in some small inclusions the cb chondrites are metal rich meteorites with characteristics that sharply distinguish them from other chondrite groups all of the cb chondrites contain impact melt regions interstitial to their chondrules fragments and metal and a major impact event or events on the cb chondrite parent body is clearly a significant stage in its history we studied three areas interstitial to chondrules and metal in the gujba cba chondrite from raman spectra the barred olivine fragments and matrix in these regions have various combinations of olivine and low ca pyroxene as well as majorite garnet mg4si4o12 a phase that forms by high pressure transformation of low ca pyroxene and wadsleyite a high pressure product of olivine compositions of the majorite suggest both majorite and majorite pyrope solid solution may be present the mineral assemblage of majorite and wadsleyite suggest minimum shock pressures and temperatures of 19 gpa and 2000 c respectively the occurrences of high pressure phases are variable from one area to another on the scale of millimeters or less suggesting heterogeneous distribution of shock and or back transformation to low pressure polymorphs throughout the meteorite the high pressure phases record a high temperature pressure impact event that is superimposed onto and thus postdates formation of the chondrules and other components in the cb chondrites the barred chondrules and metal in the cb chondrites are primary materials formed prior to the impact event either generated in an earlier planetesimal scale impact event or in the nebula

orthogonal microscopy image acquisition analysis technique for rock sections in polarizer angle domain abstract the microscopic identification of rock sections is one of the most basic research methods of petromineralogy which is important to the research of mineral composition pore throat characteristics interstitial filling etc the traditional manual identification method was time consuming and also burdened with errors due to the subjective nature of human judgment which can bring some uncertainties to the further results therefore this paper proposes a technique for image acquisition and analysis of rock sections based on sequential images of rock sections in angle domain under polarizing microscope the analysis includes the following three steps firstly based on the multi angles extinction feature of rock section the direction adaptive correlation coefficient method was used to characterize the edge of the rock sections and segment the rock grains a series of parameters including grain size roundness convexity flatness and roughness were also extracted to characterize the morphological features of rock grains quantitatively secondly the variation characteristics of multi channel parameters rgb and gray channel with angle domain were analyzed for different minerals and then the mineral composition was accurately identified on the basis of grain segmentation the pore structures including intergranular pores dissolved pores and throat were extracted and the parameters of pore structure were also obtained finally the distribution of the interstitials was characterized based on the change of the extinction characteristics of the interstitials in the pores image analysis technique based on rock sections with polarizing microscope provides an effective and convenient method for grain segmentation mineral composition classification pore identification and interstitial analysis

deep biological communities in the subduction zone of japan from bottom photographs taken during nautile dives in the kaiko project abstract twenty seven dives of the submersible nautile in the subduction zone around japan conducted in the french japanese project kaiko proved that fairly luxuriant benthic communities dominated by deep sea giant clams of the genus calyptogena family vesicomyidae were consistently present on the accretionary prism at abyssal depths benthic communities characterized by three hitherto undescribed bivalves of the genus calyptogena were found between depths of about 3800 and 4020 m at the mouth of tenryu canyon and at the top of basement swell of the zenisu ridge both situated in the eastern nankai subduction zone sporadic but discrete patches of organisms characterized by one more undescribed bivalve belonging to the genus calyptogena were observed and collected between depths of 5130 and 5960 m on the landward wall of the japan and kouriles trenches photographic inventories were prepared semiquantitatively using each series of bottom photographs taken in these areas with bow cameras of the submersible nautile observations on the sporadic but dense distribution of the clams and other characteristic associated organisms match well with the scheme that communities sustained by chemosynthetic energy sources can be present at connate water seepages in subduction zones these are to date the deepest record of benthic communities supposedly associated with chemosynthetic processes

bimodal porosity in oolitic reservoir effect on productivity and log response rodessa limestone lower cretaceous east texas basin running duke field houston county texas is on a small domal structure in the east texas basin the field currently consists of five gas wells producing from the lower cretaceous rodessa limestone seven additional gas completions have been plugged the rodessa yields water free gas production from zones with water saturations in excess of 60 porosity ranges from 7 to 14 the depositional model depicted for the rodessa in this field starts with the development of an active organic buildup this was successively overlain by ooid skeletal peloid lime sands lagoonal lime muds and subsequently by anhydrite and shale six lithofacies based on core study were recognized for the rodessa each facies has a uniform diagenetic history in the field making porosity development predictable for each facies the one grainstone facies forms the reservoir in the field and has two distinct diagenetic sequences one consists of a marine isopachous cement followed by a later partial infilling of pore space by sparry calcite the resulting intergranular porosity has a unimodal pore size distribution in the other sequence a discontinuous meteoric phreatic cement is followed by sporadic patches of sparry cement the resulting pore size distribution is bimodal with intergranular macropores and intercrystalline micropores within peloids and micritized ooids water free gas production is limited to the rock with the bimodal pore system macropores hold movable gas and micropores hold bound water within grains where core data are not available cross plotting techniques using geophysical logs are suggested as methods for separating the productive from the nonproductive grainstone

physico mechanical properties and durability performance of natural building and decorative carbonate stones from cyprus natural stone was the primary building material in cyprus in the past nowadays its use is mostly confined to decorative purposes and restoration projects this study represents the first thorough and systematic investigation of the characteristics of local carbonate stone the variety of the results recorded highlights the complexity of this natural geomaterial and hence the particular attention needed before selecting the appropriate lithotype in construction practice stones coming from the same geological formation exhibit significant variations in their physico mechanical properties the materials durability against salt crystallization is explained with reference to their pore structure and flexural strength revealing that in many cases small differences may have a significant impact on stone performance the study also investigates the use of novel microdestructive techniques in the prediction of the mechanical properties of the stones under study these techniques can be especially useful in the characterization of monumental stone where sampling is limited or when in situ characterization of stone is required natural stone has been extensively used throughout the history of mankind both for building and decorative purposes even though it is considered one of the most durable traditional geomaterials existing stone structures and monuments often show evidence of weathering and decay stress inflicted during use and by local climate are the major contributing factors to the degradation of building stone the precise response of individual stone samples is highly variable this is attributed to the complex nature and physico mechanical behaviour of natural stone understanding the materials performance under loading or different environmental conditions is therefore considered of crucial importance in ensuring the sustainable use of stone in construction practice

crustal processes at spreading centers recent discoveries and research on mid ocean ridges mor s in the last four years have greatly increased our knowledge of this fundamental type of plate boundary the last iugg review of mor research was in 1975 aumento et al 1975 and its omission as a topic in 1978 may have reflected a feeling that spreading centers were reasonably well understood since that time however there has been a surfeit of important new observations and exciting research and there is now a turmoil of innovative ideas about the processes which create and leave their imprint on two thirds of the earth s crust new seismic measurements have been made and interpreted as evidence for the existence of shallow axial magma chambers amc beneath intermediate total opening rate 5 9 cm yr and fast 9 18 cm yr spreading centers fig 1 yet there is controversy as to whether they are steady state whether they persist beneath slow ridges as well in the steady state what the dimensions and shape of the chamber are its relation to oceanic crustal stratigraphy and its relation to observations in ophiolites black smoker hydrothermal vents have been discovered in the pacific spewing forth 350 c fluids blackened by polymetallic sulfide precipitates this discovery is embroiled in debate as to how long the vents last whether they occur at slow spreading rates as well whether the enormous heat flux of the vents freeze the magma chamber even at fast spreading rates their influence on geochemical balances in the ocean and the value of the sulfide deposits commercially it has been found that our initial view of mor s as two dimensional linear structures has served us well as an initial working model but must be significantly modified to account for variations in tectonic volcanic and hydrothermal activity along strike as well as for episodicity of these processes deep sea drilling project dsdp samples have raised fundamental questions about formation of the magnetic source layer hydrothermal circulation and fault mechanisms along the mor spreading centers which penetrate existing lithosphere along strike as propagating rifts have modified our views of how plate boundaries reorient themselves and how v shaped magnetic and topographic trends are formed we have also found that transform faults may modify spreading center processes for some distance away from their intersections with mor s and that rigid plate transform faults may fail to develop at fast spreading centers under certain conditions resulting in en echelon overlapping of spreading centers this review will focus on these developments and several others only example references to these topics will be given in the text and many important topics will not be discussed directly e g petrology and geochemistry mantle convection research on lithosphere older than 1 m y however i have tried to compile and have included an extensive bibliography for u s research on a broader range of mor topics for mid 1978 to mid 1982 which is the main purpose of this report pre 1978 references are occasionally included where appropriate abstracts are not included

