sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

the northeast brazilian rift system the northeast brazilian rift basins provide important data critical to the understanding of continental rifting processes associated with the opening of the south atlantic these basins represent the locus of intersection of the southern and equatorial branches and some basins yield substantial chronostratigraphic data that constrain the temporal and spatial interaction of the rift phases similar data are not found in its counterpart in africa especially for the neocomian these early cretaceous rift basins of northeast brazil illustrate key three dimensional geometries of intracontinental rift systems mainly controlled by the basement structural framework during the main rift phase syn rift ii neocomian early barremian extensional deformation was distributed over three main rift axes 1 the gabon sergipe alagoas gsa trend 2 the reconcavo tucano jatoba rtj trend and 3 the cariri potiguar cp trend during this phase extensional deformation jumped west from the easternmost basins gsa trend to a series of ne trending intracratonic basins rtj and cp trends characterized by a set of asymmetric half grabens separated by basement highs transfer faults and or accommodation zones these basins are typically a few tens of kilometers wide and trend ne sw roughly perpendicular to the main extension direction during the neocomian preexisting upper crustal weakness zones like the dominantly ne sw trending shear zones of the brazilian pan african orogeny controlled the development of intracrustal listric normal faults internal transverse structures such as transfer faults and accommodation zones were also controlled by the local basement structural framework the megashear zones of pernambuco brazil and ngaundere africa seem to have behaved like a huge accommodation zone accommodating extensional deformation along the rtj gsa trends with simultaneous extension along the cp trend during the late barremian syn rift phase iii a significant change in rifting kinematics occurred when the cp trend was aborted and major rifting initiated at the equatorial branch during the aptian while the equatorial branch and benue trough africa experienced the main rift phase the rtj trend was aborted and the gsa trend developed a transitional phase between the rift and drift stage the gsa trend and the offshore potiguar basin represent the site of continued evolution into passive margin basins following the main rift episode

geomorphology and natural hazards in karst areas a review 1 introductionsince human beings started to colonise the world slowly migrat ing in multiple directions from the african rift and ultimatelyreaching the southernmost territories of the americas they haveinteracted with the natural environment using its resources and suf fering from its hazardous processes survival of mankind was possiblethanks to its ability to adapt to an ever changing environment and itscapability to learn and communicate the new ndings from the ear liest times geomorphic features and processes were an essential partof social survival crozier et al 2011 in karst terrains caves wereused as shelters as well as burial and sacred places playing an instru mental role in the day to day struggle for survival especially duringthe ice ages fig 1 spectacular karst landmarks such as big cave en trances blue karst springs deep collapse sinkholes cenotes or rockarches just to name a few have often become part of the naturaland supernatural heritage of our ancestors in prehistoric times the human impact on the karst environmentwas very limited like the probability of properties and people beingdamaged by karst processes e g subsidence ooding both impactsandhazardsinkarstterrainshaveincreaseddramaticallyover thelasttwo centuries along with the exponential increase in population andour capability to modify the natural environment largely related tothe economic and technological development of the societies an in creasing number of scientists consider that humans are nowadaysthe most effective geomorphic agent and a prime factor in landscapeevolution zalasiewicz et al 2010 price et al 2011 in fact the for mal de nition of the anthropocene as a new epoch of the geologicaltime scale characterised by a signi cant and global human impact onthe earth s ecosystems is being debated at the present time around25 of the earth s population lives on or nearby karst areas ford andwilliams 2007 and the increasing exploitation of karst resources such as water and building material is leading to severe environmen tal impacts and unsustainable situations drew and hotzl 1999 gunn 2004 unfortunately the number of karst areas affected bywater pollution landscape degradation and other impacts is growingveryrapidly additionally thedamagecausedbyhazardouskarstpro cesses especially subsidence sinkholes beck 2003 waltham et al 2005 gutierrez et al 2008a will most likely keep on increasing exposed human elements augment and anthropogenic changes inthe karst systems frequently result in hazard enhancement karstgeomorphologists and hydrologists can play a decisive role in pre venting natural disasters in karst areas particularly those inducedby human activities dams with leakage and sinkhole problems milanovic 2000 cooper and gutierrez 2011 mines and tunnelsaffected by ooding and subsidence li and zhou 1999 autin 2002 casagrandeet al 2005 luchaetal 2008 high speedrailwaysbuilt in sinkhole prone areas guerrero et al 2008 or developmentof sinkholes at huge rates induced by lake level yechieli et al 2006 or water table sprynskyy et al 2009 declines the importance of properly managing karst areas and mitigatingthe detrimental effects caused by human activities on these inherentlysensitive environments has been boosted by a series of conferencesand projects since the early 1990s ford 1993 williams 1993 pariseet al 2008 2009 raising public awareness on the need to protectour endangered natural resources especially in developed countries has promoted the production of karst speci c environmental impactassessments veni 1999 recently severalapproacheshavebeenpro posedtoassessthedegreeofhuman induceddisturbanceinkarstareas van beynen and townsend 2005 calo and parise 2006 de waele 2009 north et al 2009 although these studies are essential for apropermanagementofthekarstresources theymaybefutileifnotfol lowed by adequate administrative decisions and regulations 2 karst geomorphology2 1 karst processeskarst is characterised by the predominance of rock dissolution overmechanical erosion and is typical of present temperate cold andwarm and tropical environments ford and williams 2007 in karstterrains surface and subsurface geomorphology and hydrology arelargely governed by dissolution of carbonate and or evaporite rocks in the most classical common situation surface waters acidi ed byco

