large striated burrows from fluvial deposits of the neogene vinchina formation la rioja argentina a crab origin suggested by neoichnology and sedimentology abstract this study includes three aspects 1 the ichnotaxonomic treatment of large and dominantly vertical burrows ornamented with sharp bioglyphs from the fluvial neogene vinchina and toro negro formations northwest argentina 2 the description and interpretation of the sedimentary facies where these burrows occur and 3 neoichnologic observations on large ornamented burrows from seasonal wetlands of the rio pilcomayo national park argentina as possible modern analogues of the trace fossils and the sedimentary environment a new ichnogenus and ichnospecies capayanichnus vinchinensis is proposed to include the large striated burrows the new ichnotaxon is distinguished by a combination of a predominantly vertical orientation overall l shape when fully developed absence of lining and burrow bifurcation a distinct surface texture and lack of burrow enlargements the hosting sedimentary facies of the vinchina formation can be grouped into fluvial channel and splay floodplain facies associations the rivers of that unit were of two main types single channel rivers with frequent channel avulsion and overbank flow and multichannelised rivers with poorly defined margins at least some of these rivers were ephemeral or with intermittent discharge the climate was probably seasonal and semiarid as suggested by sedimentologic evidence c vinchinensis was dominantly recorded from the top of fluvial channels interpreted as abandoned channels and proximal intermediate and distal splay facies the large ornamented burrows found in an extant comparable example were constructed by freshwater crabs these burrows can be distinguished by the overall architecture the taxonomy and sex of its occupants and the environmental setting where they were found the neoichnologic signatures used in the interpretation of the fossil example include the common oval burrow cross section and the surface texture in particular the surface texture in the modern crab burrows includes abundant comma shaped marks sets of grooves oblique to burrow axis and long segmented grooves the predominantly oval cross section absence of lining and the strongly ornamented burrow surface suggest that c vinchinensis was produced by freshwater crabs the key features of the surface ornament are long sets of three four ridges whose width is in average one third of the burrow major axis other features that also point to a crab origin are a massive filling common burrow ends in a casing mudstone chevron pattern in sets of surface ridges and possible cheliped marks the new ichnotaxon is restricted in the vinchina and toro negro formations to fluvial facies and is absent in shallow lacustrine facies

burrows of a gopher like rodent possibly gregorymys geomyoidea geomyidae entoptychtinae from the early miocene harrison formation nebraska this study describes the architectural and surface morphology of small 5 6 6 7 cm diameter burrows that occur in close proximity to the daemonelix burrows of palaeocastorin beavers in the early miocene upper harrison formation nebraska the small diameter burrows are sinuous and rambling or weakly helical in morphology distinctive paired grooves from rodent incisors measuring 4 1 4 3 mm wide occur on the ceiling and sides of the burrows whereas ridge like claw marks of 4 1 mm width occur low on walls and floors scratched out chamber like areas on the sides of tunnel shafts are covered on all sides with claw marks whereas tooth marks are mostly confined to main tunnel shafts both types of marks are abundant indicating a mixed tooth and claw digging strategy that appears to have evolved in palaeocastorin beavers as well similar digging methods in two unrelated harrison rodents indicates the relative hardness of the volcanic ash rich soils which necessitated digging with teeth in addition to less resistant keratin claws the new ichnotaxon alezichnos trogodont is erected to describe these ichnofossils a possible excavator is gregorymys sp an extinct gopher like entoptychine rodent that occurs in these and correlative miocene units in the great plains the width of gregorymys incisors matches the width of incisor marks on a trogodont these burrows may represent the first recorded evidence of subterranean habitat and digging behavior in an otherwise common fossil rodent the excavator of a trogodont had a different burrow system and possibly different foraging behavior than the contemporaneous beavers providing new evidence for diversity in a subterranean miocene ecosystem

assessment of soil moisture movement in nuclear subsidence craters abstract this study was undertaken to investigate the potential ground water recharge resulting from a nuclear subsidence crater on the nevada test site results from two boreholes one completed in the subsidence crater bottom and the other completed in an adjacent undisturbed area suggest that deep infiltration of periodically ponded runoff water at the crater bottom is occurring whereas little or no deep infiltration was evident in the adjacent undisturbed area specialized drilling coring and borehole logging revealed high water contents and a unit hydraulic gradient downward beneath the subsidence crater traditional soil physics analysis via darcy s law and core samples suggested a wide range of downward fluid velocities and fluxes beneath the crater in contrast soil water tritium concentrations combined with several mixing models significantly reduced the range of estimated fluxes based upon these models it is suggested that the vertical flux beneath the crater is on the order of 0 6m year 1 it is postulated that the surface topography combined with the coarse textured soils beneath the crater allows for the deep infiltration of ephemerally ponded water at the bottom in the adjacent undisturbed and topographically flat lying site significant ponding does not occur and evaporation and transpiration processes recycle much if not all of the precipitation falling on the surface

seismic damage and behavior analysis of earth dams during the 2008 wenchuan earthquake china abstract the may 12 2008 ms 8 0 wenchuan great earthquake china caused earthquake damages of 2666 earth dams these damaged dams are in medium and small scale located in 8 provinces or municipalities of which 69 dams were at dam break risk and 331 were at high risk there were 1996 damaged dams located in sichuan province including all the 69 at dam break risk and 310 at high risk through a detailed scientific investigation earthquake damage and emergency data were collected and the isoseismal map of wenchuan earthquake with damaged dams marked on it was given also distribution feature of the above 69 dams along the fault zones were discussed typical damage types of earth dams were analyzed and the action of rare great earthquake poor quality of dam construction adverse running state of earth dams before earthquake and frequent aftershocks were concluded as four main reasons of dam damages taking 147 dams with complete geometric parameters as statistical samples some empirical graphic formulas were proposed to make rapid evaluation of damage degree finally some useful practical measures were provided to serve the post earthquake emergency danger removal also it may improve the seismic performance of dams in view of the insufficiency of local geology site effect and soil property data of damaged dams application of the qualitative results and empirical relationships to other sites should be very prudent

global positioning system measurements of present day crustal movements in the arabia africa eurasia plate collision zone we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1994 at 54 sites extending east west from the caucasus mountains of southern russia georgia and armenia to the aegean coast of turkey and north south from the southern edge of the eurasian plate pontus block to the northern edge of the arabian platform viewed from a eurasia fixed reference frame sites on the northern arabian platform move n38 13 w at 20 3 mm yr roughly consistent with the velocity implied by nuvel 1a circuit closure n23 7 w at 24 2 mm yr the motion of arabia appears to be transferred directly to the region of turkey north of the suture however eastern turkey is characterized by distributed deformation while central western turkey is characterized by coherent plate motion involving westward displacement and counterclockwise rotation of the anatolian plate internal deformation within the central part of the anatolian plate is less than 2 mm yr the anatolian plate is decoupled from eurasia along the right lateral strike slip north anatolian fault naf this different response in eastern and western turkey to the collision of arabia may result from the different boundary conditions the hellenic arc forming a free boundary to the west and the asian continent and oceanic lithosphere of the black and caspian seas forming a resistant boundary to the north and east we derive a best fitting euler vector for anatolia eurasia motion of 29 2 0 8 n 32 9 0 4 1 3 0 1 m y the mapped surface trace of the naf corresponds well to a small circle about this pole the new euler vector implies an upper bound for naf slip rate of 30 2 mm yr i e assuming all relative motion is accommodated along the naf using the nuvel 1a euler vector for arabia eurasia and the gps euler vector for anatolia eurasia we determine an arabia anatolia euler vector of 31 2 n 45 2 e 0 9 0 1 m y and an upper bound on the east anatolian fault slip rate of 15 3 mm yr the aegean trough region of western turkey deviates significantly from coherent plate rotation in addition to rotating with anatolia this region shows roughly n s extension at a rate of 14 5 mm yr taken together with satellite laser ranging results along the hellenic arc the contemporary pattern of deformation indicates increasing motions toward the arc suggesting that the westward displacement and counterclockwise rotation of anatolia is driven both by pushing from the arabian plate and by pulling or basal drag associated with the foundering african plate along the hellenic subduction zone