petroleum generation an easy and widespread process in hydrothermal systems an overview abstract the conversion of organic matter to petroleum products by hydrothermal activity is an easy process occurring in nature in many types of environments geologically immature organic matter of marine sediments has been shown to be altered to petroleum products by this process in the guaymas basin escanaba trough bransfield strait and atlantis ii deep and this process probably occurs elsewhere in active sedimented rift systems contemporary organic detritus and or viable microorganisms are also converted in part to petroleum like products when they become entrained by turbulent mixing into hydrothermal vent waters resulting in their instantaneous hydrous pyrolysis this latter case occurs in hydrothermal vent fields without a sedimentary cover emanating directly from oceanic ridges as for example on the east pacific rise at 13 n and 21 n and on the mid atlantic ridge at 26 n this process is probably also ubiquitous for all actively venting sediment starved oceanic ridges the hydrocarbon products generated in these areas have been compared in terms of composition organic matter sources and analogy to reservoir petroleum they represent a major carbon source for chemosynthetic assimilation by vent biota and are compositionally similar to normal petroleum

spatial distribution of diverse cold seep communities living on various diapiric structures of the southern barbados prism three sectors of the south barbados prism between 1000 and 2000 m depth were explored by the french submersible nautile chemosynthesis based benthic communities were discovered on several structures affected by diapirism including mud volcanoes domes and an anticlinal ridge the communities are associated with the expulsion of methane rich fluids which is a wide spread process in the area these communities are dominated by large bivalves and vestimentiferans which harbour chemoautotrophic symbiotic bacteria the symbiotic bivalves include two species of mytilidae and one of vesicomyidae with dominance of a methanotrophic mussel cartography of the benthic communities interpretation of thermal measurements and observation of sedimentary patterns have been used to define the life habits of each of the three species of symbiotic bivalves each species has a characteristic preference for different conditions of edaphic and fluid flow the dominant methanotrophic mussel appears to require high velocity vents and hard substratum the vesicomyids and the other species of mussel are able to take up sulfide from the sediments and so are associated with low seepages but also require soft sediment the three bivalve species are assumed successively to colonize the top of a diapiric ridge in a succession related to the temporal evolution of fluid flow and sedimentation the composition of the bivalve assemblages their densities and biomasses all differ between the several mud volcanoes and domes studied and these parameters are thought to be related to the spatial and temporal variations of fluid expulsion through the structures and the lithification processes linked to fluid expulsion one very active dome is at present colonized by an exceptionally large and dense population of the methanotrophic mussel in contrast communities in another area on the domes and volcanoes that are currently inactive were colonized by only a few living vesicomyids and mussels both associated with sulfur oxydizing bacteria and there were numerous empty shells the densities and biomasses of symbiotic bivalves were far greater in the area studied than in a deeper mud volcano field on the same prism that had been studied previously this is consistent with a report that methane production is greater in the southern region of this accretionary prism than in the northern numerous non symbiotic organisms were observed in and around the areas of the seeps some are endemic to the seep communities including some gastropods and shrimps others are either colonists or vagrants from the surrounding deep sea floor filter feeders were very abundant and some of these like the serpulids and large sponges may also be dependent on the chemosynthetic production faunistic composition of both symbiotic and non symbiotic taxa of the assemblages around these cold seeps is closely related to that reported for communities living on hydrocarbon seeps in the gulf of mexico

empirical prediction of porosity and permeability in sandstones current efforts to predict porosity and permeability in sandstones prior to drilling are focused on empirical and process oriented models empirical predictions are based on the correlation between porosity and permeability and a limited number of parameters obtained from calibration data sets or estimated from appropriate geologic models of these parameters the most important are detrital composition grain size sorting and temperature history or pressure history or both despite its limitations the empirical approach provides accurate predrill predictions of reservoir quality in many sandstones containing not only primary but also secondary porosity and permeability predictions of the average porosity and permeability of target sandstones are arbitrarily defined h re as accurate if they fall within 2 porosity of the mean measured porosity and within the same order of magnitude as the mean measured permeability in a sample population representing the interval of interest the effectiveness of the empirical predictive approach is illustrated by case studies from the taranaki basin new zealand and yacheng field people s republic of china these studies indicate that empirical predictions are basin specific or even play specific and require at least some understanding of fundamental processes affecting reservoir quality of a given sandstone target process oriented approaches attempting to model the effect of diagenesis on reservoir quality are hampered by inadequate quantitative understanding of the processes responsible for preserving primary porosity and generating secondary porosity and permeability until adequate quantification of the sandstone diagenesis processes is achieved empirical models have a distinct advantage over process oriented models in providing reliable predictions of reservoir quality in many sandstone intervals

seafloor facies related to upward methane flux within a giant pockmark of the lower congo basin the origin of the cold fluid venting from a giant pockmark within the lower congo basin has been elucidated based upon results of precise mapping submersible dives gravity coring and isotopic analyses realized under a total ifremer cooperative project zaiango and biozaire projects during four dives of the ifremer rov victor 6000 the bottom was filmed hard and soft samples were lifted from the sediment and water samples were collected with a ctd rosette system the detailed dip map shows that the 800 m wide giant pockmark is a composite feature due to the coalescence of multiple 100 m wide depressions that displays a broad range of biological mineralogical and chemical features on the seafloor leading to a seafloor anomaly recorded on the multibeam imagery methane rich fluids migrating through the sedimentary column from a buried palaeochannel clearly react with the sulphate rich circulating sea water to produce hydrogen sulphide and bicarbonate ions this situation leads to a concentrical arrangement of the sedimentary facies with methane related features in the centre and sulphide related features at the periphery this organization is correlated with high levels of methane up to 20 mol l measured in the centre of the giant pockmark responsible for the crystallization of gas hydrates at the bottom in this model the concentrical organization of mineralogical and biological features reflects a geochemical partitioning related to the peripheral progressive mixing of the methane flux

deep water hydrocarbon seeps in guaymas basin gulf of california abstract acoustically discovered hydrocarbon seeps along a transform fault zone on the sonoran margin of guaymas basin and in the southern trough of guaymas basin were examined and sampled during dives of dsv alvin seepage of methane and heavier hydrocarbons occurs through shallow pockmarks along the eroding crest of a steep anticline 1600 m below sea level extensive ledges of aragonite crop out around the rims of the pockmarks isotopic analysis indicates that carbonate precipitation is a result of methane oxidation seepage zones within the pockmarks support dense communities of calyptogena half buried in the mud tubeworms lamellibracheae sp have colonized many of the aragonite outcrops though the margin site is only a few kilometers from a high temperature sulfide precipitating and petroleum discharging vent system at a nearby center its structural setting is more akin to pockmarks described from continental shelves and its chemosynthetic fauna is more like that around low temperature seeps on other continental slopes and margins e g oregon u s a and japan the seep in the southern trough is a condensate type petroleum c 1 c 40 and rises as a plume from a young vent mound system about 2000 m below sea level

evidence from fluid seeps atop serpentine seamounts in the mariana forearc clues for emplacement of the seamounts and their relationship to forearc tectonics abstract the mariana forearc is a non accretionary forearc with numerous seamounts dredge hauls from these seamounts are composed primarily of serpentinite indicating a non volcanic origin in addition dredged carbonate samples reveal 1 the presence of aragonite in water depths greater than the aragonite compensation depth 2 unusual porosity and cement types 3 light carbon and heavy oxygen isotopic compositions and 4 an unusual trace element geochemistry of aragonite and calcite these mineralogic petrologic and geochemical characteristics formed the basis of a prediction that methane bearing fluids are venting from these seamounts subsequent to this prediction submersible dives on a mariana forearc seamount found and sampled chimneys seeping cool water that contains dissolved methane the serpentine substrate beneath the chimneys appears to form from cold gravitational flows of serpentine material fluid inclusion contents of chimney samples also show an earlier history of methane as well as longer chain hydrocarbons aromatics and acetate ions drilling into the flank and the summit of this seamount by the ocean drilling program during leg 125 confirmed the presence of methane other light alkanes and organic acids in the present day interstitial pore fluid of the cores the presence of aromatic compounds and organic acids if derived from the maturation of organic compounds indicates a thermogenic origin for these volatiles strontium isotopic ratios of the aragonitic chimney samples and of the present day interstitial waters range from present day seawater values to significantly lower values the strontium isotopic ratios of the pore waters within the seamount trend toward a relatively less radiogenic composition with increasing depth below the seafloor this strontium isotopic signature is probably not the consequence of near surface processes but more likely a contribution from an igneous source deeper in the lithosphere the lack of a large accretionary prism in the mariana forearc removes the complication of fluid contribution from dewatering of the prism by compression during convergence as in the oregon washington or barbados margins the organic compounds in the fluid inclusions and interstitial pore fluids as well as the isotopic and the geochemical composition of the carbonates and the dissolved constituents suggest that fluids are derived from dewatering compression and dehydration of subducted sediments and the subducting plate furthermore the composition of the fluid is influenced by thermal maturation of organics in subducted sediments as well as by a contribution from a deep igneous source

