high resolution surface and subsurface sequence stratigraphy of late middle to late ordovician late mohawkian cincinnatian foreland basin rocks kentucky and virginia the late middle to late ordovician late mohawkian to cincinnatian supersequence in kentucky and virginia was deposited in a tectonically active foreland basin during a transition from the ice free early ordovician to the glacial late ordovician this sequence was deposited in less than 12 m y is 250 500 m thick and is composed of four large third order sequences each 40 150 m thick that are regionally correlative in outcrops cores and gamma ray logs smaller scale third order parasequence sets up to 20 m thick and component parasequences 1 8 m thick make up the larger sequences and are only locally correlative subtidal dominated parasequences comprise the basal part of each sequence whereas shallower subtidal or peritidal dominated parasequences compose upper parts of sequences each large third order sequence is asymmetric and marked by lowstand transgressive and highstand systems tracts with unique lithologic and gamma ray log response characteristics ramp margin wedges rmw are poorly developed and consist of marine siltstone or grainstone packstone sheets extending into deep ramp settings these sheets have high gamma ray values in their base and lower blockier gamma ray responses in their tops transgressive systems tracts tst are thin composed of high energy locally phosphatic grainstone copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received february 7 1996 revised manuscript received may 27 1997 final acceptance june 16 1997 2department of geology virginia tech blacksburg virginia 24061 0420 present address department of earth atmospheric and planetary sciences massachusetts institute of technology cambridge massachusetts 02139 3department of geology virginia tech blacksburg virginia 24061 0420 this study was supported by nsf grant ear 9316057 to j f read a grant from mobil oil company and grants in aid of research from the geological society of america and appalachian basin industrial associates to mike pope we thank john haynes brian keith and rick major for thorough and insightful reviews of an earlier version of this manuscript

seasonal diurnal and storm scale hydrochemical variations of typical epikarst springs in subtropical karst areas of sw china soil co2 and dilution effects summary two year continuous ph conductivity temperature and water stage of the two typical epikarst springs nongla spring and maolan spring about 200 km apart in subtropical karst areas of sw china were presented our primary study objective was to understand how karst systems respond hydrochemically to recharge at different time scales and what the biogeochemical processes and controlling factors in the sw china epikarst environment are a thermodynamic model was used to link the continuous data to monthly water quality data allowing the calculation of co 2 partial pressures and calcite dolomite saturation levels on a continuous basis marked seasonal diurnal and storm scale variations were observed for ph conductivity co 2 partial pressures and calcite dolomite saturation indexes of the springs indicating that both springs are dynamic and variable systems however the coefficients of variation of these hydrogeochemical features tends to be in the order of seasonal storm scale diurnal the seasonal and diurnal variations of these features higher conductivity and lower ph in summer and at daytime lower conductivity and higher ph in winter and at nighttime tend to co vary with temperature which influences the production of co 2 in soils thus being the driving force for the variations soil co 2 effect the storm scale fluctuations occur during the spring summer rainy days due to the storm events depending on the rainfall intensities however there are differences in magnitudes and direction of the variations of these features at very high rainfall intensity the dilution effect dominates the variations characterized by the decrease in both conductivity and calcite dolomite saturation of the springs while soil co 2 effect determines the variations at lower rainfall intensity characterized by increase in co 2 partial pressure and conductivity but decrease in ph and calcite dolomite saturation in a word the hydrodynamic aspects together with hydrobiogeochemical characteristics need to be taken into account to correctly explain the hydrochemical variations of the epikarst springs results from the study demonstrate the need to redesign hydrogeochemical sampling strategies for epikarst springs in karst areas with monsoon climate like sw china i e with remarkable seasonal matching fluctuations in temperature rainfall and vegetation

reservoir implications of modern karst topography tropical karst landscapes exhibit a predominance of positive relief features relative to the negative relief features i e sink holes dolines etc of temperate karst areas and yet paradoxically have never been observed in the subsurface on seismic sections to understand why this is the case topographic profiles were made over the positive karst relief features of china java and jamaica and were used to construct synthetic seismic sections the results indicate that in most instances the magnitude of the topographic relief is sufficient to be seen on seismic sections a possibility of misinterpreting karst highs as reefs seems clear but more important in explaining the paradox is the fact that the magnitude of modern karst relief expression is largely attributable to uplift over an extended period the probability of preservation of these positive relief solution residuals is dependent on the karstification process being aborted by the deposition of overlying sediment an event not likely to occur in an uplift area uplift of well lithified carbonate minimally results in an areally extensive runoff surface that controls the development of positive karst landforms uplift also commonly induces faulting and fracturing that further control the distribution of karst land forms hydrocarbon production from the resulting karst is geared to matrix porosity the higher the matrix porosity the greater the rate of deliverability of matrix oil to produced fracture and karst conduit oil in contrast the lowering of the base level of erosion due to a fall in sea level is generally less than that induced by uplift and consequently minimizes positive karst relief development relative to that of uplift subaerial exposure induced by passive sea level fall also minimizes the potential for the related occurrence of fracturing and faulting which of itself mitigates against the general development of positive karst relief the subaerial consequences of passive sea level fall are commonly preserved in the geologic record and result in karst reservoirs dominated by extensive moldic and vuggy porosity interconnected by solution channels these reservoirs lack the production problems commonly attending fractured karst reservoirs with little matrix porosity

the burgess shale and associated cambrian formations west of the fossil gully fault zone on mount stephen british columbia west of the fossil gully fault zone on mount stephen the three lowest members only of the burgess shale formation are preserved the kicking horse shale the yoho river limestone and the campsite cliff shale the formation rests unconformably upon the takakkaw tongue formation whose dark basinal limestones conformably overlie paler shelf like limestones of the mount whyte formation mapping has resolved a long standing problem and shown that the stratigraphical position of the famous mount stephen trilobite beds lies within the campsite cliff shale it has also revealed some of the complexities of the fossil gully fault zone among which different periods and directions of component fault movements are indicated faunal evidence shows that the plagiura kochaspis to albertella and albertella to glossopleura zonal boundaries lie within the takakkaw tongue sequence within the burgess shale three distinct soft bodied communities occur at different stratigraphical levels on this mountain slope the oldest

reef development at the frasnian famennian mass extinction boundary a newly compiled global reef database indicates that the 5 6 myr long frasnian late devonian metazoan reef episode had relatively lowdiversity compared to middle devonian highs w ith over 200 genera of calcitic rugose and tabulate corals following an initial early rise after late givetian coral and stromatoporoid extinctions reefs expanded for the last time during mid frasnian sealevel highstands but declined markedly in the late frasnian rhenana linguiformis conodont zones belowthe frasnian famennian f f boundary globally metazoan reefs were wiped out by the end frasnian some famennian reefs while partly retaining the structure of the underlying carbonate platform were built by cyanobacterial consortia such as renalcis rothpletzella girvanella and epiphyton during the famennian foraminiferans with calcite walls became abundant for the first time in the phanerozoic adding a newdimension to carbonate platforms colonial rugose corals phaceloid cerioid and thamnasterioid modules were absent in the early post extinction phases up into the mid famennian and very rare and non reefbuilding later but solitary deep water lazarus corals survived locally coral sponge reefs are unknown from the 21 myr long famennian also a time of very lowplatform carbonate production rare small isolated stromatoporoid sponge and lithistid sponge patch reefs returned episodically during the famennian in north america western europe australia and china the aragonitic stromatoporoids became extinct at the end of the famennian during a late devonian tectonically very active collisional caledonian mountain building phase oceanic and atmospheric cooling accompanied by sealevel lowstand systems exposed most carbonate platforms accelerating coastal erosion and karsting this increased the amount of clastics in the shelf slope setting in the last 1 3 myr prior to the f f boundary often burying reefs immediately following there were protracted losses in nearly all major tropical shelf benthic marine invertebrates exceeded only by the end permian extinctions in severity there is no apparent link between black organic rich horizons and reef demise at or close to the f f boundary the f f boundary not also marks the largest change from widespread flooded early and mid paleozoic continental cratons to narrow distal shelves but also spikes the largest known global phanerozoic shift in atmospheric o2 enrichment and co2 drawdown this threshold matched the rise of the first tropical rainforests and expansion of terrestrial biomes on the tropical coastal lowlands formerly occupied by carbonate platforms 6 2002 elsevier science b v all rights reserved

early devonian kess kess carbonate mud mounds of the eastern anti atlas morocco and their relation to submarine hydrothermal venting abstract spectacular conical early devonian carbonate buildups up to 55 m high that crop out in the eastern anti atlas of southern morocco are microbially mediated carbonate mud mounds that were surfaced by soft bottom communities dominated by small tabulate corals they formed on the hamar laghdad elevation which was created by a submarine volcanic eruption and were associated with a network of synsedimentary radial and tangential faults that originated by uplift of the intrusive laccolithic body underlying the kess kess formation these faults served as conduits for the migration of hydrothermal fluids to the sea floor most mounds developed over cross points of radial and tangential faults vents were episodically active until the famennian but extensive vent carbonate production occurred only during the emsian preliminary geochemical results document that mud mound carbonates and calcite cements in neptunian dikes precipitated from brines comprising a mixture of hydrothermal fluids and seawater in addition carbon isotope compositions 13c as low as 18o oo pdb suggest a contribution from thermogenic methane derived presumably from underlying basaltic intrusives aerobic bacterial oxidation of methane is favored as the main process driving carbonate precipitation in and rapid lithification of the mounds

how to explain a decapod crustacean diversity hotspot in a mid cretaceous coral reef article the mid cretaceous late albian decapod crustacean fauna from the koskobilo quarry in spain is the most diverse decapod fauna known thus far from the cretaceous this may be related to the coral reef environment in which these decapods were found within the aldoirar patch reef this diversity hotspot was further inves tigated by a detailed paleoecological study focusing on variation in lithology throughout the quarry using car bonate rock hand samples thin sections and acetate peels and by studying decapod rich sites within the quarry the northern and stratigraphically oldest part of the koskobilo quarry contained mostly wackestones and biomicrites the middle to southern part contained floatstones and biosparites or biomicrites with many sponge remains whereas the southernmost and stratigraphically youngest part consisted of coral rich boundstones and biolithites fossils were more abundant and generally larger in the southern part of the quarry decapod rich siteswere restricted to the southern part of the quarry possibly inpartbecauseofanincreasedpossibility for shelter and food in a coral rich area in the southernmost part of the quarry water depth was estimated to be between 20 and 80 m for at least the southern part with energy levels apparently increasing from the northern to the south ern part of the quarry systematic collecting was performed at four decapod rich sites in the quarry to investigate differences in decapod diversity composition and size width the decapod fauna from the site within the coral rich boundstones and biolithites appears to be the most diverse based on several diversity measures has a statistically different faunal composition contains species that were not found in other parts of the quarry and con sists of smaller decapods compared to other sites more specimens of species with a smaller maximum width were found here as well as fewer specimens with a large maximum width smaller presumed juvenile specimens of the crab goniodromites laevis were also excavated here this shows that decapod size can vary within a reef paguroids hermit crabs were mostly restricted to this coral rich site some of the many decapods at this site may have been obligatory associates with the mostly branching corals one site within the floatstone and biosparite zone contained hardly any decapods which may be related to the abundance of hard to eat corallinacean red algae a site in the olazagutia quarry in the same patch reef consisting of massive colonial corals did not yield any decapods presu mably because of the inaccessible nature of the coral framestone leaving few places as shelter for decapods the results suggest that different decapod sub and microenvironments existed within this patch reef thereby explaining at least in part the high diversity of decapods known from the koskobilo quarry this is one of the first times that a detailed paleoecological study has been performed for decapods in a fossilized coral reef these results concur with modern reefs in that decapod communities also differ among subenvironments the methodologies introduced herein for studying fossil decapods in reef environments can be used as well to study the paleoecology of decapods as well as other invertebrate sf rom other periods in earth s history

