intense sub kilometer scale boundary layer rolls observed in hurricane fran high resolution observations obtained with the doppler on wheels dow mobile weather radar near the point of landfall of hurricane fran 1996 revealed the existence of intense sub kilometer scale boundary layer rolls that strongly modulated the near surface wind speed it is proposed that these structures are one cause of geographically varying surface damage patterns that have been observed after some landfalling hurricanes and that they cause much of the observed gustiness bringing high velocity air from aloft to the lowest observable levels high resolution dow radar observations are contrasted with lower resolution observations obtained with an operational weather radar which underestimated peak low level wind speeds

tectonothermal analysis of a major unit of the cantabrian zone the ponga unit variscan belt nw spain the paleothermometric evolution of the ponga unit at the core of the cantabrian zone the arcuate foreland fold and thrust belt of the variscan orogen in nw spain is analyzed using the conodont color alteration index and the kubler index of illite the results indicate that the distribution of the thermal maturity patterns is independent of the stratigraphy and the structure of the unit these include the occurrence of dominant diagenetic values and very low to low grade metamorphism in the southern area the main thermal event is interpreted to be related to hydrothermal fluids ascending through late variscan extensional faults the anomalous high heat flow in the southern sector of the ponga unit is part of a previously identified large band in the cantabrian zone where the common occurrence of low grade metamorphic rocks hydrothermal dolostones and ore mineralizations is related to an extensional orogenic episode that started near the carboniferous permian boundary soon after the closure of the asturian arc

conodont color and textural alteration an index to regional metamorphism contact metamorphism and hydrothermal alteration experimental and field data are used to extend the utility of conodonts as semi quantitative thermal indices into the regimes of regional and contact metamorphism as well as hydrothermal alteration an arrhenius plot of data from induced conodont color alteration by pyrolysis in air at 1 atm was used to generate the geologic temperatures for conodont color alteration indices cai above 300 c that is for cai values of 5 through 8 such cai values occur in very low to medium grade regionally metamorphosed contact metamorphosed and hydrothermally altered rocks the uniformity or variability of cai values within a sample together with conodont texture can help to distinguish grades and environments of metamorphism particularly in metacarbonate sequences induced cai by pyrolysis in a water methane mixture at kbar results in retardation of cai and in a disparate mixture of both low and high cai values within each experimental sample in this system color alteration processes above a cai of 2 to 3 seem to change from predominantly carbonization to predominantly loss of organic matter presumably by oxidation and volatilization of oxides these experiments approximate the type of cai mixture characteristically found in conodonts recovered from hydrothermally altered rocks these data indicate that cai values of 6 to 8 cannot be used to assess precise temperatures of hydrothermally altered rocks but may serve as useful indicators of potential mineralization

a comparison of shear and buoyancy driven planetary boundary layer flows abstract planetary boundary layer pbl flows are known to exhibit fundamental differences depending on the relative combination of wind shear and buoyancy forces these differences are not unexpected in that shear instabilities occur locally while buoyancy force sets up vigorous thermals which result in nonlocal transport of heat and momentum at the same time these two forces can act together to modify the flow field in this study four large eddy simulations less spanning the shear and buoyancy flow regimes were generated two correspond to the extreme cases of shear and buoyancy driven pbls while the other two represent intermediate pbls where both forces are important the extreme cases are used to highlight and quantify the basic differences between shear and convective pbls in 1 flow structures 2 overall statistics and 3 turbulent kinetic energy tke budget distributions results from the two intermediate les cases are used to develop and verify a velocity scaling and a tke budget mode

geothermal palaeogradients and metamorphic zonation from the conodont colour alteration index cai the conodont colour alteration index cal is potentially does not exist there are areas where cal and ki values are valuable in thermal history investigations but there are notably consistent for the anchizone boundaries however problems in its use an approach is proposed herein to anomalous correlations between cal and ki values have also overcome the problem of establishing reliable geothermal been found in some areas a cal anchizone or ancaizone is palaeogradients in areas with burial metamorphism based on defined in order to enable cal values to be used independently knowledge of the stratigraphic succession thickness the to establish a metamorphic zonation boundaries of chronostratigraphic units and the age and duration of deformation episodes although also problematical terra nova 13 79 83 2001 that a correlation between cal and kubler index ki values

