late paleozoic glacial episodes in gondwanaland reflected in transgressive regressive depositional sequences in euramerica the late paleozoic glaciation of gondwanaland comprised two short episodes in the famennian i and visean ii confined to brazil and adjacent northwest africa and a long episode that started in the namurian iiia of eastern australia and bolivia argentina expanded to cover much of gondwanaland in the stephanian asselian iiib and collapsed in the early sakmarian iiic dropstones in eastern australia indicate that small ice centers lingered to the kazanian across the belt of low latitudes north of gondwanaland short ranging fossils in widespread shallow marine and paralic deposits indicate synchronous deposition of transgressive regressive sequences in different parts of euramerica these sequences correlate with glacial events in gondwanaland at three levels a four major regressions in euramerica in the famennian 1 visean 2 namurian 3 stephanian 4 and the tastubian transgression that preceded the sterlitamakian regression 5 also recorded in gondwanaland correlate with glacial episodes i ii and iiia iiib and iiic b the time interval of cyclothemic deposition in euramerica brigantian or latest visean to sterlitamakian correlates with that of glacial episode iii and c the dominant period of the euramerican cyclothems as estimated from the middle and late pennsylvanian deposits of the mid continent of north america and of the thickest known gondwanaland glacigenic sediment the earliest permian lyons group of western australia is 0 4 ma equivalent in turn to the long orbital eccentricity period of the quaternary ice age and the dominant period of fluctuation of the late miocene antarctic ice cap the three levels of correlations confirm wanless and shepard9s 1936 hypothesis that the late paleozoic cyclothems are controlled largely by sea level fluctuations related to the gondwanaland glaciation

experimental analysis of debris motion due the obstruction from fixed obstacles in tsunami like flow conditions abstract experimental research was conducted focusing on debris motion over a horizontal apron featuring vertical obstacles in the path of the debris propagation the apron was designed as a typical representation of a harbor threatened by an inundating tsunami the experimental setup idealized often complex harbor settings the debris was a scaled down 20 foot shipping container modelled at a 1 in 40 froude length scale offand onshore regions were separated by a vertical quay wall which allowed the incoming elongated solitary wave used to represent the first part of a tsunami to steepen break and propagate over the initially dry surface as a tsunami like bore in the path of propagation a varying number of debris were entrained within the inundating bore over the horizontal apron the entrained debris interacted with regularly spaced vertical obstacles representing infrastructure and houses within the propagation path varying debris and obstacle arrangements were tested to evaluate the effects the obstacles would have on the debris maximum longitudinal displacement and the spreading angle the main conclusion is that the spreading angle of the debris is not as significantly altered by the presence of obstacles on the harbor apron whereas the maximum longitudinal displacement of the debris was significantly affected

characteristics of channel steps and reach morphology in headwater streams southeast alaska abstract the effect of timber harvesting and mass movement on channel steps and reach morphology was examined in 16 headwater streams of se alaska channel steps formed by woody debris and boulders are significant channel units in headwater streams numbers intervals and heights of steps did not differ among management and disturbance regimes a negative exponential relationship between channel gradient and mean length of step intervals was observed in the fluvial reaches

evolution and distribution of the conodonts sweetognathus and iranognathus and related genera during the permian and their implications for climate change abstract the conodont genus sweetognathus which is characterized by pustulose ornamentation on a wide flat topped carina originated in the earliest permian as s expansus from diplognathodus edentulus the asselian through artinskian part of the sweetognathus lineage is well represented in kansas by the successive evolution of s expansus s merrilli s aff s merrilli s whitei and s bucaramangus sweetognathus and iranognathus lineages were mainly confined to tropical areas from the kungurian onward the kungurian and guadalupian part of the sweetognathus lineage is well represented in south china by the successive evolution of s whitei artinskian s guizhouensis lower kungurian s subsymmetricus upper kungurian s iranicus hanzhongensis roadian and s fengshanensis capitanian an additional lineage in west texas is represented by the evolution of s sulcatus to s aff adjunctus to s adjunctus and to s bicarinum in the urals and northwestern pangea the late part of the sweetognathus lineage is represented by rare specimens of s bogoslovskajae upper artinskian lower kungurian during the late artinskian s whitei radiated into s toriyamai and s bucaramangus and also gave rise to neostreptognathodus pequopensis and probably pseudosweetognathus costatus neostreptognathodus exsculptus may have evolved from adetognathus paralautus through adetognathus telfordi sp nov iranognathus characterized by a narrow carina with poorly developed denticles and bearing subtle and smaller pustulose micro ornament replaced sweetognathus at or near the guadalupian lopingian boundary it probably also evolved from diplognathodus in the topmost guadalupian a lineage of iranognathus sp nov a to i erwini can be recognized for the guadalupian and lopingian boundary interval a lineage of iranognathus sp nov a to i movschovithschi to i sosioensis to i tarazi is found throughout the guadalupian and lopingian boundary interval and the wuchiapingian of south china sweetognathus and iranognathus tend to develop homeomorphic accessory nodes iteratively during lowstand periods of global sea level near the artinskian kungurian and guadalupian lopingian boundaries and in the late wuchiapingian sweetognathus and iranognathus seem to be equatorial warm water inhabitants distribution patterns reflect glaciation in gondwana during the asselian and sakmarian a warm climate during the artinskian cooling in north pangea during the kungurian and later permian slight amelioration during the guadalupian warming during the wuchiapingian and cooling during the changhsingian in the peri gondwana region definitions for most of the important sweetognathus species are refined three new species and subspecies iranognathus sp nov a adetognathus telfordi sp nov gullodus duani sp nov are described

derivation of isotope ratios errors and error correlations for u pb geochronology using 205pb 235u 233u spiked isotope dilution thermal ionization mass spectrometric data a comprehensive treatment of the derivation of u pb isotope ratios and their corresponding uncertainties from isotope dilution thermal ionization mass spectrometric measurements is presented standard parametric statistical methods of error propagation are utilized to convolve uncertainties associated with instrumental mass fractionation tracer subtraction blank pb and u subtraction and initial common pb correction derivations include errors and error correlations for total sample u pb and pb isotope ratios including radiogenic and initial common pb for two and three dimensional isochron calculations radiogenic u pb and pb isotope ratios for concordia and radiogenic model age calculations and the propagation of model age errors from radiogenic isotope ratios

john day formation of oregon a distal record of early cascade volcanism the john day formation in oregon consists largely of silicic to intermediate pyroclastic material ranging in age from about 19 to 37 m y stratigraphic and lithologic variations within the formation indicate that the bulk of this material was derived from vents west of the 121st meridian in or near the present day cascade range voluminous dacitic to andesite air fall material was probably derived from volcanoes within the western cascade range whereas rhyolitie ash flow tuffs and lava flows were erupted from vents farther east sparse alkali basalt and trachyandesite flows compositionally distinct from cascade range lavas were erupted from local vents within the john day outcrop area initiation of john day volcanism about 37 m y ago signified a shift in the locus of calc alkaline volcanic activity from the blue mountains to the cascade range and marked the emergence of the cascade range as a major volcanic feature

cyclothem digital correlation and biostratigraphy across the global moscovian kasimovian gzhelian stage boundary interval middle upper pennsylvanian in north america and eastern europe the long standing difficulty of correlating pennsylvanian strata among provincial faunal regions is resolved by effecting digital correlation of major glacial eustatic cyclothems that represent high stands when certain species achieved more global distribution than usual in the late moscovian early gzhelian late desmoinesian early virgilian succession in the midcontinent united states several major cyclothems are correlated by both conodont species in common and cyclothem scale with cyclothems in russia moscow basin and ukraine donets basin and the remaining cyclothems fit into the framework by position and scale in this way the suggested event marker for the global kasimovian gzhelian stage boundary first appearance of idiognathodus simulator is supported while possible event markers for the moscovian kasimovian boundary await further evaluation

quantitative radiometric and biostratigraphic calibration of the pennsylvanian early permian cisuralian time scale and pan euramerican chronostratigraphic correlation a quantitative biostratigraphic and radiometric calibration is presented for the pennsylvanian through early permian global time scale based upon high precision isotope dilution thermal ionization mass spectrometer id tims u pb zircon ages for interstratified ash beds in the parastratotype sections of the southern urals of russia twenty four ash bed ages in three outer ramp and basinal sections of the pre uralian foredeep bracket the biotic definitions of global stages and regional substages from the base of the upper pennsylvanian kasimovian stage to the base of the lower permian artinskian stage four additional ash bed ages in two sections of the eastern slope of the urals constrain the global bashkirian and serpukhovian stages quantitative stratigraphic methods conop9 are applied to a compilation of over 2000 bioevents in 22 stratigraphic sections supplemented by our dated volcanic horizons to refine the pennsylvanian early permian global time scale significant shifts in the duration of several stages are demonstrated ranging from one to six million years compared with prior estimates the unprecedented density of radiometric calibration points for the pennsylvanian permian transition provides a high resolution 0 1 ma global chronostratigraphic standard for testing and improving biostratigraphic correlations across euramerica we integrate radiometric ages biostratigraphic correlation and cyclostratigraphic tuning of major cyclothems to the long period 404 ka eccentricity cycle to elucidate the tempo magnitude and forcing of eustatic changes and cyclothemic deposition associated with the waxing and waning of gondwanan ice sheets and establish a pan euramerican chronostratigraphic framework for most of pennsylvanian and early permian time

glaciation aridification and carbon sequestration in the permo carboniferous the isotopic record from low latitudes to evaluate the isotopic record of climate change and carbon sequestration in the late paleozoic we have compiled new and published oxygen and carbon isotopic measurements of more than 2000 brachiopod shells from carboniferous through middle permian 359 260 ma strata we focus on the isotopic records from the u s midcontinent and the russian platform because these two regions provide well preserved marine fossils spanning a broad time interval both regions show a 18o increase at the mid carboniferous boundary ca 318 ma that roughly correlates with geologic evidence for an expansion of gondwanan glaciers only the russian platform record shows a 18o maximum during the glacial maximum in the asselian in contrast to a previous study korte c jasper t kozur h w and veizer j 2005 18o and 13c of permian brachiopods a record of seawater evolution and continental glaciation palaeogeogr palaeoclimatol palaeoecol 224 333 351 our data show no oxygen isotope evidence for glacial retreat in the early permian but instead show increasing 18o values related to aridification dissimilarity in the 18o trends for the epicontinental seas of north american and the russian platform suggests that at least one region experienced periodic restriction that altered regional salinities and seawater 18o values these results highlight the need for complementary proxies to identify restricted circulation in epicontinental seas carbon isotopic compositions of carbonates exhibit substantial regional variation with low values in western north america intermediate values in the midcontinent and high values in the sverdrup basin russian platform and northern spain nevertheless both u s midcontinent and russian platform records show a late serpukhovian minimum a sharp increase across the mid carboniferous boundary and a minimum centered on the kasimovian the correlative increase in brachiopod 13c and 18o values at the mid carboniferous boundary is our best isotopic evidence for a link between the carbon burial and glaciation in the permo carboniferous

