a detailed 2840 year record of explosive volcanism in a shallow ice core from dome a east antarctica a detailed history of volcanism covering the last 2840 years is reconstructed from the top 100 42 m of a 109 91 m ice core from dome a da2005 ice core east antarctica using two known volcanic stratigraphic markers the mean accumulation rate during the period ad 1260 1964 is found to be 23 2 mm w e a 1 consistent with the previously reported accumulation rate at dome a this mean accumulation rate is used to date the entire core volcanic eruptions in the period 840 bc ad 1998 are detected as outstanding sulphate events seventy eight eruptions are identified with a mean of 2 7 eruptions per century comparisons with previous antarctic ice core volcanic records are made to assess the quality of this new da2005 record in terms of dates for volcanic events the da2005 record is in good agreement with previous records in the second millennium ad ad 1000 1998 a series of volcanic signatures found in both the da2005 record and several other antarctic ice core records in the first millennium ad ad 1 1000 appear to validate the da2005 record during this time period for the older periods direct comparisons are difficult between the da2005 record and other antarctic ice core records due to the lack of well dated stratigraphic horizons

paleomagnetism of the cu zn pb bearing kupferschiefer black shale upper permian at sangerhausen germany syngenetic diagenetic and epigenetic models have been proposed for the cu zn pb kupferschiefer mineralization at sangerhausen germany paleomagnetic and rock magnetic measurements have been made on 205 specimens from mine workings on the margin of the sangerhausen syncline the mineralization is richest in the 0 5 m thick upper permian 258 2 ma kupferschiefer black marly shale nine sites and dies out over 0 2 m in the underlying weisliegend sandstones three sites and overlying zechstein carbonates two sites except for one site of fault zone gypsum characteristic remanent magnetization directions were isolated for all 14 sites using alternating field and thermal step demagnetization these directions provide a negative fold test indicating that the remanence postdates jurassic fault block tilting rock magnetic measurements show that the kupferschiefer shale marks a redox front between the oxidized weissliegend sandstones and non oxidized zechstein carbonates the 14 site directions give a late jurassic paleopole at 149 3 ma it is significantly different from the paleopole reported by e c jowett and others for primary or early diagenetic rote faule alteration that gives an age of 254 6 ma on the current apparent polar wander path and is associated with kupferschiefer mineralization we suggest that the late jurassic extensional tectonic event that formed the nearby north german basin also reactivated variscan basement faults and extended them up through the overlying strata thereby allowing hydrothermal basement fluids to ascend and epigenetically mineralize the kupferschiefer shale the possibility of a 53 3 ma mineralization age is also considered

the impact of the eruptions of mount pinatubo and cerro hudson on antarctic aerosol levels during the 1991 austral spring at the beginning of 1991 austral spring volcanic aerosols from mt pinatubo and cerro hudson were present in the polar stratosphere of the southern hemisphere satellite observations of aerosol extinction were used to identify and track the movement of these aerosols in the vicinity of the antarctic vortex during august through november 1991 a layer of mature mt pinatubo aerosols was identified near 21 km and a layer of fresh cerro hudson aerosols was identified near 12 km this altitude separation of the mt pinatubo and cerro hudson aerosols was observed throughout the period below 15 km the polar stratosphere was subject to episodes of strong wave activity which transported the cerro hudson aerosols poleward and after the middle of september they became a persistent feature beneath the vortex above 15 km signatures of mt pinatubo aerosols were observed near the vortex boundary but significant portions of the vortex interior remained free of any detectable intrusions of mt pinatubo aerosols until the final warming in mid november 13 refs 4 figs

uv induced mass independent sulfur isotope fractionation in stratospheric volcanic sulfate 1 sulfuric acid aerosols produced in the stratosphere following massive volcanic eruptions possess a mass independent sulfur isotopic signature acquired when volcanic so2 experiences uv photooxidation the volcanic data are consistent with laboratory so2 photooxidation experiments using uv light at 248 nm maximum absorption of ozone whereas sulfur isotopic anomalies previously observed in archean samples are consistent with photodissociation at 190 220 nm a mechanism of so2 photooxidation occurring in the early stage of a stratospheric volcanic plume in the range of 220 320 nm weak band absorption of so2 is also proposed since mass independent sulfur isotope anomalies in stratospheric volcanic sulfate appear to depend on the exposure of so2 to uv radiation their measurements might therefore offer the possibility to determine the degree of uv penetration in the ozone absorption window for the present and past atmospheres they can also be used to determine the stratospheric or tropospheric nature of volcanic eruptions preserved in glaciological records offering the possibility to reassess the climatic impact of past volcanic eruptions

dynamic stratigraphy as a tool in economic mineral exploration ultra pure limestones upper jurassic sw germany abstract ultra pure limestones form valuable economic minerals used in the glass paper pharmaceutical chemical and building industries both exploration and exploitation of economic materials require predictions of the subsurface stratigraphy such predictions are most reliable when the depositional processes creating these deposits are well understood we present a simple process based methology dynamic stratigraphy to break down stratigraphic packages into a hierarchy of easily recognisable genetically defined units of various scales each scale of analysis at the same time provides critical data on the composition quality volumes and preferred occurrence of economic minerals in this study upper jurassic carbonates of sw germany deposited on a deeper epicontinental ramp have been re evaluated based on newly available borehole data of an exploration programme for industrial minerals especially for ultra pure limestones carried out by the geological survey of baden wurttemberg about 2 5 km of core were slabbed and continuously studied for micro and macrofacies geochemistry colourimetry whiteness index and calibrated to the gamma ray signatures in a number of key outcrops stratal and facies patterns as well as sedimentary geometries were mapped the carbonate buildups form the most promising rock bodies hosting ultra pure limestones gamma ray signatures correlate both with major facies types and their bulk chemical composition and are thus useful for an initial evaluation of raw materials properties in both major facies associations 1 the bedded and 2 the massive microbial sponge buildup facies distinct sedimentary cycles were recognised building systematic stacking patterns and a cycle hierarchy within the buildup facies this cyclicity mirrors the whiteness and pureness of limestones the cycles are used to carry out regional correlations between and across extensive buildup complexes which are generally regarded as completely massive and homogenous based on this the occurrence and distribution of economically valuable ultra pure limestone bodies can be understood and used to develop predictive genetic models dynamic or genetic stratigraphy integrated with petrophysical measurements colourimetry gamma ray logs leads to more cost effective techniques of exploration and exploitation while similar sedimentological concepts are commonly used in the petroleum industry this study documents their usefulness also in the economic minerals industry

a northern hemisphere volcanic chemistry record 1869 1984 and climatic implications using a south greenland ice core the effect of volcanic emission of acidic aerosols on climate is well documented the presence of acid droplets in the stratosphere can reduce transmissivity and hence decrease surface temperatures since the amount and chemical composition of erupted material has important effects on regional climate knowledge of past volcanic events is of extreme importance detailed glaciochemical records provide the only milieu wherein the geochemistry of paleovolcanic events can be fully documented we present a detailed sulfate and chloride record from an ice core drilled at site 20 d 40 km sw of dye 3 in southern greenland the record spans the time period 1869 1984 with chemical analyses of approximately eight samples per year time series decomposition and locally weighted scatter plot smoothing techniques were used to extract long term trends from the data so that individual volcanic eruptions could be documented a number of events identified here have been unnoticed previously and a high percentage of the major chemical signatures documenting these events is associated with large decreases in temperature in the latitudinal zone 60 90 on many authors have pointed out that the amount of volcanic acids such as hci and h2s04 injected into the atmosphere has a very important influence on global climate yet this volcanic input has been difficult to quantify prior to 1960 our data help to alleviate this problem these individual events can be compared to available frost tree ring data from north america further establishing a volcanism climatic linkage

spatio temporal variability in volcanic sulphate deposition over the past 2 kyr in snow pits and firn cores from amundsenisen antarctica in the framework of the european project for ice coring in antarctica epica a comprehensive glaciological pre site survey has been carried out on amund senisen dronning maud land east antarctica in the past decade within this survey four intermediate depth ice cores and 13 snow pits were analyzed for their ionic compos ition and interpreted with respect to the spatial and temporal variability of volcanic sul phate deposition the comparison of the non sea salt nss sulphate peaks that are related to the well known eruptions of pinatubo and cerro hudson in ad1991 revealed sulphate depositions of comparable size 15 8 3 4 kg km 2 in 11 snow pits there is a tendency to higher annual concentrations for smaller snow accumulation rates the combination of seasonal sodium and annually resolved nss sulphate records allowed the establishment of a time scale derived by annual layer counting over the last 2000 years and thus a detailed chronology of annual volcanic sulphate deposition using a robust outlier detection algo rithm 49 volcanic eruptions were identified between ad165 and 1997 the dating uncer tainty is 3 years between ad1997 and 1601 around 5 years between ad1601 and 1257 and increasing to 24 years at ad165 improving the accuracy of the volcanic chronology during the penultimate millennium considerably abstract in the framework of the european project for ice coring in antarctica epica a comprehensive glaciological pre site survey has been carried out on amund senisen dronning maud land east antarctica in the past decade within this survey four intermediate depth ice cores and 13 snow pits were analyzed for their ionic compos ition and interpreted with respect to the spatial and temporal variability of volcanic sul phate deposition the comparison of the non sea salt nss sulphate peaks that are related to the well known eruptions of pinatubo and cerro hudson in ad1991 revealed sulphate depositions of comparable size 15 8 3 4 kg km 2 in 11 snow pits there is a tendency to higher annual concentrations for smaller snow accumulation rates the combination of seasonal sodium and annually resolved nss sulphate records allowed the establishment of a time scale derived by annual layer counting over the last 2000 years and thus a detailed chronology of annual volcanic sulphate deposition using a robust outlier detection algo rithm 49 volcanic eruptions were identified between ad165 and 1997 the dating uncer tainty is 3 years between ad1997 and 1601 around 5 years between ad1601 and 1257 and increasing to 24 years at ad165 improving the accuracy of the volcanic chronology during the penultimate millennium considerably

a 220 year continuous record of volcanic h2so4 in the antarctic ice sheet continuous h2so4 profiles observed in snow from several antarctic locations reveal four major volcanic events of the past two centuries agung krakatoa tambora and another large scale event not recorded historically acid deposition and interhemispheric distribution mechanisms are quantified and then used to obtain an order of magnitude estimate for the h2so4 emissions from these eruptions

the origin of high frequency platform carbonate cycles and third order sequences lower ordovician el paso gp west texas constraints from outcrop data and stratigraphic modeling abstract the passive margin succession of the diablo platform lower ordovician west texas is represented by the second order sauk c supersequence set consisting of a basal transgressive clastic unit the bliss sandstone above the breakup unconformity marking the second order basal lowstand transgressive phase overlain by 750 m of drift related shallow marine platform carbonates the el paso group recording the second order highstand due to late paleozoic structuring of the gondwanan passive margin present exposures in texas are in an updip shelf position and lack internal stratal geometries across depositional strike so sequences and systems tracts are identified solely by the vertical stacking patterns of depositional subfacies and higher frequency fifth order cycles accommodation plots fischer plots of high frequency cycles gauge systematic shifts in third order accommodation of two complete third order sequences each about 2 m y long and 60 140 m thick within the el paso group this is expressed in the vertical succession of cycle types systematic changes in cycle thickness and variations in subfacies as revealed by histograms of subfacies types tied to fischer plots a complete el paso shelf sequence contains a thin lowstand systems tract of quartz arenite a thick transgressive systems tract dominated by upward thickening thrombolitic subtidal cycles and a highstand systems tract marked by dolomitic thinning upward peritidal cycles containing quartz sand the el paso third order depositional sequences have been correlated by biostrat graphy and cycle stacking pattern from the franklin mountains southeast to the diablo arch northeast into the ardmore basin and thence to the appalachian basin hence the third order sequences appear to be eustatic based on biostratigraphic correlation of accommodation plots around the periphery of gondwana time series analyses suggest that a strict allocyclic milankovitch driven glacio eustatic mechanism alone is insufficient to account for the higher frequency fifth order and lower frequency third order accommodation cycles we used a two dimensional forward computer simulation to compare allocyclic and autocyclic models for high frequency cycles the allocyclic simulation superimposes a deterministic milankovitch glacio eustatic driver on a lower frequency third order accommodation cycle and generates a two dimensional synthetic cross section composed of high frequency peritidal and subtidal cycles stacked into third order sequences the autocyclic simulation is generated by a ginsburg autocyclic mechanism for high frequency cyclicity triggered by third order accommodation changes the autocyclic simulation quantitatively replicates an autocyclic mechanism for fifth order cycle development linked to onshore sediment transport and seaward progradation of tidal flats the two dimensional internal facies architecture of a third order sequence and the high frequency cycle stacking patterns are simulated in both scenarios important differences in patterns of cycles and subfacies stacking in the simulations shed light on the interpretation of the diablo platform cycles and sequences as an alternative or a supplement to autocyclicity or milankovitch forced glacio eustasy we have studied stochastic models for driving high frequency changes in relative sea level these intriguing results maintain essentially all the features observed in the rock record our smoothed sto hastic simulations suggest that the cycle problem is much more complex than presently realized