carbonate mounds from paradox to world heritage the recent marine carbonate world comprises two major compartments 1 the surface domain of the photozoan carbonates confined in space by water depth and by the penetration of light and 2 a deep domain where heterozoan mound builder guilds directly forage on fluxes of nutrients which primarily percolate from the photic zone and or are generated by in situ benthic processes locally giant cold water coral mounds tower up to heights of 150 to 250 m above the sea floor in general between 500 and 1300 m water depth and within sharply delineated provinces some 15 years of research on these giant mound provinces conveys a picture of their distribution in space and possibly sheds light on controls acting in concert globally there is no counterpart for the prolific north atlantic mound basin namb a chemical control is seen by an overlay of the mound provinces on a map of the aragonite saturation horizon ash an external physical control is inferred fromthe position of themound provinces girdling a vigorous north atlantic subtropical gyre systemand clustering close to the roof of the intermediate to deep water masses of a dynamically stratified ocean on the eastern boundary of the namb nutrient fluxes are enhanced by mixing processes driven either by internal waves between galicia and the shetlands or by the vast and heterogeneous eastern boundary upwelling system along the iberian african margins down to 10 n early diagenesis by carbonate dissolution and re precipitation driven by convecting or advecting internal fluids can contribute to stabilize such constructions facilitating an exuberant vertical accretion it is speculated that in thenorth atlantic ocean the deep water carbonate factory outclasses in size the shallow water coral reefs giant mound formation is a recurrent play of life since the dawn of the metazoans nama group upper neoproterozoic however with actors and plots varying from act to act remarkably literature reports only three occurrences of deep water mounds in the phanerozoic the modern ocean possibly the danian and the carboniferous some striking parallelisms in the development of the atlantic and the paleo tethys oceans combined with the developing insights in the controls on deep watermounds in the present ocean invite for a comparative study this has the potential to eventually shed light on the full circulation pattern of the paleo tethys ocean surface and deep comparative studies will build upon 1 modeling of ocean circulation constrained by the record of deep water carbonate systems and supported by advances in tracer and proxy tools and 2 field studies on representative and accessible continental locations the mound route that develops in morocco under the auspices of ioc unesco will provide tomulti disciplinary teams with marine and continental experience opportunities for confronting observations from the modern ocean and on key records of past oceanic basins it has the potential to eventually qualify for a unesco recognition as world heritage

petrology of futuna island lavas new hebrides an example of calc alkaline magmatism associated with the initial stages of back arc spreading abstract petrologic and chemical data are presented for samples from futuna island located behind the new hebrides island arc quartz normative basalts and basaltic andesites are the most abundant lava types there are mineralogically and chemically similar to the volcanic products of the central chain volcanic islands ambrym and aoba and other typical calc alkaline suites the lavas are enriched in the lil elements and depleted in ti and other transition elements their variations are consistent with fractionation of olivine fe ti oxide pyroxenes low ca and ca rich and plagioclase incompatible element ratios and abundances suggest that primary liquids were generated by complex mechanisms but a mantle source is needed to explain the data the most consistent problems are the concomitant and strong types of fractionation such as la ta and zr y whereas other coupled elements nb ta zr ta show chondritic ratios

architecture and depositional sequences of tertiary fault block carbonate platforms an analysis from outcrop miocene gulf of suez and computer modelling abstract this study combines outcrop with seismic data and tectonostratigraphic modelling to characterise the stratigraphy of tertiary fault block carbonate platforms seismic sections from the middle east and southeast asia indicate that carbonate platforms commonly develop on fault blocks in the late syn rift to post rift stage of basin evolution they are characterised by retrogradational or drowning morphologies with deep water clastics evaporites sealing the platforms a new tectono stratigraphic modelling program simulates the development of carbonate platforms on domino style fault blocks and predicts a distinctive tectonic control on the evolving syn rift stratigraphy detailed field work from a three dimensionally exposed miocene syn rift platform from the gulf of suez gebel abu shaar egypt shows the existence of unconformity bound depositional sequences which are predicted by the program and are interpreted to have formed in response to fault block rotation the sequences are characterised by synchronous hangingwall subsidence and footwall uplift and erosion the seismic images the modelling and the outcrop study provide different levels of information on fault block platforms and their characteristic stratigraphy the scale of the modelling is of particular value as it provides a link between the seismic scale imaging and outcrop data

spectral reflectance characteristics of the hamar laghdad hydrothermal sequence morocco implications for the methane origin on mars abstract we analyze and discuss reflectance spectra of carbonate rocks from the hamar laghdad area morocco where evidences of interactions with hydrothermal and in some cases methane enriched fluids derived from underlying volcanoclastic rocks are reported in the literature deconvolution of the rock spectra into a sum of gaussians using mgm resolved a number of both vibrational and electronic absorption features mainly assigned to co32 al oh and fe2 fe3 cu cf interaction processes respectively the associations of these absorption bands are exhaustive descriptions of the rock spectral properties a spectral model of the hamar laghdad carbonate sequence was therefore delineated based on the integration of these absorption band associations with xrf and mossbauer analyses of the rock samples the model involves pure limestones and dolostones limestone with iron carbonates mixed carbonate and al silicate impure limestones limestones with iron sulfides the model points out the complexity of the spectral characteristics of rocks that underwent hydrothermal and partly methanogenic processes but also suggests an alternative geologic scenario plausible for possible methanogenic activity in the mars geologic past

evaluating new fault controlled hydrothermal dolomitization models insights from the cambrian dolomite western canadian sedimentary basin fault controlled hydrothermal dolomitisation in tectonically complex basins can occur at any depth and from different fluid compositions including deep seated crustal or basinal brines nevertheless many studies have failed to identify the actual source of these fluids resulting in a gap in our knowledge on the likely source of magnesium of hydrothermal dolomitisation with development of new concepts in hydrothermal dolomitisation the study aims in particular to test the hypothesis that dolomitising fluids were sourced from either seawater ultramafic carbonation or a mixture between the two by utilising the cambrian mount whyte formation as an example here the large scale dolostone bodies are fabric destructive with a range of crystal fabrics including euhedral replacement rd1 and anhedral replacement rd2 since dolomite is cross cut by low amplitude stylolites dolomitisation is interpreted to have occurred shortly after deposition at a very shallow depth 1 km at this time there would have been sufficient porosity in the mudstones for extensive dolomitisation to occur and the necessary high heat flows and faulting associated with cambrian rifting to transfer hot brines into the near surface while the 18owater and 87sr 86sr ratios values of rd1 are comparable with cambrian seawater rd2 shows higher values in both parameters therefore although aspects of the fluid geochemistry are consistent with dolomitisation from seawater very high fluid temperature and salinity could be suggestive of mixing with another hydrothermal fluid the very hot temperature positive eu anomaly enriched metal concentrations and cogenetic relation with quartz could indicate that hot brines were at least partially sourced from ultramafic rocks potentially as a result of interaction between the underlying proterozoic serpentinites and co2 rich fluids this study highlights that large scale hydrothermal dolostone bodies can form at shallow burial depths via mixing during fluid pulses providing a potential explanation for the mass balance problem often associated with their genesis

middle jurassic stromatactis mud mounds in the pieniny klippen belt carpathians a possible clue to the origin of stromatactis abstract four occurrences of jurassic stromatactis mud mounds were found in the czorsztyn unit of the pieniny klippen belt western carpathians in western slovakia slavnicke podhorie babina and in the transcarpathian ukraine priborzhavskoe and veliky kamenets their stratigraphic range is from bajocian to callovian the mounds consist of micropeloidal mudstones wackestones to packstones with a fauna including pelecypods brachiopods ammonites and crinoids spicules and skeletons of siliceous sponges are abundant in every section all of the mounds contain networks of stromatactis cavities that are partially filled with radiaxial fibrous calcite rfc and locally by internal sediments at slavnicke podhorie the sparry masses that fill stromatactis cavities are weathered out and show casts of sponges parallel study of the weathered casts and their cross sections in slabs showed that they bear all the signs of stromatactis relatively flat bottoms and digitate upper parts rfc initial fillings and eventual blocky calcite later filling almost no original sponge structures were preserved this strongly supports the possible sponge related origin for stromatactis cavities

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

the middle cambrian burgess shale and its relationship to the stephen formation in the southern canadian rocky mountains the burgess shale has been an anomalous geologic unit ever since walcott named it in 1911 as the geographic equivalent of the ogygopsis shale in the middle cambrian stephen formation of southeastern british columbia but it has never been recognized outside of its type locality so its status relative to the stephen formation remained uncertain the geologic setting of the burgess shale was determined by aitken and fritz in 1968 when they recognized the cathedral escarpment and divided the stephen formation into a thin platformal succession on top of the escarpment and a thick basinal succession which included walcott s burgess shale in front fieldwork by royal ontario museum parties between 1982 and 1997 has now demonstrated that the thin and thick stephen successions lie within different facies belts and should be regarded as separate formations the stephen shale formation is part of the middle carbonate belt succession whereas the name burgess shale formation is applied to the thick basinal

a proposed nomenclature for stages and series for the cambrian of laurentia an internally consistent succession of six named regional stages from youngest to oldest sunwaptan steptoean marjuman delamaran dyeran montezuman with their boundaries defined by regional extinction events within the trilobite record is proposed for the trilobite bearing rocks of laurentia sub trilobite stage s are recommended but unnamed the three youngest stages have been named previously but the lower boundary of the marjuman is shifted downward the three older stages within the trilobite record are new if deemed necessary four regional series are also suggested from youngest to oldest millardan lincolnian waucoban and begadean each of the three youngest series accommodates two stages

atmospheric co2 sink silicate weathering or carbonate weathering it is widely accepted that chemical weathering of ca silicate rocks could potentially control long term climate change by providing feedback interaction with atmospheric co2 drawdown by means of precipitation of carbonate and that in contrast weathering of carbonate rocks has not an equivalent impact because all of the co2 consumed in the weathering process is returned to the atmosphere by the comparatively rapid precipitation of carbonates in the oceans here it is shown that the rapid kinetics of carbonate dissolution and the importance of small amounts of carbonate minerals in controlling the dissolved inorganic c dic of silicate watersheds coupled with aquatic photosynthetic uptake of the weatheringrelated dic and burial of some of the resulting organic c suggest that the atmospheric co2 sink from carbonate weathering may previously have been underestimated by a factor of about 3 amounting to 0 477 pg c a this indicates that the contribution of silicate weathering to the atmospheric co2 sink may be only 6 while the other 94 is by carbonate weathering therefore the atmospheric co2 sink by carbonate weathering might be significant in controlling both the short term and long term climate changes this questions the traditional point of view that only chemical weathering of ca silicate rocks potentially controls long term climate change

global and regional influences on equatorial shallow marine carbonates during the cenozoic abstract the se asian carbonate record allows insight into the poorly known response of equatorial marine systems to regional and global change during the cenozoic there is a marked change from larger benthic foraminifera to corals as dominant shallow marine carbonate producers in se asia around the oligo miocene boundary the early miocene acme of coral development in se asia lags oligocene coral development in the caribbean and mediterranean despite local tectonics providing apparently suitable habitable areas regional and global controls including changing co2 oceanography nutrient input and precipitation patterns are inferred to be the main cause of this lag in equatorial reefs it is inferred that moderate although falling level of co2 ca2 and ca mg when combined with the reduced salinities in humid equatorial waters all contributed to reduced aragonite saturation hindering reefal development compared with warm more arid regions during the oligocene by the early miocene atmospheric co2 levels had fallen to pre industrial levels although this was a relative arid phase globally in se asia palynological evidence indicates that the early miocene experienced everwet but more stable and less seasonal conditions than periods before or after tectonic convergence truncated deep throughflow of cool nutrient rich currents from the pacific to indian ocean around the beginning of the miocene thereby directly and perhaps indirectly though less seasonal conditions reducing nutrients it is inferred that aragonitic reefs were promoted where previously the waters had been more acidic more mesotrophic more turbid and less aragonite saturated extensive reefal development resulted in an order of magnitude expansion of shallow carbonate areas through buildup and pinnacle reef formation in the early miocene tectonics via increased habitat partitioning and reducing distances to other coral rich regions may also have contributed to enhanced reefal development declining reefal importance at the end of the early miocene resulted from uplift of land areas enhanced oceanic ventilation through thermohaline circulation and narrowing of oceanic gateways as well as increased seasonal runoff at least in se asia through initiation intensification of the monsoons implications of this study are that with current anthropogenically induced environmental changes it will be the diverse reefs of se asia that are likely to be amongst the first and hardest hit as oceanic aragonite saturation decreases and terrestrial nutrient runoff increases

