3d stratigraphic forward modelling for analysis and prediction of carbonate platform stratigraphies in exploration and production abstract stratigraphic forward modelling sfm has been used to answer important questions in stratigraphic analysis this has been demonstrated through generic modelling of synthetic data and numerous two dimensional 2d real data case studies but the method has rarely been used to further our understanding of specific real three dimensional 3d carbonate data sets by quantitative comparison this paper applies carbonate 3d a sfm program to a hydrocarbon reservoir and outcropping carbonate platforms at both exploration and production scales we show the value of sfm in the exploration and production of hydrocarbons through predicting facies distributions and stratigraphic geometries between wells and by analysing and answering fundamental questions about the formation of specific carbonate strata first the model is tested using the 3d outcrops of a miocene attached carbonate platform at nijar se spain where 78 of mapped facies are matched in the simulations second sfm of an 80 000 km 2 jurassic ramp in ne spain exploration scale predicts new facies in areas without data leads to an improved understanding of ramp evolution modification of the interpreted sea level curve and re interpretation of the main sediment transport direction application to the isolated platform reservoir judy creek devonian canada exemplifies the advantages of applying sfm at reservoir scale the simulations yield information on platform geometries and facies distributions an improved understanding of the factors that control platform evolution and propose a revised sea level history wider applications of sfm in exploration include assessment of the possibilities and probabilities of facies distributions and evaluation and ranking of different interpretations of platform evolution at the reservoir scale facies probability distributions and layer geometries derived from sfm can serve as input into static reservoir models to guide geostatistical simulations

sulfur dioxide from nevado del ruiz volcano colombia total flux and isotopic constraints on its origin abstract nevado del ruiz volcano has been releasing extraordinarily large volumes of sulfur dioxide gas from its arenas crater since september 1985 and probably since the renewal of volcanic activity began in late 1984 the combined release from eruptive and passive flux has been approximately 3 4 1 0 10 6 metric tons in the four years after november 1984 this value combined with data of others on pre eruption sulfur content of the magma allows the calculation of a minimum required volume of magma of 0 92 km 3 consideration of the continued high flux and typical ratios of erupted to degassed magma indicate that the true minimum volume of magma involved is probably at least 4 6 9 2 km 3 a systematic study of the various species of sulfur in the volcanic plume and the hydrothermal system has provided a characterization of the geochemistry and sulfur isotopic variation consideration has been given to five potential sources of the sulfur dioxide dissolution of subvolcanic evaporites remobilization and oxidation of native sulfur within summit crater fumaroles large scale release from the hydrothermal system by reduction of sulfate or water rock interaction assimilation and oxidation of a pre existing sulfide deposit and magmatic volatiles the data are most realistically explained by the passage of magmatic gas through the hydrothermal system with some disproportionation of sulfur dioxide to produce the high sulfate content and low ph of the waters this model is also most consistent with the distribution of acid sulfate chloride hot springs high chloride and fluoride content of the hydrothermal waters sulfide deposition within the volcanic pile and the transient increase in sulfate content of the acid sulfate chloride hot springs that reached a maximum approximately one year after the november 1985 eruption the magmatic model is in apparent conflict with the absence of general deformation from the time that data began to be collected about one week before the eruption until the time this manuscript was finalized september 1989 although this conflict cannot be resolved with certainty it is noted that the absence of deformation is only an indication of the lack of magma movement not of the absence of magma an alternative magmatic model considers the available geological data and proposes that the system is related to a large scale caldera in this model the degassing is related to a long term process of exsolution of magmatic volatiles from a large volume of crystallizing magma left from the construction of modern ruiz this model can better explain the combined geological and geophysical data as well as the geochemical and isotopic data the nature of the degassing data at ruiz is interesting because it is an example of an explosive eruption cycle in which the gas flux is actually dominated by passive release the nature of the degassing allows us to hypothesize that some major change in the system occurred in april may 1986 and to predict that the present high flux can be expected to last for another decade

cyclicities in triassic platform carbonates synchronizing radio isotopic and orbital clocks sedimentary cycles recorded in young sediments are often attributed to fluctuations of the earth s climate on a 10 4 10 6 year scale which in turn is governed by periodic variations in solar insolation linked to orbital milankovitch parameters a spectacular example of cyclic stratal patterns in ancient deposits is the middle triassic latemar carbonate platform w dolomites n italy based on spectral analyses from previous studies a superimposition of precession 20 ka and eccentricity 100 ka controlled sea level fluctuations has been suggested to account for the stacking hierarchy at latemar with 20 ka being assigned to each highest order depositional cycle zircon u pb isotopic ages from volcanic ash layers within the cyclic succession corroborated by biostratigraphic constraints suggest that the average time interval for every individual cycle is significantly smaller than the shortest milankovitch period and therefore challenge previously published interpretations relating distinct spectral peaks to the above mentioned hierarchy however our new spectral data indicate that cyclicities resembling milankovitch characteristics might exist but on an entirely different scale our findings show that frequency spectra should only be interpreted in combination with robust age control they also encourage the search for complementary mechanisms controlling carbonate deposition

magma at depth a retrospective analysis of the 1975 unrest at mount baker washington usa mount baker volcano displayed a short interval of seismically quiescent thermal unrest in 1975 with high emissions of magmatic gas that slowly waned during the following three decades the area of snow free ground in the active crater has not returned to pre unrest levels and fumarole gas geochemistry shows a decreasing magmatic signature over that same interval a relative microgravity survey revealed a substantial gravity increase in the 30 years since the unrest while deformation measurements suggest slight deflation of the edifice between 1981 83 and 2006 07 the volcano remains seismically quiet with regard to impulsive volcano tectonic events but experiences shallow 10 km long period earthquakes reviewing the observations from the 1975 unrest in combination with geophysical and geochemical data collected in the decades that followed we infer that elevated gas and thermal emissions at mount baker in 1975 resulted from magmatic activity beneath the volcano either the emplacement of magma at mid crustal levels or opening of a conduit to a deep existing source of magmatic volatiles decadal timescale multi parameter observations were essential to this assessment of magmatic activity

the latemar a flat topped steep fronted platform dominated by microbialites and synsedimentary cements abstract facies analyses on the latemar isolated carbonate platform suggest a higher proportion of microbial carbonates compared to literature this is evident especially in the margin upper slope zone where microbial boundstone associated with tubiphytes calcareous sponges botryoidal aragonite and radiaxial fibrous cements extended down to 250 m water depth the latemar flat topped high relief platform has been subdivided into five different facies belts inner and outermost platform margin upper and lower slope each facies belt represents subtidal environments except for the inner platform which is characterized by a peritidal facies association point counting analysis was carried out on ca 90 thin sections to quantify the different platform components microbialite and cements are most abundant they represent respectively ca 40 and ca 34 of the whole platform volume these results suggest that carbonate production at latemar occurred in a m factory microbial carbonates as well as early marine cements are most abundant on the upper slope margin and outermost platform although microbialites are found in all facies belts the presence of supratidal sedimentary facies restricted only to the inner platform and of a completely subtidal outermost platform suggests a new depositional profile for the latemar the central portion is occupied by the flat platform interior cyclically subaerially exposed facies of the subtidal outermost platform surround the inner platform and display a progressive increase in depth toward the margin the margin is submerged and essentially constituted by microbial and cement boundstone the slope is characterized by steep clinoforms 35 dominated by in situ microbialites in the upper middle portion 0 250 m depth evidently precipitated by non light dependent microbially influenced processes the lower slope is mostly detrital poor in platform top derived sediments and dominated by margin and upper slope derived rudstone and grainstone all these observations are in agreement with the slope shedding model observed in the pennsylvanian microbial margin in asturias n spain and allow the interpretation of the latemar as a flat topped steep fronted platform dominated by microbialites and cement boundstones