surficial evidence of fluid expulsion from the costa rica accretionary prism the nature and distribution of authigenic carbonates chemosynthetic bacterial mats and unique macrobenthic chemosynthetic communities of bivalves and tube worms are important for evaluating and reconstructing present and past fluid venting of accretionary complexes this paper describes the authigenic carbonates chemosynthetic fauna and fluid venting observed at the four tectonic regions of the costa rica accretionary wedge in february 1994 during an alvin diving program of 20 submersible dives we found no surficial evidence of highly focused fluid venting at the toe of the prism outermost 3 km as implied by the absence of authigenic carbonates and chemosynthetic fauna the absence of vent communities on the lower 3 km of the prism and the relatively elevated heat flow with respect to the adjacent incoming cocos plate langseth and silver this issue suggests diffuse rather than focused flow through the toe of the prism twelve active and relict vent sites marked by small clusters of live vesicomyid clams are localized at the bases and tops of out of sequence thrusts implicating fracture permeability as the fluid conduit in the lower slope region but upslope from the toe vast authigenic carbonates and seven active and relict vent sites marked by large dense clusters of chemosynthetic organisms predominate the largest mud diapir in the mid slope region fluid expulsion appears to be more restricted on the upper slope with only 2 small but dense vents marked by chemosynthetic fauna observed at one wall of one canyon

a three dimensional back analysis of the collapse of an underground cavity in soft rocks abstract the assessment of stability of man made underground caves excavated in the past and later on abandoned represents a serious challenge for land and urban planning operations especially for the areas of possible interaction of the caves with overlying structures and infrastructures several areas of southern italy are characterized by the presence of abandoned underground quarries for the extraction of soft calcarenite rocks which now threatens the overlying environment due to the risk of collapse and the consequent generation of sinkholes this work presents a back analysis of a sinkhole occurred in 2011 in the town of marsala caused by the collapse of an underground quarry as a representative case study of these phenomena based on the available geometrical and geological dataset as well as the field observations of the phenomenon in this article the assumptions and the results about the genesis of the 2011 sinkhole as derived from a three dimensional finite element back analysis aimed at reconstructing the stress strain evolution that brought to the ground failure collapse is discussed in particular the 3 d numerical analyses have been performed in order to identify the factors responsible of the genetic mechanism of the sinkhole the finite element analysis has been carried out by accounting for the geotechnical characterization of the marsala calcarenites derived from both specific laboratory tests performed on samples taken from the site and literature data available on the same rock material the numerical results have been then validated by means of the comparison with field observations and also compared with those achieved through a 2 d model of the same case study

fault related biogenic mounds in the ceduna sub basin australia implications for hydrocarbon migration abstract the early cenozoic in the bight basin represents a transitional period from the slow to fast oceanic crust spreading of the southern ocean between australia and antarctica this period is characterised by widespread igneous activity and the occurrence of biogenic mound complexes in the proximal part of the ceduna sub basin these mound complexes thrive on local topographic highs exploiting the shut down in siliciclastic sediment supply during the eocene new interpretation of 2d and 3d seismic data from the central ceduna sub basin shows additional undrilled paleocene eocene biogenic mound complexes they display rugose morphology progradational and aggradational internal organisation and high impedance contrast with the surrounding sediments these mounds typically show a clear relationship with underlying reactivated fault segments these faults intersect potential oil mature cretaceous source rock intervals and therefore one plausible mechanism for the development of fault related mound complexes in the central ceduna sub basin relies on natural hydrocarbon seeps along faults supplying nutrients for a benthic chemosynthetic organisms and localised biogenic mound growth the presence of a sub bottom profile anomaly overlaid by a vertical water column acoustic contact in close vicinity of a mound complex support this model the occurrence of seep related biogenic mounds would validate the presence of mature source rock s and hydrocarbon charge in the central ceduna sub basin if confirmed the biogenic mounds would imply fluid migration occurrence until at least the eocene

a braided distributary system on the orinoco deep sea fan abstract a long range side scan sonar gloria survey has been made of part of the orinoco deep sea fan that abuts against the deformation front of the barbados outer ridge i e in a pre orogenic setting immediately east of the deformation front sinuous channels up to 65 m deep and 3 km wide extend downslope and become very shallow a few metres or less deep and branch into a pattern that resembles stream braiding near the foot of the slope here there is a possible suprafan lobe and an almost flat perched sediment pond dammed by a buried basement ridge in this locality many of the acoustic contrasts on the sonographs are primarily due to differences in sediment type and small scale roughness rather than to variations in slope angle possible debris flows aligned along some of the braided channels have been identified from high resolution profiles this braided system of shallow channels then converges into a single channel that overtops the dam because of their braided nature the internal structure of the resulting deposits is likely to be complex these deposits should eventually be incorporated into the barbados ridge complex in contrast to this pre orogenic setting gloria sonographs also suggest that some orinoco sediment moves down along synclinical axes of folds on the barbados ridge complex i e in a syn orogenic setting

diagenetic processes influencing porosity in sandstones from the triassic buntsandstein of the iberian range spain abstract sandstones of the triassic buntsandstein of spain were studied in an attempt to quantify effects of diagenetic processes such as compaction cementation and leaching on reservoir properties samples were taken from shell well siguenza 44 3 some 110 km northeast of madrid drilled on the siguenza high in the iberian range the sandstones are arkoses to sublitharenites of a typical triassic redbed facies characteristic of the whole region the present day depth of the base buntsandstein is 538 m whilst a maximum burial depth of ca 2600 m was estimated from vitrinite reflectance 0 94 to 1 14 kaolinite temperature 76 c and illite crystallinity kuebler index 4 9 from an estimated average initial porosity of 38 porosity was reduced to the present value of 13 the strongest process to reduce porosity was found to be mechanical compaction causing a loss of 15 followed by chemical compaction pressure solution with a loss of about 6 the cement 11 4 r v apparently reduced the initial porosity by about only 5 early carbonate and sulphate cements are interpreted to have stabili sed the rock framework working against mechanical compaction and pressure solution this is supported by an increase in sutured grain contacts where early cements are absent or rare the later quartz cement interpreted to be largely the product from pressure solution has reduced porosity in a ratio of 0 5 1 this suggests that compaction continued after the formation of the late quartz cement although leaching was observed especially in feldspar grains clay and k feldspar neomorphosis is interpreted to have counteracted the formation of substantial secondary porosity permeability in the buntsandstein is generally low average 17 4 md and has been strongly affected by the alteration of feldspars to clay causing a wide range of permeability from 0 11 to 73 0 md

hydrothermal petroleum in mineralized mounds at the seabed of guaymas basin petroleum has been dredged from an active hydrothermal mound area in the southern rift of guaymas basin gulf of california this organic matter is composed of gasoline range aliphatic and aromatic hydrocarbons and predominantly residual polar asphaltic material the aliphatic hydrocarbons of two bitumen samples have very different boiling range and composition both samples contain polynuclear aromatic hydrocarbons and olefins which indicate formation at pyrolytic temperatures the overall compositional data indicate an origin from biological detritus by thermal alteration and rapid quenching by hydrothermal removal followed by condensation at the seabed

petrographic quantification of brecciated rocks by image analysis application to the interpretation of elastic wave velocities abstract this paper presents a new procedure to quantify the petrology of materials with complex and heterogenic rock fabric features the classical methodologies for petrographic quantification by image analysis are not appropriate for this kind of rock due to both the high chromatic complexity of these materials and the scale with which the samples are studied the proposed process is particularly interesting for materials with complex chromatic characteristics such as highly fractured rocks concrete etc two commercial varieties of highly fractured brecciated dolostones were selected for this study in order to test the designed methodology this new procedure is based on the analysis process of colour images obtained from mesoscopic sample scanning six petrographic parameters and diagrams have been designed in order to quantify the most influential aspects in compressional v p and shear v s ultrasonic wave propagation these petrographic parameters and diagrams are brecciation density brecciation density map clast size distribution fine grained matrix content shape preferred orientation and rose diagrams the results demonstrate that the proposed methodology is suitable for quantifying the petrography of these kinds of materials furthermore the variations measured in v p and v s are fully explained by the values measured for the following parameters brecciation density fine grained matrix content clast size distribution and preferred orientation of clasts

phase relations in the system kalsi3o8 naalsi3o8 at high pressure high temperature conditions and their implication for the petrogenesis of lingunite abstract multi anvil experiments have been made with the composition k0 2na0 8 alsi3o8 at 14 25 gpa and 1400 2400 c these experiments suggest that at subsolidus conditions the stable phase assemblages are hollandite i jadeite stishovite at pressures up to 20 gpa hollandite ii jadeite stishovite at pressures between 20 and 24 gpa and hollandite ii calcium ferrite type naalsio4 stishovite at pressures 24 gpa where hollandite i and hollandite ii are distinguished by their chemical compositions and phase diagram topology the maximum naalsi3o8 in hollandite occurs at 22 gpa and its fraction is positively correlated to temperature attaining a value of 51 mol at 2200 c at supersolidus conditions the solidus and liquidus phases around 14 gpa are hollandite i and jadeite respectively at 22 gpa however the solidus phase is jadeite while the liquidus phase is either stishovite or hollandite ii with a very low fraction of naalsi3o8 these experimental results therefore suggest that lingunite with the hollandite structure and 90 mol naalsi3o8 found in some meteorites is a disequilibrium product it is similarly proposed that the phase with the structure of jadeite but the composition of plagioclase found along with lingunite is also a disequilibrium phase