hydrothermal origin of devonian conical mounds kess kess of hamar lakhdad ridge anti atlas morocco various interpretations have been proposed for the origin of peculiar cone shaped finely crystalline devonian carbonate mounds of the hamar lakhdad ridge anti atlas morocco ranging from shallow water reefs to deep water mud mounds formed by biogenic and or hydrodynamic processes this study is the first integrated sedimentological and geochemical analysis of these structures the mounds are cone shaped steep sided circular to subelliptical in plan view and exhibit internal crude bedding parallel to the mound9s outer surface they occur in a cluster of 48 mounds on top of a volcanic massif stable isotope analyses of first stage isopachous nonluminescent cement have yielded marine values in contrast the finely crystalline carbonate that makes up the bulk of the mound and the internally sedimented mud between crusts of early marine cements have significantly lower 18 o values whereas values of 13 c are similar to those of the early marine cement strontium isotope ratios also clearly distinguish the nonluminescent early marine cements from the finely crystalline material the 87 sr 86 sr values for the former 0 707 934 0 709 392 are in or near the devonian marine range whereas the ratios for the latter 0 708 515 0 709 656 indicate a more radiogenic sr source on the basis of their lithology architecture isotope geochemistry and clustered occurrence on top of a volcanic pile we propose that the finely crystalline material that forms the mounds and the intermound beds was precipitated from hydrothermal fluids and that accretion of the material was driven by hydrothermal venting

tepees in peritidal carbonates origin via earthquake induced deformation with example from the middle cambrian of western canada abstract tepee structures are common in many ancient carbonate tidal flat successions and because analogues are known from tropical coastal areas they are well established as evidence for synsedimentary lithification of subaerially exposed carbonate sediment existing explanations involving desiccation thermal expansion and contraction fluctuating groundwater pore pressure or diagenetic force of crystallization do not adequately account for the style and degree of deformation seen in some examples such as those in the middle cambrian cathedral formation of the southern rocky mountains western canada these tepees provide evidence for essentially instantaneous events causing brittle failure of decimetre thick crusts of ooidal and pisoidal grainstone followed by their dilation rupturing separation tilting and shingling they can be explained as breccias generated by sporadic episodes of strong ground motion from earthquakes that emanated from a syndepositionally active fault system nearby variably directed tensile and compressive stresses broke crusts shifted them upwards and shuffled them laterally subsequent microbial encrustation and vigorous flushing by seawater in the resulting shelter cavities led to rapid stabilization by cementation recognition of the role of seismically induced deformation in explaining some tepee structures furnishes a proxy for synsedimentary tectonism and adds another member to the family of seismites which reflect a range of rheological properties of unlithified and lithifying sediments

evolution of late oligocene early miocene attached and isolated carbonate platforms in a volcanic ridge context maldives type yadana field offshore myanmar this study investigates the stratigraphic evolution of the late oligocene early miocene carbonate platforms of the yadana area offshore myanmar well data regional 2d and local 3d seismic surveys allow the identification of three shallow water carbonate platforms yadana 3df and 3de showing various morphologic and stratigraphic patterns influenced by the presence of a paleohigh the identification of seven seismic sequences in the yadana area constrains the stratigraphic evolution in three stages 1 development of aggrading attached and isolated platforms during the chattian 2 a period of platform emersion during the oligocene miocene transition 3 drowning of the smaller buildup 3de associated with km scale backstepping on the large platforms 3df and yadana during the aquitanian the aquitanian marks the onset of renewed volcanic activity associated with the development of fringing carbonate reefs during the burdigalian the rapid similar to 6 my development of these wide similar to 5 70 km and thick similar to 300 850 m carbonate platforms has been mainly controlled by the subsidence however the results highlight a strong overprint of eustatic fluctuations on the rates of change in accommodation and hence on the stratigraphic architecture of the carbonate platforms based on an alternative model for the cenozoic geodynamic evolution of the yadana area our results suggest that the platforms developed on a volcanic ridge of hotspot origin located in the indian ocean and not on a volcanic arc subduction jump processes are interpreted to have played a key role in the demise of all platforms by drastically changing the paleoenvironmental conditions during the early miocene and led to the present day location of the yadana ridge in a back arc setting the carbonate platforms from the yadana area are thus a representative example of the interplay between global mechanisms and local paleoenvironmental parameters on carbonate platform initiation growth and demise c 2017 elsevier ltd all rights reserved

reinterpretation of middle cambrian stratigraphy of the rifted western laurentian margin burgess shale formation and contiguous units sauk ii megasequence rocky mountains canada abstract until recently research on the renowned fossil animals of the burgess shale has advanced to a greater degree than an understanding of the rocks in which they are found studies addressing lithostratigraphy and hydrothermal petrography of the so called inner carbonate belt and adjacent chancellor group however have begun to re evaluate long standing hypotheses on the middle cambrian of western canada tectonic activity along the kicking horse rim buried remnants of neoproterozoic rifting during the cambrian period had more influence on local sedimentation than previously thought notably large scale collapse of the cathedral carbonate platform margin at 509 ma bp is evidence of reactivated basement faults these failures produced listric megatruncation surfaces having near vertical escarpments 150 m in height where they terminate against the platform the majority of what have been interpreted as shed olistoliths from the cathedral platform margin is herein shown instead to be carbonate mud mounds these grew in situ along the face of the cathedral escarpment and are associated with fossiliferous intervals in overlying basinal mudstones at three distinct stratigraphic horizons two within the burgess shale during the delamaran and marjuman stages the mounds nucleated where deep seated normal faults intersected the seafloor building primarily during periods of relative sea level transgression mound growth is associated with syndepositional exhalative activity inferred from stratigraphic relations sedimentology and geochemistry the new name monarch formation is proposed for the initial post collapse beds and mounds deposited against the cathedral escarpment early glossopleura zone the variably defined term takakkaw tongue is thereby confined to pre collapse slope deposits coeval to and correlative with the cathedral formation

the dogtooth duplex a model for the structural development of the northern purcell mountains structural analysis based on recent detailed mapping of part of the dogtooth range of the northern purcell mountains confirms and refines a previous interpretation of a duplex structure which after its formation was carried passively in the hanging wall of the out of sequence purcell thrust several parameters such as thrust spacing thrust displacement and fold shape place geometric constraints on the dogtooth duplex thrust spacing displacement ratios indicate that the older structures of the western dogtooth range can be approximated by an antiformal stack model whereas the younger structures of the eastern dogtooth range fit a hinterland dipping duplex the sole thrust of the dogtooth duplex is inferred to follow incompetent rocks in or below the basal part of the hadrynian windermere supergroup the roof thrust is inferred to follow shaley rocks probably in the middle cambrian chancellor formation from balanced restored cross sections total shortening within the duplex is estimated at 18 2

structure and tectonic development of the southern rocky mountain trench the rocky mountain trench is one of the youngest most prominent and most enigmatic structures of the canadian cordillera approximately 650 km of seismic reflection data providing regional three dimensional coverage over an area of 10 000 km include six crossings of the rocky mountain trench between 49 n and 50 15 n prominent reflections from mid proterozoic moyie sills outline thrust and fold structures of a late jurassic to early cretaceous fault system that was cut by the rocky mountain trench fault in the tertiary the near basement reflections outline a 10 km high west facing basement ramp the hinge line of which spatially coincides with the rocky mountain trench in this area this ramp is part of a mid proterozoic margin upon which the belt purcell supergroup was deposited and is preserved beneath the trench during mesozoic contraction the basal detachment of the foreland belt closely followed the craton cover contact across the basement ramp thrusting ceased and extension was initiated when a culmination of thick basinal strata was juxtaposed with the basement ramp in the eocene miocene the basement ramp and the culmination above it focused stress reactivating the basal detachment and causing extensional faulting in the southern rocky mountain trench the rocky mountain trench fault may be linked via the basal detachment to the flathead fault on the east and the eocene extensional faults that flank the omineca belt on the west

origin and evolution of fault controlled hydrothermal dolomitization fronts a new insight abstract dolomitization is one of the most significant diagenetic reactions in carbonate systems occurring where limestone caco3 is replaced by dolomite camg co3 2 under a wide range of crystallization temperatures and fluids the processes governing its formation have been well studied but the controls on the position of dolomitization fronts in ancient natural settings particularly in a fault controlled hydrothermal system htd have received remarkably little attention hence the origin and evolution of htd dolomitization fronts in the stratigraphic record remain enigmatic here a new set of mineralogical and geochemical data collected from different transects in a partially dolomitized cambrian carbonate platform in western canada are presented to address this issue systematic patterns of sudden decrease in the magnesium content mol mgco3 and increase in porosity were observed towards the margin of the body furthermore fluid temperatures are cooler and 18 owater values are less positive at the dolomitization front than within the core of the body these changes coincide with a change from poorly ordered planar e dolomite with multiple crystal zonations at the margin to an unzoned well ordered interlocking mosaic of planar s to nonplanar dolomite in the core of the body these phenomena are hypothesized to reflect dynamic self limiting processes in the formation and evolution of htd dolomitization fronts through i plummet of dolomitization potential at the head of dolomitizing fluids due to progressive consumption of magnesium and fluid cooling and ii retreat of dolomitization fronts towards the fluid source during subsequent recrystallization of the dolomite body inboard of the termination once overdolomitization took place this new insight illustrates how dolomitization fronts can record the oldest phase of dolomitization instead of the youngest as is often assumed formation of porosity is interpreted to occur as the result of acidification induced grain leaching during the development of dolomitization fronts this mechanism coupled with retrogradation of dolomitization fronts may help to explain the apparent enhancement of porosity in proximity to dolomitization fronts

weathering plants and the long term carbon cycle the chemical weathering of ca mg silicate rocks is the principal process whereby co2 is removed from the atmosphere on long or multimillion year time scales at present vascular land plants exert an important influence on weathering by recycling water and by bringing about the secretion of acids and the buildup of high levels of co2 in soils before the spread of vascular plants on the continents during the mid paleozoic chemical weathering must have been achieved by higher levels of atmospheric co2 and or by the intercession of primitive land biota such as lichens and cyanobacteria from examination of several pre vascular weathering scenarios it is concluded that in order to prohibit unreasonably high levels of atmospheric co2 weathering during the precambrian and early paleozoic must have taken place under essentially closed system abiotic conditions linear feedback or via strong regulation by primitive biota preliminary examination of modern weathering by lichens over tens to thousands of years militates against the latter possibility however much more work needs to be done on the quantitative effect of both primitive biota and vascular plants on the rate of weathering and their response to changes in atmospheric co2 before anything more definitive can be said

stratigraphic framework of productive carbonate buildups hydrocarbon productive carbonate buildups are found within a relatively narrow window of geologic time and stratigraphic settings because buildups are common exploration objectives in frontier and mature basins an understanding of their stratigraphic occurrence permits them to be more accurately explored based on a worldwide survey most production occurs in isolated periods of geologic time middle silurian late silurian late middle and late devonian late pennsylvanian and early permian late cretaceous paleocene and miocene the authors results suggest that many factors of successful buildup plays are predictable on the basis of geohistory analysis and of basin filling stratal patterns deposition of extensive source beds and thick buildups coincide with second order eustatic rises other primary controls on the temporal distribution of buildups include reef building organism type mineralogy and paleolatitude geohistory analysis indicates that periods immediately prior to or during the earliest portion of rapid increases of accommodation correspond to times of productive buildup growth during this time shelf margins step landward and buildups become progressively more areally restricted buildups eventually are unable to keep pace with high rates of accommodation increase and often are overlain by distal toes of clinoforms within regressive wedges deposited during subsequent periods with lower rates of accommodation increase themore result is a stratigraphic juxtaposition of mounded reservoir carbonate and deep marine sealing shale this basin fill position accounts for over 70 of known buildup reservoired hydrocarbons buildups deposited in overlying regressive wedges are often lower relief and prone to seal problems less