direct rate measurements of eruption plumes at augustine volcano a problem of scaling and uncontrolled variables the march april 1986 eruption of augustine volcano alaska provided an opportunity to directly measure the flux of gas aerosol and ash particles during explosive eruption most previous direct measurements of volcanic emission rates are on plumes from fuming volcanoes or on very small eruption clouds direct measurements during explosive activity are needed to understand the scale relationships between passive degassing or small eruption plumes and highly explosive events conditions on april 3 1986 were ideal high winds clear visibility moderate activity three measurements were made 1 an airborne correlation spectrometer cospec provided mass flux rates of so2 2 treated filter samples chemically characterized the plume and 3 a quartz crystal microcascade impactor provided particle size distribution atmospheric conditions on april 3 caused the development of a lee wave plume which allowed us to constrain a model of plume dispersion leading to a forecast map of concentrations of so2 at greater distances from the vent on april 3 1986 the emission rate of so2 at augustine was 24 000 t d one of the largest direct volcanic rate measurements yet recorded with a cospec the results coupled with analytical results from samples simultaneously collected on filters allow us to estimate hcl emissions at 10 000 t d and ash eruption rate at 1 5 106 t d based on other data this ash eruption rate is about 1 50 of the maximum rate during the march april activity filter samples show that the gas aerosol proportions for sulfur and chlorine are about 10 1 and 4 1 respectively by contrast measurements of augustine s plume together with ground based gas sampling in july 1986 when the volcano was in a posteruptive fuming state are 380 t d so2 and approximately 8000 t d hcl with no ash emission the observations of large cl releases at augustine support the cl abundance conclusions of johnston 1980 based on study of melt inclusions in the 1976 lavas the results reinforce the need for more measurements during eruptions and for better understanding of scaling of volcanic emissions of various eruptive components

progradation geometries of carbonate platforms examples from the triassic of the dolomites northern italy various types of progradation of triassic carbonate platforms are described from the dolomites of the southern alps the internal and external geometric relationships are exposed in spectacular natural sections and moreover their scale 500 1000 m of thickness is such that they can be compared with features found in seismic profiles the different types of progradation are controlled by a number of factors which normally interact with each other these factors include rate of basinal sedimentation rate of subsidence width of the platform depth of the surrounding basin and eustatic variations of sea level progradation is not a continuous process but episodic moments of massive debris input during which the platform advances alternate with long periods of negligible progradation during which basinal sediments accrete and onlap the toe of slope upper boundary relationships of the prograding platforms include offlap toplap and erosional truncation lower boundary relationships are horizontal climbing and descending progradations a variety of phenomena and circumstances have caused the cessation of progradation of the triassic platforms they include volcanism collapse of margins drowning rapid relative rise of sea level subaerial exposure relative fall of sea level and probably a natural decay of the system in the triassic of the dolomites two main progradation models can be put forward in the ladinian model progradation took place simultaneously with aggradation relative rise of sea level whereas the characteristic feature of the carnian model is toplap relative stillstand of sea level

gas emissions from failed and actual eruptions from cook inlet volcanoes alaska 1989 2006 cook inlet volcanoes that experienced an eruption between 1989 and 2006 had mean gas emission rates that were roughly an order of magnitude higher than at volcanoes where unrest stalled for the six events studied mean emission rates for eruptions were 13 000 t d co2 and 5200 t d so2 but only 1200 t d co2 and 500 t d so2 for non eruptive events failed eruptions statistical analysis suggests degassing thresholds for eruption on the order of 1500 and 1000 t d for co2 and so2 respectively emission rates greater than 4000 and 2000 t d for co2 and so2 respectively almost exclusively resulted during eruptive events the only exception being two measurements at fourpeaked while this analysis could suggest that unerupted magmas have lower pre eruptive volatile contents we favor the explanations that either the amount of magma feeding actual eruptions is larger than that driving failed eruptions or that magmas from failed eruptions experience less decompression such that the majority of h2o remains dissolved and thus insufficient permeability is produced to release the trapped volatile phase or both in the majority of unrest and eruption sequences increases in co2 emission relative to so2 emission were observed early in the sequence with time all events converged to a common molar value of c s between 0 5 and 2 these geochemical trends argue for roughly similar decompression histories until shallow levels are reached beneath the edifice i e from 20 35 to 4 6 km and perhaps roughly similar initial volatile contents in all cases early elevated co2 levels that we find at these high latitude andesitic arc volcanoes have also been observed at mid latitude relatively snow free basaltic volcanoes such as stromboli and etna typically such patterns are attributed to injection and decompression of deep co2 rich magma into a shallower chamber and open system degassing prior to eruption here we argue that the c s trends probably represent tapping of vapor saturated regions with high c s and then gradual degassing of remaining dissolved volatiles as the magma progresses toward the surface at these volcanoes however c s is often accentuated due to early preferential scrubbing of sulfur gases the range of equilibrium degassing is consistent with the bulk degassing of a magma with initial co2 and s of 0 6 and 0 2 wt respectively similar to what has been suggested for primitive redoubt magmas

triassic latemar cycle tops subaerial exposure of platform carbonates under tropical arid climate the triassic latemar platform in the dolomites italy is the site of several ongoing controversies perhaps the most interesting debate focuses on apparent cyclic deposition within the latemar platform whose nature and duration are still open to debate further disagreement concerns the lack of meteoric diagenesis related isotope shifts at cycle tops that bear circumstantial petrographic evidence for subaerial emergence here an evaluation of the nature of latemar cycle tops is presented combining evidence from previous work and new field petrographic and geochemical data cycle tops are ranked according to increasing exposure duration and spatial extent type i surfaces lacking unequivocal evidence of prolonged supratidal conditions type ii dolomite caps formed in warm evaporitic intertidal lagoonal waters followed by exposure of perhaps intermediate duration type iii clastic rich red calcareous horizons with some showing platform wide extent representing prolonged supratidal conditions and type iv discontinuities in tepee belts genetically related to type ii and iii surfaces but likely representing shorter lived exposure stages petrographic and geochemical criteria indicate that most diagenesis occurred in the shallow marine and burial domain whilst an extensive meteoric overprint of cycle tops is lacking this is underlined by the scarcity of meteoric diagenetic fabrics such as gravitational cements that where present are here interpreted as marine vadose in origin the scarcity of carbon and oxygen isotope signatures commonly assigned to subaerial exposure stages is best explained in the context of mid triassic climate the low latitude tropical but arid setting of the latemar situated in the western extension of the tethys ocean its isolation from nearby continental areas and overall short term emergence episodes are in agreement with a limited degree of meteoric alteration of most cycle tops high amounts of aeolian clastic material beneath some cycle tops along with high fe and mn elemental abundances argue for intermittent subaerial conditions this study proposes an enhancement of the classical allan and matthews 1982 isotope model for subaerial exposure under strongly arid climates as the subaerial exposure nature of latemar cycle tops and therefore eustasy as the cause for cyclicity have been previously challenged due to the lack of meteoric induced isotopic signatures the outcome of this study is of significance for the ongoing latemar stratigraphic controversy

character mass distribution and origin of tephra fall deposits of the 1989 1990 eruption of redoubt volcano south central alaska abstract the 1989 1990 eruption of redoubt volcano spawned about 20 areally significant tephra fall deposits between december 14 1989 and april 26 1990 tephra plumes rose to altitudes of 7 to more than 10 km and were carried mainly northward and eastward by prevailing winds where they substantially impacted air travel commerce and other activities in comparison to notable eruptions of the recent past the redoubt events produced a modest amount of tephra fall deposits 6 10 7 to 5 10 10 kg for individual events and a total volume dense rock equivalent of about 3 5 10 7 m 3 of andesite and dacite two contrasting tephra types were generated by these events pumiceous tephra fall deposits of december 14 and 15 were followed on december 16 and all later events by fine grained lithic crystal tephra deposits much of which fell as particle aggregates the change in the character of the tephra fall deposits reflects their fundamentally different modes of origin the pumiceous deposits were produced by magmatically driven explosions the finegrained lithic crystal deposits were generated by two processes hydrovolcanic vent explosions generated tephrafall deposits of december 16 and 19 such explosions continued as a tephra source but apparently with diminishing importance during events of january and february ash clouds of lithic pyroclastic flows generated by collapse of actively growing lava domes probably contributed to tephra fall deposits of all events from january 2 to april 26 and were the sole source of tephra fall for at least the last 4 deposits