oil source rock correlation of the lower paleozoic petroleum system in the baltic basin northern europe the correlation of lower paleozoic marine source rocks with reservoired oils by biomarkers is complex because of the uniform early phanerozoic biomass bacteria and algae and the lack of land plant and animal input accordingly the main source rocks for the most prolific oil province in the baltic basin are still a matter of debate the 10 source rocks and 15 oil samples from 5 northern european countries bordering the baltic sea basin were analyzed by gas chromatography gc with flame ionization detector gc mass spectrometry gcms and gcms ms to detect acyclic isoprenoids and aliphatic aromatic and nitrogen sulfur and oxygen biomarkers chemometric tools were applied to screen for meaningful source and age related biomarkers and to highlight genetics extended tricyclic terpane ratios c24 tetracyclic terpane c26 tricyclic terpane ratios and relative c29 sterane concentrations are considered the most promising biomarkers in differentiating llandovery shales from cambrian to ordovician alum shale and for correlation with expelled oil the uranium irradiation related c26 c28 triaromatic steroid concentrations provide possible distinguishing criteria for the source potential of the different alum shale units enhanced oil maturation by volcanic intrusion is highlighted by sterane biomarkers and polycyclic aromatic hydrocarbons the alum shale is here considered the main source rock for oil accumulations in lower paleozoic reservoirs of the baltic basin oil seepage occurring in ordovician limestone was mainly generated by the middle cambrian alum shale and middle cambrian sandstone reservoirs were mainly sourced by upper cambrian and lower ordovician alum shale with higher maturity considerations about the assessment of migration distance are based on carbazole concentrations and c29 sterane isomerization advanced studies to unravel detailed lower paleozoic oil source rock correlations are based on meaningful biomarkers offer approaches to significantly reduce the exploration risk in this area and could be applied to similar early paleozoic petroleum systems in other basins

shock metamorphism of elephant moraine a79001 implications for olivine ringwoodite transformation and the complex thermal history of heavily shocked martian meteorites abstract lithology a of martian meteorite elephant moraine eet a79001 contains fragments entrained within a 100 m thick shear induced shock vein these fragments the shock vein matrix and walls of olivine along the vein as well as shock deformation and transformation in rock forming minerals in the bulk rock were investigated using scanning electron microscopy the electron microprobe and raman spectroscopy the presence of ringwoodite the spinel structured high pressure mg fe 2 sio 4 polymorph has been confirmed in eeta79001 for the first time ringwoodite occurs within and around the shock vein exhibiting granular and lamellar textures in both textures ringwoodite consists of 500 nm size distinct grains ringwoodite lamellae are 115 nm to 1 3 m wide planar fractures in olivine provided sites for heterogeneous nucleation of ringwoodite analyses performed on the largest grains 1 m show that ringwoodite is consistently higher in iron fa 27 4 32 4 relative to surrounding olivine fa 25 1 267 7 implying that there was fe mg exchange during their transformation and therefore their growth was diffusion controlled in the shock environment diffusion takes place dynamically i e with concurrent deformation and grain size reduction this results in enhanced diffusion rates 10 8 m 2 s over nm m distances shock deformation in host rock minerals including strong mosaicism pervasive fracturing polysynthetic twinning pyroxene only extensive shock melting local transformation of olivine to ringwoodite and complete transformation of plagioclase to maskelynite in the bulk rock indicate that eeta79001 was strongly shocked the short shock duration 0 01 s combined with a complex thermal history resulted in crystallization of the 100 m thick shock vein in eeta79001 during the pressure release and partial back transformation of ringwoodite to olivine based on the pressure stabilities of clinopyroxene ringwoodite crystallization at the shock vein margin began at 18 gpa olivine and clinopyroxene crystallized at

rocky coast geomorphology and erosional processes a case study along the murgia coastline south of bari apulia se italy many sites along the apulian coast se italy are composed of weathered and fractured carbonate rocks affected by intense erosion and the development of slope instabilities here coastal morphology was mostly produced by quaternary tectonics the severe and selective action of modern erosion by sea waves and locally was strongly conditioned by human influences in addition due to the carbonate nature of rock masses the role exerted by karst processes has to be considered this paper provides a critical review of the common eroding processes and factors affecting coastal morphology in a typical mediterranean coastal carbonate environment a stretch of the murgia coastline south of bari between san vito and polignano a mare made up of cliffs and shore platforms interrupted by small pocket beaches was considered for qualitative and quantitative assessment of shoreline recession the coastal stretch was monitored by means of field surveys between 1997 and 2003 furthermore a comparison of vertical aerial photographs covering the period 1966 1997 scales 1 33 000 1 10 000 and 1 5000 topographic maps scales 1 5000 year 1987 1 2000 year 1982 and archival terrestrial photographs taken since the 1930s was also employed in some zones characterised by a gently sloping shore platform a significant shoreline retreat was calculated at about 20 m in the last 100 years 0 2 myr 1 which was caused above all by human activity here in fact the presence of small ancient coastal quarries

composition and spatial organization of a cold seep community on the south barbados accretionary prism tectonic geochemical and sedimentary context abstract deep faunal assemblages were observed on cold seeps between 1000 and 2000m depth along the southern termination of the barbados accretionary prism during the caracolante ii and diapicar cruises faunal composition and microdistribution of a cold seep community were analyzed at one site using deep sea photographs and seismic 3 5 kz profiles the community is dominated by large mussels up to 20cm long possibly related to the genus bathymodiolus tiny vesicomyid clams and vestimentiferan clusters in which animals are up to 2m long there is a high density of sponges three species bryozoans and gorgonians other taxa occasionally associated with this assemblage include galatheid crabs anemones holothurians and possibly pennatulaceans which are numerous at boundaries of the site a typical deep sea fauna of fish asteroids and ophiuroids is also scattered about the vicinity this seep community is distributed as a band of discontinuous colonies 40 50m in width and more than 10km in length living colonies alternate with accumulations shells and bare areas the substratum is hard mud covered by a ferrugineous crust and cemented by carbonates the early diagenetic character of the bottom and the occurrence of biological assemblages indicate that seepages of sulphur and or methane which have been revealed along the decollement zone of the barbados prism must diffuse through the sea floor these biological and geological features are located on the crests of ne sw anticlinal ridges and mud volcanoes which have been built by diaprism

generation of short chain acid anions in hydrothermally altered sediments of the guaymas basin gulf of california an initial investigation of the concentration distribution of short chain organic acid anions in hydrothermally altered sediments of the guaymas basin reveals the presence of high concentrations of acetate and propionate relative to normal marine sediments acetate and propionate concentrations appear to vary as a function of sediment temperature and reach concentrations 1100 and 200 m respectively at temperatures 100 c as in previously studied oil field formation waters these acid anions probably play a key role in the generation of co2 and hydrocarbons gases hydrogen ion ph buffering the complexing of aqueous ions and mineral dissolution and precipatation at temperatures 100 c these and other acid anions should be important substrates for heterotrophic bacterial processes including sulfate reduction

high pressure phase relations in the composition of albite naalsi3o8 constrained by an ab initio and quasi harmonic debye model and their implications abstract phase relations in the composition of albite naalsi3o8 at pressures up to 40 gpa were constrained by a theoretical method that combines the ab initio calculation and quasi harmonic debye model first the p t dependence of the thermodynamic potentials of the individual phase stishovite sio2 st the calcium ferrite type naalsio4 cf jadeite naalsi2o6 jd or the hypothetical hollandite structured naalsi3o8 na holl was derived our results are generally in consistent agreement with available experimental data and previous theoretical predictions second the gibbs free energy of the hypothetical na holl phase was compared with that of the phase assemblage jd st js or cf 2st cs our results show that the na holl phase is not a thermodynamically stable phase over the studied p t conditions of 0 40 gpa and 100 600 k which rules it out as a possible intermediate phase along the transition path from the js phase assemblage to cs phase assemblage our calculations have predicted that the js phase assemblage transforms into the cs phase assemblage at about 33 6 gpa at 0 k and the clayperon slope of this phase transition is about 0 014 gpa k this study implies that lingunite na holl found in some meteorites is not possibly a thermodynamically stable high p phase and the cf phase probably plays an important role in maintaining the sodium budget and hosting the large ion lithophile elements in the deep interior of the earth

