seismites dans le jurassique superieur du bassin anglo parisien normandie oxfordien superieur calcaire greseux de hennequeville abstract synsedimentary deformation structures are observed on the armorican border of the anglo paris basin in the late oxfordian calcaire greseux de hennequeville formation these detrital sediments are well exposed on the normandy coast between trouville and honfleur outcropping both in the cliffs and on the beach they comprise silty limestone with abundant sponge spicules rhaxella deposited in a restricted subtidal depression mostly above the storm wave base and located in the northern flanks on the sables de glos delta the formation is subdivided into three members deformational structures observed at a centimetre to metre scale and associated with massive early diagenetic cherts are developed only in the middle member which is 1 5 m thick this depositional environment was the shallowest of the whole formation the soft deformation structures are various comprising 1 low amplitude structures observed at the lower and upper surfaces of the limestone beds 2 features with a wash basin form 3 boudinage structures and 4 large scale ball and pillow structures or blagues a tabac tobacco pouches showing vertical dimension of over 1 m and observed only in a few sections of the cliffs all deformational structures are overlain by undisturbed silty limestones and silty clays suggesting a synsedimentary deformation the soft deformations are interpreted to have been induced by the liquefaction of unconsolidated spiculitic silty muds during earthquakes liquefaction may have been induced by a number of processes which affect grain supported sediments a seismic origin is supported not only from particular palaeogeographic context by reference to the whole nw of europe in the late oxfordian but also by the great lateral extent of the deformational structures which occurs along more than 4 km of coastal outcrops there is only one deformed unit the morphology and size of the seismites are directly controlled by the stratonomy and thicknesses of the limestone most of the structures have a dominant vertical trend with an upward or a downward polarity earthquakes are always difficult to recognize in the sedimentary record they were recorded in the case of the calcaire greseux de hennequeville because of a set of exceptional conditions which led to their preservation these were seismic activity associated with recurrent faulting alternating beds of porous wet and well sorted fine sands with muds favourable to thixotropic processes and deposition in a relatively protected depositional environment

experimental studies of the fluidization of layered sediments and the formation of fluid escape structures experiments demonstrate that fluid escape structures can be produced as a result of unstable fluidization behaviour where a lower base layer of granular material is inhibited from fluidizing by the presence of an overlying non fluidizing top layer before the base layer can fluidize the weight of the overlying material must be balanced and this is accomplished by base layer material pressing against the bottom surface of the confining top layer forming a static layer this static layer allows the top layer to lift away from the base layer which is then free to fluidize a water filled crack forms below the static layer and as this grows instability causes the static layer and top layer to bend and conical voids to form below the antiformal sections rupture occurs at the apex of the water void allowing the underlying water and fluidizing material to burst out through the top layer the fluidized base layer material then flows through the rupture until all of this material except that in the static layer is deposited above the previously overlying layer and a stable fluidization system results the top layer material is bent upwards around the rupture and the resulting pillar type escape structure is preserved if flow then ceases the vigour of the burst out is greatest when the base layer material has a grain size 15 of the top layer material if the base layer grain size is less than 8 of the top layer then base layer material will pass through the top layer pore spaces without forming an escape structure if cohesive material is present escape structures form when a layer of fine grained cohesive material overlies a layer of cohesionless material at low flow rates small pipes with scattered angular bends pierce the top layer and base layer material passes through them the base layer material is ejected on to the top layer and builds up around the mouth of each pipe to form constructional structures sand volcanoes this is in contrast to the cohesionless experiments where the weight of material being deposited on the top layer caused an ejecta filled depression to form around the rupture if flow then ceases both the pipes and the sand volcanoes are preserved at high flow rates where the base layer fluidizes the top cohesive layer becomes fragmented small fragments circulate within the fluidizing base layer and are preserved as floating clasts large fragments sink to the bottom of the fluidizing base layer erosion of the bottom surface of these larger fragments causes this surface to become convex downward the experimentally derived structures are similar to pillar type structures observed in the field and the processes described can be used to investigate the development of these structures fluidization experiments also demonstrate the genesis of dish structures and the cohesive behaviour can be applied to the deformation of these structures after initial formation

time specific facies and biological crises the kellwasser event interval near the frasnian famennian boundary late devonian abstract features which may be called time specific facies tsf can be linked to global bioevents or better biological crises the late devonian kellwasser kw event is a classic example of such a crisis this geologically short lived event shows recurring patterns within the critical time interval including patterns that are often minute not only do the well known lower and upper kw horizons yield specific features but also the adjacent sedimentary rocks show characteristic markers such observations were first made in facies settings of submarine rises with preferably carbonate rocks mainly cephalopod limestones but these features can now also be traced into basinal sections characterized by fine grained pelitic rocks these beds and markers are crossing traditional facies borders at exactly the same time making them perfect examples of tsf

loading fractures and liesegang laminae new sedimentary structures found in the north western north alpine foreland basin oligocene miocene south west germany abstract spectacular sedimentary structures recently found in the molasse basin oligocene miocene in southern germany were produced by soft sediment deformation under highly unusual conditions these large apparently wedge like structures loading fractures cut down into beds of marl and are filled with coarse sand and intraclasts of shale wrapping the sides of the structures is a thin continuous bed of layered dark claystone the dcb the upper and lower layers of this bed are an organic rich clay the middle layer is a laminated quartzite the precursor of the dcb was a lacustrine gyttja rich in diatom frustules it was supersaturated in silica as it was buried subsequent diffusion of oxygen into this gyttja at a burial depth of only a few metres resulted in the formation of liesegang laminae of quartz these laminae grew and amalgamated forming the layer of laminated quartzite the sediments overlying the dcb were eventually removed by erosion probably in a high energy marine environment this erosion cut down to the dcb but was unable to penetrate it the dcb remained exposed on the sea floor until a sudden depositional event occurred the deposition of a 2 5 metre thick bed of coarse sand with shale intraclasts although the dcb had been able to resist the submarine erosion it could not support the load of this new bed the quartzite layer in it therefore fractured transferring that load down onto the underlying still unconsolidated marl the intraclast rich sands were forced down into this marl carrying ahead of them the partly broken remains of the dcb

ramp style deposition of oligocene marine vedder formation san joaquin valley california abstract the oligocene vedder formation consists of well sorted medium to fine grained marine sand and shale in the subsurface of the eastern san joaquin valley updip this formation interfingers with nonmarine lagoonal facies known as the walker formation this relationship appears to be transgressive because the marine vedder generally overlies the walker formation downdip the vedder sands interfinger with middle to lower bathyal shale in a progradational manner forming upward coarsening patterns in well logs depositional water depths for the shale were determined from benthic foraminifera assemblages the vedder formation is approximately 750 ft thick along its updip part and gradually thickens to 1500 ft downdip overall deposition geometry determined from well log correlations and seismic data is generally parallel and downlapping a prominent shelf slope break is not evident rather depositional surfaces are tabular or broadly lobate with a depositional slope of 5 sup 0 10 sup 0 this geometry of constant slope between nonmarine and deep marine water depth is termed a ramp the depositional style and geometry are similar to that of the oligocene upper pleito formation which crops out in the san emigdio mountains on the southern margin of the san joaquin valley the vedder formation was deposited subsequent to a period of rapid subsidencemore about 50 cm 1000 years as determined from geohistory analysis of well data on the bakersfield arch this rapid subsidence may have induced deposition in a ramp geometry rather than a shelf slope configuration less