calcite and aragonite precipitation from seawater solutions of various salinities precipitation rates and overgrowth compositions abstract the reaction rate and composition of calcite and aragonite overgrowths precipitated from seawater solutions of various salinities i e s 5 15 25 35 44 were determined at 25 c and 10 2 5 atm co2 partial pressure using a constant disequilibrium seeded technique the rate data were fitted to an empirical rate law of the form log r n c or a 1 log k where n is the empirical reaction order and k is the rate constant calcite precipitation rates in seawater solutions do not vary appreciably as a result of salinity variations over the range investigated while those for aragonite show an increase in going from the higher i e s 35 44 to the lower i e s 5 15 25 salinity range this study also confirms previously published findings that above a given saturation state i e c 2 6 aragonite precipitates more rapidly than calcite at 25 c the incorporation of sr2 in aragonite and mg2 in calcite overgrowths are independent of the precipitation rate the partition coefficient of sr2 in aragonite is approximately equal to unity and is unaffected by salinity variations between 5 and 44 however the mg2 partition coefficient in calcite increases with decreasing salinity of the parent seawater solutions possibly as a result of variations in the sulfate content of the solutions and solids the experimental results were discussed in the context of a number of geological environments

sediment fans and sediment flows generated by snowmelt observations at austerdalsisen norway sediments in the austerdalsisen basin norway are re worked annually during the short snowmelt period in the last 10 15 years several fans have been constructed largely by sediment flows sediment water mixtures which move downslope under the influence of gravity the viscosity of the flows varies considerably and a single flow may change as a result of water or sediment loss fan characteristics reflect the nature of the sediments the mechanics of flow modes of deposition and the annual periodicity of activity

the role of the global carbonate cycle in the regulation and evolution of the earth system we review one of the most ancient of all the global biogeochemical cycles and one which reflects the profound geochemical and biological changes that have occurred as the earth system has evolved through time that of calcium carbonate caco3 in particular we highlight a mid mesozoic revolution in the nature and location of carbonate deposition in the marine environment driven by the ecological success of calcareous plankton this drove the creation of a responsive deep sea sedimentary sink of caco3 the result is that biologically driven carbonate deposition provides a significant buffering of ocean chemistry and of atmospheric co2 in the modern system however the same calcifying organisms that under pin the deep sea carbonate sink are now threatened by the continued atmospheric release of fossil fuel co2 and increasing acidity of the surface ocean we are not yet in a position to predict what the impact on caco3 production will be or how the uptake of fossil fuel co2 by the ocean will be affected this uncertainty in the future trajectory of atmospheric co2 that comes from incomplete understanding of the marine carbonate cycle is cause for concern

climatological distribution of aragonite saturation state in the global oceans aragonite saturation state arag in surface and subsurface waters of the global oceans was calculated from up to date through the year of 2012 ocean station dissolved inorganic carbon dic and total alkalinity ta data surface arag in the open ocean was always supersaturated 1 ranging between 1 1 and 4 2 it was above 2 0 2 0 4 2 between 40 n and 40 s but decreased toward higher latitude to below 1 5 in polar areas the influences of water temperature on the ta dic ratio combined with the temperature effects on inorganic carbon equilibrium and apparent solubility product k sp explain the latitudinal differences in surface arag vertically arag was highest in the surface mixed layer higher hydrostatic pressure lower water temperature and more co2 buildup from biological activity in the absence of air sea gas exchange helped maintain lower arag in the deep ocean below the thermocline aerobic decomposition of organic matter along the pathway of global thermohaline circulation played an important role in controlling arag distributions seasonally surface arag above 30 latitudes was about 0 06 to 0 55 higher during warmer months than during colder months in the open ocean waters of both hemispheres decadal changes of arag in the atlantic and pacific oceans showed that arag in waters shallower than 100 m depth decreased by 0 10 0 09 0 40 0 37 yr 1 on average from the decade spanning 1989 1998 to the decade spanning 1998 2010

production and cycling of calcium carbonate in a shelf edge reef system st croix u s virgin islands applications to the nature of reef systems in the fossil record abstract geologic reefs are the end products of not only constructive processes that produce calcium carbonate but also of destructive processes e g bioerosion and wave action that reduce solid substrate to sediment and of physical processes that rework the reef fabric and transport sediment a study was conducted at cane bay on the island of st croix u s virgin islands to quantify the suite of processes that have influenced holocene reef development data on carbonate production reef accretion bioerosion and sediment transport were used to construct a detailed carbonate budget and to apply the findings of this study to the character of reefs observed in the fossil record total carbonate production on the reef ranged from 0 to 5 78 kg m2 per year with a reef wide average of 1 21 kg m2 per year 1 13 by corals 0 02 by coralline algae 0 06 by primarily molluscs forams and echinoderms based on 7 cores only 0 91 kg m2 per year of this have been retained within the reef interior the remaining 0 24 kg m2 per year of sediment along with the 0 06 kg m2 per year contributed directly by molluscs etc are deposited within reef channels and are probably flushed from the reef by major storms of the material recovered in the cores 58 was either loose sediment and rubble or open void space much of the recognizable coral material was demonstrably reworked and out of place accretion rates across the shelf generally increased with water depth as a result of active slumping along the steepening reef face over the past 2 000 3 000 years the importance of detrital material in the reef fabric and the major role played by secondary processes that constantly rework the substrate have resulted in a reef whose interior is more of a garbage pile than an in place assemblage of corals cemented together into a rigid framework the physical similarities between the detrital fabric of the reef at cane bay and those found in many ancient deposits imply that the general processes operating along the cane bay shelf have persisted during much of the evolution of ancient reefs it is proposed that our modern models overemphasize the importance of in place framework as a criterion for an ecologic reef

holocene glacier and climate fluctuations of the maritime ice cap hogtuvbreen northern norway holocene fluctuations of a small outlet glacier from the ice cap hogtuvbreen at 65 n in coastal northern norway are reconstructed based on distal glacier fed lake sediments complemented by a moraine sequence dated by lichenometry glaciers respond to changes in accumulation season precipitation ablation season temperature and redistribution of snow by wind hence reconstructions of glacier fluctuations based on distal glacier fed lakes may give detailed information about past climate at a potentially high temporal resolution yet the importance of any of these climate components is often difficult to solve here we apply the liestol relationship which expresses the relationship between ablation season temperature and annual accumulation of snow at the equilibrium line altitude ela to the reconstructed local temperature precipitation wind ela tpw ela to infer the relative importance of winter balance and ablation season temperature as causes of reconstructed glacier variation the reconstruct

high precipitation rate in a middle triassic carbonate platform implications on the relationship between seawater saturation state and carbonate production abstract three dimensional geological modeling of the middle triassic latemar carbonate platform is coupled with facies modal analysis to estimate its carbonate precipitation rate g the 3d model strongly constrained by field data encompasses a specific stratigraphic interval of the platform bounded by two isochronous surfaces modal analysis of thin sections allows estimating the proportion of syndepositional vs postdepositional carbonate in the facies associations of the platform this together with the 3d facies distribution in the model that takes into account lateral and vertical facies variability permits to calculate the volumes of syndepositional carbonate preserved at latemar between the two considered isochrones given the peculiar characteristics of the platform that does not show evidences of strong dissolution processes or large carbonate mass loss through export in the nearby basins results can be used to estimate the average precipitation rate of the platform in the considered time interval this estimate allows discussion in relation to models of ocean water saturation state with respect to carbonates in the geological past and comparison to the calculated precipitation rates of modern tropical coral reef ecosystems at global and reef scale a high g value is found at latemar and represents the first empirical confirmation that in the triassic extremes in may have triggered high carbonate precipitation in shallow water settings moreover comparison to modern reefs points to a possible common relationship that may link seawater and precipitation rate in carbonate platform ecosystems through geological time

