the role of time versus climate in the formation of deep soils of the apennine fringe of the po valley italy abstract two very deep red soils on a loess mantled fluvial terrace of the trebbia river in northern italy were sampled and analyzed to determine their history and pedologic significance magnetostratigraphy confirms that the upper part of the terrace gravel and all of the 4 m thick loess cover is normally magnetized and therefore less than about 780 000 yr artifacts collected from the oldest loess suggest an age of about 400 000 yr for the inception of loess deposition in this area the soil horizons in loess dominantly have argillic or albic character with redoximorphic features that include mottles glossic tongues and zones of ferromanganese concretions soil colors become progressively redder with depth in the loess cover and are most red a 2 5 yr color hue in the top of the terrace gravel the upper horizons in gravel have abundant ghosts of completely weathered marl and sandstone rubification and weathering of stones diminishes with depth to fresh slightly carbonate enriched parent material at 12 m the heavy mineral composition of the sand fraction suggests minor discontinuities in loess derived horizons abundance of opaque heavy minerals and picotite which are resistant to weathering increases from the soil surface to the base of the loess is highest in the upper part of the terrace gravel and decreases from there to the c horizon in gravel depth functions of major elements to si in the medium silt fraction 10 30 m indicate a downward increase in degree of decalcification and of dissolution of primary minerals micromorphology adds detail to the interpretation of these complex soils yellow complex ferriargillans are present in almost all horizons they are rare at the top of the sequence in loess and become progressively more abundant with depth reaching a maximum in the upper 3 m of the gravel and then decreasing with further depth to 12 m we interpret this peak in abundance of yellow cutans to result from long continued clay illuviation to this depth from a succession of eluvial zones in the aggrading loessial sequence above distinctive red hematite rich argillans are abundant only in the upper horizons in the gravel the red argillans relate to initial development of the soil in gravel because they are included as pedorelicts in the deepest loess layer where they are embedded in the yellow argillans stratigraphic and pedologic evidence indicates that these soils began forming in terrace gravel for perhaps 300 000 yr during the early middle pleistocene from this relict core these soils continued developing both downward by continuing deep decalcification and argilluviation and upward as a sequence of wet alfisols developed in a succession of loess layers that began aggrading about 400 000 yr ago a paleoclimatic record can be perceived weakly in these soils mainly by thick horizons of fe mn nodules that mark boundaries between episodes of loess deposition that took place during glacial cold phases paleofeatures from one unit to another are similar in kind and intensity indicating a degree of continuity of a basic set of pedogenic processes principally declcification argilluviation and redoximorphism these soils can be regarded as vetusols because a single dominant set of pedogenic features are represented in all parts of these soils and deeper parts of these aggrading super profiles have never been isolated from continuing pedogenic change to the present

intensity of the geomagnetic field in western europe over the past 2000 years new data from ancient french pottery 1 we studied 14 groups of french pottery fragments dated between the 4th and 16th centuries the potsherds were analyzed using the thellier and thellier 1959 method revised by coe 1967 intensity values were corrected for thermoremanent magnetization trm anisotropy and cooling rate dependence of trm acquisition we first analyzed modern ceramics produced following ancient techniques and fired in a wood burning kiln inside of which field intensity was measured the recovered mean intensity is within 3 of the expected value which proves the reliability of our experimental procedure thermal experiments carried out at rapid and slow cooling rates clearly indicate that the cooling rate correction is critical in archeointensity studies our data indicate that large variations in intensity occurred in france over the last 2000 years two relative maxima in intensity are observed one between the 8th and 10th centuries and the second between the 14th and 15th centuries similarities are observed between the archeointensity data from france and ukraine yielding some evidence for eastward drift of geomagnetic sources between western and eastern europe from a d 800 to a d 1700 we also show that the dipole moment evolution proposed by mcelhinny and senanayake 1982 and yang et al 2000 for the last two millennia is likely biased toward higher values mainly because of the absence of correction for the cooling rate dependence of trm acquisition in most published archeointensity studies we finally underline a possible relationship valid at least in western europe between changes in direction and intensity of the geomagnetic field

on the origin and post depositional history of widespread massive ash deposits the case of intermediate brown tuffs ibt of lipari aeolian islands italy abstract we analysed a widespread massive ash unit outcropping on the island of lipari which belongs to the intermediate brown tuffs ibt succession of the aeolian islands italy the use of a multidisciplinary approach that integrates textural petrological and pedological methods allows us to discriminate between syn eruptive and post depositional features the deposits are dominated by uncrystallised blocky glass fragments of homogeneous shoshonitic composition confirming a provenance from hydromagmatic eruptions on the island of vulcano many glass fragments are surrounded by a coating separated by a thin void of syn eruptive origin due to alteration by aggressive acid gases in the eruptive cloud the lack of this coating in the northern part of lipari can be explained as a progressive dispersion of the gases far from the vent and or to post depositional processes the degree of soil development significantly increases from south soil profiles p1 and p2 at valle muria to north p3 and p4 at madoro and chiesa vecchia sites respectively as a response to a decrease in slope steepness which has brought about a progressive deepening of the pedogenetic front on gentler landforms and conversely its rejuvenation on steep slopes the relatively poor to moderate degree of pedogenic evolution of the studied ibt unit is consistent with its emplacement during part of the last glacial period

numerical calibration of the devonian carboniferous boundary two new u pb isotope dilution thermal ionization mass spectrometry single zircon ages from hasselbachtal sauerland germany the hasselbachtal section sauerland germany is an auxiliary global stratotype of the devonian carboniferous boundary and one of the most important reference sections for the evolution of the latest famennian to earliest tournaisian pelagic fauna biostratigraphically well controlled altered volcanic ash layers metabentonites intercalated in the section afford a perfect opportunity for a numerical fixing of this important paleozoic period boundary we have performed u pb isotope dilution thermal ionization mass spectrometry id tims analyses on sub microgram sized single zircons and zircon fragments extracted from two metabentonites beds 79 and 70 in the lowermost tournaisian part of the section bed 79 metabentonite is positioned directly above the devonian carboniferous boundary within the siphonodella sulcata conodont zone five concordant analyses form a cluster with a 2 0 6 pb 3 3 8 u concordia age of 360 5 0 8 ma zircons of the next younger metabentonite bed 70 in the lower siphonodella duplicata conodont zone yielded a tightly grouped cluster of 10 concordant analyses with a 2 0 6 pb 2 3 8 u concordia age of 360 2 0 7 ma on the basis of these two new single zircon ages and previously published late famennian u pb id tims ages the devonian carboniferous boundary is reinterpolated herein to 360 7 0 7 ma

quaternary evolution of the intermontane val d agri basin southern apennines optically stimulated luminescence osl enables the chronology of the late pleistocene evolution for the val d agri intermontane basin of southern apennines to be defined in the frame of mediterranean geodynamic and climate changes quartz sand from braided floodplain and alluvial fan depositional systems was analyzed using the coarse grained single aliquot regenerative dose sar technique the obtained optical ages are mostly consistent with other assessments radiocarbon tephrochronology and stratigraphic constraints osl allows for the dating to 56 43 ka of an asymmetric subsidence stage that forced alluvial fan progradation filling of a former lacustrine area and development of an axial alluvial plain a short period of mediterranean type pedogenesis recorded at the top of the prograding aggrading fans osl age bracket 43 32 ka corresponds with mis 3 during the subsequent stage of decline of vegetation cover possibly corresponding to mis 2 the latest progradation of alluvial fans occurred the subsequent uplift and breakthrough of the basin threshold during the latest pleistocene and holocene induced entrenchment of the drainage network the results presented here provide an example of the usefulness of osl dating in intermontane continental settings where other geochronological constraints are scarce

pliocene pleistocene vegetational and climatic evolution of the south central mediterranean abstract the vegetational history of the south central mediterranean clearly reflects the major global climatic changes of the last four million years a mediterranean type climate characterized by strong seasonality and a dry summer may have existed in this region during the early pliocene a short term climatic cooling at approximately 3 2 ma resulted in the temporary establishment of a humidity demanding flora the onset of major northern hemisphere glaciation at approximately 2 4 ma initiated an alternation between humid glacial and dry interglacial conditions vegetational differences between this region and the north west mediterranean indicate that distinct latitudinal climatic gradients probably existed in the mediterranean during the pliocene early pleistocene

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

first archaeomagnetic field intensity data from ethiopia africa 1615 12 ad abstract first archaeointensity determinations have been obtained from ethiopia seven bricks 34 specimens from the dabsan archaeological remains were subjected to archaeointensity determination by means of classical thellier thellier experiment including tests for magnetic anisotropy and magnetic cooling rate dependency the age of the dabsan palace is well controlled by historical information between 1603 when land grants were conceded to the jesuits and the catholicism was established as the official religion in ethiopia and the age of the palace foundation in 1626 27 successful archaeointensity determinations were obtained in 27 specimens from five individual bricks revealing an average field value of 33 5 1 1 t which is 11 26 lower than expected values from global geomagnetic models based on historical and archaeomagnetic data global models for 1615 ad predict a low in central southern africa related to past location of the present southern atlantic anomaly saa our results suggest that the field intensity in central africa may have been slightly lower than global model predictions this would indicate that the low could be probably more extended towards central eastern africa or more intense than previously considered further data from this region are especially welcome to delineate the evolution of the saa

pleistocene paleosol development and paleoenvironmental dynamics in east africa a multiproxy record from the homo bearing aalat pedostratigraphic succession dandiero basin eritrea abstract the climatic changes during the early middle pleistocene transition are a key to understand the ecosystem dynamics that involved the homo erectus ergaster distribution the aalat pedostratigraphic succession represents a continental archive in the african rift valley eritrea where remains of homo around 1 ma were identified high resolution magnetostratigraphy dated this succession between the base of the jaramillo subchron and the lower brunhes chron despite the present arid desert climate the aalat section records a persistence of water driven fluvio lacustrine environments which suggests a major tectonic control on sedimentation although climate changes are clearly overprinted macro and micromorphological physico chemical mineralogical and geochemical features up to now poorly available for pleistocene paleosols in east africa depict a poor to moderate degree of development although calcic and petrocalcic petrogypsic horizons at different stratigraphic heights indicate phases of geomorphic stability the concurrent alternation of these horizons with iron stained layers suggests cyclical changes from dry to wet conditions which fit well with aeolian dust fluxes and marine isotope stages of glacials and interglacials at higher latitudes stable isotope data are consistent with these climatic cycles and suggest a succession of monsoonal and non monsoonal conditions the homo erectus settlement lasted apparently for a short time span because a long high discharge fluvial sedimentation and or an aridity phase at the base of the fluvial facies could have made the area less suitable for human settling and could have hindered preservation of fossils and artifacts

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

volcanomagnetic effects observed on piton de la fournaise volcano reunion island 1985 1987 a permanent network of four to six telemetered magnetic stations has been installed on piton de la fournaise volcano in october 1985 and 1986 eight eruptive sequences have occurred since then some of which affected only the summit whereas others affected the whole massif volcanomagnetic variations are observed with each of these volcanic events the geomagnetic field intensity is measured simultaneously every minute at each station with a precision of 0 25 nt nanotesla the main results are the following volcanomagnetic variations observed with eruptions have amplitudes of several nanoteslas to more than 10 nt with characteristic time durations ranging from l min or less to several months a good correlation between the magnetic variations recorded at the different stations is observed spatial and temporal properties of the volcanomagnetic field appear to be controlled by the features of the eruptions several days before the beginning of the december 1985 march july november december 1986 and january 1987 eruptions changes in the intensity differences are observed with amplitudes of a few nanoteslas up to 5 nt at stations located close to the active part of the rift zone variations are also observed in the most remote stations for larger eruptions in march 1986 november december 1986 and january 1987 correlations between magnetic variations ground deformations and seismic activity have been observed for the december 1985 march 1986 november december 1986 and january 1987 events three main mechanisms could account for the observed volcanomagnetic variations piezomagnetic effects electrokinetic effects and electrical resistivity changes since variations in the stress field in the surroundings can modify the induced and natural magnetizations of magnetized rocks the circulation of water through the interconnected pore network microcracks faults aquifers and also the electrical resistivity of geological structures through the modification of the properties of the pore network

seismic heterogeneity of mt etna structure and activity a dense seismic array maintained temporarily for 7 weeks provides an approach to deducing the 3 d heterogeneity of the structure of the upper crust beneath mt etna volcano from the inversion of p and s wave arrivals of local earthquakes independent data from a different source array geometry using waves generated by distant shots at sea confirm a main lateral variation a high velocity body underlies part of the volcano its contrast with the surrounding thick sedimentary pile and its location extending from the present summit to the southeast suggests that it may have been built by the development and migration of past eruptive centres followed by caldera collapse local low velocity anomalies near its sharp western edge may be associated with presently active features

a reliable absolute palaeointensity determination obtained from a non ideal recorder reliable measurements of the intensity of the palaeomagnetic field are notoriously difficult to obtain the approach generally taken is to produce multiple estimates per rock unit and assume that those which meet certain minimum standards of technical quality will combine to produce an accurate mean however here using results produced from a package of 20th century basaltic lava flows from mount etna in sicily we demonstrate that this approach can fail in this case the application of typical sets of selection criteria actually introduces bias into the mean determination that we measure we demonstrate that this is caused by two types of non ideal behaviour acting in combination the first is a result of the multidomain grains that the samples contain and the second is caused by differences in the natural and laboratory cooling rates we discuss means of avoiding these sources of error in future palaeointensity studies performed on ancient rocks we also develop a new more general reliability criterion which is effective here and which we argue should be applied wherever possible in future palaeointensity studies in conjunction with standard criteria it requires two distinct types of materials which both produce some good quality palaeointensity measurements and uses their range of overlap to constrain the true palaeointensity both the application of this criterion and general reliability considerations require that future palaeointensity studies should measure many samples per cooling unit and that these should be as diverse in terms of their rock magnetic properties and cooling histories as possible

calibrating the devonian time scale a synthesis of u pb id tims ages and conodont stratigraphy the recalibrated devonian time scale represents an important improvement of devonian chronology regarding two aspects firstly a data set of 13 biostratigraphically well bracketed u pb id tims zircon and monazite ages constitutes the framework of the scale secondly approximately time linear biostratigraphic scales have been used for the interpolation between the isotopic ages the new construction thus represents a biochronometric time scale which allows the assignment of numeric ages not only to stage boundaries but also to each biozone boundary the method of interpolation applied also enables the projection of the geochronological error onto the time scale according to the newly calibrated scale the devonian lasted 57 4 5 7 ma from 418 1 3 0 to 360 7 2 7 ma this is compared to previously published time scales the longest time span ever calculated for this period the age interpolations for the eight stage boundaries are famennian tournaisian devonian carboniferous 360 7 2 7 ma frasnian famennian 376 1 3 6 ma givetian frasnian 383 7 3 1 ma eifelian givetian 388 1 2 6 ma emsian eifelian 391 9 3 4 ma pragian emsian 409 1 3 8 ma lochkovian pragian 412 3 3 5 ma pridolian lochkovian silurian devonian 418 1 3 0 ma full size table table options view in workspace download as csv the duration of the middle devonian is calibrated here as quite short with 8 2 ma and the emsian and the famennian are the longest stages with interpolated durations of 17 2 and 15 4 ma respectively together all devonian stages contain 57 conodont zones including subzones according to the standard conodont zonation giving a mean duration of about 1 ma in the highly resolved part of the time scale mid eifelian to the devonian carboniferous boundary zonal resolution averages 0 6 ma in contrast the lowest resolution is shown in the early emsian to mid eifelian interval with zonal durations of up to 5 5 ma serotinus zone

mineralogy micromorphology and chemical analysis of andosols on the island of sao miguel azores abstract a study concerning soil genesis was conducted on surface and buried volcanic soils of sao miguel island azores of eight soil profiles three were selected for detailed study of pedogenesis a series of techniques which include chemical micromorphological xrd and dxrd analysis micropicking on impregnated soil blocks tem eds and ir spectroscopy analyses were used the soils showed an incipient to moderate degree of weathering as typically occurs in many young volcanic districts four different stages of soil development were clearly identified the first stage of soil development was characterised by dominance of primary minerals and some allophane and ferrihydrite formation with an feo fed ratio of about 0 86 lom soil the second stage of soil development was indicated by halloysite and ferrihydrite formation in the lower horizons along with an feo fed ratio of about 0 62 san surface soil the third stage of soil development was characterized by halloysite and ferrihydrite formation in the lower horizon but also by clay illuviation and stronger pumice weathering and an feo fed ratio of about 0 51 san buried soil the fourth stage of soil development concerned the lix soils buried soils older than 5000 years bp which had a much higher content in hydrated halloysite and considerable amounts of goethite and hematite these soils exhibit the most expressed weathering features and an feo fed ratio of about 0 25 the presence of young surface soils and well developed buried soils can be explained by i the longer pedogenesis of buried soils or possibly by ii the presence of a climate more seasonal than that of the present day

40ar 39ar isotope constraints on the age of deformation in charnwood forest uk 40 ar 39 ar dating by a combination of spot analysis and step heating has been carried out on mica fabrics from slaty cleavage and a shear zone in the neoproterozoic to cambrian rocks of charnwood forest leicestershire the results indicate that crust adjacent to the eastern margin of the midlands microcraton was affected by localized epizonal metamorphism and penetrative deformation between 425 and 416 ma silurian to earliest devonian somewhat earlier than the acadian phase of the caledonian orogeny recorded elsewhere in southern britain the charnwood cleavage geometry suggests that the deformation arose within a dextral transpressional regime along the eastern margin of the midlands microcraton this tectonism may have overlapped with pre acadian sinistral transtensional movements documented for the welsh basin and lake district areas to the west and north of the midlands microcraton

new u pb zircon ages and the duration and division of devonian time newly determined u pb zircon ages of volcanic ashes closely tied to biostratigraphic zones are used to revise the devonian time scale they are 1 417 6 1 0 ma for an ash within the conodont zone of icriodus woschmidti i w hesperius early lochkovian 2 408 3 1 9 ma for an ash of early emsian age correlated with the conodont zones of po dehiscens lower po inversus 3 391 4 1 8 ma for an ash within the po c costatus zone and probably within the upper half of the zone eifelian and 4 381 1 1 3 ma for an ash within the range of the frasnian conodont palmatolepis punctata pa punctata zone to upper pa hassi zone u pb zircon ages for two rhyolites bracketing a palyniferous bed of the pusillites lepidophyta spore zone are dated at 363 8 2 2 ma and 363 4 1 8 ma respectively suggesting an age of363 ma for a level within the late famennian pa g expansa zone these data together with other published zircon ages suggest that the base and top of the devonian lie close to 418 ma and 362 ma respectively thus lengthening the period by20 over current estimates we suggest that the duration of the middle devonian eifelian and givetian is rather brief perhaps no longer than 11 5 myr 394 ma 382 5 ma and that the emsian and famennian are the longest stages in the period with estimated durations of15 5 myr and 14 5 myr respectively 1998 elsevier science b v all rights reserved

soils in the mediterranean region what makes them different mediterranean climates are characterized by winter rains with some months of excess rainfall over evatranspiration warm and dry summer months with moisutre deficits drying out soils and their annual vegetation xeric moisture regime they are found on western parts of all continents between the cooler temperature zone and the hot dry desert zone the largest mediterranean region surrounding the mediterranean sea extends over 4 300 000 km2 and exhibits a wide variety of soils and geo ecosystems characteristics landscape attributes are the high proportion of mountains with sleep slopes significant additions of saharan desert dust to practically all soils of the region and a large proportion of limestone and other calcareous rocks as soil parent materials characteristics soil behavior features are moderate weathering with pervection leaching lessivage of mostly 2 1 clays into b horizons xeralfs luvisols hematite induced reddening of the clays due to summer dehydration of free iron oxyhydroxides carbonate dissolution and reprecipitation with prevalence of calcic horizons xerolls calcisols in semiarid regions and development of vertisols mostly in lowlands where deep layers of swelling cracking clays have sedimented shallows soils on nearly bare slopes mostly a result of erosion subsequent to deforestation are frequent leptosols cambiosols inceptisols entisols red or brown mediterranean soils are no longer used as a separate classification group in modern well defined soil property controlled taxonomies soil taxonomy fao system but were partially replaced by duchaufour s term fersiallitic soils in some classification systems terra rossa continues to be used in some classification for hard limestone derived red soils mostly shallow the effects of man s past and current interference with the lanscape are pervasive in most regions and predictions for possible future effects on the soils and ecosystems due to greenhouse gas induced warming and rainfall change are partly negative partly still too uncertain

u pb zircon dating of paleozoic volcanic rocks from the rheno hercynian zone new age constraints for the steinkopf formation lahn dill area germany small and volumetrically subordinate outcrops of alkali rhyolitic to trachytic metavolcanic rocks are widespread in the lahn dill area of the rheinisches schiefergebirge germany these occurrences are either related to late early devonian or to middle devonian episodes of volcanic activity an unambiguous age assignment for the time of eruption could not be established so far most volcanic rocks of the study area are not suitable for application of u pb geochronology a notable exception is the steinkopf rock suite in the sw lahn dill area but a straightforward interpretation of the la icp ms u pb data is hampered by complex zircon populations recording various processes including crystallization from newly formed melt inheritance assimilation of country rocks variable degrees of pb loss and fluid assisted zr mobility a plausible evaluation of u pb zircon data of two metatrachytes and a metavolcaniclastic rock document a coherent age group at ca 390 384 ma and a probable eruption age at ca 385 ma suggesting a relationship to middle devonian givetian igneous processes zircon bearing veinlets in a metatrachyte indicate post eruptive infiltration of external hydrothermal fluids and or internal zr redistribution in late devonian to early carboniferous time 364 10 ma but this process is of rather limited importance

timing of the permian triassic biotic crisis implications from new zircon u pb age data and their limitations abstract the most profound biotic crisis in the earth s history causing the near extinction of both terrestrial and marine life occurred at the end of the permian period about 253 myr ago and marks the paleozoic mesozoic era boundary the cause of this event is still a matter of vigorous debate with both brief and catastrophic as well as gradual mechanisms having been proposed similar to a recent landmark study this study uses the u pb method on zircons from the uppermost permian lowermost triassic ash fall deposits at meishan zhejiang province se china in order to examine time and rate constraints for these events the results of both this study and previous work show that for these ash layers the effects of pb loss are combined with varying amounts and sources of inheritance resulting in an age scatter which prohibits the extraction of a statistically robust age in many cases though the effects of pb loss on the zircons analyzed in this study were reduced by leaching the grains in hydrofluoric acid as opposed to commonly applied air abrasion prior to analysis the presence within a single ash layer of multiple generations of older xenocrysts in many cases only slightly older than the depositional age has made quantitative interpretation even more difficult when these combined phenomena bias individual zircon ages by less than a percent they are extremely difficult to deconvolute and if multi grain analyses are used can become impossible to recognize because of the resulting age averaging monte carlo simulations using actual measurements of individual zircon crystals show that age excursions due to pb loss and xenocrystic contamination for the meishan bentonites are easily homogenized to the point of undetectability when replicate analyses of multi grain zircon samples are compared thus this study uses only high precision analyses of single crystals whether from our work or that of previous studies three main conclusions have emerged first our data require a significant increase in the age of the permian triassic boundary by more than 2 myr compared to the previous study which shifts the age to a value older than 253 ma second neither our data nor those from previous work can confirm or negate the possibility of a very abrupt biotic crisis third even large suites of very high quality single zircon u pb analyses for these tuffs cannot in most cases yield objective reliable and robust dates with accuracies at the sub myr level though the temptation to perform arbitrary selection of subsets of the analyses for that purpose is almost irresistible the last conclusion is not an indictment of zircon u pb dating in general other rocks and other zircon populations can and do behave very differently and further technical advances will likely improve our ability to prepare grains or sub grains of adequately enhanced quality for analysis consequently the results of the present study strongly suggest that for problems requiring time scale accuracy inferences from zircon u pb dating must be based on sufficiently large suites of single crystal or crystal domain high precision analyses

abnormal shallow palaeomagnetic inclinations from the 1950 and 1972 lava flows hawaii summary high precision palaeomagnetic sampling and measurements of 1950 mauna loa lava flows hawaii show as noted by other workers a significantly low inclination compared to the geomagnetic direction expected from available observatory data such shallow inclinations appear related to the unusually high intensity of magnetization of the 1950 basalt resulting in a high magnetic refraction for the lava flows considered other altered palaeomagnetic directions both inclination and declination on kilauea 1972 flows possibly result from displacements during and or after cooling erroneous palaeomagnetic direction imprints do not appear to be the rule

polycyclic luvisols in northern italy palaeopedological and clay mineralogical characteristics abstract two long pleistocene palaeosol sequences in the southwestern fringe of the lago maggiore region northern italy were studied by a wide range of pedological methods particular emphasis was placed on clay mineralogy in order to distinguish the weathering intensity of different palaeosols the clay mineralogical analyses showed a gradual transformation from the top to the central part of the studied sequences whereas the uppermost horizons include chlorite as a sign of weak alteration processes the underlying palaeosols are dominated by vermiculites and mixed layers the lowermost parts of the palaeosol sequences show different conditions as they contain neoformed kaolinite paleosols and pedocomplexes were correlated by mean of their pedologicial characteristics six main pedogenetic units have been identified in both sequences representing different stages of soil formation paleopedological and clay mineralogical results indicate at least four interglacial phases two of them showing warmer and more humid conditions than today and two of them showing climatic conditions comparable with the present day climate

chronostratigraphic confirmation of mis 5 age of a baymouth bar at is arenas cagliari italy in 2005 the national geological survey of italy released the new sheet 557 cagliari 1 50 000 scale a coastal barrier marine formation at is arenas cagliari sardinia italy containing strombus bubonius was reassigned a holocene age in contradiction with extensive literature published over the past century indicating an mis 5 5 age in 2007 spurred by this controversy a short note was published in il quaternario demonstrating the stratigraphic difficulties in attributing the age of this formation to the holocene later another paper signed by numerous italian geologists was published in il quaternario criticizing the holocene attribution the tectonic consequences of assigning a holocene age to these deposits are of great significance as their elevation could only be explained by strong uplift over the past few thousand years such a tectonic setting would imply a radical change in the recent geodynamic history of sardinia which is considered to be among the most stable areas of the mediterranean basin this paper provides further geochronological data for a mis 5 age for the deposits at is arenas electron spin resonance esr analyses were performed on 4 fossil shells sampled along the fossil baymouth bar the results established an mis 5 age the amino acid racemization aar and u series data that first determined a correlation with the last interglacial tyrrhenian age of this ancient shoreline is reviewed with additional documentation provided by the fossil marker s bubonius

deflection of paleomagnetic directions due to magnetization of the underlying terrain in the summers of 1989 and 1991 we made 344 near ground level measurements of the ambient geomagnetic field above recent basalts on the island of hawaii using a three component fluxgate magnetometer we studied 12 surface features including a lava pond lava channels long tilted blocks smooth sloping surfaces two fissures and a deep u shaped road cut we observed substantial differences up to 20 between the observed and expected international geomagnetic reference field igrf magnetic field directions over these features except those composed of shelly pahoehoe and a flat horizontally thin lava pond we also observed inclinations that were systematically shallower than the igrf field by up to 5 we show that these shallower inclinations can be explained by the magnetization of the regionally sloping surface of the southern side of the island we found that all of the observed inclination deflections can be explained by simple two dimensional models which assume uniform induced and remanent magnetization parameters in the local terrain our observations imply that the inclination deflections cannot be corrected without a complete knowledge of the preexisting terrain and the remanence in the underlying flows upon which the lavas cooled since this information is rarely available it is difficult or impossible to discriminate between dispersion of paleomagnetic directions caused by the magnetic terrain effect and dispersion due to other factors such as paleosecular variation psv we therefore conclude that psv dispersion parameters cannot be accurately determined from paleomagnetic measurements on highly magnetic volcanic flows we also suggest that some of the geomagnetic excursions inferred from measurements on volcanic rocks may be at least in part due to the magnetic terrain effect it is unnecessary to invoke ad hoc mechanisms such as clastic block or crustal rotations distortion of the top crust or flow deformation to explain the large between site dispersions or inclination anomalies observed in many of the paleomagnetic data from volcanic rocks our observations also bring into question the general reliability of paleomagnetic pole positions inferred from volcanic rocks as a systematic inclination deflection due to local and regional slopes and irregular terrain such as those we observed would lead to a corresponding error in the inferred paleolatitude the magnetic terrain effects also offer alternative explanations for anomalous paleomagnetically inferred plate motions

global geomagnetic field models for the past 3000 years transient or permanent flux lobes psvmod1 0 is a compilation of globally distributed palaeodirectional data from archaeomagnetic artefacts lava flows and lake sediments at 24 sites evaluated at 100 year intervals from 1000 bc to ad 1800 we estimate uncertainty in these measures of declination and inclination by comparison with predictions from standard historical models in time intervals of overlap and use the 100 year samples and their associated uncertainties to construct a sequence of minimum structure global geomagnetic field models global predictions of radial magnetic field at the coremantle boundary cmb as well as inclination and declination anomalies at the earth9s surface provide an unprecedented view of geomagnetic secular variations over the past 3000 years and demonstrate a consistent evolution of the field with time resolution of the models is poorest in the southern hemisphere where only six of the 24 sites are located several with incomplete temporal coverage low flux regions seen in the historical field near the north pole are poorly resolved but the northern hemisphere flux lobes are clearly visible in the models these lobes are not fixed in position and intensity but they only rarely venture into the pacific hemisphere the pacific region is seen to have experienced significant secular variation a strong negative inclination anomaly in the region like that seen in 0 5 ma models persists from 1000 bc until ad 1000 and then gradually evolves into the smaller positive anomaly seen today on average between 1000 bc and ad 1800 the non axial dipole contribution to the radial magnetic field at the core mantle boundary is largest in the north central pacific and beneath central asia with clear non zonal contributions at the earth9s surface average inclination anomalies are large and negative in the central pacific and most positive slightly to the east of central africa inclination anomalies decrease with increasing latitude average declinations are smallest in equatorial regions again with strong longitudinal variations largest negative departures are centred over australia and eastern asia secular variation at the earth9s surface is quantified by standard deviation of inclination and declination about their average values and at the cmb by standard deviation in radial magnetic field all three show significant geographical variations but appear incompatible with the idea that secular variation in the pacific hemisphere is permanently attenuated by greatly enhanced conductivity in d 00 beneath the region

an updated and homogeneous world secular variation data base 1 smoothing of the archaeomagnetic results the available original archaeomagnetic world data on intensity and direction have been compiled and sorted according to geographical region then after correcting them to correspond to a single site associated with each region called a world site they have been processed using the gaussian statistic for the intensity f data and bivariate statistic for the declination d and inclination i data to obtain smoothed values at regular time intervals we include a discussion of the statistical methods used we have limited the data to the last 20 centuries because the archaeomagnetic data alone do not allow us to go back further in the past we have also excluded archaeomagnetic studies at world sites where the number of data is not sufficient to perform a statistical analysis we obtained results at nine world sites for which the values of at least two of the three above quoted parameters have been calculated at 25 year intervals from the beginning of our era the results for each world site with their associated errors are given and discussed the potential of this new set of world data for improving our knowledge of the global terrestrial magnetic field tmf during the past 20 centuries is sketched these results will be completed in a second paper by analysing in the same way the data supplied for volcanic rocks and lake sediments

reply to the comment on chronology of vesuvius activity from a d 79 to 1631 based on archeomagnetism of lavas and historical sources by r lanza and e zanella

role of weathering of pillow basalt pyroclastic input and geomorphic processes on the genesis of the monte cerviero upland soils calabria italy abstract in this paper we present new data on weathering and soil formation processes affecting alkaline pillow basalts on the summit of mt cerviero calabria southern italy we investigated two representative soil profiles using an integrated approach including pedological petrographic mineralogical and geochemical investigations we distinguished the main features inherited from the hydrothermal alteration of the pillow basalts in a submarine environment from the chemical weathering processes under meteoric conditions irregular geochemical patterns and chemical index of alteration values across the soil profiles indicate a lithological discontinuity between the bedrock and the upper soil horizons as a response to soil rejuvenation in turn controlled by erosive processes and an allochthonous pyroclastic input the soil profiles display poor horizonation and an incipient to intermediate degree of weathering in line with the clay mineralogy chlorite or hydroxy interlayered vermiculite illite kaolinite and varying mixed layers the degeneration microtextures of clay and iron manganese coatings in one soil profile suggest their relict genesis with an emplacement under warm humid conditions during the last interglacial a late pleistocene to holocene age of soil development is supported by the trachytic composition of volcanic micropumices correlated to explosive eruptions from the campania province or the aeolian islands in both soil profiles geochemical indices obtained from selective extractions of pedogenetic al fe and si pools point to poor andic properties with humus al complexes prevailing over short range order minerals nonetheless the latter are consistent with the presence of volcanic glass an optically isotropic pedogenic matrix and the andosol like field features of the soil profiles even if they developed in a non volcanic area this should lead to a partial reassessment of the volcanic versus non volcanic origin of certain andosols worldwide and claims a good field work as a basis for choosing the best suited laboratory methods to fill the gap between ordinary lab and field results

buried palaeosols of nw sardinia italy as archives of the late quaternary climatic fluctuations abstract a multi disciplinary approach was performed to investigate two compound geosols included between wind blown deposits at the top and interglacial mis 5 beach sediments at the bottom located along the alghero coast north western sardinia italy a sedimentological and morphological study was carried out on the profile in the field and samples collected on the main pedomembers were subjected to several laboratory analyses consisting of physical and chemical determinations on bulk samples mineralogy xrd micromorphology on undisturbed samples thin section sem and edax micro probe analyses dating was performed by means of optically stimulated luminescence osl the studied geosols show the evidence of a complex pedosedimentary evolution around 80 to 70 ka the lower geosol underwent weathering and clay illuviation wet and warm conditions followed by calcification recalcification processes dry contrasted and finally by strong bioturbation around 70 ka the onset of the glacial period mis 4 is marked by the deposition of a sand dune capping the lower geosol these results indicate that the coastal area of the central mediterranean kept the relatively warm conditions typical of the interglacial climate for most of the early wurm and reached cold conditions only at about 70 ka possibly in relation to the rapid cooling of the heinrich event h7 the upper geosol developed on colluvial material including abundant pedorelicts and reddish earth material deposited around 50 ka before being buried by aeolian sand around 43 ka this deposit underwent pedogenesis phases possibly associated to middle wurm interstadial events indicating that in the study area these events were intense enough to influence pedogenesis

oligo miocene half graben structure in western sardinian shelf western mediterranean reflection seismic and aeromagnetic data comparison abstract an improved model of the tectonic structure of the central sector of the western sardinian shelf off the gulf of oristano from integrated interpretation of seismic and magnetic data is presented from the analysis of the aquapulse seismic reflection profiles and sparker and airgun high resolution seismic data it was possible to define the major structural features of the study area that were previously not extensively known from these analyses it was possible to recognize a prevalently nne trending extensional system the interpretation of the aeromagnetic data was performed by the analytic signal method and euler deconvolution technique in the geological context of the study area these methods show a high resolution power by solving sharp lateral magnetic discontinuities like subvertical structures and basement steps the results of the magnetic interpretation were taken as a support for the seismic interpretation and they allowed a better definition of the tectonic structure of the study area this structure of extensional type is considered as a western conjugate branch of the oligo miocene sardinian rift its evolution is related to the oligo miocene andesitic volcanism at the bottom and with a marine infilling that at the top is messinian in age

holocene soil chronofunctions southern alps new zealand abstract field and laboratory data for two soil chronosequences from the high country of the south island of new zealand suggest rapid soil formation rates the areas studied are the ben ohau range and the mt cook area where mean annual precipitation is about 1 and 4 m respectively most soil ages are estimated from the thicknesses of rock weathering rinds soil chronofunctions are derived for indices that depict field profile and color development and a modified index of profile anisotropy for laboratory data out of a possible 21 chronofunctions 16 are statistically significant at the 0 05 level and 8 are from each area most 13 of the chronofunctions best fit a power model and the remaining ones are split between linear 2 and exponential 1 models although problems exist in the purity of the chronosequences because other soil forming factors are not constant duration of pedogenesis seems to be the most significant factor in explaining the trends despite the large differences in mean annual precipitation between the two areas many of the derived curves for property vs time are quite similar

archeomagnetism of piton de la fournaise bearing on volcanic activity at la reunion island and geomagnetic secular variation in southern indian ocean historical and other recent lavas from piton de la fournaise la reunion island are studied using the large sample archeomagnetic method which provides here paleodirections of the earth magnetic field with confidence cones between 0 9 and 2 5 thus offering a precise record of the geomagnetic field and potential dating constraints ages of the lavas are known thanks to historical chronicles from 1708 or 14c dating and their analysis give information about the directional secular variation sv in a region where observatory measurements are scarce and not available before the end of the 19th century for the past 250 yr we find a high value of inclination 50 to 55 with respect to the geographic latitude 21 s connected with a very restricted directional sv conversely the older volcanic units present a larger sv with magnetic inclinations of between 31 and 46 and declinations from 16 w to 10 e these results which are in reasonable agreement with instrumental measurements made on ships in the vicinity of la reunion allow us to infer that undated lavas of the northern part of the caldera emanated from eruptions during the second half of the 1700s other volcanic products e g mare longue flow piton chisny cone and flows and pointe langevin despite their fresh morphology are necessarily older than about 1500 ad further knowledge of the path of the sv in the more distant past and therefore further archeomagnetic dating is hampered by the lack of a precise chronology through radiometric or other similar methods available models of the geomagnetic field during the last millennium which suffer from the scarcity of data in the southern hemisphere are discussed in the light of our results

reducing time scale uncertainty for the devonian by integrating astrochronology and bayesian statistics dealing with uncertainties is inherent to the scientific process in the process of building geologic time scales the reported uncertainties are at least as important as the estimates of the numerical ages currently all time scales for the devonian are based on conventional age depth models constructed by linear or cubic interpolation between different dated positions unfortunately such models tend to produce overoptimistic confidence intervals in this study we apply bayesian statistics to the devonian time scale to better incorporate stratigraphic and radioisotopic uncertainty this approach yields a devonian time scale characterized by increasing uncertainty with growing stratigraphic distance from a radioisotopically dated sample this feature is absent from the geologic time scale 2012 therefore that time scale is overoptimistic we further constrain the obtained time scale by incorporating astrochronological duration estimates for the givetian and frasnian stages the combination of radioisotopic dating and astrochronology results in a reduction of the uncertainty on the numerical age of the stage boundaries concerned by several million years for example we estimate the age of the frasnian famennian boundary at 373 9 1 4 ma

climatic and tectonic controls on pedogenesis and landscape evolution in a quaternary intramontane basin val d agri basin southern apennines italy abstract paleopedological studies of alluvial systems in intramontane valley settings provide useful tools for understanding the interaction of tectonics climate and local base level changes in controlling alluvial dynamics an example is reported from the quaternary alluvial deposits of the val d agri basin in southern italy which were accreted in response to cycles of deposition pedogenesis and erosion several buried weathering profiles representative of the main stratigraphic unconformities were characterized by field description and micromorphological analyses the profiles appear to be truncated at the top by intense erosion the main pedological features and their formative processes occurred polycyclically attesting to different and relict pedogenetic phases that are not in equilibrium with present day environmental conditions we interpret the weathering profiles as paleosols that developed mainly during pleistocene interglacial periods the peri glacial phases mainly caused erosion of devegetated slopes and soil truncation processes all of the paleosols in the val d agri basin offer useful information on the chronological reconstruction of climatic phases and the associated sequence of pedogenetic events during the quaternary in the mediterranean region

magnetic anomalies of lava fields in the canary islands possible consequences for paleomagnetic records abstract measurements of the total magnetic field have been performed above the surface of 12 lava flows in the canary islands of la palma and tenerife directions can differ by up to 15 and intensity changes reach 20 the mean flow directions do not coincide and the mean flow virtual dipole moments vdms differ by more than 10 the deviations are linked to topographic features at the surface of the flows and should persist during emplacement of the next overlying flow such effects can thus limit the resolution of paleomagnetic records of detailed geomagnetic features and the field intensity variations above the flows and between the mean flow values could explain a significant part of the scatter inherent to many paleointensity studies historical field variations have been recorded from the same flows and are in agreement with the european curve for the same period however there is also some correlation with the present field which suggest that the underlying magnetized bodies could have affected the paleomagnetic records biases induced by the crustal field would increase considerably during periods of reduced field intensity like during reversals and induce erroneous records samplings performed over large distances within each lava flow would provide the best way to average out the contribution of the anomalies in any case such effects should not be neglected in paleomagnetic studies

late quaternary catchment evolution and erosion rates in the tyrrhenian side of central italy abstract this work assessed the geomorphological evolution and erosion rates in a small clayey catchment of tyrrhenian central italy providing chronological constraints for the fluvial deposits of the area for the first time the study area is the catchment of the formone stream a left tributary of the orcia river tuscany italy a 5 km long section of the valley up to its confluence with the orcia was studied it has an area of ca 12 km 2 and elevations between ca 300 and 600 m a s l two soil samples have been radiocarbon dated one was located at the top of a fluvial terrace 20 m above the present thalweg and the other was located near the water divide of a small tributary catchment they yielded ages of 2780 40 and 14 050 70 yrs b p respectively these chronological constraints allowed us to reconstruct the geomorphological evolution of the area through topographic and gis analyses and to estimate late quaternary erosion rates the ages provided a chronological reference for the terraced fluvial deposits of the formone and the upper orcia catchments the resultant erosion rates are consistent with those in the literature both for the tyrrhenian side of central italy and for mediterranean europe moreover the results confirmed that very intense erosion processes occurred as a consequence of the pleistocene holocene climatic change as observed in the peri adriatic belt of central italy

eruptive timing and 200 year episodicity at 92 w on the hot spot influenced galapagos spreading center derived from geomagnetic paleointensity eruptive timing in mid ocean ridge systems is relatively poorly constrained despite being an important variable in our understanding of many mid ocean ridge processes including volcanic construction magma recharge flux and storage and the stability of hydrothermal systems and biological communities only a handful of absolute eruption chronologies exist yet they are essential in understanding how eruptive timing varies with important controlling variables to construct an eruptive history at one location on the galapagos spreading center we present age determinations derived from geomagnetic paleointensity to aid interpretation of the paleointensity data we also present results from on bottom magnetic anomaly measurements and forward modeling of topographic induced magnetic anomalies anomalies may lead to a 1 2 t bias in flow mean paleointensities which does not significantly affect the overall interpretation paleointensity results for the three youngest sampled units are indistinguishable consistent with the flows being emplaced in relatively rapid succession comparisons with models of geomagnetic field behavior suggest these flows were erupted sometime in the past 100 200 years the fourth sampled unit has a significantly higher paleointensity consistent with an age of roughly 400 years the possible bias in paleointensity data allows for ages as young as 50 years for the youngest three flows and 200 400 years for the oldest flow this age distribution demonstrates an episodicity in the emplacement of the largest flows at this location with a 200 300 year period of relative quiescence between emplacement of the oldest unit and the three youngest units

paleosols provide sedimentation relative age and climatic information about the alluvial fan of the river tirso central western sardinia italy four representative paleosols in the plio pleistocene alluvial fan of the river tirso central western sardinia italy were studied for paleoenvironmental information to describe the sedimentology of the alluvial fan and to define a relative chronological framework for the fan the representative depositional units and associated paleosols were characterised by fieldwork physical chemical and mineralogical analyses pedogenesis was mostly driven by the time and climate factors in the proximal fan location pedogenesis was initially influenced by a warm subtropical tropical climate of the late pliocene and subsequently by warm and humid interglacial phases of the pleistocene these phases were also responsible for soil formation in the middle fan in the distal reaches of the fan pedogenesis was driven by the different climatic pulses of the late pleistocene tyrrhenian interglacial mis 5 pleistocene eustatic sea level changes directly influenced the lowest elevations of the middle fan and the distal fan erosion and soil truncation mainly occurred in the proximal fan and at the highest elevations of the middle fan during glacial phases

basinwide stratigraphic synthesis and sequence stratigraphy upper pragian emsian and eifelian stages lower to middle devonian appalachian basin

stratigraphic architecture and quaternary evolution of the val d agri intermontane basin southern apennines italy abstract the sedimentary record of the val d agri basin is of great importance for understanding the quaternary tectonic activity and climatic variability in the southern apennines changes in tectonic controls sediment supply and climatic input have been identified the interval from 56 to 43 ka was associated with asymmetric subsidence restricted to the north eastern actively faulted margin of the basin and development of axial braided river and transverse alluvial fan systems short lasting mediterranean type pedogenesis between 43 and 32 ka mis stage 3 coexisted with progradation aggradation of the southern alluvial fan deposits and southwards tilting of the basin floor aggradation ended with consumption of accommodation space after 32 ka during a subsequent stage of decline of vegetation cover possibly as a consequence of climatic cooling probably mis stage 2 active progradation of alluvial fans occurred breakthrough of the basin threshold and entrenchment of the drainage network must therefore be attributed to a latest pleistocene to holocene age the first stages of basin opening and fill predating 56 ka have only been inferred by stratigraphic considerations the earliest lacustrine sedimentation should be middle pleistocene or older in age the following south eastward basin widening allowed progradation of alluvial fan systems which completely filled the lacustrine area tentatively late middle pleistocene pedogenesis in mediterranean like climate conditions caused the final development of a highly mature fersiallitic paleosol at the top of the fan surfaces in areas of morpho tectonic stability plausibly during mis stage 5 the study results demonstrate the potential of applying a multidisciplinary approach in an intermontane continental settings marked by a relative rapid and constant tectonic subsidence and a high rate of sediment supply during the pleistocene glacial interglacial cycles

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

eolian dust deposition on the giara di gesturi basalt plateau sardinia mineralogical study of samples from depression fills on an isolated basalt plateau in central sardinia showed that although the basalt is free of quartz and mica fair amounts of these minerals occur in the finer fractions results from x ray analyses of silt fractions and morphoscopical analyses of sand fractions indicate that the bulk of the quartz and mica is of eolian origin the eolian quartz is predominantly of medium and coarse silt size and in the upper 10 cm of the depression fills constitutes about 20 per cent of the soil mass approx 20 kg m2 eolian mica is present in smaller amounts and is of medium silt or smaller size the provenance of the eolian material could not be established with certainty although a local origin can be excluded

three millennia of directional variation of the earth s magnetic field in western europe as revealed by archeological artefacts directional secular variation of the geomagnetic field over the last 2000 years has been defined in western europe from numerous archeomagnetic studies however the number of archeomagnetic results for older periods is much more limited for this reason we present new data obtained from fired archeological structures found in two french sites loupiac and aspiran dated within the first millennium b c latest bronze earliest iron age transition 850 700 b c and iron age 525 475 b c respectively from a compilation of archeomagnetic results from western europe great britain italy and france and northern africa tunisia we propose a directional secular variation curve for western europe that covers the entire first millennium b c this curve exhibits a large clockwise motion with rapid changes during the first half of the millennium while the last four centuries b c are characterized by weak variations

the cenozoic graben system of sardinia italy geodynamic evolution from new seismic and field data abstract a tectono sedimentary scenario for the southern sardinia italy cenozoic graben system is proposed using field observations and the interpretation of onshore and offshore seismic profiles the major structural events are tied to the general geodynamic evolution of the western central mediterranean thus the extensional late oligocene aquitanian event is a consequence of an apenninic westward subduction process associated with a volcanic arc 29 30 to 15 16 my which is particularly well exposed in sardinia deposition of sub aerial clastics was followed by transgression of the rift depression at the beginning of the aquitanian subduction terminated at the opening of the oceanic provencal basin and the rotation of sardinia corsica during burdigalian time 20 21 to 15 16 my the messinian compressional event ne sw oriented documented from microtectonic data strongly affected the oligo miocene basin the superimposed plio quaternary campidano graben which is probably related to the formation of the tyrrhenian basin contains more than 600 m of syntectonic deposits a change in polarity of the master faults bounding the oligo miocene rift created a central horst type twist zone separating two depocenters in the oristano and cagliari regions emplacement of large volcanic bodies and inversion of the basin during the messinian in cagliari area has reduced the areas with potential for hydrocarbon exploration the two remaining prospective zones are the oristano sub basin and the offshore south of cagliari where burial of lower miocene marine organic matter may have been sufficient to generate hydrocarbons potential reservoirs could be pre rift mesozoic or eocene strata but are mainly excellent miocene sands derived from erosion of the granitic basement in tilted blocks

the absolute age of the eifelian tioga ash bed pennsylvania the tioga ash bed bed b of the zeigler pit union county pennsylvania lies in the polygnathus costatus costatus zone of the eifelian stage of the middle devonian series the 27 5 cm thick bed contains igneous zircon and monazite crystals that have been dated by precise u pb techniques zircons are characterized by inherited pb that occurs as barely perceptible interior regions enriched in inclusions the zircons are discordant and do not reveal the igneous age of the bed in contrast high quality monazite crystals lack any evidence of inheritance or loss of pb and multiple analyses have overlapping 207 pb 235 u ages of 390 0 pm 0 5 ma the monazite analyses are concordant or very slightly reversely discordant the consistency of the monazite data provides a new precise estimate of age for the lower eifelian

zircons to the front accretionary history of the rheno hercynian active margin variscides germany our paper reports the detrital zircon record from late devonian to late carboniferous foreland basin deposits in the rheno hercynian rh variscides of germany together with a review of petrograph

chronometric calibration of mid ordovician to tournaisian conodont zones a compilation from recent graphic correlation and isotope studies three available graphic correlation analyses are used to calibrate mid palaeozoic conodont zonations sweet s scheme for the mid to upper ordovician kleffner s for the mid to upper silurian and murphy berry s for the lower and middle lower devonian the scheme of sweet is scaled by applying the high precision u pb zircon date of tucker and others for the rocklandian and linked with that of kleffner by scaling the graptolite sequence of the ordovician silurian global stratotype section to fit two similarly derived dates from this sequence the top of kleffner s scheme all of murphy berry s as well as standard zones to the frasnian are calibrated by using tie points of the latest cambridge bp time scale gts 89 however the recent microbeam zircon date by claoue long and others for the hasselbachtal devonian carboniferous auxiliary stratotype is used to calibrate the standard famennian zones also the similarly derived but preliminary determination reported by roberts and others from the isismurra formation of new south wales is tentatively taken as the top of the tournaisian and so used to calibrate tournaisian zones despite the considerable extrapolation required to compile these schemes and their inherent errors the resultant time scale closely agrees with other dates of tucker and others from the llanvirn as well as the gts 89 homerian gorstian tie point this suggests that stratigraphic methods can be usefully applied to geochronometry the llandovery appears to have lasted longer 16 m y than usually envisaged and the ordovician silurian boundary may need to be lowered to approximately 443 5 ma certainly chrons varied widely in duration and further stratigraphic studies to estimate their relative durations as well as high resolution dating for their calibration will be crucial to more accurate biochronometries

global time scale and regional stratigraphic reference scales of central and west europe east europe tethys south china and north america as used in the devonian carboniferous permian correlation chart 2003 dcp 2003 the boundaries of the devonian carboniferous and permian stages of the global stratigraphic reference scale abbreviated to global stratigraphic scale gss are described in relation to the biostratigraphic and or lithostratigraphic units of the regional stratigraphic reference scales abbreviated to regional stratigraphic scales rss of central and west europe east europe tethys south china eastern tethys and north america in their type regions the boundaries of gss units rarely coincide with those of homonymous rss units moreover the definitions of some rss units have changed several times over the last decades and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts the stratigraphic framework proposed in our global devonian carboniferous permian correlation chart 2003 dcp 2003 devonian carboniferous permian correlation chart 2003 menning m schneider j w alekseev a s amon e o becker g von bitter p h boardman d r bogoslovskaya m braun a brocke r chernykh v chuvashov b i clayton g dusar m davydov v i dybova jachowicz s forke h c gibling m gilmour e h goretzki j grunt t a hance l heckel p h izokh n g jansen u jin y g jones p kading k ch kerp h kiersnowski h klets a klug ch korn d kossovaya o kotlyar g v kozur h w laveine j p martens th nemyrovska t l nigmadganov a l paech h j peryt t m rohn r roscher m rubidge b schiappa t a schindler e skompski s ueno k utting j vdovenko m v villa e voigt s wahlman g p wardlaw b r warrington g weddige k werneburg r weyer d wilde v winkler prins c f work d m 2004 abschlusskolloquium dfg schwerpunktprogramm 1054 evolution des systems erde wahrend des jungeren palaozoikums im spiegel der sedimentgeochemie abstracts univ erlangen germany 2004 p 43 herein abbreviated to dcp 2003 and cited as dcp 2003 in references is an attempt to reduce these errors the dcp 2003 is the stratigraphic base for project 1054 of the deutsche forschungsgemeinschaft dfg the evolution of the late palaeozoic in the light of sedimentary geochemistry this composite time scale has been carefully balanced as far as data allows to remove unnecessary artificial compression and expansion of time intervals biozonations and depositional events the ages selected in dcp 2003 are markedly different to those in the geologic time scale 1989 gts 1989 harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge pp 1 263 and in gradstein and ogg gradstein f m ogg j 1996 a phanerozoic time scale episodes 19 1 2 3 4 insert whereas they are closer to those of the geologic time scale 2004 gts 2004 gradstein f m ogg j g smith a g 2004 a geologic time scale 2004 cambridge univ press cambridge pp 1 589 mostly the ages are rounded to the nearest 0 5 ma in order to avoid estimates of questionable accuracy whereas ages of 0 1 ma in the gts 2004 and their error bars of 0 4 ma to 2 8 ma for the devonian to permian stage boundaries suggest an improved accuracy in contrast in the dcp 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows c 2006 elsevier b v all rights reserved

late quaternary climatic changes in northern cilento southern italy an integrated geomorphological and paleopedological study abstract this paper reports a contribution to the knowledge of the local morphodynamic and pedogenetic response to late quaternary climatic changes in northern cilento southern italy three representative geomorphological units and associated paleosols have been characterised in detail by field work chemical and mineralogical analyses and micromorphological observations of thin sections the data confirm an intense degree of weathering and a complex history of soil formation often representing different environments in contrast with the present pedoclimatic regime two of the three profiles reveal a polygenetic character recording typical interglacial conditions characterised by high temperatures and humidity with important soil development followed by the occurrence of periglacial conditions possibly occurring during cold glacial stages namely the last glacial at mid latitude coastal regions of southern italy the third paleosol appears essentially monogenetic and developed under interglacial like conditions

ichnological evidence for the environmental setting of the fossil lagerstatten in the devonian hunsruck slate germany analysis of the ichnology and sedimentology of the lower devonian hunsruck slate germany reveals that the distribution and preservation of the famous pyritized fauna were controlled by the deposition of fine grained turbidites that formed a firm substrate the nature of this substrate is evidenced by the preservation of laminae and the finest details of arthropod trackways the trace fossils are dominated by two ecological groups those made by epifaunal organisms and those involving burrow systems connected to the sediment water interface trace makers that moved through the sediment are poorly represented the diversity of in situ body fossils and epifaunal traces confirms that conditions within the water column remained well oxygenated even though the sediment rapidly became inhospitable the hunsruck slate konservat lagerstatten are remarkable in preserving soft tissues where unusual geochemical conditions prevailed in the environment where the animals lived rather than following transport to a different setting

clay illuviation in red mediterranean soils abstract theories regarding pedogenesis in red mediterranean soils have undergone several stages of development the concept of clay illuviation in these soils was not a part of early theories and it is not yet unanimously accepted as a leading soil forming process a methodology is presented for studying the illuviation of clay in these soils emphasizing typology of textural features and fabrics the problem of age determination is also addressed through the use of radiometric dates and correlation with archaeological artifacts clay illuviation in red mediterranean soils under present day environmental conditions suggests that it occurs presently only on humid and sub humid margins of the mediterranean basin elsewhere illuvila clay accumulations are inherited from interglacial periods red mediterranean soils during glacial periods were eroded coluviated aggraded with aeolian dust calcitic fraction of which was redistributed in form of calcitic features and eventually were affected by water logging an example of water logging of red mediterranean soils mamora morocco which took place during the last glacial cycle consists of yellow illuvial clays accompanied by a yellowing of the ground mass during earlier cycles water logging resulted in whitish grey stains in which hydromorphic textural features were deposited

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

an updated archeomagnetic directional variation curve for france over the past two millennia following 25 years of additional data acquisition abstract nearly 40 years ago emile thellier published an article summarizing the archeomagnetic data he had obtained during his career which had allowed him to recover the main features of the directional variations of the geomagnetic field in france for the last two millennia this database went on to be significantly completed 25 years ago by ileana bucur who had taken over thellier s work on archeomagnetism this forms the current basis of our knowledge of the directional evolution of the geomagnetic field in france since then archeomagnetic studies have been continued at thellier s historical laboratory in saint maur this article presents the directional archeomagnetic data obtained in france over the past 25 years in this same laboratory a total of 528 new data are presented which together with the 170 results obtained on the french territory previously listed in bucur 1994 constitute the french directional database 698 data in all all but two of these data were obtained using the experimental protocol developed by e thellier based on the analysis of large samples and on a magnetic viscosity test that has proved its reliability on numerous occasions the directions from the entire french database have been precisely defined with 95 of the 95 values being less than 1 9 and 50 being less than 0 8 the selection of 286 data with dating uncertainties of 50 years allowed us to compute a new reference directional variation curve for france since the first century bc using sliding windows the variable durations and shifts of which were adapted to the time distribution of the available data and the bivariate extension of the fisher statistics this shows ample and smooth variations fairly similar to those previously determined from a much smaller database the resulting secular variation curve is particularly well suited for use in archeomagnetic dating

statistical analysis of palaeomagnetic data from the last four centuries evidence of systematic inclination shallowing in lava flow records the main objective of this work is to compare directional declination and inclination volcanic and archaeomagnetic data for the last four centuries 1600 1990 with the historical geomagnetic predictions given by the gufm1 model which spans from 1590 to 1990 the results show statistical agreement between archaeomagnetic data and directions given by the geomagnetic field model however when comparing the volcanic data with the model predictions marked inclination shallowing is observed this systematically lower inclination has already been observed in local palaeomagnetic studies italy mexico and hawaii for the 20th century by comparing recent lava flows with the international reference geomagnetic field igrf model here we show how this inclination shallowing is statistically present at worldwide scale for the last 400 years with mean inclination deviation around 3 lower than the historical geomagnetic field model predictions

geomagnetic field variations as a dating tool application to sicilian lavas abstract over 40 historically dated mt etna lava flows have been carefully sampled for the purpose of palaeomagnetic analysis the natural remanent magnetization nrm of each lava flow contains a record of both the magnitude and direction of the earth s magnetic field at the time of its eruption our analysis has thus enabled us to determine the change of the magnetic field in sicily through historic times and to construct curves which show this secular variation of the field in both direction and magnitude in this paper the curves are used to reconsider the historical dates attributed to a number of etna lavas dates which had since been questioned by recent palaeomagnetic and geological studies in a similar manner these secular variation curves can be used as a powerful archaeological dating tool by comparison with the nrm of fired artifacts

new archaeomagnetic data recovered from the study of roman and visigothic remains from central spain 3rd 7th centuries summary new archaeomagnetic results from four heated combustion structures recovered from two archaeological sites in central spain are reported they have been dated by archaeological evidence and in two cases by radiocarbon dating rock magnetic experiments indicate low coercivity magnetic phases such as magnetite and thermally stable maghaemite as the main carriers of the remanent magnetization haematite has been observed in poorly heated baked clays archaeomagnetic directions have been obtained from either alternating field or thermal demagnetization experiments performed on 57 specimens coming from 46 independently oriented samples the four well defined archaeomagnetic directions obtained are in good agreement with previous archaeomagnetic data and with recent regional and global field models they define the beginning of easterly declination drift that was initiated around 350 400 ad and culminated around 800 850 ad and delineate the maximum in inclination that took place around 600 650 ad in addition classical thellier thellier experiments including thermal remanent magnetization anisotropy and cooling rate corrections were conducted on 23 specimens only 13 specimens corresponding to well defined single component behaviour gave reliable results new mean archaeointensities have been obtained for two of the four studied structures vbk1 64 2 5 0 t and vbt1 62 4 2 6 t the new data suggest that two relative intensity maxima occurred in western europe around 320 and 630 ad being of lower magnitude that observed in eastern europe

sims u pb zircon ages for the upper devonian snobs creek and cerberean volcanics from victoria with age uncertainty based on uo2 uo v uo u precision sensitive high resolution ion microprobe shrimp zircon 206 pb 238 u ages for the snobs creek volcanics and the overlying cerberean volcanics in central victoria are analytically indistinguishable at 373 2 1 8 and 375 0 2 0 ma 2 the shrimp data provide a refined numerical age for interbedded freshwater fish fauna of the taggerty formation and together with its recently revised givetian age based on independent faunal correlations provide a new calibration point on the devonian time scale the use of pb uo 2 rather than pb u in secondary ionization mass spectrometry sims dating reduces the range of secondary ion discrimination from zircon between spot correlations observed between uo u and uo 2 uo ratios give quantitative estimates for external sims uncertainty per spot age that are independent of assumed uniformity in zircon pb u they can exceed internal uncertainties by up to 1 5 dependent on the analytical session this has important effects on the calibration of sims ages at the sub percent level using imperfect reference zircons subject to small scale perturbations of the u pb system

activity of mount etna preceding the february 1999 fissure eruption inferred mechanism from seismological and geochemical data abstract the february 1999 eruption of mt etna took place through a fissure on the sse flank of the cone of the summit se crater this event was preceded by continuous activity since 1995 sometimes accompanied by violent outbursts from one or more of the three other summit craters ne crater voragine or chasm and bocca nuova and finally by a series of 20 short lived eruptions from the se crater between september 1998 and january 1999 these phenomena could be accounted for by invoking gradual invasion of a shallow small reservoir by more primitive basic and gas rich magma coming from depth the shallow chamber is more likely to be a plexus of dikes which had developed during the previous years 1995 1997 following variations of the local stress field owing to enhanced magma generation and accumulation at the top of the mantle magma injection and mixing is evidenced through geochemistry whereas the state of stress of the volcanic pile and underlying crust is determined using earthquake distributions and focal mechanisms the behaviour of the seismic tremor amplitude appears to be a good indicator of the state of unrest of the volcano although not always directly linked to the relative energy of degassing phenomena

two new emsian early devonian u pb zircon ages from volcanic rocks of the rhenish massif germany implications for the devonian time scale so far only few biostratigraphically well constrained isotopic ages constitute the geochronological framework of the devonian period to expand this sparse dataset two new u pb isotope dilution thermal ionization mass spectrometry id tims zircon ages were obtained from volcanic rocks of the rhenish massif germany these rocks are interbedded in emsian lower devonian marine sedimentary successions that are well documented by index fossils given that the u pb zircon data represent primary crystallization and eruption ages they provide an important contribution to the devonian time scale the older sample a stratiform volcaniclastic layer hans platte is collected from bundenbach hunsruck the type locality of the lower emsian hunsruck slate a cluster of five coherent single zircon analyses obtained from this layer yielded a weighted mean 206 pb 238 u age of 407 7 0 7 ma which is regarded as the time of eruption of the pyroclastic rock biostratigraphically the layer can be assigned to the upper part of the polygnathus excavatus conodont zone the younger u pb age was obtained from the global stratotype section and stratigraphic point section at wetteldorf eifel where the k bentonite hercules i is intercalated 13 m below the lower middle devonian boundary in the uppermost part of the polygnathus costatus patulus conodont zone some of the 19 single zircon analyses obtained from this bentonite appear to document significant influences of inheritance the 13 youngest points are however concordant and form an elongated cluster along concordia with 206 pb 238 u ages between 392 2 and 407 7 ma given the risky assumption that this age scattering is exclusively caused by varying amounts of inheritance the youngest point of this cluster represents the analysis with the least or no inheritance in this case its 206 pb 238 u age of 392 2 1 5 ma should approach the eruptional age of the bentonite the ages presented here in combination with u pb id tims zircon and monazite ages from other workers allow a recalibration of the early emsian to early eifelian interval of the devonian time scale the result is a duration of the emsian stage excluding the basal emsian p kitabicus conodont zone of more than 17 2 ma and an emsian eifelian early middle devonian boundary age of 391 8 0 4 ma

rhenium osmium geochronology of arsenopyrite in meguma group gold deposits meguma terrane nova scotia canada evidence for multiple gold mineralizing events rhenium osmium geochronology using arsenopyrite was undertaken for three gold deposits in the meguma terrane nova scotia canada in order to better constrain their age of formation and to assess the utility of arsenopyrite for dating similar deposits globally analyses of arsenopyrite from bedding concordant veins from the ovens locality southwest meguma terrane yield a precise re os isochron age of 409 5 ma arsenopyrite analyses from a bedding discordant vein at this locality indicate an identical re os age of 407 4 ma saddle reef veins from the dufferin deposit northeast meguma terrane contain arsenopyrite with a precise re os isochron age of 380 3 ma the lack of common os in some arsenopyrite samples from both the ovens and dufferin permit calculation of single mineral model ages for each deposit which are identical to those determined using the isochron method initial os compositions for the two vein types at the ovens suggest a predominately crustal source of os in the mineralizing fluids whereas a less radiogenic initial os composition for arsenopyrite from dufferin does not as clearly define a crustal metal source at a third locality the touquoy deposit the re os systematics of arsenopyrite associated with disseminated gold mineralization do not define a precise formation age possibly as a result of mixing of re and os derived from the mineralizing fluid and the shale host rock the re os ages of arsenopyrite indicate that there were at least two distinct periods of gold deposition in the meguma terrane coinciding with widespread tectonothermal events regional deformation and metamorphism associated with acadian orogenesis and widespread generation of meta and peraluminous granites and high grade metamorphism within the basement rocks under the meguma terrane the ca 407 ma age for the ovens arsenopyrite provides the best estimate for the timing of regional acadian deformation in the meguma terrane and is slightly older than previous estimates based solely on 40ar 39ar dating

distortion of the geomagnetic field in volcanic terrains an experimental study of the mount etna stratovolcano abstract the inclination i declination d and total intensity f of the geomagnetic field were measured on mount etna in 1989 1991 at a dozen sites previously sampled for archeomagnetic studies the purpose of the work was to determine the variations of these parameters at 30 cm above ground level and how the distortion from the main field can affect the archeomagnetic record of volcanic rocks ten measurements were usually performed at each site with a three component flux gate magnetometer whose estimated precision is 0 2 on direction and 50 nt on intensity this was considered sufficient on volcanic areas with highly magnetized rocks and where the geomagnetic gradient may be in excess of 1000 nt m results averaged for each site generally show small variations in intensity 3 of the total field and direction 1 5 the averaged values of the 12 sites i 52 6 d 0 3 f 44010 nt are very close to those measured in sedimentary terrain away from the volcano i 52 9 d 0 35 f 44110 nt themselves consistent with the interpolated igrf in eastern sicily the largest deviations of the geomagnetic direction have been observed on four sites three of them located on the south flank between 1900 and 700 m elevation it is suggested that these anomalies are mainly related to dyke swarms which are common within the south rift zone of mount etna our findings show that reliable archeomagnetic results can be obtained from volcanic rocks provided that lavas of the same eruption are sampled on several sites distributed over the largest possible area