impact of the cerro hudson and pinatubo volcanic eruptions on the antarctic air and snow chemistry atmospheric records of sulfate and msa in aerosols were obtained by year round samplings in the boundary layer at two coastal antarctic sites neumayer 1983 1995 and dumont d urville 1991 1997 at dumont d urville and neumayer the non sea salt sulfate nssso42 level observed from october 1991 to october 1993 exceeded by 44 and 48 ng m 3 respectively the mean level 150 ng m 3 observed during nonvolcanic years the neumayer and dumont d urville records first exhibit spring october to december 1991 nssso42 concentrations exceeding mean spring concentrations by some 100 to 150 ng m 3 caused by a significant poleward transport of the cerro hudson volcanic aerosol in the lower stratosphere beneath the polar vortex and possibly in the middle upper troposphere limited to 10 ng m 3 during winter 1992 the nssso42 perturbation reached 78 ng m 3 in fall 1993 at neumayer the latter enhancement corresponds to the input of the pinatubo volcanic aerosol advected through stratosphere troposphere air mass exchanges an enhancement of nssso42 concentrations is also recorded in snow layers deposited between 1991 and 1993 at various sites located over the high antarctic plateau on the basis of these firn data the relative impact of the three latest volcanic eruptions of global concern namely mount agung 1963 el chichon 1982 and pinatubo together with cerro hudson 1991 was evaluated in terms of sulfate input at high southern latitudes the fallout of sulfate in central antarctic snow following the cerro hudson pinatubo eruptions was slightly lower than fallout after the mount agung eruption sulfate fallout after el chichon was 2 to 3 times lower than that from either mount agung or pinatubo the enhancement of sulfate levels detected in central antarctic snow deposits during the 1991 1993 time period allows us to estimate a mean atmospheric sulfate perturbation of around 60 ng m 3 in the boundary layer of these regions i e at least 35 higher than that seen at coastal sites this observation suggests that coastal antarctic regions are less sensitive than the high plateau in detecting volcanic sulfate fallouts following eruptions of global concern atmospheric near surface year round sampling achieved at coastal antarctic sites reveals no significant enhancement of the nitrate level over 1992 and 1993 suggesting that volcanic aerosols have had a limited effect on the transfer of nitric acid from the lower antarctic stratosphere to the boundary layer in these regions

sulfur isotope variations from orebody to hand specimen scale at the mežica lead zinc deposit slovenia a predominantly biogenic pattern the mississippi valley type mvt pb zn ore district at me ica is hosted by middle to upper triassic platform carbonate rocks in the northern karavanke drau range geotectonic units of the eastern alps northeastern slovenia the mineralization at me ica covers an area of 64 km2 with more than 350 orebodies and numerous galena and sphalerite occurrences which formed epigenetically both conformable and discordant to bedding while knowledge on the style of mineralization has grown considerably the origin of discordant mineralization is still debated sulfur stable isotope analyses of 149 sulfide samples from the different types of orebodies provide new insights on the genesis of these mineralizations and their relationship over the whole mining district sphalerite and galena have 34s values in the range of 24 7 to 1 5 vcdt 13 5 5 0 and 24 7 to 1 4 10 7 5 9 respectively these values are in the range of the main mvt deposits of the drau range all sulfide 34s values are negative within a broad range with 34spyrite 34ssphalerite 34sgalena for both conformable and discordant orebodies indicating isotopically heterogeneous h2s in the ore forming fluids and precipitation of the sulfides at thermodynamic disequilibrium this clearly supports that the main sulfide sulfur originates from bacterially mediated reduction bsr of middle to upper triassic seawater sulfate or evaporite sulfate thermochemical sulfate reduction tsr by organic compounds contributed a minor amount of 34s enriched h2s to the ore fluid the variations of 34s values of galena and coarse grained sphalerite at orefield scale are generally larger than the differences observed in single hand specimens the progressively more negative 34s values with time along the different sphalerite generations are consistent with mixing of different h2s sources with a decreasing contribution of h2s from regional tsr and an increase from a local h2s reservoir produced by bsr i e sedimentary biogenic pyrite organo sulfur compounds galena in discordant ore 11 9 to 1 7 7 0 2 7 n 12 tends to be depleted in 34s compared with conformable ore 24 7 to 2 8 11 7 6 2 n 39 a similar trend is observed from fine crystalline sphalerite i to coarse open space filling sphalerite ii some variation of the sulfide 34s values is attributed to the inherent variability of bacterial sulfate reduction including metabolic recycling in a locally partially closed system and contribution of h2s from hydrolysis of biogenic pyrite and thermal cracking of organo sulfur compounds the results suggest that the conformable orebodies originated by mixing of hydrothermal saline metal rich fluid with h2s rich pore waters during late burial diagenesis while the discordant orebodies formed by mobilization of the earlier conformable mineralization

production of subtidal tubular and surficial tempestites by hurricane kate caicos platform british west indies abstract storm infilling of deep open callianassa burrows with molluscan to peloidal packstone was the dominant style of preservable sedimentation produced by the passage of hurricane kate across caicos platform british west indies on 18 november 1985 this moderate hurricane was the first to affect an actively studied portion of the carbonate platform environments of the south florida bahama region in 19 years a time during which many of our concepts of storm sedimentation have evolved prior to hurricane kate much of the shallow platform interior peloidal packstone to grapestone grainstone had a sparse seagrass cover and a highly irregular bottom caused by abundant callianassa mounds hurricane kate flattened the mounded bottom of the platform interior and caused minor smothering and erosion of the seagrass beds a thin surficial tempestite though deposited over much of the platform was difficult to identify because it lacked a coarse base instead much of the reworked surface sediment poured down the large callianassa burrow entrances and filled the vast burrow networks with either a coarse molluscan packstone or peloidal skeletal packstone storm burrow filling tubular tempestites effectively removed the coarse fraction from contributing to a surficial storm layer ten percent of the upper 75 cm of platform interior sediment consists of tubular tempestites from hurricane kate

keuper stratigraphic cycles in the paris basin and comparison with cycles in other peritethyan basins german basin and bresse jura basin abstract high resolution sequence stratigraphy of the keuper paris basin is used to establish correlations between the basin centre evaporite series and the basin margin clastics series the high resolution correlations show stratigraphic cycle geometries the keuper consists of five minor base level cycles whth occur in the upper portion of the scythian carnian major base level cycle and the lower part of the carnian liassic major base level cycle the maximum relative rate of subsidence for the base level fall phase of the scythian carnian major cycle occurs in the eastern part of the paris basin during the base level rise phase of the carnian liassic major cycle the area of highest rate of subsidence shifted westwards and northwards this shift records the first occurrence of an independent paris basin which was no longer merely the western margin of the german basin two phases of tectonic movement influenced evaporite sedimentation and sequence geometries by creating areas of subsidence where halite could accumulate the second within the marnes irisees superieures induced a general westward and northward tilt of the basin concurrent migration of depocentres to the west and north produced an intra marnes irisees superieures truncation comparison of the stratigraphic records of the paris basin and of other triassic peritethyan basins german basin bresse jura basin and south east basin reveals numerous similarities the coastal onlap curve of the german keuper aigner and bachmann 1992 exhibits many similarities with the sequence evolution of the paris basin but the triassic succession is more complete in the german basin and more cycles are observed the major difference between these two basins during the keuper is that the marnes irisees inferieures minor base level cycle does not occur in the german basin in the bresse jura basin the major difference concerns the lettenkohle one minor base level cycle is recorded in the paris basin while no cycle is observed in the bresse jura basin

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

contributions of an ancient evaporitic type reservoir to subglacial lake vostok chemistry abstract we present here the first comprehensive study of the chemical composition of accretion ice from lake vostok ion chromatographic analyses were performed on samples obtained along the deeper part of the vostok ice core samples were taken from 3350 down to 3611 m depth both in glacier ice and subglacial lake ice the total ionic contents of two accretion ice layers a few meters thick and centered around 3540 and 3590 m depth are several times lower than those of glacier ice very low concentrations were also observed in the deeper part of accretion ice below 3609 m depth elsewhere the total ionic content is variable but remains 5 to 50 times higher than in glacier ice whatever its total ionic content the ionic composition of accretion ice is significantly different from what is observed in glacier ice it is dominated by sodium chloride homogeneously distributed throughout the ice lattice as well as calcium and magnesium sulfate likely located in solid inclusions or to a lesser extent at grain boundaries chemical considerations combined with additional studies of sulfur and oxygen isotopes in sulfate and iron measurements strongly suggest that glacier water recycling and bedrock hydrolysis do not play a prominent role in providing impurities to accretion ice it is more likely that nacl rich water carrying fine sulfate salt particles is sporadically incorporated in the ice accreting in a shallow bay upstream from vostok the origin of such salty water which should also contribute to lake salinity is discussed

integrated sequence stratigraphy facies stable isotope and palynofacies analysis in a deeper epicontinental carbonate ramp late jurassic sw germany abstract sequence stratigraphy in deeper water epicontinental carbonates such as in the upper jurassic of southern germany is difficult because the recognition of parasequences sequences and sequence boundaries is impeded by the paucity in diagnostic sedimentological criteria or stratal surfaces using the genetic stratigraphic approach and integrating facies stable isotope c o and palynofacies analysis two types of genetic depositional sequences can be discriminated small scale sequences are stacked into medium scale sequences which may record a 400 kyr milankovitch signal the medium scale sequences were correlated regionally using both gamma ray logs and stable isotope records regional correlations show that the depocentres are controlled by underlying palaeotectonic elements late palaeozoic troughs the rise fall turnarounds of medium scale sequences are marked by negative 18o peaks temperature maxima and reduced absolute palynoclast contents the fall rise turnarounds are marked by positive 18o peaks temperature minima and high absolute palynoclast contents the initiation and termination of sponge microbial mounds show characteristic patterns thrombolitic microbialites form during intervals of 1 reduced input of terrestrial palynomorphs interpreted as an increase in distality 2 decreasing 13c trends interpreted to be related to decreasing nutrient supply and 3 decreasing 18o values interpreted as phases of warming and rising relative sea level in contrast thrombolitic stromatolitic microbialites were found to occur during phases of 1 increasing input of terrestrial palynomorphs interpreted as an increase in proximality 2 increasing 13c values interpreted to reflect increasing terrestrial input and nutrient supply as well as increasing 18o values interpreted as phases of cooling and relative sea level falls isotopic and palynofacies evidence suggests that bioherms were terminated by sudden input of nutrients during relative sea level falls sedimentological criteria were clearly not sufficient to delineate a robust sequence stratigraphic framework

on the appearance of cyanobacterial calcification in modern stromatolites abstract in august 1991 calcified magnesian calcite filamentous cyanobacteria scytonema mirabile appeared on the surface of a modern lacustrine stromatolite lake r2 rangiroa atoll tuamotu archipelago french polynesia previously the topmost photosynthetic layer of this sediment was devoid of such microbial biomineralisers the calcified cyanobacteria are accompanied by magnesian calcite grains which are evocative of bacterial precipitates although the appearance of cyanobacterial calcification might be related to environmental changes in the lake in particular a decrease in water salinity the persistence of non calcified specimens of a filamentous cyanobacteria phormidium crossbyanum which was once a dominant species of the lake benthos shows that calcification and environmental conditions might be only indirectly related thus attempts to use the fossil record of calcareous cyanobacterial skeletons to infer changes in the chemical composition of past oceans cannot be made without due regard of biological processes like the appearance of new competitors

assessment of the record of the 1982 el chichon eruption as preserved in greenland snow variability in the so42 and cl time series for the 1980s from 12 shallow snow pits across the greenland ice sheet is used to evaluate the record of the 1982 el chichon eruption and the potential for recording a moderate northern equatorial eruption in a single greenland ice core composition of volcanic glass found in spring 1983 snow in one of the pits in the summit region matches that from el chichon glass thereby verifying the deposition of material from the eruption high na and cl concentrations in this same layer probably represent deposition of the reaction products of halite and h2so4 as observed in the stratosphere following the eruption these findings and the presence of a cl signal in five of the other pits indicate that the cl aerosol component of some eruptions has the potential to remain aloft for at least 1 year after the eruption some of these aerosols may be adsorbed onto tephra particles distinct so42 peaks that can be confidently linked to el chichon were found in only 50 of the records developed through subseasonal sampling however in several other pits an elevated baseline thought to represent more lengthy periods of el chichon aerosol deposition as opposed to deposition from a single snowfall event were observed smoothing of the original data by the calculation of annual so42 flux resulted in the presence of high flux values between 1982 and 1984 years thought to be affected by el chichon aerosol deposition in 9 of the 12 pits these results suggest that a single ice core from anywhere in greenland may record a signal from a northern equatorial eruption of magnitude similar to that of el chichon about 75 of the time this is despite the overall high levels of so2 4 deposition from anthropogenic sources that now make identification and quantification of the volcanic so2 portion of the record more difficult than obtaining the same data for preindustrial volcanism nevertheless composite records from all the pits sampled yielded stratospheric loading 20 mt and optical depth 0 13 estimates similar to stratospheric and satellite based measurements following the eruption equally high so42 concentration and flux values in snow from 1980 to 1982 reflect deposition from the series of middle to high northern latitude volcanic eruptions 1979 1981