diagenetic alteration of the structure and δ18o signature of palaeozoic fish and conodont apatite potential use for corrected isotope signatures in palaeoenvironmental interpretation abstract the oxygen isotopic compositions of carboniferous conodonts and fish microfossils ichthyoliths from identical samples were analysed in tandem in order to test whether these phosphatic media can be reliably used for palaeoclimatic reconstruction the structure of conodonts and of most ichthyoliths analysed are somewhat analogous to the enamel and dentine bone tissue respectively of modern mammals therefore the diagenetic susceptibilities of the taxa analysed may provide important clues to other palaeoclimatic studies utilising a variety of biogenic apatite thermal maturation indices and scanning electron microscopy were used to characterise the preservation of biogenic apatite despite a high conodont colour alteration index cai of 5 5 conodont elements appear to have been only mildly affected by diagenetic alteration in contrast ichthyoliths were commonly recrystallised and exhibited diagenetic apatitic overgrowths containing amorphous pyrolytic carbon interpreted as indicating that at least some overgrowth material derived from the original biogenic apatite diagenetic alteration has resulted in ichthyolith 18 o values being systematically lower by on average 2 9 1 0 3 relative to conodont apatite conodont samples yielded regionally correlatable isotope values which can be interpreted in terms of more palaeoenvironmentally sensible palaeotemperatures relative to ichthyolith values densely crystalline enamel like conodont elements are interpreted as the more robust phosphatic medium to preserve original isotopic compositions the strong correlation r 0 8 of the 18 o values of the more structurally pristine conodont and commonly recrystallised ichthyolith apatite indicates that i despite diagenetic lowering of absolute isotope values original palaeoenvironmental records may be preserved and ii diagenetic overprinting may result in a stable offset and therefore be correctable locally

a single doppler radar study of horizontal roll convection in a lake effect snow storm abstract the boundary layer structure and circulation over lake michigan were probed with a doppler radar and an aircraft during a lake effect snow storm on 9 december 1978 evidence is presented that observed wind parallel echo bands and satellite cloud bands resulted from horizontal roll convection in the boundary layer the organization of precipitation within the roll field is discussed and the roll geometry is compared with cases of dry horizontal roll convection reported in the literature

transition from diagenesis to metamorphism in a calcareous tectonic unit of the iberian variscan belt central massif of the picos de europa nw spain transition from diagenesis to metamorphism has been characterized in the central part of the picos de europa unit cantabrian zone by conodont colour alteration index cai complemented with kubler index ki data this unit essentially comprises carboniferous limestone the study leads us to deduce two successive tectonothermal events the first event generated a pattern with palaeotemperatures increasing towards the pisuerga carrion unit located south of the picos de europa unit the present pattern is the result of an original dip to the north of the isothermal surfaces and the subsequent rising of the picos de europa unit along the frontal ramp of a deep alpine thrust this episode is interpreted as related to an extensional tectonic regime that occurred close to the carboniferous permian boundary the second event which gave rise to thermal anomalies in the pattern of the first episode was the result of hydrothermal processes in which fluid movement was facilitated by a dense network of fractures in the area close to the eastern section of the studied region these processes gave rise to numerous mineralizations and have been related to a permian extensional tectonic regime