megabreccia shedding from modern low relief carbonate platforms nicaraguan rise single channel seismic reflection data from the margins of lowrelief 150 250 m measured from edge of bank to basin carbonate platforms on the northern nicaraguan rise reveal complex seismic intervals consisting of mounded chaotic seismic facies interspersed with discontinuous parallel laminated seismic facies we interpret that these intervals contain megabreccias chaotic facies and sandy turbidites parallel laminated facies one megabreccia is exposed on the sea floor displaying an overall fan shape having individual blocks measuring nearly 300 m across and 110 m high the source area consists of a scalloped embayment with a headwall scarp 180 m high reflections within the platform are sharply truncated by this escarpment this single megabreccia is 120 m thick and extends 27 km along slope and 16 km out into the basin other megabreccias within the basin have individual blocks measuring 400 m across rocks from dredge hauls are a mixture of shallow and deep water facies shallow water facies consist of mixed skeletal grain stones and halimeda packstones deep water facies are massive chalks chalks with shallow water skeletal grains and chalk block breccias this indicates that the megabreccias formed as a result of bank margin collapse during which the ensuing debris flow eroded into slope and basin facies mixing rock types together we speculate that bank margin collapse events resulting in megabreccia formation may have been seismically triggered and we emphasize that these large scale mass wasting events occurred along margins of low relief carbonate platforms

geochemistry of basalts from central and southern new hebrides arc implication for their source rock composition abstract the basaltic rocks from the central and southern islands of the new hebrides aneityum tanna erromango efate emae tongoa and epi have geochemical features typical of island arc volcanics they are enriched in lile and depleted in zr hf nb and ta compared to n type morb the rocks were derived from a similar upper mantle source as n type morb but with a higher degree of partial melting in addition their source was enriched in lile k rb sr ba and lree probably by migrating hydrous fluids released during the dehydration of the subducted oceanic slab the basalts from futuna island which is located farther from the trench display characteristics typical of calc alkaline rocks the futuna basalts were generated from a different lile enriched upper mantle source it seems that this upper mantle source was modified by interaction with partial melts from the subducted oceanic lithosphere

iron framboids in the hydrocarbon related middle devonian hollard mound of the anti atlas mountain range in morocco evidence of potential microbial biosignatures iron framboids in the context of a middle devonian hydrocarbon seep conical mound anti atlas morocco have been thoroughly investigated through a combination of techniques including optical and high resolution scanning electron microscopy x ray diffraction energy dispersive x ray spectroscopy raman microscopy and time of flight secondary ion mass spectroscopy framboids occur embedded in laminated carbonates of the mound and are precipitated along the veins that crosscut it and served as the conduits for channeled reduced hydrocarbon rich fluids the morphology structure and composition of the framboids contribute to the reconstruction of the complex interplay between the advected fluids and the associated biological and or abiological processes a comparison of our dataset with that from modern framboids formed under similar conditions indicates that the fe rich framboids represent replaced primary pyrite framboids produced as a consequence of bacterial sulfate reduction and the anaerobic oxidation of methane

carbonate platform growth influenced by contemporaneous basaltic intrusion albian of larrano spain carbonate platform growth in active tectonic settings may be strongly influenced by the structural evolution of the basin including volcanic activity in this paper the sedimentary tectonic evolution of the duranguesado carbonate platform larrano in northern spain is described and an evolutionary depositional model is presented the albian duranguesado carbonate platform deposits are dominated by rudist and coral limestones with small intervening argillaceous limestone filled troughs 10 30 m deep the platform succession is divided into two parts the lower platform deposits were intruded by volcanics and tilted before the deposition of the upper platform succession a volcanic vent plug filling an upward flaring pipe occurs in the lower carbonate platform succession the timing of intrusion is well constrained to the early albian tectonic extension and active deep seated strike slip faults induced magma ascent at a fault intersection sedimentological analysis of these areas indicates that before volcanic intrusion they acted as weakened zones of extension and were slightly more subsident basinal areas these sites contain anomalous accumulations of siliceous sponge spicule deposits linked to the release of hydrothermal fluids on the sea floor after the phase of intrusion tilting and erosion of the platform and its associated volcanic products occurred as the intrusion cooled the platform downwarped leading to the formation of an overlying perched capping basin bordered by carbonate platforms over the volcanic plug carbonate mounds grew on local palaeohighs the presence of strike slip and magma emplacement in the duranguesado platform is related to movements between the iberian and european lithospheric plates which were accommodated by rotation and lateral movement of the crust along wrench faults

hydrologically driven variations in the karst related carbon sink fluxes insights from high resolution monitoring of three karst catchments in southwest china summary rainfall p discharge q water temperature ph and specific electrical conductivity ec of the three karst catchments banzhai huanghou and houzhai with different land uses and carbonate lithologies but similar subtropical monsoonal climate in guizhou province southwest china were monitored with ctdp 300 high resolution multi parameter data loggers during the period of may 2007 october 2013 in addition hco3 and calcium concentrations were titrated in the field and the other major ions determined in the laboratory once every one or two months simple linear regression models were used to link the continuous chemical data to in situ measured data to estimate the concentration of hco3 the co2 partial pressures and the calcite saturation indices on the high resolution logger data continuous karst related carbon sink fluxes csfs were also estimated with the continuous q and hco3 concentrations in each catchment area the primary goal of this study is to understand how discharge and hco3 concentration determine the csfs at the storm scale seasonal scale and annual scale and to estimate the csfs for the three studied catchments results show that the variation in runoff river discharge played a more important role in controlling the csfs than the variation in hco3 for all the karst catchments because of the chemostatic behavior of hco3 in the catchments soil coverage vegetation and bedrock lithology determined the csfs by controlling the proportion of precipitation that recharges groundwater and thus q and controlling the soil co2 productivity and thus hco3 the average csfs in the banzhai huanghou and houzhai karst catchments were 29 3 33 5 and 39 8 t co2 km 2 a 1 respectively which are 15 times higher than those csfs by silicate weathering in the silicate rock catchments with similar hydrology showing the dominant role of carbonate weathering in the rock weathering related carbon sink the interannual change in csfs was large 1 7 2 5 fold for this study depending mainly on the variations of catchment river discharge e g high flow year vs low flow year this suggests that the conventional view that pre and post anthropogenic riverine carbon fluxes are equal is problematic in that large changes in river hydrology caused by global climate and land use and land cover changes have already been documented

geothermal convection in the tengiz carbonate platform kazakhstan reactive transport models of diagenesis and reservoir quality a fundamental challenge in carbonate reservoir characterization is predicting the spatial distribution of diagenesis we used a reactive transport model to investigate the viability of geothermal convection and associated patterns of diagenetic porosity modification in the tengiz isolated carbonate platform reservoir before burial forced convection generates significant calcite dissolution locally up to 45 toward the platform center minor calcite cementation up to 0 4 in the slope and moderate calcite dissolution and cementation up to 1 6 in serpukhovian boundstone convective cells the patterns and rates of diagenesis proved critically sensitive to specified vertical permeability after burial with 200 m 660 ft of salt modeled subsurface temperature contrasts drive platform scale free convection flow is hydraulically closed but significant dissolution up to 7 3 after 20 m y occurred in the serpukhovian and visean platform interior and minor cementation up to 0 7 occurred toward the margin a shale filled salt withdrawal basin 500 m 1640 ft deep significantly modifies the subsurface temperature distribution and free convective flow ascending groundwaters beneath the withdrawal basin created a zone of calcite dissolution up to 24 5 in 20 m y with a mushroom geometry and minor cementation up to 2 3 in 20 m y in the distal platform interior and margin rates of diagenesis are dramatically reduced with increasing overburden as compaction retards convective flow from a generic perspective free convection persists if the salt overburden is substituted with shale although flow is reversed resulting in a different distribution of diagenesis simulations of geothermal convection provide a physically viable model for the integration of direct diagenetic observations to augment predictions of reservoir quality in tengiz and other carbonate platform reservoirs

middle cambrian carbonate platform collapse southeastern canadian rocky mountains regional erosion features termed megatruncation surfaces at the seaward margin of a middle cambrian carbonate platform in southeastern british columbia are inferred to be the proximal parts of gravity slide scars comparable in scale and morphology to modern examples in the caribbean region the surfaces truncate up to 200 m of outer platform strata and have low angle to near vertical headwalls they can be traced a minimum of 56 km along depositional strike and appear to extend at least 8 km basinward of the platform edge they therefore profoundly affect regional stratigraphy

a groundwater conceptual model and karst related carbon sink for a glacierized alpine karst aquifer southwestern china summary in the jade dragon snow mountain jdsm region yunnan province sw china an extensive hydrochemical and stable isotopic study of a glacierized alpine karst aquifer was conducted during the period 2011 2014 the objectives of the study were first to establish a conceptual hydrogeological model of the karst groundwater system second to estimate the proportion of extra glacier melt water infiltrating the karst aquifer that is being induced by the regional climate warming third to calculate the karst related flux of carbon into the karst aquifer knowledge of the local hydrogeological background from previous work was the starting point of the hydrochemical and stable isotopic study some representative spring waters and recharge waters i e glacier melt water and rainwater were investigated both spatially and temporally by hydrochemical and isotopic techniques including analysis of major and some minor ions and o and h stable isotopes a conceptual hydrogeological model of a fracture diffuse flow karst groundwater aquifer was proposed the proportion of glacier melt water infiltrating into the karst aquifer was estimated by using the karst spring as a natural pluviometer and with stable isotope analysis results show that 1 the jdsm karst aquifer is a diffuse flow system 2 it has a number of discharge areas and the jinsha river is the karst drainage base level 3 the proportion of the glacier melt water penetrating the karst aquifer is 29 and 4 the karst related carbon sink is 26 67 3 44 t km 2 a 1 as co 2 which is lower than that in non glacierized karst aquifers but over ten times larger than the carbon sink flux from silicate weathering in non karst areas showing the control of both climate and lithology on the rock weathering related carbon sink and the significance of carbonate weathering in the global carbon cycle

methods for identification of isolated carbonate buildups from seismic reflection data isolated carbonate buildups icbs are commonly attractive exploration targets however identifying icbs based only on seismic data can be difficult for a variety of reasons these include poor quality two dimensional data and a basic similarity between icbs and other features such as volcanoes erosional remnants and tilted fault blocks to address these difficulties and develop reliable methods to identify icbs 234 seismic images were analyzed the images included proven icbs and other features such as folds volcanoes and basement highs which may appear similar to icbs when imaged in seismic data from this analysis 18 identification criteria were derived to distinguish icbs from non icb features these criteria can be grouped into four categories regional constraints analysis of basic seismic geometries analysis of geophysical details and finer scale seismic geometries systematically assessing the criteria is useful because it requires critical evaluation of the evidence present in the available data working from the large scale regional geology to the fine details of seismic response it is also useful to summarize the criteria as a numerical score to facilitate comparison between different examples and different classes of icbs and non icbs our analysis of scores of different classes of features suggests that the criteria do have some discriminatory power but significant challenges remain

organic matter remains in the laminated microfabrics of the kess kess mounds hamar laghdad lower devonian morocco abstract the lower devonian kess kess mounds of the hamar laghdad ridge se morocco are one of the most spectacular carbonate buildups of the world the differential erosion highlighted their original shapes and the relationships with associated beds the origin of these buildups is still under debate and the most consistent hypothesis is related to submarine hydrothermal vents in which bacteria and or archaea played a prominent role in the carbonate biomineralization the research was focused on micro nanomorphology and biogeochemistry of the very fine dark and white wrinkled laminated microbialites to investigate the traces of prokaryotic metabolic activity which possibly induced their precipitation epifluorescence observations put in evidence a high organic matter content mainly in the dark laminae the geochemical characterization of extracted organic matter was performed through the functional group analyses by ft ir spectroscopy ft ir parameters indicate a marine origin and low thermal evolution for these organic compounds the organic matter which is characterized by the presence of stretching c c vibrations attributable to alkene and or unsaturated carboxylic acids is likely to have been synthesized by bacteria and or archaea communities