a 44 kyr paleoroughness record of the antarctic surface two 788 m conductivity records from ice cores drilled at dome c antarctica provide an unprecedented opportunity to examine the past roughness of the antarctic surface by measuring the distribution of depth differences between synchronous events in the cores the surface height distribution can be estimated during time intervals in the past for the first time we publish a record of this type and consider its paleoclimatic implications the paleoroughness originating from sastrugi and dunes on the ice sheet surface is hypothesized to be related to the wind speed temperature and accumulation rate during the period of preservation the roughness record indicates only a slight decrease in the preserved surface roughness from the last glacial period 0 031 m root mean square r m s of surface deviation to the present 0 029 m r m s this result is surprising given the large change in temperature and accumulation rate that occurred during the last climatic transition however it could be consistent with modeling results suggesting low wind speeds on the east antarctic plateau during the last ice age if the possible influences of the accumulation and temperature changes are ignored additionally the reliability of the dome c ice core record is assessed and the probability of short term events being missing from the profile is determined these results are of particular interest when constraining the proportion of events that may be synchronously matched with other ice cores the principles and results present here allow inferences about the natural variation in ice core records generally

sequence stratigraphy and tectonosedimentary history of the upper jurassic of the eastern paris basin lower and middle oxfordian northeastern france in the present study the difficulty which lies in the identification of sea level fall discontinuities in deep depositional environments led the authors to use the transgressive surfaces i e the most noticeable surfaces in the present case to determine depositional cycles four 3rd order lower and middle oxfordian cycles were identified s1 s2 s3 and s4 in the eastern paris basin these four cycles can be organised into two lower frequency cycles so i and so ii which comprise the s1 s2 and the s3 s4 cycles respectively during the time intervals of the s1 s2 and s3 cycles sedimentation occurred along a southward dipping carbonate siliciclastic ramp prograding from the northern ardennes area the s4 cycle shows the development of a reefal distally steepened ramp which subsequently evolved into a flat topped platform as a result of the compensation infill of the available accommodation space by the carbonate production during a climatic warming in this case reef growth isopach and facies maps suggest synsedimentary activities of hercynian faults coevals with the floodings of the so i and so ii cycles one of these events generated a diachronism of the maximum flooding plicatilis zone during the so ii cycle between the northwestern and southeastern parts of the studied area the depositional patterns found in the eastern paris basin and the swiss jura show great similarities for the early middle oxfordian both regions were probably connected and recorded the same tectonosedimentary evolution in contrast a tectonic control certainly generated differences between the sequence stratigraphic framework of the eastern paris basin and the eustatic chart

volcanic forcing of climate over the past 1500 years an improved ice core based index for climate models 1 understanding natural causes of climate change is vital to evaluate the relative impacts of human pollution and land surface modification on climate we have investigated one of the most important natural causes of climate change volcanic eruptions by using 54 ice core records from both the arctic and antarctica our recently collected suite of ice core data more than double the number of cores ever used before reduces errors inherent in reconstructions based on a single or small number of cores which enables us to obtain much higher accuracy in both detection of events and quantification of the radiative effects we extracted volcanic deposition signals from each ice core record by applying a high pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation we then studied the spatial pattern of volcanic sulfate deposition on greenland and antarctica and combined this knowledge with a new understanding of stratospheric transport of volcanic aerosols to produce a forcing data set as a function of month latitude and altitude for the past 1500 years we estimated the uncertainties associated with the choice of volcanic signal extraction criteria ice core sulfate deposition to stratospheric loading calibration factor and the season for the eruptions without a recorded month we forced an energy balance climate model with this new volcanic forcing data set together with solar and anthropogenic forcing to simulate the large scale temperature response the results agree well with instrumental observations for the past 150 years and with proxy records for the entire period through better characterization of the natural causes of climate change this new data set will lead to improved prediction of anthropogenic impacts on climate the new data set of stratospheric sulfate injections from volcanic eruptions for the past 1500 years as a function of latitude altitude and month is available for download in a format suitable for forcing general circulation models of the climate system

background δ 34 s values of kupferschiefer sulphides in poland pyrite marcasite nodules regional background 34s values of pyrite marcasite nodules throughout the zechstein basin in poland have been measured to help estimate the proportion of externally derived sulphur in the kupferschiefer cu ag ores the 34s values of the 17 fes2 nodules measured range widely from 25 2 to 51 9 similar to the previously published 28 to 43 range in disseminated pyrite in the kupferschiefer the wide variation cannot be attributed to pyrite versus marcasite mineralogy amount of contained chalcopyrite or sphalerite carbonate versus shale host rock early versus late formation percent of included calcite or to size shape or texture there is also no relation with proximity to the centres of copper mineralization in southwestern poland where sulphides are typically isotopically heavier the 34s values do however vary directly with percent of host rock fragments included in the nodules repeat samples that were washed with acid or hot water show the same wide variation indicating that contamination by sulphate sulphur in the host rock is not a factor neither is organic sulphur because of its small volume instead the sulphur composition may be fundamentally controlled by the formation mechanism of the nodule whereby 34s rich sulphide is preferentially concentrated possibly replacing anhydrite lenses alternatively a network of host rock inclusions might act as a more accessible conduit for later 34s rich fluids to infiltrate the nodule and add to earlier 34s poor pyrite in the ore deposits higher 34s values of ore nodules suggest less indigenous sulphur in limestone than shale lithologies an isotopic temperature of 61 c from a chalcopyrite galena pair agrees with other estimates of 105 c higher values in ore nodules veinlets than in adjacent disseminations and the calculated 34spy value from a pyrite bornite mixture support the idea that metal bearing 34s rich fluids penetrated the kupfer schiefer through a network of fractures

evidence from sulfate mass independent oxygen isotopic compositions of dramatic changes in atmospheric oxidation following massive volcanic eruptions 1 oxygen isotopic ratio measurements 17o and 18o of background and volcanic sulfate preserved in south pole snow and ice were used to investigate the impact on the oxidation state of the atmosphere by explosive volcanic eruptions by comparing different paleovolcanic events we observe a difference in the so2 oxidation pathway between moderate tens of teragrams tg of so2 and massive hundreds of tg eruptions both isotopic data and numerical simulations suggest the shutdown of stratospheric oh chemistry and the opening of unaccounted oxidation channels for so2 such as the reaction with o 3p atoms when hundreds of tg of so2 are injected into the stratosphere it is very likely that oxidation rates and pathways and concentrations of most traces gases are also dramatically affected with potentially important implications for climate forcing

a jurassic counterpart for modern kopara of the pacific atolls abstract two types of laminated sediments are compared in this paper the kimmeridgian bituminous laminites of orbagnoux french southern jura mountains and the present day kopara of the french polynesia atolls or kiritimati christmas island from the pacific ocean the kopara is made of laminated sediments several tens of centimetres thick that cover the floors of most shallow 3 rich laminae the top few centimetres host a succession of bacterial populations from aerobic to strictly anoxic most carbonate grains are precipitated in situ due to bacterial activity s l the kimmeridgian bituminous laminae of orbagnoux are partly made of flat stromatolites that show many similarities with the kopara this analogy allows us to refine the interpretation of the southern jura platform where laminated organic matter rich carbonates were deposited in many places

depositional cycles composite sea level changes cycle stacking patterns and the hierarchy of stratigraphic forcing examples from alpine triassic platform carbonates carbonate platform deposits record a complex interplay of numerous geodynamic variables of which eustasy subsidence and sediment accumulation are prime factors in determining both the kilometer scale depositional sequence scale and meter scale depositional cycle scale stratigraphic packaging in this study we looked particularly at composite eustasy that is superimposed sea level fluctuations with different frequencies defined as orders and different amplitudes and the role it plays in the linkage between meter scale cyclic stratigraphy and kilometer scale sequence stratigraphy specifically we have investigated the relationship between low frequency third order 1 10 m y period depositional cycles and their component high frequency fourth 0 1 1 m y and fifth 0 01 0 1 m y order cycles through detailed stratigraphic analyses of alpine triassic platforms complemented by computer modeling on the basis of our results we suggest that in general there exists a hierarchy of stratigraphic forcing driven by composite eustasy that results in organized stacking patterns thickness subfacies character early diagenetic attributes of high frequency typically fourth and fifth order shallow water carbonate cycles dictated by low frequency third order relative sea level effects we suggest that systematic vertical changes in stacking patterns of high frequency cycles across a larger depositional sequence are due to systematic and predictable differences in depositional space available during the rising and falling stages of a relative third order sea level change we also suggest that these systematic variations in cycle stacking patterns will exist regardless of the mechanism responsible for generating the high frequency cycles be it an autocyclic or allocyclic mechanism this approach has major implications for the use of high frequency fourth and fifth order cycle characteristics to identify third order cycles in outcrops and cores of shallow water carbonates where stratigraphic control may be less than desirable this would constitute a valuable bridge between cyclic stratigraphy at the meter scale and sequence stratigraphy at the seismic scale we present two examples from triassic buildups of the alps the ladinian latemar buildup and the norian dolomia principale where a systematic succession of high frequency cycle stacking patterns and early diagenetic features exists within an overriding third order cycle sequence reflecting the interplay of short term high frequency fourth fifth order eustasy and long term low frequency third order eustasy in accordance with the hierarchy of stratigraphic forcing central to the interpretation of these examples is the demonstration that true eustatic rhythms are recorded in the high frequency cyclicity as verified by time series analyses and the use of fischer plots these examples can be modeled by computer under conditions of lag depth constrained sedimentation uniform subsidence and composite eustasy we also present two examples one from the alpine triassic the norian lofer cyclothems and one from the pleistocene of south florida that lack both a systematic succession of high frequency cycle stacking patterns and identifiable composite rhythms in the stratigraphic record despite the existence of composite high frequency eustasy in these examples we call upon 1 local tectonic forcing in the form of short term deviations in subsidence via faulting lofer example and 2 large differences in the relative amplitudes of different orders of high frequency sea level oscillations pleistocene example to explain the lack of composite rhythms and we present computer simulations to illustrate the concepts an understanding of composite relative sea level changes and the potential for a hierarchy of stratigraphic forcing provides the link between cyclostratigraphy and sequence stratigraphy and also has important implications regarding the stratigraphy of early diagenesis

genesis of kupferschiefer cu ag deposits by convective flow of rotliegendes brines during triassic rifting extensive and rich cu ag sulfide mineralization occurs in poland across the contact between the upper permian zechstein restricted marine sequence and the lower permian rotliegende continental volcanic and clastic sequence geologic evidence suggests that the mineralization was formed during late diagenesis when metalliferous brines migrated through the rotliegende leaching metals from the volcanic detritus and up the flanks of basement highs possibly along fracture porosity to the pyritic kupferschiefer and zechstein limestone above thick evaporites in the lower zechstein preclude a vertical flow through model but metal zoning attitudes suggest that the brines overturned where the rotliegende pinched out against the highs and moved laterally along the base of the zechstein toward the basin centers presumably to sink back down into the rotliegende completing a convection cell a middle triassic paleomagnetic age for the metal zoning and kimmerian attitudes of dilatant sulfide veinlets indicate that the mineralizing event coincided with continental rifting associated with the opening of the tethys ocean slow unicellular convection may be commonplace in sandstone basins where small lateral temperature gradients delta t exist but greater velocities are necessary to form large orebodies an anomalous tensional and thermal event such as rifting can increase velocities by increasing permeability slope angle or delta t the paleothermal structure of southwestern poland was determined by modeling the conductive heat flow in 14 one dimensional geologic sections which described the evolution of the basin architecture for 10 m y in the early triassic rifting was simulated by increasing the lower boundary condition from 500 degrees to 1 000 degrees c at 25 km this thermal pulse produced a surprisingly high delta t of 25 degrees c across the lubin ore district solely from differences in thermal conductivities between the basement high 4 2 w m degrees c the sandstone 2 5 w m degrees c and the shale basin center 1 25 w m degrees c unicellular convection patterns would be induced by the lateral boundary conditions of warm basement highs and cold shale centers and by the greater horizontal permeability these cells were 15 to 20 km long 400 m high and subhorizontal a slope angle of 2 degrees and a permeability of 1 d produces a convection velocity of 13 cm yr which with a copper solubility of 1 000 mg kg in 20 to 30 percent ca na cl brines in equilibrium with hematite can form the lubin deposit in less than 6 m y using a fracture permeability of 2 d and a solubility of 300 mg kg the time needed is less than 10 m y the konrad mine can be formed in similar time periods without the continuous recycling of the brine inherent in convective flow 20 times or more the metal solubilities needed to form the lubin deposits by a flow through model would be unreasonably high natural gases likely migrated along with the metalliferous brines and helped convection by creating secondary porosity and increasing the buoyancy of the fluids because the fluids are recirculated and not expelled convection provides a way in which secondary migration of methane and petroleum can occur effectively in solution as well as in separate phases