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

the pangean ice age studies with a coupled climate ice sheet model application of an ice sheet model developed for the pleistocene to the extensive carboniferous glaciation on gondwana yields an ice sheet which has several features consistent with observations while complete deglaciation is not achieved without co2 changes the milankovich induced fluctuations in ice sheet volume are comparable to pleistocene glacial interglacial signals this result is shown to hold for a large fraction of physically reasonable parameter space the model also exhibits multiple equilibria and sharp bifurcations as infinitesimal changes in the solar constant or precipitation can lead to a qualitatively different climate the success of the model in predicting ice location in an environment quite different from the pleistocene provides additional support for the robustness of the basic model physics and suggests that the model can be applied with some confidence to other pre pleistocene glaciations

correlation of the base of the serpukhovian stage mississippian in nw europe the task group charged with proposing the gssp for the base of the serpukhovian stage mississippian lower carboniferous is likely to use the global first appearance datum fad of the conodont lochriea ziegleri in the lineage lochriea nodosa l ziegleri for the definition and correlation of the base of the stage it is important to establish that the fad of l ziegleri in different basins is penecontemporaneous ammonoids provide high resolution biostratigraphy in the late mississippian but their use in international correlation is limited by provincialism however it is possible to assess the levels of diachronism of the first occurrence datum fod of l ziegleri in sections in nw europe using ammonoid zones published conodont distribution in the rhenish slate mountains of germany show the fod of l ziegleri in the emstites novalis biozone upper part of the p2c zone of the uk and ireland but l ziegleri has also been reported as occurring in the neoglyphioceras spirale biozone p1d zone in the yoredale group of northern england the fod of l ziegleri is in either the p1c or p1d zone in nw ireland the oldest records of both l nodosa and l ziegleri are from the lusitanoceras granosum biozone p2a although there is some discrepancy in the recorded levels of the fod of l ziegleri in nw europe this may be as a result of collection failure the base of the serpukhovian based on the fad of lochriea ziegleri will be in the middle of the brigantian regional substage

bridging the gaps an overview of wood across time and space in diverse rivers abstract nearly 50 years of research focused on large wood lw in rivers provide a basis for understanding how wood enters rivers how wood decays breaks and is transported downstream and how at least temporarily stable wood influences channel geometry fluxes of water sediment and organic matter and the abundance and diversity of aquatic and riparian organisms field based studies have led to qualitative conceptual models and to numerical stimulations of river processes involving wood numerous important gaps remain however in our understanding of wood dynamics the majority of research on wood in rivers focuses on small to medium sized rivers defined using the ratio of wood piece size to channel width as channels narrower than the locally typical wood piece length small and slightly narrower than the longer wood pieces present medium although diverse geographic regions and biomes are represented by one or a few studies in each region the majority of research comes from perennial rivers draining temperate conifer forests regional syntheses most commonly focus on the pacific northwest region of north america where most of these studies originate consequently significant gaps in our understanding include lack of knowledge of wood related processes in large rivers dryland rivers and rivers of the high and low latitudes using a wood budget as an organizing framework this paper identifies other gaps related to wood recruitment transport storage and how beavers influence lw dynamics with respect to wood recruitment we lack information on the relative importance of mass tree mortality and transport of buried or surficial downed wood from the floodplain into the channel in diverse settings knowledge gaps related to wood transport include transport distances of lw and thresholds for lw mobility in small to medium rivers with respect to wood storage we have limited data on longitudinal trends in lw loads within unaltered large and great rivers and on fluctuations in lw load over time intervals greater than a few years other knowledge gaps relate to physical and ecological effects of wood including the magnitude of flow resistance caused by lw patterns of wood related sediment storage for diverse river sizes and channel geometry quantification of channel floodplain lw interactions and potential threshold effects of lw in relation to physical processes and biotic communities finally knowledge gaps are related to management of large wood and river corridors including understanding the consequences of enormous historical reductions in lw load in rivers through the forested portions of the temperate zone and how to effectively reintroduce and manage existing lw in river corridors which includes enhancing public understanding of the importance of lw addressing these knowledge gaps requires more case studies from diverse rivers as well as more syntheses and metadata analyses

morphology and distribution of fossil soils in the permo pennsylvanian wichita and bowie groups north central texas usa implications for western equatorial pangean palaeoclimate during icehouse greenhouse transition analysis of stacked permo pennsylvanian palaeosols from north central texas documents the influence of palaeolandscape position on pedogenesis in aggradational depositional settings palaeosols of the eastern shelf of the midland basin exhibit stratigraphic trends in the distribution of soil horizons structure rooting density clay mineralogy and colour that record long term changes in soil forming conditions driven by both local processes and regional climate palaeosols similar to modern histosols ultisols vertisols inceptisols and entisols all bearing morphological mineralogical and chemical characteristics consistent with a tropical humid climate represent the late pennsylvanian suite of palaeosol orders palaeosols similar to modern alfisols vertisols inceptisols aridisols and entisols preserve characteristics indicative of a drier and seasonal tropical climate throughout the lower permian strata the changes in palaeosol morphology are interpreted as being a result of an overall climatic trend from relatively humid and tropical moist conditions characterized by high rainfall in the late pennsylvanian to progressively drier semi arid to arid tropical climate characterized by seasonal rainfall in early permian time based on known late palaeozoic palaeogeography and current hypotheses for atmospheric circulation over western equatorial pangea the pennsylvanian palaeosols in this study may be recording a climate that is the result of an orographic control over regionalscale atmospheric circulation the trend towards a drier climate interpreted from the permian palaeosols may be recording the breakdown of this preexisting orographic effect and the onset of a monsoonal atmospheric circulation system over this region

stable isotopes in large herbivore tooth enamel capture a mid miocene precipitation spike in the interior pacific northwest abstract stable carbon and oxygen isotopes of fossil ungulate tooth enamel were used to investigate the paleoclimate of the pacific northwest from the mid oligocene through pleistocene particularly targeting the mid miocene climatic optimum mmco we specifically test whether precipitation as inferred from tooth enamel 13c values relative to the 13c values of atmospheric co2 13c increased with increasing partial pressure of atmospheric co2 pco2 analysis emphasized water dependent equids rhinos and proboscideans but several artiodactyls and castor were also analyzed as available values of 13c 19 5 in the lower john day 27 and 18 ma and mascall 15 16 ma localities imply relatively high mean annual precipitation map ca 550 800 mm yr values of 13c

temporal calibration and biochronology of the centenario fauna early miocene of panama abstractnew excavations along the panama canal have yielded a growing early miocene assemblage of mammals referred to as the centenario fauna despite the area s proximity to south america the mammals of the centenario fauna have entirely north american affinities the centenario fauna is distributed throughout a 115 m stratigraphic interval encompassing the uppermost culebra and cucaracha formations within the panama canal basin previously published ages constrain the age of the lower limit of the centenario fauna to no younger than 19 ma but the upper limit has remained problematical a fresh exposure of the cucaracha tuff a prominent marker horizon within our measured sections has yielded two new radioisotopic determinations 1 an 40ar 39ar age of 18 96 0 90 ma and 2 a u pb zircon age of 18 81 0 30 ma in addition magnetostratigraphic data indicate that the centenario fauna occurs within chron c5er from 18 78 to 19 05 ma on the geomagnetic polarity timescale of gee and kent these corr

paleoenvironmental reconstruction from chemical and isotopic compositions of permo pennsylvanian pedogenic minerals mineralogical and chemical analysis of late pennsylvanian and early permian paleosols from the eastern shelf of the midland basin north central texas usa are used to test hypothesized climate change in late paleozoic western equatorial pangea previously defined independently on the bases of sedimentologic and paleontologic proxies and climate models the 0 2 m size phyllosilicate fraction in the studied paleosols exhibits down profile trends in mineralogy and chemical composition that are consistent with modern weathering profiles suggesting a dominantly pedogenic origin a stratigraphic trend from kaolinite dominated profiles in upper pennsylvanian paleosols to profiles dominated by smectite and hydroxy interlayered 2 1 phyllosilicates in lower permian paleosols indicates a relatively rapid decrease in soil weathering and leaching in the latest pennsylvanian followed by a more gradual decrease in leaching throughout the early permian the chemical composition cation ratios and exchange capacity of these phyllosilicates further corroborates this shift toward less intensive leaching presumably in response to climate change from humid to progressively more arid conditions the phyllosilicates in the 0 2 m size fraction and contemporaneous pedogenic calcites from the permo pennsylvanian paleosols exhibit a long term stratigraphic increase in their 18o values of as much as 3 2 and 5 2 respectively this long term trend is consistent with a transition throughout the latest pennsylvanian through early permian toward progressively more evaporatively enriched soil waters superimposed on the long term trend is an apparent rapid enrichment 1 5 to 2 in phyllosilicate 18o values immediately above the pennsylvanian permian boundary observed oxygen isotope fractionation between the phyllosilicates and calcites within individual paleosols indicate isotopic disequilibrium between mineral pairs this is attributed to a minor detrital component in the pedogenic clay dominated phyllosilicate fraction coupled with the effects of seasonality of mineral formation inferred 18o compositions of late paleozoic meteoric water 2 to 4 are compatible with less intensive soil leaching under conditions of increasing aridity possibly coupled with a shift in local precipitation from a continental source to a marine source

prediction of effects of woody debris removal on flow resistance a simple technique for predicting the darcy weisbach friction factor for river channels with varying amounts of large woody debris was developed first debris density is determined based on measurement or visual estimation of cross sectional areas of debris formations in the plane perpendicular to flow the darcy weisbach friction factor is then computed using debris density channel geometry mean flow velocity and the debris drag coefficient the debris drag coefficient may be computed fom a power function with experimentally determined coefficients for verification of the proposed procedure debris density and friction factors were measured in river reaches in western tennessee and southeastern new south wales australia friction factors computed using the procedure were within 30 of measured values for straight sand bed reaches and within 38 of measured values for sinuous gravel bed reaches the computational procedure explained 84 of the variance in observed values

