gravity wave variability and interaction with lower frequency motions in the mesosphere and lower thermosphere over hawaii abstract radar observations of the mesosphere and lower thermosphere over kauai hawaii have provided measurements of the horizontal wind field since september 1990 horizontal velocity variances in the gravity wave band of frequencies were computed for several averaging intervals over the entire dataset the results correlated with tidal and lower frequency winds show evidence of filtering of gravity waves by tidal and other lower frequency motions spectra of gravity wave variances for two years of data display peaks at planetary wave as well as tidal periods primarily near 12 24 48 h and 16 day periods the modulation of gravity wave variance during four distinct background regimes is examined one in which the diurnal tide predominates another in which the 2 day wave is large a third in which the zonal mean wind and tidal amplitudes are large and a fourth in which the zonal mean tidal and 2 day amplitudes are all small intervals in which the diurnal tide or the 2 day wave predominates s

p t t evolution of ultrahigh temperature granulites from the saxon granulite massif germany part ii geochronology the granulites of the saxon granulite massif equilibrated at high pressure and ultrahigh temperature and were exhumed in large part under near isothermal decompression this raises the question of whether p t t data on the peak metamorphism may still be retrieved with confidence felsic and mafic granulites with geochronologically useful major and accessory phases have provided a basis to relate p t estimates with isotopic ages presented in a companion paper the assemblage garnet clinopyroxene in mafic granulite records peak temperatures of 1010 1060 c consistent with minimum estimates of around 967 c and 22 3 kbar obtained from the assemblage garnet kyanite ternary feldspar quartz in felsic granulite multiple partial overprint of these assemblages reflects a clockwise p t evolution garnet and kyanite in the felsic granulite were successively overgrown by plagioclase spinel plagioclase sapphirine plagioclase and biotite plagioclase most of this overprinting occurred within the stability field of sillimanite garnet clinopyroxene in the mafic granulite were replaced by clinopyroxene amphibole plagioclase magnetite the high p t conditions and the absence of thermal relaxation features in these granulites require a short lived metamorphism with rapid exhumation the ages of peak metamorphism 342 ma and shallow level granitoid intrusions 333 ma constrain the time span for the exhumation of the saxon granulites to about 9 ma

short period fluctuations of the diurnal tide observed with low latitude mf and meteor radars during cadre evidence for gravity wave tidal interactions mf and meteor radar data from four equatorial and subtropical sites hawaii christmas island jakarta and adelaide are used to examine diurnal tide amplitude and phase variability at mesosphere and lower thermosphere altitudes all sites exhibit significant seasonal variability with the largest amplitude fluctuations occurring at hawaii and adelaide shorter term variability is found to occur primarily on timescales of 5 to 30 days amplitude and phase fluctuations are well correlated among different sites on occasion but in general the amplitude and phase coherences are low and suggest significant local influences on the tidal structures the temporal behavior of height variations of the diurnal tide amplitude and phase is also examined cross correlations and cross spectra of these tidal parameters especially between the amplitude and phase are examined closely the tendency for phase maxima to lead amplitude maxima is consistent with tidal modulation of gravity wave propagation and momentum fluxes with a corresponding feedback by the gravity wave momentum flux divergences on the observed tidal structures these results substantially extend previous more limited studies of gravity wave tidal interactions and provide a statistical basis for the possible importance of this interaction and its influences on the diurnal tidal structure

the evolution of the patagonian ice sheet from 35 ka to the present day patice abstract we present patice a gis database of patagonian glacial geomorphology and recalibrated chronological data patice includes 58 823 landforms and 1 669 geochronological ages and extends from 38 s to 55 s in southern south america we use these data to generate new empirical reconstructions of the patagonian ice sheet pis and subsequent ice masses and ice dammed palaeolakes at 35 ka 30 ka 25 ka 20 ka 15 ka 13 ka synchronous with the antarctic cold reversal 10 ka 5 ka 0 2 ka and 2011 ad at 35 ka the pis covered of 492 6 x103 km2 had a sea level equivalent of 1 496 mm was 350 km wide and 2090 km long and was grounded on the pacific continental shelf edge outlet glacier lobes remained topographically confined and the largest generated the suites of subglacial streamlined bedforms characteristic of ice streams the pis reached its maximum extent by 33 28 ka from 38 s to 48 s and earlier around 47 ka from 48 s southwards net retreat from maximum positions began by 25 ka with ice marginal stabilisation then at 21 18 ka which was then followed by rapid irreversible deglaciation by 15 ka the pis had separated into disparate ice masses draining into large ice dammed lakes along the eastern margin which strongly influenced rates of recession glacial readvances or stabilisations occurred at least at 14 13 ka 11 ka 6 5 ka 2 1 ka and 0 5 0 2 ka we suggest that 20th century glacial recession a 1 is occurring faster than at any time documented during the holocene

