morphological and speleothemic development in brujas cave southern andean range argentine palaeoenvironmental significance abstract brujas cave in the southern andean range is a well known endokarstic site in argentina however the origin and evolution of this cave system are poorly known based on morphological cave features as well as characteristics of cave deposits we propose a meteogene drawdown cave genesis including a change from phreatic to vadose conditions related to the high rate of fluvial downcutting in the area during the vadose period various cave related deposits including authogenic calcite and gypsum speleothems allogenic volcanic ash and external tufas were deposited gypsum crusts are the oldest cave deposits identified 90 2 64 3 ky bp their origin deduced from isotopic characteristics 34 s 9 6 is related to the oxidation of pyrite contained in the jurassic limestone bedrock as well as the dissolution of overlying jurassic triassic evaporite formations gypsum crust deposition is associated with evaporation of water flowing and seeping into the cave during arid environmental conditions calcite deposits precipitated from flowing water under equilibrium conditions represent the main speleothem growth period 67 6 34 ky bp in age their stable isotope values 13 c 3 to 5 and 18 o 9 to 11 may indicate slightly humid and warm conditions related to the regional minchin lacustrine phase and global oxygen isotope stage 3 following this stage a seismic event is evidenced by accumulations of broken stalactites seepage calcite speleothems covering cave walls were deposited under disequilibrium conditions by evaporation probably during holocene time finally another more recent gypsum deposition period represented by gypsum balls has been differentiated micromorphological as well as isotopic 34 s 5 6 data indicate that these gypsum forms are related to cyclic processes solution deposition from water seeping into the cave under arid conditions in addition intense volcanic activity in the area during holocene time is deduced from allogenic volcanic ash and lapilli located mainly at the entrance cave at present limited hydrological activity is observed in the cave and small tufa deposits at karstic discharge points are evidenced we conclude that the geomorphological evolution of brujas cave was controlled by climatic changes wet and dry stages under semiarid environmental conditions in a very active tectonic and volcanic setting during late quaternary time

late quaternary paleotemperatures derived from a speleothem from cango caves cape province south africa abstract an oxygen isotope temperature record over a large part of the past 30 000 yr has been obtained for the southern cape province of south africa by combining data on the isotopic composition of a stalagmite from a deep cave with that of a confined groundwater aquifer in the same region results show that temperatures during the last glacial maximum were on average about 6 c lower than those today with peaks up to 7 c lower a detailed analysis of the past 5000 yr suggests multiple fluctuations with generally lower temperatures 1 2 c around 4500 and 3000 yr b p the carbon isotopic composition of the stalagmite indicates significant vegetation changes between the late pleistocene and today and also during the second half of the holocene

defining seismogenic sources from historical earthquake felt reports abstract we present a method that uses macroseismic intensity data to assess the location physical dimensions and orientation of the source of large historical earthquakes intensity data contain a great deal of information that can be used to constrain the essential characteristics of the seismic source in particular both the seismological theory and its practice suggest that the orientation of the source of significant earthquakes is reflected in the elongation of the associated damage pattern a plausible and easily manageable way of describing a seismic source is by representing it as an oriented rectangle the length and width of which are obtained from moment magnitude through empirical relationships this rectangle is meant to represent either the actual surface projection of the seismogenic fault or at least the projection of the portion of the earth crust where a given seismic source is likely to be located the systematic application of this method to all the m 5 5 earthquakes that occurred in the central and southern apennines italy in the past four centuries returned encouraging results that compare well with existing instrumental direct geological and geodynamic evidence the method is quite stable for different choices of the algorithm parameters and provides elongation directions that in most cases can be shown to be statistically significant in particular the resulting pattern of source orientations is rather homogeneous showing a consistent appennines parallel trend that agrees well with the ne sw extension style of deformation active in the central and southern portions of the italian peninsula

middle and late jurassic radiolarian palaeoecology versus carbon isotope stratigraphy abstract jurassic radiolarians are sensitive to palaeoclimatic palaeoceanographic changes recorded by the stable carbon isotope curve carbon isotopic variations have been linked to changes in ocean structure productivity and concentrations of greenhouse gases in the atmosphere in the middle upper jurassic terminilletto section of the umbria marche sabina apennines central italy well preserved radiolarians are present in a sequence of cherty limestones interbedded with platform derived carbonates the 13 c curve in the aalenian kimmeridgian interval indicates three main positive 13 c events in the lower bajocian late bathonian lower callovian and middle oxfordian the positive 13 c shifts are correlated to increases in visible chert in the outcrop and may represent periods of increased biological productivity of surface sea water spumellaria nassellaria ratios and the fluctuations of relative abundance of selected genera tend to correlate with 13 c and chert abundance values and seem to be related to episodes of high nutrient mobilisation from the base of the bajocian the radiolarian associations show a slight tendency towards diversification coincident with increasing 13 c values in the upper part of the middle bajocian last appearances prevail over first appearances associated with the peak of the 13 c event this may indicate maximum eutrophic conditions coincident with the late bathonian early callovian positive 13 c shift the radiolarian associations record a different trend with respect to the bajocian event when the 13 c values are increasing to a maximum radiolarian associations tend to be reduced in species diversity followed by a small diversification trend when the 13 c values are decreasing we speculate that during the callovian a more stressful palaeoenvironment due to high level of eutrophication is indicated by the combination of high productivity of biogenic silica and low carbonate input although varying preservational conditions may have influenced the observed trends in the radiolarian associations the good correlation between changes of sedimentation patterns radiolarian assemblages and 13 c positive anomalies open interesting avenues for further investigations concerning the palaeoecology of mesozoic radiolarians

contribution of calcareous nannoplankton to carbonate deposition a new approach applied to the lower jurassic of central italy abstract the upper pliensbachian lower toarcian somma section central italy which displays alternation of limestone marl lithotypes was investigated for its calcareous nannofossil and caco3 contents in order to evaluate the contribution of calcareous phytoplankton to the carbonate fraction of rocks a new method was applied combining a recently developed technique for nannofossil absolute quantification and measurements of nannofossil size our study suggests that nannofossils did not produce the bulk of carbonate mud in the studied section although they contribute to different extents to the pelagic carbonate fraction the contribution of both coccoliths and mainly the incertae sedis schizosphaerella to the carbonate fraction was important only in periods of reduced accumulation rates and or during clay deposition the highest estimated carbonate production by nannofossils in the studied section is around 83 of the total carbonate content but in a sample containing only 12 8 wt caco3 the observed limestone marl alternations therefore result from cyclical export of carbonate mud from the shallow latium abruzzi carbonate platform to the umbria marche basin and only subordinately from changes in nannoplankton productivity

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

spatial variation in stresses in peninsular italy and sicily from background seismicity abstract we have retrieved the stress tensor orientation in the italian region applying the fmsi technique gephart j 1990b fmsi a fortran program for inverting fault slickenside and earthquake focal mechanism data to obtain the regional stress tensor comput geosci 16 953 989 to fault plane solutions of 298 small earthquakes 2 5 m d istituto nazionale di geofisica in the period 1988 1995 first we verified that the stress inversion procedure generally applied to a large number of focal mechanisms of earthquakes recorded in a local seismic network could be successfully used in italy using background seismicity recorded over large 100 200 km regions then comparing the stress inversion results with other stress indicators we find that they are geologically sound for many regions in italy even if the misfit values are relatively large we also find that the largest misfit values are determined by a few earthquakes only 10 20 of the total number excluding these earthquakes from inversion the average misfit becomes much lower by 30 40 the results obtained in this study confirm the large variations of the stress field over a relatively short distance in italy but also confirm the existence of regions extending for a few hundred kilometres within which the stress is homogeneous among these most of the apennines are dominated by extension perpendicular to the trend of the mountain belt only in the northern apennines is there any clear distinction between an area of extension in the inner portion of the belt and an area under horizontal compression along the adriatic margin of the belt more rapid variations occur around calabria and sicily as expected because of the complexities linked with the tyrrhenian subduction and with active volcanism in the ionian calabrian coastal region there are hints of active nw se compression although constrained by a few data whereas in the messina strait we observe e w extension and a vertical 1 in northern and western sicily our results indicate n s to nw se compression roughly consistent with the general convergence between the european and the african plates

driving mechanism of tectonic activity in the northern apennines quantitative insights from numerical modeling 1 it is shown by numerical modeling that the recent deformation pattern observed in the northern apennines mainly characterized by progressive eastward migration and bowing of the belt thrusting activity along its external front and tensional tectonics in the internal area can be reproduced at a first approximation by applying a belt parallel se nw compression to the chain which is simulated as a structural system characterized by a high mechanical strength and decoupled from the surrounding zones the above compressional regime obtained by imposing kinematic boundary conditions to the model causes the outward escape of crustal wedges from the chain in particular the northeastward displacement of the romagna marche umbria units and the counterclockwise rotation and northwestward displacement of the ligurian units this kinematics produces compressional to transcompressional strain along the external front of the chain and tensional to transtensional strain in the internal area in line with the observed features that concern both strain style and orientation of principal strains evidence and arguments supporting the kinematic boundary conditions and the model parameterization adopted in modeling are discussed numerical experiments have also been carried out to evaluate the influence of major features of the model parameterization and boundary conditions we have adopted in modeling and to provide insights into the possible influence of strong decoupling earthquakes in the central apennines on tectonic and seismic activity in the northern apennines

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

prehistoric hand stencils at fern cave north queensland australia environmental and chronological implications of raman spectroscopy and ft ir imaging results raman spectroscopy and ft ir imaging analyses of cave wall pigment samples from north queensland australia indicate that some hand stencils were undertaken during a dry environmental phase indicating late holocene age other earlier painting episodes also took place during dry environmental periods of the terminal pleistocene and or early holocene these results represent a rare opportunity to attain chronological information for rock art in conditions where insufficient carbon is present for radiocarbon dating

structural and host rock controls on the distribution morphology and mineralogy of speleothems in the castanar cave spain t he casta nar cave central western spain formed in mixed carbonate siliciclastic rocks of neoproterozoic age the host rock is finely bedded and shows a complex network of folds and fractures with a prevalent n150e strike this structure controlled the development and the maze pattern of the cave as well as its main water routes the cave formed more than 350 ka ago as the result of both the dissolution of interbedded carbonates and weathering of siliciclastic beds which also promoted collapse of the overlying host rock at present it is a totally vadose hypergenic cave but its initial development could have been phreatic the cave s speleothems vary widely in their morphology and mineralogy in general massive speleothems stalactites stalagmites flowstones etc are associated with the main fractures of the cave and bedding planes these discontinuities offer a fairly continuous water supply other branching fibrous mostly aragonite speleothems commonly occur in the steeper cave walls and were produced by capillary seepage or drip water detailed petrographical and isotope analyses indicate that both aragonite and calcite precipitated as primary minerals in the cave waters primary calcite precipitated in waters of low magnesium content whereas aragonite precipitated from magnesium rich waters differences in isotope values for calcite 5 2 for 18 oa nd 9 6 for 13 c and aragonite 18 oo f 4 5 and 13 co f 3 5 can be explained by the fact that the more unstable mineral aragonite tends to incorporate the heavier c isotope to stabilize its structure or that aragonite precipitates in heavier waters changes in the water supply and the chemistry and instability of aragonite caused 1 inversion of aragonite to calcite which led to the transformation of aragonite needles into coarse calcite mosaics 2 micritization which appears as films or crusts of powdery opaque calcite and 3 dissolution dolomite huntite magnesite and sepiolite were identified within moonmilk deposits and crusts moonmilk occurs as a soft white powder deposit on different types of speleothems but mostly on aragonite formations huntite and magnesite formed as primary minerals whereas dolomite arose via the replacement of both huntite and aragonite owing to its variety of speleothems and location in an area of scarce karstic features the casta nar cave was declared a natural monument in 1997 and is presently the target of a protection and research programme although the main products formed in the cave and their processes are relatively well known further radiometric data are needed to better constrain the timing of these processes for example it is difficult to understand why some aragonite speleothems around 350 ka old have not yet given way to calcite which indicates that the environmental setting of the cave is still not fully understood