siberian glaciation as a constraint on permian carboniferous co2 levels reconstructions of phanerozoic co2 levels have generally relied on geochemical modeling or proxy data because the uncertainty inherent in such reconstructions is large enough to be climatically significant inverse climate modeling may help to constrain paleo co2 estimates in particular we test the plausibility of this technique by focusing on the climate from 360 to 260 ma a time in which the siberian landmass was in middle to high latitudes yet had little or no permanent land ice our climate model simulations predict a lower limit for co2 the value beneath which siberia acquires excess ice simulations provide little new information for the period in which siberia was at a relatively low paleoaltitude 360 340 ma but model results imply that paleo co2 levels had to be greater than 2 4 modern values to be consistent with an apparently ice free siberia in the late permian these results for the later period in general agree with soil co2 proxies and the timing of gondwanan deglaciation thus providing support for a significant co2 increase before the end permian boundary event our technique may be applicable to other time intervals of unipolar glaciation

astronomical calibration of the paleocene time the first complete cyclic sedimentary successions for the early paleogene from drilling multiple holes have been retrieved during two odp expeditions leg 198 shatsky rise nw pacific ocean and leg 208 walvis ridge se atlantic ocean these new records allow us to construct a comprehensive astronomically calibrated stratigraphic framework with an unprecedented accuracy for both the atlantic and the pacific oceans covering the entire paleocene epoch based on the identification of the stable long eccentricity cycle 405 kyr high resolution x ray fluorescence xrf core scanner and non destructive core logging data from sites 1209 through 1211 leg 198 and sites 1262 1267 leg 208 are the basis for such a robust chronostratigraphy former investigated marine odp sites 1001 and 1051 and land based e g zumaia sections have been integrated as well the high fidelity chronology is the prerequisite for deciphering mechanisms in relation to prominent transient climatic events as well as completely new insights into greenhouse climate variability in the early paleogene we demonstrate that the paleocene epoch covers 24 long eccentricity cycles we also show that no definite absolute age datums for the k pg boundary or the paleocene eocene thermal maximum petm can be provided by now because of still existing uncertainties in orbital solutions and radiometric dating however we provide two options for tuning of the paleocene which are only offset by 405 kyr our orbitally calibrated integrated leg 208 magnetostratigraphy is used to revise the geomagnetic polarity time scale gpts for chron c29 to c25 we established a high resolution calcareous nannofossil biostratigraphy for the south atlantic which allows a much more detailed relative scaling of stages with biozones the re evaluation of the south atlantic spreading rate model features higher frequent oscillations in spreading rates for magnetochron c28r c27n and c26n

an analytical numerical approach to the hydraulics of floating debris in river channels a new simplified approach is developed for the channel flow dynamics under woody debris transport a continuous carpet of debris is considered covering a uniform stationary current due to the floating debris the shear stresses in the fluid domain are affected as a result the velocity profile is different from the free surface flow the simple model proposed here is able to capture the essential features of flow response to woody debris transport velocity and stress profiles are analytically derived for laminar flow and compared with the zero debris condition more realistic turbulent currents are simulated with the reynolds equations where turbulent stresses are modeled by the simple mixing length concept validation is carried out by comparison with experimental velocity profiles and with direct numerical simulation of the navier stokes equations synthetic diagrams are proposed for the calculation of the flow velocity and the bed shear stresses in terms of the relevant non dimensional parameters

a flume experiment on the formation of wood jams in rivers 1 a flume experiment is carried out to explore jamming of large woody debris lwd in streams with complex morphology occurring in mountain streams with in channel boulders or vegetation in braided rivers or in floodplains during flood events non rooted defoliated lwd is modeled using wood dowels and obstacles to motion are represented by vertical wood rods congested transport of lwd is simulated by insertion of a number 100 of dowels the final position of the dowels is mapped and the observed jams are classified according to their size and position the key member of each jam is identified and its trapping mechanism evaluated either by leaning against a single obstacle or by bridging two obstacles to mimic uncongested transport the experiment is repeated for single pieces of wood with subsequent removal longer dowels and shallower water result in shorter traveled distance wood pieces travel farther when congested transport is observed the traveled distance of the wood pieces can be modeled using a gamma distribution for both congested and uncongested transport jams instead display uniform traveled distance the number of pieces displays an exponential distribution the degree of uniformity in space of jams and wood pieces is evaluated using a neighbor k statistic wood pieces show considerable clustering while jams show sparse distribution eventually the relationship between jams magnitude and position is explored showing negative correlation model application is then discussed and some conclusions and future developments are outlined

the serpukhovian in britain use of foraminiferal assemblages for dating and correlating analysis of foraminiferal assemblages from the visean serpukhovian boundary interval in britain has led to the recognition that levels correlated with the first occurrence of lochriea ziegleri at the base of the serpukhovian stage can be established by the foraminifer neoarchaediscus gregorii in england and scotland which first occurs from the single post and cockleshell limestones in northern england and laterally equivalent levels as well as asteroarchaediscus bashkiricus and a rugosus except for south wales contrary to some previous studies the base of the serpukhovian does not equate with the base of the namurian pendleian substage but lies approximately at the early late brigantian boundary based on the first occurrence of neoarchaediscus postrugosus four foraminiferal assemblages are distinguished in the early serpukhovian 7 10 and four assemblages in the late serpukhovian 11 14 despite the contrast in facies it is now recognised for the first time that throughout the midland valley of scotland northern england and south wales the foraminiferal assemblages from shallow water platform facies are completely compatible with the ammonoid subzones from deep water basinal facies with no apparent mismatches there appears to be close comparability of foraminiferal assemblages and first appearance datums of marker species with most of the international foraminiferal zonal schemes in russia supplementary material https doi org 10 6084 m9 figshare c 5240408

sea level curve for pennsylvanian eustatic marine transgressive regressive depositional cycles along midcontinent outcrop belt north america at least 55 cycles of marine inundation and withdrawal are recognized in the mid desmoinesian to mid virgilian midcontinent outcrop sequence in north america they range from widespread major cycles classic cyclothems with deep water facies extending across the northern shelf through intermediate cycles persisting as marine horizons across the shelf to minor cycles developed on the lower shelf or as parts of major cycles biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems but they may be obscured by the distinctness of the major cyclothems estimates of cycle periods range from about 40 to 120 x 10 sup 3 yr for the minor cycles up to about 235 to 400 x 10 sup 3 yr for the major cyclothems the range for all cycles corresponds well to the range of periods of earth s orbital parameters that constitute the milankovitch insolation theory for the pleistocene ice ages and it further supports gondwanan glacial control for the pennsylvanian cycles even though the dominant period of the major pennsylvanian cyclothems is up to four times longer than the dominant 100 000 yr period inmore the pleistocene the shapes of both curves display rapid marine transgression rapid melting of ice caps and slow interrupted regression slow buildup of ice caps which suggest similar linkages between the climatic effects of the orbital parameters and ice cap formation and melting at the two different scales widely separated in time 28 references 3 figures less

transport of large woody debris in the presence of obstacles flume experiments were carried out to investigate the motion of large woody debris lwd in rivers as influenced by the presence of obstacles non rooted defoliated lwd was modelled by placing properly scaled wooden dowels placed into controlled water flow obstacles were represented by wooden rods randomly placed into the flume with a specified probability distribution the results provide the probability of lodging of the dowels and statistics of the distance travelled their relationships with flow rate and depth dowel length and spatial density of the obstacles is explored this yields a general theoretical framework to approach lwd transport in rivers by combining random factors with deterministic dimensionless variables

reevaluation of the timing and extent of late paleozoic glaciation in gondwana role of the transantarctic mountains evidence from antarctica indicates that a 2000 km long section of the transantarctic mountains including victoria land the darwin glacier region and the central transantarctic mountains was not located near the center of an enormous car boniferous to early permian ice sheet as depicted in many paleo geographic reconstructions weathering profiles and soft sediment deformation immediately below the preglacial pre permian un conformity suggest an absence of ice cover during the carbonif erous otherwise multiple glacial cycles would have destroyed these features the occurrence of glaciotectonite massive and strat ified diamictite thrust sheets sandstones containing dewatering structures and lonestone bearing shales in southern victoria land and the darwin glacier region indicate that permian sedimenta tion occurred in ice marginal periglacial and or glaciomarine set tings no evidence was found that indicates the transantarctic mountains were near a glacial spreading center during the late paleozoic although these findings do not negate carboniferous glaciation in antarctica they do indicate that gondwanan glacia tion was less widespread and therefore that glacially driven changes to other earth systems i e glacioeustatic fluctuations cli mate were much smaller than previously hypothesized

constraints on pennsylvanian glacioeustatic sea level changes using oxygen isotopes of conodont apatite conodonts from u s midcontinent cyclothems were studied for oxygen isotopes in order to constrain pennsylvanian glacioeustatic sea level fluctuations pennsylvanian deposits of the midcontinent united states are composed of cyclic alternations of thin transgressive limestones offshore gray to black phosphatic shales and thick regressive limestones a sequence that is underlain and overlain by nearshore to terrestrial shales with paleosols and coal beds glacioeustatic sea level fluctuations are considered the primary cause for the formation of these cyclothems oxygen isotope analyses of conodont apatite from the black 20 1 0 5 vienna standard mean ocean water vsmow and gray shale units 20 5 0 5 vsmow show lowest average 18 o values whereas conodont elements from the regressive 21 0 0 3 vsmow and transgressive limestone units 21 1 0 6 vsmow are enriched in 18 o the maximum change in 18 o of conodonts from the black shale and carbonate units from individual cyclothems is 1 7 the 1 7 c difference in 18 o compares relatively well to pleistocene interglacial glacial changes in 18 o of equatorial surface dwelling foraminifers and suggests that pennsylvanian glacioeustatic sea level changes may have been of comparable amplitude however since the pennsylvanian glacial maxima are represented by terrestrial sediments and are not documented in the conodont oxygen isotope record pennsylvanian glacioeustatic sea level changes were probably larger than the 120 m fluctuations recorded for the pleistocene glaciations

