changes in brachiopod body size prior to the early toarcian jurassic mass extinction abstract herein we analyze the shell length as estimation of the body size of several brachiopod assemblages recorded into the extinction interval prior to the early toarcian mass extinction they were collected from representative localities around the iberian massif spain and portugal presenting different paleoenvironmental conditions the analysis performed has revealed two different trends of spatial and temporal changes in body size 1 mean size decreases in the assemblages following an anticlockwise pattern from iberian to lusitanian basins in relation to the progressive environmental stress caused by shifts on terrigenous input and in depth this diminution results from changes in the relative abundance of bigger or smaller species in each area rather than from miniaturization of the taxa 2 some new evolved or more resilient species show increasing sizes over time along the extinction interval this increase affects both big spiriferinides in the iberian basin and small rhynchonellides and koninckinides in the lusitanian basin and runs in parallel to the drop in diversity and the progressive warming of the sea water in this interval in all the localities this increase in body size has been related to the changes in diversity that could have favored the access to resources for resilient or new evolved species the observed patterns are comparable with those detected in the end permian crisis and might indicate a generalizable response to similar biotic crises

observations of nearshore circulation alongshore uniformity 1 nearshore circulation observed for 4 months on a 200 m long stretch of natural beach during the sandyduck field experiment is shown to be alongshore uniform an alongshore momentum balance between wind and wave forcing and bottom stress cross shore integrated between the shoreline and approximately 4 m water depth holds on each of five instrumented cross shore transects skill 0 87 the corresponding five best fit drag coefficients are similar consistent with the assumption that terms in the momentum balance associated with alongshore nonuniformity are negligible in addition the alongshore nonuniformity of the circulation and bathymetry were examined at five cross shore locations except near the shoreline the circulation and bathymetry were rarely strongly alongshore nonuniform and the circulation nonuniformities were usually no larger than expected from current meter noise alone near the shoreline the bathymetry was more irregular and the circulation was often detectably nonuniform although no relationship between bathymetric and circulation nonuniformities was found the closure of the alongshore momentum balances on cross shore transects and the observed alongshore uniformity of the circulation on four of five alongshore transects demonstrates that the simplified dynamics of alongshore uniform circulation are valid during the experiment

hydrogeochemical factors effecting the scaling problem in balcova geothermal field izmir turkey reservoir fluid compositions have been assessed from analytical data on water samples collected from thermal and cold waters in balcova geothermal field the results of mineral equilibrium modelling indicate that the waters with some exceptions are systematically supersaturated with respect to calcite aragonite dolomite chalcedony and quartz but undersaturated with respect to amorphous silica celestite anhydrite and gypsum and undersaturated or supersaturated with respect to barite low albite k feldspar gibbsite and fe oh 3 a calculation of mineral saturation states and geochemical analyses of scale and field observations show that carbonate minerals calcite aragonite and dolomite are most likely to be precipitated as a scale type besides carbonates scale formation risk of amorphous silica fe oh 3 a anhydrite barite and celestite minerals should be taken into account in some wells and surface equipment most of the waters with some exceptions have carbonate scaling risk at all temperatures whereas the other scaling risks only exist over a limited temperature range while silica fe oh 3 a and barite show a scaling tendency at low temperatures anhydrite and celestite scaling occurs at higher temperatures

linear modeling of infragravity waves during delilah 1 the generation of infragravity waves by directionally spread shortwaves incident on an alongshore uniform beach is investigated two mechanisms responsible for the generation of infragravity waves are considered the release of the bound infragravity waves associated with changes in the spatial variation of the incident shortwave energy and the forcing of trapped waves by obliquely incident directionally spread shortwaves the infragravity wave response is examined using linear shallow water equations taking into account the presence of bottom friction setup of the mean water level rollers and longshore current summing all infragravity contributions due to difference interactions between pairs of shortwave spectral components with the same frequency difference results in infragravity energy density spectra calculated spectra are compared with measured spectra obtained during the delilah field experiment for 11 consecutive days including calm mild and storm conditions in the comparison attention is focused on the frequency distribution of the infragravity energy density throughout the surf zone and the transformation of the root mean square infragravity wave height the measured infragravity response in the frequency range from 0 01 to 0 06 hz is reproduced by the computations with relatively broad spectra offshore and a clear nodal structure closer to shore typically 80 of the infragravity wave height variability is explained by the model of which 30 or less is due to bound infragravity waves differences occur mainly during storm events in which the infragravity energy is underpredicted in the outer surf zone and overpredicted in the inner surf zone

geothermometry and circulation depth of groundwater in semnan thermal springs northern iran semnan thermal springs with high tds and moderate temperature are located northwest of semnan the northern part of iran the spatial and temporal variations of physicochemical characteristics of the thermal and cold springs were investigated for the recognition of origin and dominant hydrogeochemical processes results show that the thermal springs have the same origin but due to different ascending flow paths and different conductive cooling mechanism their temperatures vary the chemical composition of thermal waters is controlled by dolomite halite and sulfate minerals dissolution and calcite precipitation and bacterial sulfate reduction the concentration of major and trace elements in the thermal springs does not change in wet and dry seasons notably because they are derived from old groundwater with deep circulation and high temperature seasonal change in the concentration of some trace elements is due to the seasonal variation of ph eh temperature and dilution by shallow waters decreasing so4 and carbonate saturation index and increasing na cl ratios and ca content in the dry season show dilution effect caused by the previous heavy rainfall events the temperature of the heating reservoir based on k mg chalcedony quartz and chemical equilibrium approach was approximately estimated in the range of 60 80 c hydrogeologically a conceptual model was suggested for the thermal springs the general groundwater flow direction is probably from the dolomite lar formation in chenaran anticline toward the adjacent syncline in a confined condition and then a thrust fault acts as a conduit and redirects the thermal water to the emerging springs at the surface

demise of the last two spire bearing brachiopod orders spiriferinida and athyridida at the toarcian early jurassic extinction event brachiopods were severely hit by several mass extinctions which fundamentally shaped their long evolutionary history after the devastating end permian extinction the fate of the four surviving orders differed significantly during the triassic and jurassic two orders the rhynchonellids and terebratulids are extant today whereas spiriferinids and athyridids which possess spiral brachidia suffered heavy losses at the end of the triassic and became extinct in the early jurassic toarcian event although the doom of the spire bearing orders has been thought to be related to physiological traits extinction selectivity across the end triassic and toarcian event has not been rigorously assessed previously and the reasons for their demise at the later and lesser toarcian event rather than at the earlier and greater end triassic crisis remained unexplored using primarily the paleobiology database we constructed diversity curves estimated taxonomic rates and assessed the temporal changes in geographic distribution of the two spire bearing and two other orders in the triassic jurassic interval after shared trends and similar origination rates in the post permian recovery leading to a late triassic diversity maximum the end triassic extinction was selective and preferentially eliminated the spire bearers in contrast to the rebound of rhynchonellids and terebratulids spire bearers failed to recover in the early jurassic and their repeated selective extinction at the toarcian event led to their final demise the end triassic event also terminated the worldwide geographic distribution of spire bearers confining them to the western tethys whereas the other groups were able to re establish their cosmopolitan distribution the morphologically diverse spire bearers represent specialized adaptation which further increased their extinction vulnerability compared to the other groups with conservative biconvex shell morphology another key difference is the physiological disadvantage of the fixed lophophore and passive feeding of spire bearers which became critical at times of increased environmental stress the spire bearing spiriferinids and athyridids were dead clades walking in the early jurassic and their disappearance in the early toarcian represents the last major order level extinction event for the brachiopods

hydrogeology and hydrogeochemistry of a coastal low temperature geothermal field a case study from the datca peninsula sw turkey the thermal springs at the golbasi geothermal field located in the southwest coastal region of turkey discharge from the mesozoic aged fissured carbonate aquifer the temperature specific electrical conductivity and ph values of the thermal waters are respectively 21 6 29 4 c 4020 57 200 s cm and 6 85 7 35 thermal waters are na cl type brackish to saline waters the golbasi geothermal system is fed by meteoric waters and local seawater the waters are heated at depth by high geothermal gradient caused by the recent tectonic activity in the deep and ascend to the surface through fractures and faults by convection and emerge as thermal springs the thermal waters mix in different proportions with seawater 5 58 and fresh cold waters during the moving up to the surface isotope data 18o 2h and tritium show that the thermal waters are of meteoric origin and the residence time at the reservoir is at least 50 years almost all the waters are saturated with respect to ca montmorillonite gibbsite k mica illite kaolinite fe oh 3 a calcite dolomite and barite minerals the most expected minerals that cause scaling at outlet conditions during the production and utilization of golbasi geothermal waters are calcite dolomite and some barite various chemical geothermometers na k mg ternary diagram and mineral equilibrium diagrams suggest that the reservoir temperature is around 50 100 c

frequency wavenumber velocity spectra taylor s hypothesis and length scales in a natural gravel bed river 1 macroscale turbulent coherent flow structures in a natural fast flowing river were examined with a combination of a novel 2 mhz acoustic doppler beam adb and a maximum likelihood estimator mle to characterize the streamwise horizontal length scales and persistence of coherent flow structures by measuring the frequency f streamwise wavenumber ks energy density velocity spectrum e f ks for the first time in natural rivers the adb was deployed under a range of froude numbers 0 1 0 6 at high reynolds numbers 106 based on depth and velocity conditions within a gravel bed reach of the kootenai river idaho the mle employed on the adb data increased our ability to describe river motions with relatively long 10 m length scales in 1 m water depths the e f ks spectra fell along a ridge described by v f ks where vis the mean velocity over depth consistent with taylor s hypothesis new consistent length scale measures are defined based on averaged wavelengths of the low frequencye f ks and coherence spectra energetic 50 of the total spectral energy low frequency f 1 m s lmwere found to be significantly longer than their corresponding coherence lengths suggesting that the turbulent structures evolve rapidly under these conditions this is attributed to the stretching and concomitant deformation of preexisting macroturbulent motions by the ubiquitous bathymetry induced spatial flow accelerations present in a natural gravel bed river

the influence of sea state on formation speed of alongshore variability in surf zone sand bars abstract the formation time of alongshore morphological variability in surf zone sand bars has long been known to differ from one beach to the other and from one post storm period to another here we investigate whether the type of sea state i e distant swell waves or locally generated short period wind sea affects the formation time of the emerging alongshore topographic variability a numerical modeling approach is used to examine the emergence of alongshore variability under different shore normal wave forcing a research version of delft3d operating on the time scale of wave groups is applied to a schematised bathymetry with a single bar the model is then used to investigate several wave scenarios examining the impact of peak period frequency spread and directional spread on the formation time of alongshore variability results show that an increase in wave period has a large effect changing the formation time up to o 250 in case the wave period is changed from a representative value for the dutch coast t p 5 6 s to an australian south east coast value t p 10 12 s in contrast modifications in the directional and frequency spread of the wave field result only in a minor change in the formation time examination of hydrodynamics and potential sediment transport shows that the variations in formation time are primarily related to changes in the magnitude of the time averaged flow conditions variations in the magnitude of very low frequency f f these findings indicate that the development of alongshore topographic variability may be faster at swell dominated open coasts primarily due to the occurrence of longer period swell also at a given site the arrival of a long wave period swell after a storm can accelerate the emergence of variability