survey of hydrothermally generated petroleums from the guaymas basin spreading center abstract the guaymas basin spreading center and hydrothermal system are generating an assortment of petroleum like bitumens by pyrolysis of organic matter in the overlying uncosolidated sediments samples collected by d s v alvin from hydrothermal fields in the southern trough exhibit large variations in the quantities and character of the solvent soluble organic materials various pyrolytic regimes combined with fluctuating thermal gradients and migration velocities may impart a compositional fractionation possibly by differential gaseous solubilization and hydrodynamic alteration of the multi component fluids the data suggest that differential condensation solidification biodegradation and water washing cause selective removal of components at the seabed many hydrothermal oils are unlike normal reservoir petroleums because they contain significant concentrations of polar material due to their rapid genesis and transport and probable solubilization or advection of polar immature components the biomarker distributions confirm high temperature pyrolysis at depth with variable entrainment of less thermally mature bitumens during transport data for shallow core samples from the northern trough indicate that those locations experienced variable influx predominantly volatiles of a low temperature pyrolysate

recent developments in surface and subsurface karst geomorphology an introduction abstract where dissolution processes of bedrock dominate peculiar morphologies develop and overrule all landforms controlled by other surface processes pure karst landscapes are present in many parts of the world but most of the time landscapes are shaped by a multitude of processes the comprehension of the dissolution processes that act both at the surface and underground has developed rapidly in the last half century although major achievements had already been reached at the end of the xixth century this special issue gives an overview of some of the most recent developments in surface and subsurface karst geomorphology and reviews where further studies should be fostered

hydrothermal petroleum genesis migration and deposition in guaymas basin gulf of california hydrothermal activity and seabed mounds have been explored in guaymas basin by the deep sea drilling project dsdp piston coring dredging and diving with the deep submersible research vessel dsrv alvin sedimentary organic matter derived primarily from immature degraded microbial detritus is easily converted to petroleum under the hydrothermal regime these petroleums are mature and migrate in the fluids and by diffusion to the seabed the fluid migration is aided by near critical aqueous solution and supercritical carbon dioxide and hydrocarbons petroleum compositions vary from condensates to naphthenic to waxy all with significant amounts of asphaltenes and hydrothermal products such as olefins and toxic polynuclear aromatic hydrocarbons pah the heavy ends condense at the seabed depositing mainly as a cement with the sulfides and other minerals and to a lesser extent as entrapped oil and crystalline wax in vugs and conduits of the mounds the pah are high temperature resynthesis aromatiza

