positive and negative impacts of longwall mine subsidence on a sandstone aquifer subsidence due to longwall underground coal mining changes the hydraulic properties heads yields and in some cases the groundwater chemistry of overlying bedrock aquifers a 7 year study of a sandstone aquifer overlying an active longwall mine in illinois has supported a comprehensive model of these impacts subsidence caused increases in permeability and storativity over the longwall panel these changes initially caused a major decline in water levels in the sandstone but the aquifer recovered slightly within a few months and fully within several years after mining the enhanced hydraulic properties combined with potentiometric recovery resulted in a zone of greater well yield however at sites with very poor transmissivity and inadequate recharge pathways recovery may not occur also at the study site the physical enhancement was accompanied by a deterioration in groundwater quality from slightly brackish sodium bicarbonate water to more brackish water with increased sulfate levels

orbital control on carbon cycle and oceanography in the mid cretaceous greenhouse we established a new high resolution carbonate carbon isotope record of the albian interval of the marne a fucoidi formation central apennines italy which was deposited on the southern margin of the western tethys ocean bulk carbonate sampled with 10 15 cm spacing was used for the construction of a continuous carbon isotope curve through the albian stage spectral analyses reveal prominent 400 kyr cyclicity in the 13c curve which correlates with milankovitch long eccentricity changes cycles occurring in our record resemble those observed in several cenozoic 13c records suggesting that a link between orbital forcing and carbon cycling existed also under mid cretaceous greenhouse conditions based on comparisons with cenozoic eccentricity carbon cycle links we hypothesize that 400 kyr cycles in the mid cretaceous were related to a fluctuating monsoonal regime coupled with an unstable oceanic structure which made the oceanic carbon reservoir sensitive to orbital variations in the tethys these oceanographic conditions lasted until the late albian and then were replaced by a more stable circulation mode less sensitive to orbital forcing

carbon sequestration activated by a volcanic co 2 pulse during ocean anoxic event 2 ninety four million years ago during ocean anoxic event 2 there was a marked increase in the burial of organic carbon in marine sediments measurements of stomata in fossil leaves show that the two main pulses of carbon burial were associated with a decline in atmospheric co2 levels of up to 26 the cretaceous ocean anoxic event 2 about 94 million years ago is thought to be linked to extensive volcanism which triggered a biogeochemical chain of events that eventually led to widespread marine anoxia and a remarkable increase in carbon burial in marine sediments1 2 3 it has been suggested that the event was accompanied by a substantial decrease in atmospheric co2 concentrations4 but the quantification of the drawdown remains controversial5 6 here we reconstruct atmospheric co2 concentrations throughout the ocean anoxic event from counts of the stomata in fossil leaves and use terrestrial carbon isotopes to link the reconstruction to marine records of the event7 8 we find that before the onset of ocean anoxia atmospheric co2 concentrations increased by 20 over background levels of 370 100 70 ppm this was part of a long term rise in atmospheric co2 levels presumably caused by volcanism which reached a peak of 500 400 180 ppm however two pulses of extensive carbon burial during the ocean anoxic event as indicated by positive carbon isotope excursions are associated with decreased atmospheric co2 concentrations we conclude that the sequestration of marine organic carbon led to a decrease in atmospheric co2 concentration of up to 26 during ocean anoxic event 2

ocean circulation and calcareous nannoplankton evolution during the jurassic and cretaceous abstract spatial and temporal distribution of calcareous nannoplankton aid in the reconstruction of ocean circulation during the cretaceous biogeographic patterns of calcareous nannoplankton during the late cretaceous are mostly zonal reflecting mostly latitudinal gradients of surface water temperature during the middle cretaceous calcareous nannofossil assemblages are more strongly affected by surface water fertility concentration of limiting nutrients especially in a wide tropical belt between 50 and 45 n latitudes major upwelling regions off northwest africa in the south atlantic and the equatorial pacific divergence are apparent temporal changes in the composition of middle cretaceous nannofloras are indicative of changes in surface water fertility and vertical mixing at frequencies of tens to hundreds of kiloyears ka changes in the intensity of atmospheric circulation with frequencies close to the milankovitch cycles appear to be the ultimate cause of these minor changes in the circulation of the upper ocean calcareous nannofossil preservation patterns show that during the middle cretaceous deep waters were quite homogeneous with respect to carbonate saturation in the atlantic ocean but not in the indo pacific ocean where a more distinctive calcite compensation depth ccd is apparent water mass structure of the major oceans during the mesozoic was thus quite different taxonomic evolution of calcareous nannofossils was also strongly affected by ocean circulation and fertility major peaks in the rates of diversification coincide with anoxic events that is periods of increased preservation of organic carbon in the oceans which coincide with high sea level stands during anoxic events ocean circulation was sluggish vertical mixing was slow deep ocean ventilation poor and the concentration of limiting nutrients in surface waters was low increased competition for limiting nutrients and possibly preferential cropping of the dominant forms by zooplankton resulted in increased rates oof speciation during anoxic events periods of major production of nannofossil carbonate coincided with low sea level stands when oceans were more vigorously stirred and surface waters were more fertile the first such period was the latest jurassic when calcareous nannoplankton invaded the open oceans and became the major carbonate producers in the pelagic realm during the mesozoic the frequency of peaks and troughs in evolutionary rates is on the order of 10 30 ma and appears to be irregular the coincidence of periods of anoxia with high sea level stands which in turn appear to be caused by more rapid sea floor spreading indicates that the ultimate diving forces of nannoplankton evolution are processes in the earth s mantle these major tectonically driven fluctuations in ocean atmosphere circulation with frequencies of a few million to a few tens of millions of years are hereby named fischer cycles superimposed astronomically driven milankovitch cycles affected relative abundance patterns but not taxonomic evolution of calcareous nannoplankton rates of nannoplankton extinction are about five times higher than background rates at the end of the jurassic and orders of magnitude higher in the latest cretaceous possibly indicating a terrestrial or extraterrestrial catastrophe

marine 187os 188os isotope stratigraphy reveals the interaction of volcanism and ocean circulation during oceanic anoxic event 2 high resolution osmium os isotope stratigraphy across the cenomanian turonian boundary interval from 6 sections for four transcontinental settings has produced a record of seawater chemistry that demonstrates regional variability as a function of terrestrial and hydrothermal inputs revealing the impact of palaeoenvironmental processes in every section the 187os 188os profiles show a comparable trend radiogenic values in the lead up to oceanic anoxic event 2 oae 2 an abrupt unradiogenic trend at the onset of oae 2 an unradiogenic interval during the first part of oae 2 and a return to radiogenic values towards the end of the event above the cenomanian turonian boundary the unradiogenic trend in 187os 188os is synchronous in all sections previous work suggests that activity of the caribbean lip large igneous province was the source of unradiogenic os across the oae 2 and possibly an instigator of anoxia in the oceans here we assess this hypothesis and consider the influence of activity from other lips such as the high arctic lip a brief shift to high radiogenic 187os 188os values occurred in the western interior seaway before the onset of oae 2 we evaluate this trend and suggest that a combination of factors collectively played critical roles in the initiation of oae 2 differential input of nutrients from continental and volcanogenic sources coupled with efficient palaeocirculation of the global ocean and epeiric seas enhanced productivity due to higher nutrient availability which permitted penecontemporaneous transport of continental and lip derived nutrients to trans equatorial basins

forcing mechanisms for mid cretaceous black shale formation evidence from the upper aptian and lower albian of the vocontian basin se france calcareous nannoplankton palynomorph benthic foraminifera and oxygen isotope records from the supraregionally distributed niveau paquier early albian age oceanic anoxic event 1b and regionally distributed niveau kilian late aptian age black shales in the vocontian basin se france exhibit variations that reflect paleoclimatic and paleoceanographic changes in the mid cretaceous low latitudes to quantify surface water productivity and temperature changes nutrient and temperature indices based on calcareous nannofossils were developed the nutrient index strongly varies in the precessional band whereas variations of the temperature index reflect eccentricity since polar ice caps were not present during the mid cretaceous these variations probably result from feedback mechanisms within a monsoonal climate system of the mid cretaceous low latitudes involving warm humid and cool dry cycles a model is proposed that explains the formation of mid cretaceous black shales through monsoonally driven changes in temperature and evaporation precipitation patterns the lower albian niveau paquier which has a supraregional distribution formed under extremely warm and humid conditions when monsoonal intensity was strongest bottom water ventilation in the vocontian basin was diminished probably due to increased precipitation and reduced evaporation in regions of deep water formation at low latitudes surface water productivity in the vocontian basin was controlled by the strength of monsoonal winds the upper aptian niveau kilian which has a regional distribution only formed under a less warm and humid climate than the niveau paquier low latitude deep water formation was reduced to a lesser extent and or on regional scale only the threshold for the formation of a supraregional black shale was not reached the intensity of increases in temperature and humidity controlled whether black shales developed on a regional or supraregional scale at least in the vocontian basin the increased preservation of organic matter at the sea floor was more significant in black shale formation than the role of enhanced productivity

episodes of high productivity and cooling in the early aptian alpine tethys a palynological and organic geochemical study of the early aptian selli unit oceanic anoxic event 1a of the western tethys provides new information about paleoceanography and documents pronounced changes in the regional climate pattern it also emphasizes the role of oxic degradation of organic matter even at horizons with the highest rates of organic carbon corg accumulation the absence of anoxia indicates that enhanced primary production is the main reason for these organic carbon accumulations and variations in preservation are related to pulses in primary production and nutrient recycling despite the high productivity character of the selli unit black shales the 13ccarb values are not marked by a positive shift but by an interval of unchanged values warm climatic conditions for deposition of the selli unit are inferred from the presence of southern provenance pollen and low 18o values for the interval above the selli unit changes in the pollen spectrum and an increase in 18o values reflect a hitherto undocumented late early aptian cooler and more humid climate and or a reorganization of the tethyan oceanographic circulation pattern

albian pelagic rhythms piobbico core abstract the piobbico core of aptian albian pelagic rhythmites in italy has been used to explore ways of extracting quantitative time series of geological chemical physical and biological parameters from stratigraphic sequences recognition of the precession obliquity and eccentricity cycles the option frequencies has permitted time resolution to the 104 year level individually these time series curves furnish a potential basis for precise correlations collectively they track the evolution of the depositional system in detail including its response to orbital forcing orbital cycles primarily influenced oceanic fertility and carbonate productivity by foraminifera and coccoliths as well as the aeration of bottom waters redox cycle three short magnetic reversals occur w thin the ticinella praeticinensis zone frequency spectra of variations in magnetic intensity inclination and declination yield milankovitch frequencies which are only partly explained as responses to mineralogy a computer simulation used berger s astronomically calculate precession index to drive 1 carbonate flux and 2 depth of bioturbation this achieved a stratigraphy remarkably similar to that observed each step in the computer simulation transfers spectral power from precession to eccentricity work on the piobbico core continues while project albicore aims to explore the patterns of rhythmicity in the praeticinensis zone of other areas end page 1164

correlation of early cretaceous carbon isotope stratigraphy and platform drowning events a possible link the early cretaceous carbonate carbon isotope record is marked by three positive high amplitude 1 5 excursions each covering time spans of more than 106 years they are of late valanginian hauterivian and early and late aptian age in a case study along a transect across the western tethys ocean we identified a coincidence between 13c excursions black shale formation and widespread carbonate platform drowning events we conclude that the 13c excursions reflect a change in partitioning of carbon between the organic and carbonate carbon sinks which was triggered by climate induced ecological changes in cretaceous pelagic and neritic environments episodes of intensified greenhouse climate conditions led to an increase in weathering erosion and runoff rates and to elevated nutrient transfer rates from continents into oceans the resulting increase in oceanic nutrient levels favoured marine phytoplankton production and black shale deposition while conditions for carbonate producing biotas became unfavourable partial choking of carbonate production along river influenced coasts resulted in widespread carbonate platform drowning during times of sea level rise in the valanginian and aptian widespread contemporaneous black shale deposits and drowned carbonate platforms therefore reflect the contrasting response of the marine organic and carbonate carbon pumps to nutrient enhanced phytoplankton productivity the change in marine carbon partitioning is mirrored in a shift of the 13c record towards more positive values the transition to the 13c peak values lasted up to several hundred thousand years the peaks of the excursions also covering a time span of up to several hundred thousand years reflect a new stabilisation of the carbon partitioning between carbonate and organic carbon sinks a renewed intensification of carbonate sedimentation under mesotrophic conditions was facilitated by stabilisation of the sea level rise at a high level decreasing 13c values record increasing carbonate carbon burial rates at constant or decreasing organic carbon accumulation rates these changes contributed to the stabilisation of the marine carbon budget and the global carbon cycle up to millions of years after its initial perturbation

