some observations on suspended sediment dynamics in storbregrova jotunheimen observations are reported of the dynamics of suspended sediment transport in the meltstream of storbreen in the jotunheimen fine sediment is transferred from the subglacial to the proglacial environment during low flow meltdominated periods and then removed from the catchment during high flow rainfall controlled events both diurnal and storm period sediment load discharge relationships involve clockwise hysteresis but separate multivariate rating curves define variations of load with streamflow according to 1 the relative importance of meltwater and rainfall runoff and 2 changes in the sediment source areas contributing to the stream at different times particle size variations in the suspended sediment also reflect varying source area influences

geomagnetic field for 0 3 ka 2 a new series of time varying global models 1 steadily increasing numbers of archeomagnetic and paleomagnetic data for the holocene have allowed development of temporally continuous global spherical harmonic models of the geomagnetic field extending present and historical global descriptions of magnetic field evolution the current work uses various subsets of improved data compilations details of which are given in a companion paper by donadini et al 2009 and minor modifications of standard modeling strategies using temporally and spatially regularized inversion of the data and cubic spline parameterizations for temporal variations to produce five models with enhanced spatial and temporal resolution for 0 3 ka spurious end effects present in earlier models are eliminated by enforcing large scale agreement with the gufm1 historical model for 1650 1990 a d and by extending the model range to accommodate data older than 3 ka age errors are not considered as a contribution to data uncertainties but are included along with data uncertainties in an investigation of statistical uncertainty estimates for the models using parametric bootstrap resampling techniques we find common features but also significant differences among the various models indicating intrinsic uncertainties in global models based on the currently available holocene data model cals3k 3 based on all available archeomagnetic and sediment data without a priori quality selection currently constitutes the best global representation of the past field the new models have slightly higher dipole moments than our previous models virtual axial dipole moments vadms calculated directly from the data are in good agreement with all corresponding model predictions of vadms these are always higher than the spherical harmonic dipole moment indicating the limitations of using vadms as a measure of geomagnetic dipole moments

seismic expression of magma induced crustal strains and localized fluid pressures during initial eruptive stages soufriere hills volcano montserrat 1 we explore volcanotectonic earthquake activity during the early stages of volcanic activity 1995 96 at soufriere hills volcano we focus on several zones of temporally confined seismic activity that comprise assemblages of small scale structural elements 2 4 km distant from the volcano at depths 2 4 km below sea level and consider seismicity in relation to regional tectonics and heterogeneity of stiffness and strength as revealed by the sea calipso tomography experiment the clustered seismicity and relatively aseismic zones are interpreted to reflect a broad weakened tectonic zone of ese trend that crosses montserrat and the ascent of a magmatic dike of nne trend which altered the stress distribution to promote localized fault movements and caused localized dilatation with changes in pore fluid pressures to either weaken or strengthen the rock mass depending on the local polarity of strain

recent investigations of the 0 5 ma geomagnetic field recorded by lava flows we present a synthesis of 0 5 ma paleomagnetic directional data collected from 17 different locations under the collaborative time averaged geomagnetic field initiative tafi when combined with regional compilations from the northwest united states the southwest united states japan new zealand hawaii mexico south pacific and the indian ocean a data set of over 2000 sites with high quality stable polarity and declination and inclination measurements is obtained this is a more than sevenfold increase over similar quality data in the existing paleosecular variation of recent lavas psvrl data set and has greatly improved spatial sampling the new data set spans 78 s to 53 n and has sufficient temporal and spatial sampling to allow characterization of latitudinal variations in the time averaged field taf and paleosecular variation psv for the brunhes and matuyama chrons and for the 0 5 ma interval combined the brunhes and matuyama chrons exhibit different taf geometries notably smaller departures from a geocentric axial dipole field during the brunhes consistent with higher dipole strength observed from paleointensity data geographical variations in psv are also different for the brunhes and matuyama given the high quality of our data set polarity asymmetries in psv and the taf cannot be attributed to viscous overprints but suggest different underlying field behavior perhaps related to the influence of long lived core mantle boundary conditions on core flow psv as measured by dispersion of virtual geomagnetic poles shows less latitudinal variation than predicted by current statistical psv models or by previous data sets in particular the brunhes data reported here are compatible with a wide range of models from those that predict constant dispersion as a function of latitude to those that predict an increase in dispersion with latitude discriminating among such models could be helped by increased numbers of low latitude data and new high northern latitude sites tests with other data sets and with simulations indicate that some of the latitudinal signature previously observed in vgp dispersion can be attributed to the inclusion of low quality insufficiently cleaned data with too few samples per site our matuyama data show a stronger dependence of dispersion on latitude than the brunhes data the taf is examined using the variation of inclination anomaly with latitude best fit two parameter models have axial quadrupole contributions of 2 4 of the axial dipole term and axial octupole contributions of 1 5 approximately 2 of the octupole signature is likely the result of bias incurred by averaging unit vectors

characterization of glacial silt and clay using automated mineralogy glacial erosion produces vast quantities of fine grained sediment that has a far reaching impact on earth surface processes to gain a better understanding of the production of glacial silt and clay we use automated mineralogy to quantify the microstructure and mineralogy of rock and sediment samples from 20 basins in the st elias mountains yukon canada sediments were collected from proglacial streams while rock samples were collected from ice marginal outcrops and fragmented using electrical pulse disaggregation for both rock fragments and sediments we observe a log normal distribution of grain sizes and a sub micrometer terminal grain size we find that the abrasion of silt and clay results in both rounding and the exploitation of through going fractures the abundance of inter versus intragranular fractures depends on mineralogy and size unlike the relatively larger grains where crushing and abrasion are thought to exploit and produce discrete populations of grain sizes the comminution of fines leads to a grain size composition and rounding that is continuously distributed across size and highly dependent on source rock properties

the krafla geothermal field iceland 2 the natural state of the system a model of the natural state of the krafla reservoir system in iceland has been developed the model consists of a vertical cross section which includes reservoirs in both old and new well fields the physical processes considered include mass transport conductive and convective heat transfer and boiling and condensation natural heat losses to surface manifestations springs are also included the model matches very well all relevant data from the krafla field the natural flow of hot fluids through the reservoirs is estimated as approximately 20 kg s steam escaping to surface springs constitutes the bulk of the heat losses in the area modeled conductive heat losses through the caprock are approximately 1 w m2 and heat recharge from below is about 2 w m2

hydrocarbon generation potential and thermal maturity of coal and coaly mudstones from the eocene urahoro group in the kushiro coalfield eastern hokkaido japan abstract this study reveals the hydrocarbon generation potential and thermal maturity of coal and coaly mudstones from the eocene urahoro group in the kushiro coal basin kushiro basin of eastern hokkaido japan the coal is classified as subbituminous or high volatile c bituminous and characterized by high hydrogen content 6 1 0 4 wt 1 dry ash free basis the hydrogen index hi 180 409 mg hydrocarbon g total organic carbon and random mean vitrinite reflectance vrr 0 42 0 56 indicate that the coal and coaly mudstones in the urahoro group are gas and oil prone or oil prone based on the hi and vrr values the effective oil window starts at vitrinite reflectance ranges of 0 55 to 0 80 the vitrinite reflectance of coal samples from the kushiro coal mine is inversely proportional to the hi value although each coal seam has the identical thermal history this result suggests that the vitrinite reflectance of the samples in the kushiro coal mine is suppressed based on the corrected vitrinite reflectance non suppressed vitrinite reflectance the maturity of the coal in the kushiro basin increases towards the north the non suppressed vitrinite reflectance of the samples from the northernmost part of the basin hokuyo area was approximately 0 8 which is within the start of the oil window the maturity of the coal bearing strata in the northern area of the basin could be affected by volcanic activity along the volcanic front in the hokuyo area the urahoro group overlies a sequence of cretaceous eocene marine clastic rocks nemuro group which are about 3000 4000 m in total thickness suggesting that the organic matter in the marine clastic rocks should reach higher maturity vrr 0 8

the krafla geothermal field iceland 1 analysis of well test data extensive modeling studies of the krafla geothermal field in iceland are presented in a series of four papers this first paper describes the geological settings of the field and the analysis of well test data the geothermal system at krafla is very complex with a single phase liquid reservoir overlying a two phase reservoir the reservoir rocks are volcanic with sequences of basalt flows hyloclastics and intrusions the fluid flow in the reservoir is fracture dominated considerable pressure transient data from injection tests have been gathered from the krafla wells these data are analyzed to yield the transmissivity distribution in the reservoir system as the data are complicated by various factors wellbore effects nonisothermal effects two phase flow and fractured rocks the applicability of conventional well test analysis methods is questionable the authors have developed a methodology to analyze injection tests for such systems the results obtained show that the transmissivity of the krafla reservoir is low averaging 2 darcy meters dm the average transmissivity of most commercially successful geothermal fields is an order of magnitude higher

causes and mobility of large volcanic landslides application to tenerife canary islands abstract giant volcanic landslides are one of the most hazardous geological processes due to their volume and velocity since the 1980 eruption and associated debris avalanche of mount st helens hundreds of similar events have been recognised worldwide both on continental volcanoes and volcanic oceanic islands however the causes and mobility of these enormous mass movements remain unresolved tenerife exhibits three voluminous subaerial valleys and a wide offshore apron of landslide debris produced by recurrent flank failures with ages ranging from upper pliocene to middle pleistocene we have selected the la orotava landslide for analysis of its causes and mobility using a variety of simple numerical models first the causes of the landslide have been evaluated using limit equilibrium method and 2d finite difference techniques conventional parameters including hydrostatic pore pressure and material strength properties together with three external processes dike intrusion caldera collapse and seismicity have been incorporated into the stability models the results indicate that each of the external mechanism studied is capable of initiating slope failures however we propose that a combination of these processes may be the most probable cause for giant volcanic landslides second we have analysed the runout distance of the landslide using a simple model treating both the subaerial and submarine parts of the sliding path the effect of the friction coefficient drag forces and hydroplaning has been incorporated into the model the results indicate that hydroplaning particularly can significantly increase the mobility of the landslide which may reach runout distances greater than 70 km the models presented are not considered definite and have mainly a conceptual purpose however they provide a physical basis from which to better interpret these complex geologic phenomena and should be taken into account in the prediction of future events and the assessment of landslide related hazards

particle interaction in fjord suspended sediment abstract glacial flour enters the surface layer of howe sound a fjord in southwestern british columbia as a sediment plume which moves quickly down inlet while gradually mixing with the sea water flocculation occurs in the lower brackish waters of the surface layer although mixing and diffusion are the dominant processes for sediment to enter the marine water once in the underlying marine water zooplankton pelletization and biologic agglomeration of inorganic floccules predominate this generates a response in the order of days between the two layers in terms of sedimentation of particulate matter most particles settling in the fjord environment fall as 1 sand and silt grains containing attached clay particles 2 clay clasts possibly related to river mudballs 3 mineral bearing fecal pellets from pelagic zooplankton 4 large grain inorganic and colloidal floccules and 5 inorganic biogenic agglomerates analysis of sediment trap data has led to the following conclusions 1 water turbidity cannot be used to infer the downward flux of particles 2 size distributions of sediment deposited on the sea bed are a function of non lognormal size distributions from particles composing sub laminae