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

polycyclic aromatic hydrocarbons pahs in late eocene to early pleistocene mudstones of the sylhet succession ne bengal basin bangladesh implications for source and paleoclimate conditions during himalayan uplift abstract distribution and possible sources of polycyclic aromatic hydrocarbons pahs have been investigated in 23 late eocene to early pleistocene mudstones from the sylhet succession of the northeastern bengal basin bangladesh paleoclimatic conditions in the southern himalaya region throughout the himalayan uplift were reconstructed based on combustion derived pahs and aromatic land plant derived biomarkers phenanthrene fluoranthene fla pyrene py benz a anthracene baan chrysene triphenylene chry tpn benzofluoranthenes bflas benzo e pyrene bepy benzo a pyrene bapy perylene pery indeno 1 2 3 cd pyrene inpy benzo ghi perylene bghip coronene cor and retene ret were the identified pahs fla fla py ratios 0 5 and inpy inpy bghip 0 2 from almost all sylhet samples suggest occurrence of natural wildfires low contents of baan and bapy indicate decomposition by long exposure to sunlight before sedimentation or early diagenetic weathering increased cor inpy and bghip contents suggest occurrence of larger high temperature wildfires correlation coefficients of the pahs and p values for statistical hypothesis testing showed that the positive and negative correlations within the pahs may be indicative of high or low temperatures in wildfires fungi derived pery showed negative correlations with py r 0 67 p 4 6 10 4 and fla r 0 56 p 5 0 10 3 but not with cor bflas inpy and bghip based on the correlation coefficients for all pahs and their p values five statistical groups py fla cor bflas inpy bghip baan chry tpn bapy pery and ret were recognized these groups are probably correlated with origins and depositional processes according to the results the sylhet succession was deposited in three differing paleoclimatic regimes 1 first phase late eocene to early miocene early to middle stage of himalayan uplift high contents of combustion derived pahs fla py and bepy significant gymnosperm derived ret and low pery abundances in the jaintia and barail groups indicate arid climatic conditions although wildfires could often occur 5 or 6 ring combustion pahs cor inpy and bghip contents are low suggesting that the wildfires were relatively low temperature 2 second phase middle to late miocene middle to late stage of himalayan uplift combustion derived pahs and fungi derived pery were dominant in the surma group the climate was arid to humid and seasonal with a dry season giving conditions suitable for combustion abundant fla bflas bepy cor inpy and bghip imply high temperatures in large wildfires however frequency of the wildfires decreased because of wet climate 3 third phase late miocene to pleistocene late stage of himalayan uplift moderate to high pery contents and low fla py and bepy abundances in the tipam and dupitila groups indicate establishment of more humid climate inpy bghip cor bflas and bapy were predominant intensified humid and seasonal climate arising from the himalayan monsoon decreased the incidence and frequency of general wildfires but increased the ratio of large to small wildfires

correlation between rock fabrics and physical properties of carbonate reservoir rocks three carbonate core samples from an oil and gas reservoir of the nw german basin were chosen to study the correlation between rock fabrics and physical properties of reservoir rocks detailed fabric analyses and texture investigations were carried out as well as laboratory measurements of different physical properties e g density porosity permeability electrical conductivity seismic compressional and shear wave velocities although the three core samples come from a similar depositional facies they show great differences in the occurrence and three dimensional distribution of the rock fabric elements these heterogeneities are the result of various diagenetic and tectonic processes for the correlation between the rock fabrics and the physical properties four main rock fabric types have to be considered a major constituents e g fossils ooides peloides and crystals b pore space with different pore types c fractures and d stylolites the results of the correlation clearly show that the values and anisotropies of the petrophysical properties are fairly related to the observed fabric elements with their different arrangements spatial distributions and preferred orientations these results also provide a fundamental understanding of the petrophysical responses such as seismics to the different geological features e g fractures and their dynamic changes with pressure which can be converted to different depths the knowledge gained from such correlations may lead to an improved interpretation of geophysical data for hydrocarbon exploration and production and therefore to an advanced reservoir characterization