evidence for a complex valanginian nannoconid decline in the vocontian basin south east france the early cretaceous is punctuated by widespread biocalcification crises these are characterized by decrease in the carbonate platform growth and in the pelagic realm by a decline in nannoconus relative abundance in the calcareous nannofossil assemblages the valanginian nannoconus decline started before the positive 13c excursion characterizing the weissert event the nannoconid decline is investigated in two sections of the vocontian basin la charce and vergol which are biostratigraphically well constrained and contain wellpreserved calcareous nannofossils absolute and relative abundances of nannoconus show a polyphased decline with a first decrease in the interval from the campylotoxus to the verrucosum ammonite subzones before the positive 13c shift and a second decrease from the end of the peregrinus to the base of the radiatus ammonite zones concomitant with the long term decrease in 13c these two declines are separated by an important increase in the nannoconus abundance from the verrucosum to the peregrinus ammonite subzones concomitant with a slight short term decrease of 13c biometric analysis shows size changes of n steinmannii and n kamptneri along the nannoconid decline the patterns of abundances and size changes seem to be related to paleoenvironmental changes mainly characterized by a temperature decrease and variable nutrient supply the described valanginian nannoconid recovery seems to occur during the most intense phase of the cooling event and is recorded in the vocontian basin as well as in the atlantic and tethys oceans these spatial correlations suggest a supra regional character for the valanginian nannoconid recovery event best recorded in the vocontian basin and at low latitudes

volcanism co2 and palaeoclimate a late jurassic early cretaceous carbon and oxygen isotope record a composite tethyan late jurassic early cretaceous carbon and oxygen isotope curve is presented c isotope data provide information on the evolution and perturbation of the global carbon cycle o isotope data are used as a palaeotemperature proxy in combination with palaeontological information the resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification positive c isotope anomalies in the valanginian and aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide a major warming pulse accompanies the aptian but not the valanginian c isotope event the observed change in early aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion both c isotope anomalies are accompanied by biocalcification crises that may have been triggered by p co 2 induced changes in climate and in surface water chemistry elevated nutrient levels in river influenced coastal waters and in upwelling regions further weakened marine calcification these conditions contrast with normal trophic conditions prevailing in the latest jurassic and favouring biocalcification the c and o isotope curves record a stable mode of carbon cycling and stable temperatures we conclude that biocalcification is mostly triggered and inhibited by co 2 conditions in the atmosphere ocean system

permeability variations within mining induced fractured rock mass and its influence on groundwater inrush this paper is concerned with the evaluation of permeability of fractured rock mass due to the cover stress re establishment which is a major factor in controlling water and gas flow rate induced by mining operations in fractured rock the case study considered in this paper is based on the results of observations of groundwater inrush and a decrease in water inflow from the fractured roof strata due to mining advancing in the taiping coalmine shandong province china a conceptual model of an effective porous media was used to assess the permeability distribution in the fractured zone induced by coal mining the cover stress re establishment in gob fractured rock mass was evaluated using an empirical formula based on the surface subsidence a simplified conceptual model of the fractured zone was used to evaluate the deformation of fractured zone along with the evaluation of changes in the rock permeability above the gob due to the cover stress re establishment these data were then used to calculate the water inflow rate into the panel predicted water inflow rates have been found to be in good agreement with those from monitoring data this study improved the understanding of the mechanisms of the post mining cover stress re establishment on permeability change of the overburden fracture rock strata these results can then be applied for numerical simulations of the process of overburden failure and consequent groundwater inrush due to coal mining

middle cretaceous calcareous nannofossil biogeography and preservation in the atlantic and indian oceans implications for paleoceanography abstract the quantitative study of calcareous nannofossil preservation and biogeographic distribution puts constraints on paleoceanographic models for the atlantic and indian oceans during the middle cretaceous we establish a dissolution ranking of middle cretaceous calcareous nannofossils based on susceptibility to dissolution a positive correlation of organic carbon content of the sediments and the relative abundance of watznaueria indicates that much of the carbonate dissolution was caused by the release of carbon dioxide during oxidation of organic matter the depth distribution of the most dissolution resistant species watznaueria barnesae shows relative abundance maxima at the deepest sites and a maximum where intermediate waters impinge on slopes this reflects stagnant oxygen poor bottom waters and possibly a mid water oxygen minimum zone with increased deposition and catabolic breakdown of organic matter factor analyses are performed on various data sets for three different time slices ranging in age from late aptian to early albian middle albian and late albian to cenomanian the resulting factors can be related to paleoceanographic conditions such as colder water at high latitudes high fertility upwelling conditions and neritic conditions for all three time intervals a wide tropical to subtropical zone was flanked by boreal and austral zones upwelling conditions probably existed along the north african margin and over the falkland plateau zonal upwelling is tentatively postulated for the northwestern and northeastern margin of the north atlantic in the middle albian and for the eastern margin of the north atlantic off western europe for the late albian to cenomanian we speculate on surface water current patterns location of upwelling regions and haline driven deep circulation for the middle cretaceous

planktonic foraminiferal distribution record productivity cycles evidence from the aptian albian piobbico core central italy the aptian albian scisti a fucoidi varicoloured pelagic sediments in central italy show a couplet alternation of carbonate rich carbonate poor layers which are interpreted as the sedimentary expression of precession frequency 19 23 kyr carbonate content chromatic variation and planktonic foraminiferal abundance were analysed at a 1 cm spacing for a 10 m interval of the piobbico core specifically drilled through this formation spectral analysis of these parameters shows a prominent signal equated to the c 100 kyr cycle of orbital eccentricity at a sedimentation rate of 5 mm kyr 1 the coherency of the spectral response of each parameter suggests that a single mechanism controlled the whole sedimentary record detailed study of planktonic foraminiferal distribution of the same section at 1 mm scale resolves the milankovitch frequencies of 41 kyr and 18 to 23 kyr equated with the obliquity and precessional cycles but foraminiferal abundance is not in phase with carbonate content which was largely controlled by calcareous nannofossils but peaked at intermediate carbonate values the proposed model for explaining the discrepancy at the precessional level is that foraminifera thrived at intermediate values of the precession index when the environment was only moderately fertile but stable while during highs of the precession index mixing of the water column increased fertility and caused calcareous nannofossil blooms and restriction of planktonic foraminifera to few and tolerant species the resulting bimodality of foraminiferal abundance per precessional cycle appears to be recorded in the spectrum by peaks at the 11 and 14 kyr levels cross correlation of foraminiferal abundances with the calcium carbonate curve over 1 2 myr intervals produces discrepant results apparent phase lags which we attribute to differences in the response to the fundamental eccentricity cycles

size patterns of the coccolith watznaueria barnesiae in the lower cretaceous biotic versus abiotic forcing abstract body size is a major trait allowing the assessment of the respective control of evolution vs palaeo environment on unicellular micro organisms size patterns can be retraced for fossilisable micro organisms especially for coccolithophores over geological time spans here we present coccolith size patterns of watznaueria barnesiae which was a dominant and ubiquitous taxon in the mesozoic measurements were conducted at two sites spanning the upper berriasian to lower hauterivian namely the vergol la charce section in the epicontinental vocontian basin and the odp leg 185 hole 1149b located in the nadezhda basin in the pacific ocean the obtained results were treated using multivariate analysis in order to detect significant trends of the measured parameters size values of coccoliths from both sites are remarkably similar and display comparable patterns namely a statistically significant increase in the lower valanginian until maximum sizes recorded in the aftermath of the weissert event upper valanginian although w barnesiae coccolith size fluctuations in the short term might be related to environmental changes the observed long term size patterns are interpreted as the result of directional selection in which a single phenotype is favored through time comparison with data available in the literature shows a return to a smaller size after the turonian

size variations and abundance patterns of calcareous nannofossils in mid barremian black shales of the boreal realm lower saxony basin abstract we present new quantitative calcareous nannofossil data from a barremian early cretaceous black shale interval of the boreal realm thirty samples from two sections in northern germany have been investigated the current study aims to understand the genesis of the barremian black shales so far only described from the boreal realm in a supraregional to global context by assessing the diversity patterns relative abundances and biometry of calcareous nannofossils from a distinctive late early barremian black shale horizon for morphometric size measurements three common taxa biscutum constans rhagodiscus asper and watznaueria barnesiae have been investigated the results show a decrease in size and abundance of the high fertility indicator b constans for the main black shale horizon hauptblatterton while abundances of the warm water species r asper and watznaueria spp increase deep dwelling nannoconids only flourished during black shale deposition this indicates warm oligotrophic surface waters and an expanded photic zone during the formation of the hauptblatterton black shales similar observations have been made for the oceanic anoxic event 1d oae 1d albian in the vocontian basin southern france and for the oae 2 cenomanian in the western interior seaway and southern england for w barnesiae our data confirm a high ecological tolerance and we assume a response in size if a certain limit is exceeded towards more extreme conditions nutrients therefore likely play a larger role than water temperature from our results it seems likely that nutrient availability controls both size and abundance patterns of b constans

high sea surface temperatures during the early aptian oceanic anoxic event 1a in the boreal realm the early aptian was characterized by the widespread occurrence of anoxia in the oceans known as oceanic anoxic event oae 1a intense degassing from submarine volcanic plateaus presumably resulted in high atmospheric co2 concentrations culminating in greenhouse conditions oae 1a can therefore be considered as a past natural experiment important to understand the future evolution of our climate paleotemperature estimates for oae 1a are however predominantly based on bulk oxygen isotopes which are susceptible to diagenetic overprinting while tex86 paleotemperature estimates are limited in number or derived from stratigraphically poorly constrained sections here we reconstructed for the first time sea surface water temperatures ssts based on the tex86 paleothermometer from an oae 1a section from the middle northern latitudes 39 n paleolatitude we find a sst rise starting prior to oae 1a and reaching a maximum during the event with ssts of 31 34 c 4 9 c higher than those of older hauterivian lower aptian sediments from the same sedimentary basin the end of oae 1a is marked by relatively lower ssts of 30 c these observations are supported by belemnite based oxygen isotope d18obel data and calcareous nannofossils our integrated data set clearly indicates that super greenhouse conditions prevailed during oae 1a at northern latitudes ssts are similar to those estimated for coeval low latitudinal sites suggesting that an equable warm climate with reduced latitudinal gradients characterized the early aptian

coccolithophore size rules reconstructing ancient cell geometry and cellular calcite quota from fossil coccoliths coccolithophore size rules reconstructing ancient cell geometry and cellular calcite quota from fossil coccoliths

atlantic cooling associated with a marine biotic crisis during the mid cretaceous period most of the marine biotic crises that occurred during the hot mesozoic era have been linked to episodes of extreme warmth 1 2 others however may have occurred during cooler intervals that interrupted cretaceous greenhouse warmth 3 5 there are some indications of cooling in the late aptian 6 8 116 114 myr ago but it has not been definitively linked to biotic crisis here we assess the timing and magnitude of late aptian cooling and its association with biotic crises using a suite of geochemical and micropalaeontological assessments from a marine sediment core from the north atlantic ocean as well as global biogeochemical modelling sea surface temperatures derived from the tex86 proxy suggest that surface waters cooled by about 5 degrees c during the two million years coincident with a positive delta c 13 excursion of approximately 2 parts per thousand in carbonates and organic carbon surface productivity was enhanced during this period but the abundance of planktonic foraminifera and nannoconid phytoplankton declined our simulations with a biogeochemical model indicate that the delta c 13 excursion associated with the cooling could be explained by the burial of about 812 000 gigatons of carbon over 2 5 million years about 50 of the this carbon burial occurred in the atlantic southern and tethys ocean basins we conclude that global cooling during greenhouse conditions can cause perturbations to marine ecosystems and biogeochemical cycles at scales comparable to those associated with global warming