size and composition of inorganic colloids in a peri alpine glacial flour rich lake from june 2004 to october 2005 particle size distributions psd and the mineralogy of inorganic colloids in lake brienz a glacial flour rich swiss lake and in its tributaries the aare and lutschine rivers were quantified by single particle counting based on light scattering 0 1 2 m combined with transmission electronic microscopy coupled with energy dispersive spectroscopy and selected area electron diffraction the two lake tributaries differ in terms of the geology of their catchment area and in their hydrology the river lutschine s glacial regime is unperturbed while the river aare has been significantly modified by hydroelectric installations the dependence of the colloid concentration numbers on colloid diameters can be described by a power law distribution in all cases the power law slopes in the river aare were consistently smaller and the total colloid number concentrations consistently higher mean values 3 89 and 6 2 108 ml 1 respectively than in the river lutschine 3 61 and 1 7 108 ml 1 the measured psd in the lake were dependent on season and depth homogenous in the whole epilimnion in winter and modified by river intrusions in summer in this season the presence of a river turbid plume above the thermocline is a significant source of colloids in the epilimnion where their concentration was high mean value 5 1 107 ml 1 the same main mineral types were found in the different systems 2 1 minerals feldspars chlorite and quartz with a few particles of oxides differences in their relative concentrations in the rivers essentially reflecting the geological differences of the respective catchment areas made it possible to trace the origin of the mineral colloids present in lake surface waters throughout the year the relationship between colloid size and mineralogy was assessed showing that different minerals have distinct size distributions in the rivers where almost no aggregates were observed psd would essentially be the result of the nature particle formation and mineralogy of the colloids whereas in the lake aggregation and sedimentation processes would also play a role particularly in summer

a m gurnell and m j clark eds 1987 glacio fluvial sediment transfer an alpine perspective chichester etc john wiley and sons ltd

hybrid collapse mechanism at piton de la fournaise volcano reunion island indian ocean 1 recent studies have shown that hydrothermal alteration in the core of volcanoes may weaken the edifice and trigger sector collapse lopez and williams 1993 day 1996 voight and elsworth 1997 van wyk de vries et al 2000 reid et al 2001 alteration of volcanic products must take place over long periods of times before collapse can occur so this process is considered to be less frequent than volcanic failure generated by magmatic intrusion and flank spreading however acceleration of this slow process may occur along one direction as a result of a weak lateral confinement following outward gravitational sliding of a flank of the volcano we present here evidence that the enclos fouque depression of piton de la fournaise volcano results from such a hybrid mechanism seaward sliding of the grand brule trough on top of an ancient hypovolcanic complex led to a lateral unconfined boundary along which collapse of the altered core of the edifice took place the result is a caldera like structure breached on the grand brule slide scaled experiments to simulate this process of pseudocaldera formation reveal tectonic features remarkably similar to those encountered in the field and demonstrate the mechanical consistency of the model similar processes may have played a role in the evolution of other volcanoes

gas changes in the krafla geothermal system iceland abstract a massive influx of gas was encountered in the krafla geothermal system iceland following the start of magmatic activity in the area in 1975 the gas was of magmatic origin but its composition had been modified to predominantly carbon dioxide and a small amount of hydrogen sulphide the gas concentrations of krafla borehole fluids have been monitored since and the pattern has been similar for wells in the affected leirbotnar field i e a maximum in 1977 1978 a secondary maximum in 1980 and a steady decline since the more southerly su urhli ar and hvitholar fields were not affected fumaroles were sampled extensively in 1978 1979 and 1984 1985 a similar decline was observed in the affected area but a geographical trend that had been noticed for the borehole fluids was much clearer in this case the decline is smallest in the northeastern part of the field but more pronounced to the south and west it is suggested that magmatic gas has not entered the geothermal system after 1980 and that the excess gas observed now comes from a supply located in the northeastern part of the field near the explosive crater viti

particle size analysis of the sediment suspended in a proglacial stream glacier de tsidjiore nouve switzerland hourly at a point samples of suspended sediment taken from the outflow stream of glacier de tsidjiore nouve switzerland over a 60 day sampling period n 1440 are shown to be dominantly composed of silt sized particles particle size sem and xrd analyses indicate a subglacial provenance for the suspended sediment temporal variations in particle size and sorting correspond poorly to fluctuations in water discharge being dominated by erratic hour to hour fluctuations and clockwise hysteresis over diurnal flow events examination of grain size and sorting dynamics over snowmelt and icemelt related ablation events during precipitation events and during glacier drainage events enables some inferences to be drawn regarding sediment source areas and supply regimes we conclude that although the bulk of the suspended sediment in the proglacial stream of glacier de tsidjiore nouve is derived directly from subglacial sources with occasional contributions from the valley train during rapid snowmelt and heavy rainfall periods a portion of the suspended load undergoes intermittent flush fall transfer through the proglacial zone which acts as a sediment source during rising flows and as a sink during periods of waning flow

geomagnetic excursions and paleointensities in the matuyama chron at ocean drilling program sites 983 and 984 iceland basin 1 we report natural remanent magnetization nrm directions and geomagnetic paleointensity proxies for part of the matuyama chron 0 9 2 2 ma interval from two sites located on sediment drifts in the iceland basin at ocean drilling program sites 983 and 984 mean sedimentation rates in the late matuyama chron are 15 9 and 11 5 cm kyr 1 respectively for the older part of the record 1 2 ma oxygen isotope data are too sparse to provide the sole basis for age model construction the resemblance of the volume susceptibility record and a reference 18o record led us to match the two records to derive the age models this match based on site 983 984 susceptibility is consistent with available site 983 984 benthic 18o data paleointensity proxies were derived from the slope of the nrm versus anhysteretic remanent magnetization plot for alternating field demagnetization in the 30 60 mt peak field range paleointensity lows correspond to polarity reversals at the limits of the jaramillo olduvai cobb mountain and reunion subchrons and to seven excursions in nrm component directions magnetic excursions defined here by virtual geomagnetic polar latitudes crossing the virtual geomagnetic equator are observed at 932 1048 1115 1190 1215 cobb mountain subchron 1255 1472 1480 1567 1575 gilsa subchron and 1977 ka the results indicate that geomagnetic directional excursions associated with paleointensity minima are a characteristic of the matuyama chron and probably of polarity chrons in general

hydroclimatic influence on particle size distribution of suspended sediments evacuated from debris covered chorabari glacier upper mandakini catchment central himalaya abstract sediments released from high altitude glaciers exhibit varying evacuation patterns and transport characteristics owing to the presence of thick debris cover over the glacier despite the recent needs for integrated hydrometeorological studies in the himalaya little is known about the impacts of suspended sediment on hydropower generation reservoir sedimentation and abrasion of turbine components present study involves analysis of particle size distribution of suspended sediments to understand sediment evacuation patterns and transport characteristics in variable energy conditions during the ablation season peak suspended sediments were evacuated during extreme rainfall events the estimated seasonal modern sediment erosion rate varies from 0 6 to 2 3 mm y 1 for the study period 2009 2012 the analysis shows dominance of medium silt sized to fine sand sized particles having sediment size of 0 0156 0 25 mm corresponding to 70 80 without any significant seasonal variation these transported sediments show that they are poorly sorted coarser in nature with a nearly symmetrical to coarse skewed texture and kurtosis analysis suggesting mesokurtic distribution of sediments the particle size fraction ranges between 4 65 and 5 23 which is dominantly medium to coarse silty in texture results indicate that suspended sediments are evacuated in highly variable energy conditions through subglacial transport pathways because of increase in availability of meltwater with the progressive ablation season bulk geochemical characterization has been carried out to differentiate the source of suspended sediments and intensity of weathering chemical index of alterations cia values of sediment flux range from 54 68 to 55 18 compared to the upper continental crust ucc 50 indicating moderate intensity of weathering mean seasonal 2009 2012 elemental fluxes and their contribution to the suspended sediment flux reflect that si and al are responsible for about 85 of the total detrital elemental flux trace elements show high concentrations of radioactive elements like u th pb and rb that suggest their high anomalous presence in the catchment lithology an overall study indicates that the hydroclimatic conditions over the debris covered glacier play a dominant controlling factor in erosion transportation and evacuation of suspended sediments during the ablation season

preliminary studies of the reservoir capacity and the generating potential of the baca geothermal field new mexico a 50 mw sub e geothermal power plant is being considered for the baca site in the valles caldera new mexico as a joint venture of the department of energy doe and union oil company of california to date over 20 wells have been drilled on the prospect and the data from these wells indicate the presence of a high temperature liquid dominated reservoir in this paper data from the open literature on the physical characteristics of the field are used to estimate the amount of hot water in place reservoir capacity and the length of time the reservoir can supply steam for a 50 mw sub e power plant reservoir longevity the reservoir capacity is estimated to be 10 sup 12 kg of hot fluid by volumetric calculations using existing geological geophysical and well data the criteria used are described and the sensitivity of the results discussed the longevity of the field is studied using a two phase numerical simulator shaft79 a number of cases are simulated based upon different boundary condition and upon injection and production criteria the results obtained from the simulation studies indicate that it is questionable that the baca field can supply enough steam for a 50 mw sub e power plant for 30 years more although the estimated reservoir reserves greatly exceed those needed for a 50 mw sub e power plant the low transmissivity of the reservoir would cause localized boiling and rapid pressure decline during exploitation it is therefore apparent that the conventional zero dimensional lumped parameter models cannot be used to evaluate the generation capacities of low permeability fields such as the baca field less

combining palynofacies and petrography in the study of sub bituminous tropical coals a case history from lower tertiary coals in colombia abstract colombia contains large coal reserves of late cretaceous to cenozoic age in various sedimentary basins but little is known about their potential to generate hydrocarbons in western venezuela coals are known to be potential source rocks for oil and the vicinity of these coals with coal bearing basins in colombia has prompted new studies in colombian tropical coals to develop concepts about their hydrocarbon generating potential the paleogene amaga formation studied here although of limited geographical extension is an ideal field laboratory which contains low rank coal seams in which the transformation and preservation state of organic matter permits the assessment of environment and vegetation types existing at the time of peat formation several seams up to 1 m thick have been analyzed using both bulk seam samples and ply or lithotype samples it is demonstrated that bulk seam samples are not representative for a proper evaluation of the hydrocarbon generation potential of seams one needs to evaluate all lithotype assemblages within a seam proximate analysis and rock eval pyrolysis provide a rapid and cheap way to assess the generation potential of each lithotype the potentially interesting lithotypes can be further analyzed through the combination of petrographic and palynological observations these methods permit the comparison of coal macerals with the equivalent palynofacies constituents provided that a preparation technique especially designed for tropical sub bituminous tertiary coals is used the palynofacies technique has proved to be more accurate than petrography in determining the relative proportion of the potentially oil prone constituents macerals which can be hidden or difficult to identify in petrographic polished section moreover the comparison between resinite oil observed in petrography and resins identified in palynofacies may yield indications of early hydrocarbon generation this methodology provides a fully detailed inventory of coal properties with respect to hydrocarbon generation potential the use of palynofacies is an additional tool to apprehend the floral composition and paleoenvironment of coals thereby increasing the geological and geochemical database needed to evaluate their potential such a methodology may prove very important to assess the petroleum potential of thicker coal deposits in prospective petroleum provinces such as the cerrejon coals in northern colombia