a geodynamic model of the southern apennines accretionary prism the apennines comprise a neogen quaternary accretionary prism that shows several anomalies with respect to classic alpine type mountain belts namely i low elevation ii a shallow new moho below the core of the belt iii high heat flow in the internal parts iv mainly sedimentary cover involved in the prism v a deep foredeep and vi a fully developed back arc basin the suction exerted by a relatively eastward migrating mantle can determine the eastward retreat of the subduction zone and an asthenospheric wedging at the retreating subduction hinge heat flow geochemical and seismological data support the presence of a hot mantle wedge underlying the western side of the apenninic accretionary prism a thermal model of the belt with foreland dipping isotherms fits with deepening of the seismicity toward the east mantle volatiles signatures are also widespread in springs along the apennines

relay ramps in active normal fault zones a clue to the identification of seismogenic sources 1688 sannio earthquake italy relay ramps commonly occur in areas of active extension they have relevance in terms of fault segmentation fault linkage and related seismic potential we propose consideration of field evidence of an active relay ramp in a seismic area as a clue to the definition of a seismogenic normal fault we have chosen the calore river valley as our study area it is located within the core of the apennine chain of the italian peninsula and is characterized by active extension and associated severe seismicity in particular a destructive earthquake struck the study area in 1688 we integrated data deriving from a geological field survey with original geomorphic and mesostructural analyses and new radiometric dating 40 ar 39 ar results indicate that brittle deformation detected in the northern part of mt camposauro could represent the surface expression of the ne dipping main fault of an active extensional system we refer to as the calore river fault system its structural connection with the neighboring boiano basin extensional fault system is marked by an area of complex deformation which links them and can be described as a stage 3 relay ramp given that the boiano basin fault system is a seismogenic source the identification of a relay ramp implies a seismogenic role also for the calore river fault system in turn these results allow us to suggest a new hypothesis for the seismogenic source of the 1688 sannio earthquake finally we discuss the implications on the seismic potential of two seismogenic structures linked by a relay ramp

carbon and oxygen isotope study of the active water carbonate system in a karstic mediterranean cave implications for paleoclimate research in semiarid regions abstract in a semiarid climatic zone such as the eastern mediterranean region annual rainfall variations and fractionation processes in the epikarst zone exert a profound influence on the isotopic compositions of waters seeping into a cave consequently the isotopic compositions of speleothems depositing from cave waters may show complex variations that need to be understood if they are to be exploited for paleoclimate studies this is confirmed by a four year study of the active carbonate water system in the soreq cave israel the 18o smow values of cave waters range from 6 3 to 3 5 the highest 18o values occur at the end of the dry season in waters dripping from stalactites and reflect evaporation processes in the epikarst zone whereas the lowest values occur in rapidly dripping fast drip waters at the peak of the rainy seasons however even fast drip waters are about 1 5 heavier than the rainfall above the cave which is taken to reflect the mixing of fresh with residual evaporated water in the epikarst zone 13c pdb values of dissolved inorganic carbon dic vary from 15 6 to 5 4 with fast drip waters having lower 13c values mostly 15 6 to 12 and higher dic concentrations relative to pool and stalactite drip water the low 13c values of fast drip waters and their supersaturation with respect to calcium carbonate indicates that the seepage waters have dissolved both soil co2 derived from overlying c3 type vegetation and marine dolomite host rock the 18o pdb values of various types of present day low magnesium calcite lmc speleothems range from 6 5 to 4 3 and 13c values from 13 to 5 5 and are not correlated with speleothem type an analysis of 18o values of present day calcite rafts and pool waters shows that they form in oxygen isotope equilibrium similarly the measured ranges of 13c and 18o values for all types of present day speleothems are consistent with equilibrium deposition at cave temperatures the 13c 18o range of contemporary lmc thus reflects the variations in temperatures and isotopic compositions of the presentday cave waters the 10 variation in the 13c values in waters can be modeled by a simple rayleigh calculation of the carbon isotope fractionation accompanying co2 degassing and carbonate precipitation these variations may obscure the differences in the carbon isotopic composition of speleothems that could arise when vegetation cover changes from c3 to c4 type plants this consideration emphasizes that it is necessary to characterize the full range of 13c values associated with contemporaneous speleothems in order to clarify the effects of degassing from those due to differing vegetation types isotopic studies of a number of different types of fossil lmc speleothems show many of them to exhibit isotopic trends that are similar to those of present day lmc but others show both higher and lower 18o ranges in particular the higher 18o range has been shown by independent age measurements to be associated with a period of drier conditions the results of the study thus indicate that it is necessary to work on a well calibrated cave system in semiarid climates and that the fossil speleothem record should be obtained from different types of contemporaneous deposit in order to fully characterize the 18o 13c range representative of any given climatic period

climatic ups and downs in a disturbed jurassic world the tropical warm and equable climate of the jurassic world is regularly challenged by geoscientists especially since oxygen isotopes 18 o of fossil hardparts have been used to reconstruct the paleotemperature history of seawater by applying the innovative sizer sig nifi cant zero crossings of the derivatives statistical approach to a newly compiled 18 o data base for the jurassic we demonstrate the occurrence of major and multiscale 18 o changes mainly related to climate disturbances for the fi rst time two long term anomalies in 18 o are identifi ed during the toarcian and the late jurassic in conjunction with intensive volcanism in large igneous provinces these results support a strong infl uence of repeated volcanic pulses on the modulation of pco 2 temperatures and polar ice cap volumes over protracted periods at shorter time scales 13 relatively rapid 0 5 1 m y and signifi cant warming and cooling events are identifi ed the causes of which include transient fl uctuations in greenhouse gas con centrations related to still debated mechanisms

lateglacial to holocene trace element record ba mg sr from corchia cave apuan alps central italy paleoenvironmental implications in this study mg ca sr ca and ba ca ratios in a lateglacial to holocene stalagmite cc26 from corchia cave central italy are compared with stable isotope data to define palaeohydrological changes for most of the record the trace element ratios show small absolute variability but similar patterns which are also consistent with stable isotope variations higher trace element to calcium values are interpreted as responses to decreasing moisture inducing changes in the residence time of percolation producing prior calcite precipitation and or variations in the hydrological routing statistically meaningful levels of covariability were determined using anomalies of mg ca d 18 o and d 13 c combining these three time series into a single palaeomoisture trend parameter we highlight several events of reduced moisture ca 8 9 8 4 6 2 4 2 3 1 and 2 0 ka a humid period between ca 7 9 and 8 3 ka and other shorter term wet events at ca 5 8 5 3 and 3 7 ka most of these events can be correlated with climate changes inferred from other regional studies for both extremities of the record i e before ca 12 4 ka and after ca 0 5 ka mg ca and sr ca are anti correlated and show the greatest amplitude of values a likely explanation for which involves aragonite and or gypsum precipitation the latter derived from pyrite oxidation above the cc26 drip point copyright 2014 john wiley sons ltd

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

late quaternary paleoclimate in the eastern mediterranean region from stable isotope analysis of speleothems at soreq cave israel abstract the eastern mediterranean continental paleoclimate during the past 25 000 years was determined by a high resolution petrographic stable isotopic and age study of speleothems from soreq cave israel 18o 13c trends indicate that all speleothems older than 7000 yr formed under conditions that differ from those of today the period from 25 000 to 17 000 yr b p was characterized by the highest 18o and 13c values which indicate deposition at temperatures of 12 16 c annual rainfall of 300 450 mm and vegetation typical of a mixed c3 c4type from 17 000 to 10 000 yr b p deglaciation in northern europe 18o values dropped progressively correlative with warming 2 3 c and a gradual increase in precipitation a simultaneous decrease in 13c gives a range expected for c3 type vegetation this period also shows significant 18o and 13c spikes which are correlatable with global events e g heinrich events and the younger dryas stade the speleothems that grew between 10 000 and 7000 yr b p have a unique petrography showing irregular thin laminae of various colors and much detritus they have the lowest 18o corresponding to 1000 mm rain coupled with the highest 13c caused by flooding events which stripped the soil cover from 7000 to 1000 yr b p conditions became closer to those of today this study demonstrates that global events which were recognized in northern europe and north africa are also evident in the eastern mediterranean and are reflected principally by large changes in the rainfall rate

a variation of the collapsing method to delineate structures inside a microseismic cloud we describe a modification to the collapsing method a technique that aims to find the simplest structures in a cloud of microearthquakes by utilizing the statistical uncertainties in the data in the modified collapsing method the movements of the locations are dependent on the shape of the distribution of the locations within the confidence ellipsoid and not just the position of the center of gravity as is the case in the original method additionally whereas the original collapsing method implicitly assumes that all locations belong to point structures in this modified version three types of structure are considered point line and plane principal component analysis of the locations is used to evaluate to which type of structure each location most probably belongs the modified technique has been applied to microseismic events associated with hydraulic stimulation at the fenton hill hdr field new mexico and known small scale structures were imaged

a high resolution record of holocene climate change in speleothem calcite from cold water cave northeast iowa high precision uranium thorium mass spectrometric chronology and 18o 13c isotopic analysis of speleothem calcite from cold water cave in northeast iowa have been used to chart mid holocene climate change significant shifts in 18o and 13c isotopic values coincide with well documented holocene vegetation changes temperature estimates based on 18o 16o ratios suggest that the climate warmed rapidly by about 3 c at 5900 years before present and then cooled by 4 c at 3600 years before present initiation of a gradual increase in 13c at 5900 years before present suggests that turnover of the forest soil biomass was slow and that equilibrium with prairie vegetation was not attained by 3600 years before present