palaeobiogeographic patterns of the brachiopod assemblages of the iberian subplate during the late toarcian early aalenian jurassic abstract late toarcian aalenian brachiopod assemblages recorded in different basins located in and around iberia present a pattern of spatial and temporal distribution which enables two palaeobiogeographic biochoremas to be differentiated the iberian atlantic district iad which includes the lusitanian basin asturias and the basque cantabrian basin on one hand and the iberian mediterranean district imd the latter basically comprises the iberian range and the tortosa platform of the catalonian basin changes in the composition of the assemblages throughout the stratigraphical interval studied have enabled three main stages characterizing each palaeobiochorema to be recognized the first two assemblages reflect gradual individualization and isolation with frequent endemisms these two stages correspond to the iad1 iad2 imd1 and to the imd2 assemblages respectively as from the pseudoradiosa chronozone and during the aalensis and opalinum chronozones an increase in communication between the two districts can be observed as well as between these and other remote areas this stage is represented by the iad3 and the imd3 assemblages some of the brachiopods colonizing the districts are widely dispersed due to their capacity for expansion they have been found in other tethysian basins other species are exclusive to the district basins and appear to have originated in the areas close to them for the latter species the existence of two different evolutionary factories is proposed one that supplies species to the iad mainly from generic stocks as neozeilleria soaresirhynchia or praemonticlarella and another for the species reaching the basins of the imd clearly shared by other european and north african basins the atlantic evolutionary factory remains active until the aalenian and part of the early bajocian while the mediterranean is diluted since the aalenian

water geochemistry of the seferihisar geothermal area izmir turkey abstract the na cl thermal waters of seferihisar have measured temperatures of 30 153 c and conductivities of 7400 55200 s cm they issue from upper cretaceous to paleocene bornova melange rocks which are made up of sandstone shale intercalations conglomerate mafic submarine volcanics limestone lenses serpentinite and limestone bodies and their complexes through the intersection of faults the clay rich zones of the overlying neogene terrestrial sediments cap the system the heat source is the high geothermal gradient caused by graben tectonics of the area na and cl ions mainly dominate the chemistry of thermal waters thus thermal waters of the seferihisar area appear to be mixtures of groundwaters and seawater the seawater contribution in thermal waters varies from 10 to 80 assessments from empirical chemical geothermometers mineral equilibria and silica mixing model applied on the thermal waters of the seferihisar geothermal area suggest that the temperatures of the reservoir systems vary between 60 and 180 c the seferihisar geothermal area has been physically divided into five main groups and estimated reservoir temperatures provided by the entire methods give the increase as doganbey burnu karakoc spa doganbey tuzla and cumali spa areas in ascending order of reservoir temperature hydrogeochemical assessments indicate that thermal waters were mixed with cold waters before and or after heating at depth in different proportions the results of mineral equilibrium modeling indicate that the thermal waters of seferihisar are undersaturated with respect to gypsum and amorphous silica oversaturated with respect to calcite dolomite and aragonite and undersaturated or oversaturated with respect to quartz chalcedony and anhydrite

the late triassic extinction at the norian rhaetian boundary biotic evidence and geochemical signature abstract the latest triassic was an interval of prolonged biotic extinction culminating in the end triassic extinction ete the ete is now associated with a perturbation of the global carbon cycle just before the end of the triassic that has been attributed to the extensive volcanism of the circum atlantic magmatic province camp however we attribute the onset of declining latest triassic diversity to an older perturbation of the carbon cycle 13corg of global extent at or very close to the norian rhaetian boundary nrb the nrb appears to be the culmination of stepwise biotic turnovers that characterize the latest triassic and includes global extinctions of significant marine and terrestrial fossil groups these biotic events across the nrb have been largely under appreciated yet together with a coeval disturbance of the carbon cycle were pivotal in the history of the late triassic here we present new and published 13corg data from widespread sections italy greece odp australia new zealand usa canada these sections document a previously unknown perturbation in the carbon cycle of global extent that spanned the nrb the disturbance extended across the panthalassa ocean to both sides of the pangaean supercontinent and is recorded in both the northern and southern hemispheres the onset of stepwise late triassic extinctions coincides with carbon perturbation 13corg at the nrb indicating that a combination of climatic and environmental changes impacted the biota at a global scale the nrb event may have been triggered either by gas emissions from the eruption of a large igneous province pre dating the nrb by a bolide impact of significant size or by some alternative source of greenhouse gas emissions as yet it has not been possible to clearly determine which of these trigger scenarios was responsible the evidence is insufficient to decisively identify the causal mechanism and merits further study

hydrochemical and isotopic 2h 18o and 37cl constraints on evolution of geothermal water in coastal plain of southwestern guangdong province china abstract geothermal energy is abundant in guangdong province of china however majority of it is still unexploited to take full advantage of this energy it is essential to know the information of geothermal system here physical parameters such as ph and temperature major ion na ca2 mg2 cl so42 and hco3 trace elements br sr2 li and b3 and stable isotopes 2h 18o and 37cl in geothermal water non geothermal water river water cold groundwater and seawater were used to identify the origin and evolution of geothermal water in coastal plain of southwest of guangdong two separate groups of geothermal water have been identified in study area group a located in inland of study area is characterized by na and hco3 group b located in coastal area is characterized by na and cl the relationships of components vs cl for different water samples clearly suggest the hydrochemical differences caused by mixing with seawater and water rock interactions it s evident that water rock interactions under high temperature make a significant contribution to hydrochemistry of geothermal water for both group a and group b besides seawater also plays an important role during geothermal water evolution for group b mixing ratios of seawater with geothermal water for group b are calculated by cl and br binary diagram the estimated results show that about

end cretaceous brachiopod extinctions in the chalk of denmark the results of a detailed study of the brachiopods of the most complete cretaceous tertiary boundary in denmark nye kl v show an extinction pattern for this marine invertebrate group compatible with that reported for pelagic foraminifera and coccoliths and with the impact scenario the extinction is abrupt coinciding with the maastrichtian danian boundary there is no warning in the form of decreasing density decreasing diversity or early extinction of specialized groups the basal few meters of the danian are almost devoid of brachiopods and a danian brachiopod fauna starts almost as abruptly as the maastrichtian fauna disappeared the new fauna is similar to the maastrichtian as regards density and diversity and at maximum six species are common to both stages the northwest european masstrichtian chalk is composed mainly of the remains of coccoliths and pelagic foraminifera the mass extinction of these groups led to a total cessation of chalk production the chalk is overlain by a thin clay bed deposited partly under anoxic conditions this combination of anoxia and clay deposition coupled with a cessation of productivity led to the extinction of specialized groups such as the chalk brachiopods the surviving species included forms that could survive in well aerated shallow marine waters on substrates other than chalk

diversity patterns of early jurassic brachiopod assemblages from the westernmost tethys eastern subbetic abstract a detailed faunal succession based upon 6400 brachiopods from the early jurassic in the eastern external subbetic palaeogeographical domain betic range spain is characterized and analyzed this study allows recognition of five assemblages with original biostratigraphical data in sediments where biostratigraphical markers were very scarce it also enables a sound diversity dynamics pattern to be established among the brachiopod assemblages recorded this pattern shows progressive diversification from the sinemurian to the late pliensbachian although with significant episodes during the sinemurian pliensbachian transition the first initial pulses of the disintegration of the south iberian palaeomargin played an important role in the brachiopod assemblages as a notable faunal renewal event is detected assemblage 1 to assemblage 2 maximum biodiversity and abundance were reached in the pliensbachian toarcian transition due to the partial contemporaneity of assemblages 2 and 3 and the settlement of taxa from nearby palaeogeographical basins a decrease related to the early toarcian anoxic event etoae global effect is suggested after which a slight recovery began with colonization by opportunistic taxa soaresirhynchia bouchardi but pre etoae diversity and abundance were subsequently never again reached a palaeogeographical analysis has been carried out to compare taxonomic diversity dynamics in the eastern subbetic with other representative tethyan basins this study also enables palaeobiogeographical affinities to be established for the eastern subbetic domain showing mediterranean palaeobioprovince influences until the late pliensbachian early toarcian a period when replacement occurred that shows faunal unification free connection between the sub boreal and mediterranean provinces may be inferred from the late pliensbachian early toarcian onwards

geochemical assessment of mineral scaling in kizildere geothermal field turkey the mineral scaling problems in the kizildere geothermal field along with hydrogeological and geochemical properties of this field were studied in this content chemical analyses for 26 water samples from 12 water points and an additional seven geochemical analyses and six xrd analyses of the scale samples were performed measured reservoir temperatures of wells vary from 196 in the well kd 13 to 242 c in the well r 1 geothermal reservoir waters show the water types of na hco3 and na hco3 so4 estimated mineral saturations suggest that calcite aragonite strontianite dolomite amorphous silica and barite are likely to precipitate as scales these are confirmed by the results of the geochemical and xrd data of the scale samples reservoir chemistry calculations show a fluid richer in steam and acid gases with lower concentrations in the nonvolatile constituents i e cl sio2 na etc at the reservoir geochemical modeling shows that caco3 calcite and aragonite and strontianite precipitations are inevitable for production and re injection wells and surface equipment amorphous silica scaling is the important risk of re injection wells precipitations of the minerals barite anhydrite dolomite and celestite are also possible determinations of the scaling minerals and the safety temperatures to avoid or minimize the scaling problem are the most important parts of this study it was concluded that cold injection 50 c is favored or inhibitors should be used if any mineral deposition is to be prevented or reduced in injection wells

a new occurrence of the early jurassic brachiopod anarhynchia from the canadian cordillera confirms its membership in chemosynthesis based ecosystems cold seeps where seepage of hydrocarbon rich fluids occurs in the sea floor are sites that harbor highly specialized ecosystems associated with distinctive carbonate sediments although their mesozoic record is scarce and patchy it commonly includes dimerelloid rhynchonellide brachiopods here we report a monospecific assemblage of anarhynchia from a limestone boulder of early pliensbachian early jurassic age in the inklin formation of the whitehorse trough in the stikine terrane from a locality at atlin lake in northern british columbia specimens are among the largest known mesozoic brachiopods up to 9 cm in length and described here as anarhynchia smithi n sp early precipitated carbonate cement phases of the limestone have carbon isotopic composition highly depleted in 13c indicative of the influence of microbial oxidation of methane derived from a cold seep carbonate petrography of the banded fibrous cement and other characteristic components supports this paleoenvironmental inference vol

