multiphase formation of the obři důl polymetallic skarn deposit west sudetes bohemian massif geochemistry and re os dating of sulfide mineralization the ob i d l fe cu as polymetallic sulfide skarn deposit is developed in a metamorphic series in the west sudetes bohemian massif it consists of lenses of marble calc silicate rocks and skarns we studied the gustav orebody which is located few hundred meters away from the contact with a large late orogenic variscan krkonose jizera plutonic complex kjpc emplaced into shallow crust mineralogical and fluid inclusion study evidence indicates that the main sulfide stage dominated by pyrrhotite arsenopyrite and chalcopyrite originated from aqueous hydrothermal fluids with salinity up to 8 wt nacl eq with minimum homogenization temperatures ranging from 324 to 358 c these fluids mainly replaced carbonate rich lithologies carbon oxygen and strontium isotope data in ca rich rocks imply total overprinting by channelized metasomatic fluid flow which is most probably related to the intrusion of the kjpc whereas 34s values of sulfides argue for a magmatic source of sulfur the re os age of arsenopyrite overlaps published age data for the kjpc and suggests synchronous formation of the main sulfide mineralization and pluton emplacement

fluid history related to the alpine compression at the margin of the south pyrenean foreland basin the el guix anticline the el guix anticline is the southernmost structure of the south pyrenean fold and thrust belt ne spain compressional activity in the area represents the latest stages of alpine compressional tectonics and avects the upper eocene oligocene fluvio lacustrine deposits overlying an evaporite sequence the evolution pattern of the fractures containing calcite cement consists of three stages of microfractures which reflect the evolution of the structure and the relationships between fluids and thrust development in each fracture deformation started with a network of discontinuous microfractures which acted as traps for local meteoric fluids stage 1 during the second stage dilatant thrust faults serving as the conduit for both evolved meteoric ascending and local meteoric fluids were developed migration of fluids through the thrusts was multiepisodic after the precipitation of cements in microfracture stage 2 the thrusts were practically occluded by calcite cements acting as fluid barriers and dividing the structure into diverent hydrological compartments the last stage of microfracture stage 3 is attributed to a younger phase where the circulation of fluids concerned only meteoric fluids and the previously formed fractures acted as barriers to fluid circulation meteoric fluids with high fe mn and fe mg ratios without na and sr enriched with 13c and with low 87sr 86sr with respect to their host rock were widely distributed in the structure throughout all its evolution within a relatively open palaeohydrological system evolved meteoric fluids with lower fe mn and fe mg ratios with na and sr depleted in 13c and with high 87sr 86sr with respect to their host rock were only present during thrust faults development stage 2 within a relatively closed palaeohydrological system the underlying evaporites acted as the lower boundary of the aquifer comparison with older thrust fronts of the same system reveals that the pyrenean fold and thrust belt and its deformed southern foreland basin were compartmentalised hydrologically in time and space during the early eocene when the thrust front avected soft sediment in the ainsa basin the thrust faults were dominated by a medium scale fluid flow the fluids in the basin were basically formation fluids derived from eocene marine waters trapped in the underlying eocene marls although influences of meteoric waters were also present during the middle eocene coeval with the gavarnie thrust emplacement the thrust fault was dominated by a medium scale fluid flow the fluid was basically a hypersaline sr rich brine stored within triassic redbeds no evidence of a significant input of either surface or metamorphic fluids during thrusting was found during the same period in the crystalline basement of the central pyrenees the thrust faults were dominated by a large scale fluid flow mainly derived from the underlying silicate rocks

