three dimensional seismic imaging of paleogene dike fed submarine volcanoes from the northeast atlantic margin we use three dimensional seismic data to describe the architecture of shallow intrusive igneous sill and dike complexes intruded into the upper crust as well as the internal and external geometry of extrusive conical igneous mounds that were fed by the magma conduits the conical mounds accreted on the seabed directly above the tips of the basaltic dikes between 54 9 and 54 6 ma in plan view the mounds are broadly circular 1 1 7 km in diameter and have a relief of 50 300 m they occur above a complex network of linked cuspate shaped sills and dikes intruded into paleocene and cretaceous sediments of the faeroe shetland basin northeast atlantic margin the highly organized internal structure consisting of bulbous layers arranged concentrically around a central axis along with the clear vertical link to the underlying sills and dikes indicates that they most likely represent pillowed basaltic lava and hyaloclastite mounds that were fed by the dikes and extruded onto the seafloor mounds of similar external geometry have been described from sidescan sonar images above active spreading centers in oceanic settings however such structures are rarely recognized in passive margin settings and prior to this investigation our knowledge of their three dimensional internal geometry has been largely speculative

re os geochronology of the lacustrine green river formation insights into direct depositional dating of lacustrine successions re os systematics and paleocontinental weathering abstract lacustrine sedimentary successions provide exceptionally high resolution records of continental geological processes responding to tectonic climatic and magmatic influences these successions are therefore essential for correlating geological and climatic phenomena across continents and furthermore the globe producing accurate geochronological frameworks within lacustrine strata is challenging because the stratigraphy is often bereft of biostratigraphy and directly dateable tuff horizons the rhenium osmium re os geochronometer is a well established tool for determining precise and accurate depositional ages of marine organic rich rocks lake systems with stratified water columns are predisposed to the preservation of organic rich rocks and thus should permit direct re os geochronology of lacustrine strata we present re os systematics from one of the world s best documented lacustrine systems the eocene green river formation providing accurate re os depositional dates that are supported by ar ar and u pb ages of intercalated tuff horizons precision of the green river formation re os dates is controlled by the variation in initial 187 os 188 os and the range of 187 re 188 os ratios as also documented in marine systems controls on uptake and fractionation of re and os are considered to relate mainly to depositional setting and the type of organic matter deposited with the need to further understand the chelating precursors of re and os in organic matter highlighted in addition to geochronology the re os data records the 187 os 188 os composition of lake water 1 41 1 54 at the time of deposition giving an insight into continental runoff derived from weathering of the geological hinterland of the green river formation such insights enable us to evaluate fluctuations in continental climatic tectonic and magmatic processes and provide the ability for chemostratigraphic correlation combined with direct depositional dates furthermore initial 187 os 188 os values can be used as a diagnostic tool to distinguish between lacustrine and marine depositional settings when compared to known oceanic 187 os 188 os values

the pre quaternary history of fire abstract although evidence for land vegetation comes from the silurian and maybe even earlier the first record of fossil charcoal fusain is from the late devonian for this period there are only one or two isolated records not until the early carboniferous is there a record of extensive charcoal deposits mainly preserved in near shore clastic sediments which provide evidence of significant and widespread wildfires by the late carboniferous charcoal was common or abundant in a wide range of facies including tropical wetland peats wildfire played an important role in shaping the environment at this time the latest palaeozoic and early mesozoic records of charcoal are fewer whereas important deposits of late mesozoic age are found worldwide the occurrence of charcoal at the cretaceous tertiary boundary has been highlighted as evidence for a global fire following a meteorite impact but this interpretation is questionable charcoal has been widely reported from tertiary sediments and its appearance in the quaternary and recent is not solely as a result of human impact through the past 400 million years there have been major changes in atmospheric oxygen levels that affected fire intensity and frequency fire systems thus have a long history and their impact on shaping the environment is assessed

differential compaction faults and their implications for fluid expulsion in the northern bozhong subbasin bohai bay basin china abstract a series of differential compaction faults was identified in the northern bozhong subbasin bohai bay basin china by using 3d seismic well log and lithology data the differential compaction faults display two obvious characteristics first they develop along a lithologic boundary which separates thick sandstone from underlying mudstones facies and thickness change such as an abrupt lithologic change between sandstone and mudstone a lateral thickness change of overlying sandstone are the basic controlling factors of these differential compaction faults second they have a definite strike direction according to the fault strike the differential compaction faults can be divided into three groups group a have an approximate orthogonal strike with the tectonic faults group b display a similar strike with the slope and group c show radial strikes on the circular basement uplift tectonic faults influence the planform patterns of differential compaction faults in their near vicinity and induce these faults displaying an approximate orthogonal intersection with the late period through going faults group a basin slope promote the formation of differential compaction faults by downslope gravity sliding and cause faults parallel to the strike of slope group b circular basement topography generates isotropic stress and leads the differential compaction faults above the basement dominated by radial strikes group c production and geochemistry data is an evidence of differential compaction faults developed in a late period when the strata reach a certain burial depth that the source rocks enter the oil generating window the presence of thermogenic fluid within shallow reservoirs represents as evidence of hydrocarbon drained and migrated through the differential compaction faults the differential compaction faults could serve as significant conduits for fluid expulsion and hydrocarbon accumulation in the bohai bay basin china

the cold climate origin of inertinite rich gondwana coals abstract in the inertinite rich permian coals of australian there occurs a close association between inertodetrinite and alginite of a kind which has been generally overlooked in the past the association is believed to be a consequence of the environment of deposition and especially the climate which is inferred to have been one of wet cool summers and freezing winters the inertodetrinite formed by drying out of a gelified homogenised precursor the algae lived at the periodically desiccated surface of the accumulating peat much of the evidence for these conclusions has come from the combined use of light microscopy and transmission electron microscopy

origin of inertinite rich coals of australian cratonic basins abstract the australian permian cratonic cooper and galilee basins contain extensive deposits of inertinite rich coals in contrast the contiguous foreland sydney and bowen basins are dominated by vitrinite rich coals inertinite in the cratonic basin coals is mainly botanically unstructured fragmentary inertodetrinite in the foreland basin coals semifusinite is the dominant inertinite maceral microlithotypes in the cratonic basin coals are characteristically finely banded sulfur and ash contents are low by world standards the cratonic basin coals accumulated in freshwater mires where low subsidence rates led to extensive oxidation of the peat subaerial and probably subaqueous oxidation took place due to water table fluctuations there is no evidence that these inertinite rich coals were formed from a unique flora or under climatic conditions different from vitrinite rich permian coals

a tale of shales the relative roles of production decomposition and dilution in the accumulation of organic rich strata middle upper devonian appalachian basin abstract a new consensus on the processes responsible for organic carbon burial in ancient epeiric seas has emerged more firmly grounded in the uniformitarian framework of modern oceanography and biogeochemistry this consensus recognizes the interdependent roles of sedimentation primary production and microbial metabolism in favor of earlier end member models e g production vs preservation in this study one of the classic stratigraphic sequences upon which the preservation end member was based is re interpreted in light of this new consensus the study employs an extensive new sedimentological biogeochemical database from cores drilled in western new york the database spans over 500 m and 15 my of devonian deposition in the appalachian basin and provides a framework for comparative study of organic matter burial the major conclusions are 1 few organic rich units were deposited under pervasive anoxic sulfidic water columns 2 establishment and breakdown of seasonal thermoclines on annual or longer timescales were the predominant mode of stratification and 3 under such conditions remineralization of bio limiting nutrients may have played a key role in organic matter burial by creating a eutrophication pump this pump may have augmented an already rising nutrient inventory such that productivity levels exceeded the threshold required for development of suboxic to anoxic conditions in sediments and episodically in bottom waters a final conclusion asserts that the master variable for organic matter accumulation was relative sea level change which exerted influence on clastic dilution preservation and production processes sea level rise events led to sediment starvation and organic carbon concentration in distal basin sediments as well as to decreased effectiveness of seasonal mixing and thus longer build up intervals for remineralized nutrients episodic mixing of nutrient enriched bottom waters led to enhanced production ultimately increased clastic sediment delivery and water column mixing during relative sea level fall diluted surface sediment organic content such that respiratory demand could be met by increased oxygen supply thus terminating deposition of strata enriched in organic carbon

microtektites and mass extinctions evidence for a late devonian asteroid impact glass spherules similar to microtektites have been found near the frasnian famennian boundary f f upper devonian at senzeilles belgium contemporaneous with one of the largest marine mass extinctions of the phanerozoic these spherules exhibit a wide range of compositions and display teardrop dumbbell and compound morphologies analogous to microtektites in addition they lack crystallites have few or no vesicles and have a low content of volatile material these characteristics are supportive of an impact origin the siljan ring sweden and charlevoix structure quebec canada are candidate craters of this age the presence of microtektites near the f f boundary supports the hypothesis that an impact caused the upper devonian worldwide benthic mass extinctions