variability in the mean latitude of the atlantic intertropical convergence zone as recorded by riverine input of sediments to the cariaco basin venezuela abstract changes in the strength and position of the intertropical convergence zone itcz are an important component of climate variability in the tropical atlantic the cariaco basin located on the northern margin of venezuela is sensitive to tropical atlantic climate change and its sediments provide a record of past itcz behavior today the cariaco basin experiences two distinct seasons that reflect the annual migration of the atlantic itcz between january and march when the itcz lies south of the equator northeasterly trade winds sit directly over cariaco basin and strong coastal upwelling and dry conditions dominate beginning in june july as the itcz moves north local rainfall reaches a maximum and the upwelling diminishes or disappears here we summarize new and previously published data on the river derived terrigenous fraction of cariaco basin sediments as well as comparisons to other paleoclimate records which together suggest a coherent climatologic response in the tropical atlantic triggered by a pattern of itcz migration that mimics the seasonal cycle during periods of cooler north atlantic ssts on time scales ranging from the little ice age to the younger dryas to the cold stadials of the last glacial decreased detrital delivery to cariaco basin from local rivers suggests a southward shift in the mean latitudinal position of the itcz during warm interstadials and periods of holocene and deglacial warmth northward shifts in itcz position and its belt of convective rainfall are inferred from increased detrital delivery to the basin whether the rapid shifts in itcz position and precipitation recorded by cariaco basin sediments and other regional records reflect a response to forcing originating in the high latitude atlantic or to forcing potentially sourced in the tropics is a key question yet to be fully answered

karst landforms revealed at various scales using lidar and uav in semi arid brazil consideration on karstification processes and methodological constraints abstract this paper analyzes different types of karst landforms and their relationships with fracture systems sedimentary bedding and fluvial processes we mapped karst features in the cretaceous carbonates of the jandaira formation in the potiguar basin brazil we used high resolution digital elevation models acquired using lidar and aerial orthophotographs acquired using an unmanned aerial vehicle uav we grouped and described karst evolution according to scale and degree of karstification these degrees of karst evolution are coeval fractures are opened by dissolution forming vertical fluid conduits whereas coeval dissolution occurs along horizontal layers this conduit system acts as pathways for water flow the enlargement of conduits contributes to the collapse of blocks in sinkholes and expansion of caves during an intermediate degree of karstification propagation of dissolution can cause the coalescence of sinkholes and the capture of small streams fluvial processes dominate karst dissolution at an advanced degree of karstification comparisons with previously published ground penetrating radar gpr borehole and seismic surveys in sedimentary basins indicate that these structures can be partially preserved during burial

cenozoic uplift and erosion of structural landforms in ne brazil abstract we investigate the evolution of uplifted areas in ne brazil which have been considered as residual landforms the study focuses on the 130 km long 41 km wide pereiro massif pm the structural control and the age of this uplift are the problems addressed in this study we carried out topographic analysis geomorphological and geological mapping detailed structural analysis and optically stimulated luminescence osl dating to address these problems the pm is bounded and cut by a system of steeply dipping normal and strike slip faults which control the morphology of the massif and associated sedimentary basins the maximum uplift rate of the pm is 34 m my 1 as constrained by the age of flat topography capped by miocene laterite which represents the previous peneplain subsequently uplifted by ca 600 m the minimum uplift rate is 13 m my 1 as constrained by fission track dating of differential crustal block movements across a nearby fault in the quaternary erosion occurred mainly by fault controlled scarp retreat under semi arid conditions with the formation of colluvial deposits along fault scarps and alluvial deposits in the low plains these deposits are now dated between 46 and 0 4 ka with a peak in sediment deposition in the pleistocene holocene transition it is concluded that the pm is a system of horsts and grabens that have been active in the cenozoic