phosphate regeneration from sediments of the peru continental margin by dissolution of fish debris generally oxidative regeneration of phosphate from anoxic sediments is by microbially mediated sulfate reduction processes stoichiometric modelling of such reactions takes into consideration varying proportions of decomposable organically bound p to account for the ratios among nutrients in depth concentration profiles of near surface sediments new results of interstitial water composition from sediments underlying the water masses influenced by coastal upwelling of the eastern boundary current system off peru indicate that dissolution of phosphatic fish debris represents a mechanism for remineralization of phosphate comparable to or larger in magnitude than that by oxidative regeneration of organically bound p dissolved interstitial phosphate from fish debris is revealed by an excess amount of phosphate over that predicted from a simple stoichiometric oxidative regeneration model and by anomalously high dissolved interstitial fluoride concentrations phosphate flux estimates based on diffusion from the sediment suggest that this mechanism may generate up to 10 of the nutrient pool in the waters of the peru undercurrent partitioning of p among the two sources reveals further that fish debris phosphate is about four times more important than organically bound p in nutrient generation from sediments of the peru continental margin not only does this mechanism of regeneration affect the nutrient cycling but may also control widespread phosphorite formation in this area

a positive trend in seawater 87sr 86sr values over the early middle frasnian boundary late devonian recorded in well preserved conodont elements from the holy cross mountains poland abstract over the early middle frasnian boundary interval late devonian the oceans experienced major changes in global carbon cycling and nutrient dynamics with a prominent positive carbon isotope shift at the base of the palmatolepis punctata zone middle frasnian the aim of this study was to construct seawater 87 sr 86 sr ratio curves for the pa transitans pa hassi zonal interval using well preserved conodont apatite from two sections in the holy cross mountains south central poland the final curves suggest that seawater 87 sr 86 sr values were steady at 0 70794 0 70799 during the transitans zone but began to rise in the early punctata zone towards a value of 0 70814 in the late punctata zone an increase of 0 0002 the increase in seawater 87 sr 86 sr values over the early middle frasnian boundary appears to be the second of two prominent short term rises in 87 sr 86 sr values which led to an overall shift in values from a givetian plateau of between 0 70780 and 0 70785 to a late frasnian plateau of between 0 7080 and 0 7082 correlation with a regional positive 13 c anomaly and evidence for eutrophication in the marine environment suggests that the causes of these phenomena may be linked and that the positive 87 sr 86 sr shift was caused by an increase in the continental flux of sr to the oceans i e the weathering flux a possible explanation for an increase in the weathering flux is the denudation of a new acadian eovariscan orogen which would have been mostly weathered in the humid warm tropical equatorial region

tectono thermal evolution in a region with thin skinned tectonics the western nappes in the cantabrian zone variscan belt of nw spain the palaeotemperature distribution in the transition from diagenesis to metamorphism in the western nappes of the cantabrian zone somiedo la sobia and aramo units are analysed by conodont colour alteration index cai and illite crystallinity ic structural and stratigraphic control in distribution of cai and ic values is observed both cai and ic value distributions show that anchizonal conditions are reached in the lower part of the somiedo unit a disruption of the thermal trend by basal thrusts is evidenced by cai and ic values there is an apparent discrepancy between the ic and cai values in carboniferous rocks of the aramo unit the ic has mainly anchizonal values whereas the cai has diagenetic values discrepant ic values are explained as a feature inherited from the source area in the carboniferous rocks of the la sobia unit both ic and cai indicate diagenetic conditions the anchimetamorphism predated completion of emplacement of the major nappes it probably developed previously and or during the early stages of motion of the units temperature probably decreased when the metamorphosed zones of the sheets rose along ramps and were intensely eroded in the context of the iberian variscan belt influence of tectonic factors on the metamorphism is greater in the internal parts where the strain and cleavage are always present than in the external parts cantabrian zone where brittle deformation and rock translation are dominant with an increasing role of the burial on the metamorphism

conodont alteration and tectonothermal evolution of a diagenetic unit in the iberian variscan belt ponga cuera unit nw spain tectonothermal analysis of a mainly carbonate unit located in the external part of the variscan orogen in nw spain is dealt with using the conodont colour alteration index cai and the study of textures of these microfossils the kubler index of the illite ki is used as a complementary method the area is characterized by a great uniformity in the cai values which in most cases are

