examining the ladinian crisis in light of the current knowledge of the triassic biodiversity changes abstract several mass extinctions are known from the history of life but knowledge about minor biotic crises remains incomplete the ladinian is the second stage of the middle triassic epoch available reconstructions of the diversity dynamics of fossil organisms across the entire triassic allow the proposed ladinian biotic crisis to be investigated total biodiversity curves both the conventional curve and that based on sampling standardization fail to identify the crisis but this may be explained by low resolution data or noise in fact the global generic diversity of ammonoids brachiopods and tetrapods declined significantly by 1 1 2 5 times during the ladinian as did the species diversity of conodonts bivalves radiated but their origination rate also decreased during the ladinian land plants were apparently unaffected based on the representative regional record for the northwestern caucasus the number of macroinvertebrate genera dropped by 7 5 times and brachiopods almost totally disappeared foraminifers were also affected significantly thus the proposed biotic crisis appears to have been selective it appears the ladinian biotic crisis was a relatively long term event and its magnitude is comparable to that of other minor mass extinctions e g those of the silurian early jurassic or end cenomanian there are several possible explanations for what caused the ladinian biotic crisis it is possible that global climate cooling was responsible although it is unclear why the palaeobiogeographical differentiation was not favourable for a biotic radiation a eustatic explanation for the drop in diversity is unlikely instead the crisis was mostly likely caused by unstable recovery of the earth s biota after the end permian catastrophe

end permian extinction and subsequent recovery of the ophiuroidea echinodermata a worldwide stratigraphical survey of late palaeozoic and early mesozoic ophiuroids echinodermata reveals unique extinction and recovery patterns during and after the end permian mass extinction event the ophiuroidea suffered the loss of all palaeozoic genera however this clade profited greatly from the event by undergoing a significant increase in species number in the postextinction oceans although both sampling and taphonomic biases may have affected ophiuroid diversity changeover patterns across the permian triassic p tr transition to some extent both biases cannot explain adequately the abrupt increase in species numbers and geographically wide distributions of ophiuroids in the early triassic oceans the ophiuroidea recovery follows erwin s model of a logistic increase in diversity beginning immediately after the end of the mass extinction without the survival interval morphological innovation i e emergence of advanced canal systems diversification of life habitats and biogeographical dispersal over the palaeotethyan and gondwanan regions enabled the ophiuroidea to occupy efficiently vacant ecospace created by the end permian extinction enabling the clade to recover and radiate in the early triassic oceans previously reported ophiuroids from the upper permian to lower triassic of china are also taxonomically revised these ophiaulaxoides bijieensis feng huangzhishania gulinensis feng ophiolepis shanxiensis yang and ophioderma schistovertebrata yang were described from the lower triassic while aganaster qingchangensis feng and syntomospina kaiyangensis feng came from the upper permian

the roussillon basin s france a case study to distinguish local and regional events between 6 and 3 ma the roussillon basin is a non silled miocene sedimentary basin filling a late oligocene early miocene graben the basin was intensively impacted by the 2 messinian fluvial erosion as evidenced in exposed sections in seismic profiles and in deep boreholes drilled for hydrocarbon exploration as the basin was open to the mediterranean sea the huge drop in sea level at the peak of the messinian salinity crisis is clearly recorded along with the subsequent sudden marine reflooding and the resulting prograding sedimentary filling particularly in gilbert type fan deltas here the messinian erosional surface mes is accurately mapped in a high resolution document which corrects the confusion resulting from the set of 1 50 000 scale regional maps aim of the 3d reconstruction of the mes is to modernize geological mapping a crucial challenge for mediterranean and peripheral areas thanks to a reliable chronostratigraphy provided by planktonic foraminifers calcareous nannofossils micro and macro mammal remains paleomagnetism and a 10 be cosmogenic nuclide derived study our reconstruction is one of the most comprehensive models of changes in sea level from 6 to 3 ma after the marine reflooding of the mediterranean basin at 5 46 ma the fluctuations in sea level recorded in the roussillon basin were forced by global changes following reflooding the prades large olistostrome collapsed prepared by the previous exhumation along the canigou fault the olistostrome is a good example of a local accident resulting from messinian events the exceptional changes in sea level at the peak of the messinian salinity crisis deeply marked the roussillon basin momentarily overprinting the pyrenean orogenesis key words roussillon basin messinian subaerial erosion zanclean sedimentary filling prades olistostrome

palaeoenvironments and faunal recovery after the end permian mass extinction abstract strata of the lower triassic werfen formation dolomites northern italy record deposition in a wide range of palaeoenvironments from peritidal to outer ramp settings this enables accurate assessment of faunal recovery following the end permian mass extinction by eliminating facies related effects extinction of the shelly taxa appears to be rapid and occurs in the latest permian tesero oolite horizon disappearance of the various trace fossil taxa appears to be more gradual following the extinction the lower and middle griesbachian are characterised by laminated sediments containing low diversity bedding plane assemblages ichnological geochemical and sedimentological data show evidence of widespread low oxygen conditions normally oxygenated waters return in the late griesbachian and there is a moderate increase in tiering above and below the surface macrofaunal and ichnofossil diversity decrease markedly during the smithian with the appearance of more terrigenous strata possibly reflecting an increased run off and more brackish conditions complete recovery begins in the basal spathian with an increase in tiering above and below the substrate crinoids and ammonoids appear for the first time in the werfen formation and the ichnogenus rhizocorallium re appears global correlation is hindered by poor biostratigraphy in the dolomites region however on a broad scale it appears as though many of the palaeoenvironmental changes are repeated worldwide current available data suggest that the re appearance of some trace fossil taxa e g diplocraterion rhizocorallium may be globally synchronous

early triassic recovery of the brachiopod faunas from the end permian mass extinction a global review abstract brachiopod faunas in lower triassic deposits from spitzbergen primorye of russia japan mangyslak of kazakhstan alpine europe the caucasus the middle east the himalaya south china new zealand and western usa are taxonomically and stratigraphically reviewed they comprise survivors of the end permian extinction and taxa originating in the early triassic origination of the mesozoic type taxa represents the recovery of early triassic brachiopods the initial recovery of brachiopod faunas began in the late griesbachian and the time interval between the end of extinction and the onset of the recovery of brachiopods is much shorter than previously suspected the early triassic recovery of brachiopod faunas is characterized by widespread brachiopod dispersal multiprovincialism and the presence of rare lazarus genera at that time taxonomic selectivity of the recovery brachiopod faunas favors the rhynchonellids the re population of post extinction brachiopods varies geographically there is a preference for regions either previously barren of latest permian taxa or regions where the pre extinction changhsingian and surviving brachiopods are very rare this unique biogeographic selectivity is probably partly responsible for the impoverished nature of brachiopod faunas in the triassic even mesozoic oceans five intervals of extinction survival survival recovery recovery dispersal and radiation are recognized based on variations in brachiopod faunas from the latest permian to the early triassic a dramatic reduction in brachiopod diversity at the end permian mass extinction is followed by several stepwise declines in diversity in the survival interval the time during which the surviving brachiopods are dominated by geographically widespread generalist faunas that adapted to a wide variety of environments the survival interval was followed by a slow re population of new lineages dominated by progenitor taxa