three dimensional effects of hydraulic conductivity enhancement and desaturation around mined panels changes in the three dimensional hydraulic conductivity field that accompany undermining by a longwall panel are evaluated to define the potential for changes in flow patterns and desaturation relations linking changes in conductivity with the mining induced strain field that develops around the advancing face are defined through the assumption of an equivalent porous medium with the strain partition between fractures and matrix apportioned relative to respective deformation constants model results are validated against behavior recorded at a well instrumented field site replicating the complex steady flow pattern that develops around an advancing longwall face significant hydraulic conductivity increases are restricted to strata at shallow depth ahead of the advancing face and to deep zones behind the face particularly in the caving zone and abutment shear zones these very large increases in conductivity at depth that include the out of section conductivity enhancement that develops along the panel rib exercise primary control on induced water level changes and the potential for saturation zones of desaturation are readily defined with these enabling locations of well vulnerability to water loss to be identified these zones of vulnerability are directly above the panel with their extent potentially modulated by the presence and the location of flatlying layers of low conductivity the complex response recorded in the near face region mandates use of three dimensional models to adequately represent observed behavior

orbital tuning as an inverse problem chronology of the early aptian oceanic anoxic event 1a selli level in the cismon apticore 1 orbital tuning the process of fitting sedimentary cycles to orbital periodicities can estimate with high resolution the timing and duration of key events in the geological record we formulate here orbital tuning as the inverse problem of finding the variation in sedimentation rate that matches sediment cycles with orbital periodicities instead of obtaining a single best estimate we apply a bayesian formulation and define a probability distribution of sedimentation rate variations that result in powerful orbital periodicities by sampling this distribution with a monte carlo method we quantify the uncertainty in the inferred sedimentation rates due to uncertainties in the tuning periods and to components of the sedimentary signal that are unrelated to orbital cycles the method is applied to the chronology of a 30 m interval in the cismon apticore borehole southern alps italy that includes the early aptian oceanic anoxic event 1a selli level estimated to last 1 11 0 11 ma 95 interval the 13c record shows a sudden negative shift of about 1 at the base of the selli level 22 47 ka followed by a recovery to preshift values in 240 ka consistent with a scenario where light carbon is quickly added and then flushed out of the ocean atmosphere system

determination of aquifer transmissivity from earth tide analysis the water level in an open well tapping an artesian aquifer responds to pressure head disturbance caused by earth tide dilatation of the aquifer because a finite amount of time is needed for water to flow into and out of the well there exists a phase shift or time lag between the tidal dilatation of the aquifer and the water level response in the well we derive an analytical solution that expresses the phase shift as a function of the aquifer transmissivity storage coefficient well radius and the period of the harmonic disturbance this solution is rather insensitive to the storage coefficient thus if the phase shift is known for a harmonic disturbance the transmissivity can be calculated given a rough estimate of the storage coefficient theoretical analysis shows that a significant phase shift may be present even if the disturbance is slowly varying as in the case of earth tides this opens the possibility of estimating aquifer transmissivity from water level records that show earth tide fluctuations a case study using data from a site near parkfield california is presented to illustrate application of the theory phase shifts of the o1 25 82 hour period and m2 12 42 hour period tidal constituents are chosen for analysis because they are free of systematic contamination by fluctuations in barometric pressure a brief error analysis suggests that the computed o1 phase shift is subject to large uncertainty while the computed m2 phase shift is substantially more accurate based on an assumed storage coefficient range of 10 4 to 10 6 the estimated transmissivity range is 8 10 6 to 2 10 5 m2 s while hydraulic tests have not been performed to validate these estimates the range is consistent with the transmissivity value determined by other investigators from analysis of the water level response to an earthquake

cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode oceanic anoxic events oaes were episodes of widespread marine anoxia during which large amounts of organic carbon were buried on the ocean floor under oxygen deficient bottom waters oae2 occurring at the cenomanian turonian boundary about 93 5 myr ago is the most widespread and best defined oae of the mid cretaceous although the enhanced burial of organic matter can be explained either through increased primary productivity or enhanced preservation scenarios the actual trigger mechanism corresponding closely to the onset of these episodes of increased carbon sequestration has not been clearly identified it has been postulated that large scale magmatic activity initially triggered oae2 refs 4 5 but a direct proxy of magmatism preserved in the sedimentary record coinciding closely with the onset of oae2 has not yet been found here we report seawater osmium isotope ratios in organic rich sediments from two distant sites we find that at both study sites the marine osmium isotope record changes abruptly just at or before the onset of oae2 using a simple two component mixing equation we calculate that over 97 per cent of the total osmium content in contemporaneous seawater at both sites is magmatic in origin a approximately 30 50 fold increase relative to pre oae conditions furthermore the magmatic osmium isotope signal appears slightly before the oae2 as indicated by carbon isotope ratios suggesting a time lag of up to approximately 23 kyr between magmatism and the onset of significant organic carbon burial which may reflect the reaction time of the global ocean system our marine osmium isotope data are indicative of a widespread magmatic pulse at the onset of oae2 which may have triggered the subsequent deposition of large amounts of organic matter

the mid cenomanian event prelude to oae 2 a detailed synthesis of litho and biostratigraphic investigations of the cenomanian pelagic limestones of the scaglia bianca formation in the umbria marche basin shows that the bonarelli level which is the regional sedimentary expression of the oae 2 represents the climax of a 2 myr long cycle of black shale deposition that began in the mid cenomanian planktonic foraminiferal rotalipora cushmani zone this long term cycle began with a prominent short term event named mid cenomanian event mce which is associated with several changes in the biotic and abiotic records in particular a comparison of the available litho bio and chemostratigraphic data from the umbria marche basin allows recognition of the mce based on a a significant change in the sedimentary and tectonic regimes b a reorganisation of planktonic foraminiferal assemblages c a major change in benthic foraminifera d a major turnover in the radiolarian assemblages e a 0 7 positive shift in the carbon isotope values and f a positive shift of carbonate sr ca ratio moreover the mce is preceded 400 kyr by a short term 0 5 negative excursion in the oxygen isotope record the above mentioned changes in carbon and oxygen isotope values can be confidently correlated over different basins and oceans and seem to occur in correspondence with a major sea level fall these lines of evidence define the mce as an outstanding event associated with large scale changes in the oceanic structure and palaeoclimate the mce and the subsequent cyclical deposition of organic rich beds serve as a case study to better understand differences and similarities between mesozoic black shales and cenozoic sapropels and related palaeoceanographic changes controlled by orbital climate cycles

a volcanic co2 pulse triggered the cretaceous oceanic anoxic event 1a and a biocalcification crisis the aptian oceanic anoxic event 1a oae1a ca 120 ma ago is one of the most prominent of a series of geologically brief intervals in the cretaceous characterized by the deposition of organic carbon rich sediments oaes reflect major perturbations in the global carbon cycle evidenced by sedimentary carbon isotope records however the triggering mechanisms for oaes remain controversial here we present a bulk rock and molecular marine and terrestrial bio markers c isotope record at unprecedented time resolution from the cismon section of northern italy that shows that oae1a conditions were reached over a period of several thousands of years through a stepwise perturbation of the carbon cycle the documented sequence of events is most compatible with a trigger associated with increased co 2 emissions possibly leading to a doubling of p co 2 which in turn caused larger c isotope fractionation in marine and terrestrial organisms and a major biotic crisis in the calcareous nannoplankton our data also show that a release of isotopically light carbon from partial methane hydrate dissociation probably played a minor role in the oae1a carbon cycle perturbation

effect of sand grain size on simulated mining induced overburden failure in physical model tests abstract to investigate the influence of sand grain size sgs on mining induced overburden failure in physical model tests uniaxial compressive experiments on rock like material with various sgss were performed and two sgss 0 0 5 and 0 5 1 mm were selected the young s modulus uniaxial compressive strength and tangent modulus were larger in rock like material samples with finer sgs and the failure mode changed from mostly shear failure to tensile failure with rising sgs as the mechanical characteristics of coarser sand samples are weaker the overburden breakage distance was shorter in the coarser sand model and the ratio of the average breakage distance between the two models was 1 688 the extent of the overburden fracture was heavier in the coarser sand model and closer pattern to that of the actual coal mine a large database of the heights of the overburden caved zone hcz and fractured zone hfz values with various mining height hm based on previous studies was compiled to obtain best fit parabolic empirical formulas the hcz hm and hfz hm ratios measured in the field were similar to those estimated by the proposed empirical formulas the discrepancy between the physical model test and field measurement may be explained by the fracture pattern in the overburden of the caved zone in the form of layered rectangles unlike the polygonal forms in the coal mine we propose four recommendations to optimize the physical model for such tests from the perspective of sgs the results and recommendations presented here can provide a useful guide for coal mining scientists and engineers designing models for testing of coal mining conditions

lead isotopic record of barremian aptian marine sediments implications for large igneous provinces and the aptian climatic crisis we present initial isotopic ratios of lead for early cretaceous barremian aptian sections from shatsky rise pacific and gorgo a cerbara italy our pb isotopic data track an interval representing oceanic anoxic event oae 1a which is characterized by quasi global deposition of organic carbon rich black shale pb isotopic compositions of sediments from shatsky rise decrease at the end of barremian time from radiogenic continental values to unradiogenic values and subsequently remained less radiogenic until the end of early aptian time we explain the isotopic shift by a significant increase in supply rate of unradiogenic pb most likely due to massive volcanism in contrast the pb isotopic compositions from the italian section which was situated at the western end of tethys are mostly identical to those of upper continental crust showing no significant change in supply rate of unradiogenic pb the discrepancy between two sites is attributed to quiescent deep submarine eruptions of pacific large igneous provinces lips such as the ontong java plateau ojp which severely limited dispersion of pb carrying particles out of the pacific ocean published os isotopic data from the italian section indicate two episodes of massive eruptions of ojp or contemporaneous manihiki and hikurangi plateaus starting from earliest aptian time slightly later than that indicated by the sedimentary pb isotopic record from shatsky rise differences in isotopic variations between pb and os likely reflect differences in their chemical behaviors in the oceans i e pb isotopic compositions would have varied in response to local or regional changes in sediment provenances whereas large scale changes in os inputs are required to explain variations in seawater os isotopic compositions our pb isotopic data together with the published os isotopic record provide new evidence for the eruptive history of ojp together with contemporaneous pacific plateaus and its environmental consequences starting from end barremian time and extending through early aptian time

a new technique for obtaining high resolution pore pressure records in thick claystone aquitards and its use to determine in situ compressibility 1 laboratory tests are commonly used to determine properties vertical compressibility specific storage ss and vertical hydraulic conductivity kv of claystone aquitards however whether data representative of in situ conditions can be obtained from disturbed samples is questionable here we present a method to determine the in situ and ss of a thick sequence of cretaceous aged claystone by estimating the loading efficiency of a formation from pore pressure responses to barometric pressure fluctuations we installed 10 vibrating wire pressure transducers at different depths 25 325 m below ground in a thick claystone aquitard by placing them directly within the cement bentonite grout two years of continuous transducer records using this method appeared to provide pore pressure data with a resolution of better than one part in 105 equivalent to millimeter of hydraulic head change pore pressure responses to barometric pressure changes earth tides and precipitation events can be clearly identified and the barometric responses can be easily analyzed the resulting values of 0 6 0 93 2 5 10 7 to 2 2 10 6 kpa 1 and ss 2 6 10 5 to 4 5 10 6 m 1 all decrease with depth the results are comparable with the limited existing data for in situ estimates of ss and are as much as an order of magnitude smaller than laboratory estimates of ss for similar aquitard deposits our findings suggest that the fully grouted transducer method can provide an accurate and reliable means to monitor pore pressure changes and to determine in situ parameters for bedrock aquitard systems