correlation of gulf coast provincial paleogene stages with european standard stages one of the chief goals of stratigraphy is to correlate the provincial stages used in many countries with the standard chronostratigraphic scale based on european stages in this study united states gulf coast provincial paleogene stages in their type area are correlated with the european standard paleogene stages by use of calcareous nannoplankton gulf coast provincial stage boundaries can be placed in martini9s standard calcareous nannoplankton zonation as follows midwayan sabinian boundary mid np 5 sabinian claibornian boundary base np 12 claibornian jacksonian boundary mid np 17 jacksonian vicksburgian boundary mid np 21 vicksburgian chickasawhayan boundary base np 24 upper chickasawhayan boundary mid np 24 gulf coast stages therefore correlate with the european stages as follows the midwayan stage corresponds to all of the danian stage and the lowest part of the selandian stage the sabinian stage corresponds to the rest of the selandian and the lower half of the ypresian stage the claiboraian stage includes the upper half of the ypresian all of the lutetian and approximately the lower two thirds of the bartonian the jacksonian includes the upper third of the bartonian all of the priabonian and the lower part of the rupelian the vicksburgian corresponds to all but the lowermost and uppermost fractions of the rupelian and the chickasawhayan to the upper one tenth of the rupelian and the lower one fifth of the chattian

variations in the strontium isotope composition of seawater during the paleocene and early eocene from odp leg 208 walvis ridge we refined the strontium isotope seawater curve for the paleocene and early eocene by analysis of samples recovered from the walvis ridge during ocean drilling project odp leg 208 the highest sr 87 sr 86 values occurred in the earliest paleocene at similar to 65 ma and generally decreased throughout the paleocene reaching minimum values between 53 and 51 ma in the early eocene before beginning to increase again at similar to 50 ma a plausible explanation for the sr 87 sr 86 decrease between 65 and 51 ma is increased rates of hydrothermal activity and or the eruption and weathering of large igneous provinces e g deccan traps and north atlantic strontium isotope variations closely parallel sea level and benthic delta o 18 changes during the late paleocene and early eocene supporting previous studies linking tectonic reorganization and increased volcanism to high sea level high co2 and warm global temperatures

late eocene to early oligocene calcareous nannofossils in alabama and mississippi abstract abstract the eocene oligocene boundary in the central gulf coastal plain has been placed traditionally at the contact of the shubuta member of the yazoo formation and the red bluff formation or the contact of the shubuta and the facies equivalents with the bumpnose formation calcareous nannofossils were examined from six upper eocene to lower oligocene localities in alabama and mississippi the shubuta red bluff and equivalents have a very similar calcareous nannofossil flora and both are in martini s zone np21 however from the base of the shubuta up through the red bluff 10 calcareous nannofossil extinction horizons can be used to subdivide the lower part of zone np21 discoaster saipanensis bramlette and riedel d barbadiensis tan sin hok and reticulofenestra reticulata gartner and smith which become extinct at or near the top of zone np20 are only rarely present in the 27 shubuta samples examined are poorly preserved and are assumed to have been reworked below the shubuta lies the pachuta marl member of the yazoo which was examined at one locality in mississippi and two in alabama and although the flora is poorly preserved it contains significant numbers of all three eocene species if the eocene oligocene boundary is assumed to correspond to the shubuta red bluff contact this boundary at least in the gulf coastal plain cannot be recognized using traditional calcareous nannofossil markers because of its inclusion within zone np21 this contact however appears to coincide with the last occurrence of the planktonic foraminifer globorotalia cerroazulensis s l the extinction of hantkenina spp may occur slightly below the contact the extinction of discoaster saipanensis below that of the planktonic foraminifers has also been observed on several legs of the deep sea drilling project where this offset is no more than a few meters at the red bluff type locality the separation approximates 20 m clearly in the study area the extinctions of g cerroazulensis and d saipanensis do not define the same horizon