topographically controlled breaking wave induced macrovortices part 2 changing geometries this is the second part of a series examining the behaviour of breaking wave induced macrovortices the first part examined theoretically general behaviours during startup conditions and gave computational results for macrovortex generation and their evolution on widely spaced breakwaters in this paper we extend and test qualitatively and quantitatively some of the basic results of part 1 in particular the initial longshore vortex transport for a wide range of geometries ranging from narrow rip current topographies to isolated breakwaters accounting for the presence of a shoreline is found to be necessary for the representation of longshore vortex transport results show vortex motion ranging from strongly offshore in the case of a narrow rip current to strongly longshore in the case of an isolated breakwater even with the significant approximations inherent in the analytical predictions numerical computations using time domain boussinesq type equations and laboratory experiments confirm the trends part 3 examines the horizontal mixing features of wave induced flows over isolated single breakwater configuration or multiple ripcurrent configuration submerged structures

evolution of the last koninckinids athyridida koninckinidae a precursor signal of the early toarcian mass extinction event in the western tethys abstract koninckinids are a suitable group to shed light on the biotic crisis suffered by brachiopod fauna in the early jurassic koninckinid fauna recorded in the late pliensbachian early toarcian from the easternmost subbetic basin is analyzed and identified as a precursor signal for one of the most conspicuous mass extinction events of the phylum brachiopoda a multi phased interval with episodes of changing environmental conditions whose onset can be detected from the elisa mirabile subzones up to the early toarcian extinction boundary in the lowermost serpentinum zone t oae the koninckinid fauna had a previously well established migration pattern from the intra tethyan to the nw european basins but a first phase with a progressive warming episode in the pliensbachian toarcian transition triggered a koninckinid fauna exodus from the eastern central tethys toward the westernmost mediterranean margins a second stage shows an adaptive response to more adverse conditions in the westernmost tethyan margins and finally an escape and extinction phase is detected in the atlantic areas from the mid polymorphum zone onwards up to their global extinction in the lowermost serpentinum zone this migration pattern is independent of the paleogeographic bioprovinciality and is unrelated to a facies controlled pattern the anoxic suboxic environmental conditions should only be considered as a minor factor of partial control since well oxygenated habitats are noted in the intra tethyan basins and this factor is noticeable only in the second westward migratory stage with dwarf taxa and oligotypical assemblages the analysis of cold seep proxies in the subbetic deposits suggests a radiation that is independent of methane releases in the subbetic basin

the chemistry of geothermal waters in iceland iii chemical geothermometry in geothermal investigations abstract new data from geothermal wells in iceland have permitted empirical calibration of the chalcedony and na k geothermometers in the range of 25 180 c and 25 250 c respectively the temperature functions are t c 1112 4 91 log sio 2 273 15 t c 933 0 993 log na k 273 15 concentrations are expressed in ppm these temperature functions correspond well with the chalcedony solubility data of fournier 1973 and the thermodynamic data for low albite microcline solution equilibria of heloeson 1969 a new co2 geothermometer is proposed which is considered to be useful in estimating underground temperatures in fumarolic geothermal fields its application involves analysis of co2 concentrations in the fumarole steam the temperature function which applies in the range 180 300 c is logco2 37 43 73192 t 11829 103 t2 0 18923t 86 187 logt where t is in k and co2 in moles per kg of steam

observations of steady longshore currents in the surf zone abstract steady surf zone longshore currents and directional properties of the incident wave field were measured on a beach with nearly straight and parallel depth contours selected data were processed into 64 segments each of 68 2 min duration irregularly spaced throughout an 18 day period a wide variety of incident wave and longshore current conditions were observed the radiation stress spectrum sxy f was estimated from a slope array and two current meters located seaward of the surf zone in many cases the total radiation stress sxyt sxy f f contains important contributions from a wide range of frequencies in a few instances sea and swell approach the beach from different directions quadrants resulting in a new zero sxyt the strong shears and direction reversals of the longshore current that could conceivably occur in this circumstance were not observed an eof decomposition of the mean longshore current pattern shows that most 90 of the current spatial variation in the 64 runs is

mineral saturation and scaling tendencies of waters discharged from wells 150 sc in geothermal areas of turkey aqueous species distribution was calculated from the chemical composition of water discharges from 27 selected production wells with reservoir temperatures 150 sc in seven geothermal areas including kizildere salavatli germencik kavaklidere sazdere salihli caferbeyli simav and tuzla twenty five of the water compositions are relatively dilute with electroconductivity values of 1826 to 7200 s cm and are dominated by na 410 to 2027 mg kg cl 45 to 1882 mg kg and alkalinity co2 491 to 2312 mg kg two water samples from tuzla are highly saline connate waters with cl of 35 273 to 44 140 mg kg and na of 18 200 to 22 250 mg kg mineral equilibrium modeling indicates that the aquifer waters in these selected geothermal wells with some exceptions are oversaturated with respect to calcite aragonite and celestite but undersaturated with respect to gypsum anhydrite fluorite ca montmorillonite anorthite albite low gibbsite illite kaolinite and k feldspar the waters are at near saturation with respect to chalcedony quartz amorphous silica dolomite and strontianite calculation of mineral saturation states geochemical studies and field observations show that carbonate minerals calcite aragonite and dolomite amorphous silica and sulfate minerals celestite and anhydrite are most likely to be precipitated as scales in geothermal wells assessment of calcite and amorphous silica scaling tendencies for selected well waters indicates that hot injection is favorable for tuzla well t 2 50 170 sc and for kizildere wells r 1 and kd 6 around 100 sc for the other wells cold injection 50 sc is favored if calcite and amorphous silica accumulation is to be avoided in injection wells

source of arsenic based on geological and hydrogeochemical properties of geothermal systems in western turkey abstract turkey is an area of complex geology with active tectonics and high geothermal potential especially the western part of turkey is a region of abundant geothermal activity faults accommodating the deep circulation of hydrothermal fluids of meteoric origin are the primary means by which of geothermal systems are controlled in this region many of the thermal activities are related to the improved dilation on the e w strikes of the graben faults this situation serves as a suitable environment for the presence of high levels of arsenic in geothermal water resources the highest concentrations of naturally occurring aqueous arsenic as are found in certain types of geothermal waters generally those related to major graben faults in this regard high arsenic concentrations in geothermal resources have been detected in western turkey including but not limited to biga peninsulla gediz graben kucuk and buyuk menderes graben with values ranging from 1 to 1419 ppb in geothermal fluids the thermal waters have surface temperatures of up to 100 c and reservoir temperatures range from 150 to 248 c in the menderes graben from 120 to 287 c in the gediz graben and from 153 to 174 c in biga peninsula hydrogeochemically the menderes graben and gediz graben thermal waters are of the na hco 3 ca hco 3 and na so 4 types whereas some geothermal fluids such as those of tuzla and kestanbol in the biga peninsula cesme and urla are of the na cl type

hydrogeochemistry of the thermal waters from the yenice geothermal field denizli basin southwestern anatolia turkey abstract the chemical and isotopic properties of thermal waters kamara and cizmeli and cold springs from the yenice geothermal field ygf in southwestern anatolia turkey are investigated in order to establish a conceptual hydrogeochemical hydrogeological model these thermal waters derive from menderes metamorphic rocks and emerge along normal faults they are commonly used for heating of greenhouses and bathing facilities discharge temperatures of thermal waters are 32 c to 57 c mean 51 c for kamara and 35 c to 68 c mean 47 c for cizmeli whereas deep groundwaters are 15 c to 20 1 c mean 17 c and shallow groundwaters are 12 to 16 c mean 15 c kamara and cizmeli thermal waters are mostly of na ca hco3 so4 type whereas deep groundwaters are ca mg hco3 and mg ca hco3 types and shallow groundwaters are mainly mg ca so4 hco3 and ca mg hco3 types in the reservoir of the geothermal system dissolution of host rock and ion exchange reactions changes thermal water types high correlation in some ionic ratios e g na vs cl k vs cl hco3 vs cl and high concentrations of some minor elements e g as sr b cl f in thermal waters likely derive from enhanced water rock interaction water samples from ygf have not reached complete chemical re equilibrium possibly as a result mixing with groundwater during upward flow geothermal reservoir temperatures are calculated as 89 102 c for kamara and 87 102 c for cizmeli fields based on the retrograde and prograde solubilities of anhydrite and chalcedony based on the isotope and chemical data a conceptual hydrogeochemical hydrogeological model of the ygf has been constructed very negative 18o and 2h isotopic ratios kamara mean of 8 43 and 56 9 respectively and cizmeli mean of 7 96 and 53 7 respectively and low tritium values

rip current types circulation and hazard abstract rip currents are narrow and concentrated seaward directed flows that extend from close to the shoreline through the surf zone and varying distances beyond rip currents are ubiquitous on wave exposed coasts each year they cause hundreds of drowning deaths and tens of thousands of rescues on beaches worldwide and are therefore the leading deadly hazard to recreational beach users the broad definition above masks considerable natural variability in terms of rip current occurrence in time and space flow characteristics and behaviour in particular surf zone rip currents have long been perceived as narrow flows extending well beyond the breakers flushing out the surf zone at a high rate exit flow circulation regime while more recent studies have shown that rip flow patterns can consist of quasi steady semi enclosed vortices retaining most of the floating material within the surf zone circulatory flow circulation regime building upon a growing body of rip current literature involving numerical modelling and theory together with emergence of dense lagrangian field measurements we develop a robust rip current type classification that provides a relevant framework to understand the primary morphological and hydrodynamic parameters controlling surf zone rip current occurrence and dynamics three broad categories of rip current types are described based on the dominant controlling forcing mechanism each category is further divided into two types owing to different physical driving mechanisms for a total of six fundamentally different rip current types hydrodynamically controlled 1 shear instability rips and 2 flash rips which are transient in both time and space and occur on alongshore uniform beaches bathymetrically controlled 3 channel rips and 4 focused rips which occur at relatively fixed locations and are driven by hydrodynamic processes forced by natural alongshore variability of the morphology in both the surf zone and inner shelf zone and boundary controlled 5 deflection rips and 6 shadow rips which flow against rigid lateral boundaries such as natural headlands or anthropogenic structures for each rip current type flow response to changes in hydrodynamic and morphologic forcing magnitude is examined in regard to velocity modulation and changes in circulation regime providing key force response relationships of rip currents we also demonstrate that in the real world rip currents form through a mixture of driving mechanisms and the discrete rip types defined in fact form key elements in a wide and complex spectrum of rip currents on natural beaches it is anticipated that this rip current type classification will serve as a resource for coastal scientists and non specialists with an interest in the rip current hazard and as a platform for future rip current studies finally we suggest some important future research directions highlighting the need for coastal and beach safety communities to collaborate in order to improve rip current education and awareness