particle size characteristics of suspended sediment transported in meltwater from the gangotri glacier central himalaya an indicator of subglacial sediment evacuation abstract proglacial meltwater streams draining out of the himalayan glaciers carry considerable amounts of suspended sediment with a variety of particle sizes because of the supraglacial englacial and subglacial debris as well as formation of sediments from erosion by the movement of the ice this paper examines particle size transported in the proglacial meltwater stream of gangotri glacier for seven consecutive melt seasons may october 2000 2006 in order to provide information on i temporal variations in the particle size distribution ii texture and mineralogy of the sediments and iii origin and evacuation pattern of the sediments our results indicate dominance of silt size 0 002 0 06 mm particles 71 followed by sand size 0 06 0 6 mm particles 24 and clay size

coal as a source rock for oil a review the geological debate about whether and to what extent humic coals have sourced oil is likely to continue for some time despite some important advances in our knowledge of the processes involved it is clear that not only liptinites but also perhydrous vitrinites have the potential to generate hydrocarbon liquids in the course of natural coalification some liptinites especially alginite cutinite and suberinite contain a higher proportion of aliphatic moieties in their structure than other liptinites such as sporinite and resinite and are therefore more oil prone it is of potential value to be able to predict the several environments of deposition in which coals with high liptinite contents or containing perhydrous vitrinites may have been formed review of the distribution of oil prone coals in time and space reveals that most are jurassic tertiary with key examples from australia new zealand and indonesia methods based both on experimental simulations and the examination of naturally matured samples have been used to determine the order of generation of hydrocarbons from different macerals results are not entirely consistent among the different approaches and there is much overlap in the ranges of degradation but it seems probable that in the natural environment vitrinites begin to generate early followed by labile liptinites such as suberinite then cutinite sporinite and finally alginite petroleum potential may be determined by experimental simulation of natural coalification or inferred through various micro techniques especially fluorescence and infrared ir spectroscopy or bulk techniques such as elemental analysis and 13c nmr spectroscopy the latter three techniques enable a measure of the polymethylene component of the coal which now appears to be one of the best available approaches for determining petroleum potential no method of experimental simulation of petroleum generation from coals is without criticism and comparative results are highly variable however hydrous pyrolysis confined pyrolysis and forms of open system hydrous pyrolysis approach acceptable simulations whether and to what degree generated liquid hydrocarbons are expelled has long been the central problem in oil from coal studies the structure of vitrinite was believed until recently to contain an interconnected microporous network in which generated oil would be contained until an expulsion threshold was attained recent studies show the pores are not interconnected combined with a dynamic model of pore generation it now seems that expulsion of hydrocarbons is best explained by activated diffusion of molecules to maceral boundaries and ultimately by cleats and fractures to coal seam boundaries the main reason for poor expulsion is the adsorption of oil on the organic macromolecule which may be overcome 1 if coals are thin and interbedded with clastic sediments or 2 if the coals are very hydrogen rich and generate large quantities of oil the existence of oil in vitrinite is attested to by solvent extractions fluorescence properties and by microscopic observations of oil and bitumen experimental simulation of expulsion of oil from coals has only recently been attempted the relative timing of release of generated co2 and ch4 could have considerable importance in promoting the expulsion of liquid hydrocarbons but the mechanism is unclear as it is universally agreed that dispersed organic matter dom in some shales readily generates and expels petroleum it is curious that few consistent geochemical differences have been found between coal macerals and dom in interbedded shales unambiguous evidence of expulsion from coals is limited and in particular only a few commercial oil discoveries can be confidently correlated to coals these include upper cretaceous fruitland formation coals in the usa from which oil is produced new zealand tertiary coals and middle jurassic coals from the danish north sea it is likely that coals have at least contributed to significant oil discoveries in the gippsland basin australia in the turpan basin china and in the kutei and ardjuna basins in indonesia but this remains unproven early reports that early jurassic coals in mid norway were a major source of the reservoired oils have been shown to be inaccurate none of the proposed rules of thumb for generation or expulsion of petroleum from coals seem particularly robust decisions on whether a particular coal is likely to have been an active source for oil should consider all available geological and geochemical information the assumptions made in computational models should be well understood as it is likely with new understandings of processes involved that some of these assumptions will be difficult to sustain

transport of suspended particulate matter in an antarctic fjord abstract vertical profiles of temperature salinity and light attenuation were used in conjunction with underwater photography and water samples to characterize the nature and dynamics of particle transport in an antarctic fjord most of the particles are sand sized 0 1 2 mm floccules comprised of individual grains in the 5 to 50 m size range the quartz silt grains are derived from basal debris laden meltwater originating from beneath the submerged valley glacier the meltwater buoyantly rises to form cold water interflows at mid water depths turbulent mixing near the seafloor also plays a role in the transport and break up of floccules together the midwater cold tongues and near bottom turbidity account for 87 of the total sediment load thus attesting to the importance of non surface transport mechanisms in polar fjords

magmatic gases in well fluids aid the mapping of the flow pattern in a geothermal system abstract gas composition and silica concentrations of well fluids are used in conjunction with pressure temperature and enthalpy data to obtain a model of the drilled part of the krafla geothermal field northeast iceland a magma chamber is located at 3 8 km depth under the field magmatic gases emanate from the chamber and travel via a channel reaching the surface at the hveragil eruptive fissure the composition of the gases is apparently modified on the way in that sulphur which presumably is in the form of sulphur dioxide to begin with is removed on the way and what remains is in the form of hydrogen sulphide at the end it is suggested that the major removal mechanism is the deposition of pyrite and pyrrhotite during the passage of the gases through the hydrothermal system the hydrothermal system is divided into a lower part whose temperature exceeds 300 c and whose fluids are to a varying extent affected by the magmatic gases and an upper part whose temperature is ca 200 c this upper part is a run off from the lower part but the magmatic effects have mostly disappeared there

theory of dike intrusion in a saturated porous solid a study of the pore pressure fields that develop around intruding dikes is described under the motivation that intruded geometry may be determined from pore pressures recorded in relatively remote monitoring wells the pore pressure fields induced around cylindrical and planar intrusions are described as analogues to moving point or line dislocations within an infinite saturated porous elastic medium the resulting transient pressure fields reduce to an equivalent steady state when viewed from the advancing front solutions for the moving point and line dislocations yield a dependence on common dimensionless groupings thus dimensionless pressure rise accompanying intrusion and recorded at a static location may be uniquely referenced to the dimensionless parameters representing emplacement velocity and time the resulting transient pressure response may be divided into two groups representing fast and slow emplacement where hydraulic parameters representing the host porous medium are known a priori both emplacement location and the cross sectional area may be determined uniquely for slow emplacement the intrusion rate may also be determined only a lower limiting intrusion rate may be discerned for fast emplacement field data are rare but two intrusive events at krafla iceland are examined using the proposed moving dislocation models predicted location and lower limiting intrusion rate of the krafla dikes compare favorably with field observation despite more than a 9 km separation to the monitoring well

calculation of dike trajectories from volcanic centers 1 patterns of dike swarms around volcanic centers or above mantle plumes are interpreted by a mechanical analysis of regional and dike induced stresses in which dike emplacement is controlled and guided by the stress state comparisons of dike patterns with patterns of principal stress trajectories caused by a source and a regional stress system are commonly used to infer paleostresses however dike trajectories are determined by a complex interaction between dike induced stresses and the source regional stress system we present numerical calculations based on a novel boundary integral formulation which examines the simultaneous effects of regional stresses magma pressure and dike injection on the local stress state around a continuously curving dike dike paths are calculated from the condition that dikes propagate by mode i failure our results suggest that the magnitude of the regional stresses would be 2 5 times higher than previous estimates based on principal stress trajectory analysis

correlations of suspended sediment size with bedrock lithology and glacier dynamics the hypothesized link between glacier surging and bedrock geology motivates this study of the suspended sediment size distributions sssd from surge type and non surge type glaciers we analyze sssds from proglacial streams in 20 individual basins comprising various fractions of metasedimentary ms and felsic plutonic rocks we compare the size distributions by performing tests of significance on the distribution statistics and a principal component analysis on discrete grain sizes we find that surge type and non surge type glaciers underlain solely by ms rocks have significantly different sssds while surge type glaciers as a whole have remarkably similar sssds regardless of the underlying bedrock geology these observations hint at a relationship between sediment characteristics and glacier surging though causation in either direction cannot be established without additional data

influence of extrusion rate and magma rheology on the growth of lava domes insights from particle dynamics modeling abstract lava domes are structures that grow by the extrusion of viscous silicic or intermediate composition magma from a central volcanic conduit repeated cycles of growth are punctuated by collapse as the structure becomes oversized for the strength of the composite magma that rheologically stiffens and strengthens at its surface here we explore lava dome growth and failure mechanics using a two dimensional particle dynamics model the model follows the evolution of fractured lava with solidification driven by degassing induced crystallization of magma the particle dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh based analyses due to mesh entanglement effects the deformable talus evolves naturally as a frictional carapace that caps a ductile magma core extrusion rate and magma rheology together with crystallization temperature and volatile content govern the distribution of strength in the composite structure this new model is calibrated against existing observational models of lava dome growth results show that the shape and extent of the ductile core and the overall structure of the lava dome are strongly controlled by the infusion rate the effects of extrusion rate on magma rheology are sensitive to material stiffness which in turn is a function of volatile content and crystallinity material stiffness and material strength are key model parameters which govern magma rheology and subsequently the morphological character of the lava dome and in turn stability degassing induced crystallization causes material stiffening and enhances material strength reflected in non newtonian magma behavior the increase in stiffness and strength of the injected magma causes a transition in the style of dome growth from endogenous expansion of a ductile core to stiffer and stronger intruding material capable of punching through the overlying material and resulting in the development of a spine or possibly inducing dome collapse simulation results mimic development of a megaspine upon the influx of fresh magma which leads to the re direction of magma flow creating a new shear zone and the switching of dome growth from one side to the other our model shows similar dome growth dynamics as observed at soufriere hills volcano montserrat indicating a strong correlation between extrusion rate and its subsequent effect on mechanical properties and variations in magma rheology

rapid deformation of kilauea volcano global positioning system measurements between 1990 and 1996 campaign global positioning system gps measurements from 1990 to 1996 are used to calculate surface displacement rates on kilauea volcano hawaii the gps data show that the south flank of the volcano which has generated several large earthquakes in the past 3 decades is displacing at up to 8 cm yr to the south southeast the summit and rift zones are subsiding with maximum subsidence rates of 8 cm yr observed a few kilometers south of the summit caldera elastic dislocation modeling of the gps data suggests that the active sources of deformation include deep rift opening along the upper east and east rift zone fault slip along a subhorizontal fault near the base of the volcano and deflation near the summit caldera a nonlinear optimization algorithm was used to explore the parameter space and to find the best fitting source geometry there is a broad range of model geometries that fit the data reasonably well however certain models can be ruled out including those that have shallow rift opening or shallow fault slip some offshore aseismic slip on a fault plane that dips between 258 north northwest and 88 south southeast is required best fitting slip and rift opening rates are 23 28 cm yr although rates as low as 10 cm yr are permitted by the data