effects of weathering on organic matter i changes in molecular composition of extractable organic compounds caused by paleoweathering of a lower carboniferous tournaisian marine black shale abstract a detailed bulk and molecular study on paleoweathering of a lower carboniferous tournaisian black shale from the kowala quarry in the holy cross mountains of poland revealed significant changes in total organic carbon toc total sulfur ts and extract compositions paleoweathering resulted in a 97 decrease in toc and total loss of sulfur as well as changes in carbonate contents extract yields and percentage yields of the organic fractions pyrite framboids which are used extensively in paleoecological studies decreased considerably in the partially weathered zone and totally vanished in the weathered zone the decrease in toc is accompanied by a pronounced reduction of organic compound concentrations but the degradation range differs in the individual weathering zones here we show that less stable compounds such as low molecular weight aromatics e g methylnaphthalenes dibenzofuran and dibenzothiophene isorenieratane and its diagenetic products or maleimides decrease significantly or disappear already in the partially weathered zone while the more stable polycyclic aromatic hydrocarbons pahs decrease 90 only in the weathered and highly weathered zones besides the organic matter om content the influence of paleoweathering on the distributions of organic compounds is important in the context of paleoenvironment source and maturity interpretations almost all sterane and triterpane biomarker parameters change their values in the highly weathered zone but some ratios e g the 2 meh index are almost totally resistant to change the aryl isoprenoid ratio air values decrease gradually with weathering this modifies completely the potential interpretation of the nature of the photic zone anoxia in addition to degradation of om some pahs like benzo b fluoranthene increase in concentration in the partially weathered zone due to their formation from phenyl derivatives the correct recognition of paleoweathering in outcrop and drill core samples aids in the proper interpretation of biomarker parameters and contributes to a better understanding of the processes which took place during weathering

divergent evolution in fluviokarst landscapes of central kentucky central kentucky is characterized by a mixture of karst and uvial features typically manifested as mosaic of karst rich channel poor krcp and channel rich karst poor crkp environments at the regional scale the location and distribution of krcp and crkp areas are not always systematically related to structural lithological topographic or other controls this study examines the relationship of krcp and crkp zones along the kentucky river gorge area where rapid incision in the last 1 5 million years has lowered local base levels and modi ed slopes on the edge of the inner bluegrass plateau at the scale of detailed eld mapping on foot within a 4 km2 area the development of karst and uvial features is controlled by highly localized structural and topographic constraints and can be related to slope changes associated with retreat of the kentucky river gorge escarpment a conceptual model of karst uvial transitions is presented which suggests that minor localized variations are suf cient to trigger a karst uvial or uvial karst switch when critical slope thresholds are crossed copyright 2004 john wiley sons ltd

diffraction imaging of sub vertical fractures and karst with full resolution 3d ground penetrating radar abstract vertical fractures with openings of less than one centimetre and irregular karst cause abundant diffractions in ground penetrating radar gpr records gpr data acquired with half wavelength trace spacing are uninterpretable as they are dominated by spatially undersampled scattered energy to evaluate the potential of high density 3d gpr diffraction imaging a 200 mhz survey with less than a quarter wavelength grid spacing 0 05 m 0 1 m was acquired at a fractured and karstified limestone quarry near the village of cassis in southern france after 3d migration processing diffraction apices line up in sub vertical fracture planes and cluster in locations of karstic dissolution features the majority of karst is developed at intersections of two or more fractures and is limited in depth by a stratigraphic boundary such high resolution 3d gpr imaging offers an unprecedented internal view of a complex fractured carbonate reservoir model analogue as seismic and gpr wave kinematics are similar improvements in the imaging of steep fractures and irregular voids at the resolution limit can also be expected from high density seismic diffraction imaging