the devonian lower carboniferous succession in northwest peninsular malaysia abstract a new stratigraphic nomenclature is proposed for the approximately 600 m thick mainly clastic transitional sequence between the underlying mempelam limestone and overlying kubang pasu singa formation in northwest peninsular malaysia this sequence represents shallow marine deposits of the continental margin of the sibumasu terrane during the middle palaeozoic devonian carboniferous it is separated into several formations the timah tasoh formation is an approximately 76 m sequence consisting of 40 m of laminated tentaculitid shales at the base containing monograptus yukonensis jackson and lenz and nowakia turkestanella acuaria alberti giving an early devonian pragian emsian age and about 36 m of rhythmically interbedded light coloured argillo arenites the chepor formation is about 90 m thick and consists mainly of thick red mudstone interbedded with sandstone beds of middle to late devonian age a new limestone unit is recognized and named the sanai limestone which contains conodonts of famennian age the binjal formation consists of red and white mudstone interbedded with sandstone beds showing bouma sequences the telaga jatoh formation is 9 m thick and consists mainly of radiolarian chert the wang kelian formation is composed of thick red mudstone beds interbedded with silty sandstone and contain fossils indicative of an early carboniferous visean age the succession was deposited on the outer shelf with depositional environments vertically fluctuating from prodelta to basinal marine the devonian carboniferous boundary is exposed at hutan aji and kampung guar jentik and indicates a major regressive event during the latest devonian

black shale deposition and faunal overturn in the devonian appalachian basin clastic starvation seasonal water column mixing and efficient biolimiting nutrient recycling integrated geochemical data suggest that black shale deposition in the devonian geneseo formation of western new york was initiated by the coincidence of siliciclastic starvation and the intensification of seasonal water column stratification and mixing once established however black shale deposition was maintained through efficient recycling of biolimiting nutrients which enhanced primary productivity recycling efficiency was achieved through a positive feedback loop of oscillating benthic redox conditions that enhanced n and p regeneration from sediments sustained high primary productivity by returning nutrients to the photic zone during mixing and ensured a downward flux of organic matter that drove or enhanced the episodic development of benthic anoxia during stratification this feedback was ultimately disrupted by rising siliciclastic influx which diluted organic matter and restored benthic redox stability the abrupt overturn of diverse long standing appalachian basin marine communities may have been the result of trophic resource destabilization during geneseo deposition

seismically induced soft sediment deformation structures in an active seismogenic setting the plio pleistocene karewa deposits kashmir basin nw himalaya abstract recent uplift in the nw himalaya has exposed more than 1000 m of the plio pleistocene so called karewa deposits in kashmir these deposits mostly consist of horizontal stratified sand silt clay conglomerates and lignite beds the sedimentary succession belongs to the kashmir basin that is located in a seismically active zone the area was previously affected by large earthquakes the observed soft sediment deformation structures ssds are predominantly developed in the sand silt and clay beds and include load and water escape structures intrusive sedimentary bodies convolute bedding disturbed laminites and slump structures deformation mechanism and driving forces of the ssds were seismic shock waves sediment loading and storm events as driver for the ssds are less likely and the proximity of the ssds to faults underlines the seismic origin of these structures syn and post depositional faults and deformation bands developed in the karewa deposits support the interpretation of neotectonic activity and point to an earthquake of magnitude 5 5 that struck the kashmir basin in the plio pleistocene

violent volcanism stagnant oceans and some inferences regarding petroleum strata bound ores and mass extinctions past changes from a well mixed aerated ocean to a stratified stagnant ocean are indicated by decreasing 13c of limestone opposite to prior conclusions as well as by increasing 34s of marine sulfates the proposed stagnant ocean model includes a warm co2 enriched atmosphere and a bathyal to abyssal marine system dominated by bacterial components in the food web and by consequent light carbon in organic material and biogenic carbonates culminations of prolonged stagnant episodes correspond with marine faunal extinctions of late permian and late cretaceous time and the protracted changes and correlations provide evidence against any hypothesis of mass extinction by sudden worldwide catastrophe including the asteroid impact hypothesis the cretaceous stagnant ocean taken as the prime example is attributed to climatic warming triggered by volcanic co2 greenhouse effect and several feedbacks including decreased earth albedo and increased sinking of warm evaporite brines instead of aerated polar waters marine extinctions are attributed to upward expansion of the oxygen minimum zone and to catastrophic mixing of surface waters with poisonous sulfidic waters of the deeps the stagnant ocean provided a counterbalance between deep reduction and shallow oxidation conditions that favored maximal formation of black sulfidic shales protopetroleum and sedimentary sulfide ores and shallow to mid depth barite phosphorite iron ore cherty iron formation and sulfate bearing red beds trace elements concentrated in stagnant ocean sediments include chalcophile and pt group metals negating claims that ir provides a unique fingerprint of meteorite impact and cosmic accretion

fish from the upper devonian of the shan thai terrane indicate proximity to east gondwana and south china terranes we report the first discovery of abundant devonian vertebrates from thailand an unusual form of coronodontid shark tooth with six equal sized cusps occurs only in the upper devonian of thailand shan thai terrane and south china and a new species of phoebodus is reported that occurs elsewhere only in south china and australia east gondwana terrane the occurrence of the chondrichthyan harpagodens thrinacodus ferox turner 1982 in the late devonian of thailand australia and south china predates the appearance of this species in euramerica early carboniferous these data suggest late devonian proximity of the shan thai south china and east gondwana terranes and is in accord with recent paleomagnetic data

three dimensional geological modeling supports a revised burdigalian chronostratigraphy in the north alpine foreland basin precise age data are a basic prerequisite for the correlation of a sedimentary succession with the global time scale which in turn allows one to place its biotic and other data in a global context in the north alpine foreland basin nafb a patchy distribution of outcrops and uncertainties in the correlation of strata have led to conflicting age models in particular for deposits of lower miocene burdigalian age here we present a new three dimensional geological model of the se german sector of the nafb covering an area of 13 200 km2 which helps to resolve the discrepancies the dataset comprises lithostratigraphic information from 150 boreholes supplemented by magnetostratigraphic data from six outcrops computer based 3d modeling was conducted with the open source software qgis for a 500 m thick succession comprising units of the upper marine molasse the brackish oncophora fm and the upper freshwater molasse the results provide new insights pertaining to 1 the isochrony of strata 2 subsidence and 3 synsedimentary tectonics the new data permit us to reliably place the outcrops within the regional lithostratigraphic scheme thus enabling a new correlation of their magnetic polarities with the global time scale on this basis we propose a revised age model for the middle and upper burdigalian strata in the eastern part of the nafb which is supported by previously reported 87sr 86sr age data the model indicates that the succession is substantially up to 0 8 ma younger than earlier publications have suggested furthermore it implies that the two synsedimentary tectonic events discerned may both be related to the large scale tectonic movements that affected the nafb during the late burdigalian

microfacies sequence stratigraphy and clay mineralogy of a condensed deep water section around the frasnian famennian boundary steinbruch schmidt germany abstract a multidisciplinary analysis microfacies sequential stratigraphy and clay mineralogy was made on frasnian famennian f f boundary strata of the steinbruch schmidt section in western germany three major microfacies are recognised their succession records a shallowing upward evolution from deep quiet and poorly oxygenated environments below the storm wave base to environments influenced by current activities close to the storm wave base the kellwasser horizons correspond to the deepest microfacies the shallowest microfacies correspond to fine grained calcareous tempestites or turbidites coming from a distant shelf of northwest germany the sequential pattern through the f f boundary shows the succession of seven systems tracts two sequence boundaries are located just above the lower kellwasser horizon and at the f f boundary itself these are underlined by hardgrounds suggesting time gaps the kellwasser horizons correspond to sea level highstands and the overlying beds record a transition from lowstand to transgressive systems tracts illite and kaolinite are the dominant clay minerals associated with mixed layers and traces of chlorite illite abundance is maximal during kellwasser horizons illite and kaolinite were probably inherited from a highly weathered source area although part of the illite is diagenetic kaolinite is the second most abundant clay mineral and is particularly well represented up to 50 between the kellwasser horizons an unusual clay assemblage of illite and mixed layers is associated with a bentonite layer kaolinite increases during times when thin tempestites or turbiditic microbioclastic layers come from a distant shelf during sea level falls the kaolinite percentage reaches its maximum at the top of the lowstand systems tract the high percentage of kaolinite suggests a hot wet climate and could be related to global warming

