constraints on provenance of the central european triassic using detrital zircon fission track data the type of provenance information obtained from dating detrital grains will depend upon the thermal sensitivity of the isotopic dating method for detrital zircon the two methods fission track and u pb in routine use have widely different thermal sensitivities and therefore may provide quite different provenance information zircon fission track data are sensitive to thermal overprinting in the temperature range 200 300 c and therefore have the unique ability to provide source thermal history data the purpose of this study is to evaluate the suitability of zircon fission track data for provenance studies of the triassic siliciclastic sediments of central europe with an emphasis on testing proposed sediment pathways zircon fission track data obtained during this study are consistent with a sediment pathway linking fennoscandia with the central german basin in addition during carnian times there must also have been a pathway linking the schilfsandstein formation of the german basin with the lunzersandstein of the tethyan realm pointing to a european wide fluvial transport system detrital zircon fission track data are therefore a useful means for discerning sediment source and reconstructing sediment pathways

palaeoenvironmental interpretation of fluvial red beds by statistical analysis of palaeocurrent data examples from the buntsandstein lower triassic of the eifel and bavaria in the german basin middle europe abstract palaeocurrent data from parts of the upper buntsandstein lower triassic of both the western eifel kyllburg schichten and eastern bavaria plattensandstein margin of the german triassic basin middle europe have been interpreted by circular directional statistics eigenvalue and eigenvector analysis autocorrelation analysis and vector trend analysis examination of current roses histograms of normalized vector magnitudes and plots of circular skewness of the distribution vs circular kurtosis together with the palaeocurrent plots indicate bimodal palaeocurrent distributions with bipolar orientations within long short and very short sedimentary sequences subset i of the directional data is interpreted to represent larger more continuous flows in a high energy regime of probably perennial type whereas subset ii may represent smaller partially episodic flows of probably ephemeral type with larger variability in direction and flow regime transport and sedimentation rates being significantly smaller than during deposition of subset i a part of the bimodal palaeocurrent distributions within short sedimentary sequences fits rather well into the general transport pattern other bipolarities are primarily interpreted as effects of superimposition of channels of different orientations as well as of main channels and crevasse splay channels and condensation of deposition from discontinuous or episodic flows the main mechanism creating the vertical succession of various directions is stacking of different substratum members to multistorey complexes by primary depositional restriction of formation and or secondary erosional removal of topstratum sediments the occasional occurrence of herring bone cross stratification representing bipolarities within very short depositional sequences testifies to probably episodic and random changes in water surface slopes allowing currents to reverse locally examination of long sedimentary sequences by autocorrelation analysis reveals changes of transport directions with time in a sinusoidal manner indicating a conformable environmental development of the alluvial watercourses which reflects a time cyclic trend of sedimentation by spatially continuous and time concordant shifting of the channel system the results of the statistical analysis enable an enhanced palaeoenvironmental reconstruction of the alluvial network which fits best to a transitional meandering thalweg braided channel pattern comparison of the statistical results especially in the light of vector trend surface analysis clearly reflects the different palaeogeographic positions of both investigated areas but rules out only minor influences of regionally different palaeoslopes on the alluvial depositional environment with the basic principles of fluvial style at the western margin eifel generally matching those at the eastern margin bavaria of the german basin

flash flood sediments and ichnofacies of the late pleistocene homeb silts kuiseb river namibia abstract the homeb silt formation consists of eroded remnants of fine grained alluvium that were deposited within the kuiseb river valley in southern namibia during the late pleistocene in holocene times the river deeply incised its valley fill leaving steep walled castles of relict alluvium the homeb silts this study is based on the 25 m thick type exposure of homeb silts at homeb and describes flash flood sediments that were colonised by successive generations of opportunistic arthropods the stacked flood units each comprise a massive tabular siltstone bed overlain by a narrower interval of rapidly alternating sandstone and siltstone with claystone veneers these flood units are interpreted as having accumulated under semi arid climatic conditions by episodic back flooding of the kuiseb river into embayments and tributary mouths soon after deposition as the floodwaters subsided the sediment was colonised by burrowing sediment ingesting organisms mostly arthropods that produced a taenidium ichnofacies after the floodwaters had drained the exposed sediment was colonised by grasses and burrowed by terrestrial arthropods probably ants and termites resulting in an overprint of termitichnus ichnofacies with associated pelletal chambers thirteen horizons of rhizocretions and root tubules occur toward the top of the succession and indicate a gradual reduction in the frequency of flooding these immature calcic palaeosols suggest that the climate in the central namib desert 20 000 years ago was semi arid being wetter and more seasonal than the hyperarid conditions that prevail today

the magnetic polarity stratigraphy of the mauch chunk formation pennsylvania three sections of chesterian mauch chunk formation in pennsylvania have been studied paleomagnetically to determine a late mississippian magnetic polarity stratigraphy the upper section at lavelle includes a conglomerate with abundant red siltstone rip up clasts that yielded a positive conglomerate test all samples were subjected to progressive thermal demagnetization to temperatures as high as 700 c two components of magnetization were isolated a synfolding b component and the prefolding c component the conglomerate test is positive indicating that the c component was acquired very early in the history of the sediment a coherent pattern of magnetic polarity reversals was identified five magnetozones were identified in the upper lavelle section which yields a pattern that is an excellent match with the pattern of reversals obtained from the upper mauch chunk at the original type section of the mississippian pennsylvanian boundary at pottsville pa the frequency of reversals in the upper mississippian as identified in the mauch chunk formation is approximately one to two per million years which is an average for field reversal through time

slow slip near the trench at the hikurangi subduction zone new zealand the range of fault slip behaviors near the trench at subduction plate boundaries is critical to know as this is where the world s largest most damaging tsunamis are generated our knowledge of these behaviors has remained largely incomplete partially due to the challenging nature of crustal deformation measurements at offshore plate boundaries here we present detailed seafloor deformation observations made during an offshore slow slip event sse in september and october 2014 using a network of absolute pressure gauges deployed at the hikurangi subduction margin offshore new zealand these data show the distribution of vertical seafloor deformation during the sse and reveal direct evidence for sses occurring close to the trench within 2 kilometers of the seafloor where very low temperatures and pressures exist

ecospace utilization paleoenvironmental trends and the evolution of early nonmarine biotas paleozoic nonmarine trace fossils evidence paleoenvironmental trends that are linked directly to progressive ecospace utilization spatial and functional these trends resulted in a considerable increase of ichnodiversity throughout the paleozoic colonization of nonmarine settings began as early as the late ordovician as recorded by the presence of terrestrial burrow systems associated with ancient soils in the other cases the presence of nonmarine trace fossils in cambrian and ordovician sedimentary rocks was the result of temporary colonization by marginal marine organisms and does not reflect establishment of true fresh water faunas devonian trace fossils have been reported from alluvial and alluvial lacustrine transitional environments surface arthropod trackways are dominant in marginal lake settings representing the development of true nonmarine biotas the presence of vertical burrows in fluvial deposits records the establishment of deep suspension feeding infaunal organisms trace fossils from the carboniferous reflect migration farther into the lakes ichnofossils have been reported from shallow and deep lake deposits and from alluvial and alluvial lacustrine transitional environments lake assemblages are dominated by surface grazing trails the permian was characterized by the establishment of a deep deposit feeding infauna commonly recorded by the scovenia ichnofacies represented by backfilled meniscate burrows

high density bioturbated sandstones in the mississippian mauch chunk formation eastern pennsylvania usa implications for continental ecospace exploitation abstract continental communities represented by complex rapidly evolving invertebrate ecosystems first appeared during the early palaeozoic era and are recorded in surface and subsurface bioturbation the mississippian age mauch chunk formation contains several high density bioturbated fine grained sandstones that are preserved as erosively based fluvial channel fills several of these channel sandstone bodies are almost completely homogenized by subsequent bioturbation throughout their entire thickness up to a maximum depth of 1 6 m the mauch chunk ichnofossil record demonstrates that high density bioturbation occurred at least 30 my prior to the permian and well before its widespread distribution in the triassic hence the late mississippian high density bioturbated sandstones demonstrate a much earlier high density exploitation of the continental subsurface ecospace than previously known