eclogite facies quartz veins within metabasites of the dabie shan eastern china pressure temperature time deformation path composition of the fluid phase and fluid flow during exhumation of high pressure rocks

direct ion microprobe u pb dating of fossil tooth of a permian shark abstract we report here direct ion microprobe dating of fossil tooth dentine of a permian fresh water shark orthacanthus senckenbergianus using the shrimp instrument recently installed at hiroshima university fifteen spots on the small sample approximately 2 mm 1 mm indicate a 238 u 206 pb isochron age of 266 18 ma and a tera wasserburg concordia intercept age of 266 24 ma in a three dimensional 238 u 206 pb 207 pb 206 pb 204 pb 206 pb diagram these permian ages are consistent with a 235 u 207 pb age of 453 170 ma and a 232 th 208 pb age of 235 310 ma suggesting indistinguishable depositional and early diagenetic ages of the fossil in its sedimentary sequences the success of the method depends on the chemical fractionation of uranium from lead in a specimen a few hundred microns in size and the consequent variations in lead isotopic compositions due to radioactive decay

mesospheric momentum flux studies at adelaide australia observations and a gravity wave tidal interaction model abstract we present here the results of an analysis of gravity wave momentum fluxes in the mesosphere and lower thermosphere inferred using a dual beam doppler radar near adelaide australia during june 1984 our analysis reveals that over 70 of the momentum flux and of the inferred zonal drag was due to gravity waves with observed periods less than one hour this suggests that it is the gravity waves with high intrinsic frequencies and small horizontal scales that are most effective at transporting momentum into the middle atmosphere the temporal variations in the momentum flux and flux divergence due to high frequency motions were also examined in detail in addition to daily variability a strong diurnal modulation was observed to occur this was found to be correlated with the phase of large amplitude diurnal tidal motions as a result of these observations a gravity wave tidal interaction model was proposed which accounts for all of the major features of the observed data including a reduction i

long term variability in the equatorial middle atmosphere zonal wind the high resolution doppler imager hrdi on the upper atmosphere research satellite uars has provided measurements of the horizontal wind field in the stratosphere mesosphere and lower thermosphere since november 1991 this data set which spans a period of more than 3 years has facilitated an investigation of the long term behavior of the background circulation on a nearly global basis at middle and high latitudes the zonal circulation is characterized by an annual oscillation at low latitudes 30 the most prominent long term variation above the stratopause is the mesosphere semiannual oscillation msao which maximizes near the equator at an altitude of between 80 and 85 km further analysis of the time series reveals an additional strong variation with an amplitude near 30 ms 1 and a period of about 2 years this feature shows the same altitude and latitude structure as the msao and exhibits a phase relationship with the stratospheric quasi biennial oscillation qbo observations from the christmas island mf radar 2 n 130 w confirm the presence of this mesospheric qbo mqbo these observations support recent findings from a modeling study which generates an mqbo via the selective filtering of small scale gravity waves by the underlying winds they traverse

mesospheric momentum fluxes observed by the mst radar at poker flat alaska abstract an analysis of the wave motions observed with the poker flat mst radar during the winter summer and fall of 1986 is presented in this paper monthly and daily mean winds momentum fluxes and velocity variances are investigated in detail while several features are in agreement with previous measurements some significant differences also are found to exist in our observations monthly mean horizontal winds between 82 and 89 km have amplitudes of 20 40 m s 1 westward and 10 25 m s 1 southward in july and august in fall and winter the horizontal winds between 58 and 75 km are weaker and essentially eastward monthly mean vertical velocities are predominantly downward at 0 3 m s 1 which implies a vertical wave energy flux of 0 1 w m 2 higher than that estimated at low latitudes monthly mean horizontal variances are 1600 m2 s 2 in summer and 600 m2 s 2 in fall and winter with vertical variances 3 m2 s 2 monthly mean zonal and meridional momentum fluxes contributed predominantly by wa

seasonal variation in equatorial mesospheric temperatures observed by sme abstract observations made by the solar mesosphere explorer sme satellite from 1982 through 1986 are used to examine the seasonal variation of temperature in the equatorial mesosphere between 58 5 and 90 km near the equator seasonal variability is dominated by a strong semiannual oscillation sao whose amplitude increases from about 3 k in the lower mesosphere to 7 3 k near 80 km above 80 km the amplitude of the oscillation decreases to a minimum at 83 km but increases again sharply above that level reaching 16 6 k at 90 km the highest level observed the structure of the temperature sao is consistent with previous observations of the saos in temperature and zonal wind although the very large amplitude at 90 km may be due in part to contamination by the diurnal tide just below 80 km temperatures are warm cold near the solstices equinoxes implying westerly easterly accelerations above the behavior at 58 5 km lap that at 80 km by about 2 months there is evidence in the data for a seaso

