analysis and modelling of the aeromagnetic anomalies of gran canaria canary islands abstract in this paper we present a crustal magnetic model of the volcanic island of gran canaria based on aeromagnetic data this magnetic study has made it possible to constrain the location and geometry of 1 the mafic core of gran canaria built as the result of the crystallization of magmas which rose from the mantle during the submarine and shield basaltic stages of its evolution the most intense magnetic high displayed over the nw part of the island likely shows the main feeding system of the shield volcano 2 the residual syenitic shallow magma chamber which fed the salic volcanic activity in the center of the island linked to the formation of the tejeda caldera and to the intrusion of felsic rocks which made up a cone sheet 3 a reversely magnetized linear intrusion located in the marine area to the nw of the island which could be related to the magmatic source of the submarine volcanism between gran canaria and tenerife most of these magnetic sources show a linear pattern with trends that are in close agreement with the orientations of previously identified fractures the magmatic intrusion to the nw of the island could be related with a wsw ene active fault between gran canaria and tenerife while the main trend and location of the mafic core agree with a nw se fault suggested by geological studies this means that these magnetic sources are the result of the ascent and intrusion of magma along regional fractures therefore this study provides fresh data which demonstrate the influence of regional tectonics on the growth of gran canaria during its entire evolution finally the spectral analysis of the magnetic anomaly map suggests that it is possible that rocks located at mantle like depths from the moho to about 23 km behave as magnetic sources a fact that can be related with the magmatic underplating detected by other geophysical techniques

identifying lidar sample uncertainty on terrain features from dem simulation abstract light detection and ranging lidar is an effective technology to detect highly dense point elevation data from terrain surfaces the density of lidar data points significantly affects the level of detail of a high resolution digital elevation model dem in this study the conditioned latin hypercube sampling clhs and simple random sampling srs methods select sufficient lidar samples and sequential gaussian simulation sgs generates multiple dem realizations that are a set of simulated dem maps subject to a specified mean variance and spatial structure of measured data based on dem realizations the uncertainty of a spatial feature with a specified elevation is determined the results suggest that lidar sampling patterns including the size and configuration affect the spatial distribution of the feature uncertainty especially when the sample size is small the accuracy of a dem is dependent on the choice of sampling techniques for low sampling density data unlike random sampling the clhs method replicates the distribution of spatial elevation patterns in small sample sizes hence the integrated method can assess the uncertainty of spatial features efficiently in geomorphic monitoring and management

generation of gas and oil from coal and other terrestrial organic matter abstract late carboniferous permian sedimentary rocks contain the world s largest coal reserves which have generated and released gas but little if any oil in comparison organic matter deposited in lacustrine fluvial deltaic or brackish water sediments has sourced large quantities of waxy oils in countries such as china australia the u s a argentina venezuela and indonesia plus gas and condensate in deltas worldwide why is more oil coming from land derived organic matter disseminated in sediments than from the carboniferous permian coal beds which also are land deposits the answer appears to be in the hydrogen content and the ease of migration when organic matter and coals have high hydrogen contents relative to carbon they can form oil when the hydrogen is low mainly gas is formed most of the world s coal is low in hydrogen whereas much of the terrestrial organic matter disseminated in sediments is higher in hydrogen so it forms more oil also both gas and oil are adsorbed on coal more strongly than on the disseminated kerogen of sedimentary rocks this makes migration of oil out of the coal more difficult compared to migration from conventional shale source rocks

modelling of estuarine response to sea level rise during the holocene application to the guadiana estuary sw iberia this paper focuses on simulations of the morphological evolution of an estuary during sedimentary infilling that accompanied holocene sea level rise the simulations were conducted using the estuarine sedimentation model which uses a behaviour oriented approach supported by the chronostratigraphy of the estuary s sedimentary sequence behaviour curves were computed to represent the relationship between the estuarine channel depth below maximum high tide and the net accretion at a given location relative to the average sedimentation rate of the estuary during the holocene the model was validated by comparing the observed present day bathymetry of the guadiana river estuary southeastern portugal with the corresponding simulated bathymetries for nine control sections across the estuary the best fit between simulated and actual sediment surface elevations was obtained along the cross sections in the sheltered low energy environments of the estuary the accuracy of the sedimentary stratigraphy of the best fit model was further established using 16 radiocarbon ages obtained from five boreholes in the estuary the present approach is particularly suitable for simulating long term morphological evolution in sheltered estuarine environments where tidally driven vertical aggradation dominates at centennial to millennium timescales however the accuracy of simulated sediment surface elevations and consequently the robustness of behaviour type models based on geographical information system platforms can be enhanced by incorporating i the impacts of nearshore hydrodynamic processes and episodic flood events in highly energetic channels and ii the impacts of cross currents in meandering channel sections

a gravity and magnetic study of the volcanic island of ischia naples italy abstract gravity and magnetic data for the volcanic island of ischia naples italy have been analyzed and interpreted in light of recent geological and volcanological data to define a model of the island s shallow and deep structures from the interpretation of the gravity data it appears that the shallow structures consist of pyroclastic material p 2 0 g cm 3 within these pyroclastics there are domes and lava flows of higher density and eruptive centres filled with lower density material the basement is a horst with the shallowest depth at about 1 0 km south of the centre of the island if we assign a density contrast of 0 5 g cm 3 relative to the above pyroclastics interpretation of magnetic data measured at 725 stations showed that the basement derived from the gravity interpretation is magnetized moreover this basement is less magnetized on the western side of ischia which may be caused by the anomalous thermal state of the area as indicated by surface fumaroles hot springs etc and temperature measurements in deep drillings