a new interpretation of the date of the little ice age glacier maximum at svartisen and okstindan northern norway new results concerning the dating of little ice age glacier variations at svartisen and okstindan northern norway are presented measurements of lichens of the rhizocarpon subgenus on gravestones are used to construct several local sets of lichenometric dating curves these are partly adjusted in relation to well established lichenometric dating curves from southern norway the little ice age maximum at svartisen and okstindan is thereby dated to the mid eighteenth century i e in agreement with southern norway pre viously suggested earlier little ice age advances are demonstrated to have resulted from an underestimation of the growth rates of the rhizocarpon subgenus synchroneity of little ice age maxima in southern norway and at svartisen and okstindan suggest that a north south migration of latitudinal depressional tracks can be excluded as the main forcing factor as an alternative an increased se nw trend of moist air ow in winter parallel to the coast of norway is suggested as the

on the accuracy of lichenometric dates an assessment based on the little ice age moraine sequence of nigardsbreen southern norway families of lichenometric dating curves are constructed using four historically dated moraine ridges on the glacier foreland of nigardsbreen jostedalsbreen ice cap southern norway a further 20 little ice age moraine ridges are dated in terms of median predicted dates derived from the families of curves four approaches are used to assess the accuracy of the median predicted dates 1 the extent to which the dates form a temporal sequence 2 the extent to which they agree with local independent evidence of glacier variations 3 the extent to which dates agree when the moraine sequences on the two sides of the glacier foreland are dated separately and 4 the extent to which they agree when section rhizocarpon is differentiated from lichens of the rhizocarpon subgenus as a whole it is concluded that under conditions favourable for lichenometric dating median predicted dates have attained an accuracy of 10 on the little ice age timescale realistic error limits are considered to be of the o

glacier and lake level variations in west central europe over the last 3500 years on the basis of glacier and lake level records this paper attempts for the first time a comparison between high resolution palaeohydrological and palaeoglaciological data in west central europe over the past 3500 years a data set of tree ring width radiocarbon and archaeological data in addition to historical sources were used to reconstruct fluctuations of the great aletsch the gorner and the lower grindelwald glaciers in the swiss alps the three ice streams experienced nearly synchronous advances at c 1000 600 bc and ad 500 600 800 900 1100 1200 and 1300 1860 these glacier fluctuations show strong correspondence with lake level variations reconstructed in eastern france jura mountains and pre alps and on the swiss plateau this supports the hypothesis of climatically driven fluctuations historical data available for the period since ad 1550 reveal in detail various meteorological conditions behind the successive glacier advances however in agreement with the general trend shown by th

multi scale three dimensional distribution of fracture and igneous intrusion controlled hydrothermal dolomite from digital outcrop model latemar platform dolomites northern italy abstract in recent years fracture controlled hydrothermal dolomitization in association with igneous activity has gained interest in hydrocarbon exploration the geometry and distribution of dolomite bodies in this setting are of major importance for these new plays the latemar platform presents a spectacularly exposed outcrop analogue for carbonate reservoirs affected by igneous activity and dolomitization light detection and ranging lidar scanning and digital outcrop models doms of outcrops offer a great opportunity to derive geometrical information only a few analysis methods exist to quantitatively assess huge amounts of georeferenced three dimensional lithology data this study presents a novel quantitative approach to describe three dimensional spatial variation of lithology derived from doms this approach is applied to the latemar platform to determine dolomite body geometry and distribution in relation to crosscutting dikes a high resolution photorealistic dom of the latemar platform allows description of dolomite occurrences in three dimensions with high precision at platform scale this results in a unique lithology dataset of limestone dolomite and dike positions this dataset is analyzed by true three dimensional variography for the geospatial description of dolomite distribution in most studies three dimensional geostatistics is the combination of two dimensional horizontal and one dimensional vertical variation in this study the dolomite occurrences are extensive in three dimensions and cannot be reduced to a two dimensional one dimensional case therefore the concept of two dimensional variogram maps is expanded to a three dimensional description of lithology variation three dimensional anisotropy detection is used to derive principal directions in the occurrence of dolomite two small scale

airborne measurements of particle and gas emissions from the december 1994 january 1995 eruption of popocatepetl volcano mexico abstract airborne and ground based correlation spectrometer cascade impactor and photoelectric counter together with intake filter probes measurements are described for the volcanic emissions from popocatepetl volcano mexico from december 23 1994 to january 28 1995 measurements of so 2 restarted 48 h after the eruption onset of december 21 1994 maximum sulfur dioxide 4560 t d 1 plus 3 8 10 4 t d 1 of particulate matter were ejected on december 24 1994 the maximum rate of ejection occurred coincidentally with the maximum amplitude of harmonic tremor and the maximum number of seismic type b events sulfur dioxide emission rates ranged from 1790 to 2070 t d 1 december 23 24 1994 afterwards sulfur dioxide emission rates clearly indicated a consistent decline however frequent gas and ash emission puffs exhibited so 2 fluxes reaching values as high as 3060 t d 1 the emission so 2 baseline for the period of study february 1994 january 1995 was about 1000 t d 1 ejection velocity of particulate matter was approximately 270 m s 1 reaching a height of about 2 5 km over the summit the immediate aerosol dispersion area was estimated at 6 0 10 4 km 2 maximum the microscopic structure of particles aerosol and tephra showed a fragile material probably coming from weathered crustal layers x ray fluorescence and neutron activation analysis from the impactor samples found the following elements si al ca s p cl k ni fe ti sc cu zn mn sr cr co y br se ga rb hg and pb morphological analysis shows that ash samples might be from pulverized basaltic rock indicating that the popocatepetl eruption of december 21 1994 was at low temperature the microscopic structure of puff material showed substance aggregates consisted of fragile rock water and adsorbed so 2 these aggregates were observed within water droplets of approximately 1 mm and even larger sulfur transformations in the droplets occurred intensively volcanic ash contained 5 6 of sulfur during the first expulsion hours elemental relative concentrations with respect to al show that both si and s have relative concentrations 1 i e 13 73 and 2 17 respectively in agreement with the photoelectric counter and cospec measurements

the latemar a middle triassic polygonal fault block platform controlled by synsedimentary tectonics abstract detailed field mapping of a middle triassic carbonate buildup the latemar in the western dolomites northern italy has been carried out the latemar is an isolated carbonate buildup that nucleates on a fault bounded structural high horst cut into the underlying late anisian carbonate bank of the contrin fm this study demonstrates that extensional synsedimentary tectonics is the main factor controlling its geometry and provides an age for this tectonic phase in an early phase slopes were mostly composed of well bedded clinostratified grainstones and rudstones in a later stage the deposition of grainstones was accompanied by the emplacement of clinostratified megabreccias the upper portion of slopes is a microbial boundstone with abundant tubiphytes and patches or lenses of grainstone boundstones may occasionally expand into the platform interior and downward to the base of the slope the depositional profile was that of a mounded platform the buildup is dissected by a dense framework of high angle fractures and faults and by magmatic and sedimentary dikes exhibiting two principal directions trending nnw sse and ene wsw faults trending wnw ese were also observed magmatic dikes are related to the emplacement of the nearby predazzo intrusion and are thus upper ladinian kinematic indicators of strike slip activity were observed on fault planes trending nne ssw and nnw sse that can be attributed to cenozoic alpine tectonics faults magmatic dikes and sedimentary dikes show systematic cross cutting relationships with strike slip faults cutting magmatic dikes and magmatic dikes cutting sedimentary neptunian dikes ene wsw and wnw ese faults are cut by all other structures and record the oldest tectonic activity in the region structural analysis attributes this tectonic phase to an extensional stress field with a direction of maximum extension oriented ca n s several lines of evidence including sealed faults and growth wedge geometries allow us to recognize this old tectonic phase as syndepositional and to date it to the latest anisian avisianum and crassus ammonoid biochronozones the horse shoe shape of the platform and its margins rectilinear for long tracts are explained by the existence of a network of extensional faults whose activity lasted for part of the growth of the platform the latemar is thus a polygonal fault block platform controlled by synsedimentary tectonics the resulting sedimentary architecture is that of a growth wedge deposited probably on the uplifted side of a submerged half graben continuous reactivation of faults at platform margins locally determined anomalous facies transitions with well layered platform interior directly in contact with the clinostratified slopes