observational evidence of tidal gravity wave interactions using the uwo 2 mhz radar the degree of interaction between atmospheric gravity waves and tides is an issue which is of great importance in middle atmosphere studies it is especially important with regard to tidal variability which is frequently observed in the mesosphere and lower thermosphere but as yet has not been subject to adequate study in this paper we present some strong observational evidence of such interactions made with the uwo 2 mhz radar near london canada our observations show significant correlation between gravity waves and tides diurnal at certain times of the year and the nature of the correlation is intermittent and varies with time of year it is possible that differences between tidal amplitudes at sites with mesoscale separations may be explained in terms of such phenomena we also propose a simple model which is found to be consistent with the major features of the observed data

rayleigh lidar observations of quasi sinusoidal waves in the tropical middle atmosphere 1 rayleigh lidar observations of temperature for 2 7 hours on 38 nights during the period of 18 january 5 march 1999 and for 3 hours on 29 nights during 29 february 2 april 2000 in the altitude region of 27 60 km over gadanki 13 5 n 85 e clearly show the dominance of the quasi sinusoidal waves of periods in the range of 6 13 hours in temperature in the tropical middle atmosphere during 1999 the vertical wavelength of these waves ranges from 7 1 to 17 km with a mean value of 12 0 2 4 km while during 2000 it ranges from 5 5 to 17 km with a mean value of 11 4 3 5 km the wave periods estimated from the observations during 1999 are generally greater than the observation period on each night and are estimated to be in the range of 6 5 13 1 hours with an average period of 9 7 1 8 hours which is significantly smaller than the inertial period of 53 hours the amplitudes of these waves are in the range of 1 to 8 k such sinusoidal wave modes are clearly discernible in the temperature profiles for 50 nights of observation another striking feature is that the quasi sinusoidal structure is clearly observed in the equivalent day analysis also indicating only small day to day variability in phase a property that is characteristic of atmospheric tides

erratum to metamictisation of natural zircon accumulation versus thermal annealing of radioactivity induced damage annealing of the radiation damage generated in decay events is a common phenomenon in natural zircons we have studied relationships between radiation damage age and radionuclide content of natural zircons on a micro scale the degree of metamictisation was estimated by means of confocal laser raman spectroscopic measurements raman band broadening in well ordered to moderately metamict zircons that have not experienced significant healing of the radiation damage since the time of their growth shows a nearly linear dependence on the fluence this dependence is proposed as a calibration line for examining unknown zircons in order to consider complete or incomplete damage storage which may contribute to the understanding of the low t thermal history of their host rocks seven examples for the application are presented radiation damage may anneal heterogeneously with preferred re ordering in more damaged micro areas results suggest that single point defects do not anneal continuously over geologic periods of time but are in contrast a comparably stable type of radiation damage in contrast to recrystallisation processes structural recovery due to simple thermal annealing is not necessarily connected with loss of radiogenic pb the most prominent example for this are concordant zircons from sri lanka although they are excellent standards for u pb dating sri lankan zircons should not be used as standards for structural radiation damage the experimental work is completed by monte carlo simulations of decay events in zircon

introducing a geochemical screen to identify geologically meaningful u pb dates in fossil teeth abstract previous studies have shown that radiometric dating of fossils can be complicated by post fossilisation alteration a key challenge to obtaining geologically meaningful fossilisation dates in bioapatite is identifying regions that have remained relatively undisturbed since the time of fossilisation in order to determine whether a geochemical indicator can be used to identify least disturbed regions we combine in situ trace element analysis and u pb geochronology of fossil teeth from the arroyo chijuillita member new mexico and the dinosaur park formation alberta the reliability of these u pb dates is supported by good agreement between the isotope dilution thermal ionization mass spectrometry 61 5 1 6 ma and laser ablation icp ms 64 2 2 4 ma dates for a targeted tooth region of fourteen teeth analyzed from these units two record dates within uncertainty of the depositional age one has a diffusion concave upward cross sectional yttrium profile the other a concave downward profile reflective of trace element loss it was found for teeth from both units that smaller yttrium concentration ranges are correlated with younger u pb dates likely the result of post fossilisation alteration a yttrium screen based on this relationship is proposed and is found to be a better indicator of post fossilisation open system behaviour in the samples analyzed than other geochemical features thought to be produced during fossilisation this screen provides a new tool for identifying fossil material least disturbed since fossilisation facilitating the use of bioapatite to date the time of diagenesis