sediment instability related to fluid venting in miocene authigenic carbonate deposits of the northern apennines italy chemosynthetic carbonates identified by isotopic palaeoecological and sedimentological features are concentrated in middle late miocene satellite and foredeep deposits of the northern apennines chemoherms in the foredeep are hosted in thick pelitic intervals probably deposited in intrabasinal structural highs which are entirely or partly involved in large slumps in many cases associated with extrabasinal slides sediment textures in carbonates and in the enclosing foredeep pelitic sediments indicate a link between hydrocarbon fluid venting sediment deformation and mobilisation and tectonics the intensity and style of fluid release phases directly influenced chemoherm typology and also determined overpressure conditions in low shear strength pelitic sediments favouring sediment mobilisation and influencing slope instability which widely affected the apennine foredeep chemosynthetic carbonates are associated with sites of tectonically fractured and compressed sediments in the apennine foredeep thrust belt system thus indicating a relation with the tectonic loading of the apennine thrust sheets which favoured fluid expulsion along forerunner faults possible gas hydrate contributions to fluid expulsion processes are discussed based on sediment textures compared with modern vent areas finally sediment instability may have facilitated a large amount of fluid escape thus stopping carbonate precipitation

the control of mineral constituents and textural characteristics on the petrophysical mechanical pm properties of different rocks of the himalaya abstract petrophysical and mechanical pm properties of a rock are primarily controlled by its mineral constituents and various textural parameters similar rock types in different tectonic setups may be characterized by different mineralogical compositions and textural properties because they might have suffered different deformational processes this paper presents a study on the mineralogical and textural control on various pm properties in quartzites granitoids gneisses metabasics and dolomite collected from different tectonic set ups the inter relationships among mineral constituents various textural parameters unconfined compressive strength ucs schmidt hammer rebound r value seismic wave both p and s waves velocity and their attenuation characteristics were obtained using regression analyses it has been concluded that there exists no relation between ucs and seismic wave velocity in quartzite granitoids and gneisses moderate positive relationship in metabasics and strong negative relationship in dolomite it has further been noted that in quartzite and dolomite monominerelic rocks grain size dominantly control the seismic wave velocity as the relatively coarser grained samples have higher seismic wave velocity whereas ucs is strongly controlled by grain size as well as the quantity and the orientation of the weak minerals like muscovite biotite calcite etc in gneisses and granitic gneisses preferred orientation of minerals especially the mica minerals although in present small quantity is the main factor controlling ucs and seismic velocity both these properties increase with the increase in intensity of preferred alignment of minerals whereas in metabasics it is the presence of amphibole pyroxene minerals feldspar that dominantly controls the seismic wave velocity

hot fluids burial metamorphism and thermal histories in the underthrust sediments at iodp 370 site c0023 nankai accretionary complex abstract drilling during international ocean discovery program iodp expedition 370 at site c0023 encountered instances of hydrothermal mineralization from 775 to 1121 m below seafloor fluid inclusion homogenization temperatures measured on barite veins within this interval indicate precipitation from fluids with temperatures up to 220 c and salinities ten times higher than interstitial water 16 25 c f 2 8 3 6 wt nacl patches of stratabound mineralization rhodochrosite calcite barite and anhydride are largely confined to the vicinity of veins and have vertical thicknesses and extents that can be explained by precipitation within the thermal aureoles of veins thermal maturities measured on petroleum biomarkers in underthrust sediments record a rise from pre oil window to early oil window thermal maturities basin models show that increases in thermal maturity can be explained by burial metamorphism and kinetic based calculations suggest that hot fluids would only have had a minimal effect on hydrocarbon generation however the movement of hot fluids still has geochemical implications and creates a complex thermal history where both short duration localized heating within fracture zones at hot temperatures 200 c for less than 1 yr and heating during burial over long durations 80 110 c for 0 5 2 myrs need to be considered

petrographic features influencing basic geotechnical parameters of carbonate soft rocks from apulia southern italy abstract a multidisciplinary petrographic and geotechnical approach aimed at understanding the conditioning by rock fabric on the mechanical properties of carbonate soft rocks is shown in this paper the analysed rocks extensively crop out in the apulia region and can be referred to three geological units pietra leccese late burdigalian early messinian calcarenite di gravina middle pliocene early pleistocene and salentino supersynthem midde late pleistocene 69 specimens of carbonate soft rocks belonging to all these units were selected from different sectors of apulia region and characterized according to petrographic physical and mechanical properties petrographic data allowed us to group all specimens in the following six classes i wackestone ii mud dominated packstone iii packstone iv grainstone v floatstone vi rudstone differently uniaxial compression strength ucs values classify the most part of specimens in very low and low strength revealing a dominant weak resistance and high deformability particular attention has been given to the relationships between petrographic features and physical and mechanical parameters of the apulian soft rocks by means of statistical tests based on the univariate analysis of variance one way anova and on the principal component analysis pca at first statistical analysis revealed that the rock geotechnical values are strictly dependent from the geological units particularly the samples of pietra leccese show significantly higher means of ucs young s modulus et and dry unit weight than samples of the calcarenite di gravina fm conversely samples of this latter unit have significantly higher means of porosity imbibition coefficient and permeability coefficient than those ones of the pietra leccese fm moreover statistical analysis was applied to estimate if geotechnical values differ according to the petrographic classes of the calcarenite di gravina fm and to verify the covariance between the geotechnical parameters of this unit the following results have been remarked i floatstone and rudstone have significantly higher means of ucs and dry unit weight and lower means of porosity than finer grained classes ii mud dominated packstone has significantly lower means of ucs dry unit weight et and permeability coefficient and higher means of porosity and imbibition coefficient than other petrographic classes iii grain dominated matrix free rudstone and grainstone have significantly higher values of permeability coefficient than mud dominated classes iv the occurrence of carbonate lithoclasts and of different dominant couples of sparry cement in pore spaces are two of the most important controlling factors of the rock strength and can also explains much of the intraformational variability observed in geotechnical data total porosity has not a clear correlation with permeability this means that the contribution of isolated pore spaces to the total porosity is relevant in apulian soft rocks as also suggested by the relatively low values of permeability compared to the relatively high percentages of total porosity a multidisciplinary characterization of carbonate soft rocks based on petrographic analysis and geotechnical determination of physical and mechanical properties is here recommended for future studies since this approach can give useful information to understand the peculiar behaviour of carbonate soft rocks and to drive the subsequent geotechnical investigations

a preliminary analysis of failure mechanisms in karst and man made underground caves in southern italy abstract natural and anthropogenic caves may represent a potential hazard for the built environment due to the occurrence of instability within caves that may propagate upward and eventually reach the ground surface inducing the occurrence of sinkholes in particular when caves are at shallow depth the effects at the ground surface may be extremely severe apulia region southern italy hosts many sites where hazard associated with sinkholes is very serious due to presence of both natural karst caves and anthropogenic cavities the latter being mostly represented by underground quarries the pliocene pleistocene calcarenite a typical soft rock was extensively quarried underground by digging long and complex networks of tunnels with time these underground activities have progressively been abandoned and their memory lost so that many apulian towns are nowadays located just above the caves due to urban expansion in the last decades therefore a remarkable risk exists for society which should not be left uninvestigated the present contribution deals with the analysis of the most representative failure mechanisms observed in the field for such underground instability processes and the factors that seem to influence the processes as for example those causing weathering of the rock and the consequent degradation of its physical and mechanical properties aimed at exploring the progression of instability of the cavities numerical analyses have been developed by using both the finite element method for geological settings represented by continuous soft rock mass and the distinct element method for jointed rock mass conditions both the effects of local instability processes occurring underground and the effects of the progressive enlargement of the caves on the overall stability of the rock mass have been investigated along with the consequent failure mechanisms in particular degradation processes of the rock mass as a consequence of wetting and weathering phenomena in the areas surrounding the caves have been simulated the results obtained from the numerical simulations have then been compared with what has been observed during field surveys and a satisfactory agreement between the numerical simulations and the instability processes as detected in situ has been noticed

ketones in hydrothermal petroleums and sediment extracts from guaymas basin gulf of california the polar compound nso fractions of seabed petroleums and sediment extracts from the guaymas basin hydrothermal system have been analyzed by gas chromatography and gas chromatography mass spectrometry the oils were collected from the interiors and exteriors of high temperature hydrothermal vents and represent hydrothermal pyrolysates that have migrated to the seafloor by hydrothermal fluid circulation the downcore samples are representative of both thermally unaltered and thermally altered sediments the survey has revealed the presence of oxygenated compounds correlated with samples exhibiting a high degree of thermal maturity several homologous series of related ketone isomers are enriched in the interiors of the hydrothermal vent samples or in hydrothermally altered sequences of the downcore sediments dsdp holes 477 and 481a the n alkanones range in carbon number from c11 to c33 with a cmax from 14 to 23 distributions that are similar to those of the n alkanes the alkan 2 ones are usually in highest concentrations with lower amounts of 3 4 5 6 7 and higher alkanones and they exhibit no carbon number preference there is an odd carbon number preference of alkanones observed for downcore samples the alkanones are enriched in the interiors of the hydrothermal vent spires or in downcore hydrothermally altered sediments indicating an origin at depth or in the hydrothermal fluids and not from an external biogenic deposition minor amounts of c13 and c18 isoprenoid ketones are also present simulation of the natural hydrothermal alternation process by laboratory hydrous pyrolysis techniques provided information regarding the mode of alkanone formation hydrous pyrolysis of n c32h66 at 350 c for 72 h with water only or water with inorganic additives has been studied using a stainless steel reaction vessel in each experiment oxygenated hydrocarbons including alkanones were formed from the n alkane the product distributions indicate a reaction pathway consisting of n alkanes and olefins as primary cracking products with internal olefins and alkanones as secondary reaction products hydrous pyrolyses of messel shale spiked with molecular probes have been performed under similar time and temperature constraints to produce alkanone distributions like those found in the hydrothermal vent petroleums

