geomagnetic secular variation from holocene lake sediments of soro so denmark abstract a record of geomagnetic secular variation for the last 7500 years has been obtained from three cores of lake sediment from soro so in denmark the time scale has been derived from six radiocarbon age determinations on one of the cores variations in geomagnetic declination and inclination agree well with those found in a previous study using sediments from another danish lake skanderborg so some 120 km from soro so a correlation with the record from the u k has been made but with age differences of up to 1000 years which are attributed to the dating errors inherent in the radiocarbon method when applied to lake sediments in both the u k and danish sediments the virtual geomagnetic pole path since 7500 bp appears to have had periods of both clockwise and anticlockwise motion of 1000 year duration where the looping is open interspaced with shorter periods of 500 years in which the geomagnetic behaviour is more irregular it is suggested that this indicates a possible regularity in the pattern of field behaviour during the post glacial

a refined age calibrated paleosecular variation and relative paleointensity stack for the nw barents sea implication for geomagnetic field behavior during the holocene abstract reconstruction of paleomagnetic secular variation psv of the geomagnetic field is fundamental both to assess geodynamo models and to obtain age constraints for rocks sediments and archaeological material we present refined age calibrated holocene psv and relative paleointensity rpi stack curves derived from arctic marine sediments northwestern barents sea the holocene sections of four sedimentary cores were correlated on the basis of paleomagnetic trends and age models and stacked the resultant composite psv and rpi holocene records nbs stack and the reconstructed holocene virtual geomagnetic pole vgp path were evaluated in comparison with the most recent paleomagnetic stack curves and geomagnetic field models the data indicate that during the holocene time the vgps moved within the superficial projection of the inner core tangent cylinder with the exception of short time intervals around 5600 and 3200 cal yr bp when vgps extended to lower latitudes these deviations might reflect regional geomagnetic features such as persistent geomagnetic flux lobes at core mantle boundary our data confirm that the large vgp shift observed around 5600 cal yr bp is the result of an increased radial magnetic field at the core mantle boundary over north america whilst the vgp shift around 3200 cal yr bp represents a major swing to middle latitudes toward the middle east and might be associated to a regional high paleointensity peak known as levantine iron age anomaly liaa

millennial scale cyclicity in the geodynamo inferred from a dipole tilt reconstruction constraining past changes in the strength and configuration of the geomagnetic field provides a valuable perspective on the processes that govern the geodynamo here we update a modelled dipole tilt reconstruction for the last 9000 years by using palaeomagnetic records that originate from globally well distributed sites some features predicted by earlier dipole models become more distinct due to added data sets we identify a dominant 1350 year cycle in the dipole tilt variations and two preferred states of the dipole axis with north geomagnetic pole longitudes confined to either c 120 degrees west or c 30 degrees east the dipole tilt reconstruction is shown to be consistent with independent geomagnetic field intensity data from western eurasia which show generally higher intensities when the dipole is tilted towards this region our study implies that vadm reconstructions that are constrained by a biased spatial distribution of data can show variations resulting from dipole tilt instead of true dipole moment the preferred states of the modelled dipole axis can be related to the four semi stationary high latitude flux lobes that have been observed at the core mantle boundary in long term time averaged palaeomagnetic field models the tilt episodes towards 30 degrees east in the northern hemisphere are perhaps related to the appearance of a high intensity flux lobe beneath western eurasia the dipole tilt reconstruction is highly correlated to millennial scale variations in the length of day that have been reconstructed from ancient records of eclipses which indicates that the cyclicity may constitute an important component in core flow dynamics c 2011 elsevier b v all rights reserved less

geomagnetic and mineral magnetic characterization of the anthropocene geomagnetic and mineral magnetic data provide geological indices that are both independent of human impact i e geomagnetic and respond to human induced environmental impact i e mineral magnetic we provide the first discussion of such magnetic events for help in defining the anthropocene within the holocene a potential geomagnetic marker for the anthropocene is the low dipole latitude at c 2700 cal a bp which is associated with distinct palaeosecular variation features in northerly mid to high latitude sites mineral magnetic records from lake and marine sediments identify major deforestation and soil delivery events from catchment systems in many parts of the world during the last 4000 years in europe clusters of these events occur around both 2600 cal a bp and ad 1100 the former coinciding with a low in geomagnetic field dipole latitude and peak intensity mineral magnetic records in peats and lake sediments can reflect particulate pollution from fossil fuel burning the expansion of major coal burning began c ad 1800 in western europe and eastern north america but around ad 1900 this expanded due to more widely distributed coal use and this event is the most clear mineral magnetic marker for the base of the anthropocene

leachate analyses of volcanic ashes from stromboli volcano a proxy for the volcanic gas plume composition 1 many volcanoes show a change in chemical composition of the gas phase prior to periods of eruptive activity fine grained tephra erupted from active vents and transported through volcanic plumes can adsorb and therefore rapidly scavenge volatile elements such as sulfur halogens and metal species in the form of soluble salts adhering to ash surfaces analysis of such water soluble surface materials is a suitable supplement for remote monitoring of volcanic gases at inaccessible volcanoes in this work ash samples of the 2004 to 2009 eruptive activity of stromboli volcano were sampled leached and analyzed for major and trace elements data analysis and interpretation was focused on determining the relationship between chemical composition of water soluble components adhering to volcanic ash and the volcano s activity state first results show significant temporal variations in ash leachate compositions reflecting changes in the eruptive style of the volcano in particular we reveal that ash leachates s f and mg na ratios showed marked increases prior to a large scale explosion on 15 march 2007

detransformation of the british geomagnetic secular variation record for holocene times in this note we replot the british post glacial secular variation curve in terms of actual values of declination and inclination rather than the transformed declination and inclination system used in our original paper turner thompson 1981 this should facilitate the comparison of our record with contemporaneous european archaeomagnetic data our composite record was obtained by averaging the dated records from 10 cores of lake sediment the sequence of unit vectors describing the magnetic direction record of each core was rotated so as to place its mean direction the mean over the section of core dated between 0 and 7000 bp the time span of the shortest core at zero transformed declination and inclination dt o it 0 the transformed coordinate frame of each core is thus derived from its mean direction assumed to represent the mean geomagnetic field direction over the 7000 yr period rather than from the core tube and its orientation during coring hence the problem of not knowing the azimuthal orientation and inclination of the corer during core collection is avoided and the 10 records can be averaged in this coordinate system transformed coordinates then provide a convenient generalised method of plotting averaged sediment records however in the archaeomagnetic method sample orientation is straightforward and the results can readily be plotted as absolute declination and inclination values so for consistency when comparing the two we have attempted here to detransform our record the following procedures assumptions and approximations were taken to produce the detransformed magnetograms and bauer type plots of figs 1 and 2 1 amplitude correction although the combination of 10 data sets produces a good estimate of the signature of the geomagnetic variations the following factors contribute to an overall loss of amplitude in both declination and inclination a the quality of magnetic recording varies widely between different sediments depending on the porosity of the sediment the size and shape distributions and the nature of the magnetic carrier verosub 1979 the loch lomond sediments carry a good high amplitude pattern of remanent directions of which the most recent closely follow the london observatory records the much wetter and less compacted sediments of llyn geirionydd on the

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

gas aerosol ash interaction in volcanic plumes new insights from surface analyses of fine ash particles the reactions occurring between gases aerosols and silicate ash particles in volcanic eruption plumes remain poorly understood despite the fact that they are at the origin of a range of volcanic environmental atmospheric and health effects in this study we apply x ray photoelectron spectroscopy xps a surface sensitive technique to determine the chemical composition of the nearsurface region 2 10 nm of nine ash samples collected from eight volcanoes in addition atomic force microscopy afm is used to image the nanometer scale surface structure of individual ash particles isolated from three samples we demonstrate that rapid acid dissolution of ash occurs within eruption plumes this process is favoured by the presence of fluoride and is believed to supply the cations involved in the deposition of sulphate and halide salts onto ash afm imaging also has permitted the detection of extremely thin 10 nm coatings on the surface of ash this material is probably composed of soluble sulphate and halide salts mixed with sparingly soluble fluoride compounds the surface approach developed here offers promising aspects for better appraising the role of gas aerosol ash interaction in dictating the ability of ash to act as sinks for various volcanic and atmospheric chemical species as well as sources for others c 2007 elsevier b v all rights reserved