chemostratigraphy of the jurassic system applications limitations and implications for palaeoceanography current chemostratigraphical studies of the jurassic system primarily involve the use of one sedimentary component marine organic carbon one divalent transition metal substituted in carbonate manganese and two isotopic tracers strontium isotope ratios 87 sr 86 sr and carbon isotope ratios 13 c carb and 13 c org in carbonate and in organic matter other parameters such as mg ca and sr ca ratios in calcite oxygen isotope ratios 18 o in carbonate sulphur isotope ratios 34 s in carbonate hosted sulphate nitrogen isotope ratios 15 n org in organic matter osmium isotope ratios 187 os 188 os in black shales and neodymium isotope ratios 143 nd 144 nd in various mineral phases are also useful but at present give poor resolution because the database is incomplete or compromised by various factors stratigraphical patterns in total organic carbon toc can be of either local or regional significance depending on the lateral extent of the former nutrient rich and productive water mass divalent manganese follows a similar pattern being concentrated most probably as a very early diagenetic phase only in oxygen depleted waters that typically underlie zones of elevated organic productivity shifts in mg ca and sr ca ratios on the time scale of ammonite subzones seem largely to reflect temperature changes strontium isotope ratios from pristine skeletal calcite provide a global signal 13 c values from carbonates with minimal diagenetic overprint potentially do the same although small spatial differences in palaeo water mass composition may have been locally significant oxygen isotope determinations on carbonate rocks and fossils generally yield values that are too scattered to be stratigraphically useful because they reflect palaeotemperature the evaporation precipitation balance in sea water and the impact of any diagenesis involving an aqueous phase nitrogen isotope ratios in organic matter reflect the chemistry of ancient water masses as affected by nitrate utilization and denitrification and the stratigraphical pattern of this parameter is more likely to correlate only on a regional basis neodymium isotope ratios in sea water are also water mass dependent and greatly affected by regional sources and oceanic current systems preliminary data on sulphur isotope ratios in carbonates and osmium isotope ratios in organic rich shales both potentially offering global correlation indicate that these tracers may be valuable although the records at present are not sufficiently well established to allow high resolution regional correlation in all cases biostratigraphically well dated reference sections against which the relevant geochemical data have been calibrated are required in the first instance to date studies on the stratigraphical distribution of organic carbon have been principally carried out in both northern boreal and southern tethyan europe carbon isotope stratigraphy has been undertaken primarily but not exclusively on bulk pelagic sediments from the alpine mediterranean or tethyan domain and strontium isotope stratigraphy has been undertaken largely on calcitic skeletal material belemnites and oysters from northern and southern europe in many sections including those containing ammonites multi parameter chemostratigraphy can give resolution that exceeds that attainable by classic biostratigraphical means strontium isotope ratios in skeletal calcite are a particularly powerful tool for illustrating changes in sedimentary rate and revealing gaps in the stratigraphical record

pre quaternary orogen parallel extension in the southern apennine belt italy abstract the southern apennine fold and thrust belt differs from other parts of the peri tyrrhenian orogen in most of the peri tyrrhenian belt hinterland extension is oriented at a high angle to the orogen axis and appears to be related to rifting and formation of oceanic crust within the tyrrhenian basin the southern apennines share the late stage development of normal faults related to the opening of the tyrrhenian sea but also experienced an episode of extension parallel to the strike of the tectonic belt the orogen parallel extension was apparently formed in response to the increase in length of the deformed belt during arcuation arcuation ostensibly was related to asymmetrical rifting in the hinterland which was greater in the southern tyrrhenian sea than in areas to the north and proportionately greater shortening in the frontal parts of the southern belt as compared to regions in the north during arcuation extension was spatially concentrated within structural domains and was accomplished by displacement on low angle detachment faults cutting through a previously imbricated thrust stack during the miocene pliocene nnw sse extension in the interior of the southern appennine belt formed coveally with ene wsw shortening in the foreland longitudinal extension ceased in the pleistocene when younger high angle normal faults formed in response to the easterly migration of tyrrhenian sea rifting and ne sw extension associated with lithospheric stretching

earthquake swarms in the southern apennines chain italy the 1997 seismic sequence in the sannio matese mountains abstract in this paper we analyze a seismic sequence that occurred in the sannio matese mountains southern apennines italy one of the most dangerous seismic areas of the italian peninsula on 19 march 1997 at 23 10 utc a seismic event of md 4 1 hit a zone near the border between the campania and the molise regions swarm type earthquake activity followed the main event and lasted for more than six months with alternation of intense activity and relative quiescence periods evolution of the seismic sequence both in time and space has allowed us to divide it into three stages with rather similar characteristics the seismic energy release process of this sequence exhibits the typical swarm pattern of the minor seismic sequences occurring in the southern apennines and involving relatively minor faults located in the marginal border of the chain such pattern unlike the main shock aftershock model consists of low energy events closely clustered in time and space without a single main shock about 2800 micro earthquakes were recorded from march to september 1997 by the seismic networks of the istituto nazionale di geofisica and of the osservatorio vesuviano among them only 20 events had md 3 0 a selection of 370 earthquakes recorded at a minimum of five stations with at least three s phase readings have been located between latitudes 41 20 and 41 30 and longitudes 14 36 and 14 42 the events are clustered along a nearly vertical plane striking nne ssw and dipping towards the east their hypocentral depths range from 5 to 15 km the focal mechanisms of 67 events show a variety of different solutions even if a prevalence of normal dip slip solutions with a strike component is observed the t axes distribution of all mechanisms show two trends the prevalent one is aligned along a nnw sse direction whereas the other one is along a nne ssw direction the hypocentral distribution the prevalence of focal mechanisms with fault planes striking about ne sw as well as the t axes distribution suggest that earthquakes relative to this sequence took place along nne ssw oriented faults and that the local stress field acting in this sector of the southern apennines is prevalently transtensional and is strongly controlled by local faults heterogeneities

fault plane solutions and seismicity of the italian peninsula abstract a new fault plane solution map of the italian peninsula is presented in this paper the earthquakes analyzed are included in the period 1905 1980 with magnitudes ranging 4 7 75 earthquakes are located in the crust while 31 are related to the deep and intermediate zone of the calabrian arc the large seismic events of the italian peninsula are generally associated with normal faulting while strike slip motion is mostly related to small earthquakes located along lateral segments of the mountain chain the deep and intermediate earthquakes of the tyrrhenian sea indicate predominant down dip compression and strike slip motion at the boundaries of this benioff zone this last is interpreted as a remnant of a subduction zone active since oligocene extending to 500 km depth with a very small lateral size about 300 km the present tectonics of this benioff zone is strongly conditioned by the lateral bending more so than the gravitational sinking process the coexistence of thrust and normal faulting motion associated to the earthquakes within a few tens of kilometers of each other seems to be explained by the strong lateral inhomogeneities of the crustal rocks present in this region more so than to the depth of the seismogenetic zone and the nature of the faulting process

inferences on the upper crustal structure of southern apennines italy from seismic refraction investigations and subsurface data abstract this paper presents an interpretation of crustal seismic refraction data from the northern sector of the southern apennines thrust belt a region that in historical times experienced large destructive earthquakes the data were acquired in 1992 along a seismic line 75 km long and parallel to the apenninic chain in order to determine a detailed 2 d p wave velocity model of the upper crust in an area that had not been deeply investigated by geophysical methods previously we have used a 2 d ray tracing technique based on asymptotic ray theory to model travel times of first and reflected p wave arrivals synthetic seismograms have been produced by finite difference simulations in order to check the reliability of the velocity model inferred by ray tracing modelling the interpretation of the velocity model is constrained by stratigraphic and sonic velocity logs from wells for oil exploration located close to the seismic line gravity data modelling allows to check the velocity model and to extend the structural interpretation in 3 d in the shallow crust up to a depth of 3 4 km strong lateral variations of the modelled velocities are produced by the overlapping of thrust sheets formed by 1 cenozoic flyschoid cover and basinal successions that underlie the seismic profile with p wave velocities in the 2 8 4 1 km s range and thicknesses varying between 0 5 and 4 5 km 2 mesozoic basinal sequences with a velocity of 4 8 km s and a depth of 1 5 2 1 km in the northern part of the profile 3 mesozoic limestones of the western carbonate platform with a velocity of 6 0 km s and a depth of 0 1 0 8 km in the southern part of the profile at a greater depth the model becomes more homogeneous a continuous seismic interface 3 0 4 5 km deep with a velocity of 6 0 km s is interpreted as the top of the meso cenozoic carbonate multilayer of the apulia platform characterized by an increase in seismic velocity from 6 2 to 6 6 km s at depths of 6 7 km a lower p wave velocity about 5 0 km s is hypothesized at depths ranging between 9 5 and 11 km as inferred by commercial seismic lines and data from two deep wells located in the apulia foreland and bradano foredeep this low velocity layer can be related to permo triassic clastic deposits drilled at the bottom of the apulia platform seismic data do not allow us to identify possible deeper seismic interfaces that could correspond to the top of the paleozoic crystalline basement this is probably due to the low velocity layer at the bottom of the carbonate multilayer that reflects and attenuates a great part of the seismic energy the joint interpretation of seismic refraction and well data in accordance with gravity data provides the first detailed p wave velocity model of the upper crust of the northern sector of the southern apennines which differs considerably from previous 1 d velocity models used to study the seismicity of the region and reveals new information about the structure of the thrust belt

duration of the early bajocian and the associated δ13c positive excursion based on cyclostratigraphy the early bajocian about 172 ma ago was a period of tectonic changes a global carbon isotope positive excursion and biological diversification of marine invertebrates e g ammonites radiolarians and coccolithophores unfortunately both the duration of the early bajocian and the associated palaeoenvironmental changes are still poorly constrained we propose here an estimate of the duration of this sub stage based on a cyclostratigraphic analysis of the carbonate content from the chaudon norante section french subalpine basin france the chaudon norante succession has been correlated with les dourbes section using greyscale variations to detect possible local hiatuses the duration estimated here for the entire early bajocian is 4 082 ma two intervals were identified in the positive 13 c excursion an increase of carbon isotope values lasting 1 36 ma and climax isotope values lasting for 2 72 ma a cooling at high latitudes and warming at low latitudes may have enhanced the earth s temperature gradient leading to an increase in humidity which in turn triggered ocean eutrophication at the origin of the 13 c positive excursion supplementary material the complete dataset presented in the paper a colour version of the figure 8 and correlation of 13 c excursions between our studied site and contemporaneous sites are available at www geolsoc org uk sup18555

calcite fabrics growth mechanisms and environments of formation in speleothems from the italian alps and southwestern ireland five fabrics were identified in alpine and irish caves on the basis of morphological and microstructural characteristics and re lated to growth mechanisms and growth environment columnar and fibrous fabrics grow when speleothems are continuously wet and from fluids at near equilibrium conditions low supersaturation sicc 0 35 through the screw dislocation mechanism the highly defective microcrystalline fabrics form at the same supersaturation range as co lumnar fabric but under variable discharge and the presence of growth inhibitors dendritic fabrics which have the highest density of crystal defects develop in disequilibrium conditions high supersaturation un der periodic very low flow regime periods that result in prolonged out gassing cave calcareous tufa forms in disequilibrium conditions only the calcite crystals of fabrics formed at low supersaturation seem to precipitate near isotopic equilibrium conditions

astrochronology of the valanginian stage from reference sections vocontian basin france and palaeoenvironmental implications for the weissert event abstract high resolution gamma ray measurements performed on five biostratigraphically well dated reference sections from the vocontian basin south eastern france are used to develop a new astrochronology of the valanginian stage and its subdivisions i e ammonite and calcareous nannofossil zones and subzones spectral analyses show a pervasive dominance of 405 kyr eccentricity cycles with the expression of 100 kyr eccentricity obliquity and precession previous rough estimates of valanginian stage duration ranged from 3 9 to 6 5 myr but were generally based on less reliable or indirect methods this study provides a precise duration of 5 08 myr tuning the series to the 405 kyr eccentricity cycle thus further enhancing the accuracy of the geologic time scale new durations of magnetochrons are proposed based on intercalibration between ammonite and calcareous nannofossil biozones cyclostratigraphy and carbon isotope stratigraphy after integrating orbitally calibrated durations and available radio isotopic ages for the berriasian hauterivian interval a link between the weissert event and the emplacement of the parana etendeka traps now appears unlikely strontium carbon and oxygen isotope stratigraphy sedimentological and palaeontological features clay mineralogy and the orbital record during the upper valanginian all suggest that a transient cool arid climate occurred after the carbon isotope event possibly associated with limited polar ice