solving a cold case new occurrences reinforce juvenile callianassids as the ophiomorpha puerilis tracemakers abstract the ichnotaxon ophiomorpha puerilis was erected based on material from late pleistocene shallow marine siliciclastic deposits of southeastern brazil these tiny burrows with a distinctive lining of cylindrical pellets having rounded ends were originally interpreted as burrows of juvenile callianassid shrimp with polychaetes also considered as a possible tracemaker recent discoveries of o puerilis in late pleistocene shallow marine carbonates from two localities in the bahamas and from the miami limestone of south florida described herein have expanded significantly the geographic range of the ichnotaxon and provided numerous well preserved specimens for detailed structural analysis of its burrow form and pellets the new information strengthens the interpretation of juvenile callianassids as the tracemakers resolving the cold case of the burrow s tracemaker microscopic analyses revealed that the pellets of o puerilis are constructional not fecal furthermore larger forms of ophiomorpha are common and occur in close association with o puerilis at each locality these new data allowed close comparison of o puerilis pellets with those of sergio mirim a modern callianassid from southeastern brazilian beaches ophiomorpha nodosa from brazilian pleistocene deposits and fossil polychaete burrows filled with fecal pellets as described in the literature the combined evidence allows us to exclude polychaetes as potential o puerilis tracemakers rather o puerilis records the settling and initial burrowing behavior of callianassid decapodids the characteristics of an ophiomorpha ichnofabric with the addition of o puerilis also is described and explored an emended diagnosis for the o puerilis ichnotaxon is provided based on the new structural data for this burrow

ephemeral fluvial deposits integrated outcrop and simulation studies reveal complexity ephemeral fluvial sandstones form the main reservoirs in many oil and gas fields production histories and development difficulties suggest these deposits are more complex than is commonly supposed in the petroleum industry there is inadequate published information to account for this observation relevant sedimentological literature on such deposits is qualitative and unsuitable for detailed reservoir characterization studies therefore integrated sedimentological petrophysical and fluid flow simulation studies have been conducted on outcrop analogs in the southwestern united states our key objectives were to define flow units and to find areas of sensitivity inherent both in the sediments and in the analytical and statistical procedures used to describe and model s ch systems we report results of integrated studies on the lower jurassic kayenta formation in southeastern utah the kayenta formation is a relatively proximal sand rich succession dominated by channel fill sandstones sedimentological analysis identified eight main genetic units in contrast reservoir simulations based on probe permeameter data collected at outcrop show that six of the main genetic units have uniform flow behavior intraformational mudclast conglomerates are the dominant permeability barriers both because of the clasts themselves and because they act as sites of preferential cementation stochastic permeability models conditioned to the outcrop data produce results little different from models based on averaged values for each facies the most sensitive feature of the mode s concerns the assumptions made about the mudclast conglomerates the model results show that only by integrating analytical approaches can we understand the full character of an outcrop analog in such a way that we can use it predictively

playa lake basins on the southern high plains of texas and new mexico part i hydrologic geomorphic and geologic evidence for their development playa lake basins of the southern high plains texas and new mexico may originate wherever water periodically can collect in a surficial depression they expand however by hydrologic and geomorphic processes including 1 dissolution of lithologic carbonates by infiltrating water 2 transport downward of fine grained clastic and organic material by the infiltrating ground water leading to continuing processes of oxidation and carbonate dissolution in the subsurface and 3 eolian removal of clastic material from the floor of playa lakes which at some sites appears to have deepened playa depressions evidence for largely hydrologic processes of playa basin development on the southern high plains includes 1 a geographic occurrence restricted to relatively flat areas of the high plains surface that have poorly developed fluvial drainage and which are underlain by generally unsaturated clastic and calcrete beds 2 a tendency to occur where water collects and infiltrates as along ephemeral streams and lineations suggestive of fracture systems and 3 hydrologic geochemical petrographic and bore hole data which suggest that recharge to the high plains aquifer is principally from playa lakes that various geochemical changes including carbonate dissolution and enhancement of secondary porosity occur as water moves downward through the unsaturated zone beneath playa lakes and that calcrete beds often are missing or significantly dissolved beneath playa floors

middle and late albian geography oceanography and climate and the setting of the kirchrode i and ii borehole sites abstract the paper reviews the literature on the geography oceanography and climate belts during the middle and late albian emphasis is placed on the northern hemisphere and the lower saxony basin the middle and late albian represents a time with a greenhouse climate the n s temperature gradient and the temperature gradient between the shallow and deep waters of the oceans were lower than at present meaning higher temperatures especially at middle and high latitudes a more sluggish ocean circulation than today and the absence of polar ice caps warming from the early to late albian is documented in the marine sediments by oxygen isotope studies and the poleward expansion of rudist dominated carbonate platforms in the terrigenous sediments of the northern hemisphere it is documented by northward migration of low latitude relatively arid flora the opening north atlantic was still narrow at the beginning of the albian it widened and deepened through the albian a shallow seaway between the south atlantic and the western tethys developed during the late albian wide shelf seas existed on the continental plates with rising sea level the basins of the western epicontinental seas of eurasia became increasingly connected and sedimentation gradually became more calcareous nevertheless these basins received a large clastic input from the land documenting the weathering conditions on the surrounding land masses they received also a considerable biogenic particle flux from the surface waters documenting productivity of the marine plankton because of these different origins of the sediment components as well as the connections with neighbouring seas the sediments in these shelf basins were expected to document changes in climate as well as palaeo oceanographic changes earlier interpretations based on ammonite studies that indicate changing connections between the arctic ocean and the tethys during the albian can thus be tested the lower saxony basin was a shelf sea in the southern part of the warm humid climate belt at mid latitudes in the northern hemisphere in which thick deposits of hemipelagic sediments accumulated mapping previous to our study indicated that a complete undisturbed albian basinal sequence ca 400 m thick is present below a thin quaternary cover in a sub basin between the nne ssw trending benthe and lehrte salt structures in the central part of the lower saxony basin the boreholes at the kirchrode i and ii sites 52 22 35 n 9 49 87 e and 52 22 16 n 9 49 12 e respectively in hannover were drilled into this sub basin the high sedimentation rates known for the albian of the lower saxony basin are ideal for studying climatic changes with a cyclicity of a few ten thousand to a few hundred thousand years milankovitch cyclicity

the geological problems of the large dams constructed on the euphrates river turkey abstract in order to use the energy and irrigation potential of the euphrates river a series of dams have been designed upstream to downstream keban karakaya karababa ataturk birecik and karkamis the first three of these dams have been completed construction on the birecik and karkamis dams is underway the initial plans involved a 60 m high golkoy dam downstream of the karakaya dam with the ataturk dam 60 m lower than it is currently in the belief that the cost of irrigation by the ataturk dam s water would be high the increase of the height of ataturk dam was preferred to the construction of the golkoy dam the keban dam s basement is formed by karstic rock named keban marble from the author and his colleagues studies it has been shown that water would leak from the left side of keban dam reservoir forming a spring in the keban creek in order to prevent this water leakage an intensive grouting programme was applied in spite of this when the reservoir was filled 26 30 m3 s of water leaked from the keban creek a more recent study on the volume of leakage showed it to be reduced to 7 8 m3 s with this amount remaining constant the karakaya dam is constructed on metamorphic rocks thus only allowing minimal water leakage however on the downstream side of the right slope the tillo bego senketo landslides have been an important risk to the dam if such landslides cause an artifical lake by blocking the euphrates river the karakaya hydroelectric power station could be flooded limestone forms the foundations for the ataturk dam on and around the damsite there is epithermal water 24 26 c below the aquifer deeper than 300 m with the level of the grouting curtain down to 180 200 m the grouting curtain would not be able to prevent the leakage because the level of karstification extends below the grouting curtain in february 1993 the total volume of leaking water from the damsite and its vicinity reached 10 m3 s when the reservoir level was 517 m when the reservoir is full 542 m the volume of leaking water is expected to increase under the clay core of the dam extending from the surface to 30 40 m depth high grouting pressure could not be applied so water leaked at this part of the grouting curtain and thus the amount of leaked water could not be measured

trace fossil suites and composite ichnofabrics from meandering fluvial systems the oligocene lower freshwater molasse of switzerland abstract the oligocene lower freshwater molasse of switzerland is host to spectacular outcrops of fluvial deposits in distal areas of the swiss molasse basin deposits of a north eastward draining meandering system are exposed combined sedimentologic and ichnologic observations in the chli sunnhalde and roggwil quarries allow an improved understanding of animal substrate interactions in deposits of meandering fluvial systems strata include meander belt sandstone levee sandstone and mudstone crevasse channel and splay sandstone floodplain mudstone and sandstone and paleosols while the meander belt and the more proximal crevasse channel deposits are typically unbioturbated the more distal deposits show a clear biogenic overprint with distal crevasse channel crevasse splay and floodplain deposits being intensely bioturbated simple grazing and locomotion trails included in the cochlichnus anguineus helminthoidichnites tenuis suite were formed subaqueously in ponded areas of the floodplain meniscate burrows taenidium isp suite and root trace fossils occur along the margin of these floodplain water bodies and at the top of crevasse splay deposits some of the floodplain crevasse splay and crevasse channel deposits are pervasively bioturbated by crayfish burrows camborygma litonomos suite crevasse splay deposits locally host escape trace fossils where cross cutting relationships are apparent a colonization sequence can be established as follows the cochlichnus anguineus helminthoidichnites tenuis suite is cross cut by the taenidium isp suite which in turn is cross cut by the camborygma litonomos suite and root trace fossils composite ichnofabrics are common in these meandering river deposits recording progressive lowering of the water table in overbank subenvironments frequency of depositional events was a first order control on degree of bioturbation position of the water table and degree of substrate consolidation exerted considerable influence over the types of trace fossils produced distinct bioturbation phases may result in the formation of different trace fossil suites representative of disparate ichnofacies preserved on a single bedding plane this study further supports the notion that meandering fluvial systems are characterized by trace fossil suites belonging to the scoyenia camborygma and or mermia ichnofacies