accommodation and supply a dual control on stratigraphic sequences abstract it is widely accepted that both eustatic and tectonically controlled regional changes of sea level have contributed to the record of stratigraphic sequences i suggest that environmental change be added as a third autonomous control sedimentologic principles clearly indicate that sequences and their systems tracts are controlled by the interplay of two rates the rate of change in accommodation space available for sedimentation and the rate of sediment supply sea level has direct control on accommodation but its influence on sediment supply is remote and easily overshadowed by environmental factors for instance the record of the most recent sea level rise is a transgressive systems tract where supply is low it is a prograding highstand systems tract in deltas where the supply is high examples of sequence boundaries generated by changes in sediment supply include tectonically driven shifts in sediment input into basins changes in ocean currents pulsating supply from failure of submarine slopes and drowning of carbonate platforms by environmental stress furthermore the stratigraphic sequences in fluviatile continental basins are physically removed from sea level induced changes in accommodation and must have formed by changes in the rate and pattern of supply subaerial exposure of marine sediments at the sequence boundary is a most important criterion for recognizing sea level cycles as opposed to supply cycles other criteria include downstepping of shelf breaks and characteristic patterns in the spacing of time lines within sequences some third order cycles ca 0 5 3 ma duration meet these criteria others do not cycle stacking patterns and the shifting facies belts on cratons indicate that many second and third order cycles lack pronounced exposure unconformities and represent gradual changes superimposed on more rapid shorter oscillations seismic data yield poor images of these gradational changes because they lack resolution seismic models of outcrops show that near the limits of resolution the seismic tool tends to portray rapid changes in facies and bed thickness i e lateral variations in supply as unconformities seismic unconformities do not necessarily correspond to unconformities in outcrop the succession of stratigraphic sequences is best considered a composite record of sea level and environmental change separating the various controls requires carefully planned experiments work on the oxygen isotope curve another proxy for sea level has set an example in this respect

high precision dating of volcanic events a d 1301 1995 using ice cores from law dome antarctica a record of volcanic activity over the period a d 1301 1995 has been extracted from three law dome ice cores east antarctica the record dating is unambiguous at the annual level from a d 1807 to 1995 and has an uncertainty of 1 year at a d 1301 signals from 20 eruptions are preserved in the record including those of two unknown eruptions with acid deposition beginning in a d 1810 8 and a d 1685 8 the beginning of the ice core signal from the a d 1815 tambora eruption is observed in the austral summer of a d 1816 1817 the mean observed stratospheric transport and deposition time to law dome from the eruption site is 1 5 years 0 6 years from 11 well dated eruptions the largest eruption observed in the law dome record has its maximum in a d 1460 with volcanic sulfate deposition beginning in the austral winter of a d 1459 this event is also observed in other ice core records and is attributed to the volcano kuwae with an eruption date in the range a d 1455 9 1459 9 if all sources of error are considered this is at least three years later than the date previously ascribed by dendrochronological and historical studies

metal accumulation during and after deposition of the kupferschiefer from the sangerhausen basin germany abstract a densely sampled profile 58 cm in thickness composed of 13 samples of the kupferschiefer and overlying zechstein carbonates from the sangerhausen basin germany has been analysed by various geochemical and microscopic methods in order to clarify the mechanism of base metal accumulation in this location the kupferschiefer is only slightly influenced by the hematite bearing oxidized fluids called rote faule the determination of facies dependent parameters along the profile indicates that kupferschiefer from the sangerhausen basin was largely deposited in a marine environment only at the beginning of kupferschiefer sedimentation did euxinic conditions prevail the bottom part of the profile is significantly enriched in trace elements such as cu ph zn as co ag and u the cu concentration amounts to 19 88 wt post depositional oxidation of the organic matter is observed only in the transition zone between the kupferschiefer and the zechstein conglomerate indicating the influence of ascending oxidizing brines microscopic analyses show that only fe sulfides form framboidal textures cu minerals are present along the total profile preferentially in fractures and as patchy structures composed of chalcocite chalcopyrite and bornite in the highly mineralized bottom section cu sulfides are associated with pyrobitumen sparry calcite and arsenopyrite results from maturation studies of organic matter suggest that the maximum temperature affecting the kupferschiefer was approximately 130 c a 3 step process of metal accumulation is proposed during deposition of the sediment framboidal pyrite and pyrite precursors were precipitated by bacterial so 4 2 reduction bsr during diagenesis the pyrite and pyrite precursors were largely replaced by mixed cu fe minerals and by chalcocite pr in the section with very high cu contents 8 reduced sulfur from fe sulfides was not sufficient for precipitation of cu and other trace metals from ascending solutions in this part of the profile thermochemical so 4 2 reduction tsr occurred after pyrite replacement as indicated by the presence of pyrobitumen and sparry calcite

delineating sequence stratigraphic patterns in deeper ramp carbonates quantitative palynofacies data from the upper jurassic kimmeridgian of southwest germany abstract the delineation of sequence stratigraphic patterns in deeper ramp carbonates is notoriously difficult using sedimentological criteria hence in an effort to better understand the processes controlling the formation of deeper water carbonate ramps fully quantitative palynofacies analyses were carried out on two cores from the upper jurassic kimmeridgian of the swabian marl basin sw germany to eliminate the effect of variable carbonate content absolute palynoclast abundances i e particles per gram of sediment were calculated with respect to the non carbonate fraction of the original sediment the palynofacies data were supplemented by bulk sediment oxygen isotope data and sedimentological information terrestrial and marine palynoclast groups show in phase cyclical absolute abundance patterns in both cores investigated highest carbonate adjusted absolute abundances of terrigenous palynoclasts are interpreted to indicate sea level lowstands and vice versa the in phase distribution of marine and terrestrial palynoclast groups points towards a coupling between the terrestrial and marine realms increased absolute abundances of terrigenous palynoclasts are interpreted to represent intervals of enhanced land derived nutrient input into the marine system such higher nutrient availability would have caused higher phytoplankton productivity as evidenced in increased absolute abundances of marine palynomorphs hence marine productivity in the epeiric setting of the swabian marl basin was strongly controlled by the nutrient flux from the surrounding landmasses in the palynofacies and bulk sediment 18o records two hierarchies of sequences are recognized well pronounced medium scale sequences with thicknesses of 5 20 m are built by the stacking of smaller scale sequences with thicknesses of 3 7 m heavier 18o values coincide with high absolute abundances of terrigenous palynoclasts based on this observation a model for environmental fluctuations is proposed time intervals with high sea level were characterized by relatively high water temperatures whereas time intervals with low sea level coincided with relatively low water temperatures estimates of ammonite zone ages available from the literature were used to constrain the duration of medium scale sequences when taking into account the range of dating uncertainties the obtained value of ca 370 kyr appears reasonably close to the duration of the 400 kyr eccentricity cycle we speculate that the formation of medium scale sequences as evidenced in our palynoclast and 18o records may be related to eccentricity driven insolation changes that caused sea level changes with higher insolation leading to a sea level rise this would imply that the regional record of sea level and temperature fluctuations within the epeiric swabian marl basin reflects climatic changes that occurred on a more global scale the integration with sedimentological data shows that marl dominated intervals were deposited during early sea level rise and under cooler conditions whereas limestone dominated intervals formed during intervals of high sea level and under warmer conditions

hydrocarbon biomarkers in the topla mežica zinc lead deposits northern karavanke drau range slovenia paleoenvironment at the site of ore formation the mississippi valley type zinc and lead deposits at topla 250 150 metric tons t of ore grading 10 wt zn and 3 3 wt pb and me ica 19 million metric tons mt of ore grading 5 3 wt pb and 2 7 wt zn occur within the middle to upper triassic platform carbonate rocks of the northern karavanke drau range geotectonic units of the eastern alps slovenia the ore and host rocks of these deposits have been investigated by a combination of inorganic and organic geochemical methods to determine major trace and rare earth element ree concentrations hydrocarbon distribution and stable isotope ratios of carbonates kerogen extractable organic matter and individual hydrocarbons these data combined with sedimentological evidence provide insight into the paleoenvironmental conditions at the site of ore formation the carbonate isotope composition the ree patterns and the distribution of hydrocarbon biomarkers normal alkanes and steranes suggest a marine depositional environment at topla a relatively high concentration of redox sensitive trace elements v mo u in the host dolostones and ree patterns parallel to that of the north american shale composite suggest that sediments were deposited in a reducing environment anoxic conditions enhanced the preservation of organic matter and resulted in relatively higher total organic carbon contents up to 0 4 wt the isotopic composition of the kerogen 13 c kerogen 29 4 to 25 0 15 n kerogen 13 6 to 6 8 suggests that marine algae and or bacteria were the main source of organic carbon with a very minor contribution from detrital continental plants and a varying degree of alteration extractable organic matter from topla ore is generally depleted in 13 c compared to the associated kerogen which is consistent with an indigenous source of the bitumens the mineralization correlates with 15 n kerogen values around 0 per mil 13c depleted kerogen 13c enriched n heptadecane and relatively high concentrations of bacterial hydrocarbon biomarkers indicating a high cyanobacterial biomass at the site of ore formation abundant dissimilatory sulfate reducing bacteria feeding on the cyanobacterial remains led to accumulation of biogenic h 2 s in the pore water of the sediments this biogenic h 2 s was mainly incorporated into sedimentary organic matter and diagenetic pyrite higher bacterial activity at the ore site also is indicated by specific concentration ratios of hydrocarbons which are roughly correlated with total pb plus zn contents this correlation is consistent with mixing of hydrothermal metal rich fluids and local bacteriogenic sulfide sulfur the new geochemical data provide supporting evidence that topla is a low temperature mississippi valley type deposit formed in an anoxic supratidal saline to hypersaline environment a laminated cyanobacterial mat with abundant sulfate reducing bacteria was the main site of sulfate reduction

spatial and seasonal variations of the snow chemistry at the central filchner ronne ice shelf antarctica the chemical stratigraphy of the surface firn of the central filchner ronne ice shelf was determined in conjunction with stable isotopes from shallow firn cores and snow pit samples collected at 1 1 widely distributed sites and covering a time period of at least 20 years the chemical analysis included ecm profiling and the determination of chloride non sea salt nss sulphate methanesulphonate msa nitrate and partly sodium and bromide throughout the investigated area winter time nss sulphate levels are found to be substantially negative indicating that the sulphate to sodium ratio in airborne sea salt particles is depleted by a factor of 5 approximately in relation to the bulk sea water ratio while winter firn layers appear to be marked by episodic events of large sea salt inputs pronounced annual cycles with maxima in summer firn layers are commonly observed for the ecm signal and for nss sulphate nitrate and msa at all sites for msa however this phase relation is almost reversed for depths greater than 3 4m the mean impurity levels consistently are strongly depleted with increasing distance from the ice edge by about 30 100 km for sea salt 25 100 km for msa and only 10 100 km for nss sulphate however no substantial trend is observed for nitrate it is concluded therefore that the sea salt and the biogenic sulphur compounds deposited on the filchner ronne ice shelf mainly originate from the adjacent weddell sea further important implications of the continental effects are a an atmospheric residence time of nss sulphate apparently exceeding that of msa probably due to the supplementary sulphate production on the ice shelf from biogenic so 2 and b a substantial limitation of the potential of deep ice cores already drilled on the filchner ronne ice shelf in extracting reliable net temporal changes of sea salt and biogenic sulphur species

cyanobacteria proliferation in the cenomanian turonian boundary interval of the apennine carbonate platform immediate response to the environmental perturbations associated with oae 2

stratigraphic architecture and gamma ray logs of deeper ramp carbonates upper jurassic sw germany abstract the objective of this paper is to contribute to the development of sequence stratigraphic models for extensive epicontinental carbonate systems deposited over cratonic areas epicontinental carbonates of the sw german upper jurassic were analysed in terms of microfacies sedimentology and sequence stratigraphy based on 2 5 km of core 70 borehole gamma ray logs and 24 quarries facies analysis revealed six major facies belts across the deeper parts of the carbonate ramp situated generally below fair weather wave base and mostly below average storm wave base but in the reach of occasional storm events observed stratigraphic patterns differ in some aspects from widely published sequence stratigraphic models 1 elementary sedimentary cycles are mostly more or less symmetrical and are thus referred to as genetic sequences or genetic units aaapg bull 55 1971 1137 frazier d e 1974 depositional episodes their relationship to the quaternary stratigraphic framework in the northwestern portion of the gulf basin university of texas austin bureau of economic geology geologicalo circular 71 1 aapg bull 73 1989 125 galloway w e hobday d k 1996 terrigenous clastic depositional systems 489 pp springer cross t a baker m r chapin m s clark m s gardner m h hanson m s lessenger m a little l d mcdonough k j sonnenfeld m d valasek d w williams m r witter d n 1993 applications of high resolution sequence stratigraphy to reservoir analysis edition technip 1993 11 33 bull cent rech explor prod elf aquitaine 16 1992 357 homewood p mauriaud p lafont f 2000 best practices in sequence stratigraphy elf ep mem 25 81 pp homewood p eberli g p 2000 genetic stratigraphy on the exploration and production scales elf ep mem 24 290 pp in contrast to the asymmetrical shallowing upward parasequences of the exxon approach 2 neither sequence boundaries nor maximum flooding surfaces could be clearly delineated cycle boundaries are generally not represented by sharp stratal surfaces but are always transitional and thus referred to as turnarounds nor pet soc spec publ 8 1998 171 several types of genetic sequences were delineated both major types of facies and sequences show characteristic gamma ray log signatures based on the cycle stacking and the gamma ray patterns a hierarchy of sequences was recognized probably driven in part by 100 000 and 400 000 year milankovitch signals the cyclicity allowed regional correlations across various depositional environments such as sponge microbial bioherms and coeval basins the basin wide correlation revealed evidence for a subtle clinoform type stratigraphic architecture along very gentle slopes rather than a so far assumed simple layer cake pattern