a 10 000 yr geomagnetic secular variation record from three australian maars summary detailed within lake magnetic stratigraphies enable composite declination and inclination versus depth curves to be derived for sets of 6m cores from each of three volcanic crater lakes in western victoria comprehensive radiocarbon chronologies for each sequence enable reliable timescales to be assigned to the variations in direction of the remanence the resultant time scaled curves are in satisfactory agreement and are therefore thought to provide an estimate of the geomagnetic secular variation in se australia during the last 10 000 yr amplitude attenuation occurs as an increasing function of age and probably results from long time scale remagnetization processes mean directions coincide with the geocentric axial dipole field directions at the three sites inclination oscillations are stronger and better resolved than those in declination whereas the opposite tends to be true for the european records reduction of records to a common virtual site suggests that the difference is largely of geometrical origin comparisons of vgp paths do not reveal a common dipole wobble component the sense of looping of the magnetic vector favours westward rather than eastward drift of features of the non dipole field relative field strength estimates based on normalization of nrm with respect to measures of the magnetic mineral content do not agree with australian and worldwide archaeointensity results

secular variation in north america during historical times summary the secular variation of the declination inclination and total force of the geomagnetic field has been plotted for 74 locations in north america a comparison of the occurrences of maxima and minima in the sv clirves from different stations shows little evidence of drift in north america although a declination maximum exhibits westward drift up to 1915 all other extrema in declination inclination and total intensity occur almost simultaneously over a wide area the major feature of sv in north america appears to be a 4000 nt decrease in the total field since 1850 which may be due to a decrease in the dipole moment coupled with the decay of a large non dipole anomaly situated under the continent short period changes in the rate of decrease are possibly jerks of the magnetic field maximum entropy spectral analysis of all three components of the field indicates periods of 102 and 53 yr

holocene palaeomagnetic secular variation at lake biwa central japan summary we have conducted a palaeomagnetic study on three sediment cores obtained from a single site in lake biwa central japan a total of 1430 discrete samples from three cores show strong and stable remanence which is carried by pseudo single domain magnetite palaeomagnetic records from individual cores show little scatter of directions and there is excellent correlation among the records from the site a composite palaeomagnetic secular variation psv record for the holocene was constructed after fine scale adjustment and stacking of the three records the age model is based on two wide spread tephra layers kawagodaira 3150 yr bp calendar years and kikaiakahoya 7250 yr bp our results show that the declinations and inclinations are strikingly similar to archaeomagnetic data from southwest japan for the last 2000 years the psv record from lake biwa shows good correlation in directions with that of beppu bay located about 500 km west of lake biwa although the beppu bay record shows relatively smaller amplitudes of both inclination and declination probably due to heavy smoothing of the initial results when the lake biwa record is compared with the proposed type curve for southwest japan there is considerable disagreement throughout the holocene a re analysis of the data sets and other information used to construct the type curve revealed that the discrepancy in the results was due to inadequate age determination for the cores used in previous studies we conclude that the stacked psv record from lake biwa meets the criteria required for a reliable curve moreover our results resolve the complications found in the correlation of psv records in southwest japan and thereby contribute to a better understanding of holocene psv

paleosecular variations of the geomagnetic field during the holocene from eastern asia abstract high resolution paleomagnetic secular variation psv records bear great information of dynamics processes of the earth s geomagnetic field and can be further used for inter profile correlation and for dating sediments however effects of changes in the depositional environment on psv records have not been fully determined this study constructed holocene psv records for the gravity piston core zsqd34 obtained from the northern south china sea rock magnetic and transmission electron microscope tem results indicate that single sd and psd domain magnetites are the main carrier of the natural remanent magnetization comparable to the records derived from the freshwater lakes and the modeling results we observed that direction curves from these two environments of contrasting salinity content are rather consistent the direction curves are independent of the constructed salinity however the gradual increasing trend of relative intensity since about 5 kyr might be related to the decreasing sea surface salinity furthermore on the centennial and millennial time scale the relative intensity and salinity show some positive relation suggesting a potential contribution of salinity to the paleomagnetic relative intensity recording processes

geomagnetic secular variation as recorded in british lake sediments and its application to archaeomagnetic studies abstract lake sediments can play an important role in understanding and reconstructing temporal characteristics of the geomagnetic field as they potentially offer near continuous high resolution archives of magnetic information extending throughout the holocene to date lake sediment geomagnetic data has typically been excluded from british archaeomagnetic secular variation curves svc due to uncertainties with the acquisition of magnetisation by lake sediments this paper presents the argument that with regards to british datasets the real problem lies with poor chronological control and sets out to illustrate that with british archaeomagnetic data some progress has been made the results indicate that it is not currently possible to resolve secular variation on a time scale of 100 years from published british lake sediment data but more success has been made with data from archaeological sediments this level of detail has been considered necessary for the incorporation of lake sediment data into the british archaeomagnetic dataset as the ability to resolve short term geomagnetic changes is critical for the integration of any dataset into the british svc as the latter is predominantly employed to date archaeological architecture and artefacts requires that it has the ability to resolve changes over timescales relevant to human lifetimes using currently available data this retrospective critique confirms that in archaeological sediments depositional and thermoremanent magnetisation can record the same direction over the same time interval

a late quaternary geomagnetic secular variation record from lake waiau hawaii and the question of the pacific nondipole low a continuous paleomagnetic record for the last 13 000 years was obtained from the sediments of lake waiau located near the summit of mauna kea volcano on the island of hawaii the secular variation sv of the geomagnetic field was studied using spectral analysis and precession analysis of the magnetic vector the hypothesis that there has been anomalously low geomagnetic sv in the central pacific was tested using angular dispersion analysis the inclination record has a mean value of 27 that is much lower than the 35 predicted by the geocentric axial dipole hypothesis the spectrum obtained from spectral analysis shows major inclination peaks at periodicities of approximately 3600 and 7900 years and major declination peaks at periodicities of approximately 1100 2000 3300 and 7800 years the approximately 8000 and 3500 year periodicities shown in both inclination and declination spectrums may represent the dipole and nondipole variation respectively the approximately 1100 and 2000 year periodicities are probably derived from either the sources that affect declination only or the offsets between the core sections in addition bauer plots of the magnetic vector are dominated by clockwise motion the angular dispersion calculated from lake sediments is 5 9 with respect to the mean virtual geomagnetic pole vgp and 9 1 with respect to the geographic pole both values are much lower than the 13 5 expected from paleosecular variation model g which separates the angular dispersion into components from the dipole and the quadruple families our results support the hypothesis that an anomalously low secular variation is a characteristic feature of the central pacific furthermore this geomagnetic behavior persists on time scales of 104 years regional anomalies in temperature topography or electrical conductivity at the core mantle boundary are inferred to cause the low sv

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

a lacustrine record of paleomagnetic secular variations from birkat ram golan heights israel for the last 4400 years abstract detailed paleo and rock magnetism investigations were carried out on three sediment cores from birkat ram golan heights israel based on high resolution logs of magnetic susceptibility a 5 4 m long composite profile was created that spans the last 4400 years the time interval covered by a single sample is about 26 years characteristic remanent magnetisation chrm of all 288 samples was determined by analysis of the results of progressive alternating field af demagnetisation the brown to olive coloured homogenous sediments show a fairly stable magnetisation and the obtained inclination and declination records agree with the archaeomagnetic records from iraq egypt and israel comparison of the psv records from birkat ram with those from bulgaria and hungary yielded a different behaviour of the earth s magnetic field vector over the near east and southeast europe during the last 1000 years

secular variation of the geomagnetic field data from the varved clays of soviet karelia abstract in the territory of soviet karelia 62 n 34 e a paleomagnetic study of varved clays at six sections situated in the north of lake ladoga and in the west and east of lake onega has been carried out the sections are located in different zones of deglaciation and overlap in age they cover the time interval from 16 000 to 10 200 years bp the sediment age has been defined from varvometric data palynological and radiocarbon analyses as well as from the information about geological and geomorphological development of the region the laboratory study reveals that considerable paleomagnetic information can be obtained from the varved clays geochronological and paleomagnetic studies have been carried out for each section the geomagnetic origin for the variations of magnetic properties declination inclination has been demonstrated the result of these studies is presented in a magnetochronological plot of declination and inclination variations for the northwest territory of european u s s r in the time interval 16 000 10 200 years bp maximum amplitude of the declination variation reached 70 12 000 years bp inclination variation is 50 smaller the characteristic periods for declination are 800 1750 2100 2200 and 2500 years and for inclination 900 1750 1850 2600 2700 years respectively as obtained by spectral analysis the virtual geomagnetic pole vgp moves both clockwise and counter clockwise the latter is generally predominant vgp does not reach values lower than 60 n the detailed curves of declination and inclination can be used for regional magnetostratigraphic studies and for correlation of sediments in adjacent regions such as finland and sweden