south east asia as a part of an ordovician gondwanaland a palaeobiogeographic test of a tectonic hypothesis the hypothesis that thailand and malaysia the sibumasu block were adjacent to australia in the early palaeozoic has been tested by an examination of the ordovician sequences and faunas of sibumasu and australia the relatively stenogeographic nautiloids of the two areas are remarkably similar and have a simpson index of 0 92 at the generic level two new genera of discosorids are restricted to the two blocks andgeorgina andmesaktoceras are found elsewhere only in tibet very close affinities are also evident between the gastropod polyplacophoran and rostroconch molluscs the ordovician brachiopod faunas are also very close including the genusspanodonta other very close similarities are found between the upper cambrian trilobite faunas and the ordovician conodonts and stromatoporoids no ordovician faunas younger than upper whiterockian were found during this study in either northern australia or sibumasu and a stratigraphic gap probably exists from the upper whiterockian to the upper ordovician over most of the two blocks these remarkably close faunal similarities are good evidence in favour of the hypothesis that sibumasu was adjacent to australia during the early palaeozoic similarly close faunal relationships between north china south east asia tibet and australia may also suggest close proximity of those blocks during the early palaeozoic

the late frasnian kellwasser horizons of the harz mountains germany two oxygen deficient periods resulting from different mechanisms in the harz mountains germany three late devonian sections aeketal huhnertal and kellwassertal were analyzed for major and trace element concentration the inorganic geochemical data were used to determine the environmental conditions associated with the deposition of the two late frasnian black kellwasser horizons in a submarine rise environment low ti al and zr al values and slight enrichment in nutrient and organic matter related trace elements e g ba cu and ni suggest that the kellwasser horizons were deposited during two periods of minimum detrital input but relatively elevated primary production enrichments in u v and mo in both black kellwasser horizons and values of redox indices including u th v cr and ni co indicate oxygen restricted conditions prevailed during the late frasnian times under oxygen depleted conditions reductive diagenesis caused precipitation of iron sulphides such as pyrite that are observed with sem however variations in major and trace element concentrations are not similar in the two kellwasser horizons particularly regarding redox markers the lower kellwasser horizon seems to be more o2 depleted than the upper kellwasser horizon in some german sections on the basis of these results we propose that the two kellwasser horizons are not caused by identical conditions the lower kellwasser horizon results from increased primary productivity enhanced by land derived nutrient loading and which triggered the anoxic conditions recorded in drowned platform setting in contrast the upper kellwasser horizon results from the onset of oxygen impoverished bottom water in the deepest part of the ocean due to episodic water stratification during maximum frasnian flooding oxygen depleted water may have impinged shallower environment during the linguiformis transgressive pulse nutrients would have been released from organic matter decay under reducing conditions and brought up to the photic zone during episodic water mixing

simulation of foreland basin stratigraphy using a diffusion model of mountain belt uplift and erosion an example from the central alps switzerland foreland basin stratigraphy can be considered as the result of three interacting processes thrust deformation which builds the tectonic load sedimentary and erosional processes which redistribute that load and the flexural response of the lithosphere the resultant stratigraphy of foreland basins is commonly composed of a small number of shallowing and coarsening upward cycles bounded by regional unconformities to understand the development of these unconformities we present a simple model of these three processes coupling an evolving thrust wedge on a linear elastic plate with erosion and sedimentation defined by the diffusion equation applied to topography our model demonstrates the development of regional unconformities without recourse to either eustasy or complex viscoelastic models for the continental lithosphere the model describes the thrust wedge foreland basin system in terms of four parameters 1 the effective elastic thickness of the foreland plate te 2 the sediment transport coefficient k 3 the thrust wedge advance rate 4 the surface slope of the thrust wedge the model is applied to the oligocene miocene north alpine foreland basin nafb of eastern switzerland the stratigraphy of the nafb can be simplified into two large scale shallowing upward cycles separated by an unconformity at the base of the burdigalian 22 ma geological information is taken from the nafb to estimate suitable values for the parameters listed above assuming a linear elastic lithospheric rheology the te value is estimated at 10 5 km from decompacted sediment columns data to constrain the sequential development of the thrust wedge come from structural geology the early stages 40 24 ma of compression involved a relatively low angle thrust wedge with an advance rate of approximately 2 4 mm yr at about 24 ma the wedge advance slowed down and thickened by underplating crystalline basement of the foreland plate the value for the transport coefficient has been estimated from previous studies prior to attempting to simulate the broad scale geometry of the nafb the role of each parameter was assessed individually the values for te and k are held constant throughout the simulation of the nafb at 7 5 km and 500 m yr respectively the geometry of the base burdigalian unconformity is reproduced by variations in the parameters describing the thrust wedge the surface slope angle of the wedge is increased from 2 5 to 4 over 0 2 m y and the rate of thrust advance is decreased from 2 mm yr to 0 2 mm yr during the thickening event between 24 and 23 8 ma the rejuvenation of the internal parts of the thrust load causes backtilting of the foreland basin sediments and after a time lag erosion of the distal stratigraphy over the forebulge so simulating the base burdigalian unconformity

radiolarian palaeoecology and radiolarites is the present the key to the past abstract radiolarian productivity pulses and related radiolarite deposition are phenomena difficult to understand from an exclusively actualistic viewpoint evolutionary selection pressure among silica secreting marine plankton both radiolarians and diatoms has led toward more economic usage of rapidly shrinking nutrient resources including dissolved silica of the photic zone in the late cenozoic oceans and in particular a substantial modification of oceanic cycle by the diatom explosive radiation even if there is a proved link between biomineralization and dissolved silica loading among the phytoplankton only the relative independence of modern siliceous planktic biotas from the available silica pool reflects mainly their progressive physiological specialisation during evolutionary history oceanic chemistry and productivity as well as patterns of circulation upwelling have changed radically during the phanerozoic radiolarites apparently represent an anachronistic facies as exemplified by their long lived and ocean wide distribution in palaeo pacific and hitherto highlighted actualistic models of localized intra oceanic wind driven upwelling loci are of largely questionable applicability in addition to plate drift hypersiliceous domains and intervals are explainable mostly by a large scale volcano hydrothermal activity during major plate boundary reconfigurations which in many ways favoured siliceous biotas acme and their skeletal remains accumulation and preservation factors tied to rapid voluminous submarine eruptions such as thermal buoyant megaplumes and basin overturns offer a viable alternative for traditional climatic circulation scenarios in case of hypersiliceous high productivity events irrelevant to greenhouse to icehouse climatic change the evolving carbon and silica cycles were coupled through the greenhouse effect and enhanced chemical weathering volcano hydrothermal and tectonic uplift events related mostly to extensive rifting and or accelerated oceanic spreading were the endogenous driving force that created this perturbation of the exogenous system the present biogeochemical cycle is representative only for the overall silica depleted post eocene oceanic ecosystems which broadly correlates with a major expansion of diatoms groups extremely efficient in silica removal and closely linking the silica budget with phosphorus and nitrogen cycles thus an orthodox uniformitarian approach to biosiliceous sedimentation based on a silica starved vigorous ocean is of limited significance when applied to the pre neogene settings especially in the peculiar planktic habitats of epeiric seas as well as during biotic crises marked by strong geotectonic overprint the major turnovers in marine siliceous biota composition in particular after the end permian radiolarite gap may have been coupled with discernible changes in an increasing biological control on the long term oceanic silica cycling punctuated equilibrium the evolutionary turnovers have induced a stepdown decrease of dissolved silica levels through the phanerozoic contemporaneously with the general secular trend of upward scaling of nutrient related ecological processes and increased effectiveness of resource utilization