numerical study of coastal hydrodynamics using a coupled model for hudhud cyclone in the bay of bengal abstract the past decade has witnessed an increased intensity of cyclones in the bay of bengal region with higher winds spread over a larger area the associated risk and coastal vulnerability have increased with wider destructive potential from high waves storm surges and associated coastal inundation the very severe cyclones that made landfall over the bay of bengal in the past decade had strong winds in their outer cores unlike those cyclones that made landfall in previous years the original parametric wind formulation performs well for more compact cyclones but at a radial distance far away from the cyclone centre the winds are under estimated hence there is a need to revisit and modify this formula for practical applications and this study attempts to provide a better representation of the overall radial distance in the wind field envelope the study postulates a 3 5 power law fitted to the original wind formulae which provides a reasonably good estimate for the surface wind field the recent very severe cyclones that developed over the bay of bengal provided an excellent test bed to verify this hypothesis which is supported by validation from six in situ buoys the modified wind formula used with a coupled hydrodynamic model adcirc swan simulated the storm surge and wave characteristics associated with a recent very severe cyclonic storm hudhud that made landfall in andhra located on the east coast of india in 2014 the study also investigated the dependence of coastal geomorphic features and beach slope on the variability of wave induced setup computed significant wave height and storm surge show an excellent match with wave rider buoy and tide gauge observations

strontium isotope profiles across k t boundary sequences in denmark and antarctica strontium isotope profiles derived from minimally altered samples across marine k t boundary sequences exposed at kjolby gaard and nye klov denmark and on seymour island antarctica show neither the boundary excursions nor the boundary spikes in 87sr 86sr that have been reported for k t boundary sequences from elsewhere nor do our data conform to modelled predictions of the sr isotopic response of the oceans to a positive spike in 87sr 86sr at the terminal cretaceous boundary values for 87sr 86sr with 95 confidence intervals are 0 707828 3 in denmark and 0 707832 7 in antarctica our data suggest that 87sr 86sr stopped increasing and started decreasing at least 90 ka before the k t boundary

strontium isotopic variations in jurassic and cretaceous seawater a high resolution seawater strontium isotope curve has been generated through the analysis of well dated and well preserved belemnites and oysters from the middle and upper jurassic and the lower cretaceous of great britain analysis of fe and mn concentrations in these fossils has yielded criteria for eliminating samples that are diagenetically altered the strontium isotope curve remains relatively flat through the aalenian and early bajocian rapidly descends through the late bajocian and bathonian and reaches a minimum in the callovian and oxfordian it then begins a rapid increase in the kimmeridgian and portlandian that continues through much of the early cretaceous the curve levels off in the barremian suddenly dips downwards in the aptian and recovers gradually through the albian the strontium isotopic variations are sufficiently large and the data are presented with sufficient stratigraphic detail to allow precise correlation to the classic ammonite zones and lithologic sections of great britain using the techniques of strontium isotope stratigraphy model results indicate that much of the variation in seawater 87sr86sr between 120 and 40 ma can be explained by changing the intensity of mid ocean ridge hydrothermal fluxes proportionally to estimated mid ocean ridge crustal generation rates it is also possible that the variations during the rest of the mesozoic and the permian are primarily reflections of changing hydrothermal inputs the model results have several important implications first they provide an example in which the variations in the strontium isotope curve are not necessarily driven by changes in fluvial inputs second they suggest that from at least the aptian through the eocene variations in continental weathering were minimal this heightens the importance of the rapid rise in seawater 87sr86sr beginning 40 ma as a significant transition to an extended period of increasing fluvial 87sr fluxes continuing to the present finally the results suggest that several documented short term excursions towards lower 87sr86sr in the latest triassic pliensbachian toarcian callovian oxfordian aptian albian and cenomanian turonian are interpretable as pulses of seafloor hydrothermal activity if so the strontium isotope record offers a means of constraining the timing duration and magnitude of known or proposed hydrothermal events in the geological record