ordovician floian lower darriwilian conodont biofacies of the san juan formation in the cerro viejo of huaco argentine precordillera abstract the conodont biofacies from the san juan formation at the cerro viejo of huaco central precordillera of argentina are analyzed for the identification of faunal dynamics and sea level changes the prioniodus elegans and oepikodus evae zones floian in age lower ordovician are identified in the lower san juan formation at the inner part of the huaco anticline in the western flank of the anticline the succession of the carbonate stratigraphic unit extends from the floian dapingian boundary lower middle ordovician up to the lower darriwilian middle ordovician lenodus variabilis zone for the interpretation of conodont biofacies through the los gatos creek section 5044 conodonts from rock samples of the floian to the lower darriwilian are studied conodont abundance and generic diversity graphs and cluster analysis reveal the following biofacies the juanognathus bergstroemognathus protopanderodus reutterodus drepanodus protopanderodus oepikodus juanognathus semiacontiodus and rossodus periodon protopanderodus biofacies are determined which indicate various deposits stacking from inner to middle and outer carbonate ramp environments of the san juan formation the associated analysis of biofacies and lithology allow for the recognition of two transgressive events in the san juan formation at the los gatos creek section which could be related to transgressive systems tracts tst that occurred during the lower and middle ordovician the recovered conodonts have a cai that varies from 2 to 2 5 indicating a burial paleotemperature between 60 and 155 c furthermore the variation of cai in conodonts of the same sample the presence of conodonts with corroded surface lamella recrystallization and crystal overgrowths and the presence of stylolites in limestone beds of the san juan formation indicate the circulation of hydrothermal fluids

tectonothermal evolution of a major thrust system the esla valsurbio unit cantabrian zone nw spain the tectonothermal evolution of a unit in the foreland fold and thrust belt of the iberian massif is established using the conodont colour alteration index cai the unit consists of two parts with different tectonothermal histories the esla nappe region and the valsurbio region separated by a synorogenic carboniferous basin guardo valderrueda basin the esla nappe region evolved in diacaizonal conditions corresponding to the diagenetic conditions of the pelites whose palaeotemperatures were controlled by rock burial maximum values were reached before the emplacement of the thrust nappes so tectonic superimposition is not registered by the cai overburial due to the emplacement of the thrust units was prevented by simultaneous intense erosion the geothermal gradient obtained for burial was c 35 c km 1 and the temperature reached by the older cambrian rocks was c 210 230 c the valsurbio region was affected by an extensional tectonothermal post orogenic event that gave rise to metamorphism with ancaizonal or epicaizonal conditions corresponding to anchizone or epizone of the pelites the most common maximum palaeotemperatures reached in this event fall within the range 305 415 c although higher palaeotemperatures could be reached locally as a consequence of contact metamorphism this event gave rise to subhorizontal cleavage that cuts the main variscan folds coal rank data indicate an increase in maximum palaeotemperatures eastwards from the esla nappe region to the valsurbio region through the guardo valderrueda basin

genesis and rank distribution of upper carboniferous coal basins in the cantabrian mountains northern spain abstract the cantabrian mountains located in the nw of the iberian peninsula constitute the most important coal mining district of spain anthracitic and bituminous coals high and medium rank coals have been mined in the area since the end of the nineteenth century and they currently account for about 70 of the total coal resources of the country the region forms part of the cantabrian and west asturian leonese zones of the iberian variscan fold belt and is strongly deformed by a set of imbricate thrusts coeval folds and high angle faults coal bearing successions are westphalian and stephanian pennsylvanian in age and are exposed in numerous coalfields of variable size arranged roughly parallel to the tectonic structures coal rank varies from medium rank bituminous d coals rr 0 5 to high rank anthracites a coals rr