global seawater redox trends during the late devonian mass extinction detected using u isotopes of marine limestones abstract the late devonian extinction ranks as one of the big five phanerozoic extinctions affecting up to 80 of marine species and is characterized by two major extinction events that are separated by 238 u across a 7 my interval of well dated upper devonian marine limestones from the devil s gate formation in nevada usa the measured 238 u curve shows no co variation with local sediment derived redox trends water depth dependent facies changes redox sensitive metals toc or diagnostic elemental ratios from these relationships we infer that the 238 u curve represents global seawater redox conditions two negative 238 u excursions indicating more reducing seawater are observed with durations of 3 8 my late frasnian and 1 1 my early famennian respectively steady state modeling of the observed 0 2 to 0 3 shifts in 238 u points to a 5 15 increase in the total area of anoxic seafloor during these excursions the late frasnian negative excursion is broadly coincident with the first extinction event late rhenana zone or lower kellwasser event whereas the early famennian negative excursion lower middle triangularis zones occurs after the most intense frasnian famennian boundary f f extinction event upper kellwasser event compilations of local sediment redox conditions from upper devonian marine deposits with conodont zone level age control indicates that the extinction events were coincident with widespread anoxic deposits accumulating in subtropical epeiric sea and some open ocean settings supporting previous interpretations that widespread marine anoxia had an important influence on the late devonian extinctions the temporal relationships between global ocean redox trends represented by the 238 u curve and the newly compiled subtropical marine redox sediment trends indicates that local epeiric seawaters carried a similar u isotopic composition as the open ocean for the majority of the studied interval except for a brief interval

east flank of the sibumasu block in nw thailand and myanmar and its possible northward continuation into yunnan a review and suggested tectono stratigraphic interpretation abstract the east flank of the sibumasu block was a passive continental margin and in nw thailand is marked by the absence of the autochthonous middle permian triassic platform carbonates which are widespread across the rest of sibumasu further west instead the carbonates are represented by hemipelagic cherts mudstones and sandstones including turbidites during the northward drift of sibumasu following its early permian rifting from gondwana an accretionary complex was present where palaeotethyan pelagic rocks as old as devonian were subducted beneath the sukhothai volcanic arc at the time of sibumasu s collision with the sukhothai arc beginning in the middle triassic the accretionary complex was thrust westwards across the east flank of sibumasu it is suggested that in the late triassic the thrust pile which had been the accretionary complex underwent erosion and was the source of terrigenous clastic rocks deposited further west in a foredeep basin the boundary of sibumasu s east flank with the permo triassic carbonate platform further west is the arcuate mae ping nam teng fault system notwithstanding later cenozoic strike slip displacement those faults as well as the mae yuam fault are interpreted to have had an earlier history of westward directed indosinian thrusting northwards in myanmar and yunnan the sibumasu permo triassic carbonate shelf continues as the shan plateau and baoshan block the east flank is represented by the changning menglian belt and the palaeotethys cryptic suture in thailand possibly joins with the lancangjiang suture

neptunian dykes and associated features in southern spain mechanics of formation and tectonic implications neptunian dykes and sills in jurassic carbonate platform strata of the betic region of spain occupy spaces created by wholly mechanical fracturing and displacement of the host strata and later filled by pelagic sediments from above or by precipitation of calcite from circulating solutions in some places joint bounded blocks of platform carbonates have been wholly removed possibly by sliding down submarine slopes leaving a staircase topography commonly fe encrusted that was subsequently filled by pelagic sediments other cavities that formed during cretaceous times were developed by dissolution and current erosion in moderately deep submarine environments and then filled by pelagic sediments from above none of the cavities hosted by either platform or pelagic strata contain evidence for their formation by dissolution in a subaerial environment the jurassic and cretaceous history of subsidence of the betic margins is thus simpler than in versions requiring repeated emergence to form subaerial karstic cavities

palaeoenvironmental changes at col des tribes montagne noire france a reference section for the famennian of north gondwana related areas we present detailed biostratigraphy based on conodonts and palaeoenvironmental trends deduced from microfacies and conodont abundance through the famennian late devonian at col des tribes montagne noire france the succession is characterized by micritic limestones deposited in settings oscillating between mid to outer ramp facies contain poor fauna widely dominated by nektonic organisms this section is complete and one of the most conodont rich for the famennian of the north gondwana related area the upper kellwasser event frasnian famennian boundary and the hangenberg devonian carboniferous boundary have been lithologically identified they are characterized by decimetre thick black dysoxic to anoxic argillaceous sediments the condroz and annulata events although not materialized by lithological changes have been positioned due to the precise stratigraphy the first event occurred during the deposition of condensed ferruginous facies griotte limestones and the second event during the deposition of micrites barren of benthic fauna the combination of information from both facies and conodont biofacies changes allows a general sea level curve through the entire famennian for north gondwana to be proposed for the first time at col des tribes the general trend is a slight deepening upwards from triangularis to trachytera zones then a pronounced shallowing upwards trend from upper trachytera to praesulcata zones this curve correlates with the well known reference curve from euramerica concerning the late famennian trachytera to praesulcata zones there are some discrepancies in minor cycles which can be explained by tectonical phenomena at the onset of the edification of the variscan belt in europe

measuring and modeling fault density for co2 storage plume fault encounter probability estimation emission of carbon dioxide co2 from fossil fueled power generation stations contributes to global climate change capture of co2 from such stationary sources and storage within the pores of geologic strata geologic carbon storage is one approach to mitigating anthropogenic climate change the large storage volume needed for this approach to be effective requires injection into pore space saturated with saline water in reservoir strata overlain by cap rocks one of the main concerns regarding storage in such rocks is leakage via faults such leakage requires first that the co2 plume encounter a fault and second that the properties of the fault allow co2 to flow upward considering only the first step of encounter fault population statistics suggest an approach to calculate the probability of a plume encountering a fault particularly in the early site selection stage when site specific characterization data may be lacking the resulting fault encounter probability approach is applied to a case study in the southern part of the san joaquin basin california the co2 plume from a previously planned injection was calculated to have a 4 1 chance of encountering a fully seal offsetting fault and a 9 chance of encountering a fault with a throw half the seal thickness subsequently available information indicated the presence of a half seal offsetting fault at a location 2 8 km 1 7 mi northeast of the injection site the encounter probability for a plume large enough to encounter a fault with this throw at this distance from the injection site is 25 providing a single before and after test of the encounter probability estimation method

late early miocene palaeoenvironmental changes in the north alpine foreland basin abstract the north alpine foreland basin nafb experienced rapidly changing palaeoenvironmental conditions at the end of the early miocene middle to late burdigalian paratethys stages ottnangian and karpatian with transformation of fully marine settings into brackish and eventually freshwater environments these changes were related to global sea level fluctuations climate oscillations and tectonic processes associated with the uplift of the alps this study presents a new and comprehensive data set derived from 13 boreholes and 491 core samples from the molasse basin of southwest germany that provides a significantly better understanding of late early miocene palaeoenvironments in the nafb based on lithostratigraphy biostratigraphy and palaeoecological interpretation of rich fauna and flora assemblages we show that the upper burdigalian sediments comprise a regressive lower segment grimmelfingen formation and equivalents as indicated by the occurrence of the bivalve rzehakia and a transgressive upper component kirchberg formation and equivalents characterized by the advent of new fish and mollusc assemblages furthermore we present a new lithostratigraphic concept for the kirchberg formation which forms an important part of the upper brackish molasse obm based on biostratigraphic constraints and recently published magnetostratigraphic data it appears that the regressive segment of the upper burdigalian obm sediments correlates with the end of the global third order sea level cycle bur 3 while the transgressive component reflects the karpatian transgression at the beginning of sea level cycle bur 4 this implies that the karpatian transgression actually affected the molasse basin of southern germany and upper austria whereas previous studies had considered this part of the nafb as terrestrial during that time span the new results are depicted in three palaeogeographic maps for the nafb at 18 ma 17 5 17 1 ma and 17 ma respectively