controls on the oil and gas potential of humic coals abstract humic coals are highly heterogeneous both with respect to maceral content and chemical composition although the oldest known humic coals albeit gas prone are of devonian age the majority of humic coals capable of generating and expelling non volatile oil are of cretaceous and tertiary age from australia new zealand and southeast asia in contrast the middle jurassic humic coals of the sleipner and hugin formations in the south viking graben of the north sea are primarily gasprone but have the capability to expel aliphatic rich volatile oil these coals have toc contents up to 80 and hydrogen indices hi ranging from 200 to 400 they are vitrinite rich with some containing up to 45 inertinite liptinite concentrations are generally around 10 20 chiefly as spores pollen and abundant resinite the main control on the oil potential of humic coals is the concentration of long chain aliphatic hydrocarbons in the coal matrix although the aliphatics have a high h c ratio the inference on hydrogen content from the rock eval pyrolysis hi value can be misleading for hi values below 500 mg hc g oc there is no relation between hi and the potential of the coals to generate non volatile oil consequently the hi is a poor indicator of the non volatile oil potential of humic coals a more robust indicator is the relative amount of c8 aliphatic groups also the bulk measure of liptinite content may also prove misleading when assessing the oil potential of coals high resinite concentrations can lead to an overprediction of the non volatile oil potential as they contribute significantly to the hi value but will generate primarily volatile aromatic rich oils expulsion from the sleipner and hugin coals appears to have occurred in a gaseous phase with preferential release of short chain alkanes

evidence for late paleozoic and mesozoic non dipole fields provides an explanation for the pangea reconstruction problems abstract paleomagnetic pole positions have long been calculated with the assumption that the ancient geomagnetic field was purely that of a geocentric dipole but in recent years it has become a concern that this assumption is not always valid because of long term contributions from non dipole fields in particular octupole fields we tested for the presence of a zonal octupole field in the late carboniferous permian mesozoic and early tertiary by comparing the observed paleomagnetic paleolatitude distributions for the laurentian north america and greenland and european landmasses with those predicted from the mean paleopoles such a test is possible for a good sized continent not subsequently deformed when numerous and reliable paleomagnetic results exist from sites that cover a wide range of paleolatitudes if the field were purely dipolar coeval results should form a coherent dataset such that a regression line through the individual points in an observed versus predicted paleolatitude plot has a slope of 1 if the slopes of regression lines are systematically different from 1 0 for successive time intervals and granted that the earth s radius stayed the same then it is likely that non dipole fields can be held responsible regression line slopes standard errors for three intervals analyzed are 0 78 0 04 200 300 ma 0 93 0 11 120 200 ma and 0 82 0 06 40 120 ma as might be expected with a non dipole contribution to the total geomagnetic field paleomagnetic results from the most northerly areas of laurentia and europe i e ellesmere greenland and svalbard show clearly anomalous paleolatitudes because of the agreement between the equatorial locations determined independently by paleomagnetism and equatorial rain forest occurrences d v kent p e olsen earth planet sci lett 179 2000 311 324 we argue that long term quadrupole fields are less likely than octupole fields to be the cause of the paleolatitude discrepancies estimates of the magnitude of the octupole dipole field ratio are not very precise but center around 0 1 which could cause errors in conventional paleopole determinations using the dipole formula of 7 5 because of the antisymmetry of octupole fields a comparison of paleomagnetic poles from mid northern and mid southern hemisphere locations could thus be off by as much as 15 the well known misfit between the paleomagnetic results from the laurentia european and gondwana continents in a classical pangea a configuration could be explained by such errors due to octupole fields this explanation would negate the need to seek tectonic pangea b type solutions for the misfit these solutions have generally remained unacceptable in terms of the geology of the gondwana laurussia borderzone

particle size and mineralogical composition of inorganic colloids in waters draining the adit of an abandoned mine goesdorf luxembourg particle size distributions and the mineralogy of inorganic colloids in waters draining the adit of an abandoned mine goesdorf luxembourg were quantified by single particle counting based on light scattering 100 nm 2 m combined with transmission electronic microscopy coupled with energy dispersive spectroscopy and selected area electron diffraction this water system was chosen as a surrogate for groundwaters the dependence of the colloid number concentration on colloid diameters can be described by a power law distribution in all cases power law slopes ranged from 3 30 to 4 44 depending on water ionic strength and flow conditions the same main mineral types were found in the different samples 2 1 phyllosilicates illite and mica chlorite feldspars albite and orthoclase calcite and quartz with a variable number of fe oxide particles the colloid mineralogical composition closely resembles the composition of the parent rock spatial variations in the structure and composition of the rock in contact with the waters i e fissured rock versus shear joints are reflected in the colloid composition the properties of the study colloids as well as the processes influencing them can be considered as representative of the colloids present in groundwaters

continuous geomagnetic field models for the past 7 millennia 2 cals7k 1 we present two continuous global geomagnetic field models for recent millennia cals3k 2 covering the past 3000 years and cals7k 2 covering 7000 years from 5000 bc to 1950 ad the models were determined by regularized least squares inversion of archeomagnetic and paleomagnetic data using spherical harmonics in space and cubic b splines in time they are derived from a greatly increased number of paleomagnetic directional data compared to previous efforts and for the first time a significant amount of archeointensity data is used in this kind of global model allowing the determination of evolution of geomagnetic dipole strength while data accuracy and dating uncertainties remain a limitation reliable low resolution global models can be obtained the results agree well with previous results from virtual axial dipole moment vadm studies from archeomagnetic intensity data apart from a systematic offset in strength a comparison of model predictions with the previous 3000 year model cals3k 1 gives general agreement but also some significant differences particularly for the early epochs the new models suggest that the prominent two northern hemisphere flux lobes are more stationary than cals3k 1 implied extending considerably the time span of stationary flux lobes observed in historical models between 5000 bc and 2000 bc there are time intervals of weak dipole moment where dipole power is exceeded by low degree nondipole power at the core mantle boundary model coefficients and evaluation code can be obtained from the earthref digital archive erda together with animations and snapshots plots for every 100 years at http www earthref org detailed urls for the different material are listed in appendix a

pore pressure embrittlement in a volcanic edifice the failure mode of porous rock in compression dilatant or compactant is largely governed by the overlying lithostatic pressure and the pressure of pore fluids within the rock wong solid earth 102 3009 3025 1997 both of which are subject to change in space and time within a volcanic edifice while lithostatic pressure will tend to increase monotonously with depth due to the progressive accumulation of erupted products pore pressures are prone to fluctuations during periods of volcanic unrest for example an increase in pore fluid pressure can result in rock fracture even at depths where the lithostatic pressure would otherwise preclude such dilatant behaviour a process termed pore fluid induced embrittlement we explore this phenomenon through a series of targeted triaxial experiments on typical edifice forming andesites from volcan de colima mexico we first show that increasing pore pressure over a range of timescales on the order of 1 min to 1 day can culminate in brittle failure of otherwise intact rock irrespective of the pore pressure increase rate we record comparable accelerations in acoustic emission and strain prior to macroscopic failure we further show that oscillating pore fluid pressures can cause iterative and cumulative damage ultimately resulting in brittle failure under relatively low effective mean stress conditions we find that macroscopic failure occurs once a critical threshold of damage is surpassed suggesting that only small increases in pore pressure may be necessary to trigger failure in previously damaged rocks finally we observe that inelastic compaction of volcanic rock as we may expect in much of the deep edifice can be overprinted by shear fractures due to this mechanism of embrittlement pore fluid induced embrittlement of edifice rock during volcanic unrest is anticipated to be highest closer to the conduit and as a result may assist in the development of a fractured halo zone surrounding the conduit potentially explaining commonly observed near conduit outgassing at many active volcanoes further rock embrittlement at depth may create transient outgassing pathways by linking fracture networks near the edifice to larger scale regional fault systems our experimental results affirm that pore pressure fluctuations associated with volcanic unrest may play a crucial role in dictating the evolution of a volcanic system

marine influence helps preserve the oil potential of coaly source rocks eocene mangahewa formation taranaki basin new zealand abstract many cretaceous cenozoic coaly source rocks in australasian and southeast asian basins were deposited in coastal plain environments yet the effect of early diagenetic marine influence on their oil potential is not well understood an integrated organic geochemical and petrographic study of humic coals from the eocene mangahewa formation taranaki basin new zealand was undertaken with coals predominantly from raised mire petrofacies with subordinate proportions from planar mires the total s content of 0 63 4 4 dry ash free indicated very slight to strong degrees of marine influence other than minor addition of inferred mangrove derived suberinite and associated liptodetrinite the degree of marine influence had no obvious effect on maceral or plant tissue abundance however hydrogen index hi values were up to ca 150 109 mg hc g toc higher and total c 6 oil potential up to ca 140 43 mg g toc higher among the more strongly marine influenced coals correlation of organic s with solvent extract parameters pristane phytane c 27 c 29 diasteranes steranes c 29 steranes hopanes c 35 c 35 c 34 homohopanes and oleanane index suggested that inundation of brackish water into the early diagenetic peat forming environment enhanced the bio resistance of higher plant and other lipids through sulfurization thereby helping to preserve more of the inherent h content and total oil potential of the original peat biomass conversely marine influence had only a minor effect on the capacity of mangahewa coals to generate paraffinic oil total n c 6 and non volatile n c 15 paraffinic oil potentials were instead controlled primarily by the abundance of leaf derived cutinite and associated liptodetrinite this in turn was dependent on the type of peat mire facies with planar mire facies having better potential for preservation of leaf litter than raised mire facies because of their generally higher groundwater level marine influence is nonetheless beneficial for paraffinic oil charge from coaly source rock sequences in that the associated higher his enhance the efficiency and quantum of paraffinic oil expulsion through increased saturation of the coal pore system

dike emplacement and flank instability at mount etna constraints from a poro elastic model of flank collapse this work was funded by istituto nazionale di geofisica e vulcanologia ingv and the italian dipartimento per la protezione civile dpc dpc ingv project v4 flank

source rock potential of the lowest coal seams of the marcelina formation at the paso diablo mine in the venezuelan guasare basin evidence for the correlation of amana oils with these paleocene coals abstract the aims of this work were to carry out a combined petrographic palynofacies and organic geochemical study of twelve drill core samples collected from the lowest coal seams in the paleocene marcelina formation paso diablo mine guasare basin northwestern venezuela to characterize crude oil samples from three wells in the nearby amana field and to evaluate oil source correlations of these crude oils with the paso diablo coal extracts the coals under study were classified as high volatile bituminous a or at the b a boundary and showed vitrinite contents between 50 0 and 89 4 vol liptinites ranging from 1 4 to 24 2 vol and inertinites in the 6 2 30 8 vol range results from organic geochemical investigations indicate that the guasare coals were generated in a limno telmatic to telmatic zone under fluctuating oxygen conditions a type iii kerogen with relatively high hydrogen content and a thermal maturity corresponding to the early oil window are proposed for these coals as supported by rock eval and petrographic data as well as biomarker interpretations oil generation potential from marcelina formation coals is probably due to the perhydrous nature of the vitrinite high bitumen contents and considerable liptinite concentrations mainly oil prone resinites and exsudatinites palynofacies observations denote a dominance of psilate pollen grains related to angiosperm plants and as expected type iii kerogens or humic coals in the studied seams the parent material of which contained a significant contribution of algae the non detection of 18 h oleanane does not preclude the fact that angiosperms are the dominant plants in the guasare paleomire on the other hand the characterization of the amana oils suggests that they all fall into a unique oil family the presence of 25 norhopanes in them could indicate paleobiodegradation and mixing from various hydrocarbon charges in the reservoir thus the crude oils from the amana field seem to be a mixture of one or more oil charges from the early mature marine carbonate source rocks of the la luna formation deposited under anoxic reducing conditions and a later pulse of hydrocarbon generation which originated from an unknown so far nonmarine source rock in this regard hydrocarbon liquid derived from the lowest marcelina coal seams may be tentatively identified as the latter oil charge also this work delineates some components of a currently subcommercial and hypothetical tertiary petroleum system identified and named as marcelina misoa c5 in the lake maracaibo region finally the coalbed gas contents of sampled coals were determined