paleomagnetism of the late proterozoic tsezotene formation of northwestern canada paleomagnetic evidence from 37 sites of the partly red pigmented siliciclastic tsezotene formation supports a recently proposed apparent polar wander path for the hadrynian mackenzie mountains supergroup mms the probable primary remanence has a direction at d i 271 24 k 15 95 8 with an associated pole ta 12 n 214 w n 23 specimens p m 5 9 ta becomes the oldest pole from the mms it helps bridge the gap between the apparently youngest poles of the grenville loop about 0 88 ga and the suggested younger poles from the mms a secondary pole tb 23 n 198 w n 18 sites p m 3 5 derived from a magnetic direction in hematite pigment d i 263 48 k 73 95 4 supports a magnetization found in the overlying copper cycle and in younger units of the mms as a pervasive overprint another secondary pole tc 63 n 141 w n 29 sites p m 6 6 derived from a magnetization d i 317 87 k 89 95 3 partly residing in another phase of hematite pigment is of postfolding age post paleocene this study demonstrates the importance of using several treatment methods singly and in combination when analyzing complex magnetizations

mixed layer illite smectite as a paleotemperature indicator in the amethyst vein system creede district colorado usa ordered illite smectite is the most abundant and widespread product of argillic alteration associated with the oligocene epithermal ag pb zn cu au amethyst vein system southwest colorado hydrothermal illite smectites exhibit all reichweite from 1 to 3 and span the composition range from about 25 to about 3 illite the composition and reichweite of illite smectite vary smoothly with distance from the amethyst vein with increasing distance from the vein percent illite and the reichweite decrease when composition temperature relationships of illite smectite from modern geothermal systems are applied to the fossil amethyst system isotherms describing the thermal regime at the time of argillization can be estimated temperatures near 240 c appear to have existed near the amethyst vein these temperatures agree with homogenization temperatures obtained from fluid inclusions in vein minerals the most distal illite smectites sampled about 260 m from the vein indicate temperatures near 110 c estimated thermal gradients are on the order of 0 4 to 1 c per meter although illite smectite composition and structure vary systematically with distance from the amethyst vein there are no systematic trends associated with the numerous smaller veins and veinlets in the hanging wall of the system this indicates that temperatures of both wallrock and the fluids in all but the major amethyst vein were nearly the same during clay formation apparently the hydrothermal system had reached a fairly steady mature thermal state at the time of argillization

2d spatial distribution of reflection intensity on the upper surface of the philippine sea plate off the boso peninsula japan abstract the region off the boso peninsula japan is a tectonically complex area where the pacific plate is subducting beneath both the landward plate and the philippine sea plate phs from the japan trench and the izu bonin trench as the phs is subducting under the landward plate from the sagami trough it is important to better determine the structure of this region to deepen our understanding of its seismicity previous seismic reflection studies have shown that reflections from the upper surface of the phs vary with depth being stronger in the main slip area of the slow slip events beneath the boso peninsula boso sses however the spatial relationship between the reflective area and the sses is poorly constrained this study mapped the distribution of the reflective area using data recorded by ocean bottom seismometers during an active source seismic experiment we constructed a 3d p wave velocity structure by using traveltimes of first arrivals from 18 ocean bottom seismometer records we also adapted the traveltime mapping method to reflection traveltimes projecting them to the depth distance domain to map the 2d distribution of strong reflections from the top of the phs these reflections were concentrated in two areas one near the main slip area of the boso sses and the other about 60 km to the east in the first area the absence of strong velocity contrasts near the top of the phs suggests that the reflections were generated by a thin low velocity layer in contrast the structure of the second area has a convex shape of high velocity with a high velocity gradient near the top of the phs this structure may represent boninitic material of the outer arc high partially serpentinized peridotite or gabbro displaced by intraoceanic reverse faults

paleomagnetism of pre grenvillian mafic intrusions from the grenville province southeast labrador paleomagnetic results are reported for middle proterozoic layered intrusions and dykes from within the grenville province of coastal southeastern labrador rock units studied include the little gra

post tectonic magnetizations from the cordova gabbro ontario and palaeozoic reactivation in the grenville province summary the cordova gabbro of southern ontario intrudes 1300 myr old volcanic rocks of the hastings lowlands in the grenville structural province three distinct vector magnetizations a b and c have been isolated using a combination of stable endpoints subtracted vectors from orthogonal vector plots and converging remagnetization circles the a magnetization with mean direction d 294 i 55 5 k 42 ag5 5 5 n 18 sites is a high coercivity high blocking temperature remanence recorded by 49 samples the b magnetization was isolated in 33 samples and has a mean direction d 305 5 1 1 5 k 24 ag5 9 5 n 11 sites b has lower coercivities and blocking temperatures than a where the two are superimposed the a and b palaeopoles 151 e 10 5 s dp 6 dm 8 and 165 5 e 24 n dp so dm 9 5 fall on the grenville track around 900 and 820 ma respectively the a and b magnetizations thus date from uplift and cooling following the grenvillian orogeny the third magnetization the c component has been isolated in 23 samples its mean direction is d 180 i 27 5 k 18 ag5 10 5 n 12 sites the c is a low coercivity low blocking temperature overprint of a and b its palaeopole 102 e 31 n dp 6 5 dm 12 is unlike post 1300 precambrian poles for cratonic north america but matches silurian and late ordovician poles 40ar 39ar plateau ages of 446 and 447 ma determined by lopez martinez and york for plagioclases from one of the cordova samples confirm this age assignment the c magnetization therefore records a previously unrecognized mild thermal or hydrothermal event that occurred in palaeozoic time long after the grenvillian orogeny

effect of anisotropy on the paleomagnetic contact test for a grenville dike we report a detailed paleomagnetic contact test for a mafic dike and its tonalitic gneiss host rock in the precambrian grenville province of canada directions of natural remanent magnetization nrm in the country rock were corrected for assumed deflection by the strong magnetic anisotropy due to the rock fabric using the measured anisotropy of laboratory induced thermoremanent magnetization trm the trm ellipsoids have the same principal axes as the anisotropy of magnetic susceptibility ams ellipsoids but the anisotropy of remanence is more pronounced than the ams anisotropy correction moves nrm directions in the unbaked zone almost 20 bringing them close to typical grenvillian paleofield directions the anisotropy seems to be controlled by multidomain rather than single domain magnetic minerals nrm directions from the baked gneiss near the dike contact after anisotropy correction agree well with the nrm directions from the chilled margin of the early cambrian 570 3 ma dike this positive baked contact test is augmented by the presence of a hybrid zone in which country rock nrms are increasingly overprinted by the dike nrm as one moves from the unbaked toward the baked zone the dike nrm is therefore primary however the virtual geomagnetic pole vgp for the dike nrm 51 n 131 w dp 10 dm 12 n 24 samples or 41 n 153 w dp 13 dm 18 n 4 chilled margin samples does not fall near most established cambrian paleopoles post emplacement tectonic movement of the dike is unlikely it may be that the dike cooled and acquired trm during a geomagnetic field excursion because of its geologically short cooling blocking period of a few tens of years

facies and provenance analysis of upper carboniferous to lower permian fan sequences at a convergent plate margin using phyllosilicates heavy minerals and rock fragments erbendorf trough f r g the erbendorf trough is a narrow permo carboniferous graben in the northeast bavarian crystalline basement at the saxothuringian moldanubian plate edge its elastic and volcanic rocks reflect a complex story of alluvial fan progradation and retreat unit i precambrian gneissic bedrock is followed by units ii to v a wet mixed fan debris stream flows braided streams peat swamps organic lake units vi to x reflect a retrogradational dry fan braided streams calcretes flood plain deposition with tuffaceous interbeds units xi to xii are acid extrusive rocks the uppermost part hydrothermally altered and units xiii to xiv denote a progradational dry fan the wet fan at the base is characterized by a predominance of illite stable to intermediate heavy mineral associations zircon and garnet and a clast community pointing to medium pressure metamorphic rocks in the variscan nappe the following dry fan contains various 14 a phyllosilicates besides white mica its heavy mineral suite contains more labile constituents apatite and amphibole gneissic pebbles accompany those from acid volcanic and plutonic rocks the volcanogenic rocks contain expandable 14 a phyllosilicates formed by devitrification anatase and brookite dominate the heavy minerals tio2 associated with phosphate indicates hydrothermal alteration of host rock whereas detrital tio2 and a high ztr zircon tourmaline rutile index reflect paleosol formation as shown at the wet dry fan boundary fan progradation occurred under semi arid conditions with kaolinization and formation of illite partly detrital and a moderately stable heavy mineral association apatite dominated owing to the kaolinization only quartz bearing gneisses were preserved the facies succession reflect the evolution from a fault bordered basin with various fan sections proximal vs distal preserved into a caldera like volcanotectonic depression regionally the grain size intervals reflect a passage from recycled orogen into a transitional arc which accords with the late variscan horizontal gliding of the moldanubian plate over the saxothuringian plate and basement uplift proximal to this suture