mass extinction and recovery of the early toarcian early jurassic brachiopods linked to climate change in northern and central spain abstract the early toarcian mass extinction event represented the most important mesozoic and cenozoic turnover of the population of brachiopods and severely affected other benthic fauna two main hypotheses have been proposed to explain the synchronous and global mass extinction an oceanic anoxic event or a warming episode to test both hypotheses the dynamics of the brachiopod assemblages below and above the extinction boundary are analyzed and compared with the seawater paleotemperature variations calculated from the 18 o data recorded in belemnite rostra five sections from northern and central spain well dated with ammonites have been selected for this study the sections show no indication of sedimentary breaks and contain abundant brachiopods which have been grouped into four assemblages the changes observed in the brachiopod assemblages show a close correlation with the changes in the seawater paleotemperatures the oldest assemblage assemblage 1 coincides with a cooling interval recorded to have taken place in the latest pliensbachian paleobiogeographical reconstruction shows that this assemblage was distributed at paleolatitudes between 30 and 45 n with a preference for relatively cool waters with the rise of temperatures that took place during the earliest toarcian tenuicostatum zone assemblage 1 was substituted by assemblage 2 which composed of different species of the same genera but considerably restricted to the warmer waters of lower paleolatitudes between 28 and 35 n coinciding with the rapid and pronounced increase in seawater temperature recorded at the tenuicostatum serpentinum zonal boundary all of these brachiopod species disappeared in the studied localities marking clearly the extinction boundary predominant southward currents through the laurasian seaway precluded the possible migration of the brachiopods to cooler northern waters the brachiopods disappearance is independent from the oxygenation degree of the sea bottom and therefore the rapid warming seems to be the most plausible cause of the mass extinction after the extinction event the recovery of the brachiopods was uneven subsequent to a brief pause recovery was rapid in central spain and in other southern areas of western tethys whereas in northern spain and in the whole of europe north of the french central massif brachiopods did not recover until the mid to late toarcian times

evaluation of groundwater hydrochemical characteristics and mixing behavior in the daying and qicun geothermal systems xinzhou basin this paper examines groundwater hydrochemical characteristics during mixing between thermal and non thermal groundwater in low to medium temperature geothermal fields a case study is made of daying and qicun geothermal fields in the xinzhou basin of shanxi province china the two geothermal fields have similar flow patterns with recharge sourced from precipitation in mountain areas heated through a deep cycle before flowing into overlying quaternary porous aquifers via fractures hydrochemical features of 60 ground and surface water samples were examined in the context of hydrogeologic information the average temperatures of the deep geothermal reservoirs are estimated to be 125 degrees c in daying field and 159 degrees c in qicun field based on na k mg geothermometry while slightly lower estimates are obtained using silica geothermometers hydrochemical features of thermal water are distinct from cold water thermal groundwater is mainly cl center dot so 4 na type with high tds while non thermal groundwater is mostly hcl 3 ca center dot mg and hco 3 ca type in the daying and qicun regions respectively hydrogeochemical processes are characterized by analyzing ion ratios in various waters higher contents of some minor elements in thermal waters such as f si b and sr are probably derived from extended water rock interaction and these elements can be regarded as indicators of flow paths and residence times mixing ratios between cold and thermal waters were estimated with cl na and b concentrations using a mass balance approach mixing between ascending thermal waters and overlying cold waters is extensive the proportion of water in the quaternary aquifer derived from a deep thermal source is lower in daying geothermal field than in qicun field 5 3 7 3 vs 6 3 49 3 mixing between thermal and non thermal groundwater has been accelerated by groundwater exploitation practices and is enhanced near faults shallow groundwater composition has also been affected by irrigation with low temperature thermal water c 2009 elsevier b v all rights reserved

transition zone width and implications for modeling surfzone hydrodynamics the surfzone associated with a wave breaking on a plane slope may be subdivided into three regions the transition zone the inner zone and the swash zone the transition zone is the region just shoreward of the point of wave breaking and is characterised by rapid wave decay and also by constant wave setdown and thus constant radiation stress in this paper an empirical expression for the width of this zone is developed from monochromatic wave data two techniques are proposed for the consideration of this phenomenon in the numerical modelling of surfzone hydrodynamics for random waves the implications of a zone of nearly constant radiation stress inside the breakpoint are examined with respect to wave induced current generation both cross shore and longshore and sediment transport prediction comparisons are made to both field and laboratory data from plane and undulating profiles

arab madagascan brachiopod dispersal along the north gondwana paleomargin towards the western tethys ocean during the early toarcian jurassic multiple approaches mainly focused on assessing the depositional environments paleotemperature chronostratigraphical and paleobiogeographical data morphometrical analyses and the study of the internal structure of spiriferinide brachiopods assigned to the genus calyptoria have revealed that this brachiopod fauna migrated from their arab madagascan homeland along the north gondwana paleomargin into the peri iberian epicontinental platform system in the same well known spreading episode suffered by the arab madagascan bouleiceras ammonite fauna over the worldwide distributed early toarcian platforms this brachiopod fauna has been so far overlooked as potential arab madagascan immigrant fauna as it was integrated together with diverse assemblages well established in the peri iberian basins dispersal of calyptoria stock was conditioned by the interplay of several factors such as the tectonic framework the development of epicontinental seas on both tethyan margins the early toarcian transgression the prevailing ocean current pattern and their limited ability for dispersal the revised chronostratigraphical framework of this dispersal episode reveals the coincidence with the thermal maximum recorded prior to the early toarcian mass extinction event etmee in the westernmost tethys ocean the concurrence of these factors played a significant role in the calyptoria spreading showing an inter tropical distribution between 0 and 30 in both hemispheres the taxonomical updating performed in the light of the current systematic trends support this adaptive strategy carried out by calyptoria species consisting of a sudden and practically synchronous dispersal without outstanding morphological changes instead of the diverse evolution of different brachiopod taxa in response to the environmental changes related to the etmee updating and rearranging of the species attributed to the genus calyptoria suggest a new systematic scheme for several former attributions supporting that lower toarcian occurrences of l undulata from westernmost tethyan areas belong to calyptoria thus pointing towards the dispersal from the northern peri gondwana seas to the westernmost tethyan epicontinental platforms similar adaptive strategies were linked to other extinction events supporting a possible pattern in the response of certain brachiopod populations to such biotic crises

rip currents under obliquely incident wind waves and tidal longshore currents abstract a field experiment on the nature of rip currents was conducted on the dutch coast which differs from previous rip current study sites because it is a wind sea dominated environment with mostly obliquely incident waves and tidally driven longshore currents during the experiment three distinct flow patterns obtained with gps tracked drifter instruments were observed 1 a locally governed circulation cell 2 an offshore current that is deflected shore parallel outside the surf zone and 3 a meandering longshore current the transition from rip currents flow patterns 1 and 2 to meandering longshore currents flow pattern 3 occurred gradually within the tidal cycle with longshore currents prevalent at mid to high tide rip currents at this site appeared at depressions in the surf zone bar and typically occurred when the water level fell below nap equivalent to msl even in the presence of obliquely incident waves and tidally driven longshore currents hindcast simulations of the drifter experiments were performed with the numerical model xbeach and showed good agreement with field observations the model was subsequently used to investigate the influence of tidal water level fluctuations longshore currents and obliquely incident waves on rip currents rip currents were initiated when the water level dropped below a specific threshold with the magnitude of the rip current associated with the water level the strength of the tidal current and its orientation with respect to the incident waves governed the offshore extent and orientation of the rip current in contrast to other studies that suggest that rip currents solely occur under shore normal or slightly oblique waves in this study both observations and numerical model simulations indicate that rip currents can exist under large angles of wave incidence when the rip channel is sufficiently wide and the wave height is small

chemical geothermometers applied to formation waters gulf of mexico and california basins abstract twelve chemical geothermometers based on the concentrations of silica and proportions of na k ca and mg in water from hot springs and geothermal wells are used successfully to estimate the subsurface temperatures of the reservoir rocks these 12 geothermometers together with a new geothermometer based on the concentrations of li and na were used to estimate the subsurface temperatures of more than 200 formation water samples from about 40 oil and gas fields in coastal texas and louisiana and the central valley california the samples were obtained from reservoir rocks ranging in depth from less than 1 000 m to about 5 600 m quartz na k ca mg and na li geothermometers give concordant subsurface temperatures that are within 10 c of the measured values for reservoir temperatures higher than about 75 c na li chalcedony and a modified na k geothermometers give the best results for reservoir temperatures from 40 c to 75 c subsurface temperatures higher than about 75 c calculated by chemical geothermometers are at least as reliable as those obtained by conventional methods chemical and conventional methods should be used where reliable temperature data are required end of article last page 588

hydrochemistry of the cesme geothermal area in western turkey abstract hydrochemical characterization of thermal waters discharged from springs and wells in the cesme geothermal area show that there are two groups one is of thermal waters from a lower aquifer composed of triassic karst limestones which are the main potential reservoir of the area they are of na cl type and between 37 and 62 c and have total dissolved solids tds with around 35 000 mg l the other group are thermal waters derived from an upper aquifer formed by neogene terrestrial sediments these have lower discharge temperatures 37 40 c and lower tds values due to their having mixed with local groundwater before emerging the isotopic and chemical data shows that the initial aqueous solution is a mixture of modern seawater and meteoric water in various proportions enrichment in 18o and d values and tritium contents 8 1 tu of thermal waters reflect a rapid circulation and the contribution of modern seawater the thermal waters are undersaturated with respect to gypsum but oversaturated or around equilibrium with respect to dolomite and calcite several chemical geothermometry techniques applied to cesme geothermal waters gave estimated reservoir temperatures of around 85 100 c

boussinesq modelling of transient rip currents the flow on a plane beach with a random directionally spread wave field was simulated with a boussinesq model the random wave spectra were directionally symmetric with their central direction perpendicular to the beach so no constant longshore current was generated variable wave averaged currents were generated because of the spatially variable wave field and sometimes formed offshore directed rip currents that appear in variable longshore locations the rip currents are associated with a vortex pair which is generated within the surfzone and subsequently propagates offshore analysis of the vorticity balance show that the main vorticity input occurs within the inner surfzone three different beach slopes and four different wave spectra are simulated the frequency duration and intensity of the transient rips depend on both the beach slope and the incident wave spectra the results have important engineering implications for the transport of material in the nearshore zone in particular on longshore uniform beaches