holocene secular variation in western north america paleomagnetic record from fish lake harney county oregon an 8 9 m composite section of lake sediment from fish lake steens mountain southeastern oregon has provided a high resolution record of holocene geomagnetic secular variation in western north america the section is composed of overlapping core segments with stratigraphic control based on six tephra layers and other thin distinct bands and with age control from 37 radiocarbon dates the 455 paleomagnetic samples possess a strong and stable magnetic remanence which is carried by pseudo single domain magnetite paleomagnetic records for individual core segments show low scatter and high serial correlation and where the segments overlap there is excellent agreement between records the azimuthal orientation of the composite section was recovered from the known direction of the geomagnetic field at the time of the climactic eruption of mount mazama tephra which is present in fish lake both internal and external evidence including the correspondence with an archaeomagnetic record from the southwestern united states support the conclusion that the fish lake record represents the history of geomagnetic field behavior during at least the last 10 000 years b p analysis of that record reveals that the average geomagnetic direction can not be distinguished from that of a geocentric axial dipole field and that the overall circularity of the field was clockwise but the detailed behavior was quite complex angular standard deviations of both field directions and virtual geomagnetic poles differ significantly from the values predicted from theoretical models of secular variation but are consistent with those of other holocene records when the record from fish lake is compared to the proposed type curve for east central north america there is excellent agreement for the past 6000 years provided the curves are offset by about 400 years this offset corresponds to a rate of westward drift of about 0 062 yr beyond about 6000 radiocarbon years ago good agreement between the two curves occurs when there is no offset suggesting that the field was standing rather than drifting during this time

icelandic holocene palaeolimnomagnetism abstract sediments spanning the last 9000 y from two sites in lake vatnsdalsvatn lat 66 n long 23 e in northwest iceland hold repeatable palaeomagnetic direction records the vatnsdalsvatn sediments have mean palaeomagnetic inclinations of 76 close to that expected for a geocentric axial dipole field and direction fluctuations of around 20 from the mean the palaeomagnetic directions are stable under alternating field partial demagnetization experiments a time scale for the vatnsdalsvatn sediments has been estimated from 14 c dating the pattern of palaeomagnetic secular change shows few similarities with british records 2000 km distant and a central north american record 5000 km distant

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

environmental hazards of fluoride in volcanic ash a case study from ruapehu volcano new zealand abstract the vent hosted hydrothermal system of ruapehu volcano is normally covered by a c 10 million m3 acidic crater lake where volcanic gases accumulate through analysis of eruption observations granulometry mineralogy and chemistry of volcanic ash from the 1995 1996 ruapehu eruptions we report on the varying influences on environmental hazards associated with the deposits all measured parameters are more dependent on the eruptive style than on distance from the vent early phreatic and phreatomagmatic eruption phases from crater lakes similar to that on ruapehu are likely to contain the greatest concentrations of environmentally significant elements especially sulphur and fluoride these elements are contained within altered xenolithic material extracted from the hydrothermal system by steam explosions as well as in residue hydrothermal fluids adsorbed on to particle surfaces in particular total f in the ash may be enriched by a factor of 6 relative to original magmatic contents although immediately soluble f does not show such dramatic increases highly soluble naf and casif6 phases demonstrated to be the carriers of available f in purely magmatic eruptive systems are probably not dominant in the products of phreatomagmatic eruptions through hydrothermal systems instead slowly soluble compounds such as caf2 alf3 and ca5 po4 3f dominate fluoride in these phases is released over longer periods where only one third is leached in a single 24 h water extraction this implies that estimation of soluble f in such ashes based on a single leach leads to underestimation of the f impact especially of a potential longer term environmental hazard in addition a large proportion of the total f in the ash is apparently soluble in the digestive system of grazing animals in the ruapehu case this led to several thousand sheep deaths from fluorosis

historic and paleomagnetic secular variation and the earth s core dynamo process this paper attempts to summarize briefly the recent and ongoing efforts of the geomagnetism and paleomagnetism community to understand both the earth s magnetic field secular variation and its implications for the core dynamo process secular variation is defined in this paper as the general spatio temporal variation of the field secular change will refer to the first time derivative of the spatial field strict geomagnetic definition of secular variation we will emphasize here the long term 10 year or longer behavior of the historic secular variation hsv for this is the variation that is comparable with the paleomagnetic secular variation psv two important related topics the 1969 1970 geomagnetic jerk in secular acceleration and the spatial geomagnetic field components due to crustal or mantle sources are treated more fully in other reviews

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

brownish discoloration of the summit crater lake of mt shinmoe dake kirishima volcano japan volcanic microbial coupled origin a drastic change in lake water color from blue green to brown was observed in the summit crater lake of mt shinmoe dake kirishima volcano about 8 months after its 2008 eruption the color change lasted for about 2 months april june 2009 the discoloration was attributed to a brownish color suspension that had formed in the lake water x ray fluorescence and fourier transform infrared analyses of a sample of the suspension identified schwertmannite fe8o8 oh 6 so4 a cultivation test of iron oxidizing bacteria for the sampled lake water with lakebed sediment revealed that the crater lake hosts iron oxidizing bacteria which likely participated in schwertmannite formation we suggest that pyrite fes2 provided an energy source for the iron oxidizing bacteria since the mineral was identified in hydrothermally altered tephra ejected by the august 2008 eruption from consideration of these and other factors the brownish discoloration of the summit crater lake of mt shinmoe dake was inferred to have resulted from a combined volcanic microbial process

geomagnetic palaeosecular variation 0 13 000 yr bp as recorded in sediments from three maar lakes from the west eifel germany summary geomagnetic palaeosecular variation psv profiles have been obtained from 12 cores raised from three maar lakes in the west eifel germany age control is provided by varve chronology analysis of mean inclinations suggests that a post depositional remanent magnetization pdrm was acquired in all three lakes a lock in time of 150 yr corresponding to an average lock in depth of 24 cm has been determined from a comparison with archaeomagnetic sv data stacked psv results demonstrate directional geomagnetic field behaviour through the late and post glacial in central europe and show good agreement with the holocene british master curve turner thompson 1982 psv results suggest that westward drift of the non dipole field was not persistent over the last 13 000 yr spectral analyses yield declination variations with durations of about 1800 yr in the younger holocene 0 5000 yr bp and 4300 yr between 5000 and 13 000 yr bp the inclination exhibits swings of 1000 yr duration in the younger holocene and about 2000 yr in the older part moreover inclination spectra suggest the presence of one inclination variation with a very long duration approaching the length of the time span investigated 8600 yr

distal volcanic impacts on peatlands palaeoecological evidence from alaska abstract despite the fact that volcanic ash tephra layers are found preserved in peat deposits around the world comparatively little research has investigated the impacts of distal volcanic emissions on peatlands this study investigates the impacts of several late holocene volcanic eruptions on five peatlands in southern alaska using a palaeoecological approach testate amoebae analysis peat humification analysis and a basic analysis of plant macrofossil components were applied across 11 tephra layers changes in macrofossil and testate amoebae assemblages occur across several of the tephra layers the humification results were considered unreliable because of a methodological problem a finding which may have implications for other studies using this technique redundancy analyses on testate amoebae data show statistically significant changes associated with two tephras the most likely causes of the impacts are volcanic gases acidic precipitation or tephra derived leachates the finding that some tephras are associated with impacts whereas others are not may relate to the season of the eruption or meteorological conditions at the time of ash fall these results suggest the sensitivity of peatlands and peatland microbial communities to distal volcanic products and imply that changes in key palaeoclimatic proxies may be caused by a mechanism independent of climate change implications of the results for peat based palaeoclimatic studies are discussed as are possible directions for future research

magnetic hysteresis properties of greigite fe3s4 and a new occurrence in holocene sediments from swedish lappland a new occurrence of ferrimagnetic greigite fe3s4 is reported in freshwater holocene sediments from gaskkamus gorsajavri in swedish lappland the presence of greigite was inferred from the mineral magnetic analysis of sediment cores the greigite bearing sediments possess a high saturation isothermal remanent magnetisation to susceptibility sirm ratio a characteristic shared by other natural sediments known to contain greigite the hysteresis properties measured using a vibrating sample magnetometer of natural greigite extracted from lake sediments show much higher saturation coercivity b0 c and mrsms ratio values approximately 50 mt and 0 5 respectively than synthetic samples of greigite approximately 12 mt and 0 2 the results suggest that synthetic greigite samples contain crystals ranging from small non remanence carrying superparamagnetic grains to large multi domain grains in contrast the natural samples probably consist predominantly of pseudo single domain and single domain crystals capable of carrying a chemical remanent magnetisation however the unstable nature of greigite under laboratory conditions creates difficulty in characterising its physical attributes