trace fossil evidence for restoration of marine ecosystems following the end permian mass extinction in the lower yangtze region south china abstract unlike the high abundance low diversity macrofaunas that characterize many early triassic benthic palaeocommunities ichnofossils were relatively common in the aftermath of the end permian mass extinction worldwide ichnofossils therefore are a good proxy for ecosystem recovery after the end permian biotic crisis this paper documents 14 ichnogenera and one problematic form from lower triassic successions exposed in the lower yangtze region south china post extinction ichnodiversity remained rather low throughout the griesbachian early smithian period and abruptly increased in the late smithian however several lines of evidence including extent of bioturbation burrow size trace fossil complexity and tiering levels indicate that diversification of ichnotaxa in the late smithian did not signal full marine ecosystem recovery from the permian triassic p tr mass extinction marine ichnocoenoses did not recover until the late spathian in south china the marginal sea provided hospitable habitats for tracemakers to proliferate in the aftermath of the end permian mass extinction

defining the hyporheic zone in a large tidally influenced river summary an investigation was conducted to characterize the spatial and temporal distribution of the hyporheic zone of a large tidally influenced river the field site is located on the fraser river in british columbia canada approximately 30 km from its outlet to the ocean the physical attributes of the riverbed were mapped using geophysical techniques coupled with sediment sampling the spatial and temporal distribution of groundwater composition beneath the riverbed was determined through detailed profiling contaminated fresh groundwater discharges through a narrow band of the riverbed at a distance approximately 88 105 m from the shoreline coinciding with the termination of a massive silty unit saline groundwater as part of a regional flow system dominates the riverbed sediments from 105 m beyond the shoreline towards the centre of channel three water types occur within the upper 2 m of the riverbed sediments a result of both mixing of river water contaminated fresh groundwater and saline groundwater and modification by cation exchange reactions the interaction of these waters produced distinct zones of ca hco 3 na cl and ca cl type waters the distribution of groundwater solutes indicates that during a single tidal cycle river water penetrates the riverbed to a depth of approximately 15 cm but the long term effects of tidal pumping of river water into the riverbed is observed to a depth of approximately 1 m below the river bed

the effect of terrace geology on ground water movement and on the interaction of ground water and surface water on a mountainside near mirror lake new hampshire usa the west watershed of mirror lake in the white mountains of new hampshire contains several terraces that are at different altitudes and have different geologic compositions the lowest terrace fse has 5 m of sand overlying 9 m of till the two next successively higher terraces fs2 and fs1 consist entirely of sand and have maximum thicknesses of about 7 m a fourth and highest terrace fs3 lies in the north west watershed directly adjacent to the west watershed this highest terrace has 2 m of sand overlying 8 m of till all terraces overlie fractured crystalline bedrock numerical models of hypothetical settings simulating ground water flow in a mountainside indicated that the presence of a terrace can cause local ground water flow cells to develop and that the flow patterns differ based on the geologic composition of the terrace for example more ground water moves from the bedrock to the glacial deposits beneath terraces consisting completely of sand than beneath terraces that have sand underlain by till field data from mirror lake watersheds corroborate the numerical experiments the geology of the terraces also affects how the stream draining the west watershed interacts with ground water the stream turns part way down the mountainside and passes between the two sand terraces essentially transecting the movement of ground water down the valley side transects of water table wells were installed across the stream s riparian zone above between and below the sand terraces head data from these wells indicated that the stream gains ground water on both sides above and below the sand terraces however where it flows between the sand terraces the stream gains ground water on its uphill side and loses water on its downhill side biogeochemical processes in the riparian zone of the flow through reach have resulted in anoxic ground water beneath the lower sand terrace results of this study indicate that it is useful to understand patterns of ground water flow in order to fully understand the flow and chemical characteristics of both ground water and surface water in mountainous terrain copyright 2007 john wiley sons ltd

the okavango fan and the classification of subaerial fan systems abstract controversy exists over the classification of fluvially formed subaerial fans authors either restrict alluvial fans to debris flow dominated types or extend the spectrum to fans dominated by braided rivers the okavango fan provides an end member which extends this spectrum to fans dominated by meandering and low sinuosity rivers the fan is a large 150 km radial axis shallowly sloping 0 00036 highly vegetated subaerial fan which can be subdivided into four subenvironments these are 1 the entry corridor or panhandle characterized by single and anastomosing meander belts 2 the upper fan characterized by meander belts diverging from the fan apex comprising peat confined meandering channels with interchannel swamps forming thick peats 3 the middle fan with highly confined single and anastomosing low sinuosity rivers and less common prograding meander belts whose channels are confined by thick peats with however little chance of peat preservation and 4 the lower fan in which annual floods from relatively unconfined channels spread over the fan surface and interact with pre existing aeolian and lacustrine deposits with the recognition of this new fan type the spectrum of subaerial fan types can be expressed in terms of 1 debris flow dominated fans of which the death valley fans are a member 2 braided river dominated fans of which the kosi fan is a member and 3 low sinuosity meandering losimean river dominated fans of which the okavango fan is a member this spectrum can be expressed in terms of variation in slope maximum size and percentage of surface vegetation but crucial to the evolution of the various fan types is variation in the flashy to continuous nature of the discharge and the degree of channel confinement evident on the fan surface comparable ancient examples of the three fan types are recognizable many of which provide intermediates between the ideal end members debris flow dominated and braid dominated fan types are known from throughout earth history however the losimean fan type because of its reliance on confining vegetation may only have developed after the devonian period the spectrum of subaerial fan types can be expressed on a triangular field of variation with the vertices defined by the relative importance of the processes which shaped a particular fan system be they debris flows processes associated with braided rivers or processes associated with meandering and low sinuosity rivers

the permo triassic extinction the end permian mass extinction brought the palaeozoic great experiment in marine life to a close during an interval of intense climatic tectonic and geochemical change improved knowledge of latest permian faunas coupled with recent advances in isotopic studies and biostratigraphy have greatly enhanced our understanding of the events of 250 million years ago and have begun to provide answers to many questions about the causes of extinction