origin of petroliferous bitumen from the buyuk menderes gediz geothermal graben system denizli saraykoy western turkey abstract the kb 5 well is located at the intersection of the geothermally active menderes and gediz graben systems in western turkey significant volumes of petroleum like material plm with its associated thermal water 120 c erupted onto the surface during drilling from a depth of 120 132 m i e from the claystone and marl rich early to middle pliocene kolonkoya formation the purpose of this paper is 1 to characterize this plm 2 to assess the source characteristics from which the plm was likely generated and 3 to recognize the generation mechanism considering the geothermal gradual versus the hydrothermal rapid processes analytical organic geochemistry using thin layer chromatographic separation followed by gas chromatography mass spectrometry gc ms was carried out the plm is composed primarily of polar nso compounds asphaltenes 77 this feature is similar to hydrothermal petroleums e g calcite springs yellowstone national park wyoming the plm shows n alkanes ranging from n c 19 to n c 38 i e with a maximum at n c 30 but n alkanes are depleted in n c 19 an absence of acyclic isoprenoids pristane and phytane and considerably large ucm unresolved complex mixture indicate that the plm has been subjected to a moderate degree of alteration possibly by the accompanying hot geothermal waters the source specific biomarkers i e low c 29 nh c 30 h ratio presence of gammacerane and 18 h oleanane high c 35 c 34 homohopane ratio and c 29 sterane concentration n c 28 n c 27 n c 29 c 28 27 29 r steranes c 29 r c 27 r suggest that the plm is a petroleum and was most likely generated from a tertiary source rock with a carbonate clay rich lithology the source organic matter was predominantly terrestrial and bacterial detritus deposited in relatively saline anoxic environmental conditions maturity sensitive biomarker parameters i e t m t s c 29 sterane 20 s 20 s 20 r 0 35 c 32 hopane 22 s 22 s 22 r 0 57 low diasterane regular sterane ratio correspond to a maturity level of approximately 0 50 0 60 r o this level of maturation could not be reached by such a young upper miocene lower pliocene and shallow sedimentary column max 600 m in the absence of instantaneous hydrothermal activity pahs are not detectable but series of alkylbenzenes alkyltoluenes alk 1 enes and triaromatic steranes are present the lack of organic richness and maturity in the drilled section of the kb 5 well indicates that the petroleum was generated in the deeper sections of the formation the temperature profile of the well and composition of the hydrocarbons in the petroleum suggest that the temperature of the hydrothermal activity during hydrocarbon generation was

hydrothermal petroleum generation in red sea sediments from the kebrit and shaban deeps abstract petroleum impregnated sediments and massive sulfides have been found in two deeps of the northerns red sea biological marker distributions in extracts and polar fraction degradation products were analyzed in order to elucidate the source of the petroliferous material two organic phases could be distinguished according to their source and maturity the amounts of n alkanes show a marked decrease with depth whereas the concentrations of various branched and cyclic hydrocarbons increase resulting in a humpof unresolvable compounds in a depth as shallow as 300 cm changes in concentrations and distributions of hopanoids in the kebrit deep sediments indicate a rapid increase of maturity with depth the deepest core section 300 cm and the masive sulfide reveal comparable maturation indices typical for mature oils by chemical degradation of the polar fractions a series of c 40 isoprenoids was obtained which reveals a considerable contribution from methanogenic and thermophilic archapbacteria to the immature organic matter the data suggest that petroliferous material ofthermogenic origin migrates through the younger sequences superimposes the autochthonous organic substances in the sediments and furthermore forms asphaltic impregnations in the massive sulfides

dynamic response of a rocky cliff under the sea wave pulse a study along the adriatic coast of polignano apulia italy the dynamic behavior of a rocky cliff under severe sea waves has been analyzed in the location of polignano facing on the adriatic coast of apulia southern italy in this area the classical and at the same time complex problem of the stability of a cliff in calcareous rocks is burdened by the presence on the top of the cliff of the ancient town to analyze the behavior of the cliff under the impulsive transfer of energy generated by the sea waves two types of measures were carried out on the rocky mass 1 ambient noise and 2 strong motion records the first type of measures which may be executed in a short time with a high spatial density has provided a recognition of the intrinsic and anisotropic dynamic behavior of the coastal cliff the accelerometric records carried out during heavy storms in december 2009 and january 2010 allowed to evaluate the energy transfer from waves to cliff in terms of maximum values and temporal and directional distribution to facilitate a correct interpretation of the measures also a geomechanical characterization of the rocky mass has been carried out through the rock mass rating system bieniawski the geomechanics classification in rock engineering applications proceedings of the 4th isrm cong montreux pp 51 58 1979 bieniawski engineering rock mass classifications wiley new york p 251 1989 and the markland s test a useful technique for estimating the stability of rock slopes when the rigid wedge sliding type of failure is expected pp 10 1972 the first allowed to classify the rocky masses in terms of quality the second one to individuate the potential failure mechanisms of the cliff

geochemical and biogeochemical observations on the biological communities associated with fluid venting in nankai trough and japan trench subduction zones we have studied the compositions and structure of the lamellibranchiacalyptogena sp associated with fluid venting in subduction zones off japan the gills of thecalyptogena are the habitat of symbiotic bacteria which develop owing to chemoautotrophy they most probably assimilate hydrogen sulfide methane and or carbon dioxide and reduce nitrogen the isotopic budget of methane uptake enables to establish the thermal diagenetic origin of the light hydrocarbons brought by the upwelling fluids the microscopic examination of thin sections of the bacteria enables to establish that their membranes are compatible with uptake of inorganic nutrients and to establish relations with the metabolism of archeobacteria

rock fabric heterogeneity and its influence on the petrophysical properties of a building limestone lede stone belgium as an example lede stone is an important historical stone in belgium with many ceased and disappeared historical quarries owing to its geological nature this stone exhibits considerable variation in petrophysical properties three macroscopical different facies from the solely remaining quarry area in balegem belgium were profoundly characterized for their pore network properties and petrophysical properties the pore network was exhaustively studied combining water imbibition under vacuum mercury intrusion porosimetry and x ray computed microtomography the three facies not only have a strong difference in total porosity but also differ in terms of pore connectivity and pore size distribution linked to the variability in microfacies this has profound implications on the water transfer properties such as atmospheric water absorption capillary water absorption om nidirectional drying and water vapor resistance the petrophysical behavior is illustrated with a salt ageing test the results can be used for restoration and conservation of lede stone in the built cultural heritage

interpretation of subsurface hydrocarbon shows hydrocarbons occur in the subsurface in four modes 1 continuous phase oil or gas 2 isolated droplets of oil or gas 3 dissolved hydrocarbons and 4 associated with kerogenous rocks all of these modes of occurrence can result in what is described as a subsurface hydrocarbon show each show type has markedly different implications to exploration and must be differentiated as the first step in show interpretation only continuous phase occurrences of oil and gas indicate that a trapped and potentially producible accumulation of hydrocarbons has been discovered free oil or gas recovery from the formation or subsurface hydrocarbon saturations of greater than 55 indicates a continuous phase occurrence continuous phase shows can be interpreted quantitatively the static hydrocarbon column downdip from a continuous phase occurrence can be calculated from one well bore if the subsurface oil or gas saturation capillary properties hydrocarbon water interfacial tension oil density and water density of the reservoir are known producing wells are by definition continuous phase oil or gas and estimates of oil water or gas water contacts from normally available exploration data are practical and reasonably accurate based on a documented field study continuous phase oil or gas can extend either updip or downdip from a commercial reservoir these continuous phase shows can also be interpreted quantitatively to determine how large an oil or gas column is required downdip to explain the show by this method it can be determined whether an exploratory well penetrated the updip waste zone or downdip transition zone of an oil or gas field field studies illustrate that quantitative show interpretation of noncommercial shows can provide reliable estimates of the downdip hydrocarbon column this type of data can be used in a systematic manner to explore for subtle stratigraphic and combination traps