seismic hazard and total risk analyses for large dams in euphrates basin turkey reservoirs constructed near urban areas pose a high risk potential for downstream life and property turkey is one of the most seismically active regions in the world and has at least 1200 large dams with different types major earthquakes with the potential of threatening life and property occur frequently here the euphrates basin studied in this article is located in a seismically very active part of turkey the northern part of the basin is structurally cut by numerous faults many large dams are located on or close to these faults in this paper we summarize the methods used for the analysis of seismic hazards and total risk discuss the seismic hazards of thirty two large dams constructed on the euphrates basin on the basis of the seismic activity of the dam site and their total risk as based on physical properties and the position in the basin the seismic hazard analyses have indicated that peak ground acceleration changes within a wide range 0 011 g and 0 564 g for the dam sites of the basin a seismic hazard map showing the equivalent pga peak ground acceleration values was developed so as to use for the preliminary analysis of dam structures which will be designed in the basin the total risk analyses depending on the seismic hazard rating of dam site and risk rating of the structure have concluded that fifteen large dams have high risk class in the basin these dams must be analyzed with high priority and redesigned to increase the safety of the embankments and their appurtenant structures if necessary

the miocene climatic optimum evidence from ectothermic vertebrates of central europe abstract data sets of central european temporal distributions of thermophilic ectothermic vertebrates channidae varanidae chamaeleonidae cordylidae tomistomidae alligatoridae giant turtles and of north alpine foreland basin nafb distributions of ectothermic vertebrates adapted to dryer habitats albanerpeton inexpectatum salamandra sansaniensis bufo cf viridis chamaeleo caroliquarti gekkonidae varanus hofmanni bransateryx sp are analysed two main migration events of thermophilic ectotherms at 20 ma and 18 ma in the lower miocene are discerned they indicate the beginning of the miocene climatic optimum in central europe 42 45 n palaeolatitude with a lower limit of the mean annual temperature mat of 17 4 c derived from the minimal mat of their extant relatives furthermore additional palaeobotanical data and records of bauxite point to a mat of 22 c this warm and humid optimum peaked at 18 16 5 ma ottnangian karpatian and is confirmed by the coexistence of all investigated thermophilic taxa the following period early badenian is characterised by probably unchanged temperatures but a seasonality in precipitation with dry periods up to six months two major seasonal phases between 16 3 and 15 7 ma earliest early badenian and between 14 7 and 14 5 ma early middle badenian transition are indicated by an immigration of dry adapted taxa from the surrounding karst plateau to the nafb it is presumed that the tectonical reorganisation of the central paratethys realm had considerable influence on this regional humidity pattern the warm period ended abruptly between 14 0 and 13 5 ma middle late badenian transition with major regional extinction events of most of the thermophilic groups in central europe and a drop of the mat of probably more than 7 c to temperatures around 14 8 15 7 c this drop can be attributed predominantly to a decrease of more than 11 c of the minimum cold months temperature this temperature decrease marked the beginning of a climatic zonation of the european continent and is also evidenced by a progressively southward disappearance of the crocodile diplocynodon from 38 45 n palaeolatitude to 30 37 n during the middle and earliest late miocene the results correlate well with palaeobotanical data from the mid latitudes of europe and north america and the deep sea temperature curve generated from oxygen isotope ratios

production of subtidal tubular and surficial tempestites by hurricane kate caicos platform british west indies abstract storm infilling of deep open callianassa burrows with molluscan to peloidal packstone was the dominant style of preservable sedimentation produced by the passage of hurricane kate across caicos platform british west indies on 18 november 1985 this moderate hurricane was the first to affect an actively studied portion of the carbonate platform environments of the south florida bahama region in 19 years a time during which many of our concepts of storm sedimentation have evolved prior to hurricane kate much of the shallow platform interior peloidal packstone to grapestone grainstone had a sparse seagrass cover and a highly irregular bottom caused by abundant callianassa mounds hurricane kate flattened the mounded bottom of the platform interior and caused minor smothering and erosion of the seagrass beds a thin surficial tempestite though deposited over much of the platform was difficult to identify because it lacked a coarse base instead much of the reworked surface sediment poured down the large callianassa burrow entrances and filled the vast burrow networks with either a coarse molluscan packstone or peloidal skeletal packstone storm burrow filling tubular tempestites effectively removed the coarse fraction from contributing to a surficial storm layer ten percent of the upper 75 cm of platform interior sediment consists of tubular tempestites from hurricane kate

coupled surface subsurface hydrologic model of a nuclear subsidence crater at the nevada test site a series of computer models describing overland flow ponding and infiltration was dynamically linked to simulate the movement of water during seepage beneath a nuclear subsidence feature the coupled surface subsurface hydrologic model contains a terrain analysis module an overland flow simulator using the kinematic wave equation and a numerical richards equation solver to simulate moisture migration within the vadose zone simulations resulted in successful approximations to measured surface and subsurface data the surface water overland flow component was able to reach an agreement between observed and simulated water levels following a precipitation event long term simulations underpredicted the volumetric water contents and depth of moisture fronts the flux darcian velocity at 10 m below the surface was temporally stable with a temporal mean value of 0 75 m year 1 which is in agreement with an earlier estimate of 0 60 m year 1 the mean flux at 5 m below the surface was 1 4 m year 1 long term simulations suggest that significant recharge does exist beneath surface collapse structures owing to periodic ponding

occurrence of bioglyphs on ocypode crab burrows in a modern sandy beach and its palaeoenvironmental implications abstract the ichnological term bioglyph covers biogenic sculpture on burrow walls bioglyphs in the burrows of ocypodid crabs were studied in a modern unconsolidated sandy substrate looseground on irino coast southwestern japan they are seen exclusively on sides and roof of the burrow and are characteristically seen near the distal end of the burrow moist sandy substrate where sand particles are bound together by surface tension of interstitially suspended water might allow the production of such bioglyphs although bioglyphs are only partially developed in such burrows those interpreted to have formed in semi consolidated substrates firmground are known to be sculptured over the entire burrow surface such difference in the modes of bioglyph occurrence can be used as a criterion to reconstruct the substrate consistency in the rock record

near source attenuation of peak horizontal acceleration strong motion data recorded within 50 km of the rupture zone were used to study near source attenuation characteristics of horizontal peak ground acceleration for worldwide earthquakes of magnitudes 5 0 to 7 7 the data base consisted of 229 horizontal components of peak acceleration recorded from 27 earthquakes including the 15 october 1979 imperial valley earthquake these data were found to be adequately represented by the functional relationship pga a exp b m r c m d where pga represents the mean of the peak values scaled from the two horizontal components of each recording m is richter magnitude and r is distance from the fault rupture zone peak acceleration was found to be lognormally distributed with a standard error representing a 45 per cent increase in the median estimate the regression analysis statistically confirmed the results of earthquake simulation studies that have predicted peak acceleration to become independent of magnitude and distance in the near field an extensive sensitivity study showed that predictions based on our attenuation relationships are stable with respect to reasonable model and parameter variations an analysis of residuals was used to investigate the behavior of peak acceleration with respect to various earthquake site and recording parameters the more significant findings being 1 a similarity in the level of acceleration recorded on soil or rock 2 larger than average accelerations recorded at sites located on shallow soils or in areas of steep topography 3 larger than average accelerations associated with earthquakes having reverse fault mechanisms and 4 lower than average accelerations recorded in large embedded structures

middle and late jurassic roots of brachyuran crabs palaeoenvironmental distribution during their early evolution abstract knowledge of early mesozoic crabs is still rudimentary mainly due to the poor preservational potential of crustacean decapods fossil evidence suggests that the family prosopidae is ancestral to all other brachyurans including podotremata with a very close phylogenetic relationship to homolodromiidae dromiidae homolidae latreillidae dynomenidae xanthidae cyclodorippoidea and calappoidea prosopidae is an extinct family consisting mostly of mesozoic species almost exclusively known by their carapaces this family appeared in the late early jurassic late pliensbachian and disappeared at the end of the danian the early jurassic pliensbachian oldest crab species eocarcinus praecursor withers is transitional in many of its observable traits between the macruran glypheoidea middle triassic pseudopemphix and the early brachyuran prosopids especially the earliest known species eoprosopon klugi forster late pliensbachian middle jurassic prosopids lived in shallow sea soft bottom environments the oldest known prosopid species lived on a silty sea floor as did the first known crab late early pliensbachian and their presumed ancestors pemphicidae were probably also shallow water organisms middle jurassic prosopids lived both in shallow warm waters within organic buildups shelly accumulations and on silty sea floors during the bajocian bathonian as illustrated by a new example from central poland prosopids had an evolutionary climax during the late jurassic and were widely distributed in sponge microbial oxfordian buildups and coral reef kimmeridgian tithonian environments of europe pithonoton coelopus longodromites prosopon nodoprosopon lecythocaris glaessneropsis when biohermal and reef facies retreated at the end of the jurassic favourable conditions for prosopid crabs diminished and cretaceous prosopids are rare and spatially dispersed their closely related descendants the homolodromiids preferentially inhabited soft muddy bottoms in deeper colder waters as is well documented by cenozoic and recent occurrences