detailed hydrocarbon analyser for well site and laboratory use abstract the geofina hydrocarbon meter an instrument for simultaneous thermal extraction and pyrolysis gas chromatography is described and its application to studies of source rocks reservoir rocks and caprocks is demonstrated using examples from various wells from the norwegian continental shelf the instrument allows analysis and data processing to be completed within one hour of the sample reaching the shale shaker the instrument yields detailed information on free hydrocarbons in caprocks reservoir rocks and source rocks the instrument will detect oil shows and allows identification of the types of hydrocarbons present in reservoir lithologies i e light oil heavy oil biodegraded oil or residual oil the location of the oil water contact in a reservoir can be determined and the sealing capacity of a caprock estimated detailed information on the richness and kerogen type of a source rock can also be obtained some of this information can even be acquired where oil based mud is used

the thermal response of rock to friction in the drag cutting process abstract significant friction between the cutter and the rock occurs during the drag cutting process this friction is responsible for elevating the temperature of the drag cutter and under certain conditions reducing cutter life because of this effect friction often plays a major role in determining the economics of drilling with drill bits employing polycrystalline diamond compact pdc cutters analytical models have been developed in previous studies for predicting pdc cutter temperatures and their effects on bit wear and performance the current paper investigates the effects of drag cutter friction on the rock mass and on rock chips generated during cutting the thermal and mechanical loading imposed during the cutting process is described and the thermal response of the rock to frictional heating at the cutter rock interface is investigated the results indicate that significant localized rock temperatures can develop as a result of frictional heating caused by drag cutters sliding on the rock surface although conduction of heat is severely limited during the short chip formation process it is possible to attain elevated temperatures throughout a rock chip because of the possibility of internal frictional heating caused by shear deformation it is concluded that temperatures and pressure during drag cutting are sufficient to cause metamorphic changes in some rock constituents

influence of survey strategy and interpolation model on dem quality accurate characterisation of morphology is critical to many studies in the field of geomorphology particularly those dealing with changes over time digital elevation models dems are commonly used to represent morphology in three dimensions the quality of the dem is largely a function of the accuracy of individual survey points field survey strategy and the method of interpolation recommendations concerning field survey strategy and appropriate methods of interpolation are currently lacking furthermore the majority of studies to date consider error to be uniform across a surface this study quantifies survey strategy and interpolation error for a gravel bar on the river nent blagill cumbria uk five sampling strategies were compared i cross section ii bar outline only iii bar and chute outline iv bar and chute outline with spot heights and v aerial lidar equivalent derived from degraded terrestrial laser scan tls data digital elevation models were then produced using five different common interpolation algorithms each resultant dem was differentiated from a terrestrial laser scan of the gravel bar surface in order to define the spatial distribution of vertical and volumetric error overall triangulation with linear interpolation tin or point kriging appeared to provide the best interpolators for the bar surface lowest error on average was found for the simulated aerial lidar survey strategy regardless of interpolation technique however comparably low errors were also found for the bar chute spot sampling strategy when tins or point kriging was used as the interpolator the magnitude of the errors between survey strategy exceeded those found between interpolation technique for a specific survey strategy strong relationships between local surface topographic variation as defined by the standard deviation of vertical elevations in a 0 2 m diameter moving window and dem errors were also found with much greater errors found at slope breaks such as bank edges a series of curves are presented that demonstrate these relationships for each interpolation and survey strategy the simulated aerial lidar data set displayed the lowest errors across the flatter surfaces however sharp slope breaks are better modelled by the morphologically based survey strategy the curves presented have general application to spatially distributed data of river beds and may be applied to standard deviation grids to predict spatial error within a surface depending upon sampling strategy and interpolation algorithm

surface interpolation within a continental flood basalt province an example from the palaeogene faroe islands basalt group abstract the faroe islands basalt group fibg is a continental flood basalt province with four proven lithohorizons that have abundant spot height data the spline interpolation method was used to construct spatial surfaces for the lithohorizons the resultant surfaces conform to dip and strike estimates that were previously modelled by hand and confirm the methods reliability the surfaces should be used as guides only but can be quickly and easily updated as new information becomes available the surfaces have been used for a variety of different tasks for example obtaining gross thickness estimates producing isopach maps and constructing geological cross sections an additional benefit of the spatial surfaces is the ability to constrain disparate observations in a stratigraphic framework which will be particularly important for future studies attempting to understand for example the temporal and spatial development of continental flood basalt volcanism the spline interpolation method applied in this study can be equally used for other stratigraphic horizons e g chemohorizon chronohorizon biohorizon and in other continental flood basalt provinces e g deccan traps columbia river basalt group