meteor wind radar observations of gravity wave momentum fluxes and their forcing toward the mesospheric semiannual oscillation 1 wind measurements from continuous meteor radar observations during june 2004 may 2007 are used to estimate the gravity wave momentum fluxes in the mesosphere lower thermosphere mlt region over trivandrum 8 5 n 76 9 e a low latitude station in india the radial velocity variances in the 82 98 km height region which are mainly caused by gravity waves measured by the meteor radar are used to determine the gravity wave momentum fluxes using a novel method proposed by hocking 2005 altitude profiles of momentum fluxes of short period less than 2 3 h gravity waves are estimated for three continuous years seasonal variation in the gravity wave momentum fluxes showed semi annual variation with equinoctial maximum and solstitial minimum by using estimated gravity wave momentum fluxes an attempt is made to quantify their contribution in driving the mesospheric semi annual oscillation msao the mean flow acceleration estimated from the divergence of gravity wave momentum fluxes is compared with the observed mean flow acceleration computed from monthly mean zonal winds during six msao cycles over three years this comparison reveled that the gravity wave contribution toward the westerly phase of msao varies from 20 60 while that toward the easterly phase varies from 30 70 variations are observed from cycle to cycle in the gravity wave forcing toward both phases of msao the significance of the present study lies in estimating the gravity wave momentum fluxes in the mlt region and quantifying their contribution toward the generation of msao over the low latitude for the first time

protracted diagenetic alteration of ree contents in fossil bioapatites direct evidence from lu hf isotope systematics abstract fossil bones and teeth are potentially important repository for geochemical proxy data and a target for radiometric dating the concentration of many trace elements in bones and teeth increases by orders of magnitude after death and it is this diagenetic incorporation that forms the basis for several areas of geochemical study the use of bones and teeth in this context relies on two assumptions first that target metal ions are incorporated rapidly after death reflecting a known environmental signal and second that after early incorporation the bone or tooth remains as an essentially closed system resistant to later diagenetic change a wide literature has developed exploring these assumptions but relatively little direct evidence has been used to assess the long term diagenetic stability of trace elements within bones and teeth in this study we use the lu hf isotope system to show that bones and teeth of cretaceous and triassic age from both terrestrial and marine settings experience continued long term diagenetic change most likely through gradual addition of trace elements modelling suggests that diagenetic addition after initial recrystallisation may account for 50 of the total ree content in the sampled bones the extent depending on initial uptake conditions tooth enamel and enameloid may be more resistant to late diagenetic changes but dentine is probably altered to the same extent as bone these results have significant implications for the use of bones and teeth as hosts of chronological palaeoceanographic palaeoenvironmental and taphonomic information particularly in mesozoic and palaeozoic contexts

dating multiply overprinted sn mineralized granites examples from the erzgebirge germany granites and primary tin mineralization in the erzgebirge were dated using 1 conventional u pb dating of uraninite inclusions in mica 2 rb sr dating of inclusions in quartz that represent highly evolved melts 3 re os dating of magmatic hydrothermal molybdenite and 4 chemical th u pb dating of uraninite conventional isotope dilution and thermal ion mass spectrometry and chemical th u pb dating of uraninite in granites from the ehrenfriedersdorf mining district provide ages of 323 9 3 5 ma 2 greifenstein granite and 320 6 1 9 and 319 7 3 4 ma 2 both sauberg mine in agreement with u pb apatite ages of 323 9 2 9 and 317 3 1 6 ms 2 both sauberg mine rb sr analysis of melt inclusions from zinnwald gives highly radiogenic sr isotopic compositions that with an assumed initial sr isotopic composition permit calculation of precise ages from single inclusions the scatter of the data indicates that some quartz hosted melt inclusions have been affected by partial loss of fluid exsolved from the melt inclusion re os dating of two molybdenite samples from altenberg provides ages of 323 9 2 5 and 317 9 2 4 ma 2 together with age data from the literature our new ages demonstrate that primary tin mineralization and the emplacement of the large sn specialized granites in the erzgebirge fall in a narrow range between 318 and 323 ma primary sn mineralization occurred within a short interval during post collisional collapse of the variscan orogen and was essentially synchronous over the entire erzgebirge in contrast to earlier claims no systematic age difference between granites of the eastern and western erzgebirge was established furthermore our data do not support a large age range for late variscan granites of the erzgebirge 330 290 ma as has been previously suggested

comment on in situ ion microprobe u pb dating and ree abundances of a carboniferous conodont by y sano and k terada