chemistry and stromatolites of the sea linked satonda crater lake indonesia a recent model for the precambrian sea abstract the abundance of in situ calcified stromatolites in the precambrian paleontological record and their absence from modern seas is still an enigma we report on the discovery of the first recent in situ calcified stromatolites growing in a sea linked environment the stromatolites are produced by coccoid cyanobacteria and started to grow 4000 yr ago in the crater lake of satonda island indonesia compared to seawater the lake has gained alkalinity and lost ca its ph 8 45 as well as its saturation with respect to calcite is significantly higher than in seawater the additional alkalinity is provided by biogenic co2 and subsequent weathering of volcanic silicates satonda crater lake may provide an analogue to the stromatolite sustaining precambrian marine environments which therefore may have been more alkaline than present day seawater this conclusion is congruent with the recently advanced hypothesis of an early soda ocean

the role of organically bound sulphur in stratiform ore sulphide deposits abstract low and high molecular weight organic sulphur compounds were analyzed in a selected number of samples of the permian kupferschiefer poland their significant presence in these mature samples supports the hypothesis that during deposition and shortly thereafter labile organic sulphur compounds must have been very abundant this assumption has led to a new model for metal accumulation based on a slow and gradual release of sulphur from these labile organic sulphur compounds during increasing diagenesis

a 200 year sub annual record of sulfate in west antarctica from 16 ice cores sixteen high resolution ice core records from west antarctica and south pole are used to examine the spatial and temporal distribution of sulfate for the last 200 years the preservation of seasonal layers throughout the length of each record results in a dating accuracy of better than 1 year based on known global scale volcanic events a dual transport source for west antarctic sea salt ss so4 2 and excess xs so4 2 is observed lower tropospheric for areas below 1000 m elevation and mid upper tropospheric stratospheric for areas located above 1000 m our xsso4 2 records with volcanic peaks removed do not display any evidence of an anthropogenic impact on west antarctic so4 2 concentrations but do reveal that a major climate transition takes place over west antarctica at 1940 global scale volcanic eruptions appear as significant peaks in the robust spline residual xsso 4 2 records from sites located above 1000 m elevation but do not appear in the residual records from sites located below 1000 m

changes in biomarker abundances and sulfur isotopes of pyrite across the permian triassic p tr schuchert dal section east greenland abstract in this study we report on biomarker abundances through parts of the permian triassic boundary ptb of schuchert dal east greenland that contains rich marine faunal records and excellent terrestrial palynological records biomarker abundances and sulfur isotopes are used to correlate the series of events including changes in element cycling and associated redox conditions of the ocean surrounding the collapse of the marine and terrestrial ecosystems through this record of a major crisis of life on earth during a mass extinction episode the upper schuchert dal formation contains a low diversity palynological assemblage ascribed to arborescent cordiaite conifer pteridosperm vegetation samples from this pre collapse interval are characterised by high abundances of dibenzofuran dbf dibenzothiophene dbt and biphenyl since these compounds have similar base structures and show comparable abundance curves it is plausible that they probably derive from a common source we propose that phenolic compounds of lignin of the woody plants present during this period could be the source for dbf dbt and biphenyl the redox conditions during this period of time also support the formation of dbf and dbt just above the extinction interval there is a dramatic decrease in the abundances of dbf and dbt which occurs at the same time as a sudden change in the stable sulfur isotopic composition 34s of pyrite indicating a change in redox conditions from oxic to anoxic euxinic conditions 34s values leading up to the extinction are highly depleted in the heavy sulfur isotope about 40 vs vcdt whilst shortly after the extinction interval much more positive isotope values are observed about 25 an inferred change in the biogeochemical sulfur cycle is supported by facies evidence from similar neighbouring sections it is suggested that two processes are operating closely here 1 changes in redox conditions and 2 extinction and or transgression accounting for the absence of woody material

an outer ramp to basin plain transect interacting pelagic and calciturbidite deposition in the eocene oligocene of the tuscan domain adria microplate italy abstract the interaction of ramps basin plains and turbidite systems on the scale of tens of km has been rarely observed in fossil examples deep marine eocene oligocene beds are exposed in the axial zone of the chianti mountains italy and compose a regionally continue stratigraphic succession known as the scaglia toscana formation the formation was deposited in the tuscan domain of the adria microplate this research aims at depicting its depositional architecture and evolution in the type area stratigraphic and sedimentologic analyses were performed on a ca 25 km long transect that includes depositional systems sectioned both in the down and along dip directions shaly carbonate deposits compose a complex of interacting ramps basin plains and turbidite floor fan systems ramp deposits accumulated above the lysocline and in oxic conditions basin plain beds were deposited below the lysocline and were subject to episodes of oxygen depletion turbidity flows fed elongate fan lobes characterized by poor channelisation the basin palaeogeography hampered the development of slope apron turbidite systems the eocene oligocene geodynamic setting of the tuscan domain was characterized by the evolution of a peripheral bulge and by the early structuring of a foredeep basin syn sedimentary tectonism acted a primary role in the basin scale arrangement however other mechanisms also contributed to the local facies distribution including the disposition of sediment source areas and intrabasinal confinement morphologies as well as relative oscillations of the depositional surface with respect to the lysocline and oxycline

coastal antarctic aerosol and snowfall chemistry aerosol samples have been collected at three stations on the coast of antarctica at dumont d urville station samples have been collected for 4 years at halley station for 2 years and at neumayer station for 12 years fresh snow samples have also been collected at the three sites at halley daily surface snow samples were taken as well as firn cores covering the sampling period meteorological including upper air data are available at the three sites in the subsequent papers of this special section the data from the three stations have been combined in order to make general statements about the chemistry of aerosol in coastal antarctica about the differences between sectors of antarctica and about the relationship between air concentrations and the chemistry that is eventually seen in ice cores this paper summarizes the samples collected and the sampling methods used at the three sites it also highlights the main role of each paper in this special section

methanesulfonic acid in south polar snow layers a record of strong el nino in this paper we present a detailed study of methanesulfonic acid msa and non sea salt sulfate nss so4 content in recent south polar precipitation these two species are major oxidation products of dimethylsulfide dms which is mainly produced by marine biota the nss so4 content of south polar snow layers deposited over the 1922 1984 time period remained rather stable except short term increases after the mt agung 1963 and the el chichon 1982 eruptions at the opposite the msa profile shows over the same time period several sporadic 0 5 to 2 years increases 2 to 10 times background level taking into account an uncertainty of 1 3 years in the dating of snow layers all these msa events seem to be correlated to major enso el nino southern oscillation events having occured over the last sixty years 1925 26 1941 1957 58 1972 73 and 1982 83 the relatively high msa nssso4 weight ratios r observed in the corresponding snow layers suggest that these events reflect enhanced dms emissions from the antarctic ocean this suggested connection between enso and high dms marine emissions at high southern latitudes is discussed in terms of atmospheric and oceanic circulation

phenyldibenzofurans and phenyldibenzothiophenes in marine sedimentary rocks and hydrothermal petroleum abstract the phenyl derivatives of dibenzo b d furan and dibenzo b d thiophene so far not reported in geological samples have now been identified in some sedimentary rocks bitumen and hydrothermal petroleum through a comparison of their retention times and mass spectra with those of authentic standards all four possible positional isomers were detected for each phenyldibenzo b d furan phdbf and phenydibenzo b d thiophene phdbt their elution sequence is 1 4 2 and 3 phenyldibenzo b d furan and 1 4 2 and 3 phenyldibenzo b d thiophene on apolar stationary phases in contrast to phenyldibenzofurans the distributions of the thiophene series is controlled mainly by the organic matter maturity in the most mature samples 4 2 and 3 phdbts prevail over 1 phdbt while less mature samples contain mainly 4 phdbt or 1 phdbt and 2 3 phdbts occur at comparable concentrations however in samples of low maturity in addition to the phenyldibenzo b d thiophene c 18 h 12 s series other structural isomers of c 18 h 12 s possessing very similar mass spectra were detected these are likely to be either naphthylbenzo b thiophenes and or phenylnaphtho b thiophenes phdbfs and phdbts are likely to be intermediate products in the formation of more condensed heterocyclic polycyclic aromatic compounds like triphenyleno 1 12 bcd thiophene and triphenyleno 1 12 bcd furan and benzobisbenzofurans and benzobisbenzothiophenes which are commonly detected in geological samples

temporal variations and sources of elements in the south pole atmosphere 1 nonenriched and moderately enriched elements high volume particle samples were collected from 1979 to 1983 from the south pole atmosphere and analyzed by nuclear methods the new results are combined with similar studies at the south pole there is no trend of concentrations during 12 years of sampling but concentrations of elements fluctuate through seasonal cycles concentrations of elements associated with crustal dust and sea salt showed opposite seasonal variations concentrations of most crustal elements are low during winters but double during summers concentration of marine elements are low in the summers and high in winters enrichment factors of some crustal elements such as ba la ce yb and hf are higher in the winter than summer indicating the presence of a second crustal component with a different chemical composition in the south pole atmosphere a similar difference in the crustal enrichment factor of co is due to the influence of volcanic or anthropogenic sources sulfate seasalt meteoritic particles volatiles and two different types of crustal particles are found to be components of the south polar aerosols the relative contribution of each component to total aerosol mass is as follows crustal 4 0 in summer 2 5 in winter marine elements 16 6 in summer 78 6 in winter sulfate 77 5 in summer 18 0 in winter meteoritic particles 0 1 in summer 0 1 in winter volatiles 0 9 in summer 0 5 in winter crustal component ii 0 8 in summer 0 7 in winter

microbialites in a modern lagoonal environment nature and distribution tikehau atoll french polynesia abstract microbialites including stromatolitic structures gelatinous masses and mats develop in tikehau lagoon tuamotu french polynesia on the flanks and slopes of numerous pinnacles and motu islets between 0 and 25 m deep on coral colonies algal tufts or on lagoonal sediments individual stromatolitic structures consist of hemispherical domes and are produced by monospecific populations of filamentous cyanobacteria belonging to three distinctive phormidium species symploca and possibly to one new species of schizothrix gelatinous masses hanging from the ceiling of caverns are produced by phormidium laysanense microbial mats are well developed at all depths on pinnacle slopes and are produced by either monospecific or mixed cyanobacterial populations the study of micro and ultrastructure of stromatolites reveals that they result both from trapping and binding of sediments and from carbonate precipitation in addition to phototrophic biomineralization pervasive carbonate precipitation occurred in association with decaying organic matter the basic constructional elements of the precipitated carbonate consist of 0 1 0 2 m rounded bodies that form very fine anhedral to subhedral micrite their surfaces comprise extremely small carbonate granules 20 50 nm gradual changes ageing in the ultrastructure of carbonate precipitates include the precipitation of successive euhedral calcite layers around these grains widespread development of microbialites in this pristine lagoonal environment results from rapid blooms of microbial benthic communities possibly induced by temporary and local nutrient pulses nutrients seem to undergo a restricted circulation between the sediment and pinnacle reef frameworks pinnacles and reef islets are repeatedly affected by catastrophic storm events which cause redistribution of sediments and nutrients

quantifying the pinatubo volcanic signal in south polar snow recent snow and firn core samples from south pole contain increased sulfate so42 concentrations during 1992 1994 as a result of the june 1991 pinatubo eruption and the august 1991 cerro hudson eruption in chile traces of pinatubo tephra volcanic ash were identified in the 1993 and 1994 snow layers supporting the conclusion that increased so42 in 1993 1994 is from the pinatubo eruption although the pinatubo eruption preceded hudson its so42 signal in south polar snow follows and is resolved from that of hudson the deposition of the pinatubo so42 aerosol was delayed due to the long transport to the high southern latitudes and its initial existence at high altitudes in the antarctic atmosphere multi year multi site sampling demonstrates that the volcanic signals are well preserved and spatially consistent measurements on 2 firn cores show that the south pole so so42 flux from pinatubo is 10 9 1 2 kg km 2 over 2 2 years while the hudson flux is 3 2 0 6 kg km 2 in 1 1 years these results when combined with satellite determined pinatubo sulfur dioxide so2 emission make it possible to link quantitatively the atmospheric aerosol mass loading from a low latitude volcanic eruption to its signal in polar ice cores