a multidisciplinary study of middle miocene seep carbonates from the northern apennine foredeep italy several pelitic intervals are intercalated at various levels within the marly arenaceous turbiditic successions of the middle miocene northern apennine foredeep they range in thickness from 30 to 200 m and represent sedimentation on top of ephemeral structural highs related to blind faults sediments are made up of hemipelagites and fine grained turbidites and include 13c depleted carbonates related to the rising of methane rich fluids hydrocarbon seep carbonates large portions of pelitic intervals are involved in chaotic masses by soft sediment deformation slumps slides intraformational breccias revealing an intense sediment instability during middle miocene a stratigraphic mineralogic and geochemical study was conducted on two of these pelitic intervals castagno d andrea mt citerna in order to reconstruct carbonate development the composition of fluids and to document the connections between fluid seepage and syndepositional tectonics this multidisciplinary approach has allowed us to discriminate between the two examined pelitic intervals in terms of age depositional rates and conditions organic carbon and post depositional processes seep carbonates are characterized by chemosymbiotic fossil communities autoclastic fractures and brecciation carbonate bodies show complex facies relationships as indicative of different stages in chemoherm growth the compositional study evidences the peculiar chemistry of chemoherm carbonates calcite low in mg and sr compared with carbonates in associated enclosing pelites and with modern chemoherms in general the non carbonate components within the chemoherms are enriched in detrital minerals and depleted in phyllosilicates with respect to the enclosing pelites the mineralogical changes in the clay component within the brecciated unit of the castagno d andrea chemoherms suggest authigenic precipitation of the mg rich phases isotopic analyses show the distinct carbon signature in the chemoherms from the two examined intervals castagno d andrea chemoherms more depleted from 15 8 up to 41 3 pdb than mt citerna from 5 2 up to 16 7 and the transitional 13c depletion trend observed moving from chemoherms to the enclosing pelites moderately depleted and te bouma sequence turbidites in the range of marine carbonates a slight but significant enrichment in 18o up to 1 4 pdb is observed for all chemoherms when compared to values of carbonate phases present in enclosing pelites geochemical data indicate that the brecciated facies of seep carbonates are related to an explosive release of gaseous fluids probably associated with the rise of deep hypersaline fluids

geophysical survey of a mud volcano seaward of the barbados ridge accretionary complex a detailed geophysical investigation that included multibeam bathymetry 3 5 khz channel and single channel seismic profiles 20 heat flow measurements and four piston cores was made of a mud volcano located about 8 km seaward of the toe of the barbados ridge accretionary complex in the northern guiana basin the material erupted from the volcano covers an oval area about 3 9 km with its long axis oriented e w roughly perpendicular to the deformation front a flat topped mound on the western side of the feature is the currently active center acoustic stratigraphy suggests that mud volcanism began at the site about 200 000 ma a piston core taken on the flank of the active mound sampled deposits erupted 20 000 30 000 ma that contain late miocene nannofossils heat flow on the active mound is 4 times that in the surrounding basin one dimensional modeling of this anomaly supports a low level continuing flux of mud and water at rates of 2 5 cm yr the mud volcanism appears to have arisen from the combined action of overpressured water that comes from beneath the accretionary prism and existing overpressures in the oceanic section large east west trending basement escarpments underlie the two known mud volcanoes seaward of the barbados ridge accretionary complex and they probably play an important role in developing vertical pathways for fluid to escape and in determining the location where mud volcanism starts

sandstone degradation an experimental study of accelerated weathering the investigated rock material belongs to the group of upper cretaceous quader sandstones which are very important construction stones in poland and germany the mineral composition of the rocks is relatively uniform they are quartzose sandstones the most important feature is their good workability and comparatively high weathering resistance still regardless of the apparent resemblance the observations carried on buildings and monuments show differences in weathering processes the undertaken test was an attempt to verify the proposed before rock classification performed on the basis of parameterization of porosimetric cumulative intrusion volume curves the aim of the experiment was the evaluation of the sandstone petrography including the structure texture and porosity of the rock influence on the weathering process the modelling of accelerated weathering was conducted in chamber for ageing acceleration where some weather circumstances were simulated insolation rain and frost as the result of the weathering experiment it could be stated that the dominant mechanism of the sandstones deterioration was granular disintegration and weight loss as a consequence of sample destruction the most important factor influencing rock deterioration is rock texture especially the character of grain contacts the effective porosity is a requisite of potential for the stone to take in and hold water and hence of resistance to weathering in case of silica cemented sandstones the deciding criterion influencing weathering resistance is pore structure in case of sandstones with clay cement the most important is mineral composition of the rock

high pressure polymorphs of magnesian orthopyroxene from a shock vein in the yamato 000047 lherzolitic shergottite abstract we found a simple thin shock vein less than or equal to about 60 m in width and 1 8 mm in length in the poikilitic area in the yamato y 000047 lherzolitic shergottite the shock vein occurs only in magnesian ca poor clinopyroxene which may have transformed from orthopyroxene during the pressure increase at the shock event the shock vein consists of mg0 8 fe0 2 sio3 pyroxene polymorphs such as columnar akimotoite two kinds of pyroxene glasses dendritic akimotoite and framboidal pyroxene glass in the order from the periphery to the center the compositions and textures suggest that columnar akimotoite in the periphery of the shock vein crystallized from solid state phase transition of clinopyoroxene during the cooling of the vein and the remains in the shock vein solidified from shock produced melt the glass includes two kinds of massive glass in the vein and framboidal glass in the vein center the framboidal glass is the most magnesian and may have been vitrified from perovskite crystallized from high pressure melt produced at high temperature 3000 c and high pressure 23 40 gpa dendritic akimotoites in the vein center metastably crystallized from residual shock melt the formation sequences of the constituent phases in the shock vein happen in the following order columnar akimotoites rim glass center glass framboidal glass and dendritic akimotoites the increase of the raman intensity of 660 670 cm 1 in the order of rim glass center glass and framboidal glass suggests that the formation of the pyroxene chain proceeds faster in the vein center than in the vein rim due to its slower cooling the finding of the shock vein consisting merely of high pressure polymorphs of pyroxene akimotoite and framboidal glass vitrified perovskite is the first reported among all martian meteorites

the permian kupferschiefer of southwest poland a geochemical trap for migrating metal bearing solutions abstract the ore grade cu mineralization in southwest poland is associated with the presence of the rote faule zone that overlies the contact of saxothuringian and rhenohercynian zones in these areas the soluble organic matter in the kupferschiefer is altered strongly saturated hydrocarbons and alkylated aromatic compounds are depleted significantly in comparison to non altered shale samples of a similar maturation instead unsubstituted di and tricyclic aromatic hydrocarbons are the dominant components of the extractable bitumen the observed alteration points to late diagenetic oxiadtion reactions caused by upward migrated metalliferous solutions moreover polycyclic aromatic hydrocarbons pah associated with polycyclic aromatic sulphur hydrocarbons pash are abundant in some samples these compounds are considered to originate from the underlying carboniferous strata and were carried upward to the kupferschiefer zone which acted as a geochemical trap

two distinct assemblages of high pressure liquidus phases in shock veins of the sixiangkou meteorite shock produced complex veins including earlier and later veins are identified in the sixiangkou l6 chondrite the early vein is intersected by the late vein and consists of coarse grained aggregates of ringwoodite majorite and lingunite and fragments of olivine pyroxene plagioclase metal and troilite as well as a fine grained matrix of garnet ringwoodite metal and troilite the late vein mainly consists of a fine grained matrix of garnet magnesiowustite metal and troilite as well as a small amount of coarse grained aggregates the amount of fine grained matrix suggests that the late vein was nearly completely melted whereas the early vein underwent partial melting both fine grained assemblages of garnet plus ringwoodite in the early vein and garnet plus magnesiowustite in the late vein are liquidus phases crystallized from shock induced melt based on our understanding of the liquidus assemblages the late vein experienced a higher pressure and temperature than the early vein

susceptibility mapping of instability related to shallow mining cavities in a built up environment anthropogenic activities and urbanization frequently spread over areas underlain by unstable karst ground or man made cavities leading to potential risk situations for buildings infrastructure and population the roof of the cavities may rapidly propagate upwards eventually resulting in progressive ground settlement and or sudden collapse these processes are frequently accelerated or triggered by various human activities e g overloading water recharge water table decline in this paper the susceptibility to instability of artificial cavity networks under an urban area in apulia region southern italy was assessed and evaluated here there is dense network of underground quarries excavated for the extraction of massive calcarenite for building and ornamental stone that are currently affected by severe instability problems identifying the zones of the cavities most prone to instability is of great practical importance susceptibility models have been developed analyzing the statistical relationships between the cavity sections with evidence of instability and a number of predisposing factors mainly related to the 3d geometry of the voids roof thickness and the presence of overloads the models produced by the discriminant analysis and the logistic regression approaches were independently and quantitatively evaluated through the construction of roc curves although the two models are characterized by different input data treatment as the logistic regression allows using continuous and discrete variables or any combination of both types even if they do not have a normal distribution the roc curves highlighted for both methods a satisfactory congruence between the model results and the observed data consequently from the model performance analysis the two models were evaluated comparable in terms of result reliability the methodology should be considered as a general first level analysis for near surface underground cavities aimed at identifying critical cave sectors that can be the focus of more detailed analyses especially those associated with sensitive zone related to the presence of buildings roads and frequent presence of human activity

an image analysis technique to measure grain size variation in thin sections of soft clastic sediments this paper presents a simple and fast image analysis technique to measure grain size variation in thin sections of soft elastic sediments optical and backscattered electron microscope photographs are digitised from thin sections cut by freeze drying to avoid disturbing the sediments processing of the 256 grey scale images produces binary black and white images where white pixels represent the clay rich sedimentary matrix and black pixels represent elastic grains data measured include grain surface grain perimeter and centre of gravity two indices are defined to quantify grain size d 0 equivalent disk diameter and p phase percentages the technique is applied to silt and clay laminations attributed to the d division of a distal turbidite from lake baikal the data obtained using image analysis are similar to the conventional descriptions of such deposits indices calculated on very small samples e g on a single lamina allow for greater precision in interpretation of sedimentary processes compared to photomicrographs backscattered electron microscope images have better qualities and allow to quantify variations in the grain size along a sediment core the technique produces objective and quantified grain size observations in less time than conventional petrographic methods c 1998 elsevier science b v all rights reserved