frictional melting of sedimentary rock during high speed diamond drilling an analytical sem and tem investigation abstract high speed drilling at 900 rpm with a downhole motor driven natural diamond drag bit has resulted in the extreme alteration of sedimentary rock in an offshore canadian wildcat well these effects as revealed in the rock cuttings retrieved from the drilling fluid at surface include discolouration darkening cataclasis slickensiding and partial fusion calcareous siltstones are the most susceptible to alteration especially melting whereas sandstone and limestone cuttings mainly exhibit fracturing and surface glazing analytical scanning electron microscopy reveals that the calcareous siltstones have undergone decalcification via decarbonation and the loss of cao to the drilling fluid decarbonation combined with dehydration resulted in the vesiculation and explosive fragmentation of certain cuttings analytical transmission electron microscopy shows that glass is present in the calcareous siltstone cuttings most of the modifications exhibited by the sedimentary rocks can be attributed to the effects of high strain rate deformation and frictional heating at the bit rock interface that melting took place is supported by thermal calculations which indicate that for a coefficient of friction of 0 5 temperatures of approximately 1200 c were realized at diamond rock contacts such high temperatures can accelerate the wear of diamond and its substrate and hence shorten bit life as well as obliterate potentially important geological information in the rock cuttings

shear wave velocity and attenuation structure of ischia island using broad band seismic noise records abstract in volcanic areas accurate localization of earthquakes requires detailed velocity and possibly attenuation models taking into account wide lithological variability and high geothermal gradients ischia island campania region italy is a seismically active volcano recently affected by a mw 3 9 event casamicciola august 21 2017 1 km depth due to the lack of a specific velocity model the earthquakes occurred on the island were localized using the one developed for the nearby campi flegrei caldera the aim of this work is the definition of a mean representative 1d shear wave velocity vs and attenuation q model of the shallower crust up to 2 km depth of ischia seismic noise array and spectral ratios techniques were applied to broad band seismic signals recorded by temporary and permanent networks updated after the august 2017 earthquake the values of both shear wave velocity vs and quality factor q are realistic with q values comparable with those obtained for campi flegrei and stromboli volcanic areas by taking into account stratigraphic information from deep wells and ultrasonic measurements of velocity on granite and trachytic lava samples a geological interpretation of the resulting velocity model is provided such a model can have significant implications for understanding the dynamics of a volcano mainly those leading to seismic activity

a new method of surface modeling and its application to dem construction a new method of surface modelling based on the fundamental theorem of surfaces smts is presented eight different test surfaces are employed to comparatively analyze the simulation errors of smts and the classical methods of surface modeling in gis including tli triangulated irregular network with linear interpolation spline idw inverse distance weighted and kriging numerical tests show that smts is much more accurate than the classical methods smts theoretically gives a solution to the error problem that has long troubled dem construction as a real world example smts is used to construct a dem of the da fo si coal mine in shaan xi province china its root mean square error rmse is compared with those of dems constructed by the four classical methods the results show that although smts also has a higher accuracy in the real world example the improvement of accuracy is less distinct than that expected from the numerical tests the accuracy loss seems to be caused by location differences between sampling points and the central points of lattices of the simulated surfaces two alternative ways are proposed to solve this problem

dem based morphometry of range front escarpments in attica central greece and its relation to fault slip rates in this paper we apply current geological knowledge on faulting processes to digital processing of digital elevation models dem in order to pinpoint locations of active faults the analysis is based on semiautomatic interpretation of 20 and 60 m dem and their products slope shaded relief in northern eastern attica five normal fault segments were recognized on the 20 m dem all faults strike wnw ese the faults are from west to east thriassion thfs fili fifs afidnai affs avlon avfs and pendeli pefs and range in length from 10 to 20 km all of them show geomorphic evidence for recent activity such as prominent range front escarpments v shaped valleys triangular facets and tilted footwall areas however escarpment morphometry and footwall geometry reveal systematic differences between the bexternalq segments pefs thfs and avfs and the binternalq segments affs and fifs which may be due to mechanical interaction among segments and or preexisting topography in addition transects across all five escarpments show mean scarp slope angles of 22 18f0 78 for both carbonate and metamorphic bedrock the slope angle equation for the external segments shows asymptotic behaviour with increasing height we make an empirical suggestion that slope angle is a function of the long term fault slip rate which ranges between 0 13 and 0 3 mm yr the identified faults may rupture up to magnitude 6 4 6 6 earthquakes the analysis of the 60 m dem shows a difference in fault patterns between western and northern attica which is related to crustal rheology variations d 2004 elsevier b v all rights reserved

assessment of fluid contacts and compartmentalization in sandstone reservoirs using fluid inclusions an example from the magnus oil field north sea location of an oil water contact is crucial for estimating reserves and for designing production strategies identifying hydrodynamic barriers or baffles is also important for optimizing both recovery and flow rates in some oil fields identifying fluid contacts and barriers is not always possible using conventional wireline and formation testing methods

source rock evaluation by pyrolysis gas chromatography a pyrolysis gas chromatography system has been developed for the rapid evaluation of potential source rocks for the determination of organic richness and maturation this system uses the pyrolysis methods previously described however the determination of hydrocarbon production type and the identification of contamination by migrated hydrocarbons or drilling additives are accomplished by gas chromatographic gc analysis of the thermal extracts and pyrolysis products of rock samples or isolated kerogens the production type is recognized either qualitatively by gc fingerprint traces or quantitatively by hydrocarbon composition c1 to c6 c6 to c11 c11 from the kerogen peak ii pyrolysate oil prone erogens are recognized by gc traces with a full spectrum of c1 to c28 hydrocarbons or by high concentrations of c11 compounds in contrast gas prone kerogens are characterized by the predominance of light hydrocarbons from c1 to c4 and higher contributions of aromatic compounds mixed type production is intermediate in character between the two contaminants are identified from the gc analysis of the thermally extractable material in peak i possible mineral organic matter reactions during sample heating make interpreting data from whole rock samples more difficult