complexity of saharan paleoclimate reconstruction and implications for modern human migration abstract chronological and geochemical data from scarp and scarp foot depression sediments ssds have been used for deciphering saharan paleoclimates and patterns of migration of anatomically modern humans amh u th dating of thick accumulations of ssds indicates prevalent deposition during long lasting cool glacial periods marine isotope stage mis 6 8 10 and 12 and limited deposition during warm interglacial periods mis 5 7 and 13 in contrast quaternary sediments associated with short residence hydrologic systems in sinai yielded mis 2 osl ages of 27 7 to 10 2 ka the lack of ssds of mis 2 ages and the wide range of warm and cool stages in eastern sahara is attributed to 1 lengthy travel times of groundwater prior to discharge and deposition of ssds from deep groundwater originating from distant sources and 2 sampling and dating of ssds from depressions where natural discharge has been apparently continuous through wet and dry periods given that the previously dated depression ssds could have been deposited during dry periods and that the ages of ssds reflect the timing of groundwater discharge rather than the ages of the wet periods during which recharge occurred we suggest that earlier interpretations of saharan paleoclimate and amh migrations that heavily relied on dating of ssds should be revisited

high resolution stratigraphy with strontium isotopes the isotopic ratio of strontium 87 to strontium 86 shows no detectable variation in present day ocean water but changes slowly over millions of years the strontium contained in carbonate shells of marine organisms records the ratio of strontium 87 to strontium 86 of the oceans at the time that the shells form sedimentary rocks composed of accumulated fossil carbonate shells can be dated and correlated with the use of high precision measurements of the ratio of strontium 87 to strontium 86 with a resolution that is similar to that of other techniques used in age correlation this method may prove valuable for many geological paleontological paleooceanographic and geochemical problems

the cenozoic seawater 87sr 86sr curve data review and implications for correlation of marine strata the strontium isotopic ratio 87sr 86sr in seawater changes slowly over geologic time this variation is caused by changes in the relative contribution of sr from various isotopically distinct sources within the crust the most important of these are high ratio sialic rocks from continents and low ratio mafic volcanic and mafic intrusive rocks from continental margins and ocean basins a plot of sr isotope ratio versus age for phanerozoic marine samples produces a curve exhibiting many episodes of increasing and decreasing values this variation can be used as a basis for temporal correlation of marine carbonate sulfate and phosphate sediments temporal correlations can be made between high latitude and low latitude sequences deepwater and shallow water sequences and normal marine and restricted marine hypersaline hyposaline sequences satisfactory biostratigraphic correlations between such sequences are often hampered by either the absence of age diagnostic fossils or by the provinciality of faunal and floral assemblages rapid change that took place in the 87sr 86sr of seawater during most of the cenozoic makes this era particularly well suited for precise temporal correlation the seawater curve for the cenozoic is subdivided into three segments quaternary to mid miocene mid miocene to late eocene and late eocene to early paleocene the mid miocene to late eocene curve segment exhibits a particularly steep slope making this a promising interval for high resolution stratigraphic correlation although current data generally support the present configuration of the seawater curve some revision of the curve is probably required in the vicinity of the oligocene eocene boundary establishment of the general configuration of the seawater curve for the cenozoic has promoted efforts to refine the curve on the basis of construction of detailed sr isotope profiles within individual stratigraphic sequences a sr isotope profile at deep sea drilling project dsdp site 590b suggests a complex neogene seawater curve characterized by minor slope changes in the pliocene and miocene these slope changes are not specifically identified in the seawater curve constructed from multilocation data on the basis of this more complex curve and in the absence of diagenetic complications the ultimate neogene stratigraphic resolution is estimated to range from 0 1 to 2 million years both the verification and the general stratigraphic applicability of this more complex neogene curve are largely dependent on the degree of preservation of the original seawater ratio in marine samples

eustasy and sea water sr composition application to high resolution sr isotope stratigraphy of miocene shallow water carbonates oceanic 87 sr 86 sr isotope ratios are strongly influenced by rates of silicate weathering and therefore linked not only to glaciation but also to sea level change the present study combines analysis of sequence stratigraphy and basin architecture with sr isotope stratigraphy in miocene shallow water sediments in southern portugal and crete greece the common method is to use smoothed global sea water sr isotope reference curves but here a different approach is chosen instead measured sr isotope curves are correlated with unsmoothed reference curves by identification of similar fluctuations in the order of several 100 kyr transgressive intervals are characterized by increasing sr isotope ratios interpreted as corresponding to intensified silicate weathering as a consequence of deglaciation while lowstand deposits have low sr isotope ratios comparison of sr isotope curves and sedimentary sequences in the studied basins with independent global d 18 o data and data on global sea level might suggest a general relationship supporting a connection to global climate change because of these relationships the method presented herein has a high potential for use in high resolution age dating and is also applicable in shallow water sediments