correlation of late quaternary moraines impact of climate variability glacier response and chronological resolution abstract the last decade has seen a global surge in the number and resolution of well dated geomorphological reconstructions of mountain glacier fluctuations and former ice sheet extents this has been facilitated by the widespread deployment of large samples of terrestrial cosmogenic nuclide dating tcnd allowing more sophisticated probability analyses for reducing the statistical uncertainty of moraine ages and testing of correlations at local regional and hemispheric scales geochronological advances in the field laboratory and on model calibration have taken place in parallel with modelling of palaeoclimate based on glacier reconstructions and of glacier sensitivity to temperature and precipitation forcing in spite of these advances basic conceptual issues remain this review questions whether the technical leap forward in dating has encouraged us to over reach our interpretive limits particularly in terms of the concept and practice of correlation we propose that to enable reliable correlation glacier chronologies should first be examined for their climatic integrity spatial coherence and chronological robustness even with excellent dating interpretive complexity remains due to complex climate signals and glacier response characteristics and to erosion censoring of the landform record all are issues which must be addressed to avoid either spurious lumping correlation or splitting differentiation of glacier chronologies and thus misinterpretation of the climatic significance of reconstructed glacier advances we suggest that the reliability of correlation is no better than the weakest link in the chain of reasoning which connects climatic fluctuations with dated landforms and sediments improved dating means that poor chronological resolution is less likely to be the limiting factor for correlation but shifts the focus onto other less quantifiable sources of uncertainty these conceptual statements are exemplified with reference to holocene glacial chronologies of contrasting mid latitude environments in southern norway iceland and new zealand

a complete record of holocene glacier variability at austre okstindbreen northern norway an integrated approach arctic glaciers are currently undergoing major changes but accurate knowledge about how they varied during the entire holocene is still scarce here we present a new complete glacier record from austre okstindbreen in nordland northern norway this reconstruction is based on a number of short and long cores retrieved from several downstream basins which have been analyzed by a suite of methods including geochemical elements xrf rock magnetic properties dry bulk density dbd and loss on ignition loi lake sediment distribution was surveyed and mapped prior to coring by the use of ground penetrating radar gpr independently lichen dated marginal moraines and historical information about the glacier frontal positions from old photographs and maps have made it possible to link the moraine sequence to the 210pb dated lake sediment chronology this integrated approach reveals that austre okstindbreen is the first known glacier in scandinavia to possibly have survived the holocene thermal optimum it also brackets the four largest glacier advances to c 7400 7000 1400 1200 900 700 and 300 150 years before ad 2000 b2k in contrast to most reconstructed glaciers in scandinavia the largest glacier advance was not associated with the little ice age but rather to an earlier period centred at 1300 b2k both the moraine chronology and the lacustrine records document this neoglacial advance compared to other glacier reconstructions from the northern hemisphere we identify near synchronous glacier advances occurring roughly at 4000 b2k 2700 b2k 1300 b2k and during the little ice age these correlative advances across the northern hemisphere suggest that these observed centennial scale events are a shared feature regardless of the large geographical distances separating them some minor discrepancies between different geographical areas may be caused by lack of precise dating but local climatic conditions may play a role as well

airborne filter pack measurements of s and cl in the plume of redoubt volcano alaska february may 2009 abstract filter pack data from six airborne campaigns at redoubt volcano alaska are reported here these measurements provide a rare constraint on cl output from an andesitic eruption at high emission rate 104 t d 1 so2 four s cl ratios measured during a period of lava dome growth indicate a depth of last magma equilibration of 2 5 km the s cl ratios in combination with cospec so2 emission rate measurements indicate hcl emission rates of 1500 3600 t d 1 during dome growth so2 and hcl emission rates at redoubt volcano correlate with each other and were low prior to the eruption high during the eruption and low after the eruption s cl ratios measured by filter pack at andesitic volcanoes have a small range of variance with no clear trends seen for eruptive versus passive activity the very few s cl ratio measurements by filter pack at andesitic volcanoes are not as predictive of future volcanic activity as has been demonstrated for basaltic volcanoes this may be because there are so few of these measurements we have demonstrated it is possible to collect these samples by air between explosions during lava dome building eruptions we recommend more filter pack sampling be performed at andesitic volcanoes to determine the technique s utility for volcano monitoring filter pack data has been demonstrated to be useful for calculating the depth of magma equilibration at volcanoes including redoubt volcano

biostratigraphic and radiometric age data question the milankovitch characteristics of the latemar cycles southern alps italy the combination of age diagnostic fossils in platform carbonates geometrical relationships with coeval basinal successions and single zircon u pb ages from volcaniclastic layers in basinal deposits constrain the age of a cyclic succession in the interior of the latemar platform to a narrow time span in the middle triassic with a duration shorter than 5 m y precession induced milankovitch band sea level oscillations are therefore excluded as controls for most of the 600 platform cycles reported from latemar statistical evaluation and graphic space time analyses of cycle stacking patterns alone may therefore not allow an unambiguous recognition of milankovitch frequencies in ancient platform carbonates

facies architecture of an isolated carbonate platform tracing the cycles of the latemar middle triassic northern italy the 720 m thick succession of the middle triassic latemar massif dolomites italy was used to reconstruct the lagoonal facies architecture of a small atoll like carbonate platform facies analysis of the lagoonal sediments yields a bathymetric interpretation of the lateral facies variations which reflect a syndepositional palaeorelief based on tracing of lagoonal flooding surfaces the metre scale shallowing upward cycles are interpreted to be of allocyclic origin short term sea level changes led to subaerial exposure of wide parts of the marginal zone resulting in the development of a tepee belt of varying width occasional emergence of the entire lagoon produced lagoon wide decimetre thick red exposure horizons the supratidal tepee belt in the backreef area represented the zone of maximum elevation which circumscribed the sub to peritidal lagoonal interior during most of the platform s development this tepee rim the subtidal reef and a sub to peritidal transition zone in between stabilized the platform margin the asymmetric width of facies belts within individual metre scale cycles was caused by redistribution processes that reflect palaeowinds and storm paths from the present day south and west the overall succession shows stratigraphic changes on a scale of tens of metres from a basal subtidal unit overlain by three tepee rich intervals separated by tepee poor units composed of subtidal to peritidal facies this stacking pattern reflects two third order sequences during the late anisian to early middle ladinian

a high resolution 1200 year lacustrine record of glacier and climate fluctuations in lofoten northern norway here we present the first high resolution late holocene glacier record from the lofoten archipelago in northern norway the study is based on analyses of lacustrine sediments from the distal glacier fed lake kveitvikvatnet 30 1 m a s l as well as glacial geomorphological mapping of the 4 2 km2 surrounding catchment the lake sediment cores have been examined for input of glacial derived sediments by using physical geochemical and magnetic sediment properties including x ray fluorescence xrf magnetic susceptibility ms grain size analyses dry bulk density dbd and loss on ignition loi former glacier extent has been reconstructed using aerial photography and glacial geomorphological mapping lichenometric dating has been used to construct a moraine chronology covering the recent fluctuations of the largest glacier back to ad 1740 ams radiocarbon dating reveals that the lake sediment record covers the last 1200 years thereby including both the little ice age lia and the medieval cl