using fluvial cyclicity to decipher the interaction of basement and fold thrust belt tectonics in a broken foreland basin vinchina formation miocene northwestern argentina abstract the miocene vinchina formation is made up of more than 5100 meters of siliciclastic sediments deposited mostly in fluvial environments in a broken foreland basin without any connection with the sea during a period of arid to semiarid climatic conditions repetitive changes in fluvial facies allow the subdivision of the formation into seven cyclothems each floored by a subaerial unconformity within sequence changes in fluvial systems determined by the proportion of channel vs floodplain multi story vs single story channels and channel connectedness were controlled by changes in accommodation proximal i e northern and younger sequences show transitions from braided to low sinuosity wandering or high sinuosity meandering fluvial systems whereas more distal sequences southern and older show changes from sand bed dominated to anastomosed systems bounding unconformities and facies stacking patterns are used to define six third order depositional sequences depositional sequences in the vinchina formation are either asymmetrical showing a fining upward trend or nearly symmetrical sand clock type each cyclothem is bounded by an incision surface sequence boundary developed during a base level i e fluvial equilibrium profile fall and initial base level rise floored by basal coarse grained deposits representing the low accommodation systems tract last the overlying sediments fine upward and contain both isolated and multistory sandstone bodies within extensive flood plain deposits corresponding to the early high accommodation systems tract hast this interval is sometimes capped by sheets of amalgamated sandstones corresponding to the late hast and developed during a decline in the rate of base level rise the development and or preservation of the capping amalgamated sandstones and therefore the symmetrical shape of the sequences is favored in high accommodation settings vertical and lateral facies changes recorded in the vinchina formation indicate that both the fold and thrust belt located to the west and an uplifted basement block to the north played important roles controlling subsidence source areas and drainage patterns the stratigraphic record of this broken foreland basin differ from the existing models for simple foreland basins and can be compared to those of the laramide sedimentary basins in the united states

crevasse splays from the rapidly aggrading sand bed braided niobrara river nebraska effect of base level rise base level rise of 2 35 m on the niobrara river has resulted in aggradation of the channel belt and a recent avulsion overbank areas have become flooded by rising groundwaters and more than eight crevasse splays have formed between 1993 and 1997 two crevasse splays situated on the west and east sides of the niobrara have been studied using ground penetrating radar gpr shallow boreholes and topographic surveys the vibracores and gpr profiles provide a nearly three dimensional view of the architecture of crevasse splay deposits the east splay was initiated in the winter of 1993 94 and has expanded to cover an area 200 m by 1000 m with sediment up to 2 5 m thick the west splay which was initiated by the opening of a crevasse channel through a levee in the autumn of 1995 covers an area 150 m by 250 m with up to 1 2 m of sand deposited in a single year the niobrara splays are sand dominated and characterized by bedload deposition within channels 5 30 m wide and 0 5 2 m deep with the development of slipfaces where splays prograde into standing bodies of water sedimentary structures in cores include horizontal lamination ripple lamination and sets of cross stratification there is a slight tendency for splays to coarsen up but individual beds within the splays often fine up the abundance of crevasse splays on the niobrara river contrasts with other braided river floodplains in the niobrara crevasse splay formation followed aggradation within the channel belt which occurred in response to base level rise the link between crevasse splays channel aggradation and base level rise has important implications for the interpretation of ancient braided river and floodplain sequences it is suggested that crevasse splay deposits should be an important component of aggrading fluvial sediments and hence should be preserved within the rock record in this case the aggradation and crevassing have been tied to a rise in base level elevation and it is suggested that similar deposits should be preserved where braided rivers are affected by base level rise for instance during transgression and filling of palaeovalleys

present day kinematics of the middle east and eastern mediterranean the middle east and eastern mediterranean regions contain three major strike slip fault zones the dead sea fault zone dsfz and the north and east anatolian fault zones nafz and eafz these accommodate northward motion of the african and arabian plates relative to eurasia and westward motion of the small turkish plate this study deduces an internally consistent solution for the present day kinematics of these plates which is accurate to better than 20 and applicable throughout time since 5 ma by constraining the slip senses and rates on these strike slip fault zones the 7 0 5 mm yr 1 left lateral slip rate on the dsfz is associated with counterclockwise rotation of arabia relative to africa at 0 33 m y 1 around an eulcr pole near 33 n 23 e the nafz takes up counterclockwise rotation of the turkish plate relative to eurasia at 0 83 m y 1 13 around a pole at 31 n 35 5 e with right lateral slip rate 15 mm yr 1 the resulting prediction for the eafz involves 14 mm yr 1 left lateral motion and 2 mm yr 1 of shortening between arabia and turkey the triple junction of africa arabia and turkey is near the city of kahramanmaras this locality contains a narrow promontory bounded by ssw trending left lateral faults at the edges of the arabian and turkish plates which is loosely attached to the african plate moving westward relative to its interior at 4 mm yr 1

non tetrapod trace fossils from the middle devonian tetrapod tracksite at zachelmie quarry holy cross mountains poland abstract the middle devonian eifelian dolomites exposed in the zachelmie quarry holy cross mountains southern poland contain the earliest fossil record of tetrapods low diversity but unique assemblages of trace fossils characterize the track bearing interval within the lower complex of the wojciechowice formation the reconstructed environment of the trace fossil rich beds includes ephemeral lakes and or shallow water lagoons separated from an open marine area by sparsely vegetated islands and spits the most abundant non tetrapod trace fossils from these beds are large horizontal to vertical burrows and dish circular to oval shaped shallow depressions the burrows are abundant on the upper surfaces of thick dolomicritic beds especially in some palaeosol levels but they are also associated with tetrapod trackways large semi aquatic or terrestrial animals e g arthropods or vertebrates most likely produced these burrows the circular to oval shaped depressions observed on a large surface and other smaller isolated blocks from the same stratigraphical level are interpreted as fish feeding nesting resting traces piscichnus sanctacrucensis isp nov is proposed as a new ichnospecies of the oval shaped fish trace fossil from the middle devonian of poland a single medium sized undichnia specimen a fish swimming trace is associated with the piscichnus traces the described trace fossils provide new insight into the palaeoecology and taphonomy of the middle devonian tetrapod tracksite from poland and clarify remaining controversies regarding the interpretation of some poorly preserved trace fossils from the zachelmie quarry

visualization of geotechnical data by means of geographic information system a case study in eskisehir city nw turkey recently geographic information system software s are widely used in engineering geology applications such a study was performed in the eskisehir urban area of about 30 km2 via geo engineering maps cross sections and panel block diagrams which are formed to predict the properties of foundation soil in order to determine the engineering geology properties of the region physical and mechanical characteristics of the soil profile were tested on 1 011 disturbed and 383 undisturbed samples from a total of 170 boreholes topographic lithological and geotechnical data of the region were compiled as a database in computer five geological cross sections were drawn to decipher specifically the alluvial deposits in detail in densely populated areas hence geological characteristics of the area were evaluated in a three dimensional mode five standard penetration test spt cross sections at the same directions and spt uniaxial compressive strength qu and soil class zonation maps were produced at different depths and panel block diagrams were also created to define the geo engineering properties of the investigation area in this respect the sub surface of the study area is fully visualized and useful predictor maps cross sections and panel block diagrams are performed to be used in further studies

high latitude albian climate variability palynological evidence for long term drying in a greenhouse world abstract detailed quaternary style quantitative spore pollen counts with a pollen sum based on total non angiosperm seed plants from a southern high palaeolatitude 60 65 terrestrial sequence in gippsland southeast australia has revealed strong vegetation and climate variability during the albian this variability is more pronounced than previously suggested in global early cretaceous vegetation and climate reconstructions the quantitative spore pollen record shows drying throughout the albian based on upward decreasing total ferns and variation in podocarp and total alisporites vitreisporites pollen this record suggests that although global climate during the albian is considered to have been warm stable and equable regional factors such as water availability and continentality were the main drivers of this vegetation change