observations and experiments on the origin and formation of inertinite group macerals the inertinite group macerals include fusinite semifusinite inertodetrinite macrinite micrinite and funginite and secretinite which together replace sclerotinite the macrolithotype fusain comprises fusinite and semifusinite and is now widely accepted as charcoal formed by wildfire activity however alternative origins for fusinite and semifusinite are still claimed this paper considers the use of the terms pyrofusinite degradofusinite rank fusinite and primary fusinite misleading while the definitions of the terms funginite and secretinite are also considered problematic observations made on modern wildfire derived and volcanogenic charcoal assemblages using reflectance and scanning electron microscopy together with experimental charcoalification studies demonstrate that most if not all inertinite macerals have acquired their optical and physical characteristics through the action of elevated temperatures the criteria for the identification of charcoals produced by wildfire and volcanic activity are outlined and the role of the petrographic nomenclature system is discussed

microtektite like impact glass associated with the frasnian famennian boundary mass extinction abstract glass spherules of probable impact origin occur in the late devonian hony section in belgium they are found at the stratigraphic level of the frasnian famennian boundary which is marked by one of the largest mass extinctions in the phanerozoic the hony glass spherules are chemically identical to those previously described from the stratigraphically equivalent senzeille section located 90 km to the west southwest in contrast to the senzeille layer the age of the hony spherule layer is well constrained by conodont biostratigraphy the spherules have morphological and chemical characteristics similar to tektites and microtektites they have a broad range of chemical composition with generally high k2o na2o and al2o3 na2o k2o their water content is in the range measured for tektites and impact glasses small inclusions of lechatelierite may be present in the spherules these glass spherules are likely to be the product of an impact event that occurred at or very near the frasnian famennian boundary the target rock was probably a clay rich pelitic sediment intermixed with carbonates the 368 1 ma siljan ring crater sweden is the most likely impact site candidate the hony and senzeille glass spherules represent the first substantial evidence that an impact event may be linked to the frasnian famennian mass extinction

re os depositional ages and seawater os estimates for the frasnian famennian boundary implications for weathering rates land plant evolution and extinction mechanisms four toc rich shale intervals spanning the frasnian famennian f f boundary were recovered in a drillcore west valley nx 1 from western new york usa and radiometrically dated using re os two of the black shale intervals wvc785 from 2 9 m below and wvc754 from 6 4 m above the f f boundary respectively yielded statistically overlapping ages with uncertainties of 1 1 an interpolated age and associated graphically determined uncertainty of 372 4 3 8 ma provides new absolute age constraints on the f f boundary this date is 4 1 ma younger than the latest proposed f f boundary age of 376 1 ma obtained by interpolation of u pb dates from volcanic zircon kaufmann b 2006 calibrating the devonian time scale a synthesis of u pb id tims ages and conodont stratigraphy earth science reviews 76 175 190 and within uncertainty of the international commission on stratigraphy accepted date of 374 5 2 6 ma a third date from sample wvc802 8 2 m beneath the f f boundary yielded an imprecise age of 357 23 ma owing in part to a limited re os range the initial 187os 188os 0 45 to 0 47 reflecting contemporaneous seawater os values are low but similar to the value of 0 42 reported for the exshaw fm canada at the devonian mississippian boundary ca 361 ma selby d creaser r a 2005 direct radiometric dating of the devonian mississippian time scale boundary using the re os black shale geochronometer geology 33 545 548 this may suggest fairly constant and low global continental weathering rates during the late devonian although in view of the short residence time of os in seawater 1 4 104 yr further measurements are needed to assess potential short term variation in seawater os ratios owing to low os and re abundances at the f f boundary our data are inconsistent with long term volcanism and bolide impact as potential late devonian mass extinction mechanisms in addition the frasnian famennian ocean appears to have been depleted with respect to re possibly indicating an exhaustion of the re seawater reservoir owing to high burial rates of redox sensitive elements under dysoxic anoxic conditions leading up to the f f boundary

cometary impacts into ocean their recognition and the threshold constraint for biological extinctions the montagnais impact crater is presently the only site in the ocean where the effect of a meteorite fall on marine organisms has been studied the impact crater is 45 km in diameter and was formed at 50 8 ma by a fall of probably an old cometary nucleus 3 4 km in diameter into shallow 600 m ocean comparison of the impact structure and related deposits with those on land shows several major differences of which the most significant is the absence of an elevated crater rim instead the crater perimeter is bevelled and eroded as a consequence of impact induced bottom currents and turbulent return water flow into the excavating cavity by this process most of the fall out breccia is reworked back into the crater cavity where it accumulates in much larger thickness than in impact craters on land at a microscopic scale the shock metamorphism features are about the same as those for land impacts geochemically impacts of comet nucleii may not leave a recognizable signature at the impact horizon except for a minor increase in iridium thus stratigraphic horizons associated with extinctions and or major changes in biota have to be closely examined for other impact indicators like the presence of tectites glass spherules and quartz grains with shock features occurrence of megatsunami wave deposits extensive erosion on continental margins margin failures and faunal mixing above erosional unconformities are other potential impact indicators there is no single indicator that can provide sufficient proof of an impact event such interpretations have to be based on multiparameter studies of global extent since many of the impact indicators are only of regional extent the lack of extinction of any marine plankton genera or of bottom dwellers at the montagnais impact site allows us to place a lower limit for biological extinctions caused by cometary impacts on those with nucleus 4 km in diameter the calculated frequency for a cometary impact which could result in a 10 extinction of marine genera is about 6 10 7 yr 1 and for the k t boundary type of extinctions about 2 10 8 yr 1 even allowing for a large degree of uncertainty in these estimates it is unlikely that the biological extinction events for the last 250 ma identified by sepkoski 1990 could have been all caused by meteorite impacts

u pb and re os geochronology of the aptian albian and cenomanian turonian stage boundaries implications for timescale calibration osmium isotope seawater composition and re os systematics in organic rich sediments abstract presented is the first absolute age for the basal albian from the schwicheldt ton member gault formation vohrum germany a 206 pb 238 u age of 113 1 0 3 ma is determined for chemically abraded zircon from a tuff horizon 65 cm above the aptian albian boundary the new u pb age although within uncertainty of the gts 2008 determination 112 1 ma is nominally older the younger gts 2008 basal albian age is obtained from cyclostratigraphy using an 40 ar 39 ar age from the base cenomanian the nominal difference between the gts 2008 age and new basal albian age is consistent with the documented ca 0 65 bias between u pb and 40 ar 39 ar geochronology the new 206 pb 238 u age calls into question a recently published age for the basal albian 106 9 0 4 ma determined from k ar glauconite analysis as well as the k ar age for the gl o international standard rhenium osmium isotope analysis of the basal albian grey clay of the schwicheldt ton member gault formation and basal turonian grey shale of the schwarz weisse wechselfolge hesseltal formation recording oceanic anoxic event 2 yields low and similar 187 re 188 os values 49 167 that are positively correlated with 187 os 188 os values for both sections imprecise re os ages 6 9 2 that overlap the stratigraphic boundary ages are determined aptian albian 108 9 6 2 ma cenomanian turonian 91 5 8 6 ma although the re os data suggest that organic rich sediments other than black shales are potentially amenable for re os geochronology the large uncertainties contrast with that from previous re os organic rich sediment studies the latter show sample sets with a significant spread in 187 re 188 os ratios several hundred units the imprecise re os geochronology presented here relates to the limited spread in the 187 re 188 os values the redox conditions of deposition are suggested to control the 187 re 188 os ratio of an organic rich sediment however trace element and re os data for samples from nw germany and previous re os geochronology studies show no direct relationship between 187 re 188 os values and the redox condition of the water column these results suggest that the fractionation of re and os in organic rich sediments is not controlled by water column redox conditions instead re os fractionation in organic rich sediments may be controlled by sedimentation rate recharge of re and os to the water column and or post deposition mobility of re and os within the sediment the initial os isotope composition of an organic rich sediment is inferred to reflect the seawater composition at the time of deposition for the cenomanian turonian boundary grey shale a seawater os composition of 0 33 0 02 is determined this os isotope composition contrasts with that of the stratotype section at pueblo colorado 0 15 and for those obtained from furlo italy and odp site 1260b 0 5 this data may suggest that the cenomanian turonian ocean was not homogeneous with respect to os suggesting either alternate oceanic circulation or basin dynamics