high precision mass spectrometric uranium series dating of cave deposits and implications for palaeoclimate studies calcite deposits in caves known as speleothem can provide valuable palaeoenvironmental information1 4 in particular because speleothem are deposited only in air filled caves gaps in deposition in coastal caves record high stands of sea level here we report the use of isotope dilution mass spectrometry to date speleothem by the uranium series method the use of mass spectrometry in uranium series dating was first applied to corals5 and has greatly improved the precision of this dating method the speleothem dated here a flowstone from 15 m below modern sea level in a bahamian cave records changes in sea level over the past 280 000 years the dated hiatuses in deposition indicate high sea level stands that are in general agreement with data from deep sea oxygen isotope stratigraphy6 and other estimates for the timing of high stands and glacial minima1 3 7

timing and dynamics of the last deglaciation from european and north african δ13c stalagmite profiles comparison with chinese and south hemisphere stalagmites abstract the last deglaciation and its climatic events such as the bolling allerod ba and the younger dryas yd have been clearly recorded in the 13 c profiles of three stalagmites from caves from southern france to northern tunisia the three 13 c records dated by thermal ionization mass spectrometric uranium thorium method tims show great synchroneity and similarity in shape with the chinese cave 18 o records and with the marine tropical records leading to the hypothesis of an in phase between 15 5 and 16 ka 0 5 ka postglacial warming in the northern hemisphere up to at least 45 n the ba transition appears more gradual in the speleothem records than in the greenland records and the allerod seems warmer than the bolling showing here close similarities with other marine and continental archives a north south gradient is observed in the ba trend it cools in greenland and warms in our speleothem records several climatic events are clearly recognizable a cooler period at about 14 ka older dryas od the intra allerod cold period at about 13 3 ka the yd cooling onset between 12 7 and 12 9 0 3 ka similar to the ba the yd displays a gradual climate amelioration just after its onset at 12 75 0 25 ka up to the preboreal and is punctuated by a short climatic event at 12 15 ka even though the southern hemisphere stalagmite records seem to indicate that the postglacial warming started about 3 ka 1 8 ka earlier in new zealand 41 s and about 1 to 2 ka earlier in south africa 24 1 s large age uncertainties essentially due to slow growth rates make the comparison still perilous the overall 13 c speleothem record seems to follow a baseline temperature increase controlled by the increase in insolation and punctuated by cold events possibly due to the n america freshwater lake discharges

calcareous nannofossil assemblage turnover in response to the early bajocian middle jurassic palaeoenvironmental changes in the subbetic basin abstract the calcareous nannofossil assemblages from three lower bajocian pelagic successions from the subbetic basin well dated by ammonites have been investigated biostratigraphically they encompass the njt9 to njt10a nannofossil tethyan zones pca factor analysis performed on percentage abundances of selected taxa suggests that the main factors controlling the early bajocian nannofossil assemblages of the subbetic basin were trophic level nutrient availability and nutricline depth a gradual eutrophication is recorded in the calcareous nannofossil assemblages through an increase in the percentage abundance of watznaueria spp especially in the taxa best adapted to unstable and more eutrophic conditions w britannica gr and w manivitiae gr this eutrophication is concomitant with a trend of increasing carbonate 13 c values over the early bajocian and a rise in biogenic silica production and deposits in the study sections and other basins of the western tethys around the middle part of the laeviuscula subzone a decrease in the absolute and relative abundance of the deep dwelling taxa especially crepidolithus crassus suggests a deterioration of the environmental conditions in the lower photic zone this has been interpreted as caused by a nutricline shallowing and or greater turbidity that could be related in turn to surface water stratification two different episodes have been differentiated in relation to nutricline dynamics 1 from the latest aalenian to earliest early bajocian a weak and or deep nutricline with nutrients rather uniformly spread throughout the photic zone and concomitant with mesotrophic conditions and increasing productivity is suggested 2 a shallowing of the nutricline and or increase in surface water turbidity concomitant with more eutrophic conditions is suggested for the latest early bajocian the observed decrease in the deep dwelling taxa supports the hypothesis of a climatically driven fertilization of the surface waters instead of fertilization by upwelling for the early bajocian eutrophication episode

quaternary glaciations of the southern andes abstract the southern andes comprise the southernmost portion of the andean cordillera beginning at the edge of the puna altiplano lat 27 s and ending at isla de los estados lat 55 s the late cainozoic glacial record of these mountains spans the interval from the late miocene to the present and is one of the most complete to be found anywhere in the world this has arisen for several reasons i the conterminous mountain ice cap extended to the piedmont zone on both flanks of the range where the sedimentary and morphological record has been well preserved ii periodic volcanism mainly from monogenetic fissure eruptions of basalt east of the range and from central tephra producing cones along the mountain crest has provided opportunity for the preservation and radiometric dating of interbedded glacial deposits iii a tectonically induced interval of stream incision in the mid pleistocene and simultaneous uplift has preserved glacial sediments on interfluves iv in the chilean lakes region west of the mountains late quaternary glaciers terminated in a well vegetated landscape thus creating scope for radiocarbon dating of interbedded and incorporated organic materials consequently the last glaciation in the llanquihue area of chile is one of the best dated sequences in south america thus the llanquihue glaciation is proposed as the south american equivalent of the wisconsin and weichsel glaciations of north america and north west europe respectively

facies and climate environmental changes recorded on a carbonate ramp a sedimentological and geochemical approach on middle jurassic carbonates paris basin france a detailed sedimentological geochemical and mineralogical study is carried out on the early bajocian to early callovian middle jurassic limestones of the paris basin objectives are to document and explain the facies changes in the context of the climate environmental evolution at the nw european scale deposits include 18 lithofacies which are stacked into 10 third order depositional sequences at a greater time scale 4 biosedimentary packages are distinguished by their allochems associations 1 an intracratonic carbonate environment with coral reefs and crinoid rich facies is typical of the early bajocian 2 a major facies change occurred at the early late bajocian transition with a shift from crinoid and coral rich facies to ooid rich facies during the late bajocian a southward dipping ooid ramp with successive progradational trends was emplaced 3 a large lagoon protected by ooid shoals developed during the bathonian in a muddy ramp setting 4 at the bathonian callovian boundary a second major change occurred with the lagoonal facies being superseded by an ooid bioclastic crinoids corals ramp associated with a waning of carbonate productivity retrogradational trend our geochemical study including a compilation of bibliographic data allows us to refine the existing sea surface palaeotemperature pattern a cooling from the latest early bajocian to the late bajocian and a subsequent warming from the earliest callovian to the early middle callovian transition are described using a proxy of sea surface temperatures together with 13c and mineralogical data our new 18o values suggest a palaeo climatic palaeo environmental control of facies in this shallow carbonate ramp environment

the valanginian isotope event a complex suite of palaeoenvironmental perturbations abstract the valanginian records a severe crisis of carbonate systems both on platforms and in the pelagic realm this crisis is roughly concomitant with the weissert event characterized by a positive 13c excursion of about 2 in marine carbonates however it is unclear if the response of these two carbonate systems to the global perturbations is contemporaneous or if they react differently for this purpose accumulation rates of pelagic carbonates produced by nannofossils and of platform derived carbonates have been quantified in a hemipelagic environment the vocontian basin se france that has the potential to record the reaction of both shallow water and pelagic carbonate production to a major perturbation of the carbon cycle testified by the isotope excursion also changes through time of clay input have been measured in order to evaluate variations in continental weathering rates and thus in continent derived nutrient input and climatic conditions in terms of humidity aridity accumulation rates of pelagic carbonates of platform derived carbonates and of clays were calculated on the basis of nannofossil absolute abundance and species specific masses of weight percent carbonate content of rocks and a high resolution timescale given by cyclostratigraphy the onset of the positive 13c excursion and the demise of the platforms testify for a synchronous but inverse response of the shallow water and pelagic carbonate systems to an increase in nutrient influx to marine waters as carbonate production by nannofossils decreased during the late valanginian in time of still low platform production the low temperature of marine waters coeval to a still high nutrient input recorded in the latest late valanginian possibly could explain that both platform and pelagic carbonate production contemporaneously decreased

formation of landslide dammed lakes during a wet period between 40 000 and 25 000 yr b p in northwestern argentina abstract new ams radiocarbon data from the deposits of landslide dammed lakes in the santa maria basin 26 s 66 w and the quebrada del toro 25 s 66 w in the eastern argentine cordillera show that important mass movements occurred during a wet period between 40 000 and 25 000 yr b p in addition to increased humidity during this time detailed analysis of annual layered lacustrine strata suggests enhanced inter and intra annual fluctuations in precipitation as compared to the present variations in sediment characteristics and diatom assemblages with mean periodicities of 2 to 5 and 10 to 14 years respectively suggest an influence of the el nino southern oscillation enso and the atlantic sea surface temperature dipole the atlantic dipole slightly increased rainfall every 10 14 years as at present in contrast the weak modern enso influence in this area differs from the past situation where rainfall increased significantly with enso type periodicities both increased humidity and seasonality are believed to have reduced thresholds for the generation of catastrophic mass movements in northwestern argentina

an integrated analysis of transverse structures in the northern apennines italy abstract the northern apennines have been the object of numerous studies both from a morphological and a structural point of view at present much debate is going on about the existence and interpretation of ne sw alignments described by geomorphologists boccaletti m coli m napoleone g 1977 nuovi allineamenti strutturali da immagini landsat e rapporti con l attivita sismica negli appennini boll soc geol it 96 679 694 signorini r 1953 linee tettoniche trasversali nell appennino settentrionale rend acc naz lincei 6 42 45 and partly denied by structural geologists we show new microtectonic and morphological data which contribute to a more comprehensive interpretation of these elements stress axis determination and different morphotectonic analyses have been combined the analysis of the drainage networks and of two different digital elevation models have also been considered the results lead us to interpret the ne sw alignments as large and diffuse deformation zones which may represent old transfer zones active with left lateral strike slip movements during the mountain building

a late holocene climate record from a stalagmite cold air cave northern province south africa abstract stable isotope analyses of a uranium series dated stalagmite from south africa provide a record of climate changes for the periods 4400 4000 years and 800 years ago to recent interrupted by a prolonged growth hiatus generally enriched stable oxygen isotope values interpreted here to indicate more humid conditions occurred around 800 years ago subsequently a marked depletion in oxygen and carbon isotope values occurred about 600 years ago reflecting we believe shifts toward drier cooler conditions as the regional indication of the little ice age this period with depleted yet oscillating isotope values is replaced by a period with enriched isotopes until recent times the record is notable for sharp shifts in isotopic values on the scale of decades which reflect rapid oscillations in local climate conditions

evidence for major environmental perturbation prior to and during the toarcian early jurassic oceanic anoxic event from the lusitanian basin portugal the timing and causal relationships between the pronounced negative c isotope excursion and paleoenvironmental perturbations associated with the toarcian oceanic anoxic event early jurassic remain unclear particularly because biotic crises and carbonate production decrease appear to have been initiated earlier than the main c isotope anomaly here we present a new quantification of late pliensbachian early toarcian calcareous nannofossils abundance and size from the peniche reference section portugal together with o and c isotope records of well preserved brachiopod shells from the same section the brachiopod shell 13c curve parallels that of bulk carbonate and records two pronounced negative isotopic excursions close to the pliensbachian toarcian boundary 2 and during the toarcian oceanic anoxic event 3 5 our results indicate that both c isotope negative excursions were characteristic of benthic and shallow water environments suggesting that these two carbon cycle perturbations affected all epioceanic reservoirs coeval shifts toward lower values of brachiopod oxygen isotope compositions and closely correlated northward migrations of mediterranean ammonite fauna suggest that both events coincided with major rises in seawater temperatures probably as a result of increased co2 levels and enhanced greenhouse conditions co2 induced changes in seawater chemistry likely affected the calcification potential of both neritic and pelagic systems as evidenced by synchronous drops of platform derived carbonate accumulation and drastic reductions in size 3 m of the main pelagic carbonate producer schizosphaerella we suggest that the early toarcian paleoenvironmental crisis occurred in two distinct episodes that were most likely related to two successive phases of intense volcanic degassing in the karoo ferrar province