seawater sr isotope variation over the past 300 kyr and influence of global climate cycles the past 300 000 years have been characterized by glacial inter glacial fluctuations accompanied by glacio eustatic changes in sea level and changes in continental erosion arising from varying low latitude rainfall and river drainage here we use measurements of strontium isotopes in foraminifera and corals to place limits on variations in the sr isotope composition of sea water in response to these changing inputs we find small variations of about 20 p p m in the 87sr 86sr ratio which for the foraminiferal record seem to follow a cycle close to the 100 kyr periodicity seen for a number of other climate related phenomena these are superimposed on a general increase in87sr 86sr through the cenozoic to the present on short timescales these changes are likely to be controlled by variations in the global riverine sr flux and thus by weathering rates rather than in the hydrothermal sr flux at mid ocean ridges we show that transient variations over a 50 kyr timescale can be explained on the basis of the present day global drainage system in conjunction with the perturbations expected to accompany climate changes over the past 300 kyr

the fidelity of oxygen and strontium isotope values from shallow shelf settings implications for temperature and age reconstructions abstract the oxygen and strontium isotopic ratios of marine carbonates are widely employed to derive paleotemperature and age respectively while open ocean samples are the standard source for these measures shelf settings can also provide detailed records however the implementation of shelf data for these purposes has been hindered by the perception that local environmental conditions such as freshwater influx confound regional and global signals here we directly evaluate this concern by assessing the spatial variability in the isotopic composition of biogenic carbonate precipitated along the depositional strike of an inner shelf environment data are derived from mollusc shells collected from a stratigraphically restricted transgressive unit in the early eocene 55 ma of the us gulf coastal plain gcp lithofacies and fossil assemblages suggest that an estuary was present in the westernmost study region whereas more typically marine facies predominated elsewhere isotopic composition varies predictably with paleoenvironmental setting shells from the estuary have 18o values and 87sr 86sr ratios that reflect high freshwater input specimens in the eastern gcp however from within and between outcrops separated by up to 400 km all yield similar results serial microsampling reveals congruence not only in mean 18o values but also in winter and summer extremes estimated paleotemperatures mean annual temperature of 26 c agree well with proxy and model evidence for the early eocene and the gcp and 87sr 86sr ratios are consistent with the established early eocene seawater ratio the fidelity of isotopic values relative to environment indicates that shallow shelf records have much to contribute to studies of ancient climate and ocean chemistry

paleogene calcareous nannoplankton biostratigraphy mississippi alabama and tennessee abstract distribution and abundance of calcareous nannoplankton in the paleogene formations of mississippi ms alabama al and tennessee end page 1471 tn are reported in this study these data have been used to assign each of the following nannoplankton bearing formations and members to martini s 1971 internationally recognized calcareous nannoplankton zones table end of article last page 1472

upper eocene to oligocene isotope 87sr 86sr δ18o δ13c standard section deep sea drilling project site 522 we improved upper eocene to oligocene deep sea chronostratigraphic control by integrating isotope 87sr 86sr 18o 13c stratigraphy and magnetostratigraphy most previous attempts to establish the timing of isotope fluctuations have relied upon biostratigraphic age estimates which have uncertainties of 0 5 to over 4 0 m y deep sea drilling project dsdp site 522 contains the best available upper eocene to oligocene magnetostratigraphic record which allows first order correlations of isotope records 87sr 86sr 18o 13c to the geomagnetic polarity time scale gpts empirical calibrations between the 87sr 86sr of foraminifera and magnetochronology at site 522 allow more precise correlation of unknown samples with the gpts for example shallow water and high latitude sections may be tied into the deep sea record sr isotope stratigraphic resolution for the latest eocene to oligocene is approximately 2 m y