organic matter production and preservation and evolution of anoxia in the holocene black sea dating of sediments collected in gravity cores during leg 1 of the 1988 r v knorr expedition to the black sea suggests that the onset of water column anoxia at 7 5 ka was virtually synchronous across the basin over a depth range of 200 2250 m a finely laminated organic carbon oc rich sapropel unit ii was produced as a result of this anoxia the trigger for increased oc production and development of anoxia was the spillover of saline waters through the bosporus that probably began at 9 0 ka and peaked between 7 0 and 5 5 ka this spillover enhanced vertical mixing and nutrient cycling and caused a short term 2 3 kyr burst in surface water productivity during the early part of unit ii deposition continued incursion of saline waters enhanced vertical stability and inhibited mixing of nutrients into surface waters thus limiting primary production and decreasing the oc flux to sediments beginning 5 5 ka concentration accumulation rate and degree of preservation of organic matter all decreased in the upper part of unit ii as a result of decreasing productivity but anoxia persisted throughout most of the water column the end of unit ii sapropel deposition was synchronous across the black sea as the result of the first blooms of the coccolith emiliania huxleyi which presumably marked an increase in surface water salinity above 11 and the beginning of unit i deposition the high coccolith carbonate fluxes that occurred during deposition of unit i diluted the oc concentration in the sediments but oc accumulation rates are about the same as those in upper part of unit ii

paleomagnetic dating of the most recent silicic eruptive activity at pantelleria strait of sicily we report on the paleomagnetism of ten sites in the products of the most recent silicic eruptive cycle of pantelleria strait of sicily previously radiometrically dated at 5 10 ka our comparison with proxies for geomagnetic field directions allows us to narrow considerably the time window during which these eruptions occurred the strongly peralkaline composition causes the magmas to have low viscosities locally resulting in strong agglutina tion of proximal fall deposits this allows successful extraction of paleomagnetic directions from the explosive phases of eruptions one of our sites was located in the serra della fastuca fall deposit produced by the first explosive event of the eruptive cycle the other nine sites were located in the most recent explosive pumice fall and agglutinate from cuddia del gallo and cuddia randazzo and effusive khaggiar lava products the very similar paleomagnetic directions gathered from eight internally consistent sites were compared to reference geomagnetic field directions of the last 5 10 ka directions from cuddia del gallo agglutinate and khaggiar flows translate into 5 9 to 6 2 ka ages whereas the fastuca pumices yield a slightly older age of 6 2 6 8 ka hence the most recent silicic eruptive cycle lasted at most a millennium and as little as a few centuries around 6 0 ka paleomagnetically inferred ages are in good agreement with published and calibrated by us 14 c dates from paleosols charcoals sampled below the studied volcanic units whereas k ar data are more scattered and yield 30 older ages our data show that the time elapsed since the most recent silicic eruptions at pantelleria is comparable to the quiescence period separat ing the two latest volcanic cycles

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

contamination of water supplies by volcanic ashfall a literature review and simple impact modelling abstract volcanic ash is the most widely distributed product of explosive volcanic eruptions and can disrupt vital infrastructure on a large scale previous studies of effects of ashfall on natural waters and water supplies have focused mainly on the consequences of increased levels of turbidity ash suspended in water acidity and fluoride with very little attention paid to other contaminants associated with volcanic ash the aims of this paper are twofold firstly to review previous studies of the effects of volcanic ashfall on water supplies and identify information gaps and secondly to propose a simple model for predicting effects of ashfall on water supplies using available information on ash composition we reviewed reported impacts of historic eruptions on water supplies drawing on case studies from new zealand vanuatu argentina the usa costa rica montserrat iceland and guadeloupe elevated concentrations of fluoride iron sulphate and chloride as well as turbidity and acidity have been reported in water supplies from a public health perspective the two main issues appear to be 1 outbreaks of infectious disease caused by the inhibition of disinfection by high levels of suspended ash and 2 elevated fluoride concentrations we devised a simple model using volcanic ash leachate composition data to predict effects on receiving waters applying this model to the effects of ruapehu ash from the 1995 1996 eruptions suggests that the primary effects of concern are likely to be an increase in acidity decrease in ph and increases in concentrations of the metals aluminium iron and manganese these metals are not normally considered to pose health risks and are regulated only by secondary non enforceable guidelines however exceedences of guideline values for al mn fe and ph will cause water to become undrinkable due to a bitter metallic taste and dark colour and may also cause corrosion staining and scale deposition problems in water tanks and pipes therefore the main issues following volcanic ashfall of similar composition to ruapehu ash are likely to be shortages of potable water and damage to distribution systems rather than risks to public health

between the north atlantic oscillation and the siberian high a 4000 year snow accumulation history inferred from varved lake sediments in finland clastic organic varved sediments from the boreal lake kalliojarvi central finland record changes in snow accumulation for more than 4000 years the varve record was reconstructed using digital image analysis from 4132 varve yr bp to present with 2 2 counting error and is supported by paleomagnetic data two laminae are identified in a typical varve structure 1 the minerogenic lamina which accumulates during spring as a result of catchment erosion triggered by spring floods and 2 the organic lamina which is composed of allochthonous and autochthonous organic matter that accumulates during summer autumn and winter the minerogenic influx is related to variations in snow accumulation and follows the different phases of the north atlantic oscillation nao decreased snow accumulation is related to a weakened nao phase thus the minerogenic influx record provides additional information about nao variation the fe mn ratio is related to changes in redox conditions at the lake floor the oxygen ava

correcting distorted paleosecular variation in late glacial lacustrine clay abstract an undisturbed horizontal chronostratigraphic marker horizon of laminated red glacio lacustrine clay crops out over 25 000 km 2 in northern ontario canada the primary clastic hematite laminae possess two stable vector components of magnetization we sampled a 1 6 m vertical section at overlapping 2 cm intervals in cubic specimens 8 cm 3 n 106 precisely oriented in geographic coordinates which permitted measurement of inclination and declination alternating field demagnetization 12 17 steps per specimen isolated a characteristic chrm primary component coercivity 40 mt approximately 30 shallower than the mean geomagnetic field inclination at this latitude with distorted paleosecular secular variation psv a lower coercivity overprint 20 40 mt is 6 shallower than the present geomagnetic field and similarly inclined to the depositional remanence deflection when the clay was re sedimented in the laboratory we believe this angle to be representative of the inclination of the deflected primary remanence inclination during deposition caused by the magnetic anisotropy of the clay using this as a proxy for the initial inclination the chrm hard component inclinations were restored to their original values assuming vertical compaction which averages to 51 the restored inclinations are compatible with site latitude and the restored secular variation loops centre reasonably on the geographic north pole the structural correction based on homogeneous vertical shortening over simplifies the reality of heterogeneous particulate flow in which grain rotations depend on shape size and packing and effectively combines influences of compaction and depositional settlement nevertheless this correction makes the psv data more useful and interpretable in terms of paleopole migration the more logical correction technique using anisotropy of anhysteretic remanence aarm jackson m j banerjee s k marvin j a lu r gruber w 1991 detrital remanence inclination errors and anhysteretic remanence anisotropy quantitative model and experimental results geophys j int 104 95 103 is foiled here due to the high coercivity of the remanence bearing grains and their unknown orientation distribution and shape distribution

spatial analysis of mount st helens tephra leachate compositions implications for future sampling strategies tephra particles in physically and chemically evolving volcanic plumes and clouds carry soluble sulphate and halide salts to the earth s surface ultimately depositing volcanogenic compounds into terrestrial or aquatic environments upon leaching of tephra in water these salts dissolve rapidly previous studies have investigated the spatial and temporal variability of tephra leachate compositions during an eruption in order to gain insight into the mechanisms of gas tephra interaction which emplace those salts however the leachate datasets analysed are typically small and may poorly represent the natural variability and complexity of tephra deposits here we have conducted a retrospective analysis of published leachate analyses from the 18 may 1980 eruption of mount st helens washington analysing the spatial structure of the concentrations and relative abundances of soluble ca cl na and s across the deposits we have identified two spatial features 1 concentrated tephra leachate compositions in blast deposits to the north of the volcano and 2 low s cl and na cl ratios around the washington idaho border by reference to the bulk chemistry and granulometry of the deposit and to current knowledge of gas tephra interactions we suggest that the proximal enrichments are the product of pre eruptive gas uptake during cryptodome emplacement we speculate that the low s cl and na cl ratios reflect a combination of compositional dependences on high temperature so2 uptake and preferential hcl uptake by hydrometeor tephra aggregates manifested in terrestrial deposits by tephra sedimentation and fallout patterns however despite our interrogation of the most exhaustive tephra leachate dataset available it has become clear in this effort that more detailed insights into gas tephra interaction mechanisms are prevented by the prevalent poor temporal and spatial representativeness of the collated data and the limited characterisation of the tephra deposits future leachate studies should aim to extensively sample across tephra deposit limits whilst simultaneously characterising deposit stratigraphy and tephra chemistry mineralogy and granulometry taking steps to ensure the quality and comparability of collected leachate datasets

reconstructing the holocene geomagnetic field abstract knowledge of the holocene evolution of earth s magnetic field is important for understanding geodynamo processes in the core is necessary for studying long term solar terrestrial relationships and can provide useful age constraints for archeologicaland stratigraphic applications continuous time varying global field models based on archeo and paleomagnetic data are useful tools in this regard we use a comprehensive data compilation and recently refined modelling strategies to produce cals10k 1b the first time varying spherical harmonic geomagnetic field model spanning 10 ky the model is an average obtained from bootstrap sampling to take account of uncertainties in magnetic components and ages in the data and hence has version number 1b instead of 1 this model shows less spatial and temporal resolution than earlier versions for 0 3 ka and particularly aims to provide a robust representation of the large scale field at the core mantle boundary cmb we discuss the geomagnetic dipole evolution and changes in holocene magnetic field morphology at the cmb as shown by the new reconstruction the results are compatible with earlier models cals3k 3 and cals3k 4 for 0 3 ka but reveal some clear deficiencies in the 0 7 ka cals7k 2 model prior to 3 ka cals10k 1b is able to resolve mobile and structurally evolving high latitude radial field flux lobes at the cmb in both hemispheres as well as persistent non zonal structure in the 10 ky average contributions to the average field from time varying structures in the equatorial indonesian australian region are particularly striking