a new bathymetric compilation highlighting extensive paleo ice sheet drainage on the continental shelf south georgia sub antarctica a grid derived from a new compilation of marine echo sounding data sets has allowed us to visualize and map the geomorphology of the entire continental shelf around south georgia at an unprecedented level of detail the grid is the first continuous bathymetric data set covering south georgia to include multibeam swath bathymetry and represent them at a subkilometer resolution large and previously undescribed glacially eroded troughs linked to south georgia s modern day fjords radiate from the island marking the former pathways of large outlet glaciers and ice streams a tectonic or geological influence is apparent for the major troughs where glaciers have exploited structural weaknesses on the continental block bed forms lining the troughs give some first insights into glacial dynamics within the troughs suggesting arteries of fast flowing ice occupied these topographic depressions in the past and operated over both bedrock and sedimentary substrates on the outer shelf and within the troughs large ridges and banks are also common interpreted as terminal lateral and recessional moraines marking former positions of ice sheets on the shelf and their subsequent reorganization during deglaciation a small trough mouth fan has developed at the mouth of at least one of the cross shelf troughs demonstrating a focused sediment delivery to the margin slides and slide scars are also present on parts of the margin showing that margin stability perhaps also related to glaciation has been an important factor in depositional processes on the continental slope implications of the new observations are that ice sheets have been more extensive on south georgia than any previous studies have reported their age may date back to late miocene times and evolution of the shelf system has probably involved numerous late cenozoic glacial episodes however relatively fresh seafloor geomorphology coupled with evidence from other maritime antarctic islands heard island and kerguelen island indicating extensive glaciation at the last glacial maximum raises the possibility that the extent of sub antarctic glaciation for the last glacial period has until now been underestimated

origins of co2 in permian carbonate reservoir rocks zechstein ca2 of the nw german basin lower saxony permian carbonate reservoir rocks stassfurt carbonate of the co2 province lower saxony basin nw germany are locally characterised by high amounts of co2 leading to serious problems on exploration in order to receive information on the major co2 sources and co2 migration and accumulation processes mineralogical geochemical and stable isotope analyses c 13 o 18 were carried out on authigenic precipitations within the stassfurt carbonate rocks ca2 these rocks contain early diagenetic e g formed in soft sediment carbonate minerals calcite dolomite and anhydrite in concretions and small cracks in addition large up to 2 cm wide carbonate cemented fractures formed in solid ca2 rocks semi quantitative estimates of the diagenetic mineral content showed variations between the investigated rock cores nine out of 12 ca2 rock cores are derived from wells situated in the area of modem ch4 rich reservoirs and have distinct fracture systems developed in contrast the other three rock cores are from wells characterised by co4 rich reservoirs and lack fractures of similar thickness the assumed relationship between tectonically induced fractures and the gas content of the ca2 reservoir rocks implies co2 degassing of the ca2 rocks at approximately 102 degrees c to similar to 150 degrees c assumed delta 18o pore water variation from 0 parts per thousand to 4 parts per thousand smow ree distribution indicates at least three types of fracture and crack filling carbonates two carbonate generations formed from evolving diagenetic pore waters whereas one type reflects carbonate formation under hydrothermal influence the ages of these cementations derived from rb sr and u pb isotope analyses indicate their fort nation during late stage of or after the inversion of the lower saxony basin in late cretaceous times the stable carbon isotope composition of the authigenic carbonate minerals reflects at least two carbon source endmembers available during diagenesis whereas many early formed carbonates are related to the permian c 13 rich carbon source those carbonates which precipitated or recrystallised during early to late stage diagenesis and or were induced by local tectonic events incorporated c 12 enriched co from organic degradation processes the stable oxygen isotope values of authigenic carbonates probably still reflect low temperatures of mineral formation from permian sea water as it is assumed for non recrystallised carbonates or late stage high temperature up to similar to 150 degrees c precipitation ftoin sea water derived pore waters which may have been locally influenced by o 18 enriched fluids however most of the carbonate samples investigated are recrystallised crystal enlargement of concretionary and fracture carbonate is observed and hence these carbonates are at least partly re equilibrated original o 18 content reduced with surrounding pore waters at elevated temperature similar to the authigenic carbonate at least two sources may explain the concentration carbon isotope relationship of modem co present in the ca 2 reservoir rocks an organic derived co2 endmember source delta c 13 near 20 parts per thousand is present in relatively low concentrations whereas large co concentrations derived from an endmember source with all isotope value near 0 parts per thousand although the latter source is unknown such heavy co sources are most likely attributed to carbonate decomposition processes c 2005 elsevier b v all rights reserved

geochronologic significance of lead lines from old cratons abstract lead isotope data from geologically mixed suites of archaean gneisses often yield secondary isochrons that have statistically better fits than might be expected from the geological constraints on the range of samples used accepted as true isochrons these pb pb lines are commonly used both to determine the age of the rock suite and as evidence that all the rocks that yield data points within error of the isochron were formed at the same time from the same source using within geologically reasonable limits random data for initial lead and secondary lead growth we demonstrate that heterogeneous sample sets may yield statistically valid secondary isochrons this implies that the fit to a common secondary isochron does not necessarily mean that the samples used have the same age or an isotopically similar source numerical modelling of artificial data sets suggests that high correlation between 1 and 2 values is the single most important factor that enhances the statistical fit of the samples about a lead line and smoothes the initial scatter in contrast initial scatter will be preserved in data sets with a random relation between 1 and 2 values the 1 value estimated from the lead line will be biased towards the sample with the lowest 2 value