modeling late paleozoic glaciation late paleozoic glaciation on gondwana is associated with changes in geography solar luminosity and estimated co sub 2 levels to assess the relative importance of these boundary conditions the authors conducted a suite of climate model simulations for the periods before during and after peak mid carboniferous approximately 300 ma glaciation 340 300 and 255 and 225 ma respectively orbital insolation values favorable for glaciation and interglaciation were used for each time interval results indicate that changes in geography cause significant changes in snow area but the temporal trend is not consistent with the geologic record for glaciation combined co sub 2 plus geography changes yield the best agreement with observations in addition interglacial orbital configurations result in almost ice free conditions for the glacial interval at 300 ma at a time of low co sub 2 the large simulated glacial interglacial snowline fluctuations for permian carboniferous time may explain cyclothem fluctuations at these times overall results support the importance of the co sub 2 paradigm but also indicate that a fuller understanding of past climate change requires consideration of paleogeographic luminosity and orbital insolation changes

a new ecological severity ranking of major phanerozoic biodiversity crises a new ecological severity ranking of the major phanerozoic biodiversity crises is proposed in which the capitanian crisis is ranked lesser than the frasnian late devonian but greater than the serpukhovian end mississippian and the famennian end devonian crisis is ranked as equal in ecological impact to the hirnantian end ordovician two new decouplings between taxonomic severity and ecological severity are revealed in these analyses the capitanian and famennian crises in which the ecological impact of the biodiversity loss was markedly different from the magnitude of the biodiversity loss these analyses also reveal that the great devonian interchange gdi invasive species event in the givetian biodiversity crisis may provide an important palaeoecological analog for the study of present day extinction and homogenization in ecosystems produced by modern invasive species

influence of large woody debris on channel morphology and dynamics in steep boulder rich mountain streams western cascades oregon this study used 20 year records of stream channel change and wood to test hypotheses about the long term influence of large woody debris lwd on channel morphology channel stability and sediment dynamics in a steep boulder rich mountain stream we compared two nearly adjacent reaches of third order mack creek over the period 1978 1997 after virtually all wood was removed from the channel of the lower reach in 1964 we assessed the long term legacy of wood removal using repeated crosssection surveys streamflow data lwd inventory data and detailed mapping and longitudinal profile surveys at each of 11 cross sections in the upper reach and 19 in the lower reach we calculated areas of scour and fill in response to the two largest floods in the record we used quasi likelihood logistic regression models to test the proportion of each reach that experienced change between consecutive surveys over the entire record 1978 1997 as a function of flood return periods the longitudinal profile of the site without lwd was more variable than the reach with lwd at the finest scale f1 m due to a greater frequency of boulder steps but the reach with lwd was more variable at the channel unit scale lwd created steps 1 to 2 5 m high in the wood rich reach accounted for nearly 30 of the total channel fall and created low gradient upstream channel segments one to three channel widths long as a result both reaches have the same average slope about 9 but nearly three times as much of the channel in the wood rich reach had a slope of v5 as in the reach without wood 20 4 of total channel length vs 7 5 of channel length the reach with abundant lwd was less responsive to moderate streamflow events return period f5 years but it responded similarly to peak flows with a return period of about 10 to 25 years although the average magnitude of crosssection changes was the same during the largest flood in the record 25 year return period the reach without lwd experienced scour and coarsening of the bed surface whereas the reach with lwd experienced aggradation upstream of lwd features mack creek may be representative of many steep mountain streams in which channel structure is strongly influenced by nonfluvial processes a legacy of large boulders from glacial or mass movement processes and a legacy of dead wood from ecological processes sediment limited mountain streams with large boulders when deprived of lwd appear to exhibit less morphological variation at the channel unit scale to store less sediment and to release it more readily than those with lwd d 2002 elsevier science b v all rights reserved

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

stratigraphic distribution of macerals and biomarkers in the donets basin implications for paleoecology paleoclimatology and eustacy abstract more than one hundred and thirty coal seams and coaly layers occur in the donets basin donbas twenty eight 52 samples of them ranging in age from serpukhovian late mississipian to gzhelian late pennsylvanian 33 clastics and three limestones were studied in terms of maceral composition sulphur contents and biomarker distribution diterpanes are used to estimate the contribution of different groups of plants and the height of the water table in the swamp hopanes are a measure of bacterial activity in the peat and steranes indicate the relative input of wood and algae stratigraphic trends in these parameters are discussed in relation to paleoenvironment climatic changes and eustacy a tropical climate prevailed in the donbas from serpukhovian to kasimovian times nevertheless periods with drier and wetter conditions can be distinguished based on maceral and biomarker data relatively dry conditions are observed during serpukhovian and vereian times whereas wetter climates with a maximum of coal deposition occurred during the late bashkirian most of the moscovian and the earliest kasimovian no economic coal seams are hosted in upper kasimovian and gzhelian deposits a result of a change to an arid climate our data also suggest climatic changes during sequences of different order for the second order third order and fourth order sequences relatively dry or wet conditions occurred during coal deposition in the lowstand systems tract an intermediate climate during the transgressive systems tract and the maximum flooding and a wet climate during the highstand systems tract the results for high frequency sequences support the cecil s paleoclimatic model an intermediate paleoclimate during lst sandstone and levee siltstone a wet climate during early tst coal and a dry climate during late tst limestone mfs claystone and hst deltaic siltstone coals deposited during maximum flooding periods are more enriched in c27 steranes derived from algae and contain lower proportions of c29 steranes derived from the wood of higher plants

δ18o and δ13c of permian brachiopods a record of seawater evolution and continental glaciation abstract two hundred sixty four 18 o and 13 c values of permian articulate brachiopod shells were analyzed and 81 of these values were characterized as well preserved and biostratigraphically well defined these were then utilized for construction of baseline oxygen and carbon isotope curves for the permian interval in addition 21 13 c whole rock values are reported for the wordian and capitanian the early permian asselian to artinskian times are characterized by 2 5 decrease in oxygen isotope values from 0 7 to 3 3 v pdb this is attributed to a 4 7 c increase in temperature in the southern urals concomitant with the retreat of the permo carboniferous ice sheets and return of the 18 o depleted melt water into the oceans the late permian samples from iran jolfa at kuh e ali bashi and china meishan yield 18 o values and presumably temperatures similar to those that followed the termination of the large scale glaciation in the lower permian in between the upper kungurian to capitanian samples from the delaware basin guadalupe mountains are enriched in 18 o at 1 5 to 3 we have no definitive explanation for these data but tentatively suggest that the anomaly can potentially be a result of evaporative enrichment of seawater in 18 o due to intracratonic arid setting of the basin the 18 o enriched nature of the zechstein samples 1 2 to 2 5 on the other hand is in all probability a reflection of the high evaporation rates in the zechstein sea the permian interval is characterized by a relatively constant 13 c at about 4 the exceptions are again the brachiopods from the delaware basin guadalupe mountains which show 1 6 increase in the guadalupian to values of up to 5 9 in the wordian a tentative explanation as in the case of oxygen is based on the proposition that the semi enclosed delaware basin was likely stratified with sequestration of the 13 c depleted carbon to the deeper water layers and a complementary 13 c enrichment in the upper oxygenated layer the coeval open ocean water dic may have been similar to that of the remainder of the permian interval at 4 as indicated by whole rock carbonate samples from oman sicily and iran in the latest permian the trend mimics the well known 13 c drop at the permian triassic boundary

ecological ranking of phanerozoic biodiversity crises the serpukhovian early carboniferous crisis had a greater ecological impact than the end ordovician we propose a new ecological ranking of the major phanerozoic biodiversity crises in which the serpukhovian biodiversity crisis is ranked fifth in ecological impact lesser than the late devonian but greater than the end ordovician and the end ordovician mass extinction is ranked sixth it is interesting that both the end ordovician mass extinction and the serpukhovian biodiversity crisis were triggered by glaciations other than that common trigger the two events were very different glaciation in the ordovician triggered an enormous jump in the extinction rate of marine organisms and was taxonomically very severe yet the ecological impact of those extinctions was minimal glaciation in the serpukhovian triggered a precipitous drop in the speciation rate but only moderate diversity losses yet the ecological impact of those diversity losses and ecosystem restructuring was an ecological level of magnitude larger than that seen in the end ordovician mass extinction

mapping the spatial and temporal distributions of woody debris in streams of the greater yellowstone ecosystem usa the objectives of this study were 1 to document spatial and temporal distributions of large woody debris lwd at watershed scales and investigate some of the controlling processes and 2 to judge the potential for mapping lwd accumulations with airborne multispectral imagery field surveys were conducted on the snake river soda butte creek and cache creek in the greater yellowstone ecosystem usa the amount of woody debris per kilometer is highest in 2nd order streams widely variable in 3rd and 4th order streams and relatively low in the 6th order system floods led to increases in woody debris in 2nd order streams floods redistributed the wood in 3rd and 4th order streams removing it from the channel and stranding it on bars but appeared to generate little change in the total amount of wood throughout the channel system the movement of woody debris suggests a system that is the reverse of most sediment transport systems in mountains in 1st and 2nd order tributaries the wood is too large to be moved and the system is transport limited with floods introducing new material through undercutting but not removing wood through downstream transport in the intermediate 3rd and 4th order channels the system displays characteristics of dynamic equilibrium where the channel is able remove the debris at approximately the same rate that it is introduced the spatial distribution and quantity of wood in 3rd and 4th order reaches varies widely however as wood is alternatively stranded on gravel bars or moved downstream during periods of bar mobilization in the 6th order and larger channels the system becomes supply limited where almost all material in the main stream can be transported out of the central channel by normal stream flows and deposition occurs primarily on banks or in eddy pool environments attempts to map woody debris with 1 m resolution digital four band imagery were generally unsuccessful primarily because the imagery could not distinguish the narrow logs within a pixel from the surrounding sand and gravel background and due to problems in precisely coregistering imagery and field maps

contrasting patterns of wood storage in mountain watercourses narrower and wider than the height of riparian trees abstract large wood exerts a beneficial influence on the functioning of riverine and riparian ecosystems but can be also the source of flood risk several studies have recognised a trend of decreasing amounts of large wood on unit channel area with increasing width of mountain streams this study verifies whether this trend can also be generalised for wide mountain rivers longitudinal wood distribution was compared for two watercourses in the polish carpathians second to fourth order kamienica stream 14 m wide on average and the fifth order czarny dunajec river with a mean width of 52 m in the stream both the number and the mean mass of wood deposits were unrelated to channel width and this was reflected in a lack of the relationship between total wood storage the amount of stored wood per channel length and channel width in turn specific wood storage the amount of stored wood per channel area decreased nonlinearly with increasing channel width in the wide czarny dunajec the number and the mean mass of wood deposits increased as the river widened and this was reflected in a marked trend of increasing total wood storage with increasing river width here the width related variation in total wood storage was so high that it overcame the influence of increasing channel area on calculated values of specific wood storage which also increased with increasing river width this study shows that different mechanisms known to govern large wood retention in the channels narrower and wider than the height of riparian trees are reflected in the contrasting patterns of wood storage in mountain watercourses of different relative width different relations between the tendencies of total and specific wood storage in the two types of channels emphasise the need of identifying the spatial density and the total amount of large wood