integrated characterization of carbonate ramp reservoirs using permian san andres formation outcrop analogs the san andres formation permian guadalupian of the permian basin is representative of carbonate ramp reservoirs in that it has highly stratified character complex facies and permeability structure and generally low recovery efficiencies of 30 of original oil in place the approach used here to describe carbonate ramp reservoirs such as the san andres formation produces detailed reservoir models based on integration of sequence stratigraphic analysis petrophysical quantification through definition of rock fabric flow units and fluid flow simulation synthesis of these subdisciplines clarifies which aspects of the geologic petrophysical model are most significant in predicting reservoir performance and ultimately in understanding the location of remaining oil satur tion the san andres formation crops out along the algerita escarpment a long oblique dip continuous shelf to basin exposure in the central guadalupe mountains these outcrops provide a unique opportunity to study lateral relationships in geologic and petrophysical structure analogous to those occurring between wells in subsurface reservoirs on the basis of sequence stratigraphic analysis three scales of cyclicity are recognized depositional sequences high frequency sequences and cycles examination of the cycles in two detailed window areas provides a practical scale for petrophysical quantification and fluid flow simulation an understanding of cycle position within the high frequency sequence framework also provides predictive information petrophysical analysis revealed six rock fabric groups dominated by intergranular separate vug or dense intercrystalline pore types comparison of these rock fabric groups with facies descriptions produced a rock fabric flow unit model that honors the geologic structure of the cycle and sequence framework permeability data were averaged within rock fabric flow units using a geometric mean approach based on fine scale fluid flow modeling of deterministic and stochastically generated permeability fields two dimensional black oil fluid flow models illustrate that 1 major differences in sweep efficiency and fluid flow performance are predicted when linear interwell interpolations are compared with actual interwell scale geologic structure as determined by outcrop geologic and petrophysical mapping 2 an understanding of static geologic petrophysical conditions provides only a partial understanding of reservoir performance defined by the interaction of these static properties and dynamic properties of fluid flow interaction within the flow unit architecture and 3 because of the orderly distribution of high and low permeability facies within cycle stacks of high frequency sequences this larger scale of geologic description can give a reasonable first order approximation of fluid flow patterns and early breakthrough end page 181

geochemical study on a well in the western canada basin relation of the aromatic distribution pattern to maturity of organic matter abstract thirty one rock samples from a western canada basin well have been analysed for aromatics using glass capillary gas chromatography with simultaneous flame ionization and sulfur selective flame photometric detection a uniform aromatic distribution pattern with a marked predominance of di and tricyclic aromatic hydrocarbons was observed throughout a depth interval of 3000 meters comprising cretaceous and jurassic sediments the very high relative abundance of sulfur aromatics at two narrow intervals in the triassic and mississippian is attributed to a major change in facies gradual changes with increasing depth have been observed for a series of compound ratios which had been calculated from the isomers of methyl and dimethylphenanthrene and their parent compounds these changes reflect the increasing thermal maturation of the sedimentary organic matter a methylphenanthrene index mpi has been introduced which exhibited a very good correlation with vitrinite reflectance data the mpi is the first maturity parameter which is based on a series of aromatic hydrocarbons this hydrocarbon internal maturity parameter permits the recognition and definition of maturity levels in extracts which can be compared to the maturity e g vitrinite reflectance of source rocks

kopara in polynesian atolls early stages of formation of calcareous stromatolites widespread modern calcareous stromatolites known as kopara in the vernacular language on the tuamotu archipelago have been found accreting on the bottom of shallow generally 1 m depth lakes located on the rims of these french polynesian atolls they are flat gelatinous sediments several tens of centimetres thick with lamination comprised of vertically alternating red organic rich and white carbonate rich millimetre thick laminae they originate from benthic microbial communities mainly composed of cyanobacteria generally dominated by the genus phormidium the living cyanobacteria occupy only the top 1 3 cm of the deposit the red organic matter below being made of remnants of the dead microbes essentially of polysaccharide microfibrils inherited from the sheaths and arranged into a three dimensional network enclosing pores ranging from a few tens of angstroms to a few micrometres wide the carbonates are predominantly high mg calcite 9 19 mole mgco3 which precipitated as micron size bunches within the pores on walls of the organic network it is sometimes accompanied by aragonite less than 22 of the total mineral fraction when present and lesser high mg calcite allochthonous bioclasts which occasionally form up to few centimetres thick detrital intercalations the pore waters are variable mixtures of freshwater rain or ground water and sea water from the ocean or lagoon which are feeding waters of the lakes their chemistry deviate from a straight mixture gradient with respect to ca2 mg2 and alkalinity under the influence of local calcification and bacterial processes e g ammonia production sulphate reduction within the sediments it is hypothesized that the calcification is initiated at carboxylic sites on the walls of the polysaccharide network the pores acting as confining organic compartments with increased internal supersaturation lamination is suggested to be due to the combined effects of the stratification of the microbial activity of the deposits and alternations of fresh and saline periods within the lakes lacustrine environments on oceanic atolls are found to be important habitats of modern microbialite formation

tales of volcanoes and el nino southern oscillations with the oxygen isotope anomaly of sulfate aerosol the ability of sulfate aerosols to reflect solar radiation and simultaneously act as cloud condensation nuclei renders them central players in the global climate system the oxidation of s iv compounds and their transport as stable s vi in the earth s system are intricately linked to planetary scale processes and precise characterization of the overall process requires a detailed understanding of the linkage between climate dynamics and the chemistry leading to the product sulfate this paper reports a high resolution 22 y 1980 2002 record of the oxygen triple isotopic composition of sulfate so4 aerosols retrieved from a snow pit at the south pole observed variation in the o isotopic anomaly of so4 aerosol is linked to the ozone variation in the tropical upper troposphere lower stratosphere via the ozone el nino southern oscillations enso index oei higher 17o values 3 3 4 5 and 4 2 were observed during the three largest enso events of the past 2 decades volcanic events inject significant quantities of so4 aerosol into the stratosphere which are known to affect enso strength by modulating stratospheric ozone levels oei 6 and 17o 3 3 oei 11 and 17o 4 5 and normal oxidative pathways our high resolution data indicated that 17o of sulfate aerosols can record extreme phases of naturally occurring climate cycles such as ensos which couple variations in the ozone levels in the atmosphere and the hydrosphere via temperature driven changes in relative humidity levels a longer term higher resolution oxygen triple isotope analysis of sulfate aerosols from ice cores encompassing more enso periods is required to reconstruct paleo enso events and paleotropical ozone variations

organic geochemistry and mineralogy i characterisation of organic matter associated with metal deposits abstract as geochemical appraisals of mineral regions of commercial prospectivity evolve the organic matter associated with metal rich ores has attracted greater attention petroleum basin and modern seafloor hydrothermal vent studies have suggested that organic matter can have a significant influence on the behaviour of mineralising fluids there have been many isolated reports of certain organic compositional or morphological e g pyrobitumen features showing an apparent relationships with hydrothermal fluids or minerals raising expectations that organic based parameters might be useful to mineral exploration however the understanding of organic inorganic relationships in earth systems is far from complete for example the detailed mechanics of the interaction of organics with hydrothermal fluids over geological time remain largely undefined organic geochemistry studies have traditionally involved the measurement and interpretation of the hydrocarbon composition of sedimentary rocks here we review the types of aliphatic hydrocarbons aromatic hydrocarbons and metalloporphyrins often detected from organic geochemical investigations in mineral rich regions such molecular data can be particularly diagnostic of biochemical sources and the palaeo environments at the time mineral associated organic matter was deposited sub surface trends of hydrocarbon alteration may also reflect major biogeochemical processes such as thermal maturity and biodegradation organic geochemistry data can also occasionally provide information about the nature e g origin composition temperatures and migration pathways of hydrothermal fluids and can make a contribution to holistic ore genesis models the well preserved organic matter associated with the economic here s your chance pb zn ag mine paleoproterozoic barney creek formation mcarthur basin australia and the transition metal rich early permian kupferschiefer formation germany poland have attracted significant attention a more detailed summary of the organic character of these deposits is provided to highlight the contribution organic geochemistry can make to understanding mineralisation processes most organic geochemical studies of highly mineralised regions however have not adequately addressed the significance of organic matter to mineralisation a slightly different analytical focus than traditionally used for exploration appraisal of petroleum hydrocarbons may be required to properly evaluate the significance of organic species to the mobilisation transport and deposition of ore metals the characterisation and subsequent thermodynamic modeling of organic substances and complexes within metalliferous hydrothermal systems will contribute to a better understanding of the nature and role of organic inorganic fluids or other affiliated organics in ore systems

messinian stromatolite thrombolite associations santa pola se spain an analogue for the palaeozoic stromatolite thrombolite associations are the dominant facies forming large portions of the santa pola carbonate platform se spain during deposition of the terminal carbonate complex tcc the tcc the last period of marine sedimentation in the western mediterranean associated with the messinian salinity crisis comprises a ne sw trending thrombolite reef with occasionally interlayered stromatolite horizons and a predominantply stromatolite and oolite facies in the back reef area the stromatolites are mainly dome shaped but fine columnar or wavy undulose forms can occur the stromatolites form huge bioherms extending tens to hundreds of metres they are finely laminated with alternating layers of dolomicrite and dolomicrospar the dolomicrite layers appear to be a primary dolomite precipitate whereas the dolomite crystals in the dolomicrospar layers apparently formed around a meta stable nuclei which was subsequently dissolved or degraded the low content of sand sized particles in the stromatolitic layers indicates formation under low energy conditions possibly on a tidal flat as reported from other areas in the western mediterranean deposition of the tcc at santa pola was apparently cyclic whereby stromatolites generally terminate each depositional cycle subtidal conophyton stromatolites possibly the only known occurrence younger than palaeozoic are however found on the reef slope at the base of the first tcc depositional cycle the dolomitic nature of the unadulterated stromatolitic laminations and the association of stromatolites and thrombolites as platform builders were a common feature in the early palaeozoic but are unusual in post ordovician carbonate facies we propose that the conditions during tcc deposition were very restricted possibly reflecting an environment similar to that of the early palaeozoic

genesis and evolution of bitumen in lower cretaceous lavas and implications for strata bound copper deposits north chile small strata bound copper sulfide deposits are found associated with bitumen in lower cretaceous basaltic andesite flows of the pabellon formation near copiapo north chile the physical characteristics of the bitumen and hydrocarbon biomarkers provide clues to the genesis evolution and possible role during copper mineralization biomarker analysis reveals a predominantly bacterial origin with minor contributions from phytoplankton and higher plants which were deposited in a shallow marine environment an expulsion temperature between 64 and 87 c was determined typical for low maturity petroleum this petroleum was altered during migration by mixing with brines increasing its viscosity by aromatization and sulfurization at the moment of the accumulation the temperature of the brine was under 150 c the viscous oil filled the primary and secondary porosity of the basaltic andesite which acted as an oil trap after the oil accumulation a hotter hydrothermal influx resulted in thermal alteration of the petroleum and a further decrease of light alkane concentrations high sulfur concentrations in the hydrothermal fluids led to further aromatization of the organic compounds generating highly alkylated benzonaptho and dinaphthothiophenes copper in the sulfur rich solutions was reduced triggering the precipitation of bornite chalcopyrite digenite chalcocite and covellite through thermochemical sulfate reduction the bitumen interacted with metals by virtue of its inherent reducing characteristics activated carbon and was itself oxidized to form a pyrobitumen residue

the permian kupferschiefer of southwest poland a geochemical trap for migrating metal bearing solutions abstract the ore grade cu mineralization in southwest poland is associated with the presence of the rote faule zone that overlies the contact of saxothuringian and rhenohercynian zones in these areas the soluble organic matter in the kupferschiefer is altered strongly saturated hydrocarbons and alkylated aromatic compounds are depleted significantly in comparison to non altered shale samples of a similar maturation instead unsubstituted di and tricyclic aromatic hydrocarbons are the dominant components of the extractable bitumen the observed alteration points to late diagenetic oxiadtion reactions caused by upward migrated metalliferous solutions moreover polycyclic aromatic hydrocarbons pah associated with polycyclic aromatic sulphur hydrocarbons pash are abundant in some samples these compounds are considered to originate from the underlying carboniferous strata and were carried upward to the kupferschiefer zone which acted as a geochemical trap

volcanic perturbation of the atmosphere in both polar regions 1991 1994 long term measurements by sunphotometers of the spectral dependence of aerosol optical depth are reported for several sites in the arctic and antarctic for the period january 1991 through december 1994 in the antarctic a pronounced increase of atmospheric turbidity was observed at the end of september 1991 the observed wavelength dependence in aerosol optical depth indicated that the increase was due to the presence of fresh and therefore small stratospheric aerosol particles associated with the eruption of cerro hudson in august 1991 after the breakdown of the polar vortex in mid november 1991 we measured a second significant increase of the aerosol optical depth at this time the 1 0 m aerosol optical depth was approximately 0 12 or about 10 times background levels this second incrcase is shown to be the result of the influx of mount pinatubo aerosols a similar perturbation of the aerosol optical depth was observed in the arctic with the return of sunlight in march 1992 however the increased loading of the arctic stratosphere by the pinatubo aerosols was already evident at high northern latitudes in satellite measurements at the end of 1991 stratospheric aerosol and gas experiment ii stratospheric 1 0 m optical depth measurements show that meridional transport of pinatubo aerosol from equatorial to middle and higher latitudes is greatest in the winter spring hemisphere this observation explains the observed seasonal trend of aerosol optical depth during the posteruption a significant decrease of the perturbation by mount pinatubo aerosol was observed in both polar regions by the end of 1994 the measured 1 0 m aerosol optical depths at this time were only 0 04 these values exceed the background level by about 0 01 0 02 therefore the aerosol optical depth values are still slightly higher than during undisturbed conditions in addition we show that the occurrence of volcanic aerosols caused changes in the spectral dependence of the aerosol optical depth in the arctic and the antarctic these variations including the changes in the aerosol size distribution derived from the aerosol optical depth are discussed in comparison to undisturbed conditions