the effect of streambed topography on surface subsurface water exchange in mountain catchments a numerical hydrological simulation suggested that water exchange between stream channels and adjacent aquifers is enhanced by convexities and concavities in streambed topography at st kevin gulch an effluent stream in the rocky mountains of colorado subsurface hydraulic gradients and movement of ionic tracers indicated that stream water was locally recharged into well defined flow paths through the alluvium stream water filled flow paths in the alluvium referred to as substream flow paths returned to the stream a short distance downstream 1 to 10 m recharge to the substream flow paths occurred where stream water slope increased at the transition from pools 1 to steeper channel units 5 20 return of substream flow paths to the stream occurred where stream water slope decreased at the transition from steeper channel units to pools a net water flux calculation is typically used to characterize water and solute fluxes between surface and subsurface zones of catchments along our study reach at st kevin gulch the net inflow of water from subsurface to stream 1 6 ml s 1 m 1 underestimated the gross inflow 2 7 ml s 1 m 1 by 40 the influence of streambed topography is to enhance hydrological fluxes between stream water and subsurface zones and to prolong water sediment contact times these effects could have important consequences for solute transport retention and transformation in catchments

alluvial characteristics groundwater surface water exchange and hydrological retention in headwater streams conservative solute injections were conducted in three first order montane streams of different geological composition to assess the influence of parent lithology and alluvial characteristics on the hydrological retention of nutrients three study sites were established 1 aspen creek in a sandstone siltstone catchment with a fine grained alluvium of low hydraulic conductivity 1 3 10 4 cm s 2 rio calaveras which flows through volcanic tuff with alluvium of intermediate grain size and hydraulic conductivity 1 2 10 3 cm s and 3 gallina creek located in a granite gneiss catchment of coarse poorly sorted alluvium with high hydraulic conductivity 4 1 10 3 cm s all sites were instrumented with networks of shallow groundwater wells to monitor interstitial solute transport the rate and extent of groundwater surface water exchange determined by the solute response in wells increased with increasing hydraulic conductivity the direction of surface water groundwater interaction within a stream was related to local variation in vertical and horizontal hydraulic gradients experimental tracer responses in the surface stream were simulated with a one dimensional solute transport model with inflow and storage components otis model derived measures of hydrological retention showed a corresponding increase with increasing hydraulic conductivity to assess the temporal variability of hydrological retention solute injection experiments were conducted in gallina creek under four seasonal flow regimes during which surface discharge ranged from baseflow 0 75 l s in october to high 75 l s during spring snowmelt model derived hydrological retention decreased with increasing discharge the results of our intersite comparison suggest that hydrological retention is strongly influenced by the geologic setting and alluvial characteristics of the stream catchment temporal variation in hydrological retention at gallina creek is related to seasonal changes in discharge highlighting the need for temporal resolution in studies of the dynamics of surface water groundwater interactions in stream ecosystems 1997 by john wiley sons ltd

the age of the permian triassic boundary abstract the 5 cm boundary clay bed in the chinese stratotype section through the permian triassic boundary has been recognised as a bentonite shrimp ion microprobe dating of zircons in the bentonite indicates a magmatic age of 251 2 3 4 ma 2 this is the first direct constraint on the numerical age of the permian triassic boundary future refinements of ages at this important but poorly constrained level of the phanerozoic timescale may depend on re analysis of this uniquely placed volcanic horizon and other bentonites in the fossiliferous chinese upper permian and lower triassic the utility of defining the permian triassic boundary in the chinese stratotype section in the vicinity of known dateable horizons should be considered

environmental controls on the post permian recovery of benthic tropical marine ecosystems in western palaeotethys aggtelek karst hungary climate warming during the late permian is associated with the most severe mass extinction event of the phanerozoic and the expansion of hypoxic and anoxic conditions in shallow shelf settings it has been hypothesised that wave aeration provided a habitable zone in the shallowest environments that allowed the survival and rapid recovery of benthic invertebrates during the early triassic we test this hypothesis by studying the rock and fossil records of the aggtelek karst hungary nearshore settings recorded in the bodvaszilas sandstone formation and units a and d of the szin marl formation are characterised by taxonomically homogenous fossil assemblages of low diversity and low evenness ecological and taxonomic recovery in this environmental setting was hampered by persistent environmental stress this stress is attributed to increased runoff related to climate warming during the early triassic that resulted in large salinity fluctuations increased sedimentation rates and eutrophication that led to seasonal hypoxia and an environment only favourable for opportunistic taxa in contrast shoal and mid ramp settings further offshore are characterised by high diversity faunas with a greater functional complexity prior to the late spathian tirolites carniolicus zone the shelly fossils and trace fossils are limited to settings aerated by wave activity which supports the habitable zone hypothesis in the tirolites carniolicus zone however the oxygen minimum zone retreats offshore and the habitable deeper shelf settings are rapidly colonised by shallow water taxa evidenced by the highest levels of diversity and bioturbation recorded in the study locally full recovery of marine ecosystems is not recorded until the illyrian with the establishment of a sponge reef complex

comment on origin of the highly elevated pyrenean peneplain by julien babault jean van den driessche and stephane bonnet sebastien castelltort and alain crave

in stream geomorphic structures as drivers of hyporheic exchange 1 common in stream geomorphic structures such as debris dams and steps can drive hyporheic exchange in streams exchange is important for ecological stream function and restoring function is a goal of many stream restoration projects yet the connection between in stream geomorphic form hydrogeologic setting and hyporheic exchange remains inadequately characterized we used the models hec ras modflow and modpath to simulate coupled surface and subsurface hydraulics in a gaining stream containing a single in stream geomorphic structure and to systematically evaluate the impact of fundamental characteristics of the structure and its hydrogeologic setting on induced exchange we also conducted a field study to support model results model results indicated that structure size background groundwater discharge rate and sediment hydraulic conductivity are the most important factors determining the magnitude of induced hyporheic exchange followed by geomorphic structure type depth to bedrock and channel slope model results indicated channel spanning structures were more effective at driving hyporheic flow than were partially spanning structures and weirs were more effective than were steps across most structure types downwelling flux rate increased linearly with structure size yet hyporheic residence time exhibited nonlinear behavior increasing quickly with size at low structure sizes and declining thereafter important trends in model results were observed at the field site and also interpreted using simple hydraulic theory thereby supporting the modeling approach and clarifying underlying processes