hydrocarbons from non marine source rocks abstract non marine source rocks make a significant contribution to the world s oil reserves they are particularly important as source rocks in china australia new zealand and indonesia non marine mainly lacustrine oil shales from deposits in a number of locations were collected for study samples from thailand mae sot and mae moh yugoslavia aleksinac u k lothians caithness bituminous flagstone brora skye and france autun were analysed in addition coals from the mahakam delta in indonesia and from australia and some boghead coals from a number of deposits were also analysed along with green river and messel shale samples for comparison hydrocarbon characterisation was performed mainly by thermal extraction and pyrolysis gas chromatography gas chromatography of oils produced by hydrous pyrolysis was also performed estimation of maturity was based mainly on vitrinite reflectance and spore fluorescence there are considerable differences in hydrocarbons produced by pyrolysis of the samples from the different deposits paraffinic hydrocarbons are generated in abundance by all samples in the boghead coals hydrocarbons are mostly paraffinic in the humic coals aromatics are as prominent as paraffinic hydrocarbons in the lacustrine shales and carbonates paraffinic and isoprenoid hydrocarbons vary in abundance and isoprenoids are very abundant in some of the carbonates the thermal extracts indicate that in most cases hydrocarbon generation has not started the presence of a number of homologous series in some of the immature lacustrine samples is interpreted to be related to the abundance of alginite the early generation of acyclic isoprenoid hydrocarbons as well as aromatics relative to straight chain hydrocarbons is indicated by the hydrous pyrolysis results in the case of the green river oil shales it may be an additional reason for the lack of n alkanes in early migrated bitumens found in the green river basin area along with biodegradation

biomarker analysis of oils and source rocks using a thermal extraction gc ms abstract gc ms analysis of thermally extracted hydrocarbons on sediments has been tried in practice only in the last few years it allows rapid acquisition of data normally only obtained after elaborate work up processes have been performed an oil an oil stained sandstone and source rocks 4 have been selected for this study both saturated and aromatic hydrocarbon biomarkers were monitored using mid of selected ions the machine used in this study has been developed at our laboratories the methodology is the same for both oils and source rocks so that rapid hydrocarbon characterisation and oil source rock correlations are possible

dem analysis on longitudinal and transverse profiles of steep mountainous watersheds longitudinal and transverse characteristics of watersheds are fundamental to describe watershed topography only a limited number of studies however have analyzed the characteristics of transverse profiles in watersheds and almost no studies have examined longitudinal and transverse profiles at the same time how transverse profiles change within a watershed and how longitudinal and transverse characteristics of watersheds are related remain to be examined to address these issues this study employs dems gis and computer programming techniques to acquire a series of longitudinal and transverse profiles of watersheds basic morphometric parameters representing the shape of these profiles were analyzed methods to classify the profiles and to identify points where the morphometric characteristics change abruptly were also developed these methods were then applied to severely dissected steep watersheds in the japanese alps the results show that spatial change in transverse characteristics reflects two factors general topography of the watersheds and local differences in channel development the form of the transverse profiles is also affected by erosion processes that create mature v shaped valleys with a characteristic slope angle the longitudinal and transverse profiles play different roles in determining watershed topography and the overall longitudinal slope exerts a major influence on the mean watershed slope the discontinuity of the longitudinal and transverse profiles however tends to occur at the same location which may reflect the occurrence of knickzones and their influences on the development of valley side slopes

magnetic modeling of the phlegraean volcanic district with extension to the ponza archipelago italy abstract a 3d modeling of the residual aeromagnetic anomalies of the area including the phlegraean volcanic district pvd campi flegrei caldera cfc and ischia and procida vivara islands and two volcanic islands of the ponza archipelago ventotene and s stefano has been carried out the observed residual anomalies have been reproduced with several large magnetized bodies located at 2 10 km depth in the crust a volcanological interpretation has been made possible only for those bodies that have been constrained by geological geothermal and other geophysical data the magnetized structures associated with cfc and ischia procida vivara ventotene and santo stefano islands have been interpreted as igneous bodies that may be solidified intrusions or magma reservoirs on the basis of magnetic data volcanological and magmatological history and geothermal heat flux distribution the existence of a partially solidified magma chamber is suggested at ischia a speculation shows that the magnetization intensity assumed for the magnetic bodies located at procida and south west of ventotene matches quite well with the calculated composition of a cooled residual magma resulting from crystallization processes within a chamber

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

a continental hydrological assessment of a new grid based digital elevation model of australia a rectangular grid digital elevation model dem for australia with a horizontal resolution of 1 40 degree of latitude and longitude approximately 2 5 km has recently been calculated from continent wide coverages of point elevation and stream line data using an elevation gridding technique which incorporates a drainage enforcement algorithm an automated drainage basin analysis of this dem is in close agreement with existing basin analyses both for the better surveyed coastal areas with well defined relief and for large areas of low relief that make up much of the interior lake eyre basin and the murray darling basin the analysis of the arid western plateau region differs from the currently accepted analysis but is in broad agreement with a previous analysis of palaeodrainage systems based on topographic and geological information the drainage analyses is used to calculate cumulative distributions of spatially distributed hydrologically significant terrain parameters for the murray darling and derwent river basins the adequacy of the resolution of the dem for continental hydrological analyses is assessed by comparing drainage basin analyses and cumulative distributions of terrain parameters at resolutions of 1 40th and 1 20th degree of latitude and longitude