high precision u pb zircon ca id tims dates from western european late visean bentonites three new u pb zircon chemical abrasion isotope dilution thermal ionization mass spectrometry dates obtained from late visean belgian bentonites are reported and are used to estimate the periodicity of early warnantian shallowing upwards carbonate parasequences that are interbedded with the dated bentonites early warnantian parasequences exhibit mean cycle periodicity values that are consistent with the c 100 ka milankovitch cycle which is the dominant milankovitch frequency recognized from recent pleistocene glacial records and thus strengthen the arguments for 1 these sedimentary cycles being of glacio eustatic origin and 2 the initiation of the main phase of late palaeozoic glaciation before the start of or during earliest warnantian times the new dates also provide additional high precision age constraints for the improved calibration of the mississippian time scale using the new dates the stratigraphical age of the clyde plateau volcanic formation midland valley of scotland is revised from holkerian to early asbian supplementary material u pb zircon ca id tims data tables and the method of the mean cycle periodicity calculations are available at www geolsoc org uk sup18747

high resolution early paleozoic ordovician silurian time scales for much of the geologic time scale resolving power appears to be limited by the duration of biostratigraphic zones and subzones yet these zones exploit the appearance and disappearance events of only a small fraction of the species they span computer algorithms can sequence an order of magnitude more events and make explicit the uncertainties that arise when calibrating the resulting time line an illustrative case history builds an ordovician and silurian time scale from the geologic record of the entire graptolite clade over 1900 species from more than 400 localities and sections worldwide the same approach can be applied to any stratigraphic interval with detailed biostratigraphic observations it provides the foundation for time scales and paleobiologic time lines using logic similar to graphic correlation optimizing algorithms search for a composite sequence of species first and last appearance events that minimizes the implied shortcomings of all the field observations the algorithms minimize the number of species coexistences that are implied but never observed and the net adjustments needed to bring local range charts into agreement with a single composite sequence of events after total section thicknesses have been rescaled to help normalize for variation in depositional rate mean stratigraphic thicknesses are used to scale the intervals between adjacent events in the composite sequence the resulting scaled composite sequence is converted to a relative geologic time scale by identifying stage and zone boundaries within the sequence of graptolite events this relative scale is in turn calibrated by dated volcanic ash beds that were incorporated in the search for the optimal sequence these dated events are also used to test for linearity of the scaled composite the final time scale has a potential resolving power of 0 02 0 1 m y more than ten times better than can be achieved by traditional zones graptolite zones vary widely in duration from as short as 0 1 m y to nearly 5 0 m y the mean duration of zones or zonal groupings calibrated here is 1 44 m y in the ordovician and 0 91 m y in the silurian the average uncertainty in locating zone boundaries in a single composite sequence is about one fourth of the mean zone duration the variance resulting from differences in time scales developed from differing numbers of field observations and in response to changes in the optimization criteria gives a very conservative measure of the overall robustness of the method these differences indicate an average uncertainty in the age of graptolite zone boundaries that is more nearly equal to the mean zone duration for zone duration the mean uncertainty amounts to about one half of the length of an average zone

a new chronology for middle eocene early miocene south american land mammal ages cenozoic south american land mam mal ages salmas have historically been correlated to the geologic time scale using 40 ar 39 ar dating and magnetostratigraphy at gran barranca 68 7 w 45 7 s one of south america s key areas for constraining salmas existing radioisotopic ages have uncertainties of up to 4 m y to better con strain the ages of mammalian assemblages we employed high precision 40 k y u pb dating using single zircon crystals we dated nine tuffs from the sarmiento formation containing middle eocene early miocene faunas barrancan mustersan tinguiriri can deseadan colhuehuapian and pin turan the new dates span from 39 861 0 037 ma to 19 041 0 027 ma the la can cha tuff occurring within the tinguirirican faunal level yielded an age of 33 581 0 015 ma confi rming that the vera member con tains the only fossiliferous geologic section encompassing the eocene oligocene transi tion in the southern hemisphere the pre deseadan fauna la cantera is 30 77 ma the age of the colhuehuapian is expanded to 21 1 20 1 ma and the pinturan may be as old as ca 19 ma the new u pb dates confi rm that at mospheric temperatures and vegetation remained constant across the eocene oligocene transition in patagonia and that hypsodonty occurred in south american un gulates much earlier than on any other conti nent additionally refi nement of the salma boundaries will eventually provide the con text necessary to compare faunal transitions across continents although currently too much data are missing to allow such compar isons finally the new ages provide a high resolution age model from which hypotheses about rates of environmental and evolution ary change at gran barranca can be tested

transport and deposition of large woody debris in streams a flume experiment abstract large woody debris lwd is an integral component of forested streams of the pacific northwest and elsewhere yet little is known about how far wood is transported and where it is deposited in streams in this paper we report the results of flume experiments that examine interactions among hydraulics channel geometry transport distance and deposition of floating wood these experiments were carried out in a 1 22 m wide 9 14 m long gravel bed flume using wooden dowels of various sizes as surrogate logs channel planforms were either self formed or created by hand and ranged from meanders to alternate bars floating pieces tended to orient with long axes parallel to flow in the center of the channel pieces were deposited where channel depth was less than buoyant depth typically at the head of mid channel bars in shallow zones where flow expanded and on the outside of bends we hypothesize that the distance logs travel may be a function of the channel s debris roughness a dimensionless index incorporating ratios of piece length and diameter to channel width depth and sinuosity travel distance decreased as the ratio of piece length to both channel width and radius of curvature increased but the relative importance of these variables changed with channel planform large pieces can move further than our debris roughness models predict if greater than 50 of the active channel area is deeper than the buoyant depth of the piece or if momentum is high enough to carry pieces across shallows our debris roughness model allows first order prediction of the amount of wood transport under various channel geometries

co2 forced climate and vegetation instability during late paleozoic deglaciation the late paleozoic deglaciation is the vegetated earth9s only recorded icehouse to greenhouse transition yet the climate dynamics remain enigmatic by using the stable isotopic compositions of soil formed minerals fossil plant matter and shallow water brachiopods we estimated atmospheric partial pressure of carbon dioxide pco2 and tropical marine surface temperatures during this climate transition comparison to southern gondwanan glacial records documents covariance between inferred shifts in pco2 temperature and ice volume consistent with greenhouse gas forcing of climate major restructuring of paleotropical flora in western euramerica occurred in step with climate and pco2 shifts illustrating the biotic impact associated with past co2 forced turnover to a permanent ice free world

modeling entrainment of waterlogged large wood in stream channels 1 research has led to an understanding of how floatable wood provides physical complexity and habitat in streams but little is known about large wood that does not float because it is waterlogged mineralized or naturally heavier than water to better understand the dynamics of this largely unrecognized component of streams i derived a theoretical model for predicting entrainment of waterlogged logs then constructed prototype logs to simulate waterlogged wood and used them to measure log friction and critical flow velocities at log entrainment in an alluvial creek i then modeled critical velocities under the same conditions entrainment was observed the model underpredicted critical velocities by an average of 24 with a range of error from 8 to 69 sensitivity analyses indicated that reducing lift and drag coefficients improved the average error but not the error range lack of unique drag coefficients for prototype logs winnowing of bed material from around prototype logs during entrainment tests error estimating friction for logs approaching neutral buoyancy and the variability of flow velocity common in streams were probable causes of error observed critical velocities that entrained prototype logs averaged 0 70 m s 1 critical velocities and log friction increased with branch length bed roughness and log density but only friction increased with log length friction coefficients averaged 0 62 and increased with branch length and bed roughness this model and existing equations for predicting movement of buoyant large wood can be used to compute budgets for logs with a range of attributes in streams

high precision u pb zircon age calibration of the global carboniferous time scale and milankovitch band cyclicity in the donets basin eastern ukraine 1 high precision id tims u pb zircon ages for 12 interstratified tuffs and tonsteins are used to radiometrically calibrate the detailed lithostratigraphic cyclostratigraphic and biostratigraphic framework of the carboniferous donets basin of eastern europe chemical abrasion of zircons use of the internationally calibrated earthtime mixed u pb isotope dilution tracer and improved mass spectrometry guided by detailed error analysis have resulted in an age resolution of 0 05 or 100 ka for these carboniferous volcanics this precision allows the resolution of time in the milankovitch band and confirms the long standing hypothesis that individual high frequency pennsylvanian cyclothems and bundles of cyclothems into fourth order sequences are the eustatic response to orbital eccentricity 100 and 400 ka forcing tuning of the fourth order sequences in the donets basin to the long period eccentricity cycle results in a continuous age model for the middle to late pennsylvanian moscovian kasimovian ghzelian strata of the basin and their record of biological and climatic changes through the latter portion of the late paleozoic ice age detailed fusulinid and conodont zonations allow the export of this age model to sections throughout euramerica additional ages for mississippian strata provide among the first robust radiometric calibration points within this subperiod and result in variable lowering of the base ages of its constituent stages compared to recent global time scale compilations

patterns and processes of wood debris accumulation in the queets river basin washington field surveys in the 724 km 2 queets river basin on the west slope of the olympic mountains in nw washington reveal basin wide patterns of distinctive wood debris wd accumulations that arise from different mechanisms of wd recruitment hydraulic geometry and physical characteristics of wd individual pieces of wd in an accumulation or jam can be separated into key racked and loose members ten types of wd accumulations are identified based on the mode of recruitment and the orientation of key racked and loose debris relative to the channel axis although some types of wd accumulation have few geomorphic effects others form stable in stream structures that influence alluvial morphology at both subreach and reach length scales ranging from less than 1 to greater than 10 channel widths in the queets river stable accumulations of wd directly influence channel anabranching planform geometry flood plain topography and establishment of long term riparian refugia for old growth forest development the classification of wood debris accumulations in the queets river basin is based on physical observations that offer a template potentially applicable to other forested mountain regions d 2002 elsevier science b v all rights reserved