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

models of geomagnetic secular variations on recent times for south america abstract palaeosecular variations of the geomagnetic field obtained from palaeomagnetic and radiometric studies carried out on the bottom sediments from three lakes in southwestern argentina records extend back to about 6000 years by 14c dating were compared with results from different theoretical models which suggested the possible sources of the field attempts were then made to simulate long period secular variations using modified alldredge and hurwitz s models the alldredge and hurwitz model uses a central dipole and eight radial dipoles all at the same distance from the centre of the earth as a first approximation to the sources of the geomagnetic field the modified models which have been used to describe the northern hemisphere data comprise eight radial dipoles which oscillate sinusoidally and or drift the different parameters of the models were fitted to the palaeomagnetic data from southwestern argentina the best fit was obtained with a mixed model between 6000 and 3000 years bp all radial dipoles oscillate and some of them drift as well later the drift rates become lower and finally between 1700 years bp and present times all radial dipoles only oscillate

establishing a first archaeointensity record for the sw pacific abstract the dearth of archaeomagnetic intensity data from the southern hemisphere is a limiting factor in evaluating models of global geomagnetic field evolution during the holocene here we present high quality microwave archaeointensity data obtained from 34 ceramic fragments 21 archaeological contexts from the duke of york islands fiji and vanuatu sw pacific complementary thellier type experiments corrected for anisotropy give good agreement with the microwave results the majority of the new data prior to 250 ad exhibit significantly lower intensity than predicted by current global field models cals3k 3 and arch3k for the region with an apparent intensity minimum at 250 bc reaching as low as 50 of the present day field strength between 400 ad and 1500 ad the data are broadly consistent with the global field models but with a 20 higher field between 1200 and 1400 ad these new results therefore imply that the geomagnetic field has a greater range of variability than predicted and that further data from the region are essential to better constrain the global field models the results also demonstrate that establishing an archaeomagnetic reference curve for dating sw pacific ceramic artefacts is feasible which has potentially significant implications for pacific archaeological research

the connection between geomagnetic secular variation and long range development of climate changes for the last 13 000 years the data from nne europe abstract one of the possible mechanisms of the connection between long term climate changes and geomagnetic field variations is discussed climate fluctuations with periods of n 104 105 years can be explained by milankovitch s astronomic theory the fluctuations with periods of n 102 103 years are discussed in the framework of a hypothesis on the connection with secular variations of the geomagnetic field on the basis of palaeomagnetic data from n w russian lake sediments basically from karelia and the kola peninsula for the time interval 13 000 5000 years ago the drift of virtual geomagnetic poles is calculated analysis of this data with regard to palaeotemperature and palaeoclimate phases in n ne europe is carried out the alternation of stadial cold and interstadial warm stages as a function of approaching receding from the virtual geomagnetic pole to n europe is established for the last 5 kyr the correlation is confirmed for archaeomagnetic data from the ukraine

a paleomagnetic power spectrum we construct a power spectrum of geomagnetic dipole moment variations or their proxies that spans the period range from some tens of million down to about 100 years empirical estimates of the spectrum are derived from the magnetostratigraphic time scale from marine sediment relative paleointensity records and from a time varying paleomagnetic field model for the past 7 kyr the spectrum has the most power at long periods reflecting the influence of geomagnetic reversals and in general decreases with increasing frequency decreasing period the empirical spectrum is compared with predictions from simple models discrepancies between the observed and predicted spectra are discussed in the context of i changes in reversal rate ii overall average reversal rate iii cryptochrons iv the time taken for a reversal to occur and v long term paleosecular variations and average estimates of the field strength and variance from other sources 2005 elsevier b v all rights reserved

palaeomagnetic study of the holocene and upper pleistocene sediments from lake barombi mbo cameroun first results abstract the analyses of the stable deposition and post depositional remanent magnetization carried by the lacustrine sediments contained in a 24 m sequence collected from the bottom of the maar lake barombi mbo cameroun yield well defined declination and inclination oscillations which can be attributed to palaeosecular variations of the local geomagnetic field the transformation to a time scale based on the interpolation and extrapolation of 14 c ages allows comparison of this record with contemporaneous records obtained in other parts of the world the successive inclination peaks can be individually identified with those found in western europe in spite of small chronological discrepancies which are in the range of the standard deviation of the ages normalization of the nrms by anhysteretic magnetization provides a profile of relative palaeointensities which shows similarities with that reconstructed from the same time interval in a sequence from western europe although an important phase shift appears

leaching characteristics of ash from the may 18 1980 eruption of mount st helens volcano washington leaching of freshly erupted air fall ash unaffected by rain from the may 18 1980 eruption of mount st helens volcano washington shows that ca2 na mg2 so 4 2 and cl are the predominant chemical species released on first exposure of the ash to water extremely high correlation of ca with so4 and na with cl in water leachates suggests the presence of caso4 and nacl salts on the ash the amount of water soluble material on ash increases with distance from source and with the weight fraction of small less than 63 micrometers ash particles of high surface area this suggests that surface reactions such as adsorption are responsible for concentrating the soluble material caso4 nacl and other salts are probably formed as microscopic crystals in the high temperature core of the eruption column and are then adsorbed by silicate ash particles

the immediate environmental effects of tephra emission the earth s history is punctuated by large explosive eruptions that eject large quantities of magma and silicate rock fragments into the atmosphere these tephra particles can sometimes be dispersed across millions of square kilometres or even entire continents the interaction of tephra with or in receiving environments may induce an array of physical chemical and biological effects the consequences for affected systems and any dependent communities may be chronic and localised in the event of frequent small eruptions while larger and rarer events may have acute regional scale impacts it is therefore necessary to document the range of possible impacts that tephra may induce in receiving environments and any resulting effects in interconnected systems we collate results from many studies to offer a detailed multidisciplinary and interdisciplinary review of the immediate post eruptive effects of tephra emission into the atmosphere onto vegetation soil or ice snow surfaces and in aquatic systems we further consider the repercussions that may be induced in the weeks to years afterwards in the atmosphere tephra can influence cloud properties and air chemistry by acting as ice nuclei in or by offering sites for heterogeneous reactions respectively tephra on vegetation causes physical damage and sustained coverage may elicit longer term physiological responses tephra deposits on soils may alter their capacity to exchange gas water and heat with the atmosphere or may have a specific chemical effect such as nutrient input or acidification on sensitive soils tephra deposition onto snow or ice may affect ablation rates rivers and lakes may experience turbidity increases and changes in their morphology as a result of fallout and prolonged months or years erosion from the tephra covered catchment in the first weeks after deposition tephra leaching may affect river chemistry the abundance and speciation of phytoplankton populations in lakes may be altered by tephra induced changes in water chemistry or sediment water nutrient cycling in the oceans tephra deposition may fertilise fe limited waters with potential impacts on the global carbon cycle embracing the full complexity of environmental effects caused by tephra fall demands a renewed investigative effort drawing on interdisciplinary field and laboratory studies combined with consideration of the interconnectivity of induced impacts within and between different receiving environments

palaeomagnetic secular variation and rock magnetic studies of holocene sediments from a maar lake hoya de san nicolas in central mexico summary three up to 520 cm long sediment cores from hoya san nicolas in guanajuato mexico were analysed for various magnetic properties in order to better define a palaeomagnetic secular curve for central mexico the results magnetic susceptibility hysteresis cycles anhysteretic and isothermal remanent magnetization suggest that the remanent magnetization of the sediments is controlled by ferrimagnetic minerals pseudo single domain magnetite which are suitable recorders of the geomagnetic field the age depth model indicates average deposition rates of 0 32 interval 146 198 cm and 0 45 mm yr 1 interval 200 520 cm and a basal age of about 11 600 calibrated years bp cal yr bp we used magnetic susceptibility and natural remanent magnetization to correlate the three cores a composite palaeomagnetic secular variation sv record was obtained from the cores with a stretching and stacking process and a chronology established with accelerator mass spectrometer dates on microscopic charcoal and stratigraphic correlations with other well dated holocene records from mexico and guatemala the declination and inclination results show oscillatory behaviour varying in a narrow range although a distinctive directional swing is evident between 9060 and 9810 cal yr bp the san nicolas palaeomagnetic sv curve is similar to palaeomagnetic master curves from europe and north america in shape occurrence and synchronicity of directional features especially with respect to inclination