simulating infiltration into frozen prairie soils in streamflow models a major limitation of existing operational systems when applied to forecasting or synthesizing streamflow from snowmelt on watersheds in many pans of central and northern canada is that they are incapable of accurately simulating the process of infiltration into frozen soils the results and discussion in the paper provide a method of overcoming the problem in areas of climatic and physiographic conditions similar to those of the prairies details outlining the development of a model describing snowmelt infiltration into frozen soils are presented the model is based on the concept that for practical purposes the infiltration potential of frozen soils may be generally categorized as 1 restricted impervious 2 unlimited capable of infiltrating the snow cover water equivalent and 3 limited infiltration is governed by the snow cover water equivalent and the ice content of the soil at the time of melt an empirical relationship for calculating infiltration into frozen soils of limited potential is

high elevation of low relief surfaces in mountain belts does it equate to post orogenic surface uplift we present experiments of upraising and relaxing topographies showing that peneplanation can occur above the ultimate base level sea level after active uplift the erosion of a topography bounded by a piedmont generates a final smooth and highly elevated topography smoothing at high elevation is even possible during active uplift if the evolution of topography is disrupted by the deposition of the products of erosion on its piedmont which is the case at the transition from underfilled to overfilled conditions in foreland basins

global analyses of brachiopod faunas through the ordovician and silurian transition reducing the role of the lazarus effect global analyses of 88 families and 284 genera of brachiopods from middle ashgill late ordovician to early middle rhuddanian early silurian indicate that 18 6 and 12 5 of families and 51 0 and 41 3 of genera were eliminated in the first and second phases of the end ordovician mass extinction respectively with the total loss of 28 4 of families and 69 0 of genera in the crisis new investigation demonstrates that brachiopods at both generic and familial levels suffered greater during the first phase than during the second phase four groups victims relicts survivors and new arrivals are distinguished by their stratigraphical ranges generic survivors occurring in the kosov province during the hirnantian can be split into three types with respect to their changing abundance increasing declining and lazarus taxa among the 88 genera that survived numerous declining genera occurred in the hirnantian 16 lazarus families and 18 lazarus genera are provisionally known and may be regarded

the impact of gravel extraction on groundwater dependent wetlands and lakes in the boreal plains canada the impact of gravel excavation on a groundwater dependent ecosystem gde in a glacial outwash plain was determined using a combination of time series stable isotopic measurements 2h and 18o and a numerical flow model of lake groundwater interaction isotopic analyses of the lake and groundwater indicated a shift from a dominance of evaporative enrichment to more meteoric conditions confirming the hypothesis of increased recharge following forest clearing and gravel extraction from an esker on the outwash plain the effect of these land use changes on source water for the gde was quantified by simulating the lake water budget seepage and groundwater conditions for a period spanning pre and post mining activity enhanced cycling of shallow groundwater driven by increased recharge in the gravel excavation area was predicted to cause annual groundwater discharge pulses greater than baseline conditions for the groundwater fed lake the additional groundwater discharge represents approximately 4 of the annual lake budget increasing the flushing rate of the lake the influence of regional groundwater conditions represented by variation of water table gradient and outwash hydraulic conductivity and an alternative excavation location were investigated in a sensitivity analysis simulation results illustrate that a simple groundwater capture zone analysis for the gde could be used to determine a location for gravel excavation that would reduce impact on gde water source

geologic influences on fluvial hydrology and bedload transport in small mountainous watersheds northern new mexico u s a discharge characteristics in six adjacent mountainous watersheds in northern new mexico u s a vary substantially between basins underlain by different lithologies relatively resistant gneisses and granites underlie two basins drainage areas 43 and 94 km2 that have high unit discharge 0 010 to 0 14 m3s 1 km 2 high bankfull discharge and sustained high discharge less resistant sandstones and shales underlie four basins drainage areas 96 to 215 km2 that have relatively low unit discharge 0 001 to 0 005 m3s 1 km 2 relatively low bankfull discharge and peak discharges that are not sustained as long as those in the crystalline terrane analysis of snowmelt runoff water budgets suggests that three factors control hydrologic conditions in the basins first area elevation distributions appear to control the timing and amounts of water input these distributions probably reflect the erosional resistance of the different lithologies second lithology appears to control runoff production in areas having minor amounts of storage third glacial deposits in headwater regions control discharge duration and timing via storage and return flow releases the amount of return flow released by glacial deposits however is probably controlled by the permeability of underlying bedrock therefore it appears that the duration timing and magnitude of discharge events in the study area are controlled both directly and indirectly by lithology stream power and shear stress estimates derived from bankfull discharge and bed material size data suggest that higher bedload transport rates and larger bedload particle sizes exist in streams draining crystalline rocks than in streams draining sedimentary terrane it appears that source area lithology by controlling discharge production also influences stream power bedload transport capabilities and therefore total amounts of bedload transport

long lived transfer zone paleovalleys in mountain belts an example from the tertiary of the spanish pyrenees abstract major fluvial valleys located in sediment transfer zones that link hinterland drainage basins with their depositional basins are an important but neglected element of fluvial systems studies of present day examples are limited and to date no examples have been described from the geological record tertiary synorogenic fluvial successions in the spanish pyrenees include regional scale unconformity based linear bodies of conglomerate that are interpreted as the fills of transfer zone paleovalleys these paleovalleys are sited mainly in the external zones of the mountain belt between the internal axial zone on which the drainage basin was largely established and the depositional basins one body here termed the sis conglomerate is preserved in a growth syncline between two th ust related lateral structures growth of the syncline during sedimentation permitted a 1400 m succession of clast supported pebble and cobble conglomerates to accumulate during a c 18 m y period between the middle eocene to oligocene the paleovalley served not one but a series of evolving thrust sheet top and foreland basins during this period the stability of the paleovalley was governed by its location between long lived pre existing structures that were inverted during compressional deformation this example demonstrates that fluvial paleovalleys located in transfer zones can when structurally controlled be long term features capable of accumulating and preserving a significant thickness of strata

paleozoic echinoderm hangovers waking up in the triassic echinoderms are among the marine invertebrates that underwent the most severe losses at the end permian extinction the prevailing paradigm claims an extreme bottleneck with only very few if not single holdovers hangovers herein sparking the post paleozoic radiation here we identify previously overlooked triassic echinoids ophiuroids and asteroids as unambiguous members of paleozoic stem groups these echinoderm hangovers occurred almost worldwide and had spread into a wide range of paleoenvironments by the late triassic our discovery challenges fundamentals of echinoderm evolution with respect to end permian survival and sheds new light on the early evolution of the modern clades in particular on triassic ghost lineages i e inferred but undocumented fossil record of the crown group look alikes of the paleozoic hangovers