origin evolution and geothermometry of the thermal waters in the golemezli geothermal field denizli basin sw anatolia turkey abstract the golemezli geothermal field ggf is one of the best known geothermal fields in western anatolia turkey the exploited fluids are of meteoric origin mixed with deep magmatic fluids which interacted with the metamorphic rocks of the menderes massif the geothermal fluids are channeled along quaternary faults belonging to the main normal faults system delimiting the northern side of the denizli basin and their associated transfer zones in this study hydrochemical and isotopic analyses of the thermal and cold waters allow us to determine water rock interactions fluid paths and mixing processes two groups of thermal waters have been distinguished i group 1a comprising na so4 type and ca so4 type and ii group 1b only consisting ca hco3 type waters differently two groups were recognized in the cold waters i group 2a corresponding to ca hco3 type and ii group 2b including mg hco3 type their geochemical characteristics indicate interactions with the paleozoic metamorphic rocks of the menderes massif and with the neogene lacustrine sedimentary rocks dissolution of host rock and ion exchange reactions modify thermal water composition in the reservoir of the ggf high correlation in some ionic ratios and high concentrations of some minor elements suggest an enhanced water rock interaction none of the thermal waters has been reached a complete chemical re equilibrium possibly as a result of mixing with cold water during their pathways geothermal reservoir temperatures are calculated in the range of 130 210 c for the golemezli field very negative 18o and 2h isotopic ratios are respectively between 8 37 and 8 13 and 61 09 and 59 34 for the so4 rich thermal waters and ca 8 40 and 8 32 and 57 80 and 57 41 for the hco3 rich thermal waters low tritium

bed shear stress coefficients for longshore currents over a barred profile abstract quantitative estimates are obtained of various terms in the momentum equation governing the mean alongshore flow in the surf zone on a barred beach a movable sled was instrumented with pressure current and wind sensors to measure wave and wind forcing during the superduck experiment mean currents and bottom shear stress at various locations across the surf zone were determined particular attention is devoted to precise estimation of the cross shore gradient of the radiation stress wind forcing is found to be a first order term along with wave forcing under certain conditions time dependence of the mean longshore current is due to variable wave forcing inside the surf zone as the tide modulates the depth of waves breaking on the bar bed shear stress coefficients determined as a residual of the local alongshore momentum balance tended to decrease in magnitude shoreward mean bed shear stress coefficients and estimated error are 0 004 0 0013 0 003 0 0006 and 0 001 0 0003 for offshore the bar on top and immediately in front of the bar and in the trough

vortical surf zone velocity fluctuations with 0 10 min period observations of velocity fluctuations with periods between about 4 and 30 min thus longer than infragravity waves and referred to as very low frequency vlf surf zone motions are described and compared with numerical simulations the vlf motions discussed here exclude instabilities generated by the wave driven alongshore current velocity shear that occur in the same frequency range by selecting cases with weak alongshore currents only numerical simulations are based on the linear shallow water equations including friction and forced by nonlinear difference frequency interactions between incident sea and swell waves the model is initialized with sea and swell frequency directional spectra observed seaward of the surf zone modeled and observed vlf velocity fluctuation magnitudes agree within a factor of 2 both increase approximately linearly with increasing incident wave height and rapidly decay seaward of the surf zone observed frequency wave number f ky spectra of vlf velocity fluctuations estimated with instrumented alongshore arrays are energetic in a broad range of ky in the vortical band observed and modeled vlf pressure fluctuations are relatively weak still the model momentum balance suggests that vlf pressure gradients are as important as the nonlinear wave group forcing by sea and swell in accelerating decelerating the vlf velocities model calculations demonstrate that the vlf f ky response is a function of the modulations of short wave forcing associated with the frequency directional distribution of the incident sea and swell spectra this results in vlf motions which span the surf zone and have o 50 1000 m alongshore scales with o 200 2000 s time scales given the fact that modulations of short waves resulting from directionally spread incident waves are common during field conditions we expect vlfs to be ubiquitous

end ordovician extinctions a coincidence of causes the end ordovician hirnantian extinction was the first of the five big phanerozoic extinction events and the first that involved metazoan based communities it comprised two discrete pulses both linked in different ways to an intense but short lived glaciation at the south pole the first occurring at or just below the normalograptus extraordinarius graptolite biozone mainly affected nektonic and planktonic species together with those living on the shallow shelf and in deeper water whereas the second within the n persculptus graptolite biozone was less focused eradicating faunas across a range of water depths in all about 85 of marine species were removed proposed kill mechanisms for the first phase have included glacially induced cooling falling sea level and chemical recycling in the oceans but a general consensus is lacking the second phase is more clearly linked to near global anoxia associated with a marked transgression during the late hirnantian most recently however new drivers for the extinctions have been proposed including widespread euxinia together with habitat destruction caused by plate tectonic movements suggesting that the end ordovician mass extinctions were a product of the coincidence of a number of contributing factors moreover when the deteriorating climate intensified causing widespread glaciation a tipping point was reached resulting in catastrophe

structural lithological and geodynamic controls on geothermal activity in the menderes geothermal province western anatolia turkey western turkey belongs to the regions with the highest geothermal potential in the world resulting in significant electricity production from geothermal resources located predominantly in the menderes massif although geothermal exploitation is increasingly ongoing geological and physical processes leading to the emplacement of geothermal reservoirs are hitherto poorly understood several studies on the menderes massif led to different interpretations of structural controls on the location of hot springs and of the heat source origin this paper describes geological evidence showing how heat is transmitted from the abnormally hot mantle to the geothermal reservoirs on the basis of field studies we suggest that crustal scale low angle normal faults convey hot fluids to the surface and represent the first order control on geothermal systems at the basin scale connected on low angle normal faults kilometric high angle transfer faults are characterized by dilational jogs where fluids may be strongly focused in addition favourable lithologies in the basement e g karstic marble could play a critical role in the localization of geothermal reservoirs finally a compilation of geochemical data at the scale of the menderes massif suggests an important role of the large mantle thermal anomaly which is related to the hellenic subduction heat from shallow asthenospheric mantle is suggested to be conveyed toward the surface by fluid circulation through the low angle faults hence geothermal activity in the menderes massif is not of magmatic origin but rather associated with active extensional tectonics related to the aegean slab dynamics i e slab retreat and tearing

diagnosing non meteorically induced variations in the chemistry of saline springs of the vrancea seismic area romania a monitoring operation conducted over more than seven years has been addressing chemical fluctuations displayed by several cool low discharge springs located close to the highly seismic vrancea area romania those outflows compositions proved to be strongly controlled by binary essentially isochemical mixing between a deep origin brine and meteoric freshwater by taking advantage of this particular setting there have been constructed diagrams aimed at investigating how the groundwater discharges na k mg geothermometric parameters fluctuated as a function of the chloride content taken to be an estimator of the freshwater induced dilution we made use of the reciprocal algebraic relationships existing between the equations describing the na k mg geothermometric parameters na k temperature and k mg temperature on the one hand and the so called maturity index mi on the other in an accordingly derived plot of mi against the logarithm of the chloride concentration a series of data points being quite uniformly off set from the mi dilution curve constructed for an apparently regular period suggested that episodically all concerned springwaters were simultaneously subject to some similar changes in the controlling geochemical processes one such modification intervened 3 4 months before the occurrence of the strongest earthquake m text w 5 8 of the hydrochemical monitoring period the consequently derived interpretation was that then the numerical values of certain geothermometric coefficients were likely altered such a process could be consistent with changes in the alkali feldspars solubility relationships possibly in response to episodic al si complexing which might develop within a hypothesised still active exhumation channel

hydrogeochemical characteristics and genesis of the high temperature geothermal system in the tashkorgan basin of the pamir syntax western china abstract high temperature geothermal systems in china such as those found in tenchong and tibet are common a similar system without obvious manifestations found in the tashkorgan basin in the western xinjiang autonomous region however was not expected the results from borehole measurements and predictions with geothermometers such as quartz na k and na k mg indicate that the reservoir temperature is approximately 250 260 c geothermal water is high in total dissolved solids 2 5 g l and sio 2 content 273 mg l and the water type is cl so 4 na likely resulting from water rock interactions in the granodiorite reservoirs based on isotope analysis it appears to be recharged by local precipitation and river water evidence from the relationships between major ions and the cl and molar na cl ratio suggests mixing between deep geothermal water and shallow cold groundwater during the upwelling process mixing ratios calculated by the relationship between cl and sio 2 show that the proportion from cold end members are 96 99 and 40 90 for riparian zone springs and geothermal water from boreholes respectively active regional tectonic and neo tectonic movements in the pamir syntax as well as radioactive elements in the granodiorite reservoir of the himalayan stage provide basis for the high heat flow background 150 350 mw m 2 nnw trending fault systems intersecting with overlying ne faults provide circulation conduits with high permeability for geothermal water

linking western tethyan rhynchonellide morphogroups to the key post palaeozoic extinction and turnover events abstract genetic control undoubtedly plays the most decisive role in the development of characters in rhynchonellides especially in those structural features such as shell microstructure and brachidial architecture however considering the relationship between shell microstructure and type of crura in post palaeozoic rhynchonellides supported by recent growing research the present study links this striking matching to the distribution of rhynchonellide morphogroups around the main post palaeozoic mass extinction and diversification events innovatively introducing the ribbing pattern as a feature widely argued as indicator of deeper shallower habitats and particular ecological conditions the analyses performed on the western tethys rhynchonellide database and directly on 28 species from the peri iberian margins around selected post palaeozoic extinction diversification episodes reveal a recurrent distribution pattern according to the habitat considered epicontinental vs epioceanic the smooth eurinoid septifal arcual body plan is the distinctive inhabitant of deeper epioceanic environments also being the last to withdraw from the epicontinental platforms when the environmental conditions were adverse and the pioneers or opportunistic taxa conducting repopulation of these epicontinental habitats when the conditions were re established after crises the ribbed eurinoid falciform morphogroup seems to be the more resilient stock on epicontinental platforms in relation to ecological crises conversely the ribbed leptinoid raducal group is typical inhabitant of epicontinental seas when normal conditions prevail and shows an uneven distribution unlinked to critical events suggesting a more specialist pattern with a diversification related with a secondary differentiation it is suggested that this distribution dynamic of morphogroups was controlled by the availability of requirements to generate each type of crura and microstructure in epicontinental epioceanic habitats such as metabolic or oxygen restrictions or the filter feeding efficiency of the lophophore a research line starting point is thus herein introduced which can lead to shed light into the adaptive strategies of rhynchonellides relating particular morphotypes with potential triggering factors of mass extinction events