comment on the kaiho et al paper a forest fire and soil erosion event during the late devonian mass extinction palaeogeography palaeoclimatology palaeoecology 392 2013 272 280 abstract kaiho et al 2013 palaeogeography palaeoclimatology palaeoecology 392 2013 272 280 interpreted the occurrence of elevated concentrations of high molecular weight polycyclic aromatic hydrocarbons and dibenzofuran as indicators of wildfires and enhanced run off near the frasnian famennian f f boundary we argue that other processes including weathering or hydrothermal oxidation not discussed by kaiho et al led to the observed increase in the concentration of these compounds and also changed their distribution kaiho et al s evidence for soil erosion and eutrophication induced euxinia is also weak in the case of the investigated belgian sections finally kaiho et al rather unfortunately omitted a great wealth of important data published elsewhere choosing instead to include only those which support their ideas and interpretations

kilometre scale polygonal seabed depressions in the hatton basin ne atlantic ocean constraints on the origin of polygonal faulting polygonal faulting is a widespread phenomenon in sedimentary basins worldwide it changes basin scale fluid flow patterns and alters the physical properties of the sediments making it important for hydrocarbon exploration and geohazard analysis it is generally accepted that polygonal fault patterns derive from dewatering and compaction of the host sediments but there is debate regarding the processes that control polygonal faulting new multibeam bathymetry data from the hatton basin ne atlantic show up to 10 m deep and 200 600 m wide troughs at the seabed they connect to each other forming polygons that are several hundred metres across i e of similar size as buried polygonal fault systems observed in 3d seismic data the troughs are symmetrical and resemble elongated pockmarks previously unpublished high resolution 2d seismic data from the same area show seismic disturbance zones similar to pipes observed under pockmarks elsewhere as well as faults that have all the characteristics of polygonal fault systems the observation of the wide disturbance zones is enigmatic as they appear to follow the polygonal seafloor pattern the observed extent of the polygonal sediment contraction system is substantial covering almost 37 000 km2 we calculate that some 2600 km3 of possibly carbon bearing fluids have been expelled from this system and we expect that this will affect the benthic ecosystems although so far there is only limited evidence for chemosynthetic habitats

development of san leandro synform and neotectonics of the san francisco bay block california abstract high resolution 24 channel seismic reflection data show a stratified synform beneath south san francisco bay these seismic reflection data reveal an eastward dipping bedrock surface that is about 40 m deep subbottom beneath the western south bay and that reaches a maximum observed depth of 500 800 m subbottom below the eastern half of the south bay an angular unconformity cuts both the synform and underlying bedrock the age of the unconformity is unknown but may be pleistocene when these strata forming the synform were presumably exposed subaerially during lowered sea levels the synformal strata the unconformity and some generally flat lying and overlying strata are folded near the eastern shore of the bay this folding may result from movement on the hayward fault fault interactions and localized strain partitioning or from compressional deformation in the east bay hills related to ne sw fault normal convergence between the pacific and north american plates in general reflections from sediment overlying the unconformity are flat lying except near the eastern shore of the bay whereas reflections beneath the unconformity dip eastward the overlying flat sediment section fills a shallow basin that is coincident with an elliptical residual gravity low this low appears to be related to the deeper sedimentary synformal section based on the spatial correlation between the east dipping reflections and the gravity anomaly projecting the east dipping reflections to the center of the gravity low suggests that the total section of flat lying and dipping reflections in the synform may exceed 1000 m modeling of the gravity low suggests a total low density section about 1 5 km thick at the center of the synform relative to the surrounding bedrock of presumed franciscan complex

phanerozoic atmospheric oxygen new results using the geocarbsulf model modifications of the geocarbsulf model for phanerozoic atmospheric oxygen have been made to account for new carbon isotopic data reconsideration of the fractionation of carbon isotopes between carbonate and organic matter deposited in sediments and different rates of weathering of volcanic rocks versus granitic rocks results indicate distinctly higher o2 values than geocarbsulf for the mesozoic and cenozoic lack of an appreciable drop in o2 below 15 percent at any time and a small late cenozoic decline of o2 to the present

fields of multi kilometer scale sub circular depressions in the carnegie ridge sedimentary blanket effect of underwater carbonate dissolution offshore ecuador the carnegie ridge is a volcanic ridge with a carbonate sediment drape during the salieri cruise multibeam bathymetry was collected across carnegie ridge with the simrad em120 of the r v sonne the most conspicuous features discovered on the carnegie ridge are fields of circular closed depressions widely distributed along the mid slope of the northern and southern flanks of the ridge between 1500 and 2600 m water depth these circular depressions are 1 4 km wide and typically 100 400 m deep most are flat floored and some are so densely packed that they form a honeycomb pattern the depressions were carved into the ridge sedimentary blanket which consists of carbonate sediment and has been dated from upper miocene to upper pleistocene several hypotheses including pockmark origin sediment creeping paleo topography of the volcanic basement effects of subbottom currents and both marine and subaerial karstic origins are discussed we believe that underwater dissolution process merits the most serious consideration regarding the origin of the closed depression

the stratigraphic distribution of inertinite abstract the paper presents the results of an investigation into the stratigraphic distribution of inertinite in humic coals ranging from the silurian to the neogene periods this range equals the time span during which both land plants and atmospheric oxygen evolved the survey is based on a literature study of inertinite in coals covering a variety of depositional environments and climates in all continents the inertinite percentages listed in this paper have been arranged in stratigraphic order they are the mean values based on mineral free whole coal compilations maceral compositions listed in the literature for individual subsections have been averaged to represent complete coal seams beds although this might not have been always possible due to some ambiguity in the published record moreover not all of the published and unpublished information could be used because of poor sample description obscure geographic origin or insufficient stratigraphic information the results show that there have been times in the geological past e g during the late permian in which coals were particularly rich in inertinite compared with other times e g during much of the late tertiary in which many coals contained very little inertinite occasionally such primary global trends were modulated by a diffuse distribution of inertinite percentages that correspond to differences in climate depositional settings e g active orogenic margins versus tectonically inactive shelf margins and other local or regional variations although various mechanisms for the generation of inertinite have been proposed in the past the overall pattern in its stratigraphic distribution supports the notion of incomplete combustion as the main source of inertinite in coal this points to secular variations in the atmospheric oxygen content as an explanation for the global changes in the inertinite distribution while differential subsidence and climatically influenced reaction rates governed regional and local variations in inertinite percentages

charcoal recognition taphonomy and uses in palaeoenvironmental analysis abstract charcoal predominantly the product of wildfires is abundant in many sedimentary rocks deposited in a wide range of environments from terrestrial to marine it also occurs in some volcanic rocks this paper outlines aspects of charcoal formation both natural and experimental and briefly considers the taphonomic processes leading to a final assemblage this is done using examples from recent fires and through experimentation the ways in which charcoal assemblages are recognized in the field and extraction in the laboratory are also considered methods of charcoal identification are presented the range of charcoalified plant organs that can be found is discussed and a wide range of study methods outlined including light microscopy dark field light microscopy reflectance microscopy scanning electron microscopy and synchrotron radiation x ray tomographic microscopy emphasis in this paper is on the study of macro and meso charcoal above180 m finally there is a consideration of the broad use of charcoal from plant evolution studies fire history studies vegetation studies anatomical studies climate and atmospheric studies and the wider importance of charcoal for the earth and biological sciences charcoal is information rich but yet is an under utilized resource

comparative optical properties of macerals and statistical evaluation of mis identification of vitrinite and solid bitumen from early mature middle devonian lower mississippian new albany shale implications for thermal maturity assessment abstract vitrinite reflectance vro in is used routinely to quantify thermal maturity in sedimentary basins reflectance and fluorescence of other macerals such as solid bitumen and amorphous organic matter aom can provide an independent means to assess thermal maturity and hydrocarbon generation potential however similarity in petrographic characteristics of these macerals solid bitumen and vitrinite in particular often causes difficulties with their identification and consequently reflectance can be measured on misidentified particles making reported vro values unreliable the purpose of this study is to compare reflectance values of various macerals in early mature shales and to evaluate the implications of misidentifying solid bitumen and vitrinite for assessing thermal maturity to address this issue 15 organic matter rich samples from the middle devonian lower mississippian new albany shale from a corehole in daviess county indiana were selected these samples were chosen because they had distinct and easily identified aom solid bitumen vitrinite and inertinite particles allowing for statistically relevant comparisons vro values 0 57 to 0 65 of the studied sample suite cover the early mature stage and expressed no trend with depth in comparison reflectance values of solid bitumen bro and aom aomro from the same samples are lower and range from 0 44 to 0 52 and 0 27 to 0 31 respectively these differences are accompanied by corresponding differences in chemistry of macerals as demonstrated by the micro ftir technique specifically compared to vitrinite and inertinite solid bitumen shows lower aromaticity and compared to aom and alginite it exhibits shorter aliphatic chains reflectance was observed to vary systematically samples having higher vro also feature elevated solid bitumen and aom reflectance values the relationship between vitrinite and solid bitumen can be expressed by the following equation vitrinite reflectance equivalent vroe in 0 83 bro 0 22 whereas for vitrinite and aom vroe 0 84 aomro 0 38 statistical evaluation of the differences in reflectance values caused by maceral misidentification indicates that in extreme cases when a petrographer cannot distinguish between vitrinite and solid bitumen the reflectance can be shifted by 0 06 0 09 for this set of samples such a difference could shift maturity assessment from early mature to immature in more common cases when the analyst can distinguish between the macerals but has difficulties with their overlapping reflectance interval the reflectance difference that results from misidentification is only within a 0 0 0 02 range therefore if the level of uncertainty in maceral identification can be determined the calculation of vroe values from measured bro can reduce inaccuracy in vro values for interpreting the thermal histories of sedimentary basins which in turn is essential for the assessment of oil and gas resources and for building a successful exploration model