reply to comment by yanni gunnell and marc calvet on origin of the highly elevated pyrenean peneplain gunnell and calvet 2006 hereinafter referred to as gc challenge the recent model that we proposed for the origin of the highly elevated pyrenean peneplain by contest ing our morphometric analysis of this chain and the relation we made between the morphological evolution and the piedmont sedimentation their reasoning is as follows 1 according to calvet 1996 on which their comment is largely based the high elevation low relief surfaces in the eastern pyrenees are remnants of a peneplain that devel oped before the pliocene from applanation near to sea level and which was later uplifted by 2000 m during the plio quaternary in other words gc belong to the applanation school whereas we woul d belong to the altiplanation school 2 high elevation low relief surfaces do not exist in the central pyrenees 3 therefore the relationships we made between the morphology of the central pyrenees and the pattern of the detrital sedimentation in the adjacent ebro foreland basin is meaningless 4 contrary to the initial interpretation of calvet 1996 gc recognize that crustal thickening did not develop since the pliocene in the eastern pyrenees so they appeal to another geodynamical process such as extension or lithosphere delamination to explain the supposed uplift

convective transport within stable river sediments local pressure variations of the order of 100 1000 n m2 can be observed between the upstream and downstream faces of the typically triangular shaped dunelike sediment structures that form at the sediment water interface of rivers laboratory experiments were conducted examining the influence of this localized pressure variation on contaminant transport processes within the sediment numerical modeling of the in bed flow via boundary element methods was also undertaken in order to predict convective transport under typical field conditions the laboratory experiments and numerical simulation of the in bed flow in several rivers verified that the pressure distribution observed on the sediment surface and the resulting interstitial fluid convection can control transport of chemically inert nonsorbed contaminants in stable sediments in bed peclet numbers were of the order of 100 1000 indicating the negligible influence of diffusion under the conditions examined

middle triassic carbonate platforms in eastern iberia evolution of their fauna and palaeogeographic significance in the western tethys abstract this article reports the first integrated study of the middle triassic of iberia based on the stratigraphy sedimentology and fossil fauna of muschelkalk facies of the iberian ranges and the catalan coastal ranges in spain on the basis of this study new palaeogeographic reconstructions of the westernmost tethys are proposed and the evolution of the different palaeogeographic domains of iberia e g iberian mediterranean and levantine balearic are described in these domains muschelkalk facies record the development of wide carbonate platforms that were the consequence of the first two broad marine transgressions of the mesozoic in iberia respectively late pelsonian early illyrian and late illyrian longobardian of these marine incursions the oldest only manifested in the mediterranean triassic domain catalan coastal ranges and part of the iberian ranges which acted as a palaeogeographic gulf opening northwards most of the fauna related to this first incursion show strong affinities with the alpine germanic bioprovinces related to the palaeotethys in contrast the second transgressive episode took place in a new regional palaeogeographic setting related to the intra pangea dextral shear and the northward movement of the cimmerian microcontinent a rapid sea level rise induced generalised marine flooding of the iberian mediterranean and levantine balearic triassic domains the resulting carbonate platforms yield fossil assemblages ammonoids bivalves foraminifera and conodonts that show affinities with those of both the alpine and sephardic bioprovinces related to the neotethys these assemblages point to a significant increase in diversity during the late fassanian longobardian possibly related to the prevailing wider connections between the sea corridors an increased continental run off and input of nutrients and or a general cooling of marine waters

numerical modeling of effects of small scale sedimentary variations on groundwater discharge into lakes the effect of small scale sedimentary structural variations on the order of a few tens of centimeters on groundwater lake interaction is investigated with crossflo a finite element model that simulates two dimensional steady state flow in cross section via stream functions simulations show that relatively thin continuous or discontinuous layers can strongly influence migration paths recharge discharge profiles flowline inclinations at the sediment water interface and travel times in the case of groundwater mediated contamination of lakes from sources located on land results show that the presence of thin layers can change the point of contaminant entry into a lake by several hundreds of meters further time required for the contaminants to reach the lake may be altered by decades or centuries these results stress the importance of detailed description of subsurface geology for realistic predictions of contaminant migration from groundwater into lakes and for sound lake management

geophysical constraints on the deep structure along the ecors pyrenees line the structure of the central part of the pyrenean range traversed by the ecors vertical reflection seismic line is further constrained by a joint interpretation of complementary and reprocessed data wide angle low frequency profiling of moho topography indicates an abrupt termination of the northern european moho at the north pyrenean fault and a range of possible geometries of a deeper iberian moho which does not seem to extend significantly to the north of this fault when reprocessing vertical reflection data to 25 s two way travel time strong clear straight reflections are discovered in the part of the section under the northern foreland long after the moho reflection their strong northward dip indicates that they originate in fact at reflectors at depth beneath the north pyrenean fault which may correspond to the connection between the two levels of moho the reflections then being from the northward inclined limit between the wedge of iberian crust underlying the southern edge of the european mantle a range of possible shapes is allowed by the conjunction of these seismic data which is compatible with the results of a detailed gravity profile this would indicate that the imbrication of european into iberian lithosphere has been of limited extent with respect to the surface trace of the north pyrenean fault provided no strong density contrast in the mantle part of the section contributes significantly to the gravity anomaly

a three dimensional model of the pyrenean deep structure based on gravity modelling seismic images and petrological constraints summary the present study aims at building a 3 d density model of a whole collisional mountain belt at the lithospheric scale the geometry of internal structures is constrained by seismic studies while density values are imposed by petrological considerations the model must fit both the bouguer and geoid anomalies this approach is applied to the pyrenees for which numerous geophysical data are available the crustal structure is constrained from the results of seismic profiles the most important crustal feature is the large moho jump which coincides with the surface expression of the north pyrenean fault considered as the suture between the iberian and eurasian plates the eurasian crust is about 30 km thick whereas the iberian crust is 50 km thick in the central part of the range thick sedimentary basins at the piedmont and two large heavy intracrustal bodies located in the western and central parts of the range are also important features of the crustal model at the lithospheric scale a low velocity strip under the north pyrenean fault down to 80 100 km depth interpreted as the subduction of the iberian lower crust has been revealed by tomographic models the density of this structure has been constrained using petrological arguments which assume that the crustal material is transformed into eclogite at about 12 15 kbar 40 50 km depth an eclogite type density value much higher than the mantle density is thus imposed from 50 to 100 km depth theoretical bouguer and geoid anomalies are computed for this 3 d density model using a summation of density block anomalies a good agreement is found with observations giving strong support to the proposed model the crustal structure as seen by seismic profiles explains most of the observed long wavelength negative bouguer anomaly as well the local anomalies related to the intracrustal bodies a possible mantle origin of these bodies is ruled out on the other hand the transformation of the subducted lower crust into dense eclogite provides a successful fit to the long wavelength positive geoid anomalies in addition the water released during eclogite formation may help to explain the high conductivity zone detected down to 80 km south of the north pyrenean fault the 3 d model proposed here thus reconciles petrological considerations and geophysical data