brachiopods and chemosymbiotic bivalves in phanerozoic hydrothermal vent and cold seep environments a compilation of 37 fossiliferous phanerozoic marine deposits interpreted to represent ancient hydrothermal vent or cold seep habitats reveals that articulate brachiopods particularly rhynchonellides and terebratulides were relatively common constituents of these chemosynthetic settings from the devonian through the early cretaceous but were rare in such paleoenvironments from the late cretaceous to the present late devonian vent and seep settings were dominated by rhynchonellides dzieduszyckia eoperegrinella morphologically similar to cretaceous seep restricted peregrinella all of which are purported to be closely related phylogenetically bivalve genera with extant chemosymbiotic descendants first appeared in vent seep deposits during the late jurassic and were prevalent therein after the early cretaceous these bivalves include members of five families vesicomyidae mytilidae solemyidae thyasiridae lucinidae lucinids and thyasirids are the dominant groups represented ancient hydrothermal vent and cold seep settings may provide clues to delineate better which factors e g biotic interactions differential recovery following the permian triassic mass extinction have influenced overall evolutionary patterns of dominance among brachiopods and bivalves through the phanerozoic

palaeoecology taphonomy and distribution of brachiopod assemblages from the much wenlock limestone formation of england and wales abstract fourteen faunal assemblages are recognized from bedded lithofacies in the much wenlock limestone formation of england and wales eleven comprise in situ faunas and three have reworked components autecological consideration of taxa in the eleven in situ assemblages shows that turbulence substrate type ease of feeding and the presence of other organisms in the sediment were the main ecological controls on faunal distribution interplay between these four parameters accounts for the complexity of faunal distributions and shows that to suggest faunas are depth controlled is an overgeneralisation sequential variation of the assemblages is closely related to lithofacies distribution lack of detailed sedimentological work in some previous palaeoecological studies of the much wenlock limestone formation prevented this relationship from being recognised the composition of the three assemblages composed of reworked faunas sedimentary faunal assemblages reflects a combination of sedimentary reworking and original faunal composition beds composed of reworked bioclasts cannot always be easily differentiated from beds containing in situ faunas differentiation requires a combination of palaeoecological work and detailed sedimentology thin section study indicates beds which in the field appear to be single depositional units are in fact composed of several microfacies if the nature of these beds remains undetected data is produced in which palaeocommunities completely intergrade and community boundaries are arbitrary lines through a continuum previous palaeocommunity work on wenlock brachiopods produced such arrays primarily reflecting the failure to recognise sedimentary faunal assemblages

a laboratory study of longshore currents over barred and non barred beaches abstract a detailed description is given of the results of laboratory experiments on wave driven longshore currents on both barred and non barred beaches the objective is to examine the cross shore distribution of the longshore current velocities for purely wave driven currents with emphasis on the position of maximum current velocity with respect to areas where wave energy is dissipated unidirectional obliquely incident waves both regular and random were used the measurements were performed in a large wave basin with a pump recirculation system to create spatially homogeneous longshore currents the experiments yielded information on wave transformation set up of the mean water level and the cross shore distribution of wave driven longshore current velocity a number of cases are presented and compared with each other the measurements show that in the case of purely wave driven longshore currents the maximum current velocities occur close to areas where wave breaking is most intense the effect of mixing bottom friction and wave rollers on the longshore current velocity profile are examined in more detail with help of numerical modelling existing model equations based on the assumption of alongshore uniformity are used the results for the mean longshore current profile on a barred beach are in close agreement with the measurements

mineral equilibria and geothermometry of the dalaman koycegiz thermal springs southern turkey abstract the dalaman and koycegiz thermal springs are from karstic limestones belonging to upper cretaceous to burdigalian beydaglari autochthon and carboniferous to lutetian lycian nappes they have measured temperatures of 24 41 c specific electrical conductivities of 14 310 45 600 s cm and are dominated by na 1550 8500 mg kg and cl 2725 15 320 mg kg the heat source of the geothermal systems of the area is tectonic related and the occurrence of the thermal springs is related to the young normal faults meteoric waters and seawaters recharge the reservoir rocks are heated at depth with increasing geothermal gradient and move up to the surface through the fractures and faults by convection trend and emerge as thermal springs while thermal waters move up to the surface they mix with different proportions of seawater and cold fresh waters the seawater contribution to the thermal waters varies from 24 to 78 lake waters in the area are connected with thermal waters consequently their chemical composition is influenced by the chemistry of thermal waters chemical equilibrium modelling based on measured outlet temperatures and measured ph shows that all the waters are oversaturated with respect to quartz and k mica and undersaturated with respect to al oh 3 anorthite gypsum siderite and sio2 a albite alunite aragonite ca montmorillonite calcite chalcedony chlorite dolomite fe oh 3 a fluorite gypsum illite k feldspar kaolinite and sepiolite minerals are mostly oversaturated or undersaturated mineral saturation studies of the thermal springs indicate that dolomite chalcedony and quartz are most likely to cause scaling at outlet conditions assessments from various chemical geothermometers and na k mg ternary and mineral equilibrium diagrams suggest that the reservoir temperature is around 65 90 c the temperatures obtained from quartz quartz steam loss mg li geothermometers and mineral equilibrium diagrams give the most reasonable results

benthic extinction and recovery patterns at the k t boundary in shallow water carbonates denmark abstract benthic extinction at the k t boundary in the danish basin is abrupt and indistinguishable from the termination of maastrichtian white chalk deposition the danian benthic fauna already fully established in the earliest danian nannoplankton zone np1 is essentially an impoverished maastrichtian fauna established through direct survival or limited evolution within well established clades already present in the maastrichtian of the danish basin however recovery of the early danian community is initially retarded the transition is illustrated in some detail for the locality nye klov here the lower 2 3 m of danian strata corresponding largely to the lower np1 subzone contains an extremely impoverished highly unusual dead zone community dominated by bourgueticrinid crinoids associated with other presumed soft ground specialists and devoid of such important faunal elements as cyclostome bryozoans brachiopods calcitic bivalves etc over the next metres the dead zone fauna is gradually replaced by more ordinary faunas and about 6 m above the boundary the characteristic early danian bryozoan limestone community is fully established

longshore current and wave height modulation at tidal frequency inside the surf zone data were acquired continuously during the 19 day delilah nearshore experiment with a specific objective of examining variability of the longshore current at tidal frequencies it is hypothesized that breaking wave heights inside the surf zone are strong functions of the depth which are modulated by the tidal variations and since radiation stress is a function of the wave height longshore currents are forced at the tidal frequency inside the surf zone the measured longshore current variations at tidal frequency are the same order of magnitude as the mean longshore current variations for moderate wave height conditions indicating that the tide is a dominant mechanism associated with longshore current variability simulations of the magnitude and phase of the longshore current variability with tide elevation using the model by thornton and guza 1986 are used to explain observations the measured tidal elevation and longshore current are in phase in the inner surf zone and out of phase in the outer surf zone as predicted by the model verifying the hypothesis

the vertical structure of low frequency motions in the nearshore part i observations abstractfield observations of oscillating currents in the surfzone of a natural beach show significant vertical structure in energy phase and rotation at low frequencies around 0 005 hz where most of the energy is associated with vorticity motions energy levels in the cross shore component of the flow seaward of the sandbar decay near the bottom shoreward of the bar crest the flow decays nearly linearly over the water column conversely a weaker alongshore component of the flow increases near the bottom seaward of the sandbar and is roughly depth uniform inside the bar crest near this 0 005 hz frequency band the coherence between the uppermost and successive vertically separated sensors drops off quickly with as much as a 70 80 coherence drop over the water column ranging from 2 5 to 4 m the phase relative to the uppermost sensor shifts approximately linearly over depth with as much as 50 phase lag at the bottom that can lag or lead the surface rotary coefficients also vary across the su

hydrogeochemical outline of thermal waters and geothermometry applications in anatolia turkey abstract the chemical compositions of a total of 120 thermal water samples from four different tectonically distinct regions central north east and west anatolia of turkey are presented and assessed in terms of geothermal energy potential of each region through the use of chemical geothermometers na ca hco3 type waters are the dominant water types in all the regions except that na cl type waters are typical for the coastal areas of west anatolia and for a few inland areas of west and central anatolia where deep water circulation exists the discharge temperature of the springs ranges up to 100 c and the bottom hole temperatures in drilled wells up to 232 c geothermometry applications yield reservoir temperatures of about 125 c for central anatolia 110 c for north anatolia 136 c for east anatolia and 251 c for west anatolia the latter agreeing with some of the bottom hole temperatures measured in drilled wells the results reveal that the highest geothermal energy potential in turkey is associated with the west anatolian extensional tectonics which provides a regional deep seated heat source and a widespread graben system allowing deep circulation of waters the north anatolian region bounded to the south by the dextral north anatolian fault along which most of the geothermal sites are located has the lowest energy potential probably due to the restriction of the heat source to local magmatic activities confined to pull apart basins the east anatolian region undergoing contemporary compression and the central anatolian region where the compressional regime in the east is converted to the extensional regime in the west have moderate energy potential although the recently active volcanoes suggest the presence at depth of still cooling magma chambers that are potential heat sources the lack of well developed fault systems is probably responsible for the comparatively low energy potential of these regions almost all the thermal waters of turkey are saturated with respect to calcite and hence have a significant calcite scaling potential which is particularly high for west anatolian waters

isotope geochemical characterization and geothermometrical modeling of uttarakhand geothermal field india uttarakhand geothermal area located in the central belt of the himalayan geothermal province is one of the important high temperature geothermal fields in india in this study the chemical characteristics of the thermal waters are investigated to identify the main geochemical processes affecting the composition of thermal waters during its ascent toward the surface as well as to determine the subsurface temperature of the feeding reservoir the thermal waters are mainly ca mg hco3 type with moderate silica and tds concentrations mineral saturation states calculated from phreeqc geochemical code indicate that thermal waters are supersaturated with respect to calcite dolomite aragonite chalcedony quartz si 0 and undersaturated with respect to gypsum anhydrite and amorphous silica si 0 xrd study of the spring deposit samples fairly corroborates the predicted mineral saturation state of the thermal waters stable isotopes 18o 2h data confirm the meteoric origin of the thermal waters with no oxygen 18 shift the mixing phenomenon between thermal water with shallow ground water is substantiated using tritium 3h and chemical data the extent of dilution is quantified using tritium content of thermal springs and non thermal waters classical geothermometers mixing model and multicomponent fluid geothermometry modeling geot have been applied to estimate the subsurface reservoir temperature among different classical geothermometers only quartz geothermometer provide somewhat reliable estimation 96 140 c of the reservoir temperature geot modeling results suggest that thermal waters have attained simultaneous equilibrium with respect to minerals like calcite quartz chalcedony brucite tridymite cristobalite talc at the temperature 130 5 c which is in good agreement with the result obtained from the mixing model