phanerozoic concentrations of atmospheric oxygen reconstructed from sedimentary charcoal varying concentrations of atmospheric oxygen have affected the development of animals and the role of wildfire in ecosystems reconstructions of past oxygen concentrations from fossil charcoal constrain atmospheric oxygenation over the past 400 million years variations of the earth s atmospheric oxygen concentration po2 are thought to be closely tied to the evolution of life with strong feedbacks between uni and multicellular life and oxygen1 2 on the geologic timescale po2 is regulated by the burial of organic carbon and sulphur as well as by weathering3 reconstructions of atmospheric o2 for the past 400 million years have therefore been based on geochemical models of carbon and sulphur cycling4 5 6 however these reconstructions vary widely4 5 6 7 8 9 10 particularly for the mesozoic and early cenozoic eras here we show that the abundance of charcoal in mire settings is controlled by po2 and use this proxy to reconstruct the concentration of atmospheric oxygen for the past 400 million years we estimate that po2 was continuously above 26 during the carboniferous and permian periods and that it declined abruptly around the time of the permian triassic mass extinction during the triassic and jurassic periods po2 fluctuated cyclically with amplitudes up to 10 and a frequency of 20 30 million years atmospheric oxygen concentrations have declined steadily from the middle of the cretaceous period to present day values of about 21 we conclude however that variation in po2 was not the main driver of the loss of faunal diversity during the permo triassic and triassic jurassic mass extinction events

origin of enigmatic sand injectite outcrops associated with non tectonic forced folding structure in bahrah area northern kuwait bay abstract this is a quantitative and qualitative study for the first time linking surface with subsurface geology to understand the occurrence and origin of enigmatic sand injectite outcrops in two sites within the bahrah coastal plain area northern kuwait bay field work observations and aerial photography were used to describe and characterize the surface geology and stratigraphy of the study area thirty one rock samples were obtained for petrographical fluid inclusions and strontium isotopes analyses 3d seismic data were also used to assess the subsurface geology of the area the petrography and microthermometry of fluid inclusions were used to understand the origin of fluids and gases associated with the formation of these sand injectites we found that these surface geological features represent surface manifestation of subsurface geological and biological activities processes therefore we proposed a near surface complex focused fluid injection mechanism model responsible for the formation of the sand pipes the model consists of five episodes episode 1 represents the development of near surface geobody paleoshoreline sealed by a shale layer episode 2 represents the entrapment of hydrocarbons that migrated laterally up dip within geobody interacting with mixed seawater intrusion and fresh groundwater episode 3 represents the effect of biodegradation biological processes of the entrapped hydrocarbons generating ch4 co2 and h2s gases episode 4 represents overpressure build up due to gas generation exceeding pore volume of geobody and forming non tectonic forced folds and polygonal to semi circular joints fractures network and episode 5 represents overpressure release triggered by external factor s seismic activities facilitating gases water and sand remobilisation through weakened zones of natural fractures

contrasting molybdenum cycling and isotopic properties in euxinic versus non euxinic sediments and sedimentary rocks refining the paleoproxies abstract the redox sensitive transition element molybdenum is present in the earth s crust at trace concentrations but is abundant in seawater marine sediments and ancient sedimentary rocks these occurrences have led to the development of a suite of paleoredox proxies based on the bulk concentration of mo its isotopic composition and the covariation of mo with total organic carbon toc in ancient black shales however these proxies have almost exclusively targeted the identification and interpretation of euxinic environments where bottom waters are both anoxic and sulfidic here we present a discussion of the mo geochemistry of non euxinic sediments where hydrogen sulfide is sometimes present yet always restricted to pore waters we propose a new paleoredox application that uses mo concentrations to help distinguish between environments where sulfide was present in the bottom waters and environments where sulfide was restricted to pore waters under ideal conditions it is also possible to infer the presence of mn oxides recycling in non euxinic paleoenvironments based on the mo isotope composition of ancient black shales providing a critical constraint on bottom water oxygenation

osmium isotopic evidence against an impact at the frasnian famennian boundary two sections across the frasnian famennian boundary were analyzed for re and os concentrations and 187os 188os ratios to evaluate evidence for a meteoritic input coincident with this boundary and its associated mass extinction these sections are from a siltstone and shale sequence at irish gulf in new york us and a calcareous shale and ferromanganese oxide sequence at la serre in france the irish gulf section with an initial 187os 188os of about 0 49 does not show the characteristic meteoritic os imprint with an 187os 188os of about 0 13 the integrity of the section with regard to re and os retention is indicated by the construction of an isochron with an age of 388 41 ma consistent with independently determined ages for the frasnian famennian boundary although the la serre section with os concentrations as high as 33 ppb and re concentrations ranging from 1 4 to 7 4 ppb might be expected to show excellent evidence for a meteoritic contribution the highly radiogenic isotopic composition 187os 188os 2 42 3 61 instead suggests recent massive re loss or addition of radiogenic os these possibilities prevent the reconstruction of an initial 187os 188os value for the boundary for this site assuming reasonable re concentrations prior to loss the os isotopic composition is inconsistent with a large meteoritic component this inconsistency emphasizes that platinum group element pge concentrations are not reliable indicators of extraterrestrial addition

the marine osmium isotope record over the past decade the marine osmium isotope record has been developed into a new tracer in palaeoceanographic research several analytical developments particularly in the past few years have significantly increased our ability to study the behaviour of osmium in the surficial environment the 187os 188os and osmium concentration of seawater river water rain and hydrothermal vent fluids have been measured directly recently the behaviour of osmium in estuaries critical for estimating the marine residence time of osmium has been studied our knowledge of the surficial osmium cycle has thus significantly improved in addition reconstructions of past variations in the marine 187os 188os recently have been extended back into the mesozoic this review attempts to summarize our current understanding of the marine osmium system present and past the 187os 188os of seawater during the cenozoic to first order mimics the marine 87sr 86sr record it is therefore tempting to interpret both records as reflecting increased input of radiogenic osmium and strontium resulting from enhanced continental weathering regulated by climatic tectonic processes however the marine osmium isotope system differs fundamentally from the marine strontium isotope system this review emphasizes three important differences first large impacts are capable of resetting the 187os 188os to unradiogenic values without significantly affecting the marine strontium system second organic rich sediments are characterized by high 187re 188os resulting 187os 188os ingrowth trajectories are similar to the average slope of the cenozoic 187os 188os seawater record trends towards more radiogenic 187os 188os seawater therefore can be caused by weathering of organic rich sediments at a constant rate third the marine residence time of osmium is sufficiently short to capture short periodic glacial interglacial fluctuations that are inaccessible to the buffered marine strontium isotope system this offers the opportunity to discriminate between high frequency climatic and low frequency tectonic forcing

measurement of diagenetic compaction strain from quantitative analysis of fault plane dip we developed a new technique for quantifying the amount of porosity loss during diagenetic transformation of opal a to opal ct the technique is based on 3d seismic data from offshore norway where the widely developed biosiliceous sediments of the brygge formation are deformed by a polygonal fault system evidence is shown from two study areas that the dip of the polygonal fault planes reduces abruptly across the opal a to opal ct diagenetic boundary suggesting that the fault planes were passively rotated into shallower dips due to diagenesis the reduction of fault plane dip was used to quantify the vertical compaction strain due to diagenesis using an independent assessment of the magnitude of the porosity loss we are able to validate the method based on fault plane dips and also to evaluate whether the porosity loss results in an exclusively vertical strain additionally the impact of silica diagenesis on the shear strength of the sediments and fault growth is investigated we present evidence suggesting that deviations from classical mohr coulomb behaviour may be expected during the combined processes of diagenesis and porosity collapse and may indeed be sufficient to promote continued fault growth