seasonal variation in surface subsurface water exchange and lateral hyporheic area of two stream aquifer systems abstract we used two dimensional unconfined transient groundwater flow models to investigate the interface between stream and groundwater flow systems or hyporheic zone of two first order streams that drain catchments with distinctly different alluvial sediments and bedrock lithology particle tracking showed that lateral hyporheic area planimetric area of flow paths lateral to the stream that are recharged by and return to the stream with travel times of 10 days or less differed between the two study streams and varied with discharge within each system at the rio calaveras welded tuff lateral hyporheic area ranged from 1 7 to 4 m 2 over the annual cycle in the aspen creek system sandstone lateral hyporheic area 1 1 5 m 2 was restricted to roughly half of that observed at rio calaveras the size of the hyporheic zone lateral to the streams at both sites decreased by approximately 50 during high flows sensitivity analyses indicated that changes in the hydraulic conductivity of alluvial and streambed sediments and variation in recharge rates have greatest impact on the magnitude direction and spatial distribution of stream groundwater exchange

single discharge events increase reactive efficiency of the hyporheic zone in this study we investigate the impact of single stream discharge events on water exchange solute transport and reactions in the hyporheic zone below a natural in stream gravel bar we set up a reactive transport groundwater model with streamflow scenarios that vary by event duration and peak discharge a steady ambient groundwater flow field is assumed that results in losing neutral or gaining stream conditions depending on the stream stage across the streambed dissolved oxygen organic carbon and nitrate are transported into the subsurface additional nitrate is received from upwelling groundwater aerobic respiration and denitrification are simulated for scenarios with different stream solute concentrations results show that hyporheic exchange flux solute transport and consumption increase during events however their intensities depend highly on the interplay between event characteristics and ambient groundwater conditions during events where reversals in the hydraulic gradient occur stream water and solutes infiltrate deeper into the aquifer where they have more time to react for those events the reactive efficiency of the hyporheic zone solute consumption as fraction of influx for aerobic respiration and denitrification is up to 2 7 and 10 times higher compared to base flow conditions the fraction of stream nitrate load consumed in the hyporheic zone increases with stream discharge up to 150 mg m2 h but remains below the value under base flow conditions for weak events events also increase denitrification of groundwater borne nitrate but groundwater nitrate flux to the stream decreases by up to 33 due to temporary gradient reversals

the north maladeta fault spanish central pyrenees as the vielha 1923 earthquake seismic source recent activity revealed by geomorphological and geophysical research abstract the spanish central pyrenees have been the scenario of at least two damaging earthquakes in the last 800 years analysis of macroseismic data of the most recent one the vielha earthquake 19 november 1923 has led to the identification of the north maladeta fault nmf as the seismic source of the event this e w trending fault defines the northern boundary of the maladeta batholith and corresponds to a segment of the alpine gavarnie thrust fault our study shows that the nmf offsets a reference neogene peneplain the maximum observed vertical displacement is 730 m with the northern downthrown sector slightly tilting towards the south this offset provides evidence of normal faulting and together with the presence of tectonic faceted spurs allowed us to geomorphically identify a fault trace of 17 5 km this length suggests that a maximum earthquake of mw 6 5 0 66 could occur in the area the geomorphological study was improved with a resistivity model obtained at pruedo where a unique detritic late miocene sequence crops out adjacent to the nmf the section is made up of 13 audiomagnetotelluric soundings along a 1 5 km transect perpendicular to the fault trace at pruedo and reveals the structure in depth allowing us to interpret the late miocene deposits as tectonically trapped basin deposits associated with normal faulting of the nmf the indirect age of these deposits has been constrained between 11 1 and 8 7 ma which represents a minimum age for the elevated pyrenean peneplain in this part of the pyrenees therefore we propose the maximum vertical dip slip rate for the nmf to be between 0 06 and 0 08 mm a normal faulting in this area is attributed to the vertical lithospheric stress associated with the thickened pyrenean crust

the aksay segment of the northern altyn tagh fault tectonic geomorphology landscape evolution and holocene slip rate 1 millennial slip rates have been determined for the altyn tagh fault atf at three sites near aksay 94 e in northeastern tibet by dating fluvial channels and terrace riser offsets with radiocarbon and 10be 26al surface exposure dating up to nine main surfaces are defined on the basis of morphology elevation and dating the abandonment age of some surfaces is constrained by radiocarbon dating which typically coincides with the youngest cosmogenic ages for a particular surface older surface exposure ages are taken to represent the duration of terrace emplacement cumulative offsets range from 20 to 260 m and fall in distinct groups indicative of climatically modulated regional landscape formation most samples are younger than 14 ka and postdate the last glacial maximum the end of the early holocene optimum marks the boundary between the ages of the two main terrace levels at 5 6 ka at this longitude the atf is divided into a northern and southern branch the northern atf should thus yield a minimum rate for the atf system slip rate estimates using the abandonment age of the overlying level for fill terraces or channels and the emplacement of the underlying level for strath terraces give 30 consistent results yielding an average holocene rate of 17 8 3 6 mm yr it is 9 mm yr less than the long term rate obtained near tura at 87 e 26 9 6 9 mm yr in keeping with the inference of an eastward decreasing rate on the atf due to increased thrusting to the south however it remains twice the rate determined by gps studies