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

impact of modern deepwater drilling and testing fluids on geochemical evaluations evaluation of petroleum fluid properties hydrocarbon shows and source rock characteristics requires new tools to properly recognize and correct for drilling and test induced contamination which is increasingly common in modern deepwater field operations oil exploration development and now production are more frequently conducted in deeper water environments where the challenges faced by drilling and operations can severely impact the evaluation of oil and rock geochemistry and fluid properties poorly consolidated sediments swelling clay minerals and responses to evolving environmental regulations regarding offshore disposal of drill cuttings have resulted in the widespread use of enhanced mineral oil or synthetic based muds also water based drilling fluids used in some deepwater operations contain additives that may impact fluid and rock geochemistry for example asphalt based shale stabilizers are added to aid well bore competency and prevent sticking drill pipe and polyalkylated glycols are added to depress freezing temperatures and prevent the formation of gas hydrates in the drilling mud because these and other additives are often a significant component of water based muds they may affect the geochemical signature of fluids and rocks and alter fluid properties highly saline brines are another important source of contamination as they are used in completion fluids water wet muds and are emulsified in oil wet muds brine components impact metal contents of petroleum fluid tests and complicate the determination of formation water compositions despite potential problems introduced by these additives successful strategies can be devised to accurately access key geochemical and engineering parameters

heterogeneity of oil composition within a reservoir as a reflection of accumulation history abstract the unaltered petroleums of a small oil field in the f r germany reveal pronounced spatial heterogeneities in bulk and molecular composition over most of the field area the oil in high porosity high permeability sand intervals bears a higher proportion of saturated hydrocarbons and has a higher maturity chemical signature as compared to oils occupying lower porosity lower permeability zones for all sands with less than about 13 porosity a regular relationship was observed between oil composition and porosity permeability with a decrease of the latter petrophysical properties increasingly lower chemical maturities and increasingly different bulk chemical compositions lower proportions of saturated hydrocarbons and higher proportions of nso compounds were recorded maximum contrasts measured for chemical maturities are e g 0 63 versus 0 82 vitrinite reflectance equivalents rc values calculated on the basis of the methylphenanthrene index according to radke and welte 1983 0 31 versus 0 84 for the ratio of triaromatic to mono plus triaromatic steroid hydrocarbons and 0 38 versus 0 47 for the 20s 20s 20r ratio of c29 5 h 14 h 17 h steranes these spatial heterogeneities in the composition of the oils are interpreted to reflect 1 i successive stages of trap filling due to episodes of increasing burial and maturation of the relevant source rocks in combination with 2 ii low rates of in reservoir mixing of these individual oil charges by convection or diffusion recognition of compositional heterogeneities within the oil column of individual fields may not only provide a basis for the reconstruction of reservoir filling history but may also have important implications for improving petroleum production

the ischia volcanic island southern italy inferences from potential field data interpretation abstract in this paper we present a study of the structural setting of the volcanic island of ischia by the analysis and interpretation of high resolution aeromagnetic and self potential data recently acquired over the island the magnetic data allowed us to locate the main anomaly sources and lineaments of the island and its offshore surroundings while the self potential sp data provided information on both the structural pattern of the resurgent caldera and the high temperature fluid circulation an inversion of the acquired magnetic and sp data and a joint modelling of the magnetic data and of a previous gravity data set along a sw ne profile allowed us to build a model of the island the model is characterized by the presence of an igneous very likely trachytic structure whose top is located at 1200 1750 m b s l such a body possibly formed by several neighbouring intrusions has a density contrast with the pyroclastic cover of about 0 4 gr cm 3 and its central western part below mt epomeo seems to be demagnetized the demagnetization should be connected to the high geothermal gradient measured in this portion of the island and may be due to hydro chemical alteration processes and or to the possible presence of partially melted spots within the intrusion our outcome is consistent with the results of previous geophysical geo volcanological and geothermal studies

accuracy of interpolation techniques for the derivation of digital elevation models in relation to landform types and data density one of the most important scientific challenges of digital elevation modeling is the development of numerical representations of large areas with a high resolution although there have been many studies on the accuracy of interpolation techniques for the generation of digital elevation models dems in relation to landform types and data quantity or density there is still a need to evaluate the performance of these techniques on natural landscapes of differing morphologies and over a large range of scales to perform such an evaluation we investigated a total of six sites three in the mountainous region of northern laos and three in the more gentle landscape of western france with various surface areas from micro plots hillslopes and catchments the techniques used for the interpolation of point height data with density values from 4 to 109 points km2 include inverse distance weighting idw ordinary kriging ok universal kriging uk multiquadratic radial basis function mrbf and regularized spline with tension rst the study sites exhibited coefficients of variation cv of altitude between 12 and 78 and isotropic to anisotropic spatial structures with strengths from weak with a nugget sill ratio of 0 8 to strong 0 01 irrespective of the spatial scales or the variability and spatial structure of altitude few differences existed between the interpolation methods if the sampling density was high although mrbf performed slightly better however at lower sampling densities kriging yielded the best estimations for landscapes with strong spatial structure low cv and low anisotropy while rst yielded the best estimations for landscapes with low cv and weak spatial structure under conditions of high cv strong spatial structure and strong anisotropy idw performed slightly better than the other method the prediction errors in height estimation are discussed in relation to the possible interactions with spatial scale landform types and data density these results indicate that the accuracy of interpolation techniques for dem generation should be tested not only in relation to landform types and data density but also to their applicability to multi scales