thermal damage and pore pressure effects of the brittle ductile transition in comiso limestone volcanic edifices are commonly unstable with magmatic and non magmatic fluid circulation and elevated temperature gradients having influence on the mechanical strength of edifice and basement rocks we present new mechanical characterization of the comiso limestone of the mount etna volcano italy basement to constrain the effects of regional ambient conditions associated with the volcanic system the effects of pore fluid on rock strength and the effects of distal magmatic heating 20 c to 600 c at a range of simulated depths 0 2 to 2 0 km the presence of water promotes ductile behaviour at shallow depths and causes a significant reduction in brittle rock strength compared to dry conditions thermal stressing in which specimens were heated and cooled before mechanical testing at room temperature has a variable effect for dry and saturated cases in dry conditions thermal stressing up to 450 c homogenizes the strength of the specimen such that the majority of the specimens exhibit the same peak stress at 600 c the brittle failure is promoted at lower differential stress the presence of water in thermally stressed specimens promotes ductile behaviour and reduces peak strength acoustic emission monitoring suggests that accumulated damage is associated with the heating cooling sequence particularly in the 300 450 600 c based on conduction modeling we estimate this temperature range could affect basement rocks up to 300 m away from minor sheet intrusions and much further with larger bodies considering the dyke spacing beneath etna these conditions may apply to a significant percentage of the basement promoting ductile behaviour at relatively shallow depths

experimental investigations of the weathering of suspended sediment by alpine glacial meltwater the magnitude and processes of solute acquisition by dilute meltwater in contact with suspended sediment in the channelized component of the hydroglacial system have been investigated through a suite of controlled laboratory experiments constrained by field data from haut glacier d arolla valais switzerland the effects of the water to rock ratio particle size crushing repeated wetting and the availability of protons on the rate of solute acquisition are demonstrated these free drift experiments suggest that the rock flour is extremely geochemically reactive and that dilute quickflow waters are certain to acquire solute from suspended sediment these data have important implications for hydrological interpretations based on the solute content of glacial meltwater mixing model calculations geochemical denudation rates and solute provenance studies

palaeomagnetic study of a subaerial volcanic ridge sao jorge island azores for the past 1 3 myr evidence for the cobb mountain subchron volcano flank instability and tectonomagmatic implications we present a palaeomagnetic study on 38 lava flows and 20 dykes encompassing the past 1 3 myr on s jorge island azores archipelagonorth atlantic ocean the sections sampled in the southeastern and central western parts of the island record reversed and normal polarities respectively they indicate a mean palaeomagnetic pole 81 3 degrees n 160 7 degrees e k 33 and a95 3 4 degrees with a latitude shallower than that expected from geocentric axial dipole assumption suggesting an effect of non dipolar components of the earth magnetic field virtual geomagnetic poles of eight flows and two dykes closely follow the contemporaneous records of the cobb mountain subchron odp dsdp programs and constrain the age transition from reversed to normal polarity at ca 1 207 0 017 ma volcano flank instabilities probably related to dyke emplacement along an nnwsse direction led to southwestward tilting of the lava pile towards the sea two spatially and temporally distinct dyke systems have been recognized on the island the eastern is dominated by nnwsse trending dykes emplaced before the end of the matuyama chron whereas in the central western parts the eruptive fissures oriented wnwese controlled the westward growth of the s jorge island during the brunhes chron both directions are consistent with the present day regional stress conditions deduced from plate kinematics and tectonomorphology and suggest the emplacement of dykes along pre existing fractures the distinct timing and location of each dyke system likely results from a slight shift of the magmatic source

the krafla geothermal field iceland 4 history match and prediction of individual well performance a detailed distributed parameter model in which all wells are represented individually is reported for the krafla geothermal system the model is based on a synthesis of geological geophysical geochemical and reservoir engineering data from the field numerical simulations achieve an approximate match for production rates and flowing enthalpies for 10 wells during the period 1976 1982 predictions of future field performance on a well by well basis are presented for alternative field development plans including additional production wells and reinjection of waste fluids

hydrocarbon genesis of jurassic coal measures in the turpan basin china abstract a typical case of coal derived oils in china i e the crude oils from the middle lower jurassic coal measure strata in the turpan basin is presented by means of oil source correlation it is confirmed that low maturity crude oil in the shengjinkou oil field is derived from the coal bearing qiketai formation of middle jurassic age a brackish lacustrine sediment mature crude oils in the qiketai oil field and in well taican 1 are sourced from the badaowan formation of lower jurassic age which contains coal seams as thick as 100 m results show that commercial accumulations of liquid crude oils can be generated from coals and coal measure strata containing high volatile coal of bituminous rank despite unfavourable types of source material the total hydrocarbon generating potential can be great due to the unusual abundance of organic matter

from soil aggregates to riverine flocs a laboratory experiment assessing the respective effects of soil type and flow shear stress on particles characteristics particles eroded from hillslopes and exported to rivers are recognized to be composite particles of high internal complexity their architecture and composition are known to influence their transport behaviour within the water column relative to discrete particles to date hillslope erosion studies consider aggregates to be stable once they are detached from the soil matrix however lowland rivers and estuaries studies often suggest that particle structure and dynamics are controlled by flocculation within the water column in order to improve the understanding of particle dynamics along the continuum from hillslopes to the lowland river environment soil particle behaviour was tested under controlled laboratory conditions seven flume erosion and deposition experiments designed to simulate a natural erosive event and five shear cell experiments were performed using three contrasting materials two of them were poorly developed and as such can not be considered as soils whilst the third one was a calcareous brown soil these experiments revealed that soil aggregates were prone to disaggregation within the water column and that flocculation may affect their size distribution during transport large differences in effective particle size were found between soil types during the rising limb of the bed shear stress sequence indeed at the maximum applied bed shear stress the aggregated particles median diameter was found to be three times larger for the well developed soil than for the two others differences were smaller in the falling limb suggesting that soil aggregates underwent structural changes however characterization of particles strength parameters showed that these changes did not fully turn soil aggregates into flocs but rather into hybrid soil aggregate floc particles copyright 2013 john wiley sons ltd

tracing organic matter sources in riverine suspended sediment implications for fine sediment transfers abstract the study of sediment transport in riverine systems has historically focussed on the inorganic fluxes although the suspended load is known to incorporate both inorganic and organic material research on freshwater flocculation indicates that sediment morphology and behaviour depend on both components as biologic material can alter the hydrodynamic and charge properties of composite particles which has implications for fine sediment transport and storage in stream systems this study evaluates both the supply and the quality of the organic matter comprising the suspended sediment in a salmon bearing stream in northern british columbia canada seasonally changing hydrodynamic and biologic conditions are considered in the context of suspended sediment seston size seston samples were collected in an event based design for analysis of organic matter sources suspended particulate inorganic and organic matter concentrations spm sim and som and effective particle size distributions epsd organic matter sources were assessed using carbon nitrogen c n ratios and the associated stable isotopic signals samples and environmental measurements were taken during spring melt pre spawn low flows active salmon spawning post spawn and select rainstorms spm and sim were elevated during active salmon spawning compared to that expected for the given hydrologic conditions seasonal patterns of c n ratios and stable isotopes indicate that organic matter types can be differentiated in seston samples and these sources of organic material exhibit changing dominance in the seston over time the isotopic signature of seston increases in salmon derived nutrients when live and decaying salmon are present within the study stream the largest suspended particles are observed during the period of active spawning when both live and rotting salmon modify instream conditions this appears to be a function of the combined influence of high sim low shear stress and low c n ratios the generation of increased floc or seston size is of ecological importance in this stream and riverine systems elsewhere as it regulates the freshwater transfers of locally derived nutrients and sediments out of the fluvial system

the petroleum generation potential and effective oil window of humic coals related to coal composition and age abstract a worldwide data set of more than 500 humic coals from the major coal forming geological periods has been used to analyse the evolution in the remaining hydrogen index hi and total quality index qi generation potentials with increasing thermal maturity and the effective oil window oil expulsion window all samples describe hi and qi bands that are broad at low maturities and that gradually narrow with increasing maturity the oil generation potential is completely exhausted at a vitrinite reflectance of 2 0 2 2 ro or tmax of 500 510 c the initial large variation in the generation potential is related to the original depositional conditions particularly the degree of marine influence and the formation of hydrogen enriched vitrinite as suggested by increased sulphur and hydrogen contents during initial thermal maturation the hi increases to a maximum value himax similarly qi increases to a maximum value qimax this increase in hi and qi is related to the formation of an additional generation potential in the coal structure the decline in qi with further maturation is indicating onset of initial oil expulsion which precedes efficient expulsion liquid petroleum generation from humic coals is thus a complex three phase process i onset of petroleum generation ii petroleum build up in the coal and iii initial oil expulsion followed by efficient oil expulsion corresponding to the effective oil window efficient oil expulsion is indicated by a decline in the bitumen index bi when plotted against vitrinite reflectance or tmax this means that in humic coals the vitrinite reflectance or tmax values at which onset of petroleum generation occurs cannot be used to establish the start of the effective oil window the start of the effective oil window occurs within the vitrinite reflectance range 0 85 1 05 ro or tmax range 440 455 c and the oil window extends to 1 5 2 0 ro or 470 510 c for general use an effective oil window is proposed to occur from 0 85 to 1 7 ro or from 440 to 490 c specific ranges for himax and the effective oil window can be defined for cenozoic jurassic permian and carboniferous coals cenozoic coals reach the highest himax values 220 370 mg hc g toc and for the most oil prone cenozoic coals the effective oil window may possibly range from 0 65 to 2 0 ro or 430 to 510 c in contrast the most oil prone jurassic permian and carboniferous coals reach the expulsion threshold at a vitrinite reflectance of 0 85 0 9 ro or tmax of 440 445 c

oil generation capacity of coals as a function of coal age and aliphatic structure abstract the relative proportions of aliphatic ch2 ch3 aliphatic hydrogen hali together with the aliphatic chain length in a series of carboniferous permian jurassic and cenozoic humic coals have been analysed using ftir and ruthenium tetroxide catalysed oxidation rtco followed by gc ms analysis of the n monocarboxylic acids esterified to assess their ability to generate oil most of the coals contain 2 11 vol liptinite only coals with almost similar hydrogen indices his were compared as they were considered to possess comparable hydrocarbon generation potentials all contain isolated aromatic hydrogen haro in the coal structure and a considerable proportion of aliphatic chains in the range c16 18 hi values cannot alone explain the proportion of aliphatic ch2 implying that for coals haro contributes to the measured hi cenozoic coals contain the highest proportion of aliphatic ch2 and hali and the content of longer chain aliphatics c18 increases considerably from palaeozoic to cenozoic coals aliphatic chains c18 are absent from or very restricted in the carboniferous coals and most of the permian coals indicate no or a negligible ability to generate oil jurassic coals show a slightly better potential whereas cenozoic coals contain aliphatic chains up to at least c35 demonstrating the greatest capacity to generate oil in addition to significant gas potential multivariate data analysis suggests that the aliphatic chains c24 are related to the collodetrinite liptodetrinite matrix which is a prominent constituent of cenozoic coals with regard to oil potential the coals from the major coal forming periods may be ranked carboniferous permian