on the relationship between river basin geomorphology aquifer hydraulics and ground water flow direction in alluvial aquifers the delineation of ground water flow in alluvial valley stream aquifer systems is important in studies of water availability environmental impact and aquifer remediation and is required by some states water laws published potentiometric surfaces and head data however are not always available when data are absent it is commonly assumed that ground water and dissolved solutes flow toward the river analysis of published geomorphologic and hydraulic data in 24 alluvial systems and the results of digital simulations indicate that in some cases this assumption is only valid immediately adjacent to an effluent river ground water flow in the remaining portions of an alluvial valley aquifer may be dominated by downstream or underflow components this paper investigates the nature of ground water flow in alluvial valleys and presents a new classification scheme for alluvial aquifers the geomorphologic conditions that may allow underflow to be the predominant regional ground water flow component are described in order to classify alluvial aquifers two darcy flux end member components are defined the baseflow component is that portion of the ground water flux that moves perpendicular to the river the baseflow component may flow toward the river or away from the river depending on whether the river is effluent or influent respectively the underflow component of the darcy flux moves parallel to the river and in the same direction as the stream flow the alluvial stream aquifer systems are classified based on the predominant regional ground water flow component as underflow component dominated baseflow component dominated or mixed on the basis of the results of this study we conclude that the dominant regional ground water flow component base flow or underflow can be inferred in an alluvial valley aquifer from geomorphologic data these data include the channel slope the river sinuosity the degree of penetration incision through the alluvium of the river the width to depth ratio and the fluvial depositional system the underflow component is demonstrably predominant when the following conditions exist 1 the channel gradient exceeds 0008 2 the sinuosity is less than 1 3 3 the river penetration is less than 20 4 the width to depth ratio is greater than 60 and 5 the fluvial depositional system is either valley fill or mixed load to bed load the underflow component can also be dominant on flood plains where the lateral valley slope is negligible

environmental controls on marine ecosystem recovery following mass extinctions with an example from the early triassic abstract the recovery of marine ecosystems following a mass extinction event involves an extended interval of increasing biotic diversity and ecosystem complexity the pace of recovery may be controlled by intrinsic ecosystem or extrinsic environmental factors here we present an analysis of changes in marine conditions following the end permian mass extinction with the objective of evaluating the role of environmental factors in the protracted 5 myr long recovery of marine ecosystems during the early triassic specifically our study examines changes in weathering productivity and redox proxies in three sections in south china chaohu daxiakou and zuodeng and one in northern india mud our results reveal 1 recurrent environmental perturbations during the early triassic 2 a general pattern of high terrestrial weathering rates and more intensely reducing marine redox conditions during the early griesbachian late griesbachian mid smithian and more weakly the mid spathian 3 increases in marine productivity during the aforementioned intervals except for the early griesbachian and 4 stronger and more temporally discrete intervals of environmental change in deepwater sections chaohu and daxiakou relative to shallow and intermediate sections zuodeng and mud our analysis reveals a close relationship between episodes of marine environmental deterioration and a slowing or reversal of ecosystem recovery based on metrics of biodiversity within community alpha diversity infaunal burrowing and ecosystem tiering we infer that the pattern and pace of marine ecosystem recovery was strongly modulated by recurrent environmental perturbations during the early triassic these perturbations were associated with elevated weathering and productivity fluxes implying that nutrient and energy flows were key influences on recovery more regular secular variation in deepwater relative to shallow water environmental conditions implies that perturbations originated at depth i e within the oceanic thermocline and influenced the ocean surface layer irregularly finally we compared patterns of environmental disturbance and ecosystem recovery following the other four big five phanerozoic mass extinctions to evaluate whether commonalities exist in general the pace of ecosystem recovery depends on the degree of stability of the post crisis marine environment

evolutionary models in the early triassic marine realm abstract the relative influences of extrinsic compared to intrinsic drivers of evolutionary change have long been theorized and debated in the fossil record ecological recoveries from mass extinction events present records in which to examine these contrasts competition in a low diversity world reproductive strategy reconstruction of trophic systems and ecological specialization represent possible intrinsic controls on diversification feedback between diversity and abundance shifts of marine organisms with biogeochemical cycling and environmental conditions act as extrinsic controls on recovery process and rate disentangling these evolutionary pressures is a major challenge for understanding evolutionary recovery from mass extinction the end permian mass extinction 251 88 ma represents the largest mass extinction in earth history and led to an extended recovery interval which lasted the duration of the early triassic 4 8 myr and beyond recent analyses suggest that the survivors of the mass extinction were biased toward organisms with higher metabolic rates that were more resilient against the volatile environmental changes that pervaded the early triassic including extreme temperature events low ph and low oxygen conditions we use the early triassic recovery of gastropods echinoids and ammonoids to examine the processes of taxonomic and ecological evolution in response to or in spite of extrinsic environmental perturbations the case studies of benthic gastropods and echinoids when compared to pelagic ammonoids reflect similarities and differences in recovery following the end permian mass extinction gastropods and echinoids exhibit evidence of strong extrinsic environmental limitations which implicate the availability of refugia as a control on recovery low initial taxonomic diversity of survivors may have also limited the evolutionary recovery of both clades abundant and diverse microgastropod assemblages are interpreted as an adaptation to extreme environmental conditions the morphological diversity of disarticulated echinoid spines and plates described in the southwestern united states and examination of phylogenetic ghost lineages hints at a significant hidden diversity of early triassic echinoids ammonoids experienced taxonomic resets but are shown to be resilient to repeated environmental perturbations in the boreal ocean over the duration of the early triassic ammonoids may have adapted to persistent latitudinal temperature gradients and oxygen minimum zones that developed in the early triassic ocean basins

origin of the highly elevated pyrenean peneplain 1 peneplanation of mountain ranges is generally considered the result of long term erosional processes that smooth relief and lower elevation near sea level therefore peneplain remnants at high elevation in mountain ranges are used to infer posttectonic surface uplift such an interpretation has been proposed for the pyrenees where high elevation low relief erosional surfaces rose up to more than 2000 m because the pyrenean foreland basins are filled with very thick continental deposits which have buried the early jagged landscape we challenge this hypothesis by pointing out that relief applanation does not necessarily require elevation lowering we propose an alternative interpretation in which piedmont aggradation of detrital sediment that comes from erosion of the high chain induces the rise of the base level of the range therefore reducing strongly the erosive efficiency of the drainage system and resulting in the progressive smoothing of the relief such a process allows a high elevation low relief erosional surface to develop at the scale of the range in the pyrenees occurrence of high elevation low relief erosional surface remnants does not imply a posttectonic uplift but is instead due to the dissection of the initial miocene high elevation low relief surface by the recent drainage system the erosive activity of which has been enhanced by global climate change from the late pliocene onward

a triassic sponge from vancouver island possible holdover from the cambrian tiny cap shaped fossils recovered from silicified residues in upper triassic rocks of vancouver island wrangellia are identified as a calcareous sponge nucha vancouverensis n sp nov the genus nucha pickett and jell was first reported from middle cambrian rocks of australia the triassic example constitutes the first occurrence outside the cambrian system and the continent of australia the absence of representatives in rocks between triassic and cambrian age suggests that it is a long range refugium taxon the occurrence of such a wide ranging holdover organism reinforces the role of refugia in preferential survivorship over long periods of geologic time other holdover taxa are known from volcanic displaced terranes of western american cordillera and their study may help clarify neglected aspects of survival and evolution