mid pliocene warmth stronger greenhouse and stronger conveyor abstract three million years ago prior to the onset of northern hemisphere glaciation global mean temperatures may have been as much as 3 5 c warmer than at present we present evidence based on the carbon isotopic composition of marine organic matter that atmospheric co2 levels at this time were on average only about 35 higher than the preindustrial value of 280 ppm we also present carbon isotopic evidence for stronger thermohaline circulation in the atlantic ocean during the warmest intervals and propose that the north atlantic conveyor belt may act as a positive feedback to global warming by enhancing sea ice retreat and decreasing high latitude albedo based on our results it seems unlikely that the mid pliocene warm period was a doubled co2 world

multiproxy studies of early miocene pedogenic calcretes in the santa cruz formation of southern patagonia argentina indicate the existence of a temperate warm vegetation adapted to a fluctuating water table abstract the lower miocene santa cruz formation in southern patagonia austral basin argentina contains several horizons of pedogenic calcretes which record 17 5 myr old vegetation adapted to a shallow and fluctuating water table at paleolatitude of 56 s to reconstruct the paleoenvironment paleoclimate and paleoecosystem we performed a multiproxy study of the calcretes examining abiotic and biotic components the calcretes exhibit a variety of morphologies horizontal and vertical rhizoliths laminar structure nodules massive crusts microfabrics beta predominant over alpha microfabrics and 18o and 13c values that fluctuate within each morphotype and throughout the analysed interval microfossils and phytoliths in the host material of the calcretes indicate fluctuating terrestrial freshwater and marine conditions and record an ecosystem dominated by herbaceous plants and arboreal elements in association with a typical coastal santacrucian vertebrate fauna we propose that the calcretes developed in soils in a coastal fluvial setting during pauses in floodplain aggradation that typically lasted between 8 25 ka and 400 ka years variable sedimentation rates in different parts of the coastal fluvial floodplain the fine texture of the host sediment and the influence of a fluctuating water table also influenced the formation of the calcrete a high water table in low relief areas of the floodplain created the conditions necessary to form a horizontally extended rhizolithic system that jointly with the biotic proxy can be correlated with a radicular pattern similar to the arboreal elements from coastal settings abiotic and biotic proxies of the studied interval attest to environmental fluctuations recorded at different scales that took place under temperate warm and subhumid climates with a marked rainfall seasonality with a slight increase in the aridity towards the top of the studied interval under these conditions a subtropical fauna and a c3 dominated ecosystem developed coincident with the onset of the mid miocene climatic optimum in patagonia

geologic and hydrologic controls on the movement of water through a thick heterogeneous unsaturated zone underlying an intermittent stream in the western mojave desert southern california 1 a two dimensional axially symmetric unsaturated flow model was developed to test hypotheses about geologic and hydrologic controls on the movement of water through the thick heterogeneous unsaturated zone underlying oro grande wash in the mojave desert california heterogeneity within the unsaturated zone was simulated with multiple realizations of subsurface geology estimated on the basis of transition probability markov chain statistics model results show lateral spreading of water away from the wash was best approximated by realizations that include thin horizontally extensive clay layers that impede the downward movement of water there was a wide range in model responses for these realizations and the movement of water through unsaturated zones containing thin horizontally extensive clay layers may be more difficult to predict than water movement through unsaturated zones where clay layers are less extensive for realizations having less extensive clay layers the range of model responses decreased with time and model results became increasingly similar as water encountered larger volumes of material

the golbaoi basin southeastern turkey a complex discontinuity in a major strike slip fault zone we show that the 33 km long golbaoi basin on the east anatolian fault zone marks the triple junction between the african arabian and turkish plates the main strand of the turkish arabian plate boundary the goksu fault enters this basin from the ene before splaying to form faults which develop farther southwest into the turkish african and african arabian boundaries the golba i turko u fault the turkish african boundary is shown to have slipped 16 km the prevously unrecognised kirkpmar fault the african arabian boundary has slipped 17 km we propose that this fault geometry developed at c 3 ma following earlier slip starting at c 5 ma on other strike slip faults nearby which marked the start of westward motion of the turkish plate

possible burrows of mylagaulids rodentia aplodontoidea mylagaulidae from the late miocene barstovian pawnee creek formation of northeastern colorado abstract the massive siltstone beds of the late miocene barstovian pawnee creek formation in logan county northeastern colorado contain abundant terrestrial vertebrate burrows among these are distinctive claw marked burrows attributable to the extinct mylagaulid rodent pterogaulus mylagaulus laevis korth 2000 these burrows differ in several respects from the spiraling daemonelix burrows of fossorial beavers the pawnee creek burrows are slightly ovate in cross section tubular and sinuous rather than helical they consist of primary tunnels of up to at least 7 m long and range from 11 to 18 cm in diameter they occasionally branch into secondary tunnels burrow walls and terminations show prominent parallel ridges in sets of two to three up to 9 3 mm deep and 3 7 mm wide the burrows are too large to have been made by anything but a vertebrate and their considerable length and complexity implies a mammalian excavator the meandering branching morphology resembles the burrow systems of extant fossorial rodents such as pocket gophers geomys and mole rats spalax myospalax skeletal remains of p laevis are abundant at sites where the burrows occur with at least eight individuals represented by humeri in a collected sample although mylagaulid remains are not unequivocally associated with fossil burrows the curved laterally compressed claws and phalangeal arrangement of mylagaulids produce marks very similar in size and morphology to the ridges on the burrows position and pattern of the ridges indicate downward and backward motions of the mani possibly supplemented by motions of the pedes to kick loosened soil backward a new ichnogenus alezichnos and new ichnospecies chelecharatos are erected to describe these burrows

where is the fossil evidence for gondwanan crayfish abstract crayfish body and ichnofossils recently reported from lower permian and lower triassic strata of antarctica have been reinterpreted to be the body fossils of euthycarcinoid arthropods and the burrows of small to large sized therapsids mammal like reptiles the earliest fossil evidence of crayfish presence and activity in continental deposits is still from the laurasian continents of pangea this evidence is in the form of body fossils and burrows from the upper triassic and burrows from the lower permian of the american southwest for that matter nearly all ichno and body fossils have been described from laurasian rocks with the exception of the occurrence of an isolated claw of a parastacid crayfish from paleogene deposits in queensland australia where is all the fossil evidence for gondwanan crayfish there is a rich extant diversity of parastacid crayfish in australia and they are dispersed between other gondwanan continents with the exception of africa and antarctica paleontological and ichnological evidence when taken into consideration with paleogeographic reconstructions indicates that they originated early during or slightly after the formation of pangea thus at the very least there should be trace and body fossil evidence in australia indicating the long evolutionary history of the parastacids evidence for ancient gondwanan crayfish in terrestrial and freshwater ecosystems should occur in rocks of similar ages to those in north america where ichno and body fossils have been identified

the earliest known spongeliomorpha from the lower devonian of the northwestern yangtze platform south china abstract crustacean trace fossils provide invaluable information to paleobilogical environmental and ecological interpretations in the earth history here we report an unusually large segments up to 58 mm across three dimensional burrow system from the lower devonian pingyipu formation which was deposited in a nearshore setting on the northwestern yangtze platform south china the burrow system is dominated by horizontally developed networks probably with vertical shafts connecting to the sediment water interface the burrow surfaces show no signs of lining but are characterized by scratches including ridges and bundles of ear shaped striae implying an assignation to spongeliomorpha aff s chevronensis muniz and mayoral 2001 the overall morphological and taphonomic features suggest permanent open burrows produced in a substrate with considerable firmness further investigation indicates that the burrow system may have been constructed by a colony of large unknown crustacean with thoracic appendages decorated with acute seta or denticulations they generally served a combined purpose of dwelling and perhaps feeding on microbial growth accumulating on the tunnel margins these burrows represent the earliest known three dimensional burrow systems constructed by a crustacean that may be comparable to their modern analogues in both morphological and functional aspects the unusually large size of the burrows may have been favored by a higher atmospheric oxygen level during the early devonian