detailed record of the neogene sr isotopic evolution of seawater from dsdp site 590b a detailed study of strontium isotope variations in neogene marine carbonate sediments from deep sea drilling project site 590b using techniques that allow the 87sr 86sr ratio to be determined to better than 0 00001 gives a high resolution record of the sr isotopic evolution of seawater the data show that the rate of change of the marine 87sr 86sr ratio has varied significantly even on time scales as short as 1 m y periods of particularly rapid growth appear to follow major marine regressions and probably reflect an increase in the delivery of radiogenic sr from the continents coupled with a decreased submarine carbonate dissolution rate greater carbonate compensation depth periods of relatively slowly changing 87sr 86sr follow major marine transgressions on the basis of correlations with the marine oxygen isotope record and the times of major continental glacier growth it is inferred that the effects of sea level variations are modified by climatic factors that affect the intensity of continental weathering and runoff the effects of sea floor generation rate variations are not discernible for the neogene the maximum attainable stratigraphic resolution using sr isotopes is between 0 1 and 2 m y for this time period

seawater sr isotopes at the cretaceous tertiary boundary abstract seawater 87 sr 86 sr values increase abruptly by 28 10 6 across the cretaceous tertiary boundary ktb this small but rapid shift is superimposed on the larger scale structure of the seawater sr isotope curve the time scale of radiogenic sr addition appears to be too rapid to reconcile with sources associated with volcanism and we show that the amount of sr required to produce even this small increase is too large to be derived from 1 a kt bolide of the size constrained by the ir anomaly 2 continental crust ejecta from the impact of such a bolide 3 soot from global wildfires initiated by an impact or 4 any combination of these sources the probable source of the radiogenic sr is enhanced continental weathering but the high rate of increase appears to rule out processes such as sea level regression glaciation or tectonism a plausible mechanism for rapid addition of radiogenic sr to the oceans is enhanced weathering associated with globally distributed acid rain ph 1 which is a proposed by product of a bolide impact 51 epsl vol 83

stable δ13c δ18o and strontium isotopes through the paleocene at gebel aweina eastern tethyan region abstract stable 13 c 18 o and strontium 87 sr 86 sr isotopic records have been established through the paleocene section at gebel aweina in the eastern desert egypt the section has been formed in a shelf upper bathyal environment and spans the interval from planktonic foraminiferal zones p1d to p6a or p6b integrated evaluation of isotopic results and scanning electron microscope observations suggest that strontium and whole rock 13 c records reflect primarily original isotopic trends whereas 18 o and foraminiferal 13 c values have been severely affected by diagenesis the whole rock 13 c record exhibits a continuous increase of 4 from the early paleocene to middle late paleocene the increase is followed by a stepwise 13 c decrease of the same magnitude through the late late paleocene and onwards the gross trends of this 13 c record have earlier been registered in many coeval deep sea sections but there are also some significant disparities at aweina for example the paleocene carbon isotopic changes have a higher amplitude in the deep sea the mid to late paleocene 13 c increase has been interpreted to reflect high biological productivity and or changes in the global carbon mass balance the 13 c decrease in the upper part of the aweina section can be identified as the paleocene eocene transitional long term 10 3 kyr negative 13 c shift which may reflect a major reorganisation in global oceanic circulation patterns the well known latest paleocene deep sea benthic foraminiferal extinction event has been found in the upper part of the aweina section and coincides with a distinct and rapid 13 c decrease of 1 5 the benthic extinction event and the associated 13 c anomaly thus represent important stratigraphic markers also in more shallow environments the gebel aweina 13 c record shows considerably lower values compared to the global 13 c record during early and early late paleocene and in the latest paleocene in the early late paleocene foraminiferal zones p3a to the base of p4 the aweina 13 c values increase rapidly by 1 5 and converge with the global record thereafter the two records covary up to the benthic extinction event after which they diverge the convergence between the records may reflect sea level rise and more open water mass exchange between the eastern tethys and the world ocean the similarity of pilot 13 c records from greece and tunisia with the aweina record support this interpretation diagenetic processes however cannot be ruled out and further studies are required to determine the significance of the 13 c depletions in the eastern tethyan sediments the 87 sr 86 sr ratios through the paleocene at gebel aweina are remarkably invariable close to a value of 0 7077 this is the same trend that has been reported in some earlier detailed studies conducted on well preserved calcitic material from the paleocene indicating original sr isotopic signatures at gebel aweina the homogeneity of sr isotopic ratios throughout the paleocene contrasts with the prominent changes observed in the carbon isotope record indicating a decoupling of the mechanisms regulating the mass fluxes of these elements the invariable sr isotopic ratios suggest stable conditions as regards to relative changes in mass fluxes of riverine and or hydrothermal sr during the paleocene