fluvial sedimentation of the proterozoic alwar group in the lalgarh graben northwestern india abstract the lalgarh graben one of the several tectonic elements of the proterozoic delhi basin was bounded on the east and southwest by southerly converging sub parallel faults and had a steep rugged southern terminus with centripetal transport pattern the depositional slope decreased northwestwards where the graben opened towards a wide shallow sea the dausa uplift and rajputana craton located to the east and south respectively were the main source areas the graben is characterised by a sedimentary sequence more than 3000 m thick belonging to the alwar group which rests unconformably on the basic volcanics of the raialo group the alwar sequence includes three wnw ese trending and northerly dipping sedimentary facies showing progressive grain size reduction upwards and northwards these are 1 matrix and clast supported boulder conglomerates which were deposited as debris flows and boulder sheets in an intermontane environment 2 red boulder conglomerates with brownish red sandstone and siltstone interbeds which were deposited as proximal fans and longitudinal braid bars 3 interbedded conglomerates and sandstones showing profuse development of tabular and trough cross bedding siltstone layers occur in the upper part of this facies these rocks are considered to have been deposited by megaripples and transverse bars in the middle and lower reaches of a braided river system structures associated with this facies indicate that bar dissection and current deflection occurred during a falling water level development of extensive flood plains was inhibited by frequent lateral shift of the active channels high discharge and short length of the river system the fluvial facies grades into and is overlain by sandstones which accumulated on an embayed high energy tide dominated coast

the sedimentation and paleohydrology of the mesoproterozoic stream deposits in a strike slip basin svinsaga formation telemark southern norway abstract ancient braided fluvial systems were affected by a lack of binding vegetation under variable paleoclimatic conditions and possibly characterized by unique fluvial styles during the precambrian thus the paleohydrological investigations are important in interpreting ancient fluvial systems and a comparison of different fluvial styles systems this study reports new paleohydrological and sedimentological data from the ca 1 17 ga old fluvial deposits svinsaga formation in the fennoscandian shield which is a part of the east european craton the mesoproterozoic svinsaga formation overlies a major unconformity sub svinsaga unconformity in the telemark supracrustal rocks southern norway the unconformity corresponding to a ca 170 ma hiatus ca 1347 1170 ma and carry evidence for ancient periglacial climatic conditions eleven different sedimentary lithofacies and five lithofacies associations were recognized from the svinsaga formation the lithofacies assemblages indicate that the formation represents a relatively high energy braided fluvial environment massive breccias massive and inversely to normally graded conglomerates stratified sandstones and laminated and rippled mudstones were transported by traction currents sediment gravity flows and by suspension the proximal part of the formation contains blockfield blockslope accumulations and waning flood flow cycles these are overlain by hyperconcentrated and debris flow deposits and ephemeral high energy bedforms the distal part of the formation contains dune bedforms and channel lag deposits which indicate waning discharge fluctuations the paleohydrological calculations from the channel fill conglomerates and sandstone bedforms correlate with lithofacies assemblages the estimation of paleoslope and discharge values supports the presence of a fluvial stream rather than an alluvial fan environment the stream power and water velocity systematically decreases towards the distal parts of the formation the abundance of the waning flood flow cycles ephemeral high energy sedimentary deposits and hyperconcentrated and debris flow deposits is a possible indicator of periglacial melt waters in basin margin strike slip fault evolution this melt water combined with abundantly available debris from the non vegetated high topographic landscape

geodetic data inversion based on bayesian formulation with direct and indirect prior information summary mechanical interaction between adjacent plates which causes crustal deformation in plate boundary zones is rationally represented by tangential displacement discontinuity fault slip at plate interfaces given fault slip distribution we can compute surface displacements on the basis of elastic dislocation theory thus we can determine the functional form of a stochastic model to extract information about unknown fault slip distribution from observed surface displacement data in addition to observed data we usually have prior information for example plate tectonics postulates that primary fault slip is parallel to relative plate motion this is direct prior information that bounds the values of model parameters within certain ranges from physical consideration we may impose prior constraint on the roughness of fault slip distribution this is indirect prior information that regulates the structure of stochastic models by combining the direct and indirect prior information with observed data in a proper way we constructed a bayesian model for geodetic data inversion which has a hierarchic flexible structure controlled by hyper parameters the optimum values of hyper parameters are objectively determined from observed data by using akaike s bayesian information criterion abic the inversion formula derived from the bayesian model unifies the jackson matsu ura formula with direct prior information and the yabuki matsu ura formula with indirect prior information in a rational way we demonstrated the effectiveness of the unified inversion formula through the analysis of the surface displacement data associated with the 1923 kanto earthquake in the analysis with direct and indirect prior information we obtained the bimodal distribution of fault slip almost parallel to plate convergence on the north american philippine sea plate interface if we ignore the direct prior information in the analysis additional significant distribution of fault slip perpendicular to plate convergence appears to the east which is incomprehensible from plate tectonics

late silurian and early devonian terrestrialisation ichnological insights from the lower old red sandstone of the anglo welsh basin u k abstract late silurian to early devonian deposits from the lower old red sandstone anglo welsh basin preserve a diverse assemblage of trace fossils that collectively comprise an important record of early terrestrialisation five main palaeoenvironmental categories are represented 1 perennial rivers 2 ephemeral rivers 3 floodplain lakes 4 alluvial fan and 5 marginal marine ichnocoenoses mainly reflect the activity of aquatic and or semi aquatic animals fluvial deposits preserve evidence for colonisation by eurypterids fish and myriapods ephemeral river channel margins splays preserve the most diverse ichnofauna composed of deposit feeders burrows and trackways produced by arthropods feeding and foraging in channel margin soft grounds that were colonised after fluvial flood events high densities of deposit feeding structures may indicate of explosive population growth in response to periodic acyclical replenishment of nutrients in these aquatic settings ichnotaxa common to both perennial and ephemeral fluvial environments suggest that there might have been only one aquatic ecosystem the degree to which the channel margin ichnofaunas record a truly subaerial terrestrial arthropod signature is difficult to ascertain and most trace makers were probably semi aquatic some terrestrial animals invaded channel margin areas to feed and were also capable of inhabiting high energy alluvial fan environments however the fans contain low diversity ichnological assemblages and were likely to have been inhabited by an opportunistic fauna possibly the only truly subaerial terrestrial ichnocoenosis is that of pedogenically modified mudrock with scoyenia which represents an early soil ichnofauna the majority of ichnocoenoses described from continental palaeoenvironments could be classified under the scoyenia ichnofacies marginal marine deposits contain an impoverished skolithos cruziana ichnofacies typical of silurian devonian brackish water assemblages

imaging of the early acceleration phase of the 2013 2014 boso slow slip event we analyze gps and seismic data to examine the spatiotemporal evolution of a slow slip event sse near boso peninsula central japan from december 2013 to january 2014 the evolution of this sse and its associated seismicity is divided into two distinct phases slip initially accelerated slowly with low slip rates low propagation speeds and no accompanying seismicity during the early phase and then accelerated more rapidly with higher slip rates a higher propagation speed and local earthquake swarm activity during the later phase the seismicity was highly correlated in space and time with slip rate suggesting that the swarm activity was triggered by stress loading due to the slow slip the transition from the slow to faster phase shares some similarities with the nucleation of megathrust earthquakes inferred from foreshock activities suggesting that sses may provide insights into the nucleation of large earthquakes