nd and sr isotopic mapping of the archaean proterozoic boundary in southeastern tanzania using granites as probes for crustal growth abstract granitoids of two different generations occur across the archaean proterozoic boundary in southeastern tanzania the first generation which is confined to the archaean tanzania craton yields rb sr whole rock isochron ages of 2600 ma and low mantle like initial 87sr 86sr ratios 0 702 0 704 these coupled with positive or near zero e nd values 0 2 to 2 0 suggest that these granitoids represent juvenile mantle material which was added to the continental crust at about 2600 ma the second generation of granitoids intrudes the palaeoproterozoic usagaran belt and is characterised by rb sr whole rock isochron ages of about 1900 ma these granitoids show sm nd crustal formation ages which are 200 to 600 ma older than their emplacement ages and negative e nd values 2 2 to 6 2 mixing calculations suggest that the proterozoic granitoids may have formed by partial melting of 2000 ma usagaran mantle derived material which had incorporated between 15 and 45 of an archaean component from the adjacent tanzania craton

application of ostracoda and charophyta from the late jurassic to early cretaceous tendaguru formation at tendaguru tanzania east africa biostratigraphy palaeobiogeography and palaeoecology abstract revisitation of the famous late jurassic early cretaceous dinosaur locality of tendaguru by a german tanzanian expedition in summer 2000 resulted in a new standard section micropalaeontologic samples from this section yielded a marine and nonmarine partially mixed ostracod fauna consisting of 40 taxa and some charophyte gyrogonites and utriculi a few marine taxa provided biostratigraphic information although comparable faunas from the west indian madagascan east african faunal province are stratigraphically older middle late jurassic fully marine and strongly endemic an middle oxfordian age is suggested for the lower part of the tendaguru formation nodosoclavatoroid utriculi charophyta suggest that the jurassic cretaceous boundary may be located lower in the section than supposed previously i e in the trigonia smeei member rather than in the upper saurian member in biogeographical terms the marine ostracod fauna is relatively endemic and has most similarities with that known from eastern tanzania only a few faunal links to madagascar northwest india and somalia exist and there are no links to south africa ostracods and charophytes also provided palaeoecological data for specific horizons in the lower part of the middle saurian member a regression is documented while the nonmarine late jurassic early cretaceous ostracods of tendaguru are not applicable to biostratigraphy so far they are important because the nonmarine setting is unique in this area of the tethys

dynamics of the equatorial mesosphere first results with a new generation partial reflection radar the first observations of mesospheric winds made between january august 1990 with an mf partial reflection radar located on christmas island 2 n 157 w in the central pacific are described the mean zonal winds are in general westward but show clear evidence for a wave driven circulation power spectral studies indicate that waves are present over a wide range of periods ultra fast kelvin waves are especially evident in january march with peak amplitudes 20 ms 1 and intrinsic phase speeds of 150 ms 1 indicated the kelvin waves are estimated to contribute an eastward acceleration of up to 10 ms 1 day 1 gravity wave amplitudes are also found to be almost as large as those observed at mid latitude sites which suggests that convection is a major source of gravity wave activity

mean winds tides and gravity waves during the westward phase of the mesopause semiannual oscillation msao mf radar observations of mean winds tides and gravity waves in the period range 30 120 min over tirunelveli 8 7 n 77 8 e during april 1993 when the mesopause semiannual oscillation msao was in the westward phase are presented in this work the focus herein is on the observed relationship between these dynamical parameters which is explained in the context of the current understanding of the behavior of msao winds tidal dissipation and gravity wave tide interactions the observed diurnal tide amplitude and phase variations with height indicate 1 1 wave damping and subsequent westward momentum deposition the gravity wave variances are shown to be modulated by the diurnal tide though the analysis does not lead to an estimation of gravity wave contributions to the time mean zonal flow and its shears the observations do suggest that the short term tidal variability contributes either directly or indirectly through the gravity wave tidal interactions to the variation of the strength of the time mean westward flow associated with the msao