reevaluation of early oligocene eocene and paleocene seawater strontium isotope ratios using outcrop samples from the u s gulf coast the cenozoic strontium isotope 87sr 86sr variation in seawater is largely defined using deep sea drilling project dsdp samples examination of non dsdp results particularly for the paleogene suggest that the original seawater curve of burke et al 1982 may lie above the true seawater ratio during this time to investigate this possibility we analyzed the 87sr 86sr for 230 paleogene rock and shell samples from the 83 sites in alabama mississippi and louisiana many of the samples are from classic sections on which the gulf coast paleogene stratigraphy was originally defined multiple analyses of samples from these units show very little scatter and in most cases precise agreement is obtained among geographically separated collection sites we believe that analysis of multiple samples from a unit of established age collected at more than one site yields results that most accurately define the actual seawater sr isotope ratio at any given time results from these units define a seawater variation line that tracks well within the range of dsdp data but is generally below the original seawater line of burke et al 1982 it is often assumed that samples from continental settings will exchange with high ratio sr thereby raising 87sr 86sr values our gulf coast samples which are derived from a continental setting yield individual 87sr 86sr values that are both higher and lower than the estimated contemporaneous seawater ratio an analysis of our gulf coast data and dsdp results show that the direction of isotopic exchange cannot be confidently predicted for individual samples based solely on their derivation from either continental or oceanic settings

biotic geochemical and paleomagnetic changes across the cretaceous tertiary boundary at braggs alabama exposed near braggs alabama is one of the few well studied nearly continuous shallow marine cretaceous tertiary boundary sections it allows a glimpse of the biotic and environmental changes that occurred in the latest cretaceous to earliest paleocene paleomagnetic strontium isotopic and biostratigraphic data closely constrain the age of a series of lithologic geochemical and biotic variations and suggest that no more than 100 200 ka could be missing at the boundary a major reduction in macrofaunal diversity associated with lithofacies changes occurs prior to but within 300 ka of the nannofossil defined boundary approximately 40 of the apparent faunal reduction is attributed to the lazarus effect faunal and floral assemblages trends in carbon isotopic composition of benthic invertebrates and lithologic characteristics indicate that a latest maestrichtian regression culminated near the boundary chron c29r micula murus zone significantly later than recent estimates water depths at this site remained shallow during the subsequent early paleocene zone np1 transgression and did not reach depths equivalent to those of the late maestrichtian until zone np2 relatively minor climatic changes across the boundary are suggested by a 4 c cooling trend seen in the oxygen isotope paleotemperatures a high resolution 87 sr 86 sr record from well preserved macrofossil calcite shows a pattern of smooth variation and elevated values near the boundary however the early paleocene spike of other workers was not found