paleobiology and paleoecology of an arid semiarid miocene south american ichnofauna in anastomosed fluvial deposits abstract miocene deposits of the toro negro formation in la rioja province argentina host a rich vertebrate and invertebrate ichnofauna trace fossils are recorded from the lower part of the lower member of the toro negro formation at quebrada de la troya this succession consists of sandstone intraformational breccia mudstone and few conglomerate deposited in sandy anastomosing fluvial systems developed under a semi arid climate the invertebrate ichnofauna is composed of meniscate trace fossils taenidium barretti scoyenia gracilis dwelling structures palaeophycus tubularis and grazing trails helminthopsis hieroglyphica the vertebrate ichnofauna includes avian fuscinapeda sirin incumbent footprint slender anisodactyl footprint and mammalian footprints macrauchenichnus rector cf venatoripes riojanus small heteropod footprint kidney like footprints and oval impressions tetrapod footprints and rare palaeophycus and helminthopsis are preserved on the top of exposed sandbars crevasse splay deposits preserve abundant meniscate trace fossils and dwelling tubes e g taenidium scoyenia and palaeophycus ascribed to the scoyenia ichnofacies two suites of invertebrate trace fossils can be differentiated meniscate backfill structures t barretti and other burrows p tubularis without ornamentation developed in a soft substrate and striated traces s gracilis that crosscut the former developed in a firmer substrate the toro negro depositional system displays a high preservation potential for tracks due to seasonal flooding events which rapidly buried the footprints the favorable preservational conditions and good exposure of the track bearing surface enable us to interpret the track assemblage of the toro negro formation as a sample of the original tetrapod fauna that inhabited that region at central western argentina during the miocene the identification of possible trackmakers is utilized in this work as a useful tool that contributes to our understanding of the ancient environment the paleoichnocommunity is characterized by the number of trackmakers and the relative abundance of each type of footprints a new method to measure footprint abundance is proposed the relative bioturbed area rba this measurement provides numerical characterization of the degree of bioturbation of the whole tracking surface caused by each ichnotaxa the tetrapod fauna indicated by the footprint record was compared with the body fossil record of the toro negro formation these records overlap in some ways and in other ways they are complementary the presence of large and medium to small ground sloth proterotheriid litopterns caviid rodents and birds is pointed out by both body fossils and ichnofossils body fossils include remains attributed to dasypodids glyptodontids and abrocomid rodents ichnofossils indicate the presence of macraucheniid litopterns and three types of birds shorebirds perching birds and large cursorial birds

crayfish burrows from late jurassic late cretaceous continental deposits of patagonia argentina their palaeoecological palaeoclimatic and palaeobiogeographical significance abstract the trace fossil loloichnus baqueroensis igen and isp nov from late jurassic late cretaceous continental deposits of patagonia argentina includes thickly lined mostly passively filled and y branched burrows other important features of this ichnofossil are the inner surface texture of lining showing transversal elongated and adjacent grooves and less commonly the pelletal filling of burrows l baqueroensis is recorded from the bajo grande bajo tigre punta del barco and laguna palacios formations which were deposited in different volcaniclastic environments of the deseado massif and san jorge basin geological provinces respectively the described burrows are found in many levels of palaeosols developed in reworked piroclastic deposits where they are the main component of the ichnofabrics in association with meniscate and thinly lined burrows and a diffuse and complex boxwork of small diameter burrows root traces are also present and in many cases occur inside l baqueroensis considering general morphology surface texture filling types palaeoenvironments in which they occur and comparisons with extant and fossil decapod burrows the likely trace makers of l baqueroensis were crayfishes decapoda astacidea probably parastacidae the producers of l baqueroensis inhabited soils where their burrows probably reached the water table and contained roots that were used for feeding considering climatic preferences of extant parastacids it is proposed a temperate climate for central patagonia during the deposition of the studied units the widespread presence of crayfishes during late jurassic late cretaceous times in central patagonia supports the monophyletic origin of this group during the triassic and suggests that the present restricted geographic distribution in southern south america is a relict of a broader one

evaluating quaternary activity versus inactivity on faults and folds using geomorphological mapping and trenching seismic hazard implications abstract the incorporation of active faults in seismic hazard analyses may have a significant impact on the feasibility design and cost of major engineering projects e g nuclear facilities dams especially when located in the site vicinity the regulatory definition of active versus inactive fault is generally based on whether the fault has ruptured or not after a specific chronological bound i e fault recency this work presents a methodology mainly based on geomorphological mapping and trenching for determining whether specific faults can be considered as active or inactive the approach is illustrated through the analysis of several faults located in the spanish pyrenees loiti leyre la trinidad ruesta faults the 29 km long loiti thrust was included in the neotectonic map of spain as a probable neotectonic structure previous works based on geomorphological investigations incorporated the 28 km long leyre thrust as a significant seismic source in a probabilistic seismic hazard analysis which challenged the seismic design of nearby large dams the production of detailed geomorphological strip maps along the faults allowed the recognition of specific sites where the faults are covered by quaternary deposits the establishment of chronosequences pediments terrace sequences and the available geochronological data helped identifying the most adequate morpho stratigraphic units for satisfactorily evaluating fault activity vs inactivity the excavation of trenches at the selected sites provided unambiguous information on the presence or lack of deformation in the quaternary cover overlying the fault and the origin of scarps tectonic versus erosional trenches were also useful for collecting samples and reliably measuring the relative height of terraces overlain by thick colluvium the evidence gathered by these methods were complemented with the numerical dating of non deformed slope deposits covering a fault the analysis of the longitudinal profiles of old pediment surfaces located in the proximity of a fault the examination of a cave situated next to a fault searching for speleoseismological evidence and regional geodetic and seismotectonic data gps measurements earthquake focal mechanisms the integration of all the data and especially the trenches dug in non deformed old terrace deposits 100 ka truncating the faults indicates that the analysed faults can be considered inactive and that previous neotectonic postulations were based on non valid geomorphological interpretations

psilonichnus upsilon frey curran and pemberton 1984 burrows and their environmental significance in transgressive albian lower cretaceous sands of glanow stroniczki cracow upland southern poland abstract a considerable upper albian sand lithosome developed on the external margin of the albian epicontinental sea in the polish jura chain miechow synclinorium southern poland is recognized as a shallowing up sequence within the generally transgressive albian sands in particular burrows described as the ichnospecies psilonichnus upsilon frey curran and pemberton 1984 have a particular ecologic and sedimentological significance and constitute the primary focus of this paper in the glanow stroniczki section cracow upland southern poland such burrows seem to be a crucial tool in the interpretation of basin bathymetry indicating a foreshore to backshore beach facies and probably recording a temporary break in sedimentation they were infilled by sand with pebbles or pebble material potentially during hurricane or strong storm action lithification of the burrow infillings and their enveloping concretionary halos should have progressed in a beachrock mode the glanow horst composed of jurassic biohermal limestones was likely an emerged element that neigboured or was surrounded by a beach with active fauna the psilonichnus upsilon burrows in glanow stroniczki closely resemble burrows of the modern ghost crab ocypode in modern settings representatives of ocypode are encountered in extremely shallow marine foreshore intratidal and backshore supratidal to dune environments the ichnological data from glanow stroniczki suggests that fauna behaviorally similar to ocypode may have occupied the beach backshore and to a lesser extent the foreshore zone near the emerged glanow horst

constraints on arabian plate motion and extensional history of the red sea analysis of the geologic and geophysical data from the western and northern margin of the arabian plate combined with data from the red sea gulf of aden leads to an interpretation of arabian plate motion that supports an episodic extensional history in the red sea and gulf of aden phase 1 extension began in medial to late eocene and was caused by the nw propagation of the reoriented central indian ridge spreading center it stretched and thinned continental crust along numerous wrench and normal faults that reactivated preexisting structures first phase extension stopped when the arabian plate terminally sutured to eurasia in the medial miocene and halted northward movement of arabia relative to africa the combined african arabian plates moved north more slowly constricting and thickening continental crust in the bitlis zagros sutures while the red sea remained technically quiescent and accumulated salt by the early pliocene continued northward movement was accommodated by lateral extrusion of large continental wedges north of the bitlis zagros sutures this allowed arabia to move northward faster than africa and reopen the red sea where phase 2 extension was expressed by seafloor spreading extension within the red sea gulf of aden rift system has been controlled by the interactions and effects of two factors 1 convergent processes between the north margin of the arabian plate and the eurasian plate to the north and 2 northwest propagation of extension associated with the medial eocene reorganization of the central indian spreading center

amphibian burrows and ephemeral ponds of the lower permian speiser shale kansas evidence for seasonality in the midcontinent abstract burrows attributed to the lysorophid brachydectes elongatus occur within a green mudstone lens in the lower permian wolfcampian speiser shale council grove group of eastern kansas the burrow bearing unit consists of a 100 m long lens of massive calcareous silty mudstone with a maximum thickness of 35 cm the lens also contains the fossils of fish amphibians reptiles charophytes stomachara and ostracodes carbonita the mudstone lens pinches out laterally into red pedogenically modified mudstone the burrows occur in three layers at the top of each layer is a subaerial exposure surface indicated by rhizoliths mudcracks and coarse grained lags the mudstone lens is interpreted as the deposit of a shallow ephemeral pond the burrows occur in three vertically and temporally separated clusters with concentrations up to 20 m2 the burrows show two types of architecture type i burrows are elongate elliptical tubes 4 32 cm long and 2 7 cm in width type ii burrows are short elliptical tubes 1 5 3 5 cm in length and 2 5 5 cm in width the burrow fill consists of a mudstone capped by sandy siltstone each burrow layer contains a varying number of articulated and disarticulated lysorophid skeletons within the burrows and surrounding matrix while similar to permian lungfish burrows the architecture and surficial morphology of the lysorophid burrows permits their distinction even in the absence of body fossils the occurrence of burrow layers capped by subaerial exposure surfaces and separated by layers of non burrowed massive mudstone indicates that burrowing occurred in response to episodic perhaps seasonal droughts on the permian coastal plain the lysorophid burrowing behavior is analogous to that of the extant amphibians amphiuma sp and siren intermedia which inhabit rivers and ponds in the southeastern usa