revised chronostratigraphy and biostratigraphy of the john day formation turtle cove and kimberly members oregon with implications for updated calibration of the arikareean north american land mammal age abstract although the arikareean north american land mammal age was first typified in the great plains the succession there contains significant unconformities a generally poor magnetic record relatively sparse radioisotopic calibration and a major faunal hiatus in the john day valley of central oregon however is a thick remarkably complete sequence of oligocene through early miocene strata the john day formation potentially amenable to addressing these shortcomings and long known to harbor one of the richest records of mid tertiary mammals in north america since prothero and rensberger s first magnetostratigraphic study of the john day formation in 1985 new advances in geochronology together with a more comprehensive suite of paleomagnetic sections keyed to new radioisotopic and biostratigraphic data have greatly enhanced chronostratigraphic precision in our attempt to refine john day chronostratigraphy we sampled nearly 300 sites for magnetostratigraphy over a 500 m thick interval and us

dinantian lower carboniferous biostratigraphy and chronostratigraphy in the british isles vaughan s 1905 zonation of the carboniferous limestone in the bristol district was a pioneer biostratigraphical study which because of its meticulous execution can be reinterpreted in a modern context the replacement of his scheme with a chronostratigraphical one by george et al 1976 had a similar revolutionary affect on british dinantian stratigraphy however it is now time to revise the british dinantian stages so that they more closely correspond to biostratigraphical events dinantian biostratigraphy still requires considerable refinement but it has now achieved a diversity of techniques and resolution far beyond that which was available at the time of these earlier proposals it is the most pragmatic and closest approximation to widespread chronostratigraphical correlation available this paper discusses these and related issues and presents a review and correlation of current biozonations

visions of ice sheets in a greenhouse world abstract backstripped eustatic estimates from new jersey and the russian platform show large 25 m and rapid 18 o record highlights the enigma this was the warmest interval of the past 200 my yet it was bracketed by two inferred eustatic falls of 25 m that were associated with two large 0 75 deep sea 18 o increases 92 93 ma mid turonian and 96 ma mid cenomanian we reconcile records of warm high latitudes with glacioeustasy by proposing that late cretaceous early eocene ice sheets generally reached maximum volumes of 8 12 10 6 km 3 20 30 m glacioeustatic equivalent but did not reach the antarctic coast hence coastal antarctica hence deep water remained relatively warm even though there were significant changes in sea level as the result of glaciation unlike the oligocene and younger icehouse world these ice sheets only existed during short intervals of peak milankovitch insolation leaving antarctica ice free during much of the greenhouse late cretaceous to middle eocene these results highlight the need to re evaluate the paradigm that polar ice sheets did not exist during times of warm high latitude climates

development of spatial pattern in large woody debris and debris dams in streams the spatial distribution of large woody debris lwd in streams was evaluated using neighbor k statistics following extensive wood deposition from an ice storm in the eastern adirondack mountains new york two years after wood deposition we surveyed individual pieces of lwd in one stream and surveyed debris dam locations in eight streams within the ice storm area to examine the linear pattern of debris dams within a stream we used a one dimensional version of ripley s k a second order statistic that evaluates the spatial pattern of points within a landscape both aggregated and segregated regularly spaced distributions of wood were identified individual pieces of lwd were aggregated at spatial extents ranging from 0 to 40 m and were segregated at spatial extents ranging from 80 to 100 m in two streams we found that debris dams were segregated at distances ranging from 100 to 300 m relative to randomly chosen locations but debris dams showed no significant spatial pattern in six other study streams previous studies of wood distribution in streams have not observed segregated distribution patterns spatial segregation of debris dams in the study area likely occurred in response to regularly spaced stream features or processes that allow movement of individual pieces of lwd toward more stable accumulation points neighbor k statistics can be used to identify and describe spatial pattern in large woody debris and such patterns can be used to help evaluate and identify processes responsible for their generation

the geomorphic function and characteristics of large woody debris in low gradient rivers coastal maine usa abstract the role function and importance of large woody debris lwd in rivers depend strongly on environmental context and land use history the coastal watersheds of central and northern maine northeastern u s are characterized by low gradients moderate topography and minimal influence of mass wasting processes along with a history of intensive commercial timber harvest in spite of the ecological importance of these rivers which contain the last wild populations of atlantic salmon salmo salar in the u s we know little about lwd distribution dynamics and function in these systems we conducted a cross basin analysis in seven coastal maine watersheds documenting the size frequency volume position and orientation of lwd as well as the association between lwd pool formation and sediment storage in conjunction with these lwd surveys we conducted extensive riparian vegetation surveys we observed very low lwd frequencies and volumes across the 60 km of rivers surveyed frequency of lwd 20 cm diameter ranged from 15 50 pieces km 1 and wood volumes were commonly 3 km 1 moreover most of this wood was located in the immediate low flow channel zone was oriented parallel to flow and failed to span the stream channel as a result pool formation associated with lwd is generally lacking and

base of the kiaman its definition and global stratigraphic significance defining and dating the base of the kiaman the long period of reverse polarity that spans the time from the late carboniferous to the middle permian have proven difficult in an attempt to do this an integrated stratigraphic paleomagnetic and geochronologic study was undertaken in carboniferous rocks in the northern tamworth belt of the new england orogen eastern australia new paleomagnetic measurements at 145 horizons sites in the new england orogen of eastern australia provide an accurate record of the late namurian to westphalian geomagnetic field they have high unblocking temperatures satisfy tilt conglomerate and slump tests and show excellent agreement between a wide variety of igneous and sedimentary rock types indicating that magnetism was acquired at or soon after deposition magnetite and to a lesser degree hematite are the carriers of magnetization the record is contained in sequences of glaciogene sediments and arc derived volcano sedimentary units folded into broad structures in the late permian to triassic new isotopic dates for the volcanic units indicate ages from 321 to 306 ma late namurian to westphalian magnetizations are steeply inclined downward reversed polarity in the southern hemisphere except within the clifden formation of the rocky creek syncline where a change from normal to reverse polarity referred to as the wanganui reversal records the onset of the kiaman superchron integrating complex stratigraphic isotopic and paleomagnetic data we correlate the wanganui reversal to the top of n6 in the joggins section nova scotia canada and estimate that its age is between 318 and 316 ma further work may substantiate a younger normal zone in australia that would support a slightly younger age but within these limits these considerations indicate that the wanganui reversal occurs in the late namurian marsdenian and after the time of the mississippian pennsylvania boundary the mean direction of magnetization of the upper carboniferous australian sequences is declination d 195 3 inclination i 76 9 25 95 3 1 with a paleopole at 51 9 s 141 2 e 95 5 7 and a paleolatitude of 65 0 5 6 s p 0 05 this paleolatitude is consistent with the glacial origin of some of the sedimentary units

wood storage within the active zone of a large european gravel bed river wood storage within the active zone of the dynamic gravel bed fiume tagliamento italy was investigated at eight sites along the river s main stem the quantity nature and mode of wood storage revealed a number of trends related to active zone morphology cover type and distance from the river s source relatively small quantities of wood were stored on open gravel surfaces estimates ranged from 1 to 21 t ha 1 intermediate quantities were associated with established islands 24 186 t ha 1 and large quantities were associated with pioneer islands 293 1664 t ha 1 thus variations in the geomorphological style of the river which are associated with changes in these three cover types are reflected in variations in the amount of wood that is stored in different reaches in addition although wood was found in many locations within the active zone it was preferentially stored in three specific locations i bar crests the main open gravel location for wood accumulations and pioneer islands ii the margins and iii surfaces of established islands the proportion of the stored wood that was living sprouting increased downstream and was higher on the open gravel than in association with established islands there was a downstream gradient in the dominant type of wood accumulation individual logs predominated at the most upstream site thereafter on the open gravel whole shrubs and trees dominated the more confined sites in the headwaters and middle reaches whereas jams were the most frequent form of accumulation in the downstream reaches jams were the most frequent type of accumulation associated with established islands throughout the river in contrast to small streams where debris dams constitute the major type of wood accumulation complex patterns and trends of wood storage were revealed along the tagliamento although further studies are needed it is clear that erosion of woody vegetation its subsequent transport and deposition play a major role in structuring the geomorphological and ecological character of this relatively natural large european river system insight into the mechanisms underlying the observed spatial patterns will contribute to a better understanding of the dynamic processes involved and is essential for more effective management of river ecosystems

conodont biostratigraphy of the mid carboniferous boundary in western ireland two stratigraphic sections spanning the mid carboniferous boundary were examined in the clare shale formation of the shannon basin in western ireland calcareous nodules intermittently occur within these generally non calcareous organic rich shales and these have yielded serpukhovian and bashkirian conodont elements the biostratigraphic range of the irish material is illustrated here for the first time results show that the mid carboniferous and arnsbergian chokierian boundaries are coincident at ballybunion gnathodus girtyi is restricted to the lower part of the serpukhovian stage late mississippian while g bilineatus bollandensis persists into much younger strata close to the first occurrence of declinognathodus noduliferus s l one element belonging to g postbilineatus is also present these findings support the argument that d noduliferus s l developed from g b bollandensis rather than from g girtyi the biostratigraphical tool for the identification of the mid carboniferous boundary globally and the suitability of the section at arrow canyon usa as a gssp may therefore need to be reassessed

periodicity of mesoscale phanerozoic sedimentary cycles and the role of milankovitch orbital modulation data on more than 200 mesoscale sedimentary cycles indicate that phanerozoic cycle periods are randomly distributed with respect to the four major milankovitch orbital parameters except late mississippian through late pennsylvanian cycles which show positive clustering about the 413 000 yr eccentricity period cycle periods calculated from average thicknesses and accumulation rates are strongly dependent on the former correlation coefficient 0 802 but relatively independent of the latter correlation coefficient 0 360 hence calculated period is largely a function of average cycle thickness and milankovitch range periods will be preferentially calculated for cycles with average thicknesses between 1 m and 20 m regardless of actual causes of cyclicity for individual cyclic sequences arguments for milankovitch control based solely on average period are unfounded comparison of short term holocene sedimentation rates and long term phanerozoic accumulation rates for cyclic peritidal and delta