isotopically heterogeneous initial pb and continuous 222 rn loss in fossils the u pb systematics of brachiosaurus brancai abstract diagenetic incorporation of uranium into bone material establishes a u pb system that provides a minimum age for the fossil loss of rn and ra from the 238u decay series recent mobility of u and pb and incorporation of radiogenic pb from an old basement which was available during diagenesis disturbed the u pb system all data fall in a 206pb 238u 207pb 235u concordia diagram to the right of the concordia while samples that do not experience redistribution of u pb 222rn and 226ra should define a linear array that intersects the concordia curve at the age of diagenesis and at the age of the source of inherited radiogenic pb loss of 222rn and 226ra has led to displacement of the present data set to lower 206pb 238u and therefore to younger intercept ages and to older 207pb 206pb ages the 207pb 204pb 208pb 204pb systematics demonstrates that 1 three out of 19 samples experienced significant postdiagenetic fractionation of u and pb and that 2 the diagenetic pb addition was isotopically heterogeneous the 235u 207pb 206pb 207pb and 206pb 238u 207pb 235u systematics combined demonstrate that 3 the samples experienced 5 to 18 222rn loss for a 1 9 ga old source of the diagenetically introduced pb and correspondingly more for a younger pb source and that 4 there is no unique solution for the age of the source of diagenetic pb since pb from a younger source appears in the 235u 207pb 206pb 207pb diagram in the same way as higher 222rn loss no precise age can be determined from the data although the most consistent solution falls in the range of 140 to 150 ma addition of radiogenic pb to the fossil bone is obvious only through its anomalous highly radiogenic character and the isotopic heterogeneity in 208pb 204pb no th i e no in situ 208pb growth the effect of unrecognized diagenetic additions of radiogenic pb is an overestimation of the age whereas unrecognized 222rn loss results in a too young discordant age since fossil material formed at times for which the discordia only shows a small curvature anomalies originating from diagenetic pb additions and 222rn loss may not always be recognized

direct u pb dating of cretaceous and paleocene dinosaur bones san juan basin new mexico vertebrate fossils have been important for relative dating of terrestrial rocks for decades but direct dating of these fossils has heretofore been unsuccessful in this study we employ recent advances in laser ablation in situ u pb dating techniques to directly date two dinosaur fossils from the san juan basin of northwestern new mexico and southwestern colorado united states a cretaceous dinosaur bone collected from just below the cretaceous paleogene interface yielded a u pb date of 73 6 0 9 ma in excellent agreement with a previously determined 40 ar 39 ar date of 73 04 0 25 ma for an ash bed near this site the second dinosaur bone sample from paleocene strata just above the cretaceous paleogene interface yielded a paleocene u pb date of 64 8 0 9 ma consistent with palynologic paleomagnetic and fossil mammal biochronologic data this first successful direct dating of fossil vertebrate bone provides a new methodology with the potential to directly obtain accurate dates for any vertebrate fossil

lu hf isotope systematics of fossil biogenic apatite and their effects on geochronology abstract reliable methods for direct dating of biogenic apatite from pre pleistocene fossils are currently not available and recent attempts using the lu hf decay system yielded highly inaccurate ages for both bones and teeth the geological processes accounting for this poor accuracy of lu hf chronometry are not yet understood here we explore lu hf systematics in fossil bones and teeth in detail by applying five different sample digestion techniques that are tested on bones and composites of bone and sediment our current dataset implies that dissolution methods only slightly affect the resulting lu hf ages while clear differences between the individual digestion techniques became apparent for element concentrations by analysing the insoluble leftovers from incomplete sample dissolution four main reservoirs of hf in fossil bones were identified 1 a radiogenic end member associated with apatite 2 an unradiogenic end member represented by the authigenic minerals or the embedding sediment 3 a highly unradiogenic end member that can be attributed to detrital zircon and 4 a moderately soluble phase probably a zr hf phosphate that yielded very low lu hf but a highly radiogenic hf isotope composition at the same time this zr hf phase must have been precipitated within the fossil bone sample at a late stage of burial history thereby incorporating radiogenic 176 hf released from apatite surfaces over geological timescales a second focus of our study is the effect of different sediment matrices and of crystal size on the preservation of pristine lu hf isotope compositions in bioapatite because near depositional lu hf ages of phosphate fossils have previously been reported for the london clay england and a calcareous marl from tendaguru tanzania we herein investigate specimens fossilised in carbonate matrices calcareous marl from oker germany carbonate concretions from the santana formation brazil carbonate from the eifel germany and argillaceous matrices with low permeability oil shale of messel germany posidonienschiefer of holzmaden germany materials analysed from these localities include bones teeth conodonts as well as coproliths and diagenetic minerals siderite montgomeryite and messelite near depositional lu hf ages were obtained for a bony fish sample notelops brama encapsulated in an early diagenetic carbonate concretion from the early cretaceous santana formation brazil and for conodonts from a middle devonian carbonate from the eifel germany low 176 lu 177 hf ratios in all materials from the middle eocene messel oil shale e g bones fish scales sediment siderite result in poor age precision and an age that is near depositional due to this large analytical error in agreement with previous results all other ages determined here for both bones and teeth are by far younger than respective chronostratigraphic ages a model illustrating the behaviour of lu and hf over time with respect to the fossilisation process is presented which accounts both for the formation of a late diagenetic radiogenic zr hf phase and long term open system behaviour the continuous lu hf element exchange between the fossils and the embedding sediment is probably related to the nm scale crystal size of fossil bones dentine and also of enamel that generate large surface areas facilitating sorption desorption processes and open system behaviour