palaeonvironmental and palaeoecological significance of flamingo like footprints in shallow lacustrine rocks an example from the oligocene miocene vinchina formation argentina abstract this article describes the lacustrine trace fossil assemblage of the late oligocene early miocene vinchina formation of northwest argentina the thick 5000 m continental succession of the formation is essentially fluvial with thin aeolian and lacustrine intervals the trace fossil assemblage from the lacustrine facies is dominated by bird footprints notably flamingo like palmate bird footprints and also contains invertebrate traces the assemblage is of contrasting composition with those of the ubiquitous fluvial facies of the vinchina formation we identify the possible trace maker of the web footed bird footprints and infer the palaeoenvironmental and palaeoecological meaning of the lacustrine trace fossil assemblage of the vinchina formation the lacustrine succession is mainly composed of wave rippled fine grained sandstones and siltstones and wave rippled heterolithic facies with subordinate laminated mudstone and medium grained sandstone with parallel lamination or cross bedding metre scale shallowing upward cycles are typical and desiccation cracks were observed in a single bedding plane the analysed interval was deposited in a wave dominated littoral zone of a shallow permanent lake basin ichnofossils were found mostly in three trampled horizons of the upper part of the analysed succession the trace fossil assemblage is dominated by phoenicopterichnum isp flamingo like footprints slender bird tracks without web traces and triangular and fusiform hypichnial ridges interpreted as bird undertracks the remaining trace fossils are lockeia siliquaria bivalve resting trace rusophycus isp shallow arthropod burrow taenidium barretti endostratal meniscate burrow and small hypichnial double knobs possible beak probing marks neoichnological observations on modern chilean flamingo footprints phoenicopterus chilensis suggest that phoenicopterichnum isp is morphologically akin to modern flamingo footprints although its average size is slightly smaller the likely producers of the fossil footprints are members of the palaelodidae and phoenicopteridae which are recorded in south america since the late oligocene phoenicopterichnum isp appears in cuasi parallel trackways with short pace length and forming a low angle with ripple crests by comparison with observations of modern flamingo behaviour during this study and of shorebird studies from the literature these tracks and trackways likely reflect flock feeding behaviour probably filter feeding in a subaqueous belt parallel to the waterline invertebrate ichnofossils that appear on the same slabs from trampled horizons are mainly triangular and fusiform hypichnial ridges while phoenicopterichnum isp and sparse small hypichnial double knobs also occur in consequence it is possible that these birds were foraging on small invertebrates represented by lockeia siliquaria rusophycus isp and probably taenidium barretti in the coast of the vinchina lake the only fossil evidence for these invertebrates is the impression of articulated valves probably belonging to a small mollusc potential producer of lockeia trace fossil assemblages dominated by flamingo like footprints including ichnogenera phoenicopterichnum culcitapeda and similar unnamed tracks are indicative of alkaline and or saline waters as suggested by the specialised filter feeding mechanism of late oligocene to modern phoenicopteriformes these particular assemblages are distinguished as a subset within the shorebird ichnofacies with a definite palaeoenvironmental and palaeoecological meaning the phoenicopterichnum ichnosubfacies

age and origin of the well preserved organic matter in internal sediments from the silesian cracow lead zinc deposits southern poland the molecular and petrographic characteristics of organic matter in internal sediments from the mississippi valley type lead zinc deposits in southern poland reveal immature and well preserved organic matter huminite reflectance values of organic matter in all internal sediments are low with a mean value of 0 29 corresponding to a lignite range of coalification most organic compounds in the organic matter e g cadalene retene simonellite perylene and sitosterol and its transformation products stigmastanol and stigmasta 3 5 dien one as well as lignin degradation compound products e g benzoic acid vanillin 4 benzaldehyde benzenedicarboxilic acids and hydroxybenzoic acids are of terrestrial origin monosaccharides with dominant and glucose were identified as possible remnants of cellulose degradation products suggesting an excellent state of organic matter preservation given that monosaccharides are preserved only under conditions of limited oxygen after sedimentation resulting from the rapid accumulation of internal sediments in meteoric paleokarst cavities followed by insignificant diagenesis petrologic and palynological data on internal sediments clearly indicate a middle triassic age for organic matter and for the development of a triassic meteoric karst system immediately after anisian carbonate sedimentation

helical burrow casts of therapsid origin from the beaufort group permian of south africa abstract large helical burrow casts of vertebrate origin have been discovered at several localities in the lowermost strata of the teekloof formation of the beaufort group permian in the southwestern karoo basin south africa they are not only the oldest but also the first vertebrate burrows of helical geometry to be found in rocks of pre mammalian age the burrow casts are vertically disposed spiralling tubes filled with fine grained sandstone or siltstone often with a calcareous cement tube diameters gradually increase from 60 mm in the upper entrance decline through two non contacting dextral coils to about 160 mm at the base of the spiral whereupon the tube straightens and widens into a horizontal terminal chamber burrow depths range from 0 5 0 75 m and the ramp angle ranges from 10 to 32 although within any single spiral it is constant articulated skeletons of the small dicynodont diictodon have been found within the terminal chambers and spirals of three sand filled burrows linear ridges preserved on the outer walls and floor of some of the terminal chambers resemble scratch marks possibly made by the claws and beak of diictodon during burrow excavation the sedimentary sequences at two separate localities are interpreted as having been deposited by episodic sheet floods and distributary splay fans in the proximal floodbasin areas flanking an aggrading meanderbelt rise comparison is drawn between helical burrow casts in the lower beaufort and other recorded occurrences in particular daimonelix a beaver burrow from the miocene of nebraska fundamental similarities far outweigh differences to the extent that the beaufort helical burrows may be grouped with the daimonelices it is concluded that the excavation of large helical burrows an activity usually attributed to rodents was pre empted by mammal like reptiles some 50 million years before the first anatomical mammals evolved

the effects of callianassa bioturbation on the preservation of carbonate grains in davies reef lagoon great barrier reef australia abstract coring air life excavation and tracer sediment experiments in the lagoon floor sediments of davies reef revealed that callianassid shrimp had produced during their feeding a 5 60 cm thick surface layer of moderately to poorly sorted gravel free sediment above very poorly sorted gravelrich sediment the subsurface gravel is epilithic in origin close to reef framework but consists predominantly of infaunal molluscs through most of the lagoon these infaunal skeletons tend to be buried rapidly in a well preserved state escaping the microboring that attacks all grains on the surface two geologically significant points emerge first the surface layer will not get preserved in its present form and any analyses of surface samples can give a false impression of the accumulating sedimen pile and the prevailing hydraulic regime and second the combination of continuous fine sediment recycling and surface microboring can lead to a bias in the fossil reefal limestone record with epilithic organisms seemingly subordinate to infaunal molluscs

recognition of the sedimentary architecture of dryland anabranching anastomosing rivers abstract the application of rigorous criteria for identifying fluvial style from sedimentary deposits is crucial if environmental reconstructions from stratigraphy are to be reliable from modern observations it appears that anabranching anastomosing rivers can be divided into separate humid and dryland classes each class has dissimilar characteristics to the other necessitating different criteria for their recognition in the rock record the criteria being used by sedimentologists to recognize deposits of anabranching rivers are derived solely from modern examples in humid regions heavily biased to a few specific cases in canada these criteria are dominated by the concept of ribbon sandstone bodies encased in fine grained floodplain sediment with an overall low sand to mud ratio in the succession there has been a general failure to appreciate that dryland anabranching rivers have characteristics significantly different from these and almost certainly leave a sedimentary record quite dissimilar to that previously expected avulsion or obtrusion the gradual formation of an alternative channel are the characteristic dynamic of anabranching rivers forming and maintaining coexisting multiple anabranch channels avulsion or obtrusion require stream banks to have a high resistance to erosion usually achieved by cohesive bank sediments or the reinforcement of banks by vegetative root mats in some drylands riparian vegetation can be sparse and bank resistance may depend in large part on a high clay content here channel fills are mud dominated and floodplains have a uniform fine grained character which is usually structureless because of intense pedoturbation and some bioturbation the evidence from such present day dryland anabranching rivers suggests that their sedimentary record is likely to be one of laterally extensive mud rich beds with weak or enigmatic fluvial indicators elsewhere dryland anabranching systems are sand dominated their banks reinforced with riparian gallery forests sustained by infrequent flow and a shallow water table though the stratigraphy of these has barely been investigated they are clearly different from humid region anabranching systems for their channels and islands are predominantly sandy anabranching rivers with prominent channel sandbodies separated by muddy islands have never been described from contemporary drylands the interpretation of a dryland origin for ancient stratigraphic successions with this form is made therefore without evidence that they can actually exist in the light of this such interpretations should be reevaluated