late quaternary glacier response to humidity changes in the arid andes of chile 18 29 s abstract today no glaciers exist between 18 30 s and 27 s even on mountains much higher than 6000 m these dry high mountain environments are very sensitive to changes in climatic boundary conditions particularly humidity since temperatures are far below freezing here we present a reconstruction of climatic changes since the last glacial maximum for the chilean dry andes of the southern hemisphere we reconstructed regional equilibrium line altitudes ela for three different moraine stages representing extensive past glaciations in this currently unglaciated region comparison of the regional pattern of the ela with modern climate conditions allows us to draw implications about the paleoclimatic conditions during the best preserved moraine stage ii glaciations in the northern as well as in the southern part of the research area our results suggest humid conditions in the northern part 18 24 s during late glacial times with strongly increased convective precipitation during austral summer the temporal coincidence of glaciers in the mountains and high lake levels on the altiplano tauca phase is evident to the south no simple shift of the westerlies is implied by our glacier reconstructions the northern limit of effective moisture for glacier formation did not shift significantly but stayed in the area of the present day northernmost glaciers of the westerlies at about 27 s but further south precipitation increased significantly accompanied by at least 2 3 c colder conditions the age of this glaciation is uncertain but probably of late glacial or last glacial maximum lgm times overall glaciers in the dry andes of south america clearly responded to large changes in the humidity not primarily the temperature regime with all its consequences on the environment hydrology vegetation etc illustrating the different regional responses to global climatic change

fault geometries from the space distribution of the 1990 1997 sannio benevento earthquakes inferences on the active deformation in southern apennines in this study we analyze the recent 1990 1997 seismicity that affected the northern sector sannio benevento area of the southern apennines chain we applied the best estimate method bem which collapses hypocentral clouds to the events of low energy md max 4 1 seismic sequences in order to constrain the location and geometry of the seismogenetic structures the results indicate that earthquakes aligned along three main structures two sub parallel structures striking nw se 1990 1992 benevento sequence and one structure striking ne sw 1997 sannio sequence the southernmost nw se structure which dips towards ne overlies the fault that is likely to be responsible for a larger historical earthquake io max xi mcs 1688 earthquake the northernmost nw se striking structure dips towards sw the ne sw striking structure is sub vertical and it is located at the northern tip of the fault segment supposed to be responsible for the 1688 earthquake the spatio temporal evolution of the 1990 1997 seismicity indicates a progressive migration from se benevento to nw sannio associated to a deepening of hypocenters i e from about 5 to 12 km hypocenters cluster at the interface between the major structural discontinuities e g pre existing thrust surfaces or within higher rigidity layers e g the apulia carbonates available focal mechanisms from earthquakes occurred on the recognized nw se and ne sw faults are consistent with dip slip normal solutions this evidences the occurrence of coexisting nw se and ne sw extensions in southern apennines

climato environmental controls on clay mineralogy of the hettangian bajocian successions of the mecsek mountains hungary an evidence for extreme continental weathering during the early toarcian oceanic anoxic event abstract clay mineralogy has been successfully used in palaeoclimatic interpretation of jurassic rocks in the mecsek zone hungary the clay mineral assemblages of the hettangian sinemurian fluvial and shallow marine coal bearing siliciclastic rocks gresten facies mecsek coal and vasas marl formations comprise predominantly illite smectite i s mixed layer minerals illite ill and kaolinite kao with the presence of berthierine and or chlorite these clay mineral suites suggest a humid subtropical climate with short term climate changes of high and low rainfall and a high supply of terrigenous clastics to the basin in the pliensbachian part of the sequence studied which is composed of predominantly hemipelagic mudstones allgau facies with intercalations of redeposited sandstone and limestone bodies the hosszuheteny calcareous marl mecseknadasd sandstone and kecskehat limestone formations are predominantly made up of illite and very little kaolinite and i s mixed layer minerals kao ill 1 suggesting a humid climate and intense continental weathering possibly related to the oceanic anoxic event in contrast rocks of the bajocian komlo calcareous marl formation contain high proportions of i s mixed layer mineral and illite with sparse occurrence of kaolinite kao ill 0 or kao ill

stable isotopic compositions of recent freshwater cyanobacterial carbonates from the british isles local and regional environmental controls recent 50 years old freshwater cyanobacterial carbonates from diverse environments streams lakes waterfalls throughout britain and ireland were analysed for their stable carbon and oxygen isotope compositions the mean 18o value of 5 9 pdb for river and stream data represents calcite precipitation in equilibrium with the mean oxygen isotopic composition of precipitation in central britain 7 5 smow assuming a mean water temperature of 9 c the mean 18o of lake data 4 5 pdb is statistically different reflecting the effects of residence time and or variations in the oxygen isotopic composition of rainfall carbon isotopes have wide variations in both fluviatile and lake data sets 3 to 12 pdb these variations are principally controlled in the fluviatile samples by contribution of isotopically light soil zone carbon relative to isotopically heavier carbon from limestone aquifer rock dissolution lake samples have the heaviest carbon isotope values reflecting a trend toward isotopic equilibrium between atmospheric co2 and aqueous hco 3 we infer that isotopic compositions of ancient cyanobacterial carbonates should also record environmental information although the effects of stabilization and diagenesis on primary 18o values will need careful consideration primary carbon isotope compositions should be well preserved although in marine samples values will be buffered by the isotopic composition of aqueous marine bicarbonate

detailed study of the potentino seismic zone in the southern apennines italy abstract most relevant macroseismic and instrumental data concerning past and current seismic activity of the potentino southern italy have been collected in order to study the seismic behaviour of this area ten among the most important recent and historical earthquakes occurred in the area from 1826 to 1990 have been studied by means of macroseismic methodologies macroseismic fields for all the events indicate a general isoseismal lengthening in the direction of the apennines chain northwest southeast a rapid attenuation of intensity westward of the studied area and a strong propagation eastwards this configuration is strongly dependent on the source mechanisms of the seismic events and the geological dishomogeneities of the concerned areas as regards earthquakes which have been instrumentally recorded in the campania basilicata area from 1980 to 1991 more than 1300 accurate hypocentral locations have been computed for events with m d 2 5 using data from osservatorio vesuviano o v and istituto nazionale di geofisica i n g seismic networks special emphasis is put on the potenza may 5 1990 earthquake m s 5 4 neic national earthquake information center i vii msk which was the strongest recent event in the area and was felt in a large sector of southern italy as regards the seismic sequence following this event about 110 aftershocks with m d 1 9 have been located very close to the town of potenza northeast of it with a clustering type space distribution the occurrence of the events is strongly time concentrated in so defining a main shock aftershocks typical sequence moreover the macroseismic investigation of the main event has allowed to map out isoseismal lines bounding vii vi v and iv msk areas the isoseismals pattern shows that attenuation and amplification of intensity are observed in the same areas as for the previous events beginning from may 26 1991 an increase of seismicity initiated by an earthquake of m l 4 7 neic and i vi vii msk was observed nearly in the same area as the 1990 sequence accurate locations of 84 events with m d 1 9 have been computed however this sequence seems to have a slightly different character from the 1990 one in that events are scattered in time and seismic energy release is comparable to a swarm type seismic sequence as regards the previous sequences fault plane solutions for the highest magnitude events and for appropriate groups of events have been worked out the mechanisms indicate normal faulting motion with t axes oriented orthogonal to the apenninic chain in conclusion detailed analyses on the historical and recent seismicity of the potentino area and adjacent ones have allowed to identify at least four seismogenic zones which show activity with different features such zoning represents a contribution to the seismic hazard assessment in the southern apennines on a regional scale

middle jurassic coccolith fluxes a novel approach by automated quantification coccolithophores major pelagic carbonate producers underwent important changes during the latest aalenian early bajocian ca 170 ma middle jurassic specifically a new genus called watznaueria diversified and started dominating the coccolith assemblages while this change in the coccolith assemblages is already known the impact on coccolith absolute abundances and fluxes is still misunderstood here we tested for the first time on mesozoic deposits an automated counting method using the syraco system and then compared these results with a classic counting method two neural networks were created based on the shape birefringence and size of coccoliths the first of which contained only one class and the second of which was composed of six classes based on the morphological criteria used for the neural networks coccoliths were not identified at the species level we quantified coccolith absolute abundances and estimated fluxes for the latest aalenian early bajocian in two well dated and correlated sections cabo mondego in portugal and chaudon norante in france there is a strong linear correlation between classic and automatic counting r 0 8 supporting the latter as a reliable method for coccolith absolute abundance and flux quantification in spite of under or over estimation by automatic counting with respect to classic counting the absolute abundance stratigraphic trends are remarkably similar under or over estimation may be reduced by further technical improvements such as automatic focus at cabo mondego coccolith fluxes increased from 0 2 109 coccoliths m2 yr in the latest aalenian to 700 109 coccoliths m2 yr in the middle of the laeviuscula ammonite zone early bajocian remaining high for the rest of the early bajocian at chaudon norante a similar trend was observed this coccolith flux increase is therefore considered to be a supra regional event matching an important 13cbulk carbonate positive excursion the carbon isotopic positive excursion along with the onset of radiolarian sedimentation and coccolith fluxes is related to a gradual increase in the fertility of the oceans during the early bajocian and is likely associated with warmer and more humid climates and associated enhanced continental weathering

500 ka precipitation record from southeastern australia evidence for interglacial relative aridity 230 th 234 u dating of speleothems from southeastern australia documents changes in effective precipitation over the past 500 k y at a temporal resolution not previously achieved results show that the highest effective precipitation for the southeastern interior of australia occurred during stadials and cool interstadials of the past four glacial cycles interglacials and warm interstadials as well as glacial maxima are comparatively arid we suggest that lower regional temperatures over the continent and changes in atmospheric circulation stronger walker circulation produced the observed periods of increased effective precipitation

inorganic calcite morphology roles of fluid chemistry and fluid flow abstract evaluation of calcite crystal habits and fabric and their relation to precipitating fluids in spelean environments indicates that habit variations are controlled primarily by degree of supersaturation at less than 6 times supersaturation crystal habits are limited to those with shallow to steep rhombohedral forms i e 1011 4041 with increasing supersaturation scalenohedrons extremely steep rhombohedrons pinacoids and hexagonal prisms are developed slight elongation due to differences in crystal dimensions of these forms may arise i e scalenohedrons versus shallow rhombohedrons at extreme supersaturation 12 times curvature of crystal faces or curved surfaces appear the development of fibrous versus equant fabrics is the result of changes or modification of reactant supply rates and the number of crystallites nuclei present under rapid flow conditions growth rates are accelerated and greater numbers of nuclei are present thus compromise boundaries parallel to c axis and perpendicular to flow and substrate are rapidly attained in the absence of flow fewer crystallites are present and larger well developed crystals or branching forms dictated by saturation conditions arise in the absence of flow at low supersaturation elongate composite crystals and hence fibrous fabrics may result from migration of the fluid crystal interface as a result of changing or oscillating water levels a flow control mechanism can be applied to numerous geological conditions in which transitions from fibrous to equant crystal morphologies are observed