observations of the diurnal tide from space abstract this study presents a climatology of mesospheric and lower thermospheric diurnal tidal winds obtained with the high resolution doppler imager hrdi on the upper atmosphere research satellite uars the observations reveal that although tidal structures are present at all times like the prevailing zonal winds they exhibit significant semiannual as well as other shorter term variations in amplitude results are presented for a period extending over more than one year from november 1991 to july 1993 the 1 1 diurnal tidal amplitude of the meridional component characterized by the value at an altitude of 90 km and a latitude of 22 ranges from a minimum at solstice of less than 20 m s 1 to an equinox maximum of over 70 m s 1 the vertical wavelength and phase of the tide show only slight variations throughout the year with a suggestion of semiannual variations in both

signatures of equatorial electrojet in the mesospheric partial reflection drifts over magnetic equator the partial reflection pr drifts at 98 km measured by the medium frequency mf radar operating at tirunelveli india situated close to the magnetic equator are shown to have the combined effects of mesospheric winds and the equatorial electrojet the evidences for this behavior of the pr drifts are brought out from a detailed examination of the temporal variation of the dynamical and the geometrical parameters associated with the ground diffraction pattern

highly localized cooling in daytime mesopause temperature over the dip equator during counter electrojet events first results the first observations of lowering of mesopause temperature during counter electrojet cej events over a narrow region of 150 km centered at around magnetic equator are presented the daytime mesopause temperature is measured over trivandrum 8 5 n 77 e dip lat 0 5 n india using the ground based multiwavelength dayglow photometer the unique meridional scanning capability of the instrument is extensively used in this study a lowering of temperature by as much as 25 k has been observed during certain cej events which includes a few partial cejs the gravity wave tidal interaction through vertically upward wind is proposed to be manifesting as lowering in the mesopause temperature and also as cej these observations are new and address to the issues concerning the vertical coupling processes prevailing in the equatorial mesosphere lower thermosphere ionosphere mlti region citation vineeth c t k pant c v devasia and r sridharan 2007 highly localized cooling in daytime mesopause temperature over the dip equator during counter electrojet events

timescales and mechanisms of ree and hf uptake in fossil bones abstract rare earth element ree patterns of fossil bones and teeth are widely used as proxies for provenance taphonomy and palaeoenvironment in order to investigate if fossil bones behave as closed systems over geologic time ree profiles were analysed by la icpms along cross sections of 54 bones from various well characterised and well dated settings these include terrestrial and marine diagenetic environments covering early triassic to holocene ages in general all fossil bones exhibit the highest ree concentrations at the outer rim gradually decreasing by up to four orders of magnitude toward the inner bone cortex intra bone ree concentration gradients decrease significantly from quaternary via tertiary to mesozoic specimens suggesting long term ree uptake and open system behaviour of fossil bone this view is further corroborated by 176lu 176hf dating of selected samples all yielding significantly younger ages than the known chronostratigraphic ages hence there is clear evidence for long term open system behaviour of fossil bones with respect to ree which is in marked contrast to currently accepted models suggesting that ree uptake is only early diagenetic although unexpected statistically significant four to seven point isochrons are observed for four fossil dinosaur bone samples and one upper triassic mastodonsaurus tooth with mswds ranging from 0 083 to 4 5 notably mobility of lu alone cannot account for the observed age patterns assuming constant lu uptake rates over time the radiometric ages should only be as low as half of the chronostratigraphic age however a six point isochron defined by subsamples of a single upper triassic mastodonsaurus tooth yields an age of 65 2 1 1 ma mswd 0 68 much younger than half of the stratigraphic age ca 234 ma hence hf must also undergo late diagenetic exchange likely mechanisms to account for the presence of statistically meaningful isochrons as well as for the late diagenetic exchange of both ree and hf are diffusion adsorption and dissolution reprecipitation processes

high resolution doppler imager observations of kelvin waves in the equatorial mesosphere and lower thermosphere the behavior of kelvin waves in the mesosphere and lower thermosphere is examined in three 10 day sequences of high resolution doppler imager mesospheric and lower thermospheric zonal winds at solstice eastward propagating signatures are observed in wavenumbers 1 2 and 3 of the zonal wind field with periods near 3 and 5 days these structures are coherent in latitude and altitude and maximize near or on the equator in the mesosphere lines of constant phase move downward in time implying that these waves are forced from below above 90 km the phase lines of kelvin zonal wavenumbers 2 and 3 traverse upward in time suggesting in situ or higher level sources estimates of the eliassen palm fluxes indicate that wavenumber 1 may significantly contribute to the eastward momentum budget of the equatorial lower thermosphere