early triassic gulliver gastropods spatio temporal distribution and significance for biotic recovery after the end permian mass extinction a reduction in body size lilliput effect has been repeatedly proposed for many marine organisms in the aftermath of the permian triassic pt mass extinction specifically reduced maximum sizes of benthic marine invertebrates have been proposed for the entire early triassic this concept was originally based on observations on early triassic gastropods from the western usa basin and the dolomites n italy and it stimulated subsequent studies on other taxonomic groups however only a few studies have tested the validity of the lilliput effect in gastropods to determine whether the paucity of large sized gastropods is a genuine signal or the result of a poor fossil record and insufficient sampling in combination with a review of the literature we document numerous new abundant large sized gastropods from the griesbachian outcrops of greenland and from the smithian early spathian interval in the southwestern usa we show that large sized gulliver gastropods i were present soon after the pt mass extinction ii occurred in various basins sedimentary facies and environmental contexts from shallow to deeper settings and iii belong to diverse higher rank taxa focusing on the western usa basin we investigate areas from which microgastropod shell beds were previously presented as being typical however we show that gulliver gastropods do occur in the very same areas insufficient sampling effort is probably the main reason for the rarity of reports of large early triassic gastropods which is supported by preliminary rarefaction based simulations finally it appears that the recently documented middle to late smithian climate shifts and the severe end smithian extinction of nekto pelagic faunas did not reduce maximum shell sizes of gastropods

onset of biotic and environmental recovery from the end permian mass extinction within 1 2 million years a case study of the lower triassic of the meishan section south china abstract paleontological sedimentary and geochemical data obtained from the lower triassic strata of the meishan section south china suggest that onset of biotic recovery coincided with amelioration of paleoceanographic conditions and an increase in ocean productivity the griesbachian meishanorhynchia association from meishan indicates biotic recovery between the recovery stages 1 and 2 both the initial biotic recovery and palaeoceanic environmental amelioration occurred within 1 2 myr after the end permian mass extinction in the late griesbachian

survival strategies of brachiopod faunas from the end permian mass extinction abstract global reviews reveal that 102 brachiopod species including 40 indeterminate species belonging to 43 genera within 27 families survived the end permian mass extinction in south china the himalayan regions southern tibet nepal salt range and kashmir southern alps italy arctic canada western usa and western australia of these the surviving brachiopods are most abundant and widespread in south china where they occur in 32 of the 42 permian triassic p t boundary sections around the world brachiopod faunas are the most abundant and diverse post extinction survivors and their appearance above the end permian mass extinction horizon somewhat masks recognition of the end permian extinction these surviving brachiopods occur in three stratal intervals corresponding to the mixed fauna beds mfb hereafter 1 3 of the p t boundary beds a sharp drop in diversity of the brachiopod faunas coincides with the widely accepted end permian mass extinction horizon the post extinction brachiopods were also affected by a subsequent crisis corresponding to the boundary between mfb 2 and mfb 3 so that most survivors were extinct approximately 0 7 ma after the end permian mass extinction the surviving brachiopods were mainly productida followed by spiriferida in particular small chonetids chonetid like productellids and smooth thin shelled ambocollid spiriferids are most abundant lingula is extraordinarily abundant and widespread approximately 0 7 ma after the greatest extinction when many regions became devoid of articulate brachiopods widespread broadly adapted and small sized taxa preferentially survived frequent intrageneric speciation of widespread widely adapted generalist genera enabled survival brachiopods to occupy rapidly and efficiently vacant ecospace in the aftermath of the end permian extinction the ecological habitats of the post extinction brachiopods are subdivided into nearshore epeiric sea restricted carbonate platform open carbonate platform ramp and outer shelf environments of these the survival brachiopods are most diverse in the open platform environments the nearshore zone provided ideal habitats for the nonarticulated brachiopods to occupy whereas the survivors in the outer shelf are predominantly chonetids and chonetid like productellids the most successful survivors the productid brachiopods are widely distributed in six types of ecological habitats and thus have no apparent preference for specific environments the end permian extinction resulted in the movement of biogeographical provinces towards the palaeo equator the brachiopods survived mostly in the palaeo equatorial provinces and along the southern margins of the palaeo tethys ocean

new empirical relationship between grain size distribution and hydraulic conductivity for ephemeral streambed sediments grain size distribution porosity and hydraulic conductivity were determined for 39 sediment samples collected from ephemeral streams wadis in western saudi arabia the measured hydraulic conductivity values were then compared to values calculated using 20 different empirical equations commonly used to estimate hydraulic conductivity from grain size analyses it was found that most of the hydraulic conductivity values estimated from the empirical equations correlated very poorly with the measured hydraulic conductivity values modifications of the empirical equations including changes to special coefficients and statistical offsets were made to produce modified equations that considerably improved the hydraulic conductivity estimates from grain size data for wadi sediments the chapuis hazen kozeny slichter terzaghi and barr equations produced the best correlations but still had relatively high predictive errors the chapius equation was modified for wadi sediments by incorporating mud percentage and the standard deviation in phi units into a new equation that reduced the predicted hydraulic conductivity error to 14 1 m day the equation is best applied to ephemeral stream samples that have hydraulic conductive values greater than 2 m day

pyrenean orogeny and plate kinematics 1 the evolution of the pyrenees a mountain range between iberia and eurasia has remained the subject of many debates between geologists and geophysicists for a long time by combining the identification of seafloor spreading anomalies a33o to m0 in the bay of biscay with those in the north atlantic we have derived a position of a mean pole of rotation for the entire opening of the bay of biscay four hundred kilometers of shortening took place between the iberian and eurasian plates in the pyrenean domain during the opening of the bay of biscay from chrons m0 to a33o time 118 to 80 ma the deep seismic etude continentale et oceanique par reflexion et refraction sismique ecors profile shot across the pyrenees and teleseismic data show the presence of two distinct slabs which dip to the north the southern slab is linked to the subduction of the neo tethys ocean which was created from late jurassic to early aptian simultaneously elongated back arc basins formed along the future pyrenean domain this slab was active from at least 118 ma early aptian to 100 ma late albian the northern slab active since 85 ma is linked to the subduction of the lower continental crust located south of the pyrenean domain in the upper crust normal faults as well as the north pyrenean fault became reverse faults and former back arc basins were inverted giving rise to the uplift of the pyrenees as a double asymmetrical wedge