ghost shrimps decapoda axiidea callianassidae as producers of an upper miocene trace fossil association from sublittoral deposits of lake pannon vienna basin slovakia numerous trace fossils are described from the late miocene sediments of the bzenec formation exposed at the gbely section the vienna basin slovakia during deposition of the sediments the area was part of the large long lived brackish to freshwater lake pannon most of the trace fossils are attributed herein to egbellichnus jordidegiberti igen et ispec nov and are interpreted as burrows produced by decapod crustaceans specifically by a ghost shrimp of the family callianassidae this interpretation is based on two independent lines of evidence environmental requirements of large bioturbators and the burrow morphology itself the new ichnotaxon is distinguished from other related ichnotaxa by a combination of typically inclined roughly at an angle of 45 cylindrical burrows absence of lining and tunnels making loops or bends at approximately right angles the burrow systems at gbely document the survival of ghost shrimp long after the closure of all seaways and the origin of lake pannon as today no ghost shrimp are known from long lived brackish lakes egbellichnus from gbely is the only although indirect record of ghost shrimp from a brackish lake environment reported so far

neogene deformation of the flat subduction segment of the argentine chilean andes magnetostratigraphic constraints from las juntas la rioja province argentina substantial neogene deformation occurred in the part of the andes mountains and the sierras pampeanas that overlie a subhorizontal segment of the subducting nazca plate in northern argentina the history of the volcanic arc suggests that the nazca plate attained the present low angle inclination between about 17 and 10 ma with the region underlain by the flat nazca plate widening eastward thereafter we compare the history of deformation provided by magnetostratigraphy of miocene strata in foreland and intermontane basins to the history of the subducting plate at las juntas in the precordillera thin skinned thrust belt 4 780 m of neogene nonmarine strata record the initiation and termination of sedimentation in a segment of a foreland basin magnetostratigraphic data complemented by fission track dating of an interbedded tuff indicate that the strata span from 18 to 9 ma the earliest strata correlate to the end of a time of volcanic activity in the magmatic arc and the beginning of reverse faulting in the frontal cordillera subsequently the deformation front migrated eastward generating the precordillera thrust belt and finally the sierras pampeanas basement uplifts the rate of strata accumulation varied systematically as new uplifts arose with a maximum rate exceeding 1 0 mm a between 15 and 12 ma a correlation between the deformational history and the geometric history of the subducted slab suggests that thrusting migrated eastward as the angle of subduction shallowed although large scale factors affecting the plate margin beyond the flat slab segment may have partly induced the compressional deformation this correlation suggests that processes related to flat subduction are of importance in deforming the continental plate

hazard and seismic reinforcement analysis for typical large dams following the wenchuan earthquake abstract the primary aim of this research is to analyze the hazards and seismic performance of reservoirs and typical large dams based on a field investigation following the wenchuan 8 0 earthquake the current seismic performance standards being achieved are discussed and further suggestions are given for super high dams based on field investigations statistics are also given on damaged small reservoirs and damage severities due to the many various types of earthquake threat it is of interest to note that the major structures of the medium sized hydropower stations on the minjiang river did withstand the wenchuan earthquake despite earthquake intensity exceeding engineering design expectations all the dams remained overall stable the shapai roller compacted concrete rcc arch dam and the zipingpu concrete faced rockfill cfr dam suffered damage the main earthquake induced hazards to the dam structures and to both abutments are detailed case study analyses of the hazards and reinforcement provision revealed that 1 the wenchuan earthquake proved very dangerous for small reservoirs with destroyed reservoirs widely distributed the risk of failure of small dams can be classified into three levels based on field investigation 2 the damage to and behavior of the large dams in the area affected by the earthquake prove that the chinese codes relating to the seismic design of large dams are appropriate 3 appropriate reinforcement can increase the overall stiffness of abutments riverbed foundation and the adjacent slopes further improving the seismic performance of dams 4 the design and management of emergency responses to cope with extreme conditions should be improved and a unified response platform covering all hydropower engineering projects in each valley should be established the effects to be expected and the seismic design measures to be taken still pose great challenges for engineers in respect of large dams

lungfish burrows in the upper triassic chinle and dolores formations colorado plateau abstract vertical to inclined cylindrical trace fossils that occur in the upper triassic chinle and dolores formations on the colorado plateau are interpreted to be the casts of lungfish burrows the casts which are as much as 11 cm in diameter and as much as 1 6 m long were formed by passive silicilastic and carbonate sedimentation into apparently abandoned lungfish burrows locally the burrow fillings are overwhelmingly abundant and many intersect and have destroyed former burrow fillings superposition of bioturbation episodes has obliterated most primary sedimentary structures this bioturbation has contributed to the mottled coloration and the knobby weathering texture of the rocks the burrow fillings occur ubiquitously in three lithofacies comprising 1 purple and white mottled ilicified sandstone and siltstone 2 red and brown siltstone and mudstone and 3 pink and green limestone these strata were deposited in a continental environment that included fluvial channels and floodplains sand sheets and playa mudflats and lacustrine basins marshes and deltas the identification of the trace fossils as the positive casts of lungfish burrows is based on their morphologic similarity to previously identified lungfish burrows and to available hand specimens the widespread occurrence of the lungfish burrows in the chinle and dolores formations attests to the extensive habitat that supported lungfish in the late triassic and to conditions favorable for burrow preservation analogy with the environments that support modern lungfish populations suggests that the late triassic climate in the study area provided sufficient moisture to support large populations of lungfish and that this climate was probably punctuated by seasonally dry periods

lungfish burrows in the upper triassic chinle and dolores formations colorado plateau comments on the recognition criteria of fossil lungfish burrows discussion and reply

paleoenvironmental analysis of the neotropical fossil mammal site of cerdas bolivia middle miocene based on ichnofossils and paleopedology abstract the early middle miocene langhian age site of cerdas in the southern bolivian altiplano has produced a diverse fauna of extinct mammals 15 species in seven orders and 11 families in this study we use paleosols and ichnofossils to reconstruct its paleoenvironment and the conditions in which its fossils were preserved the described paleosols represent three pedotypes and three distinct landscape surfaces in an alluvial system type 1 paleosols are interpreted as haplusteps inceptisols that formed on a proximal floodplain in a subhumid to humid patchy shrubland with seasonal variation in precipitation and associated changes in soil moisture conditions landscape 1 type 2 paleosols are interpreted as dystrudepts that formed on a well vegetated distal floodplain in a seasonal humid climate with ground covering shrubland vegetation landscape 2 type 3 paleosols are interpreted as calciustolls mollisols that formed in a shifting alluvial environment in a seasonal sub humid to semi arid open environment landscape 3 ichnofossil assemblages of cerdas include skolithos planolites macanopsis parowanichnus rhizohaloes and rhizotubules these were produced by detritivorous herbivorous and faunivorous soil arthropods as well as plant roots and represent soil communities not normally preserved as body fossils that were living within a heterogeneous alluvial environment the physical and geochemical properties of the paleosols and associated ichnofossil assemblages indicate that the paleolandscapes were composed of shrublands and open environments that experienced changes in moisture regimes due to seasonal precipitation and flooding events and had varying degrees of temporal stability our analysis is the first detailed study of pre pleistocene cenozoic paleosols and trace fossils from the southern tropics mid latitudes of south america and one of the few focused on important fossil mammal bearing sediments

hydrologic issues in arid unsaturated systems and implications for contaminant transport analysis of unsaturated flow and transport in arid regions is important not only in water resource evaluation but in contaminant transport as well partic ularly in siting waste disposal facilities and in remediat ing contaminated sites the water fluxes under consid eration have a magnitude close to the errors inherent in measuring or in calculating these water fluxes which makes it difficult to resolve basic issues such as direction and rate of water movement and controls on unsaturated flow the purpose of this paper is to review these issues on the basis of unsaturated zone studies in arid settings because individual techniques for estimating water fluxes in the unsaturated zone have limitations a variety of physical measurements and environmental tracers should be used to provide multiple independent lines of evidence to quantify flow and transport in arid regions the direction and rate of water flow are affected not only by hydraulic head gradients but also by temperature and air pressure gradients the similarity of water fluxes in a variety of settings in the southwestern united states indicates that vegetative cover may be one of the pri mary controls on the magnitude of water flow in the unsaturated zone however our understanding of the role of plants is limited most unsaturated flow in arid systems is focused beneath topographic depressions and diffuse flow is limited thick unsaturated sections and low water fluxes typical of many arid regions result in preservation of paleoclimatic variations in water flux and suggest that deep vadose zones may be out of equilib rium with current climate whereas water movement along preferred pathways is common in humid sites field studies that demonstrate preferential flow are restricted mostly to fractured rocks and root zones in arid regions results of field studies of preferential flow in humid sites generally restricted to the upper 1 2 m because of shallow water tables cannot be applied readily to thick vadose zones in arid regions

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