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

large scale longitudinal extension in the southern apennines contractional belt italy during late cenozoic thrusting the interior of the peri tyrrhenian orogenic belt in the southern apennines underwent two episodes of nearly orthogonal extension early extension was oriented subparallel to the axis of the tectonic belt and formed in response to progressive thrust belt arcuation the length of the tectonic belt increased by 50 and the longitudinal strain was accommodated by low angle normal faults concentrated in tectonic domains recording up to 150 200 extension younger extension oriented at a high angle to the orogen was accompanied by pliocene pleistocene uplift and by southeasterly migration of tyrrhenian sea rifting

fault reactivation and active tectonics on the fore arc side of the back arc rift system ne japan abstract positive basin inversion is documented using seismic reflection profiles and seismic data on the fore arc side of the back arc rift system of northern honshu japan this finding within a seismically active region is used to understand source fault geometry based on fault reactivation models seismic reflection profiles and bouguer gravity anomalies along with available surface and subsurface evidence define a 300 km long normal fault system formed in miocene time that bounds the fore arc side of the miocene back arc basin based on the geometry of the seismogenic source fault which was estimated from aftershock distribution and seismic reflection profiles reverse fault reactivation of former miocene normal faults occurred and is presently occurring across the entire seismogenic zone this contractional event began in late neogene time the total amount of shortening as inferred from sequential cross section restoration is approx 20 of the total amount of miocene extension in the fore arc side of the northern honshu thus the overall extensional architecture of the region inherited from miocene rifting was only slightly modified by the superimposed contractional deformation reverse fault reactivation seems to occur only when the dip angle of precursor normal faults is 60 or less the geometry and evolution of active thrust faults are strongly controlled by fault reactivation processes and are found in conjunction with the development of new thrust faults that propagate across the normal fault footwalls with shortcut trajectories

dating of paleolakes in the central altiplano of bolivia abstract the deposits of the extensive paleolakes of the bolivian altiplano correspond to an alternation of lacustrine episodes and dry periods a phenomenon commonly explained by climatic changes the lack of precise dating of the deposits has prevented detailed reconstruction of the evolution of paleolakes that would allow a determination of the relative influence of interconnections between neighboring basins and local climatic conditions among the five paleolakes of the northern altiplano titicaca basin and the three of the central altiplano poopo coipasa and uyuni basins only the two most recent paleolakes have been dated a 121 m long sediment core recovered from the salar de uyuni contained 11 lacustrine layers l1 l11 separated by 12 salt crusts radiocarbon dating shows that the younger layers l1 and l2 are related to the tauca lacustrine phase 12 000 16 000 cal yr bp and layers l3 and l4 to the minchin lacustrine phase 30 000 73 000 cal yr bp layer l5 located at 46 m below the surface contains a volcanic ash with well preserved biotites is here dated by the 40 ar 39 ar method the measured age of 191 000 5000 y is the first date ever obtained from a pre minchin paleolake lake escara this result combined with 14 c and u th data obtained on lakes tauca and minchin from various authors suggests that the duration of the lacustrine events increased regularly during the pleistocene in contrast paleolake levels in the northern altiplano decreased from the oldest known lake mataro 3950 m to the present titicaca level 3806 m a progressive erosion of the threshold between the northern and central altiplano may have allowed important volumes of water to overflow from the northern basin into the central altiplano the existence of large paleolakes in the central altiplano was thus not only dependent on local climatic conditions but also on additional inputs from the north where climatic conditions could have been quite different from those prevailing in the south

the impact of calcareous nannofossils on the pelagic carbonate accumulation across the jurassic cretaceous boundary abstract calcareous nannofossils were important producers of pelagic carbonates in mesozoic oceans in order to better understand the origin of mesozoic pelagic carbonates we studied upper jurassic to lower cretaceous sediments in the central atlantic ocean dsdp sites 105 367 534a with respect to their content of calcareous nannofossils the interval under investigation is characterized by a significant increase in the deposition of carbonate rich sediments a trend that goes along with the rapid radiation of calcareous nannofossils the assemblage composition and the size variation of common taxa were analyzed and subsequently the contribution of this phytoplankton group to the pelagic carbonate accumulation was calculated results reveal two long term changes of the nannofossil assemblage composition 1 the early tithonian coccolith assemblages are of low diversity watznaueria spp cyclagelosphaera spp zeugrhabdotus spp whilst the mid to late tithonian assemblage is dominated by nannoliths conusphaera mexicana polycostella beckmannii nannoconus spp and large sized watznaueria 2 the early berriasian is characterized by a shift from the late tithonian nannolith rich assemblage to a highly diverse coccolith assemblage morphometric studies of the placolith genus watznaueria show for all three dsdp sites large sized forms of this genus in the mid and late tithonian followed by a decrease of up to 2 m for the mean size in the earliest berriasian at dsdp site 105 the studied nannolith taxa show an increase in size during the mid tithonian to berriasian interval the records of both nannofossil carbonate estimates and the measured bulk rock carbonate reveal two periods of increase in the nannofossil carbonate record of dsdp site 105 a first significant increase of the carbonate accumulation is observed in the mid and late tithonian probably caused by mass occurrences of strongly calcified taxa c mexicana p beckmannii nannoconus spp watznaueria cf manivitae this interval is here named nannofossil calcification event nce the second carbonate maximum in the late berriasian is related to a rise in absolute abundances of nannofossils this peak is amplified by an overall increase of the sedimentation rate the calculated accumulation rates of nannofossils nannofossil carbonate and bulk rock carbonate for the late berriasian are on the same scale as values from recent ocean surface sediments a comparison of nannofossil carbonate values with the bulk rock carbonate content shows that on average only 27 of the total carbonate can be explained by our nannofossil carbonate estimates this discrepancy is most likely caused by the high amount of unidentifiable micrite and fragments of calcareous nannofossils other factors contributing to the error are possible inaccuracies in the determination of absolute abundances and nannofossil volume calculations the nce occurs during a long term sea level fall dry climate and presumed low pco 2 levels a decline in abundance of strongly calcified nannofossils coincides with the opening of the pacific atlantic seaway via central america which may have had a substantial impact on the palaeoceanographic situation in the central atlantic ocean these changes are here considered to have at least partly caused the shifts in abundance size and assemblage composition of calcareous nannofossils observed across the jurassic cretaceous boundary interval

active fragmentation of adria the north african promontory central mediterranean orogen global positioning system gps velocities indicate that adria no longer behaves as a rigid tectonic indenter into southern europe and is divided into northwestern and southeastern velocity domains differential motions are recognized in a velocity field determined from the peri tyrrhenian geodetic array ptga and international gps service igs sites in the circum tyrrhenian region of the central mediterranean and published gps velocities from the eastern adriatic coast in a fixed eurasian reference frame ptga and igs site velocities in sicily and southern italy are as much as 10 mm yr in a northward direction similar to gps velocities along the eastern coast of the adriatic sea in contrast velocities in northern italy are small or statistically insignificant and similar to velocities in sardinia and corsica outboard of western adria the tectonic boundary dividing adria is seismically active and passes around the southern and eastern margins of the tyrrhenian basin crosses central italy extends into the adriatic sea and follows the western margin of the dinaride tectonic belt north to the gulf of venice the eastern margin of adria is approximately located and follows the axis of the central dinaric alps southeast to the hellenic arc southeastern adria has a velocity related to northward motion of africa whereas northwestern adria has negligible differential motion in the eurasian frame and now is part of the alpine collage of southern europe

geoarchaeological reconstruction of the caverna de las brujas mendoza argentina for the planning of an archaeological intervention abstract archaeological prospection and excavation in the caverna de las brujas southern part of the province of mendoza argentina has offered the first known data on human presence in this cave this is of great interest for understanding the evolution of peopling in the southern mendoza province during the holocene four archaeological pits were excavated two in the gallery known as the sala de la virgen and another two near the cave entrance three volcanic ash levels were dated by tl techniques 7780 600 4700 500 765 200 years and a level with enough organic material was dated by 14 c analysis 3695 65 years bp the available data is sufficient to establish the origin and make a geomorphological reconstruction of the holocene levels at the same time a hypothetical model is proposed that uses geomorphological criteria to predict the stratigraphy of the unexcavated lower levels at the cave entrance the aim of this model is to help direct future archaeological excavations of the cave s oldest deposits

a method for determining significant structures in a cloud of earthquakes the interpretation of a cloud of earthquake hypocenters in terms of causative structures is not a simple task locations are subject to uncertainties which will not be the same for every earthquake the data should therefore not be interpreted simply by inspection which is difficult in the case of three dimensional data anyway instead we propose using the location uncertainties as a guide in processing the data earthquake locations are moved inside their uncertainty or confidence ellipsoids until a simplified picture of the earthquake cloud is obtained which can then be interpreted in terms of some simplified structure such as faults the aim of the approach is to give the simplest possible structure that is consistent with all the location and confidence ellipsoid data the method is applied to three synthetic sets of data these illustrate the potential and limitations of the method application to a real earthquake data set from rabaul caldera in papua new guinea gives an image of the caldera ring fault that suggests departures from the simple ring fault structure previously assumed sensitivity analysis on the rabaul data shows that the method is not unduly sensitive to the assumptions that have to be made in applying it

a 106ka paleoclimate record from drill core of the salar de atacama northern chile abstract a 100 m long salt core sqm 2005 from the salar de atacama northern chile 23 s 68 w a dry lake bed contains a 106 kyr paleoclimate record of hydrologic balances on the western slopes of the central andes of south america six u series disequilibrium dates range sequentially from 106 1 6 4 to 5 4 2 7 ka based on sedimentary structures and petrographic textures of salts and associated siliciclastic sediments interpretations of paleoenvironments and net hydrologic balance suggest that relatively wet periods saline lakes and expanded mudflats existed in the salar de atacama from 75 7 to 60 7 ka and from 53 4 to 15 3 ka with the wettest perennial lake interval from 26 7 to 16 5 ka short relatively wet periods also occurred in the holocene from 11 4 to 10 2 ka and from 6 2 to 3 5 ka these wet periods at salar de atacama correspond well with other late pleistocene climate records from the central andes that are a function of the net hydrologic budget the minchin tauca lake sequence from salar de uyuni bolivia is synchronous with the 53 4 15 3 ka saline lake wet period at salar de atacama the tauca phase coincided with the wettest perennial lake interval at salar de atacama from 26 7 to 16 5 ka the coipasa lake phase from uyuni was probably contemporaneous with the early holocene wet period at salar de atacama from 11 4 to 10 2 ka the early holocene wet interval at salar de atacama was also synchronous with the maximum holocene lake levels of the chilean altiplano lakes to the east and with grass rich rodent middens between 11 8 and 10 5 ka in age from the atacama basin the lake period at salar de atacama between 26 7 and 15 3 ka compares closely with low 18o values low anion concentrations and high accumulation rates from the sajama glacial ice core southwestern bolivia between 25 and 15 5 ka it is concluded that wet and dry phases were synchronous in the central andean plateau of southwestern bolivia and along the western flank of the andes of northern chile over the past 50 kyr this region which today receives its moisture from the amazon basin to the east probably also did so in the past the wet periods at salar de atacama are in phase with january insolation maxima at 15 s at 70 45 and 20 ka which suggests that past changes in summer insolation influenced precipitation patterns in the central andes however there are no major wet periods linked to the january insolation maximum at 93 ka and the present day extremely dry climate in the atacama desert is associated with a peak in summer insolation therefore there must be other important influences over precipitation in the central andes which modify the first order insolation controls