the use of new elevation data srtm aster for the detection and morphometric quantification of pleistocene megadunes draa in the eastern sahara and the southern namib abstract new freely available digital elevation data derived from the shuttle radar topography mission srtm 3 and the advanced spaceborne thermal emission and reflection radiometer aster allow for the first time the use of area wide high resolution elevation models they are useful for various investigations especially in regions that are devoid of detailed topographic maps in this contribution the geomorphological sedimentological geochronological and archaeological results of the cologne collaborative research centre acacia are presented showing that the southern great sand sea of egypt eastern sahara is composed of a complex dune pattern of pleistocene megadunes draa and holocene dunes a conceptual model is presented suggesting draa formed by a strong unimodal trade wind regime that acted most probably as helical roll vortices the draa differ conspicuously in their dimensions and in their evolution from the smaller longitudinal dunes which arise from the recent bimodal wind regime first results of comparative investigations in the southern namib erg namibia yielded similar conditions and a synchronous landscape development based on these results the second part of the paper evaluates the elevation data for both regions with respect to their availability for the determination of draa and dunes and the morphometric quantification of the draa due to their different resolution srtm 3 90 m aster 30 m and their different sensor technology srtm 3 radar aster stereo data both models have assets and drawbacks but can complement each other with the calculation of geomorphometric parameters elevation slope the aster digital elevation model allows the location of the draa of the great sand sea of egypt the quantification of their spatial distribution size volume and consequently the holocene dune movement in conclusion the resolution of the aster elevation model is applicable for quantitative analyses of well defined morphological elements with altitudinal variations 40 50 m the volume estimation presented provides a tool for a realistic assessment of the sand mass balance of sand seas this is not possible with the srtm 3 model and generally impossible with both models if the altitudinal variation is

retrograde oxidation of hydrothermal precipitates and petroleum in escanaba trough sediments abstract three push cores obtained near a hydrothermal vent in the escanaba trough gorda ridge have been analyzed for interstitial water chemistry inorganic solids geochemistry and organic geochemistry the inorganic analyses indicate the study area has no present hydrothermal fluid flow but the presence of a high temperature mineral phase calcite precipitate representing a temperature range of 168 199 c indicates past hydrothermal activity the presence of weathered sulfides and an extensively weathered and oxidized hydrothemal petroleum is evidence for a retrograde oxidative weathering process occurring in the sediments

hydrothermally derived petroleum examples from guaymas basin gulf of california and escanaba trough northeast pacific ocean petroleum is associated with sulfide rich sediment at two active oceanic spreading axes in the northeast pacific ocean in the guaymas basin a spreading axis in the gulf of california petroleum having a wide range of compositions forms by hydrothermal alteration of organic matter in quaternary sediment composed mainly of marine diatomaceous ooze and muddy turbidites in escanaba trough at the southern end of the gorda ridge spreading axis offshore northern california petroleum is formed by hydrothermal processes acting on mainly terrigenous organic material in quaternary turbiditic river derived sediment comparisons of the distributions of hydrocarbons n alkanes isoprenoids terpanes steranes and aromatics show that chemical differences among four petroleum samp es are such that two samples from guaymas basin can be distinguished from two samples from escanaba trough distinguishing characteristics resulting from differences in sources include n alkane distributions and certain sterane ratios distinguishing characteristics resulting from differences in thermal histories of the organic matter include hopane and sterane epimer ratios and various distributions of polycyclic aromatic hydrocarbons these oils differ from conventionally derived petroleum in that they are admixtures of products generated over a wide range of thermal regimes and their generation expulsion and migration occurred simultaneously over an instantaneous geological time period the potential economic significance of hydrothermally derived petroleum is uncertain but the act that petroleum can form at active oceanic spreading axes adds a new facet to understanding the processes of petroleum generation expulsion and migration