oceanic ridge crest processes oceanic ridge crest processes constitute a vigorous frontier of multidisciplinary research with global ramifications in the earth atmospheric and biologic sciences this deep ocean frontier is gradually opening in response to investigations which are elucidating the role of these processes in the lithosphere hydrosphere atmosphere and biosphere and the application of advanced instrumental and interpretive techniques which are increasing the quality and quantity of data these techniques include crustal drilling with borehole logging deep sea drilling project reports high resolution bathymetry sea beam etc side scan sonar seamarc i and ii gloria etc imagery with video and photography multichannel seismics determination of water column properties ctd with rosette sampler etc and submersible applications

the krafla geothermal field iceland 3 the generating capacity of the field this paper presents analytical and numerical studies of the generating capacity of the krafla field a general lumped parameter model is developed which can be used to obtain rough estimates of the generating capacity of a geothermal field based on the size of the wellfield the average formation porosity and the amount of recharge to the system the model is applied to the old wellfield at krafla more sophisticated calculations of the generating capacity of the krafla field are also performed using distributed parameter models two dimensional areal models of the various reservoir regions at krafla are developed and their generating capacities mw sub e evaluated the results obtained indicate that the old wellfield can sustain steam production of 30 mw sub e for 30 years the estimated power potential of the new wellfield is 20 mw sub e for 30 years to obtain the required steam production several additional wells may be drilled in the old and new wellfields

composite suspended sediment particles and flocculation in glacial meltwaters preliminary evidence from alpine and himalayan basins research over the last decade has shown that the suspended sediment loads of many rivers are dominated by composite particles these particles are also known as aggregates or flocs and are commonly made up of constituent mineral particles which evidence a wide range of grain sizes and organic matter the resulting in situ or effective particle size characteristics of fluvial suspended sediment exert a major control on all processes of entrainment transport and deposition the significance of composite suspended sediment particles in glacial meltwater streams has however not been established existing data on the particle size characteristics of suspended sediment in glacial meltwaters relate to the dispersed mineral fraction absolute particle size which for certain size fractions may bear little relationship to the effective or in situ distribution existing understanding of composite particle formation within freshwater environments would suggest that in stream flocculation processes do not take place in glacial meltwater systems because of the absence of organic binding agents however we report preliminary scanning electron microscopy data for one alpine and two himalayan glaciers that show composite particles are present in the suspended sediment load of the meltwater system the genesis and structure of these composite particles and their constituent grain size characteristics are discussed we present evidence for the existence of both aggregates or composite particles whose features are largely inherited from source materials and flocs which represent composite particles produced by in stream flocculation processes in the absence of organic materials the latter may result solely from electrochemical flocculation in the meltwater sediment system this type of floc formation has not been reported previously in the freshwater fluvial environment further work is needed to test the wider significance of these data and to investigate the effective particle size characteristics of suspended sediment associated with high concentration outburst events such events make a major contribution to suspended sediment fluxes in meltwater streams and may provide conditions that are conducive to composite particle formation by flocculation copyright 2002 john wiley sons ltd

particle size and mineralogical composition of inorganic colloids in glacier melting water and overlying ice in an alpine glacier oberaargletscher switzerland

cold water injection into single and two phase geothermal reservoirs approximate analytical solutions are derived for cold water injection into single and two phase porous medium geothermal reservoirs a numerical geothermal reservoir simulator is used to verify the applicability of the analytical solutions for pressure transient analysis in accordance with these numerical results the analytical solutions indicate that the pressure buildup behavior during injection into either a single phase liquid or two phase reservoir is governed by the kinematic viscosity of the cold injected fluid the falloff pressures after cold water injection into a single phase liquid reservoir except for very early shut in times are primarily controlled by the kinematic viscosity of the in situ hot reservoir fluid for two phase reservoirs however the falloff behavior is considerably more complex and cannot be fully described by the analytical solution developed in this paper

geochemical weathering at the bed of haut glacier d arolla switzerland a new model waters were sampled from 17 boreholes at haut glacier d arolla during the 1993 and 1994 ablation seasons three types of concentrated subglacial water were identified based on the relative proportions of ca 2c h co 3 and so4 2 to si type a waters are the most solute rich and have the lowest relative proportion of si they are believed to form in hydrologically inefficient areas of a distributed drainage system most solute is obtained from coupled sulphide oxidation and carbonate dissolution so cd it is possible that there is a subglacial source of o2 perhaps from gas bubbles released during regelation because the high so4 2 levels found up to 1200 eq l are greater than could be achieved if sulphides are oxidized by oxygen in saturated water at 0 c c 414 eq l a more likely alternative is that sulphide is oxidized by fe 3c in anoxic environments if this is the case exchange reactions involving fe iii and fe ii from silicates are possible these have the potential to generate relatively high concentrations of hco3 with respect to so4 2 formation of secondary weathering products such as clays may explain the low si concentrations of type a waters type b waters were the most frequently sampled subglacial water they are believed to be representative of waters flowing in more efficient parts of a distributed drainage system residence time and reaction kinetics help determine the solute composition of these waters the initial water rock reactions are carbonate and silicate hydrolysis and there is exchange of divalent cations from solution for monovalent cations held on surface exchange sites hydrolysis is followed by so cd the so4 2 concentrations usually are 414 eq l although some range up to 580 eq l which suggests that elements of the distributed drainage system may become anoxic type c waters were the most dilute yet they were very turbid their chemical composition is characterized by low so4 2 h co3 ratios and high ph type c waters were usually artefacts of the borehole chemical weathering environment true type c waters are believed to flow through sulphide poor basal debris particularly in the channel marginal zone the composition of bulk runoff was most similar to diluted type b waters at high discharge and was similar to a mixture of type b and c waters at lower discharge these observations suggest that some supraglacial meltwaters input to the bed are stored temporarily in the channel marginal zone during rising discharge and are released during declining flow little of the subglacial chemical weathering we infer is associated with the sequestration of atmospheric co2 t he progression of reactions is from carbonate and silicate hydrolysis through sulphide oxidation by first oxygen and then fe iii which drives further carbonate and silicate weathering a crude estimate of the ratio of carbonate to silicate weathering following hydrolysis is 4 1 we speculate that microbial oxidation of organic carbon also may occur both sulphide oxidation and microbial oxidation of organic carbon are likely to drive the bed towards suboxic conditions hence we believe that subglacial chemical weathering does not sequester significant quantities of atmospheric co2 and that one of the key controls on the rate and magnitude of solute acquisition is microbial activity which catalyses the reduction of fe iii and the oxidation of fes2 copyright 2002 john wiley sons ltd

stable isotopic aspects of fluid flow in the krafla namafjall and theistareykir geothermal systems of northeast iceland abstract water and steam condensates from the krafla namafjall and theistareykir geothermal systems have been studied using hydrogen and oxygen stable isotope ratios to gain more information on thermal fluid flow the effect of rifting on individual fields and the provenance of recharge to these fields at krafla there are minor differences between individual wellfields but recharge is essentially local only one well shows signs of a change in composition over a 6 year production period but a local volcanic eruption in 1984 affected fumarole steam compositions the nearby namafjall field has isotopic compositions suggesting that recharge is ultimately derived from a long distance to the south perhaps by a combination of surface and groundwater flow some local spring and shallow well compositions have been affected by the post 1975 rifting episode the undrilled theistareykir field has an inflow estimated to be of similar isotopic composition to namafjall some fumaroles have an anomalously depleted 18o composition and rayleigh condensation is postulated to explain them

the significance of particle aggregation in the overbank deposition of suspended sediment on river floodplains abstract the effects of suspended sediment aggregation on rates of overbank deposition and on the grain size composition of deposited sediment were investigated using a combined field measurement and numerical modelling approach measurements of the in situ grain size characteristics of the suspended sediment load termed the effective size distribution of the river culm devon were obtained using a custom built water elutriation system samples of suspended sediment and of sediment deposited on the floodplain were analysed in the laboratory to determine the size distributions of their constituent discrete mineral particles termed the ultimate size distribution interpretation of these field data was aided by the development of a two dimensional finite difference model of flood hydraulics and suspended sediment dispersion and deposition field measurements and model predictions show that particle aggregation results in higher relative contributions of fine size fractions to overbank deposits aggregation may also provide a mechanism for explaining the poor agreement between theoretical and observed trends in relationships between mean deposit grain size and distance from the main channel suspended sediment aggregation is shown to cause significant increases in rates of floodplain deposition increases in deposition rates resulting from aggregation may however be less than expected because of the effects of aggregate shape and density the latter may offset increases in particle size so that the settling velocities of the largest aggregates do not increase appreciably with particle diameter

loading configurations and driving mechanisms for joints based on the griffith energy balance concept abstract using the griffith energy balance concept to model joint propagation in the brittle crust two laboratory loading configurations serve as appropriate analogs for in situ conditions the dead weight load and the fixed grips load the distinction between these loading configurations is based largely on whether or not a loaded boundary moves as a joint grows during displacement of a loaded boundary the energy necessary for joint propagation comes from work by the dead weight i e a remote stress when the loaded boundary remains stationary as if held by rigid grips the energy for joint propagation develops upon release of elastic strain energy within the rock mass these two generic loading configurations serve as models for four common natural loading configurations a joint normal load a thermoelastic load a fluid load and an axial load each loading configuration triggers a different joint driving mechanism each of which is the release of energy through elastic strain and or work the four mechanisms for energy release are joint normal stretching elastic contraction poroelastic contraction under either a constant fluid drive or fluid decompression and axial shortening respectively geological circumstances favoring each of the joint driving mechanisms are as follows the release of work under joint normal stretching occurs whenever layer parallel extension keeps pace with slow or subcritical joint propagation under fixed grips a substantial crack normal tensile stress can accumulate by thermoelastic contraction until joint propagation is driven by the release of elastic strain energy within the earth the rate of joint propagation dictates which of these two driving mechanisms operates with faster propagation driven by release of strain energy like a dead weight load acting to separate the joint walls pore fluid exerts a traction on the interior of some joints joint propagation under fluid loading may be driven by a release of elastic strain energy and or work by the pore fluid during poroelastic contraction again propagation velocity dictates the driving mechanism with critical to supercritical joint propagation accompanying fluid decompression and subcritical crack propagation taking place under a constant fluid drive during axial shortening a jointing process called axial splitting may occur following wing crack growth from an initial crack tilted relative to the maximum compressive stress here the joint driving mechanism may be either the work of a remote stress i e a dead weight or the release of elastic strain energy i e fixed grips