high resolution estimate for the depositional duration of the triassic latemar platform a new magnetostratigraphy and magnetic susceptibility cyclostratigraphy from basinal sediments at rio sacuz italy 1 a new magnetostratigraphy and magnetic susceptibility cyclostratigraphy from middle triassic basinal sediments at rio sacuz northern italy suggests a depositional duration of 1 myr for most of the 670 m carbonate latemar platform giving a high resolution estimate for the duration for the latemar s deposition the new magnetostratigraphy from rio sacuz clarifies the ambiguities in a previous magnetostratigraphic study of the latemar caused by lightning strike remagnetizations our rio sacuz study was unaffected by lightning using thermal demagnetization we show a normal reversed normal reversed sequence at the latemar correlated locality of rio sacuz with a polarity interval duration of 0 25 0 5 myr for the middle triassic this gives a depositional duration of 1 2 myr rock magnetic experiments show that the magnetic carrier is magnetite suggesting a primary depositional age remanence measurement of magnetic susceptibility at 1 m intervals from rio sacuz reveals eight short eccentricity cycles 95 125 kyr bundled into slightly more than two 405 kyr long eccentricity cycles indicating a more precise duration for the rio sacuz section of 0 8 to 1 myr the shorter depositional duration required by this study forces a sub milankovitch time scale of 1 2 kyr for the latemar platform s meter scale rhythmic bedding and provides strong evidence for nonorbitally driven climate change in the middle triassic

magnetostratigraphic confirmation of a much faster tempo for sea level change for the middle triassic latemar platform carbonates new magnetostratigraphic data for the 470 m thick latemar carbonate platform which includes 600 shallowing upward bedding cycles are consistent with litho and biostratigraphic correlations of the section to a 10 m thick interval in the basinal buchenstein beds that most likely represents only 1 m y of deposition according to published u pb single crystal zircon dates a reappraisal of reported cycle stratigraphic analyses of the latemar suggests that the visibly obvious meter scale bedding is not due to milankovitch precessional forcing but rather reflects tempos an order of magnitude faster that may involve millennial scale tidal amplitude variations d 2004 elsevier b v all rights reserved

satellite measurement of sulfur dioxide from the redoubt eruptions of 1989 1990 abstract the mass of so 2 emitted by the 16 major explosive eruptions of redoubt volcano between december 1989 and april 1990 have been examined by the total ozone mapping spectrometer toms carried on the nimbus 7 satellite because of low light levels during the winter months toms could not detect so 2 at high northern latitudes thus the major eruptions from december through february could not be monitored unless winds brought the clouds to latitudes lower than about 58 n only two so 2 clouds were observed in the satellite data an approximately 100 kiloton kt cloud on december 16 over nevada and eastern california and a 10 kt cloud on march 9 directly over the volcano we speculate that the major eruption on december 15 at 1015 hour produced the 100 kt cloud seen on december 16 and the mass of so 2 injected into the atmosphere at that time was 175 50 kt

an inverse approach to the course of the little ice age glacier advance and the following deglaciation at austerdalsisen eastern svartisen northern norway the course of the little ice age lia in scandinavia is characterized by large glacier advances that started at about ad 1300 and culminated at about ad 1750 the end of the lia is marked as an unprecedented and ongoing glacier retreat that accelerated from the early 20th century the course of the lia is here presented based on fluctuations of austerdalsisen the largest valley outlet glacier draining the austre svartisen ostisen ice cap nordland northern norway during the lia glacierization austerdalsisen separated into two branches and relative to the present glacier terminus a western valley glacier advanced more than 4 km whereas a se valley glacier advanced about 3 km at present meltwater from austerdalsisen drains towards se if the glacier obtains a critical magnitude however most of the meltwater is drained westwards across a higher overflow gap based on radiocarbon dated lake sediments distal proglacial glaciolacustrine glaciofluvial sediments and historical observations the c

reconstruction of former glacier equilibrium line altitudes based on proglacial sites an evaluation of approaches and selection of sites abstract various approaches are used to record variations in glacier activity and equilibrium line altitudes elas based on proglacial sites lacustrine and terrestrial these approaches are based on a conceptual model of glacier meltwater induced sedimentation in which the minerogenic nonorganic component of the sediments is related to the occurrence of a glacier in the catchment the principal coupling to former glacier activity and elas is common for these approaches however different methods and techniques may complement each other and both possibilities and limitations are demonstrated site selection for reconstructing variations in glacier activity elas is evaluated and critical factors are discussed rerouting of glacier meltwater streams across local watersheds in combination with proglacial sites gives a distinct on off signal for former glacier activity elas together with representative lateral moraines of known age local watersheds are important for calibrating reconstructed glacier activity elas based on a chain of proglacial lakes based on the modern analogue principle various proxies can record whenever glaciers existed in a catchment in a chain of proglacial lakes with different sensitivity to record variations in glacier activity elas these proxies can be calibrated against independent records for one site approaches however variations in glacier activity elas depend on the interpretation and sensitivity of the proxies used

holocene glacier chronologies are high resolution global and inter hemispheric comparisons possible in the context of reconstruction of holocene glacier chronologies there has been a clear tendency during the past few decades towards imprecise use of the term high resolution furthermore it seems to be increasingly assumed that recently developed terrestrial cosmogenic nuclide dating tcnd is replacing earlier dating methods although recent glaciological knowledge clearly reveals the futility of oversimplified global and inter hemispheric correlation on the basis of few key sites such comparisons are widely attempted stimulated by the example of a recently published article relating to the southern alps of new zealand schaefer et al 2009 science 324 622 625 we highlight some related potential problems with the interpretation of holocene glacier chronologies in particular we consider 1 that the term high resolution should be applied only to decadal scale resolution or better and therefore not to tcnd based chronologies 2 that discontinuous moraine chronologies should not be ter

benthic carbonate factories of the phanerozoic marine carbonate precipitation occurs in three basic modes abiotic or quasi abiotic biotically induced and biotically controlled on a geologic scale these precipitation modes combine to form three carbonate production systems or factories in the benthic environment 1 tropical shallow water factory dominated by biotically controlled mainly photo autotrophic and abiotic precipitates 2 cool water factory dominated by biotically controlled mainly heterotrophic precipitates and 3 mud mound factory dominated by biotically induced mainly microbial and abiotic precipitates sediment accumulations of the factories differ in composition geometry and facies patterns and some of these differences appear prominently in seismic data thus facilitating subsurface prediction the characteristic accumulation of the tropical factory is the flat topped often reef rimmed platform in cool water systems reefs in high energy settings are scarce and hydrodynamic influence dominates producing seaward sloping shelves and deep water sediment drifts often armored by skeletal framework the typical accumulation of the mud mound factory is groups of mounds in deeper water where the mud mound factory expands into shallow water it forms rimmed platforms similar to the tropical factory the tropical factory is most productive the mud mound factory reaches 80 90 and the cool water factory 20 30 of the tropical growth rate the three factories represent end members connected by transitions in space transitions in time are linked to biotic evolution

glacier fluctuations during the past 2000 years abstract a global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions excluding antarctica highlights the nature of glacier fluctuations during the late holocene the dataset includes 275 time series of glacier fluctuations based on historical tree ring lake sediment radiocarbon and terrestrial cosmogenic nuclide data the most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and when available winter precipitation reconstructions the most important parameters for glacier mass balance in many cases major glacier advances correlate with multi decadal periods of decreased summer temperature in a few cases such as in arctic alaska and western canada some glacier advances occurred during relatively warm wet times the timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region however the number of glacier advances shows a clear pattern for the high mid and low latitudes and hence points to common forcing factors acting at the global scale globally during the first millennium ce glaciers were smaller than between the advances in 13th to early 20th centuries ce the precise extent of glacier retreat in the first millennium is not well defined however the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th early 21st centuries other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the european alps in the 3rd 6th and 9th centuries in norway during the 10th 13th centuries in southern alaska and in the 18th century in spitsbergen however no single period of common global glacier retreat of centennial duration except for the past century has yet been identified in contrast the view that the little ice age was a period of global glacier expansion beginning in the 13th century or earlier and reaching a maximum in 17th 19th centuries is supported by our data the pattern of glacier variations in the past two millennia corresponds with cooling in reconstructed temperature records at the continental and hemispheric scales the number of glacier advances also broadly matches periods showing high volcanic activity and low solar irradiance over the past two millennia although the resolution of most glacier chronologies is not enough for robust statistical correlations glacier retreat in the past 100 150 years corresponds to the anthropogenic global temperature increase many questions concerning the relative strength of forcing factors that drove glacier variations in the past 2 ka still remain