climate of the supercontinent pangea numerous climate models predict that the geography of the supercontinent pangea was conducive to the establishment of a megamonsoonal circulation in general geologic evidence supports the hypothesis of a megamonsoon that reached maximum strength in the triassic pangea in the late carboniferous had widespread peat formation in what is now central and eastern north america and europe and relatively dry conditions on the colorado plateau the equatorial region of the continent became drier through the end of the carboniferous by the permian the equatorial region of pangea was dry and indicators of aridity and rainfall seasonality became more widespread wind directions from colorado plateau eolian sandstones are consistent with an increasing influence of monsoonal circulation at this time in the triassic climate in the colorado plateau region became relatively wet though still seasonal and the few eolian sandstones indicate a major shift in wind direction at that time in addition sedimentation

sedimentological synthesis of permian fluviatile sediments of east bokaro basin bihar india abstract the early permian karharbari and barakar formations of east bokaro basin comprise the following lithofacies lithofacies a consisting of monomictic cobble and pebble conglomerate including pebbly sandstone with faint crossbeds deposited mainly by high velocity aqueous currents as channel lag deposit or longitudinal bars lithofacies b coarse to medium sandstone profusely crossbedded interpreted as channel facies formed by downcurrent migration of sand bars in low sinuosity streams lithofacies c mainly fine sandstone with interbedded siltstone characterised by small scale ripple lamination formed in a low energy environment such as swale fill and or overbank deposits lithofacies d including carbonaceous shale and coal with lack of current structures indicating quiet water deposition interpreted as backswamp and lacustrine deposits the overall context of the karharbari and barakar assemblage with relative abundance of pebbly coarse sandstone in the former and fine clastics in the latter the presence of fining upward cycles widespread development of tabular and trough crossbedding and sample to sample variation of foreset azimuths all suggest a generally alluvial environment analysis of crossbedding dip azimuth and dimensional fabric suggest that the sediment milieu in either case consisted of streams flowing persistently from the south southeast to north northwest direction it is inferred that the unidirectional system of streams flowing across the east bokaro basin changes systematically in channel sinuosity through time

clay mineral transformations in tertiary and mesozoic sediments from north sea clay mineral transformations of 10 north sea wells have been studied and several transformation stages picked out and correlated with geothermal variations smectite disappears at 149 to 167 f 65 to 75 c whereas transformations in the mixed layer illite smectite clay minerals are observed between 113 and about 212 f 45 and about 100 c at temperatures above 113 to 149 f 45 to 65 c more than 30 illitic layers are found in the mixed layered clay minerals whereas temperatures from 140 to 167 f 60 to 75 c indicate the transition zone toward more than 50 dehydrated lattice positions temperatures above 176 to 212 f 80 to 100 c mark the lower limit for mixed layer clay minerals containing more than 70 illitic la ers the major part of the clay mineral transformations apparently takes place in the mesodiagenetic zone in which most of the hydrocarbons are also formed

diagenesis of iron in proglacial sand deposits of late and post weichselian age abstract iron diagenesis was studied in quaternary sand deposits of a temperate climate using an integrated approach of sedimentary petrography and groundwater chemistry the iron bearing minerals amphiboles pyroxenes magnetite and ilmenite are all extensively altered quantitatively amphiboles and pyroxenes are by far the most important goethite and lepidocrocite are the most important of the iron oxyhydroxide weathering products and they coat quartz and feldspars as well as amphiboles and pyroxenes however lepidocrocite is absent in the unsaturated zone hematite is only present associated with magnetite and ilmenite total iron contents of the sediments range from 0 3 0 9 percent with 30 80 percent as coatings on quartz and feldspar grains 25 60 percent in the amphibole and pyrox ne fraction and only 2 15 percent in the magnetite and ilmenite fraction therefore amphiboles and pyroxenes are the most important sources of iron for these diagenetic processes the groundwater has a ph between 5 5 and 6 0 and contains 10 30 m fe2 and a low total of dissolved solids subtraction of the contribution of the dissolved solids from atmospheric precipitation indicates higher ph and hco3 sio2 ca2 na m and fe2 concentrations due to mineral reactions in the aquifer stability relationships for iron bearing minerals under the assumption of anoxic conditions show strong undersaturation for iron bearing silicates while undersaturation for magnetite and ilmenite is much less the saturation state for magnetite is strongly dependent on the iron oxide phase formed by incongruent dissolution the surfaces of iron silicates and magnetite are highly etch pitted indicating that mineral dissolution is controlled by surface reactions rather than by diffusion through alteration products the rate of mineral alteration is slow in comparison with groundwater flow thus diagenetic changes occur in the deposit as a whole rather than as a diagenetic front advancing through the deposit the abundance of feooh on all detrital grains suggests that this proglacial deposit could develop into a red bed during further diagenesis this possibility should be considered in the paleoclimatic interpretation of red beds

3 d modelling of plate interfaces and numerical simulation of long term crustal deformation in and around japan we developed a 3 d simulation model for long term crustal deformation due to steady plate subduction in and around japan by incorporating viscoelastic slip response functions into a realistic 3 d plate interface model constructed on the basis of the topography of ocean floors and hypocenter distributions of earthquakes the lithosphere asthenosphere system is modelled by an elastic surface layer overlying a maxwellian viscoelastic half space kinematic interaction at plate interfaces is rationally represented by the increase of tangential displacement discontinuity fault slip across the interfaces with this model giving the steady slip rates at plate interfaces calculated from nuvel 1a we simulated long term crustal deformation due to steady plate subduction in and around japan the simulated crustal deformation pattern is characterized by steep uplift at island arcs sharp subsidence at ocean trenches and gentle uplift at outer rises the numerical results show the strong dependence of the deformation pattern on the 3 d geometry of plate interfaces

synchronous changes in the seismicity rate and ocean bottom hydrostatic pressures along the nankai trough a possible slow slip event detected by the dense oceanfloor network system for earthquakes and tsunamis donet abstract we detected long term hydrostatic pressure changes at ocean bottom stations of the dense oceanfloor network system for earthquakes and tsunamis donet along the nankai trough off southwestern japan we detected these changes after removing the contributions of ocean mass variations and sensor drift from the records in addition we detected a decrease in the background seismicity rate of a nearby earthquake cluster that was synchronous with the hydrostatic pressure changes we interpreted these observed hydrostatic pressure changes to reflect vertical deformation of the ocean floor of 3 8 cm and we consider the cause of the seafloor crustal deformation to be a slow slip event sse beneath the stations because the pressure changes were observed at stations with distances less than 20 km to each other we inferred that the sse occurred in the shallow part of the sedimentary wedge such as on a splay fault system the synchronous observation of an sse and a seismicity rate change suggests that both were triggered by a change in the regional stress that may be associated with stress accumulation and release processes occurring along the nankai trough these data show that continuous and careful monitoring of crustal activities by donet stations provides an effective way to detect seismic and geodetic signals related to the occurrence of megathrust or other types of large earthquakes

the baganuur coal deposit mongolia depositional environments and paleoecology of a lower cretaceous coal bearing intermontane basin in eastern asia abstract the investigations involved geophysical sedimentological palynological chemical and mineralogical studies supported by field based infrared spectrometry the baganuur basin central mongolia is among the rift or pull apart basins which subsided at the boundary between the jurassic and the lower cretaceous in east asia during the berriasian peat accumulation began in the area under study in central mongolia the palynoflora is akin to the siberian palynological province based on the phytoclast assemblages and the ratios of total sulfur content to total organic content marine transgressions into this intermontane basin may be ruled out the coal interseam sediments were laid down prevalently under neutral to slightly alkaline conditions only in some carbonaceous sediments the ph of intrastratal solutions was lowered suboxic to anoxic conditions persisted during almost the entire lower cretaceous period in the baganuur basin based on the distribution of fining and coarsening upward sequences and the organic matter the basin fill has been subdivided into seven depositional units a fluvial swamp b fluvial lacustrine c deltaic fluvial d fluvial e fluvial deltaic lacustrine floodplain f lacustrine deltaic swamp g swamp fluvial a conspicuous change in the fluvial lacustrine regime and an increase in the sediment supply may be observed at the boundary between depositional units b and c a strong uplift triggered the onset of an intensive delta sedimentation lithoclasts heavy minerals e g apatite zircon garnet anatase brookite epidote sphene tourmaline and phyllosilicates e g kaolinite smectite mica chlorite attest to a mixing of detrital material one provenance area was abundant in acidic plutonic rocks as shown by the granitic lithoclasts the other in volcanic rocks which produced the vitroclastic debris deposited as tephra fallout post depositional alteration of the siliciclastic interseam sediments was favored by a distinctive facies association of transmissive and sealing horizons it led to a re deposition of ca u and sr in the siliciclastics post depositional alteration of the organic material converted it into lignite to subbituminous c coal