seismic exploration in complex terrains a processing experience in the southern apennines we discuss a data processing sequence adopted to reprocess a seismic line that crosses the italian southern apennines from the tyrrhenian sea to the adriatic margin and investigate both the overthrust and foreland areas we first determine the main causes of the very low s n ratio in the field data and then propose a processing sequence aimed at exploiting the signal content also making use of a priori geological knowledge of this area our work indicates a combination of causes for the very low quality of the seismic data these include length of the spread about 20 km that is unfavorable because of the rapid variation in the near surface geology tectonic complexity crooked line acquisition and the rough topography associated with outcropping rocks characterized by highly variable velocities based on the outcome of this data analysis we present a processing sequence driven by knowledge of the regional tectonic setting and by knowledge of the shallow subsurface geology the main effort is in remov

orbital tuning of a lower cretaceous composite record maiolica formation central italy 1 a high resolution pelagic bulk carbonate stable isotope record from a central tethyan lower cretaceous composite section is presented three well exposed sedimentary sequences chiaserna monte acuto bosso and gorgo a cerbara sections central italy cropping out throughout the maiolica formation were correlated by a detailed magnetostratigraphy lithostratigraphy and calcareous plankton biostratigraphy in order to reconstruct a continuous composite record from the middle berriasian to the lower aptian the integrated stratigraphy of the three sequences provided an accurate time framework for the new high resolution c isotope curve which is presented in this study the composite 13c signal recorded in the depth domain was analyzed by combined lomb scargle periodogram and weighted wavelet z transform wwz weighted wavelet amplitudes wwa foster wavelet spectral methodologies both appropriate for unevenly sampled curves these tools allowed us to unravel the main frequencies modulating the record and their hypothetical shift in depth respectively the long term 400 000 and 2 400 000 years eccentricity cycles were consistently recorded throughout all the composite record once band pass filtered in these two periodicity bands and compared to the lithologic pattern cycles identified throughout the composite sequence the 13c signal was used as a valuable proxy record for a reliable construction of an orbital tuning of the early cretaceous an estimated age for all the different stratigraphic events recognized throughout the composite record was reported in particular the reestimated ages of the paleomagnetic chrons documented in the upper part of the record show differences with those reported by gradstein et al 2004 up to 2 m y the valanginian carbon shift present in the middle part of the composite sequence was estimated to be 2 3 m y long the good agreement between the estimated age of the base of this positive carbon isotope excursion 136 34 m y and the predominant volcanic phase associated to the parana etendeka large igneous province intrusion confirmed a possible cause effect link between the two events

orbital scale record of the late cenomanian turonian oceanic anoxic event oae 2 in the tarfaya basin morocco high sedimentation rates up to 12 cm kyear of laminated organic carbon rich biogenic limestones in the tarfaya basin provide an unusually high millennial resolution record of the late cenomanian oceanic anoxic event oae 2 the global positive carbon isotope excursion across the cenomanian turonian corresponds to 11 light dark sedimentary cycles we interpret these cycles as a response to orbital obliquity variation and estimate the duration of the complete excursion as 440 kyear or one long eccentricity cycle on this time scale the main increase in delta 13 c values occurred over a short time interval of less than 20 kyear in the late cenomanian and reached a first maximum approximately 15 kyear prior to the bulk mainly coccoliths delta 18 o derived sea surface maximum temperature that occurs coeval to the extinction of rotalipora cushmani organic carbon accumulation rates follow obliquity cycles reaching a maximum approximately 10 kyear after the last occurrence of r cushmani then slowly decreasing during the early turonian thus the maximum temperature and the maximum organic carbon accumulation in the tarfaya basin lagged by at least 15 kyear behind the global carbon isotope shift and a proposed reduction of atmospheric co 2 content the climate change across the cenomanian turonian boundary probably occurred independent of co 2 levels and may have been controlled by different greenhouse gases water vapour and methane and changes in ocean circulation i e opening of the equatorial atlantic gateway

carbon isotope stratigraphy and ammonite faunal turnover for the middle jurassic in the southern iberian palaeomargin variations in the stable carbon isotope ratio of marine and continental sediments can reflect changes in sink and flux modifications of the palaeocarbon cycle here we report carbon isotope compositions of middle jurassic marine carbonates from the betic cordillera southern spain which represents an ideal region to link the stable carbon isotope curves directly to ammonite zones and subzones and thereby for the first time achieve an accurate chronostratigraphic calibration the five sections studied represent basin and high swell deposits of the southern iberian palaeomargin we find a similar 13 c of carbonates between different oceanic areas suggesting a homogeneous carbon isotope oceanic reservoir through the middle jurassic the aalenian bajocian transition is a critical period in ammonite evolution hence the early jurassic fauna are replaced by new ammonite families which become dominant throughout the middle and late jurassic for this reason we compared the 13 c values of carbonates with ammonite diversity and extinction rates at different taxonomical levels in order to explore the possible relationship between the carbon cycle and ammonite evolution the carbon isotope values of carbonates are not exactly linearly correlated with the extinction rate and ammonite diversity but the main faunal turnovers follow minimum 13 c values where extinct taxa are replaced by new ones likewise radiation episodes are associated with increasing 13 c values and with transgressive sea level rise all these data support the idea that perturbations in the global carbon cycle reflect rapid palaeoenvironmental changes we made detailed analyses of these faunal turnovers using them as a proxy to identify major palaeoenvironmental crises in their ecosystems forced by modification in the carbon cycle

deciphering processes controlling mid jurassic coccolith turnover the middle jurassic is characterized by major changes within the fossil coccolithophorid community with a transition from lotharingius dominated to watznaueria dominated assemblages concomitant with a significant increase in the pelagic carbonate production the mechanisms that triggered this overturn remain poorly understood here we present a compilation new and previously published data of lotharingius and watznaueria abundances through the early middle jurassic transition alongside this trends in newly acquired and literature derived carbon and oxygen isotope data were used to represent paleoceanographic indicators such as nutrient and temperature changes the nannofossil data show a rapid around 1 5 myr turnover around the aalenian bajocian transition across the aalenian bajocian boundary assemblages dominated by lotharingius spp give way to assemblages dominated by watznaueria spp coinciding with a peak in a particular morphological group of watznaueria species with a cross in the central area the proliferation of this morphogroup occurred during a time of oceanic opening and rearrangement of ocean circulation this led on to the evolution of pioneering coccolithophorid taxa but also to extinctions in several marine groups in the early bajocian the proliferation of two other morphogroups watznaueria without a central area structure and watznaueria with a bar corresponds to the major diversification of watznaueria and the beginning of its meso zoic dominance the watznaueria diversification and dominance are associated with radiation in other marine groups and these biotic changes occurred during a time of putative enhanced oceanic fertility and relatively low temperatures this study suggests that restructuring of fossil coccolithophorid communities may be favored during short turnover intervals related to major paleoceanographic change

pleistocene climatic change in southern australia and its effect on speleothem deposition in some nullarbor caves activity ratios of 234u 238u 230th 234u and 230th 232th have been determined for calcite gypsum and halite speleothems from caves of the nullarbor plain mostly in the area n and nw of mundrabilla station for the purpose of u series dating all calcite speleothems contain adequate amounts of uranium for dating but some show an excess of 230th stratigraphic relationships indicate that there were at least three phases of calcium carbonate deposition in the nullarbor caves the calcite samples with one possible exception have ages in excess of ca 400000 yrs bp this suggests that no significant amounts of calcium carbonate deposition have taken place during the last 400ka at present active deposition of speleothems is restricted almost entirely to gypsum and halite the only gypsum speleothem dated was found to have a finite age of ca 185 ka six dates on a small halite speleothem containing insect and arachnid remains indicate that it formed rapidly during holocene time

the palaeoceanographic crisis of the early aptian oae 1a in the vocontian basin se france abstract the vocontian basin se france which presents lower aptian expanded successions characterized by major lithological changes is particularly suitable to determine palaeoenvironmental changes occurring across the oae 1a a multidisciplinary study sedimentology caco3 toc carbon and oxygen stable isotopes micropalaeontology cyclostratigraphy was carried out in the notre dame de rosans section in order to establish a detailed chronological framework of these changes the oae 1a corresponds to carbon isotope segments c3 c6 and it lasted for 1 2 myr a first drop in the carbonate production occurs 500 kyr before the oae 1a upper part of the carbon isotope segment c2 and could result from both onset of urgonian carbonate platform demise and associated reducing export of platform derived sediments into the basin and nannoconid crisis a second drastic drop crash in the carbonate production is recorded within the lower part of the oae 1a latter part of segment c3 to c5 and is explained by a strong dissolution this study then shows that the onset of the major carbonate crisis that occurs before the oae 1a could be due to both rise in sea level and in marine surface water fertility whereas its acme that occurs within the oae 1a could be related to co2 induced ocean acidification black shales of the niveau goguel occur in the upper part of the oae 1a and represent the lower part of segment c6 surface waters primary producers are principally represented by cyanobacteria whereas nannofossil primary productivity is reduced and deep water anoxia prevailed during the deposition of the niveau goguel the last 300 kyr of the oae 1a are characterized by a partial recovery of both nannofossil primary productivity and pelagic carbonate production which sharply increase just after the end of the event this study also shows that organic rich layers associated to the oae 1a are diachronous in the tethyan realm

upper crustal structure of the benevento area southern italy fault heterogeneities and potential for large earthquakes summary the benevento region is part of the southern apennines seismogenic belt which experienced large destructive seismic events both in historical and in recent times the study area lies at the northern end of the irpinia fault which ruptured in 1980 with a ms 6 9 normal faulting event which caused about 3000 casualties the aims of this paper are to image lateral heterogeneities in the upper crust of the benevento region and to try to identify the fault segments that are expected to generate such large earthquakes this work is motivated by the recognition that lithological heterogeneities along major fault zones inferred from velocity anomalies reflect the presence of fault patches that behave differently during large rupture episodes in this paper we define the crustal structure of the benevento region by using the background seismicity recorded during 1991 and 1992 by a local seismic array these data offer a unique opportunity to investigate the presence of structural discontinuities of a major seismogenic zone before the occurrence of the next large earthquake the main result that we obtained is the delineation of two nw trending high velocity zones hvzs in the upper crust beneath the matese limestone massif these high velocities are interpreted as high strength regions that extend for 30 40 km down to at least 12 km depth the correspondence of these hvzs with the maximum intensity regions of historical earthquakes 1688 ad 1805 ad suggests that these anomalies delineate the extent of two fault segments of the southern apenninic belt capable of generating m 6 5 7 earthquakes the lateral offset observed between the two segments from tomographic results and isoseismal areas is possibly related to transverse right lateral faults