assessing biomarker syngeneity using branched alkanes with quaternary carbon baqcs and other plastic contaminants biomarker molecules are valuable for the elucidation of ancient microbial ecosystems and the characterization of petroleum source rocks for such studies acquisition of reliable hydrocarbon data and proof of their syngeneity are essential however contamination of geological samples with anthropogenic petroleum products during drilling storage and sampling can be particularly problematic because these hydrocarbons may over print an original indigenous biomarker profile to evaluate the extent of contamination of drill core and outcrop material we studied the distribution of hydrocarbons in 26 rocks from different locations in the world all rocks had petroleum products on their exterior surfaces twenty two samples also contained surficial hydrocarbons derived from polyethylene plastic including branched alkanes with quaternary carbon centers baqcs and alkylcyclopentanes with pronounced even over odd carbon number preference using three examples from the paleoproterozoic tawallah and mcarthur groups in northern australia we show how indigenous biomarkers can be recognized by comparing hydrocarbon distributions between exterior rock surfaces and the rock interior and how infiltration of allochthonous hydrocarbons can be assessed through the spatial distribution of characteristic polyethylene derived hydrocarbons in the rock the methods outlined in this paper give confidence in the interpretation of biomarkers in particularly sensitive applications such as the first occurrences of certain organisms in the geological record and the provenance of organic matter in meteorites

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

filtering spatial error from dems implications for morphological change estimation abstract scour and fill estimation from digital elevation model dem subtraction or differencing is an increasingly common technique in morphological and sediment transport investigations the technique is commonly used to estimate scour and fill volumes and to produce scour and fill maps that provide process based information to geomorphologists accounting for sources of uncertainty within the dem is of critical importance dem error is spatially variable and has a tendency to be greater at breaks of slope such as bar and bank edges in the past however this has been achieved using a uniform error metric across the dem resulting in over conservative estimates of error in turn this has led to over conservative scour and fill volumes and incorrect process interpretation this paper applies a new approach that permits assessment of spatially distributed error across a dem the method is tested on a sequence of field surveys of the gravel bed river nent cumbria uk the results demonstrate some dramatic differences application of conventional techniques that account for mean error across a dem led to a 15 and 31 underestimation in scour and fill volumes respectively between july and october 1998 whilst for the october 1998 june 1999 subtraction 31 and 13 of scour and fill were underestimated respectively use of a uniform error across a surface captures less change in comparison to a spatially distributed approach furthermore the changes captured using a uniform error are biased toward areas of the channel that have more local topographic variability such as bar and bank edges in contrast the use of a spatially distributed approach provides information on change from flatter surfaces such as bar tops that would otherwise be missed this study also demonstrates that estimates of morphological change can be misleading in the absence of an error filter where the raw survey data is available it is recommended that sediment budgeting studies take account of the spatial variability of error in each dem involved in the subtraction

geomorphometric analysis for characterizing landforms in morelos state mexico landforms can be described and quantified into simple relief elements by parametrization of digital elevation model dem in this research we investigate the use of morphometric parameters and a new classification scheme to characterize selected elemental forms associated with landforms we apply and test this methodology on a geomorphologically diverse region located in central mexico these simple elements are known as morphometric classes and include ridge plane channel pit peak and pass these classes correspond to real entities and are of practical significance the morphometric classes were grouped according to their areal parameters ridge plane and channel and pointed parameters pit peak and pass which can be used to form the basis of a system of characterization and classification of landforms landform elements display statistically significant compositional differences with respect to their proportions of morphometric classes this in turn can be plotted onto a diagram of characterization and classification known as a double ternary diagram dtd which comprises both areal and pointed parameters and any combination thereof the dtd is useful for studying geomorphological processes wherein areal and point values and properties have expressions which are topographically quantifiable

incorporating the effect of dem resolution and accuracy for improved flood inundation mapping summary topography plays a major role in determining the accuracy of flood inundation areas however many areas in the united states and around the world do not have access to high quality topographic data in the form of digital elevation models dem for such areas an improved understanding of the effects of dem properties such as horizontal resolution and vertical accuracy on flood inundation maps may eventually lead to improved flood inundation modeling and mapping this study attempts to relate the errors arising from dem properties such as spatial resolution and vertical accuracy to flood inundation maps and then use this relationship to create improved flood inundation maps from coarser resolution dems with low accuracy the results from the five stream reaches used in this study show that water surface elevations wse along the stream and the flood inundation area have a linear relationship with both dem resolution and accuracy this linear relationship is then used to extrapolate the water surface elevations from coarser resolution dems to get water surface elevations corresponding to a finer resolution dem application of this approach show that improved results can be obtained from flood modeling by using coarser and less accurate dems including public domain datasets such as the national elevation dataset and shuttle radar topography mission srtm dems the improvement in the wse and its application to obtain better flood inundation maps is dependent on the study reach characteristics such as land use valley shape reach length and width application of the approach presented in this study on more reaches may lead to development of guidelines for flood inundation mapping using coarser resolution and less accurate topographic datasets