lower permian conodonts from palaeo tethys ocean plate stratigraphy in the chiang mai chiang rai suture zone northern thailand abstract lower permian lower sakmarian conodonts are reported from a coherent section of ocean plate stratigraphy and from a limestone block in the palaeo tethys suture zone between lamphun and lampang south of chiang mai northern thailand conodont species from both the pelagic limestones of the ops section and the limestone block are deep water forms with distinctive biogeographic affinities comparable to faunas of the urals and north american mid continent a new name chiang mai chiang rai suture zone is here proposed for the palaeo tethys suture in northern thailand that forms the boundary between the sibumasu terrane and the sukhothai arc terrane the inthanon zone of northern thailand is interpreted as representing a fold and thrust belt west of the chiang mai chiang rai suture zone which comprises sibumasu terrane continental margin rocks and remnant klippen of chiang mai chiang rai suture zone rocks thrust as a nappe westward during the triassic collision between sibumasu and the sukhothai arc indochina terrane

towards establishing criteria for identifying trigger mechanisms for soft sediment deformation a case study of late pleistocene lacustrine sands and clays onikobe and nakayamadaira basins northeastern japan five main deformation units discrete sheets of deformed sediments that lie between a significant thickness of undeformed sediment were selected for study within late pleistocene lacustrine sands and clays in the onikobe and nakayamadaira basins northeastern japan the deformed units show evidence of deformation by a variety of mechanisms including fluidization liquefaction brittle failure and cohesive flow driving forces are thought to be primarily reverse density gradient systems but also include gravitational body force shear stress and unequal loading the main trigger mechanisms are firstly earthquakes secondly overloading from volcanic sands and thirdly to a lesser extent subaqueous currents consideration is given to criteria that allow the trigger mechanism to be identified this study shows that the following criteria can be used to identify a seismic triggering agent i setting ii the extent of the deformation units iii absence of evidence relating to other potential trigger mechanisms and iv evidence relating to other potential trigger mechanisms is present but can be seen elsewhere in the stratigraphic section associated with undeformed sediment conversely the following criteria while they are important in interpreting the driving force and deformation mechanism have no relevance to the trigger mechanism i sediment composition ii deformation structures being restricted to a single stratigraphic interval 1 m thick not necessarily correlatable over large areas and iii similarity to structures in the literature

palaeozoic and mesozoic tectonic evolution and palaeogeography of east asian crustal fragments the korean peninsula in context east and southeast asia comprises a complex assembly of allochthonous continental lithospheric crustal fragments terranes together with volcanic arcs and other terranes of oceanic and accretionary complex origins located at the zone of convergence between the eurasian indoaustralian and pacific plates the former wide separation of asian terranes is indicated by contrasting faunas and floras developed on adjacent terranes due to their prior geographic separation different palaeoclimates and biogeographic isolation the boundaries between asian terranes are marked by major geological discontinuities suture zones that represent former ocean basins that once separated them in some cases the ocean basins have been completely destroyed and terrane boundaries are marked by major fault zones in other cases remnants of the ocean basins and of subduction accretion complexes remain and provide valuable information on the tectonic history of the terranes the oceans that once separated them and timings of amalgamation and accretion the various allochthonous crustal fragments of east asia have been brought into close juxtaposition by geological convergent plate tectonic processes the gondwana derived east asia crustal fragments successively rifted and separated from the margin of eastern gondwana as three elongate continental slivers in the devonian early permian and late triassic late jurassic as these three continental slivers separated from gondwana three successive ocean basins the palaeo tethys meso tethys and cenotethys opened between these and gondwana asian terranes progressively sutured to one another during the palaeozoic to cenozoic south china and indochina probably amalgamated in the early carboniferous but alternative scenarios with collision in the permo triassic have been suggested the tarim terrane accreted to eurasia in the early permian the sibumasu and qiangtang terranes collided and sutured with simao indochina east malaya in the early middle triassic and the west sumatra terrane was transported westwards to a position outboard of sibumasu during this collisional process the permo triassic also saw the progressive collision between south and north china with possible extension of this collision being recognised in the korean peninsula culminating in the late triassic north china did not finally weld to asia until the late jurassic the lhasa and west burma terranes accreted to eurasia in the late jurassic early cretaceous and proto east and southeast asia had formed palaeogeographic reconstructions illustrating the evolution and assembly of asian crustal fragments during the phanerozoic are presented d 2005 international association for gondwana research published by elsevier b v all rights reserved

tectonic depositional and diagenetic history of monterey formation miocene central san joaquin basin california the miocene monterey formation in the central san joaquin basin of california consists of biogenic siliceous rocks with a significant terrigenous clastic component correlation of electric logs in conjunction with analysis of outcrop sections core samples and paleontologic data suggests that deposition of the monterey was controlled by an interplay of basin geometry san andreas related tectonics fluctuations in sea level and changes in climate the basin is bounded on the east by the sierran magmatic arc complex and on the west by the san andreas fault during the late saucesian through early mohnian 20 10 ma the basin was reshaped by tectonism related to the migrating mendocino triple junction creating a broad gently sloping shelf to the east that cut off the supply of clastics to the central basin with the subsequent evolution of the san andreas fault the salinian block was emplaced along the western basin margin restricting the seaway and permitting low oxygen nutrient rich waters to occupy the basin as a result laminated organic rich fine grained pelagic to hemipelagic sediments of the monterey formation were deposited a warmer climate during saucesian through luisian time with less intensive upwelling le to more calcareous less siliceous sedimentation a cooling trend during late miocene time 10 5 ma increased upwelling activity diatom productivity in the water column and deposition of diatomaceous debris although turbidites accumulated on the basin floor and terrigenous clastics were deposited on the eastern shelf relatively undiluted diatomaceous deposits developed on outer shelves and slopes atop anticlinal banks generated by wrench tectonism and in some areas of the basin floor a mid mohnian eustatic sea level rise caused fine grained deposition to extend onto the eastern shelf slightly later a mid late mohnian period of exceptionally cool temperatures resulted in the most extensive development of upwelling related siliceous sediments throughout the basin with diagenesis these deposits formed the siliceous shales and porcelanites of the monterey formation high sedimentation rates coincident with a eustatic drop in sea level led to clastic progradation in latest miocene time as the basin filled analysis of organic matter from cores of the monterey formation shows that kerogen type reflects overall sedimentation trends samples from northern and eastern areas contain abundant terrestrial organic matter whereas samples from western areas mostly contain marine kerogens source potential is thus strongly influenced by geographic locality as well as lithology maturity of kerogen was assessed using vitrinite reflectance thermal alteration indices and pyrolysis techniques the latter two appear to be the more reliable indicators of organic matter maturity in the monterey formation of the san joaquin valley although much of the monterey formation in the study area may be thermally immature portions are probably generating hydrocarbons today in deep synclinal areas

petrography and environmental controls on the formation of phanerozoic marine carbonate hardgrounds early marine seafloor lithification of carbonate sediments leads to the formation of hardgrounds and is known from rocks as old as the proterozoic hardground surfaces however are more commonly recorded in the phanerozoic sedimentological archive while ecological studies of hardground biota abound the environmental and physico chemical parameters leading to the development of seafloor lithification remain in many cases poorly understood and documented this paper reviews published evidence on the petrography mineralogy and geochemistry of phanerozoic carbonate hardgrounds within a process oriented context of their environmental controls hardgrounds typically develop in warm and shallow agitated tropical waters that are saturated with respect to caco3 but are also reported from hemi pelagic to bathyal realms and from cool water temperate settings a range of early marine cement types are documented from present day hardgrounds whereas preserved cement fabrics and related mineralogies are less diverse in early phanerozoic hardgrounds carbonate hardgrounds are widespread during calcite sea periods e g ordovician and cretaceous as opposed to some preservation bias ancient aragonite seas e g permian and triassic obviously the relation between seawater chemistry and hardground abundance and attributes is not an easy one here the concept of aragonite versus calcite seas serves as a first order template for the sake of a structured discussion whereas modern aragonite mode oceans document a significant diversity in spatial and bathymetric seawater properties this spatio temporal complexity is perhaps reflected in the scarce record of calcite sea hardgrounds from the devonian or paleogene rock record contrasted by the abundance in aragonite holocene and recent seas holocene hardgrounds allow for the direct assessment of rates of and reasons for early subaquatic lithification and in most cases escaped subsequent non marine diagenetic overprint conversely studies of ancient hardgrounds are often biased by early biological and mechanical erosion the degree of diagenetic overprint and tectonic to orogenic processes the formation distribution and physical properties of hardgrounds depend on the global climatic context greenhouse icehouse modes on sea level changes on ocean stratification on the spatial extent of epicontinental seas and carbonate depositional environments and on the spatially different mineralogies and rates of carbonate production the fabrics and mineralogies of early hardgrounds cement seem to substantially hinge on variations in atmospheric co2 thus the application of lessons from modern to ancient hardground case examples is not straightforward a holistic model explaining the full variability of controls on submarine hardground formation and their cement petrography throughout the phanerozoic is as yet lacking a more critical view on secular changes in hardground formation patterns is clearly needed future work should rely on the combination of sedimentological stratigraphic palaeoecological petrographic and geochemical approaches specific emphasis should be given to time intervals triassic carboniferous cambrian etc where the bulk of reported case studies is at best scarce