geochemical characteristics and hydrocarbon generation modeling of the kazhdumi early cretaceous gurpi late cretaceous and pabdeh paleogene formations iranian sector of the persian gulf abstract the marls and argillaceous limestones of the early cretaceous kazhdumi late cretaceous gurpi and paleogene pabdeh formations are considered as potential source rock candidates in this area the present study characterizes hydrocarbon potential type of organic matter and thermal maturity of these three formations in the iranian sector of the persian gulf also 1d basin modeling was used to analyse the burial history and timing of hydrocarbon generation in these formations a total of 179 cutting samples from 25 wells were evaluated through rock eval pyrolysis and organic petrography average total organic carbon toc content for the samples of the kazhdumi gurpi and pabdeh formations that were analyzed for the current study is 1 2 0 9 and 1 wt respectively all three formations show lower toc contents in central part relative to eastern and western parts of the study area rock eval pyrolysis and organic petrography show that the organic matter in all three formations is mainly composed of type ii and mixed type ii iii kerogen this study shows that the kazhdumi gurpi and pabdeh formations in iranian offshore areas are not as rich as onshore areas and specifically in the dezful embayment in terms of organic matter quantity and quality thermal history modeling indicates that constant heat flow values in the range of 64 73 mw m 2 gives the best fit between measured and calculated vitrinite reflectance and bottom hole temperature the rock eval t max vitrinite reflectance and the generated models suggested that in the eastern parts of the study area the kazhdumi formation is at the last stage of oil generation and the gurpi and pabdeh formations are within the main oil generation window hydrocarbon generation began in the early eocene middle eocene and early miocene in the kazhdumi gurpi and pabdeh formations respectively in the western parts of the persian gulf the kazhdumi formation is within the main oil window with hydrocarbon generation took place during the oligocene and the gurpi and pabdeh formations are early mature and immature respectively all three formations are thermally immature in the central part of the persian gulf the kazhdumi formation shows positive correlation with the crude oils of the cretaceous and tertiary reservoirs taken from the northwestern persian gulf the pabdeh and gurpi formations show no correlation with crude oils produced in the northwestern and southeastern persian gulf

why rolls are prevalent in the hurricane boundary layer recent remote sensing observations show that the hurricane boundary layer flow although energetic is not a region of homogeneous turbulence in fact the observations convincingly demonstrate that a large fraction of the turbulent flow in the regions away from the deep convective rainbands is highly organized into intense horizontal roll vortices that are approximately aligned with the mean wind and span the depth of the boundary layer these observations show that rolls strongly increase the flux of momentum between the underlying surface and the main body of the storm compared to an equivalent hurricane boundary layer flow without rolls the linear and nonlinear dynamics of hurricane boundary layer roll formation are outlined and it is shown why rolls are in fact the expected basic hurricane boundary layer state the model presented here explains the hurricane roll features currently documented in field programs and makes predictions that can be tested in future experiments the primary effects of rolls on the boundary layer fluxes are inherently nonlocal and nongradient and hence cannot be captured by standard downgradient turbulence parameterizations used in hurricane simulations however the nonlinear theory is the proper starting point for developing boundary layer parameterizations that include roll modification of the turbulent fluxes

simulation and parameterization of the turbulent transport in the hurricane boundary layer by large eddies 1 hurricane boundary layer hbl processes especially the structure of the coherent large eddy circulations lecs and their induced vertical transport are not well understood this paper introduces a large eddy simulation les framework in a weather hindcasting mode developed from a multiple scale nested weather research and forecasting wrf model using the wrf les this study investigated the structure of the hbl lecs and the associated vertical transport during the landfall of hurricane ivan 2004 the simulation shows that the hbl lecs exist in a mean stable environment and consist of well defined updraft and downdraft statistically the hbl lecs are only slightly skewed with the updrafts and downdrafts relatively evenly distributed spatially the inversion base basically envelopes the upper boundary of lecs the trough in between two adjacent lecs is where most entrainment takes place whereas the crest of the lecs is where boundary layer air detrains out of the hbl in such a way lecs directly connect the surface the hbl and the main body of a hurricane vortex and enhance the exchange of energy moisture and momentum between them it is found that the current boundary layer schemes significantly underestimate the resolved turbulent fluxes due to the fact that the effects of lecs have not been included in the parameterizations on the basis of the statistical structure of lecs simulated by the wrf les this paper proposes a conceptual updraft downdraft model that can potentially be implemented in weather forecasting models to parameterize the fluxes induced by the hbl lec transport