phreatomagmatic eruptions on the ontong java plateau an aptian 40ar 39ar age for volcaniclastic rocks at odp site 1184

milankovitch climatic origin of mid cretaceous black shale rhythms in central italy the earth s orbital variations reflected in pleistocene ice volume were also recorded in non glacial times carbonate production in pelagic mid cretaceous sediments quantified by calcium carbonate and optical densitometry time series reflects the orbital eccentricity and precessional cycles minimal eccentricity brought deep sea anoxia most of the sedimentary variability of this 100 myr old sequence lies within the milankovitch orbital frequency band

nannoplankton productivity fluctuations and rhythmically bedded pelagic carbonates of the greenhorn limestone upper cretaceous abstract comparison of calcareous nannofossil assemblages from rhythmically interbedded calcareous shales and adjacent bioturbated chalks of the greenhorn limestone cenomanian turonian of the western interior basin indicate significant changes in phytoplankton paleocommunity structure between lithotypes significantly higher shannon diversity and evenness values in the chalk assemblages indicate more stable surface water conditions with lower fertility three taxa indicative of high surface water fertility are significantly more abundant in marlstone assemblages which suggests that calcareous shale marlstone deposition corresponded with fluctuating surface water conditions with relatively high fertility the higher surface fertility and concomitant production of organic matter resulted in sediment anoxia during marlstone deposition leading to high rates of organic carbon storage reduced phytoplankton production during chalk deposition allowed oxygenation of the sea floor and establishment of diverse benthic invertebrate communities

calcareous nannofossils and milankovitch cycles the example of the albian gault clay formation southern england a quantitative study of calcareous nannofossil assemblages was carried out on the albian gault clay formation england this unit consists of grey marly claystones and marlstones with phosphatic nodules and glauconitic layers as minor lithologies two cores were analyzed in detail to focus on changes in nannofloral assemblages and consider their significance preservation of calcareous nannofossils is excellent and therefore diagenesis cannot be invoked to explain not even partially the changes registered in assemblages fast fourier spectral analysis was performed on percentages of selected nannofossil species fluctuations in abundance of both biscutum constans and watznaueria barnesae regarded as fertility and non fertility indices respectively appear to be orbitally driven because spectral analysis showed periodicities of approximately 41 kyr obliquity cycle and 100 kyr short eccentricity cycle in all the spectra the axial obliquityc cycle is a strong signal as expected at these high latitude sites from the boreal realm the same pattern was observed in another fertility controlled taxon zygodiscus cf erectus but cross correlation shows that its abundance plot is displaced with respect to that of b constans orbital perturbations induce variations in climate and ocean circulation because they influence the earth s insolation and seasonality during times of high seasonality strong gradients cause vigorous oceanic circulation a better cycling of nutrients and higher fertility whereas during times of low seasonality low gradients induce more sluggish circulation and lower fertility the carbonate content of the gault clay cores is not correlatable to the higher fertility indices as the abundance curves of b constans w barnesae and z cf erectus are displaced with respect to caco3 content variations this also means that cyclicity in nannofossil assemblages is not a result of diagenesis but an original signal abundance fluctuations of repagulum parvidentatum and combined parhabdolithus asper p splendens colder and warmer water indicators respectively provide evidence for orbital periodicities suggesting that also cyclic variations of surface water temperature might have influenced the nannofossil assemblage patterns within the gault clay

hydraulic conductivity changes and influencing factors in longwall overburden determined by slug tests in gob gas ventholes abstract this study presents the results of core log analyses from the exploration boreholes the analyses of face advance rates and the results of downhole monitoring studies performed in gob gas ventholes for calculation of changes in hydraulic properties in the longwall overburden at a mine site in southwestern sw pennsylvania section of northern appalachian basin in the first part of the study coal measure rocks in overburden strata were analyzed and the locations where possible fractures and bedding plane separations would occur were evaluated in the second part the hydraulic conductivities were computed by two different slug test analyses methods using the water level changes measured in gob gas ventholes as longwall face approached hydraulic conductivities were analyzed with respect to the changes in overburden depth the locations of the borehole and mine face advance rates these data were used to interpret the potential productivities of the gob gas ventholes as a result of fracturing and changes in hydraulic conductivities the general results showed that the probability of fracturing and bedding plane separations in the overburden increase between strong and weak rock interfaces also the probability of bedding plane separations increases as the interface is close to the extracted coal seam evaluation of slug tests showed that the hydraulic conductivity developments in the boreholes and their potential production performances are affected by the underground strata and the roof materials in situations where the roof material is stiff and thick the development of high permeability fractures around the borehole will be less results also indicated that borehole location with respect to face position affects the fracturing time and permeability evolution as well greater overburden depths generally cause earlier fracturing as longwall face approaches but eventually result in lower hydraulic conductivities and potentially less effective boreholes increasing mining rates also resulted in generally lower hydraulic conductivities in the overburden the results of this study were intended to improve the interpretation of gob gas venthole performance and to provide better siting of these boreholes

a volcanically induced climate warming and floral change preceded the onset of oae1a early cretaceous the aptian oceanic anoxic event 1a oae1a is preceded by a prominent negative c isotope excursion ncie attributed to major volcanism on the ontong java plateau that is supposed to lead to a pco2 increase and a climate change lower aptian sporomorph assemblages in two pelagic sections from the southern tethys margin n italy were analysed in order to test if the postulated climate changes affected the terrestrial vegetation at the base of the ncie the sporomorph assemblages comprise abundant bisaccate pollen reflecting a warm temperate climate several tens of kiloyears ka after the start of the ncie decreasing bisaccate pollen and increasing classopollis spp and araucariacites spp suggest the beginning of a long term temperature rise palynomorphs indicate that maximum temperatures were reached several tens of ka after the end of the ncie and the onset of oae1a the highest temperatures coincide with arid conditions which could reflect a northward shift of the hot arid northern gondwana floral province as a result of an increasing pco2 over 200 ka after the onset of oae1a reduced volcanic activity and or increased black shale deposition allowed for a drawdown of most of the excess co2 and a southward shift of floral belts

m sequence geomagnetic polarity time scale mhtc12 that steadies global spreading rates and incorporates astrochronology constraints 1 geomagnetic polarity time scales gptss have been constructed by interpolating between dated marine magnetic anomalies assuming uniformly varying spreading rates a strategy to obtain an optimal gpts is to minimize spreading rate fluctuations in many ridge systems however this has been possible only for a few spreading centers we describe here a monte carlo sampling method that overcomes this limitation and improves gpts accuracy by incorporating information on polarity chron durations estimated from astrochronology the sampling generates a large ensemble of gptss that simultaneously agree with radiometric age constraints minimize the global variation in spreading rates and fit polarity chron durations estimated by astrochronology a key feature is the inclusion and propagation of data uncertainties which weigh how each piece of information affects the resulting time scale the average of the sampled ensemble gives a reference gpts and the variance of the ensemble measures the time scale uncertainty we apply the method to construct mhtc12 an improved version of the m sequence gpts late jurassic early cretaceous 160 120 ma this gpts minimizes the variation in spreading rates in a global data set of magnetic lineations from the western pacific north atlantic and indian ocean nw of australia and it also accounts for the duration of five polarity chrons established from astrochronology cm0r through cm3r this gpts can be updated by repeating the monte carlo sampling with additional data that may become available in the future

mesozoic calcareous nannofossil evolution relation to paleoceanographic events the taxonomic evolution of jurassic and cretaceous calcareous nannofossil species is described using the following indices species diversity rate of speciation rate of extinction rate of diversification rate of turnover survivorship and species accretion the jurassic prior to the late oxfordian is characterized by positive diversification rates that is rates of speciation exceeded rates of extinction highest rates of diversification occurred in the late lias and early oxfordian during the generally regressive latest jurassic diversification rates remained low and rates of extinctions exceed rates of speciation in the early cretaceous rates of diversification are positive and peak in the early valanginian early aptian and middle albian after which time rates of extinction generally exceed rates of speciation such peaks in rate of evolution coincide with times of increased accumulation of organic carbon in the ocean anoxic events peaks in rates of extinction result in very high rates of turnover during times of major regressions in particular in the tithonian and maastrichtian survivorship analyses for three datum planes 74 5 144 and 160 ma show relatively constant extinction rates with some stepping in the older part they are best explained by a temporally fluctuating abiotic environment causing changes in the probability of extinction species accretion curves are also relatively linear with some indication of changing rates of speciation the coincidences of major changes in evolutionary rates with major paleoceanographic events are indicative of a predominantly abiotic control of nannoplankton evolution relationships of evolutionary rates of calcareous nannoplankton with deep ocean ventilation sea level and ocean fertility indicates that global tectonic processes are the ultimate causes of evolutionary change

biscutum constans coccolith size patterns across the mid cretaceous in the western tethys paleoecological implications abstract the morphometric record of the calcareous nannofossil species biscutum constans from the western tethys indicates that this species underwent marked size changes across the latest barremian cenomanian interval 28 myrs significant size reduction occurred during the core of the early aptian oceanic anoxic event oae 1a 120 ma and soon after oae 1a followed by a 9 myr long interval characterized by small specimens larger coccoliths marked the middle to late albian and particularly the lower part of the nannofossil subzone nc10a was characterized by abundant large specimens a minor size decrease coincided with the late albian oae 1d onset 100 ma but very small size was reached again during the latest cenomanian oae 2 94 4 ma the sequence of relatively long millions of years intervals marked by different average sizes is interpreted to reflect adaptation to changing paleoecological conditions temperature and fertility were not directly influencing the size of b constans on shorter time scale abrupt changes in ocean chemistry related to large igneous provinces submarine volcanism played a central role in secretion of small b constans coccoliths to face ocean acidification during oae 1a and oae 2 contrarily during the late early aptian early albian time interval smaller b constans size was related to cooler temperature which possibly also promoted co2 sequestration in cooler surface waters forcing b constans to produce small coccoliths to survive lowered ph in addition pulses of subaerial volcanism of the southern kerguelen plateau may have further affected the ocean chemistry the termination of intense volcanism and warmer temperature in the middle albian early cenomanian coincided with restoration of bigger b constans specimens

magnetic stratigraphy applied to synsedimentary slumps turbidites and basin analysis the scaglia limestone at furlo italy the previously studied italian scaglia sections at gubbio and moria consist entirely of pelagic limestone and marl by contrast the furlo section is characterized by synsedimentary slump folds and slide masses in the lower portion cenomanian coniacian and by intercalation of white calcarenitic turbidites in the upper part campanian paleocene demagnetization to 20 mt and 350 c or higher reveals a single stable direction after removal of an initial low coercivity component despite the stratigraphic complications the pattern of polarity zones clearly matches gubbio and the sea floor anomalies the abrupt faunal break at the end of the cretaceous was located and foram zonation shows that the very base of the paleocene is missing sedimentation rate determinations based on the magnetic polarity zonation have clarified the origin of stratigraphic complications in the furlo paleocene most samples were taken from pelagic beds but ten samples from calcarenitic turbidites yielded directions indistinguishable from those of adjacent pelagic beds detailed sampling of a turbidite 33 cm thick confirmed that this lithology is an accurate recorder of the geomagnetic field synsedimentary slumps range from coherent slide blocks with undeformed bedding to smoothly curving folds indicating flow of very soft sediment coherent slide blocks show declinations rotated by tens of degrees away from the typical regional direction but their inclinations are unaffected soft sediment slump folds yield typical regional directions indicating resetting of the remanent magnetization after deformation using stratigraphic structural and paleomagnetic data it is possible to identify in the lower part of the section a basal nonslumped unit overlain by seven slump units with various characteristics inter layered with four units of pelagic sediments which were deposited on older slump units but which themselves were not affected by synsedimentary slumping this paper emphasizes the value of paleomagnetic stratigraphy as a tool in detailed studies of sedimentology stratigraphy and basin analysis