nearshore circulation over transverse bar and rip morphology with oblique wave forcing there is a paucity of field data to describe the transition in nearshore circulation between alongshore meandering and rip current systems a combination of in situ current meters and surf zone drifters are used to characterize the nearshore circulation over a transverse bar and rip morphology at pensacola beach florida in the presence of relatively low energy oblique waves current speeds vary in response to the relative wave height ratio hs h which defines the degree and extent of breaking over the shoal in the absence of wave breaking the nearshore circulation was dominated by an alongshore current driven by the oblique waves as waves begin to break across the shoal 0 2 0 5 the meandering current is replaced by an unsteady rip circulation that moves offshore between the shoals before turning alongshore in the direction of wave advance outside the surf zone the increase in wave dissipation is associated with an increase in very low frequency vlf variations in the current speed across the shoal and in the rip channel that caused the circulation to oscillate between an offshore and an alongshore flow the unsteady nature of the nearshore circulation is responsible for 55 of all surf zone exits under these more dissipative conditions in contrast only 29 of the drifters released from the shoal exited the surf zone and bypassed the adjacent shoal with the alongshore meandering current while the currents had a low velocity maximum of 0 4 m s 1 and would not pose a significant hazard to the average swimmer the results of this study suggest that the transverse bar and rip morphology is sufficient to create an alongshore variation in wave dissipation that forces alongshore meandering and low energy rip circulation systems under oblique wave forcing copyright 2013 john wiley sons ltd

geochemical constraints for the origin of thermal waters from western turkey the combined chemical composition b and sr isotopes and the basic geologic setting of geothermal systems from the menderes massif in western turkey have been investigated to evaluate the origin of the dissolved constituents and mechanisms of water rock interaction four types of thermal water are present 1 a na cl of marine origin 2 a na hco3 type with high co2 content that is associated with metamorphic rocks of the menderes massif 3 a na so4 type that is also associated with metamorphic rocks of the menderes massif with h2s addition and 4 a ca mg hco3 so4 type that results from interactions with carbonate rocks at shallow depths the na cl waters are further subdivided based on br cl ratios water from the cumali seferihisar and bodrum karaada systems are deep circulated seawater br cl sea water whereas water from canakkale tuzla br cl sea water are from dissolution of messinian evaporites good correlations between different dissolved salts and temperature indicate that the chemical composition of the thermal waters from non marine geothermal systems is controlled by 1 temperature dependent water rock interactions 2 intensification of reactions due to high dissolved co2 and possibly hcl gasses and 3 mixing with overlying cold groundwater all of the thermal water is enriched in b the b isotopic composition 11b 2 3 to 18 7 n 6 can indicate either leaching of b from the rocks or b oh 3 degassing flux from deep sources the large ranges in b concentrations in different rock types as well as in thermal waters from different systems suggest the water rock mechanism 87sr 86sr ratios of the thermal water are used to differentiate between solutes that have interacted with metamorphic rocks 87sr 86sr ratio as high as 0 719479 and carbonate rocks low 87sr 86sr ratio of 0 707864

field observations of shear waves in the surf zone 1 alongshore propagating meanders of the mean alongshore current in the surf zone called shear waves have periods of a few minutes and wavelengths of a few hundred meters here shear wave properties are estimated with arrays of current meters deployed for 4 months within 300 m of the shoreline of a sandy beach shear wave velocity fluctuations are approximately horizontally isotropic with root mean square values between 10 and 40 of the mean 3 hour averaged alongshore current v cross shore variations of the time averaged shear wave momentum flux are consistent with shear wave energy generation close to shore where the breaking wave driven mean alongshore current v and current shear vx are strong and with shear wave energy dissipation and transfer back to the mean flow farther offshore where v and vx are weak in case studies where v is a narrow jet near the shoreline the observed strong decay of shear wave energy levels seaward of the jet and the cross shore and alongshore structure of shear waves within the jet are similar to predictions based on the linearly unstable modes of the observed v shear wave energy levels also are high in a marginally unstable case with a strong but weakly sheared v

effect of alongshore nonuniformities on longshore current predictions longshore currents have been primarily modeled by assuming alongshore uniformity in this paper we revisit the problem of nonuniform longshore currents to refocus attention on the importance of accounting for alongshore nonuniformity in longshore current predictions and to provide an analytical estimate of the importance of this nonuniformity we derive a semianalytical solution for the longshore currents that allows for weak alongshore variations in the bottom topography the solution shows that the alongshore pressure gradient induced by alongshore variations in the bottom topography could contribute substantially to the forcing for the longshore currents an example calculation shows that the longshore current could deviate by up to 30 from the mean for a 10 deviation of the bottom topography thus we suggest that in many practical cases it is important to include the alongshore pressure gradient to accurately model longshore currents

field observations of surf beat 1 progressive edge waves nineteen biaxial electromagnetic current meters have been used to determine the longshore and on offshore structure of currents at surf beat periods 1 4 min the sensors formed two linear arrays a long shore array within the surf zone and an on offshore array stretching from the shoreline to well beyond the breaker line analysis of the longshore current components yields a clear picture of progressive low mode edge waves with frequency wave number dispersion relations which are in remarkably good agreement with predictions some separation of edge wave modes is found with mode zero energy dominating in the frequency band 0 006 and 0 011 hz and mode one between 0 015 and 0 025 hz on offshore currents present a rather different picture which while not inconsistent with the longshore currents suggests that other sources of energy are also important to the on offshore currents these include standing edge waves probably formed by reflections at nearby scripps canyon and motions which are nonresonantly forced by incoming wave groups

quasi three dimensional modeling of rip current systems 1 the focus of the paper is the analysis of the flow in rip current systems generated by channels in longshore bars on a beach the horizontal variations of rip current systems are described through the use of the quasi three dimensional nearshore circulation model shorecirc model predictions are compared to laboratory measurements of waves and current velocities throughout the entire rip current system and show reasonable agreement the rips in the two channels are found to behave differently because of the depth variation across the basin it is found that higher bottom stress leads to more stable flow where the rip current meanders less and fewer eddies are generated the wave current interaction creates forcing which reduces the distance rip currents flow offshore and can lead to a slow pulsation of the rip current this pulsation is in addition to the instabilities of a jet which can also be present in rip currents the three dimensionality of the rip current system is found to have a significant effect on the overall circulation patterns index terms 4255 oceanography general numerical modeling 4512 oceanography physical currents 4546 oceanography physical nearshore processes keywords rip currents nearshore circulation numerical modeling waves

surf zone longshore currents and random waves field data and models abstract analytic and numerical models for longshore currents generated by obliquely incident random waves am compared with field observations five days of observations were selected during which the waves were narrow banded in both frequency and direction in keeping with model assumptions the extensive measurements included radiation stress and wave directional spectra in 9 m depth and a closely spaced array of current and pressure sensors on a line perpendicular to shore the longshore current models are based on balancing the gradient of the radiation stress with the alongshore bed shear and reynold s stresses assuming stationary wave conditions and straight and parallel bottom contours the spatial variation of wave height required to determine the gradient of the radiation stress is modeled using linear random wave theory given hrms in 9 m depth the model predicts hrms at shoreward locations with an average error of less than 9 using a nonlinear bottom shear stress formulation and the meas

the generation of surfzone eddies in a strong alongshore current abstractthe surfzone contains energetic two dimensional horizontal eddies with length scale larger than the water depth yet the dominant eddy generation mechanism is not understood the wave resolving model funwavec is used to simulate surfzone eddies in four case examples from the sandyduck field experiment that had alongshore uniform bathymetry the funwavec model is initialized with the observed bathymetry and the incident wave field in 8 m depth and reproduces the observed cross shore structure of significant wave height and mean alongshore current within the surfzone the wave resolving funwavec modeled e f ky spectra and the bulk frequency and ky integrated rotational velocities are consistent with the observations below the sea swell band 0 05 hz demonstrating that the model can be used to diagnose surfzone eddy generation mechanisms in the mean squared perturbation vorticity budget the breaking wave vorticity forcing term is orders of magnitude larger than the shear instability gene

the smooth brachiopods of the mediterranean jurassic refugees or invaders the jurassic brachiopod fauna of the alpine mediterranean region is dominated by smooth rhynchonellids and spiriferinids and sulcate or perforate terebratulids in contrast to the typical coarsely ribbed brachiopods of the contemporaneous european and african epicontinental areas the best studied example of the mediterranean brachiopod province is the pliensbachian fauna of the bakony mountains hungary there the five most abundant genera are all smooth linguithyris securithyris apringia bakonyithyris pisirhynchia these smooth genera represent different morphological types sulcate axiniform uniplicate phylogenetically related forms are known from several evolutionary lineages of discontinuous record ranging from the triassic to the recent the triassic jurassic and the neogene recent parts of these evolutionary lineages are represented by several genera while in the late cretaceous paleogene interval they seemingly disappear at least they have no record the recent relatives of the above pliensbachian genera live mostly in the deep sea three are shallow bathyal 200 400 m three deep bathyal 800 1200 m and three abyssal 2000 4500 m the abyssal genera occur mainly in the east pacific the geographical distribution of the bathyal genera shows peculiar features they are more or less confined to the western sides of the great ocean basins west pacific west indian ocean caribbean region and they are thalassobathyal i e they are living on submarine plateaus seamounts or island aprons and not on the continental slopes this pattern extrapolated to the past shows good analogy with the jurassic palaeogeographical model developed for the western part of the tethys ocean it is hypothesized that smooth mainly sulcate articulate brachiopods flourished in the bathyal or even abyssal zones during the palaeozoic they were not refugees but formed well adapted communities this stable conservative fauna may have survived the crises manifested in the shelf seas and in cases of appropriate palaeogeographical situations may have implanted its descendants to the shallow bathyal or even sublittoral regions of the western margins of the ocean basins the mediterranean microcontinent system at the western part of the jurassic tethys might have been such an invaded region correlation between plate tectonic changes of ocean continent configurations the presence of ocean basins closed on the west and the occurrence of smooth articulate brachiopod groups in shallow bathyal to sublittoral settings collectively suggest that the deep water forms invaded the shallow environments of the western tethys in early mesozoic times and the w pacific and w indian oceans in the neogene they stayed in the deep sea reservoir when a circum equatorial ocean existed in the late mesozoic

field observations of surf zone inner shelf exchange on a rip channeled beach cross shore exchange between the surf zone and the inner shelf is investigated using lagrangian and eulerian field measurements of rip current flows on a rip channeled beach in sand city california surface drifters released on the inner shelf during weak wind conditions moved seaward due to rip current pulses and then returned shoreward in an arcing pattern reentering the surf zone over shoals the cross shore velocities of the seaward and shoreward moving drifters were approximately equal in magnitude and decreased as a function of distance offshore the drifters carried seaward by the rip current had maximum cross shore velocities as they exited the surf zone and then decelerated as they moved offshore the drifters moving shoreward accelerated as they approached the surfzone boundary with maximum cross shore velocities as they reentered the surf zone over shoals it was found that stokes drift was not solely responsible for the onshore transport across the surfzone boundary the cross shore diffusivity on the inner shelf was greatest during observations of locally contained cross shore exchange these field observations provide evidence that the cross shore exchange between the surf zone and inner shelf on a rip channeled beach is due to wave driven rip current circulations and results in surface material being contained within the nearshore region