adapting palynological preparation methods in subbituminous and bituminous coals from colombia to improve palynofacies and hydrocarbon source rock evaluations abstract apart from their potential as fossil fuel bituminous and subbituminous coals in colombia may prove to be potential source rocks for the generation of hydrocarbons the assessment of such properties requires the combination of petrographic and palynofacies studies the latter correspond to the microscopic investigation in transmitted white and reflected uv lights of sedimentary organic matter insoluble in organic and inorganic solvents to date mineral acid and schulze methods have failed to produce good samples of palynofacies constituents from cenozoic coals in colombia so that the latter method had to be modified the main modifications consist in adapting the kclo 3 to hno 3 ratio in the schulze mixture and introducing two extra phases of oxidation with naoh and nh 4 oh which permit the washing off of humic substances this method yields the full spectrum of palynofacies constituents which are not destroyed or damaged by the alkali treatment neither is their fluorescence colour affected by the initial acid treatment on the contrary the particle fluorescence intensity tends to increase because of the dissolution of humic acids making their identification easier the achievements of the modified method are threefold 1 it permits the correlation between macerals in petrographic polished sections and their equivalent in palynofacies slides making the two methods complementary 2 palynofacies provides a better identification of sporomorphs than petrography resulting in better paleoenvironmental interpretations 3 palynofacies tend to give a more precise quantitative evaluation of the liptinitic constituents and consequently of the coal hydrocarbon generation potential

composite suspended sediment particles in river systems their incidence dynamics and physical characteristics most of the existing data on the effective particle size characteristics of fluvial suspended sediment derive from instantaneous sampling methods that may not be representative of the overall suspended sediment loads this presents difficulties when there is a need to incorporate effective particle size data into numerical models of floodplain sedimentation and sediment associated contaminant transfer we have used a field based water elutriation apparatus wea to assemble a large 36 flood database on the time integrated nature of the effective and absolute particle size characteristics of suspended sediment in four subcatchments of the river exe basin of southwest england these catchments encompass a wide range of terrains and fluvial environments that are broadly representative of much of the uk and temperate low relief northwest europe the wea provides important data on the physical characteristics of composite particles that are not attainable using other methods this dataset has allowed for the first time detailed interbasin comparisons of the time integrated particle size characteristics of suspended sediment and reliable estimates of the contribution of five effective size classes to the mean annual suspended sediment load of the study catchments the suspended sediment load of each river is dominated by composite rather than primary particles with for example almost 60 by mass of the sediment load of the river exe at thorverton transported as composite particles 16 m in size all the effective size classes contain significant clay components a key outcome of this study is the recognition that each catchment has a distinctive time integrated effective particle size signature in addition the time integrated effective particle size characteristics of the suspended loads in each of the catchments display much greater spatial variability than the equivalent absolute particle size distributions this indicates that the processes producing composite particles vary significantly between these catchments and this has important implications for our understanding of the dynamics of suspended sediment properties copyright 2007 john wiley sons ltd

thick dyke emplacement and internal flow a structural and magnetic fabric study of the deep seated dolerite dyke of foum zguid southern morocco 1 knowledge on forced magma injection and magma flow in dykes is crucial for the understanding of how magmas migrate through the crust to the earth s surface because many questions still persist we used the long thick and deep seated foum zguid dyke morocco to investigate dyke emplacement and internal flow by means of magnetic methods structural analysis petrography and scanning electron microscopy we also investigated how the host rocks accommodated the intrusion regarding internal flow 1 important variations of the rock magnetic properties and magnetic fabric occur with distance from dyke wall 2 anisotropy of anhysteretic remanent magnetization reveals that anisotropy of magnetic susceptibility ams results mainly from the superposition of subfabrics with distinct coercivities and that the imbrication between magnetic foliation and dyke plane is more reliable to deduce flow than the orientation of the ams maximum principal axis and 3 a dominant upward flow near the margins can be inferred the magnetic fabric closest to the dyke wall likely records magma flow best due to fast cooling whereas in the core the magnetic properties have been affected by high temperature exsolution and metasomatic effects due to slow cooling regarding dyke emplacement this study shows that the thick forceful intrusion induced deformation by homogeneous flattening and or folding of the host sedimentary strata dewatering related to heat as recorded by thick quartz veins bordering the dyke in some localities may have also helped accommodating dyke intrusion the spatial arrangement of quartz veins and their geometrical relationship with the dyke indicate a preintrusive to synintrusive sinistral component of strike slip

glacial sediment production and development of hydro electric power in glacierized areas by jim bogen glaciology section norwegian water resources and energy administration p o box 5091 majorstua n 0301 oslo 3 norway abstract this paper discusses the results of a sediment monitoring programme carried out in connection with hydro electric power development plans in the river basins surrounding the jostedalsbreen ice cap in norway whereas the highest suspended sediment transport rates occur during years with several flash flood events the bed load is more dependent upon the duration of large magnitude flood events bed load transport has been obtained from annual measurements of deltaic growth in small lakes at the front of glaciers during the years 1968 86 the mean ratio of bed load to total load amounted to 0 30 0 50 of the total load but in years with large magnitude floods this ratio decreased the mean annual suspended sediment yield of norwegian glaciers ranges from 100 tonnes km2 a i to 1300 tonnes km2 a i valley glaciers cause the highest erosion rates with the exception of the small cirque glacier trollbergdalsbreen which is thought to be a soft bed glacier the investigation programme undertaken involved monitoring the volume of suspended sediments together with the size distribution mineralogy and shape of grains in general the valley glaciers supply more sand than the smaller cirque glaciers whereas particles in the fine sand and silt size ranges in almost all of the glaciers are angular in shape methods of comparing the abrasive capacity of the sediment load at various intakes in a power plant are discussed long term sediment supply from the glaciers was investigated by studies of varves and rythmites in sediment cores from glacier fed lakes introduction during the last few years several glacier areas in norway have been developed for hydro electric power in this paper the results of a sediment monitoring programme carried out in connection with hydro electric power plans in the river basins surrounding the jostedalsbreen ice cap are discussed the hydro electric power plans on the western side the breheimen stryn project involve diversions of water at 32 intakes fig

paleomagnetic record at odp site 980 feni drift rockall for the past 1 2 myrs 1 a detailed record of variations in the direction and intensity of the geomagnetic field over the past 1 2 myrs has been obtained from an 120 m thick sedimentary section cored at odp site 980 on the feni drift north atlantic the record has high resolution due to high mean sedimentation rates 11 3 cm kyr for the brunhes chron and 5 5 cm kyr for the matuyama chron paleomagnetic measurements every 1 cm along u channel samples and high quality isotopic age control the iceland basin event is manifest by virtual geomagnetic poles crossing the equator at 190 ka the base of the recovered section lies immediately below the cobb mountain subchronozone that occurs within marine isotope stage 35 normalized remanence data can be correlated to paleointensity records from odp sites 983 and 984 700 km to the nw from site 980 and with lower resolution paleointensity data from the pacific ocean differences between the site 980 paleointensity record and the pacific records are attributed to variable sedimentation rates variable quality age control and inadequacies in the normalization procedure used to derive the paleointensity proxies

simple kinetic models of petroleum formation part iii modelling an open system abstract the movement of petroleum from organic rich source beds to potential carrier beds is the net result of two processes expulsion the release of generated petroleum from kerogen within the source bed and primary migration flow of a petroleum phase through the inorganic void networks of the source bed and all other intervening fine grained rocks expulsion is by far the more important process within the source bed orgas a simple zero dimensional model of the source rock as an open system explicitly models expulsion concurrent with oil and gas generation and oi lgas cracking as a storage threshold problem oil and gas are retained adsorbed absorbed within kerogen until their concentrations exceed the respective sorptive capacity of the residual organic carbon 0 1 and 0 02 g g ck 1 the initial hydrogen index hl 0 controls the important balance between potential sorbate petroleum and sorbant residual carbon using simple geochemical measurements the initial organic carbon is divided into initial oil inert kerogen and oil and gas generative reactive kerogen components reactive kerogens are assigned to one of five global kinetic organofacies with pre determined kinetic parameter sets governing separately rates of oil and gas generation kinetic parameters governing the rates of oil cracking within the source rock are predicted from hl 0 the two most important determinants of source rock behaviour are organofacies and hl 0 at a reference constant heating rate of 2 c ma 1 the projected oil expulsion threshold for typical organofacies members increases in the order a de 100 110 120 135 c f typically expels no oil an order of magnitude increase decrease in heating rate increases decreases these thresholds by ca 15 c typical cumulative gas mass fractions in their ultimate expulsion products are a f 0 25 0 3 0 25 0 65 and 1 0 g g 1 a value of 200 mg hc g c 1 is an approximate minimum hl 0 prerequisite for oil expulsion irrespective of absolute petroleum potential p 0 as a family coals vary dramatically in their expulsion behaviour as their hl 0 ranges both above and velow this value primary migration is efficient for expulsive source rocks movement within the source bed is limited only at low p 0 a source rocks total genetic potential p 0 thickness becomes important during migration outside the source bed it potentially restricts the primary migration distance and the excess of petroleum available for secondary migration and entrapment we evaluate primary migration approximately using a small migration loss factor no more than about 10 saturation of porosity or 1 mg g 1 coupled with an understanding of fluid potential gradients which determine migration direction within the stratigraphic architecture ultimately kerogen degradation and oil to gas cracking in the source rock are the rate limiting processes in petroleum accumulation

the terceira rift as hyper slow hotspot dominated oblique spreading axis a comparison with other slow spreading plate boundaries abstract we suggest the 550 km long terceira rift tr azores plateau is the world s slowest spreading hyper slow 4 mm a plate separation 2 3 3 8 mm a perpendicular to oblique axial segments organized accreting plate boundary in its slightly sinuous ca 300 km radius of curvature axial trace its oblique spreading angles ca 40 65 and in frequency and first motions of earthquakes the tr resembles better known ultra or super slow spreading ridges e g gakkel and southwest indian ridges interpreted simply as volcanically unfilled rift valley segments the inter island basins e g the 3200 m deep hirondelle basin are slightly wider 30 60 km but not significantly deeper 1000 2200 m than the mid atlantic ridge mar median valley 20 28 mm a 10 n 53 n however along axis segmentation wavelengths ca 100 km are double those along the central mar but make tr comparable to the ultra slow 15 16 mm a southwest indian and gakkel 7 13 mm a ridges if this segmentation wavelength reflects rayleigh taylor instabilities the viscosity contrast between the overlying axial lithosphere and the partial melt zones is about an order of magnitude greater at ca 4 16 mm a than at 20 30 mm a the tr differs dramatically from ultra slow ridges only in the large amplitude of along strike topography 2000 4000 m 4200 m total variation owing perhaps to a copious melt flux from the azores hotspot combined with a spreading rate determined greater axial flexural strength and plate thickness and slower export of volcanics from the rift axis the probable tr youth ca 1 ma requiring less than 4 km new oceanic crust suggests lack of steady state spreading conditions which may explain the published gravity evidence against tr spreading absolute plate motions support the creation of the azores plateau by successive ne jumps of the rift axis to maintain its position over a fixed hotspot