size variations of coccoliths in cretaceous oceans a result of preservation genetics and ecology abstract biometric studies of coccoliths the remains of coccolithophores offer the opportunity to survey single species instead of entire assemblages we obtained and analyzed size data of three common species biscutum constans zeugrhabdotus erectus and watznaueria barnesiae in a stratigraphically very well defined interval of early aptian age 126 ma cretaceous material is derived from four sites lower saxony basin north sea western tethys mid pacific covering nearshore to open oceanic paleosettings length and width measurements of 1986 specimens were evaluated the recorded size patterns show a larger data spread for b constans and w barnesiae in the western tethys and the mid pacific than in the north sea and the lower saxony basin the latter two sites are dominated by small coccoliths of b constans while coccoliths of w barnesiae show similar sizes at all four sites solely small specimens of z erectus characterize the samples from the north sea and the lower saxony basin while only large ones are present in the samples of the western tethys and mid pacific for explaining the recorded size patterns three theories are discussed in detail these include 1 preservation of nannofossils 2 genetics and 3 paleoecology 1 intense dissolution or overgrowth of the nannofossils may have altered the original coccolith sizes particularly when biometric data from different sites with potentially varying states of preservation are compared due to its delicate morphology z erectus appears most prone to dissolution probably explaining its size pattern 2 if the recorded size data of the remaining two species represent original patterns these can be interpreted by new findings in recent coccolithophore genetics it has been shown that size variations within a single cryptic species are only minor shifts of coccolith sizes both in recent and fossil taxa can be related to genotypic variation the varying size ranges recorded for b constans and w barnesiae may therefore reflect diversity changes of cryptic species at the different sites 3 these cryptic species may have preferred different depth habitats depending on geographically controlled factors such as sea surface temperatures light availability or trophic load

fracture characterization using earth tide analysis summary wells tapping confined aquifer systems are known to commonly produce water level fluctuations caused by strain induced earth tides in this investigation a straightforward methodology is presented for quantifying the specific storage and secondary porosity of a fractured fault zone aquifer system using earth tides water level and barometric pressure head data are smoothed and then filtered to remove low frequency responses the resulting tidal signals are used in the program baytap g to yield amplitude and phase shifts of all the major tidal groups the resulting tidal parameters can be used to compute the time dependent volumetric strain caused by the m 2 and o 1 tides stress strain hysteresis loops are produced when the reduced water levels are compared to the volumetric strain induced by these tides for amplification factors near unity representing the ratio of pressure response to tidal loading in the fracture to water level response in the well the slopes of the loops represent the specific storage of the fracture the barometric efficiency and specific storage can then be used to estimate a secondary porosity and other parameters of the aquifer system this analysis was carried out at the fractured rock research site frs in the blue ridge physiographic province in floyd county virginia

tropical warming and intermittent cooling during the cenomanian turonian oceanic anoxic event 2 sea surface temperature records from the equatorial atlantic oceanic anoxic event 2 oae 2 occurring during the cenomanian turonian c t transition is evident from a globally recognized positive stable carbon isotopic excursion and is thought to represent one of the most extreme carbon cycle perturbations of the last 100 myr however the impact of this major perturbation on and interaction with global climate remains unclear here we report new high resolution records of sea surface temperature sst based on tex86 and 18o of excellently preserved planktic foraminifera and stable organic carbon isotopes across the c t transition from black shales located offshore suriname french guiana demerara rise ocean drilling program leg 207 site 1260 and offshore senegal cape verde basin deep sea drilling project leg 41 site 367 at site 1260 where both sst proxy records can be determined a good match between conservative sst estimates from tex86 and 18o is observed we find that late cenomanian ssts in the equatorial atlantic ocean 33 c were substantially warmer than today 27 29 c and that the onset of oae 2 coincided with a rapid shift to an even warmer 35 36 c regime within the early stages of the oae a marked 4 c cooling to temperatures lower than pre oae conditions is observed however well before the termination of oae 2 the warm regime was reestablished and persisted into the turonian our findings corroborate the view that the c t transition represents the onset of the interval of peak cretaceous warmth more importantly they are consistent with the hypotheses that mid cretaceous warmth can be attributed to high levels of atmospheric carbon dioxide co2 and that major oaes were capable of triggering global cooling through the negative feedback effect of organic carbon burial led co2 sequestration evidently however the factors that gave rise to the observed shift to a warmer climate regime at the onset of oae 2 were sufficiently powerful that they were only briefly counterbalanced by the high rates of carbon burial attained during even the most extreme interval of organic carbon burial in the last 100 myr

high resolution chemostratigraphy of the late aptian early albian oceanic anoxic event oae 1b from the poggio le guaine section umbria marche basin central italy an integrated study of multiple geochemical proxies 13ccarb 13corg toc hi caco3 trace elements al ratios of the late aptian early albian oceanic anoxic event oae 1b has been performed on the pelagic sedimentary sequence of poggio le guaine umbria marche basin central italy a comparison of the newly collected stable isotope carbon curve with the records from the vocontian basin se france dsdp site 545 and hole 1049c provided a reliable and precise identification of the four main prominent black shale levels 113 jacob kilian urbino paquier and leenhardt that characterize the oae 1b the studied record shows an increase in the marine organic carbon accumulation rate in particular in the 113 jacob and urbino paquier levels in the other black shales toc values are 1 with evidence of degraded marine organic matter completely anoxic conditions were never established during the sediment deposition although evidence of oxygen depletion at the bottom of the basin is clearly documented by the distribution pattern of redox sensitive trace metals the results suggest an increase in organic carbon burial rates during the oae 1b due to the effect of enhanced surface productivity as supported by a major increase in ba al and reduced bottom water ventilation notably the kilian and urbino paquier levels from the plg section are characterized by the absence of correlative shifts in 13ccarb and 13corg the increase in the 13corg values in these levels is explained by an increase in the relative contribution of 13c enriched marine planktonic archaeal biomass while the concomitant negative excursions recorded in the 13ccarb could reflect a major contribution of isotopically light terrestrial carbonate ions from increased continental runoff during documented more humid conditions

abundance and size changes in the calcareous nannofossil schizosphaerella relation to sea level the carbonate factory and palaeoenvironmental change from the sinemurian to earliest toarcian of the paris basin abstract abundance and size changes in the calcareous nannofossil schizosphaerella are investigated throughout the upper sinemurian to lowermost toarcian of the sancerre couy core paris basin measurements from 116 samples are compared to 487 and 411 measurements of caco3 content and total organic carbon toc content respectively our results confirm that schizosphaerella was better adapted to proximal areas than coccoliths as expressed by the stepwise rise in abundance of schizosphaerella followed later on by the rise in abundance of coccoliths during the major transgression of the sinemurian the new results show that changes in the size of schizosphaerella were mostly a response to early jurassic temperature variations coldhouse greenhouse changes large average sizes of schizosphaerella correspond mostly to proximal cool environmental conditions of the late sinemurian medium average sizes correspond to more distal conditions and cool surface waters whereas small average sizes are associated with warm episodes these results suggest that the size response of schizosphaerella to the early toarcian oceanic anoxic event and to preceding environmental perturbations of the early jurassic was probably not a physiological response to lower calcification but rather represent changes in abundances of different ecophenotypes or sub species related to climate change the contribution of schizosphaerella carbonate caco3schizo to the total carbonate bulk caco3 in the paris basin was minor

numerical simulation of the noordbergum effect resulting from groundwater pumping in a layered aquifer system abstract numerical simulations were carried out to investigate the so called noordbergum effect i e reverse water level fluctuation resulting from groundwater withdrawal two specific cases were analyzed a three layer aquifer system composed of two permeable aquifers separated by a semi impermeable aquitard and a corresponding single layer aquifer system composed of an equivalent lumped material in the numerical simulation of the layered aquifer system the noordbergum effect is observed during the early time period of pumping in the overlying aquitard and unpumped aquifer while the underlying aquifer is pumped in contrast the numerical simulation results of the lumped aquifer system do not show such a reverse water level fluctuation throughout the entire domain these results strongly suggest that the noordbergum effect can be explained by the difference in poroelastic responses of the layered heterogeneous and lumped homogeneous aquifer systems to the hydraulic pumping stress the noordbergum effect is caused by two mechanisms a faster mechanical propagation deformation of the pumping stress than its hydraulic propagation drawdown from the pumped aquifer into the adjacent aquitard and unpumped aquifer due to relatively lower hydraulic conductivity of the aquitard and a mechanical amplification excessive compression in the lower part of the relatively soft aquitard however the pumping stress is evenly distributed throughout the entire domain of the lumped aquifer system without such mechanisms since it has homogeneous hydraulic and mechanical properties

potential links between ocean plateau volcanism and global ocean anoxia at the cenomanian turonian boundary the cenomanian turonian boundary is marked globally by the extinction of marine invertebrates and an increase in the accumulation and preservation of organic carbon rich sediments black shales the timing of this boundary also coincides with large scale volcanism from at least three large igneous provinces the caribbean and ontong java oceanic plateaus and the madagascar flood basalts in this paper we assess the possibility that hydrothermalism associated with large scale submarine magmatism was responsible for the reduction of dissolved o 2 in the oceans we investigate two potential mechanisms the oxidation of reduced material in hydrothermal effluents and the stimulation of primary productivity in the water column due to the injection of hydrothermal fe into surface waters with the first mechanism we find that a 10 000 km 3 submarine basalt eruption three orders of magnitude larger than recent midocean ridge eruptions could release enough reduced hydrothermal material to consume at least 6 percent of the dissolved o 2 in seawater in a well ventilated ocean such as the present ocean with the second mechanism we calculate that even a small percentage of the hydrothermal fe released from a single large flow could have led to a significant increase in primary productivity in areas where fe was the biolimiting nutrient such as open ocean areas in the pacific the potential impact of both of these o 2 reducing mechanisms at the cenomanian turonian boundary would have been significantly greater if cretaceous oceans were less well ventilated than the present oceans

orbitally induced limestone marlstone rhythms in the albian cenomanian cismon section venetian region northern italy sedimentology calcareous and siliceous plankton distribution elemental and isotope geochemistry abstract a multidisciplinary study of the upper albian cenomanian portion of the cismon section venetian region northern italy was undertaken in order to characterize the cyclic alternations of carbonate rich and carbonate poor layers and to investigate their possible origin and cyclic patterns limestone semicouplets are characterized by abundant radiolarians and micarbs micron sized calcitic fragments common planktonic foraminifera strong bioturbation good oxygenation as expressed by the mn and v v ni parameters high si al ratio low k al in the absence of pyrite and organic matter the marlstone semicouplets are on the contrary frequently laminated rich in pyrite and organic matter with common fish remains in the absence of radiolarians the mn and v v ni parameters indicate that the marlstone deposition occurred in dysoxic to anoxic conditions which allowed the preservation of organic matter the low si al ratio and high k al ratio the latter related to abundant feldspars indicate that marlstones received a substantial contribution from a terrigenous source the abundance of biogenic silica suggests that during limestone deposition surface waters were rather fertile due to an efficient recycling of nutrients from deeper waters the enhanced fertility was coupled with an efficient current system at the welloxygenated sea floor which prevented the organic matter from accumulating during marlstone deposition surface waters were less fertile than in the limestone semicouplets but still within the mesotrophic spectrum as indicated by the presence of fertility index species among calcareous nannofossils whereas the bottom waters were oxygen depleted to accommodate fertility at the surface with stagnation at the bottom the scenario implies an enhanced stratification caused by an increase in freshwater runoff monitored by 18o depleted values in the meantime the water discharge supplied the nutrients to the surface waters necessary for the calcareous nannofossils to proliferate the cyclic organization of limestone marlstone couplets as revealed by power spectral analysis seems to represent climatic cycles the alternating conditions are 1 efficient mixing highly fertile surface and near surface waters and a well oxygenated seafloor to 2 enhanced water runoff or decreased evaporation or both and oxygen depleted bottom waters we suggest that this deterministic sedimentary cyclicity could be explained by periodic orbital climatic cycles in tune with the milankovitch cycles within this scenario the latest cenomanian bonarelli level is an exceptional event marked by a large positive 13c spike it is characterized by high to very high fertility conditions in surface waters caused by increased upwelling that engendered high nutrient levels in near surface waters the enhanced production of organic matter was in excess for the oxygen available at the bottom floor thus allowing the organic matter to accumulate in the sediments