surf zone eddies coupled with rip current morphology 1 energetic very low frequency vlf frequencies 0 004 hz surf zone eddies szes were observed on a beach composed of shore connected shoals with quasi periodic 125 m incised rip channels at sand city monterey bay california incident waves consisted of predominantly shore normal narrow banded swell waves szes were located outside the gravity region in alongshore wave number ky spaced within the vlf band and did not appear to exist in higher frequency bands the szes were significant urms vlf 0 25 m s and constant in intensity within the surf zone shore connected shoals and rip channels and rapidly decreased offshore the alongshore and cross shore sze velocity variances were similar in magnitude vlf sze velocities were not forced by vlf surface elevations and were not well correlated with rip current flows r2 0 18 there is an indication that the szes were related to wave forcing with the szes statistically correlated with incoming sea swell wave height r2 0 49 f ky spectral estimates illustrate a strong relationship between rip channel spacing and sze cross shore velocities ky 0 008 m 1 and minimal sze alongshore velocity variation ky 0 m 1 data analysis suggests that the szes are not simply instabilities of an unstable rip current jet a simple conceptual model suggests that sze f ky spectra can be explained by the entire rip current circulation cells oscillating predominantly in the cross shore and slightly in the alongshore

volcano stratigraphy of the extension related silicic volcanism of the cubukludag graben western turkey an example of generation of pyroclastic density currents western turkey9s extension related cumaovasi volcanic rocks lower miocene 17 ma are excellent examples of silicic eruptions the sub aerial silicic volcanism at cubukludag graben between izmir and kusadasi in west central anatolia is mainly in the form of rhyolite domes lava flows and pyroclastic deposits the initial features of volcanism derived from phreatomagmatic explosive eruptions from silicic magma that came into contact with lake waters during neogene times most of the volcanic succession represents pyroclastic density currents pdcs known as the kuner ignimbrite the deposits are fine grained and laminated at the base and pass laterally and vertically into deposits displaying well developed traction structures soft sediment deformation and or erosion channels in the ne part of the region alternate deposits of massive diffusely stratified lapilli and ash are the main products of the later explosive stage massive lithic breccias forming the top of the sequences are the proximal facies of the pdcs the lava phase mainly consists of rhyolite extruded as dome and fissure eruptions of lavas aligned along ne sw trending faults as well as from extensional cracks that are nearly perpendicular to the main graben faults considering the tectono stratigraphical aspects and geochemical nature of the study area we propose that the cumaovasi silicic volcanism was produced by extension related crustal melting during the late early miocene period 17 ma

the chemistry of geothermal waters in iceland i calculation of aqueous speciation from 0 to 370 c abstract a computer programme has been developed to calculate the composition and aqueous speciation of geothermal reservoir waters including ph redox potential and gas partial pressures the programme is specifically suited to handle geochemical data from wet steam wells hot water wells and boiling hot springs but it may also be used for non thermal waters solubility data for selected geothermal minerals are incorporated to facilitate the study of solution mineral equilibria the programme may also be used to study chemical changes in water chemistry accompanying boiling variable degassing and cooling and how these changes disturb solution mineral equilibria

effects of wave current interaction on shear instabilities of longshore currents 1 we examine the effects of wave current interaction on the dynamics of instabilities of the surf zone longshore current we utilize coupled models for the simulation of the incident waves and the wave induced nearshore circulation the coupling between the models occurs through radiation stress gradient terms accounting for the generation of nearshore circulation and through wave current interaction terms leading to the modification of the wave field by the generated circulation field simulations are carried out with a realistic barred beach configuration and obliquely incident waves for two frictional regimes the results show that the shear instabilities of the longshore current have a significantly altered finite amplitude behavior when wave current interaction effects are included for beaches with relatively high frictional damping the primary effects are a reduction of the offshore extent of the motions and a delay of the onset of instabilities in addition the energy content of the motions within two surf zone widths is reduced the propagation speed increases and tendency to form offshore directed jets is reduced the horizontal mixing induced by the instabilities is also reduced when wavecurrent interaction is considered leading to a larger peak mean longshore current and a larger offshore current shear these effects appear to be primarily linked to a feedback mechanism whereby the incident wave field gains energy at locations of offshore directed currents for more energetic shear instability fields that occur when frictional damping is small this feedback affects the propagation speed and energy content of the instabilities near and onshore of the current peak only minimally however the offshore extent of the motions and the tendency to shed vortices offshore are still reduced a reduction in the mixing due to the instabilities is evident offshore of the current peak hence the mean longshore current profile is only affected offshore of the current peak the inclusion of wave current interaction significantly affects the shear instability signature observed in the shoreline runup for either frictional regime these results indicate that the energy content and frequency extent of the shoreline response is increased markedly due to the wavecurrent interaction process this effect appears to be related to variations in the forcing of the circulation that arise due to the refraction of the incident waves around offshore directed features of the circulation index terms 4255 oceanography general numerical modeling 4512 oceanography physical currents 4546 oceanography physical nearshore processes

epicontinental seas versus open ocean settings the kinetics of mass extinction and origination environmental perturbations during mass extinctions were likely manifested differently in epicontinental seas than in open ocean facing habitats of comparable depth here we present a dissection of origination and extinction in epicontinental seas versus open ocean facing coastal regions in the permian through cretaceous periods an interval through which both settings are well represented in the fossil record results demonstrate that extinction rates were significantly higher in open ocean settings than in epicontinental seas during major mass extinctions but not at other times and that origination rates were significantly higher in open ocean settings for a protracted interval from the late jurassic through the late cretaceous these patterns are manifested even when other paleogeographic and environmental variables are held fixed indicating that epicontinental seas and open ocean facing coastlines carry distinct macroevolutionary signatures

hydrogeochemical and isotopic characteristics of the ilica geothermal system erzurum turkey in this paper the hydrochemical isotopic characteristics of samples collected from geothermal springs in the ilica geothermal field eastern anatolia of turkey are examined and described low temperature geothermal system of ilica erzurum turkey located along the eastern anatolian fault zone was investigated for hydrogeochemical and isotopic characteristics the study of ionic and isotopic contents shows that the thermal water of ilica is mainly locally fed by groundwater which changes chemically and isotopically during its circulation within the major fault zone reaching depths the thermal spring has a temperature of 29 39 c with electrical conductivity ranging from 4 000 to 7 510 s cm and the thermal water is of na hco3 cl water type the chemical geothermometers applied in the ilica geothermal waters yielded a maximum reservoir temperature of 142 c according to the silica geothermometers the thermal waters are undersaturated with respect to gypsum anhydrite and halite and oversaturated with respect to dolomite the dolomite mineral possibly caused scaling when obtaining the thermal waters in the study area according to the enthalpy chloride mixing model cold water to the thermal water mixing ratio is changing between 69 8 and 75 the 18o 2h compositions obviously indicate meteoric origin of the waters thermal water springs derived from continental precipitation falling on to higher elevations in the study area the 13c ratio for dissolved inorganic carbonate in the waters lies between 4 63 and 6 48 in low temperature waters carbon is considered as originating from volcanic mantle co2

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

modeling surf zone tracer plumes 1 waves mean currents and low frequency eddies 1 a model that accurately simulates surf zone waves mean currents and low frequency eddies is required to diagnose the mechanisms of surf zone tracer transport and dispersion in this paper a wave resolving time dependent boussinesq model is compared with waves and currents observed during five surf zone dye release experiments in a companion paper clark et al 2011 compare a coupled tracer model to the dye plume observations the boussinesq model uses observed bathymetry and incident random directionally spread waves for all five releases the model generally reproduces the observed cross shore evolution of significant wave height mean wave angle bulk directional spread mean alongshore current and the frequency dependent sea surface elevation spectra and directional moments the largest errors are near the shoreline where the bathymetry is most uncertain the model also reproduces the observed cross shore structure of rotational velocities in the infragravity 0 004 f 0 03 hz and very low frequency vlf 0 001 f 0 004 hz bands although the modeled vlf energy is 2 3 times too large similar to the observations the dominant contributions to the modeled eddy induced momentum flux are in the vlf band these eddies are elliptical near the shoreline and circular in the mid surf zone the model data agreement for sea swell waves low frequency eddies and mean currents suggests that the model is appropriate for simulating surf zone tracer transport and dispersion

helium carbon relationships in geothermal fluids of western anatolia turkey abstract we investigate the helium carbon and oxygen hydrogen isotopic systematics and co2 3he ratios of 8 water and 6 gas samples collected from 12 geothermal fields in western anatolia turkey 3he 4he ratios of the samples r normalized to the atmospheric 3he 4he ratio ra 1 39 10 6 range from 0 27 to 1 67 and are significantly higher than the crustal production value of 0 05 fluids with relatively high r ra values are generally found in areas of significant heat potential kizildere and tuzla fields co2 3he ratios of the samples ranging from 1 6 109 to 2 3 1014 display significant variation and are mostly higher than values typical of an upper mantle source 2 109 the 13c co2 and 13c ch4 values of all fluids vary from 8 04 to 0 35 and 25 80 to 23 92 vs pdb respectively stable isotope values 18o d of the geothermal waters are conformable with the mediterranean meteoric water line and indicate a meteoric origin the temperatures calculated by gas geothermometry are significantly higher than estimates from chemical geothermometers implying that either equilibrium has not been attained for the isotope exchange reaction or that isotopic equilibration was disturbed due to gas additions en route to the surface evaluation of he co2 abundances indicates that hydrothermal degassing and calcite precipitation controlled probably by adiabatic cooling due to degassing significantly fractionate the elemental ratio co2 3he in geothermal waters such processes do not affect gas phase samples to anywhere near the same extent for the gas samples mixing between mantle and various crustal sources appears to be the main control on the observed he c systematics however crustal inputs dominate the co2 inventory considering that limestone is the main source of carbon 70 to 97 of the total carbon inventory the carbon flux from the crust is found to be at least 20 times that from the mantle as to the he inventory the mantle derived component is found to vary up to 21 of the total he content and is probably transferred to the crust by fluids degassed from deep mantle melts generated in association with the elevated geotherm and adiabatic melting accompanying current extension the range of 3he enthalpy ratios 0 000032 to 0 19 10 12 cm3 stp j of fluids in western anatolia is consistent with the release of both helium and heat from contemporary additions of mantle derived magmas to the crust the deep faults appear to have facilitated the deep circulation of the fluids and the transport of mantle volatiles and heat to the surface