paleoreef maps evaluation of a comprehensive database on phanerozoic reefs to get a better understanding of controls on reef development through time we created a comprehensive database on phanerozoic reefs the database currently comprises 2470 reefs and contains information about geographic position paleoposition age reef type dimensions environmental setting paleontological and petrographical features and reservoir quality of each buildup reef data were analyzed in two qualitatively different ways the first type of analysis was by visualization of paleogeographic reef distribution maps five examples late devonian early permian late triassic late jurassic middle miocene are presented to show the potential of paleoreef maps for paleogeographic and paleoclimatological reconstructions the second type of analysis was a numerical processing of coded reef characteristics to realize major trends in reef evolution and properties of reef carbonates the analysis of paleolatitudinal reef distributions through time shows pronounced asymmetries in some time slices probably related to climatic asymmetries rather than controlled by plate tectonic evolution alone the dominance of particular reef builders through time suggests that there are seven cycles of phanerozoic reef development first curves for the phanerozoic distribution of bioerosion in reefs bathymetric setting and debris potential of reefs are presented the observed pattern in the temporal and spatial distribution of reefs with reservoir quality may assist in hydrocarbon exploration statistical tests on the dependencies of reefal reservoir quality suggest that large size high debris potential low paleolatitude high amount of marine aragonite cement and a platform shelf edge setting favor reservoir quality reefal reservoirs are significantly enhanced in times of high evaporite sedimentation elevated burial of organic carbon low oceanic crust production low atmospheric co2 content and cool paleoclimate as well as when they are present in aragonite oceans

continental margin brine seeps their geological consequences local dissolution observed at the base of the florida escarpment appears to result from acid generated by sea floor oxidation of dissolved sulfide species carried in brines that seep from the base of the escarpment the extent of seep corrosion depends upon the amount of sulfide that has exited the platform and the efficiency with which the acid attacks the limestones of the escarpment calculations suggest that brine seepage influences the shape of these escarpments by undercutting and steepening the carbonate continental margin edges other processes competing for the dissolved sulfides are bacterial chemosynthesis and sulfide mineralization which produces organic carbon and sulfide mineral rich deposits along the unconformity that separates the buried escarpment from onlapping abyssal sediments

distribution and growth styles of isolated carbonate platforms as a function of fault propagation abstract fault control on the position and distribution of isolated carbonate platforms is investigated in northwest australia using high quality 3d seismic and borehole data from the bonaparte basin specifically we address the relationship between carbonate productivity and fault growth so as to understand what are the primary controls on the growth of isolated carbonate platforms throw depth t z and throw distance t d profiles for normal faults suggest they formed fault segments that were linked at different times in the study area this caused differential vertical movements some of the normal faults propagated to the surface while others have upper tips that are 19 530 ms two way time below the sea floor with the largest throw values comprising faults underneath isolated carbonate platforms as a result four distinct zones correlate with variable geometries and sizes of carbonate platforms which are a function of the topographic relief generated by underlying propagating faults some relay ramps form the preferred location for the initiation and development of carbonate platforms together with adjacent structural highs due to the complex effect of fault propagation to the palaeo seafloor and soft linkage through relay ramps three distinct icp types are proposed 1 in the first type fault throw is larger than carbonate productivity 2 the second type considers fault throw to be equal or less than carbonate productivity and 3 in the third type fault throw post dates the growth of the carbonate platform s the analysis of fault propagation vs carbonate platform growth shown here is important as the three icp types proposed potentially correlate with variable fracture densities and distributions within the carbonate platforms based on our results types 2 and 3 above enhance fracture and fault dominated porosity and permeability to a greater degree making them favourable targets for hydrocarbon exploration

mineralogy of erromango lavas new hebrides evidence of an early stage of fractionation in island arc basalts abstract the orogenic volcanic rocks of erromango island are divided into a quaternary theoleiitic group and an older pliocene one showing calc alkalic affinity the microprobe mineralogy of these lavas agrees with this geochemical distinction and indicates a marked iron enrichment trend in the recent tholeiitic lavas whereas titanomagnetite occurs as early formed phenocrysts al cr mg rich only in pliocene basalts some ni and mg rich olivine phenocrysts fo88 and unusual chemically zoned clinopyroxene megacrysts are described from pliocene basic lavas and interpreted as deep fractionated minerals the large compositional range of these latter diopside core to augite rim through salite intermediate zone leads us to discuss the physical conditions and the corresponding cation substitutions prevailing during their formation diopside cores crystallized at depths of about 20 km from a relatively primitive melt the formation of salite is considered to be the result of concomitant fractionation of mg rich phases and increase of f o 2 an early stage of fractionation of cr bearing diopside ni bearing olivine would account for the typical cr and ni depletion of erromango lavas

a burgess shale like fauna from the lower cambrian of north greenland the cambrian explosion refers to the major adaptive radiation of the metazoans during the earliest phanerozoic an event that is best known by the abrupt appearance of hard parts near to the precambrian cambrian boundary 550 myr bp 1 deciphering this important evolutionary episode depends largely on the study of these skeletal remains2 3 together with trace fossils that include burrows and trackways4 5 many of these latter fossils evidently represent the activities of soft bodied organisms such as worms and lightly sclerotized arthropods whose exact identity is seldom known not least because they can be fossilized only in exceptional circumstances6 however documenting the soft bodied representatives of early metazoan communities cannot be neglected if they accounted for a substantial fraction of these early biotas7 here we report a new soft bodied fauna from the lower cambrian of north greenland this assemblage has highly significant similarities with the younger burgess shale and provides additional evidence for the geological longevity of this faunal type and its widespread distribution in deeper waters of cambrian oceans

a new middle cambrian burgess shale type biota bolaspidella zone chancellor basin southeastern british columbia abstract a newly discovered burgess shale type bst biota occurs in southeastern british columbia on haiduk and tangle peaks the fossiliferous rocks of the informally named vermilion sub unit and duchesnay unit occur in the bolaspidella zone one trilobite biozone younger than the burgess shale formation the younger rocks abut the eldon escarpment in a stratigraphic and depositional relationship that mirrors that of the burgess shale formation and cathedral escarpment the biota concentrated at the eldon escarpment is hosted predominantly in the duchesnay unit and includes burgess shale genera of sponges worms some arthropods and brachiopods new taxa include an arborescent benthic graptolite with preserved fuselli microbial fossils including vendotaenid bacteria are locally abundant and range up to 750 m basinward of the escarpment in both the vermilion sub unit and duchesnay unit while concentrations of animal fossils are restricted to within 100 m in the vermilion sub unit large autochthonous carbonate mud mounds previously interpreted as platform derived olistoliths originated at the base of the escarpment probably over fluid conduits and then slid downslope bulldozing and entraining sediments in their paths local magnesian and barian rich brine pool deposits occur up to 750 m distal of the escarpment fractionation of the fluids may explain the differing geochemistries at least one mgo rich brine pool deposit on haiduk peak is fringed by abundant animal fossils including concentrations of priapulid worms this assemblage together with high density low diversity assemblages on tangle peak likely represent fringing fauna facies around brine seeps a model erected for similar fossil concentrations and distributions in the burgess shale intrabasinal comparison of the vermilion sub unit and duchesnay unit with the burgess shale formation reveals an identical stratigraphic ordering of carbonates and shales brine pool deposits major debris flow deposits carbonate mud mound growth and fossiliferous deposits the eldon and cathedral platform formations are known to share complimentary brine derived characteristics as well the stratigraphic patterns signify that the depositional processes producing the suite of older lithofacies recurred during deposition of the younger units interbasinal correlation with the wheeler and marjum formations utah identifies the duchesnay unit deposit as the youngest basinal burgess shale type deposit in north america decreasing abundance of animal fossils away from the eldon and cathedral escarpments is generally attributed to increasing development of tectonic fabrics however on haiduk peak rocks hundreds of metres basinward of the escarpment contact are essentially undeformed and contain rare planolites brachiopods and trilobites as the only macrofauna locally abundant vendotaenids and morania are evidence that bst preservation occurred at these distances the concentration of animal fossils at the escarpment is therefore a primary ecological feature not due to a preservational or rheological bias communities were clustered at the face of the escarpment where brines were seeping

cryptic coral crinoid hanging gardens from the middle devonian of southern morocco an unusual and exceptionally well preserved cryptic community of cnidarians crinoids sponges and microbes developed in a submarine cavity of middle devonian age in the hamar laghdad area morocco the biota encrusted the cavity roof and grew predominantly in an upside down position forming spectacular hanging gardens the investigated assemblage differs strikingly from both its paleozoic and modern analogues it constitutes one of a very few known examples of fossil cryptic assemblages developed in relatively deep water settings and is the first report of a cryptic paleoecosystem dominated by rugose corals the results support the view that during the middle paleozoic there was no distinct polarization between open surface and cryptic faunas in deep water environments but keen competition for space already existed in devonian cryptic assemblages the regional species pool seems to have been the main determinant of the ecological succession and structure of this cryptic community

palaeozoic low oxygen high latitude carbonates silurian and lower devonian nautiloid and scyphocrinoid limestones of the anti atlas morocco abstract high latitude silurian and lowermost devonian basinal limestones of northern gondwana are characterised by mass accumulations of orthocone nautiloids bivalves and planktonic crinoids scyphocrinoids extensive exposures in the anti atlas of morocco reveal this basinal facies passes up gradient into an iron rich bioclastic facies associated with distal shelf siliciclastics and into crinoid brachiopod dominated bioclastic blankets and shoals the limestones formed in a cool water setting in which upwelling of nutrient rich waters during sea level lowstands is interpreted to have triggered the abundance of nautiloids and scyphocrinoids preservation of organic matter in under and overlying graptolite shales as well as iron precipitation in the neighbouring shallower water sub oxic zone the nautiloid limestones proved to be good correlation markers on a regional to global scale contemporaneous siliciclastic supply into the neighbouring facies belt as well as new biostratigraphic data are taken as evidence that these limestones can be correlated to 2nd order eustatic sea level lowstands and the following transgression the low oxygen basinal facies disappeared more or less abruptly during the early devonian pragian and was replaced by a well oxygenated basinal lowstand facies suggesting the end of upwelling at the same time the first reefal build ups coral biostromes and mud mounds appear in north africa indicating a significant rise in water temperatures the change from low oxygen lowstand mass accumulations to well oxygenated basinal facies with a concomitant rise in water temperature is in accordance with recent models of a cool silurian to earliest devonian lochkovian ocean with oscillating oxic to anoxic ventilated to poorly circulated oceanic states and a warm ocean with anoxic to euxinic poorly ventilated to stagnant ocean waters from the beginning of the pragian onwards

geochemical evidence for oxygenated bottom waters during deposition of fossiliferous strata of the burgess shale formation abstract deciphering the oxygenation potential of bottom waters during deposition of the fossiliferous strata of the burgess shale is key to understanding the paleoecology of the organisms preserved as fossils and the processes involved in their preservation methods of paleo redox determination that are based upon trace fossils organic carbon content or size analysis of pyrite framboids are problematic when applied to the burgess shale fortunately patterns in redox sensitive trace elements hold great potential for determining paleo redox conditions for these greenschist facies rocks because they are independent of both age and metamorphic grade four burgess shale type bst fossil bearing sections were studied three lie within the burgess shale formation whereas one lies within the slightly younger duchesnay unit of the middle chancellor formation the geochemical proxies of seawater redox conditions that were used are mo u th v cr v v ni ni co and v sc each of these redox sensitive indices suggests that oxygenated conditions prevailed in the overlying seawater during deposition of beds within which bst preservation developed non fossiliferous beds at the base of the mt stephen trilobite beds yield three geochemical indices v v ni v sc ni co that indicate deposition under dysoxic to anoxic conditions thus the only beds to have been deposited under anoxic conditions are barren of fossils of soft bodied taxa further contradicting the notion that bottom water anoxia is a factor in bst preservation the laminated nature of the burgess shale and evidence for subsurface anoxia coupled with evidence for oxygenated bottom waters presence of bacterial mats and surficial trace fossils suggest that the burgess shale was deposited in the exaerobic zone oxic anoxic boundary at the water sediment interface implications of this reinterpretation of the depositional environment of the burgess shale include 1 taphonomic models for bst preservation must account for the presence of oxygen in bottom waters 2 paleoecological interpretations of the burgess shale need to account for a probable autochthonous benthic component in what is a complex assemblage of fossils that includes elements derived from the platform and 3 the possibility of burgess shale communities based upon chemosynthesis and or bacteria grazing must be considered