on meteorologically induced flushing in three u s east coast estuaries abstract meteorologically induced exchange with the coastal ocean is examined for three u s east coast estuaries using time series of subtidal volume flux over a common five month period a volume of water equal to that of the estuary was discharged every 86 4 135 3 and 108 8 days for narragansett delaware and chesapeake bays respectively however a large fraction of the water discharged to the shelf is recirculated ocean water for chesapeake bay outflowing estuarine water can be considered as a mixture of 2 4 3 0 water of mean estuarine salinity and the remainder water of oceanic salinity the degree of meteorological flushing is strongly influenced by mean depth as a drop in sea level of a given amplitude will force a greater fraction of water from a shallow estuary than from a deep system the relative importance of the meteorologically forced circulation and the gravitational circulation is frequency dependent as illustrated by salinity variance at the entrance to chesapeake bay seasonal salinity variance must ultimately be controlled by seasonal changes in runoff through the mechanism of gravitational circulation however the high coherence of wind induced changes in bay volume and bay entrance salinity at periods of 2 20 days suggests that meteorologically forced advection is primarily responsible for salinity variance at these time scales

onset of the mid cretaceous greenhouse in the barremian aptian igneous events and the biological sedimentary and geochemical responses basalts and biostratigraphy dated at 125 120 ma from the ontong java and manihiki plateaus in the western pacific evidence the largest volcanic event in earth history in at least the past 160 m y the intervening nova canton trough rifted at about 121 118 ma and a number of guyots and seamounts formed concurrently or slightly later geological events that probably were responses to these volcanic tectonic events occurred in the following chronostratigraphic order biotic fluctuations began at about 122 5 ma at about 122 0 ma 87sr 86sr began to decline slowly metal concentrations of co mn pb yb and cu in sediments peaked at about 121 5 121 2 ma changes in planktonic communities and sedimentation culminated in a nannoconid crisis just prior to 120 5 ma and in the selli black shale oae la at about 120 5 119 5 ma a sharp drop in 13c occurred at the beginning of the selli event and rebounded into a longer positive excursion that reached a peak after the selli event at about 119 5 118 5 ma at 120 5 ma 87sr 86sr declined rapidly and reached a minimum at about 116 113 ma we speculate that the intensity of these latter responses suggests a corresponding peak in volcanic tectonic activity at about 121 119 ma

calcareous nannoplankton response to surface water acidification around oceanic anoxic event 1a ocean acidification induced by atmospheric co2 may be a major threat to marine ecosystems particularly to calcareous nannoplankton we show that during the aptian 120 million years ago oceanic anoxic event 1a which resulted from a massive addition of volcanic co2 the morphological features of calcareous nannofossils traced the biological response to acidified surface waters we observe the demise of heavily calcified nannoconids and reduced calcite paleofluxes at the beginning of a pre anoxia calcification crisis ephemeral coccolith dwarfism and malformation represent species specific adjustments to survive lower ph whereas later abundance peaks indicate intermittent alkalinity recovery deepwater acidification occurred with a delay of 25 000 to 30 000 years after the dissolution climax nannoplankton and carbonate recovery developed over 160 000 years under persisting global dysoxia anoxia

nannofossil assemblages fine fraction stable isotopes and the paleoceanography of the valanginian barremian early cretaceous north sea basin calcareous nannofossil assemblages have been investigated in three sections from around the margins of the early cretaceous north sea basin both absolute number of nannofossils per gram and relative percent of the assemblage of different taxa abundance data have been collected absolute abundances up to 10 billion nannofossils per gram are somewhat higher than those reported previously from other stratigraphic intervals stratigraphic correlation of trends in assemblage data in different sections points toward the existence of large uniform water masses stable over long 0 5 to 1 m y time periods these water masses contained a characteristic nannoplankton which appears to have been driven largely by variations in fertility possibly tied to changes in sources of surface waters which in turn may have been controlled by relative sea level fine fraction isotopic data show fluctuations on shorter time periods 0 1 to 0 5 m y we postulate that some of these isotopic fluctuations were controlled by relative changes in sea level which affected the balance of surface waters derived from runoff and those imported from the boreal sea these oceanographic changes appear to have affected nannofossil assemblages only in discrete intervals data are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document p95 001 2 50 payment must accompany order

calcareous nannoplankton from the boreal late albian of nw germany kirchrode i borehole its biostratigraphy and cyclicity abstract one hundred and sixty samples from the continuously cored kirchrode i research borehole were examined for calcareous nannoplankton a total of 106 coccolith taxa were identified the state of preservation varied from poor to good mostly moderately good the coccolith assemblages were assigned to the eiffellithus turriseiffelii zone cc9 and prediscosphaera columnata zone cc8 of the upper albian sissingh geol en mijnb 56 1977 37 a count of the taxa was made at 5 m intervals and in certain sections at 1 m intervals this study focuses on the dating of the sequence with calcareous nannofossils and the determination of the fluctuations in the abundance of calcareous nannofossils the cyclicity found in the changes in their abundance was correlated with cycles determined for the changes in the calcium carbonate content of the sediment

absence of major vegetation and palaeoatmospheric pco2 changes associated with oceanic anoxic event 1a early aptian se france the deposition of organic rich sediments during the late early aptian oceanic anoxic event oae 1a has been interpreted to result in a major decrease of palaeoatmospheric co2 concentrations accompanied by significant changes in the terrestrial flora in order to test this hypothesis the oae 1a interval in the vocontian basin se france has been studied with a combined approach including stable carbon isotopes organic geochemistry and palynology to estimate changes in palaeoatmospheric co2 levels across the oae 1a the 13c composition of presumed algal biomarkers low molecular weight n alkanes steranes and of bulk carbonate carbon are used our results yield estimated early aptian carbon dioxide partial pressure pco2 values three to four times the preindustrial level and only a moderate drop across the black shale event this moderate drop in pco2 is supported by palynological results the frequency patterns of climate sensitive sporomorphs incl pteridophyte spores bisaccate pollen and classopollis spp display only minor fluctuations throughout the studied section and indicate relatively stable patterns of terrestrial vegetation during and after formation of the oae 1a black shale the occurrence of a characteristic early aptian carbon isotope pattern across the oae 1a interval permits accurate chemostratigraphic correlation with the well studied livello selli interval of the cismon record n italy the contemporaneous formation of individual black shale layers at both sites indicates that transient episodes of dysoxic anoxic bottom waters prevailed over large areas in the w tethys ocean independent of depositional setting comparison of the palynological data from the two locations displays significant differences in the frequency patterns of bisaccate pollen the contrasting pollen spectra are interpreted to reflect prominent changes in the palaeoceanographic current patterns and or selective sorting due to sea level rise rather than latitudinal shifts of the major floral belts

new constraints upon isotope variation during the early cretaceous barremian cenomanian from the pacific ocean carbon and oxygen isotope data from a succession of cretaceous barremian cenomanian age recovered from the pacific ocean dsdp site 463 are presented the carbon isotope curve reveals a large isotope excursion within the early aptian where 1 3 c values reach 4 8 in the l cabri g ferreolensis foraminifera zone a decrease in 1 3 c values is observed at the base g algerianus zone before a return to more positive values at the top of the g algerianus t bejaouaensis zone the pronounced early aptian positive event is preceded by a large negative isotope excursion confined to the g blowi zone synchronous with this excursion are increased total organic carbon values and increases in mn and fe concentrations integrated biostratigraphic and magnetostratigraphic data together with the carbon isotope profile suggest that the organic rich units of site 463 are correlatable with oceanic anoxic event la the input of isotopically light volcanic co 2 in concert with the intensification and upwelling of intermediate water enriched in 1 2 c could account for the observed trends a potential trigger may have been the destabilization of the water column and the prodigious co 2 emissions associated with hydrothermal activity and the emplacement of the ontong java plateau coupled with faunal evidence the subsequent positive carbon isotope excursion is interpreted to be resulting from high but decreasing productivity and possibly increasing ocean stratification resulting in strong carbon isotopic gradients and 1 3 c enriched surface waters the decrease in 1 3 c within the g algerianus zone is coincident with more positive 1 8 o values if these are interpreted in terms of temperature this interval may be characterized by a period of cooling and possibly a waning of c o r g cycling a return to lower 1 3 c values during the middle albian is considered to be related to the increased influence of upwelling as opposed to a waning of c o r g cycling upwelling introduced isotopically light carbon to the surface arresting the stratified oceanic conditions

sedimentation in the tethyan pelagic realm during the cenomanian monotonous settling or active redistribution sea bottom processes of the pelagic realm are still not completely understood and represent an intriguing subject this paper focuses on the relationships between normal settling processes redistribution of sediments and oceanographic parameters in a pelagic setting during the cenomanian five key tethyian localities in the cenomanian umbria marche and belluno basins have been studied in order to understand the interplay among sea bottom processes that acted on the sea floor the dataset consists of the mm scale sedimentological description of the sections complemented by microfacies analysis on selected samples different sedimentological indications such as presence of intraclasts lined forams pervasive plane parallel lamination suggest a continuous reworking under action of bottom currents with varying intensity and direction all the identified facies are here illustrated in detail and organized in a comprehensive schematic facies framework the facies matrix that leads to recognize two depositional facies suites the settling dominated and the traction current dominated under different oxygenation conditions our results suggest that settling of biogenic and inorganic particles represents the main source of pelagic sediments but not the unique depositional process under the action of sea bottom currents of different intensity sediments are continuously redistributed on the sea floor all the collected evidences contribute to the proposal of a comprehensive depositional model for these reworked and redistributed fine grained sediments that represent true calcareous pelagic contourites the model suggests that the identified traction related facies can be used as a proxy for bottom current intensity and indirectly as an indicator of changing ventilation regimes at the sea floor through time

estimates of subtidal volume flux in mid chesapeake bay utilizing 20 days of current meter and sea level elevation records taken in two cross sections in mid chesapeake bay an objective interpolation procedure was devised to allow the computation of vertical profiles of the laterally integrated subtidal volume fluxes at each section at 3 h intervals over the period of the experiment the presence of a classical mean estuarine circulation was observed however departures from this gravitational circulation were revealed on a shorter time scale reaching the value of 20 000 m3 s 1 over a day and featuring behaviors of reverse estuarine storage and discharge modes the volume flux computations through each cross section based on the measured current velocities the freshwater inflow and the calculated stokes transport were in agreement with each other a two layered box model of the mean subtidal circulation in the segment of the estuary bound by the two cross sections is offered a comparison was made between the computations of net volume flux into and out of the bay above these sections using two independent methods 1 the accounting of volume continuity based upon direct measurements of volume flux through the sections and 2 the direct calculation of the time rate of change of volume of the upper bay obtained from tide gauge records the agreement between the two results was found to be very good further evidence is provided for the upward phase propagation of the oscillations in the residual motion of estuarine waters

formation of fractured zones in overburden due to longwall mining the fractured zones caused by mining were studied in the overburden of the torezko snezhnyanskaya area ukraine through the change in natural gas emission from these zones during longwall coal excavation zones of interconnected fractures and separate horizontal fractures were studied with vertical wells drilled from the ground surface down to active underground workings the maximum heights of the zone of interconnected fractures and separate horizontal fractures may reach 19 41 and 53 92 times the thickness of the coal seam respectively it was found that the ratio between the maximum height of the zone of interconnected fractures and the thickness of the extracted coal seam increases with the increasing number of rock layer interfaces and decreases with the increasing stiffness of immediate roof it is shown that the growth of the zone of interconnected fractures occurred during 17 39 days at an average rate of 0 94 1 97 m day 1 and it was accompanied by increasing methane emission from overburden observation shows that the formation of separate horizontal fractures began only 11 49 5 days after the height of the zone of interconnected fractures reached its maximum value formation of separate horizontal fractures in overburden over the longwall excavation occurred as a stepped process from lower to upper sandstone sandy shale layer interfaces in the direction of the ground surface