volcanic ash leachates a review and recommendations for sampling methods tephra in plumes can scavenge and thereby rapidly deposit volatiles including sulphur halogen and metal species these may then be leached e g by rainfall potentially releasing heavy loadings to soils and water bodies several eruptions have resulted in contamination of pasture sometimes with serious impacts on livestock water quality has also been an issue in some areas affected by tephra fall this work synthesises the literature on volcanic ash leachates and considers the controls on volatile adsorption general trends emerge for basaltic intermediate and silicic tephra as well as for variable particle size and transport distance the applications of ash leachate data to plume gas geochemistry calculation of volatile budgets and environmental impact assessment are evaluated comparisons for different eruptions are hampered by disparities in leachate analysis techniques a standardised methodology is therefore proposed to facilitate future health impact assessment and volcanological interpretation of results from different sites

long period geomagnetic secular variations since 12 000 yr bp a comparison of secular variation records of the geomagnetic field inclination obtained from palaeomagnetic studies of european and north american post glacial and late glacial sediments suggests that geomagnetic westward drift has persisted through the past 12 000 yr between 12 000 and 2 500 yr bp the overall average drift rate was between 0 14 and 0 16 deg yr 1 at 2 500 yr bp it is tentatively suggested that the drift rate increased and rose to a maximum of nearly 0 5 deg yr 1 before decreasing to historically observed values of 0 25 deg yr 1

influence of volcanic gases on the epidermis of pinus halepensis mill in campi flegrei southern italy a possible tool for detecting volcanism in present and past floras abstract cuticle micromorphology together with epidermal and epistomatal wax in both current and first year old needles of conifer pinus halepensis aleppo pine trees growing under volcanic gas fumigation was analysed in pisciarelli area campi flegrei southern italy as a control current and first year old needles growing far from volcanic gas emission were also sampled using a multidisciplinary approach with sem tem and x ray volcanic gases were shown to cause degradation on epicuticular and epistomatal waxes significant statistical variations of ultrastructural components of the cuticle with 30 measurements including total thickness of the cuticle and details and proportions of all different layers and use of confidence interval revealed a high degree of sensitivity of aleppo pine to this extreme environment in the present study non significant thickness variations of the cell wall plus cuticle among current and first year old needles of both fumigated and non fumigated trees have been found however at the ultrastructural level significant variations in cell wall and total cuticle thickness especially within the three zones of b1 fibrillar layer revealed different equilibria for each of the four types of material using energy dispersive x ray microanalysis no sulphur was found in either cuticle or epidermal cells but the presence of h 2 s in the fumarole gas is suspected to cause indirect and or direct cuticle alterations of wax structure ultrastructural characters of plant cuticles related to emission of volcanic gases during the geological past are also discussed among these considerations an identification key enabling distinction between non fumigated and fumigated materials with 9 characters provides a good tool detecting the influence of volcanism for extant and fossil plants

on the current state of lake sediment palaeomagnetic research summary it is now possible to obtain high quality records of geomagnetic secular variations in the direction though not the magnitude of the ancient field type curves are presented for four regions namely north america west europe argentina and australia constructed by fitting cubic splines to data stacked from numbers of cores of post glacial sediments ways in which the results can be used to investigate the grosser properties of the ancient field are discussed

paleomagnetic secular variation and relative paleointensity during the holocene in south china huguangyan maar lake revisited the scarcity of reliable paleomagnetic secular variation psv records from east asia especially from low latitude regions impedes better understanding of global psv mechanisms here we report on a radiocarbon dated holocene psv record from a composite 6 7 m long core collected from the high sedimentation rate huguangyan maar lake hml in subtropical tropical south china rock magnetic results demonstrate that the natural remanent magnetization resides in single domain magnetite alternating field demagnetization experiments at 1 cm spacing on u channel samples reveal six distinct inclination highs at 7 500 bce 5 100 bce 4 600 bce 3 600 3 400 bce 1 600 1 200 bce and 600 800 ce three inclination lows at 4 800 bce 600 300 bce and 1 000 1 300 ce and three eastward declination trends at 3 600 3 200 bce 2 600 2 400 bce and 400 bce to 200 ce the similarity between the hml psv record and other independently dated records from east asia and geomagnetic field models corroborates the robustness of our age model and holocene psv record strikingly centennial to millennial scale psv features of the hml are comparable within age uncertainties with other holocene records from europe north america and canada suggesting that such directional patterns are likely to be hemispheric in scale although relative paleointensity data of hml are affected by environmental factors e g organic matter diagenesis the record still provides a regionally important new psv reference curve whose conspicuous features may serve as stratigraphic markers for east asian paleorecords

chronological potential of palaeomagnetic oscillations recorded in late quaternary sediments from lake tanganyika abstract the measurements of depositional and post depositional remanent magnetizations drm and pdrm in two piston cores collected at water depths of 140 m core mpu3 and 422 m core mpu12 in the southern lake tanganvika mpulungu sub basin zambia provide a palaeomagnetic record for south east central africa which spans over the last 25 5 ka ages on a conventional 14c time scale for the most characteristic inclination peaks were estimated by correlating the palaeomagnetic record with the lake barombi mbo cameroon and the western europe secular variation type curves ams 14c ages on total organic matter tom measured in mpu12 core appear to be 2 to 4 ka older in the lower part of the record from ca 25 to 15 ka bp i e during the last arid episode of the late pleistocene these apparent 14c ages exceed pdrm acquisition lagtimes evaluated to be about 800 years at most and also account for residence time of carbon in tom prior to its sedimentation therefore magnetostratigraphic correlations are believed to provide a better overall chronology for the late pleistocene and early holocene changes in lake tanganyika level major drops shown by breaks of deposition in core mpu3 at 1000 cm and 825 cm sub bottom are respectively dated at ca 21 5 ka bp and between 17 and 15 ka bp

application of the gauss theorem to the study of silicic calderas the calderas of la primavera los azufres and los humeros mexico abstract we explored applications including limitations of gauss s theorem to the study of silicic calderas first it enables us to determine the mass deficiency from calderas mass deficiency itself has also other potential applications it enables to make qualitative comparisons between calderas we can use the mass deficiency to test in a quick way and as a preliminary step to a formal gravity inversion for the feasibility of caldera types of simple geometry i e piston subsidence and funnel models this application can be done in a straightforward way once the mass deficiency has been determined for this purpose the mass deficiency is converted to the volume of material missing at the caldera subsequently for example this volume and the respective caldera diameter enable us to estimate the height of the cylinder fitting the piston subsidence model if the obtained parameters are congruent with the known geology and geophysical information then the model may be considered further in the inversion of the gravity data for the detailed structure other simple models i e the funnel model can also be analyzed in this way in particular when working with a piston subsidence caldera type the gauss theorem enables us to estimate the caldera collapse very difficult to obtain based on geologic information alone these possible uses of gauss s theorem are illustrated with the calderas of la primavera los azufres and los humeros caldera mexico the obtained mass deficiency from these calderas follow the linear mass deficiency diameter trend observed for other calderas in particular because of their diameters and mass deficiencies la primavera and krakatau calderas can be considered equiparable this comparison is of the most importance considering that la primavera is located in the neighbourhood of a metropolis guadalajara city since geophysical studies have already established a piston subsidence model for these calderas we assessed gauss s theorem used to estimate their collapses the respective estimated subsidences for la primavera 600 m los humeros 500 m and los azufres calderas 800 and 1200 m respectively are supported by borehole data these relatively small subsidences in relation to many calderas in western us can be explained by the presence of cylindrical to sub spherical magma chambers of smaller size than those underlying the western us calderas of yellowstone valles and long valley for example in an epicontinental setting of young quaternary rocks against precambrian cratonic basement in western us a reassessment of all the available geological and geophysical information was also done in particular the caldera limits were checked and corrected when necessary based on available 2 d gravity modeling gravity gradients and the location of the volcanic vents regional tectonic lineaments might explain many of the particular details of their structures la primavera caldera might have formed through a piecemeal subsidence controlled by the pre caldera tectonics los humeros caldera is an example of a caldera that evolved by incremental growth as the vulsiniani calderas in italy the los azufres caldera comprises two contiguous calderas emplaced in a regional tectonic depression

a 3500 year paleomagnetic record of late holocene secular variation from blue lake idaho three meters of sediment from blue lake idaho have provided a 3500 year paleomagnetic record with low scatter and good serial correlation comparison of the blue lake record with the record from fish lake oregon reveals differences of up to 963 years for secular variation extrema based on the separate radiocarbon chronologies for blue lake and fish lake to achieve a common time scale the blue lake record was redated using the fish lake ages for five major inclination extrema with this adjusted time scale the excellent correspondence between the declination records confirms the extremal correlations and demonstrates that paleomagnetic correlations may provide more accuracy for relative stratigraphy than radiocarbon dating the morphological agreement between the smoothed records documents secular variation features with wavelengths of 1000 2000 years and amplitudes of 10 20 in inclination and 20 30 in declination examination of the unsmoothed records indicates that features with wavelengths of less than a few hundred years and amplitudes of less than 5 are probably noise

partitioning of rare earth elements yttrium and some major elements among source rocks liquid and vapor of larderello travale geothermal field tuscany central italy rare earth elements ree yttrium and some major element concentrations have been measured in the high enthalpy fluids hef of several geothermal wells and the fluid s source rocks in the larderello travale area tuscany central italy the ree and y abundances in the hef range from 0 1 to about 10 pmol kg and are slightly higher in the hef originating from evaporite carbonate sequences calcare cavernoso than in those from phyllites the resulting rey distribution factors between hef and source rocks appkdsource rockhef defined as the ratios of rey ca in both phases range from 0 01 to 0 03 and 0 03 to 0 1 for phyllites and evaporite limestone sequences calcare cavernoso respectively ree y are more retained by the source rocks than ca hef show no inherited and with exception of a small y anomaly no acquired anomalies this indicates a static equilibrium between hef and the source rocks the absence of any eu anomalies points to temperatures less than 250 c in the source region the small negative y anomalies are the result of y depletion in the rock fractions taking part in the water rock interaction due to depressurization of the hef to about 120 c and 2 bars a liquid and a vapor phase is produced which were sampled for the determination of the ree y partitioning between the two phases the apparent partition factors between vapor and liquid appdliquidvapor of ree y range between 0 05 to 0 2 and about 3 for hef originating from the phyllites and evaporites carbonates respectively among all ionic species determined only nh4 has an apparent partition factor appdliquidvapor above one in general rey partition more easily into the vapor phase than the earth alkaline and alkaline elements no significant correlation of ree y in the vapor phase with any of the determined ionic species could be detected this probably points to the dominant presence of ion pairing such as rey oh 3o or reyo oh o

lake sediment record of the geomagnetic secular variation in britain during holocene times summary a palaeomagnetic record of the geomagnetic secular variation during the last 10000 years has been obtained from 10 cores of sediment from loch lomond scotland lake windermere north england and llyn geirionydd north wales a time scale is provided by 30 radiocarbon age determinations and pollen analyses on several of the cores the main swings and much fine detail of both declination and inclination records repeat well between cores and between lakes and the overall record is much more detailed than previous european records the new record shows that neither declination nor inclination swings have been periodic over the past 10000 years but that the main swings have become progressively shorter in duration during that time each swing is characterized by fine detail which enables use of the record as a secondary method of dating other european sediments the motion of the geomagnetic vector has been predominantly clockwise throughout the time period spanned but confirms a period of anticlockwise motion from 1100 to 600 bp first discovered by british archaeomagnetic investigations the record agrees with british and czechoslovakian archaeomagnetic records but not with japanese archaeomagnetic or north american lake sediment records this suggests that the secular changes are controlled by local growing and decaying drifting sources rather than by wobbling of the main geomagnetic dipole

geochemistry of metallic trace elements in fumarolic condensates from nicaraguan and costa rican volcanoes metallic trace element composition of volcanic gas from cerro negro momotombo san cristobal telica and masaya volcanoes in nicaragua and poas volcano in costa rica is indicated by analyses of fumarolic condensates for alkalis alkaline earths transition elements precious metals halogens and sulphate the temperatures of the fumaroles varied from 85 to 852 c element concentrations range from 104 to 10 3 ppm statistical tests indicate that the trace element constituents of the condensates are log normally distributed although there are variations in element concentrations in individual condensates the general order of decreasing elemental abundances in nicaraguan and costa rican fumarolic gas is cl so4 certain igneous rock forming elements si al fe ti f and alkalis li na k alkaline earths mg ca ba br and transition elements cr mn co ni cu zn other ore forming elements mo cd sn pb semi metals as sb sc hg and precious metals au ag li mn cr and pb were found to be near or below detection limits in many of the condensates analyzed so4 ti al k na zn sn cr and br all tend to decrease in abundance as mean fumarolic temperature between volcanoes decreases the remaining elements remain constant in abundance or behave erratically the metallic trace element composition of the nicaraguan and costa rican fumarolic condensates is very similar to condensates from subduction zone volcanoes around the pacific margin and the mediterranean metals in volcanic gas are postulated to have been transported as halogen sulphate and oxide compounds chloride and fluoride compounds are considered to be the primary transporters of metals in volcanic gas correlations between metal and halogen content vary considerably between volcanoes statistically significant correlations between metal content and both chlorine and bromine are found in the cerro negro and between metal content and bromine and fluorine in the momotombo condensates metal bearing compounds in volcanic gas are postulated from correlation matrices bromine though seldom reported in condensates is a minor but important constituent of volcanic gas with concentrations similar to those of fluorine metal bromide compounds have higher volatilities than fluoride compounds and volatilities similar to chloride compounds significant correlations between bromine content and metal concentration suggests that bromide compounds play a role in the transportation of metals in volcanic gas

rock magnetic evidence for the dissolution and authigenic growth of magnetic minerals within anoxic marine sediments of the california continental borderland the rock magnetic properties of marine sediments from the california continental borderland san pedro santa catalina and san nicolas basins have been studied in order to quantitatively assess the effects of sediment diagenesis on magnetic minerals previous studies have noted that the natural remanent magnetization in these sediments primarily carried by detrital magnetite decays to 10 or less of its surface value soon after deposition this decrease is caused by magnetite dissolution related to sediment diagenesis and is unrelated to paleoclimatic variations or changes in the regional influx of detrital magnetic material detailed rock magnetic measurements show that shifts to softer remanent coercivity and differences in the rate and degree of magnetic intensity loss with depth can be related to the dissolution process the shift to softer remanent coercivity is related to a coarsening of the magnetic mineral grain sizes with depth due to preferential dissolution of the finest grained magnetic material the intensity decreases which are linearly proportional to magnetite concentration decreases indicate that dissolution occurs with rate constants ranging from 0 3 to 1 6 kyr 1 the rate constants sulfide concentrations and magnetite grain size estimates from the borderland are consistant with previous studies of magnetite dissolution our results demonstrate the importance of both sulfide and magnetite surface area in the dissolution process anomalous peaks in viscous remanence within the sediments suggest the authigenic growth of greigite and its subsequent transformation to pyrite

time series analysis of the 10 000 yr geomagnetic secular variation record from se australia summary a 10 000 yr continuous secular variation record from intensively dated lake sediments in se australia has been subjected to periodogram and maximum entropy method analysis tests on synthetic data reveal some of the limitations of the latter method particularly when applied to complex number series anticlockwise precession of the magnetic vector at a period of 5000 1000 yr is tentatively ascribed to dipole precession and clockwise precession at a period of about 2800 yr is probably due to westward drift of features of the non dipole field the effect of calibrating the radiocarbon time scale is important and results in periodicity shifts of up to 25 per cent even for well dated lacustrine sequences power spectra are poorly constrained it is thus possible that the geomagnetic secular variation on a time scale of thousands of years is more uniform than often supposed mismatches between declination and inclination spectra can arise as a natural consequence of certain types of source mechanism and should not be simply attributed to figments of the analysis employed

the effects of volcanic ash on the maceral and chemical composition of the c coal bed emery coal field utah abstract volcanic ash which fell in the peat swamp that formed the upper cretaceous c coal bed ferron sandstone member of the mancos shale utah produced semi impermeable layers that caused the ponding of surface waters coal samples from directly above tonsteins altered volcanic ash partings are enriched in desmocollinite telinite and detrocollinite as a result of poorly drained swamp conditions coal samples from directly below tonsteins are enriched in semifusinite inertodetrinite and fusinite as a result of well drained conditions leaching of the volcanic ash or the incorporation of volcanic ash in peat provided a source for many elements including zr nb th and ce that are enriched in coal samples taken from directly above and below tonsteins

trace element geochemistry of volcanic gases and particles from 1983 1984 eruptive episodes of kilauea volcano compositional data have been obtained for volcanic gases and particles collected from fume emitted at the pu u o o vent on the east rift zone of kilauea volcano the samples were collected by pumping fume through a filter pack system consisting of a front stage particulate filter followed by four base treated filters 7lioh particles and condensed phases are trapped on the particulate filter and acidic gases are collected on the treated filters the filters are analyzed for 30 elements by instrumental neutron activation analysis fume samples were collected from the pu u o o vent for two eruptive episodes 1 7 days after episode 11 cooling vent samples and 2 the waning stage of episode 13 active vent samples additional samples were collected by aircraft from the gas plume released during the lava fountaining phase of episode 17 aircraft samples element concentrations in the vent gases were 104 g m 3 for s cl and f enrichment factors efs for the volcanic fume versus the source magma were calculated using the volatile element br as the reference element for normalization and the u s geological survey standard bhvo 1 as the magma standard this removes the ash dilution effect obtained by using an ash constituent al sc or mg as the reference element bromine normalized efs 105 range from 101 to 102 for na k and cu 102 to 105 for zn w sb in ir ag f and as and 105 for au cd re cl se and s the highest enrichment factors are for aircraft samples collected during the most gas rich phase of an eruption cycle metal and volatile element data form two groups 1 elements showing little or no variation in abundance ratios with sample type group 1 cl br and re and 2 elements that show significant variation in abundance ratios by sample type group 2 zn w sb in ir au and cd bivariate plots of elements of the first group versus elements of the second group separate by sample type the separation corresponds to samples collected during eruptive activity versus samples collected during repose periods monitoring trace metal ratios in volcanic fume could provide an additional tool for predicting volcanic eruptions the f cl ratio of cooling vent samples is higher than those of active vent or aircraft samples and the ratio is inversely correlated with efs for most volatile metals

variations in the geomagnetic dipole moment during the holocene and the past 50 kyr all absolute paleointensity data published in peer reviewed journals were recently compiled in the geomacia50 database based on the information in geomagia50 we reconstruct variations in the geomagnetic dipole moment over the past 50 kyr with a focus on the holocene period a running window approach is used to determine the axial dipole moment that provides the optimal least squares fit to the paleointensity data whereas associated error estimates are constrained using a bootstrap procedure we subsequently compare the reconstruction from this study with previous reconstructions of the geomagnetic dipole moment including those based on cosmogenic radionuclides be 10 and c 14 this comparison generally lends support to the axial dipole moments obtained in this study our reconstruction shows that the evolution of the dipole moment was highly dynamic and the recently observed rates of change 5 per century do not appear unique we observe no apparent link between the occurrence of archeomagnetic jerks and changes in the geomagnetic dipole moment suggesting that archeomagnetic jerks most likely represent drastic changes in the orientation of the geomagnetic dipole axis or periods characterized by large secular variation of the non dipole field this study also shows that the holocene geomagnetic dipole moment was high compared to that of the preceding similar to 40 kyr and that similar to 4 10 22 am 2 appears to represent a critical threshold below which geomagnetic excursions and reversals occur c 2008 elsevier b v all rights reserved less

using an independent geochronology based on palaeomagnetic secular variation psv and atmospheric pb deposition to date baltic sea sediments and infer 14c reservoir age dating of sediment cores from the baltic sea has proven to be difficult due to uncertainties surrounding the c 14 reservoir age and a scarcity of macrofossils suitable for dating here we present the results of multiple dating methods carried out on cores in the gotland deep area of the baltic sea particular emphasis is placed on the littorina stage 8 ka ago to the present of the baltic sea and possible changes in the c 14 reservoir age of our dated samples three geochronological methods are used firstly palaeomagnetic secular variations psv are reconstructed whereby ages are transferred to psv features through comparison with varved lake sediment based psv records secondly lead pb content and stable isotope analysis are used to identify past peaks in anthropogenic atmospheric pb pollution lastly c 14 determinations were carried out on benthic foraminifera elphidium spec samples from the brackish littorina stage of the baltic sea determinations carried out on smaller samples as low as 4 mu g c employed an experimental state of the art method involving the direct measurement of co2 from samples by a gas ion source without the need for a graphitisation step the first time this method has been performed on foraminifera in an applied study the psv chronology based on the uppermost littorina stage sediments produced ten age constraints between 6 29 and 1 29 cal ka bp and the pb depositional analysis produced two age constraints associated with the medieval pollution peak analysis of psv data shows that adequate directional data can be derived from both the present littorina saline phase muds and baltic ice lake stage varved glacial sediments ferrimagnetic iron sulphides most likely authigenic greigite fe3s4 present in the intermediate ancylus lake freshwater stage sediments acquire a gyroremanent magnetisation during static alternating field af demagnetisation preventing the identification of a primary natural remanent magnetisation for these sediments an inferred marine reservoir age offset delta r is calculated by comparing the foraminifera c 14 determinations to a psv pb age model this delta r is found to trend towards younger values upwards in the core possibly due to a gradual change in hydrographic conditions brought about by a reduction in marine water exchange from the open sea due to continued isostatic rebound c 2012 elsevier ltd all rights reserved

the effect of volcanism on submontane rainforest vegetation composition paleoecological evidence from danau njalau sumatra indonesia volcanic processes might have played an important role in the vegetation history of sumatra one of the largest and most tectonically active region in southeast asia palynological and macro charcoal analysis results from lake njalau in the kerinci seblat national park ksnp in sumatra indonesia provide an understanding of interactions between the volcanic deposition and vegetation in the past 5000 years the deposition of volcanic material in the depression of the lake njalau 5100 4400 cal yr bp led to the dominance of pioneer species of casuarina and myrica which grow in deforested land and volcano slopes volcanophile taxa the formation of the modern forest composition took several centuries after the volcanic deposition in the soil ended ca 900 years at ca 2400 cal yr bp this suggests that the vegetation changes were not driven by a successional pattern and soil formation was the most important environmental factor explaining this slow change in composition the palynological records s

leachability of uranium and other elements from freshly erupted volcanic ash abstract a study of leaching of freshly erupted basaltic and dacitic air fall ash and bomb fragment samples unaffected by rain shows that glass dissolution is the dominant process by which uranium is initially mobilized from air fall volcanic ash si li and v are also preferentially mobilized by glass dissolution gaseous transfer followed by fixation of soluble uranium species on volcanic ash particles is not an important process affecting uranium mobility gaseous transfer however may be important in forming water soluble phases adsorbed to ash surfaces enriched in the economically and environmentally important elements zn cu cd pb b f and ba quick removal of these adsorbed elements by the first exposure of freshly erupted ash to rain and surface water may pose short term hazards to certain forms of aquatic and terrestrial life such rapid release of material may also represent the first step in transportation of economically important elements to environments favorable for precipitation into deposits of commercial interest ash samples collected from the active guatemalan volcanoes fuego and pacaya high al basalts and santiaguito hornblende hypersthene dacite bomb fragments from augustine volcano andesite dacite alaska and heimaey basalt vestmann islands iceland and fragments of rhyolitic pumice from various historic eruptions were subjected to three successive leaches with a constant water to ash weight ratio of 4 1 the volcanic material was successively leached by 1 distilled deionized water ph 5 0 5 5 at room temperature for 24 h which removes water soluble gases and salts adsorbed on ash surfaces during eruption 2 dilute hcl solution ph 3 5 4 0 at room temperature for 24 h which continues the attack initiated by the water and also attacks acid soluble sulfides and oxides 3 a solution 0 05 m in both na co and nahco ph 9 9 at 80 c for one week which preferentially dissolves volcanic glass the first two leaches mimic interaction of ash with rain produced in the vicinity of an active eruption the third leach accelerates the effect of prolonged contact of volcanic ash with alkaline ground water present during ash diagenesis

environmental factors as complicating influences in the recovery of quantitative geomagnetic field paleointensity estimates from sediments we have recently recovered replicate records of the earth s magnetic field relative paleointensity for 12 71 000 years bp from marine sediments of the western north atlantic ocean our records are remarkably similar to two other recently published relative paleointensity records from marine and lacustrine sediments in europe this suggests to us that even over this wide region sediments may serve as reasonable correlatable recorders of fluctuations in the strength of the earth s magnetic field if this is true then similar records from around the globe could eventually provide valuable information about the deep earth processes which create the field we note however that our intensity record is significantly correlated with the down core ratio of magnetic susceptibility to anhysteretic remanent magnetism arm this ratio is a measure of the relative grain size of magnetite the primary magnetic mineral in these sediments and as such is a sediment magnetic property which is controlled only by the local depositional environment and indirectly by global climate we are concerned that the european records may be similarly biased by climatic or other environmental factors possibly synchronous with ours we caution that extreme care must be taken to understand and remove any such magnetic influences from sediment relative paleointensity records before they are used as quantitative estimators of the past intensity of the earth s magnetic field