contribution of carbonate rock weathering to the atmospheric co2 sink to accurately predict future co2 levels in the atmosphere which is crucial in predicting global climate change the sources and sinks of the atmospheric co2 and their change over time must be determined in this paper some typical cases are examined using published and unpublished data firstly the sensitivity of carbonate rock weathering including the effects by both dissolution and reprecipitation of carbonate to the change of soil co2 and runoff will be discussed and then the net amount of co2 removed from the atmosphere in the carbonate rock areas of mainland china and the world will be determined by the hydrochem discharge and carbonate rock tablet methods to obtain an estimate of the contribution of carbonate rock weathering to the atmospheric co2 sink these contributions are about 0 018 billion metric tons of carbon a and 0 11 billion metric tons of carbon a for china and the world respectively further by the dbl diffusion boundary layer model calculation the potential co2 sink by carbonate rock dissolution is estimated to be 0 41 billion metric tons of carbon a for the world therefore the potential co2 source by carbonate reprecipitation is 0 3 billion metric tons of carbon a

the lower ordovician fezouata konservat lagerstatte from morocco age environment and evolutionary perspectives abstract the lower ordovician fezouata konservat lagerstatte from southern morocco has been one of the major palaeontological discoveries of the last decade it provides a unique insight into one of the most critical periods in the evolution of marine life the cambrian ordovician transition however its potential for deciphering key trends in animal diversification was hitherto largely limited by major uncertainties concerning its stratigraphic position age and environmental setting based on extensive fieldwork fossil evidence and facies recognition our study provides clarification on these three crucial issues exceptional preservation is limited to two intervals within the fezouata shale graptolites indicate a late tremadocian age for the fezouata konservat lagerstatte as a whole which is supported by biostratigraphical evidence provided by acritarchs sedimentological features and reconstructed patterns of relative sea level changes indicate relatively shallow water environmental conditions under distal storm influence in an offshore to lower shoreface siliciclastic ramp setting the fezouata biota represents a unique and exceptional window into the palaeobiodiversity in open marine conditions thus contrasting with the other ordovician konservat lagerstatten presently known in our analyses of this new set of data we pave the way for accurate temporal faunal and environmental comparisons with other lower palaeozoic konservat lagerstatten and unlock the full potential of the fezouata biota to better understand the processes and scenarios of early animal radiations

carbonate deposition and sequence stratigraphy of the terminal cambrian grand cycle in the southern appalachians u s a abstract the cessation of shale and carbonate deposition of the conasauga group grand cycles middle to upper cambrian and the establishment of the widespread peritidal carbonate deposition of the knox group upper cambrian to lower ordovician represent a prominent change in sedimentation along the early paleozoic passive continental margin in the southern appalachians to evaluate the causes for this change this study focuses on the maynardville formation which is the uppermost carbonate unit of the conasauga group the maynardville consists of 1 a lower subtidal facies succession which is underlain by the nolichucky shale and resembles the rest of the conasauga group carbonate deposits and 2 an upper peritidal facies succession which is conformably overlain by similar peritidal deposits of the copper ridge dolomite knox group deposition of shale and subtidal carbonate took place in deep ramp nolichucky to shallow ramp subtidal shoal and lagoonal settings lower maynardville the carbonate ramp was westward sloping toward the conasauga intrashelf shale basin to the east the ramp was linked to a broad semiarid carbonate tidal flat encompassing a variety of peritidal environments upper maynardville and copper ridge the maynardville is a shallowing upward succession that formed by carbonate platform aggradation and basinward progradation the transition between the maynardville and the copper ridge dolomite is within a conformable peritidal carbonate succession that contains common siliciclastic sand size detritus this interval is interpreted as a sequence boundary correlative with the craton wide late steptoean dresbachian franconian or sauk ii sauk iii unconformity the change from a conasauga to a knox depositional style may be related to distinct stages in passive margin evolution the end of grand cycle deposition in the early late cambrian is coincident with the cessation of tectonic activity along extensional features an intracratonic graben and other fault systems and marks the transition into a mature passive margin setting the mature margin was characterized by decreased rates of thermal subsidence which coupled with the infilling of the conasauga intrashelf basin favored shallow water carbonate deposition the final stabilization of the margin is reflected in the deposition of the thick peritidal carbonate strata of the knox group

climatic and lithologic controls on the temporal and spatial variability of co2 consumption via chemical weathering an example from the australian victorian alps abstract a detailed geochemical study on river waters of the australian victorian alps was carried out to determine i the relative significance of silicate carbonate evaporite and sulfide weathering in controlling the major ion composition and ii the factors regulating seasonal and spatial variations of co2 consumption via silicate weathering in the catchments major ion chemistry implies that solutes are largely derived from evaporation of precipitation and chemical weathering of carbonate and silicate lithologies the input of solutes from rock weathering was determined by calculating the contribution of halite dissolution and atmospheric inputs using local rain and snow samples despite the lack of carbonate outcrops in the study area and waters being undersaturated with respect to calcite the dissolution of vein calcite accounts for up to 67 of the total dissolved cations generating up to 90 of dissolved ca and 97 of mg dissolved sulfate has 34s values of 16 to 20 cdt indicating that it is derived predominantly from atmospheric deposition and minor gypsum weathering and not from bacterial reduction of fes2 this militates against sulphuric acid weathering in victorian rivers ratios of si vs the atmospheric corrected na and k concentrations range from 1 1 to 4 3 suggesting incongruent weathering from plagioclase to smectite kaolinite and gibbsite estimated long term average co2 fluxes from silicate weathering range from 0 012 106 to 0 039 106 mol km2 yr with the highest values in rivers draining the basement outcrops rather than sedimentary rocks this is about one order of magnitude below the global average which is due to low relief and the arid climate in that region time series measurements show that exposure to lithology high physical erosion and long water rock contact times dominate co2 consumption fluxes via silicate weathering while variations in water temperature are not overriding parameters controlling chemical weathering because the atmospheric corrected concentrations of na k and mg act non conservative in victorian rivers the parameterizations of weathering processes and net co2 consumption rates in particular based on major ion abundances should be treated with skepticism

differentiating marine vs hydrothermal processes in devonian carbonatemounds using rare earth elements kess kess mounds anti atlas morocco abstract petrological and geochemical analyses were carried out on early devonian kess kess mound limestones of the seheb el rhassel group exposed in the hamar laghdad ridge tafilalt platform eastern anti atlas morocco in order to evaluate marine vs hydrothermal processes for the origin of the mounds hydrothermal fluid circulation affected limestone deposition resulting in the formation of a plumbing system preserved in the mound facies and inter mound facies as cavities veins and dykes shale normalized rare earth element ree patterns for limestones display pronounced light ree depletion compared to middle ree average prsn dysn 0 46 and heavy ree average prsn ybsn 0 55 a super chondritic y ho ratio up to 87 and positive la anomaly consistent with precipitation from normal marine seawater within our data set the ce anomaly as well as u and other trace element concentrations vary with facies providing evidence for variable redox conditions the presence of positive ce anomaly in carbonates of the plumbing system is consistent with precipitation under anoxic condition samples from mound facies and quartz veinlets in the upper part of the group show ree patterns consistent with precipitation from hydrothermal fluids early devonian hypothetical seawater ree patterns were calculated from samples showing normal marine ree patterns i e inter mound facies and from samples with weaker marine signature i e fossiliferous mound limestones and plumbing system deposits hypothetical patterns are slightly enriched in ree compared to modern open ocean seawater this study reveals that ree analysis is a powerful tool for understanding polygenetic carbonate systems it sheds light into the genesis of the kess kess mounds by reconstructing fluid pathways and palaeo redox conditions

introduction to the special issue commemorating the 30th anniversary of the royal tyrrell museum of palaeontology with a summary of the museum s early history and its research contributions located just west of drumheller in southern alberta canada the royal tyrrell museum of palaeontology rtmp is nestled among outcrops of the upper cretaceous horseshoe canyon formation exposed along the red deer river valley fig 1 since it officially opened on 25 september 19851 the museum has become one of alberta s must see tourist attractions a significant contributor to the local economy and earned an international reputation for the quality of its palaeontological collections and the research conducted by its scientists the rtmp is unique within canada in being the only government supported museum dedicated to palaeontology and it is one of the few such institutions in the world fig 1 the royal tyrrell museum of palaeontology a front of museum and main entrance circa 2010 looking westwards and with horizontal beds of the upper cretaceous horseshoe canyon formation exposed in the walls of the red deer river valley in the distance b aerial photograph oblique angle and looking to the north northeast the museum sits on top of the number 7 coal seam sensu gibson 1977 and at the base of the horsethief member of the horseshoe canyon formation d a eberth pers comm 2015 that stratigraphic position correlates with an age of about 71 5 ma i e late campanian and lies within the upper part of the edmontosaurus regalis pachyrhinosaurus canadensis dinosaur assemblage zone see eberth et al 2013 fig 6 c the iconic running theropod logo that until recently graced the exterior of the museum below a life sized tyrannosaurid sculpture by brian cooley one of many such sculptures by cooley that have been featured at the museum since its opening in 1985 and with the education wing opened in 2003 as the atco tyrrell learning centre in the background d the cretaceous alberta life sized diorama opened in 2007 an example of a rtmp exhibit that relies heavily on discoveries and interpretations by museum researchers in this case work done in the albertosaurus bonebed and at other localities throughout the horseshoe canyon formation all photographs courtesy of the royal tyrrell museum of palaeontology this special issue of the canadian journal of earth sciences presents a collection of papers commemorating the rtmp s 30th or pearl anniversary our rationale for doing a 30th anniversary volume was two fold first it is an opportunity to showcase the breadth of research conducted by current and former museum scientists as well as by some colleagues having a history of collaboration with the rtmp the 13 invited papers included in this volume are a mix of review and original research papers all thematically focused on the geology and palaeontology of alberta to varying degrees each contribution is the result of work supported by the rtmp and relies on specimens housed in the museum s collections second the 30th anniversary is an opportunity to reflect on the rtmp s history and its research program as is typical for most institutions the rtmp has done little to formally document its own history this year likely will be the last major milestone for which the original generation of museum staff are still working and available to share their recollections about the museum fieldwork and research already deaths and departures have winnowed away part of the original

evidence for late rifting of the cordilleran margin outlined by stratigraphic division of the lower cambrian gog group rocky mountain main ranges british columbia and alberta the lower cambrian mcnaughton formation of the gog group occupies a stratigraphic position transitional between the rift related rocks of the underlying upper proterozoic miette group and the overlying paleozoic passive margin succession a major regional unconformity overlain by a distinctive orthoquartzite marker has been traced within the mcnaughton formation this unconformity has been shown to truncate normal faults active during the deposition of the lower mcnaughton formation the lower mcnaughton formation consists of mature coarse grained fluvial sediments accumulated in hanging wall half grabens of active normal faults these faults represent the final stage of rifting on the continental margin the unconformity on the footwall blocks of these faults can be traced into the hanging wall and is overlain by the shoreface sediments of the transgressive upper mcnaughton formation formal subdivision of the mcnaughton formation into four lithostratigraphic members is proposed in order to describ