large woody debris physical process and riparian forest development in montane river networks of the pacific northwest abstract we present a conceptual biogeomorphic model of riparian forest development in montane river networks the role of physical process in driving the structure composition and spatial distribution of riparian forests is examined we classify the drainage network into disturbance process based segments including 1 debris flow and avalanche channels 2 fluvial and debris flow channels and 3 fluvial channels riparian forests are shown to be significant in the development of channel morphology through the stabilization of active floodplains and as sources of large woody debris olwd lwd is operationally defined as wood 0 1 m diameter and 1 m length lwd plays a key role in the development of montane riparian forests lwd deposited in the active channel and floodplain provides sites for vegetation colonization forest island growth and coalescence and forest floodplain development riparian forest patterns parallel the distribution of hillslope and fluvial processes through the network riparian forest structure composition and spatial distribution through the network are driven by the major disturbance processes including 1 avalanches 2 debris flows and 3 flooding riparian forest patterns also reflect the action of lwd in the organization and development of forested floodplains in gravel bedded montane river networks the focus of our examples are montane river networks of the pacific northwest usa

coupled carbon isotopic and sedimentological records from the permian system of eastern australia reveal the response of atmospheric carbon dioxide to glacial growth and decay during the late palaeozoic ice age abstract proxy geochemical records from high latitude ice proximal deposits have the potential to provide key insights into past icehouse climates but such records are rare the permian system of eastern australia contains a rich record of environmental and climatic changes that occurred in areas proximal to glaciation during the acme and waning stages of the late palaeozoic ice age within this succession a wealth of fine grained organic matter rich facies provides an opportunity to construct a bulk 13corg record that records changes in atmospheric co2 through the permian fluctuations in 13corg track changes in climate determined independently on the basis of sedimentological criteria in the same strata these patterns are also broadly consistent with multiple proxy records derived from palaeoequatorial sites the results of this geochemical investigation 1 support recent studies using the high latitude ice proximal sedimentologic and stratigraphic record and palaeoequatorial geochemical proxies that document highly variable climatic conditions within the overall permian icehouse to greenhouse transition and 2 confirms that the sedimentary record of glaciation from eastern australia reflects global changes in atmospheric co2 on several m y order timescales

the influence of geomorphology on large wood dynamics in a low gradient headwater stream understanding large wood dynamics is critical for a range of disciplines including flood risk management ecology and geomorphology despite the importance of wood in rivers our understanding of the mobility of large wood remains limited in this study individual pieces of large wood were tagged and surveyed over a 32 month period within a third and fourth order lowland forest river individual pieces of wood were found to be highly mobile with 75 of pieces moving during the survey period and a maximum transport distance of 5 6 km multivariate analyses of data from this study and two other published studies identified dimensionless wood length as the important factor in explaining likelihood of movement a length threshold of 2 5 channel widths is identified for near functional immobility with few pieces above this size moving in addition for this study wood type branching complexity location and dimensionless wood diameter were found to be important in determining mobility only for sinuous reaches with readily inundated floodplains where logjams persist over multiple years they were shown to be reworked with component pieces being transported away and replaced by newly trapped pieces the findings of this study have implications for river management and restoration the high mobility observed in this study demonstrates that only very large pieces of wood of length greater than 2 5 channel widths should be considered functionally immobile for pieces of wood of length less than the channel width the possibility of high rates of mobility and long transport distances should be anticipated

global time scale and regional stratigraphic reference scales of central and west europe east europe tethys south china and north america as used in the devonian carboniferous permian correlation chart 2003 dcp 2003 the boundaries of the devonian carboniferous and permian stages of the global stratigraphic reference scale abbreviated to global stratigraphic scale gss are described in relation to the biostratigraphic and or lithostratigraphic units of the regional stratigraphic reference scales abbreviated to regional stratigraphic scales rss of central and west europe east europe tethys south china eastern tethys and north america in their type regions the boundaries of gss units rarely coincide with those of homonymous rss units moreover the definitions of some rss units have changed several times over the last decades and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts the stratigraphic framework proposed in our global devonian carboniferous permian correlation chart 2003 dcp 2003 devonian carboniferous permian correlation chart 2003 menning m schneider j w alekseev a s amon e o becker g von bitter p h boardman d r bogoslovskaya m braun a brocke r chernykh v chuvashov b i clayton g dusar m davydov v i dybova jachowicz s forke h c gibling m gilmour e h goretzki j grunt t a hance l heckel p h izokh n g jansen u jin y g jones p kading k ch kerp h kiersnowski h klets a klug ch korn d kossovaya o kotlyar g v kozur h w laveine j p martens th nemyrovska t l nigmadganov a l paech h j peryt t m rohn r roscher m rubidge b schiappa t a schindler e skompski s ueno k utting j vdovenko m v villa e voigt s wahlman g p wardlaw b r warrington g weddige k werneburg r weyer d wilde v winkler prins c f work d m 2004 abschlusskolloquium dfg schwerpunktprogramm 1054 evolution des systems erde wahrend des jungeren palaozoikums im spiegel der sedimentgeochemie abstracts univ erlangen germany 2004 p 43 herein abbreviated to dcp 2003 and cited as dcp 2003 in references is an attempt to reduce these errors the dcp 2003 is the stratigraphic base for project 1054 of the deutsche forschungsgemeinschaft dfg the evolution of the late palaeozoic in the light of sedimentary geochemistry this composite time scale has been carefully balanced as far as data allows to remove unnecessary artificial compression and expansion of time intervals biozonations and depositional events the ages selected in dcp 2003 are markedly different to those in the geologic time scale 1989 gts 1989 harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge pp 1 263 and in gradstein and ogg gradstein f m ogg j 1996 a phanerozoic time scale episodes 19 1 2 3 4 insert whereas they are closer to those of the geologic time scale 2004 gts 2004 gradstein f m ogg j g smith a g 2004 a geologic time scale 2004 cambridge univ press cambridge pp 1 589 mostly the ages are rounded to the nearest 0 5 ma in order to avoid estimates of questionable accuracy whereas ages of 0 1 ma in the gts 2004 and their error bars of 0 4 ma to 2 8 ma for the devonian to permian stage boundaries suggest an improved accuracy in contrast in the dcp 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows c 2006 elsevier b v all rights reserved

a geomagnetic polarity timescale for the carboniferous the geomagnetic polarity pattern for the carboniferous is incompletely known but with the best resolved parts in the serpukhovian and bashkirian hence data from both igneous and sedimentary units are also used in an additional polarity bias evaluation in the tournaisian to mid visean interval polarity is mainly derived from palaeopole type palaeomagnetic studies allowing identification of polarity bias chrons seven polarity bias chrons exist in the mississippian mi1nb to mi4nb with an additional 33 conventional magnetochrons and submagnetochrons mi4r to mi9r the moscovian and gzhelian polarity is best resolved in magnetostratigraphic studies from the donets basin and the southern urals dispute about the reliability of these data is ill founded since an assessment of supporting data from palaeopole type studies suggests that these datasets currently provide the best magnetic polarity data through the pennsylvanian polarity bias assessment indicates a normal polarity bias zone in the kasimovian in the pennsylvanian there are 27 conventional magnetochrons and submagnetochrons pe1n to ci1r and one normal polarity bias chron pe8nb the kiaman superchron begins in the mid bashkirian with clear data indicating brief normal polarity submagnetochrons within the superchron the magnetochron timescale is calibrated using 31 u pb zircon dates and a quantitative bayesian based age scaling procedure

magnetic polarity stratigraphy and ages of siwalik group rocks of the potwar plateau pakistan abstract six magnetic polarity sections have been established over the potwar plateau region of pakistan including the major stratotypes of the siwalik group in all six sections the dominant feature of the magnetic polarity stratigraphy is a long normal polarity zone which is contained within the nagri formation this conspicuous normal polarity zone has been radiometrically dated at 9 5 0 6 m y which identifies it as magnetic chron 9 radiometric dates from the upper siwalik formation have also been used to identify the chron 2 3 boundary in two of the sections the magnetic polarity stratigraphy of three of the sections has been correlated securely with the accepted magnetic polarity time scale so that the ages of the local stratigraphy are indexed accordingly based exclusively on data from stratotype sections the chinji nagri and dhok pathan formations have nominal age ranges of 10 1 13 1 7 9 10 1 and 5 1 7 9 m y age fluctuations on the order of 105 years may be anticipated for these formational boundaries within radius of some 20 km of the designated stratotype mean sediment accumulation rates during the chinji nagri and dhok pathan interval range from 13 to 52 cm 103 yr essentially linear sediment accumulations are locally maintained over time intervals of several million years the chinji nagri lithofacies boundary marks a transition from slow to faster sediment accumulation over much of the potwar plateau indicating a fundamental sedimentary tectonic change at this time

permian climate development in the northern peri tethys area the lodeve basin french massif central compared in a european and global context abstract the lodeve basin which contains an exceptional long and nearly uninterrupted profile of early to late permian continental red beds is well correlated to the other european permocarboniferous basins together they cover the time span from the late pennsylvanian to the permian triassic boundary although these basins were placed within the equatorial belt for the whole permian several climatic changes are recorded in the sediments terrestrial sedimentation is governed by the interaction of climate and tectonics as well as by volcanism to a variable degree therefore small scale climatic variations of the milankovitch band are hardly discernable and if so they could not be correlated between different basins indeed larger scale climatic shifts could be identified it is shown that the shift from the carboniferous icehouse to the mesozoic warmhouse was a multi stage process this global warming resulted in a general aridisation of northern pangea indicated by outspreading playa and sabkha red beds aeolianites and evaporites several short phases of increased humidity interrupted this trend indicated by wet red beds lake sediments and coal deposits in central and southern europe these wet periods are traceable within the late stephanian lower rotliegend gzhelian asselian topmost lower rotliegend asselian sakmarian upper rotliegend i late artinskian early kungurian and upper rotliegend ii zechstein wuchiapingian the aridisation of the northern pangea which accelerated near the sakmarian artinskian transition is attributed to a reorganisation of the major ocean currents cold water currents along the western flank of the pangea indicated by the permian chert event blocks moisture transport from west onto the continent during roadian and wordian the onset of an additional cold water current along the cimmerian continents blocks moisture transport from the east both phenomena together are responsible for the maximum of aridity at the early to middle permian transition additionally the equatorial climate has been affected by an increasing seasonality within the late pennsylvanian and permian caused by the wide shifting of the zone of inter tropical convergence itc over the equator based on a new reconstruction of the pangean assembly in this paper climatic changes in the permian are interpreted and causes of the arid humid arid shifts are examined phases of higher humidity are often related to events of global impact like the waxing and waning of the gondwanan glaciation obtained in the south african karoo basin dwyka group but also regional events had strong climatic influence the zechstein transgression in the northern and southern permian basin as well as the bellerophon transgression of the southern alps caused the wet phase in the wuchiapingian