late devonian sedimentary record of the paleotethys ocean the mae sariang section northwestern thailand abstract an 11 m thick condensed sequence of late devonian limestones in northwestern thailand exhibits faunal associations and sedimentological microfacies data which are indicative of a pelagic facies setting the entire long ranging section is completely free from clastic input similar successions are known worldwide in a few sections only the mae sariang section is characterised by low sedimentation rates as recognised by a number of hardgrounds neptunian dikes and fe mn crusts the succession comprises a number of pelagic faunal elements e g conodonts cephalopods and pelagic ostracodes the fauna records rare macrofossils and the faunal diversity is low the very condensed section ranges from the late rhenana to praesulcata conodont biozones but contains some global events as undoubtedly shown by biostratigraphical and carbon isotope results including major kellwasser and hangenberg biotic crises in terms of plate tectonics this important succession most probably belongs to the inthanon zone comprising remnants of the paleotethys ocean

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

a complex subglacial clastic dyke swarm solheimajokull southern iceland abstract a complex network of clastic dykes dissects loosely consolidated holocene sediments along the east flank of the proglacial braid plain of solheimajokull southern iceland the dykes comprise downward bifurcating intrusions up to 0 5 m thick and several metres in length and are intruded into glaciogenic deposits sandy gravel gravelly sand interlaminated silt and sand and diamicton the dykes were sourced from a clast poor sandy diamicton interpreted as a subglacial till and were intruded downwards beneath solheimajokull glacier during a previous phase of advance as the glacier advanced southwards it loaded the sediment column resulting in the intrusion of dykes with a consistent south southwest dip with rare northward dipping examples the dyke fills are characterised by laminated sediment with laminae oriented parallel to the dyke margins and comprise interlaminated clay silty clay silt sand sandy gravel and diamicton in some dykes high concentrations of pebble to boulder sized clasts occur in association with rotated pods of the laminated sediment the laminae are thought to have evolved by a slow long lived intrusion process that involved the repeated fracture and expansion of the host sediments followed by viscous smearing on of subglacial material onto the dyke walls rather than rapid injection of fluidised sediment

closure of the east paleotethyan ocean and amalgamation of the eastern cimmerian and southeast asia continental fragments abstract the phanerozoic record of southeast asia preserves the history of opening and subsequent consumption of the paleotethyan ocean and the assembly of continental fragments into asia as part of the broader scale reconstruction of pangea however uncertainty remains as to which of the many suture zones in southeast asia represents the relict of the main ocean when final ocean closure occurred and the assembly history of the eastern cimmerian and southeast asia continental fragments our overview of the geological features of the suture zones the bounding continental fragments and their magmatic metamorphic and sedimentary records resolves many of these key issues the sedimentary biogeographical structural lithological geochemical and geochronological data from the changning menglian inthanon and bentong raub suture zones argue for their linkage with the longmu co shuanghu suture zone in central tibet and together constitute the main east paleotethyan ocean relict the eastward subduction of the ocean resulted in the development of a series of magmatic arc back arc basin and continental fragments in southeast asia including from west to east the lincang sukhothai east malaya arc the jinghong nan sa kaeo back arc basin the simao west indochina fragment the luang prabang loei back arc basin the south indochina fragment the wusu and truong son back arc basins the north indochina fragment the jinshajiang ailaoshan song ma branch back arc basin and the south china block assembly of these fragments resulted in indosinian high temperature and high pressure metamorphism and related tectonothermal event available data indicate a switch from subduction of the main east paleotethyan ocean to the collision of the sibumasu with simao indochina blocks at 237 ma with subsequent syn and post collisional events at 237 230 ma and 230 200 ma respectively along the changning menglian inthanon and bentong raub suture zones the timing of initial syn and post collision events along the jinshajiang ailaoshan song ma suture zone with its record of back arc basin closure is at 247 ma 247 237 ma and 237 200 ma generally 10 ma older than that along the changning menglian inthanon and bentong raub suture zones our synthesis of all available data enables establishment of a comprehensive geodynamic model for the east paleotethyan evolution this model links the spatial temporal pattern across southeast asia into a series of tectonic events including ocean back arc basin opening subduction closure subsequent assemblage and orogenic collapse along with associated igneous metamorphic and sedimentary activities

estimates of strain due to brittle faulting sampling of fault populations abstract the geometry of sampling domains is a first order consideration in the characterization of brittle fault populations in most cases descriptions of fault size distributions based on map cross section traverse or borehole data systematically underestimate the number of small faults present in a volume the geometry of sampling domains may be accounted for using an empirical proportionality between fault displacement and trace length estimates of strain in which the sampling geometry is considered suggest that small faults accommodate a significant portion of the total strain due to the brittle faulting process

controls on strain localization in a two dimensional elastoplastic layer insights into size frequency scaling of extensional fault populations 1 we use a two dimensional 2 d finite element code to investigate how mechanical properties and boundary conditions influence progressive strain localization during extension of a 2 d elastoplastic layer the deforming medium is modeled using a strain softening von mises rheology with a gaussian heterogeneity in yield strength distributed randomly in space specifically we examine the effects of changing 1 the thickness of the deforming layer 2 the basal boundary condition 3 the range of strengths in the deforming layer 4 the strength loss on failure and 5 the total accommodated strain discrete zones of plastic shear strain are observed to nucleate and grow progressively during each experiment in order to quantify and thus discriminate between the deformation patterns produced under differing conditions we calculate the size frequency distributions of the shear band populations size is defined as the total plastic strain represented by each discrete structure a wide range of size frequency distributions is observed including both power law and exponential as well as distributions that show breaks in scaling with a transition from power law at small sizes to exponential at large sizes we show that these variations in population statistics are directly reflecting a change in strain localization in space and time caused by changing model parameters furthermore by making an analogy between the model shear bands and tectonic faults we provide insights into key features of fault size frequency distributions that have been measured in continental and oceanic extensional settings and also observed in analogue experiments

the closure of palaeo tethys in eastern myanmar and northern thailand new insights from zircon u pb and hf isotope data abstract two of the major granite belts of southeast asia are the main range and eastern province together these are interpreted to represent the magmatic expression of the closure of palaeo tethys during late palaeozoic to early mesozoic times recent geochronological and geochemical work has better delineated these belts within peninsular malaysia thereby providing important constraints on the timing of palaeo tethys suturing however the northern extension of this palaeo tethyan suture is less well understood here we present new ion microprobe u pb zircon age data from northern thailand and eastern myanmar measured ages of 219 and 220 ma from the kyaing tong granite imply northern extension of the main range province into eastern myanmar the tachileik granite in far eastern myanmar yields an age of 266 ma consistent with published eastern province ages and this therefore constrains the northern extension of the palaeo tethys suture in eastern myanmar we further discuss how this suture may extend northwards into yunnan a late cretaceous age 70 ma measured in thailand represents later magmatic activity and is similar to published magmatic ages from central myanmar this younger magmatism is interpreted to be related to the subduction of neo tethys prior to india asia collision further we present new laser ablation zircon hf isotope data from eastern myanmar which suggest that palaeoproterozoic crust underlies both the main range and eastern province granites our ehf model age of ca 1750 ma from sibumasu the basement underlying eastern myanmar lies within the range of other model ages reported thus far for the baoshan block north in yunnan interpreted by some to be the northern extension of sibumasu