trace elements and ree geochemistry of middle devonian carbonate mounds maider basin eastern anti atlas morocco implications for early diagenetic processes abstract trace and rare earth elements rees have proven their utility as tools for assessing the genesis and early diagenesis of widespread geological bodies such as carbonate mounds whose genetic processes are not yet fully understood carbonates from the middle devonian conical mud mounds of the maider basin eastern anti atlas morocco have been analysed for their ree and trace element distribution collectively the carbonates from the maider basin mud mounds appear to display coherent ree patterns three different geochemical patterns possibly related with three different diagenetic events include i dyke fills with a normal marine ree pattern probably precipitated in equilibrium with seawater ii mound micrite with a particular enrichment of overall ree contents and variable ce anomaly probably related to variation of ph increase of alkalinity or dissolution remineralization of organic matter during early diagenesis and iii haematite rich vein fills precipitated from venting fluids of probable hydrothermal origin our results reinforce the hypothesis that these mounds were probably affected by an early diagenesis induced by microbial activity and triggered by abundance of dispersed organic matter whilst venting may have affected the mounds during a later diagenetic phase

benthic carbonate factories of the phanerozoic marine carbonate precipitation occurs in three basic modes abiotic or quasi abiotic biotically induced and biotically controlled on a geologic scale these precipitation modes combine to form three carbonate production systems or factories in the benthic environment 1 tropical shallow water factory dominated by biotically controlled mainly photo autotrophic and abiotic precipitates 2 cool water factory dominated by biotically controlled mainly heterotrophic precipitates and 3 mud mound factory dominated by biotically induced mainly microbial and abiotic precipitates sediment accumulations of the factories differ in composition geometry and facies patterns and some of these differences appear prominently in seismic data thus facilitating subsurface prediction the characteristic accumulation of the tropical factory is the flat topped often reef rimmed platform in cool water systems reefs in high energy settings are scarce and hydrodynamic influence dominates producing seaward sloping shelves and deep water sediment drifts often armored by skeletal framework the typical accumulation of the mud mound factory is groups of mounds in deeper water where the mud mound factory expands into shallow water it forms rimmed platforms similar to the tropical factory the tropical factory is most productive the mud mound factory reaches 80 90 and the cool water factory 20 30 of the tropical growth rate the three factories represent end members connected by transitions in space transitions in time are linked to biotic evolution

articulated halkieriids from the lower cambrian of north greenland metazoan skeletons appear abruptly in the fossil record near the base of the cambrian 540myrbp before present 1 2 in the initial stages of diversification familiar skeletal remains such as sponge spicules brachiopod valves and echinoderm ossicles are outnumbered by a remarkable array of skeletal types many of millimetric size3 9 particularly conspicuous in these early assemblages are various sclerites some of which are inferred to have formed cataphract coverings of slug like metazoans recognition of articula tory facets and fused sclerites contribute to partial scieritome reconstructions8 11 but discovery of articulated material is a vital ingredient in understanding the palaeobiology of these extinct groups here we report complete halkieriid scleritomes from the lower cambrian of north greenland this finding broadly confirms the predictions of an earlier hypothetical reconstruction11 but reveals entirely unexpected anterior and posterior shells it supports also the proposed phylogenetic link between the halkieriids and wiwoxia corrugata a metazoan with a cataphract scieritome best known from the middle cambrian burgess shale

siliciclastic sequence stratigraphy and petroleum geology where to from here modern sequence stratigraphy has its roots in the development of seismic stratigraphy in the late 1960s to middle 1970s peter r vail and his colleagues at exxon production research company developed stratigraphic techniques and principles based on time stratigraphic rather than rock stratigraphic lithostratigraphic relationships using multi fold seismic reflection data seismic stratigraphic units called depositional sequences were recognized within which the strata seemed conformable and free of any internal stratal discontinuities based on global seismic stratigraphic observations these workers inferred a eustatic signal and developed global sea level curves despite shortcomings the sequence stratigraphic approach represents a powerful geological tool at the field development scale improved reservoir source and seal prediction can enhance petroleum recovery at the exploration scale this approach can be instrumental in developing new play concepts in both mature and frontier basins to realize the full potential of this method earlier conceptual models must be substantiated and modified 80 refs 2 tabs

origin of micropores in late jurassic oxfordian micrites of the eastern paris basin france porous micritic facies either primary chalks or resulting from secondary destructive micritization can constitute important hydrocarbon or water reservoirs characterization of reservoir properties and the understanding of factors which controlled the distribution of porosity are of primary interest to evaluate the prospective reserves middle and late oxfordian limestones of the eastern paris basin show several horizons with porosities higher than 20 the porosity is mainly microporous and located either within secondary micritized grains or in the micritic matrix using sem cathodoluminescence as well as confocal microscopy stable oxygen and carbon isotope ratios and petrophysical measurements a scenario for the evolution of the micropores is proposed lime mudstones to packstones constitute the majority of the high porosity facies hpfs inner lagoonal deposits are more micritized and thus more porous than grainstones and facies rich in leiolitic oncoids and echinoid clasts are less impacted by micritization micritization was responsible for an increase of the intragranular porosity in most grain types during both eogenesis and shallow burial mineralogical stabilization dissolved aragonitic particles and allowed precipitation of calcite rhombs this process was probably enhanced below surfaces of subaerial exposure during burial ostwald ripening allowed the growth of larger micrite crystals at the expense of smaller ones during early berriasian and late aptian recharges of deep aquifers when the northern margin of the basin was exposed overgrowths on micrite crystals were more important in intervals strongly affected by chemical compaction which favored oversaturation of waters with respect to calcite in low porosity horizons lpfs the dense micritic texture of oncoids and the monocrystalline architecture of echinoid clasts prevented an intense micritization while the strong chemical compaction enhanced poronecrosis telogenetic fracturing created new fluid pathways that favored inputs of meteoric fluid in porous micrite and allowed the continuation of ostwald ripening during cenozoic times as a whole mesogenetic inputs of waters undersaturated with respect to calcite in deep aquifers during exposure of basin margins are a more efficient process than early subaerial exposure for enhancing aggrading neomorphism and appearance of microporous micrites initial mineralogical heterogeneities also impact the intensity of chemical compaction and thus the stratigraphical distribution of microporous limestones

spatial distribution and mechanisms of earthquakes in the southern new hebrides arc from a temporary land and ocean bottom seismic network and from worldwide observations in 1977 a wide aperture seismic network of land and ocean bottom stations obs was operated for 6 weeks in the southern new hebrides island arc data on the spatial distribution and mechanisms of small events recorded by this local network were integrated with worldwide observations of moderate to large size new hebrides earthquakes of the past 17 years to study the structure and deformational processes in the new hebrides subduction zone surprisingly small differences less than about 10 km were found between the locations of shallow and intermediate depth earthquakes as located by the temporary local network and by the international seismological centre using worldwide stations analysis of the p wave travel time data from the obs station closest to the trench shows limited evidence for a high velocity zone about 5 higher than the surrounding mantle associated with the descending plate the thrust zone between the descending and upper plates is defined mainly by the spatial distribution and focal mechanisms of moderate to large size events and their aftershocks but it is not very well defined by the spatial distribution of small size events located in this study shallow seismic activity located beneath the trench and beneath the interplate thrust zone indicates a lower limit of about 40 km for the thickness of the seismically active part of the descending plate beneath the thrust zone focal mechanisms of moderate to large size earthquakes located within the upper plate and geological observations on the islands suggest that the upper plate in the region of erromango and tanna is divided into a series of blocks that are differentially uplifted along mainly nw se striking faults during the obs experiment several shallow events were well located beneath the coriolis trough a riftlike feature located to the east of the volcanic arc well determined depths of these events are between 11 and 22 km the well located intermediate depth events define a 20 km thick benioff zone that has a dip of about 70 the spatial distribution of events within the descending slab is very strongly clustered in a persistent pattern that is seen in both the short term sample of small events determined by the local network and the long term sample of locations based on worldwide data several focal mechanisms of moderate to large size intermediate depth events show components of lateral extension along the strike of the arc and some show components of lateral compression both of which could be interpreted as the result of a lateral bending of the descending plate in the part of the southern new hebrides arc where the trench begins to curve around to the east

evolution of carbonate and karst critical zones abstract carbonate terrains ct underlie one fifth of terrestrial ice free land and are an important supply of potable water to the world s population and yet processes endemic to ct critical zones cz and responses of these processes to climatic and anthropogenic pressures are not well understood given the rapid dissolution rates and ability to generate well developed networks of secondary porosity these landscapes can be highly sensitive to impacts from climate change e g modifications of temperature precipitation sea level and human disturbance e g water withdrawal diversions changes in land use land cover this special issue includes 16 papers focused on ct cz processes and potential responses to climatic and human perturbations five major themes emerge from these papers namely 1 anthropogenic climate and land use changes alter ct cz weathering rate and diagenesis 2 metal and carbon fluxes in ct cz will respond to increasing hydrologic variance caused by climate change 3 endogenous and exogenous processes operating over short time periods

ikaite tufa towers in ikka fjord southwest greenland their formation by mixing of seawater and alkaline spring water abstract ikka fjord in southwest greenland is the type locality for ikaite a metastable hexahydrate of calcium carbonate here ikaite forms submarine tufa columns rising up to 18 m above the fjord bottom the columns are spectacular examples of abiogenic carbonate precipitation in a cold seawater environment and so far represent the only known formation of ikaite in seawater we have analyzed the 2h 13c 14c 18o and 87sr contents and major element and minor element compositions of ikaite and of the different water types in and around ikka fjord in order to understand the formation of the ikka columns water from inside the columns is fresh but alkaline rich in ions of sodium bicarbonate and carbonate and has a stable isotope composition identical to precipitation falling on the nearby gronnedal ika igneous complex and we conclude that the tufa columns form over submarine springs issuing from the bottom of ikka fjord dissolution of unidentified sodium carbonate minerals in carbonatites in the igneous complex probably accounts for the peculiar chemistry of the springs ikaite supersaturation and precipitation is controlled by mixing of spring water and seawater at the cold 6 c fjord bottom and precipitation is accelerated by the formation of hydrated caco3o aq ion pairs while phosphate ions in the spring water act as inhibitor for precipitation of anhydrous carbonates we propose that the spring water seeps in ikka fjord literally create their own conduits in the form of the vertical chimney like columns with ikaite forming continuously at the tops of the columns the only limits to upward growth are winter ice and the fresh water layer capping the fjord during summer

carbonate weathering related carbon sink fluxes under different land uses a case study from the shawan simulation test site puding southwest china abstract in the study of global climate change a major focus of research into the carbon cycle is to determine the fate of missing carbon sinks carbonate weathering related carbon sinks as a result of water carbonate co2 aquatic phototroph interactions may make a major contribution establishing optimal land uses which determine soil co2 concentrations and water supplies for carbonate dissolution may be a feasible and effective way to increase the sink potential elucidating both the hydrological and the hydrochemical behavior under different land uses is critical for rational planning of land use changes to increase the carbon sink given the complexity within natural karst catchments the shawan simulation test site was established at puding southwest china to simulate the influence of land uses with controlled carbonate test beds bare rock bare soil crop land grass land shrub land soil co2 concentrations hydrochemical parameters ph major ion concentrations and the spring artificial drain discharge were intensively measured from sept 1 2015 to aug 31 2016 to investigate the carbon and water responses to different land uses in different seasons in the vegetated land uses crop grass or shrub dic increased due to the increase of soil co2 resulting from stronger microbial activities and root respiration in summer and autumn growing seasons in the bare rock and soil cases there was also an increase in dic in summer and autumn due to decomposition of prior organic matter within soils and or rock pores the average dic concentration ranking high to low was grass land shrub land crop land bare soil bare rock soil co2 concentration was thus the dominant of dic concentration which is a key multiplier of carbon sink fluxes csf 0 5 dic rd where rd is depth of runoff dic is dic concentration and 0 5 because in carbonate dissolution only half of the hco3 is of atmospheric carbon origin however runoff depth ranked almost in reverse order i e from high to low bare rock bare soil crop land shrub land grass land the csf ranking from high to low was grass crop shrub bare rock bare soil a new parameter lcic land use change impact on csf is defined to compare the impacts of land use change on dic and rd and evaluate their combined effects on csf compared to bare rock the absolute values of lcic lcic s were 1 and csfs were larger for the three tanks with vegetation cover csf is smaller for bare soil lcic