the werra cyclotheme upper permian fore sudetic monocline poland insights into fluctuations of the sedimentary environment from organic geochemical studies abstract a study of the extracts of samples recording a transgressive regressive succession of the werra cyclothem zechstein upper permian from the southern margin of the european permian basin the fore sudetic monocline poland provides an insight into major sources of organic matter and diagenetic processes the studied cross section comprises all lithologies representative for the european basin including transgressive sandstones weissliegend and organic rich shales kupferschiefer followed by carbonates as well as regressive anhydrites with intercalations of rock salt due to the variable influence of overlapping diagenetic processes that affected the organic matter i e maturation and late diagenetic oxidation related to base metal mineralisation a reliable comparison of the biomarker results is only possible for the major upper part of the section ca 38 m including carbonates and evaporites but not for the oxidised first 2 3 m from the base of the kupferschiefer the transition from carbonate to evaporate sedimentation is associated with a shift to predominant even c numbered n alkanes increased abundance of carotanes and high homohopane index reflecting enhanced reducing conditions the presence of the c25 regular isoprenoid squalane biphytane and the rapid decrease in the pristane phytane ratio in the evaporites are mainly controlled by the important contribution from both halophilic and methanogenic archaea the occurrence of gammacerane in the anhydrites suggests development of water column stratification at some stages of the sea regression this is associated with appearance of specific aryl isoprenoids with a lycopane carbon skeleton most likely related to botrycoccus braunii race l algae lycopane derivative occurrence suggests that such an algal race could have occurred since permian currently known recent eocene the presence of the abundant freshwater brackish algal biomarkers in evaporititic deposits can be envisaged in the costal part of the zechstein basin with temporary salt wedge estuary water stratification the algae bloomed in the top fertile fresh brackish water layer fed by rivers and the algal biomass was deposited on the sea floor covered with evaporitic brine the stratification periodically broke down during precipitation of the rock salt presumably due to a decrease in riverine water input as revealed by characteristic disappearance of gammacerane and hopane distributions similar to those observed for the carbonate rocks the methylphenanthrenes phenanthrene ratio was used together with methyldibenzothiophenes dibenzothiophene ratio to assess maturity these maturity estimations indicate that the peak of oil window has been reached which is confirmed by other biomarker maturity parameters based on sterane and hopane distributions the maturity stage of oil generation and expulsion was further confirmed by the presence of solid bitumen as cements in the sandstone underlying kupferschiefer and bitumen veins and lenses in the carbonates

mass occurrence of oncoids at the cambrian series 2 series 3 transition implications for microbial resurgence following an early cambrian extinction abstract the traditional lower middle cambrian transition cambrian series 2 series 3 transition is marked by the first major biotic extinction of the phanerozoic eon this biotic crisis has been arguably linked to changes in ocean chemistry and or marine environments but their casual relationships remain controversial to better understand the microbial responses to paleoceanographic changes across this critical transition we have studied the environmental conditions for mass occurrence of oncoids in the western north china platform oncoids at the lower middle cambrian transition form 1 to 3 m thick massive beds show spherical subspherical morphology and contain 8 14 light dark cortical laminar couplets the light laminae are thicker and contain densely intertwined filamentous cyanobacteria that have calcified sheaths and a prostrate growth pattern the dark laminae are thinner and rich in organic matter relics pyrite framboids and heterotrophic bacteria in most oncoids cortical laminae show the same growth orientation for more than five light dark laminar couplets suggesting much less frequent grain overturning than generally thought both light and dark laminae contain well preserved organomineralization fabrics textures including extracellular polymeric substances epss nanoglobules polyhedrons and micropeloids suggesting oncoid formation in shallow marine environments with high alkalinity and active sulfate reduction the presence of pyrite framboids and heterotrophic bacterial relics implies anoxic dysoxic bottom water conditions stratigraphic correlation indicates that time equivalent oncolites and other microbialites are widespread not only in north china but also in other early cambrian successions globally the mass occurrence of oncoids coincides with the kalkarindji large igneous province of australia a prominent negative 13 c excursion roece or redlichiid olenellid extinction carbon isotope excursion a significant increase in 87 sr 86 sr and a large positive shift in 34 s the coincidence of these events suggests that the early cambrian biotic crisis may have been caused by an ocean anoxic event resulting from enhanced volcanic release of co 2 global warming and increased continental weathering preservation of massive oncolites is likely related to decreased metazoan grazing following an early cambrian biotic crisis during which archaeocyathids and many early cambrian trilobite taxa went to extinction the oncoid mass occurrence provides evidence for the resurgence of microbial life in anoxic dysoxic marine shelf environments concomitant with the early cambrian extinction event

assessing the role of bitumen in the formation of stratabound cu ag deposits insights from the lorena deposit las luces district northern chile abstract stratabound cu ag deposits located in north central chile have been grouped into two ns parallel belts according to the age of their volcanic and volcanoclastic host rocks deposits from the cretaceous belt are characterized by an unusual assemblage of cu sulfides with migrated hydrocarbons whereas the presence of organic matter has not yet been recognized in deposits from the jurassic belt here we report the first evidence of pyrobitumen in a jurassic stratabound cu ag deposit and evaluate its role in ore formation we present a micro analytical study of pyrobitumen associated with cu fe sulfides in the lorena deposit located in northern chile our approach involved a combination of surface and drill core sample characterization fe sem observations empa and xrf mapping of pyrobitumen in addition we determined the speciation of sulfur in pyrobitumen by using synchrotron xanes two main events of hypogene mineralization were identified at lorena deposit i e a pre ore and a main cu ore stage the pre ore stage is characterized by globularly shaped pyrobitumen and minor pyrite and a widespread albite alteration of the andesite host rock pre ore pyrite was replaced by chalcopyrite bornite and chalcocite providing evidence for a late cu inception in the main cu ore stage chalcocite is often associated with sharp edged angular pyrobitumen most likely indicating remobilization or a later pulse of hydrocarbons empa data show that pyrobitumen at lorena is enriched in fe 0 02 1 74 wt cu 0 02 0 87 wt s 0 01 0 43 wt and cl 0 01 0 4 wt other elements detected include v co ni cr sb as ag and au both ag and au were only detected in a few spots with au reaching up to 600 ppm desktop and synchrotron xrf mapping shows that s is homogeneously distributed within pyrobitumen with lower s concentrations observed at grain rims on the other hand empa wds x ray maps show that cu precipitated on pyrobitumen grain surfaces filling fractures and forming veinlets in addition textures showing the presence of micro to nano sized pyrobitumen inclusions within both pre ore pyrite and main ore chalcocite grains point unequivocally to the interaction of hydrothermal fluids with hydrocarbons during the formation of this deposit the high s concentrations measured in pyrobitumen and the presence of organosulfur compounds detected by xanes can be attributed to an organic source the pre ore assemblage is interpreted as formed from a petroleum aqueous fluid connate waters mixture that migrated from the sedimentary source rock into the jurassic host rocks where pyrite and pyrobitumen precipitated in the andesite late cu bearing hydrothermal fluids interacted with this pyrobitumen pyrite assemblage to form cu sulfides either by replacement of pyrite or precipitation we conclude that some of the s contained in pyrobitumen could have been released during interaction with the cu bearing hydrothermal fluid contributing at least partially to the s budget required for sulfide mineralization in the main ore stage our results provide evidence supporting pyrobitumen fluid interaction as a key process in the formation of the lorena deposit and possibly other stratabound cu ag deposits in chile

implications of in situ calcification for photosynthesis in a 3 3 ga old microbial biofilm from the barberton greenstone belt south africa timing the appearance of photosynthetic microorganisms is crucial to understanding the evolution of life on earth the ability of the biosphere to use sunlight as a source of energy photoautotrophy would have been essential for increasing biomass and for increasing the biogeochemical capacity of all prokaryotes across the range of redox reactions that support life typical proxies for photosynthesis in the rock record include features such as a mat like laminated morphology stratiform domical conical often associated with bulk geochemical signatures such as calcification and a fractionated carbon isotope signature however to date in situ calcification related to photosynthesis has not been demonstrated in the oldest known microbial mats we here use in situ nanometer scale techniques to investigate the structural and compositional architecture in a 3 3 billion year ga old microbial biofilm from the barberton greenstone belt thus documenting in situ calcification that was most likely related to anoxygenic photosynthesis the josefsdal chert microbial biofilm jcmb formed in a littoral photic environment it is characterised by a distinct vertical structural and compositional organisation the lower part is calcified in situ by aragonite progressing upwards into uncalcified kerogen characterised by up to 1 sulphur followed by an upper layer that contains intact filaments at the surface crystallites of pseudomorphed pyrite are also associated with the biofilm suggesting calcification related to the activity of heterotrophic sulphur reducing bacteria in this anoxygenic nutrient limited environment the carbon required by the sulphur reducing bacteria could only have been produced by photoautotrophy we conclude that the josfsdal chert microbial biofilm was formed by a consortium of anoxygenic microorganisms including photosynthesisers and sulphur reducing bacteria

circular geological structures outcropping in the sedimentary basins of saudi arabia abstract a number of circular geological structures outcrop in the sedimentary basins of saudi arabia several are reviewed here to assess their mode of origin they are unrelated to each other are easily seen on aerial imagery and their origins are assessed here on the basis of new fieldwork and reflection seismic data the structures range in size from hundreds of meters to several kilometers in diameter jabal rayah 28 39 n 37 11 30 e is 5 km in diameter with ring faults and anomalously steep dips in siluro devonian strata reflection seismic data demonstrate that underlying strata are structureless and jabal rayah is interpreted as a probable impact structure ash shutbah 21 37 08 n 45 39 21 e is 2 3 km in diameter and consists of a zone of concentric sub horizontal folds in mesozoic carbonates surrounding a central area of disharmonic steeply plunging folds and a mass of stratigraphically anomalous sandstone there are dissolution structures in the vicinity and although this is a viable explanation the uniquely large and complex nature of ash shutbah suggests an alternative origin by impact reflection seismic data show that underlying strata in the vicinity of ash shutbah are structureless a province of at least 100 circular structures occurs in northeast saudi arabia aerial imagery and reflection seismic data shows that these structures are a mixture of bioherms and dissolution collapse features the kidan crater 22 06 53 n 53 26 38 e is a subcircular feature approximately 100 m in diameter exposed in quaternary sabkha between large sand dunes in the rub al khali field investigation reveals an unfaulted bowl with a slightly fractured floor in sabkha facies 3d reflection seismic data shows a small fault underlying the crater leading to a fluid escape interpretation for the depression

integration of gamma ray spectrometry magnetic susceptibility and calcareous nannofossils for interpreting environmental perturbations an example from the jenkyns event lower toarcian from south iberian palaeomargin median subbetic se spain abstract the pliensbachian toarcian sedimentary rocks of the median subbetic betic cordillera se spain were deposited in the south iberian palaeomargin under hemipelagic conditions in the arroyo mingarron section se spain these deposits are composed by a marl and marl and limestone alternation with abundant radiolarians the application of magnetic susceptibility and gamma ray spectrometry to these deposits allows to interpret environmental changes related to the fluctuations in the continental influx of terrigenous and phytodetritus to a hemipelagic setting in the south iberian palaeomargin the increase of terrigenous input was coincident with the negative carbon isotopic excursion cie at the base of the njt6 nannofossil zone that correlates with the jenkyns event the increase of th and k content is related to enhanced detrital input especially oxides and silicates including clay minerals the gamma ray signal derived from u is comparatively low with respect to k and th nevertheless the u content shows an increase in the base of njt6 nannofossil zone that indicates a relative increase of organic matter content coincident with the jenkyns event changes in the calcareous nannofossil assemblages at the beginning of the njt6a nannofossil subzone and in particular the sharp decrease in abundance of the species mitrolitus jansae during the negative cie of the jenkyns event are interpreted as related to sea water stratification and a probable poor oxygenation making inhospitable the deep photic zone during this event