liquefaction features on the fraser delta evidence for prehistoric earthquakes sand dykes and sills and vented sand boils on the fraser river delta and adjacent serpentine river floodplain in southwestern british columbia record one or more major liquefaction events the source of the dykes is a shallow subsurface saturated sand unit that was deposited in foreslope and distributary channel environments during holocene progradation of the fraser delta the dykes cut steeply through a crust of delta topset muds and locally flatten out as sills in overlying peaty sediments at two sites evidence was found for venting of sand onto a subaerial or intertidal surface liquefaction and upward movement of sand and water locally deformed the intruded sediments causing some subsidence and uplift of the delta surface all observed liquefaction features are younger than ca 3500 bp and at least some are younger than 2400 bp it is not clear however whether they formed during one or several separate events a review of possible causes suggests that the liquefaction features probably are seis

neptunian dikes and sills in devonian reef complexes of canning basin western australia abstract neptunian dikes and sills are conspicuous features of early cemented limestones in devonian reef complexes of the canning basin they are sedimentary fillings of fissures formed by fracturing of the limestones soon after deposition and are most abundant in the reef subfacies but also occur in some back reef and marginal slope deposits the dikes and sills were filled with contemporary sediment including oolite peloid grainstone biomicrite and calcareous sandstone encrusting organisms renalcis and stromatolites and early radiaxial calcite cement some of the sediment is dolomitized or mineralized some dikes contain concentrically coated balls of radiaxial calcite up to 0 3 m 1 ft across sediment in the dikes and sills was cemented rapidly and repeated refracturing and infilling occurred during brief intervals the largest dikes are up to 6 km 3 5 mi long 20 m 65 ft wide and originally extended more than 80 m 260 ft below the surface however most are less than 100 m 330 ft long and 5 cm 2 in wide neptunian sills are up to 0 8 m 2 5 ft thick the principal strike directions of major dike approximately parallel the original reef fronts of underlying basement ridges lateral extension through the development of fissures amounted to as much as 6 5 and averaged about 3 in measured reef sections the fissures allowed circulation of large volumes of seawater to considerable depth within the reef complexes and must have played a significant role in early diagenesis fissuring probably resulted from earthquake shaking differential compaction of underlying sediments and slippage along bedding planes especially in the steeply dipping marginal slope deposits end of article last page 517

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

an alternative plate tectonic model for the palaeozoic early mesozoic palaeotethyan evolution of southeast asia northern thailand burma abstract an alternative model for the geodynamic evolution of southeast asia is proposed and inserted in a modern plate tectonic model the reconstruction methodology is based on dynamic plate boundaries constrained by data such as spreading rates and subduction velocities in this way it differs from classical continental drift models proposed so far the different interpretations about the location of the palaeotethys suture in thailand are revised the tertiary mae yuam fault is seen as the emplacement of the suture east of the suture we identify an indochina derived terrane for which we keep the name shan thai formerly used to identify the cimmerian block present in southeast asia now called sibumasu this nomenclatural choice was made on the basis of the geographic location of the terrane eastern shan states in burma and central thailand and in order not to introduce new confusing terminology the closure of the eastern palaeotethys is related to a southward subduction of the ocean that triggered the eastern neotethys to open as a back arc due to the presence of late carboniferous early permian arc magmatism in mergui burma and in the lhasa block south tibet and to the absence of arc magmatism of the same age east of the suture in order to explain the presence of carboniferous early permian and permo triassic volcanic arcs in cambodia upper triassic magmatism in eastern vietnam and lower permian middle permian arc volcanites in western sumatra we introduce the orang laut terranes concept these terranes were detached from indochina and south china during back arc opening of the poko song ma system due to the westward subduction of the palaeopacific this also explains the location of the cathaysian west sumatra block to the west of the cimmerian sibumasu block

vegetation induced sedimentary structures from fossil forests in the pennsylvanian joggins formation nova scotia vegetation induced sedimentary structures viss are primary structures formed by the interaction of detrital sediment with in situ plants viss provide physical evidence of vegetation s fundamental role in mediating sediment accumulation and erosion in clastic depositional systems despite the abundance of modern viss descriptions from the ancient record are surprisingly rare analysis of fossil forests in floodplain strata of the pennsylvanian joggins formation has identified seven types of viss five hydrodynamic types comprise simple forms developed around a single plant centroclinal cross strata scratch circles upturned beds and complex forms where structures have amalgamated between several plants coalesced scour fills scour and mound beds two types mudstone filled hollows downturned beds form by the decay of an entombed plant and represent infilling of an empty hollow and or soft sediment deformation hydrodynamic types are present in both dryland and wetland settings whereas decay related types occur only in dryland settings where the water table was perennially or periodically low viss represent significant accumulations of sediment and are present in a high proportion of joggins formation strata the paucity of descriptions from the ancient record suggests that these structures have been overlooked or misinterpreted as strictly hydrodynamic recognition of viss in early to middle palaeozoic strata may provide an important insight into the distribution of early land plants in oxidizing environments where organic material was not preserved

nd isotopic composition of late devonian seawater in western thailand geotectonic implications for the origin of the sibumasu terrane abstract conodonts collected from sections near the small towns of thong pha phum and mae sariang in the westernmost part of thailand are used to reconstruct the neodymium nd isotopic composition of seawater during the late devonian the study provides the first devonian seawater signatures recognized within the australian shelf of northeastern gondwana and the adjacent paleotethys ocean at thong pha phum site the seawater was characterized by very low e nd values from 13 1 to 18 2 and very high sm nd ratios between 0 36 and 0 66 in contrast the seawater at the mae sariang site was characterized by much more radiogenic signatures e nd values from 8 7 to 11 1 and uniform low sm nd ratios between 0 20 and 0 23 extremely low e nd values recognized at thong pha phum attest to a passive margin continental setting and a paleogeographic position very close to a continental area where paleoproterozoic and neoarchean rocks were eroded thus the isotopic data provide strong evidence that during late devonian time the sibumasu terrane was situated in the proximity to the archean cratons of western australia presumably adjacent to the carnarvon intracratonic basin moreover sibumasu may not have been situated in an outboard position on the shelf as previously suggested but could have been directly attached to the australian continental crust by contrast low and uniform sm nd ratios of seawater at mae sariang resemble those of the variscan and the present day oceanic seawaters therefore a pelagic setting within the paleotethys ocean is postulated for the mae sariang succession this conclusion is also constrained by minor temporal changes in e nd values and suggests that the paleozoic of mae sariang is not part of the sibumasu terrane but belongs to the inthanon zone

scaling systematics of fault sizes on a large scale range fault map abstract a large scale high quality fault map was produced for an intensively mined area of the u k south yorkshire coalfield this database has been used to investigate both the scaling properties of fault systems and the robustness of techniques for the prediction of sub resolution faulting the mapped area is 87 km 2 and contains 2257 individual fault traces with on average one throw reading available for every 82 m of fault trace recorded throw values range from 10 cm to 180 m and fault trace lengths from 10 m to 12 km two sets of normal faults nw and ne striking are present together with local wnw striking dextral strike slip zones size populations are power law over at least 2 5 orders of magnitude and the exponents of the throw maximum throw and fault trace length population curves are interrelated and taking into account the effects of resolution on trace length populations are internally consistent derivatives of the primary map reproduce resolutions typical of offshore seismics and illustrate the limitations of seismic data power law fault size distributions provide a basis for sub seismic fault prediction for this data set a fault throw resolution of better than 10 m would be required to provide an accurate prediction of the throw population down to ca 0 6m