phanerozoic ironstones an introduction and review s u m m a r y ironstones particularly ooidal ironstones have long fascinated sedimentary geologists and have generated an enormous variety of interpretations but have remained poorly understood a recent upsurge in interest in this group of rocks has generated much new information derived from many different disciplines within the earth sciences the first part of this introduction examines recent advances and attempts to produce a synthesis of them with particular reference to the genesis of marine ooidal ironstones current models for the formation of marine oolitic ironstone formations are discussed and a working model based on various lines of recent research is proposed this model invokes the intrasedimentary formation of berthierine ooids in marine environments during postoxic diagenesis the ooids may be mechanically modified and mineralogically transformed by reworking as well as by later diagenesis goethite ooids may be oxidized berthierine ooids reworked lateritic ooids or primary grains the formation of oolitic ironstoneformations is favoured by a break in clastic sediment supply continued supply of iron and physical reworking many sedimentary environments may supply these parameters but changes in sea level leading to the flooding of land masses and the reworking of suitable terrestrial soils may be both an important source for the iron and provide a break in clastic sediment supply in the second part of this introduction the terminology and classification are discussed and conventions proposed the term berthieroid is introduced as a non specific term for material of undetermined berthierine or chamosite composition the term ironstone is proposed as a petrological term and as an informal lithostratigraphic term a deposit composed of ironstones may be termed an ironstone formation it is recommended that a dunham style of classification is employed petrographically with ironstone replacing the stone of the original carbonate classification the nomenclature of allochems in ironstones is also discussed a glossary of ironstone terminology is provided

devonian rugose coral amplexus and its relation to submarine fluid seepage the rugose coral amplexus occurs frequently in the sedimentary cover of the devonian submarine volcanic intrusion in the eastern anti atlas southern morocco this study elucidates the palaeoecology of amplexus which forms very rich and mostly monospecific spot assemblages within the lower and middle devonian carbonates geological and isotopic evidences show that these associations developed at hydrothermal vents and at a cold seep site the assemblages are always spatially associated with micritic carbonate bodies occurring within bedded hemipelagic deposits the amplexus corals preferred locations in the close proximity of submarine hydrothermal fluid seepage but they generally avoided places with the most elevated temperatures the corals colonised also a hydrocarbon seep probably only in its terminal phase of development when the fluid flow was still at least periodically active this was only possible as a result of the corals following a calice in calice growth developed due to the environmental toxicity which facilitated selective survival of larvae that settled in the shelter of empty calices the amplexus corals appear to have constituted ecological opportunists thriving in the nutrient rich venting and seepage affected areas that were hostile for other benthic organisms it can be suspected that the unusual extremely simplified morphology of amplexus made it particularly well adapted to living in environments typified by harsh and unstable conditions

effect of different land use land cover on karst hydrogeochemistry a paired catchment study of chenqi and dengzhanhe puding guizhou sw china summary rainfall spring stage water temperature ph and conductivity in the paired karst spring catchments of chenqi and dengzhanhe which shared the same climatic condition but different land use land cover lulc at puding guizhou province sw china were monitored by two high resolution multi parameter auto recordable instrument of ctdp300 during the hydrological year of september 2007 september 2008 other monthly hydrogeochemical and carbon isotopic 13c variations in the paired karst catchments during the same hydrological year were also investigated a thermodynamic model was used to link the continuous data to monthly hydrogeochemical data allowing the calculation of co2 partial pressure pco2 and calcite saturation index sic on a continuous basis the primary study objective was to understand how the karst processes and karst hydrogeochemistry respond to different lulc which is essential to assessing the karst related carbon cycle marked seasonal and storm scale variations were found for ph conductivity pco2 sic and 13c of the two springs indicating that both springs were dynamic and variable systems however there were differences in the magnitude and direction of the variations of these features between the two springs the higher pco2 and hco 3 concentration and lower ph sic and 13c in chenqi spring than those in dengzhanhe spring tend to be related to the difference in lulc between chenqi and dengzhanhe spring catchments in the chenqi spring catchment there was larger soil cover and the paddy land was located in the discharge area both of which produced and kept more co2 a major driving agent for the karst processes and lower 13c in the soil aquifer system while in the dengzhanhe spring catchment area there was larger bare carbonate rock occurrence and the paddy land was located mainly in the recharge area moreover the ph increased and pco2 decreased generally in chenqi spring after rainfall possibly due to more carbonate dissolution in the larger soil cover rich in limestone fragments in the spring catchment while the ph decreased and pco2 increased generally in dengzhanhe spring after rainfall all these differences show that soil cover and land use pattern played important roles in the karst processes in other words the karst hydrogeochemistry and the karst related carbon cycle could be regulated effectively by different lulc in addition the higher concentrations of ca2 so 4 2 mg2 and conductivity of dengzhanhe spring were due to the dissolution of more gypsum and dolomite minerals in the strata of dengzhanhe spring catchment therefore the karst hydrogeochemical parameters including ph conductivity hco 3 ca2 mg2 so 4 2 pco2 sic and 13cdic could serve as good indicators of different lulc and the other environmental changes

palaeontology and depositional environments of ancient brine seeps in the middle cambrian burgess shale at the monarch british columbia canada abstract the monarch a mountain in southeastern british columbia exposes the cathedral escarpment which abuts the basinal burgess shale and an underlying limestone the upper takakkaw tongue at one section a dolomitized megabreccia representing an intraformational collapsed cavern forms the cathedral escarpment wall the megabreccia is cross cut by the subsequent megatruncation event marking the collapse of the cathedral margin which supports previous hypotheses that dolomitizing brines were active at the cathedral margin prior to and during deposition of the burgess shale epiphyton rich carbonate megablocks within the basinal strata previously interpreted as olistoliths spalled off the escarpment are unlike the peritidal strata comprising the cathedral margin and are more likely deep water carbonate mud mounds that grew in the basin near the escarpment face evidence for early brines in basinal environments at this locality includes lenses of dark magnesium rich clinochlore 30 wt mgo vs 2 in background shales within the burgess shale at the escarpment wall these clinochlores are interpreted as precipitates from seafloor brine seeps analogous to ones currently found at the foot of the florida escarpment and on the distal shelf and slope of the northern gulf of mexico like the gulf examples the brines formed standing pools on the cambrian seafloor and hosted abundant organisms in a narrow fringe around their peripheries but not within the pools sponges priapulid worms hyoliths linguliform brachiopods and trilobites predominate shales only a few metres basinward from the pools are nearly barren of animal fossils increased biologic productivity localized at the seeps would account for the patchy distribution of fossils in the burgess shale in a narrow zone close to the escarpment the discovery of brine seep deposits and associated fringing communities at the monarch shows that at least some assemblages in the burgess shale were preserved within their habitat and were supported by chemosynthesis

direct evidence of the feedback between climate and weathering long term climate moderation is commonly attributed to chemical weathering the higher the temperature and precipitation the faster the weathering rate weathering releases divalent cations to the

molar tooth structure in proterozoic carbonate rocks origin from synsedimentary earthquakes and implications for the nature and evolution of basins and marine sediment proterozoic argillaceous lime mudstones commonly contain molar tooth structure a curious synsedimentary feature consisting of crumpled generally vertically oriented veins filled with calcite microspar long enigmatic these veins are interpreted here as earthquake induced deformation structures a model is proposed whereby violent ground motion caused shrinkage dewatering and fissuring of the colloidal sea floor sediment of clay and lime mud a slurry of equant particles of lime mud segregated from the clay platelets trapped in the matrix was expelled into these voids the host bed underwent as much as 80 compaction as well as shear causing the lime mud filled fissures to be ptygmatically folded and shingled both vertically and horizontally and in places pulled apart this lime mud lithified rapidly by high mg calcite grain growth such that subsequent earthquakes shattered the folded veins in the belt basin of western north america tsunamis from different events created currents that transported ooids and coarse sand from shoals into deeper water and scoured deeply into the now consolidated sediment leaving behind a lag of vein fragments molar tooth structure is a signature of basin tectonism recorded specifically in argillaceous lime mudstones deposited in low energy settings above the thermocline in supersaturated marine water syneresis cracks are the counterpart in terrigenous facies in that silt and sand were injected into the shrinkage fissures this process points to the importance of seismically induced compaction under negligible burial smectite might have made up a significant proportion of the sediment making it more conducive to shrinkage the absence of molar tooth structure in phanerozoic strata is ascribed mainly to changes in sediment rheology brought about by increased organic binding due to diversification of the microbiota

controls on the evolution of carbonate mud mounds in the lower cretaceous cupido formation northeastern mexico abstract the lower cretaceous cupido formation in northeastern mexico represents part of an extensive post rift carbonate platform system that stretched across much of the gulf of mexico passive margin numerous sponge microbial mud mounds are found within the lower part of the cupido formation four mound types were identified at bustamante canyon and other localities in the state of nuevo leon mexico type 1 siliceous sponge microbial mounds contain boundstone core facies are the oldest mounds and are associated with adjacent deep ramp to basinal lime mudstone facies type 2 sponge microbial mounds also have boundstone core facies are associated with outer ramp wackestone packstone facies and overlie strata that contain type 1 mounds type 3 sponge microbial coral mounds contain only 40 50 boundstone core facies and overlie or are locally interstratified with type 2 mound bearing strata although type 3 mounds are associated with outer ramp packstone facies type 4 calcisponge microbial coral biodetrital dominantly skeletal packstone mounds are the youngest mounds and are associated with outer ramp packstone and ramp crest rudist packstone facies both the length and height i e synoptic relief of individual types 1 2 and 3 mounds range from a few meters to tens of meters only type 4 mounds reach several hundred meters in length and are up to 90 m thick although synoptic relief on type 4 mounds was minor systematic changes in the biota morphologies dimensions abundance stratigraphic distribution and facies associations of the lower cupido mounds were largely controlled by the initial ramp like depositional profile of the lower cupido platform and the long term second order accommodation trends that affected ramp evolution during early cretaceous time the ramp like profile was not conducive to transport of large volumes of allochthonous sediment from updip source areas to mound locations on the outer ramp this allowed slowly accumulating types 1 2 and 3 mounds to build synoptic relief because adjacent outer ramp facies accumulated at even slower rates in contrast type 4 mound cores contain abundant coarse grained skeletal sediment and also developed the least synoptic relief of all lower cupido mounds because of higher accumulation rates associated with adjacent grain rich ramp crest lithofacies we suggest that these systematic changes in mound attributes largely reflect long term second order accommodation loss and regional progradation of the lower cupido ramp during early cretaceous time accordingly the upward transition from type 1 to types 2 and 3 mounds and ultimately to type 4 buildups can be explained by the progressive shallowing of outer ramp environments as more updip facies tracts prograded eastward from late hauterivian to early aptian time there are few stratigraphic successions in the rock record that provide better evidence for the links between large scale stratigraphic relationships and mound evolution along low gradient carbonate ramps

the waulsortian type mound in the lower namurian of the lublin basin se poland abstract a unique waulsortian like mound is recognized in the lower namurian succession of the central part of the lublin basin se poland the carboniferous succession is characterized here by yoredale type cyclothems with carbonate units of relatively constant thickness an unexpected increase in thickness of the carbonate unit in the minkowice 4a well indicates the occurrence of an organic buildup at least 35 m thick sedimentological analysis reveals that its skeletal composition as well as its peloidal matrix abundant stromatactoid cavities and succession of cements indicate close analogies to similar facies in lower carboniferous waulsortian type mud mounds oxygen isotope data indicates that the formation and growth of the described mound were probably stimulated by hot water vents the occurrence of hot water vents in the open marine setting of the lublin basin is interpreted as a consequence of early namurian tectonic activity when a local tectonic compressional regime occurred in some parts of the basin the mound does not function as a hydrocarbon reservoir however its characteristics point to the presence of sedimentary traps which hitherto have not been recognized in this region