seismic evolution of the 1989 1990 eruption sequence of redoubt volcano alaska abstract redoubt volcano in south central alaska erupted between december 1989 and june 1990 in a sequence of events characterized by large tephra eruptions pyroclastic flows lahars and debris flows and episodes of dome growth the eruption was monitored by a network of five to nine seismic stations located 1 to 22 km from the summit crater notable features of the eruption seismicity include 1 small long period events beginning in september 1989 which increased slowly in number during november and early december 2 an intense swarm of long period events which preceded the initial eruptions on december 14 by 23 hours 3 shallow swarms 0 to 3 km of volcano tectonic events following each eruption on december 15 4 a persistent cluster of deep 6 to 10 km volcano tectonic earthquakes initiated by the eruptions on december 15 which continued throughout and beyond the eruption 5 an intense swarm of long period events which preceded the eruptions on january 2 and 6 nine additional intervals of increased long period seismicity each of which preceded a tephra eruption hypocenters of volcano tectonic earthquakes suggest the presence of a magma source region at 6 10 km depth earthquakes at these depths were initiated by the tephra eruptions on december 15 and likely represent the readjustment of stresses in the country rock associated with the removal of magma from these depths the locations and time history of these earthquakes coupled with the eruptive behavior of the volcano suggest this region was the source of most of the erupted material during the 1989 1990 eruption this source region appears to be connected to the surface by a narrow pipe like conduit as inferred from the hypocenters of volcano tectonic earthquakes concentrations of shallow volcano tectonic earthquakes followed each of the tephra eruptions on december 15 these shocks may represent stress readjustment in the wall rock related to the removal of magma and volatiles at these depths this shallow zone was the source area of the majority of long period seismicity through the remainder of the eruption the long period seismicity likely reflects the pressurization of the shallow portions of the magmatic system

proximal pyroclastic deposits from the 1989 1990 eruption of redoubt volcano alaska stratigraphy distribution and physical characteristics abstract more than 20 eruptive events during the 1989 1990 eruption of redoubt volcano emplaced a complex sequence of lithic pyroclastic flow surge fall ice diamict and lahar deposits mainly on the north side of the volcano the deposits record the changing eruption dynamics from initial gas rich vent clearing explosions to episodic gas poor lava dome extrusions and failures the repeated dome failures produced lithic pyroclastic flows that mixed with snow and glacial ice to generate lahars that were channelled off drift glacier into the drift river valley some of the dome failures occurred without precursory seismic warning and appeared to result solely from gravitational instability material from the disrupted lava domes avalanched down a steep partly ice filled canyon incised on the north flank of the volcano and came to rest on the heavily crevassed surface of the piedmont lobe of drift glacier most dome collapse events resulted in single monolithologic massive to reversely graded medium to coarse grained sandy pyroclastic flow deposits containing abundant dense dome clasts these deposits vary in thickness grain size and texture depending on distance from the vent and local topography deposits are finer and better sorted down flow thinner and finer on hummocks and thicker and coarser where ponded in channels cut through the glacial ice the initial vent clearing explosions emplaced unusual deposits of glacial ice snow and rock in a frozen matrix on the north and south flanks of the volcano similar deposits were described at nevado del ruiz columbia and have probably been emplaced at other snow and ice clad volcanoes but poor preservation makes them difficult to recognize in the geologic record in a like fashion most deposits from the 1989 1990 eruption of redoubt volcano may be difficult to recognize and interpret in the future because they were emplaced in an environment where glacio fluvial processes dominate and quickly obscure the primary depositional record

geochemistry of the 1989 1990 eruption of redoubt volcano part i whole rock major and trace element chemistry the 1989 1990 eruption of redoubt volcano produced medium k calc alkaline andesite and dacite of limited compositional range 58 2 63 4 sio2 and entrained quenched andesitic inclusions 55 sio2 which bear chemical similarities to the rest of the ejecta the earliest december 15 magmas are pumiceous often compositionally banded and the majority is relatively mafic 59 sio2 the most silicic magmas of the eruption are the late december to early january domes up to 63 4 sio2 subsequent magmas formed domes and rare pumices which converge on 60 sio2 chemical variations among ejecta comprise tight linear two component arrays for all elements for which the analytical uncertainty is much less than the compositional range the two component arrays are interpreted as mixing arrays between unrelated magmas because several of the arrays are at steep angles to the normal liquid line of descent additionally the felsic endmember cannot be easily related to the mafic endmember by normal high temperature igneous processes e g the silicic endmember has higher zr yet lower hf than the mafic endmember also relative enrichments of highly incompatible elements are dramatically different across the arrays the mixing event must have preceded eruption by a significant yet unspecified amount of time because groundmass glass compositions are homogeneous for all post december samples swanson et al 1994 this volume in spite of the whole rock chemical diversity this implies time for additional crystallization after the mixing event swanson et al 1994 this volume discuss evidence for a potentially different mixing event recorded only in december 15 magmas cognate cumulate xenoliths composed of pl cpx opx hb mt melt were recovered from january and april deposits these blocks differ from local batholithic country rock in their low concentrations of incompatible elements e g rb 60 wt they have mg cr ni sc and v contents higher than the andesites but lower than redoubt basalts and basaltic andesites thus they may be crystallization products of andesites but do not represent the cumulate residue of basalt fractionation the xenoliths were probably derived from a shallow or intermediate crustal chamber

aragonite dissolution sedimentation rates and carbon isotopes in deep water hemipelagites livinallongo formation middle triassic northern italy hemipelagic nodular limestones are a widespread facies in the triassic of the tethys often considered as being deposited at rather constant sedimentation rates the aim of this paper is to investigate the sedimentation rate variability in a case study from the middle triassic of the dolomites northern italy and to suggest possible causes the nodular cherty limestones of the livinallongo fm and correlated units were studied in four stratigraphic sections and compared to classical successions from the literature correlations between sections are based on ammonoid biostratigraphy and tephra stratigraphy correlation highlighted conspicuous changes in sedimentation rates through time and between sections associated with sedimentological evidence of deep water aragonite dissolution deep water dissolution is believed to have resulted in small hiatuses and in a bias of ammonoid assemblages towards taxa with more resistant shells carbonate petrography and geochemistry provide evidence of differential diagenesis of the livinallongo fm carbonate nodules were lithified at the water sediment interface and their c isotope composition is regarded as a proxy of the d 13 c of middle triassic bottom seawater the onset of nodular cherty limestones occurring contemporaneously at the basin scale and the coeval carbonate platform drowning events are tentatively explained by the inflow and local upwelling of cool deep water from panthalassa into the western tethys d 2005 elsevier b v all rights reserved

high resolution magnetostratigraphic and lithostratigraphic correlations in middle triassic pelagic carbonates from the dolomites northern italy new magnetostratigraphic and lithostratigraphic data are reported from the pedraces and belvedere limestone sections from the dolomites region of northern italy these sections are comprised of the buchenstein beds of late anisian to ladinian middle triassic age the results from pedraces and belvedere are compared with data from the biostratigraphically and isotopically constrained frotschbach and seceda sections from the literature a satisfactory magnetostratigraphic correlation is obtained on laterally traceable limestone and volcaniclastic intervals these marker beds are then used to extend lithostratigraphic correlations to additional key sections from a palaeogeographically coherent area of around 500 km2 the aim of this study is to unravel the spatial and temporal evolution of the buchenstein basin and the surrounding carbonate platforms platforms in the northwestern dolomites show an early stage of aggradation followed by progradation whereas in the central dolomites the cernera platform after fast initial aggradation drowned and became a pelagic seamount in the intervening buchenstein basin the diverential subsidence between the northwestern and central dolomites is manifested by the lateral increase of thickness of lower pietra verde volcaniclastic sediments accumulation of volcaniclastic material reworked from adjacent carbonate platform slopes characterised the more subsiding and unstable central dolomites in the pelagic carbonate intervals the persistence over tens of kilometres of bedding patterns suggests that carbonate material presumably washed out from the surrounding still active carbonate platforms was volumetrically small and homogeneously distributed throughout the uniformly subsiding buchenstein basin a milankovitch precessional origin for the platform interior cycles at latemar as suggested elsewhere implies a net accumulation rate of 2 m ma or less for the correlative interval of pelagic buchenstein beds this value divers significantly from the average value of around 10 m ma as calculated using high resolution isotopic age data for the buchenstein beds 2000 elsevier science b v all rights reserved