the uppermost crust structure of ischia southern italy from ambient noise rayleigh waves abstract ambient noise measurements were performed at the island of ischia southern italy along alignments of 2 4 7 km by using two three component seismic stations synchronous noise recordings of 2 20 h were cross correlated over 20 30 s windows stacked and iteratively band pass filtered to enhance the dispersive wave trains frequency time analysis was performed on the vertical and radial components of cross correlations and the fundamental mode rayleigh wave group velocity was obtained validation of the dispersion data was possible with those obtained from an earthquake recording along a close path the non linear inversion of average rayleigh wave group velocity dispersion curves along 13 paths receiver inter distances allowed the definition of shear wave velocity models in the uppermost 1 2 km of the crust the correlation of vs profiles vs depth and drilling stratigraphy allowed to attribute vs lower than 1 km s to tuffs and vs of 1 41 km s to very fractured lavas higher vs are found in the central area of the island in correspondence of the resurgent area the top of the trachytic lava basement with vs of 2 2 2 4 km s and density of 2 3 g cm3 is about 0 6 0 7 km deep b s l in the centre of ischia below altered very fractured lava or thermally altered tuff

geospatial analysis of a coastal sand dune field evolution jockey s ridge north carolina preservation and effective management of highly dynamic coastal features located in areas under development pressures requires in depth understanding of their evolution modern geospatial technologies such as lidar real time kinematic gps and three dimensional gis provide tools for efficient acquisition of high resolution data geospatial analysis feature extraction and quantification of change these techniques were applied to the jockey s ridge north carolina the largest active dune field on the east coast of the united states with the goal to quantify its deflation and rapid horizontal migration digitized contours photogrammetric lidar and gps point data were used to compute a multitemporal elevation model of the dune field capturing its evolution for the period of 1974 2004 in addition peak elevation data were available for 1915 and 1953 analysis revealed possible rapid growth of the dune complex between 1915 1953 followed by a slower rate of deflation that continues today the main dune peak grew from 20 1 m in 1915 to 41 8 m in 1953 and has since eroded to 21 9 m in 2004 two of the smaller peaks within the dune complex have recently gained elevation approaching the current height of the main dune steady annual rate of main peak elevation loss since 1953 suggests that increase in the number of visitors after the park was established in 1974 had little effect on the rate of dune deflation horizontal dune migration of 3 6 m yr in southerly direction has carried the sand out of the park boundaries and threatened several houses as a result the south dune section was removed and the sand was placed at the northern end of the park to serve as a potential source sand fencing has been an effective management strategy for both slowing the dune migration and forcing growth in dune elevation understanding the causes of the current movements can point to potential solutions and suggest new perspectives on management of the dune as a tourist attraction and as a recreation site while preserving its unique geomorphic character and dynamic behavior d 2005 elsevier b v all rights reserved

a robust interpolation method for constructing digital elevation models from remote sensing data abstract a digital elevation model dem derived from remote sensing data often suffers from outliers due to various reasons such as the physical limitation of sensors and low contrast of terrain textures in order to reduce the effect of outliers on dem construction a robust algorithm of multiquadric mq methodology based on m estimators mq m was proposed mq m adopts an adaptive weight function with three parts the weight function is null for large errors one for small errors and quadric for others a mathematical surface was employed to comparatively analyze the robustness of mq m and its performance was compared with those of the classical mq and a recently developed robust mq method based on least absolute deviation mq l numerical tests show that mq m is comparative to the classical mq and superior to mq l when sample points follow normal and laplace distributions and under the presence of outliers the former is more accurate than the latter a real world example of dem construction using stereo images indicates that compared with the classical interpolation methods such as natural neighbor nn ordinary kriging ok anudem mq l and mq mq m has a better ability of preserving subtle terrain features mq m replaces thin plate spline for reference dem construction to assess the contribution to our recently developed multiresolution hierarchical classification method mhc classifying the 15 groups of benchmark datasets provided by the isprs commission demonstrates that mq m based mhc is more accurate than mq l based and tps based mhcs mq m has high potential for dem construction

drilling conditions making wells unsuitable for fluid inclusion studies on drill cuttings a fluid inclusion study conducted on a well in the northern north sea showed a remarkable correlation between fluid inclusion stratigraphy responses and depths of drilling bit changes further investigation of the well data suggested that extreme temperatures occasionally had been generated at the bit sediment interface during drilling cracking of larger organic molecules to an abundance of smaller ones and trapping of these in inclusions formed by supercooling of partly melted sediment explain the correlation not all wells are consequently suitable for fluid inclusion screening analyses thus before initiating fluid inclusion studies wells that have experienced intense heat during drilling should be identified and avoided

supervised landform classification of northeast honshu from dem derived thematic maps this paper proposes a quantitative method to classify landforms using four morphometric parameters from dem derived thematic raster maps of slope and topographic openness because the different surficial processes and stages in the evolution of slopes create landscapes with different shapes these parameters may lead to a genetic interpretation of topography the raster maps of slope and topographic openness were constructed for northeast honshu japan from 50 m dems the mean and standard deviation of morphometric parameters within a 3050m by 3050m moving window on the raster maps were calculated the results for some training areas show that constructional depositional and erosional landforms with different relief have different morphometric characteristics a supervised landform classification for northeast honshu using the knowledge from the training areas revealed a ladder geomorphological structure composed of high mountains ranges and volcanoes the close relationship between the ladder geomorphological structure and volcano distribution indicates that the structure reflects the magmatic plumbing system from the upper mantle to the crust of the northeast honshu arc