field gamma ray patterns and stratigraphic reinterpretation of offshore well log data from lower jurassic organic rich units of the lusitanian basin portugal abstract lower jurassic sinemurian pliensbachian successions cropping out in onshore areas of the lusitanian basin provide detailed information of three well characterized organic rich intervals i the unit f from the coimbra formation ii the polvoeira member of the agua de madeiros formation and the iii marly limestones with organic rich facies mlof member of the vale das fontes formation despite decades of research these source rocks have not yet been properly identified and characterized in terms of extension and thickness in the basin s offshore this paper compares detailed gamma ray gr profiles from onshore outcrops coimbra montemor o velho figueira da foz monte real sao pedro de moel and peniche regions with seven offshore wells our objective is to recognise lower jurassic organic rich intervals in offshore areas of the basin highlighting their lateral extension and improving the overall stratigraphic definition of the lower jurassic in the lusitanian basin gr field measurements indicate that the highest gr values and u contents are consistently observed in the organic rich intervals reaching up to 134 api and 9 0 ppm of u in contrast the lowest api and u contents were determined in dominantly calcareous units ranging between 5 34 api and 0 1 1 4 ppm respectively wireline gamma ray logs show a good correspondence between field patterns and offshore well logs recognizing the organic rich intervals in offshore areas the highest gr values are interpreted to be linked with the 2nd and 3rd order maximum flooding intervals previously recognised in the sinemurian pliensbachian successions in the western iberian margin detailed gr maps linked to maximum flooding intervals highlight the variation of the vertical and lateral distributions of the organic rich units in offshore areas of the lusitanian basin

denitrification mechanism of the polar winter stratosphere by major volcanic eruptions the uptake of hno3 by volcanic sulfuric acid droplets is investigated using a one dimensional sulfate aerosol model and recent laboratory data hno3 uptake by volcanic sulfate particles coupled with the sedimentation of the particles may lead to irreversible transfer of hno3 from higher to lower altitudes in the polar stratosphere during winter this denitrification mechanism is found to be strongly dependent on the sulfate aerosol loading and temperature model calculations suggest that anomalously large volcanic eruptions have caused a severe denitrification of the arctic winter lower stratosphere there is conflicting evidence for this mechanism in ice core nitrate records

apparently homogenous reef limestones built by high frequency cycles upper jurassic sw germany abstract central european upper jurassic sponge microbial reefs are commonly regarded as compact massive and homogenous facies bodies a continuous study of borehole cores from sw germany clearly shows a very systematic architecture of these reefs built by sedimentary cycles of various hierarchical levels altogether five orders of cycles can be distinguished decimeter scale microcycles building meter scale mesocycles which in turn are stacked to form several meter thick macrocycles these high frequency cycles in turn are parts of basin wide medium scale and large scale cycles reported in a previous paper this paper documents the high frequency micro meso and macrocycles microcycles 0 1 0 8 m thick usually have a sharp erosional base covered by reworked sponges shells and intraclasts interpreted as storm events these bioclastic layers are colonised by a succession of thrombolitic and stromatolitic microbialites successive microcycles form distinct stacks that record gradually increasing and decreasing depositional energy thus defining mesocycles 0 5 4 m thick several mesocycles construct macrocycles 3 25 m the cycle stacking patterns were analysed by means of facies proportion diagrams the dominant microscale cyclicity records changes in water agitation possibly caused by fluctuating storm wave base the sponge microbial mounds could probably build up just to average storm wave base within the cycles of larger hierarchical levels the successive smaller scale cycles show systematic trends in their symmetry and in thickness this may be caused by variations in the ratio of accomodation space and associated energy level to carbonate production external reef geometries progradation aggradation retrogradation condensation can be related to internal cycle stacking patterns to approximate the duration of the high frequency cycles two different approaches were used firstly the duration of cycles was determined with the help of published chronostratigraphic time scales secondly cycle duration was estimated using published microbial reef growth rates both approximations result in ca 0 4 ma for the medium scale cycles and 0 1 ma for the macrocycles both are regionally correlatable thus appear to be allocyclic in nature and probably are milankovitch driven in contrast the microcycles are only locally correlatable and thus indicate an autocyclic storm induced nature this study poses the question if not more of the apparently homogenous reef bodies of other settings and geological ages may possibly also show internal high frequency cycles

northern hemisphere temperature anomalies during the 1450s period of ambiguous volcanic forcing ice core based estimates of past volcanic eruptions are the main forcing of the last millennium climate model simulations understanding the timing and magnitude of eruptions is thus critical for assessing the dynamics of the earth s climate system uncertainty associated with a major event in the 1450s originally attributed to the south pacific kuwae eruption in 1452 and recently shifted to 1458 fundamentally alters model simulations their comparison with proxy based climate reconstructions and any subsequent historical interpretation here we compile a northern hemisphere tree ring network of 25 maximum latewood density chronologies extending back over the past 650 years to analyze the 1450s temperature deviations statistically robust warm season temperature reconstructions from 20 of these records reveal a spatially coherent and exceptional cooling in 1453 summer cooling ranged from 0 4 c in the swiss alps to 6 9 c in the polar urals russia and was generally stronger across the eurasian high latitudes and northwestern north america year 1453 also marks the onset of a 15 year cold period during which network mean temperatures ranged from 2 5 c in 1453 to 0 5 c in 1468 in contrast the years 1459 1 0 c and 1460 0 4 c were not exceptionally cold in the contemporary context these findings suggest either that the original dating pointing to a major eruption in 1452 and large scale cooling in 1453 was correct or that the eruption left no substantial climatic fingerprint in northern hemisphere temperature proxies the latter appears less likely as sulfate aerosol deposits associated with the 1450s event are found in ice cores of both hemispheres

origins of carbonate in neoproterozoic stromatolites and the identification of modern analogues abstract the viewpoint in this paper is that the distinction of detrital from in situ precipitated carbonate in stromatolites is vital so that the appropriate modern analogues can be sought reviewing literature on modern stromatolites it is clear that marine stromatolites are dominated by detrital sediment although diagenetic processes can obscure the detrital nature of carbonate in mats in low salinity conditions carbonate is dominantly of precipitate origin being triggered by photosynthesis in mats in saline conditions petrographically similar precipitates occur apparently triggered variously by photosynthesis evaporation and organic matter degradation in different cases light carbon isotopes in the carbonate are a good pointer to organic degradation as a carbon source a review of criteria proposed for identifying the origin of carbonate in precambrian stromatolites shows that in different cases reliable evidence both for sediment incorporation and carbonate precipitation has been obtained although many arguments are equivocal the utility of luminescence petrography for positive identification of detritus and carbon isotope data for identification of carbon sources is outlined new petrographic and carbon isotope data are presented from four units canyon formation of east greenland draken and wilsonbreen formations of spitsbergen and atar group mauritania although environmentally diverse each displays evidence for both sediment incorporation and localized carbonate precipitation although in widely varying proportions it is recommended that luminescence studies be carried out for stromatolite microstructural work carbon isotope data indicate no distinction between early inorganic cements stromatolitic and non stromatolitic dolo micrites and indicate a common origin related to water column and microbial mat photosynthesis variably accompanied by evaporation

a 200 year sulfate record from 16 antarctic ice cores and associations with southern ocean sea ice extent chemistry data from 16 50 115m deep sub annually dated ice cores are used to investigate spatial and temporal concentration variability of sea salt ss so4 2 and excess xs so4 2 over west antarctica and the south pole for the last 200 years low elevation ice core sites in western west antarctica contain higher concentrations of so4 2 as a result of cyclogenesis over the ross ice shelf and proximity to the ross sea polynya linear correlation analysis of 15 west antarctic ice core so4 2 time series demonstrates that at several sites concentrations of ssso4 2 are higher when sea ice extent sie is greater and the inverse for xsso4 concentrations of xsso4 2 from the south pole site east antarctica are associated with sie from the weddell region and west antarctic xsso4 2 concentrations are associated with sie from the bellingshausen amundsen ross region the only notable rise of the last 200 years in xsso4 around 1940 is not related to sie fluctuations and is most likely a result of increased xsso4 2 production in the mid low latitudes and or an increase in transport efficiency from the mid low latitudes to central west antarctica these high resolution records show that the source types and source areas of ssso4 2 and xsso4 2 delivered to eastern and western west antarctica and the south pole differ from site to site but can best be resolved using records from spatial ice core arrays such as the international trans antarctic scientific expedition itase

signal variability in replicate ice cores replicate ice cores have been drilled about 10 m apart for the top 790 m of the ice sheet at dome c antarctica this provides an opportunity to examine inter core variation of the signal for identical events based on dielectric profile dep comparisons comparison of the signal from the same core a section 48 m long measured 1 year apart showed good reproducibility with peak heights varying by around 10 between the two measurements for the two replicate cores identical peaks were matched and showed variability between cores of typically a factor 1 5 this can be explained based on the likelihood of significant time periods of missing accumulation in any single core at sites with such low snow accumulation rate to synchronize core depths by matching peaks it is essential to use the pattern of peaks rather than just widely spaced individual strong peaks to derive a quantitative volcanic index from these low accumulation rate sites it will be necessary to combine or average the results from several closely spaced parallel cores

10 be and delta 2 h in polar ice cores as a probe of the solar variability s influence on climate and discussion by using the technique of accelerator mass spectrometry it is now possible to measure detailed profiles of cosmogenic cosmic ray produced 10 be in polar ice cores recent work has demonstrated that these profiles contain information on solar activity via its influence on the intensity of galactic cosmic rays arriving in the earth s atmosphere it has been known for some time that as a result of temperature dependent fractionation effects the stable isotope profiles delta 2 o and delta 2 h in polar ice cores contain palaeoclimate information thus by comparing the 10 be and stable isotope profiles in the same ice core one can test the influence of solar variability on climate and this independent of possible uncertainties in the absolute chronology of the records we present here the results of such a comparison for two antarctic ice cores one from the south pole covering the past ca 1000 years and one from dome c covering the past ca 3000 years

a 4100 year record of explosive volcanism from an east antarctica ice core extensive archives of volcanic history are available from ice cores recovered from the antarctic and greenland ice sheets that receive and preserve sulfuric acid fallout from explosive volcanic eruptions the continuous detailed average 1 2 samples per year sulfate measurements of a 200 m ice core from a remote east antarctica site plateau remote provide a record of southern hemisphere volcanism over the last 4100 years this extends the volcanic record beyond the last 1000 years covered by previous antarctic ice cores an average of 1 3 eruptions per century is recorded in east antarctic snow during the last 4100 years the record shows that on average eruptions have been more frequent and more explosive during the most recent 2000 years than in the previous 2100 years intervals up to 500 years are observed in which few explosive volcanic signals are detected these periods include 2000 1500 b c no eruptions 500 1 b c two eruptions and 700 1200 a d two eruptions this new plateau remote volcanic record is compared with those from previous antarctic ice cores covering the last 1000 years in terms of dates for volcanic events the new record is in excellent agreement with the earlier records however significant discrepancies are found between these records in relative signal magnitude volcanic flux of several well known events the discrepancies among the records may be explained by the differences in the glaciology at the ice core sites analytical techniques used for sulfate and sulfuric acid measurement and the selection of detection thresholds for volcanic signals comparison with greenland ice core volcanic records indicates that during the last millennium nine large low latitude eruptions contributed significant amounts of volcanic aerosols to the atmosphere of both hemispheres potentially affecting global climate in contrast only one or possibly two such eruptions are found in the first millennium a d

the 1452 or 1453 a d kuwae eruption signal derived from multiple ice core records greatest volcanic sulfate event of the past 700 years 1 we combined 33 ice core records 13 from the northern hemisphere and 20 from the southern hemisphere to determine the timing and magnitude of the great kuwae eruption in the mid 15th century we extracted volcanic deposition signals by applying a high pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation by accounting for the dating uncertainties associated with each record these ice core records together reveal a large volcanogenic acid deposition event during 1453 1457 a d the results suggest only one major stratospheric injection from the kuwae eruption and confirm previous findings that the kuwae eruption took place in late 1452 or early 1453 which may serve as a reference to evaluate and improve the dating of ice core records the average total sulfate deposition from the kuwae eruption was 93 kg so4 km 2 in antarctica and 25 kg so4 km 2 in greenland the deposition in greenland was probably underestimated since it was the average value of only two northern greenland sites with very low accumulation rates after taking the spatial variation into consideration the average kuwae deposition in greenland was estimated to be 45 kg so4 km 2 by applying the same technique to the other major eruptions of the past 700 years our result suggests that the kuwae eruption was the largest stratospheric sulfate event of that period probably surpassing the total sulfate deposition of the tambora eruption of 1815 which produced 59 kg so4 km 2 in antarctica and 50 kg so4 km 2 in greenland

primary copper sulphides from the kupferschiefer poland finely dispersed primary copper sulphide mineralization from the zones of cu s paragenesis in the zechstein copper bearing shale from the fore sudetic monocline poland was studied it is represented mostly by small spherules and framboids 5 to 10 m in size and framboidal clusters of digenite chalcocite and minor covellite dispersed throughout the whole shale but especially abundant in the organic rich laminae detailed microscopic and chemical microprobe descriptions of this mineralization are given and a comparison with pyrite framboids is presented digenite usually dominates over chalcocite among dispersed mineralization in contrast to that observed in larger diagenetic grains the rarity of copper sulphide framboids in comparison with spherules can probably be explained by the fast process of their homogenization the textures chemistry and some different features from pyrite framboids suggest that the copper sulphides in fe poor zones of the kupferschiefer are primary precipitates the results of the study suggest that the beginning and probably the main stage of the ore mineralization process took place during the sedimentation and or early diagenesis of the kupferschiefer