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

pathways and distances of fluid flow during low grade metamorphism evidence from pyrite deposits of the cameros basin spain new geochemical and sulphur isotopic data are presented for a number of pyrite deposits from the late jurassic early cretaceous cameros basin spain the deposits were formed at or close to the peak of metamorphism and are always related to sandstone units in the mainly metapelite sequence iron remained immobile and conservative pyrite iron being derived by sulphidation of chlorite in the host metapelites reduced sulphur however was supplied from two external sources thermochemical reduction of sulphate and release of s during metamorphism of sedimentary sulphides these sources provided isotopically heavy and light s respectively with variation in pyrite isotopic composition between different deposits resulting from differences in their relative importance at each site during metamorphism the sandstone units acted as aquifers carrying the sulphidic pore waters to locations where permeability provided by syn depositional fractures on a scale of 0 5 5 m allowed its interaction with the metapelites transport distances for sulphide during metamorphism were of the order of hundreds of metres

carbon cycle perturbation in the middle jurassic and accompanying changes in the terrestrial paleoenvironment abstract carbon isotope analyses of fossil wood from the middle jurassic ravenscar group yorkshire ne england reveal a significant excursion toward light isotopic values 13c change of 3 to 4 at about the aalenian bajocian boundary 174 ma a positive carbon isotopic excursion is also shown for the middle bajocian 170 ma but is less clearly defined these isotopic patterns are very similar to the few published marine carbonate records available for this time in particular one based on belemnites from the hebrides basin nw scotland and others from pelagic limestones in italy the similarity of the terrestrial and marine isotope curves is an indication that the observed isotopic signal is a global phenomenon through parts of the ravenscar group the scarborough formation supplementary data from bulk organic carbon and palynofacies analysis confirm that isotopic curves based on bulk analyses may be strongly influenced by the balance of terrestrial versus marine organic matter present in th

deep structure of the campanian lucanian arc southern apennine italy abstract recent exploration activities and successful discovery of large oil fields in the upper val d agri area southern apennine italy have encouraged the collection of large quantities of geological and geophysical data and their integration into comprehensive geological models here we present a series of structural profiles based on several hundred kilometres of seismic lines two and three dimensional and the results of many deep wells the best seismic lines have been extensively reprocessed and also tied to magnetotelluric data geological interpretations of those lines have been interactively tested and verified by gravity and magnetic modelling and structural balancing the wells and seismic data demonstrate that the fundamental tracts of the deep architecture of the orogen as it appears today were developed only at the end of the late pliocene the final closure of the ensialic shear zone responsible for the subduction of at least 150 km of continental lithosphere originally underlying the lagonegro basin can be dated as early pliocene the involvement of the inner apulian platform in the core of the belt and the activation of a new and more external left lateral oblique ensialic shear zone can be constrained to the late pliocene pleistocene the seismic profiles clearly show the underthrusting of the outer apulian platform unit beneath the inner apulian platform unit the thick skinned character of the plio pleistocene contractional structures is evident from the structural profiles this geometry is constrained by gravity magnetic data and structural considerations according to the relatively steep angle of dip about 10 of the apulian foreland beneath the chain the structural profiles depict the general architecture of the campanian lucanian arc the apennine platform and lagonegro unit are largely allochthonous and a part of the lagonegro basement could be buried below the apennine platform sole thrust the neogene plastic successions of the apennine platform and lagonegro basin were detached and now outcrop in the bradanic foredeep the inner apulian platform constitutes a huge thrust sheet structured as a wide antiform in the core of the belt its regional culmination roughly corresponds to the val d agri area extensional and transtensional structures cross cut the pre existing compressional structures as shown by the quaternary valleys of vallo di diano and val d agri the profiles shown also highlight the existing contrast between the deep structures in the core of the belt and the tectonic style of the lagonegro liguride and sicilide units these units were in fact subjected to brittle ductile deformation under metamorphic part of liguridi units and deep diagenetic to anchizonal conditions lagonegro units and were affected by a general overthrust shear directed towards the ne the inner apulian platform was on the contrary involved in the thrust belt together with its basement whereas the outer apulian platform affected by a subduction underwent a regional bending with associated normal faulting

fertilization of the northwestern tethys vocontian basin se france during the valanginian carbon isotope perturbation evidence from calcareous nannofossils and trace element data a high resolution calcareous nannofossil study associated with a geochemical analysis major trace elements and carbon and oxygen isotope stratigraphies was carried out in the angles section hemipelagic setting of the vocontian basin se france during the valanginian positive carbon isotope excursion the behaviour of calcareous nannofossil taxa in relation to fertility conditions was studied to elaborate new nutrient indices in this environment a high nutrient index based on biscutum spp discorhabdus rotatorius zeugrhabdotus fissus high fertility indicators and watznaueria barnesae low fertility indicator and a medium nutrient index based on lithraphidites carniolensis medium fertility indicator and w barnesae low fertility indicator these two indices show a major fertilization from the stephanophorus ammonite zone to the trinodosum ammonite zone with a maximum during the positive carbon isotope excursion since high values of the nutrient indices are in phase with high values of chemical elements related to terrigenous material and low values of the coccolith total abundance it is proposed that pulses of detrital inputs into the basin triggered the nutrification which in turn caused a biocalcification crisis of the calcareous nannofossils nutrification is also responsible for the reef demise in the surrounded platforms as indicated by the increased sr ca seawater ratio at that time the intensification of the parana etendeka volcanic activity triggering co2 excess in the atmosphere is probably responsible for an acceleration of the hydrological cycle the increased weathering and the subsequent higher terrigenous and nutrient transfer from continents to the vocontian basin in such a scenario nutrification is a dominant factor controlling neritic and hemipelagic biocalcification however one cannot exclude that the global increase of atmospheric co2 could generate chemical changes of the sea surface waters acting with the nutrification to modify the biocalcification of the carbonate producers

reactivation of deep faults beneath southern apennines evidence from the 1990 1991 potenza seismic sequences we relocate the 1990 1991 potenza southern apennines belt italy sequences and calculate focal mechanisms this seismicity clusters along an e w dextral strike slip structure second order clusters are also present and reflect the activation of minor shears the depth distribution of earthquakes evidences a peak between 14 and 20 km within the basement of the subducting apulian plate the analysed seismicity does not mirror that of southern apennines which include nw se striking normal faults and earthquakes concentrated within the first 15 km of the crust we suggest that the e w faults affecting the foreland region of apennine propagate up to 25 km of depth the potenza earthquakes reflect the reactivation of a deep preexisting fault system we conclude that the seismotectonic setting of apennines is characterized by nw se normal faults affecting the upper 15 km of the crust and by e w deeper strike slip faults cutting the crystalline basement of the chain

desert paleoenvironmental data from cave speleothems with examples from the chihuahuan somali chalbi and kalahari deserts abstract pollen bearing lake bog and spring sediments are relatively scarce in many arid and semiarid regions of the world and few are dateable beyond the 14c range we have obtained pollen spectra from speleothems collected from caves in the somali chalbi and kalahari deserts suggesting that these deposits may be an important future source of desert paleovegetation data as cave speleothems can be dated by the 230th 234u method to c 350 000 yr b p and by the tl and esr methods potentially to 1 m y b p and can sometimes give paleotemperature and paleohydrologic data they could provide a first glimpse of desert paleoenvironments during isotope stages 4 9 ages of speleothems from the chihuahuan kalahari and somali chalbi deserts suggest that there was more available moisture in the southwestern u s a and in northwestern bostwana during glacials and interstadials of the last c 300 000 years but that wetter conditions in the horn of africa corresponded with interglacials and perhaps to a lesser extent with interstadials pollen from three northern somalia speleothems indicate more mesic conditions in the horn of africa at 10 000 11 800 and 176 500 yr b p while speleothem pollen spectra from matupi cave in northeastern zaire presently surrounded by tropical rainforest suggest a savanna grassland at this cave c 14 000 yr b p

speleothems travertines and paleoclimates abstract age data for about 660 speleothems and about 140 spring deposited travertines were collected including many unpublished results these data were plotted as histograms and also as error weighted frequency curves on a 350 000 yr scale these plots clearly show periods of increased speleothem travertine growth as well as times of cessation the periods of most frequent speleothem growth were between approximately 130 000 and 90 000 yr ago and since about 15 000 yr ago such periods before 150 000 yr ago however cannot be yet recognized because of a lack of sufficient data and the associated uncertainties of dates in this age range a comparison with the oxygen isotope record of deep sea core v28 238 shows a clear relationship indicating that terrestrial calcite formation is controlled by paleoclimatic fluctuations the evident climatic stimulation of quaternary calcite formation is readily explained geochemically and is substantiated by the obvious difference in speleothem travertine growth as a function of geographic position

pacific microplate and the pangea supercontinent in the early to middle jurassic new biostratigraphic data based on radiolarians recovered from deep within the oceanic crustal section of ocean drilling program hole 801c in the western pacific along with existing radiometric information date this oceanic crust as late bajocian early bathonian 170 165 ma the overlying basal sediments at hole 801c are essentially identical in age middle bathonian 164 162 ma to the basal sediments at deep sea drilling program hole 534a in the central atlantic we estimate the time of formation of the pacific plate as 175 170 ma and the time of initial separation of the pangea supercontinent in the central atlantic as 190 180 ma we also identify a time of extensive subduction zone magmatism 175 159 ma at the eastern and western edges of pangea we suggest that the initial plate separation of pangea increased subduction rates at its outer margins and altered the plate boundaries in the pacific superocean leading to formation of the pacific plate

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

the middle cenomanian event in the equatorial atlantic the calcareous nannofossil and benthic foraminiferal response abstract in addition to oceanic anoxic event 2 oae2 other perturbations of the carbon cycle occurred during the cenomanian and turonian of which the middle cenomanian event mce is the most prominent one in palaeoecological publications however this event is strongly underrepresented in contrast to the well studied oae2 in order to fill this gap we have studied early cenomanian to late turonian calcareous nannofossil and benthic foraminiferal assemblages of ocean drilling program site 1260 at demerara rise western equatorial north atlantic in order to decipher biotic changes throughout this interval and especially across the mce our data show distinctive changes in the relative abundance of certain calcareous nannofossil taxa and a drastic decrease in benthic foraminiferal diversities and abundances associated with the mce in the lower part of the studied section and prior to the mce a mixed water column with high nutrient availability in the upper photic zone is suggested based on very high relative abundances of the mesotrophic eutrophic nannofossil species biscutum constans around the mce interval certain nannofossil taxa e g rhagodiscus asper show a distinctive decrease in relative abundance while others become more dominant taxa which increase in relative abundance after the mce e g eprolithus floralis are interpreted as either having favoured less eutrophic surface waters or having inhabited deeper parts of the photic zone in a well stratified water column this interpretation is supported by published oxygen isotope and tex86 data which suggest increased water column stratification starting with the mce and lasting to the end of the cenomanian stage as a result of the implementation of a saline intermediate to deep water mass during this interval our study shows that the mce was a significant biotic event in the cenomanian turonian equatorial atlantic characterised by a lasting change of surface and bottom water ecosystems

orbital time scale and new c isotope record for cenomanian turonian boundary stratotype previous time scales for the cenomanian turonian boundary ctb interval containing oceanic anoxic event ii oae ii vary by a factor of three in this paper we present a new orbital time scale for the ctb stratotype established independently of radiometric biostratigraphic or geochemical data sets update revisions of ctb biostratigraphic zonation and provide a new detailed carbon isotopic record for the ctb study interval the orbital time scale allows an independent assessment of basal biozone ages relative to the new ctb date of 93 55 ma gts04 the d 13 corg data document the abrupt onset of oae ii significant variability in d 13 corg values and values enriched to almost 222 these new data underscore the difficulty in defining oae ii termination using the new isotope curve and time scale estimates of oae ii duration can be determined and exported to other sites based on integration of well established chemostratigraphic and biostratigraphic datums the new data will allow more accurate calculations of biogeochemical and paleobiologic rates across the ctb