pulses of enhanced continental weathering associated with multiple late devonian climate perturbations evidence from osmium isotope compositions anomalously high rates of continental weathering have frequently been proposed as a key stimulus for the development of widespread marine anoxia during a number of late devonian environmental and biospheric crises which included a major mass extinction during the frasnian famennian transition marked by the upper and lower kellwasser horizons here this model is investigated by presenting the first stratigraphic record of osmium isotope trends 187os 188os in upper devonian strata from the kowala quarry holy cross mountains poland changes in reconstructed 187os 188os seawater values to more radiogenic compositions are documented at the base of both the lower 0 42 to 0 83 and upper 0 31 to 0 81 kellwasser horizons characteristic of the frasnian famennian transition and additionally within upper famennian shales that record a more minor environmental perturbation known as the annulata event 0 20 to 0 53 these shifts indicate the occurrence of extremely enhanced continental weathering rates at the onsets of the kellwasser crises and during the later annulata event the similarity of 187os 188os values in this study from frasnian famennian boundary and lower famennian strata between 0 4 and 0 5 to those from north american stratigraphic equivalents suggests that the 187os 188os values record global trends these findings support a causal relationship between increased continental weathering and thus nutrient supply to the marine shelf and the environmental perturbations that occurred during numerous late devonian events including both of the biospherically catastrophic kellwasser crises as well as other less severe oceanic anoxic events

fluid flow due to the advance of basin scale silica reaction zones the conversion of biogenic silica opal a to opal ct cristobalite and tridymite in biosiliceous sediment causes increased rates of water expulsion because of the reduction in sediment porosity and dehydration of the amorphous opal a phase this release of water occurs over large tracts of sedimentary basins during sediment burial within discrete diagenetic reaction zones analysis of two dimensional and three dimensional seismic data sets from basins in the northern hemisphere provides geophysical evidence for a variety of fluid conduits and roughly circular erosional depressions at the contemporaneous seabed we interpret these features as indicative of water expulsion and focused fluid flow emanating from opal a to opal ct reaction zones at burial depths within the range 200 800 m the rate at which water is expelled depends upon the degree of porosity reduction and the weight fraction of bound water at the reaction zone as well as the rate of advance of the reaction zone where the reaction is actively taking place within homogeneous biosiliceous sediment the rate of water expulsion is independent of the reaction rate this is because water is released across the entire reaction zone therefore slow reaction rates are compensated for by expulsion of water across wider reaction zones we calculate the rate and volume of water expulsion for the faeroe shetland basin where the sediment immediately below the reaction zone contains on average 30 opal ct by weight the estimated volumetric rate of water expulsion per unit surface area at the present day is 6 m3 my 1 per square meter which is greater than the vertical flux of water at the same depth from compaction of the deeper basin fill the average volumetric rate of water expulsion is 120 km3 my 1 across the whole basin biogenic silica is particularly rich in neogene successions in high latitude and equatorial regions and where silica reaction zones are identified they should be factored into sediment compaction and fluid flow histories

mercury enrichments and the frasnian famennian biotic crisis a volcanic trigger proved the frasnian famennian f f global event one of the five largest biotic crises of the phanerozoic has been inconclusively linked to rapid climatic perturbations promoted in turn by volcanic cataclysm especially in the viluy large igneous province lip of siberia conversely the triggers of four other phanerozoic mass extinction intervals have decisively been linked to lips owing to documented mercury anomalies shown as the diagnostic proxy here we report multiple hg enrichments in the two step late frasnian kellwasser crisis interval from paleogeographically distant successions in morocco germany and northern russia the distinguishing signal 1 ppm hg in the domain of closing rheic ocean was identified in different lithologies immediately below the f f boundary and approximately correlated with the onset of the main extinction pulse this key hg anomaly comparable only with an extreme spike known from the end ordovician extinction was not controlled by increased bioproductivity in an anoxic setting we suggest therefore that the global chemostratigraphic pattern near the f f boundary records a greatly increased worldwide hg input controlled by the center hill eruptive pulse of the eovariscan volcanic acme but likely not manifested exclusively by lip s consequently all five major biotic crises of the phanerozoic have now been more reliably linked to volcanic cataclysms

giant hummocks in deep water marine sediments evidence for large scale differential compaction and density inversion during early burial this paper describes large scale hummock structures from an oligocene miocene succession in the faeroe shetland trough off the northern coast of the united kingdom these hummocks have a wavelength of 1 2 km and an amplitude of about 50 m they are characterized by a polygonal planform geometry two successive depositional packages in this probably pelagic dominated interval have this form of structural expression but troughs of the younger set are directly superposed on crests of the older set they occur at a present day subsea bottom depth of about 1000 m and cover an area of 6000 km 2 this extraordinary structural configuration is attributed to a protracted depositional and deformational history in which a density inversion was established hummock formation was initiated in response to differential loading above an irregular polygonal fault system and then subsequent collapse produced syndepositional troughs in the overlying units these structures are similar in geometry to hummocks described from near surface sediments in the norway basin by p r vogt and are the largest type of density inversion deformation structure yet described from a clastic sedimentary succession

changes in fire regimes since the last glacial maximum an assessment based on a global synthesis and analysis of charcoal data fire activity has varied globally and continuously since the last glacial maximum lgm in response to long term changes in global climate and shorter term regional changes in climate vegetation and human land use we have synthesized sedimentary charcoal records of biomass burning since the lgm and present global maps showing changes in fire activity for time slices during the past 21 000 years as differences in charcoal accumulation values compared to pre industrial there is strong broad scale coherence in fire activity after the lgm but spatial heterogeneity in the signals increases thereafter in north america europe and southern south america charcoal records indicate less than present fire activity during the deglacial period from 21 000 to 11 000 cal yr bp in contrast the tropical latitudes of south america and africa show greater than present fire activity from 19 000 to 17 000 cal yr bp and most sites from indochina and australia show greater than present fire activity from 16 000 to 13 000 cal yr bp many sites indicate greater than present or near present activity during the holocene with the exception of eastern north america and eastern asia from 8 000 to 3 000 cal yr bp indonesia and australia from 11 000 to 4 000 cal yr bp and southern south america from 6 000 to 3 000 cal yr bp where fire activity was less than present regional coherence in the patterns of change in fire activity was evident throughout the post glacial period these complex patterns can largely be explained in terms of large scale climate controls modulated by local changes in vegetation and fuel load

did climate changes trigger the late devonian kellwasser crisis evidence from a high resolution conodont δ18opo4 record from south china abstract the impact of climate change on biodiversity has been the focus of studies on the phanerozoic biotic crises however it is still controversial whether climate change has caused the frasnian famennian f f biotic crisis since there is no unequivocal view on the global climate change during this critical period in order to reconstruct palaeotemperatures during the f f transition in south china eastern palaeotethys a high resolution oxygen isotope 18 o po 4 record was obtained based on 104 measurements of conodont apatite from the yangdi section the oxygen isotope record based on mono generic samples reveals an increase in 18 o po 4 by 0 7 in the lower kellwasser horizon lkh and 1 4 in the upper kellwasser horizon ukh translating into low latitude surface water cooling of 3 c and 6 c respectively these two 18 o po 4 shifts agree well with the time equivalent 18 o po 4 records from the western palaeotethys suggesting that two climate cooling pulses in conjunction with the deposition of the kellwasser horizons are a global signal during the f f transition the positive shift of 18 o po 4 coincides with positive excursion in carbon isotope of carbonates 13 c carb in the ukh indicating that enhanced burial of organic carbon resulted in a drop in atmospheric p co 2 and thus global climate cooling cooling started immediately before the upper kellwasser biotic crisis with the lowest temperature documented at the top of the ukh climate cooling during the deposition of the lkh is observed in conjunction with the sharp decline in metazoan reefs the coincidence of cooling and the kellwasser biotic crisis suggests that global cooling played a major role in the collapse of ecosystems

reply to the comment on kaiho et al a forest fire and soil erosion event during the late devonian mass extinction palaeogeogr palaeoclimatol palaeoecol 392 2013 272 280 kaiho et al 2013 showed that high values of organic molecule indices of combustion soil erosion and euxinia occurred at the frasnian famennian transition at sinsin belgium marynowski and racki 2014 commented on the paper their issues mainly address 1 the low resolution of the data 2 the reliability of the proxies 3 weathering as a cause of the peaks of the proxies 4 the discrepancy between rare charcoal occurrence and the high combustion proxy and 5 the stepwise collapse of the huge global reef ecosystem ending well before the f f boundary in response to comment 1 the positive excursion of 13ccarb marking the f f transition in the sinsin section indicates that the sinsin section has enough strata to detect environmental changes during the culmination of the late devonian stepwise mass extinction on comment 2 soil erosion was indicated not only by dibenzofuran but also by a spike of cadalene dibenzothiophene should have increased when euxinic water developed on the surface of sediments which is supported by the coincidence of isorenieratane and dibenzothiophene on the middle shelf in the late permian we show the combustion index at the cretaceous paleogene transition indicating that this ratio is useful as a proxy of combustion on comment 3 we cannot explain the high and low combustion soil erosion and euxinia index values by weathering because of the consistently well preserved state of the rock samples on comment 4 we need to detect charcoal during the f f transition and early famennian corresponding to maxima of high sea levels to clarify the discrepancy on comment 5 our model is only for the f f transition event marked by the extinction acme it may not explain the collapse of the reef ecosystem that ended before the f f boundary but it can explain the extinction acme at the f f transition