note on the very high acceleration fault zone 16 record from the 2004 parkfield earthquake a very high acceleration recording was obtained at station fault zone 16 near parkfield california during the m 6 0 parkfield earthquake of 28 september 2004 this note documents key aspects of the station the instrument and the record a preliminary reconstruction of the record is performed to produce an estimate of the true acceleration which is then integrated to obtain the estimated velocity the strong motion accelerograph at fault zone 16 is deployed at a soil site in a light fiberglass housing common in the parkfield array postearthquake testing indicates that the accelerograph operated normally instrument shake table tests indicate that the recorded acceleration is relatively accurate even at the high accelerations involved in this record that is the very high accelerations in the record are a reasonably accurate reflection of the accelerations that occurred at the site during the parkfield earthquake although the peak motion was not recorded the record itself has several unusual features the trace was lost at the top edge of the film where the excursion went beyond the recordable part of the film most unusually the traces of two accelerometers recorded on top of one another during the positive highest amplitude part of the record the accelerograph did not record the peak accelerations of the components which occurred during this time an additional aspect is that for the largest amplitude component the negative part of the acceleration was affected by momentary stalling of the recording film during the strongest shaking the constraint for the mean of the acceleration over the whole record to be zero and detailed analysis of the time trace leads to a reconstruction of the record the peak acceleration on this component is over 1 8 g and most likely over 2 g the peak velocity is estimated to be about 80 cm sec the other horizontal component goes off the film at the same time combined the horizontals yield a fault normal acceleration of over 2 2 g and most likely over 2 5 g this record is a challenge to interpret an important practical lesson is that given what has been learned about near fault accelerations any instrument deployed in the region should have a recording capacity well in excess of 2 g

sr isotopes in interstitial waters of marine sediments from deep sea drilling project cores sr isotopic compositions of interstitial sea waters have been documented in detail with cores from 37 deep sea drilling project sites the 87sr 86sr ratios are sensitive indicators of diagenetic reactions involving alteration of volcanic matter dispersed in sediments and recrystallization of carbonates effects of basalt alteration reactions except possibly for hydrothermal signals and of alteration of continental debris are minimal carbonate recrystallization has a significant effect on the geochemical mass balance of sr but diffusion of unradiogenic strontium from interstitial waters has only a small effect on the 87sr 86sr ratio of ocean water

integrated late eocene oligocene stratigraphy of the alabama coastal plain correlation of hiatuses and stratal surfaces to glacioeustatic lowerings we integrated strontium and oxygen isotopic biostratigraphic and magnetostratigraphic studies of two upper eocene oligocene boreholes drilled near bay minette and st stephens quarry ssq alabama continuous coring provided fresh unweathered material for magnetostratigraphic studies minimizing problems reported from nearby outcrops difficulties with each technique were encountered because of diagenesis absence of marker fossils and the presence of unconformities however by integrating results from isotopic stratigraphy biostratigraphy and magnetostratigraphy we correlated these relatively shallow water deposits to the geomagnetic polarity time scale gpts at the ssq borehole the upper eocene to lower oligocene section is apparently complete within our stratigraphic resolution 0 2 0 5 m y allowing us to estimate the ages of several stratal surfaces late eocene sr isotope age estimates are as expected at the ssq borehole but oligocene ages are 1 m y older than expected due to diagenesis at the bay minette borehole a latest eocene earliest oligocene and a late early oligocene hiatus were detected we correlate these two hiatuses and stratal surfaces at ssq with global 18o increases inferred to represent glacioeustatic lowerings and with evidence for hiatuses on other continental margins 1 a distinct disconformity at the base of the chickasawhay limestone at both boreholes and a hiatus at bay minette correlates with a global 18o increase we revise the age of this surface equivalent to the tb 1 1 sequence boundary making it 2 m y older than previously reported and 2 a surface at the top of the shubuta member lowermost oligocene has been interpreted both as a condensed section and a disconformity this surface at ssq and a hiatus at bay minette correlate with a sharp global 18o increase and with hiatuses on the new jersey and irish margins the timing of the hiatuses and stratal surfaces correlates with the inflection of the 18o increases and not with the maximum values supporting models that indicate that unconformities form during the maximum rates of sea level fall