multidisciplinary studies of global carboniferous stage boundaries towards a better definition and global correlations an introduction earth was very dynamic during the carboniferous with major components of the pangea supercontinent being assembled from late famennian to latest pennsylvanian times although maximum consolidation occurred during late permian early triassic time during the carboniferous period our planet also underwent at least three major icehouse periods the first two in late famennian early tournaisian and late visean bashkirian times indicate the onset of the late palaeozoic ice age lpia with ice sheets being confined to the alpine regions of southern gondwana the third icehouse regime during gzhelian early permian time represents the main episode of the lpia when a continental ice sheet developed on the australian antarctic and southern african components of southern gondwana during the tournaisian equatorial areas in euramerica were occupied by extensive arid belts in which massive carbonate deposits formed on vast platforms in that time from the late tournaisian into the visean and serpukhovian much of the equatorial belt developed into a humid tropical realm and the former arid belt split and shifted to higher latitudes shelf carbonate deposition continued over extensive areas of the continental shelves and western palaeo tethys but coal swamps were developing in the forelands of the rising appalachian and variscan orogens the late serpukhovian early bashkirian interval saw the closure of the rheic ocean and a continent continent collision between euramerica laurussia and gondwana to form pangea as a consequence a marked transition from visean carbonate deposition to the development of coal swamps and deposition of siliciclastics during the serpukhovian stage occurred in many regions

late paleozoic tropical climate response to gondwanan deglaciation coupled climate biome model simulations of the late paleozoic were developed to determine the response of pangean tropical climate to gondwanan deglaciation the model simulations predict substantial changes over equatorial pangea including continental drying a reversal of equatorial winds warming heavier 18 o values of meteoric precipitation and the expansion of deserts and the contraction of forests the magnitude of these tropical responses is sensi tive to the extent of gondwana continental ice and the deglacial rise in atmospheric pco 2 boundary conditions that are not well known for the late paleozoic nonetheless the model predictions are consistent with climatic and environmental trends determined from terrestrial proxy data implying that the deglaciation of gondwana was a transformational climate event in tropical pangea

the magnitude of late paleozoic glacioeustatic fluctuations a synthesis a comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the carboniferous and permian and that at least eight distinct phases can be recognized facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20 25 m and occasionally as much as 60 m took place throughout the early mississippian tournaisian a widely recognized glacial period middle mississippian mid chadian through holkerian shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10 25 m a decrease that matches well with the paucity of coeval glacial deposits late visean asbian through mid brigantian glacioeustatic fluctuations of 10 50 m record the initial phases of ice accumulation in advance of the widespread mid carboniferous glacial event the latest mississippian earliest pennsylvanian mid brigantian through langsettian was a time of widespread glaciation and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40 100 m although middle pennsylvanian duckmantian through asturian glacial deposits are present in eastern australia paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m glacioeustatic fluctuations of as much as 100 120 m have been widely reported from late pennsylvanian earliest permian stephanian through mid sakmarian successions in north america an increase that corresponds to the growth of large ice sheets across much of gondwana and the accumulation of ice in the northern hemisphere incision and facies juxtaposition in early middle permian mid sakmarian through kungurian successions in eastern australia indicate that glacioeustatic fluctuations of 30 70 m occurred during the waning stages of major glaciation erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in australia suggests that eustatic fluctuations of 10 60 m occurred during the final stages of glaciation in the middle to late permian roadian through capitanian but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature this review demonstrates that far field cyclic successions record changing glacial conditions in gondwana that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice that carboniferous permian glacioeustasy was more variable than previously recognized and that generalizations from short temporal intervals are probably not representative of the late paleozoic ice age as a whole although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study

rules of the road a qualitative and quantitative synthesis of large wood transport through drainage networks abstract to effectively manage wood in rivers we need a better understanding of wood mobility within river networks here we review primarily field based and some numerical studies of wood transport we distinguish small medium large and great rivers based on wood piece dimensions relative to channel and flow dimensions and dominant controls on wood transport we suggest further identification and designation of wood transport regimes as a useful way to characterize spatial temporal network heterogeneity and to conceptualize the primary controls on wood mobility in diverse river segments we draw analogies between wood and bedload transport including distinguishing eulerian and lagrangian approaches exploring transport capacity and quantifying thresholds of wood mobility we identify mobility envelopes for remobilization of wood with relation to increasing peak discharges stream size and dimensionless log lengths wood transport in natural channels exhibits high spatial and temporal variability with discontinuities along the channel network at bankfull flow and when log lengths equal channel widths although median mobilization rates increase with increasing channel size maximum mobilization rates are greatest in medium sized channels most wood is transported during relatively infrequent high flows but flows under bankfull can transport up to 30 of stored wood we use conceptual models of dynamic equilibrium of wood in storage and of spiralling wood transport paths through drainage networks as well as a metaphor of traffic on a road to explore discontinuous wood movement through a river network the primary limitations to describing wood transport are inappropriate time scales of observation and lack of sufficient data on mobility from diverse rivers improving models of wood flux requires better characterization of average step lengths within the lifetime travel path of a piece of wood we suggest that future studies focus on i continuous or high frequency monitoring of wood mobility ii monitoring changes in wood storage iii using wood characteristics to fingerprint wood sources iv quantifying volumes of wood buried within river corridors v obtaining existing or new data from unconventional sources such as citizen science initiatives and vi creating online interactive data platforms to facilitate data synthesis

identifying the spatial pattern of wood distribution in northeastern north american streams article i nfo the spatial distribution of instream wood influences important ecological processes but has proven challenging to describe quantitatively we present a modified version of a previously described metric used to quantify the spatial extent and pattern of instream wood distribution then apply this approach in evaluating the distribution of wood habitat in forested northeastern north american streams this revised metric a binned neighbor k analysis provides greater resolution in evaluating the presence of aggregated periodic or segregated wood distributions in stream ecosystems we employed this metric in evaluating the distribution of wood within 17 streams in two regions of northeastern north america our results indicate that the binned neighbor k approach more accurately represents the spatial extent at which wood accumulates in streams by identifying recurring intervals in streams within which instream wood is not present and by more accurately quantifying the spatial extent of wood aggregations and periodically repeating occurrences of accumulated wood we also used this metric to quantify the overall extent of wood organization in streams which revealed similarities and differences in instream wood distribution patterns in the two regions evaluated wood distribution patterns in both study regions were generally consistent with our expectations of increased organization at an intermediate stream size up to 10 m bankfull width then in larger streams n10 m wood was less organized these observed patterns result from landscape and ecosystem influences upon wood accumulation and movement in streams

late cretaceous chronology of large rapid sea level changes glacioeustasy during the greenhouse world we provide a record of global sea level eustatic variations of the late cretaceous 99 65 ma greenhouse world ocean drilling program leg 174ax provided a record of 11 14 upper cretaceous sequences in the new jersey coastal plain that were dated by in tegrating sr isotopic stratigraphy and biostratigraphy backstripping yielded a late cre taceous eustatic estimate for these sequences taking into account sediment loading com paction paleowater depth and basin subsidence we show that late cretaceous sea level changes were large 25 m and rapid k1 m y suggesting a glacioeustatic control three large d 18 o increases are linked to sequence boundaries others lack sufficient d 18 o data consistent with a glacioeustatic cause and with the development of small 10 6 km 3 ephemeral ice sheets in antarctica our sequence boundaries correlate with sea level falls recorded by exxon production research and sections from northwest europe and russia indicating a global cause although the exxon record differs from backstripped estimates in amplitude and shape

testing the sequence stratigraphy model response of fusulinacean fauna to sea level fluctuations examples from pennsylvanian and cisuralian of the pricaspian southern urals region

mobility of large woody debris lwd jams in a low gradient channel abstract mobility of large woody debris lwd in low gradient channels is an important but often overlooked transport process the majority of studies on lwd have focused on its role in geomorphic and ecologic river processes when jams extend across the width of the channel they have the potential to retain sediment and alter the channel profile when jams obstruct only a portion of the channel they can re direct flow altering patterns of scour and deposition the boundary complexity created by lwd has a recognized role in riverine ecosystems which has led to programs of replacing lwd in channel corridors where it was previously removed although lwd jams are common in rivers around the world they have been studied most intensely in steep forested channel reaches where they are often found to be stable channel features it is not fully known how much of the information on lwd from steep forested channels will transfer to other channel types whereas it may be reasonable to assume that the ecological benefits of lwd are similar in low gradient channels research has shown that a much higher rate of lwd transport occurs in low gradient channels with jams mobilized on timescales of 10 0 10 2 years this study evaluates the distribution and mobility of lwd over 72 km of the san antonio river a low gradient channel in southeast texas lwd jam locations were identified for 2003 and 2007 using a combination of aerial photography and field mapping each jam was cataloged according to its location in the channel cross section and the amount of channel area blocked during the four year period all the lwd jams were mobilized including those jams extending across the channel width although easily mobilized 34 jams re form in the same locations creating 34 channel locations with persistent lwd jams data from the san antonio river are applied to two models developed to predict lwd mobility and transport distances to assess the applicability of each model to a low gradient channel the locations of stable or recurring lwd jams were matched to model results where predicted lwd transport distances were equal to measured lwd jam spacing model results showed good agreement with the mean and median spacing of lwd jams when given input parameters specific to the channel and wood species the ability to predict where lwd jams will persist over time in a low gradient channel has application in watershed management persistent lwd jams can exert a greater influence on channel morphology and may require active management

interbasinal cyclostratigraphic correlation of milankovitch band transgressive regressive cycles correlation of desmoinesian missourian strata between southeastern arizona and the midcontinent of north america the cyclic pattern of deposition in the horquilla limestone of southeastern arizona resulted from glacio eustatic sea level fluctuations with periodicities within the milankovitch band the depositional surface fluctuated from above sea level to below the depth of autochthonous carbonate production by means of characteristics of the cycles correlations can be established not only between sections in the pedregosa basin of southeastern arizona but also to the midcontinent of the united states these correlations exceed the resolution of biostratigraphy and distinguish the eustatic component of relative sea level fluctuations in widely spaced basins with different depositional settings