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

hydrothermal discharge and alteration in near surface sediments from the guaymas basin gulf of california abstract in the guaymas basin gulf of california hydrothermal fluids discharge onto the seafloor via both direct emanation through hydrothermal spires and diffusely through the sediments the latter mode is the focus of this study short 20 cm sediment cores were taken in zones of diffuse hydrothermal flow for chemical investigation of interstitial fluids and bulk solids the hydrothermal component of the pore fluids was quite variable indicating the heterogenous nature of the near surface flow regimes the bulk solids chemistry indicates that the suite of cores has encountered different amounts of cumulative hydrothermal exposure dissolution of biogenic silica and deposition of large amorphous silica clasts in the sediment are related to the extent of hydrothermal exposure surface enrichments in ba are formed as barite precipitates when ba rich hydrothermal fluids mix with sulfate rich seawater at the seafloor formation of pyrite and removal of mg from the solid phases are also observed effects of hydrothermal flow through these sediments

multibeam bathymetric survey and high resolution seismic investigations on the barbados ridge complex eastern caribbean a key to the knowledge and interpretation of an accretionary wedge abstract an important problem of active margin processes is the way accretionary wedges form in response to oceanic crust subduction new data have been obtained along the barbados ridge in front of the lesser antilles tertiary island arc they include high resolution multichannel seismic data and accurate sea beam bathymetric maps both have been used to propose a 3 dimensional interpretation of tectonic and sedimentary processes related to subduction such as oceanic off scraping ductile folding relative uplift and subsidence fore arc basin evolution and mud diapirism they all improved our knowledge of the evolution of accretionary prisms and more specifically of the barbados ridge development in plio quaternary time previous tectonic events are deduced from recently published geological data from barbados and the lesser antilles islands

liquefied vs stratified sediment mobilization processes insight from the south of the barbados accretionary prism this paper discusses the nature and origin of subsurface sediment mobilization processes in deep marine clay rich environments in the studied area of the southern barbados accretionary prism new geophysical acquisitions have emphasized the spectacular widespread development of mud volcanoes that are well developed along ramp anticlines and along sigmoidal rises with trends that are oblique to the axes of the main folds of the accretionary wedge on some active mud volcanoes heat flow measurements show high positive anomalies related to high fluxes of mud transfer the mobilized solid fraction expelled by the mud volcanoes does not originate from a unique source bed but from various formations pierced by the mud conduits and is driven by the water phase the area studied also exhibits trends of structures corresponding to sub circular massive local uplifts of deformed but well preserved stratified sediments turbidites and hemipelagics no piercing shale diapirs have been encountered in this area some of these local uplift structures are complicated by the development of collapses calderas and superimposed mud volcanoes mud volcanism corresponds fundamentally to fluid displacement water and gas whereas massive sedimentary uplift corresponds to large vertical displacements of stratified solid levels but for which the deep cause could be partly the intrusion of mud plugs both are dynamic phenomena controlled by the development of overpressure at depth contributing to sedimentary mobilizations

sea level changes since the middle ages along the coast of the adriatic sea the case of st nicholas basilica bari southern italy abstract during the last decade several papers have been published to estimate the relative sea level change from coastal archaeological indicators of the last 3 4 ka bp in many locations of the italian coasts and the mediterranean sea the use of the archaeological information has been poorly focused for the middle ages due to the few available coastal installations for this period thus not allowing precise sea level estimation for the last 1000 years to complement the instrumental data available for the last 100 120 years this study discusses an archaeological marker of the middle ages used to reconstruct the story of the sea level changes in the last 1000 years at the st nicholas basilica built in 1087 ad along the coast of bari apulia southern italy the elevations of the ancient floor levels of the crypt underwent repeated flooding due to a continuous rising of the groundwater table which required restoration and uplifting of pavements between 1087 and 1956 to keep them dry the palaeo sea levels have been obtained by measuring the position of the groundwater table the elevation of which is mainly driven by sea level since the time of the construction of the basilica the elevation of the archaeological markers and the water table were compared against the latest predicted sea level curve for the holocene along the coast of bari as this coastal area is unaffected by significant vertical tectonic motion over the last 125 ky the data detail the timing of the relative sea level rise since the middle ages and can be used to improve the predicted sea level curve for this region for the last 1000 years

physical properties and textural parameters of calcarenitic rocks qualitative and quantitative evaluations abstract petrophysical and mechanical properties of sedimentary rocks are influenced by size shape and packing of grains porosity cement and matrix content all controlled strongly by depositional fabric and postdepositional processes this paper presents a study on the textural characteristics of soft and porous calcarenites and the main methods to determine petrophysical data the examined calcarenites sampled from three quarry districts located in apulia southeastern italy are fine grained and coarse grained grainstones a and d and medium grained packstones b belonging to a plio pleistocenic formation calcarenite di gravina outcropping in the whole region the study involved particularly textural analysis on thin sections using optical petrographic microscopy and evaluation of total and effective porosity by means of standard geotechnical laboratory tests mercury intrusion porosimetry and image analysis grain size frequency distribution was also carried out by traditional sieve and sedimentation analysis on disaggregated materials and image analysis computer analysis of digital images was performed on photomicrographs applying the methods of quantitative stereology to pore size and grain size distributions a comparison between results showed that each technique used has its limitations linked to the textural characteristics primarily geometry and topology of the pore network granulometry grain shape and packing of calcarenites

the pore system of sedimentary rocks as a key factor in the durability of building materials abstract we studied the pore system of six different types of sedimentary stone two limestones two sandstones one dolostone and one travertine techniques based on the direct observation of the pore system optical and scanning electron microscopes digital image analysis were combined with others used for indirect characterization mercury intrusion porosimetry n 2 adsorption hydric tests and vapour permeability in addition we performed accelerated decay tests to determine the durability of the stones and to check the consistency of the results obtained in the pore system study digital image analysis allowed us to calculate the pore size distribution and the total porosity digital image analysis always gave higher values for total porosity than those determined by porosimetry and hydric tests which only measure open porosity the density values were congruent with the mineralogy of the stones the stone that obtained the best results in the various tests in terms of its petrophysical parameters was dolostone while the worst performance was by one of the two limestones these results were confirmed by the decay tests the combined use of these different techniques gave us an accurate interpretation of the pore systems of the six different stones and also enabled us to correct misleading interpretations caused by the limitations of using one single technique our findings also provide useful information to help prevent the decay of these stones

petrography and reservoir physics i objective classification of reservoir porosity porosity observed in thin section can be objectively classified using a combination of digital acquisition procedures and pattern recognition algorithms pore types are derived from the frequency distributions of sizes and shapes of patches of porosity exposed in thin section each pore type is represented by a characteristic distribution of sizes and shapes found in thin section most sandstone reservoirs contain fewer than six pore types much of the intersample variability in reservoir physics is associated with changes in pore type abundance the advantages of this approach to porosity classification are 1 the criteria for classification are objectively defined 2 classification procedure is rapid accurate and precise 3 pore types are understood easily in ter s of conventional genetic classification schemes and 4 pore type data are related strongly to petrophysical properties

a visual determination method for uniaxial compressive strength estimation based on croatian carbonate rock materials abstract to identify visually detectable elements that influence carbonate rock strength a detailed inspection of 231 samples mainly from the adriatic carbonate platform in croatia was conducted prior to laboratory testing anova was used to detect statistically significant carbonate rock material parameters that influence ucs lithology fabric defects and porosity lfdp and their optimal classes anova was also used to find a statistically significant model that contains four major effects on the strength of carbonate rock lfdp with three two way interactions lithology fabric fabric defects and defects porosity according to four basic influential parameters the new procedure is coined lfdp determination and is described in detail the presented results indicate that the lfdp determination method is reliable enough for use in engineering geological practice on croatian carbonate rocks but also for use in other regions while the presented method may be applied to other regions worldwide its suitability to local conditions should be tested the lfdp determination method is simple efficient inexpensive and versatile it can be applied to outcrops cuts quarries tunnels borehole cores and similar however it is important to note that this method cannot replace laboratory testing and should be only used to collect preliminary information on carbonate rock material properties and possible ranges in ucs values