tectonic framework and phanerozoic evolution of sundaland abstract sundaland comprises a heterogeneous collage of continental blocks derived from the india australian margin of eastern gondwana and assembled by the closure of multiple tethyan and back arc ocean basins now represented by suture zones the continental core of sundaland comprises a western sibumasu block and an eastern indochina east malaya block with an island arc terrane the sukhothai island arc system comprising the linchang sukhothai and chanthaburi blocks sandwiched between this island arc formed on the margin of indochina east malaya and then separated by back arc spreading in the permian the jinghong nan uttaradit and sra kaeo sutures represent this closed back arc basin the palaeo tethys is represented to the west by the changning menglian chiang mai inthanon and bentong raub suture zones the west sumatra block and possibly the west burma block rifted and separated from gondwana along with indochina and east malaya in the devonian and were accreted to the sundaland core in the triassic west burma is now considered to be probably cathaysian in nature and similar to west sumatra from which it was separated by opening of the andaman sea basin south west borneo and or east java west sulawesi are now tentatively identified as the missing argoland which must have separated from nw australia in the jurassic and these were accreted to se sundaland in the cretaceous revised palaeogeographic reconstructions illustrating the tectonic and palaeogeographic evolution of sundaland and adjacent regions are presented

devonian carboniferous transition containing a hangenberg black shale equivalent in the pho han formation on cat ba island northeastern vietnam abstract on cat ba island in northeastern vietnam the devonian to carboniferous d c transition consists mainly of ramp carbonates intercalated with black shale beds beds 1 to 176 in the pho han formation and is one of the few records of the d c transition of the eastern paleotethys the three main facies of the sequence are facies 1 alternations of whitish gray to gray limestone and marl facies 2 calcirudite bed 115b and facies 3 alternations of dark gray limestone and organic carbon rich black shale beds 115c 120 and 126 129 the latest famennian siphonodella praesulcata subzone conodont assemblage of s praesulcata palmatolepis gracilis palmatolepis sigmoidalis and rhodalepis polylophodontiformis was recognized in beds 113 115c beds 105 112 commonly contain palmatolepis expansa p gracilis and p sigmoidalis bed 119 yielded a basal carboniferous index conodont siphonodella sulcata in beds 116 118 solenoporids such as pseudochaetetes elliotti and parachaetetes sp were characteristic species in organic carbon rich dark gray limestone facies 1 is characterized by bioclastic peloidal and intraclastic grainstone and packstone containing massive normal grading and cross laminations and is interpreted to represent deep ramp carbonates above storm wave base facies 2 is represented by typical lag deposits overlying a transgressive surface facies 3 comprises organic carbon rich black shale and minor scour filling bioclastic peloidal and intraclastic packstone and may represent a marginal basin plain environment surrounding a carbonate ramp the alternations of organic carbon rich black shale and dark gray packstone facies 3 show no evidence of bioturbation and have high toc contents 0 18 5 73 wt a minor succession within the transgressive lag deposits from bed 115b of facies 2 to beds 115c 120 in the lower part of facies 3 is equivalent to the hangenberg black shale s l in the middle part of the siphonodella praesulcata to siphonodella sulcata zones because beds 115b 120 characterized by no evidence of bioturbation and high toc contents are interpreted to be accumulated in anoxic to dysoxic conditions

sedimentology and architecture of the douglas creek terminal splay lake eyre central australia douglas creek terminal splay sited on the western shoreline of lake eyre north central australia covers a surface area of approximately 4 km2 with a down system length of 2 5 km from the distributary channels terminus to the splay fringe two distributary channels feed two sediment lobes which have amalgamated to form the terminal splay three primary facies associations have been identified sub dividing the creek terminus into distributary channel proximal and distal splay sections proximal splay sediments are characterized by erosionally based relatively thick 100 mm stacked sheets of coarse to medium sand which commonly display trough and planar cross bedding whereas the distal splay is characterized by thin generally 50 mm massive beds of very fine sand silt and clay the change in splay sedimentology is interpreted as reflecting the transition from bedload dominated deposition to suspended load dominated deposition from decelerating sheetfloods as they spread out from the channel onto the dry lake bed a proximal to distal splay transition zone is also noted where deposits of both facies associations interfinger laterally and vertically in scale geometry and facies associations the douglas creek terminal splay is very different to the often cited neales terminal splay complex located 70 km to the north it is suggested that these architectural differences reflect variations in discharge volume input sediment distribution and the degree of vegetation cover understanding the variation in terminal splay architecture has very significant implications for the modelling of analogous subsurface petroleum systems which at present relies on few modern day analogues

stratigraphy and facies development of the marine late devonian near the boulongour reservoir northwest xinjiang china late devonian to early carboniferous stratigraphic units within the zhulumute formation honggulelengformation stratotype hebukehe formation and the heishantou formation near the boulongourreservoir in northwestern xinjiang are fossil rich the hongguleleng and hebukehe formations are biostratigraphicallywell constrained by microfossils from the latest frasnian linguiformis to mid famenniantrachytera conodont biozones the hongguleleng formation 96 8 m is characterized by bioclastic argillaceouslimestones and marls the dominant facies intercalated with green spiculitic calcareous shales ityields abundant and highly diverse faunas of bryozoans brachiopods and crinoids with subordinatesolitary rugose corals ostracods trilobites conodonts and other fish teeth the succeeding hebukehe formation 95 7 m consists of siltstones mudstones arenites and intervals of bioclastic limestone e g blastoid hill and cherts with radiolarians a diverse ichnofauna phacopid trilobites echinoderms crinoids and blastoids together with brachiopods ostracods bryozoans and rare cephalopods have beencollected from this interval analysis of geochemical data microfacies and especially the distribution ofmarine organisms which are not described in detail here but used for facies analysis indicate a deepeningof the depositional environment at the boulongour reservoir section results presented here concernmainly the sedimentological and stratigraphical context of the investigated section additionally onelate devonian palaeo oceanic and biotic event the upper kellwasser event is recognized near the sectionbase

insight into the development of a carbonate platform through a multi disciplinary approach a case study from the upper devonian slope deposits of mount freikofel carnic alps austria italy the development and behavior of million year scaled depositional sequences recorded within palaeozoic carbonate platform has remained poorly examined therefore the understanding of palaeoenvironmental changes that occur in geological past is still limited we herein undertake a multi disciplinary approach sedimentology conodont biostratigraphy magnetic susceptibility ms and geochemistry of a long term succession in the carnic alps which offers new insights into the peculiar evolution of one of the best example of palaeozoic carbonate platform in europe the freikofel section located in the central part of the carnic alps represents an outstanding succession in a fore reef setting extending from the latest givetian indet falsiovalis conodont zones to the early famennian lower crepida conodont zone sedimentological analysis allowed to propose a sedimentary model dominated by distal slope and fore reef slope deposits the most distal setting is characterized by an autochthonous pelagic sedimentation showing local occurrence of thin bedded turbiditic deposits in the fore reef slope in a more proximal setting there is an accumulation of various autochthonous and allochthonous fine to coarse grained sediments originated from the interplay of gravity flow currents derived from the shallow water and deepwater area the temporal evolution of microfacies in the freikofel section evolves in two main steps corresponding to the freikofel unit 1 and the pal unit 2 limestones distal slope to fore reef lithologies and associate changes are from base to top of the section u1 thick bedded litho and bioclastic breccia beds with local fining upward sequence and fine grained mudstone intercalations corresponding in the fore reef setting to the dismantlement of the eifelian frasnian carbonate platform during the early to late frasnian time falsiovalis to rhenana superzones with one of the causes being the late givetian major rift pulse u2 occurrence of thin bedded red nodular and cephalopod bearing limestones with local lithoclastic grainstone intercalations corresponding to a significant deepening of the area and the progressive withdrawal of sedimentary influxes toward the basin in relation with late frasnian sea level rise ms and geochemical analyses were also performed along the freikofel section and demonstrate the inherent parallel link existing between variation in ms values and proxy for terrestrial input interpretation of ms in terms of palaeoenvironmental processes reflects that even though distality remains the major parameter influencing ms values carbonate production and water agitation also play an important role