conodont thermochronology of exhumed footwalls of low angle normal faults a pilot study in the mormon mountains tule springs hills and beaver dam mountains southeastern nevada and southwestern utah abstract u th he thermochronology is a well established dating technique used to understand the temperature time histories of rocks in a wide range of geologic settings the technique is presently restricted to rocks that contain specific accessory minerals such as apatite or zircon marine carbonates and shales typically lack these accessory phases in quantities and sizes practical for u th he dating and thus present a challenge for application of the method here we explore the utility of biogenic apatite from conodonts as a u th he thermochronometer at a well studied calibration site located in eastern nevada and southwestern utah we performed u th he thermochronometry laser ablation inductively coupled plasma mass spectrometry x ray micro computed tomography and scanning electron microscopy sem on specimens with conodont color alteration indices cai of 1 5 3 extracted from carbonate rocks in the footwalls of low angle normal faults in the mormon mountains tule spring hills and beaver dam mountains conodont u th he che dates have high scatter dates are commonly reproducible to 20 of sample means but can deviate up to 150 all cai 1 5 2 5 conodonts produce che dates younger than 240 ma consistent with thermal resetting of samples however most cai 3 conodonts give ages 2 6 older than mississippian and permian deposition average u th and rare earth element ree concentrations depend on porosity and permeability differences between albid and hyaline conodont tissue and range from we propose that microstructural changes associated with increasing cai influence che dates parent isotope loss occurs during the post cooling stage either in the outcrop or in the laboratory our hypothesis is that the double buffered formic acid procedure for dissolving dolomitized carbonates may accelerate this loss in thermally altered higher cai conodonts

helical circulations in the typhoon boundary layer 1 low level wind data from the wsr 88d in guam obtained in typhoon dale 1996 and typhoon keith 1997 are analyzed for coherent structures consistent with the results of previous studies of atlantic hurricanes velocity anomalies associated with coherent structures were found in the boundary layer of both storms a total of 99 cases of coherent structures also known as roll vortices were documented during a 6 h evaluation period for each storm storm relative roll location roll vorticity asymmetries in the upward and downward momentum fluxes and signatures of circulations transverse to the mean flow associated with roll circulations were explored the effects of terrain and convective precipitation systems such as rainbands on the occurrence of rolls were investigated the results support and extend prior findings of roll observations and can be used to help validate theoretical and numerical models of coherent structures within tropical cyclones moreover the wind variations documented in this study may have application for wave runup and wind damage potential in tropical cyclones

tectonothermal evolution of a foreland fold and thrust belt the cantabrian zone iberian variscan belt nw spain analysis of the conodont colour alteration index and the kubler index of illite allowed us the characterization of four types of very low or low grade metamorphism in the cantabrian zone cz and determination of their regional and temporal distri bution these types are 1 an orogenic variscan metamorphism present only in restricted areas of the western and north western parts of the cz where epizonal conditions are reached 2 a burial metamorphism that appears in the basal part of some nappes where anchizonal conditions are sometimes achieved the thermal peak preceded emplacement of the nappes 3 a late variscan metamorphism in the southern and south eastern parts of the cz a cleavage cutting most of the variscan folds is associated with this metamorphism which has been related to an extensional episode 4 a contact metamor phism and hydrothermal activity associated with minor intru sive bodies the extension continued after the variscan deformation giving rise to hydrothermal activity during permian times

simultaneous use of thermal indicators to analyse the transition from diagenesis to metamorphism an example from the variscan belt of northwest spain

lineal eddy features under strong shear conditions abstract large eddy simulation of a marine boundary layer bl with strong wind shear and weak buoyancy flux over a relatively large horizontal domain 25 18 km and long time period 16 h produces lineal eddy structures with along axis variations these rolls are transient their lifetime being roughly 8 h and their horizontal to vertical aspect ratio increases with time at all heights above the surface layer even above the bl temporally coherent features propogate with a speed slightly slower than the vertically averaged bl velocity the length scale of along roll variation is about four and one half times the corresponding cross roll length scale to examine the importance of the roll circulations fluxes of momentum heat and water vapor are partitioned into roll and non roll contributions and additionally separated into contributions from the ascending and descending roll regions to reveal differences in advective roll transport and in roll modulation of smaller scale transfer the roll in