the role of sea level change and marine anoxia in the frasnian famennian late devonian mass extinction johnson et al johnson j g klapper g sandberg c a 1985 devonian eustatic fluctuations in euramerica geological society of america bulletin 96 567 587 proposed one of the first explicit links between marine anoxia transgression and mass extinction for the frasnian famennian f f late devonian mass extinction this cause and effect nexus has been accepted by many but others prefer sea level fall and cooling as an extinction mechanism new facies analysis of sections in the usa and europe france germany poland and comparison with sections known from the literature in canada australia and china reveal several high frequency relative sea level changes in the late frasnian to earliest famennian extinction interval a clear signal of major transgression is seen within the early rhenana zone e g drowning of the carbonate platform in the western united states this is the base of transgressive regressive cycle iid of the johnson et al johnson j g klapper g sandberg c a 1985 devonian eustatic fluctuations in euramerica geological society of america bulletin 96 567 587 eustatic curve this was curtailed by regression and sequence boundary generation within the early linguiformis zone recorded by hardground and karstification surfaces in sections from canada to australia this major eustatic fall probably terminated platform carbonate deposition over wide areas especially in western north america the subsequent transgression in the later linguiformis zone recorded by the widespread development of organic rich shale facies is also significant because it is associated with the expansion of anoxic deposition known as the upper kellwasser event johnson et al s johnson j g klapper g sandberg c a 1985 devonian eustatic fluctuations in euramerica geological society of america bulletin 96 567 587 original transgression anoxia extinction link is thus supported although some extinction losses of platform carbonate biota during the preceeding regression cannot be ruled out conodont faunas suffered major losses during the upper kellwasser event with deep water taxa notably affected this renders unreliable any eustatic analyses utilising changes in conodont biofacies claims for a latest frasnian regression are not supported and probably reflect poor biostratigraphic dating of the early linguiformis zone sequence boundary

evidence of a widespread paleo pockmarked field in the orange basin an indication of an early eocene massive fluid escape event offshore south africa abstract the detailed interpretation and seismic attribute analysis of 2d and 3d seismic reflection data sets revealed the presence of a distinct seismic horizon displaying circular and elongated depressions in early eocene sediments along the northwestern slope of the orange basin on the southwest african margin their occurrence within a single seismic horizon indicates a contemporaneous formation process we interpret the depressions as paleo pockmarks which occur as single pockmarks predominantly nne ssw aligned pockmark trains and coalescing elongated pockmarks the paleo pockmarked surface covers an area of 2800 km 2 and has been mapped by integrating the 3d dataset with industrial 2d seismic grids the spatial and temporal occurrence of the paleo pockmarks is associated to two episodes of rapid sedimentation during the late maastrichtian to paleocene comprising fine grained shelf eroded material we propose that they were formed during the early eocene by the seepage of both 1 overpressured pore fluids from disequilibrium compaction of upper maastrichtian sediments and 2 thermogenic gas from underlying cretaceous mature source rocks we show that the location of the pockmarks is controlled by the underlying faults system of the paleo slope the paleocene eocene transition is known for its series of hyperthermal events characterized by negative excursions of the carbon isotope curve the early eocene widespread event of fluid and thermogenic gas escape identified in this work can be an example of the type of carbon release processes occurring in hydrocarbon prone sedimentary basins during this time

a forest fire and soil erosion event during the late devonian mass extinction abstract the late devonian mass extinction occurred in a stepwise manner and culminated close to the frasnian famennian f f boundary 372 million years ago organic molecular indices from marine sedimentary rocks at the sinsin section belgium indicate that the sequence of combustion of land vegetation soil erosion and anoxia euxinia occurred close to this boundary the increased concentrations of biomarkers indicating forest fire and soil erosion measured in the sinsin section suggest that fire became widespread at this time leading to various damaging consequences increased runoff and oceanic anoxia that caused marine extinctions magnetic susceptibility data in the sinsin section indicate a relatively dry climate spanning the f f boundary which would have encouraged forest fires the study of organic biomarkers presents several lines of evidence to link forest fire and soil erosion to the late devonian mass extinction

mountain building enhanced continental weathering and organic carbon burial as major causes for climatic cooling at the frasnian famennian boundary c 376 ma the late devonian was a period of drastic environmental changes as exemplified by a major biotic crisis at the frasnian famennian boundary ffb and the onset in famennian times of glaciations across southern gondwana worldwide evidence for the coeval development of the major acadian eovariscan belt led us to propose a model relating the late frasnian famennian environmental perturbations to extensive continental uplift through two atmospheric co2 depleting mechanisms 1 the intensification of silicate weathering on the continental areas as attested by a major rise in the 87 sr 86 sr composition of sea water at the ffb and 2 the massive burial of organic carbon kellwasser events in partially confined basins due to the collisional induced reduction of equatorial oceanic communications between the palaeotethysian and panthalassic oceans this process is also suggested to have been controlled by an important primary productivity connected to an increased nutrient availability triggered by the enhanced continental run off

application of organic petrography in north american shale petroleum systems a review abstract organic petrography via incident light microscopy has broad application to shale petroleum systems including delineation of thermal maturity windows and determination of organo facies incident light microscopy allows practitioners the ability to identify various types of organic components and demonstrates that solid bitumen is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity whereas oil prone type i ii kerogens have converted to hydrocarbons and are not present high magnification sem observation of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs has enabled major advances in our understanding of hydrocarbon migration and storage in shale but suffers from inability to confirm the type of organic matter present herein we review organic petrography applications in the north american shale plays through discussion of incident light photographic examples in the first part of the manuscript we provide basic practical information on the measurement of organic reflectance and outline fluorescence microscopy and other petrographic approaches to the determination of thermal maturity in the second half of the paper we discuss applications of organic petrography and sem in all of the major shale petroleum systems in north america including tight oil plays such as the bakken eagle ford and niobrara and shale gas and condensate plays including the barnett duvernay haynesville bossier marcellus utica and woodford among others our review suggests systematic research employing correlative high resolution imaging techniques and in situ geochemical probing is needed to better document hydrocarbon storage migration and wettability properties of solid bitumen at the pressure and temperature conditions of shale reservoirs

fungal origin of oxidised plant material in the palangkaraya peat deposit kalimantan tengah indonesia implications for inertinite formation in coal abstract the top 1 0 1 5 m of the 6 m thick palangkaraya peat deposit in indonesia is decaying aerobically and contains up to 22 oxidised plant material i e inertinite in contrast intervals below the level of water table fluctuation contain less than 5 oxidised material analysis of fungal remains in the peat show there is a coincident increase in total aggregate hyphal length a measure of fungal activity with the proportion of oxidised plant constituents macroscopically the top of the peat which contains the greatest proportion of oxidised material is black lacks wood fragments and would be classed as a sapric or sapric hemic peat oxidised material in the peat is predominantly epidermal cell walls of primary roots these cell walls are abnormally thickened and display a distinctive dentate structure in cross section the texture of the cell walls are either laminated or granular and often contains intercellular nodules these features together with the absence of charcoal layers in the peat suggest that oxidised constituents were derived from fungal alteration furthermore the coincident increase in fungal hyphal length with the proportion of oxidised material may suggest a causal link based on texture morphology and size the same types of oxidised plant material found in the palangkaraya peat deposit have been identified in coal beds of tertiary age from indonesia new zealand and the u s a this indicates similar fungal alteration occurred in the past and may account for some of the oxidised constituents found in coal if the palangkaraya mire is used as a model fungal alteration zones may be recognised in coals as relatively thick 0 5 2 0 m laterally extensive macroscopically dull coal

understanding and distinguishing reflectance measurements of solid bitumen and vitrinite using hydrous pyrolysis implications to petroleum assessment solid bitumen is a common organic component of thermally mature shales and typically is identified by embayment against euhedral mineral terminations and by groundmass textures however because these textures are not always present solid bitumen can be easily misidentified as vitrinite hydrous pyrolysis experiments 72 hours 300 360 c on shale and coal samples show solid bitumen reflectance bro in shales is less responsive to thermal stress than vitrinite reflectance vro in coal this effect is most pronounced at lower experimental temperatures 300 320 c whereas reflectance changes are more similar at higher temperatures 340 360 c neither a vitrinite like maceral or suppressed vitrinite was identified or measured in our sample set rather the experiments show that solid bitumen matures slower than vitrinite the data may explain some reports of vitrinite reflectance suppression particularly at lower thermal maturity vro 1 0 as a simple case of solid bitumen being mistaken for vitrinite further the experimental results confirm previous empirical observations that vro and bro are more similar at higher maturities vro 1 0 it is suggested that vitrinite reflectance suppression commonly reported from upper paleozoic marine shales of early to mid oil window maturity is a misnomer this observation has important implications to petroleum exploration models and resource assessment because it may change interpretations for the timing and spatial locations of kerogen maturation and petroleum generation