digital terrain modeling abstract this article examines how the methods and data sources used to generate dems and calculate land surface parameters have changed over the past 25 years the primary goal is to describe the state of the art for a typical digital terrain modeling workflow that starts with data capture continues with data preprocessing and dem generation and concludes with the calculation of one or more primary and secondary land surface parameters the article first describes some of ways in which lidar and radar remote sensing technologies have transformed the sources and methods for capturing elevation data it next discusses the need for and various methods that are currently used to preprocess dems along with some of the challenges that confront those who tackle these tasks the bulk of the article describes some of the subtleties involved in calculating the primary land surface parameters that are derived directly from dems without additional inputs and the two sets of secondary land surface parameters that are commonly used to model solar radiation and the accompanying interactions between the land surface and the atmosphere on the one hand and water flow and related surface processes on the other it concludes with a discussion of the various kinds of errors that are embedded in dems how these may be propagated and carried forward in calculating various land surface parameters and the consequences of this state of affairs for the modern terrain analyst

petroleum associated with polymetallic sulfide in sediment from gorda ridge a sediment sample impregnated with asphaltic petroleum and polymetallic sulfide was dredged from the southern end of gorda ridge the escanaba trough off northern california within the offshore exclusive economic zone of the united states the molecular distributions of hydrocarbons in this petroleum show that it was probably derived from terrestrial organic matter in turbidite sediment filling the escanaba trough hydrothermal activity at the gorda ridge spreading center provided the heat for petroleum formation and was the source of fluids for sulfide mineralization

integrating airborne multispectral imagery and airborne lidar data for enhanced lithological mapping in vegetated terrain practical and financial constraints associated with traditional field based lithological mapping are often responsible for the generation of maps with insufficient detail and inaccurately located contacts in arid areas with well exposed rocks and soils high resolution multi and hyperspectral imagery is a valuable mapping aid as lithological units can be readily discriminated and mapped by automatically matching image pixel spectra to a set of reference spectra however the use of spectral imagery in all but the most barren terrain is problematic because just small amounts of vegetation cover can obscure or mask the spectra of underlying geological substrates the use of ancillary information may help to improve lithological discrimination especially where geobotanical relationships are absent or where distinct lithologies exhibit inherent spectral similarity this study assesses the efficacy of airborne multispectral imagery for detailed lithological mapping in a vegetated section of the troodos ophiolite cyprus and investigates whether the mapping performance can be enhanced through the integration of lidar derived topographic data in each case a number of algorithms involving different combinations of input variables and classification routine were employed to maximise the mapping performance despite the potential problems posed by vegetation cover geobotanical associations aided the generation of a lithological map with a satisfactory overall accuracy of 65 5 and kappa of 0 54 using only spectral information moreover owing to the correlation between topography and lithology in the study area the integration of lidar derived topographic variables led to significant improvements of up to 22 5 in the overall mapping accuracy compared to spectral only approaches the improvements were found to be considerably greater for algorithms involving classification with an artificial neural network the kohonen self organizing map than the parametric maximum likelihood classifier the results of this study demonstrate the enhanced capability of data integration for detailed lithological mapping in areas where spectral discrimination is complicated by the presence of vegetation or inherent spectral similarities

combining digital elevation data srtm aster high resolution satellite imagery quickbird and gis for geomorphological mapping a multi component case study on mediterranean karst in central crete abstract remote sensing data have become more and more popular for geomorphological investigations because their steadily increasing level of detail and accessibility opens up new potentials in this context this paper examines the application and quality of digital elevation models srtm and aster dems high resolution satellite imagery quickbird and gis techniques for the detection and mapping of karst landforms mainly enclosed depressions at different scales in the ida mountains of central crete besides discussing methodological issues and evaluating suitability potentials we conducted an exemplary case study based on spatial analysis of the regional karst morphology different input datasets and processing methods are applied gis based analysis land cover classification raster calculations etc in order to carry out an area wide surveying and mapping of karst depressions the findings are supported and validated by auxiliary field studies due to the level of detail and occasional data errors an exclusive use of satellite imagery or digital elevation models for automatic karst landform detection performs insufficiently our results demonstrate that mapping karst features through remote sensing is significantly dependent on scale of interest existing environmental conditions and data quality a semi automatic data integration approach on the basis of digital datasets generated by combined satellite image processing and dem analysis yields the best results especially when indirect karst indicating variables like iron oxide rich sediments are included as detection criteria the multi component application presented in this paper provides a time saving and effective tool for meso to macro scale object detection and extensive study areas however the potential of fully automated karst feature mapping still needs to be explored in future work concerning the spatial dimension of karstification in central crete the gis based results allow differentiating further geomorphological characteristics e g by indicating a significant altitudinal change of karst forms within the study area size and shape of depressions dolines uvalas and poljes vary considerably due to the geological setting climatic impacts neotectonics and elevation