processes controlling forms of phosphorus in surficial sediments from the eastern arabian sea impinged by varying bottom water oxygenation conditions abstract the surficial sediments from the upper continental slope of the eastern arabian sea impinged by the oxygen minimum zone omz 150 1200 m water depth show varying concentrations of the biogenic element phosphorus p 0 1 0 2 in the northern and southern areas even though total organic carbon concentrations are relatively constant toc 2 5 prakash babu et al 1999 to understand this discordance 17 surface sediment samples from shelf slope and deep sea of the eastern arabian sea were investigated using a five step sequential extraction scheme to delineate the process responsible for p enrichment in omz high fractions of organic phosphorus porg 10 26 biogenic phosphorus pbio 36 48 relatively low molar corg porg ratios 322 447 and corg preactive ratios close to redfield ratio in omz sediments of the se arabian sea suggest accumulation under high surface production and low residence time of labile forms of p due to high sedimentation rates despite higher productivity in surface waters low fractions of porg 8 13 less than deep sea sediments of the study area 12 13 pbio 25 33 relatively high molar corg porg ratios 341 508 and corg preactive ratios less than redfield ratio in omz sediments from the ne arabian sea may indicate a higher degree of regeneration and diagenetic transformation of labile forms of p to other phases authigenic phosphorus paut fraction varies by a factor of 2 8 in sediments from the omz when compared to well oxygenated deep sea sediments of the study area while the ptotal remains constant significant p transformation seems to occur in ne arabian sea which is suggested by high paut fraction 50 compared to low paut fraction 10 39 in the se arabian sea sediments supply rates of phosphorus variable rates of p dissolution under varying dissolved oxygen contents in the bottom waters and early diagenetic transformation of p within the sediments seem to influence p geochemistry in sediments overlain by the omz in the eastern arabian sea

strontium isotope systematics of conodonts middle devonian eifel mountains germany abstract the eifel mountains lithological profile the stratotype for the middle devonian was densely sampled for conodonts to delineate the sr isotopic evolution of coeval sea water the 87sr 86sr curve obtained shows oscillations around a mean of about 0 7078 that have a frequency in the 105 106 yr range and an amplitude in the 10 5 10 4 range these oscillations mimic those obtained on coeval brachiopods diener et al 1996 but are shifted into more radiogenic domains by up to 10 4 model calculations suggest that the shift is due to partial 30 40 early diagenetic equilibration of conodonts with their enclosing bulk rock matrix the reality of partial recrystallisation is supported by visible neoformed blocky apatite crystals on the surface of the conodonts despite their otherwise apparently excellent preservation with cai values of 1 5 2 5 we therefore suggest that studies anticipating use of conodonts as a recorder of paleoceanographic events should be confined to specimens embedded in a relatively clean matrix such as pure limestone even these results should be cross checked by comparison with data on coeval low mg shells such as brachiopods or belemnites

the relationship between radar reflectivities and clouds associated with horizontal roll convection on 8 august 1982 abstract horizontal convective rolls hcrs and cloudstreets that occurred in northeastern colorado are studied using doppler radar data cloud photography and vertical soundings examination of the environment in which the hcrs form indicates a boundary layer wind speed that is much lower than those measured in previous studies evidence shows that the hcrs form in a well defined boundary layer yet the cloudstreets that develop seem to exist within a stable layer above a relationship between the radar reflectivity echoes and the cloudstreets is firmly established the echoes are aligned directly under the cloudstreets the echoes at lower levels are shown to be caused by convergence of particulate matter into updraft portions of the hcr circulation yet evidence indicates the cloud level echoes are due to backscatter from refractive index inhomogeneities at the surfaces of rising thermals examination of the echoes show that the strongest and tallest echoes are associated with cloud formation and tha