minor and trace element and re os chemistry of the upper devonian woodford shale permian basin west texas insights into metal abundance and basin processes the trace and minor element and re os geochemistry of the upper devonian woodford shale are analyzed in order to characterize elemental abundances to identify associations among trace elements and to constrain paleoceanographic conditions and depositional processes this organic carbon rich mudstone in the permian basin west texas is a major source of hydrocarbons in the basin and is coeval with many other upper devonian shales in north america the woodford lacks enrichment in many trace metals only mo u s and se are significantly enriched other redox sensitive elements are depleted or similar to average shale composition including pb bi cr ti cu zn co and v elements associated with granitic sources such as rare earths th ce and tio2 are also depleted relative to average shale this appears to be related to be a source control a strong basin reservoir effect is noted among several redox sensitive elements including mo cu and ni which largely accounts for the depletion dilution by biogenic silica had an additional effect on metal concentrations multivariate factors analysis identified associations between elements including groupings of rare earth elements elements enriched in granitic crust silica varying antithetically with elements in carbonate minerals organic carbon mo and u v phosphate fe and s noteworthy among the results are the different behavior of redox sensitive elements suggesting different precipitation mechanisms or varying dependence on reservoir effects a strong redox effect is noted in the toc ptot ratio at approximately the frasnian famennian boundary indicating an abrupt transition to an anoxic column boundary that coincides with a short term significant fall in sea level this suggests that anoxia was induced by isolation of the basin from the global ocean however with the exception of the uppermost famennian initial 187os 188os values determined from re os geochronology for the permian basin are similar to correlative sections of the appalachian and peace river basins of north american and the rhenohercynian basin of europe this indicates that although the permian basin became restricted during the upper devonian and early mississippian ocean connectivity remained between regional and global basins

the frasnian famennian boundary in central and eastern united states abstract the frasnian famennian f f boundary in the northern appalachian basin is found in the hanover shale and equivalent strata where it is locally associated with a black shale interval equivalent to the upper kellwasser interval in europe the boundary is immediately below the dunkirk huron black shale that represents the iie t r cycle transgression in the southern appalachian basin the southern edge of the cincinnati arch and the southeastern illinois basin the f f boundary is at or near the base of the gassaway member of the chattanooga shale or the morgan trail member of the new albany shale or was eroded during the iie t r cycle beginning in the middle triangularis zone in the western illinois basin grassy creek shale michigan basin lachine member of antrim shale and southern continental margin woodford shale the f f boundary is within black shale strata indicative of an earlier development of the iie t r transgression inboard of the appalachian basin or the juxtaposition of the iie t r transgression over the upper kellwasser black shale interval without significant or recognizable lithologic change

charcoal reflectance as a proxy for the emplacement temperature of pyroclastic flow deposits hot pyroclastic flow deposits often entomb and preserve vegetation as charcoal when studied in polished section this charcoal is highly reflective novel data from experimentally charred woods demonstrate that reflectance increases with both temperature and time at temperatures above 250 c reflectance rises rapidly for the first hour effectively stabilizing after 4 h for temperatures below 400 c however for higher temperatures reflectance only stabilizes after 24 h charcoalified woods from block and ash flow deposits generated by the soufriere hills volcano in montserrat have yielded interpreted deposit temperatures based on reflectance data of 325 525 c these temperatures compare favorably with directly measured data 365 640 c from the same deposits indicating that charcoal reflectance is useful as a temperature proxy for ancient pyroclastic flow deposits particularly where magnetic or mineral data are absent for this purpose however caution should be exercised as only a minimum temperature can be inferred where the heating duration of the deposit is unknown unlike magnetic or mineral data temperature data from charcoalified woods can be obtained from reworked deposits providing a valuable means of validating observations made about the style of eruption of volcanoes in ancient settings

differential compaction and subsidence in sedimentary basins due to silica diagenesis a case study the conversion of opal a to opal ct is a thermochemical diagenetic process that can cause kilometer scale differential compaction and differential subsidence within clastic sedimentary basins this is demonstrated for an opal a to opal ct conversion imaged by three dimensional seismic data on the northeastern atlantic margin this diagenetic front has a circular to polygonal ridge depression morphology the ridges have a relief of 10 50 m and separate circular to polygonal depressions that have diameters of 1 2 km some of which link up to form interconnected networks this morphology initially developed because the host sediments mantled an underlying polygonal fault system and the front tracked deformed stratigraphy ridges formed above the tips of the underlying faults and depressions formed between them ridge relief and width then progressively increased due to earlier opal a to opal ct conversion above ridges as well as conversion laterally along beds or bed sets this caused compaction and concomitant subsidence in the overburden and the development of a circular to polygonal network of overburden troughs aligned with the ridge system a positive feedback loop was established where additional overburden sediment above the growing ridges reached the depth of conversion ahead of adjacent areas driving more compaction and differential subsidence this paper provides the first insights into the large scale morphological characteristics of opal a to opal ct diagenetic fronts it demonstrates the potential for a local stratigraphic control on diagenetic front development and morphology and lastly highlights the potential utility of seismic reflection data for understanding diagenetic processes

excess pore pressure resulting from methane hydrate dissociation in marine sediments a theoretical approach 1 this study quantifies the excess pore pressure resulting from gas hydrate dissociation in marine sediments the excess pore pressure in confined pore spaces can be up to several tens of megapascals due to the tendency for volume expansion associated with gas hydrate dissociation on the other hand the magnitude of excess pore pressure in well connected sediment pores is generally smaller depending primarily on the hydrate dissociation rate and the sediment permeability volume expansion due to gas hydrate dissociation in well connected pore spaces is related via darcy s law to an increase in pore pressure and its gradient in sediment which drives an additional upward fluid flow through the sediment layer overlying the gas hydrate dissociation area the magnitude of this excess pore pressure is found to be proportional to the rate of gas hydrate dissociation and the depth below seafloor and inversely proportional to sediment permeability and the depth below sea level the excess pore pressure is the greatest at low initial pressures and decreases rapidly with increasing initial pressure excess pore pressure may be the result of gas hydrate dissociation due to continuous sedimentation tectonic uplift sea level fall heating or inhibitor injection the excess pore pressure is found to be potentially able 1 to facilitate or trigger submarine landslides in shallow water environments 2 to result in the formation of vertical columns of focused fluid flow and gas migration and 3 to cause the failure of a sediment layer confined by low permeability barriers in relatively deep water environments

high resolution 3d seismic data indicate focussed fluid migration pathways above polygonal fault systems of the mid norwegian margin seismic attribute analysis and interpretation of high resolution 3d and 2d seismic data reveal focussed fluid flow processes through the gas hydrate stability zone ghsz at the northern flank of the giant storegga slide diffusive fluid migration predominantly starts from a widespread polygonal fault system in fine grained sediments of the miocene kai formation the overlying 600 700 m thick plio pleistocene naust formation shows spatially related soft sediment deformation and overlying fluid conduits a low relief antiform structure connects to an overlying 250 m high 300 m wide and 3 km elongated columnar zone where seismic signatures suggest self enhanced permeability i e natural hydraulic fracturing push down effects create an elongated depression caused by increased gas accumulations where a cluster of vertical cylindrical acoustic pipe structures originates these pipe clusters pierce the ghsz and indicate focussed fluid flow pathways originating from potentially overpressured sediments high seismic reflection amplitudes at the seafloor above the pipe structures may indicate pockmarks with authigenic carbonates and or gas hydrates the observed objects and seismic features presented are not stand alone indicators for fluid flow but a joint perspective illustrates that they are vertically tied together providing new insights to the effects of focussed fluid flow

the diversification of paleozoic fire systems and fluctuations in atmospheric oxygen concentration by comparing silurian through end permian 250 million years myr charcoal abundance with contemporaneous macroecological changes in vegetation and climate we aim to demonstrate that long term variations in fire occurrence and fire system diversification are related to fluctuations in late paleozoic atmospheric oxygen concentration charcoal a proxy for fire occurs in the fossil record from the late silurian 420 myr to the present its presence at any interval in the fossil record is already taken to constrain atmospheric oxygen within the range of 13 to 35 the fire window herein we observe that as predicted atmospheric oxygen levels rise from 13 in the late devonian to 30 in the late permian so too fires progressively occur in an increasing diversity of ecosystems sequentially data of note include the occurrence of charcoal in the late silurian early devonian indicating the burning of a diminutive dominantly rhyniophytoid vegetation an apparent paucity of charcoal in the middle to late devonian that coincides with a predicted atmospheric oxygen low and the subsequent diversification of fire systems throughout the remainder of the late paleozoic first fires become widespread during the early mississippian they then become commonplace in mire systems in the middle mississippian in the pennsylvanian they are first recorded in upland settings and finally based on coal petrology become extremely important in many permian mire settings these trends conform well to changes in atmospheric oxygen concentration as predicted by modeling and indicate oxygen levels are a significant control on long term fire occurrence