geomorphic mapping in endorheic catchments in the spanish pyrenees an integrated gis analysis of karstic features abstract digital elevation models dems can be useful tools to assess morphologically and hydrologically active processes this paper presents a method to obtain accurate dems an analysis of dem errors and the benefits of gis techniques for mapping geomorphological features and active processes in the karstic endorheic catchment with three permanent lakes estana lakes in the external ranges of the spanish pyrenees field work revealed the lack of accuracy in the original dem a method was then proposed to obtain a hydrologically correct dem using a total topographic station tts and a global positioning system gps on a regular grid 246 topographic points were recorded with a gps and 237 points were measured with a tts on areas of gentle slope the mean and standard deviation of the error of the corrected dem were 1 5 and 3 2 m respectively by using a combined flow algorithm a flow accumulation map was derived from the corrected dem and the study area was divided into fifteen sub catchments the values of the indices of watershed circularity and elongation have a strong variation and the map of flow length also showed strong asymmetry maps of land use topography and lithology were created in order to establish the basis for mapping main geomorphological features the new dem also provided a basis for calculating the topography factor ls in rusle an empirical soil erosion model a map showing the error of the original dem indicates that the highest error values occur in the main karstic features of the geomorphological map hence the proposed methodology including dem correction is useful for an accurate assessment of topographical and geomorphological features in karstic environments

hydrocarbons in surface sediments from a guaymas basin hydrothermal vent site petroleum like materials found at the guaymas basin hydothermal vent site gulf of california are derived from pyrolysis of organic matter two characteristics surface sediment cores differing in temperature profiles and other parameters were collected by dsv alvin sectioned and analyzed for hydrocarbons the quantitative and qualitative composition of alkanes steranes diasteranes and triterpanes differed between these cores as well as within sections of the same core these differences apparent for scales of tens of centimeters are related to interactive physical chemical and microbial processes as well as the influence of multiple sources for the petroleum

coseismic deformation field observations and seismic fault of the 17 november 2015 m 6 5 lefkada island greece earthquake abstract on november 17 2015 07 10 07 utc a strong shallow mw6 5 earthquake occurred on the island of lefkada along a strike slip fault with right lateral sense of slip the event triggered widespread environmental effects at the south and western part of the island while the intensity and severity of these earthquake induced deformations is substantially decreased towards the eastern part of the island relocation of seismicity and inversion of geophysical gps insar data indicate that the seismic fault runs parallel to the west coast of lefkada along the aegean apulia plate boundary the fault plane strikes n20 5 e and dips to east with an angle of about 70 5 coseismic deformation was measured in the order of tens of centimeters of horizontal motion by continuous gps stations of noanet the noa gps network and by insar sentinel 1 a image pairs a coseismic uniform slip model was produced from inversion of insar data and permanent gps stations the earthquake measured mw 6 5 using both the geodetic moment produced by the slip model as well as the pgd relation of melgar et al 2015 grl in the field we observed no significant vertical motion of the shoreline or surface expression of faulting this is consistent with the predictions of the model the interferograms show a large decorrelation area that extends almost along all the western coast of lefkada this area correlates well with the mapped landslides the 2003 2015 pattern of seismicity in the ionian sea region indicates the existence of a 15 km seismic gap offshore nw cephalonia