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

emission rates of sulfur dioxide and carbon dioxide from redoubt volcano alaska during the 1989 1990 eruptions airborne measurements of sulfur dioxide emission rates in the gas plume emitted from fumaroles in the summit crater of redoubt volcano were started on march 20 1990 using the cospec method during the latter half of the period of intermittent dome growth and destruction between march 20 and mid june 1990 sulfur dioxide emission rates ranged from approximately 1250 to 5850 t d rates notably higher than for other convergent plate boundary volcanoes during periods of active dome growth emission rates following the end of dome growth from late june 1990 through may 1991 decreased steadily to less than 75 t d the largest mass of sulfur dioxide was released during the period of explosive vent clearing when explosive degassing on december 14 15 injected at least 175 000 50 000 tonnes of so2 into the atmosphere following the explosive eruptions of december 1989 redoubt volcano entered a period of intermittent dome growth from late december 1989 to mid june 1990 during which redoubt emitted a total mass of so2 ranging from 572 000 90 000 tonnes to 680 000 90 000 tonnes from mid june 1990 through may 1991 the volcano was in a state of posteruption degassing into the troposphere producing approximately 183 000 50 000 tonnes of so2 we estimate that redoubt volcano released a minimum mass of sulfur dioxide of approximately 930 000 tonnes while cospec data were not obtained frequently enough to enable their use in eruption prediction so2 emission rates clearly indicated a consistent decline in emission rates between march through october 1990 and a continued low level of emission rates through the first half of 1991 values from consecutive daily measurements of sulfur dioxide emission rates spanning the march 23 1990 eruption decreased in the three days prior to eruption that decrease was coincident with a several fold increase in the frequency of shallow seismic events suggesting partial sealing of the magma conduit to gas loss that resulted in pressurization of the shallow magma system and an increase in earthquake activity unlike the short term so2 decrease in march 1990 the long term decrease of sulfur dioxide emission rates from march 1990 through may 1991 was coincident with low rates of seismic energy release and was interpreted to reflect gradual depressurization of the shallow magma reservoir the long term declines in seismic energy release and in so2 emission rates led avo scientists to conclude on april 19 1991 that the potential for further eruptive activity from redoubt volcano had diminished and on this basis the level of concern color code for the volcano was changed from code yellow volcano is restless earthquake activity is elevated activity may include extrusion of lava to code green volcano is in its normal dormant state

dome growth and destruction during the 1989 1990 eruption of redoubt volcano abstract much of the six month long 1989 1990 eruption of redoubt volcano consisted of a dome growth and destructive phase in which 14 short lived viscous silicic andesite domes were emplaced and 13 subsequently destroyed the life span of an individual dome ranged from 3 to 21 days and volumes are estimated at 1 10 6 to 30 10 6 m 3 magma supply rates to the vent area averaged about 5 10 5 m 3 day for most of the dome building phase and ranged from a high of 2 2 10 6 m 3 per day initially to a low of 1 8 10 5 m 3 per day at the waning stages of the eruption the total volume of all domes is estimated to be about 90 10 6 m 3 and may represent as much as 60 70 of the volume for the entire eruption the site of 1989 1990 dome emplacement like that in 1966 was on the margin of a north facing amphitheatre like summit crater the domes were confined on the east and west by steep cliffs of pre eruption cone building volcanic rocks and thus were constrained to grow vertically rapid upward growth in a precarious site caused each dome to spread preferentially to the north resulting in eventual gravitational collapse as long as the present conduit remains active at redoubt volcano any dome formed in a new eruption will be confined to a narrow steeply sloping gorge leading to rapid vertical growth and a tendency to collapse gravitationally repetitive cycles of dome formation and failure similar to those seen in 1989 1990 are probably the norm and must be considered in future hazard analyses of redoubt volcano

evaluation of gases condensates and so2 emissions from augustine volcano alaska the degassing of a cl rich volcanic system after the march april 1986 explosive eruption a comprehensive gas study at augustine was undertaken in the summers of 1986 and 1987 airborne cospec measurements indicate that passive so2 emission rates declined exponentially during this period from 380 45 metric tons day t d on 7 24 86 to 27 6 t d on 8 24 87 these data are consistent with the hypothesis that the augustine magma reservoir has become more degassed as volcanic activity decreased after the spring 1986 eruption gas samples collected in 1987 from an 870 c fumarole on the andesitic lava dome show various degrees of disequilibrium due to oxidation of reduced gas species and condensation and loss of h2o in the intake tube of the sampling apparatus thermochemical restoration of the data permits removal of these effects to infer an equilibrium composition of the gases although not conclusive this restoration is consistent with the idea that the gases were in equilibrium at 870 c with an oxygen fugacity near the ni nio buffer these restored gas compositions show that relative to other convergent plate volcanoes the augustine gases are very hcl rich 5 3 6 0 mol hcl s rich 7 1 mol total s and h2o poor 83 9 84 8 mol h2o values of d and 18o suggest that the h2o in the dome gases is a mixture of primary magmatic water pmw and local seawater part of the cl in the augustine volcanic gases probably comes from this shallow seawater source additional cl may come from subducted oceanic crust because data by johnston 1978 show that cl rich glass inclusions in olivine crystals contain hornblende which is evidence for a deep source 25km for part of the cl gas samples collected in 1986 from 390 642 c fumaroles on a ramp surrounding the inner summit crater have been oxidized so severely that restoration to an equilibrium composition is not possible h and o isotope data suggest that these gases are variable mixtures of seawater fmw and meteoric steam these samples are much more h2o rich 92 97 h2o than the dome gases possibly due to a larger meteoric steam component the 1986 samples also have higher cl s s c and f cl ratios which imply that the magmatic component in these gases is from the more degassed 1976 magma thus the 1987 samples from the lava dome are better indicators than the 1986 samples of degassing within the augustine magma reservoir even though they were collected a year later and contain a significant seawater component future gas studies at augustine should emphasize fumaroles on active lava domes condensates collected from the same lava dome fumarole have enrichments ot 107 102 in cl br f b cd as s bi pb sb mo zn cu k li na si and ni lower temperature 200 650 c fumaroles around the volcano are generally less enriched in highly volatile elements however these lower termperature fumaroles have higher concentration of rock forming elements probably derived from the wall rock

an 1899 glacier inventory for nordland northern norway produced from historical maps glaciers depicted on old maps reveal their historical extents before the advent of aerial and satellite remote sensing digital glacier inventories produced from these maps can be employed in assessments of centennial scale glacier change this study reconstructs the 1899 covering the period 1882 1916 glacier extent in nordland northern norway from historical gradteigskart maps with an emphasis on examining the accuracy of the mapped glaciers glacier outlines were digitised from georectified scans of the analogue maps in a raster graphics editor and were subsequently inventoried in a gis the accuracy of the historical glacier extent was established from written descriptions and landscape photographs created during the original field surveys and further validated against independent glacier outlines of 1 the maximum little ice age extent derived from geomorphological evidence and 2 the 1945 extent derived from vertical aerial photographs an overall uncertainty of 17 is associated with our inventory nordland s glaciers covered an area of 1712 291 km2 in 1899 by 2000 total ice cover had decreased by 47 807 137 km2 at a rate of 6 10 a 1 80 14 km2 10 a 1 the approach presented here may serve as a blueprint for future studies intending to derive glacier inventories from historical maps