tectonothermal evolution of the northeastern cantabrian zone spain a tectonothermal study of the northeastern sector of the cantabrian zone ponga cuera and picos de europa units using the conodont color alteration index cai and kubler index ki methods shows a variation from diagenetic to anchizonal conditions the latter are illustrated in geological maps and cross sections the greater part of the studied area has cai values lower than 2 caused by two long periods of burial separated by a compressive interval corresponding to the variscan deformation in which thrusts were the dominant structures tectonic superimposition was balanced by intense and fast erosion and had little effect on the cai values in contrast a high thermal gradient was produced in the southern outcrops that led to recognize the transition between diagenetic and anchizonal conditions through cai values near the basal thrust of the picos de europa unit the diagenesis anchizone boundary appears a little further south through the determination of the kubler index in phyllosilicate minerals ki 0 42 cai isograds cut the variscan structures as a consequence of a thermal episode that occurred near the carboniferous permian boundary at the beginning of an extensional regime the thermal source was located further south in the adjacent pisuerga carrion unit alterations in the cai values as well as dolomitization and ore deposits locally resulted from permian mesozoic hydrothermal activity microtextural analysis of the conodonts allowed us to relate several types of apatite overgrowth to diagenetic conditions and recrystallization to anchizonal ones whereas dissolution was common during hydrothermalism alpine deformation hardly produced any changes in the previous thermal pattern but was responsible of the northwards tilting of the structure and cai isograds

an observational case for the prevalence of roll vortices in the hurricane boundary layer abstract doppler velocity data from weather surveillance radar 1988 doppler wsr 88d radars during four hurricane landfalls are analyzed to investigate the presence of organized vortices in the hurricane boundary layer hbl the wavelength depth magnitude and track of velocity anomalies were compiled through analysis of doppler velocity data the analysis reveals alternating bands of enhanced and reduced azimuthal winds closely aligned with the mean wind direction resulting statistics provide compelling evidence for the presence of organized secondary circulations or boundary layer rolls across significant areas during four hurricane landfalls the results confirm previous observations of the presence of rolls in the hbl a potential limitation of the study presented here is the resolution of the wsr 88d data in particular analysis of higher resolution data e g from the doppler on wheels is needed to confirm that data aliasing has not unduly impacted the statistics reported here momentum flux

early diagenesis of organic matter in peru continental margin sediments phosphorite precipitation abstract pore water chemistry total dissolved co 2 nh 4 no 3 no 2 po 4 si oh 4 ca mg fe mn so 4 h 2 s and f and titration alkalinity solid phase chemistry c org p org c tot n tot f si opal and s ii and sediment characteristics porosity dry bulk density and formation factors were determined on a centimeter scale spacing in the upper 20 40 cm of sediments under intense upwelling areas on the peru continental shelf these data demonstrate that carbonate fluorapatite cfa is precipitating from pore waters in the upper few centimeters of a gelatinous mud with high organic carbon content up to 20 c org very high porosity 0 96 ml cm 3 and very low dry bulk density 3 dissolved phosphate concentrations at the sediment water interface range from 20 to 100 m orders of magnitude higher than bottom water concentrations and much higher than predicted from regeneration of organic matter the mechanism of this interfacial phosphate release is unclear but is apparently uncoupled from carbon and nitrogen metabolism and thus may be linked either to dissolution of fish debris or to the presence of a microbial mat in surficial sediments fluoride is incorporated into cfa by diffusion from the overlying seawater and carbonate ions are provided from pore water alkalinity magnesium concentrations in this reaction zone are not significantly different from those of seawater suggesting that magnesium depletion is not a necessary prerequisite for cfa precipitation the environment of precipitation is interface linked rather than driven by organic diagenesis of phosphorus deeper in the sediment most of the cores display a wide range of diagenetic characteristics below the immediate interfacial region but almost all show the precipitation signature near the interface this interface linked early diagenetic porewater environment for the precipitation of cfa explains many of the geochemical characteristics of phosphorites and provides a testable model to compare the modern phosphogenic analog with ancient phosphorite deposits two of the cores display very high solid phase phosphorus and fluoride contents reflecting the presence of apparently modern pelletal apatites