the interaction between regional and local tectonics during resurgent doming the case of the island of ischia italy abstract the volcanic island of ischia is located on the tyrrhenian margin of central italy characterized by plio quaternary nw se and ne sw trending extensional fractures ischia displays a resurgent dome uplifted by at least 800 m in the last 33 ka remote sensing and field data have been collected to study the structural setting of the island the deformation pattern associated with resurgence and the superimposition of the regional and the resurgence induced stress fields nw se and ne sw extensional fracture systems predominate throughout the island and around the resurgent block suggesting a relationship with the regional extensional structures these systems were formed before resurgence and were partly reactivated during resurgence the reactivation of pre existing regional systems during resurgence confined the extent of the uplifted area n s and e w trending systems have been found exclusively at the borders of the dome and are interpreted as being induced by resurgence the topmost resurgent block shows an octagonal shape in map view and is tilted at an angle of 15 around a ne sw trending horizontal axis the block is partly bordered by high angle inward dipping regional faults more than 90 in volume of the volcanic products coeval with resurgence on ischia have been erupted outside the resurgent block area suggesting that the resurgence process locally replaced volcanic activity in the last 33 ka

dem based identification of fluvial knickzones and its application to japanese mountain rivers stream gradients of mountain bedrock rivers in central japan were examined using gis and 50 m digital elevation models to discuss the distribution of knickzones the gradients are classified into local and trend types based on the measurement lengths the transition rate from the local to trend gradients i e the decreasing rate of gradient with increasing measurement length is then obtained as the indicator of relative steepness of a river segment which permits the objective identification of fluvial knickzones the identified knickzones occur widely in the study area and indicate that the knickzone is one of the common landforms in japanese mountain rivers the knickzones are more abundant in steep upstream reaches of the rivers subjected to active erosion and rapid rock uplift this suggests a hydraulic origin of the knickzones which is similar to step pool morphology but on a much larger scale some knickzones in piedmont areas can be on the other hand consistent with tectonic faulting at the mountain foot although some influences of volcanic activities on the formation of knickzones are observed regional lithology seems to exert a relatively weak influence on the abundance of knickzones knickzones are more consistent with other local mechanisms of fluvial erosion including reach scale processes

seismically induced landslide susceptibility evaluation application of a new procedure to the island of ischia campania region southern italy in this paper we present an approach for evaluating landslide susceptibility in seismic areas it is known that earthquake induced landslide susceptibility is related to several often interplaying factors nevertheless an effective grade 2 zonation should be characterized by a good balance between simplicity quickness and reliability the gis based procedure we present employs only three factors that we believe are the most significant in this susceptibility assessment the type of outcropping rocks soils the slope angle and the mcs intensity the local annual precipitation certainly an essential factor is considered here as a parameter whose seasonal pattern is constant in time and space each of the three parameters is expressed as a significance percentage and the resulting seismic landslide susceptibility level of an area is given by the average of the significances of the first two factors multiplied by the significance of the third factor the procedure was set and tested on the volcanic island of ischia southern italy which was affected by several historical earthquake induced landslides the results of this susceptibility zonation test at ischia show a very good match between the distribution of the sources of historical landslides and the areas we identified as the most susceptible ones

33 000 yr k ar dating of the volcano tectonic horst of the isle of ischia gulf of naples the gulf of naples corresponds to a tectonic sink connected with recent volcanic activity in the south campanian area phlegrean fields ischia and vesuvius at its extreme northwest the isle of ischia was early recognized as a volcano tectonic horst by rittmann1 previous data2 concluded that its uplift ended around 300 000 yr and that the green tuff formation of which it is predominantly composed had an age of some 700 000 yr but tectonic and morphological studies together with original tephrostratigraphical observations on the slope of the horst led us to do some new k ar datings these revealed that the 780 m uplift of the horst from the sea level is younger than 33 000 yr the green tuff which was considered to be the oldest volcanic unit in the island is now dated at 56 000 yr its eruption following the dismantlement of a first volcanic complex now dated as not older than 130 000 yr

analysis of lidar derived topographic information for characterizing and differentiating landslide morphology and activity abstract this study used airborne laser altimetry lidar to examine the surface morphology of two canyon rim landslides in southern idaho the high resolution topographic data were used to calculate surface roughness slope semivariance and fractal dimension these data were combined with historical movement data global positioning systems gps and laser theodolite and field observations for the currently active landslide and the results suggest that topographic elements are related to the material types and the type of local motion of the landslide weak unconsolidated materials comprising the toe of the slide which were heavily fractured and locally thrust upward had relatively high surface roughness high fractal dimension and high vertical and lateral movement the body of the slide which predominantly moved laterally and consists mainly of undisturbed older canyon floor materials had relatively lower surface roughness than the toe the upper block consisting of a down dropped section of the canyon rim that has remained largely intact had a low surface roughness on its upper surface and high surface roughness along fractures and on its west face unrelated to landslide motion the upper block also had a higher semivariance than the toe and body the topographic data for a neighboring older and larger landslide complex which failed in 1937 are similarly used to understand surface morphology as well as to compare to the morphology of the active landslide and to understand scale dependent processes the morphometric analyses demonstrate that the active landslide has a similar failure mechanism and is topographically more variable than the 1937 landslide especially at scales 20 m weathering and the larger scale processes of the 1937 slide are hypothesized to cause the lower semivariance values of the 1937 slide at smaller scales