modification of the magnetic mineralogy in basalts due to fluid rock interactions in a high temperature geothermal system krafla iceland summary active high temperature 150 c geothermal areas like the krafla caldera ne iceland often show distinct magnetic lows in aeromagnetic anomaly maps suggesting a destruction of magnetic minerals by hydrothermal activity the main alteration processes in such an environment are low temperature oxidation 350 c maghemitization and fluid rock interactions we investigated the rock magnetic properties natural remanent magnetization nrm magnetic susceptibility and their temperature and field variation and the mineralogy using x ray diffraction microscopic methods and electron microprobe analyses of two drill cores kh1 and kh3 from the rim of the krafla caldera the drill cores have distinctly lower nrm values average 3 a m 1 compared to younger surface basalts average 20 a m 1 along with a large variation in magnetic susceptibility 1 3 10 7 4 9 10 5 m3 kg 1 the secondary mineral assemblage sulphides sphene rutile and chlorite indicates an alteration within the chlorite smectite zone for both cores without depth zoning optical miscroscopy in combination with the bitter technique and backscatter electron microscopy along with the thermomagnetic analyses allow distinguishing two different magnetomineralogical groups of titanomaghemite 1 titanomaghemite with intermediate titanium concentration and probably high vacancy concentration and 2 titanomaghemite with low titanium concentration and low vacancy concentration the mineral assemblages textures and magnetic properties deduced from the mentioned magnetic measurements indicate two stage transformation mechanism 1 dissolution of titanium at low ph under oxidizing conditions the ulvospinel component of titanomagnetite and ilmenite forms rutile or sphene and fe2 migrates out of the spinel lattice forming titanomaghemite 2 formation of pyrite and dissolution of remaining titanomaghemite under reducing and acidic conditions the latter mechanism produces ghost textures all titanomaghemite is transformed and only their former grain shapes are preserved with only paramagnetic minerals left and ferrimagnetic minerals nearly dissolved this mechanism could explain the significant magnetization loss which is seen in many local magnetic anomaly lows within the oceanic crust and volcanic islands like iceland or hawaii the production of nanoporous textures in titanomaghemites is suggested as a mechanism for the enhancement of the magnetic susceptibility values related to the hydrothermal alteration of krafla

evidence for a persistent uplifting of la palma canary islands inferred from morphological and radiometric data abstract the morpho structural evolution of la palma canary islands is characterized by vertical movements responsible for or favoring large landslides in its northern part conglomerate terraces nowadays topographically hanged and re incised by the present day barranco de las angustias reveal a recent ongoing uplift process lava flows covered by this geological unit have been sampled and dated by the k ar cassignol technique at a mean age of 507 11 ka the minimum rate of uplift inferred of about 0 4 mm yr is similar to the one deduced from the abnormal elevation of the early submarine series staudigel and schmincke j geophys res 89 1984 11195 11215 this indicates that the northern shield may have experienced a global rise fairly constant throughout most of its geological history it probably results from the combination of regional atlas tectonic processes and the existence of a swell at the island scale this global rise together with the existence of a north south fault in the basement may have controlled triggering of the sw flank collapse of the northern shield and the subsequent concentration of magma along a southern still active topographic ridge the cumbre vieja cv morphological asymmetry of this structure may result from the destabilization of its distal western part favored by strong injections at the axis tilting processes along lateral listric faults can then explain the existence of slope break ups especially on the western side of the ridge such tectonic processes are likely responsible for local superimposed uplifting contributing to the genesis and development of huge western coastal cliffs even in sub historic and historic times we show that unlike many oceanic islands la palma island has experienced important positive vertical movements rather than subsidence

links between proglacial stream suspended sediment dynamics glacier hydrology and glacier motion at midtdalsbreen norway two hourly suspended sediment concentration variations observed during the summer of 1987 in the proglacial stream draining midtdalsbreen norway are modelled using multiple regression and time series techniques suspended sediment fluctuations are influenced by stream discharge variations diurnal hysteresis effects medium term sediment supply and transport variations and the recent suspended sediment concentration history of the stream they do not appear to be influenced by seasonal exhaustion or rainfall variations possible reasons for this are discussed large positive residuals from the fitted models are major pulses of suspended sediment unrelated to discharge variations these sediment flushes correlate with periods of enhanced glacier motion they cannot be explained by enhanced sediment production by subglacial erosion but are probably due to the tapping of subglacially stored sediment during sudden changes in the hydraulics and or configuration of the subglacial hydrological system seasonal changes in the lag between glacier motion peaks and suspended sediment flushes suggest that the subglacial hydrological system evolves over the summer from a distributed to a more channelized configuration

imaging the high temperature geothermal field at krafla using vertical seismic profiling abstract geophysical exploration and in particular active source seismic imaging of geothermal fields is important to assess and optimize the exploitation of natural heat sources for energy production and direct use the first multi offset moving source vertical seismic profiling vsp experiment over the high temperature geothermal field in krafla iceland was carried out in spring 2014 with the aim to test whether vsp is a suitable method to map volcanic stratigraphy fractures dykes steam zones and magmatic bodies at this site and for volcanic environments in general in this study we present a workflow for processing the sparse krafla vsp dataset recorded with receivers in either of two boreholes the analysis involved first arrival traveltime inversion and seismic reflection processing the seismic velocity model obtained by traveltime tomography reveals structural information between the two boreholes and can be linked to an existing geological model showing that the seismic velocities are mainly controlled by lithology the zero offset seismic reflection data were processed into two corridor stacks walk away vsp reflection data were migrated with a novel multicomponent kirchhoff migration algorithm that includes p and s wave isolation to obtain separate pp ps and ss migrated images the reflections imaged in the corridor stacks can be linked to the main lithological units known from borehole logging information migrated images from the walk away data reveal reflectors below and to the sides of the two boreholes considering a priori information such as hypocenter locations from earthquake seismology studies the reflectors can be related to changes in lithology fault zones dykes and possibly the top of the krafla magma chamber we found that vsp is potentially a useful method to image the key lithological boundaries and volcanic stratigraphy in the complex magmatic environment at krafla but a priori information proved to be essential to constrain the processing and interpretation of the sparse array dataset

flocculation a key process in the sediment flux of a large glacier fed lake this study investigates the consequences of flocculation for sediment flux in glacier fed lillooet lake british columbia based on density fractal dimension in situ profiles of sediment concentration and size distribution and settling velocity equations presented in the literature sediment flux attributed to macroflocs during the late spring and summer accounts for a significant portion of sediment flux in the lake equivalent to at least one quarter of the average annual sediment flux fine sediment is reaching the lake floor faster in flocs than occurs if settling as individual grains this flux varies both spatially and temporally over the observation period suggesting a link between deposition via flocculation and the properties of bottom sediments macrofloc flux increased through june reached a peak during july and then declined into august macrofloc flux was greatest in the distal end of the first basin approximately 10 km from the point of inflow relatively high excess densities 0 1 g cm 3 at 500 m for flocs in situ are consistent with a composition dominated by inorganic primary particles microlaminations within lillooet lake varves have been linked by earlier workers to discharge events and the action of turbidity currents emanating from the lillooet river while turbidity currents undoubtedly occur in lillooet lake these results demonstrate flocculation as an adjunct process linking discharge lake level macrofloc flux bulk density and microlaminations in situ measurements of sediment settling velocity in glacier fed lakes are required to better constrain flux rates and permit comparison between flocculation in lacustrine environments with existing studies of estuarine marine and fluvial flocculation copyright 2009 john wiley sons ltd

injection and thermal breakthrough in fractured geothermal reservoirs lbl 12698 preprint submitted to the journal of geophysical research injection and thermal breakthrough in fractured geothermal reservoirs gudmundur s bodvarsson and chin fu tsang may 1981 two week loan copy this is a library circulating copy which may be borrowed for two weeks for a personal retention copy call tech info division ext 6782 prepared for the u s department of energy under contract w 7405 eng 48

seismic imaging in the krafla high temperature geothermal field ne iceland using zero and far offset vertical seismic profiling vsp data abstract among geothermal exploration methods active surface seismic methods have played only a minor role to date especially in high temperature volcanic systems reflection seismic data often reveal poor delineation of volcanic features due to the internal heterogeneity of volcanic sequences to enhance the vertical resolution one possibility is the application of downhole seismic methods like vertical seismic profiling vsp a test experiment was carried out in the krafla high temperature geothermal field ne iceland to assess the ability of vsp to image subsurface structures such as fractures zones of high permeability magmatic bodies and zones of supercritical fluids and steam logging in such hostile environments is technical challenging in many aspects but mainly due to the high temperature impact on the downhole electronic components of the measuring equipment this requires a thorough pre examination and implementation of the measurement especially to avoid delays and tool failures this paper presents results of zero and far offset vsp data from the k 18 borehole from within the krafla caldera which reveal good correlation with the surrounding lithology the raw three component seismic data display a good signal to noise ratio and dominant signal frequencies between 20 and 40 hz down to c 2200 m depth for air gun and explosive sources respectively a zero offset source comparison was also conducted to assess the use of different impulsive sources for future vsp surveys in similar settings by applying a standard vsp processing we identified stratigraphic boundaries between lavas hyaloclastites and intrusions which are in good agreement with existing well data for the zero offset vsp both p and s wave velocity models were calculated and a depth converted corridor stack was determined in addition multicomponent kirchhoff depth migration and fresnel volume migration were tested around the borehole the 3d results are promising but the specific shape and lateral extent of the reflectors could not be determined due to the restriction to only two sources and the insufficient spatial coverage aperture our study demonstrates that vertical seismic profiles can clearly detect variations in the subsurface volcanic stratigraphy in high temperature geothermal fields a more detailed reservoir characterization can be achieved by further data integration enhanced survey design including more source positions and improved processing and imaging techniques such as full waveform inversion

models of maar volcanoes lunar crater nevada usa maar volcanoes are generally understood to be the result of highly energetic explosive interaction between magma and water groundwater or surface water two end member conceptual models have been proposed to explain the dimensions diameter depth of maar craters 1 an incremental growth model where a crater grows due to subsidence and ejection of debris over the course of many explosions and the final size is an integrated result of multiple explosive events 2 a model in which the dimensions of a maar crater are the result of the largest single explosion during the lifetime of the maar major explosion dominated model in the latter case the maar size can be used to estimate the energy and depth of the largest explosion which in turn allows estimation of the magma mass involved this paper describes lunar crater maar nevada usa and tests the two models as explanations for the characteristics of the volcano in particular the major explosion dominated model this model implies magma mass and supply rates that are unrealistic and the tephra at the maar do not contain key features observed in the ejecta at large single explosion craters the incremental growth model seems most suitable based upon geological evidence

vertical axis rotation of the upper portions of the north east rift of tenerife island inferred from paleomagnetic data abstract paleomagnetic sampling sites were established in 82 dykes along an 8 km long section of the north east rift zone nerz of tenerife canary islands spain of the 70 interpretable sites 16 are of normal polarity and 54 of reversed polarity four normal polarity sites and fifteen reverse polarity sites were excluded from the grand mean calculation for statistical reasons after inverting the reverse polarity sites through the origin the in situ grand mean yields a declination d 023 8 an inclination i 42 3 95 3 2 39 0 n 51 that is discordant to the expected late miocene to pleistocene field direction d 357 6 i 38 8 95 4 7 this discordance can be explained as either a 26 clockwise vertical axis rotation or a 28 wnw side down tilt about an average 009 horizontal tilt axis the sampled section is composed of numerous semi vertical dykes cutting mainly lava flow units that are sub horizontal and cross cut by steeply dipping faults 70 90 field evidence is therefore more compatible with a vertical axis rotation rather than a horizontal axis tilt of the drilled units we argue that this clockwise vertical axis rotation is likely related to strike slip movements that occurred along the edges of the collapse scars and accommodate the emplacement and growth of the underlying intrusive core and associated dykes six new 40ar 39ar age determinations constrain the main interval of dyke emplacement within the nerz between 0 99 ma and 0 56 ma the intrusive activity in the sampled section of the rift appears to have been almost continuous with several intrusion pulses that are probably related to flank destabilisation event s during the mid pleistocene our study thus demonstrates a long lived multi faceted history that shaped the nerz