nannofossil carbonate fluxes during the early cretaceous phytoplankton response to nutrification episodes atmospheric co2 and anoxia 1 greenhouse episodes during the valanginian and aptian correlate with major perturbations in the c cycle and in marine ecosystems carbonate crises and widespread deposition of corg rich black shales quantitative analyses of nannofossil micrite were conducted on continuous pelagic sections from the southern alps northern italy where high resolution integrated stratigraphy allows precise dating of early cretaceous geological events rock forming calcareous nannofloras were quantified in smear slides and thin sections to obtain relative and absolute abundances and paleofluxes that are interpreted as the response of calcareous phytoplankton to global changes in the ocean atmosphere system increased rates of volcanism during the formation of ontong java and manihiki plateaus and the parana etendeka large igneous province lip are proposed to have caused the geological responses associated with early aptian oceanic anoxic event oae 1a and the valanginian event respectively calcareous nannofloras reacted to the new conditions of higher pco2 and fertility by drastically reducing calcification the valanginian event is marked by a 65 reduction in nannofossil paleofluxes that would correspond to a 2 3 times increase in pco2 during formation of the parana endenteka lip a 90 reduction in nannofossil paleofluxes which occurred in a 1 5 myr long interval leading into oae1a is interpreted as the result of a 3 6 times increase in pco2 produced by emplacement of the giant ontong java and manihiki plateaus high pco2 was balanced back by an accelerated biological pump during the valanginian episode but not during oae1a suggesting persisting high levels of pco2 in the late aptian and or the inability of calcareous phytoplankton to absorb excess pco2 above threshold values

short timescale thermohaline variability and residual circulation in the central segment of the coastal upwelling system of the ria de vigo northwest spain during four contrasting periods 1 sixteen hydrographic surveys were carried out in the middle segment of the ria de vigo northwest spain at 3 to 4 day intervals during february april july and september 2002 four surveys per period simultaneously an acoustic doppler current profiler adcp mooring recorded the velocity profile combination of direct current measurements with the output of an inverse model based on the time course of the distributions of salinity and temperature allowed an objective analysis of the effect of the meteorological forces on the hydrodynamics of the ria remote shelf winds explained more than 65 of the variability of the subtidal circulation which responded immediately to this forcing lag time 2 days shelf winds created a simple two layered circulation pattern with a surface outgoing current under northerly winds and a surface ingoing current under southerly winds a three layered circulation developed during the transitions from northerly to southerly winds and vice versa at the same time an empirical orthogonal function eof analysis demonstrated the lack of contribution of local winds to the subtidal dynamics of the ria continental runoff and heat exchange with the atmosphere explained less than 5 and 25 of the variability observed in the subtidal circulation of the ria de vigo

paleoenvironmental controls on the morphology and abundance of the coccolith watznaueria britannica late jurassic southern germany the coccolithophore species watznaueria britannica is dominant in middle upper jurassic calcareous nannofossil assemblages and presents morphological variation including different coccolith size shape and length of the central area and of the bridge six morphotypes can be recognized in the polarizing light microscope the aim of this work is to better understand the morphological variability of w britannica and determine if this variability is controlled by paleoecological factors in order to investigate the potential paleoecological controls on w britannica morphology and abundance we carried out a biometric study on a restricted temporal interval the late oxfordian in the swabian alb southern germany characterized by increasing carbonate production linked to climatic changes the balingen tieringen section where previous works on sedimentology nannofossil assemblage composition and 18o and 13c analyses were performed was selected for this study the variations in morphology and abundances ofw britannicawere studied on 40 samples of the balingen tieringen section presenting variable lithologies and calcium carbonate contents for each level seven biometric parameters coccolith length width and ellipticity central area length width and ellipticity and central area proportion with respect to the coccolith were measured or calculated on digitally captured images of the first 100 w britannica coccoliths observed in the light microscope the relationships between the different biometric variables were described using bivariate and principal component analyses biometric parameters and principal component factors extracted from nannofossil assemblages as well as other paleoenvironmental proxies were investigated using regression and their stratigraphic trends were compared principal component analysis of the six biometric variables 3938 measurements on w britannica coccoliths shows a reduced morphological variability compared to a significant size gradient an allometric trend recognized on the total placolith and on the central area within thew britannica assemblages suggests that the different morphotypesmay represent intra specific variability rather than different species the general trend through late oxfordian shows an increase in size ofw britannica coccoliths mainly driven by an increase in the contribution of the largemorphotypes increasing placolith size is associated with drier and warmer climatic conditions during the latest oxfordian

onset and demise of cretaceous oceanic anoxic events the coupling of surface and bottom oceanic processes in two pelagic basins of the western tethys

climate and paleoceanography controlled size variations of calcareous nannofossils during the valanginian weissert event early cretaceous abstract strata of valanginian age early cretaceous 139 8 132 9 ma record a 1 5 positive carbon isotope excursion cie the weissert event it coincides with volcanic activity of the parana etendeka large igneous province unlike the mesozoic oceanic anoxic events oaes no organic rich deposits documenting widespread perturbation of the marine carbon cycle are associated with the weissert event to study the impact of paleoceanographic changes in the valanginian on calcareous nannofossils this study analyzes coccolith size data of three species biscutum constans watznaueria barnesiae zeugrhabdotus erectus from northern germany and the western north atlantic further it presents a new valanginian carbon isotope record of organic material 13corg from northern germany the dataset records the weissert event cie in the late valanginian at both locations biometric analyses reveal size decreases of b constans coccoliths during the weissert event a size reduction of 1 m has been observed for northern germany 37 n and of 0 4 m for the north atlantic 23 n the different magnitudes of size decrease possibly reflect the different paleogeographic positions of the sites and the paleoceanographic response to the late valanginian climate variations proxy data support a link between a humid climate with increased weathering and the observed coccolith size variations this impacted nannoplankton communities either through the availability of light or by eutrophication and possibly nutrient limitation in addition to increased terrigenous input emissions of the parana etendeka volcanism possibly acted fertilizing furthermore widely dispersed volcanic emissions possibly caused increased concentrations of toxic trace metals in the surface ocean which affected marine primary producers

fractures in continental shale reservoirs a case study of the upper triassic strata in the se ordos basin central china fractures are important for shale gas reservoirs with low matrix porosity because they increase the effective reservoir space and migration pathways for shale gas thus favouring an increased volume of free gas and the adsorption of gases in shale reservoirs and they increase the specific surface area of gas bearing shales which improves the adsorption capacity we discuss the characteristics and dominant factors of fracture development in a continental organic matter rich shale reservoir bed in the yanchang formation based on observations and descriptions of fracture systems in outcrops drilling cores cast thin sections and polished sections of black shale from the upper triassic yanchang formation in the se ordos basin detailed characteristics and parameters of fractures analyses and tests of corresponding fracture segment samples and the identification of fracture segments with normal logging the results indicate that the mineral composition of the continental organic matter rich shale in the yanchang formation is clearly characterized by a low brittle mineral content and high clay mineral content relative to marine shale in the united states and china and mesozoic continental shale in other basins the total content of brittle minerals such as quartz and feldspar is c 41 with quartz and feldspar accounting for 22 and 19 respectively and mainly occurring as plagioclase with small amounts of carbonate rocks the total content of clay minerals is high at up to 52 and mainly occurs as a mixed layer of illite smectite i s which accounts for more than 58 of the total clay mineral content the upper triassic yanchang formation developed two groups of fracture joint systems a nw se trending system and near e w trending system multiple types of fractures are observed and they are mainly horizontal bedding seams and low dip angle structural fractures micro fractures are primarily observed in or along organic matter bands shale fractures were mainly formed during late jurassic late early cretaceous time under superimposed stress caused by regional wnw ese trending horizontal compressive stress and deep burial effects the extent of fracture development was mainly influenced by multiple factors tectonic factors and non tectonic factors such as the lithology rock mechanical properties organic matter abundance and brittle mineral composition and content specifically higher sand content has been observed to correspond to more rapid lithological changes and more extensive fracture development in addition higher organic matter content has been observed to correspond to greater fracture development and higher quartz feldspar and mixed layer i s contents have been observed to correspond to more extensive micro fracture development these results are consistent with the measured mechanical properties of the shale and silty shale the observations of fractures in cores and thin sections from more than 20 shale gas drilling wells and the registered anomalies from gas logging

reconstruction of short term palaeoceanographic changes during the formation of the late albian niveau breistroffer black shales oceanic anoxic event 1d se france the niveau breistroffer black shale succession in the vocontian basin se france is the regional equivalent of the widely distributed late albian oceanic anoxic event 1d the studied black shale rich interval at the col de palluel section is 6 28 m thick and comprises four black shale units with up to 2 5 wt total organic carbon toc intercalated with marlstones calcareous nannofossil palynomorph planktic foraminifera and stable isotopic data from the niveau breistroffer succession suggest that short term climate changes influenced its deposition with relatively warm and humid climate during black shale formation in comparison with relatively cool and dry climatic conditions during marlstone deposition an increase in the terrigenous marine ratio of palynomorphs indicates enhanced humidity and higher runoff during black shale formation a nutrient index based on calcareous nannofossils and the abundance pattern of small 63 125 m hedbergellid foraminifera show short term changes in the productivity of the surface water surface water productivity was reduced during black shale formation and increased during marlstone deposition a calcareous nannofossil temperature index and bulk rock oxygen isotope data indicate relative temperature changes with warmer surface waters for black shale samples at these times warm humid climate and reduced surface water productivity were accompanied by greater abundances of subsurface dwelling calcareous nannofossils nannoconids and planktic foraminifera rotaliporids these taxa presumably indicate more stratified surface water conditions we suggest that the formation of the niveau breistroffer black shales occurred during orbitally induced increase in monsoonal activity that led to increasing humidity during periods of black shale formation this in turn caused a decrease in low latitude deep water formation and probably an increase in surface water stratification the combination of these two mechanisms caused depleted o 2 concentrations in the bottom water that increased the preservation potential of organic matter

tidal responses and earthquake related changes in the water level of deep wells monitoring of the water level has been continued in 100 m deep and 500 m deep wells in the southern kanto district japan to examine the relationship between changes in the well water level and earthquake occurrence by using a bayesian approach the observed data were decomposed into four components tidal response barometric response trend drift and irregular noise components loading effects of the ocean tide on aquifer dilatation were evaluated by using schwiderski s ocean tide models and the harmonic constants compiled by the international hydrographic bureau well aquifer properties were examined based on the tidal and barometric responses of the water level coseismic water level steps were detected in both wells for two earthquakes during the observation period from april 1985 to december 1989 by calibrating the strain sensitivity of the well water levels based on the tidal responses strain changes equivalent to the coseismic steps in the water levels were estimated the coseismic strain changes obtained for the deeper well can be explained reasonably by earthquake fault models in a viscoelastic half space however those observed in the shallower well were too large and in the wrong direction to be explained by the earthquake fault models

using earth tide induced water pressure changes to measure in situ permeability a comparison with long term pumping tests good constraints on hydrogeological properties are an important first step in any quantitative model of groundwater flow field estimation of permeability is difficult as it varies over orders of magnitude in natural systems and is scale dependent here we directly compare permeabilities inferred from tidal responses with conventional large scale long term pumping tests at the same site tidally induced water pressure changes recorded in wells are used to infer permeability at ten locations in a densely fractured sandstone unit each location is either an open hole well or a port in a multilevel monitoring well tidal response is compared at each location to the results of two conventional long term and large scale pumping tests performed at the same site we obtained consistent values between the methods for a range of site specific permeabilities varying from 10 15 m2 to 10 13 m2 for both open wells with large open intervals and multilevel monitoring well we conclude that the tidal analysis is able to capture passive and accurate estimates of permeability