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

the nature and age of cenozoic contractional deformation within the ne faroe shetland basin abstract a number of large mainly ne trending and a few nne trending cenozoic to recent anticlines have been identified from commercial seismic reflection data within the ne faroe shetland basin regional seismic markers have enabled the timing of formation of these structures to be ascertained and they appear to have developed mainly during early to mid miocene times but there is also some evidence of activity through to early pliocene to recent and even of pre miocene activity the ages of the cenozoic folds within the ne faroe shetland basin partly overlap with those observed on the norwegian margin and around the faroe islands and the hatton rockall areas although in general these regions have an important older component of development mechanisms for the formation of the folds are controversial though results from this study indicate that the ne orientations of many of the folds in the ne faroe shetland basin are compatible with compression approximately orthogonal to the continental margin the change from ne to nne trending anticlines in the vicinity of the magnus and erlend lineaments transfer zones may suggest that the development of these folds was related to sinistral strike slip movement along these major structures speculatively quaternary strike slip movement along these zones may also have triggered significant slope failure and the formation of mud volcanoes and mud intrusions as evidenced by the close spatial association of the miller slide headwall and the pilot whale diapirs

evidence of wildfires and elevated atmospheric oxygen at the frasnian famennian boundary in new york usa implications for the late devonian mass extinction the devonian period experienced significant fluctuations of atmospheric oxygen o2 levels 25 13 for which the extent and timing are debated also characteristic of the devonian period at the frasnian famennian f f boundary is one of the big five mass extinction events of the phanerozoic fossilized charcoal inertinite provides a record of wildfire events which in turn can provide insight into the evolution of terrestrial ecosystems and the atmospheric composition here we report organic petrology programmed pyrolysis analysis major and trace element analyses and initial osmium isotope osi stratigraphy from five sections of upper devonian f f interval from western new york usa these data are discussed to infer evidence of a wildfire event at the f f boundary based on the evidence for a wildfire at the f f boundary we also provide an estimate of atmospheric o2 levels of 23 25 at this interval which is in agreement with the models that predict elevated po2 levels during the late devonian this coupled with our os isotope records support the currently published osi data that lacks any evidence for an extra terrestrial impact or volcanic event at the f f interval and therefore to act as a trigger for the f f mass extinction the elevated o2 level at the f f interval inferred from this study supports the hypothesis that pco2 drawdown and associated climate cooling may have acted as a driving mechanism of the f f mass extinction

extent and duration of marine anoxia during the frasnian famennian late devonian mass extinction in poland germany austria and france the intensity and extent of anoxia during the two kellwasser anoxic events has been investigatedinarangeofeuropeanlocalitiesusingamultidisciplinaryapproach pyriteframboidassay gamma ray spectrometry and sediment fabric analysis the results reveal that the development of the lower kellwasser horizon in the early late rhenana zone frasnian stage in german type sections does not always coincide with anoxic events elsewhere in europe and in some locations seafloor oxygenation improves during this interval thus this anoxic event is not universally developed in contrast the upper kellwasser horizon developed in the late linguiformis zone frasnian stage in germany correlates with a european wide anoxic event that is manifest as an intensification of anoxia inbasinallocationstothepointthatstableeuxinicconditionsweredeveloped forexample inthebasins of the holy cross mountains poland the interval also saw the spread of dysoxic waters into very shallow water for instance reefal locations and it seems reasonable to link the contemporaneous demise of many marine taxa to this phase of intense and widespread anoxia in basinal locations euxinic conditions persisted into the earliest famennian with little change of depositional conditions only in the continental margin location of austria was anoxia not developed at any time in the late devonian consequently it appears that the upper kellwasser anoxic event was an epicontinental seaway phenomenon caused by the upward expansion of anoxia from deep basinal locales rather than an oceanic anoxic event that has spilled laterally into epicontinental settings

relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas u s a analyses of 21 samples collected from a core of the 52 8 cm thick stark shale member of the dennis limestone in wabaunsee county kansas demonstrate four cycles with two orders of magnitude variations in contents of cd mo p v and zn and order of magnitude variations in contents of organic carbon cr ni se and u the observed variability in amounts and or ratios of many metals and amounts and compositions of the organic matter appear related to the cause and degree of water column stratification and the resulting absence presence of dissolved o2 or h2s high cd mo u v zn and s contents a high degree of pyritization dop 0 75 0 88 and high high v v ni 0 84 0 89 indicate the presence of h2s in a strongly stratified water column intermediate contents of metals and s intermediate dop 0 67 0 75 and intermediate v v ni 054 0 82 indicate a less strongly stratified anoxic water column whereas low metal contents and low v v ni 0 46 0 60 indicate a weakly stratified dysoxic water column high p contents at the top of the organic matter rich intervals within the stark shale member indicate that phosphate precipitation was enhanced near the boundary between anoxic and dysoxic water compositions relatively abundant terrestrial organic matter in intervals deposited from the more strongly stratified h2s bearing water column indicates a combined halocline thermocline with the fresher near surface water the transport mode for the terrestrial organic matter the predominance of algal organic matter in intervals deposited from a less strongly stratified water column indicates the absence of the halocline and the presence of the more generally established thermocline relatively low amounts of degraded hydrogen poor organic matter characterize intervals deposited in a weakly stratified dysoxic water column the inferred variability in chemistry of the depositional environments may be related to climate variations and or minor changes in sea level during the general phase of deeper water deposition responsible for this widespread shale member

post breakup compression of a passive margin and its impact on hydrocarbon prospectivity an example from the tertiary of the faeroe shetland basin united kingdom the faeroeshetland basin is part of a passive continental margin that formed as a result of multiphase extension associated with north atlantic rifting during the mesozoic and paleocene breakup was followed by postrift subsidence during the latest paleocene to late eocene and the development of at least three 70 150 km 43 93 mi long broadly north south orientated slope canyons and linked terminal fans during the middle eocene the terminal fans filled northeast southwest striking basin floor bathymetric depressions that had formed above the hanging walls of underlying dormant northeast southwest trending mesozoic extensional faults and adjacent half graben depocenters compression during the middle and late miocene caused contractional reactivation of the mesozoic extensional faults and folding of the overlying uppermost paleocene to middle miocene postrift sediments into a series of 17 northeast southwest striking anticlinal domes the switch from hanging wall bathymetric depression during terminal fan deposition to anticlinal domal high during and after the middle to late miocene compression has led to the present day spatial coincidence of a potential hydrocarbon reservoir and an effective trap the anticlines also acted as the foci for gas migration during or after compression 15 ma to present however the timing of compression and differential uplift of the basin margins during the past 15 m y approximately 45 m y after the main phase of oil migration may be a critical negative factor for oil exploration in this part of the basin this hydrocarbon phase may have spilled during the structural reorganization either updip into shallower traps or out of the hydrocarbon system via seeps

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago

the rise of fire fossil charcoal in late devonian marine shales as an indicator of expanding terrestrial ecosystems fire and atmospheric change fossil charcoal provides direct evidence for fire events that in turn have implications for the evolution of both terrestrial ecosystems and the atmosphere most of the ancient charcoal record is known from terrestrial or nearshore environments and indicates the earliest occurrences of fire in the late silurian however despite the rise in available fuel through the devonian as vascular land plants became larger and trees and forests evolved charcoal occurrences are very sparse until the early mississippian where extensive charcoal suggests well established fire systems we present data from the latest devonian and early mississippian of north america from terrestrial and marine rocks indicating that fire became more widespread and significant at this time this increase may be a function of rising o2 levels and the occurrence of fire itself may have contributed to this rise through positive feedback recent atmospheric modeling suggests an o2 low during the middle devonian around 17 5 with o2 rising steadily through the late devonian and early mississippian to 21 22 that allowed for widespread burning for the first time in devonian mississippian marine black shales fossil charcoal inertinite steadily increases up section suggesting the rise of widespread fire systems there is a concomitant increase in the amount of vitrinite preserved woody and other plant tissues that also suggests increased sources of terrestrial organic matter even as end devonian glaciation was experienced fossil charcoal continued to be a source of organic matter being introduced into the devonian oceans scanning electron and reflectance microscopy of charcoal from late devonian terrestrial sites indicate that the fires were moderately hot typically 500 600 c and burnt mainly surface vegetation dominated by herbaceous zygopterid ferns and lycopsids rather than being produced by forest crown fires the occurrence and relative abundance of fossil charcoal in marine black shales are significant in that these shales may provide a more continuous record of fire than is preserved in terrestrial environments our data support the idea that major fires are not seen in the fossil record until there is both sufficient and connected fuel and a high enough atmospheric o2 content for it to burn