trends in depth and extent of bioturbation in cambrian carbonate marine environments western united states cambrian carbonate strata of the great basin deposited below fairweather wave base but above mean storm wave base inner shelf and below mean storm wave base but above maximum storm wave base middle shelf were examined for extent and depth of bioturbation data indicate that initial extensive colonization of marine infaunal habitats occurred between tommotian and atdabanian time throughout the remaining 65 m y of cambrian time bioturbation increased although depth of bioturbation remained relatively constant at less than 6 cm during this time the amount of bioturbation in the inner shelf was greater than that in the middle shelf

sedimentation patterns of the proterozoic delhi supergroup northeastern rajasthan india and their tectonic implications abstract the proterozoic delhi supergroup occupies three ne sw trending linear belts in the northeastern part of the aravalli mountain range where its 10 km thick volcano sedimentary sequence is classified into unconformity based three groups the raialo the alwar and the ajabgarh the palaeocurrent patterns and palaeoenvironmental setting of these rocks indicate multiple palaeoslopes and locate the provenance to the east and south the interrelationship of sedimentary facies and palaeoenvironments of the delhi supergroup can best be explained by an evolving intracratonic rift basin model comparable to several well studied continental rift basins the initial down sag produced a n s trending basin which received thick carbonate facies of the lower raialo group associated with early rifting conglomerate sandstone facies association of the middle raialo developed in isolated grabens the oligomict conglomerate was deposited along the border faults in the wave and tidal reworking zones and graded to beach sandstone towards the basin centre continued extension across the basin axis resulted in outpouring of basic to acid volcanics of the upper raialo renewed rifting and associated major vertical tectonism produced some new grabens and caused wider submergence at the onset of the alwar sedimentation coarse clastics of fluvial origin developed along fault scarps in the proximal southern parts as 100 2800 m thick conglomerate bodies grading to marginal marine sandstones northwards and towards the graben centres subsequently the intervening highlands between grabens were gradually exposed another sea level rise under the influence of a still wider downwarping resulted in submergence of all the interbasin highlands and unification of all the smaller basins into a wider basin wherein the carbonate and psammo pelitic assemblage of the ajabgarh group was deposited on multi lagoonal tidal flats sedimentation was intermittently interrupted by basin wide subaqueous volcanism

shortening of recurrence interval of boso slow slip events in japan a slow slip event occurred off the coast of the boso peninsula japan from approximately 28 december 2013 to 10 january 2014 the estimated aseismic slip expanded slightly southward and westward over time with a moment magnitude of 6 5 which was the smallest value since 1996 the recurrence interval has decreased from approximately 6 4 to 2 2 years from 1996 to 2014 one explanation of this shortening is the change in coulomb failure stress due to the 2011 mw9 0 tohoku earthquake and its afterslip another interpretation is related to a scenario observed in several numerical simulation studies in which the recurrence interval of slow slip becomes shorter as the time nears a large earthquake this case will constrain the physical processes of a slip cycle the boso slow slip events together with the tohoku earthquake and its afterslip changed the stress state for the anticipated interplate earthquake near the sagami trough

woodland hypothesis for devonian tetrapod evolution abstractthe rarity of devonian tetrapods and the absence of tetrapods during the first 14 million years of the mississippian romer s gap have inspired hypotheses of fish tetrapod evolutionary transition as an escape from difficult habitats such as deserts or stagnant waters these hypotheses and romer s gap are tested here using depth to calcic horizon in paleosols of the northern appalachians as a proxy for precipitation and vegetation changes during the devonian and mississippian all tetrapod bones and trackways in this region as well as fossil tree remains were found at times of high precipitation indicated by deep calcic paleosols when subhumid woodlands expanded at the expense of semiarid shrublands in alluvial lowlands no tetrapods or tree fossils were found in abundant paleosols with the shallow calcic horizons of aridland soils the mean annual precipitation requirement of devonian mississippian tetrapods and trees was at least mm global distribution of prototetrapods and aquatic tetrapo

the potential of paleozoic nonmarine trace fossils for paleoecological interpretations abstract many late paleozoic environments have been interpreted as marine because of the co occurrence of supposedly exclusively marine trace fossils beginning in the late ordovician however nonmarine trace fossil diversity increased throughout the paleozoic this diversification of nonmarine organisms and nonmarine trace fossils was especially prevalent in devonian and later times diversification of freshwater organisms is indicated by the large number of freshwater fish arthropods annelids and molluscs that had developed by the carboniferous in addition to diverse freshwater assemblages entirely terrestrial vertebrate and invertebrate ecosystems had developed by the devonian this rapid diversification of freshwater and terrestrial organisms is inherently linked to development and diversification of land plants and subsequent shedding of large quantities of organic detritus in nonmarine and marginal marine areas nearshore marine organisms and their larvae that are able to tolerate relatively short periods of lowered salinities will follow salt water wedges inland during times of reduced freshwater discharge similarly amphidromous marine organisms will migrate periodically inland into nonmarine environments undoubtedly both of these processes were active in the paleozoic however both processes are restricted to stream distributary channels interdistributary bays or estuaries therefore the presence of diverse trace fossil assemblages in association with floodplain deposits is interpreted to reflect true nonmarine adaptation and diversity conversely diverse trace fossil assemblages in association with stream distributary channel deposits interdistributary bay deposits or estuarine deposits may reflect migration of salt water wedges inland or migration of marine organisms into freshwater environments amphidromy or both

authigenic heavy minerals a clue to unravel supergene and hypogene alteration of marine and continental sediments of triassic to cretaceous age se germany abstract siliciclastic continental marine sediments of triassic through jurassic age resting unconformably on the crystalline rocks of the central european variscides and marine deltaic sediments of cretaceous age deposited in a narrow embankment are well exposed in the wackersdorf area se germany these sediments were investigated for their variegated spectrum of authigenic heavy minerals hm and heavy mineral hm aggregates the majority of which belongs to the semi opaque group of minerals using petrographic and ore microscopy supplemented by sem edx and by empa these hms originated from supergene weathering diagenesis and hypogene alteration hydrothermal processes related to faults and unconformities the physical and chemical conditions during which these authigenic minerals developed are discussed by means of eh ph diagrams under different temperature conditions ilmenite pseudorutile anatase series may be used as a measure for the intensity of supergene alteration under rising oxygen fugacity pseudorutile and anatase also formed during hypogene alteration and developed different crystal morphologies compared with their supergene counterparts found in the above series the authigenic hm fluorite barite niccolite acanthite silver bravoite ni marcasite pyrite sphalerite galena chalcopyrite chalcocite and rhabdophane ce were produced by hypogene hydrothermal processes the hypogene mineralization in the mesozoic foreland sediments belongs to two types 1 epi mesothermal ree f mineralization controlled by the structural reactivation along a deep seated lineamentary fault zone and 2 epithermal ni cu zn as s mineralization related to the geohydraulic plane of the late variscan unconformity permo triassic peneplain

occurence of the trace fossil beaconites antarcticus in the lower carboniferous fluviatile rocks of county mayo ireland abstract large straight curved or sinuous endichnial burrows with a meniscus pattern of infilling are described from lower carboniferous red beds of county mayo ireland the burrows have been identified as beaconites antarcticus the burrows show a strong facies association being concentrated in the upper parts of sandstones deposited during floods in shallow possibly ephemeral stream channels they appear to be absent from the overlying non red fluvial sandstones which show evidence for deeper more sinuous and more permanent channels it is suggested that burrowing was related to varying moisture content of the sediment the burrows were probably formed by locomotory back packing of arthropods or vertebrates but the precise nature of the producer remains unknown

invertebrate trace fossils in semi arid to arid braided ephemeral river deposits of the mississippian middle member of the mauch chunk formation eastern pennsylvania usa abstract the rapid diversification of terrestrial ecosystems was initiated in the silurian and subsequently continued through the mississippian detailed collecting of the middle member of the mississippian mauch chunk formation in eastern pennsylvania has yielded a number of important vertebrate and invertebrate trace fossils indicating the presence of a significant terrestrial biotic diversity during the early carboniferous this report illustrates the diverse invertebrate trace fossil assemblage associated with the ephemeral river systems of the mauch chunk the mauch chunk invertebrate ichnoassemblage consists of backfilled burrows of deposit feeders both meniscate taenidium and non meniscate planolites that typically cross cut bedding arthropod trackways diplichnites diplopodichnus stiaria kouphichnium and stialla striated trails cruziana and resting traces rusophycus and surface or shallow subsurface grazing trails or burrows gordia tetrapod footprints mostly made by temnospondyl amphibians are also part of this ichnoassemblage the mauch chunk invertebrate ichnoassemblage corresponds well to the scoyenia ichnofacies in consisting of simple burrows trackways striate and bilobate trails and pits and simple meniscate burrows typically trace fossils of the scoyenia ichnofacies indicate opportunistic behaviors in subaerial environments that are temporarily or periodically inundated indeed the palaeoenvironmental setting of these traces is a semi arid to possibly arid braided ephemeral river system with extensive overbank deposits the invertebrate traces were developed both as infaunal burrows in the tops and within channel sandstones and as surface and grazing traces on in channel mudstone draped bedforms and in proximal overbank deposits the in channel mudstone draped bedforms display both vertebrate and invertebrate trace fossils the mauch chunk invertebrate ichnofossil assemblage resembles other devonian through triassic ichnoassemblages from ephemeral fluvial red beds confirming that the terrestrial invertebrate fauna had already fully colonized fluvial environments by mississippian time furthermore the development of the scoyenia ichnoguild in the mauch chunk formation in the form of abundant traces of deposit feeders of a shallow to intermediate depth infauna esp taenidium is unusually early when compared to the previously known palaeozoic record

characteristic silent earthquakes in the eastern part of the boso peninsula central japan 1 analysis of global positioning system gps data shows transient crustal deformation in the boso peninsula central japan for about fifty days from october 2002 the southeastward horizontal displacements detected suggest the occurrence of interplate aseismic slip between the philippine sea plate and the north american plate six years after a similar event in 1996 we estimate an area of aseismic slip with moment magnitude mw 6 6 centered off the boso peninsula adjacent to associated seismic activity slip evolution of the 2002 aeismic slip started on october 4 and migrated from north to south for about ten days followed by gradual subsidence and restarting of slip which lasted until december 2 propagating more southward similarities in focal area and slip process between the 1996 and the 2002 events suggest the boso aseismic slips as characteristic silent earthquakes together with the repetitive occurrence of seismic swarm in a similar region every six to seven years a more tightly coupled southern area that did not release enough energy in the 1996 event may have caused the differences in magnitude central slip area and duration between the 1996 and the 2002 events if the hypothesized recurrence interval for strain accumulation is true based on swarm seismicity

slow slip events and seismic tremor at circum pacific subduction zones 1 it has been known for a long time that slip accompanying earthquakes accounts for only a fraction of plate tectonic displacements however only recently has a fuller spectrum of strain release processes including normal slow and silent earthquakes or slow slip events and continuous and episodic slip been observed and generated by numerical simulations of the earthquake cycle despite a profusion of observations and modeling studies the physical mechanism of slow slip events remains elusive the concurrence of seismic tremor with slow slip episodes in cascadia and southwestern japan provides insight into the process of slow slip a perceived similarity between subduction zone and volcanic tremor has led to suggestions that slow slip involves fluid migration on or near the plate interface alternatively evidence is accumulating to support the notion that tremor results from shear failure during slow slip global observations of the location spatial extent magnitude duration slip rate and periodicity of these aseismic slip transients indicate significant variation that may be exploited to better understand their generation most slow slip events occur just downdip of the seismogenic zone consistent with rate and state dependent frictional modeling that requires unstable to stable transitional properties for slow slip generation at a few convergent margins the occurrence of slow slip events within the seismogenic zone makes it highly likely that transitions in frictional properties exist there and are the loci of slow slip nucleation slow slip events perturb the surrounding stress field and may either increase or relieve stress on a fault bringing it closer to or farther from earthquake failure respectively this paper presents a review of slow slip events and related seismic tremor observed at plate boundaries worldwide with a focus on circum pacific subduction zones trends in global observations of slow slip events suggest that 1 slow slip is a common phenomena observed at almost all subduction zones with instrumentation capable of recording it 2 different frictional properties likely control fast versus slow slip 3 the depth range of slow slip may be related to the thermal properties of the plate interface and 4 the equivalent seismic moment of slow slip events is proportional to their duration mo different from the mo 3 scaling observed for earthquakes

catastrophic flood hypothesis for the origin of the souris spillway saskatchewan and north dakota glacial lake spillways in the midcontinent region consist of narrow deep trenches connecting proglacial lake basins geomorphic and sedimentologic evidence from the souris and des lacs spillways in saskatchewan and north dakota indicates a catastrophic drainage of glacial lake regina the souris spillway in saskatchewan is composed of a broad upper scoured surface 5 to 10 km wide which merges with the floor of glacial lake regina the upper surface is longitudinally grooved and mantled with coarse lag deposits an inner trench 1 km wide and 20 to 45 m deep occupies the center of the spillway the two level morphology of the spillway probably developed by initial erosion of the upper level followed by incision of the inner trench a sequence of events shown by flume experiments performed by shepherd and schumm near the saskatchewan and north dakota border the flood water bifurcated into two branches as part of the water spilled over a divide into another spillway channel the two spillways in north dakota pre existing meltwater channels were occupied and enlarged by the discharge from glacial lake regina along the path of the spillways leading to the glacial lake souris basin water repeatedly breached the sides of the channels eroding shallow channels leading away from the spillway near minot north dakota a significant amount of the water spilled out toward the east and eroded a plexus of anastomosing channels with streamlined erosional remnants between the channels deposits of the flood include huge point bars located at the inside of each channel meander internally the bars generally consist of poorly sorted indistinctly bedded coarse gravel containing boulders of resistant and nonresistant lithologies as much as 3 m in diameter peak discharge of 1 10 5 m 3 s or more may have been achieved at the outlet of the lake at this rate glacial lake regina would have drained rapidly probably in less than a month the most likely cause for the rapid drainage of such proglacial lakes as glacial lake regina was high discharge inflow of water from an upstream source along the ice margin

large vertebrate burrow from the upper mississippian mauch chunk formation eastern pennsylvania usa abstract a burrow of probable amphibian origin was discovered in the upper member of the mississippian mauch chunk formation in eastern pennsylvania facies analysis of the upper member indicates that deposition occurred in an ephemeral braided stream setting the burrow is housed in a mudstone and is filled by two graded beds of conglomerate to sandstone it is characterized by a flared opening leading into a narrower slightly helical tunnel that ends in an inflated ovate chamber approximately 51 to 60 cm in diameter with a maximum height of 20 cm the flared opening is stratigraphically higher than the elevation at the base of the chamber the tunnel has a semicircular base the geometries abrupt angle changes inflated termination width to height ratios of the terminal chamber and graded fill indicate that the structure was an open void prior to sedimentation the geometry and size of this structure are incompatible with known invertebrate burrows and erosional features palaeosauropus primaevus an amphibian footprint ichnotaxon recovered from the mauch chunk formation was made by an amphibian of sufficient size to create such a large burrow this type of burrowing was most likely a response to seasonal droughts as local water sources evaporated

mid carboniferous diversification of continental ecosystems inferred from trace fossil suites in the tynemouth creek formation of new brunswick canada we report skolithos scoyenia and mermia ichnofacies from sub humid tropical fluvial megafan deposits in the lower pennsylvanian tynemouth creek formation of new brunswick canada and discuss their evolutionary and palaeoecological implications especially regarding the colonization of continental freshwater terrestrial environments the skolithos ichnofacies comprises annelid arthropod spreite in the upper storey of a fluvial channel the scoyenia ichnofacies comprises tetrapod tracks arthropleurid trackways and shallow annelid arthropod burrows in active abandoned fluvial channels and rapidly aggrading levees splays in proximal interfluve areas the mermia ichnofacies comprises abundant xiphosuran trackways along with diverse traces of other arthropods annelids mollusks and fish in shallow freshwater lakes ponds and coastal bays in slowly aggrading distal interfluve areas transitional mermia scoyenia ichnofacies comprise tetrapod mollusk and annelid arthropod traces in coastal bay deposits on the distal edge of the megafan these trace fossil suites 1 provide the clearest documentation yet of the mid carboniferous diversification event when tropical continental environments became more densely populated 2 suggest that euryhaline visitors xiphosurans microconchids and other taxa from open marine settings played a key role in this episode of freshwater colonization and 3 provide empirical support for the deja vu effect the evolutionary concept that new or empty ecospace recurrent in spatially and temporally variable environments is colonized by simple ichnocoenoses

paleomagnetism of the lac st jean anorthosite and related rocks grenville province quebec alternating field and thermal demagnetization study of the lac st jean anorthosite and related rock units in the central portion of the exposed grenville province reveals two components of magnetization one of reversed and the other of normal polarity both components are thought to have been acquired during the last regional metamorphism which was sufficiently intense in this area mostly amphibolite grade to reset any earlier magnetization corresponding paleopoles at 193 w 8 s dm 7 3 dp 4 6 and 213 w 19 s dm 10 5 dp 8 5 lie along the 950 900 ma segment of the recently calibrated grenville track of the north american apparent polar wander path a track that has thus far been defined largely by results from rock units of the western grenville

slow and delayed deformation and uplift of the outermost subduction prism following ets and seismogenic slip events beneath nicoya peninsula costa rica abstract two odp cork ocean drilling program circulation obviation retrofit kit borehole hydrologic observatory sites deployed in 2002 at the toe of the subduction prism off nicoya peninsula costa rica were visited in december 2013 the five years of seafloor and formation fluid pressure data collected since the previous visit include clear signals associated with an episodic tremor and slip ets event off the coast of nicoya peninsula in 2009 and a mw 7 6 subduction thrust earthquake beneath the peninsula in 2012 formation pressure anomalies associated with the ets event are similar to ones observed following ets events observed previously here as well as ones following very low frequency earthquake swarms within the nankai accretionary prism off southwestern japan positive and negative impulsive transients in the hanging wall and foot wall of the subduction thrust respectively suggest contractional and dilatational strain generated by local slip propagating up the thrust fault beneath the outermost prism in the case of the 2009 event the transients occurred roughly two weeks after the initiation of slip observed at gps sites along the adjacent coast at the same time a decrease in seafloor pressure at the prism site relative to the subducting plate was observed indicating concurrent uplift of the prism of 1 2 cm other events at the prism toe following ets events closer to the coast are seen in 2006 2007 2008 2010 and 2011 the time between the initiation of ets slip constrained by gps and the onset of the prism toe transients suggest up dip rupture propagation along the seaward part of the subduction thrust at rates of a few km day in the case of the 2009 event the slip at the prism toe c 11 cm estimated from the 1 2 cm uplift and the local dip on the decollement 6 is roughly a factor of 5 greater than the slip further landward estimated from gps data by dixon et al in press in other cases slip at the toe is less or unresolvable similar uplift and formation fluid pressure transients occurred two days after the 2012 nicoya thrust earthquake then episodically unrelated to aftershocks every 1 3 weeks over the next few months slip rates at the prism toe estimated from the magnitude and duration of these and ets related uplift events are roughly 5 cm day such rates are much too slow for tsunamigenesis or seismogenesis total slip of the outermost prism after the 2012 earthquake determined from the uplift accumulated until the end of the observation period and the estimated local fault dip is roughly 75 cm a significant fraction of the seismogenic slip of the mw 7 6 earthquake itself a maximum of over 3 m negative steps in formation pressure are observed at both the prism and subducting plate sites simultaneous with the 2012 thrust earthquake the sign of these steps is inconsistent with the contractional deformation predicted by an elastic fault dislocation model with slip limited to the seismogenic zone highly compliant low shear modulus sediment below the decollement or very low stress deformation along splay faults may be responsible for the co seismic dilatation observed in the outermost prism and incoming plate

palaeomagnetism of the tudor gabbro ontario evidence for divergence between grenvillia and interior laurentia summary after thermal and alternating field af cleaning the characteristic high blocking temperature a component of natural remanent magnetization nrm of the tudor gabbro of southern ontario has a mean direction d 326 i 46 k 132 95 4 8 n 8 sites the corresponding palaeopole 133 e 12 n dp 4 dm 6 confirms the palaeopole 137 e 17 n 95 8 4 reported earlier by palmer carmichael based on af cleaning only the a nrm has unblocking temperatures 515 525 c which exceed the estimated 500 c peak temperature reached locally during 1050 ma grenvillian regional metamorphism the a nrm therefore predates metamorphism and is probably a primary thermoremanence trm the age of the tudor nrm has previously been taken to be about 675 ma but recent 40ar 39ar dating by baksi has shown that this is the time of post metamorphic cooling to 200 250 c hornblendes record initial cooling of the intrusion to 590 20 c at 1110 ma and this is the best estimate of the age of the a remanence successful thellier type palaeointensity determinations on 11 tudor samples confirm that the a nrm is a trm and indicate a palaeofield at this time of 18 27 t about 50 70 per cent of the present field intensity at 27 magnetic latitude the anomalous tudor a palaeopole which lies well to the west of both 1000 800 ma grenvillian palaeopoles and 1100 1050 ma poles from interior laurentia is interpreted as recording divergence between grenvillia and interior laurentia just before the grenvillian orogeny rather than a post metamorphic extension of the apparent polar wander path as previously assumed

effective resolution and drift of paroscientific pressure sensors derived from long term seafloor measurements 1 starting with the installation of the noaa tsunami early warning system dart in 1983 the paroscientific digiquarz broadband depth sensor has been deployed for long term ocean bottom pressure measurements in numerous marine investigations the sensor turned out to be very reliable with a good signal repeatability within a broad measuring range and high resolution however up to now its long term drift noise level and effective resolution under in situ conditions at the seafloor are only known from a few published studies and for a few sensors in this study we analyze 118 long term seafloor pressure time series longer than 2 months and up to a maximum time period of 9 years to investigate effective resolution and long term drift under in situ conditions the data are from dart ifm geomar lolem and cork stations the noise level of the data and therefore the mean sensor resolution are lower than an upper threshold of 20 7 pa corresponding to 2 07 mm equivalent water level for stations installed directly on the seafloor the noise level of cork sensors is much larger with a median value of 127 pa long term sensor drift is assumed to be composed of an initial exponential part and a subsequent linear drift in situ mean drift is 0 88 0 73 kpa a determined from all available data with a slight increase of drift with deployment depth for the first time we are able to quantify effective pressure resolution and drift of the widely used paroscientific pressure gauges under in situ conditions our results provide important constrains for the interpretation of seafloor pressure records however in situ self calibration procedures for the paroscientific sensors are still needed in order to benefit from high effective resolution and long term stability and also to increase accuracy especially for the monitoring of geodynamic processes at the seafloor

significance of different modes of rhizolith preservation to interpreting paleoenvironmental and paleohydrologic settings examples from paleogene paleosols bighorn basin wyoming u s a abstract different modes of preservation of root traces rhizoliths provide information on soil moisture regimes in alluvial paleosols in the paleogene fort union and willwood formations of the bighorn basin wyoming u s a this paper links different styles of rhizolith preservation to paleosols whose other pedogenic attributes provide information on ancient soil drainage consequently the paleodrainage significance of different rhizolith preservation patterns is established more confidently rhizoliths consisting of elongate gray mottles rhizohaloes with red rims are common in relatively well drained red paleosols the gray zones are depleted of iron fe whereas the color of the rims indicates hematite accumulation these features are typical of surface water gley processes that caused fe and manganese mn to move from the root channel outward to the soil matrix calcareous rhizocretions either calcareous tubular concretions or micro accumulations of carbonate within gray rhizotubules are also common in moderately well drained red paleosols more poorly drained purple paleosols also have rhizoliths consisting of fe depletion zones however the rhizohaloes are surrounded by yellow brown goethite rims rather than red hematitic rims in many paleosols the red and yellow brown accumulation rims were partly removed by continued depletion producing abundant irregular shaped mottles the nature of the rhizohalo and the color of the fe oxide rim provide information about the intensity of gleying that a paleosol underwent the poorly drained paleosols also show rhizoliths preserved as goethite accumulations contained within gray depletion zones indicating movement of reduced fe from the matrix towards the root channel probably as a result of groundwater gley processes the goethite accumulations are intermingled locally with lignite representing preservation of the root organic material some rhizoliths are preserved as tube shaped concentrations of small 0 1 0 2 mm diameter black spheres whose color indicates a mix of mn and fe oxides these are most common in paleosols with low chroma gray matrix colors indicating very poor drainage the very poorly drained paleosols also show rhizoliths preserved in jarosite which is an oxidation product of pyrite careful observational and geochemical analysis of rhizoliths which are common in continental deposits can help produce a clearer and more thorough interpretation of ancient drainage conditions information about degree of ancient soil wetness or moisture is important for understanding past climatic conditions and for reconstructing terrestrial paleolandscapes

hardly used habitats dearth and distribution of burrowing in paleozoic and mesozoic stream and lake deposits limited use of substrate ecospace by a meager infauna in streams and lakes is indicated by analysis of more than 10 000 observations of bioturbation in permian through jurassic freshwater deposits in contrast marine substrates have been inhabited and bioturbated since the cambrian colonization of freshwater substrates differed fundamentally from that of marine substrates bioturbation enhanced flux of dissolved materials across the sediment water interface was not operating until after the paleozoic in freshwater ecosystems

fans and fan deltas precursors to the armorican quartzite ordovician in western iberia the armorican quartzite lower ordovician is a very extensive sandstone body found throughout a large part of iberia and brittany similar quartzites are present in north africa and elsewhere in iberia it generally lies unconformably on a thick folded late precambrian to cambrian turbidite sequence the complexo xisto grauvaquico cxg but there are some places where the quartzite has a conformable relationship with the underlying cxg where conformable the whole succession shows varied facies sequences including i a regressive mud sand sequence as a precursor to the main quartzite development ii submarine fan sediments of the cxg passing up into slope and then shallow marine facies or iii fluvially influenced breccio conglomerates of a marginal fan delta passing up into shallow marine sediments the inferred development of alluvial fans associated with fan deltas prograding into shallow marine environments implies steep slopes and the likelihood that faulting controlled some of the uplift the mozaic pattern of differential uplift and subsidence throughout the region suggests that the cxg was affected by local block movements rather than by regional folding the presence of upstanding blocks during the initial sedimentation of the armorican quartzite suggests that the quartz sand might have been derived from multiple sources dispersed throughout the area rather than from sources along a single shoreline at the margin of the depositional area

heavy mineral based provenance analysis of mesozoic continental marine sediments at the western edge of the bohemian massif se germany with special reference to fe ti minerals and the crystal morphology of heavy minerals during the mesozoic the epicontinental germanic basin and the regensburg strait the latter being an embayment of the tethys ocean that had subsided into the moldanubian zone of the central european variscides were filled with terrigenous continental marine sediments both sediments heavy mineral hm grains and aggregates have been studied in a drill section in the wackersdorf area se germany the majority of them belong to the semi opaque group of fe ti minerals in wackersdorf the entire stratigraphy of the basin fill which occurred between the triassic and the late cretaceous is well exposed in addition to the chemical composition of hm the morphology and texture of zircon apatite and fe ti compounds have been studied in a provenance related mineral classification provenance analysis has yielded five discrete source rock lithologies 1 moldanubian h t metamorphics 2 late paleozoic sub volcanic rocks 3 gneisses of the tepla barrandian unit 4 ophiolites of the tepla barrandian unit 5 silicified shear zones and quartz cores of pegmatites the detrital minerals include zircon tourmaline dravite schoerl apatite monazite ce th la nd xenotime biotite rutile ilmenite nigrine ilmenite rutile intergrowth sphene amphibole staurolite garnet and spinel cr mg al based on the allogenic ti and fe minerals a magnetite type source area eh 0 near surface felsic to intermediate sub volcanic rocks was distinguished from an ilmenite type source area eh 0 deeply eroded crystalline basement rocks gneiss granite shear zones the latter may be subdivided into nigrine i deep and nigrine ii intermediate subtypes according to the level of erosion in the source area at the jurassic cretaceous transition extrabasinal erosion provoked a noticeable variation of allogenic heavy minerals with the incisions of rivers into source rock lithologies 4 and 5 uplift and erosion along the western edge of the bohemian massif took place contemporaneously with spreading and closure in the central parts of the adjacent tethys ocean

a numerical analysis of grain size and colour variations of a fan lake transition upper carboniferous bechtsrieth formation southern germany abstract the upper carboniferous bechtsrieth formation of the weiden basin southern germany shows a depositional evolution from an alluvial fan to a lake the sedimentary record of the probably westphalian gc member reflects gravity slides and waterlaid deposition of braided streams the younger gsc member is dominated by floodplain and sheetflood deposition locally hosting abundant freshwater limestone and clastic sediments deposited by meandering streams they grade into the nearshore and offshore lacustrine sediments of the vc member laid down during the late stephanian these subfacies types have been numerically coded as fan ratios which normalized to a 10 m drill interval resulted from the sand mud ratio multiplied by the degree of contrast and maximum clast size supplemented by rock colour which indicates oxidizing and reducing conditions of these strata and carbonate content a discrimination of these continental environments is possible and also makes the procedure amenable to cutting examinations because these terrigenous rocks have attracted the attention of exploration geologists for their coal hydrocarbon uranium and precious metal contents the source and host environments have tentatively been described in terms of these facies codes low fan ratios between 0 and 0 75 are indicative of predominantly offshore and nearshore lacustrine environments and seem most prospective for hydrocarbons uranium and gold this approach is a rapid method to improve environmental analysis and facilitate well log correlations

geodetic data inversion using a bayesian information criterion for spatial distribution of fault slip summary we developed a new inversion method to reconstruct static images of seismic sources from geodetic data using akaike s bayesian information criterion abic coseismic surface displacements are generally related with a slip distribution on a fault surface by linear integral equations parametric expansion of the fault slip distribution by a finite number of known basis functions yields a set of observation equations expressed in a simple vector form incorporating prior constraints on the smoothness of slip distribution with the observation equations we construct a bayesian model with unknown hyperparameters the optimal values of the hyperparameters which control the structure of the bayesian model are objectively determined from observed data by using abic once the values of hyperparameters are determined we can use the maximum likelihood method to find the optimal distribution of fault slip we examined the validity of this method through a numerical experiment using theoretical data with random noise we analysed geodetic data associated with the 1946 nankaido earthquake ms 8 2 by using this method the result shows that the fault slip distribution of this earthquake has two main peaks of 4 and 6 m located off kii peninsula and muroto promontory these two high slip areas are clearly separated by a low slip zone extending along kii strait such a slip distribution corresponds with the fact that the rupture process of this earthquake in the western part is notably different from that in the eastern part

episodic slow slip events in the japan subduction zone before the 2011 tohoku oki earthquake abstract we describe two transient slow slip events that occurred before the 2011 tohoku oki earthquake the first transient crustal deformation which occurred over a period of a week in november 2008 was recorded simultaneously using ocean bottom pressure gauges and an on shore volumetric strainmeter this deformation has been interpreted as being an m6 8 episodic slow slip event the second had a duration exceeding 1 month and was observed in february 2011 just before the 2011 tohoku oki earthquake the moment magnitude of this event reached 7 0 the two events preceded interplate earthquakes of magnitudes m6 1 december 2008 and m7 3 march 9 2011 respectively the latter is the largest foreshock of the 2011 tohoku oki earthquake our findings indicate that these slow slip events induced increases in shear stress which in turn triggered the interplate earthquakes the slow slip event source area on the fault is also located within the downdip portion of the huge coseismic slip area of the 2011 earthquake this demonstrates episodic slow slip and seismic behavior occurring on the same portions of the megathrust fault suggesting that the faults undergo slip in slow slip events can also rupture seismically

an integrated perspective of the continuum between earthquakes and slow slip phenomena slow slip a mechanism by which faults can relieve stress was thought to be distinct from earthquakes however a global review of slow slip phenomena suggests that instead there is a continuum between the two types of event