the first 150 million years history of calcareous nannoplankton biosphere geosphere interactions abstract the mesozoic evolution of calcareous nannoplankton is here compared to global changes in the earth system to derive possible causal links between biosphere geosphere interactions the late triassic appearance of nannofossils represents an innovation that affected the marine carbonate system the global carbon cycle and the ocean atmosphere co2 nannofossil biodiversity generally increases through the jurassic and cretaceous with development of approximately 30 coccolith nannolith families speciations mass extinctions diversifications and turnovers correlate with global changes in the geosphere hydrosphere and atmosphere suggesting that the evolutionary patterns are intimately linked to environmental modifications coccolithophore biocalcification involves conversion of ca2 and co32 ions into caco3 when high fluxes of ca2 and inorganic c from the external environment into the cell are maintained seawater co2 availability and nutrient type and abundance are also important for the functioning of photosynthesis and calcification the role of coccolith secretion with respect to photosynthesis remains uncertain current dating of events suggests that pco2 and chemistry of the oceans ca2 mg ca ratio are instrumental in coccolith and particularly nannolith appearance and development whereas climate and sea level apparently play a secondary role availability of nutrients and biolimiting metals certainly influence nannoplankton evolution it is suggested here that there is a causal link between levels of co2 and calcite secretion by nannoplankton namely when pco2 in the ocean atmosphere system is minimum production of heavily calcified coccoliths nannoliths might provide sufficient co2 inside the cell to sustain photosynthesis on the contrary excess carbon dioxide makes calcification less indispensable or even inhibits calcite production smaller and less calcified coccoliths become dominant natural variations in atmospheric co2 are essentially triggered by igneous activity that also controls the ocean chemistry and nutrient cycling in particular the seawater mg ca ratio is related to seafloor spreading and hydrothermal processes high production of ocean crust results in high ca2 concentrations low mg2 concentrations and low mg ca ratio and vice versa accordingly the phanerozoic is subdivided into intervals of calcite and aragonite seas the appearance of calcareous nannoplankton and its maximum diversification indeed correlate with the shift from the paleozoic triassic aragonite sea to the jurassic paleogene calcite sea and the core of the latter respectively although there is a logical connection between pco2 and ca2 concentration and nannofossil diversity species richness alone cannot measure the productivity production of coccolithophores through time absolute abundances are necessary to interpret and model the distribution of calcareous nannofossils relative to the environment and quantify positive and negative feedbacks of coccolithophore biocalcification improved chronology of paleobiological and geological events will be crucial for the understanding of evolutionary processes

palaeoenvironmental vs evolutionary control on size variation of coccoliths across the lower middle jurassic size is an easily quantifiable trait probing the respective influence of evolution and palaeoenvironment on organisms through time after the stressed period that spanned across western tethys epicontinental seas during the early toarcian the following rebuilding of a restored water column ecosystem is coeval with the size increase of the lotharingius genus coccoliths one of the main pelagic producers at that time in order to quantitatively assess the coccolith size evolution during a time span of 10 myr measurements of seven morphospecies of lotharingius across the toarcian and early aalenian were performed this study was carried out on a total of 5500 specimens from samples retrieved from two distinctive palaeoenvironmental settings in the western mediterranean tethys three sections from the lusitanian basin in portugal and one section from the causses basin in southern france for each specimen coccolith length width and central area length and width were measured using specific measurement software statistical and data analysis tools were used in order to evaluate significant resemblances and or differences between different size groups and samples two main clusters are acknowledged from this study small sized lotharingius is 4 m in addition to common evolutionary processes changes in palaeoenvironmental conditions were taken into account to explain such a size distribution although background evolution pushed the lotharingius genus toward larger sizes palaeoenvironmental conditions seemed to play an important role in the toarcian early aalenian morphological evolution of this taxon the production of larger coccoliths profited from stable environmental conditions whereas smaller morphotypes dominated during periods marked by stress the transition from small to large lotharingius was synchronous in the two investigated western tethys basins at the bifrons gradata or variabilis ammonite zone boundary middle toarcian thus representing an important event for the lower jurassic calcareous nannofossil biostratigraphy

temporal changes of hydraulic properties of overburden aquifer induced by longwall mining in ningtiaota coalfield northwest china abstract characterizing the mining induced temporal changes of hydraulic properties of the overburden aquifer is significant for groundwater resource protection conventional hydrogeological methods e g hydraulic test physical model test and numerical simulation of determining hydraulic properties of the overburden aquifer cannot quantitatively analyze the temporal changes of the hydraulic properties induced by mining disturbances this paper demonstrates a quantitative determination for the temporal changes of parameters compressibility porosity and specific storage in the overburden aquifer influenced by the mining processes based on in situ continuous measurements of groundwater level that was affected by earth tide atmospheric loading and mining disturbances the results showed that when working face reached a certain distance 127 m from borehole j6 in this study those parameters compressibility porosity and specific storage of overburden aquifer began to show gradual decrease with approximately up to two order of magnitudes after the working face passed by the observation borehole j6 those properties of overburden aquifer recovered in about 80 days which might reflect the characteristic of elastic deformation of the aquifer those findings of the mining induced parameters temporal changes could improve our understanding of the mining effects on aquifer system and could be meaningful in groundwater resource protection

trace element abundances in the rock canyon anticline pueblo colorado marine sedimentary section and their relationship to caribbean plateau construction and oxygen anoxic event 2 1 rapid eruption of submarine lava flows during formation of the caribbean plateau correlates closely with ocean anoxic event 2 oae2 which bracketed the cenomanian turonian boundary 93 5 ma these events also correspond with a positive excursion in carbon isotopic composition of seawater hydrothermal activity associated with large scale submarine volcanism may have been responsible for this abrupt change in ocean chemistry we determined the distribution of major minor and trace element abundances in the rock canyon marine sedimentary section pueblo colorado after normalizing element concentrations to zr to remove the variable contribution of terrigenous material to these sediments we detected an interval of concentrated metal abundance anomalies that coincides with the abrupt beginning of the positive 13c isotope excursion the metal abundance anomalies indicate that intermittent hydrothermal activity in the form of both water rock exchange and magmatic degassing introduced large concentrations of trace metals into the cretaceous ocean at the same time that extinctions of benthic species turnover in plankton communities and increases in isotopically light organic carbon burial occurred the stratigraphic position of this interval of trace metal anomalies matches events associated with oae2 and indicates that intermittent hydrothermal activity on a massive scale triggered abrupt changes in carbon burial and deep ocean oxygen contents

tracking changes in the specific storage of overburden rock during longwall coal mining the hydraulic properties of geologic formations such as specific storage and hydraulic conductivity are known to vary spatially due to formation heterogeneity however they may also change temporally if the formation undergoes mechanical disturbance such as occurs during mining characterising changes in hydraulic properties is important for groundwater systems that are disturbed by mining conventional hydrogeological investigations rely on literature derived values or limited programs of field testing e g pumping test to define specific storage but these approaches do not consider the change in compressibility that may occur due to mechanical disturbance this paper presents for the first time direct in situ measurements of the changes in compressibility and consequently specific storage as a result of mechanical disturbance within geologic formations overlying underground mining operations the in situ measurements of compressibility are derived in this study from the pore pressure response to barometric loading or strains induced by earth tides even prior to disturbance the compressibility obtained from in situ measurements was found to be an order of magnitude lower than that measured on core samples by unconfined strength test in the laboratory the differences in compressibility for the intact formation are likely due to sample disturbance and the differences in strain level imposed by the field and laboratory methods the increase in compressibility of the overburden rock varied with the location of the monitoring site relative to longwall extraction and the level of strain the formation sustained the study found that quantifying the changes in compressibility and consequently specific storage as a result of mine induced disturbance is critical to our understanding of subsidence the extent of depressurization and the impact that mining may have on regional groundwater flow systems

timing and magnitude of early aptian extreme warming unraveling primary δ18o variation in indurated pelagic carbonates at deep sea drilling project site 463 central pacific ocean abstract in order to elucidate early aptian marine paleotemperature evolution across the period of enhanced organic carbon corg burial oceanic anoxic event oae 1a stable isotope analyses were performed on pelagic limestones at deep sea drilling project site 463 central pacific ocean the 18o data exhibit a distinct anomaly by 2 spanning the oae 1a interval i e a 6 m thick phytoplanktonic corg rich unit constrained by magneto bio and 13c stratigraphy elucidation of paleotemperature significance of the 18o shift is made by taking account of recent sr ca evidence at the same section which revealed that geochemical signals in carbonate poor lithologies are relatively unaltered against burial diagenesis by discriminating 18o values from carbonate poor samples caco3 contents 5 30 wt it appears that an abrupt rise in sea surface temperatures ssts by 8 c 1 7 shift in 18o occurred immediately before oae 1a whereas a cooling mode likely prevailed during the peak corg burial in terms of its stratigraphic relationship as to the corg rich interval and to a pronounced negative 13c excursion as well as its timescale the observed sst rise resembles those associated with the paleocene eocene thermal maximum and more strikingly jurassic toarcian oae this observation is consistent with the hypothesis that these paleoenvironmental events were driven by a common causal mechanism which was likely initiated by the greenhouse effect via massive release of ch4 or co2 from the isotopically light carbon reservoir and terminated by a negative productivity feedback

reconstructing nutricline dynamics of mid cretaceous oceans evidence from calcareous nannofossils from the niveau paquier black shale se france abstract a high resolution calcareous nannofossil record is presented from the lower albian niveau paquier black shale from the vocontian basin se france the niveau paquier black shale represents the regional equivalent of the supraregionally distributed oceanic anoxic event 1b oae 1b to reconstruct surface water fertility a nutrient index based on zeugrhabdotus erectus discorhabdus rotatorius high fertility indicators and watznaueria barnesae low fertility indicator was established using principal component analysis in addition the distribution of nannoconus spp and absolute abundances of coccoliths coccoliths per gram were used for reconstructing nutricline dynamics of the surface waters high surface water fertility coincides with low percentages of nannoconids and vice versa moreover high percentages of nannoconids correlate with low absolute abundances of all other coccoliths based on the observed nannoplankton distribution pattern and a suggested similarity in ecological requirements between nannoconids and the modern taxon florisphaera profunda a model is proposed that couples nannoconid abundances with dynamics of the nutricline time series analyses of the nutrient index show fluctuations within the precessional band the precession controlled fluctuations of the surface water fertility may represent a monsoonal signal with the nutrient supply in the surface waters depending on the strength of monsoonal activity during periods of enhanced monsoonal activity which were characterized by humid conditions and stronger winds mixing of the upper water column was enhanced during that time the abundance of nannoconids decreased as a consequence of enhanced wind stress that improved vertical mixing and led to an entrainment of nutrients into the surface waters this resulted in an increase of primary production during periods of reduced monsoonal activity marked by drier conditions and reduced wind stress the surface waters were depleted in nutrients as a result of a deep nutricline and a reduced nutrient supply to the upper photic zone in a stratified water column percentages of nannoconids increased according to the mechanisms outlined above fluctuations of the nutrient index and nannoconid percentages have been used as a proxy for reconstructing the physical structure of mid cretaceous oceans steered by precession forced monsoonal activity the results of the study show that the formation of the lower albian oae 1b from the vocontian basin occurred under strongly fluctuating surface waters fertility

origin of rhythmic albian black shales piobbico core central italy calcareous nannofossil quantitative and statistical analyses and paleoceanographic reconstructions 1 the mid cretaceous 120 90 ma was a time of excess atmospheric co2 greenhouse climate and widespread o2 deficiency in the ocean the albian is punctuated by brief intermittent episodes of anoxia dysoxia recorded as cyclic black shales in the western tethys and atlantic oceans the albian section of the piobbico core central italy contains 30 m 10 ma of rhythmic black shales that were sampled at a high resolution and examined for calcareous nannofossil assemblages and c and o stable isotopes unlike oceanic anoxic events productivity was not the primary factor controlling the deposition of albian rhythmic black shales it is suggested that during warm humid climatic cycles higher temperatures and or increased precipitation and runoff produced density stratification at a regional scale recurrent lowered salinity in the early albian and warming in the late albian are credited with causing development of a pycnocline resulting